docs(tiles): the replay pace, one refit per resize, the SSE filter, the line bound

The invariants for this performance pass: a tile's replay holds the load
queue only while xterm parses it, and destroy() settles a replay in
progress; the main terminal's resize timer refits the split's Pane B
only, leaving grid tiles to the grid's observer; the page's SSE filter
names TILE_GRID_SSE_FILTER while tiles own the terminal; grid tiles send
lines= on their full captures. Plus an "As built" note in the spec, whose
parking section still says the subscription stays [activeSessionId].

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/architecture-invariants.md

@@ -795,15 +795,15 @@ Further detail: with many sessions the horizontal strip stops being scannable, w
 
 ### Split-pane sessions
 
-**Split-pane sessions** (`showSplitButton`, header button, default OFF, per-device like `showFileViewerButton` — not in `SettingsUpdateSchema`, `displayKeys` in settings-ui.js): shows two live sessions side-by-side in one Codeman window. Pane A is the untouched, existing singleton terminal (`this.terminal`/`this._ws` in terminal-ui.js); Pane B is an independent `TerminalTile` (terminal-tile.js, constructed by the orchestration in terminal-split.js) with its own xterm instance and its own `/ws/sessions/:id/terminal` WebSocket, whose `cid` is the tab's identity with a `:tile` suffix, so it can never supersede the primary pane's socket (the registry supersedes by cid per session). ⚠️ **Pane B is deliberately plainer than Pane A** — no local-echo overlay, no CJK IME, no touch/mobile handlers, no keyboard accessory bar — since this is a desktop-only feature (a split view needs a wide viewport) and those features exist for mobile/touch input; `.btn-split` is hard-hidden below 1180px regardless of the setting by the `@media (max-width: 1179px)` rule in styles.css (mobile.css only carries a comment pointing at it: that file loads up to 1023px, so it cannot cover the 1024-1179px tablet range the feature also needs to stay off), and the per-device setting means turning it on at a desk can never sync it onto a phone in the first place. No persistence: closing the browser tab or reloading always returns to the normal single-pane view; there is no localStorage key for split state. ⚠️ Splitting a session against itself is disallowed (the picker excludes the active session), **as is splitting against a popped-out (detached) session** — `buildSplitPickerSessions()` excludes `detachedSessions` because a detached session's own window is already claiming its PTY size, and `MAX_WS_PER_SESSION` needs no change since Pane A/B are always two different sessions. ⚠️ Either pane's session ending (deleted locally or from another client) auto-collapses the split — Pane A's session ending promotes Pane B to the new single pane via `selectSession(id, { auto: true })` (an app-driven selection, so it must not spend the session's idle alert — see the Approvals Inbox note above), never by trying to hot-swap the lightweight `TerminalTile` object into the primary singleton state. ⚠️ Pane B refits on every window/sidebar/tab-rail resize via the SAME trailing-edge `ResizeObserver` callback that resizes Pane A (`throttledResize` in terminal-ui.js) — it only ever measured Pane A's own container, so without the explicit `this._forEachTile?.((tile) => tile.fit())` call there Pane B silently kept its stale PTY size through every resize that did not happen to be a divider drag. ⚠️ A dropped WebSocket writes a `[disconnected, reconnecting…]` marker into Pane B and reconnects on the primary pane's backoff ladder (`CodemanWsReconnect` plus jitter; the attempt count resets only on a successful open), then refreshes the buffer to close the output gap. ⚠️ The open handler clears `_wsClosed`/`_markerOwed` BEFORE that refresh, or the refresh re-owes the marker and stamps it under a healthy pane. ⚠️ 4003/4004/4009/4010 stop the pane for good, report once through `onExit(code)` and write a marker saying why (`CodemanWsReconnect` alone would retry 4003). ⚠️ A replacement socket detaches the old one first and every handler ignores a socket that is no longer `this.ws`, so a late 4010 from a superseded socket cannot stop its successor; `destroy()` cancels a pending reconnect. Related but distinct: `detachSession()` already opens one session in a separate OS-level browser window (`isSoloWindow`) — that is prior art for "two sessions visible at once" but not for one window with a draggable in-page divider, which is what this feature adds. ⚠️ Pane B installs its own `attachCustomKeyEventHandler` gating the same app-level chords Pane A's own handler gates (command palette, Alt+1-9/[/] tab nav, Alt+B sidebar toggle, Ctrl+Z suspend, Shift/Ctrl+Enter newline, smart-copy Ctrl+C) — without it the document capture-phase handler's `preventDefault()` (which never stops xterm) let each chord ALSO write its raw byte/escape sequence into Pane B's live PTY on top of whatever the app action did to Pane A (COD-153). Ctrl+Z is swallowed unless Pane B's own session is `mode === 'shell'`, mirroring terminal-ui.js's reasoning: in a plain shell it is the user's own job-control tool, everywhere else it silently suspends an unattended agent loop. Shift/Ctrl+Enter POSTs to `/api/sessions/:id/send-key` (`{key:'S-Enter'|'C-Enter'}`, typed by tmux `send-keys -H`: Ctrl+Enter is always a real 0x0a, Shift+Enter is the CLI's declared `capabilities.newline` chord, also 0x0a unless the CLI declares another; sent on keydown only, with the keypress and keyup swallowed too, see the keypress rule under Command palette and shortcut registry) targeting THIS pane's own `sessionId` rather than the primary pane's `activeSessionId` — without it xtermLine truncated
+**Split-pane sessions** (`showSplitButton`, header button, default OFF, per-device like `showFileViewerButton` — not in `SettingsUpdateSchema`, `displayKeys` in settings-ui.js): shows two live sessions side-by-side in one Codeman window. Pane A is the untouched, existing singleton terminal (`this.terminal`/`this._ws` in terminal-ui.js); Pane B is an independent `TerminalTile` (terminal-tile.js, constructed by the orchestration in terminal-split.js) with its own xterm instance and its own `/ws/sessions/:id/terminal` WebSocket, whose `cid` is the tab's identity with a `:tile` suffix, so it can never supersede the primary pane's socket (the registry supersedes by cid per session). ⚠️ **Pane B is deliberately plainer than Pane A** — no local-echo overlay, no CJK IME, no touch/mobile handlers, no keyboard accessory bar — since this is a desktop-only feature (a split view needs a wide viewport) and those features exist for mobile/touch input; `.btn-split` is hard-hidden below 1180px regardless of the setting by the `@media (max-width: 1179px)` rule in styles.css (mobile.css only carries a comment pointing at it: that file loads up to 1023px, so it cannot cover the 1024-1179px tablet range the feature also needs to stay off), and the per-device setting means turning it on at a desk can never sync it onto a phone in the first place. No persistence: closing the browser tab or reloading always returns to the normal single-pane view; there is no localStorage key for split state. ⚠️ Splitting a session against itself is disallowed (the picker excludes the active session), **as is splitting against a popped-out (detached) session** — `buildSplitPickerSessions()` excludes `detachedSessions` because a detached session's own window is already claiming its PTY size, and `MAX_WS_PER_SESSION` needs no change since Pane A/B are always two different sessions. ⚠️ Either pane's session ending (deleted locally or from another client) auto-collapses the split — Pane A's session ending promotes Pane B to the new single pane via `selectSession(id, { auto: true })` (an app-driven selection, so it must not spend the session's idle alert — see the Approvals Inbox note above), never by trying to hot-swap the lightweight `TerminalTile` object into the primary singleton state. ⚠️ Pane B refits on every window/sidebar/tab-rail resize via the SAME trailing-edge `ResizeObserver` callback that resizes Pane A (`throttledResize` in terminal-ui.js) — it only ever measured Pane A's own container, so without the explicit `this._forEachTile?.((tile) => tile.fit(), { grid: false })` call there (grid tiles are left out: the grid's own observer refits them on the same resize) Pane B silently kept its stale PTY size through every resize that did not happen to be a divider drag. ⚠️ A dropped WebSocket writes a `[disconnected, reconnecting…]` marker into Pane B and reconnects on the primary pane's backoff ladder (`CodemanWsReconnect` plus jitter; the attempt count resets only on a successful open), then refreshes the buffer to close the output gap. ⚠️ The open handler clears `_wsClosed`/`_markerOwed` BEFORE that refresh, or the refresh re-owes the marker and stamps it under a healthy pane. ⚠️ 4003/4004/4009/4010 stop the pane for good, report once through `onExit(code)` and write a marker saying why (`CodemanWsReconnect` alone would retry 4003). ⚠️ A replacement socket detaches the old one first and every handler ignores a socket that is no longer `this.ws`, so a late 4010 from a superseded socket cannot stop its successor; `destroy()` cancels a pending reconnect. Related but distinct: `detachSession()` already opens one session in a separate OS-level browser window (`isSoloWindow`) — that is prior art for "two sessions visible at once" but not for one window with a draggable in-page divider, which is what this feature adds. ⚠️ Pane B installs its own `attachCustomKeyEventHandler` gating the same app-level chords Pane A's own handler gates (command palette, Alt+1-9/[/] tab nav, Alt+B sidebar toggle, Ctrl+Z suspend, Shift/Ctrl+Enter newline, smart-copy Ctrl+C) — without it the document capture-phase handler's `preventDefault()` (which never stops xterm) let each chord ALSO write its raw byte/escape sequence into Pane B's live PTY on top of whatever the app action did to Pane A (COD-153). Ctrl+Z is swallowed unless Pane B's own session is `mode === 'shell'`, mirroring terminal-ui.js's reasoning: in a plain shell it is the user's own job-control tool, everywhere else it silently suspends an unattended agent loop. Shift/Ctrl+Enter POSTs to `/api/sessions/:id/send-key` (`{key:'S-Enter'|'C-Enter'}`, typed by tmux `send-keys -H`: Ctrl+Enter is always a real 0x0a, Shift+Enter is the CLI's declared `capabilities.newline` chord, also 0x0a unless the CLI declares another; sent on keydown only, with the keypress and keyup swallowed too, see the keypress rule under Command palette and shortcut registry) targetinLine truncated
 
 ### Tile grid
 
 **Tile grid** (`showTileGridButton`, header Tiles button + `Ctrl+Shift+G`, default OFF, per-device: in `displayKeys`, stripped from the settings PUT, not in `SettingsUpdateSchema`; desktop-only at 1180px by a JS width check with a live media listener plus a `@media (max-width: 1179px)` backstop, never in a solo window). 1 to 6 live sessions side by side in one window, each a `TerminalTile` (terminal-tile.js), orchestrated by tile-grid.js (load order 7.6, `CodemanApp.prototype` methods like the split's). Pure helpers live in constants.js as `window.CodemanTileGrid`: `computeTileLayout` (1x1, 2x1, 3x1 on a grid area at least 1800px wide else 2x2, 2x2, 3x2, and 3x3 up to `TILE_LAYOUT_MAX` (9), unreachable today; `fits` against a 480x240 minimum tile), `tileGridCapacity` (never more than `TILE_GRID_MAX`), `sanitizeTileGridState` (truncates a stored grid to the cap, keeps focus only if it survives), `buildTilePickerSessions`, `dragTrackFractions`, `tileNeighbor`, `tileInDirection`, `cycleTile`, `TILE_SCROLLBACK` (10,000), and `TILE_GRID_MAX` (6), the ONE cap (owner decision 7: six tested smooth on a real desktop, nine missed the headless frame bar). ⚠️ Every limit reads the cap through `_tileGridLimit()` (tile-grid.js: the window's capacity, at most the cap), never a literal, and its texts say which binds ("at most 6 tiles" vs "what this window fits"). The grid is a `<section class="tile-grid">` SIBLING of `.terminal-wrap`, swapped in by `.main.tiles-active` (no reparenting); `.main.webview-active .tile-grid` hides it like the single view.
 
-⚠️ **The main terminal is parked while the grid is open.** Opening runs `_cleanupPreviousSession()` ONCE (its snapshot is right at that moment, and it closes the main socket), and `activeSessionId` is always the FOCUSED tile's session, so everything keyed on it (files panel, git status, respawn and Ralph panels, subagent windows, voice, image paste, the tab highlight) follows focus. With the main socket closed `_wsReady` is false, so every SSE terminal handler would write the focused tile's output into the hidden xterm: `_tilesOwnTerminal()` turns `_onSessionTerminal`, `_onSessionClearTerminal`, `_onSessionNeedsRefresh` (returns `false`, which the drop recovery reads), `_scheduleDroppedOutputRecovery`, the `writeln` in `_onSessionCompletion`/`_onSessionError`, `sendResize`, `throttledResize`'s fit and `_maybeRefetchFullHistory` into no-ops; `retryConnection` and `handleInit` re-arm the TILES' sockets instead of the main one (`handleInit` keeps live tiles, drops dead ones through `_reconcileTileGrid`, and re-selects only when the focused tile is gone, so an SSE blip never hides an open web tab). ⚠️ The WebGL long-task observer watches the WHOLE page: it counts nothing while tiles own the terminal, or tile renders would write the sticky 7-day WebGL disable. The header connection dot reads the tile sockets (`_tileGridSocketState`; a tile stopped for good does not count). `_focusedPane()` answers with the focused tile even when DOM focus left every terminal, and `_forEachTile` reaches every grid tile (`{ grid: false }` skips them where tiles keep their own font size). Leaving the grid destroys every tile, resets `_lastResizeDims`, invalidates the main terminal's cached content for EVERY tiled id (`_xtermSnapshots`, `codeman-xs-<id>`, `terminalBufferCache`: written before the grid opened, and selectSession paints a snapshot as its first frame) and replays the focused session through `selectSession(id, { forceReload: true, auto: true })`.
+⚠️ **The main terminal is parked while the grid is open.** Opening runs `_cleanupPreviousSession()` ONCE (its snapshot is right at that moment, and it closes the main socket), and `activeSessionId` is always the FOCUSED tile's session, so everything keyed on it (files panel, git status, respawn and Ralph panels, subagent windows, voice, image paste, the tab highlight) follows focus. With the main socket closed `_wsReady` is false, so every SSE terminal handler would write the focused tile's output into the hidden xterm: `_tilesOwnTerminal()` turns `_onSessionTerminal`, `_onSessionClearTerminal`, `_onSessionNeedsRefresh` (returns `false`, which the drop recovery reads), `_scheduleDroppedOutputRecovery`, the `writeln` in `_onSessionCompletion`/`_onSessionError`, `sendResize`, `throttledResize`'s fit and `_maybeRefetchFullHistory` into no-ops; `retryConnection` and `handleInit` re-arm the TILES' sockets instead of the main one (`handleInit` keeps live tiles, drops dead ones through `_reconcileTileGrid`, and re-selects only when the focused tile is gone, so an SSE blip never hides an open web tab). ⚠️ The page's SSE filter names `TILE_GRID_SSE_FILTER` (constants.js, an id no session takes) instead of the focused session while tiles own the terminal: the server's filter gates only `session:terminal` batches, which the parked terminal could only parse and drop. Both places that set the filter ask `_sseFilterSessionId()`: the live re-subscribe every tile focus runs (`_updateSseSubscription`) and the connect URL an SSE reconnect rebuilds (`connectSSE`); leaving the grid re-subscribes the shown session through `selectSession`. `test/sse-tile-grid-filter.test.ts` pins the server's side in multi-user mode (the id is accepted on connect and on re-subscribe, and session/hook events still reach their owner through it). ⚠️ The WebGL long-task observer watches the WHOLE page: it counts nothing while tiles own the terminal, or tile renders would write the sticky 7-day WebGL disable. The header connection dot reads the tile sockets (`_tileGridSocketState`; a tile stopped for good does not count). `_focusedPane()` answers with the focused tile even when DOM focus left every terminal, and `_forEachTile` reaches every grid tile (`{ grid: false }` skips them where tiles keep their own font size). Leaving the grid destroys every tile, resets `_lastResizeDims`, invalidates the main terminal's cached content for EVERY tiled id (`_xtermSnapshots`, `codeman-xs-<id>`, `terminalBufferCache`: written before the grid opened, and selectSession paints a snapshot as its first frame) and replays the focused session through `selectSession(id, { forceReload: true, auto: true })`.
 
-⚠️ **One load queue.** Every capture a tile fetches (initial load, refresh after a reconnect, server `{t:'r'}` refresh, shell history pull) goes through the grid's ONE `TileLoadQueue` (terminal-tile.js, the tile's `scheduleLoad` option): concurrency 1, a history pull first, then the focused tile, then reading order; a destroyed tile's waiting loads are dropped unrun and destroy() aborts its running fetch. Each `GET /api/sessions/:id/terminal` runs synchronous tmux calls, so N tiles loading at once (after a deploy restart all N reopen within a second) would stall every WebSocket and SSE stream on the server back to back. Grid tiles load the BOUNDED window (`full=1&tail=TERMINAL_TAIL_SIZE` for a TUI, `tail=` for a shell; the `boundedLoad` option), keep `TILE_SCROLLBACK` lines and their own per-device font (`codeman-tile-font-size`, Ctrl +/- while the grid is open). A refresh clears at its turn, not when asked, so a waiting tile keeps its last frame.
+⚠️ **One load queue.** Every capture a tile fetches (initial load, refresh after a reconnect, server `{t:'r'}` refresh, shell history pull) goes through the grid's ONE `TileLoadQueue` (terminal-tile.js, the tile's `scheduleLoad` option): concurrency 1, a history pull first, then the focused tile, then reading order; a destroyed tile's waiting loads are dropped unrun and destroy() aborts its running fetch. A load holds the slot only while xterm parses its replay: `writeChunked` queues every 32 KB slice at once (one 1 MiB window at a time, since xterm's write queue throws past 50 MB) and settles on the callback of a write queued behind them, never one slice per animation frame (that pacing held the slot about a second per 1 MiB tile). ⚠️ destroy() settles a replay in progress (`_cancelReplay`): a disposed xterm never runs that callback, and an unsettled replay would hold the tile's flag and the grid's queue forever. Each `GET /api/sessions/:id/terminal` runs synchronous tmux calls, so N tiles loading at once (after a deploy restart all N reopen within a second) would stall every WebSocket and SSE stream on the server back to back. Grid tiles load the BOUNDED window (`full=1&tail=TERMINAL_TAIL_SIZE` for a TUI, `tail=` for a shell; the `boundedLoad` option), and every full capture of theirs (a TUI load, a shell history pull) also sends `lines=<TILE_SCROLLBACK + rows>`, so tmux reads no more history than the tile keeps instead of the whole history limit (the route's optional `lines` bound, docs/api-reference.md; the split's Pane B sends none), keep `TILE_SCROLLBACK` lines and their own per-device font (`codeman-tile-font-size`, Ctrl +/- while the grid is open). A refresh clears at its turn, not when asked, so a waiting tile keeps its last frame.
 
 ⚠️ **Selections.** The tile branch of `selectSession` sits right after its "already active" early return: a tiled id is FOCUSED (`_selectTiledSession`: no cleanup, replay, resize or main socket; the shared `_refreshSessionPanels`; only a user-initiated pick acknowledges the idle alert). A USER-initiated pick of a session that is not tiled leaves the grid for the single view, remembered (decision 1), and so does `leaveTiles` (a followed `#session=` link); an `auto` pick never collapses it. Whoever calls `closeTileGrid({ reselect: false })` and then selects must null `activeSessionId` first, or `_cleanupPreviousSession` saves the parked terminal's stale content as a snapshot. App-driven fallbacks pick a tile: `closeSession` captures the neighbouring tile BEFORE its await (like `wasActive`; the delete broadcast may already have removed the tile) and focuses it with `auto`; the `_onSessionDeleted` wrapper does the same for a delete from elsewhere, and leaves a close from this tab (`_closingSessions`) to `closeSession`. Ctrl+Tab and Alt+[ ] cycle the tiles. A popped-out (detached) session leaves the grid. Moving focus off a zoomed tile restores the grid (tmux `select-pane`); an automatic zoom (window too small for the minimum tile) follows focus instead.
 

docs/tile-grid-plan.md

@@ -53,6 +53,11 @@ or settled a question the spec left open. The invariants as built are in
   button (and its right-click picker), Ctrl/Cmd+click on a tab, a dragged tab, "Open group
   as tiles" and Run joining the open grid. Where this spec describes a `+`, it no longer
   exists.
+- **No SSE terminal stream while tiles own the terminal** (performance pass): the filter
+  names a fixed id no session takes (`TILE_GRID_SSE_FILTER`), not `[activeSessionId]` as
+  "Parking the main terminal" below says; the server's filter gates only terminal
+  batches, so lifecycle and hook events are unaffected, and leaving the grid
+  re-subscribes the shown session.
 - **A tile that joins before its pane exists resends its size when the pid appears**
   (`TerminalTile.paneStarted()`): the server drops a resize for a session with no PTY and
   spawns at 120x40, and Run's own resize measures the parked main terminal. Applying a