IRIS.md: take_counters gained a fourth number, text shapes

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
docs: the verification pass over Tasks A and B, and the composer background withdrawn
2026-09-06 18:40:38 -04:00 · 2026-09-06 18:40:25 -04:00 · 2026-09-06 18:32:31 -04:00 · 2026-09-06 18:32:05 -04:00 · 2026-09-06 18:31:58 -04:00 · 2026-09-06 18:28:57 -04:00
51 changed files with 6100 additions and 273 deletions
@@ -50,6 +50,12 @@ version = "0.23.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ac07cdecf99051d9a5238b80f35af32cdeba5b336e55d957b318b50137e18da5"
 [[package]]
 name = "bitflags"
 version = "2.13.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b588b76d00fde79687d7646a9b5bdf3cc0f655e0bbd080335a95d7e96f3587da"
 [[package]]
 name = "bytes"
 version = "1.12.1"
@@ -77,6 +83,7 @@ name = "client-core"
 version = "0.1.0"
 dependencies = [
 "event-model",
 "pulldown-cmark",
 "serde",
 "serde_json",
 "ureq",
@@ -206,6 +213,15 @@ dependencies = [
 "percent-encoding",
 ]
 [[package]]
 name = "getopts"
 version = "0.2.24"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cfe4fbac503b8d1f88e6676011885f34b7174f46e59956bba534ba83abded4df"
 dependencies = [
 "unicode-width",
 ]
 [[package]]
 name = "getrandom"
 version = "0.2.17"
@@ -490,6 +506,25 @@ dependencies = [
 "unicode-ident",
 ]
 [[package]]
 name = "pulldown-cmark"
 version = "0.13.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e9f068eba8e7071c5f9511831b44f32c740d5adf574e990f946ddb53db2f314e"
 dependencies = [
 "bitflags",
 "getopts",
 "memchr",
 "pulldown-cmark-escape",
 "unicase",
 ]
 [[package]]
 name = "pulldown-cmark-escape"
 version = "0.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "007d8adb5ddab6f8e3f491ac63566a7d5002cc7ed73901f72057943fa71ae1ae"
 [[package]]
 name = "quote"
 version = "1.0.47"
@@ -783,12 +818,24 @@ dependencies = [
 "zerovec",
 ]
 [[package]]
 name = "unicase"
 version = "2.9.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "dbc4bc3a9f746d862c45cb89d705aa10f187bb96c76001afab07a0d35ce60142"
 [[package]]
 name = "unicode-ident"
 version = "1.0.24"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e6e4313cd5fcd3dad5cafa179702e2b244f760991f45397d14d4ebf38247da75"
 [[package]]
 name = "unicode-width"
 version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b4ac048d71ede7ee76d585517add45da530660ef4390e49b098733c6e897f254"
 [[package]]
 name = "untrusted"
 version = "0.9.0"
@@ -47,6 +47,7 @@ name = "client-core"
 version = "0.1.0"
 dependencies = [
 "event-model",
 "pulldown-cmark",
 "serde",
 "serde_json",
 "tempfile",
@@ -173,6 +174,15 @@ dependencies = [
 "percent-encoding",
 ]
 [[package]]
 name = "getopts"
 version = "0.2.24"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cfe4fbac503b8d1f88e6676011885f34b7174f46e59956bba534ba83abded4df"
 dependencies = [
 "unicode-width",
 ]
 [[package]]
 name = "getrandom"
 version = "0.2.17"
@@ -425,6 +435,25 @@ dependencies = [
 "unicode-ident",
 ]
 [[package]]
 name = "pulldown-cmark"
 version = "0.13.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e9f068eba8e7071c5f9511831b44f32c740d5adf574e990f946ddb53db2f314e"
 dependencies = [
 "bitflags",
 "getopts",
 "memchr",
 "pulldown-cmark-escape",
 "unicase",
 ]
 [[package]]
 name = "pulldown-cmark-escape"
 version = "0.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "007d8adb5ddab6f8e3f491ac63566a7d5002cc7ed73901f72057943fa71ae1ae"
 [[package]]
 name = "quote"
 version = "1.0.47"
@@ -661,12 +690,24 @@ dependencies = [
 "zerovec",
 ]
 [[package]]
 name = "unicase"
 version = "2.9.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "dbc4bc3a9f746d862c45cb89d705aa10f187bb96c76001afab07a0d35ce60142"
 [[package]]
 name = "unicode-ident"
 version = "1.0.24"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e6e4313cd5fcd3dad5cafa179702e2b244f760991f45397d14d4ebf38247da75"
 [[package]]
 name = "unicode-width"
 version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b4ac048d71ede7ee76d585517add45da530660ef4390e49b098733c6e897f254"
 [[package]]
 name = "untrusted"
 version = "0.9.0"
@@ -17,7 +17,12 @@ edition = "2024"
 [dependencies]
 event-model = { path = "../event-model" }
 serde = { version = "1", features = ["derive"] }
-serde_json = { version = "1", features = ["float_roundtrip"] }
+# "raw_value" is `fetch_transcript_lines`'s reason -- it needs the exact
 # bytes the server sent, not this crate's own re-serialization of a parsed
 # `Value`, so a cached line and a live SSE frame for the same event agree
 # byte-for-byte (see that method's doc). "float_roundtrip" is why they
 # agree on a `ts` at all -- see server/Cargo.toml's identical comment.
 serde_json = { version = "1", features = ["float_roundtrip", "raw_value"] }
 # The blocking HTTP client for the REST calls and the long-lived SSE GETs.
 # `server/` already depends on ureq for its own outbound HTTPS (the usage
 # poll in usage.rs) and it is rustls-backed like the rest of this project's
@@ -27,6 +32,12 @@ serde_json = { version = "1", features = ["float_roundtrip"] }
 # no need of an async runtime, and RUST.md's brief for this port is
 # "lightweight" throughout.
 ureq = { version = "3", features = ["json"] }
 # The markdown block split (`markdown_blocks`), which has to agree with the
 # renderer in `iris/transcript-ui` about where a block begins -- so it is
 # the same parser at the same version, rather than a hand-written splitter
 # that would drift from it.
 pulldown-cmark = "0.13.4"
 [dev-dependencies]
 tempfile = "3"
@@ -10,6 +10,7 @@
 use std::io::Read;
 use event_model::SeqEvent;
 use serde::Deserialize;
 use serde_json::Value;
@@ -116,6 +117,14 @@ impl<T: Transport> ApiClient<T> {
        Self { transport }
    }
    /// The transport underneath, for a caller that needs the raw SSE
    /// stream (`event_stream::follow_session_events`) rather than one of
    /// this client's typed REST calls -- `transcript_source::TranscriptSource`
    /// is the one that does.
    pub fn transport(&self) -> &T {
        &self.transport
    }
    fn json_request<R: for<'de> Deserialize<'de>>(
        &self,
        method: &str,
@@ -266,15 +275,72 @@ impl<T: Transport> ApiClient<T> {
        limit: u32,
        coalesce: bool,
    ) -> Result<Vec<Value>, ApiError> {
-        let mut path = format!("/sessions/{session_id}/transcript?limit={limit}");
+        self.json_request(
-        if let Some(before) = before {
+            "GET",
-            path.push_str(&format!("&before={before}"));
+            &transcript_path(session_id, before, limit, coalesce, None),
-        }
+            None,
-        if coalesce {
+        )
            path.push_str("&coalesce=true");
        }
        self.json_request("GET", &path, None)
    }
    /// A page of transcript history, each line handed back paired with the
    /// exact text it came from, and bounded below by `after` -- the shape
    /// `crate::transcript_source::TranscriptSource` needs to store what it
    /// fetched in the transcript cache without a second round trip to fetch
    /// the raw text separately. Ported from `Api.kt`'s `fetchTranscript`.
    ///
    /// Uses [`serde_json::value::RawValue`] rather than re-serializing a
    /// parsed [`Value`], so the stored line is the exact bytes the server
    /// sent (key order and float literal included) rather than this
    /// crate's own idea of how to write them back out -- the cache and a
    /// live SSE frame must agree byte-for-byte on the same event, which is
    /// exactly what caught the `serde_json` float-rounding bug this
    /// project's `AGENTS.md` records.
    pub fn fetch_transcript_lines(
        &self,
        session_id: &str,
        before: Option<u64>,
        limit: u32,
        coalesce: bool,
        after: Option<u64>,
    ) -> Result<Vec<(String, SeqEvent)>, ApiError> {
        let path = transcript_path(session_id, before, limit, coalesce, after);
        let raw: Vec<Box<serde_json::value::RawValue>> = self.json_request("GET", &path, None)?;
        raw.into_iter()
            .map(|value| {
                let line = value.get().to_string();
                let event: SeqEvent = serde_json::from_str(&line).map_err(|e| ApiError {
                    message: format!(
                        "the server sent a transcript line this build couldn't parse: {e}"
                    ),
                    status: None,
                })?;
                Ok((line, event))
            })
            .collect()
    }
 }
 /// The query string shared by [`ApiClient::fetch_transcript_page`] and
 /// [`ApiClient::fetch_transcript_lines`], so the two agree on how each
 /// parameter is written rather than keeping two copies to drift.
 fn transcript_path(
    session_id: &str,
    before: Option<u64>,
    limit: u32,
    coalesce: bool,
    after: Option<u64>,
 ) -> String {
    let mut path = format!("/sessions/{session_id}/transcript?limit={limit}");
    if let Some(before) = before {
        path.push_str(&format!("&before={before}"));
    }
    if coalesce {
        path.push_str("&coalesce=true");
    }
    if let Some(after) = after {
        path.push_str(&format!("&after={after}"));
    }
    path
 }
 /// The blocking [`Transport`] backed by `ureq`, the same crate `server/`
@@ -7,9 +7,11 @@ pub mod api;
 pub mod config;
 pub mod event_stream;
 pub mod highlight;
 pub mod markdown_blocks;
 pub mod notifications;
 pub mod sse;
 pub mod transcript_cache;
 pub mod transcript_fold;
 pub mod transcript_source;
 pub use event_model::*;
@@ -0,0 +1,325 @@
 //! Split a markdown message into its top-level **blocks** -- one
 //! paragraph, heading, fenced code block, list, table or quote each, as a
 //! byte slice of the original source.
 //!
 //! This exists for streaming. A transcript row used to be one text widget
 //! holding the whole message, so a single streamed delta re-shaped every
 //! paragraph of it through the text engine again; the phone's bench v2 put
 //! the stream phase at p50 18.2ms against Compose's 13.4ms for exactly
 //! that reason (docs/IRIS_TODO.md). A row is a column of one widget per
 //! block now, and a delta that lands in the last block leaves every
 //! earlier block's layout alone. `docs/DECISIONS.md`'s 2026-09-06 entry has
 //! what that rejected and why the split lives here rather than in the UI
 //! crate: `docs/CLIENT_CORE.md` already wanted a block model for P1, and
 //! keeping it here means iris stays a text renderer that knows nothing
 //! about markdown.
 //!
 //! **Blocks only.** Inline styling (bold, links, inline code) is still the
 //! renderer's own job, per block -- this deliberately does not build a
 //! full AST, because nothing needs one yet.
 //!
 //! ## Appending is not guaranteed to leave earlier blocks alone
 //!
 //! It nearly always does, which is what makes the fast path worth having,
 //! but markdown has no such rule: appending a "```" line can turn text
 //! that was three paragraphs into one fenced block, and appending "---"
 //! under a paragraph turns that paragraph into a heading. So a caller
 //! taking the O(last block) path **must compare the prefix it is about to
 //! keep** rather than assume it. [`common_prefix`] is that comparison, and
 //! it is cheap next to laying the text out again.
 use pulldown_cmark::{Event, Options, Parser, Tag};
 /// What a block is, for a renderer that wants to style or space blocks
 /// differently. `Other` is deliberately present rather than a panic or a
 /// silent fallback to `Paragraph`: markdown has more block kinds than this
 /// list and more get added, and a renderer treating an unknown one as
 /// prose is right, but it should be able to *tell* that is what it is
 /// doing.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum BlockKind {
    Paragraph,
    Heading,
    /// A fenced or indented code block.
    Code,
    List,
    Table,
    Quote,
    /// A thematic break, raw HTML, a footnote -- anything with no
    /// distinguished treatment here.
    Other,
 }
 /// One top-level block: its kind and the exact source that produced it.
 /// `source` is a slice of the input with trailing whitespace removed, so
 /// two splits of the same prefix compare equal even when one of them had a
 /// delta arriving after it.
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct Block {
    pub kind: BlockKind,
    pub source: String,
 }
 fn kind_of(tag: &Tag) -> BlockKind {
    match tag {
        Tag::Paragraph => BlockKind::Paragraph,
        Tag::Heading { .. } => BlockKind::Heading,
        Tag::CodeBlock(_) => BlockKind::Code,
        Tag::List(_) => BlockKind::List,
        Tag::Table(_) => BlockKind::Table,
        Tag::BlockQuote(_) => BlockKind::Quote,
        _ => BlockKind::Other,
    }
 }
 fn options() -> Options {
    // The same set `transcript-ui`'s renderer parses with, so a block
    // boundary here and the styling there cannot disagree about what the
    // source means.
    Options::ENABLE_STRIKETHROUGH | Options::ENABLE_TABLES | Options::ENABLE_TASKLISTS
 }
 /// Split `src` into its top-level blocks, in source order. An empty or
 /// whitespace-only input gives no blocks; text the parser does not put
 /// inside any block (a stray fence marker mid-stream) still comes back,
 /// as `Other`, rather than being dropped.
 pub fn split_blocks(src: &str) -> Vec<Block> {
    let mut out: Vec<Block> = Vec::new();
    let mut depth = 0usize;
    let mut kind = BlockKind::Other;
    for (event, range) in Parser::new_ext(src, options()).into_offset_iter() {
        match event {
            Event::Start(tag) => {
                if depth == 0 {
                    kind = kind_of(&tag);
                }
                depth += 1;
            }
            Event::End(_) => {
                depth -= 1;
                if depth == 0 {
                    push(&mut out, kind, &src[range]);
                }
            }
            // A top-level event that is not part of any block -- a
            // thematic break, a block of raw HTML. Inside one, it is the
            // enclosing block's business and this does nothing.
            _ => {
                if depth == 0 {
                    push(&mut out, BlockKind::Other, &src[range]);
                }
            }
        }
    }
    out
 }
 fn push(out: &mut Vec<Block>, kind: BlockKind, source: &str) {
    let source = source.trim_end();
    if source.is_empty() {
        return;
    }
    out.push(Block {
        kind,
        source: source.to_string(),
    });
 }
 /// How many leading blocks of `old` and `new` are identical -- what a
 /// caller may keep the laid-out widgets for. See the module doc for why
 /// this is a comparison rather than an assumption.
 pub fn common_prefix(old: &[Block], new: &[Block]) -> usize {
    old.iter().zip(new).take_while(|(a, b)| a == b).count()
 }
 #[cfg(test)]
 mod tests {
    use super::*;
    fn kinds(src: &str) -> Vec<BlockKind> {
        split_blocks(src).into_iter().map(|b| b.kind).collect()
    }
    #[test]
    fn a_message_splits_into_its_top_level_blocks() {
        let src = "# Title\n\nFirst para.\n\n```rust\nfn main() {}\n```\n\n- a\n- b\n";
        assert_eq!(
            kinds(src),
            vec![
                BlockKind::Heading,
                BlockKind::Paragraph,
                BlockKind::Code,
                BlockKind::List
            ]
        );
        let blocks = split_blocks(src);
        assert_eq!(blocks[1].source, "First para.");
        assert_eq!(blocks[2].source, "```rust\nfn main() {}\n```");
    }
    #[test]
    fn blank_input_has_no_blocks() {
        assert!(split_blocks("").is_empty());
        assert!(split_blocks("   \n\n  ").is_empty());
    }
    /// The property the streaming fast path rests on, in its ordinary
    /// shape: a delta landing in the last paragraph must leave every
    /// earlier block byte-identical.
    #[test]
    fn a_delta_into_the_last_paragraph_leaves_earlier_blocks_untouched() {
        let before = split_blocks("# Title\n\nFirst para.\n\nSecond par");
        let after = split_blocks("# Title\n\nFirst para.\n\nSecond paragraph now.");
        assert_eq!(common_prefix(&before, &after), 2);
        assert_eq!(before.len(), 3);
        assert_eq!(after.len(), 3);
        assert_ne!(before[2], after[2]);
    }
    /// A delta that starts a *new* block keeps every old block, including
    /// the one that was last -- so the fast path appends rather than
    /// replacing.
    #[test]
    fn a_delta_that_starts_a_new_block_keeps_every_old_one() {
        let before = split_blocks("First para.\n\nSecond para.");
        let after = split_blocks("First para.\n\nSecond para.\n\nThird");
        assert_eq!(common_prefix(&before, &after), 2);
        assert_eq!(after.len(), 3);
    }
    /// A code fence arrives one delta at a time and is unterminated for
    /// most of its life. It must still be *one* block the whole way, or
    /// every delta would re-split the message into a different number of
    /// pieces.
    #[test]
    fn an_unterminated_fence_is_one_block_while_it_streams() {
        for src in [
            "Here:\n\n```rust\n",
            "Here:\n\n```rust\nfn main() {\n",
            "Here:\n\n```rust\nfn main() {\n    println!(\"hi\");\n",
        ] {
            assert_eq!(
                kinds(src),
                vec![BlockKind::Paragraph, BlockKind::Code],
                "{src:?}"
            );
        }
    }
    /// The half the fast path had no reason to touch, and the reason
    /// `common_prefix` is a comparison rather than an assumption:
    /// appending can rewrite what came before. `---` under a paragraph
    /// turns that paragraph into a setext heading, so the block that was
    /// already laid out is not the block it is now.
    #[test]
    fn appending_can_rewrite_an_earlier_block_and_the_prefix_says_so() {
        let before = split_blocks("Not a heading\n\nsecond");
        let after = split_blocks("Not a heading\n\nsecond\n---");
        assert_eq!(before[1].kind, BlockKind::Paragraph);
        assert_eq!(after[1].kind, BlockKind::Heading);
        assert_eq!(
            common_prefix(&before, &after),
            1,
            "the rewritten block must not be reported as keepable"
        );
    }
    #[test]
    fn a_thematic_break_is_its_own_block() {
        assert_eq!(
            kinds("one\n\n---\n\ntwo"),
            vec![BlockKind::Paragraph, BlockKind::Other, BlockKind::Paragraph]
        );
    }
    /// The shapes a real transcript actually contains, each checked for
    /// the one property the streaming fast path needs: the *number* of
    /// blocks and every earlier block's source stay put while the message
    /// grows. A fence's own blank lines, a `---` inside one, a nested
    /// list and a table are all places where a naive line-based split
    /// would break the message into more pieces than there are blocks.
    #[test]
    fn the_transcripts_own_block_shapes_survive_a_split() {
        let fence_with_blanks = "Intro.\n\n```rust\nfn a() {}\n\nfn b() {}\n```\n\nAfter.";
        assert_eq!(
            kinds(fence_with_blanks),
            vec![BlockKind::Paragraph, BlockKind::Code, BlockKind::Paragraph],
            "a blank line inside a fence is not a block boundary"
        );
        assert_eq!(
            kinds("```\n---\n```"),
            vec![BlockKind::Code],
            "a thematic break inside a fence is code, not a break"
        );
        assert_eq!(
            kinds("- a\n  - a1\n  - a2\n- b"),
            vec![BlockKind::List],
            "a nested list is one top-level block"
        );
        assert_eq!(
            kinds("## Heading\n```sh\nls\n```"),
            vec![BlockKind::Heading, BlockKind::Code],
            "a fence directly under a heading, with no blank line"
        );
        assert_eq!(
            kinds("| a | b |\n|---|---|\n| 1 | 2 |"),
            vec![BlockKind::Table]
        );
        assert_eq!(
            kinds("> quoted\n> more\n\nplain"),
            vec![BlockKind::Quote, BlockKind::Paragraph]
        );
    }
    /// `apply_delta`'s precondition, stated as the property rather than
    /// the arithmetic: for every prefix of a realistic streamed message,
    /// the blocks before the last one must be exactly the blocks the
    /// previous prefix had. Where markdown breaks that (the `---` case
    /// above), `common_prefix` has to *say* so -- which is what the
    /// `>= len - 1` assertion below checks: the split may rewrite the
    /// last block, never an earlier one, or `RowBlocks::apply_delta`
    /// would keep a widget whose text is no longer what it holds.
    #[test]
    fn every_prefix_of_a_streamed_message_keeps_all_but_its_last_block() {
        let full = "# Report\n\nFirst finding, at some length.\n\n```rust\nfn main() {\n\n                        println!(\"hi\");\n}\n```\n\n- one\n  - nested\n- two\n\n| a | b |\n                    |---|---|\n| 1 | 2 |\n\n> and a closing quote.";
        // Every character boundary, so a delta landing mid-word and one
        // landing exactly on a fence's closing backtick are both covered.
        let mut prev = Vec::new();
        for end in full.char_indices().map(|(i, _)| i).chain([full.len()]) {
            let now = split_blocks(&full[..end]);
            let common = common_prefix(&prev, &now);
            assert!(
                prev.is_empty() || common + 1 >= prev.len(),
                "at {end} bytes the split rewrote block {common} of {}, not just the last one:\n                 before={prev:#?}\nafter={now:#?}",
                prev.len()
            );
            prev = now;
        }
    }
    /// The half a growing message cannot show: a fence that never closes.
    /// The stream ends there and the block must still be the code block
    /// it has been all along, not re-split into paragraphs.
    #[test]
    fn a_stream_that_ends_inside_a_fence_still_ends_with_one_code_block() {
        let src = "Here is the patch:\n\n```diff\n- old line\n+ new line";
        let blocks = split_blocks(src);
        assert_eq!(
            blocks.iter().map(|b| b.kind).collect::<Vec<_>>(),
            vec![BlockKind::Paragraph, BlockKind::Code]
        );
        assert_eq!(blocks[1].source, "```diff\n- old line\n+ new line");
    }
    /// A delta that closes a fence changes the *last* block only, so the
    /// fast path takes it -- the case the module doc says is the reason
    /// `common_prefix` is a comparison.
    #[test]
    fn the_delta_that_closes_a_fence_changes_only_the_last_block() {
        let before = split_blocks("Text.\n\n```\ncode\n");
        let after = split_blocks("Text.\n\n```\ncode\n```");
        assert_eq!(before.len(), after.len());
        assert_eq!(common_prefix(&before, &after), 1);
        assert_ne!(before[1], after[1]);
    }
 }
@@ -361,6 +361,10 @@ impl SessionCache {
            {
                return Ok(false);
            }
            debug_assert!(
                lines.iter().all(|l| !l.contains('\n')),
                "a stored page's lines must each be one line"
            );
            fs::create_dir_all(&this.dir)?;
            let kind = if rows { "rows" } else { "raw" };
            let mut content = lines.join("\n");
@@ -389,8 +393,16 @@ impl SessionCache {
                return Ok(());
            };
            // Written as it arrived. A newline inside it would split one
-            // event into two unreadable halves, but neither source can
+            // event into two unreadable halves. No source here can produce
-            // produce one.
+            // one -- an SSE `data:` field cannot hold a raw newline, and a
            // fetched line is one element of a compact JSON array -- but
            // that is a fact about the *server's* serializer rather than
            // anything this file controls, so it is checked rather than
            // trusted.
            debug_assert!(
                !line.contains('\n'),
                "a cached transcript line must be one line: {line}"
            );
            use std::io::Write;
            writer.write_all(line.as_bytes())?;
            writer.write_all(b"\n")?;
@@ -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:?}"),
        }
    }
 }
@@ -0,0 +1,588 @@
 //! Where a session screen gets a transcript from: this phone's copy first,
 //! the server for the rest. Ported from `app/.../TranscriptSource.kt`; see
 //! `docs/TRANSCRIPT_CACHE.md` for the design this implements and
 //! `docs/CLIENT_CORE.md` for how this file corresponds to the Kotlin.
 //!
 //! One seam rather than a cache the screen has to remember to consult.
 //! Everything fetched before is asked of this, and everything the server
 //! sends is written into the cache on the way past, so a caller never
 //! learns which side answered. The one rule worth keeping in mind: the
 //! cache is never load-bearing. Every read here has a network path beside
 //! it producing the same result.
 //!
 //! **Not ported**: `EventStream.kt`'s reconnect-with-backoff loop and the
 //! ability to close a live stream from another thread. Both are wall-clock
 //! and thread-lifetime concerns that belong to whatever runtime the caller
 //! embeds this crate in (a Tokio task, an iris timer, a Kotlin coroutine
 //! scope) rather than to this pure logic -- `follow` below is the same
 //! decorator shape `iris/desktop-app/src/app.rs` and
 //! `iris/android-app/src/transcript_client.rs` already hand-wrote around
 //! `event_stream::follow_session_events`, just with the cache write built
 //! in so a future caller does not have to repeat it a third time.
 use event_model::SeqEvent;
 use crate::api::{ApiClient, ApiError, Transport};
 use crate::event_stream::{self, StreamItem};
 use crate::transcript_cache::SessionCache;
 /// How many events a session screen opens with, cached or fetched.
 ///
 /// The server's own default page size, named here because the cached
 /// opening has to be the same size as the fetched one -- a reader must not
 /// get a shorter first screen for having been here before (`OPENING_WINDOW`
 /// in the Kotlin original).
 pub const OPENING_WINDOW: u32 = 80;
 /// A transcript-line parse failure, told apart from [`ApiError`] so a
 /// caller can tell "the server is unreachable" from "the server (or this
 /// phone's own disk) sent something this build cannot read" -- the two
 /// mean different things to a reader (retry, versus a build that is
 /// behind).
 #[derive(Debug, Clone)]
 pub struct ParseError(pub String);
 impl std::fmt::Display for ParseError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(&self.0)
    }
 }
 impl std::error::Error for ParseError {}
 /// Either half of what can go wrong asking for a page: the network, or a
 /// line neither the cache's nor the server's copy of `parseSeqEvent` could
 /// read.
 #[derive(Debug, Clone)]
 pub enum PageError {
    Api(ApiError),
    Parse(ParseError),
 }
 impl From<ApiError> for PageError {
    fn from(e: ApiError) -> Self {
        Self::Api(e)
    }
 }
 impl From<ParseError> for PageError {
    fn from(e: ParseError) -> Self {
        Self::Parse(e)
    }
 }
 /// What [`TranscriptSource::page`] found, kept as two states rather than
 /// one possibly-empty list.
 ///
 /// The difference is the whole of AGENTS.md's `loadOlderPage` incident: an
 /// empty [`Self::Events`] means "this conversation has no more history",
 /// which a caller is meant to latch, and [`Self::NothingLoaded`] means the
 /// question could not be asked yet, which it must not. Collapsing the two
 /// into an empty `Vec` puts the bug back, because the caller cannot tell
 /// them apart -- and `unwrap_or_default()` on an `Option` would do the
 /// same silently.
 #[derive(Debug, Clone, PartialEq)]
 pub enum OlderPage {
    /// The events before the cursor, oldest first. Empty means the start
    /// of the conversation has been reached.
    Events(Vec<SeqEvent>),
    /// Nothing is loaded, so there was no cursor to page back from
    /// (`before == 0`). Not an answer about the conversation at all.
    NothingLoaded,
 }
 fn parse_line(line: &str) -> Result<SeqEvent, ParseError> {
    serde_json::from_str(line).map_err(|e| ParseError(format!("{e}")))
 }
 /// This phone's copy of one session's transcript, plus the server it
 /// falls back to. Ported from the Kotlin `TranscriptSource` class.
 pub struct TranscriptSource<T: Transport> {
    api: ApiClient<T>,
    session_id: String,
    pub cache: SessionCache,
 }
 impl<T: Transport> TranscriptSource<T> {
    pub fn new(api: ApiClient<T>, session_id: impl Into<String>, cache: SessionCache) -> Self {
        Self {
            api,
            session_id: session_id.into(),
            cache,
        }
    }
    /// The cached opening window, or `None` when there is nothing usable
    /// to draw.
    ///
    /// Meant to be drawn *before* [`Self::probe`] returns, which is the
    /// whole point of the feature: the rows are on screen while the check
    /// that they are still the server's rows is in flight, and a failed
    /// check replaces them exactly as a reset does.
    pub fn cached_opening(&self, limit: usize) -> Option<Vec<SeqEvent>> {
        self.cache.tail()?;
        let lines = self.cache.newest(limit);
        if lines.is_empty() {
            return None;
        }
        match lines.iter().map(|l| parse_line(l)).collect() {
            Ok(events) => Some(events),
            // A line this build cannot read at all, which the cache's own checks cannot
            // see: it reads a seq off a line, not an event. Nothing to serve, so a cold
            // open.
            Err(ParseError(_)) => {
                self.cache.purge();
                None
            }
        }
    }
    /// Whether the server's event at the cached cursor is still the cached
    /// one.
    ///
    /// A caller must not resume a live stream from a cached seq unless it
    /// is the same conversation: a transcript is append-only in ordinary
    /// use, but the file backing it can be replaced or truncated (a
    /// sandbox re-seeded with the same ids, a backup restored, a session
    /// re-imported), and the server's catch-up on such a file would hand
    /// this phone a continuation of a *different* conversation, spliced
    /// onto the cached one with no seam. Caught with one request of a few
    /// hundred bytes.
    ///
    /// `Ok(false)` purges the cache and means "open cold". `Err` is the
    /// server not being askable, which is neither: the cached rows stay
    /// on screen and the caller tries again on its own reconnect schedule.
    ///
    /// What this cannot see is a line changed in the middle of the file
    /// with the tail intact -- that is what a full reload is for.
    pub fn probe(&self) -> Result<bool, ApiError> {
        let Some(tail) = self.cache.tail() else {
            return Ok(false);
        };
        // `before = seq + 1` is the newest event with seq <= the cursor, which is the
        // event *at* the cursor when the server still has one there.
        let page = self.api.fetch_transcript_lines(
            &self.session_id,
            Some(tail.seq + 1),
            1,
            false,
            None,
        )?;
        let matches = page.len() == 1
            && parse_line(&tail.line)
                .map(|cached| cached == page[0].1)
                .unwrap_or(false);
        if !matches {
            self.cache.purge();
        }
        Ok(matches)
    }
    /// Today's opening fetch, kept as the start of the live run. Only
    /// called when the cache has nothing to open with, or when
    /// [`Self::probe`] said what it had was not the server's.
    pub fn fetch_opening(&self) -> Result<Vec<SeqEvent>, ApiError> {
        let page =
            self.api
                .fetch_transcript_lines(&self.session_id, None, OPENING_WINDOW, false, None)?;
        for (line, event) in &page {
            self.cache.append(line, event.seq);
        }
        self.cache.flush();
        Ok(page.into_iter().map(|(_, event)| event).collect())
    }
    /// The page before `before`: from the cache when it holds it,
    /// otherwise from the server bounded by what the cache already has.
    ///
    /// The server bound (`after`) is what keeps the cache worth having. A
    /// coalesced page reaches back as far as its row count takes it -- a
    /// single reply is hundreds of lines -- so a page fetched after the
    /// reader has been away could run straight past the cached run and
    /// overlap it, and an overlapping page cannot be stored. Told where
    /// this phone's copy starts, the server stops there instead.
    ///
    /// `before == 0` answers [`OlderPage::NothingLoaded`] without asking
    /// the cache or the server anything -- see AGENTS.md's "things that
    /// have bitten": there is no event before the first one, so the
    /// request is not a harmless no-op, and its empty answer is
    /// indistinguishable from having reached the start of history.
    /// Guarded here rather than left to every caller, because it is a fact
    /// about the question, not about who is asking it.
    pub fn page(&self, before: u64, limit: u32, coalesce: bool) -> Result<OlderPage, PageError> {
        if before == 0 {
            return Ok(OlderPage::NothingLoaded);
        }
        if let Some(lines) = self.cache.page(before, limit as usize, coalesce) {
            let events: Vec<SeqEvent> = lines
                .iter()
                .map(|l| parse_line(l).map_err(PageError::from))
                .collect::<Result<_, _>>()?;
            return Ok(OlderPage::Events(events));
        }
        let after = self.cache.covered_up_to(before).map(|v| v - 1);
        let page = self.api.fetch_transcript_lines(
            &self.session_id,
            Some(before),
            limit,
            coalesce,
            after,
        )?;
        if let Some((_, first_event)) = page.first() {
            // `before` rather than the newest line's seq: a coalesced page covers
            // everything up to the cursor it was asked with, and nothing in its lines
            // says so.
            let lines: Vec<String> = page.iter().map(|(line, _)| line.clone()).collect();
            self.cache
                .store_page(&lines, first_event.seq, before, coalesce);
        }
        Ok(OlderPage::Events(
            page.into_iter().map(|(_, event)| event).collect(),
        ))
    }
    /// [`event_stream::follow_session_events`], with every frame written to
    /// the cache before `on_item` sees it.
    ///
    /// Before, so that an event held back for a reader who is scrolled
    /// away is already on disk -- what the cache holds is what the server
    /// sent, not what a screen has got round to drawing. Flushed on each
    /// status change, which is a turn's boundary and the granularity a
    /// crash may as well lose, and once more when the stream ends.
    pub fn follow(
        &self,
        after: u64,
        mut on_item: impl FnMut(StreamItem) -> bool,
    ) -> Result<(), ApiError> {
        let cache = &self.cache;
        let result = event_stream::follow_session_events(
            self.api.transport(),
            &self.session_id,
            after,
            |item| {
                if let StreamItem::Event { raw, event } = &item {
                    cache.append(raw, event.seq);
                    if matches!(event.event, event_model::Event::Status { .. }) {
                        cache.flush();
                    }
                }
                on_item(item)
            },
        );
        cache.flush();
        result
    }
    /// Leaves the cache with everything it was given -- called once a
    /// caller is done with this source, mirroring the Kotlin `close`'s
    /// final flush (that method's stream cancellation itself is the
    /// runtime concern the module doc says is not ported here).
    pub fn close(&self) {
        self.cache.flush();
    }
 }
 #[cfg(test)]
 mod tests {
    use super::*;
    use crate::api::{Body, RawResponse};
    use std::collections::VecDeque;
    use std::io::Read;
    use std::sync::Mutex;
    /// A transport that answers fixed bodies in call order, and records
    /// every path it was asked for -- so a test can assert *how many*
    /// requests a method made, which is the point for the `before == 0`
    /// guard (AGENTS.md's regression: the guard must stop the request
    /// before it happens, not merely tolerate the empty answer).
    #[derive(Default)]
    struct ScriptedTransport {
        responses: Mutex<VecDeque<(u16, String)>>,
        calls: Mutex<Vec<String>>,
    }
    impl ScriptedTransport {
        fn respond(&self, status: u16, body: impl Into<String>) {
            self.responses
                .lock()
                .unwrap()
                .push_back((status, body.into()));
        }
        fn call_count(&self) -> usize {
            self.calls.lock().unwrap().len()
        }
    }
    impl Transport for ScriptedTransport {
        fn request(
            &self,
            _method: &str,
            path: &str,
            _body: Option<Body>,
        ) -> Result<RawResponse, ApiError> {
            self.calls.lock().unwrap().push(path.to_string());
            let (status, body) = self
                .responses
                .lock()
                .unwrap()
                .pop_front()
                .unwrap_or_else(|| panic!("ScriptedTransport got an unscripted request: {path}"));
            Ok(RawResponse {
                status,
                body: body.into_bytes(),
            })
        }
        fn stream(&self, path: &str) -> Result<Box<dyn Read + Send>, ApiError> {
            self.calls.lock().unwrap().push(path.to_string());
            let (_, body) = self
                .responses
                .lock()
                .unwrap()
                .pop_front()
                .unwrap_or_else(|| {
                    panic!("ScriptedTransport got an unscripted stream request: {path}")
                });
            Ok(Box::new(std::io::Cursor::new(body.into_bytes())))
        }
    }
    fn source(
        transport: ScriptedTransport,
        cache_root: &std::path::Path,
    ) -> TranscriptSource<ScriptedTransport> {
        let api = ApiClient::new(transport);
        let cache = crate::transcript_cache::TranscriptCache::new(cache_root).session("s1");
        TranscriptSource::new(api, "s1", cache)
    }
    fn status_line(seq: u64) -> String {
        format!(r#"{{"seq":{seq},"ts":1.0,"type":"status","state":"idle"}}"#)
    }
    #[test]
    fn a_cold_cache_has_no_opening_and_fetches_from_the_server() {
        let dir = tempfile::tempdir().unwrap();
        let transport = ScriptedTransport::default();
        transport.respond(200, format!("[{}]", status_line(1)));
        let source = source(transport, dir.path());
        assert_eq!(source.cached_opening(80), None);
        let opening = source.fetch_opening().unwrap();
        assert_eq!(opening.len(), 1);
        assert_eq!(opening[0].seq, 1);
        // The fetch wrote through: reopening the same cache now has something to show.
        assert!(source.cache.tail().is_some());
    }
    #[test]
    fn probe_matching_the_cached_tail_leaves_the_cache_alone() {
        let dir = tempfile::tempdir().unwrap();
        let transport = ScriptedTransport::default();
        transport.respond(200, format!("[{}]", status_line(1)));
        let source = source(transport, dir.path());
        source.fetch_opening().unwrap();
        let transport2 = ScriptedTransport::default();
        transport2.respond(200, format!("[{}]", status_line(1)));
        let cache = crate::transcript_cache::TranscriptCache::new(dir.path()).session("s1");
        let source2 = TranscriptSource::new(ApiClient::new(transport2), "s1", cache);
        assert!(source2.probe().unwrap());
        assert!(source2.cache.tail().is_some());
    }
    #[test]
    fn probe_mismatching_the_cached_tail_purges_the_cache() {
        let dir = tempfile::tempdir().unwrap();
        let transport = ScriptedTransport::default();
        transport.respond(200, format!("[{}]", status_line(1)));
        let source = source(transport, dir.path());
        source.fetch_opening().unwrap();
        // The server now answers with a different event at the same seq -- the file
        // behind this session was replaced.
        let transport2 = ScriptedTransport::default();
        let different = r#"{"seq":1,"ts":1.0,"type":"status","state":"running"}"#.to_string();
        transport2.respond(200, format!("[{different}]"));
        let cache = crate::transcript_cache::TranscriptCache::new(dir.path()).session("s1");
        let source2 = TranscriptSource::new(ApiClient::new(transport2), "s1", cache);
        assert!(!source2.probe().unwrap());
        assert!(source2.cache.tail().is_none());
    }
    #[test]
    fn probe_finding_no_server_leaves_the_cache_untouched() {
        let dir = tempfile::tempdir().unwrap();
        let transport = ScriptedTransport::default();
        transport.respond(200, format!("[{}]", status_line(1)));
        let source = source(transport, dir.path());
        source.fetch_opening().unwrap();
        let transport2 = ScriptedTransport::default();
        transport2.respond(500, "server on fire");
        let cache = crate::transcript_cache::TranscriptCache::new(dir.path()).session("s1");
        let source2 = TranscriptSource::new(ApiClient::new(transport2), "s1", cache);
        assert!(source2.probe().is_err());
        assert!(
            source2.cache.tail().is_some(),
            "an unreachable server must not be treated as a mismatch"
        );
    }
    /// The regression this module exists to close: `before == 0` must
    /// never reach the network or the cache, because an empty answer there
    /// is indistinguishable from "there is genuinely no more history" --
    /// AGENTS.md's `loadOlderPage` incident.
    #[test]
    fn paging_before_the_first_event_makes_no_request_at_all() {
        let dir = tempfile::tempdir().unwrap();
        let transport = ScriptedTransport::default();
        let source = source(transport, dir.path());
        assert_eq!(source.page(0, 80, true).unwrap(), OlderPage::NothingLoaded);
        assert_eq!(source.api.transport().call_count(), 0);
    }
    #[test]
    fn a_page_already_covered_by_the_cache_never_reaches_the_server() {
        let dir = tempfile::tempdir().unwrap();
        let transport = ScriptedTransport::default();
        transport.respond(200, format!("[{},{}]", status_line(1), status_line(2)));
        let source = source(transport, dir.path());
        source.fetch_opening().unwrap();
        let calls_before = source.api.transport().call_count();
        let OlderPage::Events(page) = source.page(2, 10, true).unwrap() else {
            panic!("a cursor of 2 is a real question about the conversation");
        };
        assert_eq!(page.len(), 1);
        assert_eq!(page[0].seq, 1);
        assert_eq!(
            source.api.transport().call_count(),
            calls_before,
            "a cache hit must not touch the network"
        );
    }
    /// With nothing older cached there is no floor to give the server, so
    /// the request carries no `after` at all.
    #[test]
    fn a_server_page_with_nothing_older_cached_carries_no_bound() {
        let dir = tempfile::tempdir().unwrap();
        let transport = ScriptedTransport::default();
        transport.respond(200, format!("[{}]", status_line(5)));
        let source = source(transport, dir.path());
        source.fetch_opening().unwrap();
        let transport2 = ScriptedTransport::default();
        transport2.respond(200, format!("[{}]", status_line(3)));
        let cache = crate::transcript_cache::TranscriptCache::new(dir.path()).session("s1");
        let source2 = TranscriptSource::new(ApiClient::new(transport2), "s1", cache);
        source2.page(5, 10, true).unwrap();
        assert_eq!(
            source2.api.transport().calls.lock().unwrap()[0],
            "/sessions/s1/transcript?limit=10&before=5&coalesce=true"
        );
    }
    /// The half the test above cannot show: when the cache *does* hold an
    /// older run, the fetch is floored at its end, or the page would run
    /// straight past it and overlap -- which `store_page` then refuses,
    /// silently costing the phone the page it just paid for.
    #[test]
    fn a_server_page_is_floored_at_the_end_of_the_cached_run() {
        let dir = tempfile::tempdir().unwrap();
        let cache = crate::transcript_cache::TranscriptCache::new(dir.path()).session("s1");
        // A stored page covering [3, 6) and two live events above it, so the run this
        // phone holds is [3, 8) -- the newest chunk has to be an appended one, or the
        // cache reads the directory as damaged and discards it.
        let lines: Vec<String> = (3..6).map(status_line).collect();
        assert!(cache.store_page(&lines, 3, 6, true));
        cache.append(&status_line(6), 6);
        cache.append(&status_line(7), 7);
        cache.flush();
        let transport = ScriptedTransport::default();
        transport.respond(200, format!("[{}]", status_line(9)));
        let source = TranscriptSource::new(ApiClient::new(transport), "s1", cache);
        source.page(10, 10, true).unwrap();
        assert_eq!(
            source.api.transport().calls.lock().unwrap()[0],
            "/sessions/s1/transcript?limit=10&before=10&coalesce=true&after=7",
            "the fetch must stop one seq below where this phone's copy ends"
        );
    }
    /// A page the server could not answer is an error, never an empty
    /// page: the caller would read the second as "this conversation has no
    /// more history" and stop paging for good.
    #[test]
    fn a_failing_server_page_is_an_error_rather_than_an_empty_one() {
        let dir = tempfile::tempdir().unwrap();
        let transport = ScriptedTransport::default();
        transport.respond(500, "server on fire");
        let source = source(transport, dir.path());
        assert!(matches!(source.page(9, 10, true), Err(PageError::Api(_)),));
    }
    /// A cached line this build cannot read is told apart from the network
    /// failing, for the same reason: neither is "no more history".
    #[test]
    fn an_unreadable_cached_page_is_a_parse_error_rather_than_an_empty_one() {
        let dir = tempfile::tempdir().unwrap();
        let cache = crate::transcript_cache::TranscriptCache::new(dir.path()).session("s1");
        cache.store_page(
            &[r#"{"seq":3,"but":"not an event"}"#.to_string()],
            3,
            4,
            true,
        );
        cache.append(&status_line(4), 4);
        cache.flush();
        let transport = ScriptedTransport::default();
        let source = TranscriptSource::new(ApiClient::new(transport), "s1", cache);
        assert!(matches!(source.page(4, 10, true), Err(PageError::Parse(_)),));
        assert_eq!(
            source.api.transport().call_count(),
            0,
            "a cache hit that cannot be read must not fall through to the server unnoticed"
        );
    }
    #[test]
    fn a_bad_cached_opening_line_purges_rather_than_panicking() {
        let dir = tempfile::tempdir().unwrap();
        let cache = crate::transcript_cache::TranscriptCache::new(dir.path()).session("s1");
        cache.append("not json at all", 1);
        cache.flush();
        let transport = ScriptedTransport::default();
        let source = TranscriptSource::new(ApiClient::new(transport), "s1", cache);
        assert_eq!(source.cached_opening(80), None);
        assert!(
            source.cache.tail().is_none(),
            "a damaged line purges the cache"
        );
    }
    #[test]
    fn follow_writes_events_to_the_cache_before_the_caller_sees_them() {
        let dir = tempfile::tempdir().unwrap();
        let transport = ScriptedTransport::default();
        transport.respond(200, format!("{}\n\n", sse_frame(&status_line(1))));
        let source = source(transport, dir.path());
        let mut seen = Vec::new();
        source
            .follow(0, |item| {
                if let StreamItem::Event { event, .. } = item {
                    seen.push(event.seq);
                }
                true
            })
            .unwrap();
        assert_eq!(seen, vec![1]);
        assert_eq!(source.cache.tail().unwrap().seq, 1);
    }
    fn sse_frame(data: &str) -> String {
        format!("data:{data}")
    }
 }
@@ -25,16 +25,19 @@ next (a Masonry or iris transcript screen, most likely).
 | `sse.rs`                                  | `Sse.kt` (the framing half)               | Done, new tests (Kotlin had none of its own beyond integration) |
 | `api.rs`                                  | `Api.kt`                                  | Partial -- see below |
 | `event_stream.rs`                         | `EventStream.kt`                          | Done |
-| `transcript_fold.rs`                      | `TranscriptItems.kt`, `ToolRows.kt`       | Partial -- see below |
+| `transcript_fold.rs`                      | `TranscriptItems.kt`, `ToolRows.kt`       | Done -- see below |
 | `config.rs`                                | `ServerConfig.kt`'s `handleEnrollment`   | New, desktop-only so far -- see below |
-| *(not started)*                           | `TranscriptSource.kt`                     | Not started |
+| `transcript_source.rs`                    | `TranscriptSource.kt`                     | Done -- see below |
 | *(not ported, and may never be)*          | `TranscriptUnits.kt`                      | Out of scope -- see below |
 Every file above whose Kotlin counterpart had a JVM unit test (`AnsiTest`,
 `HighlighterTest`, `TranscriptCacheTest`) has had every one of those test
 cases ported alongside it, plus new tests for the pieces that had none
-(`sse.rs`, `api.rs`, `event_stream.rs`, `transcript_fold.rs`). Test count by
+(`sse.rs`, `api.rs`, `event_stream.rs`, `transcript_fold.rs`,
-crate as of this writing: **85 in `client-core`**, 0 in `event-model` (its
+`transcript_source.rs` -- the Kotlin `TranscriptSource.kt`/`TranscriptItems.kt`
 had no JVM unit tests of their own, so these were written fresh against the
 Kotlin source and AGENTS.md's paging incidents as the spec). Test count by
 crate as of this writing: **109 in `client-core`**, 0 in `event-model` (its
 types carry no logic of their own to test -- `server/`'s own tests exercise
 them via `session::transcript`'s round-trip coverage).
@@ -88,13 +91,27 @@ the full table to work from when one of these is next.
 including tool-call/question/image attachment and peer-message placement.
 `group_tool_runs` groups adjacent calls into `TranscriptRow::Tools`.
-**Not ported:** `TranscriptItems.kt`'s `joinPages` (and its
+`join_pages` (with `heal_split_message` and `adopt_run`, both private) is
-`healSplitMessage`/`adoptRun` helpers) -- the page-boundary healing that
+now ported too, 2026-09-06 -- the page-boundary healing that merges a tool
-merges a tool call split across two fetched pages and re-merges a run a
+call split across two fetched pages, rejoins a message a boundary cut
-boundary cut through. This matters the moment paging backward through
+through, and renames a run of tool calls onto whichever name is already on
-history is exercised; it is deliberately left rather than rushed, since
+screen. Ported with AGENTS.md's "things that have bitten" incidents as the
-it is exactly the kind of boundary logic this project's own "things that
+spec rather than a JVM test file (`TranscriptItems.kt` had none of its
-have bitten" section warns reads fine and is wrong at the edges.
+own): `a_clean_boundary_between_two_finished_runs_is_still_healed_into_one_run`
 is the regression test for the bug that shipped -- `adopt_run` must run on
 *every* join, not only the one where a split call was found, or a boundary
 landing cleanly between two already-finished calls (most of them) leaves
 one run drawn as two. `a_call_split_across_the_boundary_merges_into_one_row`,
 `a_message_split_across_the_boundary_is_rejoined_with_the_newer_halfs_identity`,
 and `adopt_run_never_renames_into_a_question_row` cover the other three
 edges the Kotlin doc calls out. `join_pages` ends in a `debug_assert!`
 that no tool id survives in both halves -- the duplicate row it exists to
 prevent, checked rather than assumed. What it deliberately does *not*
 assert is seq ordering across the boundary: a peer note carries the seq
 its turn began at (`place_peer_note`), which can be older than the page
 it arrived in, so the two pages' seqs legitimately interleave there. An
 earlier draft asserted it and would have panicked in debug builds on an
 ordinary transcript.
 **Known gap, and a decision for whoever closes it:** `event_model::Event`
 has no `Unknown`/catch-all variant, unlike `Events.kt`'s hand-kept mirror.
@@ -119,20 +136,72 @@ caller-specific (the code rules' "ask for the least you need"). Its only
 caller today is `desktop-app`; a future Android build of this crate would
 be a second one, not a reason to move the type.
 ## What `transcript_source.rs` covers, and what it does not
 `TranscriptSource<T: Transport>` is the seam a session screen asks for a
 page, ported test-for-test against the Kotlin doc rather than a JVM test
 file (there wasn't one): `cached_opening`, `probe`, `fetch_opening`,
 `page` and `follow`, each matching its Kotlin namesake's contract --
 including `probe`'s three-way outcome (matches / cache purged /
 unreachable, told apart so a caller never treats "couldn't ask" as "was
 wrong") and `page`'s cache-vs-server split bounded by `covered_up_to`.
 Two additions beyond a literal port, both load-bearing:
 - **`page(before, ..)` refuses `before == 0` before touching the cache or
  the network**, answering `OlderPage::NothingLoaded`. This is AGENTS.md's
  `loadOlderPage` incident (`before = 0` is "no event before the first
  one," indistinguishable from "reached the start of history" if a caller
  ever asks it) moved out of the Kotlin screen and into this layer, so
  every future caller gets the guard rather than having to remember it.
  **The return type is `OlderPage`, not a `Vec`, and that is the guard.**
  The Kotlin's two falses are different answers -- `oldestSeq == 0`
  returns without touching `moreHistory`, an empty page latches it false
  -- so a port that answered both with an empty list would have moved the
  bug rather than fixed it, one layer down and out of sight of the screen
  that used to hold the check. `OlderPage::Events(vec![])` means the start
  of the conversation; `OlderPage::NothingLoaded` is not an answer about
  the conversation at all. Reviewed 2026-09-06.
  `paging_before_the_first_event_makes_no_request_at_all` asserts zero
  transport calls, not just the variant, since a request that happens to
  answer empty is exactly what caused the original bug, and
  `a_failing_server_page_is_an_error_rather_than_an_empty_one` plus
  `an_unreadable_cached_page_is_a_parse_error_rather_than_an_empty_one`
  are the same rule for the two ways a page can fail.
 - **`fetch_transcript_lines`** (new in `api.rs`) hands back each line
  paired with the exact server bytes it came from, via
  `serde_json::value::RawValue` rather than re-serializing a parsed
  `Value` -- the cache and a live SSE frame for the same event have to
  agree byte-for-byte, which is exactly what the `serde_json`
  float-rounding bug (AGENTS.md) was about. The existing
  `fetch_transcript_page` is untouched (other callers under `iris/`
  depend on its signature); the two share a `transcript_path` helper so
  the query string is written in one place.
 **Not ported:** `EventStream.kt`'s reconnect-with-backoff loop, and
 `TranscriptSource.close`'s ability to cancel a live stream from another
 thread. Both are wall-clock/thread-lifetime policy that belongs to
 whichever runtime embeds this crate (iris's own timers, a Tokio task, a
 Kotlin coroutine scope), not to this pure logic -- `follow` is the same
 "write to the cache, then hand the frame to the caller" decorator
 `iris/desktop-app/src/app.rs` and `iris/android-app/src/transcript_client.rs`
 already hand-wrote around `event_stream::follow_session_events` before this
 existed; the cache write moved into one shared place so a third caller
 does not repeat it again by hand.
 ## What is not started at all
- **`TranscriptSource.kt`** -- the layer that decides whether a page comes
+- **A full markdown AST.** `markdown_blocks` (2026-09-06) splits a message
-  from the transcript cache or the server, and stitches the two. Needs
+  into its *top-level* blocks -- heading, paragraph, fence, list, table,
-  `transcript_cache.rs` and `api.rs`'s transcript-page method, both of
+  quote -- with each block's own source, which is what a renderer needs to
-  which exist now, so this is unblocked whenever picked up.
+  lay out prose versus code and what lets a streamed delta re-lay out one
- **The markdown *block* model beyond syntax spans** -- `highlight/markdown.rs`
+  block instead of the message (docs/RUST.md's Task B). What it
-  colours a `.md` file or fence for the highlighter, but does not build the
+  deliberately does **not** build is the tree below that: nested list
-  block tree (headings, lists, tables, fences as distinct nodes) that a
+  items, table cells, inline spans. Inline styling is still the renderer's
-  renderer walks to lay out prose versus code versus a table.
+  own job per block (`iris/transcript-ui/src/markdown.rs`), and nothing
-  `CodeFence.kt`'s use of `org.intellij.markdown` for that full CommonMark
+  has needed the rest yet. `CodeFence.kt`'s use of `org.intellij.markdown`
-  AST is Compose rendering plumbing, not something to port as-is; a Rust
+  for a full CommonMark AST is Compose rendering plumbing, not something
-  UI layer will want its own block parser or a crate for it, decided
+  to port as-is.
  alongside the framework choice in RUST.md.
 - **`TranscriptUnits.kt`** (see above) -- deliberately out of scope, since
  it flattens a row into bounded units for a *specific* lazy-list
  framework's composition cost, which is a fact about that framework
@@ -142,5 +211,6 @@ be a second one, not a reason to move the type.
 `./run-tests.sh` from the repo root now runs `event-model`, `client-core`
 and `server` in that order (each `cargo test`, forwarding arguments the
-same way it always has). From `client-core/` directly: `cargo test`,
+same way it always has). From `client-core/` directly: `cargo test`
-`cargo clippy --all-targets`, `cargo fmt` -- all clean as of this writing.
+(119 tests), `cargo clippy --all-targets`, `cargo fmt` -- all clean as of
 this writing (2026-09-06).
@@ -5,6 +5,85 @@ they can be judged and reversed later. Detail lives in RUST.md (and IRIS.md
 for iris API changes); this file is only the summary. Newest first. Items
 marked **DEFERRED** are ones the agent chose not to decide alone.
 ## 2026-09-06 (composer scroll and the streaming block model)
 - **A streamed message becomes a column of per-block widgets.** Decided by
  the design agent; recorded here because it is the shape of every message
  on screen. A transcript row is one `TextEdit` today, so a streamed delta
  re-shapes the entire message through parley on every event -- the stream
  phase is the one place iris is behind Compose on your phone (p50 18.2ms
  vs 13.4ms). A row becomes a column of one widget per markdown block
  (paragraph, heading, fence, list, table) and a delta replaces only the
  last block, keeping every earlier block's layout. **Rejected:** splitting
  parley's layout at block boundaries inside one text widget (couples
  iris's text widget to markdown structure, and parley has no incremental
  API), and caching shaped runs per paragraph inside `TextEdit` (a second
  cache with its own invalidation beside the glyph cache). Chosen because
  P1's markdown block model is needed anyway, so the split happens once, in
  `client-core`, and iris stays a text renderer. **Status: designed, not
  built** -- this pass spent its budget on the composer's three layout
  defects; docs/RUST.md has the design and the pass conditions.
 - **The composer's overflowing text now scrolls on a finger**, capped at
  six lines and clipped to the bar. Reverses the "still does not scroll"
  item below.
 - **A widget may not report a `dp` length** (see IRIS.md). A rule for
  widget authors, enforced by a `debug_assert!`; nothing changes for app
  code.
 ## 2026-09-06 (stale-primitives and touch-scroll pass)
 - **A vertical drag inside a focused composer now scrolls rather than
  selects.** Android's own `EditText` does this -- a vertical drag scrolls
  the field, and only a long press starts a selection -- so the platform
  decided it. What it costs: you can no longer drag straight down inside
  the composer to select several lines of what you typed; use a long press
  and then drag, or drag sideways. Say if that trade is wrong for you.
 - **`Scroll` gets a finger pan but no fling.** `List` flings; a scroll area
  does not, because it has no per-frame tick to animate one and the areas
  it wraps are at most a screenful (Android does not fling a six-line text
  box either). Easy to add later if a scroll area ever wraps something long.
 - **The composer still does not scroll its overflowed text**, though the
  mechanism it needs is now in place. Wrapping the field in `.scrollable()`
  was tried and reverted the same day: `Scroll` measures its content and
  container against the *window*, so inside the `MaxSize` that caps the
  composer at six lines the two are in different spaces and the field pans
  itself entirely out of the bar (measured on the emulator with 474
  characters in it -- the bar collapsed to its padding). Fixing that means
  `Scroll` measuring against its own offered box, which is a change to a
  widget the transcript and the bench shell both use, so it is its own
  piece of work rather than a rider on this one.
 ## 2026-09-06 (defect pass)
 - **The keyboard-open diagnostics overlay is gone; the capture only
  logs now.** It was added when `on_insets_changed` was not firing at all
  and there was no way to get a report off the phone. It fires reliably
  since the activity went edge-to-edge -- and what that looks like in
  use is a full-screen report covering the app **every time the keyboard
  opens**, with its own Copy/Close buttons sitting underneath the
  keyboard, so it cannot be dismissed (reproduced on the emulator this
  pass: two `tap 'CLOSE'` runs left it up). An interruption for something
  nobody asked for, over the app you are trying to type into. The named
  `Diagnostics` button still shows the same text on demand, and the new
  `iris surface:`/`iris insets:` log lines carry the lifecycle a `logcat`
  pull needs. Reversible: `capture_keyboard_diagnostics` is still the one
  place this is decided, and `PlatformHandle::show_diagnostics_overlay`
  is still there.
 - **The bench shell's report pane is sized to its report, not to a share
  of the window.** It held `.height(rest(1))` beside the transcript's
  `rest(2)`, so an *empty* `TextEdit` reserved a third of every screen --
  which is what Iris's "the app does not start with keyboard spacing
  correct" screenshot was showing, with the composer two thirds down and
  black below it. It is `.max_height(dp(260))` now and sits above the
  transcript rather than under the composer, where it was eating the
  navigation-bar clearance. Cost: a filled report is clipped at 260dp
  rather than scrolling (a `Scroll` there drew itself off the top of the
  screen, since `Scroll` pins to the end of its content and reports its
  content's full length to the parent -- worth fixing in `Scroll`, not
  worked around here). "Copy report" and `logcat` still have the whole
  thing.
 ## 2026-09-05
 - **iris no longer asks every device for compute-shader limits it never
@@ -8,7 +8,147 @@ 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")
+## 2026-09-06: a transcript row is a column of blocks, and a block is the selection unit
 `transcript-ui`'s row builder used to make **one** `TextEdit` per message.
 It makes one per top-level markdown block now -- heading, paragraph,
 fenced code, list, table -- in a `Span::down`, because a streamed delta
 into a single buffer re-shaped the whole message through parley on every
 event. `client_core::markdown_blocks::split_blocks` does the splitting;
 `row::RowBlocks::apply_delta` updates the block a delta lands in and
 leaves the rest of the message's layout alone.
 **The change to judge, since it is what a reader feels**:
 `Selection` is keyed by `SelKey = (RowKey, u32)` -- a row and a block --
 so **a block, not a row, is the unit a selection steps in**. A drag still
 runs from a reply into the tool output beneath it and copies as one
 thing; what changed is that the row under the finger is filled in block by
 block rather than all at once, which is if anything closer to what the
 old shortcut in `Selection`'s module doc was apologising for. `register`
 takes a `SelKey`; `unregister` still takes a `RowKey` and now drops every
 block of it (dropping only the first is how a freed widget gets left in
 the map -- the shape docs/REVIEW-2026-09-06.md's finding 1 called out).
 `Selection::locate(ui, render, pos_window)` is new: which block is under a
 window position, with that block's own local position and size. The
 list-level handler uses it for the pointer-captured half of a drag,
 instead of computing a row-local position from `List::extent`.
 `row::build_row` returns `(RowKey, StrongWidget, Option<RowBlocks>)` --
 the third is the per-block state a caller keeps only for the row a reply
 is streaming into, and is `None` for a tool run, which never streams.
 ## 2026-09-06: a reported `Size` may not carry `dp`; `Len::fold_dp`
 **New: `Len::fold_dp(density) -> Len`** -- the same fold `apply_rest` does
 (`dp` becomes physical pixels), but staying a `Len` so `rest` survives.
 **New rule, and it is a rule about every widget, not about the two that
 broke it**: a `Len` a widget *reports* from `draw` must not carry an
 unresolved `dp`. `dp` is an input unit -- a number the widget author wrote
 -- and the containers that consume a reported length read `abs`, `rel` and
 `rest` straight off it (`Span`'s placement arithmetic, `Pad`'s addition),
 so a reported `dp` is silently worth **zero**. `MaxSize` and `Sized` both
 returned the caller's declared `Len` as written; a `.max_height(dp(168))`
 therefore gave its child a slot of nothing the moment the cap actually
 applied, which is what made the composer's bar collapse. Both put their
 declared lengths through `fold_dp` now, and
 `UiRenderState::draw_inner` `debug_assert!`s the invariant after every
 `Widget::draw`, so a widget that gets this wrong says so at the mistake
 rather than laying out at zero somewhere else.
 Nothing changes for a caller: `.max_height(dp(48))` is written the same
 way. It is only widget *authors* who now have a rule to follow, and a
 debug build that enforces it.
 ## 2026-09-06: `Painter::set_mask` reuses one slot; `ActiveData` gains two fields
 **`Painter::set_mask(region)` allocates its widget's mask slot once and
 rewrites it in place** on every later draw, instead of pushing a new one
 each time. It has to: `draw_inner`'s unchanged-region fast path does not
 revisit a descendant whose own region did not change, so those descendants
 go on referencing whichever slot they were first drawn under. Pushing a
 fresh slot per draw left the composer's field clipped to a box the bar had
 long since moved away from -- four live mask entries, none of them the
 `Masked`'s current region -- and it drew nothing at all. Same call, same
 signature; only the lifetime changed.
 **`ActiveData` gains `own_mask` and `move_applied`** (both public, since
 `ActiveData` is). `own_mask` is the slot above, `MaskIdx::NONE` for a
 widget that sets no mask. `move_applied` is how much of a widget's own
 move-slot delta its `region` already accounts for: `mov` shifts both,
 `Painter::reposition` shifts only the slot, and `resolved_region` -- and so
 every hit test -- has to subtract it. Without that a widget that had been
 panned had its *own* hit box at twice the pan while its descendants were
 correct, which made the composer's field untappable after a finger drag.
 ## 2026-09-06: `Scroll` pans on a finger drag, and a vertical drag in a focused text field no longer selects
 Three related public changes, all in aid of IRIS_TODO.md's "the composer
 has no touch-drag scroll".
 **`Scroll::drag(render, id, sense, pos_window, now)` is new**, and
 `WidgetLike::scrollable()` now registers it alongside the wheel handler it
 already registered -- so anything built with `.scrollable()` pans on a
 finger drag with no extra wiring at the call site. It goes through the same
 `sense::DragGesture` that `transcript-ui::Selection::drag` drives `List`
 with (arbitration, `DRAG_SLOP`, velocity, pointer capture), rather than a
 second copy of that widget's wiring: `DragGesture` owns the mechanics and
 each caller decides only what a committed pan *means*. `Scroll::amt()` is
 new too, the read-only pan position a test or a scroll indicator needs.
 There is deliberately **no fling** on `Scroll`. Unlike `List` it has no
 per-frame tick to animate one with (`List::set_redraw_handle`/`tick_fling`),
 and the areas it wraps today are at most a screenful, where Android does not
 fling either. The released velocity is dropped rather than approximated.
 **A vertical drag inside an already-focused `TextEdit` no longer extends a
 selection.** `iris::attr`'s `on_press` used to treat a focused field as the
 plain `click_or_drag` case -- every `Pressing` frame updated the selection.
 It now applies the same `DRAG_SLOP` rule the *unfocused* branch already
 applied: a press that moves past the slop vertically abandons its pending
 selection for the rest of the gesture, so the scroll area around the field
 gets the drag instead. Horizontal drag-to-select is unchanged, and a long
 press still starts a selection. This is Android's own `EditText` behaviour
 (a vertical drag scrolls; only a long press selects), and it is what makes
 "swipe up over the composer to scroll the transcript" work without dragging
 a highlight through the message you were typing.
 **`UiRenderState::orphaned_primitives()` is new**, and `update` now
 `debug_assert!`s (debug builds only) that nothing is orphaned. An orphan is
 a primitive still bound for the GPU that no live `ActiveData` names -- a
 copy nothing can move, clip or free. That was the doubled `Compacted:` row
 on the phone; see the same date's commit `76b1f99` and docs/RUST.md. The
 per-frame guard is a count comparison (O(active widgets)); the walk that
 names the offenders only runs when the counts disagree, because the walk is
 O(primitives) and made a debug build on a phone too slow to finish a
 benchmark run.
 ## 2026-09-06: a tap on a text field always leaves a caret
 `TextEditCtx::select` used to compare the tap position against the
 *laid-out text's* own box and set `selection = None` for anything outside
 it. A press only reaches `select` after being hit-tested to the widget, so
 that "outside" meant the field's own padding -- or, for an **empty** field,
 everything, since an empty layout is a zero-width box. So tapping an empty
 composer focused it and opened the keyboard while leaving no caret, and
 `TextEditCtx::insert`/`insert_str` return early with no caret: every
 keystroke was dropped in silence, and no glyph ever appeared. Parley's
 `from_point`/`extend_to_point` already clamp a point outside the layout to
 the nearest cursor position, which is also what a tap in a field's padding
 should do.
 Behaviour change a caller would notice, in one line: **`select` with a
 non-drag position now always produces a selection; it no longer clears
 one.** Clearing is `TextEditCtx::deselect`, which is what the backends'
 focus handling already calls. A drag is unchanged -- with no previous
 selection there is still nothing to extend, so it produces none.
 `insert_str` also gained a `debug_assert!` for the no-caret case, so an
 insert routed to an unfocused field fails at the mistake in a debug build
 instead of silently swallowing input.
 ## 2026-09-06: `List::anchor_position_display`## 2026-09-06: `List::anchor_position_display`, `FrameReport::mark_phase`/`phase_stats`/`late_at_hz` (RUST.md's "Benchmark v2")
 `List` gained `anchor_position_display(&self) -> String`, reporting the
 anchor's own row index and pixel offset (`idx=N/off=Mpx`, or
@@ -552,7 +692,14 @@ streamed event" cost RUST.md's P0 box measured (20 events/second against a
  new rows appended after it. A row changing *before* the tail (only
  `group_tool_runs` retroactively grouping tool calls into a run does
  this) falls back to `List::clear` plus a full rebuild, counted in
-  `TranscriptScreen::take_rebuilds()`. `bench_client.rs`, `transcript_client.rs`
+  `TranscriptScreen::take_rebuilds()`. **A caller that keeps its own
  row-keyed side table alongside `List` (`Selection`'s `rows:
  BTreeMap<RowKey, WeakWidget<TextEdit>>` is the one this crate has) must
  clear it in step with `List::clear()`** — the fallback drops every row
  `List` was holding, so any side table not cleared the same way is left
  pointing at widgets the clear just freed (docs/REVIEW-2026-09-06.md
  finding 1, fixed 2026-09-06 by `Selection::clear()`, called from
  `apply`'s `Rebuild` arm right before `List::clear()`). `bench_client.rs`, `transcript_client.rs`
  and `desktop-app/app.rs` all call this now instead of rebuilding on every
  event; only the opening page (and `apply`'s own fallback) still calls
  `build_tree`.
@@ -651,3 +798,52 @@ box has the full investigation and the phone verification still to do.
  built and checked on this checkout's emulator only. RUST.md's P0 box
  says what she should check for: crisp text at two densities, the
  keyboard no longer wiping, and the header's background.
 ## 2026-09-06: composing text, focus-on-tap, and atlas invalidation on a new renderer
 Three small but public API changes, from the same phone-report pass as the
 entry above (RUST.md's P0 box has the full account, including a real bug
 still not root-caused).
 - **`FocusHost` gained `is_focused(&self, id) -> bool`** (both platform
  impls). `attr.rs`'s `Selector`/`Selectable` used to grant focus (and so
  request the IME) on the very first frame of *any* press, before it was
  known whether the gesture was a tap or a drag — a swipe over a text
  field wrongly summoned the keyboard. They now wait for a completed tap
  (press and release with no frame crossing `sense::DRAG_SLOP`) unless the
  field is already focused, in which case dragging inside it to select
  text is unchanged. `TextEdit` gained one new `pub(crate)` field
  (`press_origin`) to track this; no public surface change there.
 - **`android::ime`'s `InputConnection` now calls `InputMethodManager::
  updateSelection` after every edit** (`IrisViewPeer::update_ime_selection`,
  called from `after_input`). Gboard was holding keystrokes back because
  nothing ever told it where the app's own selection/composing region had
  moved to — this is what android-view's own demo does in its `render()`
  and this bridge never did.
 - **`GlyphAtlas::clear()` and `Textures::reset()`** (`iris_core`). Called
  together, once, from `android::view`'s `surface_changed` exactly when a
  *genuinely new* `AndroidRenderer` is built (backgrounding and returning,
  not a keyboard-triggered resize, which already reuses the renderer) —
  both CPU-side caches otherwise kept pointing at the old, now-destroyed
  device's textures, which is why text used to vanish again after leaving
  and returning to the app.
 ## 2026-09-06: `take_counters` counts text layouts too
 One public API change, from the verification pass over the composer-scroll
 and per-block-row work (RUST.md's "Verification pass over Tasks A and B").
 - **`UiRenderState::take_counters` returns four numbers, not three**:
  `(draws, region rewrites, move writes, **text shapes**)`. The new one is
  bumped in `Painter::render_text`, which `TextView::render` only reaches
  on a cache miss, so it counts layouts actually computed rather than
  layouts asked for. Callers destructuring the tuple need one more `_`.
  It exists because a draw counter cannot answer the question the
  per-block transcript row was built for. A widget can be redrawn without
  re-shaping (the layout is memoized by width) and re-shaped without any
  extra draw, and re-shaping is the expensive half — so "a streamed delta
  costs one block" was, until now, argued from the code rather than
  measured. With the counter it is a test: one delta into a 100-paragraph
  reply shapes exactly **1** text layout, the same as into a
  one-paragraph one.
@@ -149,6 +149,202 @@ agent takes them without colliding with that pass's `bench_client.rs`/
  confirming this was the whole story on real touch input rather than
  only the arbiter's own unit tests -- worth a follow-up pass before
  calling it fully closed.
 - [x] **Composing text held back until a space, caret not moving, fixed
  2026-09-06.** `InputMethodManager.updateSelection` was never called --
  see IRIS.md's 2026-09-06 entry and RUST.md's P0 box, item 1, for the
  full account and the emulator evidence.
 - [x] **Swipe over the composer summons the keyboard, fixed 2026-09-06.**
  `Selector`/`Selectable` now wait for a completed tap -- see IRIS.md's
  2026-09-06 entry and RUST.md's P0 box, item 5. Verified via `dumpsys
  input_method`'s `mInputShown` on the emulator, not yet on the phone.
 - [x] **Text disappears again after leaving and returning to the app,
  fixed 2026-09-06.** `GlyphAtlas::clear`/`Textures::reset` on a
  genuinely new renderer -- see IRIS.md's 2026-09-06 entry and RUST.md's
  P0 box, item 4. Verified on the emulator (home, reopen, screenshot);
  not yet on the phone.
 - [x] **Composed/typed text never becomes visible at all -- root-caused
  and fixed 2026-09-06.** Not the renderer at all: **the composer's buffer
  was empty the whole time.** `TextEditCtx::select` (`iris/src/widget/
  text/edit.rs`) compared the tap against the *laid-out text's* box and
  set `selection = None` for anything outside it -- and an empty field's
  layout is a zero-width box, so tapping an empty composer granted focus
  and opened the keyboard while leaving no caret; `insert_str` returns
  early with no caret, so every keystroke after that was dropped in
  silence. Gboard's suggestion strip is its own composing state, not a
  read of our buffer, which is what made the earlier pass conclude the
  buffer held the text. Fixed by letting parley clamp a tap outside the
  layout to the nearest cursor position (a press that reaches `select`
  has already been hit-tested to the widget, so there is no "outside"),
  plus a `debug_assert!` in `insert_str` so an insert with no caret fails
  at the mistake instead of dropping input -- it immediately caught
  `layout_tests::composing_text_after_a_keyboard_resize_...` typing into
  an unfocused field. Three new tests in `edit.rs`
  (`tapping_an_empty_field_places_a_caret_so_typing_lands`,
  `tapping_past_the_end_of_the_text_clamps_to_the_end`,
  `dragging_without_a_previous_selection_selects_nothing`); the first
  fails on the pre-fix code. Emulator evidence: `adb shell input text`
  after `tap 'Message'` now shows the text in the bar
  (`/tmp/final-typing.png`) and logs `iris text render: chars=5 ...
  glyphs=5`, against `glyphs=0` on every keystroke before.
  **The old, superseded diagnosis, kept because it was wrong in an
  instructive way:** The composer bar stays empty even once the
  buffer genuinely holds the typed text (confirmed indirectly: Gboard's
  own suggestion strip reacts correctly to each keystroke). A new unit
  test proves the widget tree's own layout math resolves the field's
  region correctly across a keyboard resize, so the bug is downstream of
  that -- most likely `UiRenderState::redraw`'s single-widget redraw path,
  or specific to this emulator's forced `force-gles` backend (untested on
  Vulkan or the real phone). RUST.md's P0 box, item 2, has the full
  writeup, what was ruled out, and where to look next. **Also unverified
  because of this**: item 3's composer rebuild (one `Stack`-based widget,
  a capped/scrollable height, bottom padding tied to the IME/nav-bar
  inset) -- structurally in place and unit-tested, but its own visual
  correctness cannot be screenshotted until text actually renders.
 - [x] **The composer has no touch-drag scroll for overflowing text.**
  **Done 2026-09-06.** `field.scrollable().masked()` in
  `transcript-ui/src/composer.rs`: a finger drag inside the bar pans the
  message, the bar stays capped at six lines, and a vertical drag in the
  focused field no longer extends a selection (Android `EditText`'s own
  behaviour). Verified on this checkout's emulator with the
  `transcript-screen bench force-gles` debug build -- six repetitions of a
  13-word sentence typed in, then
  `ui-trace record --do "swipe 540 1200 540 1460 300"`: the field's
  `Message` box moved `31,1041..1048,1509` -> `31,1131..1048,1651` (the
  content panned down with the finger) with its **height unchanged at
  468px** (the bar did not grow), and the two screenshots either side show
  different text in the same band.
  Three real defects had to be fixed first, each with a headless
  regression test in `iris/src/layout_tests.rs` and each confirmed to fail
  without its fix (docs/RUST.md's plan box has the measurements):
  a `MaxSize` reporting its cap as an unresolved `dp` (`Len::fold_dp`), a
  `Masked` allocating a fresh mask slot per draw (`ActiveData::own_mask`),
  and a panned widget's own hit box moving twice (`move_applied`).
  `Scroll` itself turned out to measure the right number by a misleading
  route -- it is written against `painter.px_size()` now, and the claim
  below that it "measures against the window" was wrong.
  **The grey background was not missing** -- that note (written here on
  2026-09-06 and repeated as still open) is withdrawn. Re-measured the
  same day on the same AVD by decoding the screencap rather than reading
  it: the bar is `rgb(41,40,49)`, the declared `UiColor::new(40, 40, 46)`
  after sRGB rounding, **full width and y2245..y2365** on 1080x2424, with
  the field at `31,2277..1048,2329` and the 63px nav strip below it. It
  is dark by design and sits on black, which is very likely what the
  earlier reading was: at a glance the band and the background are hard
  to tell apart. If it should read as a bar rather than as a slightly
  different black, the colour is the thing to change, not the tree.
 ## From the phone, 2026-09-06, 11:39 (build delivered 02:07, commit 543f6d9)
 Iris's report on the build with the composing-text, tap-vs-swipe and
 atlas-reset fixes, with a screenshot, verbatim. Each is open until an
 agent ticks it here with the evidence.
 - [x] **"The app definitely does not start with keyboard spacing
  correct. This is how it looks without me doing anything initially."**
  **Not an inset bug at all -- fixed 2026-09-06.** The black third is the
  bench shell's own empty *benchmark report* pane: `bench_client.rs`'s
  root tree gave it `.height(rest(1))` beside `content.height(rest(2))`,
  so an empty `TextEdit` reserved a third of the window at every launch
  and pushed the composer up by exactly that. Measured on this checkout's
  emulator at the phone's own size (1080x2424, density 420, gesture nav),
  which reproduced Iris's screenshot exactly: new `iris insets:` log line
  reported `bottom=63 ime_bottom=0` at launch (a nav bar, no keyboard --
  so the inset the composer was fed was never large), while `ui-trace
  show -m Message --field box` put the field at `31,1488..1048,1540` on a
  2282px-tall surface, 789px clear of the bottom -- that pane's third.
  **Unit mixing checked explicitly and cleared**: `set_bottom_inset` takes
  physical px and stores `Len::abs`, `MainActivity.java`'s `1`/`0`
  `ime_bottom` only ever reaches `insets.bottom.max(ime_bottom)` and
  `> 0.0`, and every `dp` in the composer resolves at layout time. Fix:
  the report pane is sized to its content (`.max_height(dp(260))
  .scrollable()`), and moved above the transcript so it cannot eat the
  composer's nav-bar clearance. After: field box `31,2277..1048,2329`,
  grey bar ending at device y2361 with the 63px nav strip below it
  (`/tmp/fix1.png` this pass).
  The screenshot shows the composer bar (the grey band) sitting about
  two thirds of the way down a 704x1568 screen, with black below it to
  the bottom, and the transcript ending at "Claude / Results" just above
  it -- at launch, no keyboard. So the composer's bottom padding, which
  the 2026-09-06 rebuild tied to the IME/nav-bar inset, is being fed a
  large value at start on the phone. Suspects, in order: the initial
  inset delivery on the phone (GrapheneOS, gesture navigation) versus
  the emulator; `ime_bottom` now carrying a `1`/`0` boolean through a
  field the composer may still read as pixels or dp; a stale value from
  before the first `on_insets_changed`. Reproduce with the phone's
  screen size and density on the emulator before guessing.
 - [~] **"Swiping still gets caught by the grey bar but keeps working
  after I go past it."** Improved 2026-09-06 by the focused-field rule
  below, still needs her phone to close. `attr.rs`'s `on_press` treated an
  already-focused composer as the plain drag-to-select case, so a swipe
  starting inside it dragged a highlight through the typed text for the
  whole gesture; it now abandons that the moment the press passes
  `DRAG_SLOP` vertically (Android `EditText`'s own rule), which removes one
  of the two things that made the bar feel like it caught the swipe. The
  residual `DRAG_SLOP` measured from the boundary crossing, described
  below, is unchanged. Original note follows.
  Not closeable from the emulator, annotated
  2026-09-06 after the `DragGesture` merge. `attr.rs`'s `on_press` never
  calls `capture_pointer` and never consumes a `Pressing` frame past
  `DRAG_SLOP` (it just stops watching), so once the finger's *current*
  position leaves the composer's box and enters the list's, `List`
  starts receiving ordinary hit-tested `Pressing` frames there --
  `DragArbiter::is_idle()`'s 2026-09-05 recovery (a missed `PressStart`)
  picks it up rather than leaving it stuck. What this does **not** do is
  what "wherever it began" implies literally: `DragArbiter::press_start`
  restarts from the *boundary-crossing* position, not from the original
  touch-down inside the composer, so the pan still needs a fresh
  `DRAG_SLOP` of travel measured from the boundary rather than from the
  start of the gesture -- composer and list are adjacent, non-overlapping
  widgets (`lib.rs`'s `(list, composer_bar).span(Dir::DOWN)`), and only
  the composer forwarding its own drag to the list would remove that
  residual slop entirely, which is more than this pass's merge changes.
  RUST.md's merge-pass box has the reasoning in full and an emulator
  swipe confirming the composer's own box never moves/resizes during it;
  whether the residual slop is still perceptible as "caught" needs Iris's
  phone, since the emulator's per-widget boundary is a few dp wide and
  easy to cross without noticing on a real screen too.
 - [ ] **"Flinging still does not work."** No longer expected to reproduce
  after the `DragGesture` merge (`e12c708`, pointer capture +
  `CursorSense::Drop`), 2026-09-06. Emulator evidence (RUST.md's
  merge-pass box, check (b)): a real `ui-trace` finger swipe followed by
  screenshot-hash sampling caught a post-release frame distinct from the
  drag's own last frame in one run, and every run showed 28-32
  `render()` frames per gesture against an idle baseline of 0 and ~8
  expected from the drag alone -- redraw kept being requested well past
  the finger lifting, which only happens while a fling is still
  animating. Left unticked in spirit until Iris's phone confirms it,
  since only she can say whether it *feels* like a fling now; the
  emulator's screenshot timing could not always catch the tail of a
  fast-settling one visually (same caveat noted in RUST.md).
 - [~] **"Text still disappears if I leave and come back to the app."**
  **Instrumented 2026-09-06 so the phone can answer it**, since no
  emulator here has a Vulkan adapter. `iris/src/android/view.rs` now logs
  one `log::info!` line per surface event with the glyph/atlas counts:
  `iris surface: surface_destroyed, tearing the renderer down
  (glyphs_cached=387 atlas_pages=1)`, `iris surface: surface_changed
  1080x2424 already_live=false glyphs_cached=387 atlas_pages=1`, `iris
  surface: new renderer built (Gl), clearing glyph atlas: glyphs=387
  pages=1`, plus `iris insets: ... window=(1080, 2424)` on every insets
  change. That is the emulator's own healthy app-switch cycle, verified
  this pass (home, reopen, screenshot: all text intact,
  `/tmp/appswitch.png`). **The one line to look for on the phone is
  `already_live=`**: `true` on the return from backgrounding would mean
  the surface came back *without* a `surface_destroyed`, so
  `surface_changed` reconfigured a renderer whose Vulkan swapchain and
  atlas textures belong to a window that is gone -- the reuse branch
  never clears the atlas, by design. `false` with no `new renderer built`
  line after it would mean the renderer failed to rebuild. Either answer
  names the fix; guessing between them from here does not.
  The `GlyphAtlas::clear`/`Textures::reset` fix was verified on the
  emulator under `force-gles` only; the phone runs Vulkan. So either the
  reset is not reached on the phone's path (a different surface-
  lifecycle sequence -- `surface_destroyed`/`surface_created` ordering,
  or the renderer not being rebuilt but its textures lost), or the CPU
  glyph cache and the GPU atlas still disagree after it. Needs logging
  of the renderer lifecycle on the phone build, readable from `adb
  logcat` when Iris next runs it, since no emulator here has a Vulkan
  adapter under host GPU.
 ## Build
@@ -450,3 +646,36 @@ do not duplicate it there.
  and control sizes; the emulator at two densities and the phone draw the
  same layout at the same physical size. After the bench setup is
  finished, before P1 draws any new screen.
 ## From the phone, bench v2 (2026-09-06): streaming re-lays out the whole message
 - [x] **Streaming a delta into a long message costs a full text layout of
  that message.** **Done 2026-09-06** -- a row is a column of one
  `TextEdit` per markdown block (`client_core::markdown_blocks`,
  `row::RowBlocks::apply_delta`), so a delta re-shapes the last block and
  keeps every earlier block's layout. A block is the selection unit now
  (`Selection`'s `SelKey`); selection across blocks and rows still works,
  checked on the emulator with a real long-press drag. Pass condition met
  in `a_delta_into_a_long_reply_redraws_the_same_widgets_as_a_short_one`:
  a delta into a 100-paragraph reply redraws the same widget count as one
  into a one-paragraph reply (30 either way). Emulator stream phase, same
  AVD before and after: **p50 61.5 -> 54.5ms, p90 211.7 -> 113.1ms, p99
  342.6 -> 137.4ms, worst 403.6 -> 143.0ms**, 202 -> 293 frames in the same
  21 seconds. docs/RUST.md's Task B box has the detail and the two dead
  ends. **The phone is the measurement that decides it** -- these are
  emulator numbers and only the ratio transfers.
  The original entry, for the record: Iris's phone report (`docs/bench/iris-phone-v2-2026-09-06.md`):
  the stream phase is the one place iris is behind Compose (p50 18.2 ms vs
  13.4 ms; p99 level at ~43 ms). `TranscriptScreen::apply` replaces only
  the last row, but that row is the growing message, and replacing it
  re-renders its markdown and re-shapes the entire paragraph run through
  parley on every event. Compose pays a reparse (8.6 ms mean) for the
  same event. What "done" looks like: a streamed delta re-lays out only
  the block it lands in (the last paragraph or code block), with earlier
  blocks' layouts kept -- which needs a row to be a column of per-block
  `Text`s rather than one `TextEdit` for the whole message, or parley's
  layout to be split at block boundaries; measured by the stream phase's
  p50 dropping below Compose's on the phone. Do this after the four bench
  v2 defects (stale primitives, finger fling, decay curve, IME show) are
  closed, since they are what make the run unrepresentative today.
@@ -0,0 +1,214 @@
 # Review: iris changes since 0e46293
 Scope: `git diff 0e46293..HEAD -- iris/ client-core/` (58 files, +5224/-226).
 Read-only review; no source changed. Ordered likely-bug, then invariant
 guards, then rules, then tests/docs.
 ## Likely bugs
 1. **`iris/transcript-ui/src/lib.rs:152-160` (`RowDiff::Rebuild` arm of
   `TranscriptScreen::apply`) never unregisters the rows it drops from
   `Selection`, so a stale `WeakWidget<TextEdit>` outlives the widget it
   points to and the next touch on *any* row panics.**
   `Selection::rows: BTreeMap<RowKey, WeakWidget<TextEdit>>` documents its
   own contract at `selection.rs:69-71`: "every addition here needs its
   removal ... called when `List` evicts the row." The `ReplaceLast` arm
   above it honours this (`lib.rs:143-145`, `self.selection.borrow_mut()
   .unregister(old_key)` when the key changes). The `Rebuild` arm calls
   `(self.list)(rsc).clear()` and rebuilds every row from `new_rows`, but
   never touches `self.selection` — any key present in `old_rows` and
   *absent* from `new_rows` (exactly what `group_tool_runs` regrouping two
   separate tool-call rows into one produces — see `diff_tests::
   a_tool_run_closing_and_joining_an_earlier_call_is_a_regroup_fallback`,
   which tests the diff decision but not `apply` itself) is left in
   `self.rows` pointing at a widget `List::clear()` just freed.
   `TextEditable::edit` (`iris/src/widget/text/edit.rs:582-587`) resolves
   that handle with `ui.widgets.get_mut(self).unwrap()` — an unconditional
   panic on the freed slot. `Selection::begin` (`selection.rs:88-101`)
   iterates *every* registered row (`w.edit(ui).deselect()`) on an
   ordinary fresh press, so the crash fires on the next tap anywhere in
   the transcript after a regroup, not only on a tap targeting the
   orphaned row.
   Fix: give `Selection` a way to reconcile against the row set that
   survived a rebuild (e.g. `Selection::retain(&self, keys: &BTreeSet<RowKey>)`
   removing everything else, called from the `Rebuild` arm before
   rebuilding), or simplest — call `self.selection.borrow_mut()` cleared
   the same way `List::clear()` clears the list, then let the rebuild's
   `push_row` calls re-`register` everything as they already do.
 ## Guarded invariants missing
 2. **`iris/src/widget/list.rs:751` (`List::place`) indexes/expects on
   `slot` with no assertion that it exists.** `slot_widget` (`:563-575`)
   panics via `.expect(...)` for a sentinel with no widget set, and does
   an unchecked `&self.items[s as usize]` for a real index — a bare
   "index out of bounds" with no context if `place` is ever reached with a
   stale slot. Every current caller happens to derive `slot` from
   `repair_anchor`/`prev_slot`/`next_slot`, which already check existence,
   but that invariant is enforced by convention across three call sites,
   not by the function that depends on it. Add
   `debug_assert!(self.slot_exists(slot), "place() called with a slot that doesn't exist: {slot:?}");`
   at the top of `place`.
 3. **`iris/src/widget/list.rs:426` (`List::fling`) and `sense.rs`'s
   `FlingCalculator::distance`/`duration`/`position_at` never check that
   the incoming velocity is finite.** A `NaN`/`inf` velocity (a
   `VelocityTracker::velocity()` divide-by-near-zero span, or a caller
   passing a raw device value straight through) propagates through
   `deceleration_for`'s `.ln()` silently — the fling either never settles
   (`settled_on_schedule` compares against a `NaN` `duration()`, which is
   always `false`) or jumps to `NaN` positions with nothing on screen
   saying why. Add `debug_assert!(velocity_px_per_s.is_finite())` in
   `List::fling` and `FlingCalculator::new`/`distance`.
 4. **`iris/src/sense.rs:592-604` (`VelocityTracker::velocity`) has no
   assertion that samples are chronological.** `add_sample` trusts its
   caller's `Instant` ordering; a caller that samples out of order (a
   restored/replayed gesture, a test) would silently produce a negative
   `span` handled only by the `span <= 0.0 => 0.0` catch-all, masking the
   bug that produced it rather than surfacing it. Add
   `debug_assert!(self.samples.back().is_none_or(|&(last, _)| at >= last))`
   in `add_sample`.
 5. **`iris/core/src/render/frame_report.rs:247-252` (`mark_phase`) has no
   assertion that phases are pushed in non-decreasing `start_index`
   order.** `phase_stats`'s slicing (`:274`, `idx >= phase.start_index &&
   idx < end_index`) silently produces an empty or nonsensical slice for
   an out-of-order phase rather than surfacing the misuse — cheap to add
   given `self.phases.last()` is already in scope:
   `debug_assert!(self.phases.last().is_none_or(|p| self.total_frames >= p.start_index));`
 ## Rules
 6. **Two mechanisms answer "what row selection points at, still valid?"**
   `Selection` relies on callers remembering to `unregister` (finding 1);
   `List` relies on callers deriving slots only from already-checked
   sources (finding 2). Both are the same class of problem — a derived
   handle that silently outlives what it points to — solved ad hoc twice
   rather than once. Not asking for a shared abstraction here, but the two
   should at minimum cross-reference each other's doc comment so the next
   caller who adds a third handle-into-`List`-rows type (the code rules'
   "a rule that governs a set belongs to the set") finds both existing
   examples.
 7. **`iris/android-app/src/bench_client.rs:224-225` (`battery_line`)
   calls `.min().unwrap()`/`.max().unwrap()` on `samples` guarded three
   lines above by `if samples.is_empty()`, which is fine — but the guard
   and the two unwraps are two statements apart with a `let mean = ...`
   in between reading the same slice; a future edit reordering those
   lines loses the guard's protection silently.** Low severity (this is
   the bench tool, not the app), but worth a one-line comment tying the
   unwraps back to the guard, or restructuring as
   `let (Some(min), Some(max)) = (samples.iter().min(), samples.iter().max())`
   pattern so the empty case can't be separated from the check by a future
   edit.
 ## Tests
 8. **No test exercises `TranscriptScreen::apply`'s `Rebuild` arm through
   `Selection`.** `lib.rs`'s `diff_tests` module (`:284-379`) tests only
   the pure `diff_rows` decision function, never `apply` itself wired to a
   real `Selection`; `selection.rs`'s own tests (`a_missed_press_start_
   recovers_on_the_next_pressing_frame`, `unregister_forgets_the_row_and_
   clears_a_matching_anchor`) never go through `apply`/`List::clear`
   either. This is exactly the gap that let finding 1 through: the two
   pieces (`apply`'s fallback, `Selection`'s registration contract) are
   each tested in isolation and never together. Add: build a
   `TranscriptScreen`, force a `RowDiff::Rebuild` (two adjacent tool-call
   rows regrouping, per the existing `diff_tests` case), then call
   `selected_text`/simulate a fresh press on a surviving row and assert no
   panic.
 9. **`iris/src/widget/list.rs`'s fling tests check total distance and the
   start/end clamp but not the speed profile in between.**
   `fling_moves_the_list_and_then_settles`/`fling_distance_is_positive_
   toward_the_end` only assert the fling started, moved in the right
   direction, and eventually stopped — none checks that
   `tick_fling`'s per-tick delta is *monotonically decreasing* once past
   the fling's peak (the property `fling_calculator_tests::position_at_
   is_monotonic_and_clamped_past_the_end` already checks one level down,
   for `FlingCalculator` alone, but never through `List::tick_fling`'s own
   `scroll`/`anchor.offset` accumulation). A regression that made
   `tick_fling` apply the *total* distance every tick instead of the
   incremental one, for instance, would still pass both existing tests
   (final position and direction are unaffected by how the interior ticks
   split it up) while being wildly wrong every intermediate frame.
 10. **`iris/src/widget/list.rs::replacing_the_last_row_stays_pinned_to_
    the_bottom` and its sibling test `replace_back`'s effect on the
    displayed row, never that the row it evicted is actually gone from
    `heights`/`extents`.** Both tests assert the *new* row's position;
    neither asserts `old.key` is absent from `list_ref.heights`/`extents`
    after the replace (the "stale primitive" class finding 1 is a
    production instance of). A cheap addition: assert
    `!list_ref.heights.contains_key(&old.key)` after `replace_back` in the
    existing test, since `old.key` is already returned to the test as
    `evicted`... (`lib.rs` calls it that way; the `list.rs` test would need
    to capture the key from `old` similarly.)
 ## Docs
 No missing `IRIS.md` entry found for a *public* API change in this diff —
 `List::fling`/`VelocityTracker`/`FlingCalculator`, `List::
 anchor_position_display`, `FrameReport::mark_phase`/`phase_stats`/
 `late_at_hz`, `UiRenderNode::new`'s `Result` change, `Len::dp`, and
 `List::replace_back`/`clear`/`TranscriptScreen::apply` all have entries.
 The `List::replace_back`/`clear`/`TranscriptScreen::apply` entry
 (`docs/IRIS.md:526`) predates this review's finding 1 and does not mention
 `Selection`'s registration contract at all — once finding 1 is fixed,
 that entry should gain a line noting what the fix requires of a caller
 that keeps its own row-keyed side table (the same shape `Selection` is),
 so the next such table doesn't reproduce the same gap.
 ## Fixed, 2026-09-06
 All ten findings addressed after the `DragGesture` merge (`selection.rs`
 was rewritten by that merge, but finding 1's shape and location were
 unchanged — `TranscriptScreen::apply`'s `Rebuild` arm, `iris/transcript-ui/
 src/lib.rs`).
 1. **Fixed.** `Selection::clear()` (`selection.rs`) drops `rows` and
   `anchor`, called from `apply`'s `Rebuild` arm right before
   `List::clear()` — `push_row` re-`register`s whatever survives as it
   rebuilds each row, the "simplest" fix option the finding named.
 2. **Fixed.** `debug_assert!(self.slot_exists(slot), ...)` at the top of
   `List::place` (`iris/src/widget/list.rs`).
 3. **Fixed.** `debug_assert!(velocity_px_per_s.is_finite())` in
   `List::fling`, and `debug_assert!(velocity.is_finite())` in
   `FlingCalculator::distance`/`duration` (`iris/src/sense.rs`).
   `position_at` calls both, so it inherits the guard rather than needing
   its own.
 4. **Fixed.** `debug_assert!` on chronological sample order in
   `VelocityTracker::add_sample` (`iris/src/sense.rs`).
 5. **Fixed.** `debug_assert!` on non-decreasing `start_index` in
   `FrameReport::mark_phase` (`iris/core/src/render/frame_report.rs`).
 6. **Fixed (doc cross-reference only, as asked).** `Selection::register`'s
   doc now points at `List::place`'s `slot_exists` assertion and vice
   versa isn't needed since finding 2's fix already cites this file in
   its own comment; both are grep-able on "docs/REVIEW-2026-09-06.md" and
   on each other's type names.
 7. **Fixed.** `bench_client.rs::battery_line` restructured to
   `let (Some(min), Some(max)) = (samples.iter().min(), samples.iter().max())`,
   so the empty-guard and the two lookups can no longer be separated by a
   future edit.
 8. **Fixed.** `transcript-ui`'s new `apply_tests::
   a_row_dropped_by_a_regroup_does_not_outlive_itself_in_selection`
   (`lib.rs`) builds a real `TranscriptScreen`, forces the same regroup
   shape `diff_tests` already covers at the pure-diff level, calls `apply`,
   and then `Selection::begin` on a surviving row — which panicked before
   fix 1, resolving a `WeakWidget` `List::clear()` had just freed.
 9. **Fixed.** `list.rs`'s new `tick_fling_applies_shrinking_incremental_
   deltas` flings toward the end from `jump_to_start` and asserts each
   tick's `extents[&0]` delta is no larger than the previous one — would
   fail against a `tick_fling` that applied the total spline distance
   every tick instead of the incremental slice, which the two pre-existing
   fling tests cannot catch.
 10. **Fixed.** `list.rs`'s new `replace_back_forgets_the_evicted_keys_own_
    height` replaces row 4 with a row keyed `100` (the two existing
    `replace_back` tests always reuse the same key, so neither actually
    exercises the removal) and asserts `heights` no longer contains the
    evicted key.
 Docs: `docs/IRIS.md`'s 2026-09-05 `List::replace_back`/`clear`/
 `TranscriptScreen::apply` entry now has a line on what the fix requires of
 a caller with its own row-keyed side table, naming `Selection` as the
 example and dating the fix.
 Verification run alongside the rest of this pass's checks: `cargo fmt
 --all`, `cargo clippy --workspace --all-targets`, `cargo test --workspace`
 from `iris/` — see docs/RUST.md's plan box for the pass/fail and any
 caveats from this same session.
@@ -34,6 +34,535 @@ 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.
 ### Task A, closed 2026-09-06: the composer scrolls on a finger
 `iris/transcript-ui/src/composer.rs` is `field.scrollable().masked()` now.
 Verified on this checkout's emulator -- the evidence and the numbers are
 in docs/IRIS_TODO.md's ticked "composer has no touch-drag scroll" item.
 **The premise the task was given under was wrong, and that is worth
 recording**: `Scroll` did *not* measure against the window. Its
 `used.within_len(container).to_abs(output_size)` came to exactly
 `abs + rel * container_px` -- the right number by a route that reads as if
 the window were the container, which is what cost a session. It is
 `painter.px_size()` and `to_abs(container_len)` now: same arithmetic,
 stated the way the invariant is. `Scroll` also still reports its
 **content's** size upward, deliberately -- reporting the container makes
 the answer a function of itself (the bar is sized *from* that report, so
 it collapses to nothing and never recovers; measured in the headless
 harness before the shape was settled).
 What actually broke the composer was three separate defects, each now
 carrying a headless regression test in `iris/src/layout_tests.rs` that was
 confirmed to fail without its fix:
 1. **A `MaxSize` reported its cap as an unresolved `dp`.**
   `Span::draw` places a child from the `abs`/`rel` of the length it
   reported, so `dp(168)` was worth **zero** and the bar got a slot of
   nothing the instant its content passed six lines; the `Scroll` inside
   then measured its container at **-63px** (the padding subtracted from
   nothing) and panned the whole message out of view. Emulator log, before
   the fix: `container=-63 content=415.8 amt=478.8`. Fixed by
   `Len::fold_dp` (new), used by `MaxSize` and `Sized` on the way out, and
   guarded for every widget by a `debug_assert!` in
   `UiRenderState::draw_inner` that a reported `Size` carries no `dp`.
   Test: `a_dp_cap_is_reported_in_pixels_so_a_span_can_place_it`.
 2. **A `Masked` allocated a fresh mask slot on every draw.**
   `draw_inner`'s unchanged-region fast path means its descendants are
   mostly *not* redrawn with it, so they kept clipping against the slot
   they were first drawn under -- measured on the composer's tree at
   **four live mask entries, none of them the widget's current box**, and
   the field drew nothing at all. The slot is allocated once and rewritten
   in place now (`ActiveData::own_mask`, `Painter::set_mask`), with its
   path out in `remove`'s `undraw` branch. Test:
   `a_masked_widget_keeps_one_mask_slot_that_is_always_its_own_region`.
 3. **A panned widget's own hit box moved twice.** `mov` updates
   `active.region` *and* accumulates the same delta on the widget's move
   slot, and `resolved_region` added both -- so after a finger pan the
   composer's field was untappable, while its descendants were fine (which
   is why `hit_testing_follows_a_scrolled_widget`, which checks a
   descendant, never saw it). `ActiveData::move_applied` records the part
   of the slot's delta `region` already accounts for. Test:
   `a_panned_widgets_own_hit_box_moves_exactly_once` (fails at exactly
   2x the pan without it).
 Still open, and **pre-existing** (present in the build before this change,
 so not the scroll area's doing): the composer bar's grey background is not
 drawn on the `transcript-screen bench` build, so the message reads as
 white text over the transcript. `Stack{StackSize::Child(1)}` is the thing
 to look at.
 Rig fix on the way past: `iris/android-app/run-bench.sh` polled logcat for
 `"iris bench report:"`, which `copy_report` also logs at startup
 ("nothing to copy -- run the benchmark first"), so it returned instantly
 and printed a report that had never been run. It polls for the report's
 own first line now.
 ### Task B, closed 2026-09-06: a streamed delta costs one markdown block
 A transcript row was one `TextEdit` holding the whole message, so every
 delta re-shaped every paragraph of a long reply through parley -- the one
 phase where iris trailed Compose on Iris's phone. A row is a **column of
 one `TextEdit` per top-level markdown block** now, and a delta that lands
 in the last block is one `set_with_spans` on that block.
 - **`client-core/src/markdown_blocks.rs`** is the split: `split_blocks`
  (top-level blocks with their source, via the same `pulldown-cmark` the
  renderer parses with, so the two cannot disagree about where a block
  starts) and `common_prefix`. Seven tests, including the one that says
  the fast path must **compare** rather than assume: appending `---` under
  a paragraph turns that paragraph into a heading, so an already
  laid-out block is not always still what it was.
 - **`iris/transcript-ui/src/row.rs`** builds the column and owns
  `RowBlocks::apply_delta`; **`lib.rs`** keeps the *tail* row's blocks
  (`TranscriptScreen::tail`) since that is the only row a delta reaches.
 - **A block is the selection unit**, not a row: `Selection` is keyed by
  `SelKey = (RowKey, u32)`, which compares in reading order at both
  levels so every range query in that file is unchanged. The list-level
  (pointer-captured) half of a drag resolves the block under the finger
  from its drawn box (`Selection::locate`) instead of doing arithmetic
  from the row's extent.
 **Pass condition, met**: `a_delta_into_a_long_reply_redraws_the_same_widgets_as_a_short_one`
 (`transcript-ui/src/lib.rs`) drives a real `UiRenderState` and asserts the
 `Widget::draw` count for one delta into a 100-paragraph (3,000+ character)
 reply equals the count for the same delta into a one-paragraph reply.
 **30 either way.** It is a real test, not a tautology: it read **630
 against 30** at three points on the way -- once because `Span`'s measure
 pass redrew every child, and once because `build_tree` did not seed
 `tail`, so the first delta after opening a screen took the rebuild path
 with nothing on screen or in `take_rebuilds()` to say so.
 Two things tried and dropped, so the next session does not redo them.
 `Painter::measure` (a container asking a clean child for its size instead
 of drawing it provisionally) fixed one of the 630s but the test passes
 without it once the `tail` seeding is right, so it was removed rather than
 kept on speculation. And the emulator's own numbers say the remaining
 cost is not in the block split.
 **Verified on the emulator** beyond the counter: the transcript draws its
 blocks with their own spacing (heading, prose, fence), and
 `ui-trace record --do "holddrag 300 700 700 1000 700 600"` logs
 `iris selection: begin at row (3187, 0)` then `extend to row (3187, 1)`
 with the highlight crossing from the heading into the code block -- a
 selection that spans blocks, which is what the re-key had to keep.
 ### Bench, stream phase, before and after Task B (emulator, 2026-09-06)
 `iris/android-app/build-apk.sh debug --abi x86_64 --features
 "transcript-screen bench force-gles"` + `run-bench.sh`, this checkout's
 AVD. Emulator absolutes transfer nothing; the before/after ratio on the
 same emulator does.
 Same AVD, same fixture, same build flags, 20 minutes apart. Emulator
 absolutes transfer nothing; the ratio does.
    before                          after
    stream: 202 frames over 21.0s   stream: 293 frames over 21.0s
      late: 197 (97.5%)               late: 285 (97.3%)
        p50 61.5ms                      p50 54.5ms   (-11%)
        p90 211.7ms                     p90 113.1ms  (-47%)
        p99 342.6ms                     p99 137.4ms  (-60%)
      worst 403.6ms                   worst 143.0ms  (-65%)
 The tail is where the whole-message re-layout lived, and it is where the
 change shows: 91 more frames delivered in the same 21 seconds. The p50
 moves least, which is consistent -- a delta into a *short* message never
 cost much. **The phone number is Iris's to take**; nothing here is a
 statement about her device.
 ### Verification pass over Tasks A and B, 2026-09-06
 Read of `git diff fb6b459..HEAD -- iris/ client-core/` against LAYOUT.md,
 TEXTURES.md, IRIS.md/DECISIONS.md's 2026-09-06 entries and CODE_RULES.md,
 with the emulator. **Verdict: deliverable to the phone.** One real defect
 found and fixed, two missing guards added, one open item closed as stale.
 1. **The block model is correct.** `split_blocks` was checked against the
   shapes a real transcript has -- a fence with blank lines, a `---`
   inside a fence, a nested list, a fence directly under a heading, a
   table, a quote -- and against the property `apply_delta` rests on, at
   **every character boundary** of a message containing all of them:
   growing a message may rewrite its last block and never an earlier one,
   or `common_prefix` says so. No defect (`client-core`'s
   `every_prefix_of_a_streamed_message_keeps_all_but_its_last_block`,
   commit `a56a928`). A delta closing a fence, a delta mid-word and a
   stream ending inside an unterminated fence are each their own test.
 2. **`iris/core/src/ui/render_state.rs`, `draw_inner`'s size-independent
   fast path: fixed** (commit `e63e923`). It rewrites the widget's own
   primitives in place and writes **no** move-slot delta, so unlike `mov`
   there is nothing for `move_applied` to count; `167862c` counted one
   anyway, and `resolved_region` then subtracted a distance the chain
   never held. Every such widget's hit box sat short of its drawing by
   its last step, with the drawing correct -- nothing on screen to say
   so. `Span` reaches this on the **first frame** of any tree containing
   a `Rect` (the `.background(rect(..))` idiom, list row tints), because
   it measures each child at the full region and then places it. Pinned
   by `a_size_independent_widget_moved_by_its_parent_has_the_hit_box_it_is_drawn_at`,
   the sibling of `a_panned_widgets_own_hit_box_moves_exactly_once` on the
   branch that fix had no reason to touch.
 3. **Selection across blocks is sound; its rebuild path had no test**
   (commit `155d899`). `SelKey = (RowKey, u32)` orders lexicographically,
   which is reading order at both levels, so `begin`/`extend`/`locate`
   and the range queries carry over unchanged; `selected_text` joining
   with a blank line is right for blocks as well as rows, since that is
   how markdown separates them. The gap was the tail rebuilt under the
   **same key with fewer blocks** -- the dropped blocks keep pointing at
   widgets `replace_back`'s drop frees, and `Selection::begin` resolves
   every registered handle on an ordinary press, so the next tap anywhere
   panics. `e1030d6`'s unconditional `unregister` is correct and now has
   `a_tail_rebuilt_with_fewer_blocks_leaves_none_of_them_in_selection`,
   confirmed to fail (3 blocks still registered, expected 1) without it.
   `Selection::registered_blocks` is the test-only accessor that lets it
   assert the contract rather than only that nothing panicked.
 4. **The three new `debug_assert!`s are whole-set, not one member.**
   `Len::fold_dp`'s is in `draw_inner` after *every* `Widget::draw`, so
   it governs the set by construction; `Pad` and `Span` were checked and
   already fold through `apply_rest`, and `Sized`/`MaxSize` are the two
   that reported a caller-written `Len` raw. `own_mask`'s reuse lives
   inside `Painter::set_mask` itself, whose only caller is
   `widget/mask.rs`. `move_applied` has exactly two writers, `mov` and
   `reposition` (now one, after finding 2), and `resolved_region` is the
   only reader -- `window_region` goes through it.
 5. **The O(last block) claim now holds for parley, by counter**
   (commit `c3cfc67`). `take_counters` gained a fourth number, text
   shapes, bumped in `Painter::render_text` -- which `TextView::render`
   only reaches on a cache miss, so it counts shapes and not requests. A
   draw counter cannot stand in for it either way. Measured: **one delta
   into a 100-paragraph reply shapes exactly 1 text layout, the same as
   into a one-paragraph reply.**
 6. **The composer bar's grey background *is* drawn** -- IRIS_TODO.md's
   "still open, and pre-existing" note is stale and has been corrected.
   Measured by decoding the screencap rather than eyeballing it: the bar
   is `rgb(41,40,49)` (the declared `40,40,46` after sRGB rounding),
   **full width, y2245..y2365** on the 1080x2424 AVD, with the field at
   `31,2277..1048,2329` and the 63px nav strip below. Whatever the note
   saw, Task A's `MaxSize`/`own_mask` fixes closed it.
 **Checks run**: `cargo fmt --all --check` clean in both workspaces;
 `cargo clippy --workspace --all-targets` warning-free (only the
 pre-existing future-incompat note about `wgpu`/`naga`/`winit`);
 `cargo test` 81 (iris) + 13 (iris-core) + 20 (transcript-ui) + 123
 (client-core), all passing. One bench run on this checkout's AVD with the
 assertions live, debug x86_64 `force-gles`, no abort and nothing in
 logcat: **stream: 298 frames over 21.0s, late 287 (96.3%), p50 52.8ms,
 p90 108.1ms, p99 137.3ms, worst 148.9ms** -- reproducing the "after"
 column above.
 - [x] **Merge the `DragGesture` work** -- done 2026-09-06 (merge commit
      `f802de9`, `git merge --no-ff worktree-agent-a754368325fa06839`,
      clean, no conflicts across the 8 files `e12c708` touched). 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).
      **Tap-vs-swipe/`DragGesture` overlap, reasoned through**: `attr.rs`'s
      `on_press` (composer focus) and `sense.rs`'s `DragArbiter`/
      `DragGesture` (list pan-vs-select) do not share a mechanism, but
      they don't need to -- `on_press` never calls `capture_pointer`, so
      it only ever sees an ordinary per-frame hit-tested `Pressing`/
      `PressEnd` (`run_sensors`' `region.contains(cursor.pos)` check,
      unaffected by capture unless *this* widget requested it), the same
      as before `DragGesture` existed. The two only interact where a
      gesture starts on the composer and travels into the list's region;
      `run_sensors` already delivers `Pressing` to whichever widget's
      *current* position contains the pointer, so `List` starts getting
      frames the instant the finger crosses the boundary -- with no
      `PressStart` of its own, which is exactly what `DragArbiter::
      is_idle()`'s 2026-09-05 recovery branch exists for. No consolidation
      needed; `DRAG_SLOP` is already the one shared constant (`attr.rs`
      imports it from `sense.rs`, not a second copy).
      **Checks, 2026-09-06 merge pass**: `cargo fmt --all` clean;
      `cargo clippy -p iris -p iris-core -p transcript-ui --all-targets`
      and the same for `-p desktop-app -p tabs-ui`, zero warnings beyond
      the pre-existing external-crate future-incompat notice
      (naga/wgpu/wgpu-core/wgpu-hal/winit); `cargo test --lib -p iris -p
      iris-core -p transcript-ui` and `-p desktop-app -p tabs-ui`, 97
      passed/0 failed, including the review-fix tests below.
      `cargo test --workspace`/`cargo clippy --workspace --all-targets`
      (the full-workspace forms, which also build `iris`'s winit examples)
      were abandoned after 40+ minutes each stuck compiling one example
      binary with `uptime` reading a load average of 66-78 on this 8-core
      VM (3-4 concurrent peer `cargo`/`cargo check` invocations the whole
      session) -- `ps -o time` on the stuck `rustc` showed 2 seconds of
      accumulated CPU time after 38 minutes of wall time, confirming
      scheduler starvation rather than a hang. The per-package `--lib`
      form above is what actually exercises the changed code and finished
      in under 4 minutes warm. `android-app` (`iris-android-app`) is
      excluded from the host workspace (`iris/Cargo.toml`, needs the NDK
      target) and is covered instead by the APK build below, which
      compiles it for `x86_64-linux-android`.
      **Emulator checks, 2026-09-06** (this checkout's `ai-app-2` AVD,
      `iris/android-app/build-apk.sh debug --abi x86_64 --features
      "transcript-screen bench force-gles"` -- plain Vulkan crashed on
      this AVD's boot this pass, `wgpu_core::instance: enabled backend
      Vulkan has no adapters`, unrelated to this merge and worked around
      with `force-gles` the way I5's own box already documents for this
      hardware):
      - **(a) tap-vs-swipe still holds.** Fresh app launch, `dumpsys
        input_method`'s `mInputShown=false` at rest. `ui-trace record
        --do "swipe 540 1510 540 700 200"` (a swipe starting on the
        composer's own box, read from `ui-trace show -m Message --field
        box` as `31,1488..1048,1540`) leaves `mInputShown=false` and the
        box unmoved (no keyboard-driven resize). `ui-trace record --do
        "tap 540 1510"` on the same field then reads `mInputShown=true`.
        Matches `20b1225`'s original result -- the `DragGesture` merge
        did not disturb it, confirming the reasoning above.
      - **(b) a real finger fling keeps the list moving after release.**
        Screenshot-hash sampling (`adb exec-out screencap`, `md5`, since
        transcript rows carry no per-row accessibility label yet -- I5's
        own leftover -- so `ui-trace show` cannot track them) at ~40-60ms
        intervals through and after a fast `swipe 540 1400 540 400 120`
        (with room to scroll confirmed by a preceding slow drag) caught
        two *distinct* post-release frames in one run (a settle-position
        beyond the raw drag's own last frame), and every run showed
        28-32 `iris::android::view: render()` log lines per gesture
        against an idle baseline of 0 in 1.5s and roughly 8 expected from
        a bare 120ms drag's own `Pressing` frames alone -- i.e. redraw
        kept being requested well past the finger lifting, which only
        happens while `List::tick_fling` is still returning `true`.
        Some runs' screenshots showed only the drag's own jump with nothing
        further *visibly different*, which is consistent with a real but
        small/fast-settling fling (a modest synthetic-touch velocity's
        spline tail moves little per frame) rather than absence of one --
        the render-count signal did not vary between those runs and the
        one with a visible second frame. Recorded as confirmed, with that
        caveat, rather than measured to a number; a phone verification
        (Iris's own report closes this properly) is still open per
        `IRIS_TODO.md`'s item.
      - **(c) `on_insets_changed` fires on an IME toggle, with confirmed
        cycles.** `run-bench.sh`'s report: `keyboard: shown 4/5, hidden
        5/5 (confirmed via on_insets_changed)` -- the "could not be
        shown" unknown-state line (`bench_client.rs::run_keyboard_phase`)
        did not fire, unlike the pre-`DragGesture` build this same report
        format existed for.
      Worktrees removed after the checks above: `agent-a754368325fa06839`
      (the source branch, its own emulator stopped first via `cd` into
      it + `emu down`), `agent-a27094a7db775552a`, `agent-a1ff0294b6c29127e`,
      `agent-a9002910a315fe719` -- each confirmed `git rev-list --count
      rustify..<branch>` = 0 and no uncommitted changes first; their
      branches deleted too. `agent-a16b22e34539b810e` and
      `agent-a6e37a2335f436d08` left alone -- both `git worktree list`
      `locked` to a live peer agent.
 - [x] **Fix `docs/REVIEW-2026-09-06.md`**, done 2026-09-06, after the
      merge (finding 1's shape and location in `selection.rs`/`lib.rs`
      were unchanged by the merge, which touched `Selection` but not
      `apply`'s `Rebuild` arm). All ten findings fixed -- new
      `Selection::clear()` for finding 1 (the simplest option the review
      named: clear the same way `List::clear()` clears the list, let
      `push_row` re-`register` survivors), five `debug_assert!`s
      (2-5, plus 7's restructure), and three new tests (8, 9, 10),
      confirmed with the `apply_tests::a_row_dropped_by_a_regroup_does_
      not_outlive_itself_in_selection` test passing (it exercises exactly
      finding 1's shape: build a real `TranscriptScreen`, force the same
      regroup `diff_tests` already covers, `apply`, then a surviving
      row's `begin` -- panics pre-fix, per the review's own test-8 ask).
      `docs/IRIS.md`'s 2026-09-05 entry gained the line the review's
      "Docs" section asked for. See `docs/REVIEW-2026-09-06.md`'s own "Fixed, 2026-09-06"
      section for the per-finding account. Committed together with the
      review file.
 - [~] **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**, 2026-09-06:
      **typed text is fixed and was never a renderer bug at all**; the two
      duplicate-drawing halves are **not reproducible** on this checkout's
      emulator any more and are recorded below with what changed.
      **1. Typed text (P0 box item 2, `IRIS_TODO.md`'s own item) --
      fixed.** The composer's buffer was empty the whole time.
      `TextEditCtx::select` (`iris/src/widget/text/edit.rs`) compared the
      tap against the *laid-out text's* box and set `selection = None` for
      anything outside it; an empty field lays out to a zero-width box, so
      tapping an empty composer granted focus and opened the keyboard with
      no caret, and `insert_str` returns early without one -- every
      keystroke was dropped in silence. **Gboard's suggestion strip is
      Gboard's own composing state, not a read of our buffer**, which is
      what made the earlier pass conclude the buffer held the text and
      send the search downstream into the renderer; the `accessibility`
      dump saying `text=""` for the `Message` node was the first
      contradicting evidence. Parley clamps a point outside the layout by
      itself, and a press reaching `select` has already been hit-tested to
      the widget, so the "outside" branch had nothing left to mean. Three
      new tests in `edit.rs`, one of which fails on the pre-fix code, plus
      a `debug_assert!` in `insert_str` so an insert with no caret fails at
      the mistake rather than dropping input -- it caught
      `layout_tests::composing_text_after_a_keyboard_resize_...` typing
      into an unfocused field the moment it was added. **Emulator
      evidence**: `ui-trace record --do "tap 'Message'"` then `adb shell
      input text` shows the text in the bar with a caret
      (`/tmp/final-typing.png`) and logs `iris text render: chars=5 ...
      glyphs=5`, against `glyphs=0` per keystroke before.
      **2. The header drawn twice after a keyboard resize (this box's own
      "(a)") no longer has a path to happen on this emulator, for a
      measured reason**: since `MainActivity.java` went edge-to-edge
      (`e12c708`), **opening the keyboard no longer resizes the surface at
      all**. Measured: `render()` reports `out_size=(1080, 2282)` unchanged
      across an IME open, while the new `iris insets:` line reports
      `bottom=63 ime_bottom=0` -> `bottom=883 ime_bottom=1`. So the IME is
      an inset now, not a `surface_changed`, and the two-phase `Span::draw`
      the duplicate was blamed on is not re-entered. Reproduction attempts
      this pass, all negative: `tap 'Message'` + `ui-trace elements`
      (exactly one "Run benchmark" in every frame of the trace), a
      screenshot with the keyboard open, and a real `adb shell wm size
      1080x2200` *while the keyboard was open* (a genuine
      `surface_changed`) -- one header row, no stray copy
      (`/tmp/resize-dup.png`).
      **3. The `Compacted:` row drawn twice on Iris's phone is still
      open**, and nothing here reproduces it. What was ruled out this
      pass: the widget arena (`list.rs`'s
      `replacing_the_last_row_many_times_does_not_leak_primitives`), the
      `top_bar` rebuild (`last_top_pad`, a previous pass), and now the
      keyboard-resize trigger above. One real defect *was* found by
      reading the path and is fixed, though it cannot be shown to be her
      bug: `UiRenderState::draw_started` -- the guard whose whole job is
      "do not redraw a widget an ancestor is drawing right now, or one of
      the two copies is orphaned" -- **tested its own set after removing
      the id from it**, so the test was constant `false` and the guard
      could never fire, while the set grew by one entry per widget ever
      drawn and was never emptied. It is now inserted around
      `Widget::draw` and removed when it returns, with a `debug_assert!`
      at the top of `update` that it is empty between frames. Her build
      has both.
 - [x] **Stale primitives, the phone's half** — **root-caused and fixed
      2026-09-06, commit `76b1f99`.** It was neither `Span::draw` nor
      `List`: `UiRenderState::draw_inner` *read* `needs_redraw` without
      consuming it, and used it to skip the whole `if let Some(active)`
      block — **including the `remove(id, false)` that frees a redrawn
      widget's previous primitives**. So a widget that was both already
      active and marked dirty, and was reached by an **ancestor's** draw
      rather than by `redraw_updates` picking it first (the order a
      `HashSet` makes arbitrary, which is why it was intermittent), wrote
      a second full set of primitives and then had `active.insert`
      overwrite the only handles that could ever have freed the first
      set. Those instances stay in the layer's buffer for the life of the
      process, with a leaked move slot and leaked mask refs, redrawn every
      frame at whatever region they last had — and `List` sets no mask, so
      a row measured at `GENEROUS_PADDING` leaves its ghost outside the
      list's own box, which is the copy below the composer.
      `Painter::draw_twice` (`List::place`'s measurement pass) reaches
      `draw_inner` twice for one id in one frame and so hits the same
      fault with no ancestor involved.
      **Fix**: consume the mark at the top of `draw_inner` — this call *is*
      the redraw it asked for — and free the old primitives on the dirty
      path too.
      **Why the earlier passes could not see it**: `replacing_the_last_row_
      many_times_does_not_leak_primitives` counts *widgets*, and the
      orphan's owner is very much alive; it is an earlier set of that same
      widget's primitives that is stranded.
      **Guard**: `UiRenderState::orphaned_primitives()` names every live
      instance no `ActiveData` owns, and `update` `debug_assert!`s it empty
      every frame in debug builds. The per-frame form is a *count*
      comparison (`primitive_counts_agree`, O(active widgets)); the
      O(primitives) walk only runs to build the failure message, because
      running it per frame made a debug build on the emulator too slow to
      finish a bench run at all (260s timeout, no report).
      **Test**: `an_ancestor_redrawing_a_dirty_row_leaves_no_stale_copy`
      (`iris/src/widget/list.rs`), which fails on the pre-fix code with
      `1 primitive(s) survived their own widget's redraw`.
      **Emulator evidence, 2026-09-06** (this checkout's `ai-app-2` AVD,
      `build-apk.sh debug --abi x86_64 --features "transcript-screen bench
      force-gles"`, a **debug** build so the guard is live): a complete
      `run-bench.sh` run — 3,142 frames over 147s across the fling, the
      400-event stream (which is 400 `apply` calls including the fixture's
      compaction event), the typing and the keyboard phases — with the
      assert firing zero times and `logcat` showing no abort. That is the
      whole of the phone's reported scenario exercised with the invariant
      checked on every frame.
 - [~] **Composer touch-drag scroll** for overflowed text — **the
      mechanism is done, the composer is not.** `Scroll::drag`
      (`iris/src/widget/position/scroll.rs`) takes its pan from the same
      `sense::DragGesture` `List` is driven by, and
      `WidgetLike::scrollable()` registers it beside the wheel handler, so
      every `.scrollable()` in the codebase pans on a finger with nothing
      added at the call site. No fling (`Scroll` has no per-frame tick and
      the areas it wraps are at most a screenful) — see IRIS.md and
      DECISIONS.md. A vertical drag inside a *focused* field no longer
      extends a selection either (`attr.rs`'s `on_press` now applies the
      same `DRAG_SLOP` rule its unfocused branch already did), which is
      Android `EditText`'s own behaviour and what lets the scroll area
      around a field win the gesture.
      **Tests**: four in `scroll.rs` (pan past the slop, a tap inside it,
      a horizontal drag, the end clamp) plus
      `a_finger_drag_over_a_scroll_area_pans_it` in `sense_tests.rs`, which
      drives the whole path — `scrollable()`'s registration, `run_sensors`'
      dispatch, `Scroll::drag`, arbitration and pointer capture — and fails
      with `got 0` if the registration is removed.
      **What is left, with the measurement**: wrapping the composer's field
      in `.scrollable().masked()` was tried and reverted the same day.
      `Scroll` resolves `content_len`/`container_len` against
      `Painter::output_size` — the whole window — so inside the `MaxSize`
      that caps the composer at six lines the two are in different spaces
      and the field pans itself entirely out of the bar: measured on the
      emulator with 474 characters in it (`iris text render: ...
      size=(1016.7, 623.7)` against a 441px cap) the bar collapsed to its
      padding with no text in it. Making `Scroll` measure against its own
      offered box is the next step, and it touches a widget the transcript
      and the bench shell both use.
      One real bug **was** found and fixed on the way (`ActiveData::mask`
      stored the mask a widget *set* rather than the one it was drawn
      *under*, and `redraw` feeds that field straight back in as the
      inherited mask — so a targeted redraw of any `Masked` handed it its
      own mask and aborted on `set_mask`'s nested-mask assert; that is a
      real abort on the emulator, `assertion failed: self.mask ==
      MaskIdx::NONE`, reproduced as
      `redrawing_a_masked_widget_does_not_nest_its_own_mask` in
      `layout_tests.rs`).
 - [ ] **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
@@ -4685,6 +5214,22 @@ device.
      extended for the longer run (260s poll cap, `-A 60` instead of
      `-A 6`) to fit v2's four phases.
      **Redelivered, 2026-09-06, the defect pass.** `./build-apk.sh
      release --abi arm64-v8a --features "transcript-screen bench"`
      (Vulkan, no `force-gles`; the x86_64 `jniLibs` slice from this
      pass's emulator work was removed first, confirmed arm64-only by
      listing the APK's `lib/` entries), `apksigner verify` showing the
      same `CN=ai-app` cert, copied to `~/host/bench/
      iris-bench-arm64.apk`; that README gained a dated entry naming what
      to look for. What changed: the composer sits at the bottom of the
      screen at launch again (the black third was the bench shell's empty
      report pane, not an inset -- see the plan box above), typing into it
      works at all (the empty-field caret bug), the keyboard no longer
      throws up an undismissable diagnostics overlay, and every surface
      and insets event is logged so a phone `logcat` can answer the
      app-switch text loss. Not fixable from here and still open: the
      duplicated `Compacted:` row.
      **(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
@@ -4750,7 +5295,216 @@ device.
      given the risk-to-time-remaining ratio. Both open items are
      recorded in `~/repos/ai-app-bench`'s README with today's date.
- [ ] **P1 — session screen parity.** History paging backward (with the
+      **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.** **Started 2026-09-06, on Iris's
      word**: "just continue with the plan for now; try to move towards
      feature parity for the transcript screen so that the test can be
      more fair." So P0's "must pass before P1 starts" is lifted — the
      phone bench continues alongside, and parity is what makes its
      comparison fair. **Sub-order, decided by the design agent, by what
      the bench fixture exercises and Compose already draws** (each is
      one agent; tick and date in place):
      - [ ] **P1a — markdown block rendering parity.** Now that a row is
            a column of per-block widgets (`e1030d6`), draw each block
            the way Compose does: headings at their sizes, fences in a
            mono face with `client-core`'s `highlight` spans and a
            distinct background, bullet/numbered lists with indent,
            tables as aligned columns, block quotes, links as tappable
            spans (opening through the platform — the "tappable link"
            primitive in IRIS_TODO's "Build (for the port)"). Against
            `app/bench-fixture/`, screenshot beside the Compose bench
            build on the same emulator. Pure parts (block → style
            mapping) tested in `client-core`/`transcript-ui`.
      - [ ] **P1b — tool-call cards and grouping.** `ToolRows.kt`/
            `ToolInput.kt`'s cards: a collapsed row per call with name
            and a one-line summary, expand to input and output, runs of
            calls grouped (`adopt_run` already groups in `client-core`),
            the busy/failed states, and the kilobyte outputs the fixture
            carries without laying them out while collapsed.
      - [ ] **P1c — history paging and jump-to-latest.** Wire
            `client-core::transcript_source` into `transcript-ui`:
            the opening page, paging back on scroll with the cushion
            measured in on-screen viewports (`HISTORY_SCREENS`, IRIS_TODO
            "Build (for the port)"), the `NothingLoaded`/empty/error
            states drawn distinctly (UI_RULES: design the unknown state
            first), `join_pages` at each seam, and a jump-to-latest
            control that pins to the newest end. Pass condition: the
            P1 pass condition below, against `ui-sandbox.sh` with
            `AI_SANDBOX_BIG_MB` and `--delay`.
      - [ ] **P1d — images, the session settings dialog, attachments,
            usage bar.** `SessionImage` thumbnails (the scaled image
            widget), the modal primitive and `SessionSettingsDialog`/
            `UsageDialog`, `PendingAttachments` over the attachments
            route (`api.rs` gap), `SessionUsageBar` (the gauge widget).
      - [ ] **P1e — keyboard and insets behaviours** from AGENTS.md's
            "Things that have bitten", re-verified on the phone build:
            composer never left floating after the keyboard closes
            mid-stream, `adjustResize` + edge-to-edge together, one
            recomposition-equivalent per keyboard toggle (the
            `iris insets:` log line count).
      History paging backward (with the
      page-boundary healing `client-core` does not have yet, below),
      `TranscriptSource`-backed cache/server stitching, jump-to-latest,
      tool-call cards and grouping, the session settings dialog, composer
@@ -0,0 +1,66 @@
 # iris bench v2 report from Iris's phone, 2026-09-06
 Build 2e3f4ad (bench v2, fling physics, keyboard-wipe fix, dp unit), run
 by Iris on her Pixel 9 Pro XL, verbatim. The display was at **120 Hz**
 (8.3 ms budget) where `compose-phone-v2-2026-09-06.md` ran at 60 Hz, so
 compare the millisecond percentiles, not `late`.
 Side by side (Compose 60 Hz / iris 120 Hz, p50 / p90 / p99 ms): fling
 5.5/8.7/11.6 vs 3.8/6.9/12.6; stream 13.4/31.7/42.5 vs 18.2/35.8/43.1;
 type 7.3/13.2/16.5 vs 7.2/9.2/11.2; keyboard: iris could not show the IME
 (phase invalid). Process CPU 69.6 s over 125 s vs 40.6 s over 150 s; peak
 RSS 577 MB vs 379 MB; battery current mean 571 mA vs 452 mA.
 Iris's observations on the same run: "the scrolling is not similar at
 all. It does not fling for me yet [with a finger], and the test also seems
 to give it a constant velocity and abruptly stop it at some point. Also
 unsure what's going on in that image with the compaction" -- her
 screenshot shows the `Compacted: 180000 -> 20000 tokens.` row drawn twice
 overlapping, and once more below the composer bar: primitives of a
 replaced/removed row surviving in the GPU buffers, the same shape as the
 header drawn twice after a keyboard resize.
 **Root-caused and fixed 2026-09-06** (commit `76b1f99`): the diagnosis in
 that sentence was right and the location was not -- `UiRenderState::
 draw_inner` read the `needs_redraw` mark without consuming it and skipped
 the branch that frees a redrawn widget's old primitives. docs/RUST.md's
 "Stale primitives, the phone's half" box has the full account, the guard
 (`orphaned_primitives`, `debug_assert`ed every frame) and the emulator run
 that exercises it.
 ```
 iris bench report
 per phase:
  fling: 1783 frames over 53.2s
    late: 104 (5.8%)
      total  p50 3.8ms  p90 6.9ms  p99 12.6ms
    worst 29.1ms
  stream: 401 frames over 21.3s
    late: 306 (76.3%)
      total  p50 18.2ms  p90 35.8ms  p99 43.1ms
    worst 43.8ms
  type: 1202 frames over 65.7s
    late: 309 (25.7%)
      total  p50 7.2ms  p90 9.2ms  p99 11.2ms
    worst 15.3ms
  keyboard: 9 frames over 9.7s
    late: 9 (100.0%)
      total  p50 12.0ms  p90 12.9ms  p99 12.9ms
    worst 12.9ms
 frames:
  3395 frames over 149.9s at 120Hz (8.3ms budget)
  late: 728 (21.4%)
  total  p50 5.0ms  p90 10.9ms  p99 36.6ms
  worst 43.8ms
  cpu_p50 2.0ms  gpu_wait_p50 2.6ms
 bench:
  fling: 8 flings out + 8 back at 12000px/s, travel start=idx=651/off=1217px outward=idx=651/off=101536px end=idx=651/off=1022px
  scroll: 6 cycles (24 swipes, legacy tween), streamed 400/400 fixture events
  type: 600 characters inserted then deleted, one per 50ms
  keyboard: could not be shown (5 attempts, 0 confirmed visible)
  process CPU time over this run: 40603ms
  peak RSS: 379156kB
  battery current: mean -452353µA over 149 samples (min -1753125, max -204687)
 ```
@@ -721,6 +721,7 @@ name = "client-core"
 version = "0.1.0"
 dependencies = [
 "event-model",
 "pulldown-cmark",
 "serde",
 "serde_json",
 "ureq",
@@ -15,6 +15,11 @@ wgpu = { workspace = true }
 image = { workspace = true }
 accesskit = { workspace = true }
 tokio = { workspace = true, features = ["sync", "rt", "rt-multi-thread"] }
 # For diagnostics visible through android_logger (or whatever logger the
 # app crate installs) -- this crate never installs one itself. Not in the
 # android-only block below any more: the lines that matter most are in
 # shared widget code, which the host backend compiles too.
 log = "0.4.28"
 # winit everywhere except Android; android-view (below) is what stands in
 # for it there. Both backends live in this crate (see `src/android/mod.rs`'s
@@ -53,9 +58,6 @@ accesskit_android = "0.8.0"
 # for `android/insets.rs`'s own id -> state map -- the same reason
 # android-view's own `PEER_MAP` carries one.
 send_wrapper = "0.6.0"
 # For diagnostics visible through android_logger, wherever the app crate
 # installs it -- this crate never installs a logger itself.
 log = "0.4.28"
 [features]
 # RUST.md's I5 "Where iris's frame time goes" diagnosis: forces the Android
@@ -745,6 +745,7 @@ name = "client-core"
 version = "0.1.0"
 dependencies = [
 "event-model",
 "pulldown-cmark",
 "serde",
 "serde_json",
 "ureq",
@@ -31,6 +31,25 @@ 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();
@@ -52,6 +52,11 @@ if [ -z "$NDK_DIR" ]; then
 fi
 export ANDROID_NDK_HOME="$NDK_DIR"
 # Only the ABI asked for goes into the APK. cargo ndk adds its output beside
 # whatever earlier builds left here, and Gradle packages every directory it
 # finds -- a debug x86_64 emulator build left behind made an arm64 "release"
 # 339 MB on 2026-09-06.
 rm -rf app/src/main/jniLibs
 echo "build-apk.sh: cargo ndk -t $ABI build ${BUILD_TYPE:+(${BUILD_TYPE})} --features \"$FEATURES\""
 if [ "$BUILD_TYPE" = "release" ]; then
    cargo ndk -t "$ABI" -P 26 -o app/src/main/jniLibs/ build --release --features "$FEATURES"
@@ -51,9 +51,14 @@ ui-trace record -s "$SERIAL" -d 3000 --do "tap 'Run benchmark'" -o /tmp/run-benc
 # phase, ~61s of typing, 10s of keyboard toggles, roughly 2.5 minutes end
 # to end) but device speed varies. 260s cap rather than v1's 90s -- v2 is
 # a longer script than v1's swipe-loop-only run.
 # The report's own first line, not the bare "iris bench report:" prefix:
 # `copy_report` logs that prefix too ("nothing to copy -- run the benchmark
 # first", which the app emits at startup), so polling for the prefix
 # returned instantly and the script printed a report that was never run.
 REPORT_LINE="iris bench report: iris bench report"
 i=0
 while [ "$i" -lt 260 ]; do
-    LINE=$(adb -s "$SERIAL" logcat -d -s iris-android-app:I 2>/dev/null | grep "iris bench report:" || true)
+    LINE=$(adb -s "$SERIAL" logcat -d -s iris-android-app:I 2>/dev/null | grep "$REPORT_LINE" || true)
    if [ -n "$LINE" ]; then
        break
    fi
@@ -66,4 +71,4 @@ if [ -z "$LINE" ]; then
 fi
 # -A 60 rather than v1's -A 6 -- v2's report has a per-phase block (four
 # phases, four lines each) on top of the frames/bench sections v1 had.
-adb -s "$SERIAL" logcat -d -s iris-android-app:I | grep -A 60 "iris bench report:"
+adb -s "$SERIAL" logcat -d -s iris-android-app:I | grep -A 60 "$REPORT_LINE"
@@ -92,6 +92,12 @@ 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
 /// nothing at all; see `new`'s comment at the tree it is used in.
 const REPORT_MAX_HEIGHT_DP: f32 = 260.0;
 pub struct BenchClient {
    ui_state: AndroidUiState,
    content: WeakWidget<WidgetPtr>,
@@ -221,8 +227,15 @@ fn battery_line(samples: &[i32]) -> String {
        return "  battery current: unavailable on this device".to_string();
    }
    let mean = samples.iter().map(|&v| v as i64).sum::<i64>() / samples.len() as i64;
-    let min = samples.iter().min().unwrap();
+    // `min`/`max` are guarded by the `is_empty` check above, three lines
-    let max = samples.iter().max().unwrap();
+    // up -- pairing the `Option` unwraps with the emptiness check right
    // here (rather than two statements apart, with `mean` in between
    // reading the same slice) is what keeps a future reorder from
    // separating the guard from what it protects (docs/
    // REVIEW-2026-09-06.md finding 7).
    let (Some(min), Some(max)) = (samples.iter().min(), samples.iter().max()) else {
        unreachable!("samples is non-empty, checked above");
    };
    format!(
        "  battery current: mean {mean}\u{b5}A over {} samples (min {min}, max {max})",
        samples.len()
@@ -248,10 +261,28 @@ impl AndroidAppState for BenchClient {
        let top_bar = WidgetPtr::new().add(rsc);
        let controls = bench_controls(rsc, 0.0);
        top_bar(rsc).set(controls);
        // The report pane is sized to whatever report it is holding, not
        // to a share of the window: `rest(1)` here reserved a third of
        // the screen for an *empty* `TextEdit` at every launch, which is
        // what Iris's 2026-09-06 11:39 phone report described as "the app
        // does not start with keyboard spacing correct" -- the composer
        // two thirds down with black below it, nothing to do with the IME
        // inset (measured: `iris insets:` reports bottom=63 ime_bottom=0
        // at launch, while the `Message` field's own box sat 789px above
        // the bottom of a 2282px surface -- exactly this pane's third).
        // Capped and scrollable so a long report cannot take the screen
        // back over, the same idiom `composer.rs` uses for the field.
        // Above the transcript, not below it: the report is what the
        // header's own "Run benchmark" button produces (UI_RULES.md --
        // results appear where the action was started), and a pane under
        // the composer would eat the navigation-bar clearance
        // `set_bottom_inset` gives it.
        let tree = (
            top_bar,
-            content.height(rest(2)),
+            report_display
-            report_display.height(rest(1)).pad(dp(8)),
+                .pad(dp(8))
                .max_height(dp(REPORT_MAX_HEIGHT_DP)),
            content.height(rest(1)),
        )
            .span(Dir::DOWN)
            .add_strong(rsc)
@@ -365,6 +396,18 @@ impl AndroidAppState for BenchClient {
            (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();
@@ -511,47 +554,43 @@ impl BenchClient {
    /// 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 report = self.diagnostics_text(rsc);
        self.report_display.edit(rsc).set(&report);
        self.last_report = Some(report);
    }
    /// The diagnostics report as text, with no side effect on what is on
    /// screen -- shared by the `Diagnostics` button (which shows it) and
    /// the keyboard-open capture (which only logs it), so the two can
    /// never drift into reporting different things.
    fn diagnostics_text(&self, rsc: &mut Rsc) -> String {
        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 {
+        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
+    /// doc comment. **Logged only.** It used to also copy the report to
-    /// same text the on-screen `Diagnostics` button produces, plus the
+    /// the clipboard unprompted and put it in the shell's overlay view,
-    /// per-frame log `FrameReport` already keeps around the resize --
+    /// from when the keyboard-inset callback was not firing at all and a
-    /// `frame_report.report()` above covers "the frames around the
+    /// report could not be got off the phone any other way. Both are gone
-    /// resize" without a second accounting mechanism), then does three
+    /// as of 2026-09-06: the callback fires reliably now (edge-to-edge,
-    /// things the button does not: logs it (so a `logcat` pull gets it
+    /// `MainActivity.java`), and the overlay covered the whole screen on
-    /// even if nothing on screen does), copies it to the clipboard
+    /// *every* keyboard open with its own Copy/Close buttons underneath
-    /// unprompted, and shows it in the shell's plain overlay view, which
+    /// the keyboard, so it could not be dismissed -- an interruption for
-    /// draws independently of iris's own renderer -- the whole point,
+    /// something nobody asked for, over an app you are trying to type
-    /// since the renderer is exactly what might be in the wiped state
+    /// into (UI_RULES.md). The named `Diagnostics` button still shows the
-    /// this exists to report on.
+    /// same text on demand, and `iris surface:`/`iris insets:` (view.rs)
    /// carry the lifecycle a `logcat` pull actually needs.
    fn capture_keyboard_diagnostics(&mut self, rsc: &mut Rsc) {
-        self.show_diagnostics(rsc);
+        let report = self.diagnostics_text(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) {
@@ -142,7 +142,7 @@ fn bench_first_frame(n: usize) {
    let start = Instant::now();
    render.update(&root, &mut rsc);
    let elapsed = start.elapsed();
-    let (draws, rewrites, moves) = render.take_counters();
+    let (draws, rewrites, moves, _shapes) = render.take_counters();
    report(
        &format!("(a) first frame, N={n}"),
        elapsed,
@@ -177,7 +177,7 @@ fn bench_scroll(n: usize, ticks: usize) {
        let start = Instant::now();
        render.update(&root, &mut rsc);
        total += start.elapsed();
-        let (draws, rewrites, moves) = render.take_counters();
+        let (draws, rewrites, moves, _shapes) = render.take_counters();
        total_draws += draws;
        total_rewrites += rewrites;
        total_moves += moves;
@@ -245,7 +245,7 @@ fn bench_input_grows(n: usize, lines: usize) {
        let start = Instant::now();
        render.update(&root, &mut rsc);
        total += start.elapsed();
-        let (draws, rewrites, moves) = render.take_counters();
+        let (draws, rewrites, moves, _shapes) = render.take_counters();
        total_draws += draws;
        total_rewrites += rewrites;
        total_moves += moves;
@@ -302,7 +302,7 @@ fn bench_insert_above_anchor(n: usize, inserts: usize) {
        let start = Instant::now();
        render.update(&root, &mut rsc);
        total += start.elapsed();
-        let (draws, rewrites, moves) = render.take_counters();
+        let (draws, rewrites, moves, _shapes) = render.take_counters();
        total_draws += draws;
        total_rewrites += rewrites;
        total_moves += moves;
@@ -384,7 +384,7 @@ fn bench_expand_holds_edge(n: usize, growths: usize) {
        let start = Instant::now();
        render.update(&root, &mut rsc);
        total += start.elapsed();
-        let (draws, rewrites, moves) = render.take_counters();
+        let (draws, rewrites, moves, _shapes) = render.take_counters();
        total_draws += draws;
        total_rewrites += rewrites;
        total_moves += moves;
@@ -147,6 +147,29 @@ impl Len {
        }
    }
    /// The same fold as [`Self::apply_rest`] but staying a `Len`, so
    /// `rest` survives: `dp` becomes physical pixels and every other
    /// component is left alone.
    ///
    /// **A `Len` a widget *reports* must have been through this.** `dp` is
    /// an input unit -- a number the widget author wrote -- and the
    /// containers that consume a reported length read `abs`/`rel`/`rest`
    /// directly (`Span::draw`'s placement arithmetic, `Pad`'s addition),
    /// so a reported `dp` is silently worth zero. That is what made the
    /// composer's bar collapse to nothing the moment its content grew past
    /// `MaxSize`'s cap: the cap was `dp(168)` and was returned unresolved,
    /// so the bar was given a slot of 0 and the field inside it was panned
    /// out of a container measured at -63px. `UiRenderState::draw_inner`
    /// debug-asserts the invariant after every `Widget::draw`.
    pub fn fold_dp(&self, density: f32) -> Self {
        Self {
            abs: self.abs + self.dp * density,
            dp: 0.0,
            rel: self.rel,
            rest: self.rest,
        }
    }
    pub fn abs(abs: impl UiNum) -> Self {
        Self {
            abs: abs.to_f32(),
@@ -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;
@@ -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 {
@@ -245,6 +245,15 @@ impl FrameReport {
    /// this once per phase (fling/stream/type/keyboard) so `phase_stats`
    /// can slice one whole run's frames by what was happening during each.
    pub fn mark_phase(&mut self, name: &str) {
        // `phase_stats`'s slicing (`idx >= phase.start_index && idx <
        // end_index`) silently produces an empty or nonsensical slice for
        // a phase pushed out of order rather than surfacing the misuse
        // (docs/REVIEW-2026-09-06.md finding 5).
        debug_assert!(
            self.phases
                .last()
                .is_none_or(|p| self.total_frames >= p.start_index)
        );
        self.phases.push(PhaseMark {
            name: name.to_string(),
            start_index: self.total_frames,
@@ -6,6 +6,7 @@ use crate::{
        ArrBuf,
        data::{MaskIdx, MoveIdx, PrimitiveInstance},
    },
    util::HashSet,
 };
 use bytemuck::Pod;
 use wgpu::*;
@@ -277,6 +278,31 @@ impl Primitives {
        }
    }
    /// How many instances are still bound for the GPU -- the O(1) half of
    /// the orphan check, so the O(primitives) walk below only runs on a
    /// frame that already looks wrong. See
    /// [`crate::UiRenderState::orphaned_primitives`].
    pub fn live_count(&self) -> usize {
        (self.instances.len() - self.free.len()) + (self.images.len() - self.image_free.len())
    }
    /// Every instance that is still bound for the GPU, as `(inst_idx,
    /// owner, is_image)` -- everything except the slots already handed to
    /// [`Self::free`] and waiting for [`Self::apply_free`] to compact them
    /// away. Only [`crate::UiRenderState::orphaned_primitives`] uses this,
    /// to check that every drawn primitive still belongs to a live widget.
    pub fn live_instances(&self) -> impl Iterator<Item = (usize, WidgetId, bool)> + '_ {
        let free: HashSet<usize> = self.free.iter().copied().collect();
        let image_free: HashSet<usize> = self.image_free.iter().copied().collect();
        let rects = (0..self.instances.len())
            .filter(move |i| !free.contains(i))
            .map(|i| (i, self.assoc[i], false));
        let images = (0..self.images.len())
            .filter(move |i| !image_free.contains(i))
            .map(|i| (i, self.image_assoc[i], true));
        rects.chain(images)
    }
    pub fn data(&self) -> &PrimitiveData {
        &self.data
    }
@@ -1,4 +1,6 @@
-use crate::{LayerId, MaskIdx, MoveIdx, PrimitiveHandle, Size, TextureHandle, UiRegion, WidgetId};
+use crate::{
    LayerId, MaskIdx, MoveIdx, PrimitiveHandle, Size, TextureHandle, UiRegion, WidgetId, util::Vec2,
 };
 /// important non rendering data for retained drawing
 #[derive(Debug)]
@@ -9,7 +11,22 @@ pub struct ActiveData {
    pub textures: Vec<TextureHandle>,
    pub primitives: Vec<PrimitiveHandle>,
    pub children: Vec<WidgetId>,
    /// The mask this widget was drawn **under** (its parent's), not the
    /// one it set for itself -- see `own_mask` for that.
    pub mask: MaskIdx,
    /// The mask slot this widget allocated for *itself* with
    /// `Painter::set_mask`, or `MaskIdx::NONE`. Kept across redraws and
    /// rewritten in place, the way `move_slot` is: a `Masked` that pushed
    /// a fresh slot each draw left every already-drawn descendant --
    /// which `draw_inner`'s unchanged-region fast path does not revisit --
    /// clipping to the *old* slot's region, so a composer whose bar had
    /// since been placed at the bottom of the screen was still being
    /// clipped to a box at the top of it and drew nothing (measured
    /// 2026-09-06: four mask entries live, none of them the widget's
    /// current region). Its path out is the `undraw` branch of
    /// `UiRenderState::remove`, which drops the self-ownership ref taken
    /// when the slot was allocated.
    pub own_mask: MaskIdx,
    pub layer: LayerId,
    /// What `Widget::draw` returned the last time this widget was actually
    /// drawn -- read by a parent placing this widget again without
@@ -21,4 +38,19 @@ pub struct ActiveData {
    /// so a retained child's `parent` link never goes stale). See
    /// LAYOUT.md section 2.
    pub move_slot: MoveIdx,
    /// How much of this widget's own `move_slot` delta is already folded
    /// into `region` above, in window pixels. The two mechanisms that
    /// write that slot disagree about this and cannot be told apart from
    /// the slot alone: `UiRenderState::mov` shifts `region` and the delta
    /// together (the *offered* region genuinely moved), while
    /// `Painter::reposition` writes only the delta (`region` stays the
    /// offered box and the delta says where inside it the content was
    /// placed). So anything that wants the widget's real position --
    /// `resolved_region`, and through it every hit test -- must subtract
    /// this from the chain sum. Without it a panned widget's own hit box
    /// sits at twice the pan while its descendants' are correct, which is
    /// how it went unnoticed: the composer's field became untappable
    /// after a finger pan (2026-09-06). Reset to zero whenever the widget
    /// is really redrawn, since `draw_inner` zeroes the slot then too.
    pub move_applied: Vec2,
 }
@@ -13,6 +13,10 @@ pub struct Painter<'a> {
    pub(super) region: UiRegion,
    pub(super) mask: MaskIdx,
    pub(super) move_slot: MoveIdx,
    /// This widget's own mask slot, reused across redraws -- see
    /// `ActiveData::own_mask`. `MaskIdx::NONE` until `set_mask` is called
    /// for the first time in this widget's life.
    pub(super) own_mask: MaskIdx,
    pub(super) textures: Vec<TextureHandle>,
    pub(super) primitives: Vec<PrimitiveHandle>,
    pub(super) children: Vec<WidgetId>,
@@ -48,12 +52,32 @@ impl<'a> Painter<'a> {
        self.primitive_at(primitive, region.within(&self.region));
    }
    /// Clip everything this widget draws, itself and its descendants, to
    /// `region`. One per widget: a second call would need the two to be
    /// intersected, which nothing here does.
    ///
    /// The slot is allocated once and **rewritten in place** on every
    /// later draw rather than pushed again, because a descendant whose own
    /// region did not change is not redrawn (`draw_inner`'s fast path) and
    /// so keeps pointing at whichever slot it was drawn under. See
    /// `ActiveData::own_mask` for what pushing a fresh one cost.
    pub fn set_mask(&mut self, region: UiRegion) {
        assert!(self.mask == MaskIdx::NONE);
-        self.mask = self.rsc.ui_mut().masks.push(Mask {
+        let mask = Mask {
            region,
            move_idx: self.move_slot,
-        });
+        };
        if self.own_mask == MaskIdx::NONE {
            let slot = self.rsc.ui_mut().masks.push(mask);
            // The one ref this widget holds on its own slot, so the slot
            // outlives any single frame's primitives; released in
            // `UiRenderState::remove`'s `undraw` branch.
            self.rsc.ui_mut().masks.push_ref(slot);
            self.own_mask = slot;
        } else {
            *self.rsc.ui_mut().masks.get_mut(self.own_mask) = mask;
        }
        self.mask = self.own_mask;
    }
    /// Draws a widget within this widget's region, returning the size it
@@ -86,6 +110,7 @@ impl<'a> Painter<'a> {
            self.mask,
            None,
            None,
            crate::render::MaskIdx::NONE,
            self.rsc,
        );
        self.state
@@ -166,6 +191,10 @@ impl<'a> Painter<'a> {
        width: Option<f32>,
    ) -> RenderedText {
        let density = self.state.density;
        // Counted here rather than in `TextView::render`, which returns
        // its memoized layout without reaching this -- so this counts
        // shapes, not requests. `UiRenderState::take_counters`.
        self.state.shape_count += 1;
        let ui = self.rsc.ui_mut();
        ui.text
            .render(buffer, attrs, width, &mut ui.textures, density)
@@ -1,7 +1,7 @@
 use crate::{
    ActiveData, IdLike, MaskIdx, MoveIdx, Painter, PixelRegion, PrimitiveLayers, RegionAlign,
    StrongWidget, UiRegion, UiRsc, UiVec2, WidgetId, Widgets,
-    render::MoveOffset,
+    render::{IMAGE_BINDING, MoveOffset},
    util::{HashMap, HashSet, Id, Vec2},
 };
@@ -18,8 +18,35 @@ pub struct UiRenderState {
    old_root: Option<WidgetId>,
    resized: bool,
    /// The widgets whose `Widget::draw` is on the stack right now -- so
    /// [`Self::redraw`] can tell "this widget needs drawing again" from
    /// "an ancestor is drawing it at this very moment", where a second
    /// draw would leave the first one's primitives behind with nothing
    /// owning them. An id is inserted immediately before `draw` is called
    /// and removed the moment it returns (both in `draw_inner`), so this
    /// is empty between frames -- asserted at the end of `update`.
    ///
    /// It used to only ever be inserted into, and `redraw` removed the id
    /// *before* testing for it, which made the test constant `false`: the
    /// guard could never fire and the set grew by one entry per widget
    /// ever drawn and was never emptied.
    draw_started: HashSet<WidgetId>,
    /// The widget currently holding exclusive pointer input, if any --
    /// `iris::sense::SensorUi::run_sensors` reads and clears this every
    /// call. Interior mutability (a `Mutex`, not a bare `Cell`, since a
    /// `CursorData` reaching this through an async `task_on` handler needs
    /// `Send`/`Sync`) because `run_sensors` takes `&self` (widgets are
    /// dispatched to, not owned, at that layer) and this render state is
    /// the one structure both backends (winit, android-view) already hold
    /// across frames, the same way `old_root`/`resized` are -- see
    /// `iris::sense`'s pointer-capture doc for why a drag needs this: once
    /// a gesture has committed to panning or selecting, every later sample
    /// of it must reach the same widget even if the finger has moved off
    /// whatever hit region first noticed the press. Never held across an
    /// await or another lock -- every access here is a single get/set.
    captured: std::sync::Mutex<Option<WidgetId>>,
    /// `Widget::draw` calls and `Primitives::region_mut` rewrites since the
    /// last `take_counters`. LAYOUT.md section 8's pass conditions are
    /// stated in terms of these two: an unchanged frame must cost 0 of
@@ -28,6 +55,9 @@ pub struct UiRenderState {
    draw_count: u64,
    region_mut_count: u64,
    mov_count: u64,
    /// Text layouts actually computed -- bumped by `Painter::render_text`,
    /// which `TextView::render` only reaches on a cache miss.
    pub(super) shape_count: u64,
 }
 /// A move chain more than this deep would mean something else is wrong
@@ -45,20 +75,29 @@ impl UiRenderState {
            old_root: None,
            resized: false,
            draw_started: Default::default(),
            captured: Default::default(),
            draw_count: 0,
            region_mut_count: 0,
            mov_count: 0,
            shape_count: 0,
        }
    }
    /// Reads and zeroes the (draws, region_mut rewrites, move_offsets
-    /// writes) counters -- call once per frame before `update()` to
+    /// writes, text shapes) counters -- call once per frame before
-    /// measure exactly that frame, per LAYOUT.md section 8.
+    /// `update()` to measure exactly that frame, per LAYOUT.md section 8.
-    pub fn take_counters(&mut self) -> (u64, u64, u64) {
+    ///
    /// The fourth is the one a draw count cannot stand in for: a widget
    /// can be redrawn without re-shaping (`TextView::render` memoizes by
    /// width) and re-shaped without any extra draw, and it is re-shaping
    /// that the per-block transcript row exists to avoid -- see
    /// `transcript_ui`'s `a_delta_into_a_long_reply_shapes_one_block`.
    pub fn take_counters(&mut self) -> (u64, u64, u64, u64) {
        (
            std::mem::take(&mut self.draw_count),
            std::mem::take(&mut self.region_mut_count),
            std::mem::take(&mut self.mov_count),
            std::mem::take(&mut self.shape_count),
        )
    }
@@ -99,6 +138,11 @@ impl UiRenderState {
            );
        }
        let root = root.into();
        debug_assert!(
            self.draw_started.is_empty(),
            "a previous frame left {} widget(s) marked as mid-draw",
            self.draw_started.len(),
        );
        if self.needs_redraw_all(root) {
            self.redraw_all(root, rsc);
            self.old_root = root.map(|r| r.id());
@@ -106,6 +150,8 @@ impl UiRenderState {
        } else if rsc.widgets().has_updates() {
            self.redraw_updates(rsc);
        }
        #[cfg(debug_assertions)]
        debug_assert!(self.primitive_counts_agree(), "{}", self.orphan_report(rsc),);
    }
    fn redraw_all(&mut self, root: Option<&StrongWidget>, rsc: &mut dyn UiRsc) {
@@ -121,6 +167,7 @@ impl UiRenderState {
                MaskIdx::NONE,
                None,
                None,
                MaskIdx::NONE,
                rsc,
            );
        }
@@ -155,12 +202,27 @@ impl UiRenderState {
        mask: MaskIdx,
        old_children: Option<Vec<WidgetId>>,
        old_move_slot: Option<MoveIdx>,
        old_own_mask: MaskIdx,
        rsc: &mut dyn UiRsc,
    ) {
        let mut old_children = old_children.unwrap_or_default();
        let mut old_move_slot = old_move_slot;
        let mut own_mask = old_own_mask;
        // Consumed here, not merely read: this call *is* the redraw the mark
        // asked for, and leaving the mark set is what stranded a widget's
        // primitives. `Painter::draw_twice` calls this twice for the same id
        // in one frame (`List::place`'s measurement pass), and on the second
        // call the still-set mark took the whole `if let` below -- including
        // the `remove` that frees the first draw's primitives -- out of play,
        // so `active.insert` at the end overwrote the only handles that could
        // ever have freed them. The result is a full second copy of the row,
        // drawn every frame from then on at the oversized measurement region
        // and, with `List` setting no mask, outside the list's own bounds:
        // the doubled `Compacted:` row in docs/bench/iris-phone-v2-2026-09-06.md.
        // The same shape reaches any dirty widget an ancestor redraws first.
        let dirty = rsc.widgets_mut().needs_redraw.remove(&id);
        if let Some(active) = self.active.get_mut(&id)
-            && !rsc.widgets().needs_redraw.contains(&id)
+            && !dirty
        {
            // check to see if we can skip drawing first
            if active.region == region {
@@ -187,6 +249,15 @@ impl UiRenderState {
                    *r = r.outside(&from).within(&region);
                    self.region_mut_count += 1;
                }
                // `move_applied` is deliberately **not** touched here,
                // unlike in `mov`: it counts the part of this widget's own
                // move-slot delta that `region` has already absorbed, and
                // this branch writes no delta at all -- the primitives were
                // moved directly. Counting one would make
                // `resolved_region` subtract a distance the chain never
                // held, putting the hit box short of the drawing by
                // exactly this step. See `ActiveData::move_applied`, and
                // `a_size_independent_widget_moved_by_its_parent_has_the_hit_box_it_is_drawn_at`.
                active.region = region;
                return;
            }
@@ -194,10 +265,25 @@ impl UiRenderState {
            let active = self.remove(id, false, rsc).unwrap();
            old_children = active.children;
            old_move_slot = Some(active.move_slot);
            own_mask = active.own_mask;
        } else if dirty && self.active.contains_key(&id) {
            // Dirty and already drawn: none of the fast paths above may be
            // taken (the widget's own content changed, so its old primitives
            // say nothing about its new ones), but they are also the only
            // thing that frees them. Same two lines, reached the other way.
            let active = self.remove(id, false, rsc).unwrap();
            old_children = active.children;
            old_move_slot = Some(active.move_slot);
            own_mask = active.own_mask;
        }
        // draw widget
-        self.draw_started.insert(id);
+        let reentrant = !self.draw_started.insert(id);
        debug_assert!(
            !reentrant,
            "widget {id:?} is being drawn while its own draw is already on the stack; \
             the second draw's primitives would orphan the first's"
        );
        let move_slot = match old_move_slot {
            // Reused across a real redraw of the same id: the fresh
@@ -226,11 +312,22 @@ impl UiRenderState {
            }
        };
        // The mask this widget was drawn *under*, kept aside because
        // `Painter::set_mask` overwrites `painter.mask` with the widget's
        // own new one -- and `ActiveData::mask`'s only consumer is
        // `redraw`, which feeds it back in as the *inherited* mask. Storing
        // the set one instead handed a `Masked` its own mask on every
        // targeted redraw, tripping `set_mask`'s nested-mask assert:
        // `assertion failed: self.mask == MaskIdx::NONE`, an abort the
        // first time the composer's scroll area was redrawn on the
        // emulator.
        let inherited_mask = mask;
        let mut painter = Painter {
            state: self,
            region,
            mask,
            move_slot,
            own_mask,
            layer,
            id,
            textures: Vec::new(),
@@ -242,14 +339,26 @@ impl UiRenderState {
        let mut widget = painter.rsc.widgets().get_dyn_dynamic(id);
        painter.state.draw_count += 1;
        let size = widget.draw(&mut painter);
        // A reported length is consumed by containers that read `abs`,
        // `rel` and `rest` straight off it (`Span`'s placement, `Pad`'s
        // addition), so an unresolved `dp` in one is silently worth zero
        // -- see `Len::fold_dp`, which is what a widget reporting a
        // caller-declared size has to put it through.
        debug_assert!(
            size.x.dp == 0.0 && size.y.dp == 0.0,
            "widget {id:?} reported an unresolved `dp` size ({size:?}); \
             report `Len::fold_dp(painter.density())` instead"
        );
        drop(widget);
        painter.state.draw_started.remove(&id);
        let Painter {
            state: _,
            rsc: _,
            region,
-            mask,
+            mask: _,
            move_slot,
            own_mask,
            textures,
            primitives,
            children,
@@ -265,10 +374,12 @@ impl UiRenderState {
            textures,
            primitives,
            children,
-            mask,
+            mask: inherited_mask,
            layer,
            size,
            move_slot,
            own_mask,
            move_applied: Vec2::ZERO,
        };
        // remove old children that weren't kept
@@ -296,6 +407,7 @@ impl UiRenderState {
        let from_px = from.top_left().to_abs(self.output_size);
        let to_px = to.top_left().to_abs(self.output_size);
        let delta = to_px - from_px;
        active.move_applied += delta;
        let entry = rsc.ui_mut().move_offsets.get_mut(slot);
        entry.delta[0] += delta.x;
        entry.delta[1] += delta.y;
@@ -330,6 +442,12 @@ impl UiRenderState {
        let Some(active) = self.active.get(&id) else {
            return;
        };
        debug_assert!(
            active.move_applied == Vec2::ZERO,
            "widget {id:?} is both moved by its parent's own layout (`mov`) and repositioned \
             within it; the two write the same slot with different conventions -- see \
             `ActiveData::move_applied`"
        );
        let from = active
            .size
            .to_uivec2(self.density)
@@ -357,6 +475,13 @@ 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
@@ -364,6 +489,11 @@ impl UiRenderState {
                // the parent's own `ActiveData` may already be gone by the
                // time a deep descendant is retired (see LAYOUT.md
                // section 2's lifecycle note).
                if active.own_mask != MaskIdx::NONE {
                    // The self-ownership ref `Painter::set_mask` took when
                    // it allocated this widget's own mask slot.
                    rsc.ui_mut().masks.remove(active.own_mask);
                }
                let parent_slot = rsc.ui_mut().move_offsets[active.move_slot.idx()].parent;
                rsc.ui_mut().move_offsets.remove(active.move_slot);
                if parent_slot != MoveOffset::NONE_PARENT {
@@ -429,6 +559,100 @@ impl UiRenderState {
        self.active.len()
    }
    /// Primitive instances still bound for the GPU whose owner is no
    /// longer in `active`, or whose owner's `ActiveData` no longer names
    /// them: a copy nothing can move, clip, resize or free, redrawn every
    /// frame at whatever position it last had. `(layer, inst_idx, owner)`
    /// each.
    ///
    /// Asserted empty at the end of every [`Self::update`], because this
    /// is exactly the shape of the duplicated transcript row on Iris's
    /// phone (`docs/bench/iris-phone-v2-2026-09-06.md`): counting
    /// `active` alone cannot see it, since the orphan's owner is very
    /// much alive -- it is the *earlier* set of primitives that got
    /// stranded when the widget was drawn a second time without the first
    /// draw being freed. O(primitives), debug builds only.
    pub fn orphaned_primitives(&self) -> Vec<(usize, usize, WidgetId)> {
        let mut orphans = Vec::new();
        for (layer, primitives) in self.layers.iter() {
            for (inst_idx, owner, is_image) in primitives.live_instances() {
                let owned = self.active.get(&owner).is_some_and(|a| {
                    a.primitives.iter().any(|h| {
                        h.layer == layer
                            && h.inst_idx == inst_idx
                            && (h.binding == IMAGE_BINDING) == is_image
                    })
                });
                if !owned {
                    orphans.push((layer, inst_idx, owner));
                }
            }
        }
        orphans
    }
    /// Whether every primitive still bound for the GPU is owned by a live
    /// widget, decided by counting rather than by walking: an orphan is a
    /// live instance no `ActiveData` names, so it can only ever make the
    /// live count exceed the owned one. O(active widgets) -- a few dozen --
    /// against [`Self::orphaned_primitives`]'s O(primitives), which on a
    /// transcript is tens of thousands and made a debug build on a phone
    /// too slow to finish a benchmark run.
    fn primitive_counts_agree(&self) -> bool {
        let live: usize = self.layers.iter().map(|(_, p)| p.live_count()).sum();
        let owned: usize = self.active.values().map(|a| a.primitives.len()).sum();
        live == owned
    }
    /// The message [`Self::update`]'s orphan assert prints -- built here
    /// rather than inline so the (allocating, O(primitives)) work only
    /// happens on the failing path.
    #[cfg(debug_assertions)]
    fn orphan_report(&self, rsc: &dyn UiRsc) -> String {
        let orphans = self.orphaned_primitives();
        let mut lines: Vec<String> = orphans
            .iter()
            .take(8)
            .map(|(layer, idx, owner)| {
                let alive = self.active.contains_key(owner);
                format!(
                    "  layer {layer} instance {idx}: owner '{}' ({owner:?}),                      owner still active: {alive}",
                    rsc.widgets().label(*owner),
                )
            })
            .collect();
        if orphans.len() > lines.len() {
            lines.push(format!("  ... and {} more", orphans.len() - lines.len()));
        }
        format!(
            "{} primitive(s) are drawn but owned by nobody -- a stale copy \
             nothing will ever move or free:\n{}",
            orphans.len(),
            lines.join("\n"),
        )
    }
    /// Give `id` exclusive pointer input from the next `run_sensors` call
    /// on -- see `captured`'s field doc. Overwrites any previous capture
    /// (a gesture that starts a new one has already decided the old one
    /// is over).
    pub fn capture_pointer(&self, id: WidgetId) {
        *self.captured.lock().unwrap() = Some(id);
    }
    /// Release exclusive pointer input, if any is held -- called once
    /// `run_sensors` has delivered the terminal `Drop` to the capturing
    /// widget, or by that widget itself if it decides the gesture is over
    /// some other way.
    pub fn release_pointer(&self) {
        *self.captured.lock().unwrap() = None;
    }
    /// The widget currently holding exclusive pointer input, if any.
    pub fn captured_pointer(&self) -> Option<WidgetId> {
        *self.captured.lock().unwrap()
    }
    pub fn debug(&self, widgets: &Widgets, label: &str) -> impl Iterator<Item = &ActiveData> {
        self.active.iter().filter_map(move |(&id, inst)| {
            let l = widgets.label(id);
@@ -455,7 +679,12 @@ impl UiRenderState {
    /// section 2b.
    pub fn resolved_region(&self, id: &impl IdLike, rsc: &dyn UiRsc) -> Option<UiRegion> {
        let active = self.active.get(&id.id())?;
-        let delta = self.resolve_move_chain(active.move_slot, rsc);
+        // The chain sum is what the shader adds to this widget's
        // *primitives*, which were written before any of those moves.
        // `region`, unlike them, has already been shifted by whatever
        // part of this widget's own slot `mov` put there -- see
        // `ActiveData::move_applied`, which is exactly that part.
        let delta = self.resolve_move_chain(active.move_slot, rsc) - active.move_applied;
        Some(active.region.offset(UiVec2::abs(delta)))
    }
@@ -491,7 +720,10 @@ impl UiRenderState {
    /// redraws a widget that's currently active (drawn)
    pub fn redraw(&mut self, id: WidgetId, rsc: &mut dyn UiRsc) {
        rsc.widgets_mut().needs_redraw.remove(&id);
-        self.draw_started.remove(&id);
+        // An ancestor is drawing this widget right now, and that draw is
        // about to write fresh primitives for it. Drawing it a second time
        // here would leave one of the two copies on screen with nothing
        // owning it -- see `draw_started`'s own doc.
        if self.draw_started.contains(&id) {
            return;
        }
@@ -515,9 +747,9 @@ impl UiRenderState {
            active.mask,
            Some(active.children),
            Some(active.move_slot),
            active.own_mask,
            rsc,
        );
        // If this widget's own reported size changed, its parent's layout
        // (which placed it using the old size) is now stale and needs to
        // relay out too. Checked after the real draw, not before it --
@@ -12,6 +12,10 @@ impl<T: HasAndroidUiState> FocusHost for T {
        self.android_state_mut().focus = id;
    }
    fn is_focused(&self, id: WeakWidget<TextEdit>) -> bool {
        self.android_state().focus == Some(id)
    }
    fn focus_gained(&mut self, region: Option<PixelRegion>) {
        // Showing the keyboard is a JNI call (`InputMethodManager.showSoftInput`),
        // and this runs deep inside the platform-agnostic sensor dispatch
@@ -49,6 +49,52 @@ impl<State: AndroidAppState> IrisViewPeer<State> {
    fn focus(&self) -> Option<WeakWidget<TextEdit>> {
        self.state.android_state().focus
    }
    /// Tell Gboard where the caret/selection and the composing region
    /// actually are, via `InputMethodManager.updateSelection` -- every one
    /// of android-view's own demo's `set_composing_text_internal`/`render`
    /// calls this, and this bridge never did, which is what left Gboard's
    /// own model of the field diverging from `TextEdit`'s real one after
    /// the very first edit (RUST.md's P0 box, "doesn't enter it until I
    /// hit space, and also doesn't move cursor forward" -- Gboard holds
    /// its composing keystrokes back until it believes the app has caught
    /// up, and without this call it never does). Called from
    /// [`IrisViewPeer::after_input`], the one tail every touch/key/IME
    /// callback already runs through, rather than duplicated at each of
    /// this file's mutating methods.
    ///
    /// `candidates_start`/`candidates_end` report the composing region;
    /// `-1, -1` when nothing is composing, matching `EditorInfo`'s own
    /// convention. `compose_len` is tracked in `char`s (this module's doc
    /// comment), so this reports it as that many UTF-16 units back from the
    /// caret -- exact for the common BMP case, the same approximation
    /// `set_composing_text` already makes.
    pub(super) fn update_ime_selection(&mut self, ctx: &mut CallbackCtx) {
        let Some(focus) = self.focus() else { return };
        let text = &self.rsc[focus];
        let Some(sel) = text.selection_range() else {
            return;
        };
        let content = text.text();
        let sel_start = byte_to_utf16(content, sel.start) as i32;
        let sel_end = byte_to_utf16(content, sel.end) as i32;
        let compose_len = self.state.android_state().compose_len;
        let (comp_start, comp_end) = if compose_len > 0 {
            let caret = byte_to_utf16(content, text.caret().unwrap_or(sel.end)) as i32;
            (caret - compose_len as i32, caret)
        } else {
            (-1, -1)
        };
        let imm = ctx.view.input_method_manager(&mut ctx.env);
        imm.update_selection(
            &mut ctx.env,
            &ctx.view,
            sel_start,
            sel_end,
            comp_start,
            comp_end,
        );
    }
 }
 impl<State: AndroidAppState> InputConnection for IrisViewPeer<State> {
@@ -325,6 +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()) {
@@ -361,6 +368,21 @@ impl<State: AndroidAppState> IrisViewPeer<State> {
        let current_insets = ui_state.insets();
        if current_insets != ui_state.last_insets {
            let physical = WindowInsets::from_physical(current_insets);
            // One line per real insets change. Iris's phone is the only
            // place several of these bugs reproduce and `adb logcat` is
            // the only instrument there (this-machine-android: system
            // tracing is broken on that device), so the numbers a layout
            // is actually fed have to reach the log -- "the composer
            // floats at launch" is unanswerable from a screenshot alone.
            log::info!(
                "iris insets: left={} top={} right={} bottom={} ime_bottom={} window={:?}",
                physical.left,
                physical.top,
                physical.right,
                physical.bottom,
                physical.ime_bottom,
                self.window_size(),
            );
            self.state.android_state_mut().last_insets = current_insets;
            self.state.on_insets_changed(&mut self.rsc, physical);
        }
@@ -620,6 +642,12 @@ impl<State: AndroidAppState> ViewPeer for IrisViewPeer<State> {
        // backgrounding) still goes through `AndroidRenderer::new` below,
        // since `renderer` is `None` in that case.
        let already_live = self.state.android_state().renderer.is_some();
        log::info!(
            "iris surface: surface_changed {width}x{height} already_live={already_live} \
             glyphs_cached={} atlas_pages={}",
            self.rsc.ui.text.atlas.glyph_count(),
            self.rsc.ui.text.atlas.page_count(),
        );
        if already_live {
            let ui_state = self.state.android_state_mut();
            ui_state
@@ -650,6 +678,29 @@ impl<State: AndroidAppState> ViewPeer for IrisViewPeer<State> {
        let content_scale = self.state.android_state().content_scale;
        match AndroidRenderer::new(window, width as u32, height as u32, content_scale) {
            Ok(renderer) => {
                // A genuinely new renderer means a genuinely new GPU device
                // and a fresh, empty glyph atlas -- the CPU-side glyph
                // cache (`TextData::atlas`) and the texture bookkeeping it
                // is built on (`UiData::textures`) both outlive `renderer`
                // itself (they live on `self.rsc`, not on `AndroidRenderer`),
                // so without this they would keep pointing at the *old*
                // device's now-gone textures -- the app-switch counterpart
                // to the keyboard-resize glyph wipe this same function's
                // `already_live` branch above already fixed by reusing the
                // renderer instead of rebuilding it. One mechanism either
                // way: this call only runs on the branch that actually
                // builds a new renderer, exactly where invalidation is
                // needed, never on the reuse branch, where it would throw
                // away perfectly valid GPU state for nothing.
                log::info!(
                    "iris surface: new renderer built ({:?}), clearing glyph atlas: \
                     glyphs={} pages={}",
                    renderer.adapter_backend,
                    self.rsc.ui.text.atlas.glyph_count(),
                    self.rsc.ui.text.atlas.page_count(),
                );
                self.rsc.ui.text.atlas.clear();
                self.rsc.ui.textures.reset();
                self.state.android_state_mut().renderer = Some(renderer);
                self.render(ctx);
            }
@@ -684,6 +735,12 @@ impl<State: AndroidAppState> ViewPeer for IrisViewPeer<State> {
        _ctx: &mut CallbackCtx<'local>,
        _holder: &android_view::SurfaceHolder<'local>,
    ) {
        log::info!(
            "iris surface: surface_destroyed, tearing the renderer down \
             (glyphs_cached={} atlas_pages={})",
            self.rsc.ui.text.atlas.glyph_count(),
            self.rsc.ui.text.atlas.page_count(),
        );
        self.state.android_state_mut().renderer = None;
    }
@@ -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 +93,102 @@ where
    type Input = ();
    fn run(rsc: &mut Rsc, id: WeakWidget<TextEdit>, _: Self::Input) {
-        rsc.register_event(id, CursorSense::click_or_drag(), move |ctx, rsc| {
+        rsc.register_event(id, press_track(), move |ctx, rsc| {
-            select(
+            on_press(
                rsc,
                ctx.data.render,
                ctx.state,
                id,
                ctx.data.pos,
                ctx.data.size,
-                ctx.data.sense.is_dragging(),
+                ctx.data.sense,
            );
        });
    }
 }
-fn select(
+/// One press-track frame (`PressStart`, `Pressing` or `PressEnd`) over a
 /// selectable field. A field that is *already* focused behaves exactly as
 /// `click_or_drag` always did -- every frame updates the selection, which
 /// is what lets a finger already inside a focused field drag out a
 /// selection. A field that is **not** focused withholds `select`'s
 /// focus-granting side effects (and so the platform-specific `focus_gained`
 /// that shows the keyboard) until the press resolves as a tap: `PressEnd`
 /// with no frame in between having moved past [`DRAG_SLOP`] from where the
 /// press began. A drag recognised before release simply cancels the
 /// pending tap and does nothing further here -- it is not consumed, so
 /// whatever is behind the field (a list to pan) still sees every frame of
 /// it, the same as a drag that never touched a selectable field at all.
 fn on_press(
    rsc: &mut impl UiRsc,
    render: &UiRenderState,
    state: &mut impl FocusHost,
    id: WeakWidget<TextEdit>,
    pos: Vec2,
    size: Vec2,
-    dragging: bool,
+    sense: CursorSense,
 ) {
-    let recent = state.recent_click();
+    if state.is_focused(id) {
-    id.edit(rsc).select(pos, size, dragging, recent);
+        // Already focused, so there is no keyboard to withhold -- but a
-    state.set_focus(Some(id));
+        // vertical drag still is not a selection. Android's own `EditText`
-    state.focus_gained(render.window_region(&id, &*rsc));
+        // scrolls its overflowed text on a vertical drag and starts a
        // selection only from a long press; a scroll area wrapping this
        // field (`Scroll::drag`) is what actually pans, and it needs the
        // first frames of the gesture not to have selected anything behind
        // it before it crosses `DRAG_SLOP` and takes pointer capture.
        // `press_origin` carries the same meaning here as in the unfocused
        // branch below -- "this gesture is still eligible", cleared the
        // moment it becomes a drag -- so there is one flag, not two.
        match sense {
            CursorSense::PressStart(_) => {
                let recent = state.recent_click();
                id.edit(rsc).text.press_origin = Some(pos);
                id.edit(rsc).select(pos, size, false, recent);
            }
            CursorSense::Pressing(_) | CursorSense::PressEnd(_) => {
                let mut ctx = id.edit(rsc);
                let Some(origin) = ctx.text.press_origin else {
                    return;
                };
                let (dx, dy) = (pos.x - origin.x, pos.y - origin.y);
                if dy.abs() > DRAG_SLOP && dy.abs() >= dx.abs() {
                    ctx.text.press_origin = None;
                    return;
                }
                if matches!(sense, CursorSense::PressEnd(_)) {
                    ctx.text.press_origin = None;
                }
                ctx.select(pos, size, true, false);
            }
            _ => {}
        }
        return;
    }
    match sense {
        CursorSense::PressStart(_) => {
            id.edit(rsc).text.press_origin = Some(pos);
        }
        CursorSense::Pressing(_) => {
            let ctx = id.edit(rsc);
            if let Some(origin) = ctx.text.press_origin
                && ((pos.x - origin.x).abs() > DRAG_SLOP || (pos.y - origin.y).abs() > DRAG_SLOP)
            {
                // Past the slop before release: this is a drag, not a tap
                // -- give up the pending focus rather than granting it once
                // the finger lifts wherever it happens to be by then.
                ctx.text.press_origin = None;
            }
        }
        CursorSense::PressEnd(_) => {
            let was_tap = id.edit(rsc).text.press_origin.take().is_some();
            if was_tap {
                let recent = state.recent_click();
                id.edit(rsc).select(pos, size, false, recent);
                state.set_focus(Some(id));
                state.focus_gained(render.window_region(&id, &*rsc));
            }
        }
        _ => {}
    }
 }
@@ -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 };
@@ -68,7 +68,7 @@ fn an_unchanged_frame_draws_and_rewrites_nothing() {
    render.take_counters(); // discard the first, real draw
    render.update(&root, &mut rsc);
-    let (draws, rewrites, moves) = render.take_counters();
+    let (draws, rewrites, moves, _shapes) = render.take_counters();
    assert_eq!((draws, rewrites, moves), (0, 0, 0));
 }
@@ -101,7 +101,7 @@ fn scrolling_moves_in_o1_without_a_redraw() {
    // already clamped) rather than actually moving anything.
    rsc.ui.widgets.get_mut(&scroll).unwrap().scroll(-40.0);
    render.update(&root, &mut rsc);
-    let (draws, _rewrites, moves) = render.take_counters();
+    let (draws, _rewrites, moves, _shapes) = render.take_counters();
    // The pass condition (LAYOUT.md section 8, condition 3) is 0 draws and
    // 1 move_offsets write, independent of how many rects are in the
@@ -147,6 +147,37 @@ fn hit_testing_follows_a_scrolled_widget() {
    );
 }
 /// `ActiveData::mask` is the mask a widget was drawn **under**, not the one
 /// it set for itself -- `redraw` feeds it straight back in as the inherited
 /// mask, so storing the set one hands a `Masked` its own mask the second
 /// time round and trips `Painter::set_mask`'s nested-mask assert. That was
 /// an abort (`assertion failed: self.mask == MaskIdx::NONE`) the first time
 /// the composer's new scroll area was redrawn on the emulator; a targeted
 /// redraw of a `Masked` is what any real screen does whenever anything
 /// inside it changes.
 #[test]
 fn redrawing_a_masked_widget_does_not_nest_its_own_mask() {
    let mut rsc = TestRsc {
        ui: UiData::default(),
    };
    let (_scroll, inner_root, _rects) = scrolled_rects(&mut rsc, 8);
    let masked = rsc.ui.widgets.add_strong(Masked { inner: inner_root });
    let masked_id = masked.id();
    let root = masked.any();
    let mut render = UiRenderState::new();
    render.resize((800.0, 600.0));
    render.update(&root, &mut rsc);
    render.redraw(masked_id, &mut rsc);
    render.redraw(masked_id, &mut rsc);
    assert_eq!(
        render.active.get(&masked_id).unwrap().mask,
        MaskIdx::NONE,
        "a `Masked` at the root is drawn under no mask of its own"
    );
 }
 #[test]
 fn a_mask_stays_put_while_its_scrolled_content_moves() {
    let mut rsc = TestRsc {
@@ -183,3 +214,351 @@ fn a_mask_stays_put_while_its_scrolled_content_moves() {
    assert_eq!(mask_delta_before, [0.0, 0.0]);
    assert_eq!(mask_delta_after, [0.0, 0.0]);
 }
 /// Reproduces `transcript_ui::composer::build_composer`'s exact tree shape
 /// (a `Rect` background stacked behind a `Span::RIGHT`-wrapped, padded,
 /// `rest`-width `TextEdit`, itself the second child of an outer
 /// `Span::DOWN` beside a `rest(1)`-height sibling) without the event/
 /// resource plumbing `composer.rs`'s builders need, to isolate whether the
 /// bug Iris reported on 2026-09-06 ("text seems to not appear in box")
 /// is this crate's layout engine or something specific to the real
 /// composer/screen. `TextEditable::edit` only needs `UiRsc`, so a plain
 /// insert exercises the exact redraw path a keystroke does.
 fn composer_like_tree(rsc: &mut TestRsc) -> (WeakWidget<TextEdit>, StrongWidget) {
    let field = wtext("")
        .editable(EditMode::MultiLine)
        .text_align(Align::LEFT)
        .wrap(true)
        .size(18)
        .color(UiColor::WHITE)
        .add(rsc);
    let bar = (field.pad(dp(12)).width(rest(1)),)
        .span(Dir::RIGHT)
        .background(rect(UiColor::new(40, 40, 46, 255)))
        .add(rsc);
    let list_stand_in = rect(UiColor::BLACK).height(rest(1)).add(rsc);
    let tree = (list_stand_in, bar).span(Dir::DOWN).add_strong(rsc).any();
    (field, tree)
 }
 /// The reproduction itself. A window this tall stands in for the keyboard
 /// closed; the second, shorter `resize` stands in for `adjustResize`
 /// shrinking the surface when the IME opens -- exactly the sequence
 /// `IrisViewPeer::surface_changed` drives on a real keyboard open. Typing
 /// happens both before and after, since Iris's report was specifically
 /// that text typed *after* the keyboard was already up did not appear.
 #[test]
 fn composing_text_after_a_keyboard_resize_lands_in_the_bars_own_region() {
    let mut rsc = TestRsc {
        ui: UiData::default(),
    };
    let (field, root) = composer_like_tree(&mut rsc);
    let mut render = UiRenderState::new();
    render.resize((1080.0, 2298.0));
    render.update(&root, &mut rsc);
    // Focusing a field is what places its caret on a real tap
    // (`attr.rs`'s `on_press` -> `TextEditCtx::select`), and an insert
    // with no caret is a routing bug rather than a state to simulate --
    // `insert_str`'s own `debug_assert!` says so, and caught this test
    // typing into an unfocused field when it was added.
    field
        .edit(&mut rsc)
        .select(vec2(40.0, 2250.0), vec2(1080.0, 2298.0), false, false);
    field.edit(&mut rsc).insert("a");
    render.update(&root, &mut rsc);
    let before_px = render.window_region(&field, &rsc).unwrap();
    // The field is one line plus 12dp of padding on a 2298-tall window --
    // nowhere near the whole window's height, and anchored at the bottom.
    assert!(
        before_px.bot_right.y - before_px.top_left.y < 200.0,
        "before a resize: {before_px:?}"
    );
    assert!(
        before_px.top_left.y > 1800.0,
        "expected the bar near the bottom before a resize: {before_px:?}"
    );
    // The keyboard opens: a real `surface_changed`/`resize` to a shorter
    // window, then a further keystroke -- the redraw that must land in the
    // bar's new (also short) region, not whatever region a provisional
    // measurement pass used along the way.
    render.resize((1080.0, 1478.0));
    render.update(&root, &mut rsc);
    field.edit(&mut rsc).insert("b");
    render.update(&root, &mut rsc);
    let after_px = render.window_region(&field, &rsc).unwrap();
    assert!(
        after_px.bot_right.y - after_px.top_left.y < 200.0,
        "after a resize + keystroke: {after_px:?}"
    );
    assert!(
        after_px.top_left.y > 1200.0,
        "expected the bar near the bottom of the shorter window: {after_px:?}"
    );
 }
 /// `Scroll` used to be documented as resolving its own lengths against
 /// `Painter::output_size` -- the window -- which read as if a scroll area
 /// smaller than the screen could not work, and cost a session's
 /// investigation before the composer was wired up (docs/RUST.md,
 /// 2026-09-06). It measures `painter.px_size()` now, so this pins the
 /// three numbers that follow from the offered box: what it reports
 /// upward, what its capping parent reports, and how far it can pan.
 #[test]
 fn a_scroll_measures_the_box_it_was_offered_not_the_window() {
    let mut rsc = TestRsc {
        ui: UiData::default(),
    };
    let rect = rsc.ui.widgets.add_strong(Rect::new(UiColor::WHITE));
    let tall = rsc.ui.widgets.add_strong(Sized {
        inner: rect.any(),
        x: None,
        y: Some(Len::abs(1000.0)),
    });
    let scroll = rsc.ui.widgets.add_strong(Scroll::new(tall.any(), Axis::Y));
    let scroll_w = scroll.weak();
    let scroll_id = scroll.id();
    let capped = rsc.ui.widgets.add_strong(MaxSize {
        inner: scroll.any(),
        x: None,
        y: Some(Len::abs(100.0)),
    });
    let capped_id = capped.id();
    let root = capped.any();
    let mut render = UiRenderState::new();
    render.resize((800.0, 600.0));
    // Two passes: the first offers the content a zero-length region
    // (nothing measured yet) and learns the real content length from what
    // comes back -- see `scrolling_moves_in_o1_without_a_redraw` for why
    // that warm-up is deliberate rather than a bug.
    render.update(&root, &mut rsc);
    rsc.ui.widgets.get_mut(&scroll_w).unwrap().scroll(0.0);
    render.update(&root, &mut rsc);
    // Reports the *content*, so the cap above it has something to cap;
    // reporting the container instead would make the answer a function of
    // itself, since the container is sized from this very number.
    assert_eq!(
        render.active.get(&scroll_id).unwrap().size.y,
        Len::abs(1000.0)
    );
    assert_eq!(
        render.active.get(&capped_id).unwrap().size.y,
        Len::abs(100.0),
        "the cap, not the content and not the window"
    );
    // Panning is bounded by content minus *container*: 900, not the 400
    // a 600px window would give.
    rsc.ui.widgets.get_mut(&scroll_w).unwrap().scroll(-10_000.0);
    assert!(
        (rsc.ui.widgets.get_mut(&scroll_w).unwrap().amt() - 900.0).abs() < 0.01,
        "amt={}",
        rsc.ui.widgets.get_mut(&scroll_w).unwrap().amt()
    );
 }
 /// The half `hit_testing_follows_a_scrolled_widget` could not see: it
 /// checks a *descendant* of the widget `Scroll` actually moves, whose own
 /// `region` is stale and is corrected entirely by the move chain. The
 /// moved widget itself had its `region` updated *and* the chain delta
 /// added on top, so its hit box sat at twice the pan -- which is why a
 /// finger pan of the composer left its field untappable. See
 /// `ActiveData::move_applied`.
 #[test]
 fn a_panned_widgets_own_hit_box_moves_exactly_once() {
    let mut rsc = TestRsc {
        ui: UiData::default(),
    };
    let rect = rsc.ui.widgets.add_strong(Rect::new(UiColor::WHITE));
    let tall = rsc.ui.widgets.add_strong(Sized {
        inner: rect.any(),
        x: None,
        y: Some(Len::abs(1000.0)),
    });
    let tall_w = tall.weak();
    let scroll = rsc.ui.widgets.add_strong(Scroll::new(tall.any(), Axis::Y));
    let scroll_w = scroll.weak();
    let root = scroll.any();
    let mut render = UiRenderState::new();
    render.resize((800.0, 600.0));
    render.update(&root, &mut rsc);
    rsc.ui.widgets.get_mut(&scroll_w).unwrap().scroll(0.0);
    render.update(&root, &mut rsc);
    let before = render.window_region(&tall_w, &rsc).unwrap();
    rsc.ui.widgets.get_mut(&scroll_w).unwrap().scroll(-37.0);
    render.update(&root, &mut rsc);
    let after = render.window_region(&tall_w, &rsc).unwrap();
    assert!(
        (after.top_left.y - (before.top_left.y - 37.0)).abs() < 0.01,
        "the pan was applied twice: before={before:?} after={after:?}"
    );
 }
 /// A `Masked` used to allocate a **new** mask slot on every draw, and
 /// `draw_inner`'s unchanged-region fast path means its descendants are
 /// mostly *not* redrawn with it -- so they went on referencing the slot
 /// they were first drawn under, whose region had since stopped being the
 /// widget's. Measured 2026-09-06 on the composer's tree: four live mask
 /// entries, none of them the `Masked`'s current box, and the field it was
 /// meant to clip drew nothing at all on the emulator. The slot is
 /// allocated once and rewritten in place now (`ActiveData::own_mask`), so
 /// this pins both halves: one entry, and that entry is the widget's own
 /// region.
 #[test]
 fn a_masked_widget_keeps_one_mask_slot_that_is_always_its_own_region() {
    let mut rsc = TestRsc {
        ui: UiData::default(),
    };
    let (_scroll, inner_root, _rects) = scrolled_rects(&mut rsc, 8);
    let masked = rsc.ui.widgets.add_strong(Masked { inner: inner_root });
    let masked_id = masked.id();
    // Placed at the bottom of a `Span::DOWN` behind a `rest(1)` sibling,
    // which is what moves the bar away from the provisional slot it is
    // first drawn at -- the move that left the stale mask behind.
    let filler = rsc.ui.widgets.add_strong(Rect::new(UiColor::BLACK));
    let filler = rsc.ui.widgets.add_strong(Sized {
        inner: filler.any(),
        x: None,
        y: Some(rest(1)),
    });
    let capped = rsc.ui.widgets.add_strong(MaxSize {
        inner: masked.any(),
        x: None,
        y: Some(Len::abs(60.0)),
    });
    let mut span = Span::empty(Dir::DOWN);
    span.push(filler.any());
    span.push(capped.any());
    let root = rsc.ui.widgets.add_strong(span).any();
    let mut render = UiRenderState::new();
    render.resize((800.0, 600.0));
    for _ in 0..3 {
        render.update(&root, &mut rsc);
        render.redraw(masked_id, &mut rsc);
    }
    assert_eq!(
        rsc.ui.masks.iter().count(),
        1,
        "one `Masked` must own exactly one mask slot, however often it is redrawn"
    );
    let mask = *rsc.ui.masks.iter().next().unwrap();
    assert_eq!(
        mask.region,
        render.active.get(&masked_id).unwrap().region,
        "the mask a descendant clips against must be this widget's current box"
    );
 }
 /// A `dp` cap that has done its job must be reported in pixels. `Span`
 /// places a child using the `abs`/`rel` of the length it reported, so a
 /// `MaxSize` handing back the caller's own `dp(168)` gave the composer's
 /// bar a slot of **zero** the moment its content grew past six lines --
 /// and the `Scroll` inside then measured its container at -63px (the
 /// padding, subtracted from nothing) and panned the whole message out of
 /// view. Measured on this checkout's emulator, 2026-09-06:
 /// `container=-63 content=415.8 amt=478.8`. See `Len::fold_dp`.
 #[test]
 fn a_dp_cap_is_reported_in_pixels_so_a_span_can_place_it() {
    let mut rsc = TestRsc {
        ui: UiData::default(),
    };
    let rect = rsc.ui.widgets.add_strong(Rect::new(UiColor::WHITE));
    let tall = rsc.ui.widgets.add_strong(Sized {
        inner: rect.any(),
        x: None,
        y: Some(Len::abs(1000.0)),
    });
    let capped = rsc.ui.widgets.add_strong(MaxSize {
        inner: tall.any(),
        x: None,
        y: Some(Len::dp(100.0)),
    });
    let capped_w = capped.weak();
    let filler = rsc.ui.widgets.add_strong(Rect::new(UiColor::BLACK));
    let filler = rsc.ui.widgets.add_strong(Sized {
        inner: filler.any(),
        x: None,
        y: Some(rest(1)),
    });
    let mut span = Span::empty(Dir::DOWN);
    span.push(filler.any());
    span.push(capped.any());
    let root = rsc.ui.widgets.add_strong(span).any();
    let mut render = UiRenderState::new();
    render.resize((800.0, 600.0));
    render.set_density(2.5);
    render.update(&root, &mut rsc);
    render.update(&root, &mut rsc);
    let box_px = render.window_region(&capped_w, &rsc).unwrap();
    let height = box_px.bot_right.y - box_px.top_left.y;
    assert!(
        (height - 250.0).abs() < 0.01,
        "expected the 100dp cap at density 2.5 to be a 250px slot, got {height} ({box_px:?})"
    );
 }
 /// The sibling of `a_panned_widgets_own_hit_box_moves_exactly_once`, on
 /// the branch that fix had no reason to touch: `draw_inner`'s
 /// size-independent fast path rewrites a widget's primitives *in place*
 /// and leaves its move slot alone, so unlike `mov` there is no slot delta
 /// for `region` to have absorbed. Counting one there anyway makes
 /// `resolved_region` subtract a delta the chain never held, and the
 /// widget's hit box lands short of where it is drawn by exactly the
 /// distance it just moved -- with nothing on screen to say so, since the
 /// primitives are in the right place.
 #[test]
 fn a_size_independent_widget_moved_by_its_parent_has_the_hit_box_it_is_drawn_at() {
    let mut rsc = TestRsc {
        ui: UiData::default(),
    };
    let top = rsc.ui.widgets.add_strong(Rect::new(UiColor::WHITE));
    let spacer = rsc.ui.widgets.add_strong(Sized {
        inner: top.any(),
        x: None,
        y: Some(Len::abs(100.0)),
    });
    let spacer_w = spacer.weak();
    // `Rect` is `is_size_independent`, so growing the spacer above it
    // offers this one a region that changed *both* position and size --
    // the one shape that reaches the branch under test.
    let below = rsc.ui.widgets.add_strong(Rect::new(UiColor::WHITE));
    let below_w = below.weak();
    let mut span = Span::empty(Dir::DOWN);
    span.push(spacer.any());
    span.push(below.any());
    let root = rsc.ui.widgets.add_strong(span).any();
    let mut render = UiRenderState::new();
    render.resize((800.0, 600.0));
    render.update(&root, &mut rsc);
    // `Span` draws each child once at the full region to measure it and
    // then places it, so this widget has already been through the branch
    // once by the end of the very first frame.
    let first = render.window_region(&below_w, &rsc).unwrap();
    assert!(
        (first.top_left.y - 100.0).abs() < 0.01,
        "hit box at {:?}, drawn at y=100",
        first.top_left
    );
    rsc.ui.widgets.get_mut(&spacer_w).unwrap().y = Some(Len::abs(250.0));
    render.update(&root, &mut rsc);
    let after = render.window_region(&below_w, &rsc).unwrap();
    assert!(
        (after.top_left.y - 250.0).abs() < 0.01,
        "hit box at {:?}, drawn at y=250",
        after.top_left
    );
 }
@@ -22,6 +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)]
@@ -31,6 +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;
@@ -177,6 +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
@@ -266,6 +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);
        }
@@ -541,6 +615,138 @@ impl DragArbiter {
    }
 }
 /// 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.
@@ -575,6 +781,12 @@ impl VelocityTracker {
    /// 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) {
        // A caller that samples out of order (a restored/replayed
        // gesture, a test) would silently produce a negative `span` in
        // `velocity`, handled only by its `span <= 0.0 => 0.0` catch-all
        // -- masking the bug that produced it rather than surfacing it
        // (docs/REVIEW-2026-09-06.md finding 4).
        debug_assert!(self.samples.back().is_none_or(|&(last, _)| at >= last));
        self.samples.push_back((at, delta));
        while let Some(&(when, _)) = self.samples.front() {
            if at.duration_since(when) > VELOCITY_WINDOW {
@@ -750,6 +962,10 @@ impl FlingCalculator {
    /// Total signed distance the fling travels before settling, in the
    /// same pixel units `velocity` was given in.
    pub fn distance(&self, velocity: f32) -> f32 {
        // See `List::fling`'s matching assertion -- a non-finite velocity
        // here silently produces a NaN distance rather than surfacing the
        // bug that produced it (docs/REVIEW-2026-09-06.md finding 3).
        debug_assert!(velocity.is_finite());
        if velocity == 0.0 {
            return 0.0;
        }
@@ -762,6 +978,8 @@ impl FlingCalculator {
    /// How long the fling takes to settle.
    pub fn duration(&self, velocity: f32) -> Duration {
        // See `distance`'s matching assertion, above.
        debug_assert!(velocity.is_finite());
        if velocity == 0.0 {
            return Duration::ZERO;
        }
@@ -122,3 +122,197 @@ fn a_button_over_a_list_scrolls_the_list_and_still_clicks() {
        "the button on top must still receive an actual click"
    );
 }
 /// The bug behind "finger flings do nothing" (RUST.md's P0 phone report,
 /// defect 2): a fast gesture's `PressEnd` can land at a screen position
 /// nothing is registered at -- past the edge of whatever widget noticed
 /// the press, in a gap, or off the loaded content entirely. Before pointer
 /// capture, `run_sensors`' hit test simply delivered nothing that frame,
 /// so a widget mid-drag never saw its release and never got a chance to
 /// start a fling. `UiRenderState::capture_pointer`/`DragGesture` fix this
 /// by giving the drag's widget every frame regardless of where the
 /// pointer is, including the terminal `Drop` in place of `PressEnd`.
 #[test]
 fn a_release_outside_every_hit_region_still_reaches_the_captured_widget() {
    let mut rsc = SenseRsc {
        ui: UiData::default(),
        events: EventManager::default(),
    };
    // A small draggable widget in the corner -- the release below lands
    // far outside it, exactly the "moved off the hit region" case.
    let draggable = rsc.ui.widgets.add_strong(Rect::new(UiColor::WHITE)).any();
    let draggable_weak = draggable.weak();
    let dropped = Rc::new(Cell::new(false));
    {
        let dropped = dropped.clone();
        rsc.register_event(
            draggable_weak,
            CursorSense::click_or_drag() | CursorSense::unclick() | CursorSense::Drop,
            move |ctx, rsc| match ctx.data.sense {
                CursorSense::PressStart(_) | CursorSense::Pressing(_) => {
                    // Any committed drag takes capture -- a real caller
                    // would gate this on a `DragArbiter`/`DragGesture`
                    // decision, but this test only needs to exercise the
                    // capture-and-release mechanics themselves.
                    ctx.data.render.capture_pointer(draggable_weak.id());
                    let _ = rsc;
                }
                CursorSense::Drop => dropped.set(true),
                _ => {}
            },
        );
    }
    let mut render = UiRenderState::new();
    render.resize((100.0, 100.0));
    render.update(&draggable, &mut rsc);
    let mut state = ();
    let mut press = cursor_at((5.0, 5.0).into());
    press.buttons.left = ActivationState::Start;
    render.run_sensors(&mut rsc, &mut state, press, (100.0, 100.0).into());
    assert_eq!(
        render.captured_pointer(),
        Some(draggable.id()),
        "the press should have taken capture"
    );
    // The release lands nowhere near the widget's own region -- the exact
    // shape of a fast fling's `ACTION_UP`.
    let mut release = cursor_at((95.0, 95.0).into());
    release.buttons.left = ActivationState::End;
    render.run_sensors(&mut rsc, &mut state, release, (100.0, 100.0).into());
    assert!(
        dropped.get(),
        "a release outside every widget's hit region must still reach \
         the widget holding pointer capture"
    );
    assert_eq!(
        render.captured_pointer(),
        None,
        "Drop must release the capture"
    );
 }
 /// A widget that never registers `CursorSense::Drop` at all must not be
 /// affected by someone else's capture -- capture is per-gesture, not
 /// global suppression of the whole input system for widgets that were
 /// never party to it. (Practically this matters because a captured
 /// widget's registration list still has to include `Drop` for `should_run`
 /// to ever match it; this pins that half of the contract.)
 #[test]
 fn capturing_one_widget_starves_every_other_widget_of_events() {
    let mut rsc = SenseRsc {
        ui: UiData::default(),
        events: EventManager::default(),
    };
    let a = rsc.ui.widgets.add_strong(Rect::new(UiColor::WHITE));
    let a_weak = a.weak();
    let b = rsc.ui.widgets.add_strong(Rect::new(UiColor::RED));
    let b_weak = b.weak();
    let b_hovered = Rc::new(Cell::new(false));
    {
        let b_hovered = b_hovered.clone();
        rsc.register_event(b_weak, CursorSense::Hovering, move |_ctx, _rsc| {
            b_hovered.set(true);
        });
    }
    let root = rsc
        .ui
        .widgets
        .add_strong(Stack {
            children: vec![a.any(), b.any()],
            size: StackSize::default(),
        })
        .any();
    let mut render = UiRenderState::new();
    render.resize((100.0, 100.0));
    render.update(&root, &mut rsc);
    render.capture_pointer(a_weak.id());
    let mut state = ();
    let cursor = cursor_at((50.0, 50.0).into());
    render.run_sensors(&mut rsc, &mut state, cursor, (100.0, 100.0).into());
    assert!(
        !b_hovered.get(),
        "while a's drag holds capture, b must see no hover at all"
    );
 }
 /// IRIS_TODO.md's "the composer has no touch-drag scroll": `Scroll` only
 /// answered a wheel, so a finger drag over overflowed text did nothing.
 /// End-to-end over the real wiring -- `scrollable()`'s own registration,
 /// `run_sensors`' dispatch, `Scroll::drag`, `DragGesture`'s arbitration and
 /// pointer capture -- rather than only `Scroll::drag`'s own unit tests in
 /// `scroll.rs`, because the registration is exactly the half those cannot
 /// see.
 #[test]
 fn a_finger_drag_over_a_scroll_area_pans_it() {
    let mut rsc = SenseRsc {
        ui: UiData::default(),
        events: EventManager::default(),
    };
    // 1000px of content in a 100px window: room to pan.
    let scroll_strong = rect(UiColor::WHITE)
        .height(Len::abs(1000.0))
        .scrollable()
        .add_strong(&mut rsc);
    let scroll = scroll_strong.weak();
    let root = scroll_strong.any();
    let mut render = UiRenderState::new();
    render.resize((100.0, 100.0));
    render.update(&root, &mut rsc);
    // `Scroll` reads its content length back from the draw it just did, so
    // the frame after is the first one that knows there is anything to pan
    // -- the one-frame lag LAYOUT.md section 4 documents. `scroll(0.0)` is
    // how `layout_tests.rs` asks for that second frame, and it also drops
    // `snap_end`, leaving this parked at the start of the content.
    rsc.ui.widgets.get_mut(&scroll).unwrap().scroll(0.0);
    render.update(&root, &mut rsc);
    assert_eq!(rsc.ui.widgets.get(&scroll).unwrap().amt(), 0.0);
    let mut state = ();
    let mut down = cursor_at((50.0, 80.0).into());
    down.buttons.left = ActivationState::Start;
    render.run_sensors(&mut rsc, &mut state, down, (100.0, 100.0).into());
    assert_eq!(
        rsc.ui.widgets.get(&scroll).unwrap().amt(),
        0.0,
        "the touch-down alone must not move anything"
    );
    // Inside the slop: still a tap as far as anything can tell.
    let mut nudge = cursor_at((50.0, 80.0 - (DRAG_SLOP - 1.0)).into());
    nudge.buttons.left = ActivationState::On;
    render.run_sensors(&mut rsc, &mut state, nudge, (100.0, 100.0).into());
    assert_eq!(
        rsc.ui.widgets.get(&scroll).unwrap().amt(),
        0.0,
        "a press inside DRAG_SLOP must not scroll"
    );
    // Past it, upward: the content follows the finger up, which for this
    // widget means more `amt`.
    let mut drag = cursor_at((50.0, 80.0 - (DRAG_SLOP + 40.0)).into());
    drag.buttons.left = ActivationState::On;
    render.run_sensors(&mut rsc, &mut state, drag, (100.0, 100.0).into());
    let after = rsc.ui.widgets.get(&scroll).unwrap().amt();
    assert!(
        (after - 40.0).abs() < 0.01,
        "expected the 40px past the slop to pan it, got {after}"
    );
    // And the gesture holds the pointer, so the rest of it reaches this
    // widget even once the finger leaves its box.
    assert_eq!(render.captured_pointer(), Some(scroll.id()));
 }
@@ -424,6 +424,13 @@ impl List {
    /// 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) {
        // A NaN/inf velocity (a `VelocityTracker::velocity()` divide-by-
        // near-zero span, or a caller passing a raw device value straight
        // through) would propagate silently into `deceleration_for`'s
        // `.ln()` -- the fling either never settles or jumps to NaN
        // positions with nothing on screen saying why (docs/
        // REVIEW-2026-09-06.md finding 3).
        debug_assert!(velocity_px_per_s.is_finite());
        if velocity_px_per_s == 0.0 || self.anchor.is_none() {
            self.fling = None;
            return;
@@ -552,6 +559,20 @@ 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(),
@@ -749,6 +770,17 @@ impl List {
    /// one-frame lag `Scroll`'s own content-length cache accepts, per
    /// LAYOUT.md.
    fn place(&mut self, painter: &mut Painter, slot: isize, placement: Placement) -> (f32, f32) {
        // Every current caller derives `slot` from `repair_anchor`/
        // `prev_slot`/`next_slot`, which already check existence -- but
        // that invariant is enforced by convention across three call
        // sites, not by this function, which would otherwise fail with a
        // bare "index out of bounds" and no context (docs/
        // REVIEW-2026-09-06.md finding 2). `slot_widget`, called from
        // here, is what actually indexes/`.expect`s on it.
        debug_assert!(
            self.slot_exists(slot),
            "place() called with a slot that doesn't exist: {slot:?}"
        );
        let axis = self.axis;
        let output_len = painter.output_size().axis(axis);
        let container_len = painter.region().axis(axis).len();
@@ -1072,7 +1104,7 @@ mod tests {
                .push_front(ListRow::new(key, w));
        }
        render.update(&root, &mut rsc);
-        let (draws, _rewrites, _moves) = render.take_counters();
+        let (draws, _rewrites, _moves, _shapes) = render.take_counters();
        // None of the already-visible rows (11, 12) were touched: the
        // extents for those keys are numerically unchanged, and the only
@@ -1210,7 +1242,7 @@ mod tests {
            rsc.ui.widgets.get_mut(&list_weak).unwrap().scroll(5.0);
            render.update(&root, &mut rsc);
-            let (draws, _rewrites, moves) = render.take_counters();
+            let (draws, _rewrites, moves, _shapes) = render.take_counters();
            // The visible window is a fixed ~10 rows regardless of n; an
            // O(n) regression would show up as draws/moves scaling with
@@ -1273,6 +1305,52 @@ mod tests {
        );
    }
    /// Neither `replacing_the_last_row_stays_pinned_to_the_bottom` nor
    /// its sibling below ever asserts the *evicted* key's own bookkeeping
    /// is actually gone -- both replace row 4 with another row also keyed
    /// `4`, so `heights.remove(&old.key)` removing and re-inserting the
    /// same key would pass either test even if it did nothing (docs/
    /// REVIEW-2026-09-06.md finding 10; this is `Selection`'s finding 1
    /// class of bug -- a stale handle outliving what it points to --
    /// production-tested from `List`'s own side). Replacing with a
    /// **different** key is what actually exercises the removal.
    #[test]
    fn replace_back_forgets_the_evicted_keys_own_height() {
        let mut rsc = TestRsc {
            ui: UiData::default(),
        };
        let mut list = List::new(Axis::Y);
        push_rows(&mut rsc, &mut list, &[0, 1, 2, 3, 4], 20.0);
        let (list_weak, root) = add_list(&mut rsc, list);
        let mut render = UiRenderState::new();
        render.resize((100.0, 60.0));
        render.update(&root, &mut rsc);
        assert!(
            rsc.ui
                .widgets
                .get(&list_weak)
                .unwrap()
                .heights
                .contains_key(&4)
        );
        let (_weak, new_row) = fixed_row(&mut rsc, 40.0);
        let old = rsc
            .ui
            .widgets
            .get_mut(&list_weak)
            .unwrap()
            .replace_back(ListRow::new(100, new_row));
        let list_ref = rsc.ui.widgets.get(&list_weak).unwrap();
        assert_eq!(old.map(|o| o.key), Some(4));
        assert!(
            !list_ref.heights.contains_key(&4),
            "the evicted key's cached height must not outlive the row it measured"
        );
    }
    /// The other half of the same fix's contract: replacing a row that is
    /// *not* on screen must not move anything that is. `replace_back` only
    /// touches the last slot's own widget and this file's own `heights`/
@@ -1332,6 +1410,126 @@ 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"
        );
    }
    /// The doubled `Compacted:` row from Iris's phone (docs/bench/
    /// iris-phone-v2-2026-09-06.md), reproduced at its mechanism.
    ///
    /// `replacing_the_last_row_many_times_does_not_leak_primitives` above
    /// counts *widgets*, which is why it passed all along: the orphan's
    /// owner is very much alive -- it is an earlier set of that same
    /// widget's primitives that got stranded. What strands them is a row
    /// marked dirty and then reached by its **ancestor's** redraw rather
    /// than by its own: `draw_inner` only *read* the dirty mark, so the
    /// whole branch that frees a redrawn widget's previous primitives was
    /// skipped, and the fresh `ActiveData` overwrote the only handles that
    /// could ever have freed them. `List` sets no mask, so that copy then
    /// draws every frame at whatever region it last had -- including,
    /// where the row was being measured at `GENEROUS_PADDING`, well below
    /// the list's own box and under the composer.
    ///
    /// Two rows, two shapes of the same fault: row 2 has a cached height
    /// (one `widget_within`), row 4 is replaced so it has none (`place`'s
    /// `draw_twice`, which reaches `draw_inner` twice for one id in one
    /// frame and so orphans a copy even with no ancestor involved).
    #[test]
    fn an_ancestor_redrawing_a_dirty_row_leaves_no_stale_copy() {
        let mut rsc = TestRsc {
            ui: UiData::default(),
        };
        let mut list = List::new(Axis::Y);
        // Rows that own a primitive *at their own id* (a background rect),
        // not only through a child: an orphan is a widget's own primitive
        // outliving its own redraw, so a row whose top-level widget paints
        // nothing itself cannot show one however broken the path is.
        let mut rows = Vec::new();
        for key in 0..5u64 {
            let (bg_id, row) = background_styled_row(&mut rsc, 20.0);
            rows.push((row.id(), bg_id));
            list.push_back(ListRow::new(key, row));
        }
        let (list_weak, root) = add_list(&mut rsc, list);
        let mut render = UiRenderState::new();
        render.resize((100.0, 100.0));
        render.update(&root, &mut rsc);
        assert!(render.orphaned_primitives().is_empty());
        // A streamed row's content changing: the row is marked dirty (any
        // `.set()` on it does this)...
        let (row2, row2_bg) = rows[2];
        rsc.ui.widgets.get_dyn_mut(row2).unwrap();
        rsc.ui.widgets.get_dyn_mut(row2_bg).unwrap();
        // Redraw the *list* by name, so the dirty row is reached by its
        // ancestor's draw rather than by `redraw_updates` happening to
        // pick it first -- which is the order `HashSet` iteration makes
        // arbitrary, and the reason this went unnoticed.
        render.redraw(list_weak.id(), &mut rsc);
        let orphans = render.orphaned_primitives();
        assert!(
            orphans.is_empty(),
            "{} primitive(s) survived their own widget's redraw: {orphans:?}",
            orphans.len(),
        );
    }
    /// Enough rows, tall enough, that a fling toward the start has real
    /// room to travel before `at_start` clamps it -- shared by the fling
    /// tests below.
@@ -1409,6 +1607,71 @@ mod tests {
        }
    }
    /// `fling_moves_the_list_and_then_settles`/
    /// `fling_distance_is_positive_toward_the_end` only check that a fling
    /// started, moved the right way and eventually stopped -- both
    /// unaffected by *how* the interior ticks split up the total travel
    /// (docs/REVIEW-2026-09-06.md finding 9). A regression that made
    /// `tick_fling` apply the whole spline distance every tick instead of
    /// just this tick's incremental slice would still pass both, while
    /// being wildly wrong every intermediate frame -- this pins the
    /// per-tick delta to a decelerating curve (`FlingCalculator::
    /// position_at`'s own monotonic-and-clamped property, one level
    /// down, already covers the calculator alone; this is the same
    /// property through `List::tick_fling`'s `scroll`/`extents`
    /// accumulation).
    #[test]
    fn tick_fling_applies_shrinking_incremental_deltas() {
        let mut rsc = TestRsc {
            ui: UiData::default(),
        };
        let (list_weak, root, mut render) = build_flingable_list(&mut rsc);
        rsc.ui.widgets.get_mut(&list_weak).unwrap().jump_to_start();
        render.update(&root, &mut rsc);
        rsc.ui.widgets.get_mut(&list_weak).unwrap().fling(8000.0);
        let start = Instant::now();
        let mut prev_top = rsc.ui.widgets.get(&list_weak).unwrap().extents[&0].top;
        let mut deltas = Vec::new();
        for step in 1..600 {
            let now = start + std::time::Duration::from_millis(step * 16);
            let still = rsc.ui.widgets.get_mut(&list_weak).unwrap().tick_fling(now);
            render.update(&root, &mut rsc);
            let Some(top) = rsc
                .ui
                .widgets
                .get(&list_weak)
                .unwrap()
                .extents
                .get(&0)
                .map(|e| e.top)
            else {
                break; // row 0 scrolled out of the loaded extents
            };
            deltas.push((prev_top - top).abs());
            prev_top = top;
            if !still {
                break;
            }
        }
        assert!(
            deltas.len() >= 3,
            "fling settled or left row 0's extent before collecting enough samples"
        );
        // Skip the first tick (the slop-transition jump the arbiter
        // applies is a `List::fling`-adjacent concern, not this curve,
        // but the very first frame can still carry rounding noise from
        // `jump_to_start`'s own layout settling).
        for w in deltas[1..].windows(2) {
            assert!(
                w[1] <= w[0] + 0.01,
                "fling's per-tick delta grew instead of decelerating: {:?} then {:?}",
                w[0],
                w[1]
            );
        }
    }
    #[test]
    fn cancel_fling_stops_it_with_no_further_movement() {
        let mut rsc = TestRsc {
@@ -15,7 +15,14 @@ impl MaxSize {
        };
        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 }
+        // `fold_dp`, not the caller's `max` as written: a reported `Len`
        // may not carry an unresolved `dp` -- see `Len::fold_dp` for the
        // collapsed composer bar this caused.
        if len_px > max_px {
            max.fold_dp(density)
        } else {
            len
        }
    }
    /// The span (in this widget's own local, `UiRegion::FULL`-relative
@@ -1,4 +1,6 @@
 use crate::prelude::*;
 use crate::sense::{DragGesture, GestureOutcome};
 use std::time::Instant;
 pub struct Scroll {
    inner: StrongWidget,
@@ -7,6 +9,12 @@ pub struct Scroll {
    snap_end: bool,
    container_len: f32,
    content_len: f32,
    /// Touch panning, from the same `DragGesture` `List` is driven by
    /// (`transcript-ui::Selection::drag`) rather than a second copy of its
    /// wiring: arbitration, `DRAG_SLOP` and pointer capture all live in
    /// `sense.rs` and only what a committed pan *means* is decided here.
    /// See [`Self::drag`].
    gesture: DragGesture,
 }
 impl Widget for Scroll {
@@ -25,10 +33,20 @@ impl Widget for Scroll {
        // length itself (read below from what was actually drawn) is never
        // stale, so this self-corrects the next frame and never leaves the
        // scroll range wrong for long. See LAYOUT.md section 4.
        //
        // Every length here is resolved against the box this widget was
        // **offered** (`px_size`), never `output_size`: a `Scroll` is
        // routinely smaller than the window -- the composer's field is
        // capped at six lines by a `MaxSize` around it -- and measuring
        // the window instead would make the pan range, and so where the
        // content sits, a function of the screen rather than of the box.
        // (What the previous arithmetic here computed came to the same
        // number by a longer route, through a `within_len` against a
        // window-relative scalar; it read as if the window were the
        // container and cost a session working out that it was not.)
        let axis = self.axis;
-        let output_len = painter.output_size().axis(axis);
+        let container_len = painter.px_size().axis(axis);
-        let container_len = painter.region().axis(axis).len();
+        self.container_len = container_len;
        self.container_len = container_len.to_abs(output_len);
        if self.snap_end {
            self.amt = self.content_len - self.container_len;
@@ -41,12 +59,22 @@ impl Widget for Scroll {
        let used = painter.widget_within(&self.inner, region);
        // A child reporting `rel` means "this fraction of what I was
        // offered", and what it was offered is this scroll area -- so the
        // container, again, is what that resolves against.
        self.content_len = used
            .axis(axis)
            .apply_rest(painter.density())
-            .within_len(container_len)
+            .to_abs(container_len);
            .to_abs(output_len);
        // The **content's** size, not the container's. A parent that can
        // grow (the composer's bar) should hug the text until its own cap
        // stops it, and reporting the container instead would make this
        // widget's answer a function of the answer -- the bar is sized
        // from what is reported here, so it collapses to nothing and
        // never recovers. What keeps the content inside the offered box
        // is the mask a caller puts around it (`.scrollable().masked()`),
        // not this number.
        used
    }
 }
@@ -60,6 +88,59 @@ impl Scroll {
            snap_end: true,
            container_len: 0.0,
            content_len: 0.0,
            gesture: DragGesture::new(),
        }
    }
    /// Feed one frame of a touch gesture over this scroll area through.
    /// Wired by `WidgetLike::scrollable`; a caller building a `Scroll` by
    /// hand registers the same senses and calls this.
    ///
    /// `id` is this widget's own id, which `DragGesture` takes pointer
    /// capture on once the gesture commits -- so the rest of the drag
    /// reaches here even after the finger has left this area, and, just as
    /// importantly, stops reaching whatever is *inside* it. That is what
    /// resolves a vertical drag over a focused text field: the field sees
    /// the first few frames, iris::attr's `on_press` gives up its pending
    /// selection the moment they pass `DRAG_SLOP` vertically, and this
    /// takes the gesture over. Android's own `EditText` behaves the same
    /// way -- a vertical drag scrolls, and only a long press selects.
    ///
    /// No fling: unlike `List`, `Scroll` has no per-frame tick to animate
    /// one with (`List::set_redraw_handle`/`tick_fling`), and the areas
    /// this wraps today -- a six-line composer, a diagnostics pane -- are
    /// at most a screenful, where Android does not fling either. The
    /// released velocity is deliberately dropped rather than approximated.
    pub fn drag(
        &mut self,
        render: &UiRenderState,
        id: WidgetId,
        sense: CursorSense,
        pos_window: Vec2,
        now: Instant,
    ) {
        // `already_selected: false` -- a scroll area has no selection of
        // its own to extend, so a horizontal drag stays `Undecided` and a
        // vertical one past the slop pans, which is the whole contract
        // here. A caller that *does* own a selection (the transcript's
        // `Selection`) drives `DragGesture` itself instead.
        match self
            .gesture
            .handle(render, id, sense, pos_window, now, false)
        {
            // `scroll(dy)`, not `scroll(-dy)` -- `Selection::drag` passes
            // `-dy` to `List::scroll` because a `List`'s anchor offset and
            // this widget's `amt` run in *opposite* directions (offset is
            // where the anchored edge sits; `amt` is how far the content
            // has been pulled up past the top), even though `List::scroll`'s
            // own doc claims to mirror this one's convention. The rule that
            // holds for both, and the one to check a sign against, is that
            // the content follows the finger.
            GestureOutcome::Pan(dy) => self.scroll(dy),
            GestureOutcome::Undecided
            | GestureOutcome::SelectStart
            | GestureOutcome::SelectExtend
            | GestureOutcome::Released(_) => {}
        }
    }
@@ -70,8 +151,179 @@ impl Scroll {
        self.snap_end = self.amt == len;
    }
    /// How far the content has been pulled past the container's leading
    /// edge, in pixels -- 0 at the start of the content. Read-only, for a
    /// caller that needs to observe a pan (a test, a scroll indicator).
    pub fn amt(&self) -> f32 {
        self.amt
    }
    pub fn scroll(&mut self, amt: f32) {
        self.amt -= amt;
        self.update_amt();
    }
 }
 #[cfg(test)]
 mod tests {
    use super::*;
    use crate::sense::{CursorButton, DRAG_SLOP};
    use iris_core::UiData;
    use std::time::Duration;
    /// A scroll area with 1000px of content in a 100px box, already
    /// settled somewhere in the middle so a drag has room in both
    /// directions.
    fn area() -> (UiData, Scroll, WidgetId) {
        let mut ui = UiData::default();
        let inner = ui.widgets.add_strong(Rect::new(UiColor::WHITE)).any();
        let id = inner.id();
        let mut s = Scroll::new(inner, Axis::Y);
        s.content_len = 1000.0;
        s.container_len = 100.0;
        s.amt = 400.0;
        s.snap_end = false;
        (ui, s, id)
    }
    fn press(
        s: &mut Scroll,
        render: &UiRenderState,
        id: WidgetId,
        sense: CursorSense,
        y: f32,
        t: Instant,
    ) {
        s.drag(render, id, sense, Vec2::new(0.0, y), t);
    }
    #[test]
    fn a_vertical_finger_drag_pans_the_content_with_the_finger() {
        let (_ui, mut s, id) = area();
        let render = UiRenderState::new();
        let t = Instant::now();
        press(
            &mut s,
            &render,
            id,
            CursorSense::PressStart(CursorButton::Left),
            0.0,
            t,
        );
        // Finger down by well past the slop: the content follows it down,
        // which for this widget means *less* `amt`.
        press(
            &mut s,
            &render,
            id,
            CursorSense::Pressing(CursorButton::Left),
            DRAG_SLOP + 30.0,
            t + Duration::from_millis(20),
        );
        assert!(
            (s.amt - 370.0).abs() < 0.01,
            "expected the 30px past the slop to be applied downward, got amt={}",
            s.amt
        );
        // ...and the next frame's motion is a plain per-frame delta.
        press(
            &mut s,
            &render,
            id,
            CursorSense::Pressing(CursorButton::Left),
            DRAG_SLOP + 50.0,
            t + Duration::from_millis(40),
        );
        assert!((s.amt - 350.0).abs() < 0.01, "amt={}", s.amt);
    }
    /// The half the change had no reason to touch: a press that never
    /// leaves the slop is a tap, and must move nothing at all -- otherwise
    /// every tap on a scrollable field nudges its text.
    #[test]
    fn a_press_that_stays_inside_the_slop_does_not_scroll() {
        let (_ui, mut s, id) = area();
        let render = UiRenderState::new();
        let t = Instant::now();
        press(
            &mut s,
            &render,
            id,
            CursorSense::PressStart(CursorButton::Left),
            0.0,
            t,
        );
        for (i, y) in [1.0, -2.0, DRAG_SLOP - 0.5].into_iter().enumerate() {
            press(
                &mut s,
                &render,
                id,
                CursorSense::Pressing(CursorButton::Left),
                y,
                t + Duration::from_millis(10 * (i as u64 + 1)),
            );
        }
        press(
            &mut s,
            &render,
            id,
            CursorSense::PressEnd(CursorButton::Left),
            DRAG_SLOP - 0.5,
            t + Duration::from_millis(50),
        );
        assert!(
            (s.amt - 400.0).abs() < 0.01,
            "a tap scrolled: amt={}",
            s.amt
        );
    }
    /// A horizontal drag is not this widget's gesture: it must stay put
    /// rather than pick up the vertical noise in a sideways swipe.
    #[test]
    fn a_horizontal_drag_does_not_scroll() {
        let (_ui, mut s, id) = area();
        let render = UiRenderState::new();
        let t = Instant::now();
        s.drag(
            &render,
            id,
            CursorSense::PressStart(CursorButton::Left),
            Vec2::new(0.0, 0.0),
            t,
        );
        s.drag(
            &render,
            id,
            CursorSense::Pressing(CursorButton::Left),
            Vec2::new(120.0, 3.0),
            t + Duration::from_millis(20),
        );
        assert!((s.amt - 400.0).abs() < 0.01, "amt={}", s.amt);
    }
    /// Panning stops at the ends of the content rather than running off,
    /// which is `update_amt`'s clamp -- checked through `drag` so the two
    /// cannot drift apart.
    #[test]
    fn a_pan_past_the_end_clamps_instead_of_running_off() {
        let (_ui, mut s, id) = area();
        let render = UiRenderState::new();
        let t = Instant::now();
        s.drag(
            &render,
            id,
            CursorSense::PressStart(CursorButton::Left),
            Vec2::new(0.0, 0.0),
            t,
        );
        s.drag(
            &render,
            id,
            CursorSense::Pressing(CursorButton::Left),
            Vec2::new(0.0, 5000.0),
            t + Duration::from_millis(20),
        );
        assert!((s.amt - 0.0).abs() < 0.01, "amt={}", s.amt);
    }
 }
@@ -26,9 +26,12 @@ impl Widget for Sized {
            region.y = y.apply_rest(density).align(AxisAlign::Neg);
        }
        let used = painter.widget_within(&self.inner, region);
        // `fold_dp` on the way out: a declared size is a `Len` the caller
        // wrote (`.width(dp(48))`), and a *reported* one may not carry an
        // unresolved `dp` -- see `Len::fold_dp`.
        Size {
-            x: self.x.unwrap_or(used.x),
+            x: self.x.map(|x| x.fold_dp(density)).unwrap_or(used.x),
-            y: self.y.unwrap_or(used.y),
+            y: self.y.map(|y| y.fold_dp(density)).unwrap_or(used.y),
        }
    }
 }
@@ -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,
        }
    }
@@ -236,7 +246,21 @@ impl<'a> TextEditCtx<'a> {
        self.clear_span();
        let at = match self.text.selection {
            Some(sel) => sel.focus().index(),
-            None => return,
+            // No caret means nowhere to put the text, so this drops the
            // keystroke -- which is invisible, and was the whole of the
            // "typed text never appears" defect (see `select`'s comment).
            // A field the IME is talking to has been focused, and focusing
            // one places a caret, so reaching here is a bug in whoever
            // routed the input rather than something to recover from.
            None => {
                debug_assert!(
                    false,
                    "insert into a text field with no caret: '{}' was given input \
                     without being focused, so the keystroke would be dropped silently",
                    text,
                );
                return;
            }
        };
        let at = at.min(self.text.view.buf.text().len());
        self.text.view.buf.edit().insert_str(at, text);
@@ -358,14 +382,28 @@ impl<'a> TextEditCtx<'a> {
        // The layout borrows `self`, so the whole decision is made in here and
        // only the answer escapes.
        //
        // **A press that reaches here has already been hit-tested to this
        // widget, so there is no "outside" to clear the selection for.**
        // This used to compare `pos` against the *laid-out text's* box and
        // set `selection = None` for anything beyond it -- but the laid-out
        // text is smaller than the field (padding, and for an empty field a
        // box of literally zero width), so tapping an **empty** composer
        // granted focus, opened the keyboard, and left `selection` at
        // `None` -- and `insert_str` returns early on `None`, so every
        // keystroke after that was silently dropped and nothing ever
        // appeared. That is RUST.md's P0 box item 2, "composed text never
        // becomes visible at all": the buffer was empty the whole time, and
        // Gboard's suggestion strip (its own composing state, not ours) is
        // what made it look otherwise. Parley's `from_point`/
        // `extend_to_point` already clamp a point outside the layout to the
        // nearest cursor position, which is what a tap in a field's padding
        // should do anyway. Losing focus is a separate path
        // (`TextEditCtx::deselect`, called from the backend's focus
        // handling), not this one.
        let outcome = {
            let layout = self.layout();
-            let inside =
+            if drag {
                pos.x >= 0.0 && pos.y >= 0.0 && pos.x <= layout.width() && pos.y <= layout.height();
            if !inside {
                if drag { None } else { Some((None, None)) }
            } else if drag {
                prev_sel.map(|sel| (Some(sel.extend_to_point(layout, pos.x, pos.y)), prev_hit))
            } else {
                let hit = Selection::from_point(layout, pos.x, pos.y);
@@ -659,6 +697,39 @@ mod tests {
        assert_eq!(t.selection.unwrap().focus().index(), 0);
    }
    /// The defect itself: an empty field's laid-out text is a zero-sized
    /// box, so a tap anywhere in it used to land "outside" and clear the
    /// selection -- leaving a focused composer that silently swallowed
    /// every keystroke (RUST.md's P0 box item 2).
    #[test]
    fn tapping_an_empty_field_places_a_caret_so_typing_lands() {
        let (mut t, mut d) = edit("", EditMode::MultiLine);
        ctx(&mut t, &mut d).select(vec2(40.0, 20.0), vec2(1080.0, 2400.0), false, false);
        assert!(t.selection.is_some(), "a tap must leave a caret behind");
        ctx(&mut t, &mut d).insert("hi");
        assert_eq!(content(&t), "hi");
    }
    /// The half the fix had no reason to touch: a field that *does* hold
    /// text, tapped past the end of it (a multi-line composer's padding
    /// below the last line) keeps a caret rather than losing the one it
    /// had, and the caret lands at the nearest position -- the end.
    #[test]
    fn tapping_past_the_end_of_the_text_clamps_to_the_end() {
        let (mut t, mut d) = edit("abc", EditMode::MultiLine);
        ctx(&mut t, &mut d).select(vec2(9000.0, 9000.0), vec2(1080.0, 2400.0), false, false);
        assert_eq!(t.selection.unwrap().focus().index(), 3);
    }
    /// A drag still needs something to extend: with no previous selection
    /// there is nothing to drag from, and one must not be invented.
    #[test]
    fn dragging_without_a_previous_selection_selects_nothing() {
        let (mut t, mut d) = edit("abc", EditMode::MultiLine);
        ctx(&mut t, &mut d).select(vec2(10.0, 10.0), vec2(1080.0, 2400.0), true, false);
        assert!(t.selection.is_none());
    }
    #[test]
    fn a_single_line_field_refuses_newlines() {
        let (mut t, mut d) = edit("", EditMode::SingleLine);
@@ -698,6 +769,67 @@ 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);
@@ -69,6 +69,12 @@ impl TextView {
        }
        self.width = width;
        let tex = painter.render_text(&mut self.buf, &self.attrs, width);
        log::debug!(
            "iris text render: chars={} width={width:?} glyphs={} size={:?}",
            self.buf.text().chars().count(),
            tex.glyphs.len(),
            tex.size,
        );
        self.tex = Some(tex.clone());
        self.attrs.changed = false;
        self.buf.changed = false;
@@ -1,5 +1,6 @@
 use super::*;
 use crate::prelude::*;
 use std::time::Instant;
 // these methods should "not require any context" (require unit) because they're in core
 widget_trait! {
@@ -90,6 +91,20 @@ widget_trait! {
                    let delta = ctx.data.scroll_delta.y * 50.0;
                    ctx.widget(rsc).scroll(delta);
                })
                // A finger drag, through the same `DragGesture` the
                // transcript's `List` is panned by -- `Scroll::drag`'s doc
                // has the arbitration and why there is no fling. The wheel
                // above and this are the two inputs of one scroll, so they
                // are registered together rather than left to each caller.
                .on(
                    CursorSense::click_or_drag() | CursorSense::unclick(),
                    |ctx, rsc| {
                        let id = ctx.widget.id();
                        let (sense, pos) = (ctx.data.sense, ctx.data.cursor.pos);
                        ctx.widget(rsc)
                            .drag(ctx.data.render, id, sense, pos, Instant::now());
                    },
                )
                .add(state)
        }
    }
@@ -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 +83,31 @@ where
        .label("Message")
        .add(rsc);
-    let bar: WeakWidget = (field.pad(dp(12)).width(rest(1)),)
+    // One widget: an opaque bar sized to its own content (`.background`'s
-        .span(Dir::RIGHT)
+    // `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.
    // `.scrollable().masked()`: the finger pan (`Scroll::drag`) plus the
    // clip that keeps six lines' worth of a longer message inside the
    // bar. The mask is the caller's job rather than `Scroll`'s own,
    // because `Painter::set_mask` allows exactly one mask per widget and
    // a `Scroll` nested under another masked area would abort on the
    // second -- `.masked()` is the one mechanism for clipping and this is
    // one more use of it (tabs-ui's message area is the other).
    // Without it the overflow paints *above* the bar, over the
    // transcript: measured before this change at 58px of stray text for a
    // 475px message in a 417px box.
    let content = field
        .scrollable()
        .masked()
        .pad(dp(FIELD_PAD_DP))
        .max_height(dp(APPROX_LINE_HEIGHT_DP * MAX_LINES + FIELD_PAD_DP * 2.0))
        .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)
 }
@@ -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
@@ -66,6 +66,14 @@ pub struct TranscriptScreen {
    /// interior mutability, per `push_row`'s existing `&self`). Drained by
    /// [`Self::take_rebuilds`].
    rebuilds: std::cell::Cell<usize>,
    /// The per-block widgets of the row at the live end of the list --
    /// the only row a streamed delta ever lands in -- so
    /// [`Self::apply`]'s `ReplaceLast` can replace one markdown block
    /// instead of rebuilding the message
    /// (`row::RowBlocks::apply_delta`). `None` for a tail that has no
    /// delta path (a tool run) or before anything has been pushed. Its
    /// removal is every path that replaces or drops the tail row, below.
    tail: RefCell<Option<(RowKey, row::RowBlocks)>>,
 }
 impl TranscriptScreen {
@@ -77,8 +85,39 @@ impl TranscriptScreen {
    where
        Rsc::State: FocusHost,
    {
-        let (key, widget) = row::build_row(rsc, self.list, self.selection.clone(), row);
+        let (key, widget, blocks) = row::build_row(rsc, self.list, self.selection.clone(), row);
        (self.list)(rsc).push_back(ListRow::new(key, widget));
        *self.tail.borrow_mut() = blocks.map(|b| (key, b));
    }
    /// The `ReplaceLast` fast path: update the tail row's blocks in place
    /// if this really is a delta into the same message, and say whether
    /// that worked. `false` for anything the caller must rebuild instead
    /// -- a tail with no block state (a tool run), a row that is not a
    /// `Single`, or a change `RowBlocks::apply_delta` will not take.
    fn apply_tail_delta<Rsc: HasEvents>(&self, rsc: &mut Rsc, key: RowKey, row: &FoldedRow) -> bool
    where
        Rsc::State: FocusHost,
    {
        let FoldedRow::Single(item) = row else {
            return false;
        };
        let mut tail = self.tail.borrow_mut();
        let Some((tail_key, blocks)) = tail.as_mut() else {
            return false;
        };
        if *tail_key != key {
            return false;
        }
        let (sender, markdown_src) = row::item_content(item);
        blocks.apply_delta(
            rsc,
            self.list,
            self.selection.clone(),
            key,
            sender,
            &markdown_src,
        )
    }
    /// Apply the effect of one more folded event without rebuilding the
@@ -134,26 +173,52 @@ impl TranscriptScreen {
                }
            }
            RowDiff::ReplaceLast { common } => {
-                // Only the tail row's content changed -- rebuild that one
+                // Only the tail row's content changed. First try the
-                // row and swap it in place, keeping every row before it
+                // delta path: the row is a column of one widget per
-                // untouched.
+                // markdown block, so a delta that lands in the last block
                // is one `set_with_spans` and the earlier blocks keep
                // their layouts (`row::RowBlocks::apply_delta`, and
                // docs/DECISIONS.md for why the row is shaped that way).
                let old_key = row::row_key(&old_rows[common].key());
-                let (new_key, widget) =
+                let new_key = row::row_key(&new_rows[common].key());
-                    row::build_row(rsc, self.list, self.selection.clone(), &new_rows[common]);
+                if new_key == old_key && self.apply_tail_delta(rsc, new_key, &new_rows[common]) {
-                if new_key != old_key {
+                    for row in &new_rows[common + 1..] {
-                    self.selection.borrow_mut().unregister(old_key);
+                        self.push_row(rsc, row);
                    }
                    return;
                }
                // Otherwise rebuild that one row and swap it in place,
                // keeping every row before it untouched. `unregister`
                // unconditionally, not only when the key changed: a
                // rebuild with *fewer* blocks under the same key would
                // otherwise leave the extra blocks in `Selection`
                // pointing at widgets the `drop` below frees (the shape
                // docs/REVIEW-2026-09-06.md's finding 1 called out).
                self.selection.borrow_mut().unregister(old_key);
                let (new_key, widget, blocks) =
                    row::build_row(rsc, self.list, self.selection.clone(), &new_rows[common]);
                let evicted = (self.list)(rsc).replace_back(ListRow::new(new_key, widget));
                drop(evicted); // frees the old row's widget, same as a pop would
                *self.tail.borrow_mut() = blocks.map(|b| (new_key, b));
                for row in &new_rows[common + 1..] {
                    self.push_row(rsc, row);
                }
            }
            RowDiff::Rebuild => {
                // A row before the tail changed (a regroup) -- nothing
-                // short of a full rebuild expresses that.
+                // short of a full rebuild expresses that. `Selection`
                // gets cleared the same way `List` does, right before the
                // rows it was pointing at go with it -- `push_row` below
                // re-`register`s whatever survives as it rebuilds each
                // row (docs/REVIEW-2026-09-06.md finding 1: a key that
                // `group_tool_runs` regrouped away used to stay in
                // `Selection` pointing at a widget this `clear()` had
                // just freed, panicking the next long-press anywhere).
                self.rebuilds.set(self.rebuilds.get() + 1);
                self.selection.borrow_mut().clear();
                (self.list)(rsc).clear();
                *self.tail.borrow_mut() = None;
                for row in &new_rows {
                    self.push_row(rsc, row);
                }
@@ -205,9 +270,18 @@ where
    let selection = Rc::new(RefCell::new(Selection::new()));
    let list = List::new(Axis::Y).add(rsc);
    // The last row's block widgets are kept for the same reason
    // `push_row` keeps them: a reply that is *already* streaming when the
    // screen is built takes its next delta through `apply`, and a `None`
    // here would send that delta down the rebuild path instead -- the
    // whole message re-shaped, which is exactly what the per-block column
    // exists to avoid, and nothing on screen or in `take_rebuilds` would
    // say so.
    let mut tail = None;
    for row in &rows {
-        let (key, widget) = row::build_row(rsc, list, selection.clone(), row);
+        let (key, widget, blocks) = row::build_row(rsc, list, selection.clone(), row);
        list(rsc).push_back(ListRow::new(key, widget));
        tail = blocks.map(|b| (key, b));
    }
    // Wheel/trackpad scrolling -- the same idiom `trait_fns.rs`'s
@@ -220,6 +294,41 @@ 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| {
                // Which *block* the finger is over, resolved from its
                // drawn box rather than from the row's extent -- a row is
                // a column of one widget per markdown block now, and the
                // block is what `Selection` selects (`SelKey`).
                let row = selection
                    .borrow()
                    .locate(&*rsc, ctx.data.render, ctx.data.cursor.pos);
                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)
@@ -229,6 +338,7 @@ where
    (
        TranscriptScreen {
            tail: RefCell::new(tail),
            list,
            composer,
            selection,
@@ -377,3 +487,272 @@ mod diff_tests {
        assert_eq!(diff_rows(&old, &new), RowDiff::Rebuild);
    }
 }
 /// Exercises `TranscriptScreen::apply`'s `Rebuild` arm through a real
 /// `Selection`, the gap docs/REVIEW-2026-09-06.md finding 8 named: the
 /// pure `diff_rows` decision above and `selection.rs`'s own registration
 /// tests each pass in isolation, and neither alone catches finding 1 (a
 /// regrouped-away row's key surviving in `Selection` after `List::clear()`
 /// has already freed its widget). This fails before `Selection::clear()`
 /// existed and the `Rebuild` arm called it, with a panic from
 /// `TextEditable::edit` resolving the freed slot.
 #[cfg(test)]
 mod apply_tests {
    use super::*;
    use client_core::transcript_fold::TranscriptItem;
    struct TestFocus {
        focus: Option<WeakWidget<TextEdit>>,
    }
    impl FocusHost for TestFocus {
        fn recent_click(&mut self) -> bool {
            false
        }
        fn set_focus(&mut self, id: Option<WeakWidget<TextEdit>>) {
            self.focus = id;
        }
        fn focus_gained(&mut self, _region: Option<PixelRegion>) {}
        fn is_focused(&self, id: WeakWidget<TextEdit>) -> bool {
            self.focus == Some(id)
        }
    }
    struct TestRsc {
        ui: UiData,
        events: EventManager<TestRsc>,
    }
    impl UiRsc for TestRsc {
        fn ui(&self) -> &UiData {
            &self.ui
        }
        fn ui_mut(&mut self) -> &mut UiData {
            &mut self.ui
        }
        fn on_draw(&mut self, active: &ActiveData) {
            self.events.draw(active);
        }
        fn on_undraw(&mut self, active: &ActiveData) {
            self.events.undraw(active);
        }
        fn on_remove(&mut self, id: WidgetId) {
            self.events.remove(id);
        }
    }
    impl HasState for TestRsc {
        type State = TestFocus;
    }
    impl HasEvents for TestRsc {
        fn events(&self) -> &EventManager<Self> {
            &self.events
        }
        fn events_mut(&mut self) -> &mut EventManager<Self> {
            &mut self.events
        }
    }
    fn user(seq: u64, text: &str) -> TranscriptItem {
        TranscriptItem::UserMsg {
            seq,
            text: text.to_string(),
            attachments: Vec::new(),
        }
    }
    fn tool(seq: u64, run_id: &str) -> TranscriptItem {
        TranscriptItem::ToolRun {
            seq,
            id: format!("id{seq}"),
            run_id: run_id.to_string(),
            tool: "grep".to_string(),
            input: "x".to_string(),
            output: String::new(),
            done: false,
            asks: Vec::new(),
            images: Vec::new(),
        }
    }
    fn assistant(seq: u64, text: &str) -> TranscriptItem {
        TranscriptItem::AssistantMsg {
            seq,
            text: text.to_string(),
            settled: false,
        }
    }
    /// A reply of `paragraphs` paragraphs, the last one still growing.
    fn reply(paragraphs: usize, tail: &str) -> String {
        let mut out = String::new();
        for i in 0..paragraphs {
            out.push_str(&format!("Paragraph number {i} of a streamed reply.\n\n"));
        }
        out.push_str(tail);
        out
    }
    /// `(Widget::draw` calls, text layouts) caused by one streamed delta
    /// landing in the last paragraph of a reply that already has
    /// `paragraphs` of them.
    fn cost_of_one_delta(paragraphs: usize) -> (u64, u64) {
        let mut rsc = TestRsc {
            ui: UiData::default(),
            events: EventManager::default(),
        };
        let old_items = vec![assistant(1, &reply(paragraphs, "and the last one is st"))];
        let new_items = vec![assistant(
            1,
            &reply(paragraphs, "and the last one is still going."),
        )];
        let (screen, tree) = build_tree(
            &mut rsc,
            client_core::transcript_fold::group_tool_runs(&old_items),
        );
        let mut render = UiRenderState::new();
        render.resize((1080.0, 20000.0));
        render.update(&tree, &mut rsc);
        render.take_counters();
        screen.apply(&mut rsc, &old_items, &new_items);
        render.update(&tree, &mut rsc);
        assert_eq!(screen.take_rebuilds(), 0, "the delta path must be taken");
        let (draws, _, _, shapes) = render.take_counters();
        (draws, shapes)
    }
    /// The pass condition for docs/DECISIONS.md's per-block row: a delta
    /// costs the **last block**, not the message. A 3,000-character reply
    /// has a hundred paragraphs already laid out; redrawing one delta into it
    /// must cost exactly what the same delta costs in a one-paragraph
    /// reply, or the earlier blocks are being re-shaped.
    ///
    /// Before the split this was one `TextEdit` for the whole message, so
    /// the count was the same *number* of widgets but each redraw
    /// re-shaped every paragraph through parley -- which a draw counter
    /// cannot see. What it can see is that the count does not *grow* with
    /// the message, which it now does not and could not before, since the
    /// one widget's own layout was O(message).
    #[test]
    fn a_delta_into_a_long_reply_redraws_the_same_widgets_as_a_short_one() {
        assert!(
            reply(100, "").len() > 3_000,
            "the long case must actually be a long message"
        );
        let (short_draws, short_shapes) = cost_of_one_delta(1);
        let (long_draws, long_shapes) = cost_of_one_delta(100);
        assert_eq!(
            short_draws, long_draws,
            "a delta into a 100-paragraph reply redrew {long_draws} widgets against \
             {short_draws} for a one-paragraph reply -- the earlier blocks are not being kept"
        );
        // The half a draw counter cannot see, and the one the per-block
        // row actually exists for: a redraw is free if the text engine
        // hits its memo, and a re-shape is the expensive thing. One
        // shape, whatever the message is worth -- the block the delta
        // landed in. Before the split this was necessarily O(message),
        // since the whole reply was one buffer.
        assert_eq!(
            (short_shapes, long_shapes),
            (1, 1),
            "a delta shaped {long_shapes} text layouts in a 100-paragraph reply and \
             {short_shapes} in a one-paragraph one; it must be the last block and nothing else"
        );
    }
    #[test]
    fn a_row_dropped_by_a_regroup_does_not_outlive_itself_in_selection() {
        use client_core::transcript_fold::group_tool_runs;
        let mut rsc = TestRsc {
            ui: UiData::default(),
            events: EventManager::default(),
        };
        // Same regroup shape as diff_tests' regroup case, plus a trailing
        // row (seq 4) that survives unchanged -- what a reader would tap
        // on right after the regroup lands.
        let old_items = vec![tool(1, "run-a"), user(2, "meanwhile"), user(4, "stable")];
        let new_items = vec![tool(1, "run-a"), tool(3, "run-a"), user(4, "stable")];
        assert_eq!(
            diff_rows(&group_tool_runs(&old_items), &group_tool_runs(&new_items)),
            RowDiff::Rebuild,
            "test setup must actually exercise the Rebuild arm"
        );
        let (screen, _tree) = build_tree(&mut rsc, group_tool_runs(&old_items));
        screen.apply(&mut rsc, &old_items, &new_items);
        // The surviving row (seq 4) is what a reader's long-press would
        // land on; `begin` deselects every *other* registered row first,
        // which is exactly what used to resolve a stale `WeakWidget` left
        // by the regrouped-away rows and panic.
        let surviving_key = row::row_key(&client_core::transcript_fold::ItemKey::Seq(4));
        screen.selection.borrow_mut().begin(
            &mut rsc,
            (surviving_key, 0),
            Vec2::ZERO,
            Vec2::new(10.0, 10.0),
        );
    }
    /// The failure half of the per-block row, and the one
    /// `a_row_dropped_by_a_regroup_...` cannot reach: the tail row is
    /// rebuilt under the **same key** with *fewer* blocks than it had.
    /// `Selection` is keyed by `(row, block)`, so the blocks that no
    /// longer exist are left pointing at widgets `replace_back`'s drop
    /// frees -- and `begin` resolves every registered handle on an
    /// ordinary press, so the next tap anywhere in the transcript
    /// panics. Nothing about the key changed, which is why the
    /// `if new_key != old_key` guard this replaced could not see it.
    #[test]
    fn a_tail_rebuilt_with_fewer_blocks_leaves_none_of_them_in_selection() {
        use client_core::transcript_fold::group_tool_runs;
        let mut rsc = TestRsc {
            ui: UiData::default(),
            events: EventManager::default(),
        };
        // Three blocks, then one. The rewrite is of an *earlier* block
        // (the heading), so `RowBlocks::apply_delta` refuses it and the
        // rebuild path is the one taken -- assert that below.
        let old_items = vec![user(1, "stable"), assistant(2, "# Head\n\npara\n\n- item")];
        let new_items = vec![user(1, "stable"), assistant(2, "short")];
        assert_eq!(
            diff_rows(&group_tool_runs(&old_items), &group_tool_runs(&new_items)),
            RowDiff::ReplaceLast { common: 1 },
            "test setup must actually exercise the ReplaceLast arm"
        );
        let (screen, _tree) = build_tree(&mut rsc, group_tool_runs(&old_items));
        let tail_key = row::row_key(&client_core::transcript_fold::ItemKey::Seq(2));
        assert_eq!(
            screen
                .selection
                .borrow()
                .registered_blocks(tail_key)
                .count(),
            3,
            "the fixture must start with more blocks than it ends with"
        );
        screen.apply(&mut rsc, &old_items, &new_items);
        assert_eq!(
            screen
                .selection
                .borrow()
                .registered_blocks(tail_key)
                .count(),
            1,
            "the blocks the rebuild dropped are still registered"
        );
        // What a reader does next: press the row that survived. `begin`
        // resolves every registered handle, so a stale one panics here.
        let surviving_key = row::row_key(&client_core::transcript_fold::ItemKey::Seq(1));
        screen.selection.borrow_mut().begin(
            &mut rsc,
            (surviving_key, 0),
            Vec2::ZERO,
            Vec2::new(10.0, 10.0),
        );
    }
 }
@@ -1,11 +1,18 @@
 //! One `iris::widget::list::ListRow` per folded transcript row
-//! (`client_core::transcript_fold::TranscriptRow`). Each row's whole text
+//! (`client_core::transcript_fold::TranscriptRow`). A row is a **column of
-//! -- headings, paragraphs, inline styling -- goes through `markdown` into
+//! one `TextEdit` per top-level markdown block** (paragraph, heading,
-//! **one** `TextEdit`, which is what makes it one thing `Selection`
+//! fence, list, table -- `client_core::markdown_blocks`), each rendered
-//! (`selection.rs`) can select and what lets it wrap and scroll as a
+//! with `markdown`'s inline spans, so that RUST.md's "hard to get back"
-//! single buffer, matching RUST.md's "hard to get back" behaviour 2 (rich
+//! behaviour 2 (rich inline text) still holds within a block and
-//! inline text) and half of behaviour 1 (selectable within a row; across
+//! behaviour 1 (selection) runs across blocks and rows alike through
-//! rows is `selection.rs`'s job).
+//! `selection.rs`.
 //!
 //! It was one `TextEdit` for the whole message until 2026-09-06, which
 //! meant a streamed delta re-shaped every paragraph of a long reply
 //! through parley again -- the stream phase was the one place iris trailed
 //! Compose on Iris's phone. [`RowBlocks::apply_delta`] is the other half
 //! of the fix; docs/DECISIONS.md's entry has what the alternative shapes
 //! were and why this one.
 //!
 //! A `TranscriptRow::Tools` (a run of adjacent tool calls, grouped by
 //! `client_core::transcript_fold::group_tool_runs`) is the row that proves
@@ -17,11 +24,18 @@
 //! `list.rs`'s module doc describes for `AGENTS.md`'s `holdTopEdge`.
 use crate::markdown::render_markdown;
-use crate::selection::Selection;
+use crate::selection::{SelKey, Selection};
 use client_core::markdown_blocks::{Block, BlockKind, common_prefix, split_blocks};
 use client_core::transcript_fold::{QuestionCard, TranscriptItem, TranscriptRow as FoldedRow};
 use iris::prelude::*;
 use std::{cell::RefCell, rc::Rc, time::Instant};
 /// The gap drawn between two markdown blocks of one message. A block used
 /// to be separated by the blank line `markdown::render_markdown` put in
 /// the single buffer; now that each block is its own widget, that spacing
 /// has to be the column's.
 const BLOCK_GAP_DP: f32 = 8.0;
 /// The paragraph size every row's `TextEdit` is built at; markdown headings
 /// inside a row scale relative to a fixed set of sizes rather than this one
 /// (`markdown::heading_size`), since a heading is meant to look the same
@@ -51,7 +65,7 @@ pub fn row_key(key: &client_core::transcript_fold::ItemKey) -> RowKey {
 /// The sender label shown above a row's text, and the markdown source to
 /// render below it. `None` for a system-style note that has no sender.
-fn item_content(item: &TranscriptItem) -> (Option<&str>, String) {
+pub(crate) fn item_content(item: &TranscriptItem) -> (Option<&str>, String) {
    match item {
        TranscriptItem::UserMsg { text, .. } => (Some("You"), text.clone()),
        TranscriptItem::AssistantMsg { text, .. } => (Some("Claude"), text.clone()),
@@ -107,24 +121,53 @@ fn tool_call_markdown(tool: &str, input: &str, output: &str) -> String {
    out
 }
-/// Build one `TextEdit` from a sender label plus markdown source, register
+/// The per-block text widgets of one row, kept by `TranscriptScreen` for
-/// it with `selection` under `key`, and wire the pointer handlers that
+/// the row a reply is streaming into, so a delta can replace the block it
-/// drive `Selection::drag` -- shared by every row variant below, since a
+/// lands in instead of re-shaping the whole message
-/// selectable row is always "one TextEdit plus this wiring" regardless of
+/// (docs/DECISIONS.md, 2026-09-06). Nothing else needs it: a row that is
-/// what folded it. `list` is threaded through so that same drag can pan
+/// not the tail never changes.
-/// the list instead of selecting, per `Selection::drag`'s own doc.
+pub struct RowBlocks {
-fn build_text_row<Rsc: HasEvents>(
+    /// What each field was built from, in order -- compared against a
    /// fresh split to decide what may be kept. See
    /// `client_core::markdown_blocks`' module doc for why this is a
    /// comparison and not an assumption.
    blocks: Vec<Block>,
    fields: Vec<WeakWidget<TextEdit>>,
    column: WeakWidget<Span>,
    /// The sender label the row was built with. A delta that changes it is
    /// not a delta into the same message, so it falls back to a rebuild.
    sender: Option<String>,
 }
 /// Split for display: never empty, so a row with nothing in it yet is
 /// still one (empty) text widget rather than no widget at all -- an empty
 /// column reports a zero size and the row would vanish from the list.
 fn display_blocks(markdown_src: &str) -> Vec<Block> {
    let blocks = split_blocks(markdown_src);
    if blocks.is_empty() {
        vec![Block {
            kind: BlockKind::Paragraph,
            source: markdown_src.to_string(),
        }]
    } else {
        blocks
    }
 }
 /// One block's own `TextEdit`, registered with `selection` under
 /// `(row, block)` and wired to `Selection::drag` -- the block is the
 /// selection unit (`selection::SelKey`).
 fn build_block_field<Rsc: HasEvents>(
    rsc: &mut Rsc,
    list: WeakWidget<List>,
    selection: Rc<RefCell<Selection>>,
-    key: RowKey,
+    key: SelKey,
-    sender: Option<&str>,
+    source: &str,
-    markdown_src: &str,
+) -> WeakWidget<TextEdit>
 ) -> StrongWidget
 where
    Rsc::State: FocusHost,
 {
-    let (text, spans) = render_markdown(markdown_src, BASE_SIZE);
+    let (text, spans) = render_markdown(source, BASE_SIZE);
    let field = wtext(text)
        .spans(spans)
        .editable(EditMode::MultiLine)
@@ -137,24 +180,62 @@ where
    field
        // `| CursorSense::unclick()` on top of the usual click-or-drag set
-        // -- the arbiter inside `Selection::drag` needs the release too,
+        // -- this block's own registration only ever needs to see a
-        // to go back to idle for the next press (`DragArbiter::release`).
+        // 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,
+                    Some((key, ctx.data.pos, ctx.data.size)),
                    ctx.data.pos,
                    ctx.data.size,
                    ctx.data.cursor.pos,
                    ctx.data.sense,
                    Instant::now(),
                    ctx.data.render,
                );
            },
        )
        .add(rsc);
    field
 }
 /// Build a row from a sender label plus markdown source: a column of one
 /// `TextEdit` per top-level markdown block, under the sender's own label.
 ///
 /// One widget per block rather than one per message is what makes a
 /// streamed delta cost the last block instead of the whole reply -- see
 /// [`RowBlocks::apply_delta`] for the other half, and
 /// `client_core::markdown_blocks` for the split. Selection still runs
 /// across the whole transcript; the unit it steps in is a block now rather
 /// than a row (`selection::SelKey`).
 fn build_text_row<Rsc: HasEvents>(
    rsc: &mut Rsc,
    list: WeakWidget<List>,
    selection: Rc<RefCell<Selection>>,
    key: RowKey,
    sender: Option<&str>,
    markdown_src: &str,
 ) -> (StrongWidget, RowBlocks)
 where
    Rsc::State: FocusHost,
 {
    let blocks = display_blocks(markdown_src);
    let mut column = Span::empty(Dir::DOWN).gap(dp(BLOCK_GAP_DP));
    let mut fields = Vec::with_capacity(blocks.len());
    for (i, block) in blocks.iter().enumerate() {
        let field = build_block_field(rsc, list, selection.clone(), (key, i as u32), &block.source);
        fields.push(field);
        column.push(field.width(rest(1)).add_strong(rsc).any());
    }
    let column = column.add(rsc);
    // `.add` (weak), not `.add_strong` -- `header` is about to be embedded
    // as a child of the `.span(Dir::DOWN)` below, whose own composition is
@@ -172,12 +253,91 @@ where
        None => Span::empty(Dir::DOWN).add(rsc),
    };
-    (header, field.width(rest(1)))
+    let widget = (header, column.width(rest(1)))
        .span(Dir::DOWN)
        .gap(dp(4))
        .pad(dp(10))
        .add_strong(rsc)
-        .any()
+        .any();
    (
        widget,
        RowBlocks {
            blocks,
            fields,
            column,
            sender: sender.map(str::to_string),
        },
    )
 }
 impl RowBlocks {
    /// Bring this row up to date with `markdown_src` **without** re-laying
    /// out the blocks that did not change, and say whether that was
    /// possible. `false` means the caller must rebuild the row the
    /// ordinary way: an earlier block was rewritten (markdown allows it --
    /// a trailing `---` turns the paragraph above into a heading), the
    /// sender changed, or the message got shorter.
    ///
    /// This is the whole point of the per-block column: a delta arriving
    /// in a 3,000-character reply touches one `set_with_spans` on the last
    /// block, so parley re-shapes that block and nothing else.
    pub fn apply_delta<Rsc: HasEvents>(
        &mut self,
        rsc: &mut Rsc,
        list: WeakWidget<List>,
        selection: Rc<RefCell<Selection>>,
        key: RowKey,
        sender: Option<&str>,
        markdown_src: &str,
    ) -> bool
    where
        Rsc::State: FocusHost,
    {
        if self.sender.as_deref() != sender {
            return false;
        }
        let new_blocks = display_blocks(markdown_src);
        let common = common_prefix(&self.blocks, &new_blocks);
        // Everything already drawn must either be kept whole (`common ==
        // len`, a pure append) or be kept except for the last block, which
        // is the one a delta lands in. Anything else means an already
        // laid-out block is no longer what it was.
        if new_blocks.len() < self.blocks.len() || common + 1 < self.blocks.len() {
            return false;
        }
        debug_assert!(
            self.fields.len() == self.blocks.len(),
            "one field per block: {} fields, {} blocks",
            self.fields.len(),
            self.blocks.len()
        );
        for (i, block) in new_blocks.iter().enumerate().skip(common) {
            let (text, spans) = render_markdown(&block.source, BASE_SIZE);
            match self.fields.get(i) {
                Some(field) => field.edit(rsc).set_with_spans(&text, spans),
                None => {
                    let field = build_block_field(
                        rsc,
                        list,
                        selection.clone(),
                        (key, i as u32),
                        &block.source,
                    );
                    self.fields.push(field);
                    let child = field.width(rest(1)).add_strong(rsc).any();
                    // `get_mut` marks the column dirty, which is what gets
                    // the new block drawn; its removal half is the row's
                    // own, since the column owns the child strongly.
                    if let Some(column) = rsc.ui_mut().widgets.get_mut(&self.column) {
                        column.push(child);
                    }
                }
            }
        }
        self.blocks = new_blocks;
        true
    }
 }
 fn build_single<Rsc: HasEvents>(
@@ -186,7 +346,7 @@ fn build_single<Rsc: HasEvents>(
    selection: Rc<RefCell<Selection>>,
    key: RowKey,
    item: &TranscriptItem,
-) -> StrongWidget
+) -> (StrongWidget, RowBlocks)
 where
    Rsc::State: FocusHost,
 {
@@ -243,8 +403,15 @@ where
    where
        Rsc::State: FocusHost,
    {
        // Every block of the previous content goes first: collapsing a
        // five-block expansion back to a one-line summary registers only
        // `(key, 0)`, and blocks 1..5 would be left in `Selection`
        // pointing at widgets `ptr.replace` is about to free -- the same
        // class of bug docs/REVIEW-2026-09-06.md's finding 1 found in the
        // `Rebuild` arm, reached the other way.
        selection.borrow_mut().unregister(key);
        let text = if expanded { full } else { summary };
-        build_text_row(rsc, list, selection, key, Some("Tools"), text)
+        build_text_row(rsc, list, selection, key, Some("Tools"), text).0
    }
    let content = build_content(
@@ -293,18 +460,26 @@ pub fn build_row<Rsc: HasEvents>(
    list: WeakWidget<List>,
    selection: Rc<RefCell<Selection>>,
    row: &FoldedRow,
-) -> (RowKey, StrongWidget)
+) -> (RowKey, StrongWidget, Option<RowBlocks>)
 where
    Rsc::State: FocusHost,
 {
    match row {
        FoldedRow::Single(item) => {
            let key = row_key(&item.key());
-            (key, build_single(rsc, list, selection, key, item))
+            let (widget, blocks) = build_single(rsc, list, selection, key, item);
            (key, widget, Some(blocks))
        }
        FoldedRow::Tools(calls) => {
            let key = row_key(&calls[0].key());
-            (key, build_tools(rsc, list, selection, key, calls.clone()))
+            // `None`: a run of tool calls is never what a reply streams
            // into, and its own expand/collapse replaces the whole
            // content anyway, so there is no delta path to keep state for.
            (
                key,
                build_tools(rsc, list, selection, key, calls.clone()),
                None,
            )
        }
    }
 }
@@ -33,20 +33,26 @@
 use iris::prelude::*;
 use std::{collections::BTreeMap, time::Instant};
 /// What this selects between: a row's `RowKey` and the index of one
 /// markdown **block** inside it. A row is a column of one text widget per
 /// block since 2026-09-06 (`client_core::markdown_blocks`, and
 /// docs/DECISIONS.md for why), so the block, not the row, is the unit --
 /// `(row, block)` compares lexicographically, which is reading order for
 /// both levels, so every range query below is unchanged.
 pub type SelKey = (RowKey, u32);
 pub struct Selection {
-    rows: BTreeMap<RowKey, WeakWidget<TextEdit>>,
+    rows: BTreeMap<SelKey, WeakWidget<TextEdit>>,
-    anchor: Option<(RowKey, Vec2)>,
+    anchor: Option<(SelKey, 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.
+    /// `iris::sense::DragGesture`'s own doc for the arbitration, velocity
-    arbiter: DragArbiter,
+    /// tracking and pointer-capture mechanics this no longer owns itself
-    /// Tracks the last ~100ms of this gesture's pan deltas (in the same
+    /// -- Iris's 2026-09-06 ask (`IRIS.md`) that a drag's *mechanics* live
-    /// signed units `list.scroll` takes), so a release that turns out to
+    /// in iris's default input layer, with only the pan-vs-select
-    /// have been panning can hand `List::fling` a realistic initial
+    /// *decision* staying here.
-    /// velocity instead of one frame's noisy last delta --
+    gesture: DragGesture,
    /// IRIS_TODO.md's "swiping has no momentum."
    velocity: VelocityTracker,
 }
 impl Default for Selection {
@@ -60,22 +66,43 @@ impl Selection {
        Self {
            rows: BTreeMap::new(),
            anchor: None,
-            arbiter: DragArbiter::new(),
+            gesture: DragGesture::new(),
            velocity: VelocityTracker::new(),
        }
    }
    /// A row's selectable text became visible/known. Every addition here
-    /// needs its removal (`unregister`) -- called when `List` evicts the
+    /// needs its removal (`unregister`, or `clear` for all of them at
-    /// row (`pop_front`/`pop_back`), so this map never outgrows however
+    /// once) -- called when `List` evicts the row (`pop_front`/
-    /// many rows are actually loaded.
+    /// `pop_back`/`clear`), so this map never outgrows however many rows
-    pub fn register(&mut self, key: RowKey, text: WeakWidget<TextEdit>) {
+    /// are actually loaded. `List::place` guards the twin of this same
    /// class of bug on the list's own side (`list.rs`'s `slot_exists`
    /// assertion) -- a derived handle that silently outlives what it
    /// points to; the next caller adding a third row-keyed side table
    /// should read both.
    pub fn register(&mut self, key: SelKey, text: WeakWidget<TextEdit>) {
        self.rows.insert(key, text);
    }
-    pub fn unregister(&mut self, key: RowKey) {
+    /// Drops every registration at once -- the same shape `List::clear()`
-        self.rows.remove(&key);
+    /// clears the list, and what `TranscriptScreen::apply`'s `Rebuild` arm
-        if self.anchor.map(|(k, _)| k) == Some(key) {
+    /// calls right before it, since a full rebuild drops every row's old
    /// widget and `push_row` re-`register`s each surviving key's new one
    /// as it goes (review docs/REVIEW-2026-09-06.md finding 1: the
    /// `Rebuild` arm used to call only `List::clear()`, leaving any key
    /// dropped by the regroup -- present in the old rows, absent from the
    /// new ones -- pointing at a widget the list had just freed, so the
    /// next long-press anywhere panicked in `begin`'s deselect loop).
    pub fn clear(&mut self) {
        self.rows.clear();
        self.anchor = None;
    }
    /// Forgets every block of one row -- a row is registered block by
    /// block, so its removal has to take all of them, and taking only the
    /// first is how a freed widget would be left behind in this map.
    pub fn unregister(&mut self, row: RowKey) {
        self.rows.retain(|&(k, _), _| k != row);
        if self.anchor.map(|((k, _), _)| k) == Some(row) {
            self.anchor = None;
        }
    }
@@ -85,8 +112,8 @@ impl Selection {
    /// gives `key`'s row a collapsed caret at `pos` -- a plain click that
    /// never turns into a drag leaves exactly this and nothing else
    /// selected.
-    pub fn begin(&mut self, ui: &mut impl UiRsc, key: RowKey, pos: Vec2, size: Vec2) {
+    pub fn begin(&mut self, ui: &mut impl UiRsc, key: SelKey, pos: Vec2, size: Vec2) {
-        let rows: Vec<RowKey> = self.rows.keys().copied().collect();
+        let rows: Vec<SelKey> = self.rows.keys().copied().collect();
        for k in rows {
            if k != key
                && let Some(w) = self.rows.get(&k)
@@ -102,7 +129,7 @@ impl Selection {
    /// The drag continues, now over `key`'s row at `pos`. See the module
    /// doc for the anchor-row shortcut.
-    pub fn extend(&mut self, ui: &mut impl UiRsc, key: RowKey, pos: Vec2, size: Vec2) {
+    pub fn extend(&mut self, ui: &mut impl UiRsc, key: SelKey, pos: Vec2, size: Vec2) {
        let Some((anchor_key, _anchor_pos)) = self.anchor else {
            return;
        };
@@ -117,7 +144,7 @@ impl Selection {
        } else {
            (key, anchor_key)
        };
-        let in_range: Vec<RowKey> = self.rows.range(lo..=hi).map(|(&k, _)| k).collect();
+        let in_range: Vec<SelKey> = self.rows.range(lo..=hi).map(|(&k, _)| k).collect();
        for k in &in_range {
            let Some(w) = self.rows.get(k).copied() else {
                continue;
@@ -133,7 +160,7 @@ impl Selection {
                w.edit(ui).select_all();
            }
        }
-        let outside: Vec<RowKey> = self
+        let outside: Vec<SelKey> = self
            .rows
            .keys()
            .copied()
@@ -146,6 +173,47 @@ impl Selection {
        }
    }
    /// The block indices currently registered for `row`, in order. For a
    /// test asserting that a row's removal or rebuild took every one of
    /// its blocks with it -- the contract `unregister` states and the one
    /// a caller can get wrong silently, since a stale handle only shows
    /// up as a panic on some later, unrelated press.
    #[cfg(test)]
    pub fn registered_blocks(&self, row: RowKey) -> impl Iterator<Item = u32> + '_ {
        self.rows
            .keys()
            .filter(move |(k, _)| *k == row)
            .map(|&(_, b)| b)
    }
    /// Which registered block is under `pos_window`, with the position
    /// and size that block's own `TextEdit` wants (block-local, the way
    /// `begin`/`extend` are given them by a block's own pointer handler).
    ///
    /// For the pointer-captured half of a drag, where the event no longer
    /// reaches the widget under the finger and the list-level handler has
    /// to say where the finger is. It asks the render state for each
    /// block's drawn box rather than doing the arithmetic from the row's
    /// extent -- the box is what a hit test resolves against anyway, and
    /// it means this and a block's own handler cannot disagree about
    /// where a block is. O(blocks loaded), on one frame of a drag.
    pub fn locate(
        &self,
        ui: &impl UiRsc,
        render: &UiRenderState,
        pos_window: Vec2,
    ) -> Option<(SelKey, Vec2, Vec2)> {
        for (&key, w) in &self.rows {
            let Some(px) = render.window_region(w, ui) else {
                continue;
            };
            if px.contains(pos_window) {
                return Some((key, pos_window - px.top_left, px.size()));
            }
        }
        None
    }
    /// Whether any row currently has a non-empty selection -- what a fresh
    /// press consults so `drag` knows whether an early horizontal move is
    /// "start dragging the selection handle" rather than an ordinary tap.
@@ -165,84 +233,65 @@ 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,
+        row: Option<(SelKey, Vec2, Vec2)>,
        pos_row: Vec2,
        size: Vec2,
        pos_window: Vec2,
        sense: CursorSense,
        now: Instant,
        render: &UiRenderState,
    ) {
-        let outcome = match sense {
+        if matches!(sense, CursorSense::PressStart(_)) {
-            CursorSense::PressStart(_) => {
+            // A fresh touch-down cancels any fling still coasting from
-                let already_selected = self.has_selection(ui);
+            // the previous gesture -- `List::fling`'s own doc, and
-                self.arbiter.press_start(pos_window, now, already_selected);
+            // Android's `Scroller::abortAnimation` for the same reason.
-                self.velocity.reset();
+            list(ui).cancel_fling();
-                // A fresh touch-down cancels any fling still coasting from
+        }
-                // the previous gesture -- `List::fling`'s own doc, and
+        let already_selected = self.has_selection(ui);
-                // Android's `Scroller::abortAnimation` for the same reason.
+        let outcome =
-                list(ui).cancel_fling();
+            self.gesture
-                self.arbiter.update(pos_window, now)
+                .handle(render, list.id(), sense, pos_window, now, already_selected);
            }
            CursorSense::PressEnd(_) => {
                // 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`.
                if self.arbiter.is_panning() {
                    let v = self.velocity.velocity();
                    list(ui).fling(v);
                }
                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.velocity.reset();
                list(ui).cancel_fling();
                self.arbiter.update(pos_window, now)
            }
            _ => self.arbiter.update(pos_window, now),
        };
        match outcome {
-            DragOutcome::Undecided => {}
+            GestureOutcome::Undecided => {}
-            DragOutcome::Pan(dy) => {
+            GestureOutcome::Pan(dy) => list(ui).scroll(-dy),
-                let amt = -dy;
+            GestureOutcome::SelectStart => {
-                self.velocity.add_sample(amt, now);
+                if let Some((key, pos_row, size)) = row {
-                list(ui).scroll(amt);
+                    // 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::SelectStart => {
+            GestureOutcome::SelectExtend => {
-                // Grep-able on "iris selection" the way the frame report is
+                if let Some((key, pos_row, size)) = row {
-                // on "iris frame report" -- selection has no accessibility
+                    log::info!("iris selection: extend to row {key:?}");
-                // label of its own yet, so this is the smallest way to
+                    self.extend(ui, key, pos_row, size);
-                // 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 => {
                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) => {}
        }
    }
@@ -343,9 +392,10 @@ mod tests {
        let list = rsc.ui.widgets.add_strong(List::new(Axis::Y)).weak();
        let mut sel = Selection::new();
-        sel.register(1, field);
+        sel.register((1, 0), 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
@@ -353,22 +403,21 @@ mod tests {
        sel.drag(
            &mut rsc,
            list,
-            1,
+            Some(((1, 0), Vec2::ZERO, size)),
            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"
        );
    }
    #[test]
-    fn unregister_forgets_the_row_and_clears_a_matching_anchor() {
+    fn unregister_forgets_every_block_of_the_row_and_clears_a_matching_anchor() {
        let mut rsc = TestRsc {
            ui: UiData::default(),
        };
@@ -382,9 +431,13 @@ mod tests {
            .weak();
        let mut sel = Selection::new();
-        sel.register(5, field);
+        // Two blocks of the same row, which is what `unregister` has to
-        sel.anchor = Some((5, Vec2::ZERO));
+        // take together -- removing only the first is how a freed widget
-        assert_eq!(sel.rows.len(), 1);
+        // gets left in this map.
        sel.register((5, 0), field);
        sel.register((5, 1), field);
        sel.anchor = Some(((5, 1), Vec2::ZERO));
        assert_eq!(sel.rows.len(), 2);
        sel.unregister(5);
        assert!(sel.rows.is_empty());