Merge remote-tracking branch 'origin/rustify' into worktree-agent-ace98b0bdaf33ffff

# Conflicts: # docs/IRIS.md # docs/RUST.md
iris: the fling curve was the identity function, and the keyboard was a targetSdk
2026-09-07 15:33:25 -04:00 · 2026-09-07 12:44:01 -04:00 · 2026-09-07 12:39:53 -04:00 · 2026-09-07 12:38:55 -04:00 · 2026-09-07 12:38:19 -04:00 · 2026-09-07 12:35:20 -04:00
126 changed files with 19251 additions and 992 deletions
@@ -19,6 +19,21 @@ child process, translated into one common event model.** A new session type
 is a new driver — never a session-type branch in shared code (routes,
 transcript, app screens).
 The second one, for the Rust port on the `rustify` branch: **the phone app
 and a planned desktop app share almost all of their code.** Screens, widgets,
 folding, paging, config and the network client live in the shared crates
 (`iris`, `client-core`, `transcript-ui`, `tabs-ui`); `android-app` and
 `desktop-app` are thin entry points that own only what the platform forces
 (JNI and the IME on one side, winit and argv on the other). The two
 *layouts* will differ, to suit a phone's screen and a finger against a
 desktop's screen and a mouse -- but the widgets a layout is made of (a
 button, a text field, a list, a card) and the styling (colours, spacing,
 type) are one implementation with no per-platform copy. Anything that could
 work on both goes in a shared crate the first time it is written, and a
 platform crate growing a widget or a colour is a defect to move, not a
 convenience to keep. Iris said this on 2026-09-07; docs/RUST.md carries the
 details.
 ## Layout
 Mirrors `../dev-updater` deliberately: same stack (axum 0.8 +
@@ -261,6 +276,27 @@ Each exists because something was invisible without it.
  framework, from `atrace` text output with no trace processor needed. It is
  how the cost of a layout node per link was attributed to the framework
  rather than guessed at.
 - **`iris/android-app/build-apk.sh [debug|release] [--abi ...] [--features
  ...]`** builds iris-android-app's cdylib (`cargo ndk`) and its APK
  (Gradle) in one step and verifies the result (`aapt2`/`apksigner`), and
  **`iris/android-app/run-bench.sh [--apk PATH]`** installs it on this
  checkout's own emulator, taps "Run benchmark" by label, and prints the
  report -- written so the P0 build/install/tap/read-report cycle stops
  being retyped by hand each time (docs/RUST.md's P0 box).
 - **iris's three test layers** (docs/RUST.md's "Three test layers" has
  the commands and what each cannot answer): test at the cheapest one
  that can answer the question. `cargo test -p transcript-fixture` runs
  the real transcript screen over the bench fixture with **no window, no
  compositor and no GPU** (`iris::harness`), on a clock the test owns and
  a gesture replayed from a `t_ms action x y` file under
  `iris/transcript-fixture/touch/` -- which is how the batched 120Hz
  flick a finger actually makes is testable at all, since a `ui-trace`
  swipe is many evenly-spaced events. `iris/run-headless.sh phone --phone
  --shot …` opens the same screen in a window at the phone's own size and
  density for looking at, and `--replay FILE` drives the same recording
  into it. The emulator is for JNI, the IME, insets, the surface
  lifecycle and one verification run before a build goes to the phone --
  not for iterating on layout.
 ### Driving the UI
@@ -50,6 +50,12 @@ version = "0.23.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ac07cdecf99051d9a5238b80f35af32cdeba5b336e55d957b318b50137e18da5"
 [[package]]
 name = "bitflags"
 version = "2.13.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b588b76d00fde79687d7646a9b5bdf3cc0f655e0bbd080335a95d7e96f3587da"
 [[package]]
 name = "bytes"
 version = "1.12.1"
@@ -77,6 +83,7 @@ name = "client-core"
 version = "0.1.0"
 dependencies = [
 "event-model",
 "pulldown-cmark",
 "serde",
 "serde_json",
 "ureq",
@@ -206,6 +213,15 @@ dependencies = [
 "percent-encoding",
 ]
 [[package]]
 name = "getopts"
 version = "0.2.24"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cfe4fbac503b8d1f88e6676011885f34b7174f46e59956bba534ba83abded4df"
 dependencies = [
 "unicode-width",
 ]
 [[package]]
 name = "getrandom"
 version = "0.2.17"
@@ -490,6 +506,25 @@ dependencies = [
 "unicode-ident",
 ]
 [[package]]
 name = "pulldown-cmark"
 version = "0.13.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e9f068eba8e7071c5f9511831b44f32c740d5adf574e990f946ddb53db2f314e"
 dependencies = [
 "bitflags",
 "getopts",
 "memchr",
 "pulldown-cmark-escape",
 "unicase",
 ]
 [[package]]
 name = "pulldown-cmark-escape"
 version = "0.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "007d8adb5ddab6f8e3f491ac63566a7d5002cc7ed73901f72057943fa71ae1ae"
 [[package]]
 name = "quote"
 version = "1.0.47"
@@ -783,12 +818,24 @@ dependencies = [
 "zerovec",
 ]
 [[package]]
 name = "unicase"
 version = "2.9.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "dbc4bc3a9f746d862c45cb89d705aa10f187bb96c76001afab07a0d35ce60142"
 [[package]]
 name = "unicode-ident"
 version = "1.0.24"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e6e4313cd5fcd3dad5cafa179702e2b244f760991f45397d14d4ebf38247da75"
 [[package]]
 name = "unicode-width"
 version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b4ac048d71ede7ee76d585517add45da530660ef4390e49b098733c6e897f254"
 [[package]]
 name = "untrusted"
 version = "0.9.0"
@@ -3,9 +3,13 @@ package com.example.aiapp
 import android.content.Context
 import android.os.BatteryManager
 import android.os.Process
-import androidx.compose.animation.core.tween
+import android.view.View
-import androidx.compose.foundation.gestures.animateScrollBy
+import androidx.compose.foundation.gestures.FlingBehavior
 import androidx.compose.foundation.lazy.LazyListState
 import androidx.compose.ui.focus.FocusRequester
 import androidx.core.view.ViewCompat
 import androidx.core.view.WindowInsetsCompat
 import androidx.core.view.WindowInsetsControllerCompat
 import java.io.File
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.delay
@@ -19,27 +23,84 @@ import kotlinx.coroutines.launch
 * here against [LazyListState] and [BenchFixture] directly. Only reachable from the `bench` build
 * (see [SessionSettingsDialog]'s `onRunBenchmark`), but compiled into every build for the reason
 * [BenchFixture]'s doc comment gives.
 *
 * **v2 (2026-09-06)**, asked for by Iris because the v1 fling was too gentle to stress-test the
 * scroll path and said nothing about typing or the keyboard. Four phases now, each a slice of the
 * same [FrameStats] recording ([FrameStats.markPhase]/[FrameStats.phaseLines] -- one recorder, not
 * two): **fling** (real `FlingBehavior`, not `animateScrollBy`), **stream** (unchanged from v1),
 * **type** (600 fixed characters into the real composer `TextFieldValue`, then deleted), and
 * **keyboard** (five show/hide cycles). The exact constants below are also written into
 * `docs/RUST.md`'s P0 box, "Benchmark v2 (2026-09-06)", so the iris half implements the identical
 * spec -- changing a number here without updating that box makes the two apps measure different
 * things while looking like the same benchmark.
 */
 object BenchRun {
-    /** transcript-bench.sh's default: 6 cycles of 4 swipes each, 900px over 200ms, 500ms apart. */
+    /** transcript-bench.sh's default: 6 cycles of 4 swipes each, kept as the pre-v2 comparison. */
    private const val CYCLES = 6
    private const val SWIPE_PX = 900f
    private const val SWIPE_MS = 200
    private const val SWIPE_PAUSE_MS = 500L
    /**
     * Fling phase (v2): a real fling through the list's own [FlingBehavior], not `animateScrollBy`
     * -- Iris's ask was that it "travel way faster" than the old tween-based swipe, and a tween can
     * never exceed the distance it is told to cover in the time it is given, while a real fling
     * decays from an initial velocity the way a finger flick does. 12,000 px/s is roughly a hard,
     * fast flick on a ~420dp/in device (about 30 dp/ms-equivalent initial speed); chosen well above
     * the ~4,500 px/s a moderate `animateScrollBy` swipe implies, so this phase exercises the fast
     * end of what the platform's fling decay produces rather than the gentle one v1 measured.
     */
    private const val FLING_VELOCITY_PX_S = 12_000f
    private const val FLING_COUNT = 8
    private const val FLING_SETTLE_CAP_MS = 3_000L
    private const val FLING_PAUSE_MS = 300L
    /** stream-bench.sh's shape: a real reply arrives as many small deltas, not one big write. */
    private const val STREAM_EVENTS_PER_SEC = 20
    private const val STREAM_SECONDS = 20
    /**
-     * Scrolls, then streams, then returns the extra report lines P0 asked for (CPU time, peak RSS,
+     * Type phase (v2): sentences built from long, multisyllabic words so the composer actually
-     * battery current) -- [FrameStats] and [DebugStats] are reset first, exactly as
+     * wraps across lines rather than fitting one, and long enough (600 chars) that the composer's
-     * `copyRenderReport` resets them, so the two accountings cover the same stretch of work.
+     * own height grows over several frames, pushing the transcript above it upward the same way a
     * real long message does. Exactly this string is also in `docs/RUST.md`'s P0 box so the iris
     * half types the identical content.
     */
    const val TYPE_TEXT =
        "Benchmarking this transcript screen requires unusually long, multisyllabic words so " +
            "wrapping and reflow are properly exercised: internationalization, " +
            "counterproductiveness, disproportionately, incomprehensibility, " +
            "deinstitutionalization, uncharacteristically, overenthusiastically, " +
            "misunderstanding, straightforwardness, telecommunications, and interdisciplinary " +
            "collaboration all push a narrow composer field to wrap across several lines while " +
            "the transcript above is pushed upward by the growing keyboard-adjacent box, which " +
            "is exactly what a real reader typing a long message sees happening now!!!"
    private const val TYPE_CHAR_DELAY_MS = 50L
    /**
     * Keyboard phase (v2): five show/hide cycles, a second apart, is enough to see whether the
     * transition is ever actually observed rather than being a one-off fluke either way.
     */
    private const val KEYBOARD_CYCLES = 5
    private const val KEYBOARD_SHOW_WAIT_MS = 1_000L
    private const val KEYBOARD_HIDE_WAIT_MS = 1_000L
    /**
     * Scrolls, flings, streams, types and toggles the keyboard, then returns the extra report lines
     * P0 asked for (per-phase travel/typing/keyboard counts, plus CPU time, peak RSS, battery
     * current) -- [FrameStats] and [DebugStats] are reset first, exactly as `copyRenderReport`
     * resets them, so the two accountings cover the same stretch of work.
     */
    suspend fun run(
        context: Context,
        scope: CoroutineScope,
        listState: LazyListState,
        flingBehavior: FlingBehavior,
        composerFocus: FocusRequester,
        setComposerText: (String) -> Unit,
        view: View,
    ): List<String> {
        FrameStats.reset()
        DebugStats.reset()
@@ -55,34 +116,10 @@ object BenchRun {
            }
        }
-        // The swipe loop: transcript-bench.sh's four swipes per cycle are two drags toward newer
+        val travel = runFlingPhase(listState, flingBehavior)
-        // content and two back, so a cycle returns to where it started and the whole loop measures
+        val sent = runStreamPhase()
-        // steady-state scrolling rather than travelling somewhere new each time.
+        runTypePhase(listState, composerFocus, setComposerText, view)
-        repeat(CYCLES) {
+        val keyboard = runKeyboardPhase(context, view)
            repeat(2) {
                listState.animateScrollBy(SWIPE_PX, tween(SWIPE_MS))
                delay(SWIPE_PAUSE_MS)
            }
            repeat(2) {
                listState.animateScrollBy(-SWIPE_PX, tween(SWIPE_MS))
                delay(SWIPE_PAUSE_MS)
            }
        }
        // Pinned to the newest end before streaming starts, the way stream-bench.sh's "Jump to
        // latest" tap is -- a reply streamed into a list parked further back arrives off-screen and
        // the report would show nothing happened.
        listState.scrollToItem(0)
        var sent = 0
        val total = STREAM_EVENTS_PER_SEC * STREAM_SECONDS
        while (sent < total && BenchFixture.remainingStreamEvents() > 0) {
            BenchFixture.pushNextLiveEvent()
            sent++
            delay(1000L / STREAM_EVENTS_PER_SEC)
        }
        // Lets the last few deltas land and draw before the report is read.
        delay(300)
        samplerJob.cancel()
        val cpuMs = Process.getElapsedCpuTime() - cpuStartMs
@@ -90,13 +127,158 @@ object BenchRun {
        val batteryLine = battery.finish()
        return listOf(
-            "  scroll: $CYCLES cycles (${CYCLES * 4} swipes), streamed $sent/$total fixture events",
+            "  fling: $FLING_COUNT flings out + $FLING_COUNT back at" +
                " ${FLING_VELOCITY_PX_S.toInt()}px/s, travel $travel",
            "  scroll: $CYCLES cycles (${CYCLES * 4} swipes, legacy tween), " +
                "streamed $sent/${STREAM_EVENTS_PER_SEC * STREAM_SECONDS} fixture events",
            "  type: ${TYPE_TEXT.length} characters inserted then deleted, one per" +
                " ${TYPE_CHAR_DELAY_MS}ms",
            keyboard,
            "  process CPU time over this run: ${cpuMs}ms",
            rssLine,
            batteryLine,
        )
    }
    /**
     * Phase 1: starting pinned at the newest end, [FLING_COUNT] flings away from it (toward older
     * messages) through the list's real fling path, then [FLING_COUNT] back. Positive velocity here
     * matches this list's existing scroll-offset convention (`TranscriptList`'s `reverseLayout`
     * pins index 0 -- the newest item -- at the bottom; a positive scroll offset moves the viewport
     * toward higher indices, i.e. away from the newest end and toward older content), the same sign
     * the pre-v2 swipe loop below already used for its first two swipes.
     */
    private suspend fun runFlingPhase(
        listState: LazyListState,
        flingBehavior: FlingBehavior,
    ): String {
        FrameStats.markPhase("fling")
        listState.scrollToItem(0)
        val start = position(listState)
        repeat(FLING_COUNT) {
            listState.scroll { with(flingBehavior) { performFling(FLING_VELOCITY_PX_S) } }
            waitForSettle(listState)
            delay(FLING_PAUSE_MS)
        }
        val outward = position(listState)
        repeat(FLING_COUNT) {
            listState.scroll { with(flingBehavior) { performFling(-FLING_VELOCITY_PX_S) } }
            waitForSettle(listState)
            delay(FLING_PAUSE_MS)
        }
        val back = position(listState)
        return "start=$start outward=$outward end=$back"
    }
    private fun position(listState: LazyListState) =
        "idx=${listState.firstVisibleItemIndex}/off=${listState.firstVisibleItemScrollOffset}px"
    /** Belt-and-suspenders on top of `performFling` already suspending until its own decay ends. */
    private suspend fun waitForSettle(listState: LazyListState) {
        val startedAt = System.currentTimeMillis()
        while (
            listState.isScrollInProgress &&
                System.currentTimeMillis() - startedAt < FLING_SETTLE_CAP_MS
        ) {
            delay(16)
        }
    }
    /**
     * Phase 2 (unchanged from v1): pinned to the newest end before streaming starts, the way
     * stream-bench.sh's "Jump to latest" tap is -- a reply streamed into a list parked further back
     * arrives off-screen and the report would show nothing happened.
     */
    private suspend fun runStreamPhase(): Int {
        FrameStats.markPhase("stream")
        var sent = 0
        val total = STREAM_EVENTS_PER_SEC * STREAM_SECONDS
        while (sent < total && BenchFixture.remainingStreamEvents() > 0) {
            BenchFixture.pushNextLiveEvent()
            sent++
            delay(1000L / STREAM_EVENTS_PER_SEC)
        }
        // Lets the last few deltas land and draw before the next phase starts.
        delay(300)
        return sent
    }
    /**
     * Phase 3: focuses the real composer, shows the keyboard if the platform allows it, then types
     * [TYPE_TEXT] one character at a time through the same `TextFieldValue` state a real keystroke
     * updates, and deletes it the same way -- this is what exercises wrapping and the transcript
     * being pushed upward, not a single big write.
     */
    private suspend fun runTypePhase(
        listState: LazyListState,
        composerFocus: FocusRequester,
        setComposerText: (String) -> Unit,
        view: View,
    ) {
        FrameStats.markPhase("type")
        listState.scrollToItem(0)
        composerFocus.requestFocus()
        showIme(view.context, view)
        // Lets focus and the keyboard's opening animation land before typing starts, so the frames
        // this phase records are the wrap/reflow it is measuring, not the keyboard opening.
        delay(300)
        var typed = ""
        for (ch in TYPE_TEXT) {
            typed += ch
            setComposerText(typed)
            delay(TYPE_CHAR_DELAY_MS)
        }
        delay(200)
        while (typed.isNotEmpty()) {
            typed = typed.dropLast(1)
            setComposerText(typed)
            delay(TYPE_CHAR_DELAY_MS)
        }
    }
    /**
     * Phase 4: [KEYBOARD_CYCLES] show/hide cycles through the same [WindowInsetsControllerCompat]
     * path a real IME toggle goes through, reporting how many of each were actually confirmed by
     * [android.view.WindowInsets.isVisible] rather than assumed from having asked -- UI_RULES:
     * never present an inferred value as a measured one. If the platform never shows it even once,
     * this says so in words rather than reporting a phase with no keyboard in it.
     */
    private suspend fun runKeyboardPhase(context: Context, view: View): String {
        FrameStats.markPhase("keyboard")
        var shown = 0
        var hidden = 0
        repeat(KEYBOARD_CYCLES) {
            showIme(context, view)
            delay(KEYBOARD_SHOW_WAIT_MS)
            if (imeVisible(view)) shown++
            hideIme(context, view)
            delay(KEYBOARD_HIDE_WAIT_MS)
            if (!imeVisible(view)) hidden++
        }
        return if (shown == 0) {
            "  keyboard: could not be shown ($KEYBOARD_CYCLES attempts, 0 confirmed visible)"
        } else {
            "  keyboard: shown $shown/$KEYBOARD_CYCLES, hidden $hidden/$KEYBOARD_CYCLES" +
                " (confirmed via isImeVisible)"
        }
    }
    private fun controller(context: Context, view: View): WindowInsetsControllerCompat? {
        val window = context.activity()?.window ?: return null
        return WindowInsetsControllerCompat(window, view)
    }
    private fun showIme(context: Context, view: View) {
        controller(context, view)?.show(WindowInsetsCompat.Type.ime())
    }
    private fun hideIme(context: Context, view: View) {
        controller(context, view)?.hide(WindowInsetsCompat.Type.ime())
    }
    private fun imeVisible(view: View): Boolean =
        ViewCompat.getRootWindowInsets(view)?.isVisible(WindowInsetsCompat.Type.ime()) ?: false
    /** VmHWM from /proc/self/status: the process's high-water mark, in kB, since it started. */
    private fun peakRssLine(): String {
        val kb =
@@ -134,6 +134,13 @@ fun debugReport(
     * render-report button reads exactly as it did before this existed.
     */
    extra: List<String> = emptyList(),
    /**
     * Bench v2's per-phase frame accounting ([FrameStats.phaseLines]) --
     * fling/stream/type/keyboard, each a slice of the same frames the whole-run sections below
     * still cover in full. Empty on every path but the scripted bench run, same reasoning as
     * [extra].
     */
    phaseFrames: List<String> = emptyList(),
 ): String = buildString {
    appendLine("ai-app render report")
    appendLine(device)
@@ -148,6 +155,11 @@ fun debugReport(
    appendLine("transcript:")
    transcript.forEach { appendLine(it) }
    appendLine()
    if (phaseFrames.isNotEmpty()) {
        appendLine("per phase:")
        phaseFrames.forEach { appendLine(it) }
        appendLine()
    }
    appendLine("frames:")
    frames.forEach { appendLine(it) }
    appendLine()
@@ -42,6 +42,21 @@ object FrameStats {
    private val gpu = ArrayList<Long>()
    private var since = System.currentTimeMillis()
    /**
     * Where a named phase of a scripted run (bench v2's fling/stream/type/keyboard) started, as an
     * index into [total] and a wall-clock time -- not a second recorder, just a mark on this one,
     * so a phase's frames are the same [FrameMetrics] the whole-run report already has, sliced.
     */
    private data class PhaseMark(val name: String, val startIndex: Int, val startMs: Long)
    private val phaseMarks = ArrayList<PhaseMark>()
    /** Call at the start of each named phase of a scripted run; see [BenchRun]. */
    @Synchronized
    fun markPhase(name: String) {
        phaseMarks += PhaseMark(name, total.size, System.currentTimeMillis())
    }
    @Synchronized
    fun add(metrics: FrameMetrics) {
        // The first frame after a window opens includes inflating it and is nobody's scroll.
@@ -69,6 +84,7 @@ object FrameStats {
        listOf(total, waited, input, animation, layout, draw, sync, issue, swap, gpu).forEach {
            it.clear()
        }
        phaseMarks.clear()
        since = System.currentTimeMillis()
    }
@@ -95,6 +111,38 @@ object FrameStats {
        ) + if (gpu.isEmpty()) emptyList() else listOf(phase("gpu   ", gpu))
    }
    /**
     * One block per [markPhase] call: how many frames landed between that mark and the next (or the
     * end of the run, for the last one), how many were late, the total/p50/p90/p99, the worst
     * single frame, and how long the phase actually ran. Marks with no frames between them (a phase
     * that finished before a frame was drawn) still get a line rather than being silently dropped
     * -- UI_RULES' "say what you don't know" applies to a phase as much as to a single number.
     */
    @Synchronized
    fun phaseLines(refreshHz: Float): List<String> {
        if (phaseMarks.isEmpty()) return emptyList()
        val budget = if (refreshHz > 0) 1000.0 / refreshHz else 16.7
        val lines = ArrayList<String>()
        phaseMarks.forEachIndexed { i, mark ->
            val endIndex = if (i + 1 < phaseMarks.size) phaseMarks[i + 1].startIndex else total.size
            val endMs =
                if (i + 1 < phaseMarks.size) phaseMarks[i + 1].startMs
                else System.currentTimeMillis()
            val samples = total.subList(mark.startIndex, endIndex)
            val seconds = (endMs - mark.startMs) / 1000.0
            lines += "  ${mark.name}: ${samples.size} frames over ${"%.1f".format(seconds)}s"
            if (samples.isEmpty()) {
                lines += "    no frames recorded in this phase"
            } else {
                val late = samples.count { it / 1_000_000.0 > budget }
                lines += "    late: $late (${percent(late, samples.size)})"
                lines += "    " + phase("total ", samples)
                lines += "    worst ${"%.1fms".format(samples.max() / 1_000_000.0)}"
            }
        }
        return lines
    }
    /** How long the frames recorded here spent in their draw phase, and how many there were. */
    @Synchronized fun drawPhase(): Pair<Long, Int> = draw.sum() to draw.size
@@ -187,13 +187,20 @@ class MainActivity : ComponentActivity() {
            model = null,
            keepsOwnTranscript = false,
            permissionMode = null,
            effort = null,
            takesEffort = false,
            imported = false,
            notify = false,
            autoResume = false,
            autoResumeMessage = "",
            resumeAt = null,
            cwd = null,
            contextTokens = null,
            maxImageEdge = null,
            usageProvider = null,
            status = "idle",
            lastActivity = 0.0,
            subagents = 0,
        )
    // launchMode="singleTop": an enrollment scan, or a notification tapped while the app is open,
@@ -12,6 +12,7 @@ import androidx.activity.result.PickVisualMediaRequest
 import androidx.activity.result.contract.ActivityResultContracts
 import androidx.compose.foundation.background
 import androidx.compose.foundation.clickable
 import androidx.compose.foundation.gestures.ScrollableDefaults
 import androidx.compose.foundation.gestures.awaitEachGesture
 import androidx.compose.foundation.gestures.awaitFirstDown
 import androidx.compose.foundation.layout.Box
@@ -64,12 +65,15 @@ import androidx.compose.runtime.snapshots.Snapshot
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.drawWithContent
 import androidx.compose.ui.focus.FocusRequester
 import androidx.compose.ui.focus.focusRequester
 import androidx.compose.ui.graphics.graphicsLayer
 import androidx.compose.ui.input.pointer.PointerEventPass
 import androidx.compose.ui.input.pointer.pointerInput
 import androidx.compose.ui.layout.onSizeChanged
 import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.platform.LocalDensity
 import androidx.compose.ui.platform.LocalView
 import androidx.compose.ui.semantics.contentDescription
 import androidx.compose.ui.semantics.semantics
 import androidx.compose.ui.text.TextRange
@@ -354,6 +358,17 @@ fun SessionScreen(
    // `rememberSaveable`, and this screen restores by its own anchor instead -- two restores would
    // fight over the first frame.
    val listState = remember(address) { LazyListState() }
    // The list's own fling path -- what a real flick decays through -- captured here so BenchRun's
    // fling phase can drive `LazyListState.scroll` through exactly the `FlingBehavior` this
    // screen's
    // `TranscriptList` already uses by not overriding it (its `LazyColumn` takes no `flingBehavior`
    // argument, so this is the same default it gets).
    val flingBehavior = ScrollableDefaults.flingBehavior()
    // Where BenchRun's type phase focuses before it types, and the view it toggles the keyboard on
    // -- both bench-only, but cheap enough (a remembered object, a CompositionLocal read) to hold
    // unconditionally rather than behind a second code path only the bench build compiles.
    val composerFocus = remember { FocusRequester() }
    val view = LocalView.current
    // Whether the newest message is on screen right now. The list is reversed, so the newest end is
    // the scrolling start: nothing behind you is exactly being at the bottom. Asked of the scroll
    // state rather than of item indices, because a zero-height first item makes an index ambiguous.
@@ -1256,6 +1271,10 @@ fun SessionScreen(
                    FrameStats.drawPhase().let { (nanos, count) -> drawAccounting(nanos, count) },
                crash = lastCrash(context),
                extra = extra,
                // Empty outside a BenchRun.run pass -- copyRenderReport's own reset below clears
                // the
                // marks along with everything else, so an ordinary copy never has any to show.
                phaseFrames = FrameStats.phaseLines(context.refreshHz()),
            )
        context.copyToClipboard("ai-app render report", report)
        // Also to the log, so a session driving the app over adb can read the same report the
@@ -1270,15 +1289,24 @@ fun SessionScreen(
        Toast.makeText(context, "Copied render report", Toast.LENGTH_SHORT).show()
    }
    val copyRenderReport = { buildAndCopyReport() }
-    // Bench build only: P0's scripted scroll-and-stream benchmark (BenchRun.kt), against the
+    // Bench build only: P0's scripted fling/stream/type/keyboard benchmark (BenchRun.kt), against
-    // fixture session opened below instead of a real server. Null everywhere else -- see
+    // the fixture session opened below instead of a real server. Null everywhere else -- see
    // [SessionSettingsDialog]'s onRunBenchmark.
    val runBenchmark: (() -> Unit)? =
        if (BuildConfig.FIXTURE_MODE) {
            {
                settingsOpen = false
                scope.launch {
-                    val extra = BenchRun.run(context, scope, listState)
+                    val extra =
                        BenchRun.run(
                            context = context,
                            scope = scope,
                            listState = listState,
                            flingBehavior = flingBehavior,
                            composerFocus = composerFocus,
                            setComposerText = { text -> input = atEnd(text) },
                            view = view,
                        )
                    buildAndCopyReport(extra)
                }
            }
@@ -1777,7 +1805,10 @@ fun SessionScreen(
                            input = it
                            saveDraft(context, summary.id, it.text)
                        },
-                        modifier = Modifier.fillMaxWidth(),
+                        // BenchRun's type phase requests focus on this exact field
                        // (`composerFocus`)
                        // so it types through the real composer rather than a stand-in.
                        modifier = Modifier.fillMaxWidth().focusRequester(composerFocus),
                        // No longer "(+image)": the images are on screen above this, and a
                        // placeholder saying so said it in words beside the thing itself.
                        placeholder = { Text("Message") },
@@ -47,6 +47,7 @@ name = "client-core"
 version = "0.1.0"
 dependencies = [
 "event-model",
 "pulldown-cmark",
 "serde",
 "serde_json",
 "tempfile",
@@ -173,6 +174,15 @@ dependencies = [
 "percent-encoding",
 ]
 [[package]]
 name = "getopts"
 version = "0.2.24"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cfe4fbac503b8d1f88e6676011885f34b7174f46e59956bba534ba83abded4df"
 dependencies = [
 "unicode-width",
 ]
 [[package]]
 name = "getrandom"
 version = "0.2.17"
@@ -425,6 +435,25 @@ dependencies = [
 "unicode-ident",
 ]
 [[package]]
 name = "pulldown-cmark"
 version = "0.13.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e9f068eba8e7071c5f9511831b44f32c740d5adf574e990f946ddb53db2f314e"
 dependencies = [
 "bitflags",
 "getopts",
 "memchr",
 "pulldown-cmark-escape",
 "unicase",
 ]
 [[package]]
 name = "pulldown-cmark-escape"
 version = "0.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "007d8adb5ddab6f8e3f491ac63566a7d5002cc7ed73901f72057943fa71ae1ae"
 [[package]]
 name = "quote"
 version = "1.0.47"
@@ -661,12 +690,24 @@ dependencies = [
 "zerovec",
 ]
 [[package]]
 name = "unicase"
 version = "2.9.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "dbc4bc3a9f746d862c45cb89d705aa10f187bb96c76001afab07a0d35ce60142"
 [[package]]
 name = "unicode-ident"
 version = "1.0.24"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e6e4313cd5fcd3dad5cafa179702e2b244f760991f45397d14d4ebf38247da75"
 [[package]]
 name = "unicode-width"
 version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b4ac048d71ede7ee76d585517add45da530660ef4390e49b098733c6e897f254"
 [[package]]
 name = "untrusted"
 version = "0.9.0"
@@ -17,7 +17,12 @@ edition = "2024"
 [dependencies]
 event-model = { path = "../event-model" }
 serde = { version = "1", features = ["derive"] }
-serde_json = { version = "1", features = ["float_roundtrip"] }
+# "raw_value" is `fetch_transcript_lines`'s reason -- it needs the exact
 # bytes the server sent, not this crate's own re-serialization of a parsed
 # `Value`, so a cached line and a live SSE frame for the same event agree
 # byte-for-byte (see that method's doc). "float_roundtrip" is why they
 # agree on a `ts` at all -- see server/Cargo.toml's identical comment.
 serde_json = { version = "1", features = ["float_roundtrip", "raw_value"] }
 # The blocking HTTP client for the REST calls and the long-lived SSE GETs.
 # `server/` already depends on ureq for its own outbound HTTPS (the usage
 # poll in usage.rs) and it is rustls-backed like the rest of this project's
@@ -27,6 +32,12 @@ serde_json = { version = "1", features = ["float_roundtrip"] }
 # no need of an async runtime, and RUST.md's brief for this port is
 # "lightweight" throughout.
 ureq = { version = "3", features = ["json"] }
 # The markdown block split (`markdown_blocks`), which has to agree with the
 # renderer in `iris/transcript-ui` about where a block begins -- so it is
 # the same parser at the same version, rather than a hand-written splitter
 # that would drift from it.
 pulldown-cmark = "0.13.4"
 [dev-dependencies]
 tempfile = "3"
@@ -10,6 +10,7 @@
 use std::io::Read;
 use event_model::SeqEvent;
 use serde::Deserialize;
 use serde_json::Value;
@@ -116,6 +117,14 @@ impl<T: Transport> ApiClient<T> {
        Self { transport }
    }
    /// The transport underneath, for a caller that needs the raw SSE
    /// stream (`event_stream::follow_session_events`) rather than one of
    /// this client's typed REST calls -- `transcript_source::TranscriptSource`
    /// is the one that does.
    pub fn transport(&self) -> &T {
        &self.transport
    }
    fn json_request<R: for<'de> Deserialize<'de>>(
        &self,
        method: &str,
@@ -266,15 +275,72 @@ impl<T: Transport> ApiClient<T> {
        limit: u32,
        coalesce: bool,
    ) -> Result<Vec<Value>, ApiError> {
-        let mut path = format!("/sessions/{session_id}/transcript?limit={limit}");
+        self.json_request(
-        if let Some(before) = before {
+            "GET",
-            path.push_str(&format!("&before={before}"));
+            &transcript_path(session_id, before, limit, coalesce, None),
-        }
+            None,
-        if coalesce {
+        )
            path.push_str("&coalesce=true");
        }
        self.json_request("GET", &path, None)
    }
    /// A page of transcript history, each line handed back paired with the
    /// exact text it came from, and bounded below by `after` -- the shape
    /// `crate::transcript_source::TranscriptSource` needs to store what it
    /// fetched in the transcript cache without a second round trip to fetch
    /// the raw text separately. Ported from `Api.kt`'s `fetchTranscript`.
    ///
    /// Uses [`serde_json::value::RawValue`] rather than re-serializing a
    /// parsed [`Value`], so the stored line is the exact bytes the server
    /// sent (key order and float literal included) rather than this
    /// crate's own idea of how to write them back out -- the cache and a
    /// live SSE frame must agree byte-for-byte on the same event, which is
    /// exactly what caught the `serde_json` float-rounding bug this
    /// project's `AGENTS.md` records.
    pub fn fetch_transcript_lines(
        &self,
        session_id: &str,
        before: Option<u64>,
        limit: u32,
        coalesce: bool,
        after: Option<u64>,
    ) -> Result<Vec<(String, SeqEvent)>, ApiError> {
        let path = transcript_path(session_id, before, limit, coalesce, after);
        let raw: Vec<Box<serde_json::value::RawValue>> = self.json_request("GET", &path, None)?;
        raw.into_iter()
            .map(|value| {
                let line = value.get().to_string();
                let event: SeqEvent = serde_json::from_str(&line).map_err(|e| ApiError {
                    message: format!(
                        "the server sent a transcript line this build couldn't parse: {e}"
                    ),
                    status: None,
                })?;
                Ok((line, event))
            })
            .collect()
    }
 }
 /// The query string shared by [`ApiClient::fetch_transcript_page`] and
 /// [`ApiClient::fetch_transcript_lines`], so the two agree on how each
 /// parameter is written rather than keeping two copies to drift.
 fn transcript_path(
    session_id: &str,
    before: Option<u64>,
    limit: u32,
    coalesce: bool,
    after: Option<u64>,
 ) -> String {
    let mut path = format!("/sessions/{session_id}/transcript?limit={limit}");
    if let Some(before) = before {
        path.push_str(&format!("&before={before}"));
    }
    if coalesce {
        path.push_str("&coalesce=true");
    }
    if let Some(after) = after {
        path.push_str(&format!("&after={after}"));
    }
    path
 }
 /// The blocking [`Transport`] backed by `ureq`, the same crate `server/`
@@ -0,0 +1,100 @@
 //! A span of milliseconds, written the way somebody reads it -- the port
 //! of `Durations.kt`'s `formatMillis`/`formatMillisText`, with its tests.
 //!
 //! Only the tool-timeout half is here. `formatSpan` (the usage
 //! countdown's rounding-up rule) belongs with whatever draws the usage
 //! bar, and nothing in this crate needs it yet.
 /// A span of milliseconds, written the way somebody reads it.
 ///
 /// A tool's timeout arrives as `480000`, which nobody reads as eight
 /// minutes. The rule has two halves, because a short span and a long one
 /// are read for different things. Under a minute the question is "roughly
 /// how long", so only the largest unit is shown and a fraction carries the
 /// rest -- `2.5s`. At a minute or more the question is "how long exactly",
 /// so every unit with something in it is written out -- `5d 12h 4m`. Empty
 /// units are left out rather than written as zero.
 ///
 /// Sub-second precision is dropped past a minute: nothing that takes days
 /// is measured in milliseconds.
 pub fn format_millis(ms: i64) -> String {
    if ms < 0 {
        return format!("-{}", format_millis(-ms));
    }
    if ms < 1000 {
        return format!("{ms}ms");
    }
    if ms < 60_000 {
        let tenths = (ms + 50) / 100;
        let (whole, rest) = (tenths / 10, tenths % 10);
        return if rest == 0 {
            format!("{whole}s")
        } else {
            format!("{whole}.{rest}s")
        };
    }
    let seconds = ms / 1000;
    [
        ("d", seconds / 86_400),
        ("h", seconds / 3600 % 24),
        ("m", seconds / 60 % 60),
        ("s", seconds % 60),
    ]
    .iter()
    .filter(|(_, n)| *n > 0)
    .map(|(unit, n)| format!("{n}{unit}"))
    .collect::<Vec<_>>()
    .join(" ")
 }
 /// `text` as a span when it is a whole number of milliseconds, and
 /// unchanged when it is not.
 pub fn format_millis_text(text: &str) -> String {
    match text.trim().parse::<i64>() {
        Ok(ms) => format_millis(ms),
        Err(_) => text.to_string(),
    }
 }
 #[cfg(test)]
 mod tests {
    use super::*;
    /// The two ways a span of time is written here, and the rule each of
    /// them follows -- ported from `DurationsTest.kt`, whose doc says why:
    /// both are read off a screen to make a decision, so what matters is
    /// that the shortest form that answers the question is what appears.
    #[test]
    fn under_a_minute_is_the_largest_unit_alone() {
        assert_eq!(format_millis(30), "30ms");
        assert_eq!(format_millis(999), "999ms");
        assert_eq!(format_millis(1000), "1s");
        assert_eq!(format_millis(2500), "2.5s");
        // One decimal, rounded rather than cut: 2.46s is nearer two and a
        // half than two and four.
        assert_eq!(format_millis(2460), "2.5s");
        assert_eq!(format_millis(59_900), "59.9s");
    }
    #[test]
    fn a_minute_or_more_is_every_unit_that_has_something_in_it() {
        // The figure this rule was written for: a tool timeout, which
        // arrives as milliseconds and is unreadable as 480000.
        assert_eq!(format_millis(480_000), "8m");
        assert_eq!(format_millis(60_000), "1m");
        assert_eq!(format_millis(90_000), "1m 30s");
        assert_eq!(format_millis(475_440_000), "5d 12h 4m");
        // Empty units are left out rather than written as zero: the labels
        // say which is which, and "5d 0h 4m" is only longer.
        assert_eq!(format_millis(432_240_000), "5d 4m");
    }
    #[test]
    fn only_a_whole_number_of_milliseconds_is_rewritten() {
        assert_eq!(format_millis_text(" 480000 "), "8m");
        // A timeout a tool expressed some other way is its own words,
        // passed through rather than guessed at.
        assert_eq!(format_millis_text("2 minutes"), "2 minutes");
        assert_eq!(format_millis_text(""), "");
    }
 }
@@ -5,11 +5,15 @@
 pub mod ansi;
 pub mod api;
 pub mod config;
 pub mod durations;
 pub mod event_stream;
 pub mod highlight;
 pub mod markdown_blocks;
 pub mod notifications;
 pub mod sse;
 pub mod tool_summary;
 pub mod transcript_cache;
 pub mod transcript_fold;
 pub mod transcript_source;
 pub use event_model::*;
@@ -0,0 +1,325 @@
 //! Split a markdown message into its top-level **blocks** -- one
 //! paragraph, heading, fenced code block, list, table or quote each, as a
 //! byte slice of the original source.
 //!
 //! This exists for streaming. A transcript row used to be one text widget
 //! holding the whole message, so a single streamed delta re-shaped every
 //! paragraph of it through the text engine again; the phone's bench v2 put
 //! the stream phase at p50 18.2ms against Compose's 13.4ms for exactly
 //! that reason (docs/IRIS_TODO.md). A row is a column of one widget per
 //! block now, and a delta that lands in the last block leaves every
 //! earlier block's layout alone. `docs/DECISIONS.md`'s 2026-09-06 entry has
 //! what that rejected and why the split lives here rather than in the UI
 //! crate: `docs/CLIENT_CORE.md` already wanted a block model for P1, and
 //! keeping it here means iris stays a text renderer that knows nothing
 //! about markdown.
 //!
 //! **Blocks only.** Inline styling (bold, links, inline code) is still the
 //! renderer's own job, per block -- this deliberately does not build a
 //! full AST, because nothing needs one yet.
 //!
 //! ## Appending is not guaranteed to leave earlier blocks alone
 //!
 //! It nearly always does, which is what makes the fast path worth having,
 //! but markdown has no such rule: appending a "```" line can turn text
 //! that was three paragraphs into one fenced block, and appending "---"
 //! under a paragraph turns that paragraph into a heading. So a caller
 //! taking the O(last block) path **must compare the prefix it is about to
 //! keep** rather than assume it. [`common_prefix`] is that comparison, and
 //! it is cheap next to laying the text out again.
 use pulldown_cmark::{Event, Options, Parser, Tag};
 /// What a block is, for a renderer that wants to style or space blocks
 /// differently. `Other` is deliberately present rather than a panic or a
 /// silent fallback to `Paragraph`: markdown has more block kinds than this
 /// list and more get added, and a renderer treating an unknown one as
 /// prose is right, but it should be able to *tell* that is what it is
 /// doing.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum BlockKind {
    Paragraph,
    Heading,
    /// A fenced or indented code block.
    Code,
    List,
    Table,
    Quote,
    /// A thematic break, raw HTML, a footnote -- anything with no
    /// distinguished treatment here.
    Other,
 }
 /// One top-level block: its kind and the exact source that produced it.
 /// `source` is a slice of the input with trailing whitespace removed, so
 /// two splits of the same prefix compare equal even when one of them had a
 /// delta arriving after it.
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct Block {
    pub kind: BlockKind,
    pub source: String,
 }
 fn kind_of(tag: &Tag) -> BlockKind {
    match tag {
        Tag::Paragraph => BlockKind::Paragraph,
        Tag::Heading { .. } => BlockKind::Heading,
        Tag::CodeBlock(_) => BlockKind::Code,
        Tag::List(_) => BlockKind::List,
        Tag::Table(_) => BlockKind::Table,
        Tag::BlockQuote(_) => BlockKind::Quote,
        _ => BlockKind::Other,
    }
 }
 fn options() -> Options {
    // The same set `transcript-ui`'s renderer parses with, so a block
    // boundary here and the styling there cannot disagree about what the
    // source means.
    Options::ENABLE_STRIKETHROUGH | Options::ENABLE_TABLES | Options::ENABLE_TASKLISTS
 }
 /// Split `src` into its top-level blocks, in source order. An empty or
 /// whitespace-only input gives no blocks; text the parser does not put
 /// inside any block (a stray fence marker mid-stream) still comes back,
 /// as `Other`, rather than being dropped.
 pub fn split_blocks(src: &str) -> Vec<Block> {
    let mut out: Vec<Block> = Vec::new();
    let mut depth = 0usize;
    let mut kind = BlockKind::Other;
    for (event, range) in Parser::new_ext(src, options()).into_offset_iter() {
        match event {
            Event::Start(tag) => {
                if depth == 0 {
                    kind = kind_of(&tag);
                }
                depth += 1;
            }
            Event::End(_) => {
                depth -= 1;
                if depth == 0 {
                    push(&mut out, kind, &src[range]);
                }
            }
            // A top-level event that is not part of any block -- a
            // thematic break, a block of raw HTML. Inside one, it is the
            // enclosing block's business and this does nothing.
            _ => {
                if depth == 0 {
                    push(&mut out, BlockKind::Other, &src[range]);
                }
            }
        }
    }
    out
 }
 fn push(out: &mut Vec<Block>, kind: BlockKind, source: &str) {
    let source = source.trim_end();
    if source.is_empty() {
        return;
    }
    out.push(Block {
        kind,
        source: source.to_string(),
    });
 }
 /// How many leading blocks of `old` and `new` are identical -- what a
 /// caller may keep the laid-out widgets for. See the module doc for why
 /// this is a comparison rather than an assumption.
 pub fn common_prefix(old: &[Block], new: &[Block]) -> usize {
    old.iter().zip(new).take_while(|(a, b)| a == b).count()
 }
 #[cfg(test)]
 mod tests {
    use super::*;
    fn kinds(src: &str) -> Vec<BlockKind> {
        split_blocks(src).into_iter().map(|b| b.kind).collect()
    }
    #[test]
    fn a_message_splits_into_its_top_level_blocks() {
        let src = "# Title\n\nFirst para.\n\n```rust\nfn main() {}\n```\n\n- a\n- b\n";
        assert_eq!(
            kinds(src),
            vec![
                BlockKind::Heading,
                BlockKind::Paragraph,
                BlockKind::Code,
                BlockKind::List
            ]
        );
        let blocks = split_blocks(src);
        assert_eq!(blocks[1].source, "First para.");
        assert_eq!(blocks[2].source, "```rust\nfn main() {}\n```");
    }
    #[test]
    fn blank_input_has_no_blocks() {
        assert!(split_blocks("").is_empty());
        assert!(split_blocks("   \n\n  ").is_empty());
    }
    /// The property the streaming fast path rests on, in its ordinary
    /// shape: a delta landing in the last paragraph must leave every
    /// earlier block byte-identical.
    #[test]
    fn a_delta_into_the_last_paragraph_leaves_earlier_blocks_untouched() {
        let before = split_blocks("# Title\n\nFirst para.\n\nSecond par");
        let after = split_blocks("# Title\n\nFirst para.\n\nSecond paragraph now.");
        assert_eq!(common_prefix(&before, &after), 2);
        assert_eq!(before.len(), 3);
        assert_eq!(after.len(), 3);
        assert_ne!(before[2], after[2]);
    }
    /// A delta that starts a *new* block keeps every old block, including
    /// the one that was last -- so the fast path appends rather than
    /// replacing.
    #[test]
    fn a_delta_that_starts_a_new_block_keeps_every_old_one() {
        let before = split_blocks("First para.\n\nSecond para.");
        let after = split_blocks("First para.\n\nSecond para.\n\nThird");
        assert_eq!(common_prefix(&before, &after), 2);
        assert_eq!(after.len(), 3);
    }
    /// A code fence arrives one delta at a time and is unterminated for
    /// most of its life. It must still be *one* block the whole way, or
    /// every delta would re-split the message into a different number of
    /// pieces.
    #[test]
    fn an_unterminated_fence_is_one_block_while_it_streams() {
        for src in [
            "Here:\n\n```rust\n",
            "Here:\n\n```rust\nfn main() {\n",
            "Here:\n\n```rust\nfn main() {\n    println!(\"hi\");\n",
        ] {
            assert_eq!(
                kinds(src),
                vec![BlockKind::Paragraph, BlockKind::Code],
                "{src:?}"
            );
        }
    }
    /// The half the fast path had no reason to touch, and the reason
    /// `common_prefix` is a comparison rather than an assumption:
    /// appending can rewrite what came before. `---` under a paragraph
    /// turns that paragraph into a setext heading, so the block that was
    /// already laid out is not the block it is now.
    #[test]
    fn appending_can_rewrite_an_earlier_block_and_the_prefix_says_so() {
        let before = split_blocks("Not a heading\n\nsecond");
        let after = split_blocks("Not a heading\n\nsecond\n---");
        assert_eq!(before[1].kind, BlockKind::Paragraph);
        assert_eq!(after[1].kind, BlockKind::Heading);
        assert_eq!(
            common_prefix(&before, &after),
            1,
            "the rewritten block must not be reported as keepable"
        );
    }
    #[test]
    fn a_thematic_break_is_its_own_block() {
        assert_eq!(
            kinds("one\n\n---\n\ntwo"),
            vec![BlockKind::Paragraph, BlockKind::Other, BlockKind::Paragraph]
        );
    }
    /// The shapes a real transcript actually contains, each checked for
    /// the one property the streaming fast path needs: the *number* of
    /// blocks and every earlier block's source stay put while the message
    /// grows. A fence's own blank lines, a `---` inside one, a nested
    /// list and a table are all places where a naive line-based split
    /// would break the message into more pieces than there are blocks.
    #[test]
    fn the_transcripts_own_block_shapes_survive_a_split() {
        let fence_with_blanks = "Intro.\n\n```rust\nfn a() {}\n\nfn b() {}\n```\n\nAfter.";
        assert_eq!(
            kinds(fence_with_blanks),
            vec![BlockKind::Paragraph, BlockKind::Code, BlockKind::Paragraph],
            "a blank line inside a fence is not a block boundary"
        );
        assert_eq!(
            kinds("```\n---\n```"),
            vec![BlockKind::Code],
            "a thematic break inside a fence is code, not a break"
        );
        assert_eq!(
            kinds("- a\n  - a1\n  - a2\n- b"),
            vec![BlockKind::List],
            "a nested list is one top-level block"
        );
        assert_eq!(
            kinds("## Heading\n```sh\nls\n```"),
            vec![BlockKind::Heading, BlockKind::Code],
            "a fence directly under a heading, with no blank line"
        );
        assert_eq!(
            kinds("| a | b |\n|---|---|\n| 1 | 2 |"),
            vec![BlockKind::Table]
        );
        assert_eq!(
            kinds("> quoted\n> more\n\nplain"),
            vec![BlockKind::Quote, BlockKind::Paragraph]
        );
    }
    /// `apply_delta`'s precondition, stated as the property rather than
    /// the arithmetic: for every prefix of a realistic streamed message,
    /// the blocks before the last one must be exactly the blocks the
    /// previous prefix had. Where markdown breaks that (the `---` case
    /// above), `common_prefix` has to *say* so -- which is what the
    /// `>= len - 1` assertion below checks: the split may rewrite the
    /// last block, never an earlier one, or `RowBlocks::apply_delta`
    /// would keep a widget whose text is no longer what it holds.
    #[test]
    fn every_prefix_of_a_streamed_message_keeps_all_but_its_last_block() {
        let full = "# Report\n\nFirst finding, at some length.\n\n```rust\nfn main() {\n\n                        println!(\"hi\");\n}\n```\n\n- one\n  - nested\n- two\n\n| a | b |\n                    |---|---|\n| 1 | 2 |\n\n> and a closing quote.";
        // Every character boundary, so a delta landing mid-word and one
        // landing exactly on a fence's closing backtick are both covered.
        let mut prev = Vec::new();
        for end in full.char_indices().map(|(i, _)| i).chain([full.len()]) {
            let now = split_blocks(&full[..end]);
            let common = common_prefix(&prev, &now);
            assert!(
                prev.is_empty() || common + 1 >= prev.len(),
                "at {end} bytes the split rewrote block {common} of {}, not just the last one:\n                 before={prev:#?}\nafter={now:#?}",
                prev.len()
            );
            prev = now;
        }
    }
    /// The half a growing message cannot show: a fence that never closes.
    /// The stream ends there and the block must still be the code block
    /// it has been all along, not re-split into paragraphs.
    #[test]
    fn a_stream_that_ends_inside_a_fence_still_ends_with_one_code_block() {
        let src = "Here is the patch:\n\n```diff\n- old line\n+ new line";
        let blocks = split_blocks(src);
        assert_eq!(
            blocks.iter().map(|b| b.kind).collect::<Vec<_>>(),
            vec![BlockKind::Paragraph, BlockKind::Code]
        );
        assert_eq!(blocks[1].source, "```diff\n- old line\n+ new line");
    }
    /// A delta that closes a fence changes the *last* block only, so the
    /// fast path takes it -- the case the module doc says is the reason
    /// `common_prefix` is a comparison.
    #[test]
    fn the_delta_that_closes_a_fence_changes_only_the_last_block() {
        let before = split_blocks("Text.\n\n```\ncode\n");
        let after = split_blocks("Text.\n\n```\ncode\n```");
        assert_eq!(before.len(), after.len());
        assert_eq!(common_prefix(&before, &after), 1);
        assert_ne!(before[1], after[1]);
    }
 }
@@ -0,0 +1,244 @@
 //! A tool call's input, read rather than dumped -- the port of
 //! `ToolInput.kt`'s `parseToolInput`, which is what both the collapsed
 //! card's one-line summary and the expanded card's key/value list are
 //! derived from.
 //!
 //! Every tool's input arrives as JSON, and showing it raw makes the reader
 //! parse `{"command":"…","timeout":120000}` themselves to find the one
 //! line they care about. So the fields that carry the meaning are pulled
 //! out, and anything left over is still shown, because dropping a field
 //! would be claiming the tool has no other input when it might.
 //!
 //! Pure, and here rather than in the widget crate, for the reason the rest
 //! of this crate exists: the derivation is the same on a phone and on a
 //! desktop, and it is testable without a renderer.
 use crate::durations::format_millis_text;
 use crate::highlight::Language;
 use serde_json::{Map, Value};
 /// A tool call's input, split into the parts a card draws separately.
 #[derive(Debug, Clone, PartialEq, Eq, Default)]
 pub struct ToolInput {
    /// The thing that will actually be run or read, if this tool has one.
    pub subject: Option<String>,
    /// The language [`ToolInput::subject`] is written in, for
    /// highlighting.
    pub language: Option<Language>,
    /// The tool's own one-line summary, when it wrote one.
    pub description: Option<String>,
    /// How long the call may take, in the largest units it fits. Shown
    /// apart because it is a limit on the call rather than part of what
    /// the call does.
    pub timeout: Option<String>,
    /// Everything else, as `name: value` lines. Never dropped.
    pub rest: Vec<String>,
 }
 impl ToolInput {
    /// The one line to show when there is only room for one: what this
    /// call is for.
    pub fn title(&self) -> Option<&str> {
        self.description
            .as_deref()
            .or(self.subject.as_deref())
            // A subject that is only whitespace would draw as an empty
            // summary line, which reads as a tool with nothing to say
            // rather than as one whose subject was blank.
            .filter(|t| !t.trim().is_empty())
    }
 }
 /// Which field of which tool is the subject.
 ///
 /// A table rather than a chain of `if`s: adding a tool is a row, and the
 /// shape stops any of them from being the special case that gets its own
 /// code path. Unknown tools fall through to "no subject, everything is
 /// rest".
 const SUBJECTS: &[(&str, &str, Option<Language>)] = &[
    ("Bash", "command", Some(Language::Shell)),
    ("Read", "file_path", None),
    ("Write", "file_path", None),
    ("Edit", "file_path", None),
    ("Glob", "pattern", None),
    ("Grep", "pattern", None),
    ("WebFetch", "url", None),
 ];
 /// Fields that are the tool's own prose about itself rather than input to
 /// it.
 const DESCRIPTIONS: &[&str] = &["description", "prompt"];
 /// One JSON value as the Kotlin's `JSONObject.optString`/`get` wrote it: a
 /// string is its own characters, anything else is its JSON form.
 ///
 /// One function rather than two, because the same coercion decides both
 /// what a subject reads as and what a leftover field's value reads as, and
 /// two copies would eventually disagree about a number.
 fn as_text(value: &Value) -> String {
    match value {
        Value::String(s) => s.clone(),
        other => other.to_string(),
    }
 }
 fn non_blank(value: Option<&Value>) -> Option<String> {
    let text = as_text(value?);
    (!text.trim().is_empty()).then_some(text)
 }
 /// Split `input` (a tool call's JSON) into the parts a card draws.
 ///
 /// Input that is not a JSON object -- older transcripts and some tools
 /// send a bare string -- is still the input, so it is still shown, as the
 /// whole of `rest`.
 pub fn parse_tool_input(tool: &str, input: &str) -> ToolInput {
    let Ok(Value::Object(json)) = serde_json::from_str::<Value>(input) else {
        return ToolInput {
            rest: match input.trim().is_empty() {
                true => Vec::new(),
                false => vec![input.to_string()],
            },
            ..ToolInput::default()
        };
    };
    parse_object(tool, &json)
 }
 fn parse_object(tool: &str, json: &Map<String, Value>) -> ToolInput {
    let (subject_key, language) = SUBJECTS
        .iter()
        .find(|(name, ..)| *name == tool)
        .map(|(_, key, language)| (Some(*key), *language))
        .unwrap_or((None, None));
    let subject = subject_key.and_then(|key| non_blank(json.get(key)));
    let description = DESCRIPTIONS
        .iter()
        .find_map(|key| non_blank(json.get(*key)));
    let timeout = non_blank(json.get("timeout")).map(|t| format_millis_text(&t));
    // Sorted, so the leftovers are in the same order every time this call
    // is drawn rather than in whatever order the JSON happened to arrive
    // in. A field is left out only when it is already drawn somewhere
    // else on the card.
    let mut keys: Vec<&String> = json
        .keys()
        .filter(|k| Some(k.as_str()) != subject_key || subject.is_none())
        .filter(|k| !DESCRIPTIONS.contains(&k.as_str()) || description.is_none())
        .filter(|k| k.as_str() != "timeout" || timeout.is_none())
        .collect();
    keys.sort();
    let rest = keys
        .into_iter()
        .map(|key| format!("{key}: {}", as_text(&json[key])))
        .collect();
    ToolInput {
        subject,
        language,
        description,
        timeout,
        rest,
    }
 }
 #[cfg(test)]
 mod tests {
    use super::*;
    #[test]
    fn each_tool_in_the_table_has_its_own_subject() {
        // One assertion per row of `SUBJECTS`, because the table is the
        // whole of the rule and a row lost in an edit would otherwise
        // only show up as a card with no summary line.
        let cases = [
            ("Bash", r#"{"command":"ls -la"}"#, "ls -la"),
            ("Read", r#"{"file_path":"/tmp/x.rs"}"#, "/tmp/x.rs"),
            ("Write", r#"{"file_path":"/tmp/y.rs"}"#, "/tmp/y.rs"),
            ("Edit", r#"{"file_path":"/tmp/z.rs"}"#, "/tmp/z.rs"),
            ("Glob", r#"{"pattern":"**/*.rs"}"#, "**/*.rs"),
            ("Grep", r#"{"pattern":"fn main"}"#, "fn main"),
            ("WebFetch", r#"{"url":"https://x/y"}"#, "https://x/y"),
        ];
        for (tool, input, expected) in cases {
            let parsed = parse_tool_input(tool, input);
            assert_eq!(parsed.subject.as_deref(), Some(expected), "{tool}");
            assert_eq!(parsed.title(), Some(expected), "{tool}");
            assert!(parsed.rest.is_empty(), "{tool}: {:?}", parsed.rest);
        }
        assert_eq!(
            parse_tool_input("Bash", r#"{"command":"ls"}"#).language,
            Some(Language::Shell),
            "a Bash command is shell, and is the one row that names a language"
        );
    }
    #[test]
    fn a_tools_own_description_is_what_the_one_line_says() {
        // The description wins over the subject: it is the tool's own
        // prose about what this call is for, which is what a reader
        // scanning a collapsed run is looking for.
        let parsed = parse_tool_input(
            "Bash",
            r#"{"command":"cargo test -p iris","description":"Run the iris tests"}"#,
        );
        assert_eq!(parsed.title(), Some("Run the iris tests"));
        assert_eq!(parsed.subject.as_deref(), Some("cargo test -p iris"));
        assert!(parsed.rest.is_empty(), "{:?}", parsed.rest);
    }
    #[test]
    fn a_timeout_is_read_as_a_span_and_kept_apart_from_the_rest() {
        let parsed = parse_tool_input("Bash", r#"{"command":"sleep 500","timeout":480000}"#);
        assert_eq!(parsed.timeout.as_deref(), Some("8m"));
        assert!(parsed.rest.is_empty(), "{:?}", parsed.rest);
    }
    #[test]
    fn every_field_not_drawn_elsewhere_is_still_shown() {
        // The half the "never dropped" promise is about: a tool this
        // build has never heard of has no subject, so *everything* is
        // rest -- and a known tool's extra fields are too.
        let parsed = parse_tool_input(
            "Edit",
            r#"{"file_path":"/a.rs","old_string":"x","new_string":"y","replace_all":true}"#,
        );
        assert_eq!(
            parsed.rest,
            vec![
                "new_string: y".to_string(),
                "old_string: x".to_string(),
                "replace_all: true".to_string(),
            ],
            "sorted, and a non-string value written as JSON"
        );
        let unknown = parse_tool_input("SomeNewTool", r#"{"b":2,"a":"one"}"#);
        assert_eq!(unknown.subject, None);
        assert_eq!(unknown.rest, vec!["a: one".to_string(), "b: 2".to_string()]);
    }
    #[test]
    fn input_that_is_not_an_object_is_still_the_input() {
        // Older transcripts and some tools send a bare string; a card
        // that dropped it would claim the call had no input at all.
        assert_eq!(
            parse_tool_input("Bash", "just a string").rest,
            vec!["just a string".to_string()]
        );
        assert_eq!(parse_tool_input("Bash", "   ").rest, Vec::<String>::new());
        assert_eq!(parse_tool_input("Bash", "").title(), None);
    }
    #[test]
    fn a_blank_subject_is_no_subject_rather_than_an_empty_summary_line() {
        let parsed = parse_tool_input("Bash", r#"{"command":"   ","other":1}"#);
        assert_eq!(parsed.subject, None);
        assert_eq!(parsed.title(), None);
        // Not dropped just because it was blank -- it is still a field
        // the call carried.
        assert_eq!(
            parsed.rest,
            vec!["command:    ".to_string(), "other: 1".to_string()]
        );
    }
 }
@@ -361,6 +361,10 @@ impl SessionCache {
            {
                return Ok(false);
            }
            debug_assert!(
                lines.iter().all(|l| !l.contains('\n')),
                "a stored page's lines must each be one line"
            );
            fs::create_dir_all(&this.dir)?;
            let kind = if rows { "rows" } else { "raw" };
            let mut content = lines.join("\n");
@@ -389,8 +393,16 @@ impl SessionCache {
                return Ok(());
            };
            // Written as it arrived. A newline inside it would split one
-            // event into two unreadable halves, but neither source can
+            // event into two unreadable halves. No source here can produce
-            // produce one.
+            // one -- an SSE `data:` field cannot hold a raw newline, and a
            // fetched line is one element of a compact JSON array -- but
            // that is a fact about the *server's* serializer rather than
            // anything this file controls, so it is checked rather than
            // trusted.
            debug_assert!(
                !line.contains('\n'),
                "a cached transcript line must be one line: {line}"
            );
            use std::io::Write;
            writer.write_all(line.as_bytes())?;
            writer.write_all(b"\n")?;
@@ -78,6 +78,11 @@ pub enum TranscriptItem {
        input: String,
        output: String,
        done: bool,
        /// Whether the result that arrived said the call failed
        /// ([`Event::ToolEnd`]'s `is_error`). Meaningless while `done` is
        /// false, and [`ToolState::of`] is the only thing that reads the
        /// pair, so the two cannot be combined wrongly at a call site.
        failed: bool,
        asks: Vec<QuestionCard>,
        images: Vec<String>,
    },
@@ -112,6 +117,13 @@ pub enum TranscriptItem {
    ClearedNote {
        seq: u64,
    },
    /// The account's usage limit stopped the turn; `resets_at` is epoch
    /// seconds when the dialect said when it lifts (`LimitNote` in
    /// `TranscriptItems.kt`).
    LimitNote {
        seq: u64,
        resets_at: Option<f64>,
    },
    CompactedNote {
        seq: u64,
        pre_tokens: Option<u64>,
@@ -131,6 +143,7 @@ impl TranscriptItem {
            | Self::CommandRow { seq, .. }
            | Self::Note { seq, .. }
            | Self::ClearedNote { seq }
            | Self::LimitNote { seq, .. }
            | Self::CompactedNote { seq, .. } => *seq,
            Self::QuestionCard(card) => card.seq,
        }
@@ -286,6 +299,201 @@ fn split_run(tail: &[TranscriptItem], behind: Option<&str>) -> Vec<TranscriptIte
    out
 }
 /// Puts a page of older items in front of the ones already loaded, healing
 /// whatever the page boundary cut in two. Ported from `TranscriptItems.kt`'s
 /// `joinPages`.
 ///
 /// Two things straddle a boundary: a tool call separated from its result,
 /// and a message separated from the rest of itself. Both were one thing
 /// before the transcript was cut into pages.
 ///
 /// A boundary lands wherever it lands, and roughly half the time that is
 /// between a call and its result. The newer page then holds a `ToolEnd`
 /// whose start it never saw, which `fold_event` draws as a row of its own
 /// -- correctly, because a call that renders as nothing is indistinguishable
 /// from one that never happened. When the older page arrives it brings the
 /// real `ToolStart`, and concatenating the two lists left *both*: the same
 /// call twice.
 ///
 /// Merged by the call's own id rather than by position, because position is
 /// exactly what a page boundary destroys. The older row wins on what a
 /// start knows and the newer on what an end knows, which is the only way
 /// round that loses nothing.
 ///
 /// The third thing is the *run*, and it is the one the Kotlin original used
 /// to miss (AGENTS.md's "things that have bitten"): every page ends up
 /// here, but `adopt_run` must run on *every* join, not only the one where a
 /// split call was found -- a boundary landing cleanly between two finished
 /// calls, which is most of them, would otherwise leave the older page's
 /// calls under the run name they were folded with. On screen: one run of
 /// tool calls drawn as two groups, with the seam wherever the reader
 /// happened to have paged.
 pub fn join_pages(earlier: &[TranscriptItem], later: &[TranscriptItem]) -> Vec<TranscriptItem> {
    let (older, newer) = heal_split_message(earlier, later);
    let started_earlier: std::collections::HashSet<&str> = older
        .iter()
        .filter_map(TranscriptItem::as_tool_run)
        .collect();
    // Owned rather than borrowed from `newer`: `kept` below needs to consume `newer` by
    // value, and a map borrowing it would keep that alive.
    let ended_later: std::collections::HashMap<String, TranscriptItem> = newer
        .iter()
        .filter_map(|item| item.as_tool_run().map(|id| (id.to_string(), item.clone())))
        .filter(|(id, _)| started_earlier.contains(id.as_str()))
        .collect();
    let healed: Vec<TranscriptItem> = older
        .into_iter()
        .map(|row| match row {
            TranscriptItem::ToolRun {
                seq,
                id,
                run_id,
                tool,
                input,
                asks: row_asks,
                images: row_images,
                ..
            } if ended_later.contains_key(id.as_str()) => {
                let &TranscriptItem::ToolRun {
                    ref output,
                    done,
                    failed,
                    asks: ref half_asks,
                    images: ref half_images,
                    ..
                } = &ended_later[id.as_str()]
                else {
                    unreachable!("filtered to ToolRun above");
                };
                TranscriptItem::ToolRun {
                    seq,
                    id,
                    run_id,
                    tool,
                    input,
                    output: output.clone(),
                    done,
                    failed,
                    // Kept from both halves: a question or an image can be
                    // attached to either, depending on which side of the
                    // boundary its event fell.
                    asks: row_asks.into_iter().chain(half_asks.clone()).collect(),
                    images: row_images.into_iter().chain(half_images.clone()).collect(),
                }
            }
            other => other,
        })
        .collect();
    let kept: Vec<TranscriptItem> = newer
        .into_iter()
        .filter(|item| match item.as_tool_run() {
            Some(id) => !ended_later.contains_key(id),
            None => true,
        })
        .collect();
    let mut out = adopt_run(&healed, &kept);
    out.extend(kept);
    // What this function exists to prevent, checked rather than assumed: the same
    // call drawn twice, once from the page that saw its start and once from the page
    // that saw its end. Not a seq-ordering check -- a peer note is stamped with the
    // seq its turn began at, which can be older than the page it arrived in, so the
    // two pages' seqs legitimately interleave at the boundary.
    debug_assert!(
        {
            let mut ids: Vec<&str> = out.iter().filter_map(TranscriptItem::as_tool_run).collect();
            let before = ids.len();
            ids.sort_unstable();
            ids.dedup();
            ids.len() == before
        },
        "join_pages left the same tool call in both halves"
    );
    out
 }
 /// Rejoins a message the page boundary cut, and hands back the two pages to
 /// concatenate. Ported from `TranscriptItems.kt`'s `healSplitMessage`.
 ///
 /// `fold_event` never leaves two assistant messages next to each other
 /// inside one page, so two meeting at a join are always the two halves of
 /// one reply, and leaving them apart drew a single answer as two with a
 /// paragraph break through the middle of a sentence.
 ///
 /// The newer half keeps its identity, for the reason `adopt_run`'s doc
 /// gives. It grows by what the older half brings, which is safe here and
 /// nowhere else -- the join is at the oldest end of what is loaded, so the
 /// growth extends off the top of the screen.
 fn heal_split_message(
    earlier: &[TranscriptItem],
    later: &[TranscriptItem],
 ) -> (Vec<TranscriptItem>, Vec<TranscriptItem>) {
    let (
        Some(TranscriptItem::AssistantMsg {
            text: head_text, ..
        }),
        Some(TranscriptItem::AssistantMsg {
            seq: tail_seq,
            text: tail_text,
            settled: tail_settled,
        }),
    ) = (earlier.last(), later.first())
    else {
        return (earlier.to_vec(), later.to_vec());
    };
    let merged = TranscriptItem::AssistantMsg {
        seq: *tail_seq,
        text: format!("{head_text}{tail_text}"),
        settled: *tail_settled,
    };
    let mut newer = vec![merged];
    newer.extend(later[1..].iter().cloned());
    (earlier[..earlier.len() - 1].to_vec(), newer)
 }
 /// Hands the older calls at the join the name of the run they are joining.
 /// Ported from `TranscriptItems.kt`'s `adoptRun`.
 ///
 /// The two pages were folded separately, so a run split by the boundary
 /// came back as two runs with two names. Naming the joined run after the
 /// *older* half would be the obvious way round and is wrong: the newer half
 /// is the part already on screen, and renaming it is renaming the row the
 /// reader is looking at, which is how a list loses its anchor.
 fn adopt_run(earlier: &[TranscriptItem], later: &[TranscriptItem]) -> Vec<TranscriptItem> {
    let Some(TranscriptItem::ToolRun { run_id, tool, .. }) = later.first() else {
        return earlier.to_vec();
    };
    // A question is in a run of its own on both sides of the join, the same as it would be
    // had the two pages been folded as one. Without this the heal would merge a group
    // straight through the row the reader was asked something on.
    if tool == ASK_USER_QUESTION {
        return earlier.to_vec();
    }
    let joining = run_id.clone();
    let tail_len = earlier
        .iter()
        .rev()
        .take_while(|item| matches!(item, TranscriptItem::ToolRun { tool, .. } if tool != ASK_USER_QUESTION))
        .count();
    if tail_len == 0 {
        return earlier.to_vec();
    }
    let split = earlier.len() - tail_len;
    let mut out = earlier[..split].to_vec();
    out.extend(earlier[split..].iter().cloned().map(|mut item| {
        // `take_while` above already restricted this slice to non-question tool calls;
        // this just guards the invariant rather than trusting it silently.
        debug_assert!(
            matches!(&item, TranscriptItem::ToolRun { tool, .. } if tool != ASK_USER_QUESTION),
            "adopt_run must never rename a question's own run"
        );
        if let TranscriptItem::ToolRun { run_id, .. } = &mut item {
            *run_id = joining.clone();
        }
        item
    }));
    out
 }
 /// Folds one transcript event onto `items`, the way `foldEvent` does in
 /// `TranscriptItems.kt`. Every wire event has a case; see the module doc
 /// for the one difference from the Kotlin original (no `Unknown` fallback
@@ -361,6 +569,7 @@ pub fn fold_event(items: &[TranscriptItem], entry: &SeqEvent) -> Vec<TranscriptI
                input: input.to_string(),
                output: String::new(),
                done: false,
                failed: false,
                asks: Vec::new(),
                images: Vec::new(),
            });
@@ -371,15 +580,23 @@ pub fn fold_event(items: &[TranscriptItem], entry: &SeqEvent) -> Vec<TranscriptI
                *out = output.clone();
            }
        }),
-        Event::ToolEnd { id, output } => {
+        Event::ToolEnd {
            id,
            output,
            is_error,
        } => {
            if items.iter().any(|i| i.as_tool_run() == Some(id.as_str())) {
                update_tool(items, id, |item| {
                    if let TranscriptItem::ToolRun {
-                        output: out, done, ..
+                        output: out,
                        done,
                        failed,
                        ..
                    } = item
                    {
                        *out = output.clone();
                        *done = true;
                        *failed = *is_error;
                    }
                })
            } else {
@@ -393,6 +610,7 @@ pub fn fold_event(items: &[TranscriptItem], entry: &SeqEvent) -> Vec<TranscriptI
                    input: String::new(),
                    output: output.clone(),
                    done: true,
                    failed: *is_error,
                    asks: Vec::new(),
                    images: Vec::new(),
                });
@@ -449,6 +667,7 @@ pub fn fold_event(items: &[TranscriptItem], entry: &SeqEvent) -> Vec<TranscriptI
                    input,
                    output,
                    done,
                    failed,
                    images,
                } if asks.iter().any(|a| &a.id == id) => {
                    for ask in asks.iter_mut() {
@@ -464,6 +683,7 @@ pub fn fold_event(items: &[TranscriptItem], entry: &SeqEvent) -> Vec<TranscriptI
                        input,
                        output,
                        done,
                        failed,
                        asks,
                        images,
                    }
@@ -525,6 +745,14 @@ pub fn fold_event(items: &[TranscriptItem], entry: &SeqEvent) -> Vec<TranscriptI
            items.push(TranscriptItem::ClearedNote { seq });
            items
        }
        Event::LimitReached { resets_at } => {
            let mut items = items.to_vec();
            items.push(TranscriptItem::LimitNote {
                seq,
                resets_at: *resets_at,
            });
            items
        }
        Event::Compacted {
            pre_tokens,
            post_tokens,
@@ -541,6 +769,74 @@ pub fn fold_event(items: &[TranscriptItem], entry: &SeqEvent) -> Vec<TranscriptI
    }
 }
 /// What became of one tool call -- every state a card has to be able to
 /// draw, including the two that are not answers.
 ///
 /// The pair this enum exists for is [`ToolState::Succeeded`] against
 /// [`ToolState::NoResult`]. A call that finished having printed nothing
 /// and a call whose result never arrived both leave an empty `output`,
 /// and drawing them the same way states a verdict nobody reached: "it
 /// worked and said nothing" reads as a fact, where the truth is that the
 /// turn ended before anything came back.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum ToolState {
    /// Started, no result yet, and the session is still working -- the
    /// ordinary state of a call in flight.
    Running,
    /// Stopped on the reader: a permission or question this call carries
    /// has not been answered, so nothing is happening until somebody
    /// answers it. Distinct from [`Self::Running`] because whose move it
    /// is differs, which is the Compose card's "your turn".
    Deciding,
    /// A result arrived and the tool did not report a failure.
    Succeeded,
    /// A result arrived and the tool reported that the call failed
    /// (`is_error`).
    Failed,
    /// No result ever arrived and the session is not working any more --
    /// the turn was interrupted, or the process went away. Not a verdict
    /// on the call: it says only that nobody found out.
    NoResult,
 }
 impl ToolState {
    /// The state of one call. `session_working` is
    /// [`session_working`]'s answer for the session this call is in --
    /// the only thing here that is not a property of the call itself, and
    /// what separates "still running" from "never came back".
    ///
    /// Written once, over the fields rather than per call site, because
    /// the five states are decided by four conditions and every place
    /// that re-derived a subset of them got a different subset.
    pub fn of(item: &TranscriptItem, session_working: bool) -> Option<Self> {
        let TranscriptItem::ToolRun {
            done, failed, asks, ..
        } = item
        else {
            return None;
        };
        debug_assert!(
            !failed || *done,
            "a call cannot have failed before its result arrived"
        );
        Some(if asks.iter().any(|ask| ask.answers.is_empty()) {
            // Ahead of `done`: a call waiting on permission has not
            // finished either, and which of the two the reader is being
            // told about is the one they can act on.
            Self::Deciding
        } else if !*done {
            match session_working {
                true => Self::Running,
                false => Self::NoResult,
            }
        } else if *failed {
            Self::Failed
        } else {
            Self::Succeeded
        })
    }
 }
 /// One row as the transcript draws it: a run of consecutive tool calls, or
 /// anything else. Ported from `ToolRows.kt`'s `TranscriptRow` and
 /// `groupToolRuns` -- the Compose card rendering in that file is not part
@@ -780,6 +1076,7 @@ mod tests {
            Event::ToolEnd {
                id: "x".to_string(),
                output: "done".to_string(),
                is_error: false,
            },
        )]);
        assert_eq!(
@@ -792,6 +1089,7 @@ mod tests {
                input: String::new(),
                output: "done".to_string(),
                done: true,
                failed: false,
                asks: Vec::new(),
                images: Vec::new(),
            }]
@@ -939,4 +1237,284 @@ mod tests {
        let err = fold_page(&values).unwrap_err();
        assert!(err.contains("couldn't parse"));
    }
    fn tool_start(seq: u64, id: &str, tool: &str) -> SeqEvent {
        event(
            seq,
            Event::ToolStart {
                id: id.to_string(),
                tool: tool.to_string(),
                input: serde_json::json!({}),
            },
        )
    }
    fn tool_end(seq: u64, id: &str, output: &str) -> SeqEvent {
        event(
            seq,
            Event::ToolEnd {
                id: id.to_string(),
                output: output.to_string(),
                is_error: false,
            },
        )
    }
    /// AGENTS.md's "things that have bitten": `joinPages` used to run
    /// `adoptRun` only on the path where a *split* call was found, so a
    /// boundary landing cleanly between two already-finished calls -- most
    /// of them -- left the older page's calls under the run name they were
    /// folded with, drawing one run of tool calls as two groups. Two
    /// finished, unrelated calls (no id in common) must still end up under
    /// one run name after the join.
    #[test]
    fn a_clean_boundary_between_two_finished_runs_is_still_healed_into_one_run() {
        let older = fold_all(&[tool_start(1, "a", "Bash"), tool_end(2, "a", "old output")]);
        let newer = fold_all(&[tool_start(3, "b", "Bash"), tool_end(4, "b", "new output")]);
        let joined = join_pages(&older, &newer);
        let run_ids: Vec<_> = joined
            .iter()
            .map(|item| match item {
                TranscriptItem::ToolRun { run_id, .. } => run_id.as_str(),
                other => panic!("expected only ToolRun items, got {other:?}"),
            })
            .collect();
        assert_eq!(
            run_ids,
            vec!["b", "b"],
            "the older call must adopt the newer, already-on-screen run's name"
        );
    }
    #[test]
    fn a_call_split_across_the_boundary_merges_into_one_row() {
        let older = fold_all(&[tool_start(1, "x", "Bash")]);
        let newer = fold_all(&[tool_end(2, "x", "the result")]);
        let joined = join_pages(&older, &newer);
        assert_eq!(
            joined,
            vec![TranscriptItem::ToolRun {
                seq: 1,
                id: "x".to_string(),
                run_id: "x".to_string(),
                tool: "Bash".to_string(),
                input: "{}".to_string(),
                output: "the result".to_string(),
                done: true,
                failed: false,
                asks: Vec::new(),
                images: Vec::new(),
            }],
            "the older half's tool/input and the newer half's output/done must both survive"
        );
    }
    #[test]
    fn a_message_split_across_the_boundary_is_rejoined_with_the_newer_halfs_identity() {
        let older = vec![TranscriptItem::AssistantMsg {
            seq: 1,
            text: "Hel".to_string(),
            settled: false,
        }];
        let newer = vec![
            TranscriptItem::AssistantMsg {
                seq: 2,
                text: "lo".to_string(),
                settled: true,
            },
            TranscriptItem::UserMsg {
                seq: 3,
                text: "next".to_string(),
                attachments: Vec::new(),
            },
        ];
        let joined = join_pages(&older, &newer);
        assert_eq!(
            joined,
            vec![
                TranscriptItem::AssistantMsg {
                    seq: 2,
                    text: "Hello".to_string(),
                    settled: true,
                },
                TranscriptItem::UserMsg {
                    seq: 3,
                    text: "next".to_string(),
                    attachments: Vec::new(),
                },
            ]
        );
    }
    /// A question is in a run of its own on both sides of a join -- healing
    /// must never rename the run of calls the reader was asked something
    /// on, the same rule `splitRun` enforces for a live turn boundary.
    #[test]
    fn adopt_run_never_renames_into_a_question_row() {
        let older = fold_all(&[tool_start(1, "a", "Bash"), tool_end(2, "a", "done")]);
        let newer = vec![TranscriptItem::ToolRun {
            seq: 3,
            id: "q".to_string(),
            run_id: "q".to_string(),
            tool: ASK_USER_QUESTION.to_string(),
            input: "{}".to_string(),
            output: String::new(),
            done: false,
            failed: false,
            asks: Vec::new(),
            images: Vec::new(),
        }];
        let joined = join_pages(&older, &newer);
        match &joined[0] {
            TranscriptItem::ToolRun { run_id, .. } => assert_eq!(run_id, "a"),
            other => panic!("expected a ToolRun, got {other:?}"),
        }
    }
 }
 /// [`ToolState`] is what a card colours itself by, so each of its five
 /// states is asserted from the events that actually produce it rather than
 /// from a hand-built item -- a mapping that agreed with a fixture and
 /// disagreed with the fold would be invisible until it was on screen.
 #[cfg(test)]
 mod tool_state_tests {
    use super::*;
    fn event(seq: u64, e: Event) -> SeqEvent {
        SeqEvent {
            seq,
            ts: 0.0,
            event: e,
        }
    }
    fn fold_all(events: &[SeqEvent]) -> Vec<TranscriptItem> {
        events
            .iter()
            .fold(Vec::new(), |items, e| fold_event(&items, e))
    }
    fn start(id: &str) -> SeqEvent {
        event(
            1,
            Event::ToolStart {
                id: id.to_string(),
                tool: "Bash".to_string(),
                input: serde_json::json!({"command": "ls"}),
            },
        )
    }
    fn end(id: &str, output: &str, is_error: bool) -> SeqEvent {
        event(
            2,
            Event::ToolEnd {
                id: id.to_string(),
                output: output.to_string(),
                is_error,
            },
        )
    }
    fn state_of(events: &[SeqEvent], session_working: bool) -> ToolState {
        let items = fold_all(events);
        ToolState::of(&items[0], session_working).expect("the fixture's first item is a tool call")
    }
    #[test]
    fn a_result_that_arrived_is_read_from_is_error() {
        assert_eq!(
            state_of(&[start("a"), end("a", "ok", false)], false),
            ToolState::Succeeded
        );
        assert_eq!(
            state_of(&[start("a"), end("a", "No such file", true)], false),
            ToolState::Failed
        );
    }
    /// The pair this enum exists for. Both calls have an empty `output`
    /// and nothing else distinguishes them, so a card that only looked at
    /// the text would draw the interrupted one as a call that ran fine and
    /// printed nothing.
    #[test]
    fn a_call_that_printed_nothing_is_not_a_call_that_never_answered() {
        assert_eq!(
            state_of(&[start("a"), end("a", "", false)], false),
            ToolState::Succeeded,
            "a result arrived; it was empty"
        );
        assert_eq!(
            state_of(&[start("a")], false),
            ToolState::NoResult,
            "no result, and the session is not working any more"
        );
    }
    /// The same call, mid-turn: still running rather than abandoned. The
    /// only thing separating the two is the session's own status, which is
    /// why `of` takes it.
    #[test]
    fn no_result_while_the_session_works_is_still_running() {
        assert_eq!(state_of(&[start("a")], true), ToolState::Running);
    }
    #[test]
    fn an_unanswered_ask_is_the_readers_move_whatever_else_is_true() {
        let asking = event(
            3,
            Event::Question {
                id: "q1".to_string(),
                prompt: "Allow?".to_string(),
                header: None,
                options: vec![QuestionOption {
                    label: "Allow".to_string(),
                    description: None,
                    preview: None,
                }],
                multi_select: false,
                about: Some("a".to_string()),
            },
        );
        let answered = event(
            4,
            Event::Answered {
                id: "q1".to_string(),
                answers: vec!["Allow".to_string()],
            },
        );
        // Ahead of both "still running" and "no result": the reader can
        // act on this one, and cannot act on either of those.
        assert_eq!(
            state_of(&[start("a"), asking.clone()], true),
            ToolState::Deciding
        );
        assert_eq!(
            state_of(&[start("a"), asking.clone()], false),
            ToolState::Deciding
        );
        assert_eq!(
            state_of(
                &[start("a"), asking, answered, end("a", "ok", false)],
                false
            ),
            ToolState::Succeeded,
            "once it is answered the call is an ordinary one again"
        );
    }
    #[test]
    fn nothing_but_a_tool_call_has_a_tool_state() {
        assert_eq!(
            ToolState::of(
                &TranscriptItem::UserMsg {
                    seq: 1,
                    text: "hi".to_string(),
                    attachments: Vec::new(),
                },
                true
            ),
            None
        );
    }
 }
@@ -0,0 +1,588 @@
 //! Where a session screen gets a transcript from: this phone's copy first,
 //! the server for the rest. Ported from `app/.../TranscriptSource.kt`; see
 //! `docs/TRANSCRIPT_CACHE.md` for the design this implements and
 //! `docs/CLIENT_CORE.md` for how this file corresponds to the Kotlin.
 //!
 //! One seam rather than a cache the screen has to remember to consult.
 //! Everything fetched before is asked of this, and everything the server
 //! sends is written into the cache on the way past, so a caller never
 //! learns which side answered. The one rule worth keeping in mind: the
 //! cache is never load-bearing. Every read here has a network path beside
 //! it producing the same result.
 //!
 //! **Not ported**: `EventStream.kt`'s reconnect-with-backoff loop and the
 //! ability to close a live stream from another thread. Both are wall-clock
 //! and thread-lifetime concerns that belong to whatever runtime the caller
 //! embeds this crate in (a Tokio task, an iris timer, a Kotlin coroutine
 //! scope) rather than to this pure logic -- `follow` below is the same
 //! decorator shape `iris/desktop-app/src/app.rs` and
 //! `iris/android-app/src/transcript_client.rs` already hand-wrote around
 //! `event_stream::follow_session_events`, just with the cache write built
 //! in so a future caller does not have to repeat it a third time.
 use event_model::SeqEvent;
 use crate::api::{ApiClient, ApiError, Transport};
 use crate::event_stream::{self, StreamItem};
 use crate::transcript_cache::SessionCache;
 /// How many events a session screen opens with, cached or fetched.
 ///
 /// The server's own default page size, named here because the cached
 /// opening has to be the same size as the fetched one -- a reader must not
 /// get a shorter first screen for having been here before (`OPENING_WINDOW`
 /// in the Kotlin original).
 pub const OPENING_WINDOW: u32 = 80;
 /// A transcript-line parse failure, told apart from [`ApiError`] so a
 /// caller can tell "the server is unreachable" from "the server (or this
 /// phone's own disk) sent something this build cannot read" -- the two
 /// mean different things to a reader (retry, versus a build that is
 /// behind).
 #[derive(Debug, Clone)]
 pub struct ParseError(pub String);
 impl std::fmt::Display for ParseError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(&self.0)
    }
 }
 impl std::error::Error for ParseError {}
 /// Either half of what can go wrong asking for a page: the network, or a
 /// line neither the cache's nor the server's copy of `parseSeqEvent` could
 /// read.
 #[derive(Debug, Clone)]
 pub enum PageError {
    Api(ApiError),
    Parse(ParseError),
 }
 impl From<ApiError> for PageError {
    fn from(e: ApiError) -> Self {
        Self::Api(e)
    }
 }
 impl From<ParseError> for PageError {
    fn from(e: ParseError) -> Self {
        Self::Parse(e)
    }
 }
 /// What [`TranscriptSource::page`] found, kept as two states rather than
 /// one possibly-empty list.
 ///
 /// The difference is the whole of AGENTS.md's `loadOlderPage` incident: an
 /// empty [`Self::Events`] means "this conversation has no more history",
 /// which a caller is meant to latch, and [`Self::NothingLoaded`] means the
 /// question could not be asked yet, which it must not. Collapsing the two
 /// into an empty `Vec` puts the bug back, because the caller cannot tell
 /// them apart -- and `unwrap_or_default()` on an `Option` would do the
 /// same silently.
 #[derive(Debug, Clone, PartialEq)]
 pub enum OlderPage {
    /// The events before the cursor, oldest first. Empty means the start
    /// of the conversation has been reached.
    Events(Vec<SeqEvent>),
    /// Nothing is loaded, so there was no cursor to page back from
    /// (`before == 0`). Not an answer about the conversation at all.
    NothingLoaded,
 }
 fn parse_line(line: &str) -> Result<SeqEvent, ParseError> {
    serde_json::from_str(line).map_err(|e| ParseError(format!("{e}")))
 }
 /// This phone's copy of one session's transcript, plus the server it
 /// falls back to. Ported from the Kotlin `TranscriptSource` class.
 pub struct TranscriptSource<T: Transport> {
    api: ApiClient<T>,
    session_id: String,
    pub cache: SessionCache,
 }
 impl<T: Transport> TranscriptSource<T> {
    pub fn new(api: ApiClient<T>, session_id: impl Into<String>, cache: SessionCache) -> Self {
        Self {
            api,
            session_id: session_id.into(),
            cache,
        }
    }
    /// The cached opening window, or `None` when there is nothing usable
    /// to draw.
    ///
    /// Meant to be drawn *before* [`Self::probe`] returns, which is the
    /// whole point of the feature: the rows are on screen while the check
    /// that they are still the server's rows is in flight, and a failed
    /// check replaces them exactly as a reset does.
    pub fn cached_opening(&self, limit: usize) -> Option<Vec<SeqEvent>> {
        self.cache.tail()?;
        let lines = self.cache.newest(limit);
        if lines.is_empty() {
            return None;
        }
        match lines.iter().map(|l| parse_line(l)).collect() {
            Ok(events) => Some(events),
            // A line this build cannot read at all, which the cache's own checks cannot
            // see: it reads a seq off a line, not an event. Nothing to serve, so a cold
            // open.
            Err(ParseError(_)) => {
                self.cache.purge();
                None
            }
        }
    }
    /// Whether the server's event at the cached cursor is still the cached
    /// one.
    ///
    /// A caller must not resume a live stream from a cached seq unless it
    /// is the same conversation: a transcript is append-only in ordinary
    /// use, but the file backing it can be replaced or truncated (a
    /// sandbox re-seeded with the same ids, a backup restored, a session
    /// re-imported), and the server's catch-up on such a file would hand
    /// this phone a continuation of a *different* conversation, spliced
    /// onto the cached one with no seam. Caught with one request of a few
    /// hundred bytes.
    ///
    /// `Ok(false)` purges the cache and means "open cold". `Err` is the
    /// server not being askable, which is neither: the cached rows stay
    /// on screen and the caller tries again on its own reconnect schedule.
    ///
    /// What this cannot see is a line changed in the middle of the file
    /// with the tail intact -- that is what a full reload is for.
    pub fn probe(&self) -> Result<bool, ApiError> {
        let Some(tail) = self.cache.tail() else {
            return Ok(false);
        };
        // `before = seq + 1` is the newest event with seq <= the cursor, which is the
        // event *at* the cursor when the server still has one there.
        let page = self.api.fetch_transcript_lines(
            &self.session_id,
            Some(tail.seq + 1),
            1,
            false,
            None,
        )?;
        let matches = page.len() == 1
            && parse_line(&tail.line)
                .map(|cached| cached == page[0].1)
                .unwrap_or(false);
        if !matches {
            self.cache.purge();
        }
        Ok(matches)
    }
    /// Today's opening fetch, kept as the start of the live run. Only
    /// called when the cache has nothing to open with, or when
    /// [`Self::probe`] said what it had was not the server's.
    pub fn fetch_opening(&self) -> Result<Vec<SeqEvent>, ApiError> {
        let page =
            self.api
                .fetch_transcript_lines(&self.session_id, None, OPENING_WINDOW, false, None)?;
        for (line, event) in &page {
            self.cache.append(line, event.seq);
        }
        self.cache.flush();
        Ok(page.into_iter().map(|(_, event)| event).collect())
    }
    /// The page before `before`: from the cache when it holds it,
    /// otherwise from the server bounded by what the cache already has.
    ///
    /// The server bound (`after`) is what keeps the cache worth having. A
    /// coalesced page reaches back as far as its row count takes it -- a
    /// single reply is hundreds of lines -- so a page fetched after the
    /// reader has been away could run straight past the cached run and
    /// overlap it, and an overlapping page cannot be stored. Told where
    /// this phone's copy starts, the server stops there instead.
    ///
    /// `before == 0` answers [`OlderPage::NothingLoaded`] without asking
    /// the cache or the server anything -- see AGENTS.md's "things that
    /// have bitten": there is no event before the first one, so the
    /// request is not a harmless no-op, and its empty answer is
    /// indistinguishable from having reached the start of history.
    /// Guarded here rather than left to every caller, because it is a fact
    /// about the question, not about who is asking it.
    pub fn page(&self, before: u64, limit: u32, coalesce: bool) -> Result<OlderPage, PageError> {
        if before == 0 {
            return Ok(OlderPage::NothingLoaded);
        }
        if let Some(lines) = self.cache.page(before, limit as usize, coalesce) {
            let events: Vec<SeqEvent> = lines
                .iter()
                .map(|l| parse_line(l).map_err(PageError::from))
                .collect::<Result<_, _>>()?;
            return Ok(OlderPage::Events(events));
        }
        let after = self.cache.covered_up_to(before).map(|v| v - 1);
        let page = self.api.fetch_transcript_lines(
            &self.session_id,
            Some(before),
            limit,
            coalesce,
            after,
        )?;
        if let Some((_, first_event)) = page.first() {
            // `before` rather than the newest line's seq: a coalesced page covers
            // everything up to the cursor it was asked with, and nothing in its lines
            // says so.
            let lines: Vec<String> = page.iter().map(|(line, _)| line.clone()).collect();
            self.cache
                .store_page(&lines, first_event.seq, before, coalesce);
        }
        Ok(OlderPage::Events(
            page.into_iter().map(|(_, event)| event).collect(),
        ))
    }
    /// [`event_stream::follow_session_events`], with every frame written to
    /// the cache before `on_item` sees it.
    ///
    /// Before, so that an event held back for a reader who is scrolled
    /// away is already on disk -- what the cache holds is what the server
    /// sent, not what a screen has got round to drawing. Flushed on each
    /// status change, which is a turn's boundary and the granularity a
    /// crash may as well lose, and once more when the stream ends.
    pub fn follow(
        &self,
        after: u64,
        mut on_item: impl FnMut(StreamItem) -> bool,
    ) -> Result<(), ApiError> {
        let cache = &self.cache;
        let result = event_stream::follow_session_events(
            self.api.transport(),
            &self.session_id,
            after,
            |item| {
                if let StreamItem::Event { raw, event } = &item {
                    cache.append(raw, event.seq);
                    if matches!(event.event, event_model::Event::Status { .. }) {
                        cache.flush();
                    }
                }
                on_item(item)
            },
        );
        cache.flush();
        result
    }
    /// Leaves the cache with everything it was given -- called once a
    /// caller is done with this source, mirroring the Kotlin `close`'s
    /// final flush (that method's stream cancellation itself is the
    /// runtime concern the module doc says is not ported here).
    pub fn close(&self) {
        self.cache.flush();
    }
 }
 #[cfg(test)]
 mod tests {
    use super::*;
    use crate::api::{Body, RawResponse};
    use std::collections::VecDeque;
    use std::io::Read;
    use std::sync::Mutex;
    /// A transport that answers fixed bodies in call order, and records
    /// every path it was asked for -- so a test can assert *how many*
    /// requests a method made, which is the point for the `before == 0`
    /// guard (AGENTS.md's regression: the guard must stop the request
    /// before it happens, not merely tolerate the empty answer).
    #[derive(Default)]
    struct ScriptedTransport {
        responses: Mutex<VecDeque<(u16, String)>>,
        calls: Mutex<Vec<String>>,
    }
    impl ScriptedTransport {
        fn respond(&self, status: u16, body: impl Into<String>) {
            self.responses
                .lock()
                .unwrap()
                .push_back((status, body.into()));
        }
        fn call_count(&self) -> usize {
            self.calls.lock().unwrap().len()
        }
    }
    impl Transport for ScriptedTransport {
        fn request(
            &self,
            _method: &str,
            path: &str,
            _body: Option<Body>,
        ) -> Result<RawResponse, ApiError> {
            self.calls.lock().unwrap().push(path.to_string());
            let (status, body) = self
                .responses
                .lock()
                .unwrap()
                .pop_front()
                .unwrap_or_else(|| panic!("ScriptedTransport got an unscripted request: {path}"));
            Ok(RawResponse {
                status,
                body: body.into_bytes(),
            })
        }
        fn stream(&self, path: &str) -> Result<Box<dyn Read + Send>, ApiError> {
            self.calls.lock().unwrap().push(path.to_string());
            let (_, body) = self
                .responses
                .lock()
                .unwrap()
                .pop_front()
                .unwrap_or_else(|| {
                    panic!("ScriptedTransport got an unscripted stream request: {path}")
                });
            Ok(Box::new(std::io::Cursor::new(body.into_bytes())))
        }
    }
    fn source(
        transport: ScriptedTransport,
        cache_root: &std::path::Path,
    ) -> TranscriptSource<ScriptedTransport> {
        let api = ApiClient::new(transport);
        let cache = crate::transcript_cache::TranscriptCache::new(cache_root).session("s1");
        TranscriptSource::new(api, "s1", cache)
    }
    fn status_line(seq: u64) -> String {
        format!(r#"{{"seq":{seq},"ts":1.0,"type":"status","state":"idle"}}"#)
    }
    #[test]
    fn a_cold_cache_has_no_opening_and_fetches_from_the_server() {
        let dir = tempfile::tempdir().unwrap();
        let transport = ScriptedTransport::default();
        transport.respond(200, format!("[{}]", status_line(1)));
        let source = source(transport, dir.path());
        assert_eq!(source.cached_opening(80), None);
        let opening = source.fetch_opening().unwrap();
        assert_eq!(opening.len(), 1);
        assert_eq!(opening[0].seq, 1);
        // The fetch wrote through: reopening the same cache now has something to show.
        assert!(source.cache.tail().is_some());
    }
    #[test]
    fn probe_matching_the_cached_tail_leaves_the_cache_alone() {
        let dir = tempfile::tempdir().unwrap();
        let transport = ScriptedTransport::default();
        transport.respond(200, format!("[{}]", status_line(1)));
        let source = source(transport, dir.path());
        source.fetch_opening().unwrap();
        let transport2 = ScriptedTransport::default();
        transport2.respond(200, format!("[{}]", status_line(1)));
        let cache = crate::transcript_cache::TranscriptCache::new(dir.path()).session("s1");
        let source2 = TranscriptSource::new(ApiClient::new(transport2), "s1", cache);
        assert!(source2.probe().unwrap());
        assert!(source2.cache.tail().is_some());
    }
    #[test]
    fn probe_mismatching_the_cached_tail_purges_the_cache() {
        let dir = tempfile::tempdir().unwrap();
        let transport = ScriptedTransport::default();
        transport.respond(200, format!("[{}]", status_line(1)));
        let source = source(transport, dir.path());
        source.fetch_opening().unwrap();
        // The server now answers with a different event at the same seq -- the file
        // behind this session was replaced.
        let transport2 = ScriptedTransport::default();
        let different = r#"{"seq":1,"ts":1.0,"type":"status","state":"running"}"#.to_string();
        transport2.respond(200, format!("[{different}]"));
        let cache = crate::transcript_cache::TranscriptCache::new(dir.path()).session("s1");
        let source2 = TranscriptSource::new(ApiClient::new(transport2), "s1", cache);
        assert!(!source2.probe().unwrap());
        assert!(source2.cache.tail().is_none());
    }
    #[test]
    fn probe_finding_no_server_leaves_the_cache_untouched() {
        let dir = tempfile::tempdir().unwrap();
        let transport = ScriptedTransport::default();
        transport.respond(200, format!("[{}]", status_line(1)));
        let source = source(transport, dir.path());
        source.fetch_opening().unwrap();
        let transport2 = ScriptedTransport::default();
        transport2.respond(500, "server on fire");
        let cache = crate::transcript_cache::TranscriptCache::new(dir.path()).session("s1");
        let source2 = TranscriptSource::new(ApiClient::new(transport2), "s1", cache);
        assert!(source2.probe().is_err());
        assert!(
            source2.cache.tail().is_some(),
            "an unreachable server must not be treated as a mismatch"
        );
    }
    /// The regression this module exists to close: `before == 0` must
    /// never reach the network or the cache, because an empty answer there
    /// is indistinguishable from "there is genuinely no more history" --
    /// AGENTS.md's `loadOlderPage` incident.
    #[test]
    fn paging_before_the_first_event_makes_no_request_at_all() {
        let dir = tempfile::tempdir().unwrap();
        let transport = ScriptedTransport::default();
        let source = source(transport, dir.path());
        assert_eq!(source.page(0, 80, true).unwrap(), OlderPage::NothingLoaded);
        assert_eq!(source.api.transport().call_count(), 0);
    }
    #[test]
    fn a_page_already_covered_by_the_cache_never_reaches_the_server() {
        let dir = tempfile::tempdir().unwrap();
        let transport = ScriptedTransport::default();
        transport.respond(200, format!("[{},{}]", status_line(1), status_line(2)));
        let source = source(transport, dir.path());
        source.fetch_opening().unwrap();
        let calls_before = source.api.transport().call_count();
        let OlderPage::Events(page) = source.page(2, 10, true).unwrap() else {
            panic!("a cursor of 2 is a real question about the conversation");
        };
        assert_eq!(page.len(), 1);
        assert_eq!(page[0].seq, 1);
        assert_eq!(
            source.api.transport().call_count(),
            calls_before,
            "a cache hit must not touch the network"
        );
    }
    /// With nothing older cached there is no floor to give the server, so
    /// the request carries no `after` at all.
    #[test]
    fn a_server_page_with_nothing_older_cached_carries_no_bound() {
        let dir = tempfile::tempdir().unwrap();
        let transport = ScriptedTransport::default();
        transport.respond(200, format!("[{}]", status_line(5)));
        let source = source(transport, dir.path());
        source.fetch_opening().unwrap();
        let transport2 = ScriptedTransport::default();
        transport2.respond(200, format!("[{}]", status_line(3)));
        let cache = crate::transcript_cache::TranscriptCache::new(dir.path()).session("s1");
        let source2 = TranscriptSource::new(ApiClient::new(transport2), "s1", cache);
        source2.page(5, 10, true).unwrap();
        assert_eq!(
            source2.api.transport().calls.lock().unwrap()[0],
            "/sessions/s1/transcript?limit=10&before=5&coalesce=true"
        );
    }
    /// The half the test above cannot show: when the cache *does* hold an
    /// older run, the fetch is floored at its end, or the page would run
    /// straight past it and overlap -- which `store_page` then refuses,
    /// silently costing the phone the page it just paid for.
    #[test]
    fn a_server_page_is_floored_at_the_end_of_the_cached_run() {
        let dir = tempfile::tempdir().unwrap();
        let cache = crate::transcript_cache::TranscriptCache::new(dir.path()).session("s1");
        // A stored page covering [3, 6) and two live events above it, so the run this
        // phone holds is [3, 8) -- the newest chunk has to be an appended one, or the
        // cache reads the directory as damaged and discards it.
        let lines: Vec<String> = (3..6).map(status_line).collect();
        assert!(cache.store_page(&lines, 3, 6, true));
        cache.append(&status_line(6), 6);
        cache.append(&status_line(7), 7);
        cache.flush();
        let transport = ScriptedTransport::default();
        transport.respond(200, format!("[{}]", status_line(9)));
        let source = TranscriptSource::new(ApiClient::new(transport), "s1", cache);
        source.page(10, 10, true).unwrap();
        assert_eq!(
            source.api.transport().calls.lock().unwrap()[0],
            "/sessions/s1/transcript?limit=10&before=10&coalesce=true&after=7",
            "the fetch must stop one seq below where this phone's copy ends"
        );
    }
    /// A page the server could not answer is an error, never an empty
    /// page: the caller would read the second as "this conversation has no
    /// more history" and stop paging for good.
    #[test]
    fn a_failing_server_page_is_an_error_rather_than_an_empty_one() {
        let dir = tempfile::tempdir().unwrap();
        let transport = ScriptedTransport::default();
        transport.respond(500, "server on fire");
        let source = source(transport, dir.path());
        assert!(matches!(source.page(9, 10, true), Err(PageError::Api(_)),));
    }
    /// A cached line this build cannot read is told apart from the network
    /// failing, for the same reason: neither is "no more history".
    #[test]
    fn an_unreadable_cached_page_is_a_parse_error_rather_than_an_empty_one() {
        let dir = tempfile::tempdir().unwrap();
        let cache = crate::transcript_cache::TranscriptCache::new(dir.path()).session("s1");
        cache.store_page(
            &[r#"{"seq":3,"but":"not an event"}"#.to_string()],
            3,
            4,
            true,
        );
        cache.append(&status_line(4), 4);
        cache.flush();
        let transport = ScriptedTransport::default();
        let source = TranscriptSource::new(ApiClient::new(transport), "s1", cache);
        assert!(matches!(source.page(4, 10, true), Err(PageError::Parse(_)),));
        assert_eq!(
            source.api.transport().call_count(),
            0,
            "a cache hit that cannot be read must not fall through to the server unnoticed"
        );
    }
    #[test]
    fn a_bad_cached_opening_line_purges_rather_than_panicking() {
        let dir = tempfile::tempdir().unwrap();
        let cache = crate::transcript_cache::TranscriptCache::new(dir.path()).session("s1");
        cache.append("not json at all", 1);
        cache.flush();
        let transport = ScriptedTransport::default();
        let source = TranscriptSource::new(ApiClient::new(transport), "s1", cache);
        assert_eq!(source.cached_opening(80), None);
        assert!(
            source.cache.tail().is_none(),
            "a damaged line purges the cache"
        );
    }
    #[test]
    fn follow_writes_events_to_the_cache_before_the_caller_sees_them() {
        let dir = tempfile::tempdir().unwrap();
        let transport = ScriptedTransport::default();
        transport.respond(200, format!("{}\n\n", sse_frame(&status_line(1))));
        let source = source(transport, dir.path());
        let mut seen = Vec::new();
        source
            .follow(0, |item| {
                if let StreamItem::Event { event, .. } = item {
                    seen.push(event.seq);
                }
                true
            })
            .unwrap();
        assert_eq!(seen, vec![1]);
        assert_eq!(source.cache.tail().unwrap().seq, 1);
    }
    fn sse_frame(data: &str) -> String {
        format!("data:{data}")
    }
 }
@@ -25,16 +25,19 @@ next (a Masonry or iris transcript screen, most likely).
 | `sse.rs`                                  | `Sse.kt` (the framing half)               | Done, new tests (Kotlin had none of its own beyond integration) |
 | `api.rs`                                  | `Api.kt`                                  | Partial -- see below |
 | `event_stream.rs`                         | `EventStream.kt`                          | Done |
-| `transcript_fold.rs`                      | `TranscriptItems.kt`, `ToolRows.kt`       | Partial -- see below |
+| `transcript_fold.rs`                      | `TranscriptItems.kt`, `ToolRows.kt`       | Done -- see below |
 | `config.rs`                                | `ServerConfig.kt`'s `handleEnrollment`   | New, desktop-only so far -- see below |
-| *(not started)*                           | `TranscriptSource.kt`                     | Not started |
+| `transcript_source.rs`                    | `TranscriptSource.kt`                     | Done -- see below |
 | *(not ported, and may never be)*          | `TranscriptUnits.kt`                      | Out of scope -- see below |
 Every file above whose Kotlin counterpart had a JVM unit test (`AnsiTest`,
 `HighlighterTest`, `TranscriptCacheTest`) has had every one of those test
 cases ported alongside it, plus new tests for the pieces that had none
-(`sse.rs`, `api.rs`, `event_stream.rs`, `transcript_fold.rs`). Test count by
+(`sse.rs`, `api.rs`, `event_stream.rs`, `transcript_fold.rs`,
-crate as of this writing: **85 in `client-core`**, 0 in `event-model` (its
+`transcript_source.rs` -- the Kotlin `TranscriptSource.kt`/`TranscriptItems.kt`
 had no JVM unit tests of their own, so these were written fresh against the
 Kotlin source and AGENTS.md's paging incidents as the spec). Test count by
 crate as of this writing: **109 in `client-core`**, 0 in `event-model` (its
 types carry no logic of their own to test -- `server/`'s own tests exercise
 them via `session::transcript`'s round-trip coverage).
@@ -88,13 +91,27 @@ the full table to work from when one of these is next.
 including tool-call/question/image attachment and peer-message placement.
 `group_tool_runs` groups adjacent calls into `TranscriptRow::Tools`.
-**Not ported:** `TranscriptItems.kt`'s `joinPages` (and its
+`join_pages` (with `heal_split_message` and `adopt_run`, both private) is
-`healSplitMessage`/`adoptRun` helpers) -- the page-boundary healing that
+now ported too, 2026-09-06 -- the page-boundary healing that merges a tool
-merges a tool call split across two fetched pages and re-merges a run a
+call split across two fetched pages, rejoins a message a boundary cut
-boundary cut through. This matters the moment paging backward through
+through, and renames a run of tool calls onto whichever name is already on
-history is exercised; it is deliberately left rather than rushed, since
+screen. Ported with AGENTS.md's "things that have bitten" incidents as the
-it is exactly the kind of boundary logic this project's own "things that
+spec rather than a JVM test file (`TranscriptItems.kt` had none of its
-have bitten" section warns reads fine and is wrong at the edges.
+own): `a_clean_boundary_between_two_finished_runs_is_still_healed_into_one_run`
 is the regression test for the bug that shipped -- `adopt_run` must run on
 *every* join, not only the one where a split call was found, or a boundary
 landing cleanly between two already-finished calls (most of them) leaves
 one run drawn as two. `a_call_split_across_the_boundary_merges_into_one_row`,
 `a_message_split_across_the_boundary_is_rejoined_with_the_newer_halfs_identity`,
 and `adopt_run_never_renames_into_a_question_row` cover the other three
 edges the Kotlin doc calls out. `join_pages` ends in a `debug_assert!`
 that no tool id survives in both halves -- the duplicate row it exists to
 prevent, checked rather than assumed. What it deliberately does *not*
 assert is seq ordering across the boundary: a peer note carries the seq
 its turn began at (`place_peer_note`), which can be older than the page
 it arrived in, so the two pages' seqs legitimately interleave there. An
 earlier draft asserted it and would have panicked in debug builds on an
 ordinary transcript.
 **Known gap, and a decision for whoever closes it:** `event_model::Event`
 has no `Unknown`/catch-all variant, unlike `Events.kt`'s hand-kept mirror.
@@ -119,20 +136,72 @@ caller-specific (the code rules' "ask for the least you need"). Its only
 caller today is `desktop-app`; a future Android build of this crate would
 be a second one, not a reason to move the type.
 ## What `transcript_source.rs` covers, and what it does not
 `TranscriptSource<T: Transport>` is the seam a session screen asks for a
 page, ported test-for-test against the Kotlin doc rather than a JVM test
 file (there wasn't one): `cached_opening`, `probe`, `fetch_opening`,
 `page` and `follow`, each matching its Kotlin namesake's contract --
 including `probe`'s three-way outcome (matches / cache purged /
 unreachable, told apart so a caller never treats "couldn't ask" as "was
 wrong") and `page`'s cache-vs-server split bounded by `covered_up_to`.
 Two additions beyond a literal port, both load-bearing:
 - **`page(before, ..)` refuses `before == 0` before touching the cache or
  the network**, answering `OlderPage::NothingLoaded`. This is AGENTS.md's
  `loadOlderPage` incident (`before = 0` is "no event before the first
  one," indistinguishable from "reached the start of history" if a caller
  ever asks it) moved out of the Kotlin screen and into this layer, so
  every future caller gets the guard rather than having to remember it.
  **The return type is `OlderPage`, not a `Vec`, and that is the guard.**
  The Kotlin's two falses are different answers -- `oldestSeq == 0`
  returns without touching `moreHistory`, an empty page latches it false
  -- so a port that answered both with an empty list would have moved the
  bug rather than fixed it, one layer down and out of sight of the screen
  that used to hold the check. `OlderPage::Events(vec![])` means the start
  of the conversation; `OlderPage::NothingLoaded` is not an answer about
  the conversation at all. Reviewed 2026-09-06.
  `paging_before_the_first_event_makes_no_request_at_all` asserts zero
  transport calls, not just the variant, since a request that happens to
  answer empty is exactly what caused the original bug, and
  `a_failing_server_page_is_an_error_rather_than_an_empty_one` plus
  `an_unreadable_cached_page_is_a_parse_error_rather_than_an_empty_one`
  are the same rule for the two ways a page can fail.
 - **`fetch_transcript_lines`** (new in `api.rs`) hands back each line
  paired with the exact server bytes it came from, via
  `serde_json::value::RawValue` rather than re-serializing a parsed
  `Value` -- the cache and a live SSE frame for the same event have to
  agree byte-for-byte, which is exactly what the `serde_json`
  float-rounding bug (AGENTS.md) was about. The existing
  `fetch_transcript_page` is untouched (other callers under `iris/`
  depend on its signature); the two share a `transcript_path` helper so
  the query string is written in one place.
 **Not ported:** `EventStream.kt`'s reconnect-with-backoff loop, and
 `TranscriptSource.close`'s ability to cancel a live stream from another
 thread. Both are wall-clock/thread-lifetime policy that belongs to
 whichever runtime embeds this crate (iris's own timers, a Tokio task, a
 Kotlin coroutine scope), not to this pure logic -- `follow` is the same
 "write to the cache, then hand the frame to the caller" decorator
 `iris/desktop-app/src/app.rs` and `iris/android-app/src/transcript_client.rs`
 already hand-wrote around `event_stream::follow_session_events` before this
 existed; the cache write moved into one shared place so a third caller
 does not repeat it again by hand.
 ## What is not started at all
- **`TranscriptSource.kt`** -- the layer that decides whether a page comes
+- **A full markdown AST.** `markdown_blocks` (2026-09-06) splits a message
-  from the transcript cache or the server, and stitches the two. Needs
+  into its *top-level* blocks -- heading, paragraph, fence, list, table,
-  `transcript_cache.rs` and `api.rs`'s transcript-page method, both of
+  quote -- with each block's own source, which is what a renderer needs to
-  which exist now, so this is unblocked whenever picked up.
+  lay out prose versus code and what lets a streamed delta re-lay out one
- **The markdown *block* model beyond syntax spans** -- `highlight/markdown.rs`
+  block instead of the message (docs/RUST.md's Task B). What it
-  colours a `.md` file or fence for the highlighter, but does not build the
+  deliberately does **not** build is the tree below that: nested list
-  block tree (headings, lists, tables, fences as distinct nodes) that a
+  items, table cells, inline spans. Inline styling is still the renderer's
-  renderer walks to lay out prose versus code versus a table.
+  own job per block (`iris/transcript-ui/src/markdown.rs`), and nothing
-  `CodeFence.kt`'s use of `org.intellij.markdown` for that full CommonMark
+  has needed the rest yet. `CodeFence.kt`'s use of `org.intellij.markdown`
-  AST is Compose rendering plumbing, not something to port as-is; a Rust
+  for a full CommonMark AST is Compose rendering plumbing, not something
-  UI layer will want its own block parser or a crate for it, decided
+  to port as-is.
  alongside the framework choice in RUST.md.
 - **`TranscriptUnits.kt`** (see above) -- deliberately out of scope, since
  it flattens a row into bounded units for a *specific* lazy-list
  framework's composition cost, which is a fact about that framework
@@ -142,5 +211,6 @@ be a second one, not a reason to move the type.
 `./run-tests.sh` from the repo root now runs `event-model`, `client-core`
 and `server` in that order (each `cargo test`, forwarding arguments the
-same way it always has). From `client-core/` directly: `cargo test`,
+same way it always has). From `client-core/` directly: `cargo test`
-`cargo clippy --all-targets`, `cargo fmt` -- all clean as of this writing.
+(119 tests), `cargo clippy --all-targets`, `cargo fmt` -- all clean as of
 this writing (2026-09-06).
@@ -5,6 +5,157 @@ they can be judged and reversed later. Detail lives in RUST.md (and IRIS.md
 for iris API changes); this file is only the summary. Newest first. Items
 marked **DEFERRED** are ones the agent chose not to decide alone.
 ## 2026-09-06 (how a tool call looks, P1b)
 - **A card that never got a result says "no result", in yellow, and it is
  a state Compose cannot say.** A call that finished having printed
  nothing and a call whose turn was interrupted before anything came back
  both leave an empty output. Compose draws both as an ordinary finished
  call, which reads as a fact somebody established. There are five states
  now, each with a word and a colour: nothing at all for a call that
  worked, "running" (grey), "your turn" (peach, Compose's own wording and
  colour), "failed" (red), "no result" (yellow).
 - **A failed call is drawn as failed, which needed a field on the wire.**
  `is_error` is on the CLI's `tool_result` and was being dropped; the
  server now carries it to the phone. Reversible, but the alternative is a
  card that says a call succeeded because it cannot tell.
 - **A group's cards do not each carry their own surface.** Compose gives
  each card a fill and squares the corners where it faces a neighbour, so
  a run reads as one object broken into parts. iris has no per-corner
  radius, and -- more to the point -- a group built the way Compose builds
  it hit a framework layout defect that drew every card's text a card
  below its own box. So a group is one surface with its cards on it,
  separated by a small gap, and the 4dp inset Compose holds them off the
  edge by is gone. Worth revisiting once the layout defect is fixed
  (docs/IRIS_TODO.md).
 - **A long tool output is capped at 80 lines or 4 kB with a "Show all N
  lines".** Compose draws the whole thing, and gets away with it because
  its `Text` inside a `LazyColumn` lays out lazily; here the output is one
  text widget and shaping a hundred kilobytes of it costs what the file
  editor's 32 kB limit was measured against. If iris's text gets cheaper,
  this is the number to move.
 - **A card's command is clipped, not pannable, and its summary line is
  clipped rather than ellipsised.** Both are framework gaps rather than
  choices (`scrollable_on` on a non-editable text draws nothing; there is
  no overflow ellipsis), and both are worse than Compose today. Named here
  because they are visible.
 ## 2026-09-06 (how a markdown block looks, P1a)
 - **A table is drawn as padded monospace columns, not as a grid.** Your
  call to reverse. Compose draws a real grid: cells on a tint, each
  column with a 136dp floor, scrolling sideways when there are too many.
  iris has no grid widget, and building one would be a widget per
  markdown feature -- which is the thing the block model exists to avoid.
  In a monospace face a character count *is* a pixel width, so padding
  each cell to its column's width is alignment, the widths are still
  measured from the cells, and a table that is too wide pans sideways
  through the same mechanism a code fence already uses. The header is
  bold with a rule under it, and a long cell wraps inside its column
  (capped at 28 characters, which is what fits three columns across a
  phone). **What it trades:** no cell borders, and a table looks like
  code rather than like a table. If you want the grid, it is a new widget
  and it is a day's work.
 - **Three block frames, and only three.** A heading, paragraph and list
  are plain text with spans; a fence and a table are a rounded panel that
  does not wrap; a quote is a bar with the text padded past it.
  Everything else markdown says is expressed in span styles, which cost
  no widgets and no layout nodes. So a new markdown feature is a span,
  not a widget.
 - **A list's marker is part of the text, so a wrapped item's second line
  returns to the left margin.** Compose keeps it indented by giving the
  marker its own column. Doing the same here needs per-line indent in
  iris's text attributes; it is written down rather than done, because
  the list items in a real reply are usually one line.
 - **A link opens on a tap and not on the end of a drag.** A press that
  panned the transcript past a link, or that held long enough to start a
  selection, does not follow it -- decided by the same gesture machine
  that decides pan-versus-select, so there is one rule rather than two
  that can disagree.
 ## 2026-09-06 (composer scroll and the streaming block model)
 - **A streamed message becomes a column of per-block widgets.** Decided by
  the design agent; recorded here because it is the shape of every message
  on screen. A transcript row is one `TextEdit` today, so a streamed delta
  re-shapes the entire message through parley on every event -- the stream
  phase is the one place iris is behind Compose on your phone (p50 18.2ms
  vs 13.4ms). A row becomes a column of one widget per markdown block
  (paragraph, heading, fence, list, table) and a delta replaces only the
  last block, keeping every earlier block's layout. **Rejected:** splitting
  parley's layout at block boundaries inside one text widget (couples
  iris's text widget to markdown structure, and parley has no incremental
  API), and caching shaped runs per paragraph inside `TextEdit` (a second
  cache with its own invalidation beside the glyph cache). Chosen because
  P1's markdown block model is needed anyway, so the split happens once, in
  `client-core`, and iris stays a text renderer. **Status: designed, not
  built** -- this pass spent its budget on the composer's three layout
  defects; docs/RUST.md has the design and the pass conditions.
 - **The composer's overflowing text now scrolls on a finger**, capped at
  six lines and clipped to the bar. Reverses the "still does not scroll"
  item below.
 - **A widget may not report a `dp` length** (see IRIS.md). A rule for
  widget authors, enforced by a `debug_assert!`; nothing changes for app
  code.
 ## 2026-09-06 (stale-primitives and touch-scroll pass)
 - **A vertical drag inside a focused composer now scrolls rather than
  selects.** Android's own `EditText` does this -- a vertical drag scrolls
  the field, and only a long press starts a selection -- so the platform
  decided it. What it costs: you can no longer drag straight down inside
  the composer to select several lines of what you typed; use a long press
  and then drag, or drag sideways. Say if that trade is wrong for you.
 - **`Scroll` gets a finger pan but no fling.** `List` flings; a scroll area
  does not, because it has no per-frame tick to animate one and the areas
  it wraps are at most a screenful (Android does not fling a six-line text
  box either). Easy to add later if a scroll area ever wraps something long.
 - **The composer still does not scroll its overflowed text**, though the
  mechanism it needs is now in place. Wrapping the field in `.scrollable()`
  was tried and reverted the same day: `Scroll` measures its content and
  container against the *window*, so inside the `MaxSize` that caps the
  composer at six lines the two are in different spaces and the field pans
  itself entirely out of the bar (measured on the emulator with 474
  characters in it -- the bar collapsed to its padding). Fixing that means
  `Scroll` measuring against its own offered box, which is a change to a
  widget the transcript and the bench shell both use, so it is its own
  piece of work rather than a rider on this one.
 ## 2026-09-06 (defect pass)
 - **The keyboard-open diagnostics overlay is gone; the capture only
  logs now.** It was added when `on_insets_changed` was not firing at all
  and there was no way to get a report off the phone. It fires reliably
  since the activity went edge-to-edge -- and what that looks like in
  use is a full-screen report covering the app **every time the keyboard
  opens**, with its own Copy/Close buttons sitting underneath the
  keyboard, so it cannot be dismissed (reproduced on the emulator this
  pass: two `tap 'CLOSE'` runs left it up). An interruption for something
  nobody asked for, over the app you are trying to type into. The named
  `Diagnostics` button still shows the same text on demand, and the new
  `iris surface:`/`iris insets:` log lines carry the lifecycle a `logcat`
  pull needs. Reversible: `capture_keyboard_diagnostics` is still the one
  place this is decided, and `PlatformHandle::show_diagnostics_overlay`
  is still there.
 - **The bench shell's report pane is sized to its report, not to a share
  of the window.** It held `.height(rest(1))` beside the transcript's
  `rest(2)`, so an *empty* `TextEdit` reserved a third of every screen --
  which is what Iris's "the app does not start with keyboard spacing
  correct" screenshot was showing, with the composer two thirds down and
  black below it. It is `.max_height(dp(260))` now and sits above the
  transcript rather than under the composer, where it was eating the
  navigation-bar clearance. Cost: a filled report is clipped at 260dp
  rather than scrolling (a `Scroll` there drew itself off the top of the
  screen, since `Scroll` pins to the end of its content and reports its
  content's full length to the parent -- worth fixing in `Scroll`, not
  worked around here). "Copy report" and `logcat` still have the whole
  thing.
 ## 2026-09-05
 - **iris no longer asks every device for compute-shader limits it never
@@ -264,24 +415,30 @@ marked **DEFERRED** are ones the agent chose not to decide alone.
  | app | build | GPU mode | frames | janky % | p50 | p90 | p99 | worst | cpu p50 | gpu-wait p50 |
  |---|---|---|---|---|---|---|---|---|---|---|
  | Compose (in-app report) | debug | host (virgl) | 1268 | 96.4% late | 20.0ms | 28.4ms | 37.7ms | -- | -- | -- |
-  | iris (`FrameReport`) | **release**, `force-gles` | host (virgl) | 62 | 41.94% | 15.0ms | 21.8ms | 37.1ms | 37.1ms | 0.2ms | 12.9ms |
+  | iris (`FrameReport`), **best of three, 2026-09-05** | release, `force-gles` | host (virgl) | 439 | 46.24% | 15.7ms | 23.3ms | 31.2ms | 57.4ms | 1.2ms | 13.2ms |
  Under real GPU rendering iris's median frame is *faster* than
  Compose's, not the 2-3x-slower shape the software-mode table shows. A
  new split inside `FrameReport` (redraw-to-submit vs. submit-to-present,
  commit `e2a1fad`) says why: iris's own CPU work per frame is a median
-  0.2ms -- almost the entire frame is time spent handing the frame to the
+  ~1ms -- almost the entire frame is time spent handing the frame to the
  driver, not in iris's layout/text/primitive code. This is consistent
  with the earlier software-mode gap being mostly SwiftShader's CPU
-  rasterisation cost rather than an iris-specific slowness, but is not
+  rasterisation cost rather than an iris-specific slowness. **Still not
-  proof of it: a same-mode software `force-gles` run to isolate the
+  proof, and now closed as unanswerable rather than merely untaken**: a
-  backend crashed for an unrelated reason (SwiftShader's GL path reports
+  same-mode software `force-gles` run to isolate the backend was retried
-  itself as OpenGL ES 3.0, which has no compute shaders, and iris's device
+  2026-09-05 after fixing the compute-limit crash the first attempt hit,
-  request assumes them unconditionally) — real scope to fix, not done
+  and hit a second, structural wall instead — SwiftShader's ES 3.0 GL
-  here — and the two apps' frame populations still differ in kind the same
+  path has no storage-buffer capacity at all, and `shader.wgsl` reads
-  way the software-mode caveats describe. A real intermittent touch-
+  `var<storage>` buffers unconditionally, so reaching that path needs a
-  scroll dropout was also reproduced this pass (six consecutive swipes
+  shader rewrite, not a limits fix (RUST.md's I5 box, "The three
-  produced zero redraws while taps kept working; an identical retry then
+  remaining I5 verifications, closed 2026-09-05," item 2). The
-  succeeded) and is not explained. RUST.md's I5 box, "Where iris's frame
+  intermittent touch-scroll dropout this pass also reproduced is
-  time goes, 2026-09-05, the `-gpu host` pass," has the full account. The
+  root-caused and fixed as of the same date (a missed `ACTION_DOWN` on a
-  iris-vs-Masonry choice itself is still Iris's to make.
+  row's padding/header left `DragArbiter` stuck in `Idle`); three clean
  `iris-scroll.sh` runs post-fix each scrolled all 24/24 swipes, replacing
  the single-attempt 62-frame reading this table used to carry. RUST.md's
  I5 box, "Where iris's frame time goes, 2026-09-05, the `-gpu host`
  pass," and "The three remaining I5 verifications, closed 2026-09-05,"
  have the full account. The iris-vs-Masonry choice itself is still
  Iris's to make.
@@ -8,6 +8,451 @@ capability that moved. Small and trivial changes do not go here.
 An entry gives the date, what changed, why, and a short before/after where
 it helps judge the change without the session that made it. Newest first.
 ## 2026-09-07: a headless harness, replayed touch, and physical-pixel desktop layout
 Layer 1 and 2 of docs/RUST.md's "Three test layers".
 **New: `iris::harness`** -- a screen driven in-process with no window, no
 compositor and no GPU, on a clock the caller advances. `Harness::new(size,
 density)` gives you an `Rsc`, a `UiRenderState` and a state that
 implements `FocusHost`/`OpenUrl` by *recording* what the platform was
 asked for (`keyboard_shown`, `opened_urls`) rather than doing it;
 `frame(t_ms)`/`frames_until(..)` run frames, `touch(action, pos, t_ms)`
 feeds one pointer sample the way Android's `on_touch_event` does, and
 `replay(&TouchScript)` runs a whole recorded gesture. `TouchScript` parses
 a plain `t_ms action x y` file (`down`/`move`/`up`/`cancel`), so the
 batched 120Hz flick shape your phone actually delivers is a file that
 `cargo test` can replay -- something the emulator cannot produce at all.
 **New: `List::fling_velocity() -> Option<f32>`**, what the release
 measured, readable where it landed rather than by re-timing the gesture.
 **Changed: `List` starts a fling's curve at its first `tick_fling`, not
 at the release.** The only clock it reads is now the one its driver hands
 it; in a running app the difference is at most a frame.
 **Changed: the desktop backend lays out in physical pixels with a
 density, exactly as Android does.** `iris::default::content_scale(window)`
 is the desktop's `content_scale` -- winit's scale factor, overridable with
 the `IRIS_SCALE` environment variable -- and it now feeds
 `UiRenderState::set_density`/`TextData::density` instead of dividing
 coordinates into a separate "logical" space. That division had
 `UiRenderState::resize` (physical) and the window uniform (logical)
 disagreeing on any display whose scale factor is not 1.0, and rasterised
 glyphs at one resolution to display them at another. `Input::event` lost
 its `scale_factor` parameter as a result, and `DefaultUiState::
 window_size()` now answers physical pixels. On a 1.0 display nothing
 changes. The override is what lets `run-headless.sh --phone` open a window
 at your phone's own 1080x2424 and 2.55.
 ## 2026-09-07: the fling curve was the identity function
 You said the fling "seems to just be linear velocity with an abrupt stop."
 It was, exactly: `android_fling_spline`'s lookup returned `t` for every
 `t`. Two halves of AOSP's spline build loop had been transposed, which made
 its two tables identical, and the lookup interpolated one against the
 other -- which reduces algebraically to `t`. So a fling coasted at its
 release speed for the whole (correctly computed) duration and stopped dead
 at the end of it.
 Ported exactly now from `OverScroller.java` and Compose's
 `SplineBasedDecay.kt`, which agree line for line. One public addition:
 **`FlingCalculator::velocity_at(velocity, elapsed) -> f32`**, beside the
 existing `position_at` -- AOSP's `mCurrVelocity` and Compose's
 `FlingInfo.velocity`. It is what makes "is this decelerating" answerable
 rather than inferred, and it is what `List::tick_fling`'s new
 `iris fling tick:` debug line reports each frame.
 The lesson worth keeping, since it cost two builds on your phone: every
 test the calculator had compared it with itself -- monotonic, correctly
 signed, integrates to the closed form, per-tick deltas non-increasing --
 and **all of them pass on a straight line**. The numbers now come from
 `iris/benches/fling_spline_reference.py`, a separate hand transcription of
 the two sources, checked in beside the tests.
 ## 2026-09-07: the Android insets bridge counts its own dispatches
 `AndroidUiState::insets_report() -> String` is new, and the bench app's
 Diagnostics pane shows it. It carries the last insets plus **how many times
 the platform has delivered any**, because "the keyboard did not push
 anything up" has two causes that look identical on screen -- the listener
 never fired, or it fired with a zero height -- and you have no logcat on
 the phone. `dispatches=0` prints a sentence saying so rather than the
 numbers, which would be defaults rather than measurements.
 ## 2026-09-07: widgets can animate, and a fling finally moves
 Iris's phone said "fling still doesn't work" twice. The velocity was only
 half of it: **nothing in iris advanced an animation between input
 events**, so `List::fling` stored a speed that nothing ever applied. Three
 public changes come out of fixing that.
 **`Widget::tick(&mut self, now: Instant) -> bool`** is a new trait method,
 defaulted to `false`, so no existing widget changes. A widget that
 overrides it is animating; answering `false` is how it stops.
 **`UiData::animate(id)` and `UiData::tick_animations(now) -> bool`** are
 the registry and its driver. A gesture that starts an animation registers
 the widget; each backend calls `tick_animations` once per frame before the
 draw and asks for another frame while it answers `true`. That answer is
 the *only* thing in iris that makes a frame happen without an input event,
 and an animation's path out is its own `tick` returning false -- nothing
 has to remember to unregister it.
    // before: the velocity was stored and never applied
    list(ui).fling(-v);
    // after
    list(ui).fling(-v);
    let id = list.id();
    ui.ui_mut().animate(id);
 The two calls are deliberate rather than folded into `fling`: the velocity
 is the list's business and whether anything animates at all is the frame
 loop's, and a caller driving its own frames (the benchmark, the headless
 tests) still calls `tick_fling` directly.
 **`FlingCalculator` needs the real display density, and its coefficient
 was wrong.** `new(density)` takes physical pixels per `dp` and the
 velocity handed to it must be in those same physical pixels -- the
 density does *not* cancel out, contrary to what that type's doc used to
 claim. Separately, `physical_coefficient` multiplied by the scroll
 friction (0.015) where AOSP multiplies by its own tuning constant 0.84, a
 factor of 56 inside an exponential. Together they gave an ordinary flick a
 **45-second** coast, which nobody could see while flings never animated.
 `List` reads its density from the painter now, and
 `a_flick_lasts_what_aosps_own_formula_says_it_does` pins the absolute
 numbers (0.59s and 621px for 3000px/s at density 2.75) against AOSP's
 formula -- the check every previous test could not make, because they all
 compared the calculator with itself.
 **`MOVE_CHAIN_LIMIT` is 64, not 16**, in `render_state.rs` and
 `shader.wgsl` alike. It bounds a walk so a cyclic `parent` cannot hang
 either side; it was never meant as a claim about tree depth, and the
 transcript screen's composer field sits 17 slots below the root. Past the
 bound both walks silently stop summing, so a widget draws and hit-tests
 short with nothing to say so; the CPU assert now prints the chain, so a
 cycle and a deep tree can be told apart.
 ## 2026-09-06: tool cards, `ToolState`, and a screen that knows whether its session is working
 `transcript_ui::tool` is new: a card per tool call, a group per run
 (P1b). Three things in the public surface follow from it.
 **`client_core::transcript_fold::ToolState`** is what a card colours
 itself by -- `Running`, `Deciding`, `Succeeded`, `Failed`, `NoResult` --
 built by `ToolState::of(&item, session_working)`. The pair it exists for
 is `Succeeded` against `NoResult`: a call that finished having printed
 nothing and a call whose result never arrived both leave an empty
 `output`, and drawing them the same way states a verdict nobody reached.
 Only the session's own status separates them, which is why `of` takes it.
 **`event_model::Event::ToolEnd` gained `is_error`** (`#[serde(default)]`,
 so an older transcript still parses), and
 `client_core::transcript_fold::TranscriptItem::ToolRun` gained `failed`.
 Without them a result was everything a card knew and a broken call drew
 exactly as confidently as one that worked -- the missing state, not a
 wrong one. Every construction site of both had to gain a field; the value
 comes from the CLI's own `tool_result`, read in one place
 (`import::tool_result_is_error`) by both the live translator and the
 import replay.
 **`TranscriptScreen::set_session_working(rsc, bool)`** is new, and is the
 only thing that writes it. Before: a card with no result was drawn the
 same whether its turn was still going or had been interrupted. After:
 only the *newest* row can say "running", because every row behind it
 belongs to a turn that has ended, and changing the flag redraws that one
 row rather than the screen. `TranscriptScreen::expand_tail_tools(rsc,
 bool)` joins it, answering whether there was a tool run to act on -- a
 group's expanded appearance is otherwise unreachable from anything that
 cannot press the screen.
 **`transcript_ui::row::build_row` now returns a `TailRow`** rather than an
 `Option<RowBlocks>`: `Blocks` for a message (a delta costs the last
 markdown block) or `Tools` for a run (an arriving result costs one card).
 One mechanism for "what can this row change cheaply", asked of the row
 rather than decided again at each call site. It also takes the row's own
 `working` flag.
 Two smaller ones. `client_core::tool_summary::parse_tool_input` is
 `ToolInput.kt`'s subject/description/timeout/rest split, and
 `client_core::durations::format_millis` is `Durations.kt`'s -- both pure,
 both with the Kotlin's own tests ported.
 ## 2026-09-06: a tap is its own gesture outcome, and opening a URL is a backend capability
 Three related additions, all for following a markdown link.
 **`iris::platform::OpenUrl`** is a new trait beside `attr::FocusHost`, and
 has the same shape: declared in `iris`, implemented once per backend (a
 detached `xdg-open`/`open`/`start` on the desktop, an `ACTION_VIEW` intent
 on Android, deferred to the next view callback exactly the way
 `pending_show_keyboard` is). A widget asks for the capability by bound --
 `Rsc::State: FocusHost + OpenUrl` -- instead of a caller threading a
 callback down through every builder. One method, not a general "run an
 intent": a narrower capability is a narrower thing to get wrong. Nothing
 is returned; the platform either shows a browser or does not, and both
 are outside the process.
 **`GestureOutcome::Tapped`** is new. `Released(None)` used to mean both
 "the press ended having selected something" and "the press ended having
 done nothing at all", and only the second is a tap. Any caller that acts
 on a tap -- following a link -- must not also act when the finger was
 panning the list past that link, so the distinction is made once, in the
 gesture machine every widget already shares, rather than timed again per
 widget. `DragArbiter::is_undecided()` is what answers it.
 `Selection::drag` returns the outcome now instead of `()`.
 **`DragArbiter`/`DragGesture` take an axis** (`::on(Axis)`; `::new()` is
 still vertical). A code fence pans across its own long lines exactly the
 way a transcript pans down its rows, and the two were the same state
 machine with `dx` and `dy` swapped. `WidgetLike::scrollable_on(axis)`
 joins `scrollable()` for the same reason. Before this, a horizontal
 `Scroll` existed but could not be dragged by a finger at all -- its
 arbiter only ever committed on the vertical axis.
 Two smaller ones in the same pass. **`TextEditCtx::byte_at(pos, size)`**
 answers which byte of the text a tap landed on, doing the same
 region-relative transform `select` does, without handing out the parley
 layout a caller could shape against stale text. And **`Rect::radius` now
 takes a `Len`**, so a corner can be written in `dp` and come out the same
 physical size on every display; a bare number still means physical pixels.
 **One behaviour change worth knowing about**: `Rect::is_size_independent()`
 answers `false` now. It answered `true`, and a `Rect` fills whatever
 region it is given -- so `draw_inner`'s fast path, which rewrites a
 widget's primitives in place instead of redrawing it, could not reproduce
 what `draw` would have done. A `.background(rect(..))` behind
 variable-height content kept the size of the provisional pass its parent
 `Span` had drawn it at, which on the transcript screen meant one code
 block's panel covering every block below it. Costs one primitive's redraw
 when a rect is resized.
 ## 2026-09-06: a transcript row is a column of blocks, and a block is the selection unit
 `transcript-ui`'s row builder used to make **one** `TextEdit` per message.
 It makes one per top-level markdown block now -- heading, paragraph,
 fenced code, list, table -- in a `Span::down`, because a streamed delta
 into a single buffer re-shaped the whole message through parley on every
 event. `client_core::markdown_blocks::split_blocks` does the splitting;
 `row::RowBlocks::apply_delta` updates the block a delta lands in and
 leaves the rest of the message's layout alone.
 **The change to judge, since it is what a reader feels**:
 `Selection` is keyed by `SelKey = (RowKey, u32)` -- a row and a block --
 so **a block, not a row, is the unit a selection steps in**. A drag still
 runs from a reply into the tool output beneath it and copies as one
 thing; what changed is that the row under the finger is filled in block by
 block rather than all at once, which is if anything closer to what the
 old shortcut in `Selection`'s module doc was apologising for. `register`
 takes a `SelKey`; `unregister` still takes a `RowKey` and now drops every
 block of it (dropping only the first is how a freed widget gets left in
 the map -- the shape docs/REVIEW-2026-09-06.md's finding 1 called out).
 `Selection::locate(ui, render, pos_window)` is new: which block is under a
 window position, with that block's own local position and size. The
 list-level handler uses it for the pointer-captured half of a drag,
 instead of computing a row-local position from `List::extent`.
 `row::build_row` returns `(RowKey, StrongWidget, Option<RowBlocks>)` --
 the third is the per-block state a caller keeps only for the row a reply
 is streaming into, and is `None` for a tool run, which never streams.
 ## 2026-09-06: a reported `Size` may not carry `dp`; `Len::fold_dp`
 **New: `Len::fold_dp(density) -> Len`** -- the same fold `apply_rest` does
 (`dp` becomes physical pixels), but staying a `Len` so `rest` survives.
 **New rule, and it is a rule about every widget, not about the two that
 broke it**: a `Len` a widget *reports* from `draw` must not carry an
 unresolved `dp`. `dp` is an input unit -- a number the widget author wrote
 -- and the containers that consume a reported length read `abs`, `rel` and
 `rest` straight off it (`Span`'s placement arithmetic, `Pad`'s addition),
 so a reported `dp` is silently worth **zero**. `MaxSize` and `Sized` both
 returned the caller's declared `Len` as written; a `.max_height(dp(168))`
 therefore gave its child a slot of nothing the moment the cap actually
 applied, which is what made the composer's bar collapse. Both put their
 declared lengths through `fold_dp` now, and
 `UiRenderState::draw_inner` `debug_assert!`s the invariant after every
 `Widget::draw`, so a widget that gets this wrong says so at the mistake
 rather than laying out at zero somewhere else.
 Nothing changes for a caller: `.max_height(dp(48))` is written the same
 way. It is only widget *authors* who now have a rule to follow, and a
 debug build that enforces it.
 ## 2026-09-06: `Painter::set_mask` reuses one slot; `ActiveData` gains two fields
 **`Painter::set_mask(region)` allocates its widget's mask slot once and
 rewrites it in place** on every later draw, instead of pushing a new one
 each time. It has to: `draw_inner`'s unchanged-region fast path does not
 revisit a descendant whose own region did not change, so those descendants
 go on referencing whichever slot they were first drawn under. Pushing a
 fresh slot per draw left the composer's field clipped to a box the bar had
 long since moved away from -- four live mask entries, none of them the
 `Masked`'s current region -- and it drew nothing at all. Same call, same
 signature; only the lifetime changed.
 **`ActiveData` gains `own_mask` and `move_applied`** (both public, since
 `ActiveData` is). `own_mask` is the slot above, `MaskIdx::NONE` for a
 widget that sets no mask. `move_applied` is how much of a widget's own
 move-slot delta its `region` already accounts for: `mov` shifts both,
 `Painter::reposition` shifts only the slot, and `resolved_region` -- and so
 every hit test -- has to subtract it. Without that a widget that had been
 panned had its *own* hit box at twice the pan while its descendants were
 correct, which made the composer's field untappable after a finger drag.
 ## 2026-09-06: `Scroll` pans on a finger drag, and a vertical drag in a focused text field no longer selects
 Three related public changes, all in aid of IRIS_TODO.md's "the composer
 has no touch-drag scroll".
 **`Scroll::drag(render, id, sense, pos_window, now)` is new**, and
 `WidgetLike::scrollable()` now registers it alongside the wheel handler it
 already registered -- so anything built with `.scrollable()` pans on a
 finger drag with no extra wiring at the call site. It goes through the same
 `sense::DragGesture` that `transcript-ui::Selection::drag` drives `List`
 with (arbitration, `DRAG_SLOP`, velocity, pointer capture), rather than a
 second copy of that widget's wiring: `DragGesture` owns the mechanics and
 each caller decides only what a committed pan *means*. `Scroll::amt()` is
 new too, the read-only pan position a test or a scroll indicator needs.
 There is deliberately **no fling** on `Scroll`. Unlike `List` it has no
 per-frame tick to animate one with (`List::set_redraw_handle`/`tick_fling`),
 and the areas it wraps today are at most a screenful, where Android does not
 fling either. The released velocity is dropped rather than approximated.
 **A vertical drag inside an already-focused `TextEdit` no longer extends a
 selection.** `iris::attr`'s `on_press` used to treat a focused field as the
 plain `click_or_drag` case -- every `Pressing` frame updated the selection.
 It now applies the same `DRAG_SLOP` rule the *unfocused* branch already
 applied: a press that moves past the slop vertically abandons its pending
 selection for the rest of the gesture, so the scroll area around the field
 gets the drag instead. Horizontal drag-to-select is unchanged, and a long
 press still starts a selection. This is Android's own `EditText` behaviour
 (a vertical drag scrolls; only a long press selects), and it is what makes
 "swipe up over the composer to scroll the transcript" work without dragging
 a highlight through the message you were typing.
 **`UiRenderState::orphaned_primitives()` is new**, and `update` now
 `debug_assert!`s (debug builds only) that nothing is orphaned. An orphan is
 a primitive still bound for the GPU that no live `ActiveData` names -- a
 copy nothing can move, clip or free. That was the doubled `Compacted:` row
 on the phone; see the same date's commit `76b1f99` and docs/RUST.md. The
 per-frame guard is a count comparison (O(active widgets)); the walk that
 names the offenders only runs when the counts disagree, because the walk is
 O(primitives) and made a debug build on a phone too slow to finish a
 benchmark run.
 ## 2026-09-06: a tap on a text field always leaves a caret
 `TextEditCtx::select` used to compare the tap position against the
 *laid-out text's* own box and set `selection = None` for anything outside
 it. A press only reaches `select` after being hit-tested to the widget, so
 that "outside" meant the field's own padding -- or, for an **empty** field,
 everything, since an empty layout is a zero-width box. So tapping an empty
 composer focused it and opened the keyboard while leaving no caret, and
 `TextEditCtx::insert`/`insert_str` return early with no caret: every
 keystroke was dropped in silence, and no glyph ever appeared. Parley's
 `from_point`/`extend_to_point` already clamp a point outside the layout to
 the nearest cursor position, which is also what a tap in a field's padding
 should do.
 Behaviour change a caller would notice, in one line: **`select` with a
 non-drag position now always produces a selection; it no longer clears
 one.** Clearing is `TextEditCtx::deselect`, which is what the backends'
 focus handling already calls. A drag is unchanged -- with no previous
 selection there is still nothing to extend, so it produces none.
 `insert_str` also gained a `debug_assert!` for the no-caret case, so an
 insert routed to an unfocused field fails at the mistake in a debug build
 instead of silently swallowing input.
 ## 2026-09-06: `List::anchor_position_display`## 2026-09-06: `List::anchor_position_display`, `FrameReport::mark_phase`/`phase_stats`/`late_at_hz` (RUST.md's "Benchmark v2")
 `List` gained `anchor_position_display(&self) -> String`, reporting the
 anchor's own row index and pixel offset (`idx=N/off=Mpx`, or
 `idx=more-before`/`idx=more-after`/`idx=none`) -- what a scripted
 benchmark reads to report fling travel. Note the anchor does not
 necessarily change *slot* over a long scroll (this widget's own documented
 design: the anchor is a stable identity, not re-derived from what's on
 screen each frame), so this is not the same measurement as a Compose
 `LazyListState.firstVisibleItemIndex`, which does track the true topmost
 visible row -- the `off` half is what actually reflects how far a fling
 travelled.
 `iris_core::render::frame_report::FrameReport` gained three methods for
 per-phase benchmark reporting: `mark_phase(name)` records a named phase
 boundary at the current frame/instant; `phase_stats(now, refresh_hz)`
 returns one `PhaseStats` (frames, wall duration, late count/percent,
 p50/p90/p99, worst) per marked phase, sliced from the existing ring by a
 new parallel `index_ring`; `late_at_hz(refresh_hz)` gives the whole run's
 late count/percent judged against an arbitrary refresh rate rather than
 the fixed 60Hz `JANK_THRESHOLD` every existing caller still uses (a
 separate method, not a parameter on `report()`, so nothing else changes
 behaviour). `RING_CAPACITY` grew 4096->16384 to hold a full multi-phase
 run without evicting earlier phases' samples.
 ## 2026-09-06: `List::fling`, `VelocityTracker`, `FlingCalculator` (IRIS_TODO.md's "swiping has no momentum")
 `iris::widget::List` gained a real fling: `fling(velocity_px_per_s)` starts
 one (cancelled by the next touch-down via `cancel_fling`, or automatically
 once it settles or reaches loaded content's start/end), `is_scrolling()`
 reports whether one is running, and `tick_fling(now: Instant) -> bool`
 advances it and returns whether it is still going -- a caller that owns a
 `RequestRedraw` handle can hand it to the list once via the new
 `set_redraw_handle`, after which `List` re-arms its own next frame while
 flinging with no further polling needed; a caller driving a scripted
 benchmark instead calls `tick_fling` itself in a loop, same as it already
 drives `scroll`.
 The physics is `iris::sense::FlingCalculator` + `VelocityTracker`
 (`sense.rs`, beside `DragArbiter`): a port of AOSP `SplineOverScroller`'s
 deceleration curve (the same one Compose's own `ScrollableDefaults.
 flingBehavior()` uses), cited at the definition, so a fling here travels
 the same distance a Compose `LazyColumn` would for the same initial
 velocity. `VelocityTracker` estimates that velocity from the drag's last
 ~100ms of samples rather than one frame's last delta. Unit-tested:
 velocity from known samples, fling distance/duration against the closed-
 form spline result (within 1%), cancel-on-touch, and the start/end clamp
 (a fling stops rather than scrolling into content that was never loaded).
 Before: a touch-drag panned exactly as far as the finger moved and stopped
 dead on release. After: releasing mid-drag continues scrolling and
 decelerates, matching the muscle memory every other Android scroll view
 already trained. `transcript_ui::selection::Selection::drag` wires this in
 -- a release only flings if the gesture had committed to panning
 (`DragArbiter::is_panning`, new), never a selection or an undecided tap.
 ## 2026-09-06: `UiRenderNode::new` returns `Result`, not `Self` (RUST.md's P0 box, phone-crash fix)
 `iris_core::UiRenderNode::new(device, queue, config)` now returns
 `Result<Self, String>` instead of `Self`. Why: it used to let a bind-group-
 layout validation failure reach wgpu's default error handler, which panics
 with no way for a caller to intervene -- exactly what aborted the P0 bench
 APK on Iris's phone with the crash report truncated to "wgpu error:
 Validation Error" and nothing else recoverable. It now runs its creation
 calls inside wgpu error scopes and returns the full error text (wgpu's own
 "Caused by" chain) as `Err` instead.
 Both callers changed to match: `android::render::AndroidRenderer::new`
 itself now returns `Result<Self, String>` too, building a fuller report
 (adapter identity, the limits/downlevel flags a layout validates against,
 then wgpu's text) on failure -- its caller,
 `android::view::IrisViewPeer::surface_changed`, logs that report as one
 logcat line and shows it on screen (a new `IrisView.showRendererError`,
 called via an ordinary JNI method call rather than a new `native fn`)
 instead of letting the process abort. `default::render::UiRenderer::new`
 (the winit/desktop backend) still panics on failure -- there is no
 on-screen fallback there -- but the panic message is now the same full
 text rather than whatever wgpu's own handler would have printed.
 No change for an app that never constructs a `UiRenderNode` directly (every
 current one goes through `AndroidRenderer`/`UiRenderer`), but anyone who
 does needs an `?`/`.expect()`/`match` at the call site now. Full audit and
 the named hypothesis for what actually failed on the phone are in
 RUST.md's P0 box, "iris bench crash on the phone, 2026-09-06."
 ## 2026-09-05: `AndroidAppState::platform_ready` (RUST.md's P0 box, iris half)
 Added a second, optional lifecycle method to `iris::android::AndroidAppState`
@@ -437,3 +882,188 @@ with a number instead of a guess (RUST.md's I5 box).
  blocked handing the frame to the driver," not a confirmed GPU-completion
  time. Enough to separate "iris is slow building the frame" from "iris is
  slow handing it off," not enough to claim an exact GPU budget.
 ## 2026-09-05: `List::replace_back`/`List::clear`, and `TranscriptScreen::apply`
 Fixes the "every client refolds and rebuilds the whole widget tree per
 streamed event" cost RUST.md's P0 box measured (20 events/second against a
 ~3,200-row transcript). Two small additions to `iris::widget::List`
 (`iris/src/widget/list.rs`), plus one new method on `transcript-ui`'s
 `TranscriptScreen`.
 - **`List::replace_back(row: ListRow) -> Option<ListRow>`**: swaps the
  *last* row's widget for a new one without moving it — same slot index,
  so an anchor already pinned there (in particular a list flush with its
  own end) stays pinned, and a `List` scrolled elsewhere is untouched.
  `None` if the list is empty. `RowKey` may differ between the old and new
  row; only `heights`/`extents` care, and both are invalidated for the
  evicted key the same way `pop_back` already does.
 - **`List::clear()`**: drops every loaded row and resets to `List::new`'s
  state (`more_before`/`more_after` untouched — a caller that wants those
  cleared too calls `set_more_before(None)`/`set_more_after(None)` itself).
  The fallback path for a change that touches more than the tail.
 - **`transcript_ui::TranscriptScreen::apply(&self, rsc, old: &[TranscriptItem], new: &[TranscriptItem])`**:
  the incremental alternative to rebuilding the whole screen from
  `transcript_ui::build_tree` on every folded event. Diffs the two
  `group_tool_runs` outputs and picks the cheapest update: nothing changed
  (no-op), a pure append (`push_row`, unchanged cost), or — the common
  streaming case, a delta into a still-open assistant message — a rebuild
  of just the one changed row via `List::replace_back`, with any further
  new rows appended after it. A row changing *before* the tail (only
  `group_tool_runs` retroactively grouping tool calls into a run does
  this) falls back to `List::clear` plus a full rebuild, counted in
  `TranscriptScreen::take_rebuilds()`. **A caller that keeps its own
  row-keyed side table alongside `List` (`Selection`'s `rows:
  BTreeMap<RowKey, WeakWidget<TextEdit>>` is the one this crate has) must
  clear it in step with `List::clear()`** — the fallback drops every row
  `List` was holding, so any side table not cleared the same way is left
  pointing at widgets the clear just freed (docs/REVIEW-2026-09-06.md
  finding 1, fixed 2026-09-06 by `Selection::clear()`, called from
  `apply`'s `Rebuild` arm right before `List::clear()`). `bench_client.rs`, `transcript_client.rs`
  and `desktop-app/app.rs` all call this now instead of rebuilding on every
  event; only the opening page (and `apply`'s own fallback) still calls
  `build_tree`.
 - **`TextEditCtx::set_with_spans(text, spans)`**: `set()` plus a fresh
  `Vec<SpanStyle>` in one call, needed because a streamed row's markdown
  re-renders to both a new string and a new span list on every delta and
  the two have to land together — a stale span list drawn against new
  text can point past its end. `set()` itself is unchanged (still clears
  spans to none, as before).
 Measured on this checkout's emulator (`iris/android-app/run-bench.sh`,
 release, x86_64, `force-gles`): worst-frame and p99 during the streaming
 phase dropped from 369.3ms/284.5ms (full rebuild per event, prior pass) to
 ~101–130ms/~76–103ms across three runs (this fix) — see RUST.md's P0 box
 for the full numbers and the comparison's caveats (different AVD
 instances, not a controlled A/B on identical hardware state).
 ## 2026-09-06: bundled fonts, `content_scale`, `AndroidAppState::on_insets_changed`
 From RUST.md's P0 box, working Iris's first real-phone report (font/scale/
 inset bugs the emulator never showed).
 - **`TextData` now bundles Noto Sans + Noto Sans Mono** (regular/bold/
  italic/bold-italic static faces, OFL) and registers them ahead of the
  platform's own fonts in the `SansSerif`/`Monospace` generic-family
  lists, rather than relying on the platform's font enumeration alone.
  `TextData::font_diagnostics() -> FontDiagnostics` reports what was found
  and what each style axis resolved to — logged once at startup and shown
  on a screen's Diagnostics page if it has one. Adds ~3.6 MB uncompressed
  to any binary linking `iris-core`; `build-apk.sh`'s own output says the
  delivered (compressed) number.
 - **`UiRenderNode::new`/`resize` now take the window size explicitly**
  (`window_size: impl Into<Vec2>`) instead of deriving it from the
  surface's physical `SurfaceConfiguration`. Existing callers pass a
  *logical* size (physical ÷ density/scale-factor) now; this is what makes
  a `font_size: 16.0` 16 dp instead of 16 raw device pixels on a
  high-density phone. Before this, `scale_factor` did not exist anywhere
  in the crate, on either platform.
 - **`AndroidUiState::content_scale: f32`** (`DisplayMetrics.density`, read
  once in `new_peer`) and the desktop equivalent (`window.scale_factor()`)
  now divide every physical-pixel number before it reaches layout or
  touch handling — see `content_scale`'s own field doc for the full list
  of what depends on it.
 - **New: `AndroidAppState::on_insets_changed(&mut self, rsc, LogicalInsets)`**,
  a default-no-op hook called from `render()` exactly when
  `AndroidUiState::insets()` changes. Nothing previously consumed
  `insets().top` at all; a screen with chrome under the status bar
  implements this to pad it, in the same logical units `content_scale`
  converts everything else to.
 - **New: `iris_core::WgpuErrorLog`**, installed via `Device::
  on_uncaptured_error` on the Android device (wgpu's default handler is an
  unconditional panic outside `UiRenderNode::new`'s own error scopes).
  Explicit `Arc`-backed value passed to the callback and kept on
  `AndroidRenderer`, not a global — a caller wanting one on desktop builds
  its own the same way.
 ## 2026-09-06: `Len::dp`, physical pixels throughout, the keyboard glyph wipe
 Iris's phone report on build a9232ac (screenshots): text now the right
 size but blurry; the keyboard still wipes every glyph; the header buttons
 have nothing behind them. All three are fixed; this entry is the public
 API side. docs/LAYOUT.md has the layout-side writeup, docs/RUST.md's P0
 box has the full investigation and the phone verification still to do.
 - **The keyboard wipe was `surface_changed` rebuilding the whole renderer
  on every resize**, including an IME-driven one — a fresh, empty glyph
  atlas while the CPU-side glyph cache kept UV coordinates from the old
  one. `surface_changed` now calls `AndroidRenderer::resize` (reconfigures
  the surface and window uniform only) when a renderer is already live,
  and only builds a new one when there genuinely isn't one yet.
 - **`Len` has a third field, `dp`** (Android's dp / CSS's reference pixel,
  1/160in), beside the existing `abs` (now explicitly *physical* pixels)
  and `rel`/`rest`. `len_fns::dp`/`Len::dp` construct one, used exactly
  like `abs`/`rel`/`rest` — `dp(16)` instead of a bare `16` wherever a
  size should look the same physical size on any density. This is the
  unit IRIS_TODO.md's "density-independent length unit" item asked for;
  it replaces the previous stopgap (the whole rendered scene divided by
  `content_scale` then implicitly stretched back up), which is also what
  made text blurry — a glyph rasterised at the small, pre-stretch size and
  then upscaled onto the real framebuffer.
 - **`UiRenderState`/`Painter` gained `density()`/`set_density()`** (physical
  pixels per dp). Every place a length resolves (`Len::apply_rest`,
  `Size::to_uivec2`) now takes it; `Span::gap` and `Padding`'s four sides
  moved from a bare `f32` to `Len` so they take `dp(...)` too. A bare
  number anywhere is unaffected — still `abs`, physical pixels.
 - **Text is rasterised at physical resolution now.** `TextBuffer::shape`
  takes `density` and multiplies `font_size`/`line_height` (and any span
  override) by it before handing them to parley, so the atlas holds a
  bitmap at the size it is actually shown at rather than a low-resolution
  one stretched afterward.
 - **Everything at the Android boundary is physical pixels now** — window
  size, touch coordinates, insets (`LogicalInsets` renamed
  `WindowInsets`). The previous "logical" division by `content_scale` is
  gone; `content_scale` now feeds `set_density` instead.
 - Not yet verified on Iris's actual phone (this pass had no device) —
  built and checked on this checkout's emulator only. RUST.md's P0 box
  says what she should check for: crisp text at two densities, the
  keyboard no longer wiping, and the header's background.
 ## 2026-09-06: composing text, focus-on-tap, and atlas invalidation on a new renderer
 Three small but public API changes, from the same phone-report pass as the
 entry above (RUST.md's P0 box has the full account, including a real bug
 still not root-caused).
 - **`FocusHost` gained `is_focused(&self, id) -> bool`** (both platform
  impls). `attr.rs`'s `Selector`/`Selectable` used to grant focus (and so
  request the IME) on the very first frame of *any* press, before it was
  known whether the gesture was a tap or a drag — a swipe over a text
  field wrongly summoned the keyboard. They now wait for a completed tap
  (press and release with no frame crossing `sense::DRAG_SLOP`) unless the
  field is already focused, in which case dragging inside it to select
  text is unchanged. `TextEdit` gained one new `pub(crate)` field
  (`press_origin`) to track this; no public surface change there.
 - **`android::ime`'s `InputConnection` now calls `InputMethodManager::
  updateSelection` after every edit** (`IrisViewPeer::update_ime_selection`,
  called from `after_input`). Gboard was holding keystrokes back because
  nothing ever told it where the app's own selection/composing region had
  moved to — this is what android-view's own demo does in its `render()`
  and this bridge never did.
 - **`GlyphAtlas::clear()` and `Textures::reset()`** (`iris_core`). Called
  together, once, from `android::view`'s `surface_changed` exactly when a
  *genuinely new* `AndroidRenderer` is built (backgrounding and returning,
  not a keyboard-triggered resize, which already reuses the renderer) —
  both CPU-side caches otherwise kept pointing at the old, now-destroyed
  device's textures, which is why text used to vanish again after leaving
  and returning to the app.
 ## 2026-09-06: `take_counters` counts text layouts too
 One public API change, from the verification pass over the composer-scroll
 and per-block-row work (RUST.md's "Verification pass over Tasks A and B").
 - **`UiRenderState::take_counters` returns four numbers, not three**:
  `(draws, region rewrites, move writes, **text shapes**)`. The new one is
  bumped in `Painter::render_text`, which `TextView::render` only reaches
  on a cache miss, so it counts layouts actually computed rather than
  layouts asked for. Callers destructuring the tuple need one more `_`.
  It exists because a draw counter cannot answer the question the
  per-block transcript row was built for. A widget can be redrawn without
  re-shaping (the layout is memoized by width) and re-shaped without any
  extra draw, and re-shaping is the expensive half — so "a streamed delta
  costs one block" was, until now, argued from the code rather than
  measured. With the counter it is a test: one delta into a 100-paragraph
  reply shapes exactly **1** text layout, the same as into a
  one-paragraph one.
@@ -117,6 +117,375 @@ order and what "done" looks like. Tick and date them in place.
  screen wants the same thing (P1's own transcript rows already read
  their content from a `TextEdit` for the same reason).
 ## From the phone, 2026-09-06
 Found on Iris's own phone while working RUST.md's P0 box's phone-report
 follow-ups. Recorded here rather than fixed in that pass, so a follow-up
 agent takes them without colliding with that pass's `bench_client.rs`/
 `android/view.rs`/`android/sense.rs` changes.
 - [x] **Swiping has no momentum, fixed 2026-09-06.** `List::fling`/
  `VelocityTracker`/`FlingCalculator` (`iris/src/widget/list.rs`,
  `iris/src/sense.rs`) -- IRIS.md's 2026-09-06 entry has the full account.
  Wired through `Selection::drag`'s release path, cancelled by the next
  touch-down, clamped at the loaded content's start/end. Verified by unit
  test (fling distance against the closed-form spline result, cancel-on-
  touch, the clamp), not yet by an on-device or emulator feel-check --
  that is still open.
 - [x] **Scrolling down sometimes jitters the text, fixed 2026-09-06.**
  Root-caused by reading `DragArbiter::update`'s `Undecided`-to-`Panning`
  transition rather than by an on-device trace (no emulator was used this
  pass): it was the first named suspect, not the second. `self.last` stays
  at the press origin for every `Undecided` frame (nothing pans while the
  gesture might still be a selection), so the frame that finally crosses
  `DRAG_SLOP` returned `Pan(dy)` with `dy` measured from `press_start` --
  the *whole* pre-threshold drag, applied to the list in one step, however
  many frames it had taken to get there. Fixed by applying only the
  excess past `DRAG_SLOP` on that one frame (`dy - DRAG_SLOP.copysign
  (dy)`), the same "consume the slop, don't replay it" rule Android's own
  touch handling follows. New regression test,
  `crossing_the_slop_by_a_little_pans_by_a_little` (`iris/src/sense.rs`).
  **Not yet done**: an emulator trace of the real per-frame offset
  confirming this was the whole story on real touch input rather than
  only the arbiter's own unit tests -- worth a follow-up pass before
  calling it fully closed.
 - [x] **Composing text held back until a space, caret not moving, fixed
  2026-09-06.** `InputMethodManager.updateSelection` was never called --
  see IRIS.md's 2026-09-06 entry and RUST.md's P0 box, item 1, for the
  full account and the emulator evidence.
 - [x] **Swipe over the composer summons the keyboard, fixed 2026-09-06.**
  `Selector`/`Selectable` now wait for a completed tap -- see IRIS.md's
  2026-09-06 entry and RUST.md's P0 box, item 5. Verified via `dumpsys
  input_method`'s `mInputShown` on the emulator, not yet on the phone.
 - [x] **Text disappears again after leaving and returning to the app,
  fixed 2026-09-06.** `GlyphAtlas::clear`/`Textures::reset` on a
  genuinely new renderer -- see IRIS.md's 2026-09-06 entry and RUST.md's
  P0 box, item 4. Verified on the emulator (home, reopen, screenshot);
  not yet on the phone.
 - [x] **Composed/typed text never becomes visible at all -- root-caused
  and fixed 2026-09-06.** Not the renderer at all: **the composer's buffer
  was empty the whole time.** `TextEditCtx::select` (`iris/src/widget/
  text/edit.rs`) compared the tap against the *laid-out text's* box and
  set `selection = None` for anything outside it -- and an empty field's
  layout is a zero-width box, so tapping an empty composer granted focus
  and opened the keyboard while leaving no caret; `insert_str` returns
  early with no caret, so every keystroke after that was dropped in
  silence. Gboard's suggestion strip is its own composing state, not a
  read of our buffer, which is what made the earlier pass conclude the
  buffer held the text. Fixed by letting parley clamp a tap outside the
  layout to the nearest cursor position (a press that reaches `select`
  has already been hit-tested to the widget, so there is no "outside"),
  plus a `debug_assert!` in `insert_str` so an insert with no caret fails
  at the mistake instead of dropping input -- it immediately caught
  `layout_tests::composing_text_after_a_keyboard_resize_...` typing into
  an unfocused field. Three new tests in `edit.rs`
  (`tapping_an_empty_field_places_a_caret_so_typing_lands`,
  `tapping_past_the_end_of_the_text_clamps_to_the_end`,
  `dragging_without_a_previous_selection_selects_nothing`); the first
  fails on the pre-fix code. Emulator evidence: `adb shell input text`
  after `tap 'Message'` now shows the text in the bar
  (`/tmp/final-typing.png`) and logs `iris text render: chars=5 ...
  glyphs=5`, against `glyphs=0` on every keystroke before.
  **The old, superseded diagnosis, kept because it was wrong in an
  instructive way:** The composer bar stays empty even once the
  buffer genuinely holds the typed text (confirmed indirectly: Gboard's
  own suggestion strip reacts correctly to each keystroke). A new unit
  test proves the widget tree's own layout math resolves the field's
  region correctly across a keyboard resize, so the bug is downstream of
  that -- most likely `UiRenderState::redraw`'s single-widget redraw path,
  or specific to this emulator's forced `force-gles` backend (untested on
  Vulkan or the real phone). RUST.md's P0 box, item 2, has the full
  writeup, what was ruled out, and where to look next. **Also unverified
  because of this**: item 3's composer rebuild (one `Stack`-based widget,
  a capped/scrollable height, bottom padding tied to the IME/nav-bar
  inset) -- structurally in place and unit-tested, but its own visual
  correctness cannot be screenshotted until text actually renders.
 - [x] **The composer has no touch-drag scroll for overflowing text.**
  **Done 2026-09-06.** `field.scrollable().masked()` in
  `transcript-ui/src/composer.rs`: a finger drag inside the bar pans the
  message, the bar stays capped at six lines, and a vertical drag in the
  focused field no longer extends a selection (Android `EditText`'s own
  behaviour). Verified on this checkout's emulator with the
  `transcript-screen bench force-gles` debug build -- six repetitions of a
  13-word sentence typed in, then
  `ui-trace record --do "swipe 540 1200 540 1460 300"`: the field's
  `Message` box moved `31,1041..1048,1509` -> `31,1131..1048,1651` (the
  content panned down with the finger) with its **height unchanged at
  468px** (the bar did not grow), and the two screenshots either side show
  different text in the same band.
  Three real defects had to be fixed first, each with a headless
  regression test in `iris/src/layout_tests.rs` and each confirmed to fail
  without its fix (docs/RUST.md's plan box has the measurements):
  a `MaxSize` reporting its cap as an unresolved `dp` (`Len::fold_dp`), a
  `Masked` allocating a fresh mask slot per draw (`ActiveData::own_mask`),
  and a panned widget's own hit box moving twice (`move_applied`).
  `Scroll` itself turned out to measure the right number by a misleading
  route -- it is written against `painter.px_size()` now, and the claim
  below that it "measures against the window" was wrong.
  **The grey background was not missing** -- that note (written here on
  2026-09-06 and repeated as still open) is withdrawn. Re-measured the
  same day on the same AVD by decoding the screencap rather than reading
  it: the bar is `rgb(41,40,49)`, the declared `UiColor::new(40, 40, 46)`
  after sRGB rounding, **full width and y2245..y2365** on 1080x2424, with
  the field at `31,2277..1048,2329` and the 63px nav strip below it. It
  is dark by design and sits on black, which is very likely what the
  earlier reading was: at a glance the band and the background are hard
  to tell apart. If it should read as a bar rather than as a slightly
  different black, the colour is the thing to change, not the tree.
 ## From the phone, 2026-09-06, 11:39 (build delivered 02:07, commit 543f6d9)
 Iris's report on the build with the composing-text, tap-vs-swipe and
 atlas-reset fixes, with a screenshot, verbatim. Each is open until an
 agent ticks it here with the evidence.
 - [x] **"The app definitely does not start with keyboard spacing
  correct. This is how it looks without me doing anything initially."**
  **Not an inset bug at all -- fixed 2026-09-06.** The black third is the
  bench shell's own empty *benchmark report* pane: `bench_client.rs`'s
  root tree gave it `.height(rest(1))` beside `content.height(rest(2))`,
  so an empty `TextEdit` reserved a third of the window at every launch
  and pushed the composer up by exactly that. Measured on this checkout's
  emulator at the phone's own size (1080x2424, density 420, gesture nav),
  which reproduced Iris's screenshot exactly: new `iris insets:` log line
  reported `bottom=63 ime_bottom=0` at launch (a nav bar, no keyboard --
  so the inset the composer was fed was never large), while `ui-trace
  show -m Message --field box` put the field at `31,1488..1048,1540` on a
  2282px-tall surface, 789px clear of the bottom -- that pane's third.
  **Unit mixing checked explicitly and cleared**: `set_bottom_inset` takes
  physical px and stores `Len::abs`, `MainActivity.java`'s `1`/`0`
  `ime_bottom` only ever reaches `insets.bottom.max(ime_bottom)` and
  `> 0.0`, and every `dp` in the composer resolves at layout time. Fix:
  the report pane is sized to its content (`.max_height(dp(260))
  .scrollable()`), and moved above the transcript so it cannot eat the
  composer's nav-bar clearance. After: field box `31,2277..1048,2329`,
  grey bar ending at device y2361 with the 63px nav strip below it
  (`/tmp/fix1.png` this pass).
  The screenshot shows the composer bar (the grey band) sitting about
  two thirds of the way down a 704x1568 screen, with black below it to
  the bottom, and the transcript ending at "Claude / Results" just above
  it -- at launch, no keyboard. So the composer's bottom padding, which
  the 2026-09-06 rebuild tied to the IME/nav-bar inset, is being fed a
  large value at start on the phone. Suspects, in order: the initial
  inset delivery on the phone (GrapheneOS, gesture navigation) versus
  the emulator; `ime_bottom` now carrying a `1`/`0` boolean through a
  field the composer may still read as pixels or dp; a stale value from
  before the first `on_insets_changed`. Reproduce with the phone's
  screen size and density on the emulator before guessing.
 - [~] **"Swiping still gets caught by the grey bar but keeps working
  after I go past it."** Improved 2026-09-06 by the focused-field rule
  below, still needs her phone to close. `attr.rs`'s `on_press` treated an
  already-focused composer as the plain drag-to-select case, so a swipe
  starting inside it dragged a highlight through the typed text for the
  whole gesture; it now abandons that the moment the press passes
  `DRAG_SLOP` vertically (Android `EditText`'s own rule), which removes one
  of the two things that made the bar feel like it caught the swipe. The
  residual `DRAG_SLOP` measured from the boundary crossing, described
  below, is unchanged. Original note follows.
  Not closeable from the emulator, annotated
  2026-09-06 after the `DragGesture` merge. `attr.rs`'s `on_press` never
  calls `capture_pointer` and never consumes a `Pressing` frame past
  `DRAG_SLOP` (it just stops watching), so once the finger's *current*
  position leaves the composer's box and enters the list's, `List`
  starts receiving ordinary hit-tested `Pressing` frames there --
  `DragArbiter::is_idle()`'s 2026-09-05 recovery (a missed `PressStart`)
  picks it up rather than leaving it stuck. What this does **not** do is
  what "wherever it began" implies literally: `DragArbiter::press_start`
  restarts from the *boundary-crossing* position, not from the original
  touch-down inside the composer, so the pan still needs a fresh
  `DRAG_SLOP` of travel measured from the boundary rather than from the
  start of the gesture -- composer and list are adjacent, non-overlapping
  widgets (`lib.rs`'s `(list, composer_bar).span(Dir::DOWN)`), and only
  the composer forwarding its own drag to the list would remove that
  residual slop entirely, which is more than this pass's merge changes.
  RUST.md's merge-pass box has the reasoning in full and an emulator
  swipe confirming the composer's own box never moves/resizes during it;
  whether the residual slop is still perceptible as "caught" needs Iris's
  phone, since the emulator's per-widget boundary is a few dp wide and
  easy to cross without noticing on a real screen too.
 - [ ] **"Flinging still does not work."** No longer expected to reproduce
  after the `DragGesture` merge (`e12c708`, pointer capture +
  `CursorSense::Drop`), 2026-09-06. Emulator evidence (RUST.md's
  merge-pass box, check (b)): a real `ui-trace` finger swipe followed by
  screenshot-hash sampling caught a post-release frame distinct from the
  drag's own last frame in one run, and every run showed 28-32
  `render()` frames per gesture against an idle baseline of 0 and ~8
  expected from the drag alone -- redraw kept being requested well past
  the finger lifting, which only happens while a fling is still
  animating. Left unticked in spirit until Iris's phone confirms it,
  since only she can say whether it *feels* like a fling now; the
  emulator's screenshot timing could not always catch the tail of a
  fast-settling one visually (same caveat noted in RUST.md).
 - [~] **"Text still disappears if I leave and come back to the app."**
  **Instrumented 2026-09-06 so the phone can answer it**, since no
  emulator here has a Vulkan adapter. `iris/src/android/view.rs` now logs
  one `log::info!` line per surface event with the glyph/atlas counts:
  `iris surface: surface_destroyed, tearing the renderer down
  (glyphs_cached=387 atlas_pages=1)`, `iris surface: surface_changed
  1080x2424 already_live=false glyphs_cached=387 atlas_pages=1`, `iris
  surface: new renderer built (Gl), clearing glyph atlas: glyphs=387
  pages=1`, plus `iris insets: ... window=(1080, 2424)` on every insets
  change. That is the emulator's own healthy app-switch cycle, verified
  this pass (home, reopen, screenshot: all text intact,
  `/tmp/appswitch.png`). **The one line to look for on the phone is
  `already_live=`**: `true` on the return from backgrounding would mean
  the surface came back *without* a `surface_destroyed`, so
  `surface_changed` reconfigured a renderer whose Vulkan swapchain and
  atlas textures belong to a window that is gone -- the reuse branch
  never clears the atlas, by design. `false` with no `new renderer built`
  line after it would mean the renderer failed to rebuild. Either answer
  names the fix; guessing between them from here does not.
  The `GlyphAtlas::clear`/`Textures::reset` fix was verified on the
  emulator under `force-gles` only; the phone runs Vulkan. So either the
  reset is not reached on the phone's path (a different surface-
  lifecycle sequence -- `surface_destroyed`/`surface_created` ordering,
  or the renderer not being rebuilt but its textures lost), or the CPU
  glyph cache and the GPU atlas still disagree after it. Needs logging
  of the renderer lifecycle on the phone build, readable from `adb
  logcat` when Iris next runs it, since no emulator here has a Vulkan
  adapter under host GPU.
 ## From the phone, 2026-09-06, 22:16 (build from 20303e0, delivered via ai-app-bench 95e25fe)
 Iris's report, verbatim, with a screenshot. Phone: Mali-G715 (Vulkan),
 `content_scale: 2.55`, 120Hz. Open until ticked with phone-side evidence.
 - [ ] **"Fling still doesn't work."** -> on `ed04d4c`, 2026-09-07:
  *"flinging now does technically do something, but it seems to just be
  linear velocity with an abrupt stop."* **It was exactly that, and the
  arithmetic said so.** `distance_fraction(t)` returned `t` for every `t`
  -- a constant-speed slide for the whole duration, then a stop at full
  distance -- because two halves of AOSP's spline build loop were
  transposed, which made `SPLINE_POSITION` and `SPLINE_TIME` identical, and
  the lookup bracketed `t` between `SPLINE_TIME` entries rather than
  between even time steps. The two cancelled to the identity. Ported
  exactly now from `OverScroller.java` and
  `androidx.compose.animation:animation:1.12.0`'s `SplineBasedDecay.kt`
  (they agree line for line), with `iris/benches/fling_spline_reference.py`
  as an independent transcription supplying the numbers the tests assert
  on. Emulator, 2026-09-07: a released `v=3750` decelerates
  `3746 -> 2624 -> 1834 -> 1144 -> 752 -> 449 -> 243 -> 83px/s` across 32
  frames; a flick into the end of the list stops there in one tick with no
  overshoot; a tap 200ms into a fling ends it at 11 ticks instead of 32.
  **Open until the phone says so** -- a flick should now visibly slow
  before it stops. Its earlier three defects (the velocity, the missing
  animation registration, the 56x coefficient) are all still fixed and were
  never the linear part.* Second report; the emulator's
  `ui-trace` swipe flings (verified 2026-09-06 with `render()` counts),
  a finger on the phone does not. What differs: a real flick at 120Hz is
  batched by Android into few `MotionEvent`s with *historical* samples
  (`getHistoricalX/Y/EventTime`), and can be DOWN, one or two MOVEs, UP
  inside `DRAG_SLOP`'s worth of frames; a `ui-trace` swipe is many
  evenly-spaced MOVEs. Suspects, in order: `android/sense.rs` reading
  only each event's final position (the velocity tracker sees two
  samples, or one); the release path starting a fling only from a
  gesture already in `Panning`, so a flick that crosses the slop on its
  last sample is treated as a tap; `ACTION_CANCEL`/pointer-capture
  delivering no `Drop`. Log the release decision (samples, span,
  velocity, outcome) at `info` so the next logcat settles it.
 - [x] **"I can't reopen keyboard by tapping on message box after it
  already happened once."** *(Fixed 2026-09-07: `attr.rs`'s already-
  focused branch calls `focus_gained` on a tap inside `DRAG_SLOP`.
  Emulator: first tap `mInputShown=true`, back gesture, second tap
  `mInputShown=true`. Negative control with that one call removed leaves
  the second tap at `false`; a horizontal and a vertical swipe over the
  focused field both leave it at `false`, so the earlier "swiping over
  the input bar brings up the keyboard" has not returned.)* The field stays focused after the keyboard
  is dismissed (back gesture, or the IME's own hide), so `on_press`'s
  already-focused branch never requests the IME again. Android's
  `EditText` shows the IME on every tap of a focused field; do the same
  (`FocusHost`: a tap on a focused field requests the IME, idempotent
  when it is already shown).
 - [ ] **"Message box does not push up the scroll area."**
  **Reopened by the phone on 2026-09-07** -- *"similarly, the keyboard
  raising up does not push things upwards"* -- after being ticked on
  emulator evidence the day before (`ime_bottom=883`, composer box
  `31,2277..1048,2329` -> `31,1457..1048,1509`). The JNI half was right;
  what was wrong is one line of `iris/android-app/app/build.gradle`:
  **`targetSdk = 34`** against `compileSdk = 37`, while the Compose app in
  `app/` targets 37 and *does* push up on her phone. Below target 35 the
  window keeps the legacy behaviour, where `adjustResize` shrinks it for
  the IME and `getInsets(ime()).bottom` therefore measures zero;
  `setDecorFitsSystemWindows(false)` opts out of that and still takes on
  the API 36 emulator here, which is why every test run passed. Now
  `targetSdk = 37`, plus a `WindowInsetsAnimation.Callback` for the devices
  where only the animation path carries the height -- which also makes the
  push-up animate (`ime_bottom=509, 663, 833, 881, 883` instead of one
  jump). **This is a reading, not a measurement**: no Android 17 device is
  reachable from here. So the Diagnostics pane now prints
  `insets: dispatches=N left=… ime_bottom=… ime_visible=…` --
  **screenshot that line with the keyboard open.** `ime_bottom` in the
  hundreds and the composer risen means fixed; `dispatches` climbing with
  `ime_bottom=0` means the reading was wrong and the window is still being
  resized; `dispatches=0` means the listener is not firing at all, which is
  a third thing again.* Since
  `MainActivity` went edge-to-edge (`e12c708`), `adjustResize` no
  longer resizes the window, so the app owns the IME inset -- but
  `ime_bottom` is passed through JNI as the boolean `1`/`0` (the
  2026-09-06 "(b)" fix), so nothing has the inset's *height* to pad the
  transcript and composer with. Pass both: `isVisible(ime())` and
  `getInsets(ime()).bottom` in px; the list's bottom padding and the
  composer's position follow the height, the visibility drives the
  boolean the `imePadding` rule in AGENTS.md's "Things that have bitten"
  describes.
 - [x] **"Picture is what happens if I leave the app and come back,
  which completely removes text, and then I tap on the debug info. The
  textures are definitely getting cooked for some reason after leaving
  the app and resuming."** Screenshot: every glyph drawn *before* the
  resume is fragments; the diagnostics text drawn *after* is perfect;
  the report says `atlas format: Rgba8Unorm, views live: 0`. Reading:
  `Textures::reset`/`GlyphAtlas::clear` on the new renderer emptied the
  GPU atlas, but the per-widget cached text primitives (`TextView`'s
  render cache -- the one `c3cfc67`'s shape counter is keyed on) still
  carry the old atlas coordinates and are re-submitted as-is; only
  widgets drawn fresh after the resume shape and upload again. Fix: a
  renderer rebuild invalidates every cached text render (one
  generation counter on the atlas, checked at `TextView::render`, or
  a full-tree redraw with caches dropped), with a `debug_assert!` that
  no submitted glyph quad references an atlas generation older than the
  live one. Reproducible on the emulator by forcing a renderer rebuild
  (home + return, or `surface_destroyed`/`surface_created`) on a screen
  with text already drawn -- the earlier "verified" home/reopen check
  screenshotted the emulator's GLES path, where a resume may not
  destroy the surface at all.
  **Fixed in `ba2afba` and confirmed on the phone (Iris, 2026-09-07:
  "the resume glyph corruption is fixed").** Closed. The emulator could
  never have settled it -- no Vulkan adapter here, and the GLES path may
  not destroy the surface at all -- so the phone was the only place this
  could be answered, and it has been. `clearing_the_atlas_re_renders_
  cached_text_instead_of_reusing_it` is what keeps it.
  The reading above is right and the mechanism is one step narrower than
  "cached text primitives". `IrisViewPeer::surface_changed`
  (`iris/src/android/view.rs`) *does* already force a full-tree redraw
  after a rebuild: it calls `render.resize(...)` unconditionally, which
  sets `UiRenderState::resized`, which makes the next `update` take
  `redraw_all` rather than `redraw_updates`. So every widget's `draw`
  really does run again after the resume. What survives it is one cache
  further in: `TextView::render` (`iris/src/widget/text/mod.rs`) returns
  its cached `RenderedText` whenever the wrap width, buffer and attrs are
  unchanged -- true of every pre-resume row -- so `TextData::place` is
  never reached, nothing is re-rasterised into the fresh atlas, and the
  *old* atlas's `uv_min`/`uv_max`/`layer` are re-submitted verbatim. Only
  text whose content changed after the resume (the diagnostics pane Iris
  tapped) re-shapes, which is exactly the split in her screenshot.
  `Painter::glyphs` has one call site in the whole workspace, that one,
  so there is no second holder of a `RenderedText` to fix.
  The fix, in `ba2afba`: `GlyphAtlas::generation`, bumped by
  `GlyphAtlas::clear`; `RenderedText::generation` recording which atlas
  its glyphs were placed against; `Painter::atlas_generation()`;
  `TextView::render`'s cache key gains it; and a `debug_assert_eq!` in
  `Painter::glyphs` that a submitted quad's generation is the live one.
  Headless test
  `clearing_the_atlas_re_renders_cached_text_instead_of_reusing_it`
  (`iris/src/widget/text/mod.rs`): draw, `atlas.clear()`, `resize`, draw
  again, and assert the atlas holds the same glyph count again -- it
  stays at 0 without the fix, because the cache short-circuits before
  `place`.
 ## Build
 - [x] **Benchmarks**, not unit tests, run on demand (2026-09-05; a
@@ -306,22 +675,31 @@ order and what "done" looks like. Tick and date them in place.
    `row.rs`'s `build_text_row` is where one would go, keyed to something
    stable per row (its sender + a short excerpt, matching what a screen
    reader announcing a chat message would say).
-  - [ ] **A tappable link and a background chip behind inline code.**
+  - [x] **A tappable link** — done 2026-09-06 (P1a). `TextEditCtx::
-    Both need per-range glyph geometry that `TextEditCtx` does not expose
+    byte_at(pos, size)` answers which byte a tap landed on without
-    outside `iris::widget::text` (`edit.rs`'s `layout()` helper is
+    handing out the parley layout, `GestureOutcome::Tapped` says the
-    private) — see `markdown.rs`'s module doc for the exact shape the fix
+    press committed to neither a pan nor a selection, and
-    would take (the same primitive `TextEdit::draw`'s own selection
+    `iris::platform::OpenUrl` is the capability each backend implements
-    highlight already uses internally,
+    (`xdg-open`/`open`/`start`; an `ACTION_VIEW` intent on Android,
-    `iris/src/widget/text/edit.rs:99`).
+    deferred to `after_input` the way `pending_show_keyboard` is).
  - [ ] **A background chip behind inline code.** Still needs per-range
    glyph *geometry* — a run's boxes, not one offset — which
    `TextEditCtx` does not expose outside `iris::widget::text`
    (`edit.rs`'s `layout()` helper is private). The same primitive
    `TextEdit::draw`'s own selection highlight uses internally,
    `iris/src/widget/text/edit.rs:99`. `byte_at` above deliberately did
    not open that up: a tap needs one offset and a chip needs the run.
  - [ ] **`Selection`'s anchor-row shortcut.** The row a drag started in
    is selected in full (`select_all`) the moment the drag leaves it,
    rather than "from the click point to whichever edge points away from
    the drag" — needs the same private `layout()` access as the item
    above. `selection.rs`'s module doc has the exact reasoning.
-  - [ ] **No syntax highlighting inside a fenced code block.**
+  - [x] **Syntax highlighting inside a fenced code block** — done
-    `client_core::highlight` exists (built for the file explorer) and
+    2026-09-06 (P1a). `client_core::highlight::spans_of` by language,
-    could feed per-token `SpanStyle`s into a code block's span; wiring it
+    converted from its char indices to `SpanStyle`'s byte offsets, in
-    in was not attempted this pass.
+    the same Catppuccin palette `Theme.kt` uses. A language the scanner
    has no rules for stays plain rather than being coloured by the
    nearest one's.
 - [ ] **Masks defined relative to each other.** Wanted: mask A multiplies
  by something *and also* applies mask B — a mask can reference a parent
@@ -341,6 +719,109 @@ order and what "done" looks like. Tick and date them in place.
  everything, the same way input is**. Whatever the mechanism, a widget
  that does not animate must pay nothing and import nothing for it.
 ## Found by P1a (2026-09-06)
 - [x] **`Rect` claimed to be size-independent, and it is not.** A `Rect`
  fills whatever region it is handed, so `draw_inner`'s size-independent
  fast path -- which rewrites primitives with
  `r.outside(&from).within(&region)` rather than redrawing -- could not
  reproduce its `draw`, and a `.background(rect(..))` kept the size of
  the *provisional* full-region pass `Span` does in phase 1. One fenced
  code block's panel covered every block below it and every row below
  that. Fixed in `iris/src/widget/rect.rs`; the reason is written at the
  definition. Suspect the same cause for anything else tinted with a
  background rect.
 - [x] **A wrapped transcript row tripped `reposition`'s debug assert.**
  Settled 2026-09-06 by giving the move slot one owner instead of two.
  `mov` accumulates a delta on it, `reposition` overwrote it, and both
  legitimately land on one widget in one frame: `List::place`'s
  Bottom-known branch offers a row a same-size box that has *moved*
  (`mov`), then corrects the placement inside it when the row's cached
  height no longer matches what the row reports (`reposition`). The
  slot now always means `move_applied + repositioned`
  (`ActiveData::repositioned`, `iris/core/src/ui/render_state.rs`), so
  `reposition` adds the move rather than dropping it -- the assert is
  gone and the arithmetic is right. Test:
  `a_widget_moved_by_its_parent_and_then_placed_inside_it_lands_at_the_placement`
  in `layout_tests.rs`, which lands the child at the *offered* position
  (-100px) instead of the placement (100px) without the fix, and a
  `debug_assert_eq!` in `reposition` that nothing but those two ever
  writes the slot. Verified with the `.wrap(true)` repro (draws, no
  panic) and an emulator bench run with assertions live.
 - [ ] **Desktop colours are washed out: the winit surface is sRGB and
  the shader writes the palette's bytes as linear.** Mocha Crust
  (17,17,27) is drawn as (73,73,91), measured off
  `run-headless.sh --shot`. Android is correct, so this is the surface
  format rather than the palette -- but it makes the desktop build
  useless as a colour reference, which is exactly what P1a needed it for
  when the emulator could not draw glyphs.
 - [x] **Every glyph was a solid box on the GLES backend -- iris's bug,
  not the emulator's.** Fixed 2026-09-06. The atlas is one
  `texture_2d_array` and `GpuTextures::new` created it with **one
  layer**; wgpu-hal picks the GL target from the descriptor
  (`(false, 1) => TEXTURE_2D`), so under GLES that array was a
  `GL_TEXTURE_2D` bound to the shader's `sampler2DArray`, the unit was
  incomplete, every `textureSample` returned (0,0,0,1), and
  `draw_glyph`'s `color.a *= texel.a` filled the quad. `MIN_ARRAY_LAYERS
  = 2` in `iris/core/src/render/texture.rs`, with a `debug_assert!` at
  `create_array_texture`. Vulkan (the phone, the desktop's default
  backend) was never affected. Reproduce the class in seconds without an
  emulator: `iris`'s `force-gles` feature now switches the **desktop**
  backend too -- `./run-headless.sh transcript --shot /tmp/x.png -- -p
  transcript-ui --features iris/force-gles`.
 - [ ] **The bench report pane draws over the transcript rows instead of
  replacing them.** Visible on the emulator for the first time now that
  glyphs render there (`/tmp/emu-final.png`, 2026-09-06): after a bench
  run the report's lines and the transcript's occupy the same rows in the
  top third of the screen, both legible, neither on top. Pre-existing --
  the same overlap is in a screenshot taken before the move-slot fix -- so
  it is its own item, most likely the report pane not masking or not
  claiming its region.
 ## Found by P1b (2026-09-06), all with a headless repro
 Each was found by looking at `iris/run-headless.sh transcript -- -p
 transcript-ui` rather than at a diff, and each is worked around in
 `transcript-ui/src/tool.rs` rather than fixed here. docs/RUST.md's P1b box
 has the fuller account.
 - [ ] **A `Span` of `Pad`ded children inside another `Span` places those
  children a slot out of step.** Each child drew its content one sibling's
  height below its own box. Repro: `IRIS_TOOLS_EXPANDED=1
  iris/run-headless.sh transcript --shot /tmp/x.png -- -p transcript-ui`
  with `tool.rs`'s group built as `Span(DOWN)[header, Pad(Span(DOWN)
  [cards]), bar]` instead of the single `Span` it uses now. Bisected:
  removing the inner `Span` fixes it, and so does removing the children's
  own `Pad`; the background `Stack`, the `Sized` wrappers and the
  `WidgetPtr` per child make no difference. **Not** the `mov`-vs-
  `reposition` fault f5b8893 fixed -- it survives that commit. The
  workaround costs the group the 4dp inset its Compose counterpart holds
  its cards off the edge by, so this is worth fixing.
 - [ ] **`scrollable_on(Axis::X)` on a non-editable `Text` draws nothing.**
  The panel is drawn and the text inside it is not. A markdown fence does
  the same to a `TextEdit` and is fine, so it is the widget kind rather
  than the chain. `tool.rs`'s `raw_block` is `masked()` only until this is
  fixed, which means a long command is clipped rather than pannable.
 - [ ] **No overflow ellipsis.** `TextAttrs` can wrap or not wrap; there is
  no "one line, ellipsised" the way `maxLines = 1` + `TextOverflow.
  Ellipsis` gives Compose. A tool card's summary is clipped instead, so
  nothing on screen says it was cut. Whichever end is cut has to be a
  choice when this lands: a path is identified by its tail, a command by
  its head.
 - [ ] **A drawn chevron.** `Chevron.kt` draws its own strokes precisely
  because a chevron from a font is a glyph a system font may not have --
  and the bundled `NotoSans-Regular.ttf` indeed has no U+25B8/25BE/25B4,
  while `NotoSansMono-Regular.ttf` does. `tool.rs` sets the mark in the
  monospace face as a result. A real fix needs a line/path primitive;
  iris has rects, text and textures only.
 - [ ] **A tool card's text is not selectable.** `Selection` is keyed
  `(RowKey, block index)` and a card has no markdown blocks, so nothing in
  a card registers. Compose's `SelectionContainer` covers tool output,
  which is the text people most want to copy. Needs a key for "the nth
  text of this row" that a card can mint without colliding with a
  message's blocks.
 ## Build (for the port)
 Widgets `RUST.md`'s "The port, in order (decided 2026-09-05)" needs and
@@ -385,3 +866,92 @@ do not duplicate it there.
  redundant. Decide after the layout change lands, by writing a button
  both ways and keeping the one that is shorter to explain; delete the
  other rather than keeping two ways.
 ## Build (asked for by Iris, 2026-09-06): a density-independent length unit
 - [x] **A third length kind beside relative and pixels, so display scales
  "just work".** Done 2026-09-06 — `Len::dp`/`len_fns::dp`, resolved
  against `UiRenderState`/`Painter::density()` at `apply_rest` time; text
  additionally rasterises at the resolved (physical) size instead of
  scaling a low-resolution bitmap afterward, which was making text blurry.
  `Span::gap`/`Padding` moved from `f32` to `Len` so they take `dp(...)`
  too; transcript-ui's row/composer padding and one example migrated.
  `em` was not added — nothing in this pass needed a text-relative unit,
  and `dp`'s own doc says why it and physical pixels are kept as separate
  fields rather than one the caller pre-multiplies. Not yet verified on
  Iris's own phone at two densities (this pass had no device) — see
  docs/RUST.md's P0 box and docs/IRIS.md's 2026-09-06 entry for what to
  check. Iris's words: "another length type similar to absolute &
  relative, so instead there would be relative, pixels, and another unit
  like em or whatever is standard. That way different display scales
  should just work." Today a length is either a fraction of the parent
  (`rest`/relative) or physical pixels, and the phone drew 16 px text at
  roughly a third of its intended size until the P0 fixes applied the
  display's scale factor globally. That global scale is a stopgap for the
  benchmark; the real shape is a unit resolved against the display's
  density at layout time — Android's `dp` / CSS's reference pixel is the
  standard (1 unit = 1/160 in), with `em` as the text-relative option —
  so a widget author writes `16.dp()` once and never sees the scale.
  Done when: `Length` (or whatever the enum is called) has the third
  variant; every place that resolves a length takes the density; the
  examples and `transcript-ui` use the new unit for text sizes, padding
  and control sizes; the emulator at two densities and the phone draw the
  same layout at the same physical size. After the bench setup is
  finished, before P1 draws any new screen.
 ## From the phone, bench v2 (2026-09-06): streaming re-lays out the whole message
 - [x] **Streaming a delta into a long message costs a full text layout of
  that message.** **Done 2026-09-06** -- a row is a column of one
  `TextEdit` per markdown block (`client_core::markdown_blocks`,
  `row::RowBlocks::apply_delta`), so a delta re-shapes the last block and
  keeps every earlier block's layout. A block is the selection unit now
  (`Selection`'s `SelKey`); selection across blocks and rows still works,
  checked on the emulator with a real long-press drag. Pass condition met
  in `a_delta_into_a_long_reply_redraws_the_same_widgets_as_a_short_one`:
  a delta into a 100-paragraph reply redraws the same widget count as one
  into a one-paragraph reply (30 either way). Emulator stream phase, same
  AVD before and after: **p50 61.5 -> 54.5ms, p90 211.7 -> 113.1ms, p99
  342.6 -> 137.4ms, worst 403.6 -> 143.0ms**, 202 -> 293 frames in the same
  21 seconds. docs/RUST.md's Task B box has the detail and the two dead
  ends. **The phone is the measurement that decides it** -- these are
  emulator numbers and only the ratio transfers.
  The original entry, for the record: Iris's phone report (`docs/bench/iris-phone-v2-2026-09-06.md`):
  the stream phase is the one place iris is behind Compose (p50 18.2 ms vs
  13.4 ms; p99 level at ~43 ms). `TranscriptScreen::apply` replaces only
  the last row, but that row is the growing message, and replacing it
  re-renders its markdown and re-shapes the entire paragraph run through
  parley on every event. Compose pays a reparse (8.6 ms mean) for the
  same event. What "done" looks like: a streamed delta re-lays out only
  the block it lands in (the last paragraph or code block), with earlier
  blocks' layouts kept -- which needs a row to be a column of per-block
  `Text`s rather than one `TextEdit` for the whole message, or parley's
  layout to be split at block boundaries; measured by the stream phase's
  p50 dropping below Compose's on the phone. Do this after the four bench
  v2 defects (stale primitives, finger fling, decay curve, IME show) are
  closed, since they are what make the run unrepresentative today.
 ## From the phone, 2026-09-07 (build from ed04d4c)
 - [ ] **"Some transcript blocks will be hidden until I uncover enough of
  them."** Two screenshots of the bench app's transcript at the top
  edge, both wrong in opposite directions: in one, rows scrolled above
  the viewport are still drawn and bleed *through* the header bar
  (`version = "0.1.0"` and a paragraph visible behind "Run benchmark /
  Copy report / Diagnostics"), so the list's mask is not clipping at
  the header's bottom edge; in the other, scrolled a little further,
  the row that straddles the top edge is not drawn at all -- black from
  the header down to "You", where the previous shot showed a paragraph
  -- so a row is culled as soon as its *top* leaves the viewport rather
  than when its *bottom* does. Suspects: the list's visible-range test
  (`iris/src/widget/list.rs`) comparing a row's top against the
  viewport top; the mask region for the transcript set from the
  window rather than from the area under the header; and the two-phase
  provisional/real draw noted in `03c6be8`'s header-duplicate
  investigation, which was never root-caused and has the same shape.
  Reproduce at layer 1 of the test rig: a headless screen with a row
  straddling the top edge must place that row, and a primitive above
  the header's bottom must be masked. Fix both with one rule: a row is
  drawn if any part of it intersects the viewport, and the viewport is
  the list's own region.
@@ -861,6 +861,58 @@ unspecified rather than getting them wrong:
  conditions, so the remaining slack was accepted rather than chased
  further.
 ## Density: `Len::dp`, resolved at `apply_rest` time (2026-09-06)
 Iris asked for a third length kind beside `abs` (physical pixels) and
 `rel`/`rest` (a fraction of the parent) — IRIS_TODO.md's "density-
 independent length unit" — after the P0 phone pass found 16px text
 drawing at roughly a third size on a real phone. The fix that shipped
 first (RUST.md's P0 box) was a global stopgap: divide the whole window
 into a "logical" coordinate space (physical ÷ `content_scale`) and let
 the shader's NDC mapping stretch it back up onto the real framebuffer.
 That fixed the *size* but not the *sharpness* — a glyph rasterised at the
 small, pre-stretch size and then stretched onto more physical pixels than
 it has texels for is blurry, which is exactly what Iris's next report
 said.
 **The fix**: `Len` gained a `dp` field, resolved against a `density: f32`
 (physical pixels per dp) at the one place a `Len` becomes a `UiScalar`
 (`Len::apply_rest`) — `abs + dp * density`. `density` lives on
 `UiRenderState` (`set_density`/`density()`) and `Painter` (`density()`),
 set once from `DisplayMetrics.density` in `android::view::new_peer`; the
 desktop backend has no per-monitor density wired up yet and stays at
 `1.0`. Every layout call site that used to call `.apply_rest()`/
 `.to_uivec2()` now passes `painter.density()` (nine call sites — `Span`,
 `Sized`, `MaxSize`, `Aligned`, `Scroll`, `List::place`, and
 `UiRenderState::reposition` itself). This also meant the Android
 boundary's global logical-space stopgap could come out entirely: window
 size, touch coordinates and insets are physical pixels again, matching
 `AndroidRenderer`'s own swapchain resolution, with `dp` doing the
 per-length work the global divide used to do for everything at once.
 **Text is the case that needed more than the `Len` plumbing.** A widget's
 `font_size`/`line_height` are plain `f32`, not routed through `Len` at
 all (there is no sensible `rel`/`rest` for a font size). `TextBuffer::
 shape` now takes `density` directly and multiplies `font_size`/
 `line_height` (and any span override) by it before handing them to
 parley — so the size that reaches both the line-breaker and the
 rasteriser (`TextData::place`, which reads back whatever `shape` set) is
 the display's *physical* size, and the glyph atlas holds a bitmap at the
 resolution it is actually shown at. `GlyphKey.size` already keys on the
 resolved size, so a cache entry is naturally per-physical-size with no
 further change. The one caller with no `Painter` to read density from
 (`TextEditCtx::layout`, cursor movement and hit-testing) reads a second
 copy kept directly on `TextData` (`TextData::density`) instead — an
 accepted duplication rather than threading a `Painter` into every input
 handler for one field, the same tradeoff `AndroidRenderer::content_scale`
 already makes for the Diagnostics page.
 **What did not change**: `rel`/`rest` are unaffected (already
 resolution-independent, a fraction of the parent). `Span::gap` and
 `Padding`'s four sides moved from bare `f32` to `Len` so `dp(...)` works
 on them the same as any other size; a bare number is still `abs`,
 physical pixels, unchanged.
 ## For IRIS.md
 When this lands, copy this entry into `IRIS.md` (newest first):
@@ -895,3 +947,95 @@ When this lands, copy this entry into `IRIS.md` (newest first):
 > `SizeCtx` and `Cache` are gone with it — see `LAYOUT.md` for the full
 > design, the move-offset mechanism this shipped alongside, and the file
 > list.
 ## Masks with a shape (decided 2026-09-07, not yet built)
 Iris, on the code block's scrolling: "the code block scrolling currently
 masks in an inner rectangle. Ideally masks should have a shape
 associated with them, rounded rectangle being one of them, and/or
 another widget you can select, so that the mask becomes the parent
 container with rounded edges. Make sure alpha works properly with it,
 eg. on the corners where alpha should be decreased / multiplied."
 **What exists.** `Mask` in `shader.wgsl`/`data.rs` is two `UiSpan`s and
 a `move_idx`; `fs_main` resolves it and does `color *= 0.0` outside the
 rectangle -- a hard cut on a pixel boundary. `Masked` (`widget/mask.rs`)
 sets the painter's mask to its own region. Separately, `draw_rounded_rect`
 already produces an anti-aliased rounded edge from
 `distance_from_rect(pos, center, corner, radius)` with a half-pixel
 `smoothstep`, and the border variant multiplies a second coverage in.
 **Design** (revised the same day on Iris's two corrections: hit-testing
 applies the shape too, and a mask should reference a primitive rather
 than carry a copy of its shape).
 1. **A mask is a reference to a primitive already drawn, plus how to
   use it.** `Mask { kind, idx, flags, parent }`: the primitive's
   binding (`RECT`, `TEXTURE`, `GLYPH`) and slot, flags (today one:
   *alpha only* -- take the primitive's coverage and ignore its colour,
   which is the default and the only mode until a need for another
   appears), and the enclosing mask's slot for nesting. The fragment
   stage evaluates the referenced primitive *at the masked pixel* --
   for a `Rect`, the same `draw_rounded_rect` coverage from the same
   SDF; for a texture or glyph, the sampled alpha -- and does
   `color.a *= coverage`. Nothing about the shape is copied: a rounded
   container's corner and its children's clipped corner are the same
   primitive's arithmetic, and a texture mask (an alpha image as the
   clip) works with no new shader path.
   What this needs from the data layout: evaluating a primitive at an
   arbitrary pixel means its placement (its spans and `move_idx`, today
   vertex attributes) has to be readable from a storage buffer in the
   fragment stage. If it is not already there, put it there once, for
   every primitive, rather than keeping a second copy for masks -- the
   vertex stage can read the same buffer. Textures: the shader binds one
   image at a time (see `masks_layout`'s comment on why an image's own
   bind group must not name the masks buffer), so a texture mask is
   limited to what the fragment can sample without a bind-group switch:
   the atlas, and the primitive's own bound image when the masked
   primitive is drawn in the same image's batch. Say so at the flag.
 2. **Nested masks chain and multiply, like moves.** `parent` walks up
   the chain, bounded like `resolve_move` (`MOVE_CHAIN_LIMIT`'s sibling;
   debug-assert on overflow and print the chain); coverages multiply,
   so a pixel inside two feathered corners is dimmed by both, which is
   what a compositor does and what "alpha should be multiplied" asks.
 3. **`.masked()` points the mask at the current widget's own
   primitives.** `Masked` stops describing a region: it records which
   primitive(s) the wrapping widget drew this frame (the painter knows
   -- it just allocated the slots) and sets the mask to reference them.
   So a rounded `Rect` widget's `.masked()` clips its children to
   itself by pointing at the rect it already draws; an image widget's
   `.masked()` clips to its alpha. No radius or shape argument exists to
   fall out of sync. When a widget draws more than one primitive (a
   bordered rect is one primitive; a card with a stripe is two), the
   mask references the *first* and the doc says so; a widget that wants
   another names it.
 4. **Hit-testing applies the shape.** A press is inside a masked
   subtree only if the mask's coverage at that point is above one half.
   For a `Rect` that is the same rounded-rect SDF evaluated on the CPU
   -- one function in the shared crate, with the WGSL a transliteration
   of it and a test that compares the two at a grid of points
   (`headless` renders to a buffer and reads back, or the Rust version
   is checked against the values the shader produced once and recorded).
   For a texture, the CPU needs the alpha: keep the alpha channel of an
   image used as a mask readable on the CPU (it was uploaded from CPU
   memory; keeping the alpha plane is a quarter of the image), and read
   it at the point. A masked corner that cannot be tapped and a masked
   corner that is not drawn are then the same corner.
 **Rejected.** A stencil buffer (a second pass per mask level and no
 anti-aliasing); the scissor rectangle (rectangles only, no alpha);
 rendering a masked subtree to an offscreen texture and compositing
 (a texture allocation per mask, every frame it scrolls, on the phone).
 **Pass conditions.** A headless test draws a rounded container with a
 masked child that overhangs all four sides and asserts the child's
 coverage at a corner pixel equals the container's own coverage there
 (same primitive evaluated, so exactly equal, not approximately); a
 nested-mask test asserts the product at a pixel inside both feathers; a
 texture-mask test clips a rect to an alpha image and asserts a
 transparent texel masks fully; a hit-test asserts a press in a
 container's clipped corner misses and one just inside the curve hits,
 and that the CPU SDF and the shader agree at a grid of points; a
 `run-headless.sh --phone` screenshot of a scrolled code block shows
 rounded corners with no square pixels poking out at the top and bottom
 of the scrolled content. Record the commands in RUST.md when it lands.
@@ -0,0 +1,214 @@
 # Review: iris changes since 0e46293
 Scope: `git diff 0e46293..HEAD -- iris/ client-core/` (58 files, +5224/-226).
 Read-only review; no source changed. Ordered likely-bug, then invariant
 guards, then rules, then tests/docs.
 ## Likely bugs
 1. **`iris/transcript-ui/src/lib.rs:152-160` (`RowDiff::Rebuild` arm of
   `TranscriptScreen::apply`) never unregisters the rows it drops from
   `Selection`, so a stale `WeakWidget<TextEdit>` outlives the widget it
   points to and the next touch on *any* row panics.**
   `Selection::rows: BTreeMap<RowKey, WeakWidget<TextEdit>>` documents its
   own contract at `selection.rs:69-71`: "every addition here needs its
   removal ... called when `List` evicts the row." The `ReplaceLast` arm
   above it honours this (`lib.rs:143-145`, `self.selection.borrow_mut()
   .unregister(old_key)` when the key changes). The `Rebuild` arm calls
   `(self.list)(rsc).clear()` and rebuilds every row from `new_rows`, but
   never touches `self.selection` — any key present in `old_rows` and
   *absent* from `new_rows` (exactly what `group_tool_runs` regrouping two
   separate tool-call rows into one produces — see `diff_tests::
   a_tool_run_closing_and_joining_an_earlier_call_is_a_regroup_fallback`,
   which tests the diff decision but not `apply` itself) is left in
   `self.rows` pointing at a widget `List::clear()` just freed.
   `TextEditable::edit` (`iris/src/widget/text/edit.rs:582-587`) resolves
   that handle with `ui.widgets.get_mut(self).unwrap()` — an unconditional
   panic on the freed slot. `Selection::begin` (`selection.rs:88-101`)
   iterates *every* registered row (`w.edit(ui).deselect()`) on an
   ordinary fresh press, so the crash fires on the next tap anywhere in
   the transcript after a regroup, not only on a tap targeting the
   orphaned row.
   Fix: give `Selection` a way to reconcile against the row set that
   survived a rebuild (e.g. `Selection::retain(&self, keys: &BTreeSet<RowKey>)`
   removing everything else, called from the `Rebuild` arm before
   rebuilding), or simplest — call `self.selection.borrow_mut()` cleared
   the same way `List::clear()` clears the list, then let the rebuild's
   `push_row` calls re-`register` everything as they already do.
 ## Guarded invariants missing
 2. **`iris/src/widget/list.rs:751` (`List::place`) indexes/expects on
   `slot` with no assertion that it exists.** `slot_widget` (`:563-575`)
   panics via `.expect(...)` for a sentinel with no widget set, and does
   an unchecked `&self.items[s as usize]` for a real index — a bare
   "index out of bounds" with no context if `place` is ever reached with a
   stale slot. Every current caller happens to derive `slot` from
   `repair_anchor`/`prev_slot`/`next_slot`, which already check existence,
   but that invariant is enforced by convention across three call sites,
   not by the function that depends on it. Add
   `debug_assert!(self.slot_exists(slot), "place() called with a slot that doesn't exist: {slot:?}");`
   at the top of `place`.
 3. **`iris/src/widget/list.rs:426` (`List::fling`) and `sense.rs`'s
   `FlingCalculator::distance`/`duration`/`position_at` never check that
   the incoming velocity is finite.** A `NaN`/`inf` velocity (a
   `VelocityTracker::velocity()` divide-by-near-zero span, or a caller
   passing a raw device value straight through) propagates through
   `deceleration_for`'s `.ln()` silently — the fling either never settles
   (`settled_on_schedule` compares against a `NaN` `duration()`, which is
   always `false`) or jumps to `NaN` positions with nothing on screen
   saying why. Add `debug_assert!(velocity_px_per_s.is_finite())` in
   `List::fling` and `FlingCalculator::new`/`distance`.
 4. **`iris/src/sense.rs:592-604` (`VelocityTracker::velocity`) has no
   assertion that samples are chronological.** `add_sample` trusts its
   caller's `Instant` ordering; a caller that samples out of order (a
   restored/replayed gesture, a test) would silently produce a negative
   `span` handled only by the `span <= 0.0 => 0.0` catch-all, masking the
   bug that produced it rather than surfacing it. Add
   `debug_assert!(self.samples.back().is_none_or(|&(last, _)| at >= last))`
   in `add_sample`.
 5. **`iris/core/src/render/frame_report.rs:247-252` (`mark_phase`) has no
   assertion that phases are pushed in non-decreasing `start_index`
   order.** `phase_stats`'s slicing (`:274`, `idx >= phase.start_index &&
   idx < end_index`) silently produces an empty or nonsensical slice for
   an out-of-order phase rather than surfacing the misuse — cheap to add
   given `self.phases.last()` is already in scope:
   `debug_assert!(self.phases.last().is_none_or(|p| self.total_frames >= p.start_index));`
 ## Rules
 6. **Two mechanisms answer "what row selection points at, still valid?"**
   `Selection` relies on callers remembering to `unregister` (finding 1);
   `List` relies on callers deriving slots only from already-checked
   sources (finding 2). Both are the same class of problem — a derived
   handle that silently outlives what it points to — solved ad hoc twice
   rather than once. Not asking for a shared abstraction here, but the two
   should at minimum cross-reference each other's doc comment so the next
   caller who adds a third handle-into-`List`-rows type (the code rules'
   "a rule that governs a set belongs to the set") finds both existing
   examples.
 7. **`iris/android-app/src/bench_client.rs:224-225` (`battery_line`)
   calls `.min().unwrap()`/`.max().unwrap()` on `samples` guarded three
   lines above by `if samples.is_empty()`, which is fine — but the guard
   and the two unwraps are two statements apart with a `let mean = ...`
   in between reading the same slice; a future edit reordering those
   lines loses the guard's protection silently.** Low severity (this is
   the bench tool, not the app), but worth a one-line comment tying the
   unwraps back to the guard, or restructuring as
   `let (Some(min), Some(max)) = (samples.iter().min(), samples.iter().max())`
   pattern so the empty case can't be separated from the check by a future
   edit.
 ## Tests
 8. **No test exercises `TranscriptScreen::apply`'s `Rebuild` arm through
   `Selection`.** `lib.rs`'s `diff_tests` module (`:284-379`) tests only
   the pure `diff_rows` decision function, never `apply` itself wired to a
   real `Selection`; `selection.rs`'s own tests (`a_missed_press_start_
   recovers_on_the_next_pressing_frame`, `unregister_forgets_the_row_and_
   clears_a_matching_anchor`) never go through `apply`/`List::clear`
   either. This is exactly the gap that let finding 1 through: the two
   pieces (`apply`'s fallback, `Selection`'s registration contract) are
   each tested in isolation and never together. Add: build a
   `TranscriptScreen`, force a `RowDiff::Rebuild` (two adjacent tool-call
   rows regrouping, per the existing `diff_tests` case), then call
   `selected_text`/simulate a fresh press on a surviving row and assert no
   panic.
 9. **`iris/src/widget/list.rs`'s fling tests check total distance and the
   start/end clamp but not the speed profile in between.**
   `fling_moves_the_list_and_then_settles`/`fling_distance_is_positive_
   toward_the_end` only assert the fling started, moved in the right
   direction, and eventually stopped — none checks that
   `tick_fling`'s per-tick delta is *monotonically decreasing* once past
   the fling's peak (the property `fling_calculator_tests::position_at_
   is_monotonic_and_clamped_past_the_end` already checks one level down,
   for `FlingCalculator` alone, but never through `List::tick_fling`'s own
   `scroll`/`anchor.offset` accumulation). A regression that made
   `tick_fling` apply the *total* distance every tick instead of the
   incremental one, for instance, would still pass both existing tests
   (final position and direction are unaffected by how the interior ticks
   split it up) while being wildly wrong every intermediate frame.
 10. **`iris/src/widget/list.rs::replacing_the_last_row_stays_pinned_to_
    the_bottom` and its sibling test `replace_back`'s effect on the
    displayed row, never that the row it evicted is actually gone from
    `heights`/`extents`.** Both tests assert the *new* row's position;
    neither asserts `old.key` is absent from `list_ref.heights`/`extents`
    after the replace (the "stale primitive" class finding 1 is a
    production instance of). A cheap addition: assert
    `!list_ref.heights.contains_key(&old.key)` after `replace_back` in the
    existing test, since `old.key` is already returned to the test as
    `evicted`... (`lib.rs` calls it that way; the `list.rs` test would need
    to capture the key from `old` similarly.)
 ## Docs
 No missing `IRIS.md` entry found for a *public* API change in this diff —
 `List::fling`/`VelocityTracker`/`FlingCalculator`, `List::
 anchor_position_display`, `FrameReport::mark_phase`/`phase_stats`/
 `late_at_hz`, `UiRenderNode::new`'s `Result` change, `Len::dp`, and
 `List::replace_back`/`clear`/`TranscriptScreen::apply` all have entries.
 The `List::replace_back`/`clear`/`TranscriptScreen::apply` entry
 (`docs/IRIS.md:526`) predates this review's finding 1 and does not mention
 `Selection`'s registration contract at all — once finding 1 is fixed,
 that entry should gain a line noting what the fix requires of a caller
 that keeps its own row-keyed side table (the same shape `Selection` is),
 so the next such table doesn't reproduce the same gap.
 ## Fixed, 2026-09-06
 All ten findings addressed after the `DragGesture` merge (`selection.rs`
 was rewritten by that merge, but finding 1's shape and location were
 unchanged — `TranscriptScreen::apply`'s `Rebuild` arm, `iris/transcript-ui/
 src/lib.rs`).
 1. **Fixed.** `Selection::clear()` (`selection.rs`) drops `rows` and
   `anchor`, called from `apply`'s `Rebuild` arm right before
   `List::clear()` — `push_row` re-`register`s whatever survives as it
   rebuilds each row, the "simplest" fix option the finding named.
 2. **Fixed.** `debug_assert!(self.slot_exists(slot), ...)` at the top of
   `List::place` (`iris/src/widget/list.rs`).
 3. **Fixed.** `debug_assert!(velocity_px_per_s.is_finite())` in
   `List::fling`, and `debug_assert!(velocity.is_finite())` in
   `FlingCalculator::distance`/`duration` (`iris/src/sense.rs`).
   `position_at` calls both, so it inherits the guard rather than needing
   its own.
 4. **Fixed.** `debug_assert!` on chronological sample order in
   `VelocityTracker::add_sample` (`iris/src/sense.rs`).
 5. **Fixed.** `debug_assert!` on non-decreasing `start_index` in
   `FrameReport::mark_phase` (`iris/core/src/render/frame_report.rs`).
 6. **Fixed (doc cross-reference only, as asked).** `Selection::register`'s
   doc now points at `List::place`'s `slot_exists` assertion and vice
   versa isn't needed since finding 2's fix already cites this file in
   its own comment; both are grep-able on "docs/REVIEW-2026-09-06.md" and
   on each other's type names.
 7. **Fixed.** `bench_client.rs::battery_line` restructured to
   `let (Some(min), Some(max)) = (samples.iter().min(), samples.iter().max())`,
   so the empty-guard and the two lookups can no longer be separated by a
   future edit.
 8. **Fixed.** `transcript-ui`'s new `apply_tests::
   a_row_dropped_by_a_regroup_does_not_outlive_itself_in_selection`
   (`lib.rs`) builds a real `TranscriptScreen`, forces the same regroup
   shape `diff_tests` already covers at the pure-diff level, calls `apply`,
   and then `Selection::begin` on a surviving row — which panicked before
   fix 1, resolving a `WeakWidget` `List::clear()` had just freed.
 9. **Fixed.** `list.rs`'s new `tick_fling_applies_shrinking_incremental_
   deltas` flings toward the end from `jump_to_start` and asserts each
   tick's `extents[&0]` delta is no larger than the previous one — would
   fail against a `tick_fling` that applied the total spline distance
   every tick instead of the incremental slice, which the two pre-existing
   fling tests cannot catch.
 10. **Fixed.** `list.rs`'s new `replace_back_forgets_the_evicted_keys_own_
    height` replaces row 4 with a row keyed `100` (the two existing
    `replace_back` tests always reuse the same key, so neither actually
    exercises the removal) and asserts `heights` no longer contains the
    evicted key.
 Docs: `docs/IRIS.md`'s 2026-09-05 `List::replace_back`/`clear`/
 `TranscriptScreen::apply` entry now has a line on what the fix requires of
 a caller with its own row-keyed side table, naming `Selection` as the
 example and dating the fix.
 Verification run alongside the rest of this pass's checks: `cargo fmt
 --all`, `cargo clippy --workspace --all-targets`, `cargo test --workspace`
 from `iris/` — see docs/RUST.md's plan box for the pass/fail and any
 caveats from this same session.
@@ -33,3 +33,14 @@ one in place when it turns out to need a decision.
      that would work today, for Claude sessions, and it is the option that was
      not chosen.
 ## From Iris's phone log export, 2026-09-07 (Compose app)
 - [ ] **Crash on 2026-09-03 11:40, `IllegalArgumentException: Reversed
  range is not supported`** at `ToolInput.kt:200` (`highlighted`, inside
  `ToolInputView` -> `RawBlock` -> `ToolCard`). An `AnnotatedString`
  range was built with end before start while highlighting a tool
  input. Found in the per-package system log she exported; the tool
  input that triggered it is not in the log. Reproduce by fuzzing
  `highlighted` with inputs whose token boundaries collapse, and guard
  the range construction.
@@ -0,0 +1,73 @@
 # Compose bench report from Iris's phone, 2026-09-06
 The Compose half of P0 (RUST.md), run by Iris on her own phone and pasted
 back verbatim. The iris half's report goes beside it in this directory
 when it exists. Her caveat, worth keeping with the numbers: "I don't think
 this is entirely fair because the UI for iris is more minimal" -- the
 Compose screen also draws the usage bar, the status row and tool cards,
 which the iris bench screen does not yet. Her impression of the iris build
 before its first-touch bug: "it already feels very smooth so far".
 What to read first: the phone runs at 120 Hz, so the budget is 8.3 ms;
 `late` is measured against that. Compose's tail is the streaming phase --
 `markdown reparsed while streaming: 396, 8.5ms mean, 25.8ms worst` and
 `record: one block: 398, 6.3ms mean, 19.9ms worst` -- which is exactly the
 path iris's `TranscriptScreen::apply` (replace the last row only) is meant
 to beat. Process CPU over the run is 20.9 s of a 38.5 s run; peak RSS
 587 MB; battery current mean 419 mA.
 ```
 ai-app render report
 device: Pixel 9 Pro XL (Google), Android 17
 build: release
 transcript:
  43 events, 41 rows, 93 units loaded
  viewport 1333px, 2 units visible
  on screen: the list's own 0px, AssistantMsg 24520px
  0 tool calls and 0 groups open
 frames:
  1613 frames over 38.5s at 120Hz (8.3ms budget)
  late: 742 (46.0%)
  total  p50 7.7ms  p90 29.2ms  p99 41.1ms
  waited p50 0.5ms  p90 12.9ms  p99 27.2ms
  input  p50 0.0ms  p90 0.0ms  p99 0.0ms
  anim   p50 1.1ms  p90 5.8ms  p99 9.5ms
  layout p50 0.0ms  p90 0.1ms  p99 0.2ms
  draw   p50 0.4ms  p90 15.9ms  p99 27.9ms
  sync   p50 0.1ms  p90 0.5ms  p99 1.0ms
  issue  p50 1.1ms  p90 1.7ms  p99 3.0ms
  swap   p50 0.4ms  p90 0.5ms  p99 0.7ms
  gpu    p50 1.8ms  p90 2.1ms  p99 6.6ms
 where the draw phase went:
  draw phase 3.83ms per frame, of which:
    the transcript: 0.25ms (measure 0.15, place 0.10, record 0.00)
    everything else: 3.58ms (93%)
 work since this was last copied:
  draw: the whole transcript: 12, 0.2ms total, 0.0ms mean, 0.0ms worst
  grouped tool runs: 398, 10.3ms total, 0.0ms mean, 0.1ms worst
  markdown cut into pieces: 1, 0.0ms total, 0.0ms mean, 0.0ms worst
  markdown parsed while composing: 7, 3.0ms total, 0.4ms mean, 0.5ms worst
  markdown ready: 46
  markdown reparsed while streaming: 396, 3384.6ms total, 8.5ms mean, 25.8ms worst
  markdown warmed: 1, 1.4ms total, 1.4ms mean, 1.4ms worst
  measure: the whole transcript: 957, 248.7ms total, 0.3ms mean, 15.7ms worst
  message composed: 403
  message cut into parts: 1, 0.1ms total, 0.1ms mean, 0.1ms worst
  place: the whole transcript: 1319, 162.4ms total, 0.1ms mean, 1.3ms worst
  record: one block: 398, 2498.7ms total, 6.3ms mean, 19.9ms worst
  session screen recomposed: 413
  status row recomposed: 1
  unit composed: 538
  units flattened: 399, 44.3ms total, 0.1ms mean, 0.5ms worst
  usage bar recomposed: 413
 bench:
  scroll: 6 cycles (24 swipes), streamed 400/400 fixture events
  process CPU time over this run: 20907ms
  peak RSS: 587356kB
  battery current: mean -418509µA over 39 samples (min -1988281, max -107812)
 ```
@@ -0,0 +1,93 @@
 # Compose bench v2 report from Iris's phone, 2026-09-06
 Bench v2 (fling / stream / type / keyboard, RUST.md's P0 box) on the
 Compose `bench` build, run by Iris on her Pixel 9 Pro XL, verbatim. Note
 the display was at **60 Hz** for this run (16.7 ms budget) where the v1
 run was at 120 Hz -- the phone's adaptive refresh rate decides, and
 `late` is judged against whichever it was, so compare a run with a run at
 the same rate. The iris v2 report goes beside this when it exists.
 What it says: fling, type and keyboard are all essentially clean on
 Compose (0.1%, 0.9% and 0% late; fling p50 5.5 ms, p99 11.6 ms). The
 whole tail is the streaming phase again -- 41.9% late, p99 42.5 ms,
 driven by `markdown reparsed while streaming` (8.6 ms mean, 30.3 ms
 worst) and `record: one block` (6.3 ms mean, 25.5 ms worst). Process CPU
 69.6 s over the 125.5 s run; peak RSS 577 MB; battery current mean
 571 mA over 126 samples.
 ```
 ai-app render report
 device: Pixel 9 Pro XL (Google), Android 17
 build: release
 transcript:
  108 events, 26 rows, 58 units loaded
  viewport 1531px, 2 units visible
  on screen: the list's own 0px, AssistantMsg 24520px
  0 tool calls and 0 groups open
 per phase:
  fling: 3278 frames over 32.7s
    late: 4 (0.1%)
      total  p50 5.5ms  p90 8.7ms  p99 11.6ms
    worst 49.0ms
  stream: 1041 frames over 21.3s
    late: 436 (41.9%)
      total  p50 13.4ms  p90 31.7ms  p99 42.5ms
    worst 52.5ms
  type: 2446 frames over 61.5s
    late: 23 (0.9%)
      total  p50 7.3ms  p90 13.2ms  p99 16.5ms
    worst 38.9ms
  keyboard: 358 frames over 10.0s
    late: 0 (0.0%)
      total  p50 6.3ms  p90 8.6ms  p99 11.1ms
    worst 12.0ms
 frames:
  7122 frames over 125.5s at 60Hz (16.7ms budget)
  late: 463 (6.5%)
  total  p50 6.0ms  p90 13.8ms  p99 34.0ms
  waited p50 0.5ms  p90 1.1ms  p99 19.9ms
  input  p50 0.0ms  p90 0.0ms  p99 0.0ms
  anim   p50 0.7ms  p90 4.5ms  p99 7.6ms
  layout p50 0.1ms  p90 0.1ms  p99 0.2ms
  draw   p50 0.7ms  p90 2.9ms  p99 21.9ms
  sync   p50 0.1ms  p90 0.2ms  p99 0.6ms
  issue  p50 1.4ms  p90 2.4ms  p99 3.2ms
  swap   p50 0.4ms  p90 0.8ms  p99 1.2ms
  gpu    p50 1.5ms  p90 2.1ms  p99 6.6ms
 where the draw phase went:
  draw phase 1.74ms per frame, of which:
    the transcript: 0.24ms (measure 0.10, place 0.14, record 0.00)
    everything else: 1.51ms (86%)
 work since this was last copied:
  draw: the whole transcript: 280, 1.9ms total, 0.0ms mean, 0.0ms worst
  grouped tool runs: 407, 18.6ms total, 0.0ms mean, 0.2ms worst
  markdown cut into pieces: 40, 0.4ms total, 0.0ms mean, 0.0ms worst
  markdown parsed while composing: 2, 1.6ms total, 0.8ms mean, 1.1ms worst
  markdown ready: 323
  markdown reparsed while streaming: 395, 3406.9ms total, 8.6ms mean, 30.3ms worst
  markdown warmed: 40, 38.2ms total, 1.0ms mean, 4.3ms worst
  measure: the whole transcript: 1978, 683.9ms total, 0.3ms mean, 15.9ms worst
  message composed: 397
  message cut into parts: 40, 2.9ms total, 0.1ms mean, 0.2ms worst
  place: the whole transcript: 4308, 996.0ms total, 0.2ms mean, 2.4ms worst
  record: one block: 394, 2472.7ms total, 6.3ms mean, 25.5ms worst
  session screen recomposed: 1630
  status row recomposed: 1
  transcript page from server: 10
  unit composed: 927
  units flattened: 408, 85.5ms total, 0.2ms mean, 1.8ms worst
 bench:
  fling: 8 flings out + 8 back at 12000px/s, travel start=idx=0/off=0px outward=idx=188/off=182px end=idx=0/off=0px
  scroll: 6 cycles (24 swipes, legacy tween), streamed 400/400 fixture events
  type: 600 characters inserted then deleted, one per 50ms
  keyboard: shown 5/5, hidden 5/5 (confirmed via isImeVisible)
  process CPU time over this run: 69564ms
  peak RSS: 577452kB
  battery current: mean -571483µA over 126 samples (min -2361718, max -99218)
 ```
@@ -0,0 +1,31 @@
 # iris bench report from Iris's phone, 2026-09-06, before the phone fixes
 Build 46246ea (Vulkan, bench v1: 24-swipe scroll loop then 400 streamed
 events), run by Iris on her Pixel 9 Pro XL before the first-touch wipe,
 the missing bold faces, the density scale and the status-bar inset were
 fixed -- so the rows were drawn at roughly a third of their intended size
 and the run may have included frames after the wipe. Preliminary, kept
 because it is the first iris number from real hardware. Compare with
 `compose-phone-2026-09-06.md`, taken on the same phone with the same
 fixture and gesture loop.
 Reading it: the phone is 120 Hz (8.3 ms budget). `janky%` here counts
 frames over 16.7 ms, so it is not Compose's `late` (over 8.3 ms). Like for
 like: iris p50 6.2 ms vs Compose 7.7 ms; p90 32.0 vs 29.2; p99 42.1 vs
 41.1. `cpu_p50=4.7ms` is iris's own per-frame CPU work on the phone,
 against 0.2-0.4 ms on the emulator's x86 cores. Process CPU 15.6 s vs
 20.9 s, but over a shorter run (692 frames vs 1613 -- iris only renders on
 change and had no fling settle time), so per-second CPU is not directly
 comparable; peak RSS 365 MB vs 587 MB. Battery current mean 563 mA vs
 419 mA is the one figure that reads worse, and it is the least
 comparable: 22 samples vs 39, over runs of different length and different
 idle share. Bench v2's per-phase accounting is what makes these comparable.
 ```
 iris bench report
 frames=692 janky%=32.37 p50=6.2ms p90=32.0ms p99=42.1ms worst=52.6ms (measures redraw-start to after present() is called, not GPU/compositor completion) cpu_p50=4.7ms gpu_wait_p50=1.3ms (redraw-start-to-submit vs. submit-to-after-present)
  scroll: 6 cycles (24 swipes), streamed 400/400 fixture events
  process CPU time over this run: 15554ms
  peak RSS: 365328kB
  battery current: mean -563493µA over 22 samples (min -1807812, max -132812)
 ```
@@ -0,0 +1,66 @@
 # iris bench v2 report from Iris's phone, 2026-09-06
 Build 2e3f4ad (bench v2, fling physics, keyboard-wipe fix, dp unit), run
 by Iris on her Pixel 9 Pro XL, verbatim. The display was at **120 Hz**
 (8.3 ms budget) where `compose-phone-v2-2026-09-06.md` ran at 60 Hz, so
 compare the millisecond percentiles, not `late`.
 Side by side (Compose 60 Hz / iris 120 Hz, p50 / p90 / p99 ms): fling
 5.5/8.7/11.6 vs 3.8/6.9/12.6; stream 13.4/31.7/42.5 vs 18.2/35.8/43.1;
 type 7.3/13.2/16.5 vs 7.2/9.2/11.2; keyboard: iris could not show the IME
 (phase invalid). Process CPU 69.6 s over 125 s vs 40.6 s over 150 s; peak
 RSS 577 MB vs 379 MB; battery current mean 571 mA vs 452 mA.
 Iris's observations on the same run: "the scrolling is not similar at
 all. It does not fling for me yet [with a finger], and the test also seems
 to give it a constant velocity and abruptly stop it at some point. Also
 unsure what's going on in that image with the compaction" -- her
 screenshot shows the `Compacted: 180000 -> 20000 tokens.` row drawn twice
 overlapping, and once more below the composer bar: primitives of a
 replaced/removed row surviving in the GPU buffers, the same shape as the
 header drawn twice after a keyboard resize.
 **Root-caused and fixed 2026-09-06** (commit `76b1f99`): the diagnosis in
 that sentence was right and the location was not -- `UiRenderState::
 draw_inner` read the `needs_redraw` mark without consuming it and skipped
 the branch that frees a redrawn widget's old primitives. docs/RUST.md's
 "Stale primitives, the phone's half" box has the full account, the guard
 (`orphaned_primitives`, `debug_assert`ed every frame) and the emulator run
 that exercises it.
 ```
 iris bench report
 per phase:
  fling: 1783 frames over 53.2s
    late: 104 (5.8%)
      total  p50 3.8ms  p90 6.9ms  p99 12.6ms
    worst 29.1ms
  stream: 401 frames over 21.3s
    late: 306 (76.3%)
      total  p50 18.2ms  p90 35.8ms  p99 43.1ms
    worst 43.8ms
  type: 1202 frames over 65.7s
    late: 309 (25.7%)
      total  p50 7.2ms  p90 9.2ms  p99 11.2ms
    worst 15.3ms
  keyboard: 9 frames over 9.7s
    late: 9 (100.0%)
      total  p50 12.0ms  p90 12.9ms  p99 12.9ms
    worst 12.9ms
 frames:
  3395 frames over 149.9s at 120Hz (8.3ms budget)
  late: 728 (21.4%)
  total  p50 5.0ms  p90 10.9ms  p99 36.6ms
  worst 43.8ms
  cpu_p50 2.0ms  gpu_wait_p50 2.6ms
 bench:
  fling: 8 flings out + 8 back at 12000px/s, travel start=idx=651/off=1217px outward=idx=651/off=101536px end=idx=651/off=1022px
  scroll: 6 cycles (24 swipes, legacy tween), streamed 400/400 fixture events
  type: 600 characters inserted then deleted, one per 50ms
  keyboard: could not be shown (5 attempts, 0 confirmed visible)
  process CPU time over this run: 40603ms
  peak RSS: 379156kB
  battery current: mean -452353µA over 149 samples (min -1753125, max -204687)
 ```
@@ -150,6 +150,19 @@ pub enum Event {
    ToolEnd {
        id: String,
        output: String,
        /// Whether the tool reported that the call *failed*, from the
        /// CLI's own `is_error` on the `tool_result`.
        ///
        /// Added 2026-09-06 with the tool-call cards (RUST.md's P1b),
        /// because without it a result is the only thing a card has and a
        /// failed call is drawn as confidently as a successful one -- the
        /// missing state, not a wrong one. `#[serde(default)]` so a
        /// transcript written before this field, or a peer on an older
        /// build, reads back as "not reported to have failed" rather than
        /// failing to parse; that is the same claim the field's absence
        /// used to make implicitly.
        #[serde(default)]
        is_error: bool,
    },
    /// An image the session produced or was sent, saved under the session
    /// dir and referenced by id; the phone fetches it by URL.
@@ -305,6 +318,25 @@ pub enum Event {
    /// it, which is why this is written down rather than left to be inferred
    /// from a second example that does not exist.
    Cleared,
    /// The account behind this session has no quota left, so the turn stopped
    /// without finishing.
    ///
    /// Its own event rather than an [`Event::Error`] carrying the dialect's
    /// sentence, because two things act on it that cannot read English: the
    /// transcript draws it as a state the session is in rather than as a
    /// failure of something it did, and `crate::resume` schedules the message
    /// that picks the work back up. Recognising it belongs to the driver, which
    /// is the only layer that knows its dialect's wording -- above here nothing
    /// matches on strings.
    ///
    /// `resets_at` is epoch seconds, and `None` is a real state: the dialect
    /// said the limit was hit without saying when it lifts. Nothing here
    /// invents one -- what the wait is actually decided against is the usage
    /// endpoint, and this is the hint that starts the waiting.
    LimitReached {
        #[serde(default, skip_serializing_if = "Option::is_none")]
        resets_at: Option<f64>,
    },
    Error {
        message: String,
    },
@@ -721,6 +721,7 @@ name = "client-core"
 version = "0.1.0"
 dependencies = [
 "event-model",
 "pulldown-cmark",
 "serde",
 "serde_json",
 "ureq",
@@ -964,9 +965,9 @@ dependencies = [
 [[package]]
 name = "dlib"
-version = "0.5.2"
+version = "0.5.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "330c60081dcc4c72131f8eb70510f1ac07223e5d4163db481a04a0befcffa412"
+checksum = "ab8ecd87370524b461f8557c119c405552c396ed91fc0a8eec68679eab26f94a"
 dependencies = [
 "libloading",
 ]
@@ -1757,6 +1758,7 @@ dependencies = [
 "fxhash",
 "image",
 "parley",
 "pollster",
 "swash",
 "wgpu",
 ]
@@ -2873,9 +2875,9 @@ checksum = "a993555f31e5a609f617c12db6250dedcac1b0a85076912c436e6fc9b2c8e6a3"
 [[package]]
 name = "quick-xml"
-version = "0.38.4"
+version = "0.41.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b66c2058c55a409d601666cffe35f04333cf1013010882cec174a7467cd4e21c"
+checksum = "e660451e55124f798a69a5af3f49ccfbefbd41910eefd25caf2393e1f3473ec1"
 dependencies = [
 "memchr",
 ]
@@ -3056,6 +3058,15 @@ version = "0.8.52"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0c6a884d2998352bb4daf0183589aec883f16a6da1f4dde84d8e2e9a5409a1ce"
 [[package]]
 name = "rig-input"
 version = "0.1.0"
 dependencies = [
 "iris",
 "wayland-client",
 "wayland-protocols-wlr",
 ]
 [[package]]
 name = "ring"
 version = "0.17.14"
@@ -3644,6 +3655,18 @@ dependencies = [
 "once_cell",
 ]
 [[package]]
 name = "transcript-fixture"
 version = "0.1.0"
 dependencies = [
 "client-core",
 "event-model",
 "iris",
 "serde_json",
 "transcript-ui",
 "winit",
 ]
 [[package]]
 name = "transcript-ui"
 version = "0.1.0"
@@ -3892,9 +3915,9 @@ dependencies = [
 [[package]]
 name = "wayland-backend"
-version = "0.3.12"
+version = "0.3.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fee64194ccd96bf648f42a65a7e589547096dfa702f7cadef84347b66ad164f9"
+checksum = "38a91b4eaddff87b1cd1074985e3713da4af2c49742d1b356b2c01670a67a078"
 dependencies = [
 "cc",
 "downcast-rs",
@@ -3906,9 +3929,9 @@ dependencies = [
 [[package]]
 name = "wayland-client"
-version = "0.31.12"
+version = "0.31.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b8e6faa537fbb6c186cb9f1d41f2f811a4120d1b57ec61f50da451a0c5122bec"
+checksum = "e3c36a0f861ad76d0901f2800b46321410d9f73f2ea88aac0650d86c32688073"
 dependencies = [
 "bitflags 2.10.0",
 "rustix 1.1.3",
@@ -3940,9 +3963,9 @@ dependencies = [
 [[package]]
 name = "wayland-protocols"
-version = "0.32.10"
+version = "0.32.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "baeda9ffbcfc8cd6ddaade385eaf2393bd2115a69523c735f12242353c3df4f3"
+checksum = "23d0c813de3daa2ed6520af85a3bd49b0e722a3078506899aa9686fea58dc4b6"
 dependencies = [
 "bitflags 2.10.0",
 "wayland-backend",
@@ -3965,9 +3988,9 @@ dependencies = [
 [[package]]
 name = "wayland-protocols-wlr"
-version = "0.3.10"
+version = "0.3.12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e9597cdf02cf0c34cd5823786dce6b5ae8598f05c2daf5621b6e178d4f7345f3"
+checksum = "eb04e52f7836d7c7976c78ca0250d61e33873c34156a2a1fc9474828ec268234"
 dependencies = [
 "bitflags 2.10.0",
 "wayland-backend",
@@ -3978,9 +4001,9 @@ dependencies = [
 [[package]]
 name = "wayland-scanner"
-version = "0.31.8"
+version = "0.31.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5423e94b6a63e68e439803a3e153a9252d5ead12fd853334e2ad33997e3889e3"
+checksum = "338e30461b3a2b67d70eb30a6d89f8e0c93a833e07d2ae89085cd070c4a00ac0"
 dependencies = [
 "proc-macro2",
 "quick-xml",
@@ -3989,9 +4012,9 @@ dependencies = [
 [[package]]
 name = "wayland-sys"
-version = "0.31.8"
+version = "0.31.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1e6dbfc3ac5ef974c92a2235805cc0114033018ae1290a72e474aa8b28cbbdfd"
+checksum = "d8eab23fefc9e41f8e841df4a9c707e8a8c4ed26e944ef69297184de2785e3be"
 dependencies = [
 "dlib",
 "log",
@@ -15,6 +15,11 @@ wgpu = { workspace = true }
 image = { workspace = true }
 accesskit = { workspace = true }
 tokio = { workspace = true, features = ["sync", "rt", "rt-multi-thread"] }
 # For diagnostics visible through android_logger (or whatever logger the
 # app crate installs) -- this crate never installs one itself. Not in the
 # android-only block below any more: the lines that matter most are in
 # shared widget code, which the host backend compiles too.
 log = "0.4.28"
 # winit everywhere except Android; android-view (below) is what stands in
 # for it there. Both backends live in this crate (see `src/android/mod.rs`'s
@@ -53,9 +58,6 @@ accesskit_android = "0.8.0"
 # for `android/insets.rs`'s own id -> state map -- the same reason
 # android-view's own `PEER_MAP` carries one.
 send_wrapper = "0.6.0"
 # For diagnostics visible through android_logger, wherever the app crate
 # installs it -- this crate never installs a logger itself.
 log = "0.4.28"
 [features]
 # RUST.md's I5 "Where iris's frame time goes" diagnosis: forces the Android
@@ -64,7 +66,11 @@ log = "0.4.28"
 # default) or virgl's GLES path, without a second env-var plumbing path that
 # nothing on this machine can hand to an already-launched Android process
 # (there is no `am start` environment and no system-property reader here to
-# add one). Android-only; `android/render.rs` is the only reader.
+# add one). Read by `android/render.rs` and, so the GLES path can be
 # reproduced on a machine with a real GPU rather than only in the emulator,
 # by `default/render.rs`:
 #     ./run-headless.sh transcript --shot /tmp/x.png -- -p transcript-ui \
 #         --features iris/force-gles
 force-gles = []
 [dev-dependencies]
@@ -83,13 +89,21 @@ name = "message_list"
 harness = false
 [workspace]
-members = ["core", "macro", "tabs-ui", "transcript-ui", "desktop-app"]
+members = [
    "core",
    "macro",
    "tabs-ui",
    "transcript-ui",
    "transcript-fixture",
    "rig-input",
    "desktop-app",
 ]
 # android-app pulls in android-view, which needs the NDK sysroot to link
 # -- excluded so `cargo build --workspace --all-targets` on the host stays
 # buildable. Cross-compile it from its own directory (its own single-crate
 # workspace, since it has no `[workspace]` table of its own and this
 # exclusion stops it inheriting this one): `cd android-app && cargo ndk
-# -t x86_64 -P 26 build`.
+# -t x86_64 -P 29 build`.
 exclude = ["android-app"]
 [workspace.package]
@@ -745,6 +745,7 @@ name = "client-core"
 version = "0.1.0"
 dependencies = [
 "event-model",
 "pulldown-cmark",
 "serde",
 "serde_json",
 "ureq",
@@ -1773,6 +1774,7 @@ dependencies = [
 "serde_json",
 "tabs-ui",
 "tokio",
 "transcript-fixture",
 "transcript-ui",
 ]
@@ -1785,6 +1787,7 @@ dependencies = [
 "fxhash",
 "image",
 "parley",
 "pollster",
 "swash",
 "wgpu",
 ]
@@ -3862,6 +3865,17 @@ dependencies = [
 "once_cell",
 ]
 [[package]]
 name = "transcript-fixture"
 version = "0.1.0"
 dependencies = [
 "client-core",
 "event-model",
 "iris",
 "serde_json",
 "transcript-ui",
 ]
 [[package]]
 name = "transcript-ui"
 version = "0.1.0"
@@ -29,6 +29,10 @@ log = "0.4.28"
 # which Cargo's `unused_dependencies` lint (on by default) correctly flags.
 tabs-ui = { path = "../tabs-ui", optional = true }
 transcript-ui = { path = "../transcript-ui", optional = true }
 # P0's bench build only: the fixture and the folded screen both bench
 # clients open, shared with the headless harness and the desktop window
 # (docs/RUST.md's "Three test layers").
 transcript-fixture = { path = "../transcript-fixture", optional = true }
 client-core = { path = "../../client-core", optional = true }
 event-model = { path = "../../event-model", optional = true }
 serde_json = { version = "1", features = ["float_roundtrip"], optional = true }
@@ -65,7 +69,7 @@ force-gles = ["iris/force-gles"]
 # `event-model` -- `lib.rs`'s `ActiveClient` selection gives this feature
 # priority over `transcript-screen`'s own `TranscriptClient` when both are
 # listed, which is how this crate's build command names both explicitly.
-bench = ["transcript-screen", "dep:libc", "dep:tokio"]
+bench = ["transcript-screen", "dep:transcript-fixture", "dep:libc", "dep:tokio"]
 [profile.release]
 panic = "abort"
@@ -13,8 +13,37 @@ android {
    defaultConfig {
        applicationId = "dev.iris.android.demo"
-        minSdk = 26
+        // 29, not 26: `iris::android::view`'s touch handler dates each
-        targetSdk = 34
+        // sample with `MotionEvent.getEventTimeNanos` and
        // `getHistoricalEventTimeNanos`, both API 29, and a missing JNI
        // method there is a hard crash on the first touch rather than a
        // degraded fling. Raised deliberately rather than guarded at
        // runtime: nothing this app is built for runs below 29, and an
        // untested fallback path is its own defect. `build-apk.sh`'s
        // `cargo ndk -P` is kept at the same number.
        minSdk = 29
        // 37, matching `compileSdk` and the Compose app in `app/` -- which
        // is the one part of this that is measured rather than reasoned:
        // that app targets 37 and its keyboard does push the transcript up
        // on Iris's phone, and this one targeted 34 and does not
        // (2026-09-07). The emulator here is API 36 and the push-up works
        // there at either target, so the target is the only difference the
        // two devices do not share.
        //
        // The mechanism, stated as the reading it is: below targetSdk 35
        // a window keeps the legacy behaviour, where `adjustResize` shrinks
        // the window for the IME and `getInsets(ime()).bottom` therefore
        // measures the overlap with an already-shrunk window -- zero, with
        // nothing left to push up. `MainActivity`'s
        // `setDecorFitsSystemWindows(false)` opts out of that, and on API
        // 36 it still takes; Android 16 deprecated it and Android 17 is
        // where it appears not to. At 35+ edge-to-edge is not opt-in, so
        // the app is handed the real overlap without relying on a
        // deprecated call. If the phone still reports `ime_bottom=0` with
        // a nonzero `dispatches` in the Diagnostics pane, this reading was
        // wrong and the `WindowInsetsAnimation.Callback` in
        // `MainActivity` is the other half to look at.
        targetSdk = 37
        versionCode = 1
        versionName = "1.0"
    }
@@ -1,6 +1,17 @@
 package dev.iris.android.demo;
 import android.app.Activity;
 import android.content.ClipData;
 import android.content.ClipboardManager;
 import android.content.Context;
 import android.view.Gravity;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.Button;
 import android.widget.FrameLayout;
 import android.widget.LinearLayout;
 import android.widget.ScrollView;
 import android.widget.TextView;
 import org.linebender.android.rustview.RustView;
@@ -16,7 +27,7 @@ public final class IrisView extends RustView {
    protected native long newViewPeer(Context context);
    native void applyWindowInsetsNative(
-            long peer, int left, int top, int right, int bottom, int imeBottom);
+            long peer, int left, int top, int right, int bottom, int imeBottom, int imeVisible);
    native void unregisterInsetsNative(long peer);
@@ -24,8 +35,9 @@ public final class IrisView extends RustView {
        super(context);
    }
-    void applyWindowInsets(int left, int top, int right, int bottom, int imeBottom) {
+    void applyWindowInsets(
-        applyWindowInsetsNative(mViewPeer, left, top, right, bottom, imeBottom);
+            int left, int top, int right, int bottom, int imeBottom, int imeVisible) {
        applyWindowInsetsNative(mViewPeer, left, top, right, bottom, imeBottom, imeVisible);
    }
    @Override
@@ -33,4 +45,112 @@ public final class IrisView extends RustView {
        unregisterInsetsNative(mViewPeer);
        super.onDetachedFromWindow();
    }
    /**
     * Called from the Rust side (iris/src/android/view.rs's
     * `show_renderer_error`) when `AndroidRenderer::new` fails instead of
     * drawing -- an ordinary instance method rather than a `native` one,
     * since this call is Rust reaching into Java rather than the other
     * direction. Replaces the whole activity content with plain,
     * selectable, scrollable text rather than leaving the last frame (or a
     * blank surface) on screen with no way to report what happened:
     * UI_RULES.md's "a failure is reported where it happened, and says
     * what to do next." No dialog and no styling beyond what is needed to
     * read and copy the text -- this path exists for exactly the crash it
     * replaces, so it must not depend on anything that could itself fail
     * to render.
     */
    void showRendererError(String report) {
        Context context = getContext();
        if (!(context instanceof Activity)) {
            return;
        }
        Activity activity = (Activity) context;
        TextView text = new TextView(activity);
        text.setText(report);
        text.setTextIsSelectable(true);
        text.setGravity(Gravity.TOP | Gravity.START);
        int pad = (int) (16 * activity.getResources().getDisplayMetrics().density);
        text.setPadding(pad, pad, pad, pad);
        ScrollView scroll = new ScrollView(activity);
        scroll.addView(text);
        activity.setContentView(scroll);
    }
    private static final String DIAGNOSTICS_OVERLAY_TAG = "iris-diagnostics-overlay";
    /**
     * The bench build's keyboard diagnostics capture
     * (`bench_client.rs`'s `on_insets_changed` /
     * `capture_keyboard_diagnostics`, via `bench_jni.rs`'s
     * `PlatformHandle::show_diagnostics_overlay`): unlike
     * `showRendererError` above, this adds a panel *over* this view
     * (`MainActivity`'s `FrameLayout` still holds `IrisView` underneath,
     * running) rather than replacing the activity's content, and gives it
     * a Copy button and a Close that removes the panel -- so it draws
     * (and can be read) whether or not iris itself is still putting
     * anything on screen, without abandoning the session that produced
     * it. Runs on the UI thread regardless of which thread calls it,
     * since the call comes from a background task (a delayed capture
     * after the keyboard opens), and touching the view tree off the UI
     * thread is undefined.
     */
    void showDiagnosticsOverlay(String report) {
        Context context = getContext();
        if (!(context instanceof Activity)) {
            return;
        }
        Activity activity = (Activity) context;
        activity.runOnUiThread(() -> {
            ViewGroup parent = (ViewGroup) getParent();
            if (parent == null) {
                return;
            }
            View existing = parent.findViewWithTag(DIAGNOSTICS_OVERLAY_TAG);
            if (existing != null) {
                parent.removeView(existing);
            }
            float density = activity.getResources().getDisplayMetrics().density;
            int pad = (int) (16 * density);
            LinearLayout overlay = new LinearLayout(activity);
            overlay.setTag(DIAGNOSTICS_OVERLAY_TAG);
            overlay.setOrientation(LinearLayout.VERTICAL);
            overlay.setBackgroundColor(0xEE000000);
            overlay.setPadding(pad, pad, pad, pad);
            TextView text = new TextView(activity);
            text.setText(report);
            text.setTextIsSelectable(true);
            text.setTextColor(0xFFFFFFFF);
            ScrollView scroll = new ScrollView(activity);
            scroll.addView(text);
            overlay.addView(scroll, new LinearLayout.LayoutParams(
                    LinearLayout.LayoutParams.MATCH_PARENT, 0, 1f));
            LinearLayout buttonRow = new LinearLayout(activity);
            buttonRow.setOrientation(LinearLayout.HORIZONTAL);
            buttonRow.setPadding(0, pad, 0, 0);
            Button copy = new Button(activity);
            copy.setText("Copy");
            copy.setOnClickListener(v -> {
                ClipboardManager clipboard =
                        (ClipboardManager) activity.getSystemService(Context.CLIPBOARD_SERVICE);
                if (clipboard != null) {
                    clipboard.setPrimaryClip(ClipData.newPlainText("iris diagnostics", report));
                }
            });
            Button close = new Button(activity);
            close.setText("Close");
            close.setOnClickListener(v -> parent.removeView(overlay));
            buttonRow.addView(copy);
            buttonRow.addView(close);
            overlay.addView(buttonRow);
            parent.addView(overlay, new FrameLayout.LayoutParams(
                    FrameLayout.LayoutParams.MATCH_PARENT, FrameLayout.LayoutParams.MATCH_PARENT));
        });
    }
 }
@@ -4,7 +4,9 @@ import android.app.Activity;
 import android.os.Build;
 import android.os.Bundle;
 import android.view.WindowInsets;
 import android.view.WindowInsetsAnimation;
 import android.widget.FrameLayout;
 import java.util.List;
 /**
 * The android-view backend's demo activity (RUST.md's I2): one IrisView
@@ -31,17 +33,107 @@ public final class MainActivity extends Activity {
        setContentView(layout);
        view.requestFocus();
        // RUST.md's P0 box, defect 4 ("keyboard: could not be shown"):
        // `logcat` showed the platform's own IME open/resize happening
        // while `setOnApplyWindowInsetsListener` fired only once, at
        // attach, and never again for a pure keyboard toggle -- a plain
        // (non-edge-to-edge) window is only guaranteed that one initial
        // dispatch; `adjustResize` handling the IME entirely by resizing
        // the window is not itself a trigger for a fresh one. Opting into
        // edge-to-edge (a platform call, API 30+, no new dependency) is
        // what makes the system redeliver insets on every change,
        // including the ones this activity actually cares about --
        // `getSystemWindowInset*` below is unaffected by this (it has
        // always reported the raw system-bar/IME overlap regardless of
        // who consumes it), so the on-screen bars and the padding Rust
        // already derives from those four numbers are unchanged; only the
        // callback's firing became reliable.
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
            getWindow().setDecorFitsSystemWindows(false);
        }
        // **The keyboard's height arrives twice, over two different
        // paths, and the phone needs the second one** (Iris, 2026-09-07:
        // the emulator pushed the composer up and her Pixel did not).
        // `setOnApplyWindowInsetsListener` is the platform's *settled*
        // answer; `WindowInsetsAnimation.Callback` is the running one, and
        // an IME that animates in delivers every intermediate height
        // through the callback with the static dispatch arriving only at
        // the ends -- on some devices only at `onEnd`. Registering both
        // means neither device depends on the other's timing, and it is
        // also what makes the push-up *animate* with the keyboard rather
        // than jump when it lands.
        //
        // The two do not disagree, because they are the same call with the
        // same numbers read out of whichever `WindowInsets` is current.
        // `DISPATCH_MODE_CONTINUE_ON_SUBTREE` so this view consuming
        // nothing keeps the ordinary dispatch running underneath.
        // `onEnd` re-reads the root's insets rather than trusting the last
        // `onProgress`: an animation interrupted mid-flight never delivers
        // its final frame, which is exactly the fault the Compose app hit
        // (AGENTS.md, "the composer can get stuck floating above the
        // bottom of the screen").
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
            view.setWindowInsetsAnimationCallback(new WindowInsetsAnimation.Callback(
                    WindowInsetsAnimation.Callback.DISPATCH_MODE_CONTINUE_ON_SUBTREE) {
                @Override
                public WindowInsets onProgress(
                        WindowInsets insets, List<WindowInsetsAnimation> running) {
                    sendInsets(view, insets);
                    return insets;
                }
                @Override
                public void onEnd(WindowInsetsAnimation animation) {
                    WindowInsets settled = view.getRootWindowInsets();
                    if (settled != null) {
                        sendInsets(view, settled);
                    }
                }
            });
        }
        view.setOnApplyWindowInsetsListener((v, insets) -> {
-            int left = insets.getSystemWindowInsetLeft();
+            sendInsets((IrisView) v, insets);
            int top = insets.getSystemWindowInsetTop();
            int right = insets.getSystemWindowInsetRight();
            int bottom = insets.getSystemWindowInsetBottom();
            int imeBottom = 0;
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
                imeBottom = insets.getInsets(WindowInsets.Type.ime()).bottom;
            }
            ((IrisView) v).applyWindowInsets(left, top, right, bottom, imeBottom);
            return insets;
        });
    }
    /** Read one `WindowInsets` and hand it to the Rust side. The only
     * place that reads these fields, so the static dispatch and the
     * animation callback above cannot come to report different things. */
    private static void sendInsets(IrisView view, WindowInsets insets) {
        int left = insets.getSystemWindowInsetLeft();
        int top = insets.getSystemWindowInsetTop();
        int right = insets.getSystemWindowInsetRight();
        int bottom = insets.getSystemWindowInsetBottom();
        // **Two separate answers, because they are separate questions**
        // (Iris's phone, 2026-09-06: "message box does not push up the
        // scroll area"). `isVisible(ime())` says whether the keyboard is
        // up; `getInsets(ime()).bottom` says how tall it is. An earlier
        // pass sent the boolean *as* the height (0 or 1) because under
        // plain `adjustResize` the window shrinks to make room and the ime
        // inset therefore measures a zero overlap by construction -- true
        // then, and no longer true now that this is an edge-to-edge window
        // (`targetSdk` 35+, plus the `setDecorFitsSystemWindows` call
        // above for the devices below that), which is exactly the case
        // where the system stops resizing and hands the app the real
        // overlap instead. Sending 1 for it left the Rust side padding the
        // composer by one physical pixel, so the keyboard covered the bar
        // and the transcript alike.
        //
        // The visibility is still sent in its own right rather than
        // inferred from `height > 0`: the two disagree during the
        // keyboard's slide-in and -out (visible, height still climbing),
        // and "is the IME up" drives the bench's own state machine
        // (`bench_client.rs`'s `ime_state`) where a half-open frame
        // reading as "closed" is a miscount.
        int imeBottom = 0;
        int imeVisible = 0;
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
            imeBottom = insets.getInsets(WindowInsets.Type.ime()).bottom;
            imeVisible = insets.isVisible(WindowInsets.Type.ime()) ? 1 : 0;
        }
        view.applyWindowInsets(left, top, right, bottom, imeBottom, imeVisible);
    }
 }
@@ -0,0 +1,95 @@
 #!/bin/sh
 # Builds iris-android-app end to end: the cdylib (cargo ndk, straight into
 # app/src/main/jniLibs/) then the APK (Gradle). Written to stop re-typing
 # the same incantation by hand every time (ANDROID_HOME/NDK exports, the
 # cargo ndk invocation, the keystore env for a release build, apksigner/
 # aapt2 verification) -- see docs/RUST.md's P0 box. Same shape as `app/
 # build-apk.sh` (the Compose app's own build script) and `app/
 # iris-scroll.sh` (no coordinates, set -eu, exit 0 on success).
 #
 # Usage: ./build-apk.sh [debug|release] [--abi arm64-v8a|x86_64] [--features "a b c"]
 #   debug/release default to debug (matches this-machine-android's "the
 #   emulator stays on debug" rule -- pass `release` explicitly for a phone
 #   build). --abi defaults to arm64-v8a (a phone/real device); pass
 #   x86_64 for this checkout's own AVD. --features defaults to
 #   "transcript-screen bench" -- deliberately *without* `force-gles`, unlike
 #   an earlier version of this default. `force-gles` (`iris/Cargo.toml`'s
 #   own doc) exists only to force the emulator off its default software
 #   Vulkan and onto GLES for one specific measurement (RUST.md's I5, "Where
 #   iris's frame time goes") -- it was never meant to reach a real device,
 #   but this script's old default put it in every arm64 build regardless,
 #   so the P0 bench APK delivered to Iris's phone forced GLES there too.
 #   That is the named hypothesis in RUST.md's P0 box ("iris bench crash on
 #   the phone, 2026-09-06"): a real Vulkan driver is what a phone should
 #   run, and GLES is the backend the same box's own SwiftShader finding
 #   already flagged as the fragile one for this shader's storage buffers.
 #   Pass `--features "transcript-screen force-gles bench"` explicitly for
 #   an emulator backend-isolation run; never for a build meant for a phone.
 set -eu
 cd "$(dirname "$0")"
 BUILD_TYPE="debug"
 ABI="arm64-v8a"
 FEATURES="transcript-screen bench"
 case "${1:-}" in
    debug|release) BUILD_TYPE="$1"; shift ;;
 esac
 while [ $# -gt 0 ]; do
    case "$1" in
        --abi) ABI="$2"; shift 2 ;;
        --features) FEATURES="$2"; shift 2 ;;
        *) echo "build-apk.sh: unknown argument: $1" >&2; exit 1 ;;
    esac
 done
 SDK_ROOT="$HOME/Android/Sdk"
 export ANDROID_HOME="$SDK_ROOT"
 export ANDROID_SDK_ROOT="$SDK_ROOT"
 NDK_DIR=$(ls -d "$SDK_ROOT"/ndk/*/ 2>/dev/null | sort -V | tail -1)
 if [ -z "$NDK_DIR" ]; then
    echo "build-apk.sh: no NDK found under $SDK_ROOT/ndk" >&2
    exit 1
 fi
 export ANDROID_NDK_HOME="$NDK_DIR"
 # Only the ABI asked for goes into the APK. cargo ndk adds its output beside
 # whatever earlier builds left here, and Gradle packages every directory it
 # finds -- a debug x86_64 emulator build left behind made an arm64 "release"
 # 339 MB on 2026-09-06.
 rm -rf app/src/main/jniLibs
 echo "build-apk.sh: cargo ndk -t $ABI build ${BUILD_TYPE:+(${BUILD_TYPE})} --features \"$FEATURES\""
 if [ "$BUILD_TYPE" = "release" ]; then
    cargo ndk -t "$ABI" -P 29 -o app/src/main/jniLibs/ build --release --features "$FEATURES"
 else
    cargo ndk -t "$ABI" -P 29 -o app/src/main/jniLibs/ build --features "$FEATURES"
 fi
 GRADLE_TASK="assembleDebug"
 APK_DIR="app/build/outputs/apk/debug"
 APK_NAME="app-debug.apk"
 if [ "$BUILD_TYPE" = "release" ]; then
    GRADLE_TASK="assembleRelease"
    APK_DIR="app/build/outputs/apk/release"
    APK_NAME="app-release.apk"
    # Same key `app/build-apk.sh` (the Compose app) generates once under
    # ~/.config/ai-app/release.jks -- see AGENTS.md's "Checking your work".
    export AI_APP_KEYSTORE="$HOME/.config/ai-app/release.jks"
    if [ ! -f "$AI_APP_KEYSTORE" ]; then
        echo "build-apk.sh: no release key at $AI_APP_KEYSTORE -- run app/build-apk.sh once first" >&2
        exit 1
    fi
    export AI_APP_KEYSTORE_PASSWORD
    AI_APP_KEYSTORE_PASSWORD=$(cat "$AI_APP_KEYSTORE.password")
 fi
 gradle ":app:$GRADLE_TASK" --console=plain
 APK_PATH="$(pwd)/$APK_DIR/$APK_NAME"
 BUILD_TOOLS=$(ls -d "$SDK_ROOT"/build-tools/*/ | sort -V | tail -1)
 echo "--- aapt2 dump badging ---"
 "${BUILD_TOOLS}aapt2" dump badging "$APK_PATH" | head -5
 if [ "$BUILD_TYPE" = "release" ]; then
    echo "--- apksigner verify ---"
    "${BUILD_TOOLS}apksigner" verify --print-certs "$APK_PATH"
 fi
 echo "$APK_PATH"
@@ -0,0 +1,74 @@
 #!/bin/sh
 # Installs and runs the iris `bench` build on this checkout's own emulator
 # (per this-machine-android's per-checkout-AVD rule; `emu serial` picks it)
 # and prints the report -- the iris half of `app/transcript-bench.sh`'s
 # job. No coordinates: the button is found by its accessibility label
 # through `ui-trace`, per AGENTS.md's "Driving the UI".
 #
 # Usage: ./run-bench.sh [--apk PATH]
 #   Defaults to this checkout's own release APK
 #   (app/build/outputs/apk/release/app-release.apk) if it exists, else the
 #   debug one -- build one first with ./build-apk.sh.
 set -eu
 cd "$(dirname "$0")"
 APK=""
 while [ $# -gt 0 ]; do
    case "$1" in
        --apk) APK="$2"; shift 2 ;;
        *) echo "run-bench.sh: unknown argument: $1" >&2; exit 1 ;;
    esac
 done
 if [ -z "$APK" ]; then
    if [ -f app/build/outputs/apk/release/app-release.apk ]; then
        APK=app/build/outputs/apk/release/app-release.apk
    else
        APK=app/build/outputs/apk/debug/app-debug.apk
    fi
 fi
 if [ ! -f "$APK" ]; then
    echo "run-bench.sh: no APK at $APK -- run ./build-apk.sh first" >&2
    exit 1
 fi
 SERIAL=$(emu serial)
 PKG=$(aapt2 dump badging "$APK" 2>/dev/null | sed -n "s/^package: name='\\([^']*\\)'.*/\\1/p")
 if [ -z "$PKG" ]; then
    BUILD_TOOLS=$(ls -d "$HOME"/Android/Sdk/build-tools/*/ | sort -V | tail -1)
    PKG=$("${BUILD_TOOLS}aapt2" dump badging "$APK" | sed -n "s/^package: name='\\([^']*\\)'.*/\\1/p")
 fi
 echo "run-bench.sh: installing $APK ($PKG) on $SERIAL"
 adb -s "$SERIAL" install -r "$APK" >/dev/null
 adb -s "$SERIAL" shell am force-stop "$PKG"
 adb -s "$SERIAL" logcat -c
 adb -s "$SERIAL" shell am start -n "$PKG/dev.iris.android.demo.MainActivity" >/dev/null
 ui-trace record -s "$SERIAL" -d 3000 --do "tap 'Run benchmark'" -o /tmp/run-bench-tap.txt >/dev/null
 # Poll for the report line rather than a fixed sleep -- the run itself is
 # a fixed script (RUST.md's "Benchmark v2": 16 flings, a 20s streaming
 # phase, ~61s of typing, 10s of keyboard toggles, roughly 2.5 minutes end
 # to end) but device speed varies. 260s cap rather than v1's 90s -- v2 is
 # a longer script than v1's swipe-loop-only run.
 # The report's own first line, not the bare "iris bench report:" prefix:
 # `copy_report` logs that prefix too ("nothing to copy -- run the benchmark
 # first", which the app emits at startup), so polling for the prefix
 # returned instantly and the script printed a report that was never run.
 REPORT_LINE="iris bench report: iris bench report"
 i=0
 while [ "$i" -lt 260 ]; do
    LINE=$(adb -s "$SERIAL" logcat -d -s iris-android-app:I 2>/dev/null | grep "$REPORT_LINE" || true)
    if [ -n "$LINE" ]; then
        break
    fi
    i=$((i + 1))
    sleep 1
 done
 if [ -z "$LINE" ]; then
    echo "run-bench.sh: no report after 260s -- check logcat by hand" >&2
    exit 1
 fi
 # -A 60 rather than v1's -A 6 -- v2's report has a per-phase block (four
 # phases, four lines each) on top of the frames/bench sections v1 had.
 adb -s "$SERIAL" logcat -d -s iris-android-app:I | grep -A 60 "$REPORT_LINE"
@@ -1,11 +1,14 @@
 //! JNI calls the `bench` feature needs that go through the shell's own
 //! Java side rather than anything `iris`/`android-view` already wraps:
 //! `BatteryManager.getIntProperty(BATTERY_PROPERTY_CURRENT_NOW)` for the
-//! per-second battery sample, and `ClipboardManager.setPrimaryClip` for
+//! per-second battery sample, `ClipboardManager.setPrimaryClip` for the
-//! the "Copy report" control (P0's iris half, docs/RUST.md). Neither is
+//! "Copy report" control (P0's iris half, docs/RUST.md), and -- added for
-//! part of `android_view::context`'s own `Context`/`Resources` wrappers
+//! RUST.md's "Benchmark v2" -- `Display.getRefreshRate()` for the phase
-//! (that file's own `// TODO: more methods?`), so this calls them
+//! report's real late-frame budget and `InputMethodManager.
-//! directly rather than growing that crate's wrapper for two one-off
+//! showSoftInput`/`hideSoftInputFromWindow` for the keyboard phase. None
 //! of these are part of `android_view::context`'s own `Context`/
 //! `Resources` wrappers (that file's own `// TODO: more methods?`), so
 //! this calls them directly rather than growing that crate's wrapper for
 //! calls this crate alone needs.
 //!
 //! Holds its own `JavaVM` + `GlobalRef` to the view (handed in through
@@ -131,4 +134,119 @@ impl PlatformHandle {
        .ok()?;
        Some(())
    }
    /// The display's own refresh rate in Hz (`View::getDisplay()` ->
    /// `Display::getRefreshRate()`), for RUST.md's "Benchmark v2": late
    /// frames are judged against *this* device's real budget, not an
    /// assumed 60Hz -- a 90Hz or 120Hz phone would otherwise call frames
    /// "late" that met their own faster deadline. `None` if the view is
    /// not yet attached to a window (`getDisplay` returns `null`) or the
    /// platform reports a non-positive rate, which is not a real answer
    /// either.
    pub fn refresh_rate_hz(&self) -> Option<f32> {
        let mut guard = self.vm.attach_current_thread().ok()?;
        let env: &mut JNIEnv = &mut guard;
        let display = env
            .call_method(
                self.view.as_obj(),
                "getDisplay",
                "()Landroid/view/Display;",
                &[],
            )
            .ok()?
            .l()
            .ok()?;
        if display.is_null() {
            return None;
        }
        let rate = env
            .call_method(&display, "getRefreshRate", "()F", &[])
            .ok()?
            .f()
            .ok()?;
        if rate > 0.0 { Some(rate) } else { None }
    }
    /// `InputMethodManager.showSoftInput(view, 0)` -- the keyboard phase's
    /// own show, called directly rather than through the focus-driven
    /// `pending_show_keyboard` path `android/view.rs` uses for a real tap,
    /// since RUST.md's "Benchmark v2" spec asks for this "through the
    /// shell's InputMethodManager" independent of focus state. `true` only
    /// if the platform itself reports the request succeeded -- whether the
    /// IME actually became visible is confirmed separately, from
    /// `on_insets_changed`, per UI_RULES.md ("never present an inferred
    /// value as a measured one").
    pub fn show_ime(&self) -> bool {
        self.try_toggle_ime(true).unwrap_or(false)
    }
    /// `InputMethodManager.hideSoftInputFromWindow(windowToken, 0)`.
    pub fn hide_ime(&self) -> bool {
        self.try_toggle_ime(false).unwrap_or(false)
    }
    fn try_toggle_ime(&self, show: bool) -> Option<bool> {
        let mut guard = self.vm.attach_current_thread().ok()?;
        let env: &mut JNIEnv = &mut guard;
        let context = self.context(env)?;
        let imm = self.system_service(env, &context, "input_method")?;
        if show {
            env.call_method(
                &imm,
                "showSoftInput",
                "(Landroid/view/View;I)Z",
                &[JValue::Object(self.view.as_obj()), JValue::Int(0)],
            )
            .ok()?
            .z()
            .ok()
        } else {
            let token = env
                .call_method(
                    self.view.as_obj(),
                    "getWindowToken",
                    "()Landroid/os/IBinder;",
                    &[],
                )
                .ok()?
                .l()
                .ok()?;
            env.call_method(
                &imm,
                "hideSoftInputFromWindow",
                "(Landroid/os/IBinder;I)Z",
                &[JValue::Object(&token), JValue::Int(0)],
            )
            .ok()?
            .z()
            .ok()
        }
    }
    /// Shows `report` in the shell's plain-view diagnostics overlay
    /// (`IrisView.showDiagnosticsOverlay`) -- a real `TextView` plus Copy
    /// and Close controls, added over whatever iris itself is drawing
    /// rather than replacing it (unlike `android::view::show_renderer_error`,
    /// which exists for the case the renderer can never recover from and
    /// intentionally never returns). Called from a background task after
    /// the keyboard-open delay (`bench_client.rs`'s `on_insets_changed`),
    /// so the Java side hops onto the UI thread itself before touching the
    /// view tree -- see that method's own comment.
    pub fn show_diagnostics_overlay(&self, report: &str) -> bool {
        self.try_show_diagnostics_overlay(report).is_some()
    }
    fn try_show_diagnostics_overlay(&self, report: &str) -> Option<()> {
        let mut guard = self.vm.attach_current_thread().ok()?;
        let env: &mut JNIEnv = &mut guard;
        let jreport = env.new_string(report).ok()?;
        env.call_method(
            self.view.as_obj(),
            "showDiagnosticsOverlay",
            "(Ljava/lang/String;)V",
            &[JValue::Object(jreport.as_ref())],
        )
        .ok()?;
        Some(())
    }
 }
@@ -20,14 +20,22 @@
 //! **Reuses `iris/desktop-app`'s `app.rs` shape almost exactly** --
 //! `fold_event`/`group_tool_runs`/`fold_page`/`raw_seq` from
 //! `client_core::transcript_fold`, a `generation` counter guarding against
-//! a stale background response, and a full rebuild of the widget tree on
+//! a stale background response. What differs is only the redraw
-//! every event (same tradeoff, same reason: `push_row` cannot update a row
+//! mechanism: android-view has no `winit::EventLoopProxy`, so this uses
-//! already on screen, and this rig's conversations are small). What
+//! `iris::task::Tasks::redraw_handle` (new, added alongside this box) to
-//! differs is only the redraw mechanism: android-view has no
+//! request a frame after each `TaskCtx::update` instead of relying on
-//! `winit::EventLoopProxy`, so this uses `iris::task::Tasks::redraw_handle`
+//! `Tasks::spawn`'s single end-of-future redraw -- see that method's own
-//! (new, added alongside this box) to request a frame after each
+//! doc for why.
-//! `TaskCtx::update` instead of relying on `Tasks::spawn`'s single
+//!
-//! end-of-future redraw -- see that method's own doc for why.
+//! **Streaming no longer costs a full rebuild** (fixed after the P0 gate
 //! showed why it mattered -- 20 events/second means 20 rebuilds/second of
 //! a ~3,200-row transcript otherwise): `apply_event` calls
 //! `transcript_ui::TranscriptScreen::apply` with the item list before and
 //! after `fold_event`, which updates only the row(s) that actually
 //! changed (almost always just the one open assistant message) instead of
 //! refolding and rebuilding every row. `rebuild_transcript` still runs
 //! the whole widget tree once, for the opening page and for `apply`'s own
 //! rare regroup fallback.
 use client_core::api::{ApiClient, UreqTransport};
 use client_core::event_stream::{StreamItem, follow_session_events};
@@ -360,8 +368,17 @@ impl TranscriptClient {
    }
    fn apply_event(&mut self, rsc: &mut AndroidRsc<Self>, event: &SeqEvent) {
        let old_items = self.items.clone();
        self.items = fold_event(&self.items, event);
-        self.rebuild_transcript(rsc);
+        match &self.screen {
            // The common path: update only the row(s) that actually
            // changed instead of refolding and rebuilding all ~3,200 of
            // them per event (RUST.md's P0 streaming-phase fix).
            Some(screen) => screen.apply(rsc, &old_items, &self.items),
            // No screen yet (the opening page hasn't landed) -- build one
            // the ordinary way once it has.
            None => self.rebuild_transcript(rsc),
        }
    }
    fn send_message(&mut self, session_id: String, text: String) {
@@ -0,0 +1,152 @@
 #!/usr/bin/env python3
 """AOSP's fling spline, transcribed independently of the Rust port.
 This exists so the numbers in `sense.rs`'s `the_spline_matches_aosps_own_table`
 and `a_flick_decelerates_the_way_aosp_says_it_does` are not the Rust code
 grading its own homework. Every test iris's fling had before 2026-09-07
 compared the curve with itself -- monotonic, signed, integrates to the closed
 form -- and all of them passed while `distance_fraction(t)` was returning
 exactly `t` (see `android_fling_spline`'s doc comment). Numbers checked into a
 test have to come from somewhere else, and this is the somewhere else.
 Transcribed by hand from, and only from:
  * frameworks/base `core/java/android/widget/OverScroller.java`,
    `SplineOverScroller`'s static initialiser, `getSplineDeceleration`,
    `getSplineFlingDistance`, `getSplineFlingDuration` and `update`.
  * androidx.compose.animation:animation:1.12.0 `SplineBasedDecay.kt`
    (`computeSplineInfo`, `AndroidFlingSpline.flingPosition`) and
    `FlingCalculator.kt` (`computeDeceleration`, `flingDistance`,
    `flingDuration`, `FlingInfo.position`/`velocity`). The two agree line for
    line, which is why iris ports one curve rather than two.
 Run it with no arguments; it prints the table entries and the (velocity,
 density, t) points the Rust tests assert on.
 """
 NB_SAMPLES = 100
 INFLEXION = 0.35
 START_TENSION = 0.5
 END_TENSION = 1.0
 P1 = START_TENSION * INFLEXION
 P2 = 1.0 - END_TENSION * (1.0 - INFLEXION)
 # ViewConfiguration.getScrollFriction(), and SplineOverScroller's own
 # "look and feel tuning" constant -- a different number in a different place
 # of the same formula, which is the pair iris got the wrong way round once.
 SCROLL_FRICTION = 0.015
 TUNING = 0.84
 GRAVITY_EARTH = 9.80665
 INCHES_PER_METER = 39.37
 import math
 DECELERATION_RATE = math.log(0.78) / math.log(0.9)
 def spline_positions():
    """SPLINE_POSITION: distance fraction at each of 101 even time steps."""
    position = [0.0] * (NB_SAMPLES + 1)
    x_min = 0.0
    for i in range(NB_SAMPLES):
        alpha = i / NB_SAMPLES
        x_max = 1.0
        while True:
            x = x_min + (x_max - x_min) / 2.0
            coef = 3.0 * x * (1.0 - x)
            # Solved on the P1/P2 curve...
            tx = coef * ((1.0 - x) * P1 + x * P2) + x * x * x
            if abs(tx - alpha) < 1e-5:
                break
            if tx > alpha:
                x_max = x
            else:
                x_min = x
        # ...and sampled on the tension curve.
        position[i] = coef * ((1.0 - x) * START_TENSION + x * END_TENSION) + x * x * x
    position[NB_SAMPLES] = 1.0
    return position
 POSITION = spline_positions()
 def fling_sample(t):
    """(distance fraction, velocity fraction) at time fraction `t`."""
    t = min(max(t, 0.0), 1.0)
    index = int(t * NB_SAMPLES)
    if index >= NB_SAMPLES:
        return 1.0, 0.0
    t_inf = index / NB_SAMPLES
    t_sup = (index + 1) / NB_SAMPLES
    velocity_coef = (POSITION[index + 1] - POSITION[index]) / (t_sup - t_inf)
    return POSITION[index] + (t - t_inf) * velocity_coef, velocity_coef
 def physical_coefficient(density):
    return GRAVITY_EARTH * INCHES_PER_METER * density * 160.0 * TUNING
 def deceleration(velocity, density):
    return math.log(
        INFLEXION * abs(velocity) / (SCROLL_FRICTION * physical_coefficient(density))
    )
 def fling_distance(velocity, density):
    l = deceleration(velocity, density)
    return (
        SCROLL_FRICTION
        * physical_coefficient(density)
        * math.exp(DECELERATION_RATE / (DECELERATION_RATE - 1.0) * l)
    )
 def fling_duration_s(velocity, density):
    l = deceleration(velocity, density)
    return math.exp(l / (DECELERATION_RATE - 1.0))
 def position_at(velocity, density, t_seconds):
    d = fling_duration_s(velocity, density)
    return fling_distance(velocity, density) * fling_sample(t_seconds / d)[0]
 def velocity_at(velocity, density, t_seconds):
    d = fling_duration_s(velocity, density)
    return fling_sample(t_seconds / d)[1] * fling_distance(velocity, density) / d
 if __name__ == "__main__":
    print("SPLINE_POSITION at a few indices (index: value)")
    for i in (0, 1, 10, 25, 50, 75, 99, 100):
        print(f"  {i:3}: {POSITION[i]:.6f}")
    print()
    print("distance/velocity fraction at time fractions")
    for t in (0.0, 0.1, 0.25, 0.5, 0.75, 0.9, 1.0):
        d, v = fling_sample(t)
        print(f"  t={t:<5} distance={d:.6f} velocity={v:.6f}")
    print()
    # 2.55 is Iris's Pixel 9 Pro XL (docs/bench/iris-phone-v2-2026-09-06.md);
    # 2.75 is this checkout's emulator.
    for density in (2.55, 2.75):
        for velocity in (5000.0, 11064.0):
            dur = fling_duration_s(velocity, density)
            print(
                f"density={density} v={velocity}: "
                f"distance={fling_distance(velocity, density):.3f}px "
                f"duration={dur:.4f}s"
            )
            # Deliberately not round fractions. The velocity coefficient is
            # piecewise *constant* across each of the 100 samples, so it
            # steps at t = k/100 and a test asserting on 0.75 is asserting
            # on which side of a discontinuity the last float landed --
            # which is genuinely different between Python and Rust and says
            # nothing about the curve.
            for frac in (0.125, 0.335, 0.505, 0.755):
                t = frac * dur
                print(
                    f"    t={frac:>4} of duration ({t:.4f}s): "
                    f"pos={position_at(velocity, density, t):.3f}px "
                    f"vel={velocity_at(velocity, density, t):.3f}px/s"
                )
@@ -142,7 +142,7 @@ fn bench_first_frame(n: usize) {
    let start = Instant::now();
    render.update(&root, &mut rsc);
    let elapsed = start.elapsed();
-    let (draws, rewrites, moves) = render.take_counters();
+    let (draws, rewrites, moves, _shapes) = render.take_counters();
    report(
        &format!("(a) first frame, N={n}"),
        elapsed,
@@ -177,7 +177,7 @@ fn bench_scroll(n: usize, ticks: usize) {
        let start = Instant::now();
        render.update(&root, &mut rsc);
        total += start.elapsed();
-        let (draws, rewrites, moves) = render.take_counters();
+        let (draws, rewrites, moves, _shapes) = render.take_counters();
        total_draws += draws;
        total_rewrites += rewrites;
        total_moves += moves;
@@ -245,7 +245,7 @@ fn bench_input_grows(n: usize, lines: usize) {
        let start = Instant::now();
        render.update(&root, &mut rsc);
        total += start.elapsed();
-        let (draws, rewrites, moves) = render.take_counters();
+        let (draws, rewrites, moves, _shapes) = render.take_counters();
        total_draws += draws;
        total_rewrites += rewrites;
        total_moves += moves;
@@ -302,7 +302,7 @@ fn bench_insert_above_anchor(n: usize, inserts: usize) {
        let start = Instant::now();
        render.update(&root, &mut rsc);
        total += start.elapsed();
-        let (draws, rewrites, moves) = render.take_counters();
+        let (draws, rewrites, moves, _shapes) = render.take_counters();
        total_draws += draws;
        total_rewrites += rewrites;
        total_moves += moves;
@@ -384,7 +384,7 @@ fn bench_expand_holds_edge(n: usize, growths: usize) {
        let start = Instant::now();
        render.update(&root, &mut rsc);
        total += start.elapsed();
-        let (draws, rewrites, moves) = render.take_counters();
+        let (draws, rewrites, moves, _shapes) = render.take_counters();
        total_draws += draws;
        total_rewrites += rewrites;
        total_moves += moves;
@@ -5,6 +5,12 @@ edition.workspace = true
 [dependencies]
 wgpu = { workspace = true }
 # Only for `UiRenderNode::new`'s `push_error_scope`/`pop_error_scope` pair
 # (renderer-creation error reporting, RUST.md's P0 phone-crash box) --
 # `block_on` turns that one async pop into the same synchronous call shape
 # `device_limits()`'s two callers already use for `request_adapter`/
 # `request_device`, rather than making this crate's one entry point async.
 pollster = { workspace = true }
 bytemuck ={ workspace = true }
 image = { workspace = true }
 parley = { workspace = true }
@@ -0,0 +1,201 @@
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@@ -9,7 +9,31 @@ pub struct Size {
 #[derive(Debug, Clone, Copy, PartialEq)]
 pub struct Len {
    /// Physical pixels -- a raw device pixel, unaffected by the display's
    /// density. Rare to want directly (a hairline border is the usual
    /// case); most sizes should be `dp` instead. See `dp`'s own doc for why
    /// the two are kept separate rather than one field a caller has to
    /// remember to pre-multiply.
    pub abs: f32,
    /// Density-independent pixels -- Android's `dp` / CSS's reference pixel
    /// (1 unit = 1/160in), resolved against the display's density at
    /// layout time (`apply_rest`'s `density` parameter) rather than at the
    /// point a widget is built, since density is a property of the device
    /// this ends up running on, not of the widget tree. This is the unit
    /// IRIS_TODO.md's "a density-independent length unit" item asked for,
    /// 2026-09-06: before it existed, every size in the tree was `abs`
    /// (physical pixels), and the only way to make a 16px design draw at
    /// the right *size* on a denser display was a single global multiply
    /// applied to the whole rendered scene after layout -- which is also
    /// what made text blurry (RUST.md's P0 box, "blurry ... glyphs drawn
    /// at logical size and stretched by the scale"): a glyph rasterised at
    /// 16 physical px and then stretched 3x by that global multiply is a
    /// 48px area sampled from a 16px bitmap. Resolving `dp` per-length at
    /// layout time instead means the font size handed to the text shaper
    /// is already the physical size (`16.0.dp() * 3.0`), so the glyph
    /// atlas rasterises at the display's real resolution and nothing
    /// downstream needs to stretch anything.
    pub dp: f32,
    pub rel: f32,
    pub rest: f32,
 }
@@ -67,10 +91,10 @@ impl Size {
        }
    }
-    pub fn to_uivec2(self) -> UiVec2 {
+    pub fn to_uivec2(self, density: f32) -> UiVec2 {
        UiVec2 {
-            x: self.x.apply_rest(),
+            x: self.x.apply_rest(density),
-            y: self.y.apply_rest(),
+            y: self.y.apply_rest(density),
        }
    }
@@ -98,26 +122,66 @@ impl Size {
 impl Len {
    pub const ZERO: Self = Self {
        abs: 0.0,
        dp: 0.0,
        rel: 0.0,
        rest: 0.0,
    };
    pub const REST: Self = Self {
        abs: 0.0,
        dp: 0.0,
        rel: 0.0,
        rest: 1.0,
    };
-    pub fn apply_rest(&self) -> UiScalar {
+    /// Resolves to a `UiScalar`, folding `dp` into `abs` pixels against
    /// `density` (physical pixels per dp -- 1.0 on a desktop or an
    /// unscaled display, `content_scale` on Android; see `dp`'s field
    /// doc). Every other component of `Len` is already resolution-
    /// independent (`rel` is a fraction of the parent; `rest` becomes a
    /// fraction too, below), so `density` only ever touches this one term.
    pub fn apply_rest(&self, density: f32) -> UiScalar {
        UiScalar {
            rel: self.rel + if self.rest > 0.0 { 1.0 } else { 0.0 },
-            abs: self.abs,
+            abs: self.abs + self.dp * density,
        }
    }
    /// The same fold as [`Self::apply_rest`] but staying a `Len`, so
    /// `rest` survives: `dp` becomes physical pixels and every other
    /// component is left alone.
    ///
    /// **A `Len` a widget *reports* must have been through this.** `dp` is
    /// an input unit -- a number the widget author wrote -- and the
    /// containers that consume a reported length read `abs`/`rel`/`rest`
    /// directly (`Span::draw`'s placement arithmetic, `Pad`'s addition),
    /// so a reported `dp` is silently worth zero. That is what made the
    /// composer's bar collapse to nothing the moment its content grew past
    /// `MaxSize`'s cap: the cap was `dp(168)` and was returned unresolved,
    /// so the bar was given a slot of 0 and the field inside it was panned
    /// out of a container measured at -63px. `UiRenderState::draw_inner`
    /// debug-asserts the invariant after every `Widget::draw`.
    pub fn fold_dp(&self, density: f32) -> Self {
        Self {
            abs: self.abs + self.dp * density,
            dp: 0.0,
            rel: self.rel,
            rest: self.rest,
        }
    }
    pub fn abs(abs: impl UiNum) -> Self {
        Self {
            abs: abs.to_f32(),
            dp: 0.0,
            rel: 0.0,
            rest: 0.0,
        }
    }
    pub fn dp(dp: impl UiNum) -> Self {
        Self {
            abs: 0.0,
            dp: dp.to_f32(),
            rel: 0.0,
            rest: 0.0,
        }
@@ -125,6 +189,7 @@ impl Len {
    pub fn rel(rel: impl UiNum) -> Self {
        Self {
            abs: 0.0,
            dp: 0.0,
            rel: rel.to_f32(),
            rest: 0.0,
        }
@@ -132,6 +197,7 @@ impl Len {
    pub fn rest(ratio: impl UiNum) -> Self {
        Self {
            abs: 0.0,
            dp: 0.0,
            rel: 0.0,
            rest: ratio.to_f32(),
        }
@@ -144,6 +210,15 @@ pub mod len_fns {
    pub fn abs(abs: impl UiNum) -> Len {
        Len {
            abs: abs.to_f32(),
            dp: 0.0,
            rel: 0.0,
            rest: 0.0,
        }
    }
    pub fn dp(dp: impl UiNum) -> Len {
        Len {
            abs: 0.0,
            dp: dp.to_f32(),
            rel: 0.0,
            rest: 0.0,
        }
@@ -151,6 +226,7 @@ pub mod len_fns {
    pub fn rel(rel: impl UiNum) -> Len {
        Len {
            abs: 0.0,
            dp: 0.0,
            rel: rel.to_f32(),
            rest: 0.0,
        }
@@ -158,14 +234,15 @@ pub mod len_fns {
    pub fn rest(ratio: impl UiNum) -> Len {
        Len {
            abs: 0.0,
            dp: 0.0,
            rel: 0.0,
            rest: ratio.to_f32(),
        }
    }
 }
-impl_op!(Len Add add; abs rel rest);
+impl_op!(Len Add add; abs dp rel rest);
-impl_op!(Len Sub sub; abs rel rest);
+impl_op!(Len Sub sub; abs dp rel rest);
 impl_op!(Size Add add; x y);
 impl_op!(Size Sub sub; x y);
@@ -187,6 +264,9 @@ impl std::fmt::Display for Len {
        if self.abs != 0.0 {
            write!(f, "{} abs;", self.abs)?;
        }
        if self.dp != 0.0 {
            write!(f, "{} dp;", self.dp)?;
        }
        if self.rel != 0.0 {
            write!(f, "{} rel;", self.rel)?;
        }
@@ -2,14 +2,63 @@ use crate::{Align, GlyphAtlas, GlyphKey, PlacedGlyph, RegionAlign, Textures, UiC
 use parley::{
    Alignment, AlignmentOptions, FontContext, FontFamily, FontFamilyName, FontStyle, FontWeight,
    GenericFamily, Layout, LayoutContext, LineHeight, PositionedLayoutItem, StyleProperty,
    fontique::{Blob, FamilyId},
 };
 use std::ops::Range;
 use std::sync::Arc;
 use swash::{
    FontRef,
    scale::{Render, ScaleContext, Source, StrikeWith},
    zeno::{Format, Vector},
 };
 /// Bundled fonts, registered over the system collection rather than relied
 /// on alone -- see `TextData::register_bundled_fonts`'s doc comment for
 /// why. Static weight/style cuts, not a variable font: parley/fontique
 /// resolve a variable font's weight axis by picking normalized coordinates
 /// on whatever single face registers for the family, and a phone whose
 /// system "Roboto" is actually the variable "Roboto Flex" is exactly the
 /// device class this sidesteps, rather than depends on working correctly.
 /// Noto Sans, OFL-licensed (`assets/fonts/OFL.txt`), chosen for coverage
 /// breadth (a transcript's content is not known in advance) over a
 /// smaller-footprint alternative -- see the doc comment for the size this
 /// added.
 const NOTO_SANS_REGULAR: &[u8] = include_bytes!("../../assets/fonts/NotoSans-Regular.ttf");
 const NOTO_SANS_BOLD: &[u8] = include_bytes!("../../assets/fonts/NotoSans-Bold.ttf");
 const NOTO_SANS_ITALIC: &[u8] = include_bytes!("../../assets/fonts/NotoSans-Italic.ttf");
 const NOTO_SANS_BOLD_ITALIC: &[u8] = include_bytes!("../../assets/fonts/NotoSans-BoldItalic.ttf");
 const NOTO_SANS_MONO_REGULAR: &[u8] = include_bytes!("../../assets/fonts/NotoSansMono-Regular.ttf");
 const NOTO_SANS_MONO_BOLD: &[u8] = include_bytes!("../../assets/fonts/NotoSansMono-Bold.ttf");
 /// What starting up found about text rendering, for the on-screen
 /// Diagnostics page and the one startup log line (RUST.md's P0 box, "log
 /// once at startup ... the number of font families found, the default
 /// family resolved"). Built once by `TextData::font_diagnostics` --
 /// `Default::default` still exists for callers (tests, examples) that
 /// don't need the report.
 #[derive(Clone, Debug)]
 pub struct FontDiagnostics {
    /// `Collection::family_names().count()` after registering the bundled
    /// fonts -- system families plus the two bundled ones.
    pub families_found: usize,
    /// The family `GenericFamily::SansSerif` resolves to first -- the
    /// bundled "Noto Sans" unless registration itself failed.
    pub default_family: Option<String>,
    /// The family `GenericFamily::Monospace` resolves to first.
    pub default_mono_family: Option<String>,
    /// One resolved family name per style axis this crate actually uses
    /// (`SpanStyle::bold`/`italic`), so a report can say plainly whether a
    /// bold/italic request is landing on a real face rather than being
    /// silently absorbed by whatever the sans-serif default resolves to
    /// for every weight (RUST.md's P0 box, "bold words render as blank
    /// gaps" -- a family that resolves but has no distinct bold face is
    /// exactly what produced that).
    pub regular_resolved: Option<String>,
    pub bold_resolved: Option<String>,
    pub italic_resolved: Option<String>,
    pub mono_resolved: Option<String>,
 }
 /// Everything text needs that outlives one string: the font collection, the
 /// layout scratch space, the glyph rasteriser and the atlas they fill.
 pub struct TextData {
@@ -17,15 +66,182 @@ pub struct TextData {
    pub layout_cx: LayoutContext<UiColor>,
    scale_cx: ScaleContext,
    pub atlas: GlyphAtlas,
    /// Physical pixels per dp -- a second copy of
    /// `UiRenderState::density`, kept here too because `TextEditCtx::layout`
    /// (cursor movement and hit-testing, `widget/text/edit.rs`) shapes text
    /// from an event callback that has a `TextData` but no `Painter`, so it
    /// has nowhere else to read the display's density from. Both copies are
    /// set together, from the one place either backend learns the real
    /// value (`android::view::new_peer`); this is the same accepted
    /// duplication as `AndroidRenderer::content_scale`; a single source of
    /// truth would mean carrying a `Painter` (or output size) into every
    /// input handler for the sake of one field.
    pub density: f32,
 }
 impl Default for TextData {
    fn default() -> Self {
-        Self {
+        let mut data = Self {
            font_cx: FontContext::new(),
            layout_cx: LayoutContext::new(),
            scale_cx: ScaleContext::new(),
            atlas: GlyphAtlas::default(),
            density: 1.0,
        };
        data.register_bundled_fonts();
        data
    }
 }
 impl TextData {
    /// Registers Noto Sans (regular/bold/italic/bold-italic) and Noto Sans
    /// Mono (regular/bold) as static faces, and puts them **first** in the
    /// `SansSerif`/`Monospace` generic-family fallback lists -- ahead of,
    /// not instead of, whatever the platform already found, so a script
    /// Noto Sans lacks (CJK, emoji, ...) still falls through to the system
    /// font the same as before this existed.
    ///
    /// Exists because text rendering must not depend on the platform's own
    /// font enumeration succeeding or resolving weight/style the way this
    /// crate assumes: RUST.md's P0 box found bold spans on a real phone
    /// rendering as blank gaps of the correct advance width (the glyph
    /// simply wasn't rasterised -- `TextData::place`'s `None` arm), while
    /// the emulator's system fonts happened to resolve every style. A
    /// bundled, static-per-style family removes fontique's Android font
    /// scan (`fontique::backend::android::SystemFonts::new`, which parses
    /// `/system/fonts` and `/system/etc/fonts.xml`) from the path a glyph
    /// has to survive to reach the screen at all.
    ///
    /// Cost: six static `.ttf`s, ~3.6 MB uncompressed
    /// (`iris/core/assets/fonts/`), landing in the APK compressed --
    /// `build-apk.sh`'s own output is what says the delivered number, not
    /// this comment.
    fn register_bundled_fonts(&mut self) {
        fn register(cx: &mut FontContext, bytes: &'static [u8]) -> Option<FamilyId> {
            let blob = Blob::new(Arc::new(bytes));
            cx.collection
                .register_fonts(blob, None)
                .into_iter()
                .map(|(id, _)| id)
                .next()
        }
        let sans_id = register(&mut self.font_cx, NOTO_SANS_REGULAR);
        register(&mut self.font_cx, NOTO_SANS_BOLD);
        register(&mut self.font_cx, NOTO_SANS_ITALIC);
        register(&mut self.font_cx, NOTO_SANS_BOLD_ITALIC);
        let mono_id = register(&mut self.font_cx, NOTO_SANS_MONO_REGULAR);
        register(&mut self.font_cx, NOTO_SANS_MONO_BOLD);
        if let Some(sans_id) = sans_id {
            let existing: Vec<_> = self
                .font_cx
                .collection
                .generic_families(GenericFamily::SansSerif)
                .collect();
            self.font_cx.collection.set_generic_families(
                GenericFamily::SansSerif,
                std::iter::once(sans_id).chain(existing),
            );
            let existing: Vec<_> = self
                .font_cx
                .collection
                .generic_families(GenericFamily::SystemUi)
                .collect();
            self.font_cx.collection.set_generic_families(
                GenericFamily::SystemUi,
                std::iter::once(sans_id).chain(existing),
            );
        }
        if let Some(mono_id) = mono_id {
            let existing: Vec<_> = self
                .font_cx
                .collection
                .generic_families(GenericFamily::Monospace)
                .collect();
            self.font_cx.collection.set_generic_families(
                GenericFamily::Monospace,
                std::iter::once(mono_id).chain(existing),
            );
        }
    }
    /// Builds the startup report -- see `FontDiagnostics`. Queries the
    /// collection directly (`fontique::Query`) rather than shaping a real
    /// string, since all that's needed is which family each axis lands on.
    pub fn font_diagnostics(&mut self) -> FontDiagnostics {
        use parley::fontique::{Attributes, FontWidth, QueryStatus};
        let families_found = self.font_cx.collection.family_names().count();
        let default_family_id = self
            .font_cx
            .collection
            .generic_families(GenericFamily::SansSerif)
            .next();
        let default_family = default_family_id
            .and_then(|id| self.font_cx.collection.family_name(id).map(str::to_string));
        let default_mono_family_id = self
            .font_cx
            .collection
            .generic_families(GenericFamily::Monospace)
            .next();
        let default_mono_family = default_mono_family_id
            .and_then(|id| self.font_cx.collection.family_name(id).map(str::to_string));
        // Resolves the family a (generic family, weight, style) query lands
        // on, without holding the `Query`'s borrow of `collection` across
        // the `family_name` lookup that needs it back -- the `FamilyId` is
        // captured out of the closure first, then looked up once `query`
        // (and its borrow) has been dropped.
        let mut resolve_family =
            |generic: GenericFamily, weight: FontWeight, style: FontStyle| -> Option<String> {
                let mut family_id = None;
                {
                    let mut query = self
                        .font_cx
                        .collection
                        .query(&mut self.font_cx.source_cache);
                    query.set_families([generic]);
                    query.set_attributes(Attributes {
                        width: FontWidth::NORMAL,
                        style,
                        weight,
                    });
                    query.matches_with(|font| {
                        family_id = Some(font.family.0);
                        QueryStatus::Stop
                    });
                }
                family_id.and_then(|id| self.font_cx.collection.family_name(id).map(str::to_string))
            };
        let regular_resolved = resolve_family(
            GenericFamily::SansSerif,
            FontWeight::NORMAL,
            FontStyle::Normal,
        );
        let bold_resolved = resolve_family(
            GenericFamily::SansSerif,
            FontWeight::BOLD,
            FontStyle::Normal,
        );
        let italic_resolved = resolve_family(
            GenericFamily::SansSerif,
            FontWeight::NORMAL,
            FontStyle::Italic,
        );
        let mono_resolved = resolve_family(
            GenericFamily::Monospace,
            FontWeight::NORMAL,
            FontStyle::Normal,
        );
        FontDiagnostics {
            families_found,
            default_family,
            default_mono_family,
            regular_resolved,
            bold_resolved,
            italic_resolved,
            mono_resolved,
        }
    }
 }
@@ -159,7 +375,7 @@ pub struct TextBuffer {
    /// `set_spans` forces `shaped` to `None` directly, the same way `edit`
    /// does, since spans change far less often than a naive equality check
    /// on the whole `Vec` would cost to compute every frame.
-    shaped: Option<(TextAttrs, Option<f32>)>,
+    shaped: Option<(TextAttrs, Option<f32>, f32)>,
 }
 impl TextBuffer {
@@ -215,19 +431,42 @@ impl TextBuffer {
        Vec2::new(self.layout.width(), self.layout.height())
    }
-    /// Lay the text out, unless it is already laid out for these attributes and
+    /// Lay the text out, unless it is already laid out for these
-    /// this width.
+    /// attributes, this width and this density.
-    pub fn shape(&mut self, data: &mut TextData, attrs: &TextAttrs, width: Option<f32>) {
+    ///
-        if self.shaped.as_ref() == Some(&(attrs.clone(), width)) {
+    /// **`attrs.font_size`/`line_height` and every span's own `font_size`
    /// are density-independent (dp) units, multiplied by `density` here --
    /// the one place text crosses from the widget tree's dp sizes into the
    /// physical pixels the shaper and rasteriser (`TextData::place`) both
    /// then work in.** This is what makes glyphs sharp on a dense display:
    /// before this existed, `font_size` was already a physical-pixel value
    /// (RUST.md's P0 box's global-scale stopgap resolved density by
    /// stretching the whole rendered frame afterward instead), so a glyph
    /// was rasterised small and then upscaled by whatever the display's
    /// scale factor was -- exactly the blur Iris's report described.
    /// Multiplying here instead means the font size hitting `ScaleContext`
    /// in `place` below is already the display's real physical size, so
    /// the atlas holds a bitmap at the resolution it is actually shown at.
    /// `GlyphKey.size` already keys on that resolved `font_size`
    /// (`(font_size * 16.0).round()`), so a cache entry is naturally per
    /// physical size with no change needed there.
    pub fn shape(
        &mut self,
        data: &mut TextData,
        attrs: &TextAttrs,
        width: Option<f32>,
        density: f32,
    ) {
        if self.shaped.as_ref() == Some(&(attrs.clone(), width, density)) {
            return;
        }
        let mut builder = data
            .layout_cx
            .ranged_builder(&mut data.font_cx, &self.text, 1.0, true);
        builder.push_default(StyleProperty::FontFamily(attrs.family.family()));
-        builder.push_default(StyleProperty::FontSize(attrs.font_size));
+        builder.push_default(StyleProperty::FontSize(attrs.font_size * density));
        builder.push_default(StyleProperty::LineHeight(LineHeight::Absolute(
-            attrs.line_height,
+            attrs.line_height * density,
        )));
        builder.push_default(StyleProperty::Brush(attrs.color));
        for span in &self.spans {
@@ -239,7 +478,7 @@ impl TextBuffer {
                builder.push(StyleProperty::FontFamily(family.family()), range.clone());
            }
            if let Some(size) = span.font_size {
-                builder.push(StyleProperty::FontSize(size), range.clone());
+                builder.push(StyleProperty::FontSize(size * density), range.clone());
            }
            if span.bold {
                builder.push(StyleProperty::FontWeight(FontWeight::BOLD), range.clone());
@@ -255,7 +494,7 @@ impl TextBuffer {
        self.layout.break_all_lines(width);
        self.layout
            .align(Alignment::Start, AlignmentOptions::default());
-        self.shaped = Some((attrs.clone(), width));
+        self.shaped = Some((attrs.clone(), width, density));
    }
 }
@@ -362,6 +601,11 @@ pub struct RenderedText {
    pub glyphs: std::sync::Arc<Vec<PlacedGlyph>>,
    pub size: Vec2,
    pub color: UiColor,
    /// The [`GlyphAtlas::generation`] the glyphs above were placed against.
    /// A holder must re-render rather than re-emit these quads once the
    /// atlas has moved on (`GlyphAtlas::clear`'s doc says what happens
    /// otherwise); `Painter::glyphs` debug-asserts it.
    pub generation: u64,
 }
 impl TextData {
@@ -372,13 +616,15 @@ impl TextData {
        attrs: &TextAttrs,
        width: Option<f32>,
        textures: &mut Textures,
        density: f32,
    ) -> RenderedText {
-        buffer.shape(self, attrs, width);
+        buffer.shape(self, attrs, width, density);
        let glyphs = self.place(buffer, textures);
        RenderedText {
            glyphs: std::sync::Arc::new(glyphs),
            size: buffer.size(),
            color: attrs.color,
            generation: self.atlas.generation(),
        }
    }
 }
@@ -141,6 +141,27 @@ impl Textures {
        self.updates.push(Update::Patch(handle.slot, rect));
    }
    /// Forget every image, page and pending update -- what a genuinely new
    /// GPU device needs alongside [`crate::render::atlas::GlyphAtlas::
    /// clear`], which this module's own doc references: every slot number
    /// and every queued [`Update`] here describes the *old* device's
    /// textures (an `Update::Push`/`Update::Patch` already drained into a
    /// renderer that no longer exists is gone for good, and a fresh
    /// `UiRenderNode`'s own texture manager starts with none of them
    /// applied), so nothing is lost by starting this bookkeeping over too.
    /// Any `TextureHandle` a caller still holds across the reset (none in
    /// the transcript screen this reset is wired up for today -- confirmed
    /// by grep, the only standalone (non-atlas) image anywhere in this
    /// workspace is `iris/widget/image.rs`'s `Image`, used by the separate
    /// `tabs-ui` example) is left pointing at a slot this instance no
    /// longer recognises and needs reinserting via `add`/`add_page` again
    /// -- the same pre-existing gap a renderer restart already left for
    /// such a handle before this method existed, just named rather than
    /// silent now.
    pub fn reset(&mut self) {
        *self = Self::new();
    }
    pub fn free(&mut self) {
        for (kind, idx) in self.recv.try_iter() {
            self.images[idx as usize] = None;
@@ -71,6 +71,10 @@ struct Page {
 #[derive(Default)]
 pub struct GlyphAtlas {
    pages: Vec<Page>,
    /// Bumped by [`GlyphAtlas::clear`], so anything holding placed glyphs
    /// from an earlier atlas can tell that its coordinates are stale --
    /// see that method's doc for what goes wrong without it.
    generation: u64,
    /// `None` for a glyph that rasterised to nothing -- a space, say. Cached
    /// too, so it is not re-rasterised on every layout.
    entries: HashMap<GlyphKey, Option<GlyphEntry>>,
@@ -166,6 +170,13 @@ impl GlyphAtlas {
        self.entries.insert(key, None);
    }
    /// Which atlas the entries handed out right now belong to. A
    /// [`crate::RenderedText`] records this when it is built and is only
    /// reusable while it still matches.
    pub fn generation(&self) -> u64 {
        self.generation
    }
    pub fn page_count(&self) -> usize {
        self.pages.len()
    }
@@ -173,6 +184,36 @@ impl GlyphAtlas {
    pub fn glyph_count(&self) -> usize {
        self.entries.len()
    }
    /// Forget every page and every rasterised entry -- what a genuinely new
    /// GPU device needs (`android::view::IrisViewPeer::surface_changed`'s
    /// "not already live" branch, e.g. after backgrounding): the pages this
    /// atlas remembers are `TextureHandle`s into the *old* device's
    /// textures, which no longer exist, and every `GlyphEntry`'s `uv_min`/
    /// `uv_max`/`layer` point into them. Without this, a glyph already
    /// cached here is treated as "already placed" and never re-inserted
    /// into the fresh (empty) atlas the new renderer actually has --
    /// exactly the "rectangles stay, glyphs disappear" bug the resize path
    /// (`AndroidRenderer::resize`) was built to avoid for the reuse case;
    /// this is its counterpart for the case where the renderer really is
    /// new. Dropping `pages` also drops its `TextureHandle`s, which send a
    /// free message back through their `Textures`; see `Textures::reset`'s
    /// doc for why that is harmless here.
    /// Bumping `generation` here is the other half of the same
    /// invalidation: emptying this atlas does nothing about the
    /// `RenderedText`s widgets are *already holding*
    /// (`iris::widget::TextView`'s `tex` cache), whose `PlacedGlyph`s carry
    /// `uv_min`/`uv_max`/`layer` into the atlas that has just been thrown
    /// away. Those redraw perfectly happily and sample whatever now sits at
    /// those coordinates -- the fragments-of-other-glyphs Iris photographed
    /// after resuming the app on 2026-09-06. One counter, checked where the
    /// cache is read, is what makes a cached render un-reusable across a
    /// renderer rebuild.
    pub fn clear(&mut self) {
        self.pages.clear();
        self.entries.clear();
        self.generation += 1;
    }
 }
 fn fits(page: &Page, need_w: u32, need_h: u32) -> bool {
@@ -1,15 +1,87 @@
-use std::time::Duration;
+use std::time::{Duration, Instant};
 /// The frame budget `dumpsys gfxinfo` also uses to call a frame "janky": the
 /// 60Hz vsync period. Kept as the same threshold so a percentage from this
-/// report and a percentage from `gfxinfo` mean the same thing.
+/// report and a percentage from `gfxinfo` mean the same thing. Only a
 /// fallback now that a caller can read the display's real refresh rate
 /// (`report_at_hz`/`mark_phase`'s callers) -- most devices are 60Hz, but a
 /// 90Hz or 120Hz phone judged against this constant would call every frame
 /// "late" that merely met its own, faster budget.
 pub const JANK_THRESHOLD: Duration = Duration::from_nanos(16_666_667);
 /// Enough frames for several minutes of scrolling before the oldest ones
 /// start being overwritten -- the same "diagnostic, not a log" sizing
 /// `FrameStats.kt`'s `CAP` uses on the Compose side, chosen independently
 /// here since a `Duration` is smaller than the six `Long` arrays it keeps.
-const RING_CAPACITY: usize = 4096;
+/// Bumped from 4096 for RUST.md's "Benchmark v2": a fling+stream+type+
 /// keyboard run is ~6,500+ frames on the Compose side, comfortably under
 /// this so `phase_stats` never has to report a phase as partially evicted.
 const RING_CAPACITY: usize = 16384;
 /// One `mark_phase` call: the wall-clock instant and the (0-based,
 /// never-reset-by-`reset`-except-at-`reset`-time) absolute frame index at
 /// which a phase began -- `phase_stats` slices `index_ring` against this to
 /// find which recorded samples belong to which phase, since the ring
 /// itself only keeps the most recent `RING_CAPACITY` samples' *values*,
 /// not which phase they were in.
 struct PhaseMark {
    name: String,
    start_index: u64,
    start_at: Instant,
 }
 /// One phase's own slice of a report -- RUST.md's "Benchmark v2" spec's
 /// "per-phase blocks in `FrameReport`... frames, late count/percent...
 /// p50/p90/p99, worst, duration". `Display` matches the shape
 /// `docs/bench/compose-phone-v2-2026-09-06.md`'s report already uses, so
 /// the two apps' reports read the same way side by side.
 pub struct PhaseStats {
    pub name: String,
    /// How many frames were recorded during this phase in total -- may
    /// exceed `late + (samples counted)` if some of this phase's frames
    /// have since been evicted from the ring by a very long run; that
    /// case is named in the `Display` rather than silently under-counted.
    pub frames: u64,
    pub duration: Duration,
    pub late: u64,
    pub late_percent: f64,
    pub p50: Duration,
    pub p90: Duration,
    pub p99: Duration,
    pub worst: Duration,
    /// `false` if this phase's frame count exceeds how many samples of it
    /// are still in the ring -- the percentiles above are then computed
    /// over whatever survived, not the whole phase. UI_RULES.md: this is
    /// the "we don't fully know" state, named rather than folded silently
    /// into a number that looks exact.
    pub complete: bool,
 }
 impl std::fmt::Display for PhaseStats {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        writeln!(
            f,
            "  {}: {} frames over {:.1}s{}",
            self.name,
            self.frames,
            self.duration.as_secs_f64(),
            if self.complete {
                ""
            } else {
                " (ring evicted some of this phase)"
            },
        )?;
        writeln!(f, "    late: {} ({:.1}%)", self.late, self.late_percent)?;
        writeln!(
            f,
            "      total  p50 {:.1}ms  p90 {:.1}ms  p99 {:.1}ms",
            self.p50.as_secs_f64() * 1000.0,
            self.p90.as_secs_f64() * 1000.0,
            self.p99.as_secs_f64() * 1000.0,
        )?;
        write!(f, "    worst {:.1}ms", self.worst.as_secs_f64() * 1000.0)
    }
 }
 /// A per-frame wall-time report iris keeps of itself, because `dumpsys
 /// gfxinfo` cannot see a `SurfaceView`'s own GPU-drawn frames at all
@@ -41,6 +113,11 @@ pub struct FrameReport {
    /// "Where iris's frame time goes" CPU/GPU split, added 2026-09-05).
    /// `ring[i] - submit_ring[i]` is that frame's `redraw_to_submit` half.
    submit_ring: Box<[Duration; RING_CAPACITY]>,
    /// The absolute (0-based, since the last `reset`) frame index each
    /// `ring`/`submit_ring` slot's sample belongs to -- what `phase_stats`
    /// slices against `PhaseMark::start_index` to tell which recorded
    /// frames fall in which phase.
    index_ring: Box<[u64; RING_CAPACITY]>,
    /// How many of `ring`'s slots hold a real sample -- saturates at
    /// `RING_CAPACITY`, unlike `total_frames` below which keeps counting.
    len: usize,
@@ -50,6 +127,12 @@ pub struct FrameReport {
    /// correct even once the ring itself only holds the most recent frames.
    total_frames: u64,
    janky_frames: u64,
    /// `mark_phase` calls since the last `reset`, oldest first -- see
    /// `phase_stats`. Empty on an ordinary run that never calls
    /// `mark_phase`, so `phase_stats` returns an empty `Vec` and a caller
    /// prints no "per phase:" section at all, matching RUST.md's "empty/
    /// absent on an ordinary 'Copy' press, which never marks a phase."
    phases: Vec<PhaseMark>,
 }
 /// One resolved reading. `Display` is the log line both the "Frame report"
@@ -107,10 +190,12 @@ impl FrameReport {
        Self {
            ring: Box::new([Duration::ZERO; RING_CAPACITY]),
            submit_ring: Box::new([Duration::ZERO; RING_CAPACITY]),
            index_ring: Box::new([0; RING_CAPACITY]),
            len: 0,
            pos: 0,
            total_frames: 0,
            janky_frames: 0,
            phases: Vec::new(),
        }
    }
@@ -131,6 +216,7 @@ impl FrameReport {
    pub fn record_split(&mut self, total: Duration, submit_to_present: Duration) {
        self.ring[self.pos] = total;
        self.submit_ring[self.pos] = submit_to_present;
        self.index_ring[self.pos] = self.total_frames;
        self.pos = (self.pos + 1) % RING_CAPACITY;
        self.len = (self.len + 1).min(RING_CAPACITY);
        self.total_frames += 1;
@@ -142,12 +228,98 @@ impl FrameReport {
    /// Clears every counter and every sample -- what the "Reset frame
    /// report" control calls, so a report covers only what was scrolled
    /// after the button was pressed (the same reason `FrameStats.kt`'s
-    /// `reset()` exists on the Compose side).
+    /// `reset()` exists on the Compose side). Also clears every phase
    /// mark, so a fresh run starts with no "per phase:" section until it
    /// marks one of its own.
    pub fn reset(&mut self) {
        self.len = 0;
        self.pos = 0;
        self.total_frames = 0;
        self.janky_frames = 0;
        self.phases.clear();
    }
    /// Marks the start of a named phase at the current moment -- every
    /// frame recorded from here until the next `mark_phase` (or `reset`)
    /// belongs to it. RUST.md's "Benchmark v2": a scripted bench run calls
    /// this once per phase (fling/stream/type/keyboard) so `phase_stats`
    /// can slice one whole run's frames by what was happening during each.
    pub fn mark_phase(&mut self, name: &str) {
        // `phase_stats`'s slicing (`idx >= phase.start_index && idx <
        // end_index`) silently produces an empty or nonsensical slice for
        // a phase pushed out of order rather than surfacing the misuse
        // (docs/REVIEW-2026-09-06.md finding 5).
        debug_assert!(
            self.phases
                .last()
                .is_none_or(|p| self.total_frames >= p.start_index)
        );
        self.phases.push(PhaseMark {
            name: name.to_string(),
            start_index: self.total_frames,
            start_at: Instant::now(),
        });
    }
    /// One [`PhaseStats`] per `mark_phase` call since the last `reset`,
    /// oldest first. `now` closes the last phase's wall-clock span (there
    /// is no "next phase" instant to use for it); `refresh_hz` is what
    /// each phase's own `late`/`late_percent` is judged against, read from
    /// the display rather than assumed -- RUST.md's "Benchmark v2": "late
    /// count/% against the display's refresh rate."
    pub fn phase_stats(&self, now: Instant, refresh_hz: f32) -> Vec<PhaseStats> {
        if self.phases.is_empty() || refresh_hz <= 0.0 {
            return Vec::new();
        }
        let budget = Duration::from_secs_f64(1.0 / refresh_hz as f64);
        self.phases
            .iter()
            .enumerate()
            .map(|(i, phase)| {
                let (end_index, end_at) = match self.phases.get(i + 1) {
                    Some(next) => (next.start_index, next.start_at),
                    None => (self.total_frames, now),
                };
                let frames = end_index.saturating_sub(phase.start_index);
                let mut samples: Vec<Duration> = (0..self.len)
                    .filter(|&j| {
                        let idx = self.index_ring[j];
                        idx >= phase.start_index && idx < end_index
                    })
                    .map(|j| self.ring[j])
                    .collect();
                let complete = samples.len() as u64 >= frames;
                if samples.is_empty() {
                    return PhaseStats {
                        name: phase.name.clone(),
                        frames,
                        duration: end_at.saturating_duration_since(phase.start_at),
                        late: 0,
                        late_percent: 0.0,
                        p50: Duration::ZERO,
                        p90: Duration::ZERO,
                        p99: Duration::ZERO,
                        worst: Duration::ZERO,
                        complete,
                    };
                }
                samples.sort_unstable();
                let pct = |p: usize| samples[(samples.len() * p / 100).min(samples.len() - 1)];
                let late = samples.iter().filter(|&&d| d > budget).count() as u64;
                PhaseStats {
                    name: phase.name.clone(),
                    frames,
                    duration: end_at.saturating_duration_since(phase.start_at),
                    late,
                    late_percent: 100.0 * late as f64 / samples.len() as f64,
                    p50: pct(50),
                    p90: pct(90),
                    p99: pct(99),
                    worst: *samples.last().expect("checked not empty above"),
                    complete,
                }
            })
            .collect()
    }
    /// `None` if nothing has been recorded since the last reset -- the
@@ -186,6 +358,28 @@ impl FrameReport {
            gpu_wait_p50: median(submit_samples),
        })
    }
    /// `(late count, late percent)` over every sample still in the ring,
    /// judged against `refresh_hz`'s own frame budget rather than the
    /// fixed 60Hz `JANK_THRESHOLD` -- RUST.md's "Benchmark v2": "late
    /// count/% against the display's refresh rate... print 'at N Hz (X ms
    /// budget)' like Compose does." A separate method from `report()`
    /// rather than a parameter on it, so `report()`'s own `janky_percent`
    /// (and the exact-boundary test pinned to `JANK_THRESHOLD`) is
    /// unaffected for every existing caller that never measured a real
    /// refresh rate. `(0, 0.0)` with nothing recorded or a non-positive
    /// `refresh_hz`.
    pub fn late_at_hz(&self, refresh_hz: f32) -> (u64, f64) {
        if self.len == 0 || refresh_hz <= 0.0 {
            return (0, 0.0);
        }
        let budget = Duration::from_secs_f64(1.0 / refresh_hz as f64);
        let late = self.ring[..self.len]
            .iter()
            .filter(|&&d| d > budget)
            .count() as u64;
        (late, 100.0 * late as f64 / self.len as f64)
    }
 }
 impl Default for FrameReport {
@@ -296,4 +490,68 @@ mod tests {
        // same pattern here.
        assert!(stats.worst <= Duration::from_millis(5));
    }
    #[test]
    fn no_marks_means_no_phases() {
        let mut r = FrameReport::new();
        r.record(Duration::from_millis(5));
        assert!(r.phase_stats(Instant::now(), 60.0).is_empty());
    }
    #[test]
    fn phases_slice_frames_by_when_they_were_marked() {
        let mut r = FrameReport::new();
        r.mark_phase("a");
        for _ in 0..5 {
            r.record(Duration::from_millis(10)); // 10ms: late at 60Hz (16.7ms budget)... no, 10<16.7, not late
        }
        r.mark_phase("b");
        for _ in 0..3 {
            r.record(Duration::from_millis(20)); // 20ms: late at 60Hz
        }
        let now = Instant::now();
        let phases = r.phase_stats(now, 60.0);
        assert_eq!(phases.len(), 2);
        assert_eq!(phases[0].name, "a");
        assert_eq!(phases[0].frames, 5);
        assert_eq!(phases[0].late, 0);
        assert_eq!(phases[0].worst, Duration::from_millis(10));
        assert_eq!(phases[1].name, "b");
        assert_eq!(phases[1].frames, 3);
        assert_eq!(phases[1].late, 3);
        assert_eq!(phases[1].late_percent, 100.0);
        assert_eq!(phases[1].worst, Duration::from_millis(20));
        assert!(phases[0].complete);
        assert!(phases[1].complete);
    }
    #[test]
    fn the_last_phase_runs_until_now() {
        let mut r = FrameReport::new();
        r.mark_phase("only");
        r.record(Duration::from_millis(1));
        std::thread::sleep(Duration::from_millis(20));
        let now = Instant::now();
        let phases = r.phase_stats(now, 60.0);
        assert_eq!(phases.len(), 1);
        assert!(phases[0].duration >= Duration::from_millis(20));
    }
    #[test]
    fn reset_clears_phase_marks() {
        let mut r = FrameReport::new();
        r.mark_phase("a");
        r.record(Duration::from_millis(1));
        r.reset();
        assert!(r.phase_stats(Instant::now(), 60.0).is_empty());
    }
    #[test]
    fn late_at_hz_uses_the_given_refresh_rate_not_the_fixed_60hz_constant() {
        let mut r = FrameReport::new();
        // 10ms is under 60Hz's 16.7ms budget but over 120Hz's 8.3ms one.
        r.record(Duration::from_millis(10));
        assert_eq!(r.late_at_hz(60.0), (0, 0.0));
        assert_eq!(r.late_at_hz(120.0), (1, 100.0));
    }
 }
@@ -4,6 +4,7 @@ use crate::{
    util::{HashMap, Vec2},
 };
 use data::WindowUniform;
 use pollster::FutureExt;
 use wgpu::{
    util::{BufferInitDescriptor, DeviceExt},
    *,
@@ -65,6 +66,57 @@ pub fn device_limits() -> Limits {
    }
 }
 /// A capped log of wgpu's *uncaptured* errors -- everything that reaches
 /// `Device::on_uncaptured_error` rather than one of `UiRenderNode::new`'s
 /// own error scopes, i.e. every wgpu error raised outside device/pipeline
 /// creation: a validation failure during an ordinary frame's `update`/
 /// `draw`, for instance. wgpu's default handler for these is `panic!` with
 /// no caller able to intervene -- exactly what aborted the P0 bench APK
 /// once already (this file's `UiRenderNode::new` doc comment) -- so both
 /// platform backends install a handler here instead of leaving the default
 /// in place, per RUST.md's P0 box ("every wgpu uncaptured error ... it
 /// must never panic in release").
 ///
 /// Cheap to `Clone` (an `Arc` around the real storage) rather than a
 /// process-wide static, so a caller builds one alongside its `Device`,
 /// hands one clone to `on_uncaptured_error`'s closure and keeps the other
 /// for the Diagnostics page to read -- context passed explicitly, per
 /// AGENTS.md/CODE_RULES.md's "no globals" rather than reached for through a
 /// `OnceLock`.
 #[derive(Clone)]
 pub struct WgpuErrorLog {
    errors: std::sync::Arc<std::sync::Mutex<std::collections::VecDeque<String>>>,
 }
 /// How many uncaptured errors the log keeps -- old ones drop off the front
 /// rather than being trimmed on read, so a build spraying errors every
 /// frame doesn't grow this without bound.
 const WGPU_ERROR_LOG_CAP: usize = 20;
 impl Default for WgpuErrorLog {
    fn default() -> Self {
        Self {
            errors: std::sync::Arc::new(std::sync::Mutex::new(std::collections::VecDeque::new())),
        }
    }
 }
 impl WgpuErrorLog {
    pub fn record(&self, error: impl std::fmt::Display) {
        let mut errors = self.errors.lock().unwrap();
        if errors.len() >= WGPU_ERROR_LOG_CAP {
            errors.pop_front();
        }
        errors.push_back(error.to_string());
    }
    /// A snapshot for the Diagnostics page -- cloned rather than held,
    /// since the lock must not outlive one call.
    pub fn snapshot(&self) -> Vec<String> {
        self.errors.lock().unwrap().iter().cloned().collect()
    }
 }
 pub struct UiRenderNode {
    uniform_group: BindGroup,
    primitive_layout: BindGroupLayout,
@@ -152,7 +204,7 @@ impl UiRenderNode {
        queue: &Queue,
        ui: &mut UiData,
        ui_render: &mut UiRenderState,
-    ) {
+    ) -> FrameUpdateStats {
        self.active.clear();
        for (i, primitives) in ui_render.layers.iter_mut() {
            self.active.push(i);
@@ -236,6 +288,10 @@ impl UiRenderNode {
        if rebuild_main {
            self.rsc_group = Self::rsc_group(device, &self.rsc_layout, &self.textures);
        }
        FrameUpdateStats {
            masks_resized,
            moves_resized,
        }
    }
    /// Takes a size rather than a window type: this is the only thing the
@@ -251,26 +307,69 @@ impl UiRenderNode {
        queue.write_buffer(&self.window_buffer, 0, bytemuck::cast_slice(slice));
    }
-    pub fn new(device: &Device, queue: &Queue, config: &SurfaceConfiguration) -> Self {
+    /// Builds every bind group layout, the pipeline, and the two storage
    /// buffers this needs -- fallibly, since this is exactly the call that
    /// aborted the process on Iris's phone in a release build with no
    /// message beyond "wgpu error: Validation Error" (RUST.md's P0 box,
    /// "iris bench crash on the phone, 2026-09-06"). wgpu's own default
    /// behaviour for an uncaptured error is `panic!` with no caller able to
    /// intervene, so every `create_bind_group_layout`/`create_render_pipeline`
    /// call below runs inside three nested error scopes (one per
    /// `ErrorFilter`) instead: whichever scope catches something, its
    /// `wgpu::Error`'s `Display` is wgpu-core's own `format_error` output
    /// (`"Validation Error\n\nCaused by:\n  ..."`, the same text the panic
    /// would have printed before Android's crash reporter truncated it) and
    /// becomes this function's `Err`. Both callers
    /// (`android::render::AndroidRenderer::new`, `default::render::
    /// UiRenderer::new`) already call `Device`-creation with
    /// `pollster::block_on`, so returning a plain `Result` here rather than
    /// making this `async fn` keeps that same synchronous shape.
    pub fn new(
        device: &Device,
        queue: &Queue,
        config: &SurfaceConfiguration,
        window_size: impl Into<Vec2>,
    ) -> Result<Self, String> {
        // Popped in reverse of this order, once every creation call below
        // has run -- `Device::push_error_scope`'s own contract.
        let oom_scope = device.push_error_scope(ErrorFilter::OutOfMemory);
        let validation_scope = device.push_error_scope(ErrorFilter::Validation);
        let internal_scope = device.push_error_scope(ErrorFilter::Internal);
        let shader = device.create_shader_module(ShaderModuleDescriptor {
            label: Some("UI Shape Shader"),
            source: ShaderSource::Wgsl(SHAPE_SHADER.into()),
        });
-        // Seeded from the surface's own size, not `WindowUniform::default()`
+        // Seeded from the caller's own reported size, not
-        // (0, 0): the vertex shader divides by `window.dim` to reach clip
+        // `WindowUniform::default()` (0, 0): the vertex shader divides by
-        // space, so a window this buffer disagrees with means every
+        // `window.dim` to reach clip space, so a window this buffer
-        // primitive's position is NaN/Inf and is dropped before
+        // disagrees with means every primitive's position is NaN/Inf and is
-        // rasterization -- the clear colour still reaches the screen (the
+        // dropped before rasterization -- the clear colour still reaches
-        // pass runs regardless) while nothing drawn on top of it ever does.
+        // the screen (the pass runs regardless) while nothing drawn on top
-        // winit's backend gets away with the old default because winit
+        // of it ever does. winit's backend gets away with the old default
-        // fires an initial `WindowEvent::Resized` that calls `resize()`
+        // because winit fires an initial `WindowEvent::Resized` that calls
-        // before the first frame; android-view has no such automatic
+        // `resize()` before the first frame; android-view has no such
-        // event, so `AndroidRenderer::new` built a node whose window buffer
+        // automatic event, so `AndroidRenderer::new` built a node whose
-        // was never corrected -- this is I2's "nothing draws" bug (RUST.md).
+        // window buffer was never corrected -- this is I2's "nothing draws"
-        let window_uniform = WindowUniform {
+        // bug (RUST.md).
-            width: config.width as f32,
+        //
-            height: config.height as f32,
+        // **Deliberately not `config.width`/`config.height`**: those are
        // the surface's *physical* pixel size, which the swapchain needs,
        // but everything downstream of this uniform (layout, hit-testing,
        // glyph/rect positions) works in the caller's own units -- on
        // Android that's *logical* (physical / density) since RUST.md's P0
        // box ("text is far too small"), on desktop it's whatever
        // `default::render::UiRenderer::new` already divides by
        // `window.scale_factor()`. Passing it in explicitly, rather than
        // deriving it from `config` here, is what keeps this crate from
        // needing to know either platform's notion of density at all.
        let window_uniform = {
            let size = window_size.into();
            WindowUniform {
                width: size.x,
                height: size.y,
            }
        };
        let window_buffer = device.create_buffer_init(&BufferInitDescriptor {
            label: Some("window"),
@@ -373,7 +472,18 @@ impl UiRenderNode {
            cache: None,
        });
-        Self {
+        // Reverse of the push order above. Only one of these should ever be
        // `Some` in practice -- three separate scopes exist to name *which*
        // kind of error it was, not because more than one is expected at
        // once.
        let internal_err = internal_scope.pop().block_on();
        let validation_err = validation_scope.pop().block_on();
        let oom_err = oom_scope.pop().block_on();
        if let Some(err) = validation_err.or(oom_err).or(internal_err) {
            return Err(err.to_string());
        }
        Ok(Self {
            uniform_group,
            primitive_layout,
            rsc_layout,
@@ -387,7 +497,7 @@ impl UiRenderNode {
            move_offsets,
            masks_layout,
            masks_group,
-        }
+        })
    }
    fn bind_group_0(
@@ -554,4 +664,26 @@ impl UiRenderNode {
    pub fn take_image_bind_group_creates(&mut self) -> u64 {
        self.textures.take_bind_group_creates()
    }
    /// Atlas-array `grow_array` calls since the last call -- same calling
    /// convention as `take_image_bind_group_creates` (call once per frame,
    /// before `update()`, to read exactly the previous frame's tally). Part
    /// of the Diagnostics page's per-frame report (RUST.md's P0 box, "the
    /// first input frame" investigation): if a report ever shows a grow
    /// landing on the same frame the glyphs vanished, that is the
    /// coincidence to chase first.
    pub fn take_atlas_pages_grown(&mut self) -> u64 {
        self.textures.take_pages_grown()
    }
 }
 /// What `UiRenderNode::update` changed this frame that a caller building a
 /// per-frame diagnostic report cares about -- see `take_image_bind_group_creates`/
 /// `take_atlas_pages_grown` for the two counters this doesn't carry (they
 /// use the existing "call before update()" convention instead, so as not
 /// to disturb `bench_images`' documented counts).
 #[derive(Clone, Copy, Debug, Default)]
 pub struct FrameUpdateStats {
    pub masks_resized: bool,
    pub moves_resized: bool,
 }
@@ -6,6 +6,7 @@ use crate::{
        ArrBuf,
        data::{MaskIdx, MoveIdx, PrimitiveInstance},
    },
    util::HashSet,
 };
 use bytemuck::Pod;
 use wgpu::*;
@@ -277,6 +278,31 @@ impl Primitives {
        }
    }
    /// How many instances are still bound for the GPU -- the O(1) half of
    /// the orphan check, so the O(primitives) walk below only runs on a
    /// frame that already looks wrong. See
    /// [`crate::UiRenderState::orphaned_primitives`].
    pub fn live_count(&self) -> usize {
        (self.instances.len() - self.free.len()) + (self.images.len() - self.image_free.len())
    }
    /// Every instance that is still bound for the GPU, as `(inst_idx,
    /// owner, is_image)` -- everything except the slots already handed to
    /// [`Self::free`] and waiting for [`Self::apply_free`] to compact them
    /// away. Only [`crate::UiRenderState::orphaned_primitives`] uses this,
    /// to check that every drawn primitive still belongs to a live widget.
    pub fn live_instances(&self) -> impl Iterator<Item = (usize, WidgetId, bool)> + '_ {
        let free: HashSet<usize> = self.free.iter().copied().collect();
        let image_free: HashSet<usize> = self.image_free.iter().copied().collect();
        let rects = (0..self.instances.len())
            .filter(move |i| !free.contains(i))
            .map(|i| (i, self.assoc[i], false));
        let images = (0..self.images.len())
            .filter(move |i| !image_free.contains(i))
            .map(|i| (i, self.image_assoc[i], true));
        rects.chain(images)
    }
    pub fn data(&self) -> &PrimitiveData {
        &self.data
    }
@@ -80,11 +80,17 @@ var<storage> masks: array<Mask>;
@group(3) @binding(1)
 var<storage> move_offsets: array<MoveOffset>;
-// A move chain more than this deep means something else is wrong (an
+// The bound on the parent walk, kept in step with `MOVE_CHAIN_LIMIT` in
-// accidental cycle) -- kept in step with `MOVE_CHAIN_LIMIT` in
+// render_state.rs, which walks the identical chain on the CPU side for
-// render_state.rs, which walks the identical bound on the CPU side for
+// hit-testing. Bounded so a malformed chain (a cyclic `parent`) cannot
-// hit-testing. Bounded so a malformed chain cannot hang the GPU.
+// hang the GPU -- not a claim about how deep a real tree gets. It was 16
-const MOVE_CHAIN_LIMIT: u32 = 16u;
+// and that was too small: the transcript screen's composer field sits 17
 // slots below the root, measured 2026-09-07 on this checkout's emulator
 // by tapping it (the CPU walk's own debug assert names the chain now).
 // Past the bound both walks simply stop summing, so the widget draws and
 // hit-tests short by whatever the outer slots held, with nothing on
 // screen to say so.
 const MOVE_CHAIN_LIMIT: u32 = 64u;
 /// Sums the pixel delta along the parent chain starting at `idx`, shared by
 /// the vertex stage (a primitive's own corners) and the fragment stage (its
@@ -5,6 +5,10 @@ use crate::{PatchRect, TextureKind, TextureUpdate, Textures};
 use super::atlas::PAGE;
 /// The fewest layers the glyph atlas array is ever created with. Two, not
 /// one, for the GLES reason written on `create_array_texture`.
 const MIN_ARRAY_LAYERS: u32 = 2;
 /// What one texture slot is, GPU-side. Parallel to `Textures`' own slot
 /// numbering (`TextureKind`'s `Image`/`Page`), so a slot's index means the
 /// same thing on both sides without a second map to keep in sync.
@@ -67,6 +71,12 @@ pub struct GpuTextures {
    /// unchanging image list is zero, the same way `UiRenderState`'s
    /// `draw_count`/`region_mut_count` prove the layout side.
    bind_group_creates: u64,
    /// `grow_array` calls since the last `take_pages_grown` -- the
    /// Diagnostics page's per-frame report (RUST.md's P0 box, "the first
    /// input frame" investigation) reads this alongside `bind_group_creates`
    /// to say whether *this* frame's glyph disappearance, if any, coincided
    /// with the atlas array being recreated.
    pages_grown: u64,
 }
 impl GpuTextures {
@@ -226,6 +236,7 @@ impl GpuTextures {
    /// array's view, which invalidates every bind group that referenced it,
    /// so this also rebuilds all of them before returning.
    fn grow_array(&mut self, rsc_layout: &BindGroupLayout) {
        self.pages_grown += 1;
        let new_capacity = self.array_capacity * 2;
        let new_texture = Self::create_array_texture(&self.device, new_capacity);
        if self.page_count > 0 {
@@ -353,7 +364,26 @@ impl GpuTextures {
        })
    }
    /// The atlas is sampled as a `texture_2d_array`, and **a one-layer
    /// array is not one on the GLES backend**: wgpu-hal picks the GL
    /// texture target from the descriptor alone
    /// (`gles::Texture::get_info_from_desc`, `(false, 1) => TEXTURE_2D`),
    /// so a capacity of 1 creates a `GL_TEXTURE_2D` and binds it to the
    /// shader's `sampler2DArray`. GL then treats that unit as incomplete
    /// and every `textureSample` returns (0, 0, 0, 1) -- which, through
    /// `draw_glyph`'s `color.a *= texel.a`, draws every glyph as a solid
    /// filled box. That was iris's appearance on the emulator's GLES for
    /// two days (RUST.md, "the emulator cannot draw iris's glyphs"), and
    /// it is a real defect on any device whose adapter is GL rather than
    /// Vulkan, not an emulator artifact. So the array never has fewer than
    /// `MIN_ARRAY_LAYERS` layers; the second layer costs one page of
    /// texture memory and is used by the next atlas page anyway.
    fn create_array_texture(device: &Device, capacity: u32) -> Texture {
        debug_assert!(
            capacity >= MIN_ARRAY_LAYERS,
            "glyph atlas array asked for {capacity} layers; fewer than {MIN_ARRAY_LAYERS} is a \
             GL_TEXTURE_2D on the GLES backend and draws every glyph as a box"
        );
        device.create_texture(&TextureDescriptor {
            label: Some("glyph atlas array"),
            size: Extent3d {
@@ -375,7 +405,7 @@ impl GpuTextures {
    pub fn new(device: &Device, queue: &Queue) -> Self {
        let sampler = default_sampler(device);
        let null_view = null_texture_view(device);
-        let array_capacity = 1;
+        let array_capacity = MIN_ARRAY_LAYERS;
        let array_texture = Self::create_array_texture(device, array_capacity);
        let array_view = array_texture.create_view(&TextureViewDescriptor {
            dimension: Some(TextureViewDimension::D2Array),
@@ -392,6 +422,7 @@ impl GpuTextures {
            sampler,
            null_view,
            bind_group_creates: 0,
            pages_grown: 0,
        }
    }
@@ -402,6 +433,12 @@ impl GpuTextures {
        std::mem::take(&mut self.bind_group_creates)
    }
    /// Reads and zeroes the atlas-array-grow counter -- see `pages_grown`'s
    /// field comment.
    pub fn take_pages_grown(&mut self) -> u64 {
        std::mem::take(&mut self.pages_grown)
    }
    pub fn array_view(&self) -> &TextureView {
        &self.array_view
    }
@@ -1,4 +1,6 @@
-use crate::{LayerId, MaskIdx, MoveIdx, PrimitiveHandle, Size, TextureHandle, UiRegion, WidgetId};
+use crate::{
    LayerId, MaskIdx, MoveIdx, PrimitiveHandle, Size, TextureHandle, UiRegion, WidgetId, util::Vec2,
 };
 /// important non rendering data for retained drawing
 #[derive(Debug)]
@@ -9,7 +11,22 @@ pub struct ActiveData {
    pub textures: Vec<TextureHandle>,
    pub primitives: Vec<PrimitiveHandle>,
    pub children: Vec<WidgetId>,
    /// The mask this widget was drawn **under** (its parent's), not the
    /// one it set for itself -- see `own_mask` for that.
    pub mask: MaskIdx,
    /// The mask slot this widget allocated for *itself* with
    /// `Painter::set_mask`, or `MaskIdx::NONE`. Kept across redraws and
    /// rewritten in place, the way `move_slot` is: a `Masked` that pushed
    /// a fresh slot each draw left every already-drawn descendant --
    /// which `draw_inner`'s unchanged-region fast path does not revisit --
    /// clipping to the *old* slot's region, so a composer whose bar had
    /// since been placed at the bottom of the screen was still being
    /// clipped to a box at the top of it and drew nothing (measured
    /// 2026-09-06: four mask entries live, none of them the widget's
    /// current region). Its path out is the `undraw` branch of
    /// `UiRenderState::remove`, which drops the self-ownership ref taken
    /// when the slot was allocated.
    pub own_mask: MaskIdx,
    pub layer: LayerId,
    /// What `Widget::draw` returned the last time this widget was actually
    /// drawn -- read by a parent placing this widget again without
@@ -21,4 +38,32 @@ pub struct ActiveData {
    /// so a retained child's `parent` link never goes stale). See
    /// LAYOUT.md section 2.
    pub move_slot: MoveIdx,
    /// How much of this widget's own `move_slot` delta is already folded
    /// into `region` above, in window pixels. The two mechanisms that
    /// write that slot disagree about this and cannot be told apart from
    /// the slot alone: `UiRenderState::mov` shifts `region` and the delta
    /// together (the *offered* region genuinely moved), while
    /// `Painter::reposition` writes only the delta (`region` stays the
    /// offered box and the delta says where inside it the content was
    /// placed). So anything that wants the widget's real position --
    /// `resolved_region`, and through it every hit test -- must subtract
    /// this from the chain sum. Without it a panned widget's own hit box
    /// sits at twice the pan while its descendants' are correct, which is
    /// how it went unnoticed: the composer's field became untappable
    /// after a finger pan (2026-09-06). Reset to zero whenever the widget
    /// is really redrawn, since `draw_inner` zeroes the slot then too.
    pub move_applied: Vec2,
    /// The offset the last `Painter::reposition` placed this widget's
    /// content at *within* `region`, in window pixels. The move slot has
    /// exactly one owner and one meaning:
    /// `move_offsets[move_slot] == move_applied + repositioned`. `mov`
    /// adds to the first, `reposition` overwrites the second (it
    /// recomputes `from` afresh every call, so repeating it must land on
    /// the same answer rather than drifting), and both then rewrite the
    /// slot from the sum -- which is what lets a parent both move a child
    /// with its own layout and place it inside that moved region in one
    /// frame. `List::place`'s Bottom-known branch does exactly that once a
    /// row's blocks wrap. Reset to zero on a real redraw, with
    /// `move_applied` and the slot itself.
    pub repositioned: Vec2,
 }
@@ -24,6 +24,46 @@ pub struct UiData {
    /// id (never reallocated), so a retained descendant's `parent` index
    /// never goes stale -- see LAYOUT.md section 2.
    pub move_offsets: TrackedArena<MoveOffset, u32>,
    /// Every widget whose [`crate::Widget::tick`] should run before the
    /// next frame -- today, a `List` coasting through a fling. Added by
    /// [`Self::animate`] when the animation starts and removed by
    /// [`Self::tick_animations`] the frame its `tick` answers `false`, so
    /// a stopped animation costs nothing and a dropped widget cannot be
    /// ticked (`get_dyn_mut` answers `None` and it is dropped the same
    /// way).
    animating: Vec<WidgetId>,
 }
 impl UiData {
    /// Ask for `id`'s [`crate::Widget::tick`] to run every frame until it
    /// says it is done. Idempotent -- registering an already-animating
    /// widget is the ordinary case (a second fling before the first
    /// settled) and must not tick it twice per frame.
    pub fn animate(&mut self, id: WidgetId) {
        if !self.animating.contains(&id) {
            self.animating.push(id);
        }
    }
    /// Tick every registered widget to `now`, drop the ones that finished,
    /// and say whether any is still going -- which is a backend's cue to
    /// ask for another frame. Called once per frame *before* the draw, so
    /// what the frame draws is this instant's position rather than the
    /// previous one's.
    pub fn tick_animations(&mut self, now: std::time::Instant) -> bool {
        // Taken out and put back rather than iterated in place: `tick`
        // needs `&mut` on the widget arena this list lives beside, and a
        // widget is free to register another one while ticking.
        let mut registered = std::mem::take(&mut self.animating);
        registered.retain(|&id| match self.widgets.get_dyn_mut(id) {
            Some(widget) => widget.tick(now),
            None => false,
        });
        for id in registered {
            self.animate(id);
        }
        !self.animating.is_empty()
    }
 }
 pub trait UiRsc {
@@ -13,6 +13,10 @@ pub struct Painter<'a> {
    pub(super) region: UiRegion,
    pub(super) mask: MaskIdx,
    pub(super) move_slot: MoveIdx,
    /// This widget's own mask slot, reused across redraws -- see
    /// `ActiveData::own_mask`. `MaskIdx::NONE` until `set_mask` is called
    /// for the first time in this widget's life.
    pub(super) own_mask: MaskIdx,
    pub(super) textures: Vec<TextureHandle>,
    pub(super) primitives: Vec<PrimitiveHandle>,
    pub(super) children: Vec<WidgetId>,
@@ -48,12 +52,32 @@ impl<'a> Painter<'a> {
        self.primitive_at(primitive, region.within(&self.region));
    }
    /// Clip everything this widget draws, itself and its descendants, to
    /// `region`. One per widget: a second call would need the two to be
    /// intersected, which nothing here does.
    ///
    /// The slot is allocated once and **rewritten in place** on every
    /// later draw rather than pushed again, because a descendant whose own
    /// region did not change is not redrawn (`draw_inner`'s fast path) and
    /// so keeps pointing at whichever slot it was drawn under. See
    /// `ActiveData::own_mask` for what pushing a fresh one cost.
    pub fn set_mask(&mut self, region: UiRegion) {
        assert!(self.mask == MaskIdx::NONE);
-        self.mask = self.rsc.ui_mut().masks.push(Mask {
+        let mask = Mask {
            region,
            move_idx: self.move_slot,
-        });
+        };
        if self.own_mask == MaskIdx::NONE {
            let slot = self.rsc.ui_mut().masks.push(mask);
            // The one ref this widget holds on its own slot, so the slot
            // outlives any single frame's primitives; released in
            // `UiRenderState::remove`'s `undraw` branch.
            self.rsc.ui_mut().masks.push_ref(slot);
            self.own_mask = slot;
        } else {
            *self.rsc.ui_mut().masks.get_mut(self.own_mask) = mask;
        }
        self.mask = self.own_mask;
    }
    /// Draws a widget within this widget's region, returning the size it
@@ -86,6 +110,7 @@ impl<'a> Painter<'a> {
            self.mask,
            None,
            None,
            crate::render::MaskIdx::NONE,
            self.rsc,
        );
        self.state
@@ -165,8 +190,21 @@ impl<'a> Painter<'a> {
        attrs: &TextAttrs,
        width: Option<f32>,
    ) -> RenderedText {
        let density = self.state.density;
        // Counted here rather than in `TextView::render`, which returns
        // its memoized layout without reaching this -- so this counts
        // shapes, not requests. `UiRenderState::take_counters`.
        self.state.shape_count += 1;
        let ui = self.rsc.ui_mut();
-        ui.text.render(buffer, attrs, width, &mut ui.textures)
+        ui.text
            .render(buffer, attrs, width, &mut ui.textures, density)
    }
    /// Which glyph atlas the glyphs handed out right now belong to --
    /// what a widget caching a [`RenderedText`] across frames has to
    /// compare against before re-emitting it (`GlyphAtlas::clear`).
    pub fn atlas_generation(&mut self) -> u64 {
        self.rsc.ui_mut().text.atlas.generation()
    }
    /// Draw a laid-out string: one quad per glyph, all sampling the atlas.
@@ -175,6 +213,18 @@ impl<'a> Painter<'a> {
    /// absolute pixel offset from it, so re-drawing after a resize is this loop
    /// and nothing else.
    pub fn glyphs(&mut self, text: &RenderedText, origin: UiRegion) {
        // A caller re-emitting quads placed against an atlas that has since
        // been cleared draws every glyph from coordinates now holding
        // something else. Caught at the submission rather than on screen,
        // where it reads as fragments of unrelated letters.
        debug_assert_eq!(
            text.generation,
            self.atlas_generation(),
            "glyphs placed against atlas generation {} submitted against {}: the holder did not \
             re-render after the atlas was cleared",
            text.generation,
            self.atlas_generation(),
        );
        let flags_for = |is_color| {
            if is_color {
                GlyphPrimitive::IS_COLOR
@@ -210,6 +260,12 @@ impl<'a> Painter<'a> {
        self.state.output_size
    }
    /// Physical pixels per `dp` -- see `UiRenderState::density`'s field
    /// doc. What `Len::dp`'s `apply_rest` call resolves against.
    pub fn density(&self) -> f32 {
        self.state.density
    }
    pub fn px_size(&mut self) -> Vec2 {
        self.region.size().to_abs(self.state.output_size)
    }
@@ -1,7 +1,7 @@
 use crate::{
    ActiveData, IdLike, MaskIdx, MoveIdx, Painter, PixelRegion, PrimitiveLayers, RegionAlign,
    StrongWidget, UiRegion, UiRsc, UiVec2, WidgetId, Widgets,
-    render::MoveOffset,
+    render::{IMAGE_BINDING, MoveOffset},
    util::{HashMap, HashSet, Id, Vec2},
 };
@@ -9,11 +9,44 @@ pub struct UiRenderState {
    pub active: HashMap<WidgetId, ActiveData>,
    pub layers: PrimitiveLayers,
    pub(super) output_size: Vec2,
    /// Physical pixels per `dp` -- see `Len::dp`'s field doc. `1.0` (an
    /// unscaled display) until a backend that knows its own density calls
    /// `set_density` (Android's `content_scale`, read at `surface_changed`
    /// time); the winit backend has no analogous per-monitor value wired up
    /// yet and stays at the default.
    pub(super) density: f32,
    old_root: Option<WidgetId>,
    resized: bool,
    /// The widgets whose `Widget::draw` is on the stack right now -- so
    /// [`Self::redraw`] can tell "this widget needs drawing again" from
    /// "an ancestor is drawing it at this very moment", where a second
    /// draw would leave the first one's primitives behind with nothing
    /// owning them. An id is inserted immediately before `draw` is called
    /// and removed the moment it returns (both in `draw_inner`), so this
    /// is empty between frames -- asserted at the end of `update`.
    ///
    /// It used to only ever be inserted into, and `redraw` removed the id
    /// *before* testing for it, which made the test constant `false`: the
    /// guard could never fire and the set grew by one entry per widget
    /// ever drawn and was never emptied.
    draw_started: HashSet<WidgetId>,
    /// The widget currently holding exclusive pointer input, if any --
    /// `iris::sense::SensorUi::run_sensors` reads and clears this every
    /// call. Interior mutability (a `Mutex`, not a bare `Cell`, since a
    /// `CursorData` reaching this through an async `task_on` handler needs
    /// `Send`/`Sync`) because `run_sensors` takes `&self` (widgets are
    /// dispatched to, not owned, at that layer) and this render state is
    /// the one structure both backends (winit, android-view) already hold
    /// across frames, the same way `old_root`/`resized` are -- see
    /// `iris::sense`'s pointer-capture doc for why a drag needs this: once
    /// a gesture has committed to panning or selecting, every later sample
    /// of it must reach the same widget even if the finger has moved off
    /// whatever hit region first noticed the press. Never held across an
    /// await or another lock -- every access here is a single get/set.
    captured: std::sync::Mutex<Option<WidgetId>>,
    /// `Widget::draw` calls and `Primitives::region_mut` rewrites since the
    /// last `take_counters`. LAYOUT.md section 8's pass conditions are
    /// stated in terms of these two: an unchanged frame must cost 0 of
@@ -22,12 +55,22 @@ pub struct UiRenderState {
    draw_count: u64,
    region_mut_count: u64,
    mov_count: u64,
    /// Text layouts actually computed -- bumped by `Painter::render_text`,
    /// which `TextView::render` only reaches on a cache miss.
    pub(super) shape_count: u64,
 }
-/// A move chain more than this deep would mean something else is wrong
+/// The bound on the parent walk -- see `resolve_move` in shader.wgsl,
-/// (an accidental cycle) -- see `resolve_move` in shader.wgsl, which walks
+/// which walks the identical chain and must be kept in step with this
-/// the identical bound and must be kept in step with this constant.
+/// constant. It exists so a cyclic `parent` link cannot hang either walk,
-pub const MOVE_CHAIN_LIMIT: usize = 16;
+/// not as a statement about how deep a real tree gets: it was 16, and the
 /// transcript screen's composer field turned out to sit **17** slots below
 /// the root (measured 2026-09-07 on this checkout's emulator, by tapping
 /// the composer in a debug build -- the assert in `resolve_move_chain`
 /// prints the chain). A chain past the bound is not reported anywhere at
 /// run time; both walks just stop summing, so the widget is drawn and hit
 /// tested short by whatever the outer slots held.
 pub const MOVE_CHAIN_LIMIT: usize = 64;
 impl UiRenderState {
    pub fn new() -> Self {
@@ -35,23 +78,33 @@ impl UiRenderState {
            active: Default::default(),
            layers: Default::default(),
            output_size: Vec2::ZERO,
            density: 1.0,
            old_root: None,
            resized: false,
            draw_started: Default::default(),
            captured: Default::default(),
            draw_count: 0,
            region_mut_count: 0,
            mov_count: 0,
            shape_count: 0,
        }
    }
    /// Reads and zeroes the (draws, region_mut rewrites, move_offsets
-    /// writes) counters -- call once per frame before `update()` to
+    /// writes, text shapes) counters -- call once per frame before
-    /// measure exactly that frame, per LAYOUT.md section 8.
+    /// `update()` to measure exactly that frame, per LAYOUT.md section 8.
-    pub fn take_counters(&mut self) -> (u64, u64, u64) {
+    ///
    /// The fourth is the one a draw count cannot stand in for: a widget
    /// can be redrawn without re-shaping (`TextView::render` memoizes by
    /// width) and re-shaped without any extra draw, and it is re-shaping
    /// that the per-block transcript row exists to avoid -- see
    /// `transcript_ui`'s `a_delta_into_a_long_reply_shapes_one_block`.
    pub fn take_counters(&mut self) -> (u64, u64, u64, u64) {
        (
            std::mem::take(&mut self.draw_count),
            std::mem::take(&mut self.region_mut_count),
            std::mem::take(&mut self.mov_count),
            std::mem::take(&mut self.shape_count),
        )
    }
@@ -60,6 +113,20 @@ impl UiRenderState {
        self.resized = true;
    }
    /// Sets the physical-pixels-per-dp ratio every `Len::dp` in the tree
    /// resolves against from the next layout pass on -- see `density`'s
    /// field doc. Not folded into `resize` because the two change on
    /// different triggers (a surface resize on every rotation or keyboard
    /// open; a density change only if the app follows the display to a
    /// different screen, which Android surfaces separately).
    pub fn set_density(&mut self, density: f32) {
        self.density = density;
    }
    pub fn density(&self) -> f32 {
        self.density
    }
    pub fn update<'a>(&mut self, root: impl Into<Option<&'a StrongWidget>>, rsc: &mut dyn UiRsc) {
        // safety mechanism for memory leaks; might wanna return a result instead so user can
        // decide whether to panic or not
@@ -78,6 +145,11 @@ impl UiRenderState {
            );
        }
        let root = root.into();
        debug_assert!(
            self.draw_started.is_empty(),
            "a previous frame left {} widget(s) marked as mid-draw",
            self.draw_started.len(),
        );
        if self.needs_redraw_all(root) {
            self.redraw_all(root, rsc);
            self.old_root = root.map(|r| r.id());
@@ -85,6 +157,8 @@ impl UiRenderState {
        } else if rsc.widgets().has_updates() {
            self.redraw_updates(rsc);
        }
        #[cfg(debug_assertions)]
        debug_assert!(self.primitive_counts_agree(), "{}", self.orphan_report(rsc),);
    }
    fn redraw_all(&mut self, root: Option<&StrongWidget>, rsc: &mut dyn UiRsc) {
@@ -100,6 +174,7 @@ impl UiRenderState {
                MaskIdx::NONE,
                None,
                None,
                MaskIdx::NONE,
                rsc,
            );
        }
@@ -134,12 +209,27 @@ impl UiRenderState {
        mask: MaskIdx,
        old_children: Option<Vec<WidgetId>>,
        old_move_slot: Option<MoveIdx>,
        old_own_mask: MaskIdx,
        rsc: &mut dyn UiRsc,
    ) {
        let mut old_children = old_children.unwrap_or_default();
        let mut old_move_slot = old_move_slot;
        let mut own_mask = old_own_mask;
        // Consumed here, not merely read: this call *is* the redraw the mark
        // asked for, and leaving the mark set is what stranded a widget's
        // primitives. `Painter::draw_twice` calls this twice for the same id
        // in one frame (`List::place`'s measurement pass), and on the second
        // call the still-set mark took the whole `if let` below -- including
        // the `remove` that frees the first draw's primitives -- out of play,
        // so `active.insert` at the end overwrote the only handles that could
        // ever have freed them. The result is a full second copy of the row,
        // drawn every frame from then on at the oversized measurement region
        // and, with `List` setting no mask, outside the list's own bounds:
        // the doubled `Compacted:` row in docs/bench/iris-phone-v2-2026-09-06.md.
        // The same shape reaches any dirty widget an ancestor redraws first.
        let dirty = rsc.widgets_mut().needs_redraw.remove(&id);
        if let Some(active) = self.active.get_mut(&id)
-            && !rsc.widgets().needs_redraw.contains(&id)
+            && !dirty
        {
            // check to see if we can skip drawing first
            if active.region == region {
@@ -166,6 +256,15 @@ impl UiRenderState {
                    *r = r.outside(&from).within(&region);
                    self.region_mut_count += 1;
                }
                // `move_applied` is deliberately **not** touched here,
                // unlike in `mov`: it counts the part of this widget's own
                // move-slot delta that `region` has already absorbed, and
                // this branch writes no delta at all -- the primitives were
                // moved directly. Counting one would make
                // `resolved_region` subtract a distance the chain never
                // held, putting the hit box short of the drawing by
                // exactly this step. See `ActiveData::move_applied`, and
                // `a_size_independent_widget_moved_by_its_parent_has_the_hit_box_it_is_drawn_at`.
                active.region = region;
                return;
            }
@@ -173,10 +272,25 @@ impl UiRenderState {
            let active = self.remove(id, false, rsc).unwrap();
            old_children = active.children;
            old_move_slot = Some(active.move_slot);
            own_mask = active.own_mask;
        } else if dirty && self.active.contains_key(&id) {
            // Dirty and already drawn: none of the fast paths above may be
            // taken (the widget's own content changed, so its old primitives
            // say nothing about its new ones), but they are also the only
            // thing that frees them. Same two lines, reached the other way.
            let active = self.remove(id, false, rsc).unwrap();
            old_children = active.children;
            old_move_slot = Some(active.move_slot);
            own_mask = active.own_mask;
        }
        // draw widget
-        self.draw_started.insert(id);
+        let reentrant = !self.draw_started.insert(id);
        debug_assert!(
            !reentrant,
            "widget {id:?} is being drawn while its own draw is already on the stack; \
             the second draw's primitives would orphan the first's"
        );
        let move_slot = match old_move_slot {
            // Reused across a real redraw of the same id: the fresh
@@ -205,11 +319,22 @@ impl UiRenderState {
            }
        };
        // The mask this widget was drawn *under*, kept aside because
        // `Painter::set_mask` overwrites `painter.mask` with the widget's
        // own new one -- and `ActiveData::mask`'s only consumer is
        // `redraw`, which feeds it back in as the *inherited* mask. Storing
        // the set one instead handed a `Masked` its own mask on every
        // targeted redraw, tripping `set_mask`'s nested-mask assert:
        // `assertion failed: self.mask == MaskIdx::NONE`, an abort the
        // first time the composer's scroll area was redrawn on the
        // emulator.
        let inherited_mask = mask;
        let mut painter = Painter {
            state: self,
            region,
            mask,
            move_slot,
            own_mask,
            layer,
            id,
            textures: Vec::new(),
@@ -221,14 +346,26 @@ impl UiRenderState {
        let mut widget = painter.rsc.widgets().get_dyn_dynamic(id);
        painter.state.draw_count += 1;
        let size = widget.draw(&mut painter);
        // A reported length is consumed by containers that read `abs`,
        // `rel` and `rest` straight off it (`Span`'s placement, `Pad`'s
        // addition), so an unresolved `dp` in one is silently worth zero
        // -- see `Len::fold_dp`, which is what a widget reporting a
        // caller-declared size has to put it through.
        debug_assert!(
            size.x.dp == 0.0 && size.y.dp == 0.0,
            "widget {id:?} reported an unresolved `dp` size ({size:?}); \
             report `Len::fold_dp(painter.density())` instead"
        );
        drop(widget);
        painter.state.draw_started.remove(&id);
        let Painter {
            state: _,
            rsc: _,
            region,
-            mask,
+            mask: _,
            move_slot,
            own_mask,
            textures,
            primitives,
            children,
@@ -244,10 +381,13 @@ impl UiRenderState {
            textures,
            primitives,
            children,
-            mask,
+            mask: inherited_mask,
            layer,
            size,
            move_slot,
            own_mask,
            move_applied: Vec2::ZERO,
            repositioned: Vec2::ZERO,
        };
        // remove old children that weren't kept
@@ -275,6 +415,7 @@ impl UiRenderState {
        let from_px = from.top_left().to_abs(self.output_size);
        let to_px = to.top_left().to_abs(self.output_size);
        let delta = to_px - from_px;
        active.move_applied += delta;
        let entry = rsc.ui_mut().move_offsets.get_mut(slot);
        entry.delta[0] += delta.x;
        entry.delta[1] += delta.y;
@@ -309,17 +450,38 @@ impl UiRenderState {
        let Some(active) = self.active.get(&id) else {
            return;
        };
        let move_applied = active.move_applied;
        let repositioned = active.repositioned;
        let from = active
            .size
-            .to_uivec2()
+            .to_uivec2(self.density)
            .align(RegionAlign::TOP_LEFT)
            .within(&active.region);
        let slot = active.move_slot;
        let from_px = from.top_left().to_abs(self.output_size);
        let to_px = to.top_left().to_abs(self.output_size);
        let delta = to_px - from_px;
        // Not `delta` alone: a parent may have `mov`ed this widget to a
        // region that itself moved earlier in the same frame, and that
        // part of the slot is `move_applied`'s, not this call's. Writing
        // `delta` on its own dropped it and put the content back at the
        // pre-move position. `from` is computed against `active.region`,
        // which `mov` already updated, so `delta` is purely the placement
        // inside the region and the two summands never overlap.
        let entry = rsc.ui_mut().move_offsets.get_mut(slot);
-        entry.delta = [delta.x, delta.y];
+        debug_assert_eq!(
            entry.delta,
            [
                move_applied.x + repositioned.x,
                move_applied.y + repositioned.y
            ],
            "widget {id:?}'s move slot was written by something other than `mov`/`reposition`; \
             the slot is theirs and means `move_applied + repositioned` -- see `ActiveData`"
        );
        entry.delta = [move_applied.x + delta.x, move_applied.y + delta.y];
        if let Some(active) = self.active.get_mut(&id) {
            active.repositioned = delta;
        }
        self.mov_count += 1;
    }
@@ -336,6 +498,13 @@ impl UiRenderState {
            active.textures.clear();
            rsc.ui_mut().textures.free();
            if undraw {
                // A captured widget that goes away mid-gesture (List's
                // virtualisation retiring a row, a rebuild) must not leave
                // the pointer permanently captured by an id nothing will
                // ever draw again -- `captured`'s own path out.
                if *self.captured.lock().unwrap() == Some(id) {
                    *self.captured.lock().unwrap() = None;
                }
                // Permanent removal: retire this widget's own move slot
                // (the self-ownership ref taken when it was allocated) and
                // the up-link ref it held on its parent's slot -- read from
@@ -343,6 +512,11 @@ impl UiRenderState {
                // the parent's own `ActiveData` may already be gone by the
                // time a deep descendant is retired (see LAYOUT.md
                // section 2's lifecycle note).
                if active.own_mask != MaskIdx::NONE {
                    // The self-ownership ref `Painter::set_mask` took when
                    // it allocated this widget's own mask slot.
                    rsc.ui_mut().masks.remove(active.own_mask);
                }
                let parent_slot = rsc.ui_mut().move_offsets[active.move_slot.idx()].parent;
                rsc.ui_mut().move_offsets.remove(active.move_slot);
                if parent_slot != MoveOffset::NONE_PARENT {
@@ -408,6 +582,100 @@ impl UiRenderState {
        self.active.len()
    }
    /// Primitive instances still bound for the GPU whose owner is no
    /// longer in `active`, or whose owner's `ActiveData` no longer names
    /// them: a copy nothing can move, clip, resize or free, redrawn every
    /// frame at whatever position it last had. `(layer, inst_idx, owner)`
    /// each.
    ///
    /// Asserted empty at the end of every [`Self::update`], because this
    /// is exactly the shape of the duplicated transcript row on Iris's
    /// phone (`docs/bench/iris-phone-v2-2026-09-06.md`): counting
    /// `active` alone cannot see it, since the orphan's owner is very
    /// much alive -- it is the *earlier* set of primitives that got
    /// stranded when the widget was drawn a second time without the first
    /// draw being freed. O(primitives), debug builds only.
    pub fn orphaned_primitives(&self) -> Vec<(usize, usize, WidgetId)> {
        let mut orphans = Vec::new();
        for (layer, primitives) in self.layers.iter() {
            for (inst_idx, owner, is_image) in primitives.live_instances() {
                let owned = self.active.get(&owner).is_some_and(|a| {
                    a.primitives.iter().any(|h| {
                        h.layer == layer
                            && h.inst_idx == inst_idx
                            && (h.binding == IMAGE_BINDING) == is_image
                    })
                });
                if !owned {
                    orphans.push((layer, inst_idx, owner));
                }
            }
        }
        orphans
    }
    /// Whether every primitive still bound for the GPU is owned by a live
    /// widget, decided by counting rather than by walking: an orphan is a
    /// live instance no `ActiveData` names, so it can only ever make the
    /// live count exceed the owned one. O(active widgets) -- a few dozen --
    /// against [`Self::orphaned_primitives`]'s O(primitives), which on a
    /// transcript is tens of thousands and made a debug build on a phone
    /// too slow to finish a benchmark run.
    fn primitive_counts_agree(&self) -> bool {
        let live: usize = self.layers.iter().map(|(_, p)| p.live_count()).sum();
        let owned: usize = self.active.values().map(|a| a.primitives.len()).sum();
        live == owned
    }
    /// The message [`Self::update`]'s orphan assert prints -- built here
    /// rather than inline so the (allocating, O(primitives)) work only
    /// happens on the failing path.
    #[cfg(debug_assertions)]
    fn orphan_report(&self, rsc: &dyn UiRsc) -> String {
        let orphans = self.orphaned_primitives();
        let mut lines: Vec<String> = orphans
            .iter()
            .take(8)
            .map(|(layer, idx, owner)| {
                let alive = self.active.contains_key(owner);
                format!(
                    "  layer {layer} instance {idx}: owner '{}' ({owner:?}),                      owner still active: {alive}",
                    rsc.widgets().label(*owner),
                )
            })
            .collect();
        if orphans.len() > lines.len() {
            lines.push(format!("  ... and {} more", orphans.len() - lines.len()));
        }
        format!(
            "{} primitive(s) are drawn but owned by nobody -- a stale copy \
             nothing will ever move or free:\n{}",
            orphans.len(),
            lines.join("\n"),
        )
    }
    /// Give `id` exclusive pointer input from the next `run_sensors` call
    /// on -- see `captured`'s field doc. Overwrites any previous capture
    /// (a gesture that starts a new one has already decided the old one
    /// is over).
    pub fn capture_pointer(&self, id: WidgetId) {
        *self.captured.lock().unwrap() = Some(id);
    }
    /// Release exclusive pointer input, if any is held -- called once
    /// `run_sensors` has delivered the terminal `Drop` to the capturing
    /// widget, or by that widget itself if it decides the gesture is over
    /// some other way.
    pub fn release_pointer(&self) {
        *self.captured.lock().unwrap() = None;
    }
    /// The widget currently holding exclusive pointer input, if any.
    pub fn captured_pointer(&self) -> Option<WidgetId> {
        *self.captured.lock().unwrap()
    }
    pub fn debug(&self, widgets: &Widgets, label: &str) -> impl Iterator<Item = &ActiveData> {
        self.active.iter().filter_map(move |(&id, inst)| {
            let l = widgets.label(id);
@@ -434,7 +702,12 @@ impl UiRenderState {
    /// section 2b.
    pub fn resolved_region(&self, id: &impl IdLike, rsc: &dyn UiRsc) -> Option<UiRegion> {
        let active = self.active.get(&id.id())?;
-        let delta = self.resolve_move_chain(active.move_slot, rsc);
+        // The chain sum is what the shader adds to this widget's
        // *primitives*, which were written before any of those moves.
        // `region`, unlike them, has already been shifted by whatever
        // part of this widget's own slot `mov` put there -- see
        // `ActiveData::move_applied`, which is exactly that part.
        let delta = self.resolve_move_chain(active.move_slot, rsc) - active.move_applied;
        Some(active.region.offset(UiVec2::abs(delta)))
    }
@@ -442,26 +715,56 @@ impl UiRenderState {
    /// pixel delta along the parent chain starting at `slot`. Both walks
    /// share `MOVE_CHAIN_LIMIT` as their bound so the two cannot disagree
    /// about where the chain ends.
-    fn resolve_move_chain(&self, mut slot: MoveIdx, rsc: &dyn UiRsc) -> Vec2 {
+    fn resolve_move_chain(&self, slot: MoveIdx, rsc: &dyn UiRsc) -> Vec2 {
        let offsets = &rsc.ui().move_offsets;
        let mut delta = Vec2::ZERO;
        let mut at = slot;
        for i in 0..MOVE_CHAIN_LIMIT {
-            let entry = &offsets[slot.idx()];
+            let entry = &offsets[at.idx()];
            delta.x += entry.delta[0];
            delta.y += entry.delta[1];
            if entry.parent == MoveOffset::NONE_PARENT {
                return delta;
            }
-            slot = Id::preset(entry.parent);
+            at = Id::preset(entry.parent);
            // The chain itself, not just the fact that it was too long: a
            // cycle and a tree genuinely nested deeper than the shader can
            // follow are different faults with different fixes, and the
            // slot numbers are the only thing that tells them apart.
            debug_assert!(
                i + 1 < MOVE_CHAIN_LIMIT,
-                "move offset chain exceeded MOVE_CHAIN_LIMIT; a widget's `parent` link is \
+                "move offset chain exceeded MOVE_CHAIN_LIMIT ({MOVE_CHAIN_LIMIT}): {chain} -- a \
-                 probably cyclic"
+                 repeated slot means a `parent` link is cyclic, all-distinct slots mean the tree \
                 nests deeper than shader.wgsl's own walk of the same bound",
                chain = Self::move_chain_debug(slot, offsets)
            );
        }
        delta
    }
    /// The parent chain from `slot`, as `slot(dx, dy) -> ...`, walked twice
    /// `MOVE_CHAIN_LIMIT` so a cycle shows up as a repeated slot number
    /// rather than as a chain that merely stops. Only ever called from the
    /// failed assertion above.
    fn move_chain_debug(slot: MoveIdx, offsets: &[MoveOffset]) -> String {
        let mut parts = Vec::new();
        let mut at = slot;
        for _ in 0..MOVE_CHAIN_LIMIT * 2 {
            let entry = &offsets[at.idx()];
            parts.push(format!(
                "{}({}, {})",
                at.idx(),
                entry.delta[0],
                entry.delta[1]
            ));
            if entry.parent == MoveOffset::NONE_PARENT {
                break;
            }
            at = Id::preset(entry.parent);
        }
        parts.join(" -> ")
    }
    pub fn window_region(&self, id: &impl IdLike, rsc: &dyn UiRsc) -> Option<PixelRegion> {
        let region = self.resolved_region(id, rsc)?;
        Some(region.to_px(self.output_size))
@@ -470,7 +773,10 @@ impl UiRenderState {
    /// redraws a widget that's currently active (drawn)
    pub fn redraw(&mut self, id: WidgetId, rsc: &mut dyn UiRsc) {
        rsc.widgets_mut().needs_redraw.remove(&id);
-        self.draw_started.remove(&id);
+        // An ancestor is drawing this widget right now, and that draw is
        // about to write fresh primitives for it. Drawing it a second time
        // here would leave one of the two copies on screen with nothing
        // owning it -- see `draw_started`'s own doc.
        if self.draw_started.contains(&id) {
            return;
        }
@@ -494,9 +800,9 @@ impl UiRenderState {
            active.mask,
            Some(active.children),
            Some(active.move_slot),
            active.own_mask,
            rsc,
        );
        // If this widget's own reported size changed, its parent's layout
        // (which placed it using the old size) is now stale and needs to
        // relay out too. Checked after the real draw, not before it --
@@ -41,6 +41,25 @@ pub trait Widget: Any {
    fn access_role(&self) -> accesskit::Role {
        accesskit::Role::Unknown
    }
    /// Advance whatever this widget is animating to `now`, and say whether
    /// it is still animating afterwards. Default: nothing is, so a widget
    /// opts in by overriding this *and* by something calling
    /// [`crate::UiData::animate`] with its id when the animation starts --
    /// which is that animation's path out, since the driver
    /// ([`crate::UiData::tick_animations`]) drops every id whose `tick`
    /// answers `false`.
    ///
    /// Called once per frame, before the frame's draw, by whichever
    /// backend owns the surface; a `true` answer is what makes that
    /// backend ask for another frame. So this is the only thing in iris
    /// that moves without an input event, and a widget that animates
    /// without registering simply never moves -- which is exactly how a
    /// finger fling looked on Iris's phone before this existed.
    #[allow(unused_variables)]
    fn tick(&mut self, now: std::time::Instant) -> bool {
        false
    }
 }
 impl Widget for () {
@@ -15,23 +15,19 @@
 //! +-----------+--------------------------------------+
 //! ```
 //!
-//! **Deliberately left simple, and why**: every incoming SSE event refolds
+//! **Incoming SSE events go through `TranscriptScreen::apply`**, not a
-//! the *entire* transcript (`client_core::transcript_fold::fold_event` is
+//! full rebuild: `client_core::transcript_fold::fold_event` folds the new
-//! already `O(items)` and a desktop session's conversation is small) and
+//! item list as before, then `apply` updates only the row(s) that actually
-//! rebuilds the whole right-hand widget tree from scratch, rather than
+//! changed (almost always the one still-open assistant message a delta
-//! reaching for `TranscriptScreen::push_row`'s incremental append.
+//! landed in) instead of rebuilding the whole right-hand widget tree from
-//! `push_row` cannot update a row already on screen -- only append a new
+//! scratch. `rebuild_transcript` still runs the whole tree once, for a
-//! one -- and a streaming assistant reply is exactly a row whose *text*
+//! freshly loaded/selected session and for `apply`'s own rare
-//! keeps changing after it first appears (see `transcript-ui`'s own doc on
+//! full-rebuild fallback (a `group_tool_runs` regroup touching a row
-//! `fold_event` folding deltas into one growing item). A full rebuild
+//! before the tail). The composer's in-progress text survives a rebuild
-//! shows that growth correctly at the cost of redrawing everything each
+//! (`rebuild_transcript`'s `in_progress` local) since the user typing a
-//! time; fine for this proof, wrong for a long, fast-streaming transcript
+//! followup while a reply streams in is the one case a naive rebuild
-//! -- the incremental path that fixes it needs `transcript-ui` to expose
+//! would otherwise lose data on -- `apply`'s own path never touches the
-//! updating a row in place, which it does not yet. The composer's
+//! composer at all, so this only matters on the fallback.
 //! in-progress text survives a rebuild (`rebuild_transcript`'s
 //! `in_progress` local) since the user typing a followup while a reply
 //! streams in is the one case a naive rebuild would otherwise lose data
 //! on.
 //!
 //! Background network I/O (`client_core::api`/`event_stream`, both
 //! blocking by design -- see `client-core`'s `Cargo.toml`) runs on plain
@@ -209,8 +205,12 @@ impl DefaultAppState for Client {
                event,
            } => {
                if self.current(&session_id, generation) {
                    let old_items = self.items.clone();
                    self.items = fold_event(&self.items, &event);
-                    self.rebuild_transcript(rsc);
+                    match &self.screen {
                        Some(screen) => screen.apply(rsc, &old_items, &self.items),
                        None => self.rebuild_transcript(rsc),
                    }
                }
            }
            AppEvent::StreamEnded {
@@ -68,12 +68,15 @@ fn build_row<Rsc: UiRsc + 'static>(rsc: &mut Rsc, i: usize) -> StrongWidget {
        let mut span = Span::empty(Dir::DOWN);
        span.push(text);
        span.push(img);
-        span.pad(8.0).background(rect(tint)).add_strong(rsc).any()
+        span.pad(dp(8.0))
            .background(rect(tint))
            .add_strong(rsc)
            .any()
    } else {
        wtext(row_text(i))
            .wrap(true)
            .color(text_color)
-            .pad(8.0)
+            .pad(dp(8.0))
            .background(rect(tint))
            .add_strong(rsc)
            .any()
@@ -0,0 +1,32 @@
 [package]
 name = "rig-input"
 version.workspace = true
 edition.workspace = true
 # Layer 2's input half (docs/RUST.md's "Three test layers"): replays one
 # of the `.touch` files the headless tests use into whatever window is
 # under a Wayland compositor, so the *same recording* drives the
 # assertion layer and the layer a person looks at.
 #
 # It exists because this machine's compositor has no pointer to move.
 # `run-headless.sh` starts sway on the headless backend with no input
 # devices at all (`WLR_LIBINPUT_NO_DEVICES=1`, `LIBSEAT_BACKEND=noop`),
 # so `swaymsg seat - cursor press` reports success and nothing reaches
 # the client -- `swaymsg -t get_seats` shows `capabilities: 0`. wlroots
 # 0.19 dropped `WLR_HEADLESS_INPUTS`, and ydotool's uinput device would
 # be ignored by a compositor that is not reading libinput. The
 # virtual-pointer protocol is what is left, and it is a client protocol,
 # so it needs no devices and no root.
 # Named for what it does rather than for the crate, since the crate may
 # grow a keyboard replay beside it.
 [[bin]]
 name = "replay-touch"
 path = "src/main.rs"
 [dependencies]
 # `TouchScript` -- the same parser the harness uses, so a file that
 # replays here and one that replays headless can never disagree.
 iris = { path = ".." }
 wayland-client = "0.31.15"
 wayland-protocols-wlr = { version = "0.3.12", features = ["client"] }
@@ -0,0 +1,164 @@
 //! Replays a `.touch` file into the compositor as a left-button drag --
 //! see this crate's `Cargo.toml` for why it exists rather than
 //! `swaymsg seat - cursor`.
 //!
 //!     WAYLAND_DISPLAY=… replay-touch WIDTH HEIGHT FILE
 //!
 //! `WIDTH`/`HEIGHT` are the output's own size, because the virtual
 //! pointer protocol positions absolutely against an extent rather than
 //! in pixels; passing the output size makes a script's coordinates mean
 //! the same pixels they mean in the headless tests.
 //!
 //! Replayed in real time (the sleeps between samples are the gaps in the
 //! file), because winit has no timestamp on a pointer event and dates
 //! each one when it arrives -- so a 20ms flick has to actually take
 //! 20ms here, unlike layer 1 where the sample carries its own time.
 use iris::harness::{TouchAction, TouchScript};
 use std::time::Duration;
 use wayland_client::protocol::wl_pointer::ButtonState;
 use wayland_client::protocol::{wl_registry, wl_seat};
 use wayland_client::{Connection, Dispatch, QueueHandle, delegate_noop};
 use wayland_protocols_wlr::virtual_pointer::v1::client::{
    zwlr_virtual_pointer_manager_v1::ZwlrVirtualPointerManagerV1,
    zwlr_virtual_pointer_v1::ZwlrVirtualPointerV1,
 };
 /// `linux/input-event-codes.h`. The protocol takes the kernel's own
 /// button code, not a wayland enum.
 const BTN_LEFT: u32 = 0x110;
 /// How long the pointer sits at the gesture's first position before the
 /// script starts -- see the comment at the pre-step in `main`.
 const SETTLE: Duration = Duration::from_millis(200);
 #[derive(Default)]
 struct Globals {
    seat: Option<wl_seat::WlSeat>,
    manager: Option<ZwlrVirtualPointerManagerV1>,
 }
 impl Dispatch<wl_registry::WlRegistry, ()> for Globals {
    fn event(
        state: &mut Self,
        registry: &wl_registry::WlRegistry,
        event: wl_registry::Event,
        _: &(),
        _: &Connection,
        qh: &QueueHandle<Self>,
    ) {
        let wl_registry::Event::Global {
            name,
            interface,
            version,
        } = event
        else {
            return;
        };
        match interface.as_str() {
            "wl_seat" => {
                state.seat = Some(registry.bind(name, version.min(7), qh, ()));
            }
            "zwlr_virtual_pointer_manager_v1" => {
                state.manager = Some(registry.bind(name, version.min(2), qh, ()));
            }
            _ => {}
        }
    }
 }
 delegate_noop!(Globals: ignore wl_seat::WlSeat);
 delegate_noop!(Globals: ZwlrVirtualPointerManagerV1);
 delegate_noop!(Globals: ZwlrVirtualPointerV1);
 fn main() {
    let args: Vec<String> = std::env::args().skip(1).collect();
    let [width, height, path] = args.as_slice() else {
        eprintln!("usage: replay-touch WIDTH HEIGHT FILE");
        std::process::exit(2);
    };
    let (width, height) = (parse(width, "WIDTH"), parse(height, "HEIGHT"));
    let text = std::fs::read_to_string(path)
        .unwrap_or_else(|e| fail(&format!("could not read {path}: {e}")));
    let script = TouchScript::parse(&text).unwrap_or_else(|e| fail(&e));
    let conn = Connection::connect_to_env().unwrap_or_else(|e| {
        fail(&format!(
            "no wayland display ({e}); is WAYLAND_DISPLAY set?"
        ))
    });
    let mut queue = conn.new_event_queue();
    let qh = queue.handle();
    let display = conn.display();
    display.get_registry(&qh, ());
    let mut globals = Globals::default();
    queue
        .roundtrip(&mut globals)
        .unwrap_or_else(|e| fail(&format!("wayland roundtrip failed: {e}")));
    let manager = globals.manager.as_ref().unwrap_or_else(|| {
        fail(
            "this compositor does not offer zwlr_virtual_pointer_manager_v1, so a pointer cannot \
             be synthesised; sway and every wlroots compositor do",
        )
    });
    let pointer = manager.create_virtual_pointer(globals.seat.as_ref(), &qh, ());
    // Put the pointer where the gesture starts and let the compositor
    // settle before anything is pressed. Without this the press is
    // dropped: sway has just learned about this pointer, and a button
    // sent in the same breath as the motion that first puts it over a
    // window arrives before there is a focused surface to send it to --
    // winit sees `CursorEntered`, the moves and the *release*, never the
    // press, so the gesture reads as a hover and nothing scrolls. Found
    // by printing winit's own events; the settle is what fixed it.
    if let Some(first) = script.samples.first() {
        pointer.motion_absolute(0, first.pos.x as u32, first.pos.y as u32, width, height);
        pointer.frame();
        conn.flush()
            .unwrap_or_else(|e| fail(&format!("flush: {e}")));
        std::thread::sleep(SETTLE);
    }
    let mut previous = 0;
    for sample in &script.samples {
        std::thread::sleep(Duration::from_millis(sample.t_ms - previous));
        previous = sample.t_ms;
        let t = sample.t_ms as u32;
        pointer.motion_absolute(t, sample.pos.x as u32, sample.pos.y as u32, width, height);
        // One frame per sample, so the compositor delivers them as
        // separate pointer frames rather than coalescing the whole
        // gesture -- the shape the file recorded is the point.
        pointer.frame();
        // The button goes in a frame of its own, *after* the motion has
        // been committed. Sent in the same frame as the motion that
        // first puts the pointer over the window, sway drops it: the
        // client sees `CursorEntered` and the moves but never a
        // `MouseInput { state: Pressed }`, so the whole gesture reads as
        // a hover and nothing scrolls. Found exactly that way, by
        // printing winit's events.
        let state = match sample.action {
            TouchAction::Down => Some(ButtonState::Pressed),
            TouchAction::Up | TouchAction::Cancel => Some(ButtonState::Released),
            TouchAction::Move => None,
        };
        if let Some(state) = state {
            pointer.button(t, BTN_LEFT, state);
            pointer.frame();
        }
        conn.flush()
            .unwrap_or_else(|e| fail(&format!("flush: {e}")));
    }
    pointer.destroy();
    conn.flush().ok();
 }
 fn parse(text: &str, what: &str) -> u32 {
    text.parse()
        .unwrap_or_else(|_| fail(&format!("{what} is not a whole number: {text:?}")))
 }
 fn fail(message: &str) -> ! {
    eprintln!("replay-touch: {message}");
    std::process::exit(1);
 }
@@ -3,6 +3,25 @@
 #
 #   ./run-headless.sh tabs [-- cargo args]
 #   ./run-headless.sh tabs --shot /tmp/tabs.png --seconds 4
 #   ./run-headless.sh phone --phone --shot /tmp/p.png -- -p transcript-fixture
 #   ./run-headless.sh phone --phone --replay transcript-fixture/touch/flick-120hz.touch \
 #       --shot /tmp/p.png -- -p transcript-fixture
 #
 # `--phone` is layer 2 of docs/RUST.md's "Three test layers": the output
 # and the window take Iris's phone's own size and density (1080x2424 at
 # `content_scale` 2.55, from docs/bench/iris-phone-v2-2026-09-06.md,
 # carried in `transcript_fixture::PHONE_*`), and `IRIS_SCALE` hands that
 # density to iris the way `DisplayMetrics.density` does on Android
 # (`iris::default::content_scale`). So a screenshot from here and one
 # from the phone are the same layout at the same density, and what
 # differs is only the renderer. Without it the output stays desktop-
 # shaped, which is what every other example wants.
 #
 # `--replay FILE` drives one of the `.touch` recordings the headless
 # tests use (`iris/transcript-fixture/touch/`) into the window through
 # `rig-input`'s `replay-touch` -- one recording, both layers. With
 # `--shot` it also writes `<shot>-before.png` from just before the
 # gesture, since "the list moved" is a claim about two pictures.
 #
 # `--bin` runs a real crate binary instead of an example (E4's
 # `desktop-app`, which is a window a person runs, not a demo) --
@@ -29,19 +48,31 @@ here=$(cd "$(dirname "$0")" && pwd)
 run="${XDG_RUNTIME_DIR:-/tmp}/iris-headless"
 seconds=3
 shot=""
 replay=""
 example=""
 kind=example
 phone=no
 # The phone Iris runs the bench on. Not typed from memory: these are
 # `transcript_fixture::PHONE_WIDTH`/`PHONE_HEIGHT`/`PHONE_SCALE`, which
 # in turn come from her own reports -- keep the three in step.
 PHONE_MODE=1080x2424@120Hz
 PHONE_SCALE=2.55
 DESKTOP_MODE=1920x1200@60Hz
 while [ $# -gt 0 ]; do
    case "$1" in
        --shot) shot=$2; shift 2 ;;
        --seconds) seconds=$2; shift 2 ;;
        --bin) kind=bin; shift ;;
        --phone) phone=yes; shift ;;
        --replay) replay=$2; shift 2 ;;
        --) shift; break ;;
        *) example=$1; shift ;;
    esac
 done
-[ -n "$example" ] || { echo "usage: $0 NAME [--bin] [--shot PNG] [--seconds N] [-- cargo args]" >&2; exit 2; }
+[ -n "$example" ] || { echo "usage: $0 NAME [--bin] [--phone] [--replay TOUCH] [--shot PNG] [--seconds N] [-- cargo args]" >&2; exit 2; }
 [ -z "$replay" ] || [ -f "$replay" ] || { echo "run-headless: no touch script at $replay" >&2; exit 2; }
 mkdir -p "$run"
 export SWAYSOCK="$run/sway.sock"
@@ -78,6 +109,27 @@ export WAYLAND_DISPLAY
 echo "run-headless: $WAYLAND_DISPLAY (sway $(swaymsg -t get_version --raw | sed -n 's/.*"human_readable":"\([^"]*\)".*/\1/p'))" >&2
 # Set every run rather than only when it changes: this compositor is
 # reused across runs (see the socket comment above), so a desktop-shaped
 # run after a phone-shaped one would otherwise inherit the phone's output
 # and silently screenshot the wrong size.
 if [ "$phone" = yes ]; then
    mode=$PHONE_MODE
    export IRIS_SCALE="$PHONE_SCALE"
    echo "run-headless: phone-shaped output $PHONE_MODE at IRIS_SCALE=$PHONE_SCALE" >&2
 else
    mode=$DESKTOP_MODE
 fi
 swaymsg output HEADLESS-1 mode "$mode" >/dev/null
 # The extent `replay-touch` positions against, so a script's coordinates
 # are the output's own pixels.
 out_w=${mode%x*}
 out_h=${mode#*x}; out_h=${out_h%@*}
 # Built before the app starts, so a compile error is not reported as a
 # window that failed to move.
 [ -z "$replay" ] || cargo build --bin replay-touch -p rig-input >&2
 cd "$here"
 if [ "$kind" = bin ]; then
    cargo build --bin "$example" "$@" >&2
@@ -111,6 +163,18 @@ while [ $i -lt "$((seconds * 2))" ]; do
    i=$((i + 1)); sleep 0.5
 done
 if [ -n "$replay" ] && kill -0 "$pid" 2>/dev/null; then
    if [ -n "$shot" ]; then
        grim "${shot%.png}-before.png"
        echo "run-headless: wrote ${shot%.png}-before.png (before the gesture)" >&2
    fi
    "$here/target/debug/replay-touch" "$out_w" "$out_h" "$replay"
    # A fling outlives the finger: the gesture's own last sample is not
    # when the list stops. Long enough for Android's spline to settle
    # (`FlingCalculator::duration` tops out around a second and a half).
    sleep 2
 fi
 if kill -0 "$pid" 2>/dev/null; then
    [ -n "$shot" ] && grim "$shot" && echo "run-headless: wrote $shot" >&2
    kill "$pid" 2>/dev/null || true
@@ -12,6 +12,10 @@ impl<T: HasAndroidUiState> FocusHost for T {
        self.android_state_mut().focus = id;
    }
    fn is_focused(&self, id: WeakWidget<TextEdit>) -> bool {
        self.android_state().focus == Some(id)
    }
    fn focus_gained(&mut self, region: Option<PixelRegion>) {
        // Showing the keyboard is a JNI call (`InputMethodManager.showSoftInput`),
        // and this runs deep inside the platform-agnostic sensor dispatch
@@ -49,6 +49,52 @@ impl<State: AndroidAppState> IrisViewPeer<State> {
    fn focus(&self) -> Option<WeakWidget<TextEdit>> {
        self.state.android_state().focus
    }
    /// Tell Gboard where the caret/selection and the composing region
    /// actually are, via `InputMethodManager.updateSelection` -- every one
    /// of android-view's own demo's `set_composing_text_internal`/`render`
    /// calls this, and this bridge never did, which is what left Gboard's
    /// own model of the field diverging from `TextEdit`'s real one after
    /// the very first edit (RUST.md's P0 box, "doesn't enter it until I
    /// hit space, and also doesn't move cursor forward" -- Gboard holds
    /// its composing keystrokes back until it believes the app has caught
    /// up, and without this call it never does). Called from
    /// [`IrisViewPeer::after_input`], the one tail every touch/key/IME
    /// callback already runs through, rather than duplicated at each of
    /// this file's mutating methods.
    ///
    /// `candidates_start`/`candidates_end` report the composing region;
    /// `-1, -1` when nothing is composing, matching `EditorInfo`'s own
    /// convention. `compose_len` is tracked in `char`s (this module's doc
    /// comment), so this reports it as that many UTF-16 units back from the
    /// caret -- exact for the common BMP case, the same approximation
    /// `set_composing_text` already makes.
    pub(super) fn update_ime_selection(&mut self, ctx: &mut CallbackCtx) {
        let Some(focus) = self.focus() else { return };
        let text = &self.rsc[focus];
        let Some(sel) = text.selection_range() else {
            return;
        };
        let content = text.text();
        let sel_start = byte_to_utf16(content, sel.start) as i32;
        let sel_end = byte_to_utf16(content, sel.end) as i32;
        let compose_len = self.state.android_state().compose_len;
        let (comp_start, comp_end) = if compose_len > 0 {
            let caret = byte_to_utf16(content, text.caret().unwrap_or(sel.end)) as i32;
            (caret - compose_len as i32, caret)
        } else {
            (-1, -1)
        };
        let imm = ctx.view.input_method_manager(&mut ctx.env);
        imm.update_selection(
            &mut ctx.env,
            &ctx.view,
            sel_start,
            sel_end,
            comp_start,
            comp_end,
        );
    }
 }
 impl<State: AndroidAppState> InputConnection for IrisViewPeer<State> {
@@ -45,16 +45,38 @@ pub struct Insets {
    pub top: i32,
    pub right: i32,
    pub bottom: i32,
-    /// The keyboard's own inset (`WindowInsetsCompat.Type.ime()`), separate
+    /// The keyboard's own inset (`WindowInsets.Type.ime()`), in physical
-    /// from `bottom` (the system bars): a layout wants to know about the
+    /// pixels, separate from `bottom` (the system bars): a layout wants to
-    /// keyboard specifically, since it usually means "make room" rather
+    /// know about the keyboard specifically, since it usually means "make
-    /// than "stay clear of a corner".
+    /// room" rather than "stay clear of a corner".
    pub ime_bottom: i32,
    /// `WindowInsets.isVisible(ime())` -- whether the keyboard is up, which
    /// is **not** the same question as `ime_bottom > 0` and is why the two
    /// are carried separately. They disagree for the frames the keyboard
    /// spends sliding: visible, with a height still on its way to the full
    /// one. Anything asking "make how much room" reads `ime_bottom`;
    /// anything asking "is the keyboard up" reads this. See
    /// `MainActivity.java`'s comment for the history -- the height used to
    /// be sent *as* this boolean, which is what left the composer padded by
    /// one pixel on Iris's phone.
    pub ime_visible: bool,
 }
 #[derive(Default)]
 pub struct Shared {
    pub insets: Insets,
    /// How many times Java has called `applyWindowInsetsNative` for this
    /// peer, whether or not the numbers changed. Deliberately **not** a
    /// field of `Insets`, which is compared for equality each frame to
    /// decide whether to re-run `on_insets_changed`; a counter in there
    /// would make every dispatch look like a change.
    ///
    /// It exists because "the keyboard does not push anything up" has two
    /// completely different causes that look identical on screen -- the
    /// listener never fired, or it fired with a zero `ime_bottom` -- and
    /// Iris has no logcat on her phone (docs/IRIS_TODO.md). This number is
    /// in the `Diagnostics` overlay, so one screenshot separates them.
    pub updates: u64,
 }
 type SharedMap = HashMap<jlong, SendWrapper<Rc<RefCell<Shared>>>>;
@@ -89,15 +111,19 @@ extern "system" fn apply_window_insets<'local>(
    right: jint,
    bottom: jint,
    ime_bottom: jint,
    ime_visible: jint,
 ) {
    if let Some(shared) = map().lock().unwrap().get(&peer) {
-        shared.borrow_mut().insets = Insets {
+        let mut shared = shared.borrow_mut();
        shared.insets = Insets {
            left,
            top,
            right,
            bottom,
            ime_bottom,
            ime_visible: ime_visible != 0,
        };
        shared.updates += 1;
    }
    // Insets can change (the keyboard opening) with no resize and no
    // touch, so nothing else here would otherwise ask for a frame.
@@ -115,7 +141,7 @@ pub fn register_native_methods<'local, 'other_local>(
        &[
            NativeMethod {
                name: "applyWindowInsetsNative".into(),
-                sig: "(JIIIII)V".into(),
+                sig: "(JIIIIII)V".into(),
                fn_ptr: apply_window_insets as *mut c_void,
            },
            NativeMethod {
@@ -17,13 +17,15 @@ mod attr;
 mod ime;
 mod input;
 mod insets;
 mod platform;
 mod render;
 mod view;
 pub use insets::Insets;
 pub use render::AndroidRenderer;
 pub use view::{
-    AndroidAppState, AndroidRsc, AndroidUiState, HasAndroidUiState, IrisViewPeer, new_peer,
+    AndroidAppState, AndroidRsc, AndroidUiState, HasAndroidUiState, IrisViewPeer, WindowInsets,
    new_peer,
 };
 /// Registers the extra native methods this backend needs beyond what
@@ -0,0 +1,89 @@
 use crate::platform::OpenUrl;
 use android_view::{
    View,
    jni::{
        JNIEnv,
        objects::{JObject, JValue},
    },
 };
 use super::view::HasAndroidUiState;
 /// Android's URL opener. Like `FocusHost::focus_gained`'s keyboard, the
 /// real work is a JNI call and this runs deep inside the sensor dispatch
 /// with no `CallbackCtx` in reach -- so it raises a flag that
 /// `IrisViewPeer::after_input` consumes, exactly as
 /// `pending_show_keyboard` does.
 ///
 /// Last request wins: two links cannot be tapped in one frame, and a URL
 /// left queued from a frame that somehow never reached `after_input`
 /// would open at some unrelated later tap, which is worse than dropping
 /// it.
 impl<T: HasAndroidUiState> OpenUrl for T {
    fn open_url(&mut self, url: &str) {
        self.android_state_mut().pending_open_url = Some(url.to_string());
    }
 }
 /// `startActivity(new Intent(ACTION_VIEW, Uri.parse(url)))` on the view's
 /// own context.
 ///
 /// `FLAG_ACTIVITY_NEW_TASK` because the context here is the view's, which
 /// may be an application context rather than the activity's -- Android
 /// throws `AndroidRuntimeException` for a non-activity context without it,
 /// and it is harmless when the context *is* an activity's.
 ///
 /// Every failure is logged with the URL and returns; there is nothing to
 /// fall back to, and the reader will see that nothing happened.
 pub(super) fn open_url<'local>(env: &mut JNIEnv<'local>, view: &View<'local>, url: &str) {
    match try_open_url(env, view, url) {
        Ok(()) => {}
        Err(e) => {
            // A pending Java exception makes every later JNI call fail in
            // ways nowhere near here, so it is cleared at the boundary.
            let _ = env.exception_clear();
            log::warn!("could not open {url}: {e}");
        }
    }
 }
 fn try_open_url<'local>(
    env: &mut JNIEnv<'local>,
    view: &View<'local>,
    url: &str,
 ) -> Result<(), android_view::jni::errors::Error> {
    let context = env
        .call_method(&view.0, "getContext", "()Landroid/content/Context;", &[])?
        .l()?;
    let jurl = env.new_string(url)?;
    let uri = env.call_static_method(
        "android/net/Uri",
        "parse",
        "(Ljava/lang/String;)Landroid/net/Uri;",
        &[JValue::Object(jurl.as_ref())],
    )?;
    let action = env.new_string("android.intent.action.VIEW")?;
    let intent = env.new_object(
        "android/content/Intent",
        "(Ljava/lang/String;Landroid/net/Uri;)V",
        &[JValue::Object(action.as_ref()), JValue::Object(&uri.l()?)],
    )?;
    env.call_method(
        &intent,
        "addFlags",
        "(I)Landroid/content/Intent;",
        &[JValue::Int(FLAG_ACTIVITY_NEW_TASK)],
    )?;
    env.call_method(
        &context,
        "startActivity",
        "(Landroid/content/Intent;)V",
        &[JValue::Object(&JObject::from(intent))],
    )?;
    Ok(())
 }
 /// `android.content.Intent.FLAG_ACTIVITY_NEW_TASK`. A constant rather than
 /// a static-field read: it is part of the platform's stable ABI and
 /// reading it costs two more JNI calls that can each fail.
 const FLAG_ACTIVITY_NEW_TASK: i32 = 0x1000_0000;
@@ -48,10 +48,65 @@ pub struct AndroidRenderer {
    config: SurfaceConfiguration,
    encoder: CommandEncoder,
    pub ui: UiRenderNode,
    /// The adapter identity, kept past `new()` for the Diagnostics page --
    /// `Adapter` itself is not `Clone`, so the three fields the page shows
    /// are copied out once here rather than holding the adapter.
    pub adapter_name: String,
    pub adapter_backend: Backend,
    pub adapter_driver: String,
    /// Every uncaptured wgpu error since this renderer was created -- see
    /// `iris_core::WgpuErrorLog`'s doc comment. Installed on `device` in
    /// `new()`, kept here so the Diagnostics page and the per-frame log in
    /// `update()` can both read it without a global.
    pub wgpu_errors: iris_core::WgpuErrorLog,
    /// Frames drawn on this surface -- what gates the first-10-frames log
    /// `update()` writes (RUST.md's P0 box, "the first input frame"
    /// investigation): a fresh surface is exactly what Iris's own report
    /// says renders correctly at first, so the frames that matter are the
    /// first several after each `surface_changed`, not an arbitrary window
    /// during a long-running session.
    frame_count: u64,
    /// Physical pixels per dp -- see `android::view::AndroidUiState::
    /// content_scale`'s field comment for what this feeds.
    content_scale: f32,
 }
 /// One frame's worth of the counters `render/mod.rs`'s doc comments on
 /// `FrameUpdateStats`/`take_image_bind_group_creates`/
 /// `take_atlas_pages_grown` describe -- assembled here because the three
 /// live on two different calling conventions (`FrameUpdateStats` from this
 /// exact `update()` call; the other two describe the *previous* frame,
 /// same as `bench_images`' existing use of them) and a diagnostic reader
 /// should not have to know that split.
 #[derive(Clone, Copy, Debug, Default)]
 pub struct FrameDiagnostics {
    pub masks_resized: bool,
    pub moves_resized: bool,
    /// From the previous frame's `update()` -- see the struct doc.
    pub atlas_pages_grown_prev: u64,
    pub image_bind_group_creates_prev: u64,
 }
 impl AndroidRenderer {
-    pub fn new(window: NativeWindow, width: u32, height: u32) -> Self {
+    /// `Err` holds a full, human-readable report -- wgpu's own error text
    /// (`UiRenderNode::new`'s doc comment) plus the adapter identity and
    /// the limits/downlevel flags bind-group-layout validation checks
    /// against -- rather than the panic wgpu's default error handler would
    /// otherwise raise with no caller able to see it. This is what aborted
    /// the P0 bench APK on Iris's phone with only "wgpu error: Validation
    /// Error" surviving into the crash report (RUST.md's P0 box, "iris
    /// bench crash on the phone, 2026-09-06"): `create_bind_group_layout`
    /// validates against *this* adapter's downlevel capabilities and
    /// limits, which a desktop GPU and the emulator's software renderers
    /// never exercised. The caller (`android::view::IrisViewPeer::
    /// surface_changed`) logs this one-line-flattened and shows it on
    /// screen instead of aborting the process.
    pub fn new(
        window: NativeWindow,
        width: u32,
        height: u32,
        content_scale: f32,
    ) -> Result<Self, String> {
        // `force-gles` (RUST.md's I5 "Where iris's frame time goes") swaps
        // the software-Vulkan (SwiftShader) path for GLES/virgl on the same
        // build, to isolate whether the backend itself explains the frame
@@ -84,6 +139,18 @@ impl AndroidRenderer {
            .block_on()
            .expect("Could not get adapter!");
        // Requesting the device itself still panics on failure: that is a
        // `RequestDeviceError` (a limit or feature the adapter cannot grant
        // at all), a different and already-diagnosable failure from the one
        // this function now recovers from -- `RUST.md`'s "Software mode ...
        // crashes for a third, different reason" is exactly that class, and
        // its message already names the limit and the requested/allowed
        // values with no truncation risk (it never reaches wgpu's
        // uncaptured-error path). What this function's `Result` return
        // covers is the *next* class of failure: the adapter grants the
        // device, and validation only fails once a specific bind group
        // layout is checked against it.
        // Same request as the winit backend's `UiRenderer::new` -- no
        // binding-array features, see TEXTURES.md's "Recommended shape".
        // `iris_core::device_limits()` is shared between the two backends;
@@ -96,6 +163,30 @@ impl AndroidRenderer {
            .block_on()
            .expect("Could not get device!");
        // wgpu's default handler for an error raised outside `UiRenderNode::
        // new`'s own error scopes (i.e. everything past device creation --
        // an ordinary frame's `update`/`draw`) is `panic!`, unconditionally,
        // with no caller able to intervene: the same mechanism that aborted
        // the P0 bench APK once already, just at a different call site. Log
        // and record instead of letting that default stand -- RUST.md's P0
        // box, "every wgpu uncaptured error ... it must never panic in
        // release".
        let wgpu_errors = iris_core::WgpuErrorLog::default();
        let wgpu_errors_for_handler = wgpu_errors.clone();
        device.on_uncaptured_error(std::sync::Arc::new(move |error| {
            log::error!("iris wgpu uncaptured error: {error}");
            wgpu_errors_for_handler.record(error);
        }));
        let info = adapter.get_info();
        let adapter_name = info.name.clone();
        let adapter_backend = info.backend;
        let adapter_driver = if info.driver_info.is_empty() {
            info.driver.clone()
        } else {
            format!("{} {}", info.driver, info.driver_info)
        };
        let surface_caps = surface.get_capabilities(&adapter);
        let surface_format = surface_caps
            .formats
@@ -117,16 +208,121 @@ impl AndroidRenderer {
        surface.configure(&device, &config);
        let encoder = Self::create_encoder(&device);
-        let ui = UiRenderNode::new(&device, &queue, &config);
+        // Physical pixels, matching the swapchain's own `width`/`height`
        // exactly -- see `android::view::AndroidUiState::content_scale`'s
        // field comment for why this is no longer divided into a separate
        // logical space (that stopgap is what made text blurry, RUST.md's
        // P0 box). `Len::dp` folds the density in at layout time instead,
        // so nothing here needs to know it at all.
        let window_size = iris_core::util::Vec2::new(width as f32, height as f32);
        let ui = match UiRenderNode::new(&device, &queue, &config, window_size) {
            Ok(ui) => ui,
            Err(wgpu_error) => return Err(Self::diagnostic(&adapter, &wgpu_error)),
        };
-        Self {
+        Ok(Self {
            surface,
            device,
            queue,
            config,
            encoder,
            ui,
-        }
+            adapter_name,
            adapter_backend,
            adapter_driver,
            wgpu_errors,
            frame_count: 0,
            content_scale,
        })
    }
    /// The adapter identity plus every limit and downlevel flag
    /// `create_bind_group_layout` validates a storage buffer or texture
    /// binding against, followed by wgpu's own error text -- everything a
    /// person reading this off a screenshot needs to tell "this adapter
    /// lacks X" from "this is a bug in the layout." Named explicitly rather
    /// than `{limits:?}`/`{flags:?}` wholesale, because `Limits` alone is
    /// dozens of fields nobody asked for -- these are exactly the ones
    /// `UiRenderNode::new`'s layouts (`rsc_layout`, `masks_layout`,
    /// `primitive_layout`) can fail against, per `CreateBindGroupLayoutError`
    /// (`wgpu-core::binding_model`) and its downlevel-flag checks
    /// (`wgpu-core::device::resource`, `VERTEX_STORAGE` in particular --
    /// the one storage buffer here, `move_offsets`, that is visible to the
    /// vertex stage).
    fn diagnostic(adapter: &Adapter, wgpu_error: &str) -> String {
        let info = adapter.get_info();
        let limits = adapter.limits();
        let downlevel = adapter.get_downlevel_capabilities();
        format!(
            "iris could not start rendering. Copy this text and send it to Iris.\n\n\
             adapter: {name} ({backend:?}), driver: {driver} {driver_info}\n\
             limits: max_storage_buffers_per_shader_stage={max_storage_buffers} \
             max_sampled_textures_per_shader_stage={max_sampled_textures} \
             max_bind_groups={max_bind_groups} \
             max_bindings_per_bind_group={max_bindings} \
             max_storage_buffer_binding_size={max_storage_binding} \
             min_storage_buffer_offset_alignment={min_storage_align}\n\
             downlevel flags: {flags:?}\n\n\
             {wgpu_error}",
            name = info.name,
            backend = info.backend,
            driver = info.driver,
            driver_info = info.driver_info,
            max_storage_buffers = limits.max_storage_buffers_per_shader_stage,
            max_sampled_textures = limits.max_sampled_textures_per_shader_stage,
            max_bind_groups = limits.max_bind_groups,
            max_bindings = limits.max_bindings_per_bind_group,
            max_storage_binding = limits.max_storage_buffer_binding_size,
            min_storage_align = limits.min_storage_buffer_offset_alignment,
            flags = downlevel.flags,
        )
    }
    /// The Diagnostics page's whole report: adapter identity, font
    /// resolution, the atlas's own view count, every uncaptured wgpu error
    /// so far, and the frame report -- RUST.md's P0 box, "a named
    /// `Diagnostics` control ... adapter info, limits, fonts found, atlas
    /// format/pages, wgpu errors so far, frame report". One string rather
    /// than a struct the caller formats, since the only consumer is a
    /// plain `TextView` with a "copy this and send it to Iris" affordance,
    /// the same shape `surface_changed`'s crash report already uses
    /// (UI_RULES.md: a failure -- or here, a state worth reporting --
    /// carries enough to act on where it's shown).
    pub fn diagnostics_report(
        &self,
        font: &iris_core::FontDiagnostics,
        frame_report: &str,
    ) -> String {
        let errors = self.wgpu_errors.snapshot();
        let errors_text = if errors.is_empty() {
            "none".to_string()
        } else {
            errors.join("\n  ")
        };
        format!(
            "iris diagnostics. Copy this text and send it to Iris.\n\n\
             adapter: {name} ({backend:?}), driver: {driver}\n\
             content_scale: {content_scale}\n\
             atlas format: Rgba8Unorm, views live: {views}\n\
             fonts: {families_found} families found, default={default_family:?} \
             mono={default_mono_family:?}\n\
             fonts resolved: regular={regular:?} bold={bold:?} italic={italic:?} \
             mono={mono:?}\n\
             wgpu errors since surface creation:\n  {errors_text}\n\n\
             {frame_report}",
            name = self.adapter_name,
            backend = self.adapter_backend,
            driver = self.adapter_driver,
            content_scale = self.content_scale,
            views = self.ui.view_count(),
            families_found = font.families_found,
            default_family = font.default_family,
            default_mono_family = font.default_mono_family,
            regular = font.regular_resolved,
            bold = font.bold_resolved,
            italic = font.italic_resolved,
            mono = font.mono_resolved,
        )
    }
    fn create_encoder(device: &Device) -> CommandEncoder {
@@ -135,8 +331,31 @@ impl AndroidRenderer {
        })
    }
-    pub fn update(&mut self, ui: &mut UiData, render: &mut UiRenderState) {
+    /// Returns what changed this frame -- see `FrameDiagnostics`'s doc
-        self.ui.update(&self.device, &self.queue, ui, render);
+    /// comment for why two of its four fields describe the *previous*
    /// frame rather than this one. `IrisViewPeer::render` logs this for
    /// the first `DIAGNOSTIC_FRAMES` frames after each `surface_changed`,
    /// per RUST.md's P0 box ("the first input frame" investigation): the
    /// glyph-wipe Iris reported happens on the first tap or scroll after a
    /// fresh surface, so that is exactly the window a report needs to
    /// cover, not an arbitrary slice of a long session.
    pub fn update(&mut self, ui: &mut UiData, render: &mut UiRenderState) -> FrameDiagnostics {
        let atlas_pages_grown_prev = self.ui.take_atlas_pages_grown();
        let image_bind_group_creates_prev = self.ui.take_image_bind_group_creates();
        let stats = self.ui.update(&self.device, &self.queue, ui, render);
        self.frame_count += 1;
        FrameDiagnostics {
            masks_resized: stats.masks_resized,
            moves_resized: stats.moves_resized,
            atlas_pages_grown_prev,
            image_bind_group_creates_prev,
        }
    }
    /// Frames drawn on this surface so far -- see `frame_count`'s field
    /// comment.
    pub fn frame_count(&self) -> u64 {
        self.frame_count
    }
    /// Draws and presents one frame, returning the time spent in
@@ -179,15 +398,27 @@ impl AndroidRenderer {
        submit_start.elapsed()
    }
    /// Physical pixels -- the unit layout and hit-testing use, matching
    /// the window uniform's own units. See
    /// `android::view::AndroidUiState::content_scale`'s field comment.
    pub fn size(&self) -> iris_core::util::Vec2 {
-        (self.config.width, self.config.height).into()
+        iris_core::util::Vec2::new(self.config.width as f32, self.config.height as f32)
    }
    /// Reconfigures the surface and rewrites the window uniform for a new
    /// physical size -- deliberately the *only* two things this does.
    /// `device`, `ui`'s atlas, buffers and bind groups are untouched, so a
    /// call here (as opposed to a fresh `AndroidRenderer::new`) never
    /// invalidates a glyph the CPU-side cache already placed in the atlas.
    /// See `android::view::IrisViewPeer::surface_changed`'s doc comment for
    /// why that distinction matters -- it is what keeps text on screen
    /// across an IME resize.
    pub fn resize(&mut self, width: u32, height: u32) {
        self.config.width = width;
        self.config.height = height;
        self.surface.configure(&self.device, &self.config);
-        self.ui.resize((width, height), &self.queue);
+        let size = iris_core::util::Vec2::new(width as f32, height as f32);
        self.ui.resize(size, &self.queue);
    }
 }
@@ -4,8 +4,12 @@ use accesskit_android::Adapter as AccessAdapter;
 use android_view::{
    AccessibilityNodeInfo, AccessibilityNodeProvider, Bundle, CallbackCtx, Context,
    InputConnection, KeyEvent, MotionEvent, Rect, View, ViewPeer,
-    jni::{JNIEnv, JavaVM, objects::GlobalRef, sys::jint},
+    jni::{
-    ndk::event::{Keycode, MotionAction},
+        JNIEnv, JavaVM,
        objects::{GlobalRef, JValue},
        sys::{jint, jlong},
    },
    ndk::event::{Axis, Keycode, MotionAction},
 };
 // `marker::Sized` explicitly: `crate::prelude::*` below also brings in the
 // `Sized` *widget* (`widget::position::sized::Sized`), and an unqualified
@@ -16,7 +20,7 @@ use std::{
    marker::{PhantomData, Sized},
    rc::Rc,
    sync::Arc,
-    time::Instant,
+    time::{Duration, Instant},
 };
 use super::{
@@ -29,6 +33,10 @@ use super::{
 /// `Option` because a `SurfaceView`'s surface does not outlive backgrounding
 /// the way a winit `Window` does -- `surfaceDestroyed`/`surfaceCreated` can
 /// happen any number of times over the life of one `IrisViewPeer`.
 /// How many frames after each `surface_changed` `render()` logs a full
 /// diagnostic line for -- see the log site's own comment.
 const DIAGNOSTIC_FRAMES: u64 = 10;
 pub struct AndroidUiState {
    pub root: Option<StrongWidget>,
    pub renderer: Option<AndroidRenderer>,
@@ -46,6 +54,10 @@ pub struct AndroidUiState {
    /// inside the platform-agnostic sensor dispatch with no `CallbackCtx`
    /// in reach.
    pub pending_show_keyboard: bool,
    /// A URL a tapped link asked the platform to open, for the same
    /// reason `pending_show_keyboard` is a flag rather than a call --
    /// see `android/platform.rs`.
    pub pending_open_url: Option<String>,
    /// Window insets, filled in from outside the normal `ViewPeer` callback
    /// path -- see `android/insets.rs` for why they need a registry of
    /// their own.
@@ -62,10 +74,41 @@ pub struct AndroidUiState {
    /// because `dumpsys gfxinfo` cannot see a `SurfaceView`'s own
    /// GPU-drawn frames at all. See `iris_core::FrameReport`'s own doc.
    pub frame_report: FrameReport,
    /// `DisplayMetrics.density` (`new_peer`'s doc comment): physical pixels
    /// per dp on this device, read once at view construction and carried
    /// on `UiRenderState::density` (`render.set_density`, `new_peer`) from
    /// then on -- every `Len::dp` in the widget tree resolves against it at
    /// layout time (`Len::dp`'s field doc, IRIS_TODO.md's
    /// "density-independent length unit" item, 2026-09-06).
    ///
    /// **Everything else in this module is physical pixels, matching the
    /// real wgpu surface/swapchain resolution** -- window size, touch
    /// coordinates, insets. That is a correction from an earlier version
    /// of this comment, which had `window_size`/`surface_changed`'s
    /// `UiRenderState::resize` call divide by `content_scale` into a
    /// *logical* coordinate space instead, as a global stopgap for
    /// RUST.md's P0 box's phone report ("text is far too small"). That
    /// stopgap fixed the size but not the *sharpness*: dividing to logical
    /// units meant a `16.0`-sized glyph rasterised at 16 physical px and
    /// then implicitly upscaled ~3x by the NDC mapping onto the real
    /// physical framebuffer -- the exact "blurry ... glyphs drawn at
    /// logical size and stretched by the scale" Iris reported next.
    /// Resolving `dp` at layout time replaces it: a widget author writes
    /// `dp(16)` for a size that should look the same physical size on any
    /// density, and everything downstream (layout, hit-testing, the window
    /// uniform, and the font size handed to the text shaper) works in the
    /// display's own physical pixels throughout, so nothing is
    /// rasterised at one resolution and displayed at another.
    pub content_scale: f32,
    /// The last insets `render()` saw -- compared each frame so
    /// `AndroidAppState::on_insets_changed` fires only when they actually
    /// change (once at startup for the status bar, again if the device
    /// rotates), not every frame.
    last_insets: Insets,
 }
 impl AndroidUiState {
-    fn new(shared: Rc<RefCell<Shared>>) -> Self {
+    fn new(shared: Rc<RefCell<Shared>>, content_scale: f32) -> Self {
        Self {
            root: None,
            renderer: None,
@@ -74,16 +117,41 @@ impl AndroidUiState {
            last_click: Instant::now(),
            compose_len: 0,
            pending_show_keyboard: false,
            pending_open_url: None,
            shared,
            access_adapter: Default::default(),
            access: AccessTree::new(),
            frame_report: FrameReport::new(),
            content_scale,
            last_insets: Insets::default(),
        }
    }
    pub fn insets(&self) -> Insets {
        self.shared.borrow().insets
    }
    /// The insets state as one line for a diagnostics pane, including how
    /// many times the platform has delivered any -- see
    /// `insets::Shared::updates` for why the count is the load-bearing
    /// part. `dispatches=0` says the listener has never run and the
    /// numbers beside it are defaults rather than measurements, which is
    /// the distinction a screenshot otherwise cannot make (UI_RULES.md,
    /// "design the unknown state first").
    pub fn insets_report(&self) -> String {
        let shared = self.shared.borrow();
        let i = shared.insets;
        if shared.updates == 0 {
            return "insets: dispatches=0 -- the platform has never called \
                    onApplyWindowInsets, so nothing below was measured"
                .to_string();
        }
        format!(
            "insets: dispatches={} left={} top={} right={} bottom={} ime_bottom={} \
             ime_visible={}",
            shared.updates, i.left, i.top, i.right, i.bottom, i.ime_bottom, i.ime_visible,
        )
    }
 }
 impl HasRoot for AndroidUiState {
@@ -120,6 +188,54 @@ pub trait AndroidAppState: HasAndroidUiState {
    /// storing them has no effect on that mechanism.
    #[allow(unused_variables)]
    fn platform_ready(&mut self, rsc: &mut AndroidRsc<Self>, vm: JavaVM, view: GlobalRef) {}
    /// Called from `render()` whenever `AndroidUiState::insets()` differs
    /// from what it was last frame -- once at startup for the status bar
    /// (RUST.md's P0 box: "the status-bar inset is not applied" reported
    /// the two top buttons sitting under it, because nothing read `.top`
    /// at all), and again on a rotation or the keyboard opening/closing.
    /// `insets` is in the same physical-pixel units everything else in the
    /// tree now uses (`AndroidUiState::content_scale`'s field comment), so
    /// a widget can add it to a layout size directly -- `dp(...) +
    /// abs(insets.top)` if the widget wants a density-independent size
    /// plus the system bar's own (already-physical) height. The default
    /// does nothing -- most screens have no chrome that sits under a
    /// system bar.
    #[allow(unused_variables)]
    fn on_insets_changed(&mut self, rsc: &mut AndroidRsc<Self>, insets: WindowInsets) {}
 }
 /// `insets::Insets` as `f32`, for the widget-facing callback above -- a
 /// distinct type from `insets::Insets` so a caller of `on_insets_changed`
 /// is not coupled to that module's own (`i32`, JNI-shaped) representation.
 /// Both are physical pixels; this used to divide by `content_scale` into a
 /// separate *logical* unit (hence the old name, `LogicalInsets`), back when
 /// the rest of layout was logical too -- see `AndroidUiState::content_scale`'s
 /// field comment for why that stopgap is gone.
 #[derive(Clone, Copy, Default, Debug, PartialEq)]
 pub struct WindowInsets {
    pub left: f32,
    pub top: f32,
    pub right: f32,
    pub bottom: f32,
    /// How much of the window the keyboard covers, in physical pixels --
    /// what a layout pads by. See `insets::Insets::ime_visible` for why
    /// "is the keyboard up" is a separate field rather than this one
    /// compared against zero.
    pub ime_bottom: f32,
    pub ime_visible: bool,
 }
 impl WindowInsets {
    fn from_physical(insets: Insets) -> Self {
        Self {
            left: insets.left as f32,
            top: insets.top as f32,
            right: insets.right as f32,
            bottom: insets.bottom as f32,
            ime_bottom: insets.ime_bottom as f32,
            ime_visible: insets.ime_visible,
        }
    }
 }
 /// The android-view analogue of `default::DefaultRsc` -- identical in
@@ -196,6 +312,12 @@ pub struct IrisViewPeer<State: AndroidAppState> {
    pub(super) render: UiRenderState,
    pub(super) state: State,
    task_recv: TaskMsgReceiver<AndroidRsc<State>>,
    /// `(an Instant, the input-event nanosecond stamp it was taken at)`,
    /// captured from the first `MotionEvent` this view receives and never
    /// changed after -- how `on_touch_event` dates every touch sample. Its
    /// path out is the peer's own drop: it holds nothing but two numbers
    /// and is meaningless to any other view.
    input_clock: Option<(Instant, jlong)>,
 }
 impl<State: 'static, I: RscIdx<AndroidRsc<State>>> std::ops::Index<I> for AndroidRsc<State> {
@@ -219,12 +341,13 @@ impl<State: AndroidAppState> IrisViewPeer<State> {
        }
    }
-    /// Common tail for every callback that might have changed the cursor,
+    /// One pointer sample through the sensors, plus the platform calls a
-    /// the text focus, or the widget tree: run the sensors that touch
+    /// handler can only ask for by raising a flag. Split out of
-    /// input feeds, then ask for a frame if the result needs drawing.
+    /// [`Self::after_input`] because a batched `MotionEvent` carries
-    /// Mirrors `default::DefaultApp::window_event`'s tail, split across
+    /// several samples that all belong to the same *frame*
-    /// android-view's several entry points instead of winit's one.
+    /// (`on_touch_event`): each one is a real input frame the widgets must
-    pub(super) fn after_input(&mut self, ctx: &mut CallbackCtx) {
+    /// see, but only the last one ends the frame and asks for a redraw.
    fn run_input_frame(&mut self, ctx: &mut CallbackCtx) {
        let window_size = self.window_size();
        let ui_state = self.state.android_state_mut();
        let cursor = ui_state.cursor.clone();
@@ -241,6 +364,25 @@ impl<State: AndroidAppState> IrisViewPeer<State> {
        if std::mem::take(&mut ui_state.pending_show_keyboard) {
            show_soft_input(&mut ctx.env, &ctx.view);
        }
        if let Some(url) = ui_state.pending_open_url.take() {
            super::platform::open_url(&mut ctx.env, &ctx.view, &url);
        }
    }
    /// Common tail for every callback that might have changed the cursor,
    /// the text focus, or the widget tree: run the sensors that touch
    /// input feeds, then ask for a frame if the result needs drawing.
    /// Mirrors `default::DefaultApp::window_event`'s tail, split across
    /// android-view's several entry points instead of winit's one.
    pub(super) fn after_input(&mut self, ctx: &mut CallbackCtx) {
        self.run_input_frame(ctx);
        // RUST.md's P0 box, "doesn't enter it until I hit space, and also
        // doesn't move cursor forward": Gboard needs `updateSelection`
        // after every edit to keep its own model of the field in sync, or
        // it holds keystrokes back rather than trusting a screen it
        // believes is stale. See `update_ime_selection`'s own doc.
        self.update_ime_selection(ctx);
        let ui_state = self.state.android_state_mut();
        ui_state.cursor.end_frame();
@@ -266,10 +408,40 @@ impl<State: AndroidAppState> IrisViewPeer<State> {
    /// these in until that is root-caused; removing them loses the exact
    /// evidence a `logcat` capture needs to reproduce the state.
    fn render(&mut self, ctx: &mut CallbackCtx) {
-        let ui_state = self.state.android_state();
+        if self.state.android_state().renderer.is_none() {
        if ui_state.renderer.is_none() {
            return;
        }
        // See `AndroidAppState::on_insets_changed`'s doc comment: fires
        // exactly when insets actually differ from last frame, not every
        // frame -- most frames this is one `Insets` equality check against
        // a `Copy` struct. Done before `ui_state` is bound below, since
        // `on_insets_changed` needs `&mut self.state`/`&mut self.rsc` both.
        let ui_state = self.state.android_state();
        let current_insets = ui_state.insets();
        if current_insets != ui_state.last_insets {
            let physical = WindowInsets::from_physical(current_insets);
            // One line per real insets change. Iris's phone is the only
            // place several of these bugs reproduce and `adb logcat` is
            // the only instrument there (this-machine-android: system
            // tracing is broken on that device), so the numbers a layout
            // is actually fed have to reach the log -- "the composer
            // floats at launch" is unanswerable from a screenshot alone.
            log::info!(
                "iris insets: left={} top={} right={} bottom={} ime_bottom={} \
                 ime_visible={} window={:?}",
                physical.left,
                physical.top,
                physical.right,
                physical.bottom,
                physical.ime_bottom,
                physical.ime_visible,
                self.window_size(),
            );
            self.state.android_state_mut().last_insets = current_insets;
            self.state.on_insets_changed(&mut self.rsc, physical);
        }
        let ui_state = self.state.android_state();
        log::debug!(
            "render(): root={:?} widgets={} active={} root_px={:?} out_size={:?}",
            ui_state.root.is_some(),
@@ -288,18 +460,50 @@ impl<State: AndroidAppState> IrisViewPeer<State> {
        // both count. See `iris_core::FrameReport`'s own doc for exactly
        // what this does and does not measure.
        let frame_start = Instant::now();
        // Anything moving on its own -- today a `List` coasting through a
        // fling -- is advanced here, before the draw, and asks for the
        // next frame at the end of this one. See
        // `UiData::tick_animations`; `default/mod.rs`'s
        // `RedrawRequested` arm is the same two lines for winit.
        let animating = self.rsc.ui.tick_animations(frame_start);
        let ui_state = self.state.android_state_mut();
        self.render.update(&ui_state.root, &mut self.rsc);
        let ui_state = self.state.android_state_mut();
        let Some(renderer) = &mut ui_state.renderer else {
            return;
        };
-        renderer.update(&mut self.rsc.ui, &mut self.render);
+        let frame_diagnostics = renderer.update(&mut self.rsc.ui, &mut self.render);
        // First `DIAGNOSTIC_FRAMES` frames after each `surface_changed`
        // only -- RUST.md's P0 box, "the first input frame" investigation:
        // the glyph-wipe Iris reported happens on the first tap or scroll
        // after a fresh surface, so a report from that window is what
        // would show whether an atlas grow, a masks/move_offsets resize, or
        // a fresh wgpu error coincided with it. `frame_count()` was just
        // incremented inside `update()`, so `<=` counts frame 1 through
        // `DIAGNOSTIC_FRAMES` inclusive.
        if renderer.frame_count() <= DIAGNOSTIC_FRAMES {
            log::info!(
                "iris frame diagnostics: frame={} masks_resized={} moves_resized={} \
                 atlas_pages_grown_prev={} image_bind_group_creates_prev={} wgpu_errors={}",
                renderer.frame_count(),
                frame_diagnostics.masks_resized,
                frame_diagnostics.moves_resized,
                frame_diagnostics.atlas_pages_grown_prev,
                frame_diagnostics.image_bind_group_creates_prev,
                renderer.wgpu_errors.snapshot().len(),
            );
        }
        let submit_to_present = renderer.draw();
        self.state
            .android_state_mut()
            .frame_report
            .record_split(frame_start.elapsed(), submit_to_present);
        // A frame callback is one-shot, so an animation that wants
        // another frame has to say so every frame -- unlike `after_input`,
        // which only has to ask when input dirtied something.
        if animating {
            ctx.view.post_frame_callback(&mut ctx.env);
        }
        let ui_state = self.state.android_state();
        log::debug!(
            "render(): after update active={} root_px={:?}",
@@ -337,6 +541,31 @@ fn show_soft_input<'local>(env: &mut JNIEnv<'local>, view: &View<'local>) {
    imm.show_soft_input(env, view, 0);
 }
 /// Replaces the activity's content with a plain, selectable, scrollable
 /// text view holding `report` -- the on-screen half of `surface_changed`'s
 /// renderer-failure path (UI_RULES.md: "a failure is reported where it
 /// happened, and says what to do next," here "copy this and send it").
 /// Goes through an ordinary instance method on the Java side
 /// (`IrisView.showRendererError`) rather than a new `native` method: this
 /// call is Rust reaching *into* Java, the opposite direction from every
 /// `native fn` android-view/`IrisView` declare, and an ordinary virtual
 /// call resolves against `ctx.view`'s real runtime class (`IrisView`) the
 /// same way any other JNI method call here does. Silently does nothing on
 /// any JNI failure -- there is no more-fallback screen to fall back to,
 /// and the `log::error!` in `surface_changed` already reached logcat
 /// first.
 fn show_renderer_error<'local>(env: &mut JNIEnv<'local>, view: &View<'local>, report: &str) {
    let Ok(message) = env.new_string(report) else {
        return;
    };
    let _ = env.call_method(
        &view.0,
        "showRendererError",
        "(Ljava/lang/String;)V",
        &[JValue::Object(message.as_ref())],
    );
 }
 impl<State: AndroidAppState> ViewPeer for IrisViewPeer<State> {
    fn on_key_down<'local>(
        &mut self,
@@ -379,9 +608,71 @@ impl<State: AndroidAppState> ViewPeer for IrisViewPeer<State> {
    ) -> bool {
        self.drain_tasks();
        let action = event.action_masked(&mut ctx.env);
        // Device (physical) pixels, same space layout now uses throughout
        // -- see `AndroidUiState::content_scale`'s field comment.
        let x = event.x(&mut ctx.env);
        let y = event.y(&mut ctx.env);
        // The event's own clock, converted through one anchor taken on the
        // first touch this view ever sees. Android reports sample times in
        // the `SystemClock.uptimeMillis()` base, which is the same
        // `CLOCK_MONOTONIC` an `Instant` reads, so a single
        // `(Instant, nanos)` pair converts every later sample exactly.
        // Anchoring **once** rather than per event is what keeps the times
        // ordered: a fresh `Instant::now()` per event, minus each sample's
        // age inside it, can date a later event's first historical sample
        // before the previous event's last one whenever delivery jitters by
        // more than the batch spans -- and `VelocityTracker::add_sample`'s
        // debug assert would rightly fire on that. See `CursorState::time`.
        let event_time = event.event_time_nanos(&mut ctx.env);
        let (anchor_at, anchor_nanos) =
            *self.input_clock.get_or_insert((Instant::now(), event_time));
        let at = |sample_time: jlong| {
            anchor_at + Duration::from_nanos(sample_time.saturating_sub(anchor_nanos).max(0) as u64)
        };
        // **Historical samples first.** A flick on a 120Hz screen is
        // delivered as one or two `MotionEvent`s with the intermediate
        // positions batched inside them, so reading only `x()`/`y()` threw
        // away every sample but the last: the velocity tracker saw one
        // `Pan` for the whole gesture, `VelocityTracker::velocity` answers
        // 0.0 below two samples, and the release therefore flung at zero --
        // Iris's phone, twice ("fling still doesn't work"), while a
        // `ui-trace` swipe, which is many evenly-spaced events, flung fine.
        // Replayed one at a time through the sensors rather than summarised,
        // so the arbiter, the tracker and any other sensor all see the same
        // motion the finger actually made; only the last sample ends the
        // frame (`after_input`).
        if matches!(action, MotionAction::Move) {
            let history = event.history_size(&mut ctx.env);
            // Android documents the historical samples as oldest first and
            // the event's own sample as the newest of the batch; everything
            // downstream (`VelocityTracker`, `DragArbiter`'s long-press
            // clock) assumes it, so say so here rather than at each reader.
            let mut previous = anchor_nanos;
            for pos in 0..history {
                let hx = event.historical_axis(&mut ctx.env, Axis::X, 0, pos);
                let hy = event.historical_axis(&mut ctx.env, Axis::Y, 0, pos);
                let ht = event.historical_event_time_nanos(&mut ctx.env, pos);
                debug_assert!(
                    ht >= previous,
                    "historical sample {pos} of {history} is dated {ht}ns, before the {previous}ns \
                     sample ahead of it -- the input clock is not what this assumes"
                );
                previous = ht;
                let ui_state = self.state.android_state_mut();
                ui_state.cursor.pos = vec2(hx, hy);
                ui_state.cursor.time = at(ht);
                self.run_input_frame(ctx);
            }
            debug_assert!(
                event_time >= previous,
                "the event's own sample is dated {event_time}ns, before its last historical \
                 sample at {previous}ns"
            );
        }
        let ui_state = self.state.android_state_mut();
        ui_state.cursor.time = at(event_time);
        match action {
            MotionAction::Down => {
                ui_state.cursor.pos = vec2(x, y);
@@ -391,6 +682,13 @@ impl<State: AndroidAppState> ViewPeer for IrisViewPeer<State> {
            MotionAction::Move => {
                ui_state.cursor.pos = vec2(x, y);
            }
            // `Cancel` ends the gesture the same way `Up` does, and must:
            // a release that never arrives leaves whichever widget took
            // pointer capture holding it forever, with every later touch
            // delivered to a drag nobody is performing. Confirmed present
            // before this pass rather than assumed -- it was one of the
            // three suspects listed for the phone's missing fling, and it
            // is not the cause.
            MotionAction::Up | MotionAction::Cancel => {
                ui_state.cursor.pos = vec2(x, y);
                ui_state.cursor.buttons.left.update(false);
@@ -431,7 +729,6 @@ impl<State: AndroidAppState> ViewPeer for IrisViewPeer<State> {
        height: i32,
    ) {
        self.drain_tasks();
        let window = holder.surface(&mut ctx.env).to_native_window(&mut ctx.env);
        // The layout engine's own notion of the canvas size is separate
        // from the wgpu surface's -- winit's backend sets it from
        // `WindowEvent::Resized`, and there is no equivalent automatic
@@ -440,13 +737,130 @@ impl<State: AndroidAppState> ViewPeer for IrisViewPeer<State> {
        // nothing but the clear colour: the widget tree laid out against
        // whatever size `UiRenderState::new` starts at instead of the
        // surface's real one.
-        self.render.resize((width as u32, height as u32));
+        //
-        // Drop the old renderer (and the surface it owns) before building
+        // **Physical pixels, matching `AndroidRenderer`'s own
-        // one from the new window -- see `AndroidRenderer`'s doc comment.
+        // `size()`/`resize()`/`new()`** -- `AndroidUiState::content_scale`'s
-        let ui_state = self.state.android_state_mut();
+        // field comment. This call sets `UiRenderState::output_size`, which
-        ui_state.renderer = None;
+        // every `rel`/`rest` length resolves against and every `abs`
-        ui_state.renderer = Some(AndroidRenderer::new(window, width as u32, height as u32));
+        // pixel-region compares to directly; a `dp(56)` height now folds
-        self.render(ctx);
+        // in the density at `Len::apply_rest` time instead of this call
        // dividing the whole window into a separate logical space, which
        // is what used to make every `abs`-unit size (a fixed `.height(56)`
        // in particular) mean something different from a `rest`-based one.
        self.render.resize((width as f32, height as f32));
        // **Reuse the existing renderer (device, atlas, buffers, bind
        // groups) when one is already live -- only reconfigure the
        // surface.** `surfaceChanged` fires on *every* size or format
        // change, not only on a genuinely new `Surface`/window: showing
        // the IME under `adjustResize` resizes the same `SurfaceView` and
        // is reported through this exact callback. Rebuilding the whole
        // `AndroidRenderer` here used to mean a fresh `UiRenderNode::new`
        // -- a brand-new, empty glyph atlas and fresh GPU buffers -- while
        // `iris_core`'s CPU-side glyph cache (`primitive/text.rs`) kept the
        // atlas coordinates it had already handed out against the *old*
        // atlas. Every glyph then drew from a UV rectangle that pointed
        // into a texture that had just been recreated empty, so text
        // vanished on the first keyboard open while rects (which never go
        // through the atlas) kept drawing -- exactly the "rectangles stay,
        // glyphs disappear" Iris reported. Confirmed by reading this path
        // end to end (no fresh-atlas rebuild anywhere in `resize()` below,
        // only in `AndroidRenderer::new`) before changing anything, per
        // AGENTS.md's "verify before finishing".
        //
        // `AndroidRenderer::resize` only reconfigures the wgpu surface and
        // rewrites the window uniform -- device, atlas, buffers and bind
        // groups are untouched, so the glyph cache's coordinates stay
        // valid. A genuinely new surface (after `surface_destroyed`, e.g.
        // backgrounding) still goes through `AndroidRenderer::new` below,
        // since `renderer` is `None` in that case.
        let already_live = self.state.android_state().renderer.is_some();
        log::info!(
            "iris surface: surface_changed {width}x{height} already_live={already_live} \
             glyphs_cached={} atlas_pages={}",
            self.rsc.ui.text.atlas.glyph_count(),
            self.rsc.ui.text.atlas.page_count(),
        );
        if already_live {
            let ui_state = self.state.android_state_mut();
            ui_state
                .renderer
                .as_mut()
                .expect("checked Some above")
                .resize(width as u32, height as u32);
            self.render(ctx);
            return;
        }
        let window = holder.surface(&mut ctx.env).to_native_window(&mut ctx.env);
        // `AndroidRenderer::new` used to panic here through wgpu's own
        // default uncaptured-error handler on a bind-group-layout
        // validation failure -- exactly what aborted the P0 bench APK on
        // Iris's phone with the message truncated to "wgpu error:
        // Validation Error" and nothing else recoverable from the crash
        // report (RUST.md's P0 box, "iris bench crash on the phone,
        // 2026-09-06"). It now returns the full diagnostic instead; this is
        // the one place in the app that can turn it into something a
        // person can read, since `ctx.view`/`ctx.env` (needed to reach the
        // Java side) are only in scope inside a `ViewPeer` callback.
        //
        // `content_scale` reaches `AndroidRenderer` only for the
        // Diagnostics page's report text now -- window size and the
        // shader's window uniform are physical pixels throughout (see the
        // `resize` call above), not divided by it.
        let content_scale = self.state.android_state().content_scale;
        match AndroidRenderer::new(window, width as u32, height as u32, content_scale) {
            Ok(renderer) => {
                // A genuinely new renderer means a genuinely new GPU device
                // and a fresh, empty glyph atlas -- the CPU-side glyph
                // cache (`TextData::atlas`) and the texture bookkeeping it
                // is built on (`UiData::textures`) both outlive `renderer`
                // itself (they live on `self.rsc`, not on `AndroidRenderer`),
                // so without this they would keep pointing at the *old*
                // device's now-gone textures -- the app-switch counterpart
                // to the keyboard-resize glyph wipe this same function's
                // `already_live` branch above already fixed by reusing the
                // renderer instead of rebuilding it. One mechanism either
                // way: this call only runs on the branch that actually
                // builds a new renderer, exactly where invalidation is
                // needed, never on the reuse branch, where it would throw
                // away perfectly valid GPU state for nothing.
                log::info!(
                    "iris surface: new renderer built ({:?}), clearing glyph atlas: \
                     glyphs={} pages={}",
                    renderer.adapter_backend,
                    self.rsc.ui.text.atlas.glyph_count(),
                    self.rsc.ui.text.atlas.page_count(),
                );
                self.rsc.ui.text.atlas.clear();
                self.rsc.ui.textures.reset();
                self.state.android_state_mut().renderer = Some(renderer);
                self.render(ctx);
            }
            Err(report) => {
                // One line for logcat (UI_RULES.md: "the full text for
                // whoever can read the log" lives here), the multi-line
                // original on screen -- `show_renderer_error` below.
                log::error!("iris renderer init failed: {}", report.replace('\n', " | "));
                // Deferred, not called directly: `Activity::setContentView`
                // tears the old view hierarchy down synchronously, which
                // fires `IrisView`'s own `onFocusChanged` before
                // `setContentView` returns -- straight back into this same
                // `IrisViewPeer` through `on_focus_changed` while
                // `with_peer` (android-view's dispatch, `view.rs` upstream)
                // still holds this peer's `RefCell` borrow for the
                // `surface_changed` call in progress. Found by inducing a
                // validation error and hitting `RefCell already borrowed`
                // at exactly that reentrant call (RUST.md's P0 box).
                // `push_dynamic_deferred_callback` runs after `with_peer`
                // drops the borrow, which is what every other callback in
                // this file that reaches into Java already relies on
                // (`raise_if_enabled`, above).
                ctx.push_dynamic_deferred_callback(move |env, view| {
                    show_renderer_error(env, view, &report);
                });
            }
        }
    }
    fn surface_destroyed<'local>(
@@ -454,6 +868,12 @@ impl<State: AndroidAppState> ViewPeer for IrisViewPeer<State> {
        _ctx: &mut CallbackCtx<'local>,
        _holder: &android_view::SurfaceHolder<'local>,
    ) {
        log::info!(
            "iris surface: surface_destroyed, tearing the renderer down \
             (glyphs_cached={} atlas_pages={})",
            self.rsc.ui.text.atlas.glyph_count(),
            self.rsc.ui.text.atlas.page_count(),
        );
        self.state.android_state_mut().renderer = None;
    }
@@ -557,10 +977,19 @@ impl<State: AndroidAppState> AccessibilityNodeProvider for IrisViewPeer<State> {
 /// `register_view_class`, which wants a plain function pointer) -- see
 /// `iris/android-app/src/lib.rs`.
 pub fn new_peer<'local, State: AndroidAppState>(
-    env: JNIEnv<'local>,
+    mut env: JNIEnv<'local>,
    view: View<'local>,
-    _context: Context<'local>,
+    context: Context<'local>,
 ) -> android_view::jni::sys::jlong {
    // `DisplayMetrics.density` -- physical pixels per dp on this device.
    // Read once here, at the one point in this file already handed a
    // `Context`, and carried on `AndroidUiState` from then on (see
    // `content_scale`'s field comment for what depends on it).
    let content_scale = context
        .resources(&mut env)
        .display_metrics(&mut env)
        .density(&mut env);
    log::info!("iris: new_peer content_scale={content_scale}");
    let vm = env.get_java_vm().unwrap();
    let global_view = env.new_global_ref(&view.0).unwrap();
    let redraw: Arc<dyn RequestRedraw> = Arc::new(AndroidRedrawHandle::new(vm, global_view));
@@ -572,17 +1001,25 @@ pub fn new_peer<'local, State: AndroidAppState>(
        state: Default::default(),
        _state: PhantomData,
    };
    // See `TextData::density`'s field doc for why this is set alongside
    // `render.set_density` below rather than read from there.
    rsc.ui.text.density = content_scale;
    let shared = Rc::new(RefCell::new(Shared::default()));
-    let ui_state = AndroidUiState::new(shared.clone());
+    let ui_state = AndroidUiState::new(shared.clone(), content_scale);
    let mut state = State::new(ui_state, &mut rsc);
    let platform_vm = env.get_java_vm().unwrap();
    let platform_view = env.new_global_ref(&view.0).unwrap();
    state.platform_ready(&mut rsc, platform_vm, platform_view);
    let mut render = UiRenderState::new();
    // Every `Len::dp` in the tree resolves against this from now on -- see
    // `UiRenderState::density`'s field doc and `Len::dp`'s.
    render.set_density(content_scale);
    let peer = IrisViewPeer {
        rsc,
-        render: UiRenderState::new(),
+        render,
        state,
        task_recv,
        input_clock: None,
    };
    let id = android_view::register_view_peer(peer);
    super::insets::register(id, shared);
@@ -18,10 +18,22 @@ pub trait FocusHost {
    /// side effect the way a real double-click timer does.
    fn recent_click(&mut self) -> bool;
    fn set_focus(&mut self, id: Option<WeakWidget<TextEdit>>);
-    /// Called after a `TextEdit` becomes the focus target, with the region
+    /// Called on every tap that should put the IME on `id`: the tap that
-    /// it was hit in (`None` when the widget could not be located, which
+    /// *makes* a `TextEdit` the focus target, and any later tap on one that
-    /// happens for one it was just deselected from).
+    /// already is. `region` is where it was hit (`None` when the widget
    /// could not be located, which happens for one it was just deselected
    /// from). Implementations must be idempotent -- both backends' calls
    /// (`showSoftInput`, `set_ime_cursor_area`) already are, which is what
    /// lets the repeat tap be handled by the same call rather than by a
    /// second "re-show" entry point beside it.
    fn focus_gained(&mut self, region: Option<PixelRegion>);
    /// Whether `id` is the current focus target -- what [`select`] uses to
    /// tell a fresh press (which must wait to see whether it becomes a tap
    /// or a drag before focusing/showing the IME, Iris 2026-09-06: "if I
    /// swipe over the input bar it brings up the keyboard") from a drag
    /// continuing inside a field that was already focused (an ordinary
    /// drag-to-select, unaffected).
    fn is_focused(&self, id: WeakWidget<TextEdit>) -> bool;
 }
 /// Helper shared by every `FocusHost` impl, so the double-click window is
@@ -33,6 +45,17 @@ pub fn recent_click(last_click: &mut Instant) -> bool {
    recent
 }
 /// `PressStart`/`Pressing`/`PressEnd`, all for the left button -- what
 /// [`Selector`]/[`Selectable`] register instead of [`CursorSense::
 /// click_or_drag`], so their shared handler (`on_press`, below) sees every
 /// frame of a gesture and can tell a completed tap from a drag itself,
 /// rather than reacting to `PressStart` alone the way `click_or_drag`'s
 /// consumer used to (Iris, 2026-09-06: "if I swipe over the input bar it
 /// brings up the keyboard").
 fn press_track() -> CursorSenses {
    CursorSense::click() | CursorSense::Pressing(CursorButton::Left) | CursorSense::unclick()
 }
 pub struct Selector;
 impl<Rsc: HasEvents, W: Widget + 'static> WidgetAttr<Rsc, W> for Selector
@@ -42,7 +65,7 @@ where
    type Input = WeakWidget<TextEdit>;
    fn run(rsc: &mut Rsc, container: WeakWidget<W>, id: Self::Input) {
-        rsc.register_event(container, CursorSense::click_or_drag(), move |ctx, rsc| {
+        rsc.register_event(container, press_track(), move |ctx, rsc| {
            let region = ctx.data.render.window_region(&id, &*rsc).unwrap();
            let id_pos = region.top_left;
            let container_pos = ctx
@@ -53,14 +76,14 @@ where
                .top_left;
            let pos = ctx.data.pos + container_pos - id_pos;
            let size = region.size();
-            select(
+            on_press(
                rsc,
                ctx.data.render,
                ctx.state,
                id,
                pos,
                size,
-                ctx.data.sense.is_dragging(),
+                ctx.data.sense,
            );
        });
    }
@@ -75,31 +98,122 @@ where
    type Input = ();
    fn run(rsc: &mut Rsc, id: WeakWidget<TextEdit>, _: Self::Input) {
-        rsc.register_event(id, CursorSense::click_or_drag(), move |ctx, rsc| {
+        rsc.register_event(id, press_track(), move |ctx, rsc| {
-            select(
+            on_press(
                rsc,
                ctx.data.render,
                ctx.state,
                id,
                ctx.data.pos,
                ctx.data.size,
-                ctx.data.sense.is_dragging(),
+                ctx.data.sense,
            );
        });
    }
 }
-fn select(
+/// One press-track frame (`PressStart`, `Pressing` or `PressEnd`) over a
 /// selectable field. A field that is *already* focused behaves exactly as
 /// `click_or_drag` always did -- every frame updates the selection, which
 /// is what lets a finger already inside a focused field drag out a
 /// selection. A field that is **not** focused withholds `select`'s
 /// focus-granting side effects (and so the platform-specific `focus_gained`
 /// that shows the keyboard) until the press resolves as a tap: `PressEnd`
 /// with no frame in between having moved past [`DRAG_SLOP`] from where the
 /// press began. A drag recognised before release simply cancels the
 /// pending tap and does nothing further here -- it is not consumed, so
 /// whatever is behind the field (a list to pan) still sees every frame of
 /// it, the same as a drag that never touched a selectable field at all.
 fn on_press(
    rsc: &mut impl UiRsc,
    render: &UiRenderState,
    state: &mut impl FocusHost,
    id: WeakWidget<TextEdit>,
    pos: Vec2,
    size: Vec2,
-    dragging: bool,
+    sense: CursorSense,
 ) {
-    let recent = state.recent_click();
+    if state.is_focused(id) {
-    id.edit(rsc).select(pos, size, dragging, recent);
+        // Already focused, so there is no keyboard to withhold -- but a
-    state.set_focus(Some(id));
+        // vertical drag still is not a selection. Android's own `EditText`
-    state.focus_gained(render.window_region(&id, &*rsc));
+        // scrolls its overflowed text on a vertical drag and starts a
        // selection only from a long press; a scroll area wrapping this
        // field (`Scroll::drag`) is what actually pans, and it needs the
        // first frames of the gesture not to have selected anything behind
        // it before it crosses `DRAG_SLOP` and takes pointer capture.
        // `press_origin` carries the same meaning here as in the unfocused
        // branch below -- "this gesture is still eligible", cleared the
        // moment it becomes a drag -- so there is one flag, not two.
        match sense {
            CursorSense::PressStart(_) => {
                let recent = state.recent_click();
                id.edit(rsc).text.press_origin = Some(pos);
                id.edit(rsc).select(pos, size, false, recent);
            }
            CursorSense::Pressing(_) | CursorSense::PressEnd(_) => {
                let mut ctx = id.edit(rsc);
                let Some(origin) = ctx.text.press_origin else {
                    return;
                };
                let (dx, dy) = (pos.x - origin.x, pos.y - origin.y);
                if dy.abs() > DRAG_SLOP && dy.abs() >= dx.abs() {
                    ctx.text.press_origin = None;
                    return;
                }
                let ended = matches!(sense, CursorSense::PressEnd(_));
                if ended {
                    ctx.text.press_origin = None;
                }
                ctx.select(pos, size, true, false);
                // A tap on a field that is *already* focused asks for the
                // keyboard again (Iris's phone, 2026-09-06: "I can't reopen
                // keyboard by tapping on message box after it already
                // happened once"). Dismissing the IME -- back gesture, or
                // its own hide button -- takes the keyboard away but leaves
                // the field focused, so without this the one branch that
                // requests it (the unfocused one below) never runs again
                // and the field is permanently unable to summon it.
                // Android's own `EditText` does exactly this: every tap on
                // a focused field calls `showSoftInput`, which is a no-op
                // when the keyboard is already up.
                //
                // Gated on the same tap-vs-drag test the unfocused branch
                // uses, not on `PressEnd` alone, so a drag-to-select that
                // happens to finish inside the field does not summon a
                // keyboard the reader was not asking for.
                if ended && dx.abs() <= DRAG_SLOP && dy.abs() <= DRAG_SLOP {
                    state.focus_gained(render.window_region(&id, &*rsc));
                }
            }
            _ => {}
        }
        return;
    }
    match sense {
        CursorSense::PressStart(_) => {
            id.edit(rsc).text.press_origin = Some(pos);
        }
        CursorSense::Pressing(_) => {
            let ctx = id.edit(rsc);
            if let Some(origin) = ctx.text.press_origin
                && ((pos.x - origin.x).abs() > DRAG_SLOP || (pos.y - origin.y).abs() > DRAG_SLOP)
            {
                // Past the slop before release: this is a drag, not a tap
                // -- give up the pending focus rather than granting it once
                // the finger lifts wherever it happens to be by then.
                ctx.text.press_origin = None;
            }
        }
        CursorSense::PressEnd(_) => {
            let was_tap = id.edit(rsc).text.press_origin.take().is_some();
            if was_tap {
                let recent = state.recent_click();
                id.edit(rsc).select(pos, size, false, recent);
                state.set_focus(Some(id));
                state.focus_gained(render.window_region(&id, &*rsc));
            }
        }
        _ => {}
    }
 }
@@ -1,5 +1,5 @@
 use crate::prelude::*;
-use winit::dpi::{LogicalPosition, LogicalSize};
+use winit::dpi::{PhysicalPosition, PhysicalSize};
 impl<T: HasDefaultUiState> FocusHost for T {
    fn recent_click(&mut self) -> bool {
@@ -10,13 +10,19 @@ impl<T: HasDefaultUiState> FocusHost for T {
        self.default_state_mut().focus = id;
    }
    fn is_focused(&self, id: WeakWidget<TextEdit>) -> bool {
        self.default_state().focus == Some(id)
    }
    fn focus_gained(&mut self, region: Option<PixelRegion>) {
        let state = self.default_state_mut();
        let Some(region) = region else { return };
        state.window.set_ime_allowed(true);
        // Physical, like everything else this backend hands winit --
        // `default::content_scale`.
        state.window.set_ime_cursor_area(
-            LogicalPosition::<f32>::from(region.top_left.tuple()),
+            PhysicalPosition::<f32>::from(region.top_left.tuple()),
-            LogicalSize::<f32>::from(region.size().tuple()),
+            PhysicalSize::<f32>::from(region.size().tuple()),
        );
    }
 }
@@ -1,4 +1,10 @@
 // `CursorState::time` is the sample's own time on every backend. winit
 // carries no timestamp on a pointer event, so the moment it is handed to
 // us is the closest measurement available here -- which is also what the
 // drag code used to do for itself with `Instant::now()`, before Android's
 // batched samples made the difference matter (see `sense::CursorState`).
 use crate::prelude::*;
 use std::time::Instant;
 use winit::{
    event::{MouseButton, MouseScrollDelta, WindowEvent},
    keyboard::{Key, NamedKey},
@@ -11,13 +17,19 @@ pub struct Input {
 }
 impl Input {
    /// winit's pointer coordinates are physical pixels, which is the
    /// space the whole tree is laid out and hit-tested in -- see
    /// `default::content_scale`. Nothing is converted here; `dp(...)`
    /// resolves against the density at layout time instead.
    pub fn event(&mut self, event: &WindowEvent) -> bool {
        match event {
            WindowEvent::CursorMoved { position, .. } => {
                self.cursor.pos = Vec2::new(position.x as f32, position.y as f32);
                self.cursor.exists = true;
                self.cursor.time = Instant::now();
            }
            WindowEvent::MouseInput { state, button, .. } => {
                self.cursor.time = Instant::now();
                let buttons = &mut self.cursor.buttons;
                let pressed = state.is_pressed();
                match button {
@@ -37,6 +49,7 @@ impl Input {
                    delta.y = 0.0;
                }
                self.cursor.scroll_delta = delta;
                self.cursor.time = Instant::now();
            }
            WindowEvent::CursorLeft { .. } => {
                self.cursor.exists = false;
@@ -67,9 +80,12 @@ impl Input {
 }
 impl DefaultUiState {
    /// Physical pixels, matching `WindowEvent::Resized` (what
    /// `UiRenderState::resize` is given) and the swapchain -- see
    /// `default::content_scale`.
    pub fn window_size(&self) -> Vec2 {
        let size = self.renderer.window().inner_size();
-        (size.width, size.height).into()
+        Vec2::new(size.width as f32, size.height as f32)
    }
    pub fn cursor_state(&self) -> &CursorState {
@@ -15,6 +15,7 @@ mod access;
 mod app;
 mod attr;
 mod input;
 mod platform;
 mod render;
 pub use access::*;
@@ -24,6 +25,38 @@ pub use render::*;
 pub type Proxy<Event> = EventLoopProxy<Event>;
 /// The desktop's `content_scale`: physical pixels per dp, the same
 /// quantity Android reads from `DisplayMetrics.density` and feeds to
 /// `UiRenderState::set_density` (`android::view::AndroidUiState::
 /// content_scale`'s field comment). Everything in this backend is
 /// physical pixels -- the window size, the pointer, the widget tree --
 /// and `dp(...)` is what resolves against this at layout time, exactly
 /// as on the phone. That is a correction from an earlier version that
 /// divided winit's coordinates into a separate "logical" space instead:
 /// it left `UiRenderState::resize` (physical, from `WindowEvent::
 /// Resized`) and the window uniform (logical) disagreeing on any
 /// display whose scale factor is not 1.0, and it rasterised glyphs at
 /// one resolution to display them at another -- the blur the phone's own
 /// stopgap produced before `dp` existed.
 ///
 /// **`IRIS_SCALE` overrides it**, which is how a phone-shaped desktop
 /// window runs the phone's density (`run-headless.sh --phone`,
 /// docs/RUST.md's layer 2). An unparsable value is a typo in a command
 /// somebody just typed, so it says so and uses the window's own answer
 /// rather than silently laying out at the wrong density.
 pub fn content_scale(window: &Window) -> f32 {
    match std::env::var("IRIS_SCALE") {
        Err(_) => window.scale_factor() as f32,
        Ok(text) => match text.trim().parse::<f32>() {
            Ok(scale) if scale > 0.0 => scale,
            _ => {
                log::warn!("IRIS_SCALE={text:?} is not a positive number; using the window's own");
                window.scale_factor() as f32
            }
        },
    }
 }
 pub struct DefaultUiState {
    pub root: Option<StrongWidget>,
    pub renderer: UiRenderer,
@@ -213,8 +246,16 @@ impl<State: DefaultAppState> AppState for DefaultApp<State> {
        window.set_visible(true);
        let default_state = DefaultUiState::new(window, access_adapter);
        let (mut rsc, task_recv) = DefaultRsc::init(default_state.window.clone());
        // Both copies of the density, set before the first widget is
        // built so text shapes at the right size on the opening frame --
        // the same pair `android::view::new_peer` sets from
        // `content_scale`. See `iris_core::TextData::density` for why the
        // shaper keeps its own.
        let scale = content_scale(default_state.window.as_ref());
        rsc.ui.text.density = scale;
        let state = State::new(default_state, &mut rsc, proxy);
-        let render = UiRenderState::new();
+        let mut render = UiRenderState::new();
        render.set_density(scale);
        Self {
            rsc,
            state,
@@ -265,9 +306,21 @@ impl<State: DefaultAppState> AppState for DefaultApp<State> {
        match &event {
            WindowEvent::CloseRequested => event_loop.exit(),
            WindowEvent::RedrawRequested => {
                // Before the draw, so this frame shows this instant's
                // position (`UiData::tick_animations`' own doc), and the
                // window is asked for another frame while anything is
                // still moving -- the winit half of what
                // `IrisViewPeer::render`'s `post_frame_callback` does on
                // Android. Nothing else in iris moves without an input
                // event.
                let animating = rsc.ui_mut().tick_animations(std::time::Instant::now());
                let ui_state = state.default_state_mut();
                render.update(&ui_state.root, rsc);
                ui_state.renderer.update(&mut rsc.ui, render);
                ui_state.renderer.draw();
                if animating {
                    ui_state.window.request_redraw();
                }
                // I4 (RUST.md): only produces a `TreeUpdate` when the named
                // set actually changed this frame -- see `AccessTree`'s doc
                // comment. `render` reflects the draw that just happened,
@@ -0,0 +1,33 @@
 use crate::platform::OpenUrl;
 use crate::prelude::HasDefaultUiState;
 /// The desktop's URL opener: the platform's own "open this with whatever
 /// is registered for it" command, detached so a browser starting slowly
 /// cannot stall the event loop.
 ///
 /// A command rather than a crate: `xdg-open`/`open`/`start` is what every
 /// such crate shells out to anyway, and this is one call site.
 impl<T: HasDefaultUiState> OpenUrl for T {
    fn open_url(&mut self, url: &str) {
        let (program, first): (&str, &[&str]) = if cfg!(target_os = "macos") {
            ("open", &[])
        } else if cfg!(target_os = "windows") {
            // `start` is a shell builtin, and its first argument is the
            // window title -- an empty one, or a URL containing `&` ends
            // up split.
            ("cmd", &["/C", "start", ""])
        } else {
            ("xdg-open", &[])
        };
        match std::process::Command::new(program)
            .args(first)
            .arg(url)
            .spawn()
        {
            Ok(_) => {}
            // Named with the command that failed and the link it was for,
            // since neither is recoverable from the OS error alone.
            Err(e) => log::warn!("could not open {url} with {program}: {e}"),
        }
    }
 }
@@ -1,5 +1,5 @@
 use crate::task::RequestRedraw;
-use iris_core::{UiData, UiRenderNode, UiRenderState};
+use iris_core::{UiData, UiRenderNode, UiRenderState, util::Vec2};
 use pollster::FutureExt;
 use std::sync::Arc;
 use wgpu::*;
@@ -66,7 +66,11 @@ impl UiRenderer {
        self.config.width = size.width;
        self.config.height = size.height;
        self.surface.configure(&self.device, &self.config);
-        self.ui.resize((size.width, size.height), &self.queue);
+        // Physical, matching `new`'s own seed -- see the comment there.
        self.ui.resize(
            Vec2::new(size.width as f32, size.height as f32),
            &self.queue,
        );
    }
    fn create_encoder(device: &Device) -> CommandEncoder {
@@ -79,7 +83,16 @@ impl UiRenderer {
        let size = window.inner_size();
        let instance = Instance::new(&InstanceDescriptor {
-            backends: Backends::PRIMARY,
+            // `force-gles` on the desktop too, not just on Android: the
            // GLES backend has behaviour of its own (a one-layer array
            // texture is a `GL_TEXTURE_2D` -- see
            // `GpuTextures::create_array_texture`), and a machine with a
            // real GPU is where that is cheap to reproduce and screenshot.
            backends: if cfg!(feature = "force-gles") {
                Backends::GL
            } else {
                Backends::PRIMARY
            },
            ..Default::default()
        });
@@ -141,7 +154,19 @@ impl UiRenderer {
        let encoder = Self::create_encoder(&device);
-        let ui = UiRenderNode::new(&device, &queue, &config);
+        // Unlike the Android backend, the desktop backend has no on-screen
        // fallback to show a diagnostic through, so a renderer-creation
        // failure still panics here -- but now with wgpu's full "Caused
        // by:" chain as the message, since `UiRenderNode::new` returns it
        // rather than letting wgpu's own default handler panic first (see
        // that function's doc comment).
        // Physical size, the same units the swapchain, `WindowEvent::
        // Resized`, the pointer and the widget tree all use -- see
        // `default::content_scale` for why this backend stopped dividing
        // into a separate logical space, and what disagreed while it did.
        let physical_size = Vec2::new(size.width as f32, size.height as f32);
        let ui = UiRenderNode::new(&device, &queue, &config, physical_size)
            .expect("Could not create iris render node!");
        Self {
            surface,
@@ -0,0 +1,396 @@
 //! Layer 1 of docs/RUST.md's "Three test layers": a whole screen driven
 //! in-process with **no window, no compositor and no GPU**, on an
 //! explicit clock and a replayed touch stream.
 //!
 //! `layout_tests.rs` and `sense_tests.rs` already build trees over
 //! `UiRenderState` with a hand-rolled `Rsc` each; this is the same idea
 //! carried far enough to open a real app screen (`transcript-ui`'s, over
 //! the bench fixture -- see the `transcript-fixture` crate) at the
 //! phone's size and density, feed it a recorded flick, and assert on
 //! where the list ended up. What it answers that the emulator cannot:
 //! Android batches a 120Hz flick into one or two `MotionEvent`s
 //! (`CursorState::time`), and a `ui-trace` swipe is many evenly-spaced
 //! ones -- so the gesture shape a finger actually makes is only
 //! reproducible from a *file* of timestamped samples.
 //!
 //! It is a third backend in the sense `default/` and `android/` are, and
 //! deliberately the smallest one: the platform half of each of those
 //! (a surface, an IME, a URL opener) becomes a recorded fact here --
 //! [`HarnessState::keyboard_shown`], [`HarnessState::opened_urls`] --
 //! so a test can assert the platform *was asked*, which is the only
 //! thing either backend does with those calls anyway.
 //!
 //! ```ignore
 //! let mut h = Harness::new(phone_size(), PHONE_SCALE);
 //! let screen = transcript_ui::build(&mut h.rsc, &mut h.state, rows);
 //! h.frame(0);
 //! h.replay(&TouchScript::parse(include_str!("flick.touch"))?);
 //! h.frames_until(20, 2_000, 8);
 //! ```
 use crate::prelude::*;
 use std::marker::PhantomData;
 use std::sync::Arc;
 use std::sync::atomic::{AtomicUsize, Ordering};
 use std::time::{Duration, Instant};
 /// One replayed pointer sample: what Android's `MotionEvent` carries, cut
 /// down to the part iris reads (`IrisViewPeer::on_touch_event`).
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub enum TouchAction {
    Down,
    Move,
    Up,
    /// The gesture taken away by the system (a parent view claiming it, a
    /// call arriving). It ends the press exactly as `Up` does -- a
    /// release that never arrives leaves pointer capture held forever --
    /// which is why a replay file can say it.
    Cancel,
 }
 impl TouchAction {
    fn parse(word: &str) -> Option<Self> {
        match word {
            "down" => Some(Self::Down),
            "move" => Some(Self::Move),
            "up" => Some(Self::Up),
            "cancel" => Some(Self::Cancel),
            _ => None,
        }
    }
 }
 #[derive(Clone, Copy, Debug)]
 pub struct TouchSample {
    /// Milliseconds since the start of the recording -- the sample's own
    /// time, which becomes `CursorState::time`. See that field's doc for
    /// why a replay may not date its samples by when the loop got to
    /// them.
    pub t_ms: u64,
    pub action: TouchAction,
    pub pos: Vec2,
 }
 /// A recorded gesture: one `t_ms action x y` line per sample, `#` and
 /// blank lines ignored. Deliberately a plain text file rather than a
 /// serialisation format -- it is written by hand as often as it is
 /// recorded, and a diff of one has to be readable.
 pub struct TouchScript {
    pub samples: Vec<TouchSample>,
 }
 impl TouchScript {
    /// Parses a script, naming the line and what was wrong with it: these
    /// are hand-written files, so a typo is the ordinary case and
    /// "expected 4 fields" without a line number is not enough to fix it.
    pub fn parse(text: &str) -> Result<Self, String> {
        let mut samples: Vec<TouchSample> = Vec::new();
        for (i, line) in text.lines().enumerate() {
            let line = line.split('#').next().unwrap_or("").trim();
            if line.is_empty() {
                continue;
            }
            let at = |what: &str| format!("touch script line {}: {what}: {line:?}", i + 1);
            let mut words = line.split_whitespace();
            let (Some(t), Some(action), Some(x), Some(y), None) = (
                words.next(),
                words.next(),
                words.next(),
                words.next(),
                words.next(),
            ) else {
                return Err(at("expected `t_ms action x y`"));
            };
            let t_ms: u64 = t.parse().map_err(|_| at("t_ms is not a whole number"))?;
            let action = TouchAction::parse(action)
                .ok_or_else(|| at("action is not down/move/up/cancel"))?;
            let x: f32 = x.parse().map_err(|_| at("x is not a number"))?;
            let y: f32 = y.parse().map_err(|_| at("y is not a number"))?;
            if let Some(last) = samples.last()
                && t_ms < last.t_ms
            {
                return Err(at("samples must be in time order"));
            }
            samples.push(TouchSample {
                t_ms,
                action,
                pos: Vec2::new(x, y),
            });
        }
        Ok(Self { samples })
    }
    /// The last sample's time, i.e. how long the recording runs.
    pub fn end_ms(&self) -> u64 {
        self.samples.last().map(|s| s.t_ms).unwrap_or(0)
    }
 }
 /// Counts the frames something asked for without drawing any -- the
 /// harness's `RequestRedraw`. A `List` coasting through a fling asks for
 /// the next frame through this (`List::set_redraw_handle`), so a test can
 /// tell "nothing moved" from "nothing was even asked to move".
 #[derive(Default)]
 pub struct RedrawCounter(AtomicUsize);
 impl RedrawCounter {
    pub fn count(&self) -> usize {
        self.0.load(Ordering::Relaxed)
    }
 }
 impl RequestRedraw for RedrawCounter {
    fn request_redraw(&self) {
        self.0.fetch_add(1, Ordering::Relaxed);
    }
 }
 /// The harness's app state: what each real backend keeps for the platform
 /// half, recorded instead of performed.
 pub struct HarnessState {
    pub root: Option<StrongWidget>,
    pub focus: Option<WeakWidget<TextEdit>>,
    last_click: Instant,
    /// How many times a tap asked for the keyboard (`FocusHost::
    /// focus_gained` with a region -- `showSoftInput` on Android,
    /// `set_ime_cursor_area` on winit). The platform's own answer is not
    /// available here, so this says what was *asked*, and a test must not
    /// read it as "the IME is up".
    pub keyboard_shown: usize,
    /// Every URL a tapped link asked the platform to open, in order.
    pub opened_urls: Vec<String>,
 }
 impl HarnessState {
    fn new() -> Self {
        Self {
            root: None,
            focus: None,
            last_click: Instant::now(),
            keyboard_shown: 0,
            opened_urls: Vec::new(),
        }
    }
 }
 impl HasRoot for HarnessState {
    fn set_root(&mut self, root: StrongWidget) {
        self.root = Some(root);
    }
 }
 impl FocusHost for HarnessState {
    fn recent_click(&mut self) -> bool {
        crate::attr::recent_click(&mut self.last_click)
    }
    fn set_focus(&mut self, id: Option<WeakWidget<TextEdit>>) {
        self.focus = id;
    }
    fn is_focused(&self, id: WeakWidget<TextEdit>) -> bool {
        self.focus == Some(id)
    }
    fn focus_gained(&mut self, region: Option<PixelRegion>) {
        if region.is_some() {
            self.keyboard_shown += 1;
        }
    }
 }
 impl OpenUrl for HarnessState {
    fn open_url(&mut self, url: &str) {
        self.opened_urls.push(url.to_string());
    }
 }
 /// The harness's `Rsc` -- identical in substance to `DefaultRsc`/
 /// `AndroidRsc` minus the windowing, for the same reason those two are
 /// separate types (`AndroidRsc`'s own doc).
 pub struct HarnessRsc {
    pub ui: UiData,
    pub events: EventManager<Self>,
    pub tasks: Tasks<Self>,
    pub state: WidgetState,
    _state: PhantomData<HarnessState>,
 }
 impl UiRsc for HarnessRsc {
    fn ui(&self) -> &UiData {
        &self.ui
    }
    fn ui_mut(&mut self) -> &mut UiData {
        &mut self.ui
    }
    fn on_draw(&mut self, active: &ActiveData) {
        self.events.draw(active);
    }
    fn on_undraw(&mut self, active: &ActiveData) {
        self.events.undraw(active);
    }
    fn on_remove(&mut self, id: WidgetId) {
        self.events.remove(id);
        self.state.remove(id);
    }
 }
 impl HasState for HarnessRsc {
    type State = HarnessState;
 }
 impl HasEvents for HarnessRsc {
    fn events(&self) -> &EventManager<Self> {
        &self.events
    }
    fn events_mut(&mut self) -> &mut EventManager<Self> {
        &mut self.events
    }
 }
 impl HasTasks for HarnessRsc {
    fn tasks_mut(&mut self) -> &mut Tasks<Self> {
        &mut self.tasks
    }
 }
 impl HasWidgetState for HarnessRsc {
    fn widget_state(&self) -> &WidgetState {
        &self.state
    }
    fn widget_state_mut(&mut self) -> &mut WidgetState {
        &mut self.state
    }
 }
 impl<I: RscIdx<HarnessRsc>> std::ops::Index<I> for HarnessRsc {
    type Output = I::Output;
    fn index(&self, index: I) -> &Self::Output {
        index.get(self)
    }
 }
 impl<I: RscIdx<HarnessRsc>> std::ops::IndexMut<I> for HarnessRsc {
    fn index_mut(&mut self, index: I) -> &mut Self::Output {
        index.get_mut(self)
    }
 }
 /// A screen running with no window: the widget tree, the frame loop and
 /// the pointer, all advanced by the caller. See the module doc.
 pub struct Harness {
    pub rsc: HarnessRsc,
    pub render: UiRenderState,
    pub state: HarnessState,
    task_recv: TaskMsgReceiver<HarnessRsc>,
    redraws: Arc<RedrawCounter>,
    cursor: CursorState,
    /// Time zero. Every `t_ms` in this harness is an offset from here, so
    /// nothing reads the wall clock -- see [`Self::at`].
    base: Instant,
    size: Vec2,
 }
 impl Harness {
    /// `size` is in physical pixels and `density` is physical pixels per
    /// dp, the pair Android reads from the surface and
    /// `DisplayMetrics.density` (`AndroidUiState::content_scale`). The
    /// phone's own numbers are `transcript_fixture::PHONE_SIZE`/
    /// `PHONE_SCALE`.
    pub fn new(size: Vec2, density: f32) -> Self {
        let redraws = Arc::new(RedrawCounter::default());
        let (tasks, task_recv) = Tasks::init(redraws.clone());
        let mut rsc = HarnessRsc {
            ui: UiData::default(),
            events: EventManager::default(),
            tasks,
            state: WidgetState::default(),
            _state: PhantomData,
        };
        rsc.ui.text.density = density;
        let mut render = UiRenderState::new();
        render.set_density(density);
        render.resize(size);
        Self {
            rsc,
            render,
            state: HarnessState::new(),
            task_recv,
            redraws,
            cursor: CursorState::default(),
            base: Instant::now(),
            size,
        }
    }
    /// The `Instant` this harness means by `t_ms`. Public because a
    /// caller driving `List::tick_fling` or `DragGesture` by hand needs
    /// to date those calls on the same clock the touch samples use.
    pub fn at(&self, t_ms: u64) -> Instant {
        self.base + Duration::from_millis(t_ms)
    }
    pub fn size(&self) -> Vec2 {
        self.size
    }
    /// How many frames were asked for so far -- see [`RedrawCounter`].
    pub fn redraws(&self) -> usize {
        self.redraws.count()
    }
    /// One frame at `t_ms`: drain finished tasks, advance anything
    /// animating, lay out and "draw". The same three steps
    /// `DefaultApp::window_event`'s `RedrawRequested` arm and
    /// `IrisViewPeer::render` take, minus handing primitives to a GPU.
    pub fn frame(&mut self, t_ms: u64) {
        while let Ok(update) = self.task_recv.try_recv() {
            update(&mut self.state, &mut self.rsc);
        }
        let now = self.at(t_ms);
        self.rsc.ui.tick_animations(now);
        self.render.update(&self.state.root, &mut self.rsc);
    }
    /// Frames every `step_ms` up to and including `end_ms` -- what a
    /// fling needs, since it moves only while something ticks it
    /// (`List::fling`'s doc). Returns the time of the last frame run.
    pub fn frames_until(&mut self, from_ms: u64, end_ms: u64, step_ms: u64) -> u64 {
        debug_assert!(step_ms > 0, "a frame loop with no step never ends");
        let mut t = from_ms;
        while t <= end_ms {
            self.frame(t);
            t += step_ms;
        }
        t - step_ms
    }
    /// One pointer sample through the sensors, then the frame it belongs
    /// to -- `IrisViewPeer::on_touch_event` and `after_input`, in one
    /// call. Each sample is its own input frame, dated by the sample
    /// rather than by when this ran.
    pub fn touch(&mut self, action: TouchAction, pos: Vec2, t_ms: u64) {
        self.cursor.time = self.at(t_ms);
        self.cursor.pos = pos;
        match action {
            TouchAction::Down => {
                self.cursor.exists = true;
                self.cursor.buttons.left.update(true);
            }
            TouchAction::Move => {}
            TouchAction::Up | TouchAction::Cancel => self.cursor.buttons.left.update(false),
        }
        let cursor = self.cursor.clone();
        self.render
            .run_sensors(&mut self.rsc, &mut self.state, cursor, self.size);
        self.frame(t_ms);
        self.cursor.end_frame();
    }
    /// Replays a whole recorded gesture. Nothing is inserted between the
    /// samples: a file with three lines produces three input frames, so
    /// the batched shape a real flick arrives in is preserved exactly as
    /// recorded rather than smoothed into evenly-spaced motion.
    pub fn replay(&mut self, script: &TouchScript) {
        for sample in &script.samples {
            self.touch(sample.action, sample.pos, sample.t_ms);
        }
    }
 }
@@ -68,7 +68,7 @@ fn an_unchanged_frame_draws_and_rewrites_nothing() {
    render.take_counters(); // discard the first, real draw
    render.update(&root, &mut rsc);
-    let (draws, rewrites, moves) = render.take_counters();
+    let (draws, rewrites, moves, _shapes) = render.take_counters();
    assert_eq!((draws, rewrites, moves), (0, 0, 0));
 }
@@ -101,7 +101,7 @@ fn scrolling_moves_in_o1_without_a_redraw() {
    // already clamped) rather than actually moving anything.
    rsc.ui.widgets.get_mut(&scroll).unwrap().scroll(-40.0);
    render.update(&root, &mut rsc);
-    let (draws, _rewrites, moves) = render.take_counters();
+    let (draws, _rewrites, moves, _shapes) = render.take_counters();
    // The pass condition (LAYOUT.md section 8, condition 3) is 0 draws and
    // 1 move_offsets write, independent of how many rects are in the
@@ -147,6 +147,37 @@ fn hit_testing_follows_a_scrolled_widget() {
    );
 }
 /// `ActiveData::mask` is the mask a widget was drawn **under**, not the one
 /// it set for itself -- `redraw` feeds it straight back in as the inherited
 /// mask, so storing the set one hands a `Masked` its own mask the second
 /// time round and trips `Painter::set_mask`'s nested-mask assert. That was
 /// an abort (`assertion failed: self.mask == MaskIdx::NONE`) the first time
 /// the composer's new scroll area was redrawn on the emulator; a targeted
 /// redraw of a `Masked` is what any real screen does whenever anything
 /// inside it changes.
 #[test]
 fn redrawing_a_masked_widget_does_not_nest_its_own_mask() {
    let mut rsc = TestRsc {
        ui: UiData::default(),
    };
    let (_scroll, inner_root, _rects) = scrolled_rects(&mut rsc, 8);
    let masked = rsc.ui.widgets.add_strong(Masked { inner: inner_root });
    let masked_id = masked.id();
    let root = masked.any();
    let mut render = UiRenderState::new();
    render.resize((800.0, 600.0));
    render.update(&root, &mut rsc);
    render.redraw(masked_id, &mut rsc);
    render.redraw(masked_id, &mut rsc);
    assert_eq!(
        render.active.get(&masked_id).unwrap().mask,
        MaskIdx::NONE,
        "a `Masked` at the root is drawn under no mask of its own"
    );
 }
 #[test]
 fn a_mask_stays_put_while_its_scrolled_content_moves() {
    let mut rsc = TestRsc {
@@ -183,3 +214,444 @@ fn a_mask_stays_put_while_its_scrolled_content_moves() {
    assert_eq!(mask_delta_before, [0.0, 0.0]);
    assert_eq!(mask_delta_after, [0.0, 0.0]);
 }
 /// Reproduces `transcript_ui::composer::build_composer`'s exact tree shape
 /// (a `Rect` background stacked behind a `Span::RIGHT`-wrapped, padded,
 /// `rest`-width `TextEdit`, itself the second child of an outer
 /// `Span::DOWN` beside a `rest(1)`-height sibling) without the event/
 /// resource plumbing `composer.rs`'s builders need, to isolate whether the
 /// bug Iris reported on 2026-09-06 ("text seems to not appear in box")
 /// is this crate's layout engine or something specific to the real
 /// composer/screen. `TextEditable::edit` only needs `UiRsc`, so a plain
 /// insert exercises the exact redraw path a keystroke does.
 fn composer_like_tree(rsc: &mut TestRsc) -> (WeakWidget<TextEdit>, StrongWidget) {
    let field = wtext("")
        .editable(EditMode::MultiLine)
        .text_align(Align::LEFT)
        .wrap(true)
        .size(18)
        .color(UiColor::WHITE)
        .add(rsc);
    let bar = (field.pad(dp(12)).width(rest(1)),)
        .span(Dir::RIGHT)
        .background(rect(UiColor::new(40, 40, 46, 255)))
        .add(rsc);
    let list_stand_in = rect(UiColor::BLACK).height(rest(1)).add(rsc);
    let tree = (list_stand_in, bar).span(Dir::DOWN).add_strong(rsc).any();
    (field, tree)
 }
 /// The reproduction itself. A window this tall stands in for the keyboard
 /// closed; the second, shorter `resize` stands in for `adjustResize`
 /// shrinking the surface when the IME opens -- exactly the sequence
 /// `IrisViewPeer::surface_changed` drives on a real keyboard open. Typing
 /// happens both before and after, since Iris's report was specifically
 /// that text typed *after* the keyboard was already up did not appear.
 #[test]
 fn composing_text_after_a_keyboard_resize_lands_in_the_bars_own_region() {
    let mut rsc = TestRsc {
        ui: UiData::default(),
    };
    let (field, root) = composer_like_tree(&mut rsc);
    let mut render = UiRenderState::new();
    render.resize((1080.0, 2298.0));
    render.update(&root, &mut rsc);
    // Focusing a field is what places its caret on a real tap
    // (`attr.rs`'s `on_press` -> `TextEditCtx::select`), and an insert
    // with no caret is a routing bug rather than a state to simulate --
    // `insert_str`'s own `debug_assert!` says so, and caught this test
    // typing into an unfocused field when it was added.
    field
        .edit(&mut rsc)
        .select(vec2(40.0, 2250.0), vec2(1080.0, 2298.0), false, false);
    field.edit(&mut rsc).insert("a");
    render.update(&root, &mut rsc);
    let before_px = render.window_region(&field, &rsc).unwrap();
    // The field is one line plus 12dp of padding on a 2298-tall window --
    // nowhere near the whole window's height, and anchored at the bottom.
    assert!(
        before_px.bot_right.y - before_px.top_left.y < 200.0,
        "before a resize: {before_px:?}"
    );
    assert!(
        before_px.top_left.y > 1800.0,
        "expected the bar near the bottom before a resize: {before_px:?}"
    );
    // The keyboard opens: a real `surface_changed`/`resize` to a shorter
    // window, then a further keystroke -- the redraw that must land in the
    // bar's new (also short) region, not whatever region a provisional
    // measurement pass used along the way.
    render.resize((1080.0, 1478.0));
    render.update(&root, &mut rsc);
    field.edit(&mut rsc).insert("b");
    render.update(&root, &mut rsc);
    let after_px = render.window_region(&field, &rsc).unwrap();
    assert!(
        after_px.bot_right.y - after_px.top_left.y < 200.0,
        "after a resize + keystroke: {after_px:?}"
    );
    assert!(
        after_px.top_left.y > 1200.0,
        "expected the bar near the bottom of the shorter window: {after_px:?}"
    );
 }
 /// `Scroll` used to be documented as resolving its own lengths against
 /// `Painter::output_size` -- the window -- which read as if a scroll area
 /// smaller than the screen could not work, and cost a session's
 /// investigation before the composer was wired up (docs/RUST.md,
 /// 2026-09-06). It measures `painter.px_size()` now, so this pins the
 /// three numbers that follow from the offered box: what it reports
 /// upward, what its capping parent reports, and how far it can pan.
 #[test]
 fn a_scroll_measures_the_box_it_was_offered_not_the_window() {
    let mut rsc = TestRsc {
        ui: UiData::default(),
    };
    let rect = rsc.ui.widgets.add_strong(Rect::new(UiColor::WHITE));
    let tall = rsc.ui.widgets.add_strong(Sized {
        inner: rect.any(),
        x: None,
        y: Some(Len::abs(1000.0)),
    });
    let scroll = rsc.ui.widgets.add_strong(Scroll::new(tall.any(), Axis::Y));
    let scroll_w = scroll.weak();
    let scroll_id = scroll.id();
    let capped = rsc.ui.widgets.add_strong(MaxSize {
        inner: scroll.any(),
        x: None,
        y: Some(Len::abs(100.0)),
    });
    let capped_id = capped.id();
    let root = capped.any();
    let mut render = UiRenderState::new();
    render.resize((800.0, 600.0));
    // Two passes: the first offers the content a zero-length region
    // (nothing measured yet) and learns the real content length from what
    // comes back -- see `scrolling_moves_in_o1_without_a_redraw` for why
    // that warm-up is deliberate rather than a bug.
    render.update(&root, &mut rsc);
    rsc.ui.widgets.get_mut(&scroll_w).unwrap().scroll(0.0);
    render.update(&root, &mut rsc);
    // Reports the *content*, so the cap above it has something to cap;
    // reporting the container instead would make the answer a function of
    // itself, since the container is sized from this very number.
    assert_eq!(
        render.active.get(&scroll_id).unwrap().size.y,
        Len::abs(1000.0)
    );
    assert_eq!(
        render.active.get(&capped_id).unwrap().size.y,
        Len::abs(100.0),
        "the cap, not the content and not the window"
    );
    // Panning is bounded by content minus *container*: 900, not the 400
    // a 600px window would give.
    rsc.ui.widgets.get_mut(&scroll_w).unwrap().scroll(-10_000.0);
    assert!(
        (rsc.ui.widgets.get_mut(&scroll_w).unwrap().amt() - 900.0).abs() < 0.01,
        "amt={}",
        rsc.ui.widgets.get_mut(&scroll_w).unwrap().amt()
    );
 }
 /// The half `hit_testing_follows_a_scrolled_widget` could not see: it
 /// checks a *descendant* of the widget `Scroll` actually moves, whose own
 /// `region` is stale and is corrected entirely by the move chain. The
 /// moved widget itself had its `region` updated *and* the chain delta
 /// added on top, so its hit box sat at twice the pan -- which is why a
 /// finger pan of the composer left its field untappable. See
 /// `ActiveData::move_applied`.
 #[test]
 fn a_panned_widgets_own_hit_box_moves_exactly_once() {
    let mut rsc = TestRsc {
        ui: UiData::default(),
    };
    let rect = rsc.ui.widgets.add_strong(Rect::new(UiColor::WHITE));
    let tall = rsc.ui.widgets.add_strong(Sized {
        inner: rect.any(),
        x: None,
        y: Some(Len::abs(1000.0)),
    });
    let tall_w = tall.weak();
    let scroll = rsc.ui.widgets.add_strong(Scroll::new(tall.any(), Axis::Y));
    let scroll_w = scroll.weak();
    let root = scroll.any();
    let mut render = UiRenderState::new();
    render.resize((800.0, 600.0));
    render.update(&root, &mut rsc);
    rsc.ui.widgets.get_mut(&scroll_w).unwrap().scroll(0.0);
    render.update(&root, &mut rsc);
    let before = render.window_region(&tall_w, &rsc).unwrap();
    rsc.ui.widgets.get_mut(&scroll_w).unwrap().scroll(-37.0);
    render.update(&root, &mut rsc);
    let after = render.window_region(&tall_w, &rsc).unwrap();
    assert!(
        (after.top_left.y - (before.top_left.y - 37.0)).abs() < 0.01,
        "the pan was applied twice: before={before:?} after={after:?}"
    );
 }
 /// A `Masked` used to allocate a **new** mask slot on every draw, and
 /// `draw_inner`'s unchanged-region fast path means its descendants are
 /// mostly *not* redrawn with it -- so they went on referencing the slot
 /// they were first drawn under, whose region had since stopped being the
 /// widget's. Measured 2026-09-06 on the composer's tree: four live mask
 /// entries, none of them the `Masked`'s current box, and the field it was
 /// meant to clip drew nothing at all on the emulator. The slot is
 /// allocated once and rewritten in place now (`ActiveData::own_mask`), so
 /// this pins both halves: one entry, and that entry is the widget's own
 /// region.
 #[test]
 fn a_masked_widget_keeps_one_mask_slot_that_is_always_its_own_region() {
    let mut rsc = TestRsc {
        ui: UiData::default(),
    };
    let (_scroll, inner_root, _rects) = scrolled_rects(&mut rsc, 8);
    let masked = rsc.ui.widgets.add_strong(Masked { inner: inner_root });
    let masked_id = masked.id();
    // Placed at the bottom of a `Span::DOWN` behind a `rest(1)` sibling,
    // which is what moves the bar away from the provisional slot it is
    // first drawn at -- the move that left the stale mask behind.
    let filler = rsc.ui.widgets.add_strong(Rect::new(UiColor::BLACK));
    let filler = rsc.ui.widgets.add_strong(Sized {
        inner: filler.any(),
        x: None,
        y: Some(rest(1)),
    });
    let capped = rsc.ui.widgets.add_strong(MaxSize {
        inner: masked.any(),
        x: None,
        y: Some(Len::abs(60.0)),
    });
    let mut span = Span::empty(Dir::DOWN);
    span.push(filler.any());
    span.push(capped.any());
    let root = rsc.ui.widgets.add_strong(span).any();
    let mut render = UiRenderState::new();
    render.resize((800.0, 600.0));
    for _ in 0..3 {
        render.update(&root, &mut rsc);
        render.redraw(masked_id, &mut rsc);
    }
    assert_eq!(
        rsc.ui.masks.iter().count(),
        1,
        "one `Masked` must own exactly one mask slot, however often it is redrawn"
    );
    let mask = *rsc.ui.masks.iter().next().unwrap();
    assert_eq!(
        mask.region,
        render.active.get(&masked_id).unwrap().region,
        "the mask a descendant clips against must be this widget's current box"
    );
 }
 /// A `dp` cap that has done its job must be reported in pixels. `Span`
 /// places a child using the `abs`/`rel` of the length it reported, so a
 /// `MaxSize` handing back the caller's own `dp(168)` gave the composer's
 /// bar a slot of **zero** the moment its content grew past six lines --
 /// and the `Scroll` inside then measured its container at -63px (the
 /// padding, subtracted from nothing) and panned the whole message out of
 /// view. Measured on this checkout's emulator, 2026-09-06:
 /// `container=-63 content=415.8 amt=478.8`. See `Len::fold_dp`.
 #[test]
 fn a_dp_cap_is_reported_in_pixels_so_a_span_can_place_it() {
    let mut rsc = TestRsc {
        ui: UiData::default(),
    };
    let rect = rsc.ui.widgets.add_strong(Rect::new(UiColor::WHITE));
    let tall = rsc.ui.widgets.add_strong(Sized {
        inner: rect.any(),
        x: None,
        y: Some(Len::abs(1000.0)),
    });
    let capped = rsc.ui.widgets.add_strong(MaxSize {
        inner: tall.any(),
        x: None,
        y: Some(Len::dp(100.0)),
    });
    let capped_w = capped.weak();
    let filler = rsc.ui.widgets.add_strong(Rect::new(UiColor::BLACK));
    let filler = rsc.ui.widgets.add_strong(Sized {
        inner: filler.any(),
        x: None,
        y: Some(rest(1)),
    });
    let mut span = Span::empty(Dir::DOWN);
    span.push(filler.any());
    span.push(capped.any());
    let root = rsc.ui.widgets.add_strong(span).any();
    let mut render = UiRenderState::new();
    render.resize((800.0, 600.0));
    render.set_density(2.5);
    render.update(&root, &mut rsc);
    render.update(&root, &mut rsc);
    let box_px = render.window_region(&capped_w, &rsc).unwrap();
    let height = box_px.bot_right.y - box_px.top_left.y;
    assert!(
        (height - 250.0).abs() < 0.01,
        "expected the 100dp cap at density 2.5 to be a 250px slot, got {height} ({box_px:?})"
    );
 }
 /// The sibling of `a_panned_widgets_own_hit_box_moves_exactly_once`, on
 /// the branch that fix had no reason to touch: `draw_inner`'s
 /// size-independent fast path rewrites a widget's primitives *in place*
 /// and leaves its move slot alone, so unlike `mov` there is no slot delta
 /// for `region` to have absorbed. Counting one there anyway makes
 /// `resolved_region` subtract a delta the chain never held, and the
 /// widget's hit box lands short of where it is drawn by exactly the
 /// distance it just moved -- with nothing on screen to say so, since the
 /// primitives are in the right place.
 #[test]
 fn a_size_independent_widget_moved_by_its_parent_has_the_hit_box_it_is_drawn_at() {
    let mut rsc = TestRsc {
        ui: UiData::default(),
    };
    let top = rsc.ui.widgets.add_strong(Rect::new(UiColor::WHITE));
    let spacer = rsc.ui.widgets.add_strong(Sized {
        inner: top.any(),
        x: None,
        y: Some(Len::abs(100.0)),
    });
    let spacer_w = spacer.weak();
    // `Rect` is `is_size_independent`, so growing the spacer above it
    // offers this one a region that changed *both* position and size --
    // the one shape that reaches the branch under test.
    let below = rsc.ui.widgets.add_strong(Rect::new(UiColor::WHITE));
    let below_w = below.weak();
    let mut span = Span::empty(Dir::DOWN);
    span.push(spacer.any());
    span.push(below.any());
    let root = rsc.ui.widgets.add_strong(span).any();
    let mut render = UiRenderState::new();
    render.resize((800.0, 600.0));
    render.update(&root, &mut rsc);
    // `Span` draws each child once at the full region to measure it and
    // then places it, so this widget has already been through the branch
    // once by the end of the very first frame.
    let first = render.window_region(&below_w, &rsc).unwrap();
    assert!(
        (first.top_left.y - 100.0).abs() < 0.01,
        "hit box at {:?}, drawn at y=100",
        first.top_left
    );
    rsc.ui.widgets.get_mut(&spacer_w).unwrap().y = Some(Len::abs(250.0));
    render.update(&root, &mut rsc);
    let after = render.window_region(&below_w, &rsc).unwrap();
    assert!(
        (after.top_left.y - 250.0).abs() < 0.01,
        "hit box at {:?}, drawn at y=250",
        after.top_left
    );
 }
 /// A parent that both `mov`s a child (its own layout moved the box it
 /// offers) and `reposition`s it inside that box in the same frame -- what
 /// `List::place`'s Bottom-known branch does once a row's cached height
 /// stops matching what the row reports, which is reachable as soon as a
 /// transcript row's blocks wrap (docs/IRIS_TODO.md's "Found by P1a").
 struct MoveThenPlace {
    inner: StrongWidget,
    /// Where the child is *offered* a (constant-size) box, moved between
    /// frames by the test.
    offer_top: f32,
    /// Where the child is then placed within this widget's own region.
    place_top: f32,
 }
 impl Widget for MoveThenPlace {
    fn draw(&mut self, painter: &mut Painter) -> Size {
        let offer = UiRegion::new(
            UiSpan::FULL,
            UiSpan::new(
                UiScalar::abs(self.offer_top),
                UiScalar::abs(self.offer_top + 40.0),
            ),
        );
        painter.widget_within(&self.inner, offer);
        let place = UiRegion::new(
            UiSpan::FULL,
            UiSpan::new(
                UiScalar::abs(self.place_top),
                UiScalar::abs(self.place_top + 40.0),
            ),
        );
        painter.reposition(&self.inner, place);
        Size::default()
    }
 }
 /// `mov` accumulates a delta onto a widget's move slot and `reposition`
 /// overwrites it, and both can legitimately land on one widget in one
 /// frame (see `MoveThenPlace`). `reposition` used to write its own delta
 /// alone, which dropped the move and put the child back at the position
 /// the offered box had *before* it moved; a `debug_assert!` that
 /// `move_applied` was zero hid that behind a panic instead of fixing it.
 /// The slot has one owner and one meaning now --
 /// `move_applied + repositioned` -- so the child stays where it was
 /// placed however its offered box moves. Fails at the offer's position
 /// (200) rather than the placement's (100) without that.
 #[test]
 fn a_widget_moved_by_its_parent_and_then_placed_inside_it_lands_at_the_placement() {
    let mut rsc = TestRsc {
        ui: UiData::default(),
    };
    let rect = rsc.ui.widgets.add_strong(Rect::new(UiColor::WHITE));
    let child = rsc.ui.widgets.add_strong(Sized {
        inner: rect.any(),
        x: None,
        y: Some(Len::abs(40.0)),
    });
    let child_w = child.weak();
    let parent = rsc.ui.widgets.add_strong(MoveThenPlace {
        inner: child.any(),
        offer_top: 0.0,
        place_top: 100.0,
    });
    let parent_w = parent.weak();
    let root = parent.any();
    let mut render = UiRenderState::new();
    render.resize((200.0, 400.0));
    render.update(&root, &mut rsc);
    let before = render.window_region(&child_w, &rsc).unwrap();
    assert!(
        (before.top_left.y - 100.0).abs() < 0.01,
        "the child should be drawn where it was placed, not where it was offered: {before:?}"
    );
    // Move the offered box without changing its size (the `mov` fast path)
    // and place the child at the same spot as before. Marking the parent
    // dirty is what a real container's own content change does; the child
    // itself is untouched, which is the case `mov` exists for.
    {
        let parent = rsc.ui.widgets.get_mut(&parent_w).unwrap();
        parent.offer_top = 200.0;
    }
    rsc.ui.widgets.needs_redraw.insert(parent_w.id());
    render.update(&root, &mut rsc);
    let after = render.window_region(&child_w, &rsc).unwrap();
    assert!(
        (after.top_left.y - 100.0).abs() < 0.01,
        "the placement did not change, so neither should the child: before={before:?} \
         after={after:?}"
    );
 }
@@ -21,6 +21,8 @@ pub mod default;
 pub mod attr;
 pub mod event;
 pub mod harness;
 pub mod platform;
 pub mod sense;
 pub mod state;
 pub mod task;
@@ -47,6 +49,7 @@ pub mod prelude {
    pub use event::*;
    pub use iris_core::*;
    pub use iris_macro::*;
    pub use platform::*;
    pub use sense::*;
    pub use state::*;
    pub use task::*;
@@ -0,0 +1,22 @@
 //! Capabilities a widget tree needs from whatever is hosting it, that
 //! neither iris nor the app can perform itself.
 //!
 //! Same shape as [`crate::attr::FocusHost`], and for the same reason: the
 //! interface is declared here, below, and implemented by each backend
 //! above (`default/platform.rs`, `android/platform.rs`), so a widget can
 //! ask for the capability by trait bound instead of a caller threading a
 //! callback down through every builder.
 /// Hand a URL to whatever the platform opens URLs with.
 ///
 /// One method rather than a general "run an intent"/"exec" surface: the
 /// only thing a transcript needs is to follow a link a reader tapped, and
 /// a narrower capability is a narrower thing to get wrong.
 ///
 /// **Nothing is reported back.** There is no answer worth branching on --
 /// the platform either shows a browser or does not, and both are outside
 /// this process -- so failures are logged where they happen (each impl)
 /// rather than turned into a `Result` every call site would discard.
 pub trait OpenUrl {
    fn open_url(&mut self, url: &str);
 }
@@ -51,6 +51,7 @@ fn cursor_at(pos: Vec2) -> CursorState {
        exists: true,
        buttons: Default::default(),
        scroll_delta: Vec2::ZERO,
        ..Default::default()
    }
 }
@@ -122,3 +123,197 @@ fn a_button_over_a_list_scrolls_the_list_and_still_clicks() {
        "the button on top must still receive an actual click"
    );
 }
 /// The bug behind "finger flings do nothing" (RUST.md's P0 phone report,
 /// defect 2): a fast gesture's `PressEnd` can land at a screen position
 /// nothing is registered at -- past the edge of whatever widget noticed
 /// the press, in a gap, or off the loaded content entirely. Before pointer
 /// capture, `run_sensors`' hit test simply delivered nothing that frame,
 /// so a widget mid-drag never saw its release and never got a chance to
 /// start a fling. `UiRenderState::capture_pointer`/`DragGesture` fix this
 /// by giving the drag's widget every frame regardless of where the
 /// pointer is, including the terminal `Drop` in place of `PressEnd`.
 #[test]
 fn a_release_outside_every_hit_region_still_reaches_the_captured_widget() {
    let mut rsc = SenseRsc {
        ui: UiData::default(),
        events: EventManager::default(),
    };
    // A small draggable widget in the corner -- the release below lands
    // far outside it, exactly the "moved off the hit region" case.
    let draggable = rsc.ui.widgets.add_strong(Rect::new(UiColor::WHITE)).any();
    let draggable_weak = draggable.weak();
    let dropped = Rc::new(Cell::new(false));
    {
        let dropped = dropped.clone();
        rsc.register_event(
            draggable_weak,
            CursorSense::click_or_drag() | CursorSense::unclick() | CursorSense::Drop,
            move |ctx, rsc| match ctx.data.sense {
                CursorSense::PressStart(_) | CursorSense::Pressing(_) => {
                    // Any committed drag takes capture -- a real caller
                    // would gate this on a `DragArbiter`/`DragGesture`
                    // decision, but this test only needs to exercise the
                    // capture-and-release mechanics themselves.
                    ctx.data.render.capture_pointer(draggable_weak.id());
                    let _ = rsc;
                }
                CursorSense::Drop => dropped.set(true),
                _ => {}
            },
        );
    }
    let mut render = UiRenderState::new();
    render.resize((100.0, 100.0));
    render.update(&draggable, &mut rsc);
    let mut state = ();
    let mut press = cursor_at((5.0, 5.0).into());
    press.buttons.left = ActivationState::Start;
    render.run_sensors(&mut rsc, &mut state, press, (100.0, 100.0).into());
    assert_eq!(
        render.captured_pointer(),
        Some(draggable.id()),
        "the press should have taken capture"
    );
    // The release lands nowhere near the widget's own region -- the exact
    // shape of a fast fling's `ACTION_UP`.
    let mut release = cursor_at((95.0, 95.0).into());
    release.buttons.left = ActivationState::End;
    render.run_sensors(&mut rsc, &mut state, release, (100.0, 100.0).into());
    assert!(
        dropped.get(),
        "a release outside every widget's hit region must still reach \
         the widget holding pointer capture"
    );
    assert_eq!(
        render.captured_pointer(),
        None,
        "Drop must release the capture"
    );
 }
 /// A widget that never registers `CursorSense::Drop` at all must not be
 /// affected by someone else's capture -- capture is per-gesture, not
 /// global suppression of the whole input system for widgets that were
 /// never party to it. (Practically this matters because a captured
 /// widget's registration list still has to include `Drop` for `should_run`
 /// to ever match it; this pins that half of the contract.)
 #[test]
 fn capturing_one_widget_starves_every_other_widget_of_events() {
    let mut rsc = SenseRsc {
        ui: UiData::default(),
        events: EventManager::default(),
    };
    let a = rsc.ui.widgets.add_strong(Rect::new(UiColor::WHITE));
    let a_weak = a.weak();
    let b = rsc.ui.widgets.add_strong(Rect::new(UiColor::RED));
    let b_weak = b.weak();
    let b_hovered = Rc::new(Cell::new(false));
    {
        let b_hovered = b_hovered.clone();
        rsc.register_event(b_weak, CursorSense::Hovering, move |_ctx, _rsc| {
            b_hovered.set(true);
        });
    }
    let root = rsc
        .ui
        .widgets
        .add_strong(Stack {
            children: vec![a.any(), b.any()],
            size: StackSize::default(),
        })
        .any();
    let mut render = UiRenderState::new();
    render.resize((100.0, 100.0));
    render.update(&root, &mut rsc);
    render.capture_pointer(a_weak.id());
    let mut state = ();
    let cursor = cursor_at((50.0, 50.0).into());
    render.run_sensors(&mut rsc, &mut state, cursor, (100.0, 100.0).into());
    assert!(
        !b_hovered.get(),
        "while a's drag holds capture, b must see no hover at all"
    );
 }
 /// IRIS_TODO.md's "the composer has no touch-drag scroll": `Scroll` only
 /// answered a wheel, so a finger drag over overflowed text did nothing.
 /// End-to-end over the real wiring -- `scrollable()`'s own registration,
 /// `run_sensors`' dispatch, `Scroll::drag`, `DragGesture`'s arbitration and
 /// pointer capture -- rather than only `Scroll::drag`'s own unit tests in
 /// `scroll.rs`, because the registration is exactly the half those cannot
 /// see.
 #[test]
 fn a_finger_drag_over_a_scroll_area_pans_it() {
    let mut rsc = SenseRsc {
        ui: UiData::default(),
        events: EventManager::default(),
    };
    // 1000px of content in a 100px window: room to pan.
    let scroll_strong = rect(UiColor::WHITE)
        .height(Len::abs(1000.0))
        .scrollable()
        .add_strong(&mut rsc);
    let scroll = scroll_strong.weak();
    let root = scroll_strong.any();
    let mut render = UiRenderState::new();
    render.resize((100.0, 100.0));
    render.update(&root, &mut rsc);
    // `Scroll` reads its content length back from the draw it just did, so
    // the frame after is the first one that knows there is anything to pan
    // -- the one-frame lag LAYOUT.md section 4 documents. `scroll(0.0)` is
    // how `layout_tests.rs` asks for that second frame, and it also drops
    // `snap_end`, leaving this parked at the start of the content.
    rsc.ui.widgets.get_mut(&scroll).unwrap().scroll(0.0);
    render.update(&root, &mut rsc);
    assert_eq!(rsc.ui.widgets.get(&scroll).unwrap().amt(), 0.0);
    let mut state = ();
    let mut down = cursor_at((50.0, 80.0).into());
    down.buttons.left = ActivationState::Start;
    render.run_sensors(&mut rsc, &mut state, down, (100.0, 100.0).into());
    assert_eq!(
        rsc.ui.widgets.get(&scroll).unwrap().amt(),
        0.0,
        "the touch-down alone must not move anything"
    );
    // Inside the slop: still a tap as far as anything can tell.
    let mut nudge = cursor_at((50.0, 80.0 - (DRAG_SLOP - 1.0)).into());
    nudge.buttons.left = ActivationState::On;
    render.run_sensors(&mut rsc, &mut state, nudge, (100.0, 100.0).into());
    assert_eq!(
        rsc.ui.widgets.get(&scroll).unwrap().amt(),
        0.0,
        "a press inside DRAG_SLOP must not scroll"
    );
    // Past it, upward: the content follows the finger up, which for this
    // widget means more `amt`.
    let mut drag = cursor_at((50.0, 80.0 - (DRAG_SLOP + 40.0)).into());
    drag.buttons.left = ActivationState::On;
    render.run_sensors(&mut rsc, &mut state, drag, (100.0, 100.0).into());
    let after = rsc.ui.widgets.get(&scroll).unwrap().amt();
    assert!(
        (after - 40.0).abs() < 0.01,
        "expected the 40px past the slop to pan it, got {after}"
    );
    // And the gesture holds the pointer, so the rest of it reaches this
    // widget even once the finger leaves its box.
    assert_eq!(render.captured_pointer(), Some(scroll.id()));
 }
@@ -102,7 +102,7 @@
 use crate::prelude::*;
 use iris_core::util::HashMap;
-use std::collections::VecDeque;
+use std::{collections::VecDeque, sync::Arc, time::Instant};
 /// A stable identifier for a loaded row, reused across pages so that a row
 /// already measured and drawn is not treated as new when data is inserted
@@ -213,6 +213,63 @@ pub struct List {
    /// row is evicted (`pop_front`/`pop_back`) so this cannot grow past
    /// however many rows are currently loaded.
    heights: HashMap<RowKey, f32>,
    /// A fling in progress, or `None` if the list is at rest -- see
    /// `fling`/`tick_fling`/`is_scrolling`, IRIS_TODO.md's "swiping has no
    /// momentum."
    fling: Option<Fling>,
    /// What `tick_fling` re-arms every frame a fling is still running, so
    /// the list keeps animating without needing a caller to poll it --
    /// set once via `set_redraw_handle` by whoever owns the surface this
    /// list draws into (the same handle `iris::task::Tasks::redraw_handle`
    /// hands out elsewhere). `None` for a list that never flings
    /// (headless tests, a caller driving `tick_fling` by hand as
    /// `bench_client.rs`'s scripted phases do).
    redraw: Option<Arc<dyn RequestRedraw>>,
    /// Physical pixels per `dp`, copied from the painter on every `draw`
    /// -- what [`Self::fling`] hands `FlingCalculator`. 1.0 until this
    /// list has been drawn once, which is also the only state in which a
    /// fling is impossible (`fling` needs an anchor, and an anchor comes
    /// from a draw).
    ///
    /// It has to be the real one: the deceleration constant is
    /// `GRAVITY * 39.37 * density * 160 * friction`, and the velocity fed
    /// in is in the same physical pixels the touch events arrive in, so a
    /// hardcoded 1.0 against a 2.75-density screen does not cancel out --
    /// it makes the fling last exponentially too long. Measured on this
    /// checkout's emulator, 2026-09-07, once flings could animate at all:
    /// a flick that should coast for about a second ran for **45
    /// seconds**.
    density: f32,
    /// Whether the last `draw` found no more content above the topmost
    /// visible row (its top edge at or past the viewport's own top, with
    /// no `prev_slot`) -- what `tick_fling` clamps a fling moving toward
    /// the start against. Stale (from whatever the last draw found) on a
    /// list that hasn't drawn yet; `false` by default, matching "assume
    /// there is more content until a draw proves otherwise."
    at_start: bool,
    /// The mirror of `at_start` for the newest end.
    at_end: bool,
 }
 /// One in-flight fling: the physics answer (`FlingCalculator`) plus how
 /// much of its total distance has already been applied to the anchor, so
 /// `tick_fling` only ever moves the list by this frame's *incremental*
 /// delta -- matching every other place in this widget that scrolls by
 /// writing `anchor.offset`.
 struct Fling {
    calc: FlingCalculator,
    velocity: f32,
    /// When the fling's own curve begins -- **the first `tick_fling`,
    /// not the release**. It is set there rather than in `fling` so the
    /// only clock this widget reads is the one its driver hands it: a
    /// caller running frames on an explicit clock (`iris::harness`, and
    /// `bench_client.rs`'s scripted phases) would otherwise start every
    /// fling at the wall clock and advance it on a different one, and a
    /// fling released at t=500ms would arrive already over. The
    /// difference in a running app is at most one frame, since that is
    /// how soon the fling is first ticked.
    started_at: Option<Instant>,
    applied: f32,
 }
 impl List {
@@ -226,6 +283,11 @@ impl List {
            snap_end: true,
            viewport_len: 0.0,
            last_viewport_len: 0.0,
            fling: None,
            redraw: None,
            density: 1.0,
            at_start: false,
            at_end: false,
            pending_tap: None,
            extents: HashMap::default(),
            heights: HashMap::default(),
@@ -317,6 +379,40 @@ impl List {
        self.extents.clear();
    }
    /// Swap the last row's widget for a new one **without moving it**: the
    /// slot index is unchanged, so an anchor already pointing at this slot
    /// (in particular `snap_end`'s pinned-to-newest case) stays pinned, and
    /// an anchor pointing anywhere else -- this row scrolled out of view --
    /// is untouched, so nothing currently on screen moves. This is what a
    /// streamed reply needs: the row whose *content* keeps changing after
    /// it first appears is still the same row by position, even if its
    /// `RowKey` happens to change too (rare -- only `heights`/`extents` care
    /// about the key, and both are invalidated here the same way
    /// `pop_back` already invalidates them for the row it removes).
    /// `None` if the list is empty. O(1), same as `push_back`/`pop_back`.
    pub fn replace_back(&mut self, row: ListRow) -> Option<ListRow> {
        let idx = self.items.len().checked_sub(1)?;
        let old = std::mem::replace(&mut self.items[idx], row);
        self.heights.remove(&old.key);
        self.extents.clear();
        Some(old)
    }
    /// Drop every loaded row and reset to the same state `List::new` would
    /// give -- the fallback path for a change `apply`-style incremental
    /// callers can't express as a replace-or-append (RUST.md: `group_tool_runs`
    /// regrouping an earlier row). `more_before`/`more_after` are left
    /// alone: a full paging reset is a different operation from "the
    /// content changed," and a caller that wants both calls
    /// `set_more_before(None)`/`set_more_after(None)` itself.
    pub fn clear(&mut self) {
        self.items.clear();
        self.anchor = None;
        self.snap_end = true;
        self.heights.clear();
        self.extents.clear();
    }
    /// Move the anchor's edge by `amt` pixels. Positive moves later
    /// content into view (mirrors `Scroll::scroll`'s sign convention).
    /// Deliberately unclamped -- see the module doc's "what is not
@@ -327,6 +423,168 @@ impl List {
        }
    }
    /// Give this list a way to ask for another frame on its own, so a
    /// fling keeps animating without a caller polling it every tick --
    /// see the `redraw` field's doc. Pass the same handle
    /// `iris::task::Tasks::redraw_handle` hands a `spawn`ed task; a list
    /// that never calls this can still `fling`, but has to be driven by a
    /// caller-owned loop instead (`bench_client.rs`'s scripted phases do
    /// exactly that, since they need to await settling rather than let it
    /// run in the background).
    pub fn set_redraw_handle(&mut self, handle: Arc<dyn RequestRedraw>) {
        self.redraw = Some(handle);
    }
    /// Start a fling at `velocity_px_per_s` (this widget's own pixel
    /// space, same sign convention as `scroll`'s `amt`: positive continues
    /// moving later content into view). Cancels any fling already in
    /// progress. A caller with a live touch/press must cancel this on the
    /// next touch-down (`cancel_fling`) -- `AndroidFlingSpline`'s curve
    /// has no idea a finger came back down, and Android's own `Scroller`
    /// relies on the view calling `abortAnimation` for the same reason.
    ///
    /// The density handed to `FlingCalculator` is this list's own
    /// (`self.density`, taken from the painter in `draw`), not `1.0`: it
    /// does **not** cancel out of the spline -- see `FlingCalculator`'s
    /// doc, which used to claim the opposite, and the 45-second coast that
    /// claim produced.
    ///
    /// **Sets the fling; it does not drive it.** A fling moves only while
    /// something calls [`Self::tick_fling`] once per frame, and what does
    /// that in a running app is `UiData::tick_animations`, over the ids
    /// `UiData::animate` was given. So a caller starting a fling from a
    /// gesture registers the list in the same breath:
    ///
    /// ```ignore
    /// list(ui).fling(-velocity);
    /// let id = list.id();
    /// ui.ui_mut().animate(id);
    /// ```
    ///
    /// Split that way because the two halves have different owners: the
    /// velocity is the list's business, and whether anything animates at
    /// all is the frame loop's. Missing the second call is what a finger
    /// fling did on Iris's phone for two builds -- the velocity was right
    /// and nothing ever advanced it, which looks exactly like a list that
    /// stops dead under the finger. A caller driving frames itself
    /// (`bench_client.rs`'s fling phase, the headless tests) calls
    /// `tick_fling` directly instead and does not register.
    pub fn fling(&mut self, velocity_px_per_s: f32) {
        // A NaN/inf velocity (a `VelocityTracker::velocity()` divide-by-
        // near-zero span, or a caller passing a raw device value straight
        // through) would propagate silently into `deceleration_for`'s
        // `.ln()` -- the fling either never settles or jumps to NaN
        // positions with nothing on screen saying why (docs/
        // REVIEW-2026-09-06.md finding 3).
        debug_assert!(velocity_px_per_s.is_finite());
        if velocity_px_per_s == 0.0 || self.anchor.is_none() {
            self.fling = None;
            return;
        }
        self.fling = Some(Fling {
            calc: FlingCalculator::new(self.density),
            velocity: velocity_px_per_s,
            started_at: None,
            applied: 0.0,
        });
    }
    /// Whether a fling is currently animating. What a caller's own
    /// per-frame loop polls to know when to stop driving `tick_fling`
    /// (`bench_client.rs`'s fling phase) or to decide whether the list is
    /// "moving on its own" for any other purpose.
    pub fn is_scrolling(&self) -> bool {
        self.fling.is_some()
    }
    /// The velocity a fling in progress is coasting at, in this list's
    /// own pixel space -- `None` when nothing is flinging. What a
    /// release's decision looks like from the outside: a
    /// `GestureOutcome::Released(Some(v))` is the only thing that puts a
    /// value here, so a test (or a diagnostic) can read what the gesture
    /// measured at the place it landed, rather than re-timing the
    /// gesture itself.
    pub fn fling_velocity(&self) -> Option<f32> {
        self.fling.as_ref().map(|f| f.velocity)
    }
    /// Cancel any fling in progress with no further movement -- the next
    /// touch-down's job, per `fling`'s own doc.
    pub fn cancel_fling(&mut self) {
        self.fling = None;
    }
    /// Advance an in-flight fling to `now`, applying this call's share of
    /// its total travel via `scroll` and re-arming this list's own redraw
    /// handle (if it has one) for another frame. Returns whether the
    /// fling is still going after this call -- `false` either because it
    /// settled on its own spline-decided schedule or because it reached
    /// `at_start`/`at_end` (the module doc's clamp: a fling must not carry
    /// the list past content that does not exist, unlike an ordinary
    /// touch-pan, which this widget already leaves unclamped by design).
    ///
    /// Safe to call even with no fling active (a no-op returning `false`),
    /// so a caller does not need to check `is_scrolling` first.
    pub fn tick_fling(&mut self, now: Instant) -> bool {
        let Some(f) = &mut self.fling else {
            return false;
        };
        let elapsed = now.saturating_duration_since(*f.started_at.get_or_insert(now));
        let target = f.calc.position_at(f.velocity, elapsed);
        let delta = target - f.applied;
        f.applied = target;
        let settled_on_schedule = elapsed >= f.calc.duration(f.velocity);
        let velocity = f.velocity;
        // The evidence that the spline is actually being followed, at the
        // one granularity where a linear coast and a decelerating one look
        // different: successive `dy` and `speed` shrinking. It was neither
        // observable nor observed while `distance_fraction` returned `t`
        // (`android_fling_spline`'s doc), which is why this is here rather
        // than the total-travel line the release log already carries.
        log::debug!(
            "iris fling tick: t={:.3}s dy={:+.1}px speed={:.0}px/s of {:.0} left={:.1}px",
            elapsed.as_secs_f32(),
            delta,
            f.calc.velocity_at(velocity, elapsed),
            velocity,
            f.calc.distance(velocity) - target,
        );
        self.scroll(delta);
        // Clamp: a fling moving toward the start that has already reached
        // it (or one moving toward the end that has already reached that)
        // stops rather than continuing to spend its remaining distance on
        // a part of the list that will never scroll further.
        let hit_bound = (velocity < 0.0 && self.at_start) || (velocity > 0.0 && self.at_end);
        if settled_on_schedule || hit_bound {
            self.fling = None;
            return false;
        }
        if let Some(redraw) = &self.redraw {
            redraw.request_redraw();
        }
        true
    }
    /// The anchor's own row index and pixel offset, formatted the same
    /// shape Compose's `firstVisibleItemIndex`/`firstVisibleItemScrollOffset`
    /// report (`idx=N/off=Mpx`) -- what RUST.md's "Benchmark v2" fling
    /// phase reads before/after/between its fling runs so the two apps'
    /// travel can be compared directly. `more_before`/`more_after`
    /// sentinels print as `idx=more-before`/`idx=more-after` rather than
    /// leaking their internal `isize` representation; `idx=none` if the
    /// list has never drawn (no anchor yet -- e.g. right after
    /// `jump_to_end` and before the next frame runs `repair_anchor`).
    pub fn anchor_position_display(&self) -> String {
        match self.anchor {
            None => "idx=none".to_string(),
            Some(a) if a.slot == BEFORE_SLOT => "idx=more-before".to_string(),
            Some(a) if a.slot == AFTER_SLOT => "idx=more-after".to_string(),
            Some(a) => format!("idx={}/off={}px", a.slot, a.offset.round() as i64),
        }
    }
    /// Snap to the newest content (last item, or the `more_after`
    /// sentinel if set), bottom-aligned to the viewport. O(1).
    pub fn jump_to_end(&mut self) {
@@ -372,6 +630,20 @@ impl List {
        self.extents.get(&key).map(|e| (e.top, e.bottom))
    }
    /// The row whose on-screen box (as of the last layout) contains
    /// `viewport_pos`, or `None` if it falls outside every row currently
    /// drawn (a gap, a header, or off the loaded content entirely). O
    /// (visible rows), same as `reanchor_at_tap`. What a caller resolves a
    /// pointer-captured gesture's row-under-the-finger against once the
    /// gesture is no longer being delivered through any one row's own hit
    /// region -- see `iris::sense`'s pointer-capture doc.
    pub fn key_at(&self, viewport_pos: f32) -> Option<RowKey> {
        self.extents
            .iter()
            .find(|(_, ext)| viewport_pos >= ext.top && viewport_pos <= ext.bottom)
            .map(|(&key, _)| key)
    }
    fn slot_exists(&self, slot: isize) -> bool {
        match slot {
            BEFORE_SLOT => self.more_before.is_some(),
@@ -569,12 +841,24 @@ impl List {
    /// one-frame lag `Scroll`'s own content-length cache accepts, per
    /// LAYOUT.md.
    fn place(&mut self, painter: &mut Painter, slot: isize, placement: Placement) -> (f32, f32) {
        // Every current caller derives `slot` from `repair_anchor`/
        // `prev_slot`/`next_slot`, which already check existence -- but
        // that invariant is enforced by convention across three call
        // sites, not by this function, which would otherwise fail with a
        // bare "index out of bounds" and no context (docs/
        // REVIEW-2026-09-06.md finding 2). `slot_widget`, called from
        // here, is what actually indexes/`.expect`s on it.
        debug_assert!(
            self.slot_exists(slot),
            "place() called with a slot that doesn't exist: {slot:?}"
        );
        let axis = self.axis;
        let output_len = painter.output_size().axis(axis);
        let container_len = painter.region().axis(axis).len();
        let density = painter.density();
        let resolve = move |used: Size| -> f32 {
            used.axis(axis)
-                .apply_rest()
+                .apply_rest(density)
                .within_len(container_len)
                .to_abs(output_len)
        };
@@ -663,8 +947,20 @@ impl List {
 const GENEROUS_PADDING: f32 = 100_000.0;
 impl Widget for List {
    /// A `List` animates exactly one thing, a fling
    /// ([`Self::tick_fling`]). The registration that makes this run is
    /// `UiData::animate` beside the `fling` call -- see `fling`'s own doc.
    fn tick(&mut self, now: Instant) -> bool {
        self.tick_fling(now)
    }
    fn draw(&mut self, painter: &mut Painter) -> Size {
        let axis = self.axis;
        // Learned from the frame rather than passed in: a fling's
        // deceleration is a physical quantity and needs the real display
        // density, and `draw` is where this widget meets the only thing
        // that knows it. See `fling`.
        self.density = painter.density();
        let output_len = painter.output_size().axis(axis);
        self.viewport_len = painter.region().axis(axis).len().to_abs(output_len);
@@ -690,26 +986,33 @@ impl Widget for List {
        };
        let (mut top, mut bottom) = self.place(painter, anchor.slot, placement);
-        let mut idx = anchor.slot;
+        let mut idx_top = anchor.slot;
        while top > 0.0 {
-            let Some(prev) = self.prev_slot(idx) else {
+            let Some(prev) = self.prev_slot(idx_top) else {
                break;
            };
            let (t, _) = self.place(painter, prev, Placement::Bottom(top));
            top = t;
-            idx = prev;
+            idx_top = prev;
        }
-        idx = anchor.slot;
+        let mut idx_bottom = anchor.slot;
        while bottom < self.viewport_len {
-            let Some(next) = self.next_slot(idx) else {
+            let Some(next) = self.next_slot(idx_bottom) else {
                break;
            };
            let (_, b) = self.place(painter, next, Placement::Top(bottom));
            bottom = b;
-            idx = next;
+            idx_bottom = next;
        }
        // What `tick_fling` clamps a fling against -- see `at_start`'s
        // field doc. `top`/`bottom` are the extreme edges actually placed
        // this frame, and `prev_slot`/`next_slot` returning `None` is what
        // "no more content" means everywhere else in this widget.
        self.at_start = self.prev_slot(idx_top).is_none() && top >= 0.0;
        self.at_end = self.next_slot(idx_bottom).is_none() && bottom <= self.viewport_len;
        self.update_snap_end();
        Size::REST
    }
@@ -884,7 +1187,7 @@ mod tests {
                .push_front(ListRow::new(key, w));
        }
        render.update(&root, &mut rsc);
-        let (draws, _rewrites, _moves) = render.take_counters();
+        let (draws, _rewrites, _moves, _shapes) = render.take_counters();
        // None of the already-visible rows (11, 12) were touched: the
        // extents for those keys are numerically unchanged, and the only
@@ -1022,7 +1325,7 @@ mod tests {
            rsc.ui.widgets.get_mut(&list_weak).unwrap().scroll(5.0);
            render.update(&root, &mut rsc);
-            let (draws, _rewrites, moves) = render.take_counters();
+            let (draws, _rewrites, moves, _shapes) = render.take_counters();
            // The visible window is a fixed ~10 rows regardless of n; an
            // O(n) regression would show up as draws/moves scaling with
@@ -1032,4 +1335,570 @@ mod tests {
            assert!(moves <= 12, "n={n}: expected O(visible) moves, got {moves}");
        }
    }
    /// The streamed-reply case (RUST.md's "streaming still costs a full
    /// rebuild" fix, `transcript-ui::TranscriptScreen::apply`): a delta
    /// swaps the last row's widget for a taller one, same key, same slot.
    /// A list flush with its own end (the default, `snap_end`) must stay
    /// flush -- the row grows *upward* from the pinned bottom edge, not
    /// the other way around, exactly like an ordinary resize of that same
    /// row would (`expanding_a_row_holds_the_bottom_edge_when_tap_is_lower`).
    #[test]
    fn replacing_the_last_row_stays_pinned_to_the_bottom() {
        let mut rsc = TestRsc {
            ui: UiData::default(),
        };
        let mut list = List::new(Axis::Y);
        push_rows(&mut rsc, &mut list, &[0, 1, 2, 3, 4], 20.0);
        let (list_weak, root) = add_list(&mut rsc, list);
        let mut render = UiRenderState::new();
        render.resize((100.0, 60.0));
        render.update(&root, &mut rsc);
        // Row 4 is flush with the viewport's bottom edge before the replace.
        {
            let list_ref = rsc.ui.widgets.get(&list_weak).unwrap();
            assert!((list_ref.extents[&4].bottom - 60.0).abs() < 0.01);
        }
        let (_weak, new_row) = fixed_row(&mut rsc, 40.0);
        let old = rsc
            .ui
            .widgets
            .get_mut(&list_weak)
            .unwrap()
            .replace_back(ListRow::new(4, new_row));
        assert!(
            old.is_some(),
            "replace_back should hand back the row it evicted"
        );
        render.update(&root, &mut rsc);
        let list_ref = rsc.ui.widgets.get(&list_weak).unwrap();
        let row4 = list_ref.extents[&4];
        assert!(
            (row4.bottom - 60.0).abs() < 0.01,
            "still pinned to the newest end after the replace: {row4:?}"
        );
        assert!(
            (row4.top - 20.0).abs() < 0.01,
            "grew upward, from the pinned bottom edge: {row4:?}"
        );
    }
    /// Neither `replacing_the_last_row_stays_pinned_to_the_bottom` nor
    /// its sibling below ever asserts the *evicted* key's own bookkeeping
    /// is actually gone -- both replace row 4 with another row also keyed
    /// `4`, so `heights.remove(&old.key)` removing and re-inserting the
    /// same key would pass either test even if it did nothing (docs/
    /// REVIEW-2026-09-06.md finding 10; this is `Selection`'s finding 1
    /// class of bug -- a stale handle outliving what it points to --
    /// production-tested from `List`'s own side). Replacing with a
    /// **different** key is what actually exercises the removal.
    #[test]
    fn replace_back_forgets_the_evicted_keys_own_height() {
        let mut rsc = TestRsc {
            ui: UiData::default(),
        };
        let mut list = List::new(Axis::Y);
        push_rows(&mut rsc, &mut list, &[0, 1, 2, 3, 4], 20.0);
        let (list_weak, root) = add_list(&mut rsc, list);
        let mut render = UiRenderState::new();
        render.resize((100.0, 60.0));
        render.update(&root, &mut rsc);
        assert!(
            rsc.ui
                .widgets
                .get(&list_weak)
                .unwrap()
                .heights
                .contains_key(&4)
        );
        let (_weak, new_row) = fixed_row(&mut rsc, 40.0);
        let old = rsc
            .ui
            .widgets
            .get_mut(&list_weak)
            .unwrap()
            .replace_back(ListRow::new(100, new_row));
        let list_ref = rsc.ui.widgets.get(&list_weak).unwrap();
        assert_eq!(old.map(|o| o.key), Some(4));
        assert!(
            !list_ref.heights.contains_key(&4),
            "the evicted key's cached height must not outlive the row it measured"
        );
    }
    /// The other half of the same fix's contract: replacing a row that is
    /// *not* on screen must not move anything that is. `replace_back` only
    /// touches the last slot's own widget and this file's own `heights`/
    /// `extents` caches for that one key -- nothing about `Anchor` changes
    /// -- so the already-placed rows above it should come out at the exact
    /// same boxes on the next frame.
    #[test]
    fn replacing_the_last_row_out_of_view_does_not_move_visible_rows() {
        let mut rsc = TestRsc {
            ui: UiData::default(),
        };
        let mut list = List::new(Axis::Y);
        push_rows(&mut rsc, &mut list, &[0, 1, 2, 3, 4], 20.0);
        let (list_weak, root) = add_list(&mut rsc, list);
        let mut render = UiRenderState::new();
        render.resize((100.0, 60.0));
        // Settle at the default (bottom) anchor first -- `jump_to_start`
        // does not touch `snap_end`, and `repair_anchor` only leaves a
        // freshly-set anchor's offset alone once `viewport_len` has
        // already matched `last_viewport_len` once, the same reason
        // `moves_stay_o1_across_list_size` settles before the tick it
        // actually measures.
        render.update(&root, &mut rsc);
        // Scrolled to the oldest content: rows 0,1,2 visible, row 4 is far
        // below the viewport.
        rsc.ui.widgets.get_mut(&list_weak).unwrap().jump_to_start();
        render.update(&root, &mut rsc);
        let (before0, before1, before2) = {
            let list_ref = rsc.ui.widgets.get(&list_weak).unwrap();
            assert!(!list_ref.extents.contains_key(&4));
            (
                list_ref.extents[&0],
                list_ref.extents[&1],
                list_ref.extents[&2],
            )
        };
        let (_weak, new_row) = fixed_row(&mut rsc, 999.0);
        rsc.ui
            .widgets
            .get_mut(&list_weak)
            .unwrap()
            .replace_back(ListRow::new(4, new_row));
        render.update(&root, &mut rsc);
        let list_ref = rsc.ui.widgets.get(&list_weak).unwrap();
        for (key, before) in [(0u64, before0), (1, before1), (2, before2)] {
            let after = list_ref.extents[&key];
            assert_eq!(
                (after.top, after.bottom),
                (before.top, before.bottom),
                "row {key} moved after an off-screen replace"
            );
        }
    }
    /// RUST.md's P0 phone report (Iris's screenshot, 2026-09-06): a
    /// replaced row's primitives drawn a second time, overlapping the
    /// replacement. Reproduces the exact path `TranscriptScreen::apply`'s
    /// `ReplaceLast` case drives up to 400 times during a streamed reply
    /// (`bench_client.rs`'s stream phase): the last slot's widget is
    /// swapped for a brand-new one, same key, and (since a fresh widget
    /// has no cached height) placed via `place`'s `draw_twice` path every
    /// time -- the provisional-then-real two-draw sequence LAYOUT.md
    /// documents as the one place in this crate that deliberately draws a
    /// widget twice. If `draw_inner`'s old-children diffing or
    /// `UiRenderState::remove`'s primitive freeing ever failed to retire
    /// the evicted widget (or the provisional draw's own primitives), it
    /// would show up here as `active_widgets` growing without bound.
    /// **Passes as written** -- this pins the widget-arena layer as
    /// correct in isolation; see the P0 box for where the duplicate was
    /// actually chased to instead (`Span`'s two-phase draw and the
    /// `redraw_all`-vs-`redraw_updates` split, still open).
    #[test]
    fn replacing_the_last_row_many_times_does_not_leak_primitives() {
        let mut rsc = TestRsc {
            ui: UiData::default(),
        };
        let mut list = List::new(Axis::Y);
        for key in 0..5u64 {
            let (_bg_id, row) = background_styled_row(&mut rsc, 20.0);
            list.push_back(ListRow::new(key, row));
        }
        let (list_weak, root) = add_list(&mut rsc, list);
        let mut render = UiRenderState::new();
        render.resize((100.0, 100.0));
        render.update(&root, &mut rsc);
        let before = render.active_widgets();
        for i in 0..400u32 {
            // A varying height keeps every replace on the `draw_twice`
            // (cache-miss) path rather than settling into the O(1)
            // same-size `mov` fast path once the height happens to repeat.
            let (_bg_id, new_row) = background_styled_row(&mut rsc, 20.0 + (i % 3) as f32);
            rsc.ui
                .widgets
                .get_mut(&list_weak)
                .unwrap()
                .replace_back(ListRow::new(4, new_row));
            render.update(&root, &mut rsc);
        }
        let after = render.active_widgets();
        assert_eq!(
            before, after,
            "400 replaces of the last row must leave exactly the same \
             number of active widgets as before a leaked id (and the \
             primitives that live as long as its ActiveData does) would \
             show up here as growth"
        );
    }
    /// The doubled `Compacted:` row from Iris's phone (docs/bench/
    /// iris-phone-v2-2026-09-06.md), reproduced at its mechanism.
    ///
    /// `replacing_the_last_row_many_times_does_not_leak_primitives` above
    /// counts *widgets*, which is why it passed all along: the orphan's
    /// owner is very much alive -- it is an earlier set of that same
    /// widget's primitives that got stranded. What strands them is a row
    /// marked dirty and then reached by its **ancestor's** redraw rather
    /// than by its own: `draw_inner` only *read* the dirty mark, so the
    /// whole branch that frees a redrawn widget's previous primitives was
    /// skipped, and the fresh `ActiveData` overwrote the only handles that
    /// could ever have freed them. `List` sets no mask, so that copy then
    /// draws every frame at whatever region it last had -- including,
    /// where the row was being measured at `GENEROUS_PADDING`, well below
    /// the list's own box and under the composer.
    ///
    /// Two rows, two shapes of the same fault: row 2 has a cached height
    /// (one `widget_within`), row 4 is replaced so it has none (`place`'s
    /// `draw_twice`, which reaches `draw_inner` twice for one id in one
    /// frame and so orphans a copy even with no ancestor involved).
    #[test]
    fn an_ancestor_redrawing_a_dirty_row_leaves_no_stale_copy() {
        let mut rsc = TestRsc {
            ui: UiData::default(),
        };
        let mut list = List::new(Axis::Y);
        // Rows that own a primitive *at their own id* (a background rect),
        // not only through a child: an orphan is a widget's own primitive
        // outliving its own redraw, so a row whose top-level widget paints
        // nothing itself cannot show one however broken the path is.
        let mut rows = Vec::new();
        for key in 0..5u64 {
            let (bg_id, row) = background_styled_row(&mut rsc, 20.0);
            rows.push((row.id(), bg_id));
            list.push_back(ListRow::new(key, row));
        }
        let (list_weak, root) = add_list(&mut rsc, list);
        let mut render = UiRenderState::new();
        render.resize((100.0, 100.0));
        render.update(&root, &mut rsc);
        assert!(render.orphaned_primitives().is_empty());
        // A streamed row's content changing: the row is marked dirty (any
        // `.set()` on it does this)...
        let (row2, row2_bg) = rows[2];
        rsc.ui.widgets.get_dyn_mut(row2).unwrap();
        rsc.ui.widgets.get_dyn_mut(row2_bg).unwrap();
        // Redraw the *list* by name, so the dirty row is reached by its
        // ancestor's draw rather than by `redraw_updates` happening to
        // pick it first -- which is the order `HashSet` iteration makes
        // arbitrary, and the reason this went unnoticed.
        render.redraw(list_weak.id(), &mut rsc);
        let orphans = render.orphaned_primitives();
        assert!(
            orphans.is_empty(),
            "{} primitive(s) survived their own widget's redraw: {orphans:?}",
            orphans.len(),
        );
    }
    /// Enough rows, tall enough, that a fling toward the start has real
    /// room to travel before `at_start` clamps it -- shared by the fling
    /// tests below.
    fn build_flingable_list(rsc: &mut TestRsc) -> (WeakWidget<List>, StrongWidget, UiRenderState) {
        let mut list = List::new(Axis::Y);
        push_rows(rsc, &mut list, &(0..200).collect::<Vec<_>>(), 20.0);
        let (list_weak, root) = add_list(rsc, list);
        let mut render = UiRenderState::new();
        render.resize((100.0, 600.0));
        render.update(&root, rsc);
        (list_weak, root, render)
    }
    #[test]
    fn fling_moves_the_list_and_then_settles() {
        let mut rsc = TestRsc {
            ui: UiData::default(),
        };
        let (list_weak, root, mut render) = build_flingable_list(&mut rsc);
        // A fling toward the start: negative velocity, matching `scroll`'s
        // sign convention (`Selection::drag` calls `scroll(-dy)` for a
        // downward finger motion revealing older content).
        rsc.ui.widgets.get_mut(&list_weak).unwrap().fling(-8000.0);
        assert!(rsc.ui.widgets.get(&list_weak).unwrap().is_scrolling());
        let start = Instant::now();
        let mut last_still_scrolling = true;
        for step in 0..600 {
            let now = start + std::time::Duration::from_millis(step * 16);
            last_still_scrolling = rsc.ui.widgets.get_mut(&list_weak).unwrap().tick_fling(now);
            render.update(&root, &mut rsc);
            if !last_still_scrolling {
                break;
            }
        }
        assert!(
            !last_still_scrolling,
            "fling never settled within 600 steps"
        );
        assert!(!rsc.ui.widgets.get(&list_weak).unwrap().is_scrolling());
    }
    /// The half `fling` itself does not do: a registered list is advanced
    /// by the frame loop's own driver, and unregisters itself when the
    /// fling settles. Written against `UiData::tick_animations` rather
    /// than `tick_fling` because the defect it pins is exactly the gap
    /// between the two -- a fling with a correct velocity that nothing
    /// ever advanced, which is what a finger fling did on the phone.
    #[test]
    fn a_registered_fling_is_driven_by_tick_animations_and_then_unregisters() {
        let mut rsc = TestRsc {
            ui: UiData::default(),
        };
        let (list_weak, root, mut render) = build_flingable_list(&mut rsc);
        let before = rsc
            .ui
            .widgets
            .get(&list_weak)
            .unwrap()
            .anchor_position_display();
        rsc.ui.widgets.get_mut(&list_weak).unwrap().fling(-8000.0);
        rsc.ui.animate(list_weak.id());
        let start = Instant::now();
        let mut animating = true;
        let mut steps = 0;
        while animating && steps < 600 {
            animating = rsc
                .ui
                .tick_animations(start + std::time::Duration::from_millis(steps * 16));
            render.update(&root, &mut rsc);
            steps += 1;
        }
        assert!(!animating, "the driver never stopped within 600 frames");
        assert!(steps > 1, "the fling settled without ever moving");
        assert!(!rsc.ui.widgets.get(&list_weak).unwrap().is_scrolling());
        assert_ne!(
            before,
            rsc.ui
                .widgets
                .get(&list_weak)
                .unwrap()
                .anchor_position_display(),
            "the list is where it started -- the fling was registered but never applied"
        );
        // Nothing left registered, so the next frame costs nothing: the
        // path out of `animate` is the `false` answer, not a caller
        // remembering to remove it.
        assert!(!rsc.ui.tick_animations(start));
    }
    #[test]
    fn fling_distance_is_positive_toward_the_end() {
        let mut rsc = TestRsc {
            ui: UiData::default(),
        };
        let (list_weak, root, mut render) = build_flingable_list(&mut rsc);
        // Start scrolled away from the newest end so there is room for an
        // end-ward fling to actually move.
        rsc.ui.widgets.get_mut(&list_weak).unwrap().jump_to_start();
        render.update(&root, &mut rsc);
        let before = rsc.ui.widgets.get(&list_weak).unwrap().extents[&0];
        rsc.ui.widgets.get_mut(&list_weak).unwrap().fling(8000.0);
        let start = Instant::now();
        for step in 0..600 {
            let now = start + std::time::Duration::from_millis(step * 16);
            let still = rsc.ui.widgets.get_mut(&list_weak).unwrap().tick_fling(now);
            render.update(&root, &mut rsc);
            if !still {
                break;
            }
        }
        let list_ref = rsc.ui.widgets.get(&list_weak).unwrap();
        // Row 0 either scrolled out of the loaded extents (flung well past
        // it) or moved upward (smaller top) -- either way, real motion
        // happened toward the end rather than staying put.
        if let Some(after) = list_ref.extents.get(&0) {
            assert!(
                after.top < before.top,
                "fling toward the end did not move content up"
            );
        }
    }
    /// `fling_moves_the_list_and_then_settles`/
    /// `fling_distance_is_positive_toward_the_end` only check that a fling
    /// started, moved the right way and eventually stopped -- both
    /// unaffected by *how* the interior ticks split up the total travel
    /// (docs/REVIEW-2026-09-06.md finding 9). A regression that made
    /// `tick_fling` apply the whole spline distance every tick instead of
    /// just this tick's incremental slice would still pass both, while
    /// being wildly wrong every intermediate frame -- this pins the
    /// per-tick delta to a decelerating curve (`FlingCalculator::
    /// position_at`'s own monotonic-and-clamped property, one level
    /// down, already covers the calculator alone; this is the same
    /// property through `List::tick_fling`'s `scroll`/`extents`
    /// accumulation).
    #[test]
    fn tick_fling_applies_shrinking_incremental_deltas() {
        let mut rsc = TestRsc {
            ui: UiData::default(),
        };
        let (list_weak, root, mut render) = build_flingable_list(&mut rsc);
        rsc.ui.widgets.get_mut(&list_weak).unwrap().jump_to_start();
        render.update(&root, &mut rsc);
        rsc.ui.widgets.get_mut(&list_weak).unwrap().fling(8000.0);
        let start = Instant::now();
        let mut prev_top = rsc.ui.widgets.get(&list_weak).unwrap().extents[&0].top;
        let mut deltas = Vec::new();
        for step in 1..600 {
            let now = start + std::time::Duration::from_millis(step * 16);
            let still = rsc.ui.widgets.get_mut(&list_weak).unwrap().tick_fling(now);
            render.update(&root, &mut rsc);
            let Some(top) = rsc
                .ui
                .widgets
                .get(&list_weak)
                .unwrap()
                .extents
                .get(&0)
                .map(|e| e.top)
            else {
                break; // row 0 scrolled out of the loaded extents
            };
            deltas.push((prev_top - top).abs());
            prev_top = top;
            if !still {
                break;
            }
        }
        assert!(
            deltas.len() >= 3,
            "fling settled or left row 0's extent before collecting enough samples"
        );
        // Skip the first tick (the slop-transition jump the arbiter
        // applies is a `List::fling`-adjacent concern, not this curve,
        // but the very first frame can still carry rounding noise from
        // `jump_to_start`'s own layout settling).
        for w in deltas[1..].windows(2) {
            assert!(
                w[1] <= w[0] + 0.01,
                "fling's per-tick delta grew instead of decelerating: {:?} then {:?}",
                w[0],
                w[1]
            );
        }
        // Non-increasing is not deceleration: a fling that coasts at a
        // constant speed and then stops dead satisfies every `<=` above,
        // and that is exactly what iris shipped until 2026-09-07
        // (`android_fling_spline`'s doc). Over the samples collected here
        // -- the earliest part of the curve, since row 0 leaves the loaded
        // extents soon after -- AOSP's spline has already lost more than
        // a fifth of its speed.
        let (first, last) = (deltas[1], *deltas.last().unwrap());
        assert!(
            last < first * 0.8,
            "fling barely slowed across {} ticks: {first} -> {last}",
            deltas.len()
        );
    }
    #[test]
    fn cancel_fling_stops_it_with_no_further_movement() {
        let mut rsc = TestRsc {
            ui: UiData::default(),
        };
        let (list_weak, root, mut render) = build_flingable_list(&mut rsc);
        rsc.ui.widgets.get_mut(&list_weak).unwrap().fling(-8000.0);
        let start = Instant::now();
        rsc.ui
            .widgets
            .get_mut(&list_weak)
            .unwrap()
            .tick_fling(start + std::time::Duration::from_millis(16));
        render.update(&root, &mut rsc);
        assert!(rsc.ui.widgets.get(&list_weak).unwrap().is_scrolling());
        rsc.ui.widgets.get_mut(&list_weak).unwrap().cancel_fling();
        assert!(!rsc.ui.widgets.get(&list_weak).unwrap().is_scrolling());
        let before = rsc.ui.widgets.get(&list_weak).unwrap().extents[&199];
        // A tick after cancelling must be a no-op -- this is what a fresh
        // touch-down relies on to stop a fling in its tracks.
        let still = rsc
            .ui
            .widgets
            .get_mut(&list_weak)
            .unwrap()
            .tick_fling(start + std::time::Duration::from_millis(200));
        render.update(&root, &mut rsc);
        assert!(!still);
        let after = rsc.ui.widgets.get(&list_weak).unwrap().extents[&199];
        assert_eq!((before.top, before.bottom), (after.top, after.bottom));
    }
    #[test]
    fn fling_toward_the_start_stops_at_the_first_row() {
        let mut rsc = TestRsc {
            ui: UiData::default(),
        };
        let (list_weak, root, mut render) = build_flingable_list(&mut rsc);
        // An enormous velocity that would travel far past all 200 rows if
        // unclamped -- this is exactly what IRIS_TODO.md's "way faster...
        // better for stress testing" fling asks for.
        rsc.ui.widgets.get_mut(&list_weak).unwrap().fling(-50_000.0);
        let start = Instant::now();
        for step in 0..2000 {
            let now = start + std::time::Duration::from_millis(step * 16);
            let still = rsc.ui.widgets.get_mut(&list_weak).unwrap().tick_fling(now);
            render.update(&root, &mut rsc);
            if !still {
                break;
            }
        }
        let list_ref = rsc.ui.widgets.get(&list_weak).unwrap();
        assert!(
            list_ref.at_start,
            "fling should have clamped at the first row"
        );
        let first = list_ref.extents[&0];
        assert!(
            first.top >= -0.5,
            "clamped fling overshot the first row's top: {}",
            first.top
        );
    }
    #[test]
    fn anchor_position_display_before_any_draw_is_none() {
        let list = List::new(Axis::Y);
        assert_eq!(list.anchor_position_display(), "idx=none");
    }
    #[test]
    fn anchor_position_display_reports_slot_and_offset() {
        let mut rsc = TestRsc {
            ui: UiData::default(),
        };
        let (list_weak, root, mut render) = build_flingable_list(&mut rsc);
        let _ = (&root, &mut render);
        let list_ref = rsc.ui.widgets.get(&list_weak).unwrap();
        assert!(list_ref.anchor_position_display().starts_with("idx="));
        assert!(!list_ref.anchor_position_display().contains("none"));
    }
 }
@@ -17,14 +17,15 @@ impl Widget for Aligned {
        // already-resolved region double-applies that composition and is
        // wrong for any widget nested below the root.
        let used = painter.widget(&self.inner);
        let density = painter.density();
        let region = match self.align.tuple() {
-            (Some(x), Some(y)) => used.to_uivec2().align(RegionAlign { x, y }),
+            (Some(x), Some(y)) => used.to_uivec2(density).align(RegionAlign { x, y }),
            (Some(x), None) => {
-                let x = used.x.apply_rest().align(x);
+                let x = used.x.apply_rest(density).align(x);
                UiRegion::new(x, UiSpan::FULL)
            }
            (None, Some(y)) => {
-                let y = used.y.apply_rest().align(y);
+                let y = used.y.apply_rest(density).align(y);
                UiRegion::new(UiSpan::FULL, y)
            }
            (None, None) => UiRegion::FULL,
@@ -9,13 +9,20 @@ pub struct MaxSize {
 impl MaxSize {
    /// Caps a reported length at `max`, comparing in pixels since `Len`'s
    /// rel/abs/rest components are not otherwise comparable.
-    fn clamp(len: Len, max: Option<Len>, output: f32) -> Len {
+    fn clamp(len: Len, max: Option<Len>, output: f32, density: f32) -> Len {
        let Some(max) = max else {
            return len;
        };
-        let len_px = len.apply_rest().to_abs(output);
+        let len_px = len.apply_rest(density).to_abs(output);
-        let max_px = max.apply_rest().to_abs(output);
+        let max_px = max.apply_rest(density).to_abs(output);
-        if len_px > max_px { max } else { len }
+        // `fold_dp`, not the caller's `max` as written: a reported `Len`
        // may not carry an unresolved `dp` -- see `Len::fold_dp` for the
        // collapsed composer bar this caused.
        if len_px > max_px {
            max.fold_dp(density)
        } else {
            len
        }
    }
    /// The span (in this widget's own local, `UiRegion::FULL`-relative
@@ -24,11 +31,11 @@ impl MaxSize {
    /// start, if it does not. Needed so the child is never painted bigger
    /// than the size this widget reports for it -- see the identical
    /// requirement noted on `Sized::draw`.
-    fn clamp_region(offered_px: f32, max: Option<Len>, output: f32) -> UiSpan {
+    fn clamp_region(offered_px: f32, max: Option<Len>, output: f32, density: f32) -> UiSpan {
        let Some(max) = max else {
            return UiSpan::FULL;
        };
-        let max_scalar = max.apply_rest();
+        let max_scalar = max.apply_rest(density);
        let max_px = max_scalar.to_abs(output);
        if offered_px > max_px {
            max_scalar.align(AxisAlign::Neg)
@@ -41,15 +48,16 @@ impl MaxSize {
 impl Widget for MaxSize {
    fn draw(&mut self, painter: &mut Painter) -> Size {
        let output = painter.output_size();
        let density = painter.density();
        let offered = painter.px_size();
        let region = UiRegion {
-            x: Self::clamp_region(offered.x, self.x, output.x),
+            x: Self::clamp_region(offered.x, self.x, output.x, density),
-            y: Self::clamp_region(offered.y, self.y, output.y),
+            y: Self::clamp_region(offered.y, self.y, output.y, density),
        };
        let used = painter.widget_within(&self.inner, region);
        Size {
-            x: Self::clamp(used.x, self.x, output.x),
+            x: Self::clamp(used.x, self.x, output.x, density),
-            y: Self::clamp(used.y, self.y, output.y),
+            y: Self::clamp(used.y, self.y, output.y, density),
        }
    }
 }