diff --git a/CLAUDE.md b/CLAUDE.md
index ccc5232a..47b16edc 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -276,7 +276,9 @@ Codeman is a Claude Code session manager with web interface and autonomous Ralph
 
 **Full-scrollback replay**: `GET /api/sessions/:id/terminal?full=1` returns the whole tmux scrollback ALONE (`source='mux-full-history'`), superseding the byte buffer. First load of each non-shell TUI session requests it (`_fullHistoryLoaded`); Shell selection and drop recovery use a bounded 1 MiB `?tail=`, and a Shell scroll-to-top pulls a bounded `?full=1&tail=` window (a window no longer than the browser's buffer is skipped before the downgrade guard, so it never marks the session exhausted); the unbounded pull stays behind **Load full history**. A Shell split-pane Pane B has its own copy of the bounded pull against its own xterm (`TerminalTile._pullHistory`, terminal-tile.js); keep the two in step. → [architecture-invariants#split-pane-sessions](docs/architecture-invariants.md#split-pane-sessions) ⚠️ The capture ends with a RELATIVE cursor move back to the pane's caret (never `CUP`), so no line-deleting transform may run over it; those skips key on `isFullCapture`, never on `?full=1` alone. ⚠️ A re-pull must never shrink the buffer (`_replayWouldShrinkBuffer()`). ⚠️ `captureCols`/`captureRows` are absent when no frame was positioned: test `Number.isFinite`, never truthiness. ⚠️ A frame dropped at the 128 KiB render cap MUST be recovered, and the recovery verifies itself: `_scheduleDroppedOutputRecovery` re-arms (bounded by `DROP_RECOVERY_MAX_ATTEMPTS`) while `_onSessionNeedsRefresh` reports no repaint, but never after a capture-fetch `'deadline'`. → [architecture-invariants#full-scrollback-replay](docs/architecture-invariants.md#full-scrollback-replay)
 
-**Split-pane sessions** (`showSplitButton`, header button, default OFF, desktop-only, per-device): a second live session ("Pane B") beside the active one, in a `TerminalTile` (terminal-tile.js; the picker, divider and auto-collapse stay in terminal-split.js) with its own xterm + WebSocket, resizable via a draggable divider. Pane B reconnects after a drop, sends input through the exactly-once queue over its own socket (`_registerInputSocket`), has clickable paths and image paste, and owns its geometry (no 40x10 floor, `zc` columns adopted, font changes call `tile.fit()`). ⚠️ Only typed input enters that persisted queue: xterm's query replies are dropped and focus/mouse reports go out ephemeral. ⚠️ App-level terminal actions find their pane through `_focusedPane()` (the terminal focused last), never `this.terminal`. Still plainer than the primary pane (no local-echo overlay, CJK IME or touch handlers) and NOT persisted across reloads. The planned tile grid reuses `TerminalTile` (`docs/tile-grid-plan.md`). → [architecture-invariants#split-pane-sessions](docs/architecture-invariants.md#split-pane-sessions)
+**Split-pane sessions** (`showSplitButton`, header button, default OFF, desktop-only, per-device): a second live session ("Pane B") beside the active one, in a `TerminalTile` (terminal-tile.js; the picker, divider and auto-collapse stay in terminal-split.js) with its own xterm + WebSocket, resizable via a draggable divider. Pane B reconnects after a drop, sends input through the exactly-once queue over its own socket (`_registerInputSocket`), has clickable paths and image paste, and owns its geometry (no 40x10 floor, `zc` columns adopted, font changes call `tile.fit()`). ⚠️ Only typed input enters that persisted queue: xterm's query replies are dropped and focus/mouse reports go out ephemeral. ⚠️ App-level terminal actions find their pane through `_focusedPane()` (the terminal focused last), never `this.terminal`. Still plainer than the primary pane (no local-echo overlay, CJK IME or touch handlers) and NOT persisted across reloads. The tile grid (below) reuses `TerminalTile`, and the two are never open together. → [architecture-invariants#split-pane-sessions](docs/architecture-invariants.md#split-pane-sessions)
+
+**Tile grid** (`showTileGridButton`, header Tiles button + `Ctrl+Shift+G`, default OFF, desktop-only at 1180px, per-device; tile-grid.js, design `docs/tile-grid-plan.md`): 1 to 9 live sessions side by side, each a `TerminalTile` with a header (state dot, name, menu, zoom, +, ×), laid out by count (`CodemanTileGrid`, constants.js) with draggable column/row dividers, zoom (tmux-style), an Attach overlay, and per-device persistence (`codeman:tile-grid`, ids only, restored INSIDE `handleInit` in place of the single-view select, so the main terminal never loads on that page load). While the grid is open the main terminal is PARKED: `activeSessionId` is the focused tile's session, and every main-terminal path that would write, fetch, resize or reconnect stands aside through `_tilesOwnTerminal()` (the WebGL long-task observer included). ⚠️ Every capture a tile fetches (initial, reconnect refresh, `{t:'r'}`, history pull) goes through ONE `TileLoadQueue` (concurrency 1, a deadline covering the body), because each is a synchronous tmux call on the server. ⚠️ Only a USER-initiated pick of a non-tiled session (or `leaveTiles`, a followed link) leaves the grid; an `auto` selection never collapses it, and every app-driven fallback (close, delete, restore) picks a tile. A caller of `closeTileGrid({ reselect: false })` must null `activeSessionId` before any `_cleanupPreviousSession`, or the parked terminal's stale content is saved as a snapshot. ⚠️ The grid and the split are never open together. ⚠️ Tile chords go through `tileShortcutFor` and are swallowed in every xterm key handler BEFORE the Shift+Enter gate; the toggle follows `showTileGridButton` (OFF: inert). ⚠️ A divider drag reflows locally per frame and sends ONE resize per affected tile at pointer-up. ⚠️ Sessions Run from this tab join the open grid (`_joinTileGridFromRun`, called from `_ensureCreatedSessionVisible`); sessions created elsewhere never do. ⚠️ An agent that exited in a live pane (`paneExit`) cannot be re-attached in place (both attach routes refuse while the pane's tmux client runs, and say so in a 200 envelope): its tile shows the exit and points at Close session. → [architecture-invariants#tile-grid](docs/architecture-invariants.md#tile-grid)
 
 **Terminal touch gestures: link taps and text selection**: on touch devices xterm's linkifier and SelectionService never see the gesture, so both are driven explicitly (terminal-ui.js). ⚠️ A tap activates the link under it through the SAME provider as the hover linkifier (`_terminalLinkAtPoint`), synchronously inside `touchend` (keeps the user gesture `window.open` needs) and BEFORE any mouse report; the caret's logical line (`_tapIsOnCaretLine`) and TUI-owned rows (`_isActionableMobileTerminalTap`) keep their meaning. ⚠️ Gate on the caret line, never on tap intent (a shell calls every tap `'input'`). ⚠️ Long-press selects via xterm's public `select()`; keep the three guards: suppress the compat mouse pair after `touchend`, the bounded focus guard + `contextmenu` suppression for the platform long-press, and no closing `terminal.focus()` on phones. Tests: `test/terminal-touch-tap.test.ts`. → [architecture-invariants#terminal-touch-gestures-link-taps-and-text-selection](docs/architecture-invariants.md#terminal-touch-gestures-link-taps-and-text-selection)
 
@@ -325,7 +327,7 @@ Codeman is a Claude Code session manager with web interface and autonomous Ralph
 
 ### Frontend
 
-Frontend JS modules have `@fileoverview` with `@dependency`/`@loadorder` tags. Load order: `constants.js`(1) → `i18n.js`(1.5) → `mobile-handlers.js`(2) → `voice-input.js`(3) → `notification-manager.js`(4) → `keyboard-accessory.js`(5) → `input-cjk.js`(5.5) → `mobile-ime-preview.js`(5.52) → `terminal-keycode229-recovery.js`(5.55) → `sanitize-html.js`(5.6) → `tab-layout-browser.js`(5.9) → `app.js`(6) → `tab-rail-resize.js`(6.5) → `terminal-ui.js`(7) → `terminal-tile.js`(7.4) → `terminal-split.js`(7.5) → `respawn-ui.js`(8) → `ralph-panel.js`(9) → `orchestrator-panel.js`(9.5) → `cron-ui.js`(9.7) → `settings-ui.js`(10) → `panels-ui.js`(11) → `readmymind-ui.js`(11.3) → `ultracode-panel.js`(11.5) → `approvals-ui.js`(11.6) → `reboot-restore-ui.js`(11.65) → `admin-ui.js`(11.7) → `session-ui.js`(12) → `host-wake-ui.js`(12.2) → `webview-tabs.js`(12.5) → `mobile-overview.js`(12.55) → `home-sessions.js`(12.56) → `git-status-ui.js`(12.57) → `entrance-animations.js`(12.6) → `ralph-wizard.js`(13) → `api-client.js`(14) → `subagent-windows.js`(15) → `ultracode-windows.js`(15.5) → `session-lineage.js`(15.6) → `image-input.js`(16). `i18n.js` translates static + newly inserted application DOM while skipping terminal/response/file/user-name surfaces; `input-cjk.js` handles CJK IME composition via an always-visible textarea below the terminal (`window.cjkActive` blocks xterm's onData). `terminal-keycode229-recovery.js` forwards a committed `input` event that xterm's `_inputEvent` guard drops (Chrome-on-Android soft keyboards send `composed: true` after a keydown), and only when xterm emitted no canonical data for that keystroke. ⚠️ **That decision is settled at the NEXT keydown as well as on its own zero-delay timer** (#441): the drain runs from xterm's custom key handler, which fires BEFORE xterm processes that key, so a soft keyboard that commits the last character and sends Enter in one InputConnection transaction puts the character on the wire ahead of the `\r`. On the timer alone that character is not merely late, it is LOST: xterm emits the `\r` first and bumps the canonical counter past the candidate's snapshot, so the candidate stands down (measured, `hell\r` where the user typed `hello`). The trade is that a keydown decides with less evidence than the timer did, since xterm's own keyCode-229 rescue has not run yet; that is safe for Enter, which clears the textarea so the pending diff emits nothing. Ordering is pinned by `test/terminal-keycode229-recovery.browser.test.ts`, which the CI gate does NOT run. `mobile-ime-preview.js` (iOS WebKit only) paints the text an IME is composing: an iOS IME commit is routed into the local-echo overlay through the ordinary printable/paste branch and then `_transferMobileImeCommitToLocalEcho`, and without local echo the preview clears only on output parsed AFTER the commit (or its 2 s fallback). ⚠️ It watches keydown in the capture phase on `terminal.element`, never on the textarea, because xterm finalizes the composition and emits the commit in its own capture listener on the textarea.
+Frontend JS modules have `@fileoverview` with `@dependency`/`@loadorder` tags. Load order: `constants.js`(1) → `i18n.js`(1.5) → `mobile-handlers.js`(2) → `voice-input.js`(3) → `notification-manager.js`(4) → `keyboard-accessory.js`(5) → `input-cjk.js`(5.5) → `mobile-ime-preview.js`(5.52) → `terminal-keycode229-recovery.js`(5.55) → `sanitize-html.js`(5.6) → `tab-layout-browser.js`(5.9) → `app.js`(6) → `tab-rail-resize.js`(6.5) → `terminal-ui.js`(7) → `terminal-tile.js`(7.4) → `terminal-split.js`(7.5) → `tile-grid.js`(7.6) → `respawn-ui.js`(8) → `ralph-panel.js`(9) → `orchestrator-panel.js`(9.5) → `cron-ui.js`(9.7) → `settings-ui.js`(10) → `panels-ui.js`(11) → `readmymind-ui.js`(11.3) → `ultracode-panel.js`(11.5) → `approvals-ui.js`(11.6) → `reboot-restore-ui.js`(11.65) → `admin-ui.js`(11.7) → `session-ui.js`(12) → `host-wake-ui.js`(12.2) → `webview-tabs.js`(12.5) → `mobile-overview.js`(12.55) → `home-sessions.js`(12.56) → `git-status-ui.js`(12.57) → `entrance-animations.js`(12.6) → `ralph-wizard.js`(13) → `api-client.js`(14) → `subagent-windows.js`(15) → `ultracode-windows.js`(15.5) → `session-lineage.js`(15.6) → `image-input.js`(16). `i18n.js` translates static + newly inserted application DOM while skipping terminal/response/file/user-name surfaces; `input-cjk.js` handles CJK IME composition via an always-visible textarea below the terminal (`window.cjkActive` blocks xterm's onData). `terminal-keycode229-recovery.js` forwards a committed `input` event that xterm's `_inputEvent` guard drops (Chrome-on-Android soft keyboards send `composed: true` after a keydown), and only when xterm emitted no canonical data for that keystroke. ⚠️ **That decision is settled at the NEXT keydown as well as on its own zero-delay timer** (#441): the drain runs from xterm's custom key handler, which fires BEFORE xterm processes that key, so a soft keyboard that commits the last character and sends Enter in one InputConnection transaction puts the character on the wire ahead of the `\r`. On the timer alone that character is not merely late, it is LOST: xterm emits the `\r` first and bumps the canonical counter past the candidate's snapshot, so the candidate stands down (measured, `hell\r` where the user typed `hello`). The trade is that a keydown decides with less evidence than the timer did, since xterm's own keyCode-229 rescue has not run yet; that is safe for Enter, which clears the textarea so the pending diff emits nothing. Ordering is pinned by `test/terminal-keycode229-recovery.browser.test.ts`, which the CI gate does NOT run. `mobile-ime-preview.js` (iOS WebKit only) paints the text an IME is composing: an iOS IME commit is routed into the local-echo overlay through the ordinary printable/paste branch and then `_transferMobileImeCommitToLocalEcho`, and without local echo the preview clears only on output parsed AFTER the commit (or its 2 s fallback). ⚠️ It watches keydown in the capture phase on `terminal.element`, never on the textarea, because xterm finalizes the composition and emits the commit in its own capture listener on the textarea.
 
 **Entrance animations** (`entrance-animations.js`, all OFF by default): opt-in animations for tabs, terminal, windows and connection lines, chosen via `data-tab-anim` / `data-term-anim` / `data-win-anim` / `data-line-anim` on `<html>`; the default `legacy` theme short-circuits every hook. ⚠️ Tabs and lines are destroyed mid-animation on re-render, so re-apply to the fresh element by id with a negative `animation-delay` (resume, never restart). ⚠️ Terminal-pane styles may animate only transform / opacity / clip-path (anything else resizes the PTY via FitAddon); `blur` is the ONE sanctioned `filter` exception, do not generalise it. ⚠️ Line glow lives in `--line-glow` so blur keyframes interpolate. Persisted per-device in `codeman:*Anim` localStorage keys, never in `SettingsUpdateSchema`; lab at `?animlab=1`. Test: `test/entrance-animations.test.ts`. → [architecture-invariants#entrance-animations](docs/architecture-invariants.md#entrance-animations)
 
@@ -347,7 +349,7 @@ Frontend JS modules have `@fileoverview` with `@dependency`/`@loadorder` tags. L
 
 **Settings surface** (`#appSettingsModal` + `#sessionOptionsModal` + `#createCaseModal`): one `set-*` language shared through a single `:is(...)` id scope in styles.css. App Settings' rail is a table of contents over ONE scrolling document (`switchSettingsTab` scrolls); Session Options and Add Case really switch (`switchOptionsTab` / `switchCaseModalTab`), and their larger per-modal size blocks are the design, not drift. ⚠️ **The load/save contract is `getElementById` by id**: renaming or dropping a control id silently stops it loading or saving. ⚠️ The Session Options "Session" entry still keys off `context` (label-only rename). ⚠️ Add Case keeps its legacy `.form-row` markup via an adapter; every `<details>` there needs `.set-adv-chev` plus both marker suppressions. ⚠️ Model cards and the effort segment are views over hidden `<select>`s, which stay the source of truth. ⚠️ `.modal-tabs*` classes are retired; `admin-ui.js` needs `.set-rail-items` + `.set-doc` to survive any restructure. Guard: `test/app-settings-structure.test.ts`. → [architecture-invariants#settings-surface-app-settings-session-options-add-case](docs/architecture-invariants.md#settings-surface-app-settings-session-options-add-case)
 
-**Header button visibility**: most header controls are opt-in and hidden by a marker class (`btn-multimonitor--hidden`, `btn-response-viewer-header--hidden`, `btn-file-viewer--hidden`, `btn-cron--hidden`) that `applyHeaderVisibilitySettings()` (settings-ui.js) toggles after settings load; the multi-monitor button is instead stripped at render by `renderIndexHtml`. ⚠️ Hiding must go through the marker class: the base rules are `display:inline-flex !important`, so an inline style cannot override them. Current desktop default is WS/CPU/MEM + File Viewer + gear, with the token chip and lifecycle-log button OFF. ⚠️ New header controls must not leak onto phones; `test/mobile-header-buttons-policy.test.ts` is the static guard. → [architecture-invariants#header-button-visibility-multi-monitor-response-viewer-file-viewer-cron](docs/architecture-invariants.md#header-button-visibility-multi-monitor-response-viewer-file-viewer-cron)
+**Header button visibility**: most header controls are opt-in and hidden by a marker class (`btn-multimonitor--hidden`, `btn-response-viewer-header--hidden`, `btn-file-viewer--hidden`, `btn-cron--hidden`, and the desktop-gated `btn-split--hidden` / `btn-tile-grid--hidden`, which also need a `@media (max-width: 1179px)` backstop) that `applyHeaderVisibilitySettings()` (settings-ui.js) toggles after settings load; the multi-monitor button is instead stripped at render by `renderIndexHtml`. ⚠️ Hiding must go through the marker class: the base rules are `display:inline-flex !important`, so an inline style cannot override them. Current desktop default is WS/CPU/MEM + File Viewer + gear, with the token chip and lifecycle-log button OFF. ⚠️ New header controls must not leak onto phones; `test/mobile-header-buttons-policy.test.ts` is the static guard. → [architecture-invariants#header-button-visibility-multi-monitor-response-viewer-file-viewer-cron](docs/architecture-invariants.md#header-button-visibility-multi-monitor-response-viewer-file-viewer-cron)
 
 **Gesture control** (camera hand-tracking overlay, opt-in, default OFF): `CODEMAN_GESTURE=1` makes the feature *available*; `gestureControlEnabled` turns it on. The bundle is injected by `renderIndexHtml` only when enabled, which is why that method is `async` and reads settings with `readSettings(true)` (a fresh read: a post-save reload lands inside the 2s cache TTL and would otherwise render the pre-toggle state). **Source lives in `packages/gesture-control/`; edit there, run `npm run build:gesture`, and commit the regenerated bundle** because dev serves the committed bundle with no runtime bundler. The MediaPipe wasm + model are fetched separately and gitignored. ⚠️ Keep `MP_VERSION` in `fetch-gesture-assets.mjs` in sync with `@mediapipe/tasks-vision`. → [architecture-invariants#gesture-control-the-source-package](docs/architecture-invariants.md#gesture-control-the-source-package)
 
@@ -385,7 +387,7 @@ Frontend JS modules have `@fileoverview` with `@dependency`/`@loadorder` tags. L
 
 **SSE staleness watchdog** (`computeSseStale()` in constants.js, `_checkSseStale()` + a 5s interval in app.js): an `EventSource` can stop delivering without erroring, so the client forces a reconnect when nothing arrives. ⚠️ The server keepalive must stay the named `sse:heartbeat` event (`cleanupDeadClients()`, sse-stream-manager.ts), never an SSE comment, which `EventSource` cannot observe; its no-op client listener must stay registered. ⚠️ Judge staleness only while `connected` and online (the loop breaker). ⚠️ The liveness stamp lives inside `addListener`. ⚠️ Clear the interval only at the top of `connectSSE()`, or intervals stack. → [architecture-invariants#sse-staleness-watchdog](docs/architecture-invariants.md#sse-staleness-watchdog)
 
-**Z-index layers** (keep new overlays consistent with this stack): local echo overlay (7; with local echo on it also draws the iOS IME composition preview, as an underlined tail after its pending text via `setComposition`), iOS IME composition preview span when local echo is off (6 inside `.xterm-helpers`, whose own z-index 5 is its EFFECTIVE layer, so it sits UNDER the overlay and must never be used while the overlay shows text), terminal touch-selection bar (900, below floating agent windows), subagent windows + split picker menu (1000), plan agents (1100), mobile/tablet fixed header (1200), modals on ≤768px (1300, must beat the fixed header), log viewers (2000), connection-loss overlay (2500), image popups (3000), response viewer (5000, backdrop 4999), file-preview overlay (5100, must outrank the response viewer that launches it), toasts/path picker (10000+), custom-model center-status banner (10001; its `[hidden]` must re-assert `display: none` or `dismiss()` leaves an invisible click-blocker), custom-model swap-confirm/context-warning modals (10010). → [architecture-invariants#z-index-layers](docs/architecture-invariants.md#z-index-layers)
+**Z-index layers** (keep new overlays consistent with this stack): local echo overlay (7; with local echo on it also draws the iOS IME composition preview, as an underlined tail after its pending text via `setComposition`), iOS IME composition preview span when local echo is off (6 inside `.xterm-helpers`, whose own z-index 5 is its EFFECTIVE layer, so it sits UNDER the overlay and must never be used while the overlay shows text), terminal touch-selection bar (900, below floating agent windows), subagent windows + split picker menu + Tiles picker (1000), plan agents (1100), mobile/tablet fixed header (1200), modals on ≤768px (1300, must beat the fixed header), log viewers (2000), connection-loss overlay (2500), image popups (3000), response viewer (5000, backdrop 4999), file-preview overlay (5100, must outrank the response viewer that launches it), toasts/path picker (10000+), custom-model center-status banner (10001; its `[hidden]` must re-assert `display: none` or `dismiss()` leaves an invisible click-blocker), custom-model swap-confirm/context-warning modals (10010). → [architecture-invariants#z-index-layers](docs/architecture-invariants.md#z-index-layers)
 
 **Respawn presets**: `solo-work` (3s/60min), `subagent-workflow` (45s/240min), `team-lead` (90s/480min), `ralph-todo` (8s/480min), `overnight-autonomous` (10s/480min).
 
diff --git a/docs/architecture-invariants.md b/docs/architecture-invariants.md
index 533ba908..4bac36ee 100644
--- a/docs/architecture-invariants.md
+++ b/docs/architecture-invariants.md
@@ -793,7 +793,25 @@ 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 xterm's plain `\r` would submit an incomplete prompt instead of adding a line to it. Smart-copy Ctrl+C/Ctrl+Shift+C is re-implemented against `this.terminal` (Pane B's own) rather than reusing `app.copyTerminalSelection()`, which reads Pane A's terminal and would copy the wrong pane's selection; Ctrl+Shift+C never falls through even with nothing to copy, mirroring terminal-ui.js's own `ev.shiftKey` branch. ⚠️ **This is a UX-parity fix, not an interrupt-safety one** — verified live in a real browser: xterm's `evaluateKeyboardEvent` routes a shifted ctrl-letter into a branch that assigns `c.key` only for two special cases (`_`→US, `@`→NUL), so it emits no data for Ctrl+Shift+C at all regardless of any application gate; a synthetic keydown with the gate removed produces zero WS frames, proving no accidental interrupt reaches the PTY either way. What gating the whole copy block on `hasSelection()` (an earlier draft) actually cost: with no selection, a selection-less Ctrl+Shift+C fell straight to `return true`, silently ceding the keystroke to the BROWSER's own handling (e.g. Chrome's Inspect-Element binding) with no feedback and no copy attempt — Pane A always intercepts it. Ctrl+V goes through the primary pane's paste trap aimed at Pane B (`_handleImagePaste({ terminal, sessionId })`), so a pasted image uploads to Pane B's session. ⚠️ `buildSplitPickerSessions()` also excludes any session with `pid === null` (an exited CLI, a crash-looped session whose breaker tripped, a restore that never re-attached): Pane B has no equivalent of `selectSession()`'s auto re-attach POST, so a pane opened onto one has nothing reading its tmux pane — no `terminal` events ever arrive, and `Session.write()` silently drops every keystroke with no ack either way, so the loss is invisible behind a socket that reports healthy. Pane B's keystrokes go through the exactly-once queue (`_sendInputAsync`) over its own socket, registered in the app's input-socket map (`_registerInputSocket` / `_inputSocketFor`), so they are seq-tagged, ACKed (`{t:'ia'}` is routed by the RECEIVING socket's session, since the frame names none), redelivered after a drop, and the ACK clears the idle alert. ⚠️ What xterm generates never enters that persisted queue: query replies are dropped (`shouldSuppressTerminalQueryResponse`, as the primary pane drops them) and focus/mouse reports go through `_sendInputEphemeral`, or a reload would replay them as typed text. ⚠️ A SHELL Pane B pulls scrollback itself when the wheel goes up at the top of its buffer (`_maybeLoadMoreHistory`/`_pullHistory`): tmux repaints a burst of output instead of scrolling it, so Pane B's own xterm holds about one screen of scrollback while tmux holds every line, and it loaded history exactly once at connect and never again. It is the same bounded pull as Pane A's (`?full=1&tail=TERMINAL_TAIL_SIZE`, no rewrite when the window holds no more rows than the pane already has or the pane is at its `scrollback + rows` cap, and a 60 s back-off instead of 4 s when that skipped window was truncated or the pane is full, since each ask costs the server a whole-history `capture-pane`), against Pane B's OWN terminal rather than `app.terminal`, so it cannot share `_maybeRefetchFullHistory`. The wheel listener is capture-phase because xterm `stopPropagation()`s the events it consumes; the alternate-screen skip (nano, vim, less) only matters for a direct-PTY shell, since under tmux the browser xterm never enters the alternate buffer; skipped too for a detached session (mirrors `_sendResize()`'s own check and app.js's `_maybeRefetchFullHistory`), since its own window already owns its PTY size and scrollback. Live frames arriving from the response onward, a `{t:'c'}` clear frame included, are held with their arrival time (`_liveQueue`, opened right after `await fetch(...)` beside `capturedAt`; a frame from before it is replaced by the capture or written unchanged, so the pane keeps painting during the round trip) and replayed in order only if they arrived after the capture (the response's arrival stands in for the capture instant, as in `_finishBufferLoad`, so a frame inside that one round trip can be lost or doubled); the request uses the primary pane's budget (`CodemanFetchDeadline.terminalFetchDeadlineMs({ full: true })`, 45 s, 10 s only if that helper is absent) and the body read gets 10 s once the headers land, because from then on the pull holds the pane's live output. The request phase holds no live output, but it does hold the single-flight flag, so a coalesced `{t:'r'}` refresh and a marker owed by a close (below) wait for the response, at worst for that whole budget (accepted: a Codeman restart resets an in-flight request along with the socket, so that pull fails at once and stamps the marker). ⚠️ The "disconnected" marker must be the LAST thing on screen. A replay's own `\x1bc` would otherwise wipe a marker written before the pull and paint a fresh, current-looking history while `onData` keeps silently dropping every keystroke on the dead socket (a Codeman restart drops the socket while the tmux session, and so the HTTP pull, still succeeds), so `_pullHistory()` re-stamps it after the live-frame flush. A close DURING any load (a pull, a refresh; `connect()` awaits the initial load before it creates the socket, so no close lands in that one) writes nothing: `_onSocketClosed()` sets `_markerOwed` while `_bufferLoading` is true, since written there it would sit above the held frames the pull flushes after a skip, a downgrade, a failed fetch or the deadline, above a refresh's replay, or land mid-way through a chunked replay. Each load settles the marker in its OWN `finally` (`_stampMarkerIfOwed()`), after the queue flush, EXCEPT when a trailing refresh is pending: that refresh's `clear()` is synchronous while xterm parses a `write()` on a later tick, so a marker stamped just before it lands in the freshly cleared buffer ABOVE the refresh's replay (a second, stale copy; the default fake terminal in `test/terminal-tile-unit.test.ts` writes synchronously and cannot show it, so an async-parse fake there pins it). The marker stays owed instead, and the trailing refresh, which re-owes it on a closed socket anyway, writes the one copy below its own replay. Anything that wipes the terminal on a closed socket (a replay's `\x1bc`, a refresh's `clear()`) sets `_markerOwed` too, so the marker is rewritten whether or not the close landed during the load. Tracked via `_wsClosed`/`_markerOwed` rather than routed through `_onLiveOutput()`, since a close landing before the response is stamped before the cutoff and would be dropped with the rest of the pre-capture queue. There is no "Load full history" banner in Pane B, so a shell history past that 1 MiB window stays out of reach there. Non-shell Pane B is unchanged: it already loads `full=1`, and its history is out of scope for this pull (codex and Claude's inline renderer do grow tmux history; this just isn't how they recover it). ⚠️ App-level terminal actions find their pane through `_focusedPane()`, the terminal focused LAST (not `document.activeElement`, which the mic or a header button takes): Ctrl+L, Ctrl+Shift+R, voice and image paste act on Pane B while it holds the keyboard. Ctrl+W is not an app shortcut at all (Close Session has no default key), so it reaches whichever pane is focused as delete-word. ⚠️ Geometry: `TerminalTile.fit()` sends the size the xterm actually holds, unfloored (the divider's 20% clamp leaves about 28 columns), skips an unchanged size, re-sends on every fresh socket, and adopts the PTY's column count from `{t:'zc'}`; the font, family and weight setters call `tile.fit()`, never a local refit alone (#464). Design: `docs/split-pane-sessions-plan.md`; the tile class: `docs/tile-grid-plan.md`.
+**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 xterm's plain `\r` would submit an incomplete prompt instead of adding a line to it. Smart-copy Ctrl+C/Ctrl+Shift+C is re-implemented against `this.terminal` (Pane B's own) rather than reusing `app.copyTerminalSelection()`, which reads Pane A's terminal and would copy the wrong pane's selection; Ctrl+Shift+C never falls through even with nothing to copy, mirroring terminal-ui.js's own `ev.shiftKey` branch. ⚠️ **This is a UX-parity fix, not an interrupt-safety one** — verified live in a real browser: xterm's `evaluateKeyboardEvent` routes a shifted ctrl-letter into a branch that assigns `c.key` only for two special cases (`_`→US, `@`→NUL), so it emits no data for Ctrl+Shift+C at all regardless of any application gate; a synthetic keydown with the gate removed produces zero WS frames, proving no accidental interrupt reaches the PTY either way. What gating the whole copy block on `hasSelection()` (an earlier draft) actually cost: with no selection, a selection-less Ctrl+Shift+C fell straight to `return true`, silently ceding the keystroke to the BROWSER's own handling (e.g. Chrome's Inspect-Element binding) with no feedback and no copy attempt — Pane A always intercepts it. Ctrl+V goes through the primary pane's paste trap aimed at Pane B (`_handleImagePaste({ terminal, sessionId })`), so a pasted image uploads to Pane B's session. ⚠️ `buildSplitPickerSessions()` also excludes any session with `pid === null` (an exited CLI, a crash-looped session whose breaker tripped, a restore that never re-attached): Pane B has no equivalent of `selectSession()`'s auto re-attach POST, so a pane opened onto one has nothing reading its tmux pane — no `terminal` events ever arrive, and `Session.write()` silently drops every keystroke with no ack either way, so the loss is invisible behind a socket that reports healthy. Pane B's keystrokes go through the exactly-once queue (`_sendInputAsync`) over its own socket, registered in the app's input-socket map (`_registerInputSocket` / `_inputSocketFor`), so they are seq-tagged, ACKed (`{t:'ia'}` is routed by the RECEIVING socket's session, since the frame names none), redelivered after a drop, and the ACK clears the idle alert. ⚠️ What xterm generates never enters that persisted queue: query replies are dropped (`shouldSuppressTerminalQueryResponse`, as the primary pane drops them) and focus/mouse reports go through `_sendInputEphemeral`, or a reload would replay them as typed text. ⚠️ A SHELL Pane B pulls scrollback itself when the wheel goes up at the top of its buffer (`_maybeLoadMoreHistory`/`_pullHistory`): tmux repaints a burst of output instead of scrolling it, so Pane B's own xterm holds about one screen of scrollback while tmux holds every line, and it loaded history exactly once at connect and never again. It is the same bounded pull as Pane A's (`?full=1&tail=TERMINAL_TAIL_SIZE`, no rewrite when the window holds no more rows than the pane already has or the pane is at its `scrollback + rows` cap, and a 60 s back-off instead of 4 s when that skipped window was truncated or the pane is full, since each ask costs the server a whole-history `capture-pane`), against Pane B's OWN terminal rather than `app.terminal`, so it cannot share `_maybeRefetchFullHistory`. The wheel listener is capture-phase because xterm `stopPropagation()`s the events it consumes; the alternate-screen skip (nano, vim, less) only matters for a direct-PTY shell, since under tmux the browser xterm never enters the alternate buffer; skipped too for a detached session (mirrors `_sendResize()`'s own check and app.js's `_maybeRefetchFullHistory`), since its own window already owns its PTY size and scrollback. Live frames arriving from the response onward, a `{t:'c'}` clear frame included, are held with their arrival time (`_liveQueue`, opened right after `await fetch(...)` beside `capturedAt`; a frame from before it is replaced by the capture or written unchanged, so the pane keeps painting during the round trip) and replayed in order only if they arrived after the capture (the response's arrival stands in for the capture instant, as in `_finishBufferLoad`, so a frame inside that one round trip can be lost or doubled); the request uses the primary pane's budget (`CodemanFetchDeadline.terminalFetchDeadlineMs({ full: true })`, 45 s, 10 s only if that helper is absent) and the body read gets 10 s once the headers land, because from then on the pull holds the pane's live output. The request phase holds no live output, but it does hold the single-flight flag, so a coalesced `{t:'r'}` refresh and a marker owed by a close (below) wait for the response, at worst for that whole budget (accepted: a Codeman restart resets an in-flight request along with the socket, so that pull fails at once and stamps the marker). ⚠️ The "disconnected" marker must be the LAST thing on screen. A replay's own `\x1bc` would otherwise wipe a marker written before the pull and paint a fresh, current-looking history while `onData` keeps silently dropping every keystroke on the dead socket (a Codeman restart drops the socket while the tmux session, and so the HTTP pull, still succeeds), so `_pullHistory()` re-stamps it after the live-frame flush. A close DURING any load (a pull, a refresh; `connect()` awaits the initial load before it creates the socket, so no close lands in that one) writes nothing: `_onSocketClosed()` sets `_markerOwed` while a load's work runs (`_loadRunning`; a load that only waits in the tile grid's queue writes the marker at once, and its refresh clears the screen only when its turn comes), since written there it would sit above the held frames the pull flushes after a skip, a downgrade, a failed fetch or the deadline, above a refresh's replay, or land mid-way through a chunked replay. Each load settles the marker in its OWN `finally` (`_stampMarkerIfOwed()`), after the queue flush, EXCEPT when a trailing refresh is pending: that refresh's `clear()` is synchronous while xterm parses a `write()` on a later tick, so a marker stamped just before it lands in the freshly cleared buffer ABOVE the refresh's replay (a second, stale copy; the default fake terminal in `test/terminal-tile-unit.test.ts` writes synchronously and cannot show it, so an async-parse fake there pins it). The marker stays owed instead, and the trailing refresh, which re-owes it on a closed socket anyway, writes the one copy below its own replay. Anything that wipes the terminal on a closed socket (a replay's `\x1bc`, a refresh's `clear()`) sets `_markerOwed` too, so the marker is rewritten whether or not the close landed during the load. Tracked via `_wsClosed`/`_markerOwed` rather than routed through `_onLiveOutput()`, since a close landing before the response is stamped before the cutoff and would be dropped with the rest of the pre-capture queue. There is no "Load full history" banner in Pane B, so a shell history past that 1 MiB window stays out of reach there. Non-shell Pane B is unchanged: it already loads `full=1`, and its history is out of scope for this pull (codex and Claude's inline renderer do grow tmux history; this just isn't how they recover it). ⚠️ App-level terminal actions find their pane through `_focusedPane()`, the terminal focused LAST (not `document.activeElement`, which the mic or a header button takes): Ctrl+L, Ctrl+Shift+R, voice and image paste act on Pane B while it holds the keyboard. Ctrl+W is not an app shortcut at all (Close Session has no default key), so it reaches whichever pane is focused as delete-word. ⚠️ Geometry: `TerminalTile.fit()` sends the size the xterm actually holds, unfloored (the divider's 20% clamp leaves about 28 columns), skips an unchanged size, re-sends on every fresh socket, and adopts the PTY's column count from `{t:'zc'}`; the font, family and weight setters call `tile.fit()`, never a local refit alone (#464). Every capture a pane fetches carries a deadline covering the body (`CodemanFetchDeadline`), so a capture that never answers cannot hold its single-flight flag forever. Design: `docs/split-pane-sessions-plan.md`; the tile class: `docs/tile-grid-plan.md`.
+
+### 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 9 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, 3x3; `fits` against a 480x240 minimum tile), `tileGridCapacity`, `sanitizeTileGridState`, `buildTilePickerSessions`, `dragTrackFractions`, `tileNeighbor`, `tileInDirection`, `cycleTile`, `TILE_SCROLLBACK` (10,000). 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 })`.
+
+⚠️ **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.
+
+⚠️ **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.
+
+⚠️ **Chords.** `toggle-tile-grid` (Ctrl+Shift+G), `focus-tile-*` (Alt+Shift+Arrows), `zoom-tile` (Alt+Shift+Enter) and `remove-tile` (unbound) are registry entries kept OUT of `SHORTCUT_ACTIONS`: `tileShortcutFor` decides whether one applies (the toggle while the grid is open, or where one could open AND `showTileGridButton` is on; the rest only while it is open), the capture handler dispatches it, and the main terminal's and every tile's xterm key handler return false for it, for every event type and BEFORE the Shift+Enter gate (Alt+Shift+Enter would otherwise send `S-Enter`). Outside the grid the focus chords reach the terminal untouched.
+
+⚠️ **Chrome.** The header is a fixed 24px sibling of the body, refreshed in place on every tab render (`_renderSessionTabsImmediate` wrapper), never by rewriting the tile (that would take its xterm along) and never growing (#464: the body holds the xterm). Header buttons stop pointerdown, so acting on an unfocused tile does not focus it. × removes the tile only; killing stays behind the session menu's Close session. The `needs` pulse animates `box-shadow` only. Dividers are their own 6px grid tracks (`gap: 0`), tiles placed explicitly; a drag uses pointer capture, reflows the affected tiles locally per animation frame and sends ONE `fit()` (one PTY resize) per affected tile at pointer-up; closing the grid or removing a tile mid-drag tears it down. A tab dragged onto a tile replaces it (or swaps two tiles); tiles and empty slots handle `dragover`/`drop` in the CAPTURE phase and stop it, because the drag carries the session id as text and xterm's helper textarea would type it into the PTY.
+
+⚠️ **Attach.** A tile whose session has no PTY (`pid === null`) or whose socket closed because it exited (4009) shows an Attach overlay (absolute, the body keeps its size): `POST /interactive` (or `/shell`) with NO body, one in flight per session, a tripped PTY-exit breaker only through the same confirm as the single view, then the tile is remounted (a stopped socket cannot reconnect). The routes report a refusal in the ENVELOPE of a 200, so the response body is read, not `res.ok`. An agent that exited in a live pane (`paneExit`) cannot be started again in place (both routes refuse while the pane's tmux client runs): its tile shows the exit and points at Close session.
+
+⚠️ **Persistence and joining.** `codeman:tile-grid` holds `{ v: 1, open, ids, focused, zoomed, colFr, rowFr }`, ids only, written as the grid changes; closing keeps it as `open: false` (the Tiles toggle, the picker and Ctrl/Cmd+click bring it back), the last tile leaving forgets it, a solo window never reads or writes it, an automatic zoom is not stored. Sessions created by THIS tab's Run join the open grid (`_joinTileGridFromRun`, called from session-ui.js `_ensureCreatedSessionVisible`; a wrapper from tile-grid.js would be overwritten by session-ui.js's later `Object.assign`); sessions created elsewhere arrive only by `session:created` and never join. Tests: `test/tile-grid-*.test.ts` over the shared vm harness `test/mocks/tile-grid-vm.ts`.
 
 ### Gesture control: the setting
 
@@ -979,7 +997,7 @@ Tests: `test/mobile-prompt-composer.test.ts` (in the CI gate, deliberately not u
 
 ### Z-index layers
 
-**Z-index layers**: subagent windows (1000), split picker menu (1000, `.split-picker-menu`), plan agents (1100), mobile/tablet fixed header (1200, `mobile.css`), modals on ≤768px (1300 — must beat the fixed header or the modal close button is buried), log viewers (2000), connection-loss overlay (2500, above the fixed header and modals), image popups (3000), response viewer (5000, backdrop 4999), file-preview overlay (5100 — must outrank the response viewer, which can launch it; at its old 2000 a path clicked in the chat opened BEHIND the chat), toasts/path picker (10000+, deliberately above the preview), the custom-model center-status banner (10001, `.center-status-banner` — `[hidden]` must re-assert `display: none` over its own `display: flex`, same trap as `.home-sessions[hidden]`, or `dismiss()` leaves an invisible click-blocker dead centre on screen), the swap-confirm and context-warning modals (10010, `#customModelSwapConfirmModal`/`#customModelContextWarningModal` — must clear both the plain `.modal` z-index of 1000 and the center-status banner it can appear over), terminal touch-selection bar (900 — above terminal content and the local-echo overlay, deliberately BELOW floating agent windows so it can never cover their controls), local echo overlay (7), iOS IME composition preview (EFFECTIVE layer depends on its home: with local echo on it is part of the local echo overlay at 7, drawn by `setComposition()` as an underlined tail after the pending text; with local echo off it is a span at z-index 6 inside `.xterm-helpers`, but `.xterm-helpers` is its own z-index 5 stacking context, so the span's effective layer is 5. That is below the overlay's 7, which is why the span cannot be used while the overlay holds text: typed text never reaches the PTY before Enter, the PTY cursor that places the span stays at the prompt start, and the overlay's opaque line div covers it).
+**Z-index layers**: subagent windows (1000), split picker menu (1000, `.split-picker-menu`), Tiles picker (1000, `.tile-picker-menu`; a tile's + menu reuses `.tab-rail-action-menu`, 2000), plan agents (1100), mobile/tablet fixed header (1200, `mobile.css`), modals on ≤768px (1300 — must beat the fixed header or the modal close button is buried), log viewers (2000), connection-loss overlay (2500, above the fixed header and modals), image popups (3000), response viewer (5000, backdrop 4999), file-preview overlay (5100 — must outrank the response viewer, which can launch it; at its old 2000 a path clicked in the chat opened BEHIND the chat), toasts/path picker (10000+, deliberately above the preview), the custom-model center-status banner (10001, `.center-status-banner` — `[hidden]` must re-assert `display: none` over its own `display: flex`, same trap as `.home-sessions[hidden]`, or `dismiss()` leaves an invisible click-blocker dead centre on screen), the swap-confirm and context-warning modals (10010, `#customModelSwapConfirmModal`/`#customModelContextWarningModal` — must clear both the plain `.modal` z-index of 1000 and the center-status banner it can appear over), terminal touch-selection bar (900 — above terminal content and the local-echo overlay, deliberately BELOW floating agent windows so it can never cover their controls), local echo overlay (7), iOS IME composition preview (EFFECTIVE layer depends on its home: with local echo on it is part of the local echo overlay at 7, drawn by `setComposition()` as an underlined tail after the pending text; with local echo off it is a span at z-index 6 inside `.xterm-helpers`, but `.xterm-helpers` is its own z-index 5 stacking context, so the span's effective layer is 5. That is below the overlay's 7, which is why the span cannot be used while the overlay holds text: typed text never reaches the PTY before Enter, the PTY cursor that places the span stays at the prompt start, and the overlay's opaque line div covers it).
 
 ## Security layers
 
diff --git a/docs/tile-grid-plan.md b/docs/tile-grid-plan.md
index bffaebe6..161a01db 100644
--- a/docs/tile-grid-plan.md
+++ b/docs/tile-grid-plan.md
@@ -1,10 +1,37 @@
 # Tile Grid: Design Spec
 
-**Status**: PR 1 (tile foundation) implemented on `feat/terminal-tile`, local only; PR 2 (the grid) proposed. Builds on `docs/split-pane-sessions-plan.md`; the split pane stays.
+**Status**: PR 1 (tile foundation) implemented on `feat/terminal-tile`; PR 2 (the grid) implemented on `feat/tile-grid`, both local only. Builds on `docs/split-pane-sessions-plan.md`; the split pane stays.
 **Author**: Claude (planning session with the maintainer), 2026-10-06
-**Branches**: PR 1 `feat/terminal-tile`, PR 2 `feat/tile-grid` stacked on it (worktree `claudeman-tiles`)
+**Branches**: PR 1 `feat/terminal-tile`, PR 2 `feat/tile-grid` stacked on it (worktrees `claudeman-tiles`, `claudeman-tilegrid`)
 **Scope**: v1 is fully designed here; follow-ups are named at the end and explicitly deferred.
 
+## As built: where PR 2 differs from this spec
+
+The design below stands; these are the places the built grid deliberately went another way,
+or settled a question the spec left open. The invariants as built are in
+`docs/architecture-invariants.md#tile-grid`.
+
+- **An agent that exited in a live pane (`paneExit`) gets no Attach button.** Both attach
+  routes (`/interactive`, `/shell`) refuse while the pane's tmux client still runs ("Session
+  already has a running process") and report that in the envelope of a 200, so the
+  edge-case row below cannot work without a server change. The tile shows the exit and
+  points at Close session. A session with no PTY (`pid === null`) and a socket closed with
+  4009 do get Attach. Restarting an exited agent in place is a follow-up.
+- **`Ctrl+Shift+G` follows `showTileGridButton`** (the applied default while the owner's
+  answer is pending): with the setting off the toggle chord is inert. A grid opened another
+  way (Ctrl/Cmd+click, a dropped tab, "Open group as tiles") keeps all its chords.
+- **Dividers are grid tracks.** Each gap between columns and rows is its own 6px track (the
+  grid gap is 0) and tiles are placed explicitly in reading order, which is also what the
+  empty-slot drop targets need. Fractions reset when the column or row count changes.
+- **Zoom follows tmux.** Moving focus to another tile restores the grid; an automatic zoom
+  (window too small for the minimum tile) follows focus instead.
+- **Tile loads are bounded** (`boundedLoad`), carry a fetch deadline covering the body (Pane
+  B too), and a refresh clears the screen at its turn in the queue, so a waiting tile keeps
+  its last frame.
+- **4009 lands on the Attach overlay**, and 4003/4004/4010 remove the tile.
+- **"+ / New session in this case"** runs the normal Run for that case and joins through
+  the same auto-join as any Run from this tab.
+
 ## Problem
 
 Codeman's terminal area shows exactly one session at a time. The split pane
diff --git a/docs/wiki/Keyboard-Shortcuts.md b/docs/wiki/Keyboard-Shortcuts.md
index f8a88812..4844c9aa 100644
--- a/docs/wiki/Keyboard-Shortcuts.md
+++ b/docs/wiki/Keyboard-Shortcuts.md
@@ -39,6 +39,19 @@ from its tab, or bind a key to it in App Settings → Shortcuts.
 
 Anything you copy is cleaned on the way to the clipboard: each line loses the padding spaces a full-screen program paints across the rest of the row. Leading indentation is left exactly as it is, so indented code, a `git log` message body and `git diff` context lines paste back the way they looked on screen. An `Alt+drag` rectangular selection is copied exactly as it looks, so its columns stay lined up.
 
+## Tile grid
+
+| Shortcut                    | Action                                                       |
+| --------------------------- | ------------------------------------------------------------ |
+| `Ctrl+Shift+G`              | Open or close the tile grid (needs the Tiles setting on).     |
+| `Alt+Shift+Arrows`          | Focus the tile to the left, right, above or below.            |
+| `Alt+Shift+Enter`           | Zoom the focused tile, or restore the grid.                   |
+| `Ctrl`+click / `Cmd`+click a tab | Add that session to the grid.                            |
+
+While the grid is open, `Ctrl+Tab` and `Alt+[` / `Alt+]` cycle through the tiles, and the
+terminal shortcuts above act on the focused tile. **Remove Focused Tile** has no key by
+default. See [Tile Grid](Tile-Grid).
+
 ## Everything else
 
 | Shortcut       | Action                          |
diff --git a/docs/wiki/Settings-Reference.md b/docs/wiki/Settings-Reference.md
index 63335691..25b674ee 100644
--- a/docs/wiki/Settings-Reference.md
+++ b/docs/wiki/Settings-Reference.md
@@ -57,7 +57,7 @@ supervised by systemd or launchd; npm installs report as non-updatable. See
 Chips for every optional header control, with a live preview of the resulting header:
 
 Run, Font Size, System Stats, Redraw Terminal, Response Viewer, Away Digest, Session
-Manager, Attachments, File Viewer, Multi-monitor, Split, Plan Usage, Lifecycle Log, Monitor,
+Manager, Attachments, File Viewer, Multi-monitor, Split, Tiles, Plan Usage, Lifecycle Log, Monitor,
 Project Insights, File Browser, Subagents, Approvals Inbox, Read My Mind, Ultracode Agents,
 Ultracode Windows, Cron.
 
@@ -71,7 +71,9 @@ window; off lists every file by its full path.
 Most default to off. The stock desktop header is system stats, File Viewer, and the gear.
 New header controls never appear on phones. Split is desktop-only regardless of this
 setting — the button and the feature both stay off below a ~1180px viewport, where two
-resizable panes plus their divider have nowhere to go.
+resizable panes plus their divider have nowhere to go. **Tiles** is desktop-only the same
+way; it also enables the `Ctrl+Shift+G` grid toggle on this device. See
+[Tile Grid](Tile-Grid).
 
 This section also holds background-agent tracking, including whether to track agents for
 every session or only the active tab.
diff --git a/docs/wiki/The-Dashboard.md b/docs/wiki/The-Dashboard.md
index 46a67628..94aa65b6 100644
--- a/docs/wiki/The-Dashboard.md
+++ b/docs/wiki/The-Dashboard.md
@@ -118,6 +118,7 @@ The right side of the header. Almost all of these are off until you enable them
 | Cron ⏰                | Off                | Scheduled jobs.                                                                   |
 | Multi-monitor          | Off, macOS         | Opens a window spanning every display.                                            |
 | Split                  | Off, desktop only  | View a second session beside the active one, with a draggable divider.           |
+| Tiles                  | Off, desktop only  | Up to nine live sessions side by side. See [Tile Grid](Tile-Grid).               |
 | Tunnel indicator       | When a tunnel runs | Cloudflare tunnel status.                                                        |
 | Admin panel            | Multi-user only    | User administration.                                                              |
 
diff --git a/docs/wiki/Tile-Grid.md b/docs/wiki/Tile-Grid.md
new file mode 100644
index 00000000..1959bdae
--- /dev/null
+++ b/docs/wiki/Tile-Grid.md
@@ -0,0 +1,93 @@
+# Tile Grid
+
+Watch and drive up to nine sessions at once, side by side in one window. Each tile is a
+full live terminal: it reads, it takes your keystrokes, and it shows at a glance whether
+its agent is working, idle, or waiting on you.
+
+The grid is a desktop feature. It needs a window at least about 1180px wide, and it is
+never offered in a popped-out session window.
+
+## Turning it on
+
+**App Settings → Header & Panels → Tiles.** This is a per-device setting, off by default,
+so turning it on at your desk never puts the button on your phone. It shows a **Tiles**
+button in the header, beside Split, and enables `Ctrl+Shift+G`.
+
+## Opening a grid
+
+- **Tiles button**: with the grid closed it opens a picker, a checkbox per open session in
+  tab order. It starts with the grid you last had (or the session you are on), says how many
+  tiles this window fits, and greys out the rest. **Open tiles** shows them. With the grid
+  open, the same button closes it.
+- **`Ctrl+Shift+G`**: toggles the grid. Opening brings back the grid you last had, else an
+  open split as two tiles, else the session you are on.
+- **`Ctrl`+click (or `Cmd`+click) a tab**: adds that session to the grid and focuses it,
+  opening the grid if it was closed. On macOS use `Cmd`: `Ctrl`+click there opens the tab's
+  rename instead.
+- **Drag a tab onto a tile** to replace that tile with it (the replaced session keeps
+  running), or onto an empty slot to add it. Dragging a session that is already tiled onto
+  another tile swaps the two.
+- **"Open group as tiles"** in a tab group's menu, in the vertical tab rail with groups.
+- **Run**: a session you start from this browser tab's Run button while the grid is open
+  joins it. Sessions started elsewhere (an agent, another device, a cron job) do not.
+
+The layout follows the tile count: 1x1, 2x1, three side by side on a wide screen (else a
+2x2 with one empty slot), 2x2, 3x2, 3x3.
+
+## A tile
+
+Each tile has a small header: `● name ......... ⋯ ⤢ + ×`
+
+| Part   | What it does                                                                                     |
+| ------ | ------------------------------------------------------------------------------------------------ |
+| `●`    | The session's state: working, idle, waiting on you, needs you (red, and the tile's border pulses), error, ended. Hover the header for how long. |
+| name   | Double-click to rename the session.                                                              |
+| `⋯`    | The session menu: options, open in a new window, close the session.                              |
+| `⤢`    | Zoom: the tile fills the grid; press it again (or `Alt+Shift+Enter`) to get the grid back.        |
+| `+`    | Add a session that is not tiled yet, or start a new session in this tile's case.                  |
+| `×`    | Remove the tile. The session keeps running; close it from `⋯` if you want it gone.                |
+
+Click a tile to focus it. The focused tile has the accent border, takes your keyboard, and
+is the session every panel follows: files, git status, respawn and Ralph, subagent windows,
+voice and image paste. Tabs of tiled sessions carry a small underline.
+
+Drag the thin lines between tiles to resize columns and rows. A tile never gets smaller than
+about 60 columns; when the window is too small for all the tiles, the grid shows the focused
+one on its own until the window is big enough again.
+
+A tile whose session is not running shows **Not attached** with an **Attach** button. A tile
+whose agent exited inside its pane says so instead; close that session from `⋯`.
+
+## Keys
+
+| Shortcut                 | Action                                                     |
+| ------------------------ | ---------------------------------------------------------- |
+| `Ctrl+Shift+G`           | Open or close the grid.                                     |
+| `Alt+Shift+Arrows`       | Focus the tile to the left, right, above or below.          |
+| `Alt+Shift+Enter`        | Zoom the focused tile, or restore the grid.                 |
+| `Ctrl+Tab`, `Alt+[` `]`  | Cycle through the tiles.                                    |
+| `Ctrl+L`                 | Clear the focused tile.                                     |
+| `Ctrl` `+` / `Ctrl` `-`  | Tile font size (tiles have their own, smaller font).        |
+
+All of them can be rebound in App Settings → Shortcuts, where **Remove Focused Tile** can
+also get a key. Outside the grid, `Alt+Shift+Arrows` and `Alt+Shift+Enter` go to the
+terminal as usual. With the Tiles setting off, `Ctrl+Shift+G` does nothing.
+
+## Leaving the grid
+
+Clicking the tab of a session that is not tiled (or picking it with `Alt+1-9` or the
+session finder) shows that session on its own, the normal single view. The grid is
+remembered: the Tiles button or `Ctrl+Shift+G` brings it straight back. Going Home does the
+same. Narrowing the window below the desktop width also returns to the single view.
+
+The grid is saved on this device and comes back when you reload the page, with its focus,
+zoom and column widths. A session that was closed in the meantime is simply left out.
+
+The grid and Split are never open together: opening the grid turns an open split into two
+tiles, and Split is unavailable while the grid is open.
+
+## Read next
+
+- [The Dashboard](The-Dashboard) - the single view, tabs and the header.
+- [Keyboard Shortcuts](Keyboard-Shortcuts) - every binding.
+- [Settings Reference](Settings-Reference) - where the Tiles setting lives.
diff --git a/docs/wiki/_Sidebar.md b/docs/wiki/_Sidebar.md
index 2e6d54b5..73662db4 100644
--- a/docs/wiki/_Sidebar.md
+++ b/docs/wiki/_Sidebar.md
@@ -11,6 +11,7 @@
 **Using it**
 
 - [The Dashboard](The-Dashboard)
+- [Tile Grid](Tile-Grid)
 - [Agent CLIs](Agent-CLIs)
 - [Custom Model Endpoints](Custom-Model-Endpoints)
 - [Working With Files](Working-With-Files)
diff --git a/src/web/public/index.html b/src/web/public/index.html
index 4000553c..18da5d46 100644
--- a/src/web/public/index.html
+++ b/src/web/public/index.html
@@ -833,6 +833,15 @@
               <div><kbd>Enter</kbd> / <kbd>Space</kbd></div><div>Activate Focused Tab</div>
             </div>
           </section>
+          <section class="shortcut-section">
+            <h4>Tiles</h4>
+            <div class="shortcuts-grid">
+              <div><kbd>Ctrl</kbd>+<kbd>Shift</kbd>+<kbd>G</kbd></div><div>Toggle Tile Grid</div>
+              <div><kbd>Alt/Option</kbd>+<kbd>Shift</kbd>+<kbd>Arrows</kbd></div><div>Focus Tile Left / Right / Up / Down</div>
+              <div><kbd>Alt/Option</kbd>+<kbd>Shift</kbd>+<kbd>Enter</kbd></div><div>Zoom Focused Tile</div>
+              <div><kbd>Ctrl/Cmd</kbd>+<kbd>Click</kbd> a tab</div><div>Add the Session to the Tile Grid</div>
+            </div>
+          </section>
           <section class="shortcut-section">
             <h4>Terminal</h4>
             <div class="shortcuts-grid">
diff --git a/test/help-modal-shortcuts.test.ts b/test/help-modal-shortcuts.test.ts
index 0d54e95d..60fcfb50 100644
--- a/test/help-modal-shortcuts.test.ts
+++ b/test/help-modal-shortcuts.test.ts
@@ -53,6 +53,13 @@ describe('help modal shortcuts', () => {
     expectShortcut(helpModal, ['Escape'], 'Close Panels');
   });
 
+  it('documents the tile grid chords', () => {
+    expectShortcut(helpModal, ['Ctrl', 'Shift', 'G'], 'Toggle Tile Grid');
+    expectShortcut(helpModal, ['Alt/Option', 'Shift', 'Arrows'], 'Focus Tile Left / Right / Up / Down');
+    expectShortcut(helpModal, ['Alt/Option', 'Shift', 'Enter'], 'Zoom Focused Tile');
+    expectShortcut(helpModal, ['Ctrl/Cmd', 'Click'], 'Add the Session to the Tile Grid');
+  });
+
   it('documents terminal input shortcuts without advertising stale run shortcuts', () => {
     expectShortcut(helpModal, ['Ctrl', 'C'], 'Copy Selection');
     expectShortcut(helpModal, ['Ctrl', 'Shift', 'C'], 'Copy Selection');