Merge remote-tracking branch 'origin/main' into refresh

capture-pane trims trailing spaces, so a line's background stopped at its
last glyph and the client's own background showed through the rest as
stripes. -N keeps the padding, and with it the colour.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

crates/maestro-daemon/src/panes.rs

@@ -39,6 +39,10 @@ pub trait Panes: std::fmt::Debug + Send + Sync + 'static {
     fn pipe_pane(&self, id: Uuid, sink_command: &str) -> Result<(), TmuxError>;
 
     fn resize_window(&self, id: Uuid, cols: u16, rows: u16) -> Result<(), TmuxError>;
+
+    /// Escape-sequence snapshot of the pane's current screen, or `None` when
+    /// there is no pane to capture. See [`Tmux::capture_pane`].
+    fn capture_pane(&self, id: Uuid) -> Result<Option<Vec<u8>>, TmuxError>;
 }
 
 impl Panes for Tmux {
@@ -76,6 +80,10 @@ impl Panes for Tmux {
     fn resize_window(&self, id: Uuid, cols: u16, rows: u16) -> Result<(), TmuxError> {
         Tmux::resize_window(self, id, cols, rows)
     }
+
+    fn capture_pane(&self, id: Uuid) -> Result<Option<Vec<u8>>, TmuxError> {
+        Tmux::capture_pane(self, id)
+    }
 }
 
 // ---------------------------------------------------------------------------
@@ -92,6 +100,7 @@ pub enum Op {
     SendKeys,
     PipePane,
     ResizeWindow,
+    CapturePane,
 }
 
 /// One recorded call, in the order the manager made it. Rollback ordering is a
@@ -116,6 +125,7 @@ pub enum Call {
         cols: u16,
         rows: u16,
     },
+    CapturePane(Uuid),
 }
 
 /// In-memory [`Panes`] for tests.
@@ -133,6 +143,7 @@ struct FakeState {
     live: HashSet<Uuid>,
     panes: HashMap<Uuid, PaneInfo>,
     calls: Vec<Call>,
+    captures: HashMap<Uuid, Vec<u8>>,
     fail: HashMap<Op, String>,
 }
 
@@ -162,6 +173,12 @@ impl FakePanes {
         self.lock().live.contains(&id)
     }
 
+    /// Screen snapshot `capture_pane` hands back for `id`. Unset means "no
+    /// pane", which is what a dead session looks like.
+    pub fn set_capture(&self, id: Uuid, bytes: impl Into<Vec<u8>>) {
+        self.lock().captures.insert(id, bytes.into());
+    }
+
     pub fn set_pane_info(&self, id: Uuid, info: PaneInfo) {
         self.lock().panes.insert(id, info);
     }
@@ -242,6 +259,12 @@ impl Panes for FakePanes {
     fn resize_window(&self, id: Uuid, cols: u16, rows: u16) -> Result<(), TmuxError> {
         self.record(Call::ResizeWindow { id, cols, rows }, Op::ResizeWindow)
     }
+
+    fn capture_pane(&self, id: Uuid) -> Result<Option<Vec<u8>>, TmuxError> {
+        self.record(Call::CapturePane(id), Op::CapturePane)?;
+        let st = self.lock();
+        Ok(st.captures.get(&id).cloned())
+    }
 }
 
 #[cfg(test)]

crates/maestro-daemon/src/pty.rs

@@ -141,8 +141,21 @@ impl PtyBridge {
     /// `subscribe()` keeps the reader task from publishing in between, so
     /// the seam has no gap and no duplicates.
     pub fn subscribe_with_replay(&self) -> (Vec<u8>, broadcast::Receiver<Vec<u8>>) {
+        self.subscribe_with_snapshot(|| None)
+    }
+
+    /// As [`Self::subscribe_with_replay`], but lets the caller supply the
+    /// replay payload instead of the raw byte buffer — used to hand a fresh
+    /// client tmux's own view of the screen, which the byte tail cannot
+    /// reconstruct for a full-screen program. `capture` runs while the reader
+    /// is held off, so the payload and the live stream still meet with no gap
+    /// and no duplicate. Returning `None` falls back to the byte buffer.
+    pub fn subscribe_with_snapshot<F>(&self, capture: F) -> (Vec<u8>, broadcast::Receiver<Vec<u8>>)
+    where
+        F: FnOnce() -> Option<Vec<u8>>,
+    {
         let guard = self.replay.lock_for_snapshot();
-        let snapshot = guard.snapshot();
+        let snapshot = capture().unwrap_or_else(|| guard.snapshot());
         let rx = match &self.sender {
             Some(tx) => tx.subscribe(),
             // Sealed: hand back the scrollback plus a receiver that is already

crates/maestro-daemon/src/session.rs

@@ -260,8 +260,29 @@ impl SessionManager {
         &self,
         id: Uuid,
     ) -> Option<(Vec<u8>, broadcast::Receiver<Vec<u8>>)> {
+        let tmux = self.inner.tmux.clone();
         let sessions = self.inner.sessions.lock().await;
-        sessions.get(&id).map(|r| r.bridge.subscribe_with_replay())
+        let rec = sessions.get(&id)?;
+        // For a live session, tmux's own screen beats the byte tail: the tail
+        // starts mid-stream, so a full-screen program (an agent TUI) replayed
+        // from it renders as garbage until something forces a repaint. A dead
+        // session has no pane left to capture, so it keeps the byte tail.
+        let alive = rec.session.status == SessionStatus::Running;
+        // The capture shells out to tmux while the replay lock is held, which
+        // parks the reader for the length of one tmux round-trip. That only
+        // happens on attach, and the alternative is a seam in the stream.
+        Some(rec.bridge.subscribe_with_snapshot(|| {
+            if !alive {
+                return None;
+            }
+            match tmux.capture_pane(id) {
+                Ok(snapshot) => snapshot,
+                Err(e) => {
+                    tracing::warn!(error = ?e, %id, "capture-pane failed; replaying raw bytes");
+                    None
+                }
+            }
+        }))
     }
 
     pub async fn has(&self, id: Uuid) -> bool {

crates/maestro-daemon/src/tmux.rs

@@ -246,6 +246,70 @@ impl Tmux {
         check(out)
     }
 
+    /// Escape-sequence snapshot of a pane's current screen (#…), for clients
+    /// that just attached.
+    ///
+    /// The raw byte replay buffer cannot reconstruct a full-screen program:
+    /// its tail starts mid-stream, long after the app set up the modes,
+    /// colours and cursor position that give those bytes meaning. A browser
+    /// refresh therefore painted garbage until something forced the app to
+    /// repaint. tmux already holds the authoritative screen, so ask it.
+    ///
+    /// Returns `Ok(None)` when the session or the tmux server is gone — the
+    /// caller falls back to the byte replay, which is all a dead session has.
+    pub fn capture_pane(&self, id: Uuid) -> Result<Option<Vec<u8>>, TmuxError> {
+        let name = session_name(id);
+        let start = format!("-{CAPTURE_HISTORY_LINES}");
+        // One invocation, so tmux runs both commands in a single pass of its
+        // command queue: the cursor position cannot belong to an older screen
+        // than the captured content. Two invocations raced — a program that
+        // switched to the alternate screen in between produced a snapshot with
+        // the new screen and the old cursor.
+        let out = self
+            .cmd()
+            .args([
+                "display-message",
+                "-p",
+                "-t",
+                &name,
+                "-F",
+                "#{cursor_x} #{cursor_y} #{pane_height} #{alternate_on} #{cursor_flag}",
+                ";",
+                "capture-pane",
+                "-p",
+                "-e",
+                // Keep trailing spaces, so a line's background colour reaches
+                // the edge instead of stopping at the last glyph and letting
+                // the client's own background show through.
+                "-N",
+                "-t",
+                &name,
+                "-S",
+                &start,
+            ])
+            .output()?;
+        let Some(stdout) = soft_output(out)? else {
+            return Ok(None);
+        };
+        let Some((head, content)) = stdout.split_once('\n') else {
+            return Ok(None);
+        };
+        let Some(geom) = parse_screen_geometry(head) else {
+            return Ok(None);
+        };
+        let mut lines: Vec<&str> = content
+            .strip_suffix('\n')
+            .unwrap_or(content)
+            .split('\n')
+            .collect();
+        // Scrollback belongs to the normal screen. Replaying it under an
+        // alternate-screen program would paste the shell's history behind it.
+        if geom.alternate {
+            lines.drain(..lines.len().saturating_sub(geom.pane_height));
+        }
+        Ok(Some(render_screen_snapshot(&lines, geom)))
+    }
+
     /// `tmux resize-window -t maestro-<id> -x <cols> -y <rows>`.
     pub fn resize_window(&self, id: Uuid, cols: u16, rows: u16) -> Result<(), TmuxError> {
         let name = session_name(id);
@@ -446,6 +510,124 @@ fn new_session_args(
     args
 }
 
+/// How much scrollback a fresh attach inherits from tmux's history, in lines.
+/// Enough to land in context after a browser refresh without making the first
+/// frame huge.
+const CAPTURE_HISTORY_LINES: usize = 300;
+
+/// Cursor position and screen geometry of a pane, from `display-message`.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+struct ScreenGeometry {
+    cursor_x: usize,
+    cursor_y: usize,
+    pane_height: usize,
+    alternate: bool,
+    cursor_visible: bool,
+}
+
+fn parse_screen_geometry(s: &str) -> Option<ScreenGeometry> {
+    let line = s.lines().next()?;
+    let mut it = line.split_whitespace();
+    let cursor_x = it.next()?.parse().ok()?;
+    let cursor_y = it.next()?.parse().ok()?;
+    let pane_height: usize = it.next()?.parse().ok()?;
+    let alternate = it.next()? == "1";
+    // Older tmux without `cursor_flag` just means "assume visible".
+    let cursor_visible = it.next().map(|f| f == "1").unwrap_or(true);
+    if pane_height == 0 {
+        return None;
+    }
+    Some(ScreenGeometry {
+        cursor_x,
+        cursor_y,
+        pane_height,
+        alternate,
+        cursor_visible,
+    })
+}
+
+/// Turn captured pane lines into bytes a fresh terminal can replay: clear,
+/// print the lines, then put the cursor back where the pane has it.
+///
+/// The cursor is restored with *relative* moves so the snapshot renders the
+/// same whatever height the client's terminal has — it may not match the
+/// pane's yet, since the client's first `Resize` arrives after this.
+fn render_screen_snapshot(lines: &[&str], geom: ScreenGeometry) -> Vec<u8> {
+    // Screen rows are the last `pane_height` captured lines; anything before
+    // them is scrollback.
+    let screen_top = lines.len().saturating_sub(geom.pane_height);
+    let cursor_row = (screen_top + geom.cursor_y).min(lines.len().saturating_sub(1));
+    // Trailing blank rows would scroll the real content off a short client
+    // terminal, so drop them — but never the cursor's own row or anything
+    // above it, which is where a program that draws below its cursor lives.
+    let last = lines
+        .iter()
+        .rposition(|l| !strip_sgr(l).trim().is_empty())
+        .unwrap_or(0)
+        .max(cursor_row);
+
+    let mut out = Vec::new();
+    // Put the client on the same buffer the pane is using, so a program's
+    // repaints stay out of the client's scrollback while it runs.
+    if geom.alternate {
+        out.extend_from_slice(b"\x1b[?1049h");
+    }
+    out.extend_from_slice(b"\x1b[H\x1b[2J\x1b[m");
+    for (i, line) in lines[..=last].iter().enumerate() {
+        if i > 0 {
+            out.extend_from_slice(b"\r\n");
+        }
+        out.extend_from_slice(line.as_bytes());
+    }
+    out.extend_from_slice(b"\x1b[m\r");
+    if last > cursor_row {
+        out.extend_from_slice(format!("\x1b[{}A", last - cursor_row).as_bytes());
+    }
+    if geom.cursor_x > 0 {
+        out.extend_from_slice(format!("\x1b[{}C", geom.cursor_x).as_bytes());
+    }
+    if !geom.cursor_visible {
+        out.extend_from_slice(b"\x1b[?25l");
+    }
+    out
+}
+
+/// Text of a line with SGR escapes removed, for emptiness checks.
+fn strip_sgr(line: &str) -> String {
+    let mut out = String::with_capacity(line.len());
+    let mut chars = line.chars();
+    while let Some(c) = chars.next() {
+        if c != '\x1b' {
+            out.push(c);
+            continue;
+        }
+        // Skip CSI ... final-byte. Anything else escape-ish is not produced by
+        // `capture-pane -e`, so treating it the same way is harmless.
+        for c in chars.by_ref() {
+            if c.is_ascii_alphabetic() {
+                break;
+            }
+        }
+    }
+    out
+}
+
+/// `Ok(None)` when tmux failed because the server or the target is gone,
+/// `Ok(Some(stdout))` on success, `Err` for anything else.
+fn soft_output(out: Output) -> Result<Option<String>, TmuxError> {
+    if out.status.success() {
+        return Ok(Some(String::from_utf8_lossy(&out.stdout).into_owned()));
+    }
+    let stderr = String::from_utf8_lossy(&out.stderr);
+    if is_no_server_error(&stderr) || stderr.contains("can't find") {
+        return Ok(None);
+    }
+    Err(TmuxError::NonZero {
+        code: out.status.code().unwrap_or(-1),
+        stderr: stderr.into_owned(),
+    })
+}
+
 fn check(out: Output) -> Result<(), TmuxError> {
     if out.status.success() {
         Ok(())
@@ -461,6 +643,85 @@ fn check(out: Output) -> Result<(), TmuxError> {
 mod tests {
     use super::*;
 
+    #[test]
+    fn parse_screen_geometry_reads_cursor_and_alternate_flag() {
+        let g = parse_screen_geometry("12 3 40 1 0\n").unwrap();
+        assert_eq!(
+            g,
+            ScreenGeometry {
+                cursor_x: 12,
+                cursor_y: 3,
+                pane_height: 40,
+                alternate: true,
+                cursor_visible: false,
+            }
+        );
+        let g = parse_screen_geometry("0 0 24 0").unwrap();
+        assert!(!g.alternate);
+        assert!(g.cursor_visible, "missing cursor_flag means visible");
+        assert!(parse_screen_geometry("0 0 0 0").is_none());
+        assert!(parse_screen_geometry("garbage").is_none());
+    }
+
+    #[test]
+    fn snapshot_clears_prints_lines_and_parks_the_cursor() {
+        // Two scrollback lines, then a 3-row screen with the cursor on row 1.
+        let lines = ["old", "older", "prompt> hi", "", ""];
+        let out = render_screen_snapshot(
+            &lines,
+            ScreenGeometry {
+                cursor_x: 10,
+                cursor_y: 0,
+                pane_height: 3,
+                alternate: false,
+                cursor_visible: true,
+            },
+        );
+        let out = String::from_utf8(out).unwrap();
+        assert_eq!(
+            out,
+            "\x1b[H\x1b[2J\x1b[mold\r\nolder\r\nprompt> hi\x1b[m\r\x1b[10C"
+        );
+    }
+
+    #[test]
+    fn snapshot_keeps_rows_below_the_cursor_and_moves_back_up() {
+        let lines = ["prompt> hi", "hint line", ""];
+        let out = render_screen_snapshot(
+            &lines,
+            ScreenGeometry {
+                cursor_x: 0,
+                cursor_y: 0,
+                pane_height: 3,
+                alternate: true,
+                cursor_visible: false,
+            },
+        );
+        let out = String::from_utf8(out).unwrap();
+        assert!(out.starts_with("\x1b[?1049h\x1b[H\x1b[2J"), "{out:?}");
+        assert!(
+            out.ends_with("prompt> hi\r\nhint line\x1b[m\r\x1b[1A\x1b[?25l"),
+            "{out:?}"
+        );
+    }
+
+    #[test]
+    fn snapshot_ignores_colour_only_rows_when_trimming() {
+        let lines = ["text", "\x1b[38;5;4m\x1b[m", ""];
+        let out = String::from_utf8(render_screen_snapshot(
+            &lines,
+            ScreenGeometry {
+                cursor_x: 4,
+                cursor_y: 0,
+                pane_height: 3,
+                alternate: false,
+                cursor_visible: true,
+            },
+        ))
+        .unwrap();
+        assert_eq!(out, "\x1b[H\x1b[2J\x1b[mtext\x1b[m\r\x1b[4C");
+    }
+
     /// Every phrasing must be recognised: an unmatched one makes
     /// `list_sessions` fail, and a failed pass reaps nothing.
     #[test]

crates/maestro-daemon/tests/session_manager.rs

@@ -188,6 +188,64 @@ async fn create_captures_initial_output_in_replay_buffer() {
     fx.manager.kill(s.id, false).await.unwrap();
 }
 
+/// A fresh attach must land on the pane's *current* screen. Replaying the raw
+/// byte tail instead reproduced a browser refresh painting garbage over an
+/// agent TUI: the tail starts mid-stream, so the clears, modes and cursor
+/// moves that gave those bytes meaning are long gone.
+#[tokio::test]
+async fn attach_replay_is_the_current_screen_not_the_byte_tail() {
+    let fx = DaemonFixture::new();
+    let cwd = TempDir::new().unwrap();
+
+    let s = fx
+        .manager
+        .create(CreateSessionRequest {
+            cwd: cwd.path().to_path_buf(),
+            // Print a line, then switch to the alternate screen the way a
+            // full-screen program does on startup. Only the second marker is
+            // on the pane; the first belongs to the screen behind it.
+            command: "sh -c 'printf STALE_MARKER_LINE\\\\n; sleep 0.5; printf \"\\\\033[?1049h\\\\033[2J\\\\033[HLIVE_MARKER\"; exec sleep 30'"
+                .into(),
+            env: HashMap::new(),
+            metadata: HashMap::new(),
+            worktree: None,
+        })
+        .await
+        .expect("create");
+
+    let want = b"LIVE_MARKER";
+    let deadline = std::time::Instant::now() + Duration::from_secs(5);
+    let mut replay = Vec::new();
+    while std::time::Instant::now() < deadline {
+        let (bytes, _rx) = fx
+            .manager
+            .subscribe_pty_with_replay(s.id)
+            .await
+            .expect("subscribe");
+        replay = bytes;
+        if replay.windows(want.len()).any(|w| w == want) {
+            break;
+        }
+        tokio::time::sleep(Duration::from_millis(50)).await;
+    }
+
+    let text = String::from_utf8_lossy(&replay).into_owned();
+    assert!(
+        replay.starts_with(b"\x1b[?1049h\x1b[H\x1b[2J"),
+        "replay did not start with an alternate-screen snapshot: {text:?}"
+    );
+    assert!(
+        text.contains("LIVE_MARKER"),
+        "replay lost the live screen: {text:?}"
+    );
+    assert!(
+        !text.contains("STALE_MARKER_LINE"),
+        "replay carried bytes from behind the alternate screen: {text:?}"
+    );
+
+    fx.manager.kill(s.id, false).await.unwrap();
+}
+
 /// Regression for NAP-228: after `recover`, PTY output must reach new
 /// subscribers. Before the fix tmux's stale `pipe-pane` (with `-o`) silently
 /// kept feeding the old FIFO and the revived manager's subscribers saw