client-core: an unasked page is not an empty one, and two guarded invariants

Review of 73251d6's port of TranscriptSource/joinPages.

`TranscriptSource::page` answered `before == 0` with an empty `Vec`, which
is the same value it answers "this conversation has no more history" with.
That is the state the Kotlin keeps apart: `loadOlderPage` returns false at
`oldestSeq == 0` *without* touching `moreHistory`, and returns false on an
empty page *by latching it*. Collapsing the two moved AGENTS.md's paging
bug one layer down rather than fixing it. `page` returns `OlderPage` now --
`Events(vec![])` is the start of the conversation, `NothingLoaded` is not
an answer about the conversation at all.

`join_pages`' `debug_assert!` on seq ordering across the boundary is not a
true invariant: a peer note carries the seq its turn began at, which can be
older than the page it arrived in, so an ordinary transcript would have
panicked a debug build there. Replaced with the one the function exists to
enforce -- no tool id surviving in both halves.

`fetch_transcript_lines` stores `RawValue`'s exact server bytes, so the
"neither source can produce a newline" comment in `SessionCache::append`
now rests on the server's serializer staying compact rather than on a
local normalization. Checked with a `debug_assert!` in `append` and
`store_page` rather than trusted.

Tests for the failure half, which the port had none of: a 500 mid-page, a
cached line this build cannot read, and the `after` bound in the case that
actually carries one (the existing test asserted only the case with no
bound). `cargo fmt`, `cargo clippy --all-targets`, `cargo test` (112) clean
in client-core; `cargo check -p desktop-app` clean.

client-core/Cargo.toml

@@ -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

client-core/src/api.rs

@@ -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,
@@ -266,6 +275,61 @@ impl<T: Transport> ApiClient<T> {
         limit: u32,
         coalesce: bool,
     ) -> Result<Vec<Value>, ApiError> {
+        self.json_request(
+            "GET",
+            &transcript_path(session_id, before, limit, coalesce, None),
+            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}"));
@@ -273,8 +337,10 @@ impl<T: Transport> ApiClient<T> {
     if coalesce {
         path.push_str("&coalesce=true");
     }
-        self.json_request("GET", &path, None)
+    if let Some(after) = after {
+        path.push_str(&format!("&after={after}"));
     }
+    path
 }
 
 /// The blocking [`Transport`] backed by `ureq`, the same crate `server/`

client-core/src/lib.rs

@@ -11,5 +11,6 @@ pub mod notifications;
 pub mod sse;
 pub mod transcript_cache;
 pub mod transcript_fold;
+pub mod transcript_source;
 
 pub use event_model::*;

client-core/src/transcript_cache.rs

@@ -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
-            // produce one.
+            // event into two unreadable halves. No source here can produce
+            // 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")?;

client-core/src/transcript_fold.rs

@@ -294,6 +294,199 @@ 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,
+                    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,
+                    // 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
@@ -955,4 +1148,134 @@ 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(),
+            },
+        )
+    }
+
+    /// 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,
+                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,
+            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:?}"),
+        }
+    }
 }

client-core/src/transcript_source.rs

@@ -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}")
+    }
+}

docs/CLIENT_CORE.md

@@ -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
-crate as of this writing: **85 in `client-core`**, 0 in `event-model` (its
+(`sse.rs`, `api.rs`, `event_stream.rs`, `transcript_fold.rs`,
+`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
-`healSplitMessage`/`adoptRun` helpers) -- the page-boundary healing that
-merges a tool call split across two fetched pages and re-merges a run a
-boundary cut through. This matters the moment paging backward through
-history is exercised; it is deliberately left rather than rushed, since
-it is exactly the kind of boundary logic this project's own "things that
-have bitten" section warns reads fine and is wrong at the edges.
+`join_pages` (with `heal_split_message` and `adopt_run`, both private) is
+now ported too, 2026-09-06 -- the page-boundary healing that merges a tool
+call split across two fetched pages, rejoins a message a boundary cut
+through, and renames a run of tool calls onto whichever name is already on
+screen. Ported with AGENTS.md's "things that have bitten" incidents as the
+spec rather than a JVM test file (`TranscriptItems.kt` had none of its
+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.
@@ -119,12 +136,61 @@ 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
-  from the transcript cache or the server, and stitches the two. Needs
-  `transcript_cache.rs` and `api.rs`'s transcript-page method, both of
-  which exist now, so this is unblocked whenever picked up.
 - **The markdown *block* model beyond syntax spans** -- `highlight/markdown.rs`
   colours a `.md` file or fence for the highlighter, but does not build the
   block tree (headings, lists, tables, fences as distinct nodes) that a
@@ -142,5 +208,6 @@ 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`,
-`cargo clippy --all-targets`, `cargo fmt` -- all clean as of this writing.
+same way it always has). From `client-core/` directly: `cargo test`
+(109 tests), `cargo clippy --all-targets`, `cargo fmt` -- all clean as of
+this writing (2026-09-06).

docs/IRIS.md

@@ -8,6 +8,62 @@ 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: `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
@@ -513,3 +569,114 @@ 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.

docs/IRIS_TODO.md

@@ -117,6 +117,114 @@ 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.
+- [ ] **Composed/typed text never becomes visible at all -- found
+  2026-09-06, not fixed.** 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.
+- [ ] **The composer has no touch-drag scroll for overflowing text.** The
+  2026-09-06 rebuild caps the field at ~6 lines and wraps it in
+  `.scrollable()` for a wheel/trackpad scroll, but a real finger drag over
+  text that has overflowed the cap does not scroll it -- `Scroll`'s touch
+  handling is a follow-up, the same shape `List`'s own touch-drag pan
+  needed before I3/I5.
+
+## 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.
+
+- [ ] **"The app definitely does not start with keyboard spacing
+  correct. This is how it looks without me doing anything initially."**
+  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."** A pan that starts on the composer is held by
+  the composer until the finger leaves its region, then the list takes
+  over. The tap-vs-swipe fix in `attr.rs` stops the *focus*, but the
+  press frames are still being handled by the field rather than passed
+  to the list from the first slop-crossing frame. The `DragGesture`
+  merge (RUST.md's plan box) should make this one mechanism: once a
+  gesture commits to a pan, the list captures it wherever it began.
+- [ ] **"Flinging still does not work."** Expected on this build: finger
+  flings are dropped by per-widget hit testing, which `DragGesture`'s
+  pointer capture (commit `e12c708`, not yet merged at 02:07) targets.
+  Stays open until verified on her phone, not the emulator.
+- [ ] **"Text still disappears if I leave and come back to the app."**
+  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.
+
 ## Build
 
 - [x] **Benchmarks**, not unit tests, run on demand (2026-09-05; a
@@ -385,3 +493,53 @@ 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
+
+- [ ] **Streaming a delta into a long message costs a full text layout of
+  that message.** 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.

docs/LAYOUT.md

@@ -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):

docs/RUST.md

@@ -34,6 +34,87 @@ the emulator, not by Mesa" and "the present mode was not the cause" are
 worth as much as the successes, because they are what stops the next
 session spending an afternoon on them again.
 
+## Where things stand (2026-09-06, orchestrator plan)
+
+Written by the design agent on picking the branch up after a `/clear`, so
+the next session can resume from here. P0 is delivered and Iris's phone
+report v2 is in (`docs/bench/iris-phone-v2-2026-09-06.md`); **P1 stays
+gated on her verdict**, so this pass works the P0 defects and the pure
+prerequisites in this order. Each item is ticked here by the agent that
+closes it.
+
+- [ ] **Merge the `DragGesture` work** left complete but unmerged in the
+      worktree branch `worktree-agent-a754368325fa06839` (commit
+      `e12c708`, 2026-09-06 02:10, two minutes after the last merge to
+      `rustify`; already contains `rustify` at `543f6d9`). It targets two
+      of the four bench-v2 defects: finger flings dropped by per-widget
+      hit testing (pointer capture + `CursorSense::Drop`), and IME insets
+      never redelivered (`MainActivity.java` edge-to-edge). Before
+      merging: build, clippy, tests; then on the emulator confirm the
+      three things `20b1225` (tap-vs-swipe focus) and the phone asked for
+      still hold together — a swipe over the composer does not summon
+      the keyboard, a tap does, a finger fling on the list keeps moving
+      after the finger lifts, and `on_insets_changed` now fires on an
+      IME toggle. Then remove the worktree.
+- [ ] **Fix `docs/REVIEW-2026-09-06.md`** (after the merge, since the
+      review's finding 1 is in `selection.rs`, which the merge rewrites).
+      Finding 1 is a real crash — `TranscriptScreen::apply`'s `Rebuild`
+      arm leaves `Selection` holding `WeakWidget`s to freed rows, and the
+      next tap anywhere panics. Findings 2–5 are `debug_assert!`s on
+      invariants, 8 and 10 are the missing tests. Commit the review file
+      with the fixes.
+- [ ] **Iris's 11:39 phone report on the 02:07 build** (four items,
+      verbatim in `IRIS_TODO.md`'s "From the phone, 2026-09-06, 11:39"):
+      composer floating two thirds down the screen at launch with black
+      below it; a swipe starting on the composer held until the finger
+      leaves it; no fling (expected, `DragGesture` unmerged); text still
+      lost on app-switch on the phone despite the emulator-verified
+      atlas reset. The first and last are the same class as the next
+      box and go to that agent; the middle two are the merge box's.
+- [ ] **Stale primitives and invisible composer text** — the header drawn
+      twice after a keyboard resize, the `Compacted:` row drawn twice on
+      Iris's phone, and typed text never appearing (P0 box item 2). All
+      three sit on the `redraw_updates` targeted-redraw path and may be
+      one bug; the P0 box says the next step is instrumentation inside
+      `Span::draw`/`draw_inner` showing where each placement's
+      primitives actually land on the frame it goes wrong.
+      `list.rs`'s new `replacing_the_last_row_many_times_does_not_leak_
+      primitives` test already pins the widget arena as *not* the leak.
+- [ ] **Composer touch-drag scroll** for overflowed text — now that
+      dragging is a default-input `DragGesture`, `Scroll` should get its
+      touch pan from the same mechanism `List` uses, not a copy.
+- [ ] **Streaming re-layout** (IRIS_TODO.md's last section) — after the
+      above, since they make the stream phase unrepresentative today.
+- [x] **client-core prerequisites for P1, in parallel** (pure Rust,
+      disjoint from `iris/`), closed 2026-09-06: `TranscriptSource`'s
+      cache-vs-server stitching (new `client-core/src/transcript_source.rs`)
+      and `joinPages`/`healSplitMessage`/`adoptRun` page-boundary healing
+      (new functions in `transcript_fold.rs`), per `CLIENT_CORE.md`. Ported
+      against the Kotlin source and AGENTS.md's paging incidents as the
+      spec (`TranscriptSource.kt`/`TranscriptItems.kt` had no JVM unit
+      tests of their own to port test-for-test). `client-core` goes from
+      85 to 109 tests; `cargo test`/`clippy --all-targets`/`fmt` all clean.
+      Both AGENTS.md regressions have a dedicated test: `loadOlderPage`'s
+      `before == 0` guard moved into `TranscriptSource::page` itself
+      (`paging_before_the_first_event_makes_no_request_at_all` asserts
+      zero transport calls, not just an empty result), and
+      `a_clean_boundary_between_two_finished_runs_is_still_healed_into_one_run`
+      pins `adopt_run` running on *every* join rather than only the
+      split-call path. One incidental fix needed to port `TranscriptSource`
+      faithfully: `api.rs` gained `fetch_transcript_lines` (additive, the
+      existing `fetch_transcript_page` untouched since `iris/` depends on
+      its signature), which pairs each event with the exact server bytes
+      it came from via `serde_json::value::RawValue` rather than
+      re-serializing a parsed `Value` -- needed so the cache and a live SSE
+      frame agree byte-for-byte, the same class of bug as the
+      `float_roundtrip` fix. Deliberately not ported: `EventStream.kt`'s
+      reconnect/backoff and cross-thread stream cancellation, which are
+      runtime policy for whichever framework embeds this crate, not pure
+      logic -- see `CLIENT_CORE.md`'s new section for the full account.
+- **Then**: redeliver `~/host/bench/iris-bench-arm64.apk` for Iris with
+  its README saying what changed, and record any choice she should see in
+  `DECISIONS.md`.
+
 ## Where things stand (2026-09-05)
 
 - **Streaming no longer costs a full rebuild** (P0's box, "Streaming no
@@ -4315,6 +4396,603 @@ device.
       confirming the phase marks partition the whole run rather than
       overlapping or dropping frames between them.
 
+      **Iris's first real phone report, 2026-09-06** (the redelivered,
+      no-`force-gles` APK above): no crash. Two screenshots, before any
+      touch: headings/links/code/table all render correctly. Four defects
+      found and worked this pass:
+
+      1. **Every glyph disappears on the first tap or scroll; rectangles
+         stay drawn** (the keyboard case is the same thing -- a tap on the
+         composer). **Not root-caused this pass.** Audited `GpuTextures`'
+         atlas-grow/patch path, `ArrBuf`'s resize-on-length-change
+         contract, and the masks/move_offsets/rsc bind-group rebuild logic
+         in `core/src/render/mod.rs` against wgpu's queue-ordering
+         contract -- everything read as spec-correct (a `queue.write_texture`/
+         `write_buffer` issued before a later `queue.submit` is guaranteed
+         visible to it on the same queue, and a dropped `Buffer`/`Texture`/
+         `BindGroup` still in flight is kept alive by wgpu's own tracker).
+         No violation found by static reading; reproducing needs either
+         the phone or a Mali driver trace, neither available this pass.
+         Instrumented for the next report instead: `Device::
+         on_uncaptured_error` is now installed on the Android device
+         (`WgpuErrorLog`, `android::render::AndroidRenderer`), and
+         `IrisViewPeer::render` logs masks/moves-resized, atlas
+         pages-grown and image bind-group creates for the first 10 frames
+         after every `surface_changed` -- exactly the window this bug
+         lands in. The bench screen's new "Diagnostics" button (below)
+         surfaces the error log and adapter identity on demand.
+      2. **Bold words render as blank gaps of the correct advance width**
+         (regular, links, inline code render fine). Fixed by bundling Noto
+         Sans/Noto Sans Mono (regular/bold/italic/bold-italic, static
+         cuts, OFL) into `iris-core` and registering them ahead of the
+         platform's own fonts -- `core/src/primitive/text.rs`'s
+         `TextData::register_bundled_fonts`. Named hypothesis, not
+         confirmed on the phone: the system "Roboto" on a modern Android
+         device is the variable "Roboto Flex," and this crate's glyph
+         path (`TextData::place`) does not apply `Synthesis`/variable-axis
+         correction at all -- a bundled *static* per-style face sidesteps
+         the question rather than answering it. `TextData::font_diagnostics`
+         reports what got resolved; logged once at startup and shown on
+         the Diagnostics page.
+      3. **Text far too small** -- iris had no device-pixel-ratio handling
+         on *either* platform before this pass (grepped for `scale_factor`
+         across the whole crate: zero hits). `DisplayMetrics.density`
+         (Android) / `Window::scale_factor()` (desktop) now divides every
+         physical-pixel number (window size, touch coordinates, the
+         shader's window uniform) down to logical units before it reaches
+         layout, so a `font_size: 16.0` is 16 dp rather than 16 raw device
+         pixels on a ~3x-density phone. Cost a second, real bug found only
+         by measuring on this checkout's emulator after the first fix
+         landed: `android::view::IrisViewPeer::surface_changed`'s call
+         into `UiRenderState::resize` (the layout engine's own notion of
+         the canvas, which every widget's absolute `PixelRegion` is
+         computed against) was still being handed raw physical
+         `width`/`height`, while `AndroidRenderer`'s side of the same
+         resize had already switched to logical -- splitting layout and
+         the shader into two different units. A fixed-size widget (the
+         bench screen's `.height(56)` button row) exposed it at ~40
+         physical px against the ~147px `56 * content_scale` predicts;
+         a proportional (`rest(n)`) size hid it by adapting to whichever
+         total it was given. Both are logical now. **Not fully verified**:
+         a fresh-install emulator screenshot after both fixes shows
+         visibly larger, readable text (`docs/bench/` has neither
+         screenshot committed -- see AGENTS.md on transcripts/screenshots
+         not going in this repo -- but the before/after is described in
+         the commit), and the button row's own height still isn't
+         obviously matching `56 * content_scale` on this run -- worth a
+         second look with `ui-trace show --field box` once there's time,
+         but not a blocker for the magnitude of the original bug (3x too
+         small).
+      4. **Status-bar inset not applied** -- confirmed nothing in this
+         app ever read `insets().top` at all (`android/insets.rs` has
+         carried `Insets.top` since it was written; nothing consumed it).
+         Fixed with a new, generic hook: `AndroidAppState::
+         on_insets_changed(rsc, LogicalInsets)`, called from `render()`
+         exactly when `AndroidUiState::insets()` changes, in logical units
+         matching everything else `content_scale` now divides.
+         `BenchClient::on_insets_changed` rebuilds the root tree with
+         `Padding::top(insets.top)` on the button row -- rebuilding the
+         whole tree rather than one `WidgetPtr` slot's content, because
+         the first attempt (a `Pad` dropped into an unrelated `WidgetPtr`
+         slot with no height override of its own) did not propagate the
+         wrapped span's fixed height correctly, which is what surfaced
+         finding 3's `UiRenderState::resize` bug in the first place.
+         Verified via `ui-trace show --field box`: the button row's top
+         (150 physical px) sits 8px below `statusBarBackground`'s bottom
+         edge (142px) on this checkout's emulator.
+
+      **A named `Diagnostics` control now exists** (RUST.md's own earlier
+      ask): a third button on the bench screen's top row, filling the
+      existing benchmark-report `TextEdit` with adapter identity/backend/
+      driver, font resolution, the atlas's live view count, every
+      uncaptured wgpu error since surface creation, and the frame report
+      -- `android::render::AndroidRenderer::diagnostics_report`. Uses the
+      existing "Copy report" button/clipboard path rather than a second
+      one.
+
+      **Verified this pass, this checkout's emulator** (`EMU_GPU` default,
+      `--features force-gles` -- this cold `emu up` again enumerated zero
+      Vulkan adapters, the same pre-existing flakiness earlier boxes
+      documented, not something this pass's diff caused): `cargo fmt --all
+      -- --check`, `cargo clippy --workspace --all-targets` (zero warnings
+      beyond the pre-existing wgpu future-incompat notice), `cargo test
+      --workspace` (all passing, unchanged pure-logic counts), `cargo ndk
+      -t x86_64 -P 26 check` clean, `./run-bench.sh` end to end
+      (`frames=691`, 24/24 swipes, 400/400 streamed events, no crash),
+      fresh-install screenshots and `ui-trace` box readouts for the four
+      items above. **Not verified this pass**: the actual phone (no
+      access), and item 1's root cause (needs either the phone's next
+      Diagnostics-page report or a Mali trace).
+
+      **Recorded but not fixed this pass** (a follow-up agent takes these,
+      to avoid colliding with this pass's `bench_client.rs`/`view.rs`
+      changes) -- see `IRIS_TODO.md`'s "From the phone, 2026-09-06":
+      swiping has no momentum (stops exactly where the finger releases,
+      unlike Compose's fling), and scrolling down sometimes jitters the
+      text.
+
+      **Redelivered, 2026-09-06, later the same day.** New arm64 APK
+      (Vulkan, no `force-gles`, bundled fonts, content-scale fix,
+      Diagnostics control), same `dev.iris.android.demo.bench` id, same
+      `CN=ai-app` signing cert, copied to `~/host/bench/
+      iris-bench-arm64.apk` and `~/repos/ai-app-bench/iris/build/outputs/
+      apk/release/iris-bench-arm64.apk`; that repo's own README gained a
+      dated entry. Still not confirmed on Iris's actual phone.
+
+      **Redelivered again, 2026-09-06, a later pass.** Iris's report on
+      build a9232ac, with screenshots: text now the right size but
+      **blurry**; opening the keyboard still **wipes every glyph**
+      (rects stay, only text disappears); the **header buttons have
+      nothing behind them and overlap the transcript text**.
+
+      **1. The keyboard wipe.** Hypothesis (given in the task, confirmed
+      by reading the path before changing anything, per AGENTS.md):
+      `android::view::IrisViewPeer::surface_changed` fires on *every*
+      `SurfaceView` size/format change, not only a genuinely new
+      `Surface` -- showing the IME under `adjustResize` resizes the same
+      surface through this exact callback. The handler unconditionally
+      set `renderer = None` and called `AndroidRenderer::new`, which
+      builds a fresh, empty glyph atlas and fresh GPU buffers via
+      `UiRenderNode::new`, while `iris_core`'s CPU-side glyph cache
+      (`primitive/text.rs`) kept the atlas UV coordinates it had already
+      handed out against the *old* atlas -- every glyph then drew from a
+      rectangle pointing into a texture that had just been recreated
+      empty. Confirmed by reading `AndroidRenderer::resize` (already
+      existed, already did none of that -- only `surface.configure` and
+      the window uniform) against what `surface_changed` was actually
+      calling instead. **Fix**: `surface_changed` now calls
+      `AndroidRenderer::resize` when a renderer is already live, and only
+      builds a new one when `surface_changed` finds `renderer` still
+      `None` (a genuinely new surface -- after `surface_destroyed`, e.g.
+      backgrounding). Not independently re-verified against a forced IME
+      resize on this pass's emulator (no display keyboard exercised
+      end-to-end here); the reasoning is a direct code read plus the
+      existing `resize` path already being surface-only, not a
+      screenshot diff -- **the next agent with emulator time should do
+      the before/after screenshot this box originally asked for.**
+
+      **2. The blur.** Root cause: the P0 fix that made text the right
+      *size* (dividing the whole window into a "logical" space, then
+      letting the shader's NDC mapping stretch it back onto the real
+      framebuffer) rasterised each glyph at the small, pre-stretch size
+      and then displayed it stretched onto more physical pixels than it
+      had texels for. **Fix, and the density-independent length unit
+      Iris asked for the same day (IRIS_TODO.md) turned out to be the
+      same fix**: `Len::dp`, resolved against a `density` now carried on
+      `UiRenderState`/`Painter`, replaces the global stretch -- window
+      size, touch and insets are physical pixels throughout again
+      (`WindowInsets`, renamed from `LogicalInsets`), and
+      `TextBuffer::shape` multiplies `font_size`/`line_height` by density
+      before handing them to parley, so the atlas rasterises at the
+      display's real physical resolution. Full design in docs/LAYOUT.md's
+      "Density: `Len::dp`" section and the public-API summary in
+      docs/IRIS.md's 2026-09-06 entry.
+
+      **3. The header.** Only each button's own `rect(...)` painted
+      anything, so the gaps between/around them and the status-bar strip
+      above showed `CLEAR_COLOR` (black) one layer back, and the row's
+      reserved height was three `abs` (now-physical-pixel) button boxes
+      -- smaller than the dp-correct size the transcript below uses,
+      which is what read as "overlap" once the two disagreed. Fixed with
+      a `HEADER_SURFACE` rect stacked behind the whole row and every
+      header size moved onto `dp(...)`.
+
+      **4. Keyboard diagnostics, so Iris can report back even if a
+      keyboard-triggered regression persists.** `on_insets_changed` now
+      edge-triggers ~500ms after `ime_bottom` becomes non-zero, capturing
+      the same report the on-screen Diagnostics button produces, logging
+      it, copying it to the clipboard unprompted, and showing it in a new
+      plain-view overlay (`IrisView.showDiagnosticsOverlay`, Copy/Close)
+      that draws independently of iris's own renderer.
+
+      **Verified this pass**: `cargo fmt --all`, `cargo clippy --workspace
+      --all-targets` and `cargo clippy` on `android-app` (both `-D
+      warnings`, zero beyond the pre-existing `tabs-ui` unused-dependency
+      and wgpu future-incompat notices), `cargo test --workspace` (all
+      passing), `cargo ndk -t arm64-v8a check`/`clippy` for both the
+      `transcript-screen bench` feature set.
+
+      **Then run on this checkout's own emulator** (x86_64 debug,
+      `--features "transcript-screen force-gles bench"` -- this AVD has no
+      Vulkan adapter under a plain `-gpu host` boot, matching every prior
+      emulator finding in this file): `run-bench.sh` end to end, no crash,
+      `frames=534 janky%=79.03 ... cpu_p50=1.3ms`, 24/24 swipes, 400/400
+      streamed events -- unchanged in shape from prior readings, so the
+      diff cost nothing on the success path. **Header background**:
+      screenshot confirms the `HEADER_SURFACE` panel now sits behind all
+      three buttons (`/tmp/bench-after-run.png` this pass). **Keyboard
+      wipe**: forced a real `surface_changed` two ways -- `adb shell wm
+      size 1080x1900` (screenshot before/after, text intact) and actually
+      opening the soft keyboard via `settings put secure
+      show_ime_with_hard_keyboard 1` + tapping the message field
+      (ui-trace confirmed a real resize, elements moved -547px; keyboard
+      visible in the screenshot, text still fully rendered, not wiped).
+      Both are real evidence the reuse-renderer fix works, though neither
+      is the literal before/after diff this box originally asked for --
+      **still worth a deliberate side-by-side screenshot pair in a future
+      pass.**
+
+      **Found during this same verification, not fixed, needs a follow-up
+      pass**: after the keyboard-triggered resize, the top button row
+      appeared to render a **second time**, well below its real position,
+      inside the transcript's scroll area (same colours/text, unmistakably
+      the same three buttons) -- and a tap aimed at the composer's
+      "Message" field landed on "Run benchmark" instead (a second
+      benchmark run started, visible in logcat as two `iris bench report:`
+      lines from one session). Only seen after a resize with the keyboard
+      genuinely open; the plain `wm size` resize screenshot pair did not
+      show it, nor did the fresh-install screenshot before either resize.
+      **Not root-caused this pass** -- time ran out before isolating
+      whether this is the `Span::DOWN` two-phase draw (LAYOUT.md's
+      provisional-then-real placement) leaving a phase-1 primitive
+      retained somewhere it should have been moved from, something
+      specific to the keyboard's `on_insets_changed` rebuild racing a
+      redraw, or unrelated to this pass's changes entirely (not verified
+      against a build predating this session's commits, so do not treat
+      "caused by this pass" as established -- MACHINE.md's pinned rule
+      about not attributing without measuring applies here too). Also
+      noteworthy: `capture_keyboard_diagnostics` never fired in this
+      session (no "iris keyboard diagnostics" log line) despite the
+      keyboard visibly opening -- `on_insets_changed`'s `ime_bottom` may
+      not be populated the way expected on this emulator/API level, or
+      the duplicate-row state above interfered; **also needs a follow-up
+      pass** before relying on the auto-capture on a real phone.
+
+      **Not verified this pass**: anything on Iris's real phone, the
+      two-density crispness check IRIS_TODO.md's unit item asks for, and
+      the two open items just above.
+
+      **Fling and jitter, 2026-09-06.** The two `IRIS_TODO.md` "From the
+      phone" items this box's own text names as follow-ups are fixed --
+      `List::fling`/`VelocityTracker`/`FlingCalculator` (IRIS.md's
+      2026-09-06 entry) and the `DragArbiter` slop-release jump (fixed by
+      applying only the excess past `DRAG_SLOP` on the crossing frame,
+      not the whole pre-threshold drag) -- both wired through
+      `Selection::drag`'s release path, both covered by new unit tests in
+      `iris/src/sense.rs` and `iris/src/widget/list.rs`. **Root-caused by
+      reading `DragArbiter::update` and testing it directly, not by an
+      emulator trace** -- this pass did not open an emulator, so the
+      "trace the list's offset per frame" verification this box's own
+      todo asked for is still open, as is a feel-check of the fling on
+      real touch input.
+
+      **Benchmark v2, iris half, done 2026-09-06, later the same day.**
+      `bench_client.rs` implements all four phases against the identical
+      constants this box's "Benchmark v2" spec names: fling (8 out + 8
+      back at 12,000px/s through `List::fling`, waiting for
+      `!is_scrolling()` capped 3s with a 300ms pause between, travel
+      reported as `idx=N/off=Mpx` via a new `List::anchor_position_display`
+      -- note this list's anchor does not necessarily change *slot* during
+      a long scroll (the module's own documented design: the anchor is
+      named by identity, not re-derived from what's on screen), so an
+      iris travel reading is not apples-to-apples with Compose's
+      `firstVisibleItemIndex`, which does change slot -- a real difference
+      in what the two numbers mean, not a bug, and worth reading `off`
+      rather than `idx` when comparing runs), stream (unchanged), type
+      (the exact 600-character `TYPE_TEXT` constant, verified by a unit
+      test, one char per 50ms into the composer's real `TextEdit` via
+      `.set()` -- the same whole-string-replace shape `BenchRun.kt`'s own
+      `setComposerText` uses, not a per-character insert), and keyboard
+      (5 cycles through `bench_jni.rs`'s new `show_ime`/`hide_ime`
+      `InputMethodManager` calls, confirmed from `on_insets_changed`'s
+      real `ime_bottom` transitions via a new `ImeState` counter rather
+      than assumed from the JNI call succeeding).
+
+      `iris_core::render::frame_report::FrameReport` gained `mark_phase`/
+      `phase_stats`/`late_at_hz` (new unit tests in `frame_report.rs`):
+      phases are sliced by absolute frame index against a second ring
+      (`index_ring`) alongside the existing duration ring, and late/jank
+      is judged against a real Hz read from `bench_jni.rs`'s new
+      `refresh_rate_hz` (`View::getDisplay().getRefreshRate()`) rather
+      than the fixed 60Hz `JANK_THRESHOLD` every other caller still uses
+      -- a separate method, not a parameter on the existing one, so
+      nothing else in the codebase changes behaviour. `RING_CAPACITY`
+      4096->16384 since one full v2 run is 3,000+ frames.
+
+      **A real deadlock, found and fixed while wiring this up.** Getting
+      a value back out of a task spawned via `rsc.spawn_task` has no
+      built-in return channel (`ctx.update`'s closures are fire-and-
+      forget), so a new `read_from_state` helper sends the result through
+      an `mpsc` channel and polls for it. Its first version only worked
+      for the *first* call in a chain: nothing about `ctx.update` drains
+      itself, so unless something calls `redraw.request_redraw()` after
+      *this specific* enqueue, nothing ever runs the closure -- and every
+      call after the first relied on a stale, already-fired
+      `request_redraw()` from a previous step. The fix is structural:
+      `read_from_state` now takes the redraw handle and calls it itself,
+      immediately after enqueueing, every time.
+
+      **Verified end to end, this checkout's own emulator (cold `emu up`,
+      `force-gles`, x86_64 -- this AVD again enumerates zero Vulkan
+      adapters on a cold boot, matching every prior finding in this
+      file):**
+
+          iris bench report
+          per phase:
+            fling: 1481 frames over 53.2s
+              late: 158 (10.7%)
+                total  p50 11.2ms  p90 16.9ms  p99 26.5ms
+              worst 43.3ms
+            stream: 401 frames over 20.8s
+              late: 342 (85.3%)
+                total  p50 26.1ms  p90 49.1ms  p99 57.2ms
+              worst 61.3ms
+            type: 1202 frames over 63.1s
+              late: 89 (7.4%)
+                total  p50 12.8ms  p90 15.1ms  p99 23.3ms
+              worst 26.7ms
+            keyboard: 9 frames over 9.1s
+              late: 2 (22.2%)
+                total  p50 6.3ms  p90 25.8ms  p99 25.8ms
+              worst 25.8ms
+
+          frames:
+            3093 frames over 146.3s at 60Hz (16.7ms budget)
+            late: 591 (19.1%)
+            total  p50 12.4ms  p90 22.2ms  p99 51.2ms
+            worst 61.3ms
+            cpu_p50 0.7ms  gpu_wait_p50 11.6ms
+
+          bench:
+            fling: 8 flings out + 8 back at 12000px/s, travel start=idx=651/off=1336px outward=idx=651/off=101672px end=idx=651/off=1427px
+            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: 43303ms
+            peak RSS: 193152kB
+            battery current: mean 900000µA over 146 samples (min 900000, max 900000)
+
+      Read this the same way every prior emulator smoke run in this box
+      is read: software rasterisation, not a phone number, and the
+      battery line is the emulator's fixed mocked-charger constant again.
+      **Travel**: the `idx` stays fixed at 651 through the whole fling in
+      both directions (see the `anchor_position_display` caveat above) --
+      `off` is what actually moved, growing to 101,672px outward before
+      the return trip brings it back near its start, which is real, large
+      motion (a fast, hard fling, matching Iris's "travel way faster"
+      ask), just not directly comparable to Compose's idx-188-reached
+      reading from the same box's earlier v2 entry. **`keyboard: could
+      not be shown`**: expected given the ime-inset finding below, not a
+      new regression.
+
+      Redelivered: `./build-apk.sh release --abi arm64-v8a --features
+      "transcript-screen bench"` (Vulkan, no `force-gles`; the x86_64
+      jniLibs slice left over from emulator testing was removed first so
+      the delivered APK is arm64-only, confirmed via `aapt2 dump
+      badging`), `apksigner verify` shows the same `CN=ai-app` cert,
+      copied to `~/host/bench/iris-bench-arm64.apk` and `~/repos/
+      ai-app-bench/iris/build/outputs/apk/release/iris-bench-arm64.apk`;
+      that repo's own README gained a dated entry. `run-bench.sh`
+      extended for the longer run (260s poll cap, `-A 60` instead of
+      `-A 6`) to fit v2's four phases.
+
+      **(a) The header-duplicate bug (found by a concurrent pass on this
+      branch): investigated, not fixed.** Reproduced reliably
+      (`ui-trace record --do "tap 'Message'"` then `adb exec-out
+      screencap`): the three-button row renders a second, full copy
+      inside the transcript area the moment the keyboard opens. Read
+      `Span::draw`'s own two-phase placement doc (a provisional
+      full-region draw to learn each child's size, then a real
+      `widget_within` placement) as the most likely mechanism, since it
+      is the one place in this tree that deliberately draws a widget
+      twice in normal operation and relies on the two draws landing at
+      the same place to stay a cheap move rather than a visible second
+      copy -- and `UiRenderState::update`'s `redraw_all`-vs-
+      `redraw_updates` split (LAYOUT.md) means a `.set()`-driven targeted
+      redraw of just `top_bar` and a resize-driven full redraw of the
+      whole tree are two structurally different code paths that could in
+      principle disagree about where that widget's primitives belong on a
+      frame where both fire close together. **One concrete, testable
+      hypothesis was ruled out**: `on_insets_changed` rebuilding
+      `top_bar` on every call, including ones only about `ime_bottom`
+      (nothing to do with the header's own padding). Added a guard
+      (`last_top_pad`, skips the rebuild unless `insets.top` itself
+      changed) and reproduced the *exact same* duplicate afterward --
+      unchanged, byte-for-byte, in the same screenshot -- so repeated
+      rebuilding is not the cause; the guard is kept anyway since it is a
+      real (if here insufficient) reduction in needless work. **Not
+      root-caused**: doing so needs either instrumentation inside
+      `Span::draw`/`draw_inner` to see the two placements' actual regions
+      on the frame the bug happens, or the phone. Left for a follow-up
+      pass rather than guessed at further.
+
+      **(b) Why the keyboard phase and the keyboard-open auto-diagnostics
+      both read "not confirmed": a real, named platform interaction,
+      partly fixed.** `MainActivity.java`'s manifest declares
+      `windowSoftInputMode="adjustResize"` (AGENTS.md's own "Things that
+      have bitten": without it the keyboard pans the window off screen
+      instead of resizing it). Under `adjustResize`, `WindowInsets.
+      Type.ime()`'s own inset *amount* is defined to read zero once the
+      window has already resized to avoid the overlap that inset would
+      otherwise describe -- confirmed by reading Android's own
+      `WindowInsets` contract, not guessed at. So the numeric `ime_bottom`
+      this app was reading is *structurally* never going to be positive
+      here, independent of anything wrong in `iris`'s own code -- the same
+      trap AGENTS.md already names for the Compose side
+      (`WindowInsets.isImeVisible` "does not share the failure mode").
+      **Fixed**: `MainActivity.java`'s `OnApplyWindowInsetsListener` now
+      reads `insets.isVisible(WindowInsets.Type.ime())` (a boolean,
+      unaffected by resize-vs-pan) and passes `1`/`0` through the
+      existing `ime_bottom` JNI field instead of the always-zero numeric
+      inset -- correct on its own terms, and kept, but **did not by
+      itself make the keyboard phase or the auto-diagnostics fire on this
+      emulator**: `logcat` shows the platform's own `InsetsController:
+      show(ime(), fromIme=false)`/window-resize events happening (the
+      keyboard genuinely opens, confirmed by screenshot), but no further
+      `setOnApplyWindowInsetsListener` callback at all after the initial
+      one at attach. Named hypothesis, not confirmed: a plain (non-edge-
+      to-edge) `Activity` that has not called `WindowCompat.
+      setDecorFitsSystemWindows(window, false)` may not get insets
+      redelivered for a pure IME toggle handled entirely via resize --
+      only the initial attach-time dispatch is guaranteed. Confirming and
+      fixing that needs opting the activity into edge-to-edge, which is a
+      real window-behaviour change interacting with the exact
+      `adjustResize` setting AGENTS.md protects, not attempted this pass
+      given the risk-to-time-remaining ratio. Both open items are
+      recorded in `~/repos/ai-app-bench`'s README with today's date.
+
+      **Composing text, the tap-vs-swipe focus rule, and app-switch text
+      loss, 2026-09-06.** Iris's report on this same dc01f88 build: typing
+      doesn't enter text or move the caret until a space is hit; typed
+      text doesn't visibly appear and there is empty black space below the
+      composer bar; text disappears again after leaving and returning to
+      the app; and (a follow-up message the same day) swiping over the
+      composer bar wrongly summons the keyboard.
+
+      1. **The caret/composing bug's cause**: `android/ime.rs`'s
+         `InputConnection` never called `InputMethodManager.updateSelection`
+         after an edit -- confirmed by reading android-view's own demo
+         (`~/src/android-view/demo/src/lib.rs`'s `render()`), which calls it
+         every time its editor's generation changes. Without it, Gboard has
+         no confirmation the app is keeping up and holds keystrokes back
+         rather than trusting a screen it believes is stale -- exactly
+         "doesn't enter it until I hit space." **Fix**: `IrisViewPeer::
+         update_ime_selection` (new, `ime.rs`) reports the real selection
+         and (an approximation, `compose_len` chars back from the caret)
+         the composing region, called from `after_input`'s existing tail so
+         every touch/key/IME callback already runs it. The buffer-level
+         half (`replace`/`insert_str` correctly advancing the caret) was
+         already correct and is now covered by four new unit tests in
+         `iris/src/widget/text/edit.rs` (composing, `commitText`,
+         `deleteSurroundingText`, `setSelection`). **Verified**: on the
+         emulator (`force-gles`, no Vulkan adapter on this AVD), tapping a
+         real Gboard key now shows a real, single-character-appropriate
+         suggestion strip ("H | How | Hey") rather than stale state, and a
+         `render()` log line fires for every keystroke -- both confirm the
+         `InputConnection` calls are landing and are being processed, which
+         a hand-typed `adb shell input text` did *not* reliably exercise on
+         this AVD (no `render()` at all followed one such call -- most
+         likely a modern `input text` no longer round-trips through
+         `commitText` the way older docs assume; Gboard-key taps are the
+         real path and the one this fix was verified against).
+
+      2. **A second, deeper bug found while verifying (1), not root-caused
+         this pass**: composed text never becomes visible on screen at
+         all -- the grey composer bar stays empty, with no glyph anywhere
+         in the frame, confirmed on repeated Gboard-key taps and across a
+         keyboard-resize. **Ruled out**: the widget tree's own layout math.
+         A new unit test, `layout_tests::
+         composing_text_after_a_keyboard_resize_lands_in_the_bars_own_region`,
+         builds the composer's exact tree shape (`Stack{rect, Span{Pad{
+         TextEdit}}}` inside an outer `Span::DOWN`) with no GPU or window,
+         resizes it the way a real keyboard-triggered `surface_changed`
+         does, edits the field both before and after, and asserts the
+         field's `window_region` stays a small box near the bottom of
+         whichever window size is current -- it passes, both before and
+         after this pass's composer rebuild (item 3 below), so the CPU-side
+         region a redraw lands at is provably correct. The bug is
+         therefore downstream of that -- most likely something specific to
+         the GPU-side redraw a content-only edit takes (`UiRenderState::
+         redraw`, which redraws a single dirtied widget directly at its
+         stored region rather than re-running its ancestors' layout) or to
+         this AVD's forced `force-gles` backend (the only one available
+         here; Iris's phone deliveries have used real Vulkan) -- neither
+         isolated this pass. **Not attributable to this pass's changes**:
+         reproduced identically before touching `composer.rs` (the very
+         first build tested, before the composer rebuild below, already
+         had it) and the render-engine files this pass did not touch
+         (`core/src/render/mod.rs`, `core/src/ui/render_state.rs`) are the
+         likely next place to look -- specifically `UiRenderState::redraw`'s
+         reuse of a widget's own last-drawn region versus a full tree walk.
+         **Needs**: either a Vulkan-capable emulator boot or the real phone
+         to rule `force-gles` in or out, and a GPU-side primitive dump
+         (the existing `frame diagnostics` log line, extended to name which
+         primitives a frame actually wrote) to see whether the glyph quads
+         are emitted at all or emitted somewhere off-screen.
+
+      3. **The composer bar rebuilt as one widget**, per this box's own
+         ask: `transcript_ui::composer::build_composer` (unchanged
+         `Stack{background, Span{Pad{TextEdit}}}` idiom, the same one the
+         header row's `HEADER_SURFACE` already uses) now also caps the
+         field at roughly six lines (`MaxSize` + `.scrollable()` for a
+         wheel/trackpad overflow scroll -- a real touch-drag scroll on
+         overflowing composer text is not wired and is a follow-up) and
+         wraps the whole bar in one `Pad` whose `bottom` a new
+         `Composer::set_bottom_inset(rsc, inset)` rewrites in place
+         whenever the platform's insets change, called from
+         `bench_client.rs`'s existing `on_insets_changed` with
+         `insets.bottom.max(insets.ime_bottom)` -- the IME's own inset
+         while it is open, the navigation bar's otherwise. Rewritten in
+         place rather than rebuilt through a `WidgetPtr` swap (`top_bar`'s
+         own pattern) because the field is strongly owned inside this tree
+         and cannot be re-added to a new wrapper without panicking
+         ("was already added") -- rebuilding would also drop focus,
+         selection and in-progress text on every keyboard toggle.
+         **Verified**: `ui-trace` box readouts before/after a keyboard
+         open on the emulator (the field's row correctly reports a
+         547px move matching the real IME-triggered resize); the
+         known-separate "top row renders twice after a keyboard resize"
+         bug this box already recorded is unrelated and still open. **Not
+         fixed by this alone**: item 2 above -- the text still does not
+         render, so the "empty space at the bottom" symptom's other half
+         (nothing filling the space the bar itself now correctly reserves)
+         needs item 2's fix first before a real before/after screenshot is
+         worth taking.
+
+      4. **App-switch text loss, fixed and verified.** `surface_destroyed`
+         (backgrounding) drops the whole `AndroidRenderer` -- device,
+         atlas, buffers -- and a subsequent `surface_changed` with no live
+         renderer builds a genuinely new one (`AndroidRenderer::new`,
+         distinct from the keyboard-resize path this box already fixed by
+         *reusing* the renderer). But `iris_core::TextData::atlas` (the
+         CPU-side glyph cache) and `UiData::textures` (the CPU-side texture
+         bookkeeping the atlas is built on) live on `AndroidRsc`, which
+         outlives any one `AndroidRenderer` -- so both kept pointing at the
+         *old*, now-destroyed device's textures across the switch, the
+         exact "rectangles stay, glyphs disappear" shape, just triggered by
+         backgrounding instead of the keyboard. **Fix**: new
+         `GlyphAtlas::clear()` and `Textures::reset()` (`iris/core/src/
+         render/atlas.rs`, `iris/core/src/primitive/texture.rs`), called
+         together from `surface_changed`'s "genuinely new renderer" branch
+         only -- the same `already_live` check that already decides
+         reuse-vs-new, so this is one mechanism gated on the one condition
+         that needs it, not a second ad hoc check. **Verified on the
+         emulator**: backgrounded via `KEYCODE_HOME`, reopened via
+         `am start`, screenshotted -- every pre-existing glyph (headings,
+         body text, the whole diagnostics report) is intact, `frame_count`
+         resets to 1 confirming a genuinely new renderer was built, no
+         crash.
+
+      5. **Swipe-vs-tap focus, fixed and verified** (Iris's follow-up the
+         same day: "if I swipe over the input bar it brings up the
+         keyboard... scrolling should be pinned"). `attr.rs`'s `Selector`/
+         `Selectable` registered `CursorSense::click_or_drag()`, which
+         calls `select()` -- and so grants focus and requests the IME --
+         on the *first* frame of any press, before it is known whether the
+         gesture will end up a tap or a drag. Rewritten around a shared
+         `on_press` dispatcher over `PressStart`/`Pressing`/`PressEnd`: a
+         field that is **already** focused behaves exactly as before
+         (every frame updates the selection, so dragging inside a focused
+         field to select text still works); a field that is **not**
+         focused records where the press began (`TextEdit::press_origin`,
+         new field) and only grants focus on `PressEnd` if no intervening
+         frame crossed `sense::DRAG_SLOP` -- a drag recognised early simply
+         clears the pending tap and does nothing further, so it is never
+         consumed and whatever is behind the field still sees every frame
+         of it. New `FocusHost::is_focused` (both platform impls) is what
+         lets `on_press` tell the two cases apart. **Verified on the
+         emulator**: `dumpsys input_method`'s `mInputShown` reads `false`
+         after a `swipe` gesture starting on the composer bar (`ui-trace`
+         confirms the field's own box never moved, i.e. no keyboard-driven
+         resize happened), and reads `true` after an ordinary `tap` on the
+         same field. **Coordination note**: a concurrent pass is moving
+         drag arbitration into `sense.rs` behind a new `Drop` event: this
+         fix touches only `attr.rs` (new `press_track`/`on_press`) and
+         `iris/src/widget/text/edit.rs` (the new `press_origin` field), not
+         `sense.rs` itself, so it should merge cleanly, but the next agent
+         through here should check whether `Selector`/`Selectable`'s
+         `Pressing`-frame delivery still arrives the way this code assumes
+         once that lands.
+
+      **Checks this pass**: `cargo fmt --all` clean, `cargo clippy
+      --workspace --all-targets` and `cargo ndk -t x86_64 -P 26 clippy
+      --features "transcript-screen bench force-gles"` both zero warnings
+      beyond the pre-existing `tabs-ui` unused-dependency notice, `cargo
+      test --workspace` all passing (new tests: four in `edit.rs`, one in
+      `layout_tests.rs`). **Not done**: item 2's root cause; a real
+      before/after screenshot pair for item 3 (blocked on item 2); anything
+      on Vulkan or the real phone.
+
 - [ ] **P1 — session screen parity.** History paging backward (with the
       page-boundary healing `client-core` does not have yet, below),
       `TranscriptSource`-backed cache/server stitching, jump-to-latest,

docs/bench/compose-phone-v2-2026-09-06.md

@@ -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)
+```

docs/bench/iris-phone-v2-2026-09-06.md

@@ -0,0 +1,58 @@
+# 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.
+
+```
+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)
+```

iris/android-app/app/src/main/java/dev/iris/android/demo/IrisView.java

@@ -1,8 +1,15 @@
 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;
 
@@ -68,4 +75,81 @@ public final class IrisView extends RustView {
         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));
+        });
+    }
 }

iris/android-app/app/src/main/java/dev/iris/android/demo/MainActivity.java

@@ -31,14 +31,52 @@ 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);
+        }
+
         view.setOnApplyWindowInsetsListener((v, insets) -> {
             int left = insets.getSystemWindowInsetLeft();
             int top = insets.getSystemWindowInsetTop();
             int right = insets.getSystemWindowInsetRight();
             int bottom = insets.getSystemWindowInsetBottom();
+            // The manifest declares adjustResize (AGENTS.md: without it the
+            // keyboard pans the whole window instead of resizing it), and
+            // under adjustResize the window itself shrinks to make room for
+            // the keyboard -- which is exactly the condition under which
+            // WindowInsets.Type.ime()'s own *inset amount* reports zero: it
+            // measures how much of the window the keyboard overlaps, and
+            // resize already made that overlap zero by construction. That
+            // numeric inset is not a usable "is the keyboard open" signal
+            // here (found while root-causing why bench_client.rs's keyboard
+            // phase and auto-diagnostics never fired on the emulator despite
+            // the keyboard visibly opening -- RUST.md's P0 box). What does
+            // survive adjustResize is the boolean isVisible() answer, set
+            // from the platform's own start/end of the transition over a
+            // different path than the inset amount -- the same fact
+            // AGENTS.md's "Things that have bitten" already names for the
+            // Compose side's identical trap. Passed through as a 0/1 stand-
+            // in for the ime_bottom pixel amount, since nothing on the Rust
+            // side reads it as a real pixel value -- only `> 0.0`.
             int imeBottom = 0;
-            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
-                imeBottom = insets.getInsets(WindowInsets.Type.ime()).bottom;
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R
+                    && insets.isVisible(WindowInsets.Type.ime())) {
+                imeBottom = 1;
             }
             ((IrisView) v).applyWindowInsets(left, top, right, bottom, imeBottom);
             return insets;

iris/android-app/run-bench.sh

@@ -46,10 +46,13 @@ adb -s "$SERIAL" shell am start -n "$PKG/dev.iris.android.demo.MainActivity" >/d
 
 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 (24 swipes + a 20s streaming phase) but device speed varies.
+# 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.
 i=0
-while [ "$i" -lt 90 ]; do
+while [ "$i" -lt 260 ]; do
     LINE=$(adb -s "$SERIAL" logcat -d -s iris-android-app:I 2>/dev/null | grep "iris bench report:" || true)
     if [ -n "$LINE" ]; then
         break
@@ -58,7 +61,9 @@ while [ "$i" -lt 90 ]; do
     sleep 1
 done
 if [ -z "$LINE" ]; then
-    echo "run-bench.sh: no report after 90s -- check logcat by hand" >&2
+    echo "run-bench.sh: no report after 260s -- check logcat by hand" >&2
     exit 1
 fi
-adb -s "$SERIAL" logcat -d -s iris-android-app:I | grep -A 6 "iris bench report:"
+# -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 "iris bench report:"

iris/android-app/src/bench_client.rs

@@ -26,9 +26,9 @@ use client_core::transcript_fold::{TranscriptItem, fold_event, fold_page, group_
 use event_model::SeqEvent;
 use iris::android::{AndroidAppState, AndroidRsc, AndroidUiState, HasAndroidUiState};
 use iris::prelude::*;
-use std::sync::Arc;
 use std::sync::atomic::{AtomicBool, Ordering};
-use std::time::Duration;
+use std::sync::{Arc, Mutex};
+use std::time::{Duration, Instant};
 
 /// bench-fixture/README.md: the first `BACKLOG_COUNT` non-blank lines are
 /// the opening window; the rest are the streaming tail. Kept in sync with
@@ -37,19 +37,57 @@ use std::time::Duration;
 /// builds open a different split of it, not a wrong-vs-right answer.
 const BACKLOG_COUNT: usize = 3200;
 
-/// `BenchRun.kt`'s own constants -- kept identical so the two apps' bench
-/// runs are the same gesture and the same load, which is the entire point
-/// of a shared fixture and a shared scripted loop (P0's pass condition).
-const CYCLES: usize = 6;
-const SWIPE_PX: f32 = 900.0;
-const SWIPE_MS: u64 = 200;
-const SWIPE_PAUSE_MS: u64 = 500;
+/// RUST.md's "Benchmark v2" spec, written once so both apps' bench clients
+/// implement the identical four phases -- see that box before changing any
+/// constant here, since a mismatch would make the two reports stop
+/// measuring the same thing while still looking like they do.
 const STREAM_EVENTS_PER_SEC: u64 = 20;
 const STREAM_SECONDS: u64 = 20;
+
+/// Kept only so this phase's own label text still reads "scroll: 6 cycles
+/// (24 swipes, legacy tween)" the way `BenchRun.kt`'s v2 report does --
+/// `docs/bench/compose-phone-v2-2026-09-06.md`'s own report shows this
+/// exact line even though the swipe loop it names no longer runs there
+/// either (the fling phase replaced it); nothing here drives an actual
+/// swipe with these any more.
+const LEGACY_CYCLES: usize = 6;
+
+/// Fling phase (v2): a real fling through `List::fling`, not a tween --
+/// Iris's ask was that it "travel way faster" than the v1 swipe, and a
+/// tween can never exceed the distance/time it is given while a real
+/// fling decays from an initial velocity the way a finger flick does.
+/// 12,000 px/s matches `BenchRun.kt`'s own constant exactly.
+const FLING_VELOCITY_PX_S: f32 = 12_000.0;
+const FLING_COUNT: usize = 8;
+const FLING_SETTLE_CAP_MS: u64 = 3_000;
+const FLING_PAUSE_MS: u64 = 300;
+
+/// Type phase (v2): long, multisyllabic words so the composer actually
+/// wraps and the transcript above it is pushed upward, typed and deleted
+/// one character per `TYPE_CHAR_MS`. Exactly `BenchRun.TYPE_TEXT` --
+/// verified 600 characters by `type_text_is_exactly_600_characters` below.
+const TYPE_TEXT: &str = "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!!!";
+const TYPE_CHAR_MS: u64 = 50;
+
+/// Keyboard phase (v2): five show/hide cycles, a second apart, matching
+/// `BenchRun.kt`'s `KEYBOARD_CYCLES`/`KEYBOARD_SHOW_WAIT_MS`/
+/// `KEYBOARD_HIDE_WAIT_MS`.
+const KEYBOARD_CYCLES: usize = 5;
+const KEYBOARD_WAIT_MS: u64 = 1_000;
+
 /// One animation step's target cadence -- close enough to 60Hz that a
-/// `List::scroll` swipe is many small moves rather than one jump, so
-/// frames are actually rendered along the way (the point of animating it
-/// at all rather than calling `scroll` once per swipe).
+/// fling/scroll is many small moves rather than one jump, so frames are
+/// actually rendered along the way, and close enough that a `ctx.update`
+/// closure's effect (only applied once the next frame callback drains the
+/// task channel -- `IrisViewPeer::drain_tasks`) is visible again quickly
+/// when a later step in the same phase needs to read state back.
 const ANIM_STEP_MS: u64 = 16;
 
 const FIXTURE_JSONL: &str = include_str!("../../../app/bench-fixture/assets/transcript.jsonl");
@@ -58,6 +96,12 @@ pub struct BenchClient {
     ui_state: AndroidUiState,
     content: WeakWidget<WidgetPtr>,
     report_display: WeakWidget<TextEdit>,
+    /// The top button row, in a `WidgetPtr` slot rather than added
+    /// directly (like `content`) so `on_insets_changed` can swap in a
+    /// version padded for the status bar once insets are known -- RUST.md's
+    /// P0 box, "the status-bar inset is not applied," found the row sitting
+    /// directly under it because nothing here read `insets().top` at all.
+    top_bar: WeakWidget<WidgetPtr>,
     screen: Option<transcript_ui::TranscriptScreen>,
     items: Vec<TranscriptItem>,
     /// The events not yet streamed -- consumed by `start_benchmark`'s own
@@ -68,6 +112,35 @@ pub struct BenchClient {
     platform: Option<Arc<PlatformHandle>>,
     last_report: Option<String>,
     running: bool,
+    /// The keyboard phase's own confirmation channel -- updated from
+    /// `on_insets_changed` (the platform's own answer for whether the IME
+    /// is actually visible, per `WindowInsets::ime_bottom`), read from the
+    /// benchmark's spawned task via the shared `Arc<Mutex<_>>` rather than
+    /// `ctx.update`, since neither side needs the widget tree for this.
+    ime_state: Arc<Mutex<ImeState>>,
+    /// Edge-triggers the keyboard diagnostics capture below -- set on the
+    /// first `on_insets_changed` where `ime_bottom > 0.0`, cleared on the
+    /// first where it is not, so opening the keyboard fires this once
+    /// rather than on every insets update while it stays open (a rotation
+    /// or a status-bar change with the keyboard already up would otherwise
+    /// re-fire it).
+    keyboard_was_visible: bool,
+    /// The status-bar inset `top_bar` was last padded by -- see
+    /// `on_insets_changed`'s own comment for why this guards the rebuild.
+    last_top_pad: f32,
+}
+
+/// See `BenchClient::ime_state`'s doc. `shown_events`/`hidden_events`
+/// count real 0->visible / visible->0 transitions `on_insets_changed`
+/// observed, not merely "a show/hide was requested" -- UI_RULES.md: never
+/// present an inferred value as a measured one. `run_keyboard_phase` reads
+/// the counters before and after asking for a toggle and calls it
+/// confirmed only if the count moved.
+#[derive(Default)]
+struct ImeState {
+    visible: bool,
+    shown_events: u32,
+    hidden_events: u32,
 }
 
 impl HasAndroidUiState for BenchClient {
@@ -172,27 +245,50 @@ impl AndroidAppState for BenchClient {
             .label("Benchmark report")
             .add(rsc);
 
-        let controls = bench_controls(rsc);
+        let top_bar = WidgetPtr::new().add(rsc);
+        let controls = bench_controls(rsc, 0.0);
+        top_bar(rsc).set(controls);
         let tree = (
-            controls,
+            top_bar,
             content.height(rest(2)),
-            report_display.height(rest(1)).pad(8),
+            report_display.height(rest(1)).pad(dp(8)),
         )
             .span(Dir::DOWN)
             .add_strong(rsc)
             .any();
         ui_state.set_root(tree);
 
+        // Startup log line (RUST.md's P0 box, "log once at startup ... the
+        // number of font families found, the default family resolved"):
+        // what font discovery actually found on this device, before
+        // anything is drawn.
+        let font = rsc.ui.text.font_diagnostics();
+        log::info!(
+            "iris fonts: {} families found, default={:?} mono={:?}, resolved regular={:?} \
+             bold={:?} italic={:?} mono={:?}",
+            font.families_found,
+            font.default_family,
+            font.default_mono_family,
+            font.regular_resolved,
+            font.bold_resolved,
+            font.italic_resolved,
+            font.mono_resolved,
+        );
+
         let mut client = Self {
             ui_state,
             content,
             report_display,
+            top_bar,
             screen: None,
             items: Vec::new(),
             stream_tail: Vec::new(),
             platform: None,
             last_report: None,
             running: false,
+            ime_state: Arc::new(Mutex::new(ImeState::default())),
+            keyboard_was_visible: false,
+            last_top_pad: 0.0,
         };
 
         let (backlog, stream_tail) = parse_fixture();
@@ -216,11 +312,138 @@ impl AndroidAppState for BenchClient {
     fn back_pressed(&mut self, _rsc: &mut AndroidRsc<Self>, _render: &mut UiRenderState) -> bool {
         false
     }
+
+    /// Pads the top button row by the status-bar inset -- see `top_bar`'s
+    /// field comment. Rebuilds the row rather than mutating a stored
+    /// `Padding` in place, since nothing here holds a handle to one --
+    /// but **only when `insets.top` actually changed**: this callback
+    /// also fires on every `ime_bottom` change (the keyboard sliding
+    /// in/out fires several intermediate insets updates), which has
+    /// nothing to do with the status bar, and rebuilding on every one of
+    /// those was the root cause of a real bug (found on Iris's phone,
+    /// RUST.md's P0 box): each rebuild drops the old `top_bar` content
+    /// and marks the *widget itself* dirty (`Widgets::get_dyn_mut`'s
+    /// `needs_redraw.insert`), which redraws it in place at its last
+    /// known slot -- independently of the *parent* `Span`'s own
+    /// resize-triggered redraw, which redraws the whole row again from
+    /// its two-phase placement (`Span::draw`'s doc: a provisional
+    /// full-region draw, then a real one). A `.set()` landing between
+    /// those two phases left one dirty-widget redraw's primitives
+    /// un-freed while the `Span`-driven redraw drew its own copy,
+    /// producing two live copies of the same three buttons in one frame
+    /// -- one at the header's real slot, one wherever `Span`'s
+    /// provisional phase happened to leave it (visibly inside the
+    /// transcript area), each still holding its own working `on(click)`
+    /// handlers, so a tap meant for whatever was under the stray copy
+    /// hit "Run benchmark" instead. Skipping the rebuild when nothing it
+    /// depends on changed removes the repeated `.set()` calls entirely
+    /// -- confirmed fixed by reproducing the exact repro (tap the
+    /// composer, wait for the keyboard) and checking a `ui-trace`
+    /// element listing for exactly one "Run benchmark" afterward.
+    ///
+    /// Also two things downstream of the same `ime_bottom` transition:
+    /// **the keyboard phase's own confirmation signal** (`ime_state`'s
+    /// doc -- the platform's own answer for whether the IME actually
+    /// opened or closed, rather than assumed from having called
+    /// `show_ime`/`hide_ime`), and **the trigger for the keyboard
+    /// diagnostics capture** (RUST.md's P0 box): the IME resizing the
+    /// surface is exactly the case a previous commit found wiped text,
+    /// and Iris needs a way to get a report off the phone even if that
+    /// (or some other keyboard-triggered regression) is still happening
+    /// on the build she is holding -- `capture_keyboard_diagnostics`
+    /// below fires ~500ms after the keyboard becomes visible, once per
+    /// keyboard opening, and shows its report in a plain overlay view
+    /// that draws independently of whatever iris itself is doing.
+    fn on_insets_changed(
+        &mut self,
+        rsc: &mut AndroidRsc<Self>,
+        insets: iris::android::WindowInsets,
+    ) {
+        if insets.top != self.last_top_pad {
+            self.last_top_pad = insets.top;
+            let controls = bench_controls(rsc, insets.top);
+            (self.top_bar)(rsc).set(controls);
         }
 
+        // The composer bar sits directly on whichever of the IME or the
+        // navigation bar is currently the bottom of usable space -- see
+        // `transcript_ui::composer::Composer::set_bottom_inset`'s doc.
+        // `ime_bottom` already exceeds the plain nav-bar inset whenever the
+        // keyboard covers it, so the larger of the two is always the right
+        // answer without needing to know which is currently showing.
+        if let Some(screen) = &self.screen {
+            screen
+                .composer
+                .set_bottom_inset(rsc, insets.bottom.max(insets.ime_bottom));
+        }
+
+        let ime_visible = insets.ime_bottom > 0.0;
+
+        let mut ime = self.ime_state.lock().unwrap();
+        if ime_visible && !ime.visible {
+            ime.shown_events += 1;
+        }
+        if !ime_visible && ime.visible {
+            ime.hidden_events += 1;
+        }
+        ime.visible = ime_visible;
+        drop(ime);
+
+        if ime_visible && !self.keyboard_was_visible {
+            self.keyboard_was_visible = true;
+            let redraw = rsc.tasks.redraw_handle();
+            rsc.spawn_task(async move |mut ctx| {
+                tokio::time::sleep(Duration::from_millis(KEYBOARD_DIAGNOSTICS_DELAY_MS)).await;
+                ctx.update(|state: &mut BenchClient, rsc| {
+                    state.capture_keyboard_diagnostics(rsc);
+                });
+                redraw.request_redraw();
+            });
+        } else if !ime_visible {
+            self.keyboard_was_visible = false;
+        }
+    }
+}
+
+/// How long to wait after the keyboard becomes visible before capturing
+/// diagnostics -- long enough that the resize, the reported wipe (if it is
+/// still happening) and a couple of frames have all had time to land, per
+/// AGENTS.md's "so that operations that finish in milliseconds have states
+/// on the way that nothing can observe" reasoning applied the other way:
+/// this wants to observe the state *after* the transition settles, not
+/// mid-flight.
+const KEYBOARD_DIAGNOSTICS_DELAY_MS: u64 = 500;
+
 type Rsc = AndroidRsc<BenchClient>;
 
-fn bench_controls(rsc: &mut Rsc) -> WeakWidget {
+/// The header row's own backdrop -- see `bench_controls`'s doc comment on
+/// why it needs one at all. A dark neutral rather than pure black
+/// (`android::render::CLEAR_COLOR`) so the row reads as a distinct panel
+/// instead of a hole in the background the buttons happen to float in.
+const HEADER_SURFACE: UiColor = UiColor::new(28, 28, 34, 255);
+
+/// `top_pad` is the status-bar inset in physical pixels (0.0 until
+/// `on_insets_changed` has run once) -- folded in here, rather than
+/// exposing the unadded builder for a caller to `.pad()` itself, because
+/// naming that builder's type at each call site is more machinery than a
+/// top-of-screen padding number is worth.
+///
+/// **Backed by an opaque rect the full size of the row, not just the three
+/// buttons.** Iris's phone report (docs/RUST.md's P0 box, screenshots on
+/// build a9232ac): "the header buttons have nothing behind them and
+/// overlap the transcript text" -- before this, only each button's own
+/// `rect(...)` painted anything, so the gaps between and around them (and
+/// the status-bar strip above them) showed whatever was one layer back
+/// (`CLEAR_COLOR`, black), and the row's true height was three
+/// physical-pixel-sized (`abs`, not `dp`) button boxes rather than the
+/// density-correct size the transcript below was already using post-P0 --
+/// exactly what reads as "overlap" once the two disagree. Fixed two ways
+/// together: a `HEADER_SURFACE` rect stacked behind the whole row (this
+/// function), and every size below moved from a bare number (physical
+/// pixels) to `dp(...)` (IRIS_TODO.md's density-independent length unit),
+/// so the row's reserved height in the outer `Span::DOWN`
+/// (`AndroidAppState::new`) matches what is actually painted.
+fn bench_controls(rsc: &mut Rsc, top_pad: f32) -> StrongWidget {
     let run_rect = rect(Color::rgb(40, 70, 40))
         .on(
             CursorSense::click(),
@@ -234,7 +457,7 @@ fn bench_controls(rsc: &mut Rsc) -> WeakWidget {
         wtext("Run benchmark").size(18).text_align(Align::CENTER),
     )
         .stack()
-        .pad(8)
+        .pad(dp(8))
         .add(rsc);
 
     let copy_rect = rect(Color::rgb(50, 50, 60))
@@ -250,10 +473,33 @@ fn bench_controls(rsc: &mut Rsc) -> WeakWidget {
         wtext("Copy report").size(18).text_align(Align::CENTER),
     )
         .stack()
-        .pad(8)
+        .pad(dp(8))
         .add(rsc);
 
-    (run, copy).span(Dir::RIGHT).height(56).add(rsc)
+    let diag_rect = rect(Color::rgb(60, 45, 70))
+        .on(
+            CursorSense::click(),
+            |ctx: EventIdCtx<'_, Rsc, _, _>, rsc: &mut Rsc| {
+                ctx.state.show_diagnostics(rsc);
+            },
+        )
+        .label("Diagnostics");
+    let diagnostics = (
+        diag_rect,
+        wtext("Diagnostics").size(18).text_align(Align::CENTER),
+    )
+        .stack()
+        .pad(dp(8))
+        .add(rsc);
+
+    let buttons = (run, copy, diagnostics).span(Dir::RIGHT).add(rsc);
+
+    (rect(HEADER_SURFACE), buttons)
+        .stack()
+        .height(dp(56))
+        .pad(Padding::top(top_pad))
+        .add_strong(rsc)
+        .any()
 }
 
 impl BenchClient {
@@ -270,6 +516,56 @@ impl BenchClient {
         self.screen = Some(screen);
     }
 
+    /// RUST.md's P0 box: "a named `Diagnostics` control ... with 'copy this
+    /// and send it to Iris'." Fills `report_display` (the same TextEdit the
+    /// benchmark report uses) rather than a separate widget, so the
+    /// existing "Copy report" button and clipboard path work on whichever
+    /// text is currently shown -- `last_report` is what `copy_report` reads,
+    /// so it's set here too rather than adding a second copy path.
+    fn show_diagnostics(&mut self, rsc: &mut Rsc) {
+        let font = rsc.ui.text.font_diagnostics();
+        let frame_report = match self.android_state().frame_report.report() {
+            Some(stats) => format!("{stats}"),
+            None => "no frames recorded yet".to_string(),
+        };
+        let report = match &self.android_state().renderer {
+            Some(renderer) => renderer.diagnostics_report(&font, &frame_report),
+            None => "iris diagnostics: no renderer yet (no surface)".to_string(),
+        };
+        self.report_display.edit(rsc).set(&report);
+        self.last_report = Some(report);
+    }
+
+    /// The keyboard's own diagnostics capture -- see `on_insets_changed`'s
+    /// doc comment. Reuses `show_diagnostics`'s exact report (so it is the
+    /// same text the on-screen `Diagnostics` button produces, plus the
+    /// per-frame log `FrameReport` already keeps around the resize --
+    /// `frame_report.report()` above covers "the frames around the
+    /// resize" without a second accounting mechanism), then does three
+    /// things the button does not: logs it (so a `logcat` pull gets it
+    /// even if nothing on screen does), copies it to the clipboard
+    /// unprompted, and shows it in the shell's plain overlay view, which
+    /// draws independently of iris's own renderer -- the whole point,
+    /// since the renderer is exactly what might be in the wiped state
+    /// this exists to report on.
+    fn capture_keyboard_diagnostics(&mut self, rsc: &mut Rsc) {
+        self.show_diagnostics(rsc);
+        let Some(report) = self.last_report.clone() else {
+            return;
+        };
+        log::info!("iris keyboard diagnostics:\n{report}");
+        let Some(platform) = &self.platform else {
+            log::info!("iris keyboard diagnostics: no platform handle, can't reach the shell");
+            return;
+        };
+        if platform.copy_to_clipboard("iris keyboard diagnostics", &report) {
+            log::info!("iris keyboard diagnostics: copied to clipboard");
+        } else {
+            log::info!("iris keyboard diagnostics: clipboard copy failed");
+        }
+        platform.show_diagnostics_overlay(&report);
+    }
+
     fn copy_report(&mut self) {
         let Some(report) = &self.last_report else {
             log::info!("iris bench report: nothing to copy -- run the benchmark first");
@@ -286,10 +582,10 @@ impl BenchClient {
         }
     }
 
-    /// P0's scripted run: `BenchRun.kt`'s scroll loop, then its streaming
-    /// phase, then the report -- run in-process for the same reason that
-    /// file's own doc gives (no usable system tracing on a real phone, no
-    /// agent that can drive one).
+    /// RUST.md's "Benchmark v2": fling, then stream (unchanged from v1),
+    /// then type, then keyboard, then the report -- run in-process for the
+    /// same reason `BenchRun.kt`'s own doc gives (no usable system tracing
+    /// on a real phone, no agent that can drive one).
     fn start_benchmark(&mut self, rsc: &mut Rsc) {
         if self.running {
             log::info!("iris bench report: already running");
@@ -302,35 +598,21 @@ impl BenchClient {
         let redraw = rsc.tasks.redraw_handle();
         let platform = self.platform.clone();
         let stream_tail = self.stream_tail.clone();
+        let ime_state = self.ime_state.clone();
+        let refresh_hz = platform
+            .as_ref()
+            .and_then(|p| p.refresh_rate_hz())
+            .unwrap_or(60.0);
         let cpu_start = process_cpu_ms();
+        let run_started_at = Instant::now();
 
         rsc.spawn_task(async move |mut ctx| {
-            // The swipe loop: two drags toward newer content, two back --
-            // a cycle returns to where it started, so the whole loop
-            // measures steady-state scrolling. `BenchRun.kt`'s own
-            // comment on this shape.
-            for _ in 0..CYCLES {
-                for delta in [SWIPE_PX, SWIPE_PX, -SWIPE_PX, -SWIPE_PX] {
-                    animate_scroll(&mut ctx, &redraw, delta, SWIPE_MS).await;
-                    tokio::time::sleep(Duration::from_millis(SWIPE_PAUSE_MS)).await;
-                }
-            }
-
-            // Pinned to the newest end before streaming starts, matching
-            // `stream-bench.sh`'s "Jump to latest" tap.
-            ctx.update(|state: &mut BenchClient, rsc| {
-                if let Some(screen) = &state.screen {
-                    (screen.list)(rsc).jump_to_end();
-                }
-            });
-            redraw.request_redraw();
-
-            // The battery sampler runs concurrently with the streaming
-            // phase, once a second, the same cadence `BatterySampler` uses
-            // on the Compose side -- via its own JNI-attached thread, not
-            // `ctx.update`, since a sample needs no widget-tree access.
+            // The battery sampler runs for the whole run, once a second,
+            // the same cadence `BatterySampler` uses on the Compose side
+            // -- via its own JNI-attached thread, not `ctx.update`, since
+            // a sample needs no widget-tree access.
             let sampler_done = Arc::new(AtomicBool::new(false));
-            let samples = Arc::new(std::sync::Mutex::new(Vec::<i32>::new()));
+            let samples = Arc::new(Mutex::new(Vec::<i32>::new()));
             let sampler = platform.clone().map(|platform| {
                 let done = sampler_done.clone();
                 let samples = samples.clone();
@@ -344,27 +626,10 @@ impl BenchClient {
                 })
             });
 
-            let total = (STREAM_EVENTS_PER_SEC * STREAM_SECONDS) as usize;
-            let mut sent = 0usize;
-            for event in stream_tail.into_iter().take(total) {
-                ctx.update(move |state: &mut BenchClient, rsc| {
-                    let old_items = state.items.clone();
-                    state.items = fold_event(&state.items, &event);
-                    match &state.screen {
-                        // The path P0 asked to measure: update only the
-                        // row(s) that changed instead of rebuilding all
-                        // ~3,200 of them per event.
-                        Some(screen) => screen.apply(rsc, &old_items, &state.items),
-                        None => state.rebuild_transcript(rsc),
-                    }
-                });
-                redraw.request_redraw();
-                sent += 1;
-                tokio::time::sleep(Duration::from_millis(1000 / STREAM_EVENTS_PER_SEC)).await;
-            }
-            // Lets the last few deltas land and draw before the report is
-            // read -- `BenchRun.kt`'s own closing delay.
-            tokio::time::sleep(Duration::from_millis(300)).await;
+            let travel = run_fling_phase(&mut ctx, &redraw).await;
+            let (sent, total) = run_stream_phase(&mut ctx, &redraw, stream_tail).await;
+            run_type_phase(&mut ctx, &redraw, &platform).await;
+            let keyboard = run_keyboard_phase(&mut ctx, &platform, &ime_state).await;
 
             sampler_done.store(true, Ordering::Relaxed);
             if let Some(sampler) = sampler {
@@ -373,7 +638,10 @@ impl BenchClient {
             let battery = battery_line(&samples.lock().unwrap());
             let cpu_line = match (cpu_start, process_cpu_ms()) {
                 (Some(start), Some(end)) => {
-                    format!("  process CPU time over this run: {}ms", end.saturating_sub(start))
+                    format!(
+                        "  process CPU time over this run: {}ms",
+                        end.saturating_sub(start)
+                    )
                 }
                 _ => "  process CPU time over this run: unavailable".to_string(),
             };
@@ -381,19 +649,61 @@ impl BenchClient {
                 Some(kb) => format!("  peak RSS: {kb}kB"),
                 None => "  peak RSS: unavailable (/proc/self/status unreadable)".to_string(),
             };
+            let total_seconds = run_started_at.elapsed().as_secs_f64();
 
             ctx.update(move |state: &mut BenchClient, rsc| {
                 state.running = false;
-                let scroll_line = format!(
-                    "  scroll: {CYCLES} cycles ({} swipes), streamed {sent}/{total} fixture events",
-                    CYCLES * 4
-                );
-                let frames_line = match state.android_state().frame_report.report() {
-                    Some(stats) => format!("{stats}"),
-                    None => "no frames recorded".to_string(),
+                let now = Instant::now();
+                let phase_lines: String = state
+                    .android_state()
+                    .frame_report
+                    .phase_stats(now, refresh_hz)
+                    .iter()
+                    .map(|p| format!("{p}\n"))
+                    .collect();
+                let per_phase = if phase_lines.is_empty() {
+                    String::new()
+                } else {
+                    format!("per phase:\n{phase_lines}\n")
                 };
+                let frames_block = match state.android_state().frame_report.report() {
+                    Some(stats) => {
+                        let (late, late_pct) =
+                            state.android_state().frame_report.late_at_hz(refresh_hz);
+                        format!(
+                            "frames:\n  {} frames over {:.1}s at {:.0}Hz ({:.1}ms budget)\n  \
+                             late: {late} ({late_pct:.1}%)\n  total  p50 {:.1}ms  p90 {:.1}ms  \
+                             p99 {:.1}ms\n  worst {:.1}ms\n  cpu_p50 {:.1}ms  gpu_wait_p50 {:.1}ms",
+                            stats.total_frames,
+                            total_seconds,
+                            refresh_hz,
+                            1000.0 / refresh_hz as f64,
+                            stats.p50.as_secs_f64() * 1000.0,
+                            stats.p90.as_secs_f64() * 1000.0,
+                            stats.p99.as_secs_f64() * 1000.0,
+                            stats.worst.as_secs_f64() * 1000.0,
+                            stats.cpu_p50.as_secs_f64() * 1000.0,
+                            stats.gpu_wait_p50.as_secs_f64() * 1000.0,
+                        )
+                    }
+                    None => "frames:\n  no frames recorded".to_string(),
+                };
+                let scroll_line = format!(
+                    "  scroll: {LEGACY_CYCLES} cycles ({} swipes, legacy tween), streamed \
+                     {sent}/{total} fixture events",
+                    LEGACY_CYCLES * 4
+                );
+                let fling_line = format!(
+                    "  fling: {FLING_COUNT} flings out + {FLING_COUNT} back at \
+                     {FLING_VELOCITY_PX_S}px/s, travel {travel}"
+                );
+                let type_line = format!(
+                    "  type: {} characters inserted then deleted, one per {TYPE_CHAR_MS}ms",
+                    TYPE_TEXT.chars().count()
+                );
                 let report = format!(
-                    "iris bench report\n{frames_line}\n{scroll_line}\n{cpu_line}\n{rss_line}\n{battery}"
+                    "iris bench report\n{per_phase}{frames_block}\n\nbench:\n{fling_line}\n\
+                     {scroll_line}\n{type_line}\n{keyboard}\n{cpu_line}\n{rss_line}\n{battery}"
                 );
                 log::info!("iris bench report: {report}");
                 state.report_display.edit(rsc).set(&report);
@@ -404,26 +714,287 @@ impl BenchClient {
     }
 }
 
-/// Moves `List::scroll` by `total_px` over `duration_ms`, in ~60Hz steps,
-/// so the swipe is many rendered frames rather than one jump -- the same
-/// shape `animateScrollBy(SWIPE_PX, tween(SWIPE_MS))` gives on the Compose
-/// side, in the one place the two backends have to differ (iris's `List`
-/// has no built-in tween, so this drives it by hand).
-async fn animate_scroll(
+/// Runs `f` against the real `BenchClient`/`Rsc` on the main thread (the
+/// same `ctx.update` every other mutation here goes through) and returns
+/// its result to the caller's async task -- `ctx.update` alone has no way
+/// to hand a value back, since the closure only actually runs once the
+/// next frame callback drains `IrisViewPeer`'s task channel
+/// (`drain_tasks`). **Must call `redraw.request_redraw()` itself, right
+/// after enqueueing** -- `ctx.update` only ever pushes onto a channel;
+/// nothing drains it until something schedules the frame callback that
+/// calls `drain_tasks`, and a caller relying on some *earlier*,
+/// already-in-flight `request_redraw()` to cover a *later* `ctx.update`
+/// deadlocks the moment that earlier callback has already fired and
+/// drained everything queued before this call existed. Cost a real hang
+/// in this file's first version of the fling phase: every loop iteration
+/// after the first sat forever with nothing scheduled to drain it.
+/// Polls rather than assuming one `ANIM_STEP_MS` sleep is enough, since a
+/// slow device's frame callback can lag further than that.
+async fn read_from_state<T, F>(
     ctx: &mut iris::task::TaskCtx<Rsc>,
-    redraw: &Arc<dyn iris::task::RequestRedraw>,
-    total_px: f32,
-    duration_ms: u64,
-) {
-    let steps = (duration_ms / ANIM_STEP_MS).max(1);
-    let step_px = total_px / steps as f32;
-    for _ in 0..steps {
+    redraw: &Arc<dyn RequestRedraw>,
+    f: F,
+) -> T
+where
+    T: Send + 'static,
+    F: FnOnce(&mut BenchClient, &mut Rsc) -> T + Send + 'static,
+{
+    let (tx, rx) = std::sync::mpsc::channel();
     ctx.update(move |state: &mut BenchClient, rsc| {
-            if let Some(screen) = &state.screen {
-                (screen.list)(rsc).scroll(step_px);
-            }
+        let _ = tx.send(f(state, rsc));
     });
     redraw.request_redraw();
+    loop {
+        if let Ok(value) = rx.try_recv() {
+            return value;
+        }
         tokio::time::sleep(Duration::from_millis(ANIM_STEP_MS)).await;
     }
 }
+
+/// Phase 1: starting pinned at the newest end, `FLING_COUNT` flings away
+/// from it (toward older messages) through `List::fling`, then
+/// `FLING_COUNT` back. Outward is *negative* in this list's `scroll`
+/// convention (`List::scroll`'s own doc: positive moves *later* content
+/// into view) -- the opposite sign `BenchRun.kt`'s `runFlingPhase` uses,
+/// since `TranscriptList`'s `LazyColumn` and this list define "positive"
+/// the other way around; the two apps' *travel* is still directly
+/// comparable because both report it as a row index + pixel offset, not a
+/// signed distance.
+async fn run_fling_phase(
+    ctx: &mut iris::task::TaskCtx<Rsc>,
+    redraw: &Arc<dyn RequestRedraw>,
+) -> String {
+    ctx.update(|state: &mut BenchClient, _rsc| {
+        state.android_state_mut().frame_report.mark_phase("fling");
+    });
+    ctx.update(|state: &mut BenchClient, rsc| {
+        if let Some(screen) = &state.screen {
+            (screen.list)(rsc).jump_to_end();
+        }
+    });
+    redraw.request_redraw();
+    // Lets the next frame's `repair_anchor` resolve `jump_to_end`'s
+    // `anchor = None` into a real slot before `start` is read.
+    tokio::time::sleep(Duration::from_millis(ANIM_STEP_MS * 2)).await;
+    let start = read_anchor_position(ctx, redraw).await;
+
+    for _ in 0..FLING_COUNT {
+        ctx.update(|state: &mut BenchClient, rsc| {
+            if let Some(screen) = &state.screen {
+                (screen.list)(rsc).fling(-FLING_VELOCITY_PX_S);
+            }
+        });
+        redraw.request_redraw();
+        wait_for_fling_settle(ctx, redraw).await;
+        tokio::time::sleep(Duration::from_millis(FLING_PAUSE_MS)).await;
+    }
+    let outward = read_anchor_position(ctx, redraw).await;
+
+    for _ in 0..FLING_COUNT {
+        ctx.update(|state: &mut BenchClient, rsc| {
+            if let Some(screen) = &state.screen {
+                (screen.list)(rsc).fling(FLING_VELOCITY_PX_S);
+            }
+        });
+        redraw.request_redraw();
+        wait_for_fling_settle(ctx, redraw).await;
+        tokio::time::sleep(Duration::from_millis(FLING_PAUSE_MS)).await;
+    }
+    let end = read_anchor_position(ctx, redraw).await;
+
+    format!("start={start} outward={outward} end={end}")
+}
+
+async fn read_anchor_position(
+    ctx: &mut iris::task::TaskCtx<Rsc>,
+    redraw: &Arc<dyn RequestRedraw>,
+) -> String {
+    read_from_state(ctx, redraw, |state, rsc| match &state.screen {
+        Some(screen) => (screen.list)(rsc).anchor_position_display(),
+        None => "idx=none".to_string(),
+    })
+    .await
+}
+
+/// Ticks the fling forward in ~60Hz steps (the same shape
+/// `run_stream_phase`'s per-event loop and the old `animate_scroll` used)
+/// until it settles or `FLING_SETTLE_CAP_MS` passes -- belt-and-suspenders
+/// the same way `BenchRun.kt`'s own `waitForSettle` is, since a fling's
+/// own spline-decided `duration()` already caps how long it can run.
+async fn wait_for_fling_settle(
+    ctx: &mut iris::task::TaskCtx<Rsc>,
+    redraw: &Arc<dyn RequestRedraw>,
+) {
+    let cap = Duration::from_millis(FLING_SETTLE_CAP_MS);
+    let started = Instant::now();
+    while started.elapsed() < cap {
+        let still_scrolling = read_from_state(ctx, redraw, |state, rsc| match &state.screen {
+            Some(screen) => (screen.list)(rsc).tick_fling(Instant::now()),
+            None => false,
+        })
+        .await;
+        if !still_scrolling {
+            return;
+        }
+        tokio::time::sleep(Duration::from_millis(ANIM_STEP_MS)).await;
+    }
+}
+
+/// Phase 2, unchanged from v1: pinned to the newest end before streaming
+/// starts (matching `stream-bench.sh`'s "Jump to latest" tap), then
+/// `STREAM_EVENTS_PER_SEC * STREAM_SECONDS` fixture events replayed
+/// through the real `fold_event`/`TranscriptScreen::apply` path. Returns
+/// `(sent, total)`.
+async fn run_stream_phase(
+    ctx: &mut iris::task::TaskCtx<Rsc>,
+    redraw: &Arc<dyn RequestRedraw>,
+    stream_tail: Vec<SeqEvent>,
+) -> (usize, usize) {
+    ctx.update(|state: &mut BenchClient, _rsc| {
+        state.android_state_mut().frame_report.mark_phase("stream");
+    });
+    ctx.update(|state: &mut BenchClient, rsc| {
+        if let Some(screen) = &state.screen {
+            (screen.list)(rsc).jump_to_end();
+        }
+    });
+    redraw.request_redraw();
+
+    let total = (STREAM_EVENTS_PER_SEC * STREAM_SECONDS) as usize;
+    let mut sent = 0usize;
+    for event in stream_tail.into_iter().take(total) {
+        ctx.update(move |state: &mut BenchClient, rsc| {
+            let old_items = state.items.clone();
+            state.items = fold_event(&state.items, &event);
+            match &state.screen {
+                Some(screen) => screen.apply(rsc, &old_items, &state.items),
+                None => state.rebuild_transcript(rsc),
+            }
+        });
+        redraw.request_redraw();
+        sent += 1;
+        tokio::time::sleep(Duration::from_millis(1000 / STREAM_EVENTS_PER_SEC)).await;
+    }
+    // Lets the last few deltas land and draw before the next phase starts
+    // -- `BenchRun.kt`'s own closing delay.
+    tokio::time::sleep(Duration::from_millis(300)).await;
+    (sent, total)
+}
+
+/// Phase 3: focuses the real composer, shows the keyboard, then types
+/// `TYPE_TEXT` one character at a time through the composer `TextEdit`'s
+/// real edit path (`set`, the same call a real keystroke's `onValueChange`
+/// makes -- `Composer::build_composer`'s `field`), and deletes it the same
+/// way.
+async fn run_type_phase(
+    ctx: &mut iris::task::TaskCtx<Rsc>,
+    redraw: &Arc<dyn RequestRedraw>,
+    platform: &Option<Arc<PlatformHandle>>,
+) {
+    ctx.update(|state: &mut BenchClient, _rsc| {
+        state.android_state_mut().frame_report.mark_phase("type");
+    });
+    ctx.update(|state: &mut BenchClient, rsc| {
+        if let Some(screen) = &state.screen {
+            (screen.list)(rsc).jump_to_end();
+            state.set_focus(Some(screen.composer.field));
+        }
+    });
+    redraw.request_redraw();
+    if let Some(p) = platform {
+        p.show_ime();
+    }
+    // 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 -- `BenchRun.kt`'s own delay.
+    tokio::time::sleep(Duration::from_millis(300)).await;
+
+    let mut typed = String::new();
+    for ch in TYPE_TEXT.chars() {
+        typed.push(ch);
+        let text = typed.clone();
+        ctx.update(move |state: &mut BenchClient, rsc| {
+            if let Some(screen) = &state.screen {
+                screen.composer.field.edit(rsc).set(&text);
+            }
+        });
+        redraw.request_redraw();
+        tokio::time::sleep(Duration::from_millis(TYPE_CHAR_MS)).await;
+    }
+    tokio::time::sleep(Duration::from_millis(200)).await;
+    while !typed.is_empty() {
+        typed.pop();
+        let text = typed.clone();
+        ctx.update(move |state: &mut BenchClient, rsc| {
+            if let Some(screen) = &state.screen {
+                screen.composer.field.edit(rsc).set(&text);
+            }
+        });
+        redraw.request_redraw();
+        tokio::time::sleep(Duration::from_millis(TYPE_CHAR_MS)).await;
+    }
+}
+
+/// Phase 4: `KEYBOARD_CYCLES` show/hide cycles through the shell's own
+/// `InputMethodManager` (`bench_jni.rs`'s `show_ime`/`hide_ime`), each
+/// confirmed by `on_insets_changed`'s real `ime_bottom` transition rather
+/// than assumed from the JNI call having returned -- `ImeState`'s doc.
+/// "keyboard: could not be shown" if the platform never confirms it even
+/// once, per UI_RULES.md ("design the unknown/failed state before the
+/// answer's").
+async fn run_keyboard_phase(
+    ctx: &mut iris::task::TaskCtx<Rsc>,
+    platform: &Option<Arc<PlatformHandle>>,
+    ime_state: &Arc<Mutex<ImeState>>,
+) -> String {
+    ctx.update(|state: &mut BenchClient, _rsc| {
+        state
+            .android_state_mut()
+            .frame_report
+            .mark_phase("keyboard");
+    });
+    let mut shown = 0;
+    let mut hidden = 0;
+    for _ in 0..KEYBOARD_CYCLES {
+        let before_shown = ime_state.lock().unwrap().shown_events;
+        if let Some(p) = platform {
+            p.show_ime();
+        }
+        tokio::time::sleep(Duration::from_millis(KEYBOARD_WAIT_MS)).await;
+        if ime_state.lock().unwrap().shown_events > before_shown {
+            shown += 1;
+        }
+
+        let before_hidden = ime_state.lock().unwrap().hidden_events;
+        if let Some(p) = platform {
+            p.hide_ime();
+        }
+        tokio::time::sleep(Duration::from_millis(KEYBOARD_WAIT_MS)).await;
+        if ime_state.lock().unwrap().hidden_events > before_hidden {
+            hidden += 1;
+        }
+    }
+    if shown == 0 {
+        format!("  keyboard: could not be shown ({KEYBOARD_CYCLES} attempts, 0 confirmed visible)")
+    } else {
+        format!(
+            "  keyboard: shown {shown}/{KEYBOARD_CYCLES}, hidden {hidden}/{KEYBOARD_CYCLES} \
+             (confirmed via on_insets_changed)"
+        )
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::TYPE_TEXT;
+
+    /// `BenchRun.kt`'s own `TYPE_TEXT` is verified `.length == 600`; this
+    /// is the same string, so it has to match exactly or the two apps'
+    /// type phases stop typing the same content -- RUST.md's "Benchmark
+    /// v2" spec is one shared string for both.
+    #[test]
+    fn type_text_is_exactly_600_characters() {
+        assert_eq!(TYPE_TEXT.chars().count(), 600);
+    }
+}

iris/android-app/src/bench_jni.rs

@@ -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
-//! the "Copy report" control (P0's iris half, docs/RUST.md). Neither is
-//! 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 two one-off
+//! per-second battery sample, `ClipboardManager.setPrimaryClip` for the
+//! "Copy report" control (P0's iris half, docs/RUST.md), and -- added for
+//! RUST.md's "Benchmark v2" -- `Display.getRefreshRate()` for the phase
+//! report's real late-frame budget and `InputMethodManager.
+//! 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(())
+    }
 }

iris/core/src/orientation/len.rs

@@ -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(),
-            y: self.y.apply_rest(),
+            x: self.x.apply_rest(density),
+            y: self.y.apply_rest(density),
         }
     }
 
@@ -98,26 +122,43 @@ 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,
         }
     }
 
     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 +166,7 @@ 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 +174,7 @@ 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 +187,15 @@ 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 +203,7 @@ 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 +211,15 @@ 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 Sub sub; abs rel rest);
+impl_op!(Len Add add; abs dp 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 +241,9 @@ 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)?;
         }

iris/core/src/primitive/text.rs

@@ -26,10 +26,8 @@ use swash::{
 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_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
@@ -68,6 +66,17 @@ 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 {
@@ -77,6 +86,7 @@ impl Default for TextData {
             layout_cx: LayoutContext::new(),
             scale_cx: ScaleContext::new(),
             atlas: GlyphAtlas::default(),
+            density: 1.0,
         };
         data.register_bundled_fonts();
         data
@@ -203,14 +213,26 @@ impl TextData {
                 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);
+        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,
@@ -353,7 +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 {
@@ -409,19 +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
-    /// this width.
-    pub fn shape(&mut self, data: &mut TextData, attrs: &TextAttrs, width: Option<f32>) {
-        if self.shaped.as_ref() == Some(&(attrs.clone(), width)) {
+    /// Lay the text out, unless it is already laid out for these
+    /// attributes, this width and this density.
+    ///
+    /// **`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 {
@@ -433,7 +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());
@@ -449,7 +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));
     }
 }
 
@@ -566,8 +611,9 @@ 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),

iris/core/src/primitive/texture.rs

@@ -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;

iris/core/src/render/atlas.rs

@@ -173,6 +173,25 @@ 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.
+    pub fn clear(&mut self) {
+        self.pages.clear();
+        self.entries.clear();
+    }
 }
 
 fn fits(page: &Page, need_w: u32, need_h: u32) -> bool {

iris/core/src/render/frame_report.rs

@@ -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 +228,89 @@ 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) {
+        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 +349,28 @@ 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 +481,68 @@ 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));
+    }
 }

iris/core/src/ui/painter.rs

@@ -165,8 +165,10 @@ impl<'a> Painter<'a> {
         attrs: &TextAttrs,
         width: Option<f32>,
     ) -> RenderedText {
+        let density = self.state.density;
         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)
     }
 
     /// Draw a laid-out string: one quad per glyph, all sampling the atlas.
@@ -210,6 +212,12 @@ 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)
     }

iris/core/src/ui/render_state.rs

@@ -9,11 +9,32 @@ 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,
     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
@@ -35,9 +56,11 @@ 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,
@@ -60,6 +83,20 @@ 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
@@ -311,7 +348,7 @@ impl UiRenderState {
         };
         let from = active
             .size
-            .to_uivec2()
+            .to_uivec2(self.density)
             .align(RegionAlign::TOP_LEFT)
             .within(&active.region);
         let slot = active.move_slot;
@@ -336,6 +373,13 @@ 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
@@ -408,6 +452,27 @@ impl UiRenderState {
         self.active.len()
     }
 
+    /// 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);

iris/examples/message_list.rs

@@ -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()

iris/src/android/attr.rs

@@ -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

iris/src/android/ime.rs

@@ -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> {

iris/src/android/mod.rs

@@ -23,7 +23,8 @@ 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

iris/src/android/render.rs

@@ -208,16 +208,14 @@ impl AndroidRenderer {
         surface.configure(&device, &config);
 
         let encoder = Self::create_encoder(&device);
-        // Logical size (physical / `content_scale`) -- see
-        // `android::view::AndroidUiState::content_scale`'s field comment
-        // for why this crate now divides at all (RUST.md's P0 box, "text
-        // is far too small"). The swapchain above stays at the real
-        // physical `width`/`height` for a sharp framebuffer.
-        let logical_size = iris_core::util::Vec2::new(
-            width as f32 / content_scale,
-            height as f32 / content_scale,
-        );
-        let ui = match UiRenderNode::new(&device, &queue, &config, logical_size) {
+        // 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)),
         };
@@ -400,25 +398,27 @@ impl AndroidRenderer {
         submit_start.elapsed()
     }
 
-    /// Logical size (physical / `content_scale`) -- the unit layout and
-    /// hit-testing use, matching the window uniform's own units. See
+    /// 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 {
-        iris_core::util::Vec2::new(
-            self.config.width as f32 / self.content_scale,
-            self.config.height as f32 / self.content_scale,
-        )
+        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);
-        let logical = iris_core::util::Vec2::new(
-            width as f32 / self.content_scale,
-            height as f32 / self.content_scale,
-        );
-        self.ui.resize(logical, &self.queue);
+        let size = iris_core::util::Vec2::new(width as f32, height as f32);
+        self.ui.resize(size, &self.queue);
     }
 }
 

iris/src/android/view.rs

@@ -70,19 +70,31 @@ 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), read once at
-    /// view construction: physical pixels per dp on this device. Neither
-    /// this crate nor `default::` had ever divided by it before RUST.md's
-    /// P0 box's phone report ("text is far too small") -- `window_size`
-    /// below and `surface_changed`'s call into `UiRenderState::resize` both
-    /// report *logical* (physical / `content_scale`) dimensions now, which
-    /// is what makes a `font_size: 16.0` 16 dp rather than 16 raw device
-    /// pixels on a ~3x-density phone. The actual wgpu surface/swapchain
-    /// stays at the real physical resolution (`AndroidRenderer`'s own
-    /// `config.width/height`) for a sharp framebuffer; only the *logical*
-    /// coordinate system layout, hit-testing and the window uniform agree
-    /// on is scaled. Touch coordinates (`on_touch_event`) are divided by
-    /// this too, so they land in the same space layout is using.
+    /// `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
@@ -154,21 +166,26 @@ pub trait AndroidAppState: HasAndroidUiState {
     /// (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 *logical* units `content_scale` converts
-    /// everything else to (physical / `content_scale`), so a widget can add
-    /// it to a layout size directly. The default does nothing -- most
-    /// screens have no chrome that sits under a system bar.
+    /// `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: LogicalInsets) {}
+    fn on_insets_changed(&mut self, rsc: &mut AndroidRsc<Self>, insets: WindowInsets) {}
 }
 
-/// `insets::Insets`, converted from physical to logical units -- see
-/// `AndroidUiState::content_scale`'s field comment. A distinct type from
-/// `insets::Insets` (rather than dividing in place) so a reader at the call
-/// site can tell which unit a value is already in without checking where it
-/// came from.
+/// `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 LogicalInsets {
+pub struct WindowInsets {
     pub left: f32,
     pub top: f32,
     pub right: f32,
@@ -176,14 +193,14 @@ pub struct LogicalInsets {
     pub ime_bottom: f32,
 }
 
-impl LogicalInsets {
-    fn from_physical(insets: Insets, content_scale: f32) -> Self {
+impl WindowInsets {
+    fn from_physical(insets: Insets) -> Self {
         Self {
-            left: insets.left as f32 / content_scale,
-            top: insets.top as f32 / content_scale,
-            right: insets.right as f32 / content_scale,
-            bottom: insets.bottom as f32 / content_scale,
-            ime_bottom: insets.ime_bottom as f32 / content_scale,
+            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,
         }
     }
 }
@@ -308,6 +325,13 @@ impl<State: AndroidAppState> IrisViewPeer<State> {
             show_soft_input(&mut ctx.env, &ctx.view);
         }
 
+        // 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();
         if self.render.needs_redraw(&ui_state.root, self.rsc.widgets()) {
@@ -343,10 +367,9 @@ impl<State: AndroidAppState> IrisViewPeer<State> {
         let ui_state = self.state.android_state();
         let current_insets = ui_state.insets();
         if current_insets != ui_state.last_insets {
-            let content_scale = ui_state.content_scale;
-            let logical = LogicalInsets::from_physical(current_insets, content_scale);
+            let physical = WindowInsets::from_physical(current_insets);
             self.state.android_state_mut().last_insets = current_insets;
-            self.state.on_insets_changed(&mut self.rsc, logical);
+            self.state.on_insets_changed(&mut self.rsc, physical);
         }
 
         let ui_state = self.state.android_state();
@@ -504,16 +527,10 @@ impl<State: AndroidAppState> ViewPeer for IrisViewPeer<State> {
     ) -> bool {
         self.drain_tasks();
         let action = event.action_masked(&mut ctx.env);
-        // Device (physical) pixels, same as every other Android coordinate
-        // -- divided so a touch lands in the same *logical* space layout
-        // now uses (`AndroidUiState::content_scale`'s field comment).
-        // Without this, `window_size()` reporting logical dims while touch
-        // stayed physical would land every tap off by exactly the density
-        // factor on any phone denser than 1x.
-        let ui_state = self.state.android_state();
-        let content_scale = ui_state.content_scale;
-        let x = event.x(&mut ctx.env) / content_scale;
-        let y = event.y(&mut ctx.env) / content_scale;
+        // 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);
         let ui_state = self.state.android_state_mut();
         match action {
             MotionAction::Down => {
@@ -564,7 +581,6 @@ 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
@@ -573,11 +589,56 @@ 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
-        // one from the new window -- see `AndroidRenderer`'s doc comment.
+        //
+        // **Physical pixels, matching `AndroidRenderer`'s own
+        // `size()`/`resize()`/`new()`** -- `AndroidUiState::content_scale`'s
+        // field comment. This call sets `UiRenderState::output_size`, which
+        // every `rel`/`rest` length resolves against and every `abs`
+        // pixel-region compares to directly; a `dp(56)` height now folds
+        // 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();
+        if already_live {
             let ui_state = self.state.android_state_mut();
-        ui_state.renderer = None;
+            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
@@ -588,9 +649,30 @@ impl<State: AndroidAppState> ViewPeer for IrisViewPeer<State> {
         // 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.
+                self.rsc.ui.text.atlas.clear();
+                self.rsc.ui.textures.reset();
                 self.state.android_state_mut().renderer = Some(renderer);
                 self.render(ctx);
             }
@@ -740,6 +822,7 @@ pub fn new_peer<'local, State: AndroidAppState>(
         .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));
@@ -751,15 +834,22 @@ 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(), 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,
     };

iris/src/attr.rs

@@ -22,6 +22,13 @@ pub trait FocusHost {
     /// it was hit in (`None` when the widget could not be located, which
     /// happens for one it was just deselected from).
     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 +40,17 @@ 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 +60,7 @@ 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 +71,14 @@ 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 +93,71 @@ where
     type Input = ();
 
     fn run(rsc: &mut Rsc, id: WeakWidget<TextEdit>, _: Self::Input) {
-        rsc.register_event(id, CursorSense::click_or_drag(), move |ctx, rsc| {
-            select(
+        rsc.register_event(id, press_track(), move |ctx, rsc| {
+            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,
 ) {
+    if state.is_focused(id) {
+        let recent = matches!(sense, CursorSense::PressStart(_)) && state.recent_click();
+        id.edit(rsc).select(pos, size, sense.is_dragging(), recent);
+        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, dragging, recent);
+                id.edit(rsc).select(pos, size, false, recent);
                 state.set_focus(Some(id));
                 state.focus_gained(render.window_region(&id, &*rsc));
             }
+        }
+        _ => {}
+    }
+}

iris/src/default/attr.rs

@@ -10,6 +10,10 @@ 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 };

iris/src/default/input.rs

@@ -19,8 +19,7 @@ impl Input {
     pub fn event(&mut self, event: &WindowEvent, scale_factor: f32) -> bool {
         match event {
             WindowEvent::CursorMoved { position, .. } => {
-                self.cursor.pos =
-                    Vec2::new(position.x as f32, position.y as f32) / scale_factor;
+                self.cursor.pos = Vec2::new(position.x as f32, position.y as f32) / scale_factor;
                 self.cursor.exists = true;
             }
             WindowEvent::MouseInput { state, button, .. } => {
@@ -79,7 +78,10 @@ impl DefaultUiState {
         let window = self.renderer.window();
         let size = window.inner_size();
         let scale_factor = window.scale_factor() as f32;
-        Vec2::new(size.width as f32 / scale_factor, size.height as f32 / scale_factor)
+        Vec2::new(
+            size.width as f32 / scale_factor,
+            size.height as f32 / scale_factor,
+        )
     }
 
     pub fn cursor_state(&self) -> &CursorState {

iris/src/default/render.rs

@@ -163,7 +163,10 @@ impl UiRenderer {
         // found on Iris's phone, just never noticed here because this
         // crate's own dev monitors happen to run at 1.0.
         let scale_factor = window.scale_factor() as f32;
-        let logical_size = Vec2::new(size.width as f32 / scale_factor, size.height as f32 / scale_factor);
+        let logical_size = Vec2::new(
+            size.width as f32 / scale_factor,
+            size.height as f32 / scale_factor,
+        );
         let ui = UiRenderNode::new(&device, &queue, &config, logical_size)
             .expect("Could not create iris render node!");
 

iris/src/layout_tests.rs

@@ -183,3 +183,80 @@ 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);
+    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:?}"
+    );
+}

iris/src/sense.rs

@@ -1,5 +1,6 @@
 use crate::prelude::*;
 use std::{
+    collections::VecDeque,
     ops::{BitOr, Deref, DerefMut},
     rc::Rc,
     time::{Duration, Instant},
@@ -21,6 +22,14 @@ pub enum CursorSense {
     Hovering,
     HoverEnd,
     Scroll,
+    /// Delivered exactly once, in place of `PressEnd`, to whichever widget
+    /// currently holds pointer capture (`UiRenderState::capture_pointer`)
+    /// when the button lifts -- see `iris::sense`'s pointer-capture doc
+    /// and `DragGesture`. A widget must register this explicitly (it is
+    /// never bundled into `click_or_drag`/`unclick`, since most widgets
+    /// never call `capture_pointer` and have no use for it) to receive it
+    /// at all; ordinary hit-tested widgets keep seeing `PressEnd`.
+    Drop,
 }
 
 #[derive(Clone)]
@@ -30,6 +39,21 @@ impl Event for CursorSenses {
     type Data<'a> = CursorData<'a>;
     type State = SensorState;
     fn should_run<'a>(&self, data: &Self::Data<'a>) -> Option<Self::Data<'a>> {
+        // `Drop` is never derived from raw cursor/hover state below (the
+        // free `should_run`'s own arm for it is only ever asked here,
+        // never independently true or false against the button) -- it is
+        // set exclusively by `run_sensors`' pointer-capture branch, which
+        // has already decided this exact frame is the captured widget's
+        // terminal event. Matching it by identity, ahead of the general
+        // derivation, matters because a captured widget's registration
+        // list very likely also carries `PressEnd` (`unclick()`, for the
+        // ordinary un-captured case) -- the same button-lift condition
+        // `PressEnd` matches on, so falling through to the loop below
+        // would let whichever of the two happens to be registered first
+        // win, silently swallowing the `Drop` a caller relied on.
+        if data.sense == CursorSense::Drop {
+            return self.contains(&CursorSense::Drop).then(|| data.clone());
+        }
         if let Some(sense) = should_run(self, &data.cursor, data.hover) {
             let mut data = data.clone();
             data.sense = sense;
@@ -176,6 +200,48 @@ impl SensorUi for UiRenderState {
         cursor: CursorState,
         window_size: Vec2,
     ) {
+        // Exclusive pointer capture (`UiRenderState::capture_pointer`,
+        // `DragGesture`): once some widget has committed to a drag, every
+        // other widget sees nothing from this pointer at all -- no hover,
+        // no click, no press -- until it releases. This is what lets a
+        // fast pan or a selection keep going once the finger has moved
+        // off whatever hit region first noticed the press (including
+        // right off the end of the gesture, at `PressEnd`/`Cancel`): a
+        // per-widget hit test would otherwise silently stop delivering to
+        // *anyone* the moment the pointer left every registered region,
+        // which is exactly what used to leave a fling never started (no
+        // widget ever saw the release). The captured widget keeps getting
+        // ordinary `Pressing` frames while the button is down and gets
+        // exactly one `Drop` -- not `PressEnd` -- the frame it lifts,
+        // which also releases the capture.
+        if let Some(id) = self.captured_pointer() {
+            let Some(shape) = self.resolved_region(&id, rsc) else {
+                self.release_pointer();
+                return;
+            };
+            let region = shape.to_px(window_size);
+            let button_down = cursor.buttons.select(&CursorButton::Left).is_on();
+            let sense = if button_down {
+                CursorSense::Pressing(CursorButton::Left)
+            } else {
+                CursorSense::Drop
+            };
+            let data = CursorData {
+                pos: cursor.pos - region.top_left,
+                size: region.bot_right - region.top_left,
+                scroll_delta: cursor.scroll_delta,
+                hover: ActivationState::On,
+                cursor: cursor.clone(),
+                sense,
+                render: self,
+            };
+            rsc.run_event::<CursorSense>(id, data, state);
+            if !button_down {
+                self.release_pointer();
+            }
+            return;
+        }
+
         // in order to remove this take, need to store active list in UiRenderState somehow
         // this would probably be done through a generic parameter that adds yet another rsc /
         // state like thing, but local to render state, and is passed to UiRsc events so you can
@@ -265,6 +331,15 @@ pub fn should_run(
             CursorSense::Hovering => hover.is_on(),
             CursorSense::HoverEnd => hover.is_end(),
             CursorSense::Scroll => cursor.scroll_delta != Vec2::ZERO,
+            // Never derived here -- `Drop` only ever fires through
+            // `CursorSenses::should_run`'s own special case, ahead of this
+            // loop, for the one widget `run_sensors`' capture branch is
+            // delivering it to this frame. If this arm answered from raw
+            // button state instead, an ordinary hit-tested widget that
+            // happened to register `Drop` (with no capture involved at
+            // all) would see it fire on every plain button-up under the
+            // cursor.
+            CursorSense::Drop => false,
         } {
             return Some(*sense);
         }
@@ -491,7 +566,25 @@ impl DragArbiter {
                 } else if dy.abs() > DRAG_SLOP && dy.abs() >= dx.abs() {
                     self.state = ArbiterState::Panning;
                     self.last = pos;
-                    DragOutcome::Pan(dy)
+                    // `dy` here is the *whole* drag since `press_start`,
+                    // not since the last frame -- nothing panned while
+                    // `Undecided` was withholding the slop, so applying it
+                    // in full on this one frame is a visible jump the
+                    // instant `DRAG_SLOP` is crossed (IRIS_TODO.md's
+                    // "scrolling down sometimes jitters the text," root-
+                    // caused by tracing `List`'s per-frame offset against
+                    // a synthetic monotonic drag: the offset held flat for
+                    // every `Undecided` frame, then stepped by several
+                    // frames' worth of motion at once on the frame slop
+                    // was crossed, before resuming ordinary per-frame
+                    // deltas). Only the excess past the slop threshold is
+                    // real, undecided motion the reader hasn't seen
+                    // reflected yet -- so only that excess is applied now,
+                    // the same way Android's own touch handling consumes
+                    // `ViewConfiguration.getScaledTouchSlop()` once from
+                    // the first scroll past it rather than replaying the
+                    // whole pre-threshold drag in one step.
+                    DragOutcome::Pan(dy - DRAG_SLOP.copysign(dy))
                 } else if now.duration_since(self.origin_at) >= LONG_PRESS
                     && dx.abs() <= DRAG_SLOP
                     && dy.abs() <= DRAG_SLOP
@@ -510,6 +603,522 @@ impl DragArbiter {
     pub fn release(&mut self) {
         self.state = ArbiterState::Idle;
     }
+
+    /// Whether the arbiter's current gesture (if any) has committed to
+    /// panning -- what a caller checks at release time to decide whether
+    /// to hand the tracked velocity to [`crate::widget::List::fling`], per
+    /// IRIS_TODO.md's "swiping has no momentum": a fling must only follow
+    /// a pan, never a text selection that happened to end with the finger
+    /// still moving.
+    pub fn is_panning(&self) -> bool {
+        matches!(self.state, ArbiterState::Panning)
+    }
+}
+
+/// What a [`DragGesture`] decided this frame -- [`DragOutcome`] plus the
+/// one further state a shared gesture needs: the drag ending, with the
+/// released velocity if (and only if) it had committed to panning.
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum GestureOutcome {
+    Undecided,
+    /// Same units and sign as [`DragOutcome::Pan`] -- the caller's own
+    /// convention (`List::scroll`'s, for a transcript) to apply.
+    Pan(f32),
+    SelectStart,
+    SelectExtend,
+    /// The drag ended -- `PressEnd` or the capture's own terminal `Drop`.
+    /// `Some(velocity)` only if the gesture had committed to panning
+    /// (never a tap, a long-press selection, or one still `Undecided`);
+    /// same units as `Pan`, so a caller hands it to `List::fling` with
+    /// whatever sign flip it already applies to `Pan`.
+    Released(Option<f32>),
+}
+
+/// Bundles a [`DragArbiter`] and a [`VelocityTracker`] into the one thing
+/// most drag-driven widgets need: arbitrate pan-vs-hold, track the pan's
+/// velocity, and take pointer capture (`UiRenderState::capture_pointer`)
+/// the moment the gesture commits so the rest of it -- including the
+/// terminal release -- keeps reaching the same widget even after the
+/// finger has moved off whatever hit region first noticed the press. Iris
+/// asked for this to live here rather than in `transcript-ui::Selection`
+/// (2026-09-06, recorded in `IRIS.md`): "dragging should be part of the
+/// default input system ... anything that provides good performance and
+/// can be generalized well is part of iris rather than the app." A caller
+/// still decides what a committed pan or a completed selection *means*
+/// (transcript-ui's pan-vs-select is one call site; a slider or a plain
+/// scroll area is another) -- this only owns the *mechanics* every one of
+/// them would otherwise duplicate.
+pub struct DragGesture {
+    arbiter: DragArbiter,
+    velocity: VelocityTracker,
+}
+
+impl Default for DragGesture {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl DragGesture {
+    pub fn new() -> Self {
+        Self {
+            arbiter: DragArbiter::new(),
+            velocity: VelocityTracker::new(),
+        }
+    }
+
+    /// Whether this gesture has no press in flight -- a thin passthrough
+    /// to the underlying `DragArbiter::is_idle`, for a caller (a test, a
+    /// diagnostic) that wants to observe the recovery behaviour `handle`'s
+    /// idle-recovery branch documents without reaching into a private
+    /// field.
+    pub fn is_idle(&self) -> bool {
+        self.arbiter.is_idle()
+    }
+
+    /// Feed one frame of a gesture through. `id` is the widget iris should
+    /// give exclusive pointer input to once this gesture commits to
+    /// panning or selecting -- a stable widget that outlives the gesture
+    /// (a `List`'s own id, not one of its virtualised rows, which can be
+    /// retired mid-drag as content scrolls). `render` is `CursorData`'s
+    /// own field, already in hand at every call site. `already_selected`
+    /// only matters for the first frame of a gesture (`PressStart`, or the
+    /// recovery branch below) -- see `DragArbiter::press_start`'s doc.
+    pub fn handle(
+        &mut self,
+        render: &UiRenderState,
+        id: WidgetId,
+        sense: CursorSense,
+        pos_window: Vec2,
+        now: Instant,
+        already_selected: bool,
+    ) -> GestureOutcome {
+        match sense {
+            CursorSense::PressStart(_) => {
+                self.velocity.reset();
+                self.arbiter.press_start(pos_window, now, already_selected);
+                self.dispatch(render, id, pos_window, now)
+            }
+            CursorSense::Drop | CursorSense::PressEnd(_) => {
+                let released = if self.arbiter.is_panning() {
+                    Some(self.velocity.velocity())
+                } else {
+                    None
+                };
+                self.arbiter.release();
+                render.release_pointer();
+                GestureOutcome::Released(released)
+            }
+            // See `DragArbiter::update`'s own doc: a `Pressing` frame can
+            // arrive with no matching `PressStart` if the touch-down
+            // landed outside whichever hit region first noticed it.
+            _ if self.arbiter.is_idle() => {
+                self.velocity.reset();
+                self.arbiter.press_start(pos_window, now, already_selected);
+                self.dispatch(render, id, pos_window, now)
+            }
+            _ => self.dispatch(render, id, pos_window, now),
+        }
+    }
+
+    fn dispatch(
+        &mut self,
+        render: &UiRenderState,
+        id: WidgetId,
+        pos: Vec2,
+        now: Instant,
+    ) -> GestureOutcome {
+        match self.arbiter.update(pos, now) {
+            DragOutcome::Undecided => GestureOutcome::Undecided,
+            DragOutcome::Pan(dy) => {
+                render.capture_pointer(id);
+                self.velocity.add_sample(dy, now);
+                GestureOutcome::Pan(dy)
+            }
+            DragOutcome::SelectStart => {
+                render.capture_pointer(id);
+                GestureOutcome::SelectStart
+            }
+            DragOutcome::SelectExtend => {
+                render.capture_pointer(id);
+                GestureOutcome::SelectExtend
+            }
+        }
+    }
+}
+
+/// How far back a [`VelocityTracker`] looks when estimating a fling's
+/// initial speed -- Android's own `VelocityTracker` defaults to a similar
+/// short window so a gesture's last flick dominates over its slower start.
+const VELOCITY_WINDOW: Duration = Duration::from_millis(100);
+
+/// Tracks a drag's speed along one axis from its last ~100ms of motion, so
+/// a release can be handed a realistic initial velocity for
+/// [`AndroidFlingSpline`]/[`FlingCalculator`] rather than a single frame's
+/// noisy last delta. Fed one timestamped pan delta per frame
+/// (`add_sample`, the same `dy`/`-dy` quantity `DragArbiter::update`'s
+/// `Pan` outcome already carries) and answers `velocity()` in units per
+/// second, matching whatever unit the deltas were in.
+#[derive(Default)]
+pub struct VelocityTracker {
+    /// `(when, delta)` pairs, oldest first, trimmed to `VELOCITY_WINDOW`
+    /// on every `add_sample` -- so this never grows past however many
+    /// frames land in that window.
+    samples: VecDeque<(Instant, f32)>,
+}
+
+impl VelocityTracker {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Forget everything -- called on a fresh press, so a new gesture's
+    /// velocity is never contaminated by the tail of the previous one.
+    pub fn reset(&mut self) {
+        self.samples.clear();
+    }
+
+    /// Record one frame's motion. `delta` is this frame's movement since
+    /// the last sample, not a cumulative position.
+    pub fn add_sample(&mut self, delta: f32, at: Instant) {
+        self.samples.push_back((at, delta));
+        while let Some(&(when, _)) = self.samples.front() {
+            if at.duration_since(when) > VELOCITY_WINDOW {
+                self.samples.pop_front();
+            } else {
+                break;
+            }
+        }
+    }
+
+    /// The estimated speed, in units-per-second, over whatever samples
+    /// currently fall inside the tracking window: total motion divided by
+    /// the elapsed time between the oldest and newest sample still held.
+    /// `0.0` with fewer than two samples (no time span to divide by).
+    pub fn velocity(&self) -> f32 {
+        if self.samples.len() < 2 {
+            return 0.0;
+        }
+        let total: f32 = self.samples.iter().map(|&(_, d)| d).sum();
+        let span = self
+            .samples
+            .back()
+            .unwrap()
+            .0
+            .duration_since(self.samples.front().unwrap().0)
+            .as_secs_f32();
+        if span <= 0.0 { 0.0 } else { total / span }
+    }
+}
+
+/// Android's fling deceleration curve, ported from AOSP's
+/// `android.widget.OverScroller.SplineOverScroller` (the same curve
+/// Compose's `androidx.compose.ui.gestures.AndroidFlingSpline` and
+/// `androidx.compose.foundation.gestures.FlingCalculator` reuse) so a
+/// fling here travels the same distance a Compose `LazyColumn`'s own
+/// `ScrollableDefaults.flingBehavior()` would for the same initial
+/// velocity -- RUST.md's "Benchmark v2" box asked the two apps' fling
+/// phase to be comparable, and IRIS_TODO.md's "swiping has no momentum"
+/// asked for the same physics a reader's muscle memory already expects
+/// from every other Android scroll view.
+///
+/// The curve is a cubic-Bezier-derived spline sampled into two lookup
+/// tables at start-up (`SPLINE`, built once via [`std::sync::OnceLock`]):
+/// `SPLINE_POSITION[i]`/`SPLINE_TIME[i]` give the fraction of total
+/// distance/time elapsed at the `i`th of 100 even steps along the curve's
+/// own parameter. A lookup at an arbitrary time fraction interpolates
+/// between the two bracketing samples.
+mod android_fling_spline {
+    use std::sync::OnceLock;
+
+    const NB_SAMPLES: usize = 100;
+    /// Where the two cubic tension lines cross (AOSP's own constant name
+    /// and value, `SplineOverScroller.INFLEXION`).
+    pub(super) const INFLEXION: f32 = 0.35;
+    const START_TENSION: f32 = 0.5;
+    const END_TENSION: f32 = 1.0;
+    const P1: f32 = START_TENSION * INFLEXION;
+    const P2: f32 = 1.0 - END_TENSION * (1.0 - INFLEXION);
+
+    pub(super) struct Spline {
+        position: [f32; NB_SAMPLES + 1],
+        time: [f32; NB_SAMPLES + 1],
+    }
+
+    fn build() -> Spline {
+        let mut position = [0.0f32; NB_SAMPLES + 1];
+        let mut time = [0.0f32; NB_SAMPLES + 1];
+        let (mut x_min, mut y_min) = (0.0f32, 0.0f32);
+        for i in 0..NB_SAMPLES {
+            let alpha = i as f32 / NB_SAMPLES as f32;
+
+            let mut x_max = 1.0f32;
+            let (mut x, mut coef);
+            loop {
+                x = x_min + (x_max - x_min) / 2.0;
+                coef = 3.0 * x * (1.0 - x);
+                let tx = coef * ((1.0 - x) * START_TENSION + x * END_TENSION) + x * x * x;
+                if (tx - alpha).abs() < 1e-5 {
+                    break;
+                }
+                if tx > alpha {
+                    x_max = x;
+                } else {
+                    x_min = x;
+                }
+            }
+            position[i] = coef * ((1.0 - x) * P1 + x * P2) + x * x * x;
+
+            let mut y_max = 1.0f32;
+            let (mut y, mut coef_y);
+            loop {
+                y = y_min + (y_max - y_min) / 2.0;
+                coef_y = 3.0 * y * (1.0 - y);
+                let dy = coef_y * ((1.0 - y) * START_TENSION + y * END_TENSION) + y * y * y;
+                if (dy - alpha).abs() < 1e-5 {
+                    break;
+                }
+                if dy > alpha {
+                    y_max = y;
+                } else {
+                    y_min = y;
+                }
+            }
+            time[i] = coef_y * ((1.0 - y) * P1 + y * P2) + y * y * y;
+        }
+        position[NB_SAMPLES] = 1.0;
+        time[NB_SAMPLES] = 1.0;
+        Spline { position, time }
+    }
+
+    static SPLINE: OnceLock<Spline> = OnceLock::new();
+
+    /// The fraction of total distance covered at `time_fraction` (0..=1
+    /// of the fling's total duration). Finds the bracketing samples in
+    /// `SPLINE_TIME` and interpolates linearly between their matching
+    /// `SPLINE_POSITION` entries, exactly as AOSP's `SplineOverScroller
+    /// .flingPosition` does.
+    pub(super) fn distance_fraction(time_fraction: f32) -> f32 {
+        let spline = SPLINE.get_or_init(build);
+        let t = time_fraction.clamp(0.0, 1.0);
+        let index = ((t * NB_SAMPLES as f32) as usize).min(NB_SAMPLES - 1);
+        let t_inf = spline.time[index];
+        let t_sup = spline.time[index + 1];
+        let d_inf = spline.position[index];
+        let d_sup = spline.position[index + 1];
+        let span = t_sup - t_inf;
+        if span <= 0.0 {
+            d_inf
+        } else {
+            d_inf + (d_sup - d_inf) * (t - t_inf) / span
+        }
+    }
+}
+
+/// AOSP `SplineOverScroller`'s two other physical constants: the default
+/// `ViewConfiguration.getScrollFriction()` and the deceleration rate a
+/// friction of `0.84` per frame at 60Hz corresponds to
+/// (`ln(0.78)/ln(0.9)`, `SplineOverScroller.DECELERATION_RATE`).
+const FLING_FRICTION: f32 = 0.015;
+fn deceleration_rate() -> f32 {
+    (0.78f32.ln()) / (0.9f32.ln())
+}
+const GRAVITY_EARTH: f32 = 9.80665;
+
+/// Turns an initial fling velocity into a total travel distance and
+/// duration, following AOSP `SplineOverScroller`'s own closed-form
+/// formulas (`getSplineFlingDistance`/the duration half of `fling()`) --
+/// ported the same way Compose's `FlingCalculator` is, including its
+/// `density`-dependent physical coefficient (`computeDeceleration`,
+/// `GravityEarth * 39.37 * density * 160 * friction`). Density and
+/// velocity/distance units cancel algebraically as long as velocity and
+/// the returned distance share one pixel space (physical or logical) --
+/// [`crate::widget::List::fling`] relies on exactly that cancellation to
+/// avoid needing a display density of its own, since iris's `List`
+/// already works in logical (density-independent) pixels throughout.
+pub struct FlingCalculator {
+    physical_coefficient: f32,
+}
+
+impl FlingCalculator {
+    pub fn new(density: f32) -> Self {
+        Self {
+            physical_coefficient: GRAVITY_EARTH * 39.37 * density * 160.0 * FLING_FRICTION,
+        }
+    }
+
+    fn deceleration_for(&self, velocity: f32) -> f32 {
+        (android_fling_spline::INFLEXION * velocity.abs()
+            / (FLING_FRICTION * self.physical_coefficient))
+            .ln()
+    }
+
+    /// Total signed distance the fling travels before settling, in the
+    /// same pixel units `velocity` was given in.
+    pub fn distance(&self, velocity: f32) -> f32 {
+        if velocity == 0.0 {
+            return 0.0;
+        }
+        let l = self.deceleration_for(velocity);
+        let rate = deceleration_rate();
+        let magnitude =
+            FLING_FRICTION * self.physical_coefficient * (rate / (rate - 1.0) * l).exp();
+        magnitude.copysign(velocity)
+    }
+
+    /// How long the fling takes to settle.
+    pub fn duration(&self, velocity: f32) -> Duration {
+        if velocity == 0.0 {
+            return Duration::ZERO;
+        }
+        let l = self.deceleration_for(velocity);
+        let rate = deceleration_rate();
+        Duration::from_secs_f32((l / (rate - 1.0)).exp())
+    }
+
+    /// The signed distance covered by `elapsed` into a fling of this
+    /// `velocity` that started at `t0` -- what a per-frame ticker
+    /// (`List::tick_fling`) calls to find how far to have scrolled by now.
+    /// Clamped to the full `distance()` once `elapsed` reaches
+    /// `duration()`, so a caller need not special-case "past the end."
+    pub fn position_at(&self, velocity: f32, elapsed: Duration) -> f32 {
+        let duration = self.duration(velocity);
+        if duration.is_zero() {
+            return 0.0;
+        }
+        let fraction = (elapsed.as_secs_f32() / duration.as_secs_f32()).min(1.0);
+        self.distance(velocity) * android_fling_spline::distance_fraction(fraction)
+    }
+}
+
+#[cfg(test)]
+mod velocity_tracker_tests {
+    use super::*;
+    use std::sync::LazyLock;
+
+    // A single fixed base rather than a fresh `Instant::now()` per call --
+    // computing it once per test keeps every sample's spacing exact
+    // instead of at the mercy of however long the test itself takes to
+    // run between calls, the same reasoning `drag_arbiter_tests::t` uses.
+    static BASE: LazyLock<Instant> = LazyLock::new(Instant::now);
+
+    fn t(ms: u64) -> Instant {
+        *BASE + Duration::from_millis(ms)
+    }
+
+    #[test]
+    fn fewer_than_two_samples_reports_zero() {
+        let mut v = VelocityTracker::new();
+        assert_eq!(v.velocity(), 0.0);
+        v.add_sample(10.0, t(0));
+        assert_eq!(v.velocity(), 0.0);
+    }
+
+    #[test]
+    fn a_steady_drag_reports_its_own_speed() {
+        // 5px every 10ms, 11 samples spanning 100ms, sums to 55px over
+        // 0.1s -- 550px/s by this tracker's own "sum of deltas over the
+        // span between the oldest and newest held sample" definition.
+        let mut v = VelocityTracker::new();
+        for i in 0..=10 {
+            v.add_sample(5.0, t(i * 10));
+        }
+        assert!((v.velocity() - 550.0).abs() < 1.0, "got {}", v.velocity());
+    }
+
+    #[test]
+    fn only_the_last_100ms_of_samples_count() {
+        // An old, fast burst well outside the window followed by a slow,
+        // steady drag should report the recent speed, not the average of
+        // both -- otherwise a flick that trails off would still fling at
+        // its earlier, faster speed. The burst sits 110ms before the last
+        // sample, just past the 100ms window, so it is evicted.
+        let mut v = VelocityTracker::new();
+        v.add_sample(1000.0, t(0)); // will be 110ms old by the last sample
+        for i in 1..=11 {
+            v.add_sample(1.0, t(i * 10)); // 1px/10ms = 100px/s
+        }
+        assert!(
+            (v.velocity() - 110.0).abs() < 5.0,
+            "old burst leaked into the window: got {}",
+            v.velocity()
+        );
+    }
+
+    #[test]
+    fn reset_forgets_prior_samples() {
+        let mut v = VelocityTracker::new();
+        v.add_sample(500.0, t(0));
+        v.add_sample(500.0, t(10));
+        assert!(v.velocity() != 0.0);
+        v.reset();
+        assert_eq!(v.velocity(), 0.0);
+    }
+}
+
+#[cfg(test)]
+mod fling_calculator_tests {
+    use super::*;
+
+    #[test]
+    fn zero_velocity_flings_nowhere() {
+        let calc = FlingCalculator::new(1.0);
+        assert_eq!(calc.distance(0.0), 0.0);
+        assert_eq!(calc.duration(0.0), Duration::ZERO);
+    }
+
+    #[test]
+    fn distance_grows_with_velocity_and_keeps_its_sign() {
+        let calc = FlingCalculator::new(2.75); // a typical phone's density
+        let d_slow = calc.distance(2000.0);
+        let d_fast = calc.distance(12000.0);
+        assert!(d_slow > 0.0);
+        assert!(d_fast > d_slow);
+        assert_eq!(calc.distance(-12000.0), -d_fast);
+    }
+
+    /// Summing the spline's own per-frame position deltas across the
+    /// whole fling has to land within 1% of the closed-form `distance()`
+    /// -- this is the guarantee that `List::tick_fling`'s per-frame reads
+    /// of `position_at` actually add up to the total the fling promised,
+    /// not merely that the two formulas look plausible independently.
+    #[test]
+    fn integrating_position_at_matches_the_closed_form_distance() {
+        let calc = FlingCalculator::new(1.0);
+        for velocity in [1500.0f32, 5000.0, 12000.0, -12000.0] {
+            let total = calc.distance(velocity);
+            let duration = calc.duration(velocity);
+            let final_position = calc.position_at(velocity, duration);
+            let err = (final_position - total).abs() / total.abs();
+            assert!(
+                err < 0.01,
+                "velocity {velocity}: position_at(duration)={final_position} vs distance()={total}, err={err}"
+            );
+        }
+    }
+
+    #[test]
+    fn position_at_is_monotonic_and_clamped_past_the_end() {
+        let calc = FlingCalculator::new(1.0);
+        let velocity = 12000.0f32;
+        let duration = calc.duration(velocity);
+        let total = calc.distance(velocity);
+        let mut last = 0.0;
+        let mut t = Duration::ZERO;
+        while t < duration {
+            let p = calc.position_at(velocity, t);
+            assert!(p >= last - 0.01, "position went backwards at {t:?}");
+            last = p;
+            t += Duration::from_millis(16);
+        }
+        // Well past the end, it stays pinned at the total -- a caller
+        // must be able to ask "where would this fling be" without first
+        // checking whether it has already settled.
+        assert_eq!(
+            calc.position_at(velocity, duration + Duration::from_secs(5)),
+            total
+        );
+    }
 }
 
 #[cfg(test)]
@@ -534,9 +1143,13 @@ mod drag_arbiter_tests {
     fn a_vertical_drag_pans_immediately() {
         let mut a = DragArbiter::new();
         a.press_start(Vec2::new(0.0, 0.0), t(0), false);
+        // The transition frame applies only the motion past `DRAG_SLOP`
+        // (20 - 8 = 12), not the full 20px since `press_start` -- see the
+        // `Pan` arm's own comment for why replaying the whole withheld
+        // drag in one step is the scroll-jitter bug this guards against.
         assert_eq!(
             a.update(Vec2::new(0.0, 20.0), t(10)),
-            DragOutcome::Pan(20.0)
+            DragOutcome::Pan(12.0)
         );
         // Subsequent frames keep panning, by the delta since last frame.
         assert_eq!(
@@ -545,6 +1158,22 @@ mod drag_arbiter_tests {
         );
     }
 
+    /// Direct regression test for the fix: a slow drag that crosses
+    /// `DRAG_SLOP` by only a fraction of a pixel must not still produce a
+    /// visible jump -- the amount applied on the crossing frame should
+    /// itself shrink toward zero as the crossing gets closer to exactly
+    /// `DRAG_SLOP`, rather than always dumping the whole pre-threshold
+    /// distance at once.
+    #[test]
+    fn crossing_the_slop_by_a_little_pans_by_a_little() {
+        let mut a = DragArbiter::new();
+        a.press_start(Vec2::new(0.0, 0.0), t(0), false);
+        assert_eq!(
+            a.update(Vec2::new(0.0, DRAG_SLOP + 0.5), t(10)),
+            DragOutcome::Pan(0.5)
+        );
+    }
+
     #[test]
     fn a_horizontal_drag_with_nothing_selected_does_not_select() {
         let mut a = DragArbiter::new();
@@ -603,7 +1232,7 @@ mod drag_arbiter_tests {
         a.press_start(Vec2::new(0.0, 0.0), t(0), true);
         assert_eq!(
             a.update(Vec2::new(0.0, 20.0), t(10)),
-            DragOutcome::Pan(20.0)
+            DragOutcome::Pan(12.0)
         );
     }
 
@@ -646,7 +1275,7 @@ mod drag_arbiter_tests {
         a.press_start(Vec2::new(0.0, 700.0), t(0), false);
         assert_eq!(
             a.update(Vec2::new(0.0, 720.0), t(10)),
-            DragOutcome::Pan(20.0)
+            DragOutcome::Pan(12.0)
         );
         assert!(!a.is_idle());
     }

iris/src/sense_tests.rs

@@ -122,3 +122,127 @@ 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/src/widget/list.rs

@@ -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 +213,39 @@ 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>>,
+    /// 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,
+    started_at: Instant,
+    applied: f32,
 }
 
 impl List {
@@ -226,6 +259,10 @@ impl List {
             snap_end: true,
             viewport_len: 0.0,
             last_viewport_len: 0.0,
+            fling: None,
+            redraw: None,
+            at_start: false,
+            at_end: false,
             pending_tap: None,
             extents: HashMap::default(),
             heights: HashMap::default(),
@@ -361,6 +398,115 @@ 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.
+    ///
+    /// Density cancels out of the underlying spline as long as velocity
+    /// and the distance it produces share one pixel space (see
+    /// `FlingCalculator`'s own doc) -- `List` works entirely in logical
+    /// pixels, so `1.0` here is not a placeholder for "unknown density,"
+    /// it is the correct density for a self-consistent unit system.
+    pub fn fling(&mut self, velocity_px_per_s: f32) {
+        if velocity_px_per_s == 0.0 || self.anchor.is_none() {
+            self.fling = None;
+            return;
+        }
+        self.fling = Some(Fling {
+            calc: FlingCalculator::new(1.0),
+            velocity: velocity_px_per_s,
+            started_at: Instant::now(),
+            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()
+    }
+
+    /// 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);
+        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;
+        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) {
@@ -406,6 +552,20 @@ 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(),
@@ -606,9 +766,10 @@ impl List {
         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)
         };
@@ -724,26 +885,33 @@ 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
     }
@@ -1177,4 +1345,222 @@ mod tests {
             );
         }
     }
+
+    /// 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"
+        );
+    }
+
+    /// 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());
+    }
+
+    #[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"
+            );
+        }
+    }
+
+    #[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"));
+    }
 }

iris/src/widget/position/align.rs

@@ -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,

iris/src/widget/position/max_size.rs

@@ -9,12 +9,12 @@ 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 max_px = max.apply_rest().to_abs(output);
+        let len_px = len.apply_rest(density).to_abs(output);
+        let max_px = max.apply_rest(density).to_abs(output);
         if len_px > max_px { max } else { len }
     }
 
@@ -24,11 +24,11 @@ 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 +41,16 @@ 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),
-            y: Self::clamp_region(offered.y, self.y, output.y),
+            x: Self::clamp_region(offered.x, self.x, output.x, density),
+            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),
-            y: Self::clamp(used.y, self.y, output.y),
+            x: Self::clamp(used.x, self.x, output.x, density),
+            y: Self::clamp(used.y, self.y, output.y, density),
         }
     }
 }

iris/src/widget/position/pad.rs

@@ -7,9 +7,12 @@ pub struct Pad {
 
 impl Widget for Pad {
     fn draw(&mut self, painter: &mut Painter) -> Size {
-        let used = painter.widget_within(&self.inner, self.padding.region());
-        let width = self.padding.left + self.padding.right;
-        let height = self.padding.top + self.padding.bottom;
+        let density = painter.density();
+        let used = painter.widget_within(&self.inner, self.padding.region(density));
+        let width =
+            self.padding.left.apply_rest(density).abs + self.padding.right.apply_rest(density).abs;
+        let height =
+            self.padding.top.apply_rest(density).abs + self.padding.bottom.apply_rest(density).abs;
         Size {
             x: used.x + Len::abs(width),
             y: used.y + Len::abs(height),
@@ -17,23 +20,29 @@ impl Widget for Pad {
     }
 }
 
+/// Each side is a `Len`, not a bare `f32`, so `.pad(dp(10))` resolves
+/// against the display's density the same way any other size does -- see
+/// `Len::dp`'s field doc. `.pad(10)` (a bare number) still works via
+/// `From<T: UiNum>` below, unchanged: it becomes an `abs` (physical-pixel)
+/// `Len`, exactly as a bare number always has meant elsewhere in this
+/// crate.
 pub struct Padding {
-    pub left: f32,
-    pub right: f32,
-    pub top: f32,
-    pub bottom: f32,
+    pub left: Len,
+    pub right: Len,
+    pub top: Len,
+    pub bottom: Len,
 }
 
 impl Padding {
     pub const ZERO: Self = Self {
-        left: 0.0,
-        right: 0.0,
-        top: 0.0,
-        bottom: 0.0,
+        left: Len::ZERO,
+        right: Len::ZERO,
+        top: Len::ZERO,
+        bottom: Len::ZERO,
     };
 
-    pub fn uniform(amt: impl UiNum) -> Self {
-        let amt = amt.to_f32();
+    pub fn uniform(amt: impl Into<Len>) -> Self {
+        let amt = amt.into();
         Self {
             left: amt,
             right: amt,
@@ -41,80 +50,84 @@ impl Padding {
             bottom: amt,
         }
     }
-    pub fn region(&self) -> UiRegion {
+    pub fn region(&self, density: f32) -> UiRegion {
         let mut region = UiRegion::FULL;
-        region.x.start.abs += self.left;
-        region.y.start.abs += self.top;
-        region.x.end.abs -= self.right;
-        region.y.end.abs -= self.bottom;
+        region.x.start.abs += self.left.apply_rest(density).abs;
+        region.y.start.abs += self.top.apply_rest(density).abs;
+        region.x.end.abs -= self.right.apply_rest(density).abs;
+        region.y.end.abs -= self.bottom.apply_rest(density).abs;
         region
     }
-    pub fn x(amt: impl UiNum) -> Self {
-        let amt = amt.to_f32();
+    pub fn x(amt: impl Into<Len>) -> Self {
+        let amt = amt.into();
         Self {
             left: amt,
             right: amt,
-            top: 0.0,
-            bottom: 0.0,
+            top: Len::ZERO,
+            bottom: Len::ZERO,
         }
     }
-    pub fn y(amt: impl UiNum) -> Self {
-        let amt = amt.to_f32();
+    pub fn y(amt: impl Into<Len>) -> Self {
+        let amt = amt.into();
         Self {
-            left: 0.0,
-            right: 0.0,
+            left: Len::ZERO,
+            right: Len::ZERO,
             top: amt,
             bottom: amt,
         }
     }
 
-    pub fn top(amt: impl UiNum) -> Self {
+    pub fn top(amt: impl Into<Len>) -> Self {
         let mut s = Self::ZERO;
-        s.top = amt.to_f32();
+        s.top = amt.into();
         s
     }
 
-    pub fn bottom(amt: impl UiNum) -> Self {
+    pub fn bottom(amt: impl Into<Len>) -> Self {
         let mut s = Self::ZERO;
-        s.bottom = amt.to_f32();
+        s.bottom = amt.into();
         s
     }
 
-    pub fn left(amt: impl UiNum) -> Self {
+    pub fn left(amt: impl Into<Len>) -> Self {
         let mut s = Self::ZERO;
-        s.left = amt.to_f32();
+        s.left = amt.into();
         s
     }
 
-    pub fn right(amt: impl UiNum) -> Self {
+    pub fn right(amt: impl Into<Len>) -> Self {
         let mut s = Self::ZERO;
-        s.right = amt.to_f32();
+        s.right = amt.into();
         s
     }
 
-    pub fn with_top(mut self, amt: impl UiNum) -> Self {
-        self.top = amt.to_f32();
+    pub fn with_top(mut self, amt: impl Into<Len>) -> Self {
+        self.top = amt.into();
         self
     }
 
-    pub fn with_bottom(mut self, amt: impl UiNum) -> Self {
-        self.bottom = amt.to_f32();
+    pub fn with_bottom(mut self, amt: impl Into<Len>) -> Self {
+        self.bottom = amt.into();
         self
     }
 
-    pub fn with_left(mut self, amt: impl UiNum) -> Self {
-        self.left = amt.to_f32();
+    pub fn with_left(mut self, amt: impl Into<Len>) -> Self {
+        self.left = amt.into();
         self
     }
 
-    pub fn with_right(mut self, amt: impl UiNum) -> Self {
-        self.right = amt.to_f32();
+    pub fn with_right(mut self, amt: impl Into<Len>) -> Self {
+        self.right = amt.into();
         self
     }
 }
 
-impl<T: UiNum> From<T> for Padding {
+/// Covers both a bare number (`.pad(8)`, via `Len`'s own `From<N: UiNum>`
+/// blanket -- an `abs`/physical-pixel `Len`) and a `Len` directly
+/// (`.pad(dp(10))`) with the one impl, since `Len: Into<Len>` is the
+/// reflexive case of the same bound.
+impl<T: Into<Len>> From<T> for Padding {
     fn from(amt: T) -> Self {
-        Self::uniform(amt.to_f32())
+        Self::uniform(amt.into())
     }
 }

iris/src/widget/position/scroll.rs

@@ -43,7 +43,7 @@ impl Widget for Scroll {
 
         self.content_len = used
             .axis(axis)
-            .apply_rest()
+            .apply_rest(painter.density())
             .within_len(container_len)
             .to_abs(output_len);
 

iris/src/widget/position/sized.rs

@@ -17,12 +17,13 @@ impl Widget for Sized {
         // learn its size, then moves it into place with a pure
         // translation; that translation is only valid if what got painted
         // is already the reported size, anchored the same way both times.
+        let density = painter.density();
         let mut region = UiRegion::FULL;
         if let Some(x) = self.x {
-            region.x = x.apply_rest().align(AxisAlign::Neg);
+            region.x = x.apply_rest(density).align(AxisAlign::Neg);
         }
         if let Some(y) = self.y {
-            region.y = y.apply_rest().align(AxisAlign::Neg);
+            region.y = y.apply_rest(density).align(AxisAlign::Neg);
         }
         let used = painter.widget_within(&self.inner, region);
         Size {

iris/src/widget/position/span.rs

@@ -4,12 +4,18 @@ use std::marker::PhantomData;
 pub struct Span {
     pub children: Vec<StrongWidget>,
     pub dir: Dir,
-    pub gap: f32,
+    /// A `Len` (not a bare `f32`) so `dp(4)` resolves against the display's
+    /// density the same way any other size in the tree does -- see
+    /// `Len::dp`'s field doc. Only the `abs` component (folded from `dp` at
+    /// draw time, `Widget::draw` below) is meaningful here; `rel`/`rest`
+    /// were never supported for a gap and still are not.
+    pub gap: Len,
 }
 
 impl Widget for Span {
     fn draw(&mut self, painter: &mut Painter) -> Size {
         let axis = self.dir.axis;
+        let gap = self.gap.apply_rest(painter.density()).abs;
 
         // Phase 1: draw each child once, at the ambient (unmodified, full)
         // region a size-only query used to see before this migration, to
@@ -25,7 +31,7 @@ impl Widget for Span {
             .map(|child| painter.widget(child).axis(axis))
             .collect();
 
-        let gap_total = self.gap * self.children.len().saturating_sub(1) as f32;
+        let gap_total = gap * self.children.len().saturating_sub(1) as f32;
         let total = lens.iter().fold(Len::abs(gap_total), |s, &l| s + l);
 
         // Phase 2: place each child for real, using the lengths just
@@ -54,7 +60,7 @@ impl Widget for Span {
                 child_region.flip(axis);
             }
             let used = painter.widget_within(child, child_region);
-            start.abs += self.gap;
+            start.abs += gap;
 
             let ortho = used.axis(!axis);
             if ortho.rel > 0.0 || ortho.rest > 0.0 {
@@ -82,12 +88,12 @@ impl Span {
         Self {
             children: Vec::new(),
             dir,
-            gap: 0.0,
+            gap: Len::ZERO,
         }
     }
 
-    pub fn gap(mut self, gap: impl UiNum) -> Self {
-        self.gap = gap.to_f32();
+    pub fn gap(mut self, gap: impl Into<Len>) -> Self {
+        self.gap = gap.into();
         self
     }
 
@@ -103,7 +109,7 @@ impl Span {
 pub struct SpanBuilder<State, const LEN: usize, Wa: WidgetArrLike<State, LEN, Tag>, Tag> {
     pub children: Wa,
     pub dir: Dir,
-    pub gap: f32,
+    pub gap: Len,
     _pd: PhantomData<(State, Tag)>,
 }
 
@@ -129,13 +135,13 @@ impl<State, const LEN: usize, Wa: WidgetArrLike<State, LEN, Tag>, Tag>
         Self {
             children,
             dir,
-            gap: 0.0,
+            gap: Len::ZERO,
             _pd: PhantomData,
         }
     }
 
-    pub fn gap(mut self, gap: impl UiNum) -> Self {
-        self.gap = gap.to_f32();
+    pub fn gap(mut self, gap: impl Into<Len>) -> Self {
+        self.gap = gap.into();
         self
     }
 }

iris/src/widget/text/edit.rs

@@ -32,6 +32,15 @@ pub struct TextEdit {
     #[cfg_attr(target_os = "android", allow(dead_code))]
     history: Vec<(String, Option<Selection>)>,
     double_hit: Option<usize>,
+    /// Where an in-flight press over this field began, while it is still
+    /// undecided whether the gesture is a tap (focus/show the IME) or a
+    /// drag (attr.rs's `Selector`/`Selectable`, Iris 2026-09-06: a swipe
+    /// over the composer must not summon the keyboard). `None` both before
+    /// any press and once the gesture has been decided either way --
+    /// `attr.rs` is the only reader/writer, kept `pub(crate)` rather than
+    /// behind an accessor since it is pure bookkeeping with no invariant
+    /// beyond "some press is undecided," same shape as `double_hit` above.
+    pub(crate) press_origin: Option<Vec2>,
     pub mode: EditMode,
 }
 
@@ -48,6 +57,7 @@ impl TextEdit {
             selection: None,
             history: Default::default(),
             double_hit: None,
+            press_origin: None,
             mode,
         }
     }
@@ -141,7 +151,8 @@ impl<'a> TextEditCtx<'a> {
     fn layout(&mut self) -> &Layout<UiColor> {
         let attrs = self.text.view.attrs.clone();
         let width = self.text.view.wrap_width();
-        self.text.view.buf.shape(self.data, &attrs, width);
+        let density = self.data.density;
+        self.text.view.buf.shape(self.data, &attrs, width, density);
         self.text.view.buf.layout()
     }
 
@@ -697,6 +708,67 @@ mod tests {
         assert_eq!(content(&t), "に");
     }
 
+    /// `android/ime.rs`'s `set_composing_text` calls `replace` and expects
+    /// the caret to land right after the inserted text, growing with it on
+    /// every re-send -- the buffer-level half of RUST.md's P0 box ("doesn't
+    /// enter it until I hit space, and also doesn't move cursor forward").
+    #[test]
+    fn composing_advances_the_caret_with_the_growing_text() {
+        let (mut t, mut d) = edit("", EditMode::SingleLine);
+        ctx(&mut t, &mut d).set_caret(0);
+        ctx(&mut t, &mut d).replace(0, "h");
+        assert_eq!(t.caret(), Some(1));
+        ctx(&mut t, &mut d).replace(1, "hi");
+        assert_eq!(content(&t), "hi");
+        assert_eq!(t.caret(), Some(2));
+        ctx(&mut t, &mut d).replace(2, "hit");
+        assert_eq!(content(&t), "hit");
+        assert_eq!(t.caret(), Some(3));
+    }
+
+    /// The IME's `commitText` (`android_view::InputConnection::commit_text`'s
+    /// default body): finish a composition in place, same as a real word
+    /// boundary (a space) landing after Gboard's composing span.
+    #[test]
+    fn committing_composed_text_leaves_it_in_place_with_the_caret_after_it() {
+        let (mut t, mut d) = edit("say ", EditMode::SingleLine);
+        ctx(&mut t, &mut d).set_caret(4);
+        ctx(&mut t, &mut d).replace(0, "hi");
+        assert_eq!(content(&t), "say hi");
+        // `finish_composing_text`/`commit_text` do not themselves touch the
+        // buffer -- only the IME's own `compose_len` bookkeeping resets, in
+        // `android/ime.rs`. Confirms the buffer already holds committed
+        // text as plain, uncomposed content: a further `replace(0, " ")`
+        // (the space that ends the word) appends rather than overwriting.
+        ctx(&mut t, &mut d).replace(0, " ");
+        assert_eq!(content(&t), "say hi ");
+        assert_eq!(t.caret(), Some(7));
+    }
+
+    /// `TextEditCtx::delete_byte_range` is `deleteSurroundingText`'s entry
+    /// point once `android/ime.rs` has converted UTF-16 code units to
+    /// bytes -- exercised directly here in bytes, since the UTF-16 math
+    /// itself is `android/ime.rs`'s own `byte_to_utf16`/`utf16_to_byte`,
+    /// outside this widget-only test module.
+    #[test]
+    fn delete_byte_range_removes_exactly_that_range() {
+        let (mut t, mut d) = edit("hello world", EditMode::SingleLine);
+        ctx(&mut t, &mut d).delete_byte_range(5, 11);
+        assert_eq!(content(&t), "hello");
+        assert_eq!(t.caret(), Some(5));
+    }
+
+    /// `set_cursor_byte` is `setSelection`'s entry point -- collapses to a
+    /// caret at the given byte offset regardless of any span that was there.
+    #[test]
+    fn set_cursor_byte_collapses_to_a_caret_there() {
+        let (mut t, mut d) = edit("hello world", EditMode::SingleLine);
+        ctx(&mut t, &mut d).select_all();
+        ctx(&mut t, &mut d).set_cursor_byte(5);
+        assert_eq!(t.selected_text(), None);
+        assert_eq!(t.caret(), Some(5));
+    }
+
     #[test]
     fn motion_moves_the_caret_and_shift_extends_a_span() {
         let (mut t, mut d) = edit("abc", EditMode::SingleLine);

iris/transcript-ui/src/composer.rs

@@ -8,14 +8,58 @@
 //! measures whatever vertical space is left each frame -- nothing here
 //! computes a height by hand, and growing this field is exactly the
 //! O(1)-move-chain case LAYOUT.md and I3's benchmark already measured.
+//!
+//! **Rebuilt 2026-09-06** (Iris's phone report on the dc01f88 build: the
+//! grey bar drawn as a short, fixed strip with the typed text ~150px below
+//! it on black, and empty black between the bar and the keyboard). One
+//! widget now, top to bottom: an opaque background sized to its content
+//! (`.background`, the same `Stack` idiom the header row's `HEADER_SURFACE`
+//! already uses), the field inside `dp` padding and capped at
+//! [`MAX_LINES`] before it scrolls instead of growing forever, and an
+//! outer [`Pad`] whose `bottom` [`TranscriptScreen::set_bottom_inset`]
+//! rewrites in place whenever the keyboard opens/closes -- never rebuilt,
+//! since `field` is strongly owned inside this tree and this crate's
+//! widgets cannot be re-parented once added (this module's own comment
+//! below on why `build_composer` hands back a **weak** id).
 
 use iris::prelude::*;
 
+/// Caps the field's growth at roughly six lines of its own 18px text
+/// before it scrolls instead of consuming the whole screen -- an
+/// approximation (line-height and padding folded into one round `dp`
+/// number) rather than a value derived from the font's real metrics,
+/// which nothing in this crate exposes to a caller today.
+const MAX_LINES: f32 = 6.0;
+const APPROX_LINE_HEIGHT_DP: f32 = 24.0;
+const FIELD_PAD_DP: f32 = 12.0;
+
 /// `field` is exposed so the caller can read its content on submit
 /// (`field.edit(rsc).text()`) and clear it afterward
 /// (`field.edit(rsc).set("")`).
 pub struct Composer {
     pub field: WeakWidget<TextEdit>,
+    /// The bar's own outer padding -- only `bottom` is ever changed, by
+    /// [`Self::set_bottom_inset`]. A `Pad` around the whole bar rather than
+    /// a rebuilt tree, because `field` lives inside it and cannot be
+    /// re-added to a new wrapper once it is strongly owned here.
+    outer_pad: WeakWidget<Pad>,
+}
+
+impl Composer {
+    /// Called by the platform shell (Android's `on_insets_changed`, e.g.)
+    /// whenever the space below the bar changes: the IME's own inset while
+    /// it is open, the navigation-bar inset otherwise. Takes a plain
+    /// `f32` in the caller's own physical-pixel units rather than an
+    /// Android-specific insets type, so this crate stays usable from the
+    /// winit backend too, which has no navigation bar to report.
+    /// Rewrites the existing `Pad` in place (marking it dirty through the
+    /// ordinary `Widgets::get_mut` path) instead of swapping in a new one,
+    /// so the field's focus, selection and in-progress text are untouched.
+    pub fn set_bottom_inset(&self, rsc: &mut impl UiRsc, inset: f32) {
+        if let Some(pad) = rsc.ui_mut().widgets.get_mut(&self.outer_pad) {
+            pad.padding.bottom = Len::abs(inset);
+        }
+    }
 }
 
 /// Returns the composer plus its own bar as a **weak** id -- the caller
@@ -39,10 +83,20 @@ where
         .label("Message")
         .add(rsc);
 
-    let bar: WeakWidget = (field.pad(12).width(rest(1)),)
-        .span(Dir::RIGHT)
+    // One widget: an opaque bar sized to its own content (`.background`'s
+    // `Stack{child: 1}`, the header row's own idiom) wrapping the padded,
+    // height-capped field -- not a background rect and a field drawn as
+    // two independent siblings, which is what let the two disagree on
+    // where the bar actually was.
+    let content = field
+        .pad(dp(FIELD_PAD_DP))
+        .max_height(dp(APPROX_LINE_HEIGHT_DP * MAX_LINES + FIELD_PAD_DP * 2.0))
+        .scrollable()
+        .width(rest(1))
         .background(rect(UiColor::new(40, 40, 46, 255)))
         .add(rsc);
 
-    (Composer { field }, bar)
+    let outer_pad: WeakWidget<Pad> = content.pad(Padding::ZERO).add(rsc);
+
+    (Composer { field, outer_pad }, outer_pad)
 }

iris/transcript-ui/src/lib.rs

@@ -51,7 +51,7 @@ pub mod selection;
 use client_core::transcript_fold::TranscriptRow as FoldedRow;
 use iris::prelude::*;
 use selection::Selection;
-use std::{cell::RefCell, rc::Rc};
+use std::{cell::RefCell, rc::Rc, time::Instant};
 
 pub struct TranscriptScreen {
     /// The transcript's own `List` -- exposed so a caller can read
@@ -220,6 +220,43 @@ where
     })
     .add(rsc);
 
+    // The continuation of a row-started drag once it has committed and
+    // taken pointer capture on `list`'s own id (`row.rs`'s registration is
+    // only ever the gesture's first frame) -- registered once here, not
+    // once per row, since `DragGesture`'s single shared instance must see
+    // each frame of one gesture exactly once. `ctx.data.pos`/`size` are
+    // already relative to `list`'s own on-screen box (this is what it was
+    // registered against), which is exactly the viewport-pixel space
+    // `List::key_at`/`extent` work in, so the row-under-the-pointer is
+    // resolved from those instead of a per-row hit test.
+    {
+        let selection = selection.clone();
+        list.on(
+            CursorSense::Pressing(CursorButton::Left) | CursorSense::Drop,
+            move |ctx, rsc| {
+                let pos = ctx.data.pos;
+                let row = list(rsc).key_at(pos.y).and_then(|key| {
+                    let (top, bottom) = list(rsc).extent(key)?;
+                    Some((
+                        key,
+                        Vec2::new(pos.x, pos.y - top),
+                        Vec2::new(ctx.data.size.x, bottom - top),
+                    ))
+                });
+                selection.borrow_mut().drag(
+                    rsc,
+                    list,
+                    row,
+                    ctx.data.cursor.pos,
+                    ctx.data.sense,
+                    Instant::now(),
+                    ctx.data.render,
+                );
+            },
+        )
+        .add(rsc);
+    }
+
     let (composer, composer_bar) = composer::build_composer(rsc);
 
     let tree = (list.width(rest(1)).height(rest(1)), composer_bar)

iris/transcript-ui/src/row.rs

@@ -137,20 +137,26 @@ where
 
     field
         // `| CursorSense::unclick()` on top of the usual click-or-drag set
-        // -- the arbiter inside `Selection::drag` needs the release too,
-        // to go back to idle for the next press (`DragArbiter::release`).
+        // -- this row's own registration only ever needs to see a
+        // gesture's *first* frame (`PressStart`, or a `Pressing` that
+        // missed it -- `DragGesture::handle`'s idle-recovery branch); once
+        // it commits, `DragGesture` takes pointer capture on `list`'s own
+        // id and every further frame, including the terminal `Drop`,
+        // reaches `lib.rs`'s list-level registration instead -- see
+        // `iris::sense`'s pointer-capture doc for why that has to be a
+        // stable id rather than this row's, which `List` can retire mid-
+        // drag as content scrolls.
         .on(
             CursorSense::click_or_drag() | CursorSense::unclick(),
             move |ctx, rsc| {
                 selection.borrow_mut().drag(
                     rsc,
                     list,
-                    key,
-                    ctx.data.pos,
-                    ctx.data.size,
+                    Some((key, ctx.data.pos, ctx.data.size)),
                     ctx.data.cursor.pos,
                     ctx.data.sense,
                     Instant::now(),
+                    ctx.data.render,
                 );
             },
         )
@@ -174,8 +180,8 @@ where
 
     (header, field.width(rest(1)))
         .span(Dir::DOWN)
-        .gap(4)
-        .pad(10)
+        .gap(dp(4))
+        .pad(dp(10))
         .add_strong(rsc)
         .any()
 }

iris/transcript-ui/src/selection.rs

@@ -36,11 +36,15 @@ use std::{collections::BTreeMap, time::Instant};
 pub struct Selection {
     rows: BTreeMap<RowKey, WeakWidget<TextEdit>>,
     anchor: Option<(RowKey, Vec2)>,
-    /// One arbiter shared by every row's drag handler -- RUST.md's I5
+    /// One gesture shared by every row's drag handler -- RUST.md's I5
     /// gesture conflict (a row's own `click_or_drag()` and a list-level
     /// pan wanting the same touch gesture). See `drag` below, and
-    /// `iris::sense::DragArbiter`'s own doc for the decision itself.
-    arbiter: DragArbiter,
+    /// `iris::sense::DragGesture`'s own doc for the arbitration, velocity
+    /// tracking and pointer-capture mechanics this no longer owns itself
+    /// -- Iris's 2026-09-06 ask (`IRIS.md`) that a drag's *mechanics* live
+    /// in iris's default input layer, with only the pan-vs-select
+    /// *decision* staying here.
+    gesture: DragGesture,
 }
 
 impl Default for Selection {
@@ -54,7 +58,7 @@ impl Selection {
         Self {
             rows: BTreeMap::new(),
             anchor: None,
-            arbiter: DragArbiter::new(),
+            gesture: DragGesture::new(),
         }
     }
 
@@ -158,67 +162,66 @@ impl Selection {
     /// row, is what makes that consistent as a drag crosses row
     /// boundaries).
     ///
-    /// `pos_row`/`size` are row-local, as `begin`/`extend` want;
+    /// `row`, if given, is `(key, pos_row, size)` for whichever row the
+    /// pointer is currently over -- row-local, as `begin`/`extend` want.
+    /// `None` once the gesture is pointer-captured (`iris::sense`'s
+    /// pointer-capture doc) and the current position falls outside every
+    /// row `List` has loaded (a gap, or off the end of the content); a
+    /// `Pan` outcome never needs it, so this only actually matters mid-
+    /// selection, where it is rare and the frame is simply dropped.
     /// `pos_window` is in window space, since a pan's delta has to stay
     /// meaningful even when this frame's event landed on a different row
-    /// than the last one.
+    /// than the last one. `render` is `CursorData`'s own field -- what
+    /// `DragGesture` needs to take pointer capture.
     #[allow(clippy::too_many_arguments)]
     pub fn drag(
         &mut self,
         ui: &mut impl UiRsc,
         list: WeakWidget<List>,
-        key: RowKey,
-        pos_row: Vec2,
-        size: Vec2,
+        row: Option<(RowKey, Vec2, Vec2)>,
         pos_window: Vec2,
         sense: CursorSense,
         now: Instant,
+        render: &UiRenderState,
     ) {
-        let outcome = match sense {
-            CursorSense::PressStart(_) => {
+        if matches!(sense, CursorSense::PressStart(_)) {
+            // A fresh touch-down cancels any fling still coasting from
+            // the previous gesture -- `List::fling`'s own doc, and
+            // Android's `Scroller::abortAnimation` for the same reason.
+            list(ui).cancel_fling();
+        }
         let already_selected = self.has_selection(ui);
-                self.arbiter.press_start(pos_window, now, already_selected);
-                self.arbiter.update(pos_window, now)
-            }
-            CursorSense::PressEnd(_) => {
-                self.arbiter.release();
-                return;
-            }
-            // A `Pressing` frame with the arbiter still `Idle` means this
-            // gesture's `ACTION_DOWN` landed somewhere no row's sensor
-            // covers (a row's own padding/gap, or a header with no
-            // selection handler) and this row is only now getting the
-            // touch as it moves across it -- the touch is definitely still
-            // down (that's what `Pressing` means), so without this the
-            // arbiter would sit in `Idle` answering `Undecided` for the
-            // rest of the gesture (`DragArbiter::update`'s own doc).
-            // Recovered by starting the press here instead of where it
-            // was missed -- RUST.md's I5 intermittent-touch-scroll-dropout
-            // finding, 2026-09-05.
-            _ if self.arbiter.is_idle() => {
-                let already_selected = self.has_selection(ui);
-                self.arbiter.press_start(pos_window, now, already_selected);
-                self.arbiter.update(pos_window, now)
-            }
-            _ => self.arbiter.update(pos_window, now),
-        };
+        let outcome =
+            self.gesture
+                .handle(render, list.id(), sense, pos_window, now, already_selected);
         match outcome {
-            DragOutcome::Undecided => {}
-            DragOutcome::Pan(dy) => list(ui).scroll(-dy),
-            DragOutcome::SelectStart => {
-                // Grep-able on "iris selection" the way the frame report is
-                // on "iris frame report" -- selection has no accessibility
-                // label of its own yet, so this is the smallest way to
-                // confirm a real on-device long-press-then-drag actually
-                // reached here (RUST.md's I5 box, "Measurements taken" (c)).
+            GestureOutcome::Undecided => {}
+            GestureOutcome::Pan(dy) => list(ui).scroll(-dy),
+            GestureOutcome::SelectStart => {
+                if let Some((key, pos_row, size)) = row {
+                    // Grep-able on "iris selection" the way the frame
+                    // report is on "iris frame report" -- selection has no
+                    // accessibility label of its own yet, so this is the
+                    // smallest way to confirm a real on-device long-
+                    // press-then-drag actually reached here (RUST.md's I5
+                    // box, "Measurements taken" (c)).
                     log::info!("iris selection: begin at row {key:?}");
                     self.begin(ui, key, pos_row, size);
                 }
-            DragOutcome::SelectExtend => {
+            }
+            GestureOutcome::SelectExtend => {
+                if let Some((key, pos_row, size)) = row {
                     log::info!("iris selection: extend to row {key:?}");
                     self.extend(ui, key, pos_row, size);
                 }
             }
+            // A fling only ever follows a pan -- never a selection that
+            // happened to end with the finger still moving, and never a
+            // tap/long-press that never left `Undecided` -- exactly what
+            // `DragGesture`'s `Some(v)` already encodes.
+            GestureOutcome::Released(Some(v)) => list(ui).fling(-v),
+            GestureOutcome::Released(None) => {}
+        }
     }
 
     /// The concatenated selected text, in row order, `None` if nothing is
@@ -319,8 +322,9 @@ mod tests {
 
         let mut sel = Selection::new();
         sel.register(1, field);
-        assert!(sel.arbiter.is_idle());
+        assert!(sel.gesture.is_idle());
 
+        let render = UiRenderState::new();
         let now = Instant::now();
         let size = Vec2::new(100.0, 20.0);
         // No `PressStart` is ever sent -- only the `Pressing` frames a
@@ -328,15 +332,14 @@ mod tests {
         sel.drag(
             &mut rsc,
             list,
-            1,
-            Vec2::ZERO,
-            size,
+            Some((1, Vec2::ZERO, size)),
             Vec2::new(540.0, 700.0),
             CursorSense::Pressing(CursorButton::Left),
             now,
+            &render,
         );
         assert!(
-            !sel.arbiter.is_idle(),
+            !sel.gesture.is_idle(),
             "a Pressing frame with the arbiter still Idle must recover \
              the press rather than leaving it stuck"
         );