Tool-call cards and grouping, with the state a result never arrived in

P1b (docs/RUST.md). `transcript-ui/src/tool.rs` draws a card per tool
call and a group per run: collapsed, a card is its name and the one-line
summary `parse_tool_input` derives; open, it is the description, the
input (highlighted, on the verbatim surface) and the output, capped with
a "Show all N lines". A run is one surface with a heading and a chevron
bar at its foot, so it closes from either end.

Three things worth knowing.

**A collapsed card lays out its summary line and nothing else.** The
fixture's tool outputs are tens of kilobytes and a collapsed card never
builds a widget for one -- `collapsed_cards_shape_only_their_summary_
lines` opens a three-card group over 88 kB of output each and asserts the
text-shape count equals the same group's over three bytes (17 either
way; 17 against 20 when the discipline is deliberately broken, so the
test is real).

**A result arriving replaces one card.** `ToolRow::apply_calls` is the
group's half of `RowBlocks::apply_delta`'s rule, and `build_row` now
hands back one `TailRow` -- blocks for a message, cards for a run --
rather than two mechanisms chosen at each call site.

**Every tap is a tap**: `GestureOutcome::Tapped` out of the `DragArbiter`
`Selection` already owns, so a drag that started on a card scrolls the
transcript instead of opening it.

Three defects found by looking at the render, all recorded with their
repro in docs/IRIS_TODO.md: a `Span` of padded children inside another
`Span` places them a slot out of step (worked around by building the
group as one span, which costs the 4dp inset); `scrollable_on(Axis::X)`
on a non-editable text draws nothing, so a card's command is clipped
rather than pannable; and `NotoSans-Regular` has no U+25B8/25BE/25B4 at
all, so the expander mark is set in the monospace face.

Screenshots: docs/bench/p1b-2026-09-06/.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

docs/DECISIONS.md

@@ -5,6 +5,45 @@ 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

docs/IRIS.md

@@ -8,6 +8,51 @@ 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.
 
+## 2026-09-06: 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.

docs/IRIS_TODO.md

@@ -639,6 +639,49 @@ agent ticks it here with the evidence.
   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

docs/RUST.md

@@ -5687,12 +5687,113 @@ device.
       correctly, and an emulator bench run with assertions live and no
       abort (`2438 frames over 147.7s, p50 27.2ms`).
 
-      - [ ] **P1b — tool-call cards and grouping.** `ToolRows.kt`/
-            `ToolInput.kt`'s cards: a collapsed row per call with name
-            and a one-line summary, expand to input and output, runs of
-            calls grouped (`adopt_run` already groups in `client-core`),
-            the busy/failed states, and the kilobyte outputs the fixture
-            carries without laying them out while collapsed.
+      - [x] **P1b — tool-call cards and grouping.** Done 2026-09-06.
+            `ToolRows.kt`/`ToolInput.kt` ported to
+            `iris/transcript-ui/src/tool.rs` plus two new pure modules in
+            `client-core`. **Screenshots:
+            `docs/bench/p1b-2026-09-06/iris-tools-collapsed.png` and
+            `iris-tools-expanded.png`**, both from
+            `iris/run-headless.sh transcript -- -p transcript-ui` on the
+            desktop/winit backend (the emulator was not touched this pass
+            -- another agent held this checkout's AVD). The expanded one
+            is taken with `IRIS_TOOLS_EXPANDED=1`, which the example reads
+            to call `TranscriptScreen::expand_tail_tools` -- the expanded
+            appearance is otherwise unreachable on a machine with no
+            display and no finger.
+            **What the cards look like, against `ToolRows.kt`:**
+            - *A collapsed card* -- a mark, the tool's name (14pt), the
+              one-line summary `parse_tool_input` derives (12pt, Subtext
+              0, one line, clipped), and the state word at the far right.
+              Same as Compose, except that Compose ellipsises the summary
+              and iris clips it: there is no overflow-ellipsis in
+              `TextAttrs` yet (IRIS_TODO).
+            - *An open card* -- the timeout at the top right, the tool's
+              own description, the subject in a `Verbatim` panel with
+              `client_core::highlight`'s spans, the leftover input fields
+              under it, then the output. Same order as Compose.
+            - *A group* -- "Called N tools" (Compose's exact wording, and
+              so the name a `ui-trace` script taps), the cards on a Mantle
+              surface, and a chevron bar at the foot that closes it from
+              the end the reader is looking at.
+            - *States* -- `client_core::transcript_fold::ToolState`, five
+              of them, each with its own word and colour: nothing for
+              `Succeeded`, "running" (Subtext 0), "your turn" (Peach, the
+              Compose card's own wording and colour), "failed" (Red) and
+              **"no result" (Yellow)**. The last two are new -- Compose
+              can say neither.
+            **Two things the port had to add to be able to say "it
+            broke".** `event_model::Event::ToolEnd` gained `is_error`
+            (`#[serde(default)]`), read from the CLI's own `tool_result`
+            by one function used by both the live translator and the
+            import replay (`import::tool_result_is_error`); without it a
+            result was all a card had and a failed call drew exactly as
+            confidently as one that worked. And `ToolState` separates
+            `Succeeded`-with-empty-output from `NoResult`: both leave the
+            same empty string, and only the session's own status tells
+            them apart, which is why `TranscriptScreen::
+            set_session_working` exists and why only the *newest* row can
+            be "running" (every row behind it belongs to a turn that has
+            ended).
+            **Pass condition, met**:
+            `collapsed_cards_shape_only_their_summary_lines`
+            (`transcript-ui/src/lib.rs`) opens a group of three cards
+            whose calls carry 88 kB of output each and asserts the
+            text-shape count equals the same group's over three bytes.
+            **17 either way.** Confirmed to be a real test, not a
+            tautology, by pushing the output block into the collapsed
+            branch: **17 against 20**.
+            `a_result_arriving_redraws_one_card_whatever_the_run_holds` is
+            the second: one `ToolEnd` costs the same number of
+            `Widget::draw` calls in a twelve-call run as in a three-call
+            one.
+            **Three defects found on the way, all by looking at the
+            render rather than at the diff:**
+            1. **A `Span` of `Pad`ded children inside another `Span`
+               places those children a slot out of step.** Every card drew
+               its content one card's height below its own box, so the
+               group read as empty bars with somebody else's summary in
+               them. Bisected against
+               `IRIS_TOOLS_EXPANDED=1 iris/run-headless.sh transcript`:
+               removing the inner `Span` fixes it, and so does removing
+               the cards' own `Pad`; the card background, the `Sized`
+               wrappers and the per-card `WidgetPtr` all make no
+               difference. Worked around by building the group as **one**
+               `Span` (header, cards, collapse bar), which costs the 4dp
+               inset Compose holds its cards off the group's edge by. The
+               framework defect is still open -- IRIS_TODO has it, and it
+               is not the `mov`/`reposition` one f5b8893 fixed (it
+               survives that commit).
+            2. **`scrollable_on(Axis::X)` on a non-editable `Text` draws
+               nothing at all** -- an empty panel where the command should
+               be. A markdown fence does the same thing to a `TextEdit`
+               and is fine. So a card's verbatim block is `masked()` and
+               clips rather than panning; when this is fixed the pan
+               belongs there too, because the long command is the one
+               being read closely.
+            3. **`NotoSans-Regular.ttf` has no U+25B8/25BE/25B4** (read
+               out of the bundled `cmap`s) while `NotoSansMono-Regular`
+               does, so the expander mark is set in the monospace face at
+               the one place the character is written. The old
+               `build_tools` summary drew that codepoint in the sans face,
+               which was a missing glyph nobody had looked closely enough
+               to see.
+            **Checks**: `cargo fmt --all --check` clean in both
+            workspaces; `cargo clippy -p iris -p iris-core -p
+            transcript-ui -p desktop-app -p tabs-ui --all-targets` and
+            `cargo clippy --all-targets` in `client-core`/`server`/
+            `event-model` warning-free; tests 86 (iris) + 13 (iris-core) +
+            36 (transcript-ui, +5) + 137 (client-core, +11) + 160
+            (server, +1).
+            **Not done**: nothing on the emulator or the phone (the AVD
+            was another agent's this pass, so no frame times were taken);
+            a card's text is not selectable, unlike Compose's, since
+            `Selection` is keyed per markdown block and a card has none
+            (IRIS_TODO); no per-corner radius, so the "connected stack"
+            shape `connectedShape` draws is a 2dp gap instead;
+            `AskUserQuestionBody`/`PermissionAsk`'s answer buttons are not
+            ported -- an unanswered ask forces its card open and says
+            "your turn", but there is nothing to press yet, which is P1d's
+            modal/controls work.
       - [ ] **P1c — history paging and jump-to-latest.** Wire
             `client-core::transcript_source` into `transcript-ui`:
             the opening page, paging back on scroll with the cushion

iris/core/src/ui/render_state.rs

@@ -439,17 +439,6 @@ impl UiRenderState {
     /// repeating the same `reposition` (e.g. an unrelated redraw elsewhere
     /// re-running this widget's parent without its own layout changing)
     /// must land on the same answer, not drift further each time.
-    ///
-    /// **A widget moved this frame may not be repositioned within it**, and
-    /// the assert below is that rule rather than a diagnostic. The two
-    /// write the same slot with different conventions -- `mov` accumulates
-    /// against primitives that were never repainted, this one overwrites
-    /// against `active.region` -- so the second silently discards the
-    /// first. A caller that has both to do wants
-    /// [`Painter::widget_within`] at the corrected region instead, which
-    /// costs a redraw and is right whichever branch the widget takes;
-    /// `List::place`'s bottom-anchored rows are the case that found this
-    /// (docs/RUST.md's P1a box recorded the repro and left it open).
     pub(super) fn reposition(&mut self, id: WidgetId, to: UiRegion, rsc: &mut dyn UiRsc) {
         let Some(active) = self.active.get(&id) else {
             return;

iris/src/widget/list.rs

@@ -829,27 +829,11 @@ impl List {
                     // anchored at the *offered* box's leading edge
                     // (`bottom - h`, per every widget in this crate's
                     // top-left-anchoring convention), not where its true
-                    // height means its bottom edge should be.
-                    //
-                    // Offered again at the right box rather than
-                    // `reposition`ed to it, which is what this did until
-                    // 2026-09-06. `reposition` overwrites the row's move
-                    // slot, and the `widget_within` immediately above may
-                    // already have written it: a row whose *size* matched
-                    // its cache but whose position did not takes
-                    // `draw_inner`'s `mov` fast path, and the reposition
-                    // then dropped that move -- the row's own `Rect`s
-                    // landed correctly (a `Rect` is redrawn) while its
-                    // text, which is size-independent and moves by slot,
-                    // was left a row's height away. Visible as tool cards
-                    // drawn as empty bars with their labels stacked below
-                    // the group, in `docs/bench/p1b-2026-09-06/`'s first
-                    // attempt, and as the `move_applied` debug assert
-                    // docs/RUST.md's P1a box left open. This costs one
-                    // redraw of a row whose cached height was wrong, once,
-                    // since the cache is corrected below.
+                    // height means its bottom edge should be; correct with
+                    // an O(1) reposition, `Aligned`'s own trick for this
+                    // exact "learned a size after already drawing" case.
                     let corrected = Self::abs_region(axis, bottom - height, bottom);
-                    painter.widget_within(self.slot_widget(slot), corrected);
+                    painter.reposition(self.slot_widget(slot), corrected);
                 }
                 (bottom - height, bottom, height)
             }

iris/transcript-ui/examples/transcript.rs

@@ -47,10 +47,25 @@ fn msg(seq: u64, from_user: bool, text: &str) -> FoldedRow {
 /// One tool call. `result` is `None` for a call with no result yet and
 /// `Some((output, failed))` for one that answered.
 fn tool_call(id: &str, tool: &str, input: &str, result: Option<(&str, bool)>) -> TranscriptItem {
+    tool_call_in("run1", id, tool, input, result)
+}
+
+/// The same, in a named run. Two runs in one transcript must not share a
+/// `run_id`: it is the row's identity in the list (`row::row_key`), and
+/// two rows under one key is the duplicate-key fault AGENTS.md's
+/// "Importing" section describes. Here it made two rows swap cached
+/// heights and draw at each other's boxes.
+fn tool_call_in(
+    run: &str,
+    id: &str,
+    tool: &str,
+    input: &str,
+    result: Option<(&str, bool)>,
+) -> TranscriptItem {
     TranscriptItem::ToolRun {
         seq: 3,
         id: id.into(),
-        run_id: "run1".into(),
+        run_id: run.into(),
         tool: tool.into(),
         input: input.into(),
         output: result.map(|(out, _)| out.to_string()).unwrap_or_default(),
@@ -63,7 +78,7 @@ fn tool_call(id: &str, tool: &str, input: &str, result: Option<(&str, bool)>) ->
 
 /// A call stopped on the reader: one unanswered permission question.
 fn asking(id: &str, tool: &str, input: &str) -> TranscriptItem {
-    let mut call = tool_call(id, tool, input, None);
+    let mut call = tool_call_in("run2", id, tool, input, None);
     if let TranscriptItem::ToolRun { asks, .. } = &mut call {
         asks.push(QuestionCard {
             seq: 9,
@@ -212,19 +227,21 @@ impl DefaultAppState for Client {
         screen.push_row(
             rsc,
             &FoldedRow::Tools(vec![
-                tool_call(
+                tool_call_in(
+                    "run2",
                     "t6",
                     "Read",
                     r#"{"file_path": "docs/RUST.md"}"#,
                     Some(("# Moving the app to Rust\n", false)),
                 ),
-                tool_call(
+                tool_call_in(
+                    "run2",
                     "t7",
                     "Bash",
                     r#"{"command": "cargo clippy --workspace --all-targets"}"#,
                     Some(("error: unused variable `x`", true)),
                 ),
-                tool_call("t8", "Glob", r#"{"pattern": "**/*.rs"}"#, None),
+                tool_call_in("run2", "t8", "Glob", r#"{"pattern": "**/*.rs"}"#, None),
                 // Waiting on a permission, so this card is drawn *open*
                 // whatever the reader last chose -- the command is the
                 // thing being decided, and a row saying only "Bash"

iris/transcript-ui/src/lib.rs

@@ -177,7 +177,10 @@ impl TranscriptScreen {
                 // A tool call is drawn as a card, never as markdown, so a
                 // row that kept blocks and now holds one is a different
                 // row -- rebuild it.
-                if matches!(item, client_core::transcript_fold::TranscriptItem::ToolRun { .. }) {
+                if matches!(
+                    item,
+                    client_core::transcript_fold::TranscriptItem::ToolRun { .. }
+                ) {
                     return false;
                 }
                 blocks.apply_delta(
@@ -886,10 +889,7 @@ mod apply_tests {
         rsc: &mut TestRsc,
         items: &[TranscriptItem],
     ) -> (TranscriptScreen, StrongWidget, UiRenderState) {
-        let (screen, tree) = build_tree(
-            rsc,
-            client_core::transcript_fold::group_tool_runs(items),
-        );
+        let (screen, tree) = build_tree(rsc, client_core::transcript_fold::group_tool_runs(items));
         let mut render = UiRenderState::new();
         render.resize((1080.0, 20000.0));
         render.update(&tree, rsc);
@@ -1037,7 +1037,11 @@ mod apply_tests {
         screen.apply(&mut rsc, &before, &after);
         render.update(&tree, &mut rsc);
         assert_eq!(screen.take_rebuilds(), 0);
-        assert_eq!(screen.tail_card_count(), 3, "the group closed under a result");
+        assert_eq!(
+            screen.tail_card_count(),
+            3,
+            "the group closed under a result"
+        );
 
         assert!(screen.expand_tail_tools(&mut rsc, false));
         assert_eq!(screen.tail_card_count(), 0);
@@ -1061,7 +1065,11 @@ mod apply_tests {
         assert_eq!(screen.tail_card_count(), 2);
         screen.apply(&mut rsc, &before, &after);
         render.update(&tree, &mut rsc);
-        assert_eq!(screen.take_rebuilds(), 0, "an appended call is not a rebuild");
+        assert_eq!(
+            screen.take_rebuilds(),
+            0,
+            "an appended call is not a rebuild"
+        );
         assert_eq!(screen.tail_card_count(), 3);
     }
 
@@ -1091,5 +1099,4 @@ mod apply_tests {
         // than cards -- and nothing panicked on the way.
         assert_eq!(screen.tail_card_count(), 0);
     }
-
 }

iris/transcript-ui/src/markdown.rs

@@ -399,7 +399,12 @@ fn options() -> Options {
 /// (`highlight`'s module doc), so the offsets are walked once rather than
 /// converted per span -- a fence is scanned on every delta that lands in
 /// it, and it is the only block a delta re-renders.
-pub(crate) fn highlight_into(spans: &mut Vec<SpanStyle>, text: &str, range: Range<usize>, language: Language) {
+pub(crate) fn highlight_into(
+    spans: &mut Vec<SpanStyle>,
+    text: &str,
+    range: Range<usize>,
+    language: Language,
+) {
     let code = &text[range.clone()];
     // char index -> byte offset within `code`, plus the end, so a span's
     // `end` is always in range.

iris/transcript-ui/src/row.rs

@@ -501,14 +501,8 @@ where
     };
     if let Some(calls) = calls {
         let key = row_key(&calls[0].key());
-        let (widget, tools) = crate::tool::build_tool_row(
-            rsc,
-            list,
-            selection,
-            key,
-            calls.to_vec(),
-            working,
-        );
+        let (widget, tools) =
+            crate::tool::build_tool_row(rsc, list, selection, key, calls.to_vec(), working);
         return (key, widget, Some(TailRow::Tools(tools)));
     }
     let FoldedRow::Single(item) = row else {

iris/transcript-ui/src/tool.rs

@@ -77,11 +77,6 @@ const LABEL_SIZE: f32 = 11.0;
 /// The room inside a card, and so the height a bar of one line of text
 /// comes to (`ToolRows.kt`'s `GROUP_INSET_LARGE`).
 const CARD_PAD_DP: f32 = 12.0;
-/// How far the stack of calls is held off the edge of the surface it sits
-/// on -- the container's own padding, not an indent.
-const GROUP_INSET_DP: f32 = 4.0;
-/// Enough to read the join as a join rather than as one tall card.
-const GROUP_GAP_DP: f32 = 2.0;
 /// A card's corner: `shapes.medium`, the same as every other card in the
 /// app.
 const CARD_RADIUS_DP: f32 = 12.0;
@@ -107,6 +102,10 @@ const RAW_PAD_DP: f32 = 8.0;
 /// many short lines, a minified file is one enormous one.
 const OUTPUT_LINES: usize = 80;
 const OUTPUT_BYTES: usize = 4096;
+/// A cap of nothing would draw an empty panel and a "Show all" for every
+/// output there is, which reads as a rendering fault rather than as a cap.
+/// Checked at compile time, since both are constants.
+const _: () = assert!(OUTPUT_LINES > 0 && OUTPUT_BYTES > 0);
 
 /// The mark that says a card opens, always drawn from the **monospace**
 /// face.
@@ -151,9 +150,6 @@ struct Shared {
     /// draws no cards at all. Its path out is [`build_content`], which
     /// clears it before building whatever replaces them.
     cards: RefCell<Vec<WeakWidget<WidgetPtr>>>,
-    /// The column those cards sit in, so a call appended to a run can be
-    /// pushed into it. `None` unless the group is open.
-    column: RefCell<Option<WeakWidget<Span>>>,
     /// The whole row's content, swapped when the group opens or closes.
     /// Filled in immediately after construction -- the `WidgetPtr` cannot
     /// exist before the `Rc` every handler inside it captures.
@@ -225,12 +221,26 @@ fn on_tap<Rsc: HasEvents>(
 /// pass resolves against -- the two-step contract that module's doc
 /// describes for `AGENTS.md`'s `holdTopEdge`.
 fn note_tap(rsc: &mut impl UiRsc, shared: &Shared) {
-    let (top, _bottom) = (shared.list)(rsc).extent(shared.key).unwrap_or((0.0, 0.0));
-    (shared.list)(rsc).note_tap(top);
+    // Only when the list actually has an extent for this row. `None`
+    // means the row has not been drawn yet -- which happens the moment
+    // something opens a group before the first frame
+    // (`TranscriptScreen::expand_tail_tools`, the headless screenshot) --
+    // and standing in `0.0` for it tells the layout pass to hold an edge
+    // at the top of the viewport that nothing was ever at. The whole list
+    // then places itself against that invented anchor: rows drawn at each
+    // other's cached heights, tool cards as empty bars with their text a
+    // group's height below them (`docs/bench/p1b-2026-09-06/`'s first
+    // attempt). Nothing to hold is not the same as an edge at zero.
+    if let Some((top, _bottom)) = (shared.list)(rsc).extent(shared.key) {
+        (shared.list)(rsc).note_tap(top);
+    }
 }
 
 fn text<Rsc>(content: impl Into<String>, size: f32, color: UiColor) -> TextBuilder<Rsc> {
-    wtext(content).size(size).color(color).text_align(Align::LEFT)
+    wtext(content)
+        .size(size)
+        .color(color)
+        .text_align(Align::LEFT)
 }
 
 /// A verbatim block: monospace on the surface everything verbatim in this
@@ -238,9 +248,14 @@ fn text<Rsc>(content: impl Into<String>, size: f32, color: UiColor) -> TextBuild
 ///
 /// Not wrapped for `ToolInput.kt`'s reason -- a wrapped command hides
 /// where its arguments end, and the long one is the one being read
-/// closely. The same `scrollable_on(Axis::X).masked()` a markdown fence
-/// gets in `row.rs`, so a command and a fence behave the same way under a
-/// finger.
+/// closely. A long line is **clipped** here rather than pannable, which a
+/// markdown fence (`row.rs`'s `BlockFrame::Verbatim`) is not: adding
+/// `.scrollable_on(Axis::X)` to this non-editable `Text` made it draw
+/// nothing at all -- an empty panel where the command should be, seen on
+/// 2026-09-06 in `docs/bench/p1b-2026-09-06/` and bisected to that one
+/// call (the fence, which does the same thing to a `TextEdit`, is fine).
+/// Recorded in docs/IRIS_TODO.md; when it is fixed, the pan belongs here
+/// too, because the long command is the one being read closely.
 fn raw_block<Rsc: HasEvents>(rsc: &mut Rsc, body: TextBuilder<Rsc>) -> StrongWidget
 where
     Rsc::State: FocusHost,
@@ -251,7 +266,6 @@ where
         .wrap(false)
         .add(rsc);
     field
-        .scrollable_on(Axis::X)
         .masked()
         .pad(dp(RAW_PAD_DP))
         .background(rect(VERBATIM_BACKGROUND).radius(dp(RAW_RADIUS_DP)))
@@ -311,7 +325,6 @@ fn group_label(count: usize) -> String {
 /// from the top, and the line saying what went wrong is nearly always the
 /// first. (A path is identified by its other end; this is not a path.)
 fn capped(output: &str) -> Option<(&str, usize)> {
-    debug_assert!(OUTPUT_LINES > 0 && OUTPUT_BYTES > 0, "an empty cap shows nothing at all");
     let by_lines = output
         .char_indices()
         .filter(|(_, c)| *c == '\n')
@@ -425,17 +438,25 @@ where
     // A call waiting on permission is shown open whatever the reader last
     // chose: the command is the thing being decided, and a row saying only
     // "Bash" cannot be decided on (`ToolRows.kt`).
-    let open =
-        shared.state.borrow().open.get(id).copied().unwrap_or(false) || call_state == ToolState::Deciding;
+    let open = shared.state.borrow().open.get(id).copied().unwrap_or(false)
+        || call_state == ToolState::Deciding;
 
     let mut header = Span::empty(Dir::RIGHT).gap(dp(GAP_DP));
     header.push(
-        text(if open { OPEN_MARK } else { CLOSED_MARK }, BODY_SIZE, MUTED_COLOR)
-            .family(Family::Monospace)
+        text(
+            if open { OPEN_MARK } else { CLOSED_MARK },
+            BODY_SIZE,
+            MUTED_COLOR,
+        )
+        .family(Family::Monospace)
+        .add_strong(rsc)
+        .any(),
+    );
+    header.push(
+        text(tool.clone(), NAME_SIZE, NAME_COLOR)
             .add_strong(rsc)
             .any(),
     );
-    header.push(text(tool.clone(), NAME_SIZE, NAME_COLOR).add_strong(rsc).any());
     match (open, parsed.title()) {
         // Open, the summary is redundant -- the input below is the same
         // thing in full -- and the space goes to the timeout instead, at
@@ -562,7 +583,13 @@ where
             debug_assert!(false, "tapped card {index} is no longer in the row");
             return;
         };
-        let was = for_tap.state.borrow().open.get(&id).copied().unwrap_or(false);
+        let was = for_tap
+            .state
+            .borrow()
+            .open
+            .get(&id)
+            .copied()
+            .unwrap_or(false);
         for_tap.state.borrow_mut().open.insert(id, !was);
         redraw_card(rsc, &for_tap, index);
     });
@@ -608,7 +635,6 @@ where
     Rsc::State: FocusHost + OpenUrl,
 {
     shared.cards.borrow_mut().clear();
-    *shared.column.borrow_mut() = None;
     let count = shared.calls.borrow().len();
     debug_assert!(count > 0, "a tool row with no calls has nothing to draw");
 
@@ -641,23 +667,23 @@ where
             .add_strong(rsc)
             .any(),
     );
-    let mut column = Span::empty(Dir::DOWN).gap(dp(GROUP_GAP_DP));
+    // The cards go straight into the group's own `Span`, not into a
+    // second one inside it. **A `Span` of `Pad`ded children inside another
+    // `Span` places those children a slot out of step** -- each card's
+    // content drew one card's height below its own box, so the cards read
+    // as empty bars with somebody else's summary in them. Bisected on
+    // 2026-09-06 against `iris/run-headless.sh transcript` with
+    // `IRIS_TOOLS_EXPANDED=1`: removing the inner `Span` fixes it and
+    // removing the cards' own `Pad` fixes it, while the card background,
+    // the `Sized` wrappers and the per-card `WidgetPtr` all make no
+    // difference. It is a framework defect rather than this file's --
+    // docs/RUST.md's P1b box and docs/IRIS_TODO.md carry the repro -- and
+    // one `Span` is the shape that works today. What it costs is the 4dp
+    // inset the Compose group holds its cards off its edge by; the cards'
+    // own padding stands in for it.
     for index in 0..count {
-        column.push(build_card_ptr(rsc, shared, index).0);
+        group.push(build_card_ptr(rsc, shared, index).0);
     }
-    let column = column.add(rsc);
-    *shared.column.borrow_mut() = Some(column);
-    group.push(
-        column
-            .width(rest(1))
-            .pad(Padding {
-                left: dp(GROUP_INSET_DP),
-                right: dp(GROUP_INSET_DP),
-                ..Padding::ZERO
-            })
-            .add_strong(rsc)
-            .any(),
-    );
     // Shutting it from here anchors the other end: the reader is at the
     // bottom of a long group, and what they are looking at is what follows
     // it (`ToolRows.kt`'s `CollapseBar`).
@@ -728,7 +754,6 @@ where
         calls: RefCell::new(calls),
         state: RefCell::new(ToolRowState::default()),
         cards: RefCell::new(Vec::new()),
-        column: RefCell::new(None),
         content: RefCell::new(None),
         list,
         selection,
@@ -857,19 +882,15 @@ impl ToolRow {
         for index in changed {
             redraw_card(rsc, &self.shared, index);
         }
-        for index in old.len()..calls.len() {
-            let Some(column) = *self.shared.column.borrow() else {
-                // Only a group has a column to append to, and a lone card
-                // that gained a neighbour is a different row.
-                return false;
-            };
-            let (widget, _card) = build_card_ptr(rsc, &self.shared, index);
-            // `get_mut` marks the column dirty, which is what gets the new
-            // card drawn; its removal half is the row's own, since the
-            // column owns the child strongly (`RowBlocks::apply_delta`).
-            if let Some(column) = rsc.ui_mut().widgets.get_mut(&column) {
-                column.push(widget);
-            }
+        // A call *joining* the run rebuilds the row's content rather than
+        // appending one card: the group's `Span` holds its collapse bar
+        // after the cards, and `Span::push` would put the new card behind
+        // it. That is still O(this row) -- every other row is untouched --
+        // and it is much rarer than a result arriving, which is the case
+        // the per-card `WidgetPtr` above exists for.
+        if calls.len() > old.len() {
+            let content = build_content(rsc, &self.shared);
+            self.shared.set_content(rsc, content);
         }
         true
     }