iris-android-app: the bench's fixture half comes from transcript-fixture

The fixture bytes, the backlog/tail split and the fold into a screen
were `bench_client.rs`'s alone; they are `transcript-fixture`'s now, so
the Android bench, the headless harness and the phone-shaped desktop
window open one screen from one copy (AGENTS.md: nothing UI-shaped in a
platform crate). What stays here is the JNI half -- clipboard, battery,
IME, the report and the four phases.

Built with `cargo ndk -t arm64-v8a -P 29 build --features
"transcript-screen bench"`; the two warnings it prints (bench_jni's
unused overlay methods, the unused `tabs-ui` dependency under this
feature set) predate this change.

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

iris/android-app/Cargo.lock

@@ -1774,6 +1774,7 @@ dependencies = [
  "serde_json",
  "tabs-ui",
  "tokio",
+ "transcript-fixture",
  "transcript-ui",
 ]
 
@@ -3864,6 +3865,17 @@ dependencies = [
  "once_cell",
 ]
 
+[[package]]
+name = "transcript-fixture"
+version = "0.1.0"
+dependencies = [
+ "client-core",
+ "event-model",
+ "iris",
+ "serde_json",
+ "transcript-ui",
+]
+
 [[package]]
 name = "transcript-ui"
 version = "0.1.0"

iris/android-app/Cargo.toml

@@ -29,6 +29,10 @@ log = "0.4.28"
 # which Cargo's `unused_dependencies` lint (on by default) correctly flags.
 tabs-ui = { path = "../tabs-ui", optional = true }
 transcript-ui = { path = "../transcript-ui", optional = true }
+# P0's bench build only: the fixture and the folded screen both bench
+# clients open, shared with the headless harness and the desktop window
+# (docs/RUST.md's "Three test layers").
+transcript-fixture = { path = "../transcript-fixture", optional = true }
 client-core = { path = "../../client-core", optional = true }
 event-model = { path = "../../event-model", optional = true }
 serde_json = { version = "1", features = ["float_roundtrip"], optional = true }
@@ -65,7 +69,7 @@ force-gles = ["iris/force-gles"]
 # `event-model` -- `lib.rs`'s `ActiveClient` selection gives this feature
 # priority over `transcript-screen`'s own `TranscriptClient` when both are
 # listed, which is how this crate's build command names both explicitly.
-bench = ["transcript-screen", "dep:libc", "dep:tokio"]
+bench = ["transcript-screen", "dep:transcript-fixture", "dep:libc", "dep:tokio"]
 
 [profile.release]
 panic = "abort"

iris/android-app/src/bench_client.rs

@@ -6,14 +6,11 @@
 //!
 //! **Reuses `transcript_client.rs`'s shape** (folded items, the same
 //! `TranscriptScreen::apply` incremental update on every event) with the
-//! network half replaced by the checked-in fixture, embedded with
-//! `include_str!` -- `app/bench-fixture/assets/transcript.jsonl`,
-//! 1,915,760 bytes, generated by `app/bench-fixture/generate.py` and never
-//! a real transcript (that file's own README). The first 3,200 lines are
-//! the opening backlog, folded once through
-//! `client_core::transcript_fold::fold_page` exactly as a real
-//! `/transcript` page would be (then a full `transcript_ui::build_tree`,
-//! same as any first load); the remaining ~400 are the streaming tail,
+//! network half replaced by the checked-in fixture. Reading that fixture
+//! and folding it into a screen is **`transcript-fixture`'s** job, not
+//! this file's -- the same crate the headless harness and the
+//! phone-shaped desktop window open, so all three measure one screen
+//! (AGENTS.md's sharing rule; moved out of here 2026-09-07). The tail is
 //! replayed one at a time through `fold_event` -- the same fold path a
 //! live SSE reply arrives on -- by the "Run benchmark" control below.
 //! Streaming through `apply` rather than a full rebuild per event is what
@@ -22,7 +19,7 @@
 
 use crate::bench_jni::PlatformHandle;
 use android_view::jni::{JavaVM, objects::GlobalRef};
-use client_core::transcript_fold::{TranscriptItem, fold_event, fold_page, group_tool_runs};
+use client_core::transcript_fold::{TranscriptItem, fold_event};
 use event_model::SeqEvent;
 use iris::android::{AndroidAppState, AndroidRsc, AndroidUiState, HasAndroidUiState};
 use iris::prelude::*;
@@ -30,13 +27,6 @@ use std::sync::atomic::{AtomicBool, Ordering};
 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
-/// `BenchFixture.kt`'s identical constant by hand -- both read the same
-/// checked-in file, so a mismatch would only mean the two apps' bench
-/// builds open a different split of it, not a wrong-vs-right answer.
-const BACKLOG_COUNT: usize = 3200;
-
 /// 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
@@ -90,8 +80,6 @@ const KEYBOARD_WAIT_MS: u64 = 1_000;
 /// 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");
-
 /// How much of the screen a *filled* benchmark report may take before it
 /// scrolls instead of growing -- roughly a third of a phone screen, the
 /// share the pane used to reserve unconditionally. An empty report takes
@@ -158,31 +146,6 @@ impl HasAndroidUiState for BenchClient {
     }
 }
 
-/// Parses the fixture once: `serde_json::Value`s for the backlog
-/// (`fold_page` takes a page of raw wire JSON, same as a real
-/// `/transcript` response) and folded `SeqEvent`s for the tail (`fold_event`
-/// takes one live wire event at a time, same as a real SSE frame).
-fn parse_fixture() -> (Vec<serde_json::Value>, Vec<SeqEvent>) {
-    let lines: Vec<&str> = FIXTURE_JSONL
-        .lines()
-        .filter(|line| !line.trim().is_empty())
-        .collect();
-    let mut backlog = Vec::with_capacity(BACKLOG_COUNT.min(lines.len()));
-    let mut stream_tail = Vec::new();
-    for (i, line) in lines.iter().enumerate() {
-        let value: serde_json::Value =
-            serde_json::from_str(line).expect("bench fixture is generated JSON, always valid");
-        if i < BACKLOG_COUNT {
-            backlog.push(value);
-        } else {
-            let event: SeqEvent = serde_json::from_value(value)
-                .expect("bench fixture event matches event-model's SeqEvent");
-            stream_tail.push(event);
-        }
-    }
-    (backlog, stream_tail)
-}
-
 fn placeholder<Rsc: HasEvents>(rsc: &mut Rsc, message: &str) -> StrongWidget {
     wtext(message.to_string())
         .color(Color::WHITE)
@@ -322,12 +285,12 @@ impl AndroidAppState for BenchClient {
             last_top_pad: 0.0,
         };
 
-        let (backlog, stream_tail) = parse_fixture();
-        client.stream_tail = stream_tail;
-        match fold_page(&backlog) {
-            Ok(items) => {
-                client.items = items;
-                client.rebuild_transcript(rsc);
+        match transcript_fixture::build_screen(rsc) {
+            Ok((opened, tree)) => {
+                client.items = opened.items;
+                client.stream_tail = opened.stream_tail;
+                (client.content)(rsc).set(tree);
+                client.screen = Some(opened.screen);
             }
             Err(message) => {
                 client.show_message(rsc, &format!("Couldn't fold the bench fixture: {message}"))
@@ -546,8 +509,7 @@ impl BenchClient {
     }
 
     fn rebuild_transcript(&mut self, rsc: &mut Rsc) {
-        let rows = group_tool_runs(&self.items);
-        let (screen, tree) = transcript_ui::build_tree(rsc, rows);
+        let (screen, tree) = transcript_ui::build_tree(rsc, transcript_fixture::rows(&self.items));
         (self.content)(rsc).set(tree);
         self.screen = Some(screen);
     }

iris/transcript-fixture/src/lib.rs

@@ -100,22 +100,49 @@ pub fn rows(items: &[TranscriptItem]) -> Vec<TranscriptRow> {
     group_tool_runs(items)
 }
 
-/// Build the transcript screen over the fixture's opening page and make
-/// it the root -- what every layer of the rig opens. Returns the screen
-/// and the items behind it, so a caller can go on streaming the tail
-/// through `fold_event`/`TranscriptScreen::apply` as the Android bench
-/// does.
-pub fn open<Rsc: HasEvents>(
-    rsc: &mut Rsc,
-    ui_state: &mut impl HasRoot,
-) -> Result<(transcript_ui::TranscriptScreen, Vec<TranscriptItem>), String>
+/// Everything a caller needs to run the fixture as an app screen would:
+/// the screen, the folded items behind it, and the events not yet
+/// streamed. The tree itself comes back separately from
+/// [`build_screen`], since whoever takes it owns it.
+pub struct Opened {
+    pub screen: transcript_ui::TranscriptScreen,
+    pub items: Vec<TranscriptItem>,
+    /// The tail, for a caller that goes on replaying it one event at a
+    /// time through `fold_event`/`TranscriptScreen::apply` -- the
+    /// streaming phase of either app's benchmark.
+    pub stream_tail: Vec<SeqEvent>,
+}
+
+/// Build the transcript screen over the fixture's opening page, without
+/// claiming the window's root -- `transcript_ui::build_tree`'s own split,
+/// for a caller (the Android bench) that puts the screen inside a shell
+/// of its own.
+pub fn build_screen<Rsc: HasEvents>(rsc: &mut Rsc) -> Result<(Opened, StrongWidget), String>
 where
     Rsc::State: FocusHost + OpenUrl,
 {
     let fixture = Fixture::parse();
     let items = fixture.backlog_items()?;
-    let screen = transcript_ui::build(rsc, ui_state, rows(&items));
-    Ok((screen, items))
+    let (screen, tree) = transcript_ui::build_tree(rsc, rows(&items));
+    Ok((
+        Opened {
+            screen,
+            items,
+            stream_tail: fixture.stream_tail,
+        },
+        tree,
+    ))
+}
+
+/// [`build_screen`] with the screen as the window's root -- what the
+/// headless harness and the desktop window open.
+pub fn open<Rsc: HasEvents>(rsc: &mut Rsc, ui_state: &mut impl HasRoot) -> Result<Opened, String>
+where
+    Rsc::State: FocusHost + OpenUrl,
+{
+    let (opened, tree) = build_screen(rsc)?;
+    ui_state.set_root(tree);
+    Ok(opened)
 }
 
 #[cfg(test)]

iris/transcript-fixture/tests/phone_screen.rs

@@ -17,11 +17,10 @@ use transcript_fixture::{PHONE_FRAME_MS, PHONE_SCALE, phone_size};
 /// anchor, which is what every assertion about scroll position reads.
 fn opened() -> (Harness, transcript_ui::TranscriptScreen) {
     let mut h = Harness::new(phone_size(), PHONE_SCALE);
-    let (screen, _items) =
-        transcript_fixture::open(&mut h.rsc, &mut h.state).expect("the fixture folds");
+    let opened = transcript_fixture::open(&mut h.rsc, &mut h.state).expect("the fixture folds");
     h.frame(0);
     h.frame(PHONE_FRAME_MS);
-    (h, screen)
+    (h, opened.screen)
 }
 
 fn script(name: &str, text: &str) -> TouchScript {