fix(terminal): bound live xterm backpressure

CLAUDE.md

@@ -224,7 +224,7 @@ Codeman is a Claude Code session manager with web interface and autonomous Ralph
 
 **Circuit breakers**: the Ralph breaker prevents respawn thrashing (`CLOSED` → `HALF_OPEN` → `OPEN`; reset via `/api/sessions/:id/ralph-circuit-breaker/reset`). **Distinct: the PTY-exit breaker** (`session-pty-exit-breaker.ts`) trips after repeated rapid PTY exits and blocks auto-restarts. ⚠️ It resets ONLY via an explicit `{clearBreaker:true}` body on `POST /api/sessions/:id/interactive`; the frontend's auto-reattach in `selectSession()` sends no body and must never clear it. → [architecture-invariants#circuit-breakers-ralph--pty-exit](docs/architecture-invariants.md#circuit-breakers-ralph-and-pty-exit)
 
-**Full-scrollback replay**: `GET /api/sessions/:id/terminal?full=1` returns the entire tmux scrollback, bounded by the configured history limit. On success the capture is returned ALONE (`source='mux-full-history'`), superseding the byte buffer so nothing duplicates. The first load of each non-shell TUI session per page requests `full=1` (`_fullHistoryLoaded` Set); Shell selection always starts from a bounded 1 MiB `?tail=` window and loads the rest only when **Load full history** is pressed. Ordinary Shell scrolling must not trigger a multi-megabyte reset+replay on xterm's main thread. Other modes may re-pull at the TOP (cooldown-guarded — tmux repaints bursty output in place, so browser scrollback shrinks while tmux's history stays complete). ⚠️ That re-pull must never DOWNGRADE the buffer: a repaint-mode CLI pane keeps no tmux history, so its capture is one frame and the reset+rewrite would delete history mid-scroll — `_replayWouldShrinkBuffer()` refuses it and slows that session's cooldown to 60s. → [architecture-invariants#full-scrollback-replay](docs/architecture-invariants.md#full-scrollback-replay)
+**Full-scrollback replay**: `GET /api/sessions/:id/terminal?full=1` returns the entire tmux scrollback, bounded by the configured history limit. On success the capture is returned ALONE (`source='mux-full-history'`), superseding the byte buffer so nothing duplicates. The first load of each non-shell TUI session per page requests `full=1` (`_fullHistoryLoaded` Set); Shell selection and automatic drop recovery always use a bounded 1 MiB `?tail=` window. Shell loads the rest only when **Load full history** is pressed; ordinary scrolling must not trigger a multi-megabyte reset+replay on xterm's main thread. Other modes may re-pull at the TOP (cooldown-guarded — tmux repaints bursty output in place, so browser scrollback shrinks while tmux's history stays complete). Live writes are one-chunk-in-flight, released by xterm's parse callback, so xterm's private queue cannot bypass the browser's 128 KiB render cap. While WebSocket owns terminal I/O, duplicate SSE terminal events are dropped before JSON parsing, and recovery is single-flight per active session. ⚠️ A full re-pull must never DOWNGRADE the buffer: a repaint-mode CLI pane keeps no tmux history, so its capture is one frame and the reset+rewrite would delete history mid-scroll — `_replayWouldShrinkBuffer()` refuses it and slows that session's cooldown to 60s. → [architecture-invariants#full-scrollback-replay](docs/architecture-invariants.md#full-scrollback-replay)
 
 **Terminal touch gestures: link taps and text selection**: on a touch device xterm's own handlers see neither — `touch-action: none` plus touchstart's preventDefault suppress the browser's compatibility mouse events, `_installMobileTapMouseGuard` drops the trusted ones that still arrive, and the synthetic `mousedown`/`mouseup` pair dispatched for mouse REPORTING goes to the `.xterm` root, an ANCESTOR of the screen element the linkifier and SelectionService listen on. So both gestures are driven explicitly. ⚠️ **A tap activates the link under it** through the SAME provider that feeds the hover linkifier (`_terminalLinkAtPoint`, containment mirroring xterm's `_linkAtPosition`), synchronously inside `touchend` — that is what keeps the user gesture `window.open` needs — and BEFORE any mouse report, mirroring `_handleDesktopTerminalClick`'s skip for a hovered link. Two rows keep their meaning: the caret's logical line (`_tapIsOnCaretLine`, where a tap places the cursor in text the USER typed) and TUI-owned rows (`_isActionableMobileTerminalTap`, answering a dialog). ⚠️ The caret line is the boundary rather than the tap INTENT, because a shell classifies every tap as `'input'` and gating on that would leave every URL in shell output inert. ⚠️ **Long-press selects** by driving xterm's public `select()` (renderer-independent — under WebGL the glyphs are pixels and native selection cannot exist), drag or a further tap extends, and Copy goes through `copyTerminalSelection()` for its execCommand fallback on plain-HTTP installs. Three guards are load-bearing and each came from a real phone: the compat mouse pair after `touchend` (xterm focuses on mousedown and SelectionService resets the model there, so the keyboard sprang up and the selection vanished on lift), the platform's own ~500ms long-press (Android Chrome focuses the nearest editable element — the helper textarea — through no event a handler can preventDefault, so a bounded focus guard blurs it and `contextmenu` is suppressed for the gesture window), and `copyTerminalSelection()`'s closing `terminal.focus()` (right on desktop, wrong on a phone). Tests: `test/terminal-touch-tap.test.ts`.
 

docs/architecture-invariants.md

@@ -92,7 +92,7 @@ Implementation detail extracted from `CLAUDE.md` so that file stays small enough
 
 ### Full-scrollback replay
 
-**Full-scrollback replay** (COD-164/#148, reworked for #205): `GET /api/sessions/:id/terminal?full=1` returns the ENTIRE tmux scrollback (capture-pane `-e -S -<lines>` bounded by the configured history limit, explicit `maxBuffer` from the terminal-history config, early byte-cap before normalization, CRLF-normalized for shell panes). On success the capture is returned ALONE (`source='mux-full-history'` — it supersedes the byte buffer; no duplication). The first load of each non-shell TUI session per page requests `full=1` (`_fullHistoryLoaded` Set in app.js — the old one-shot `_initialFullBufferLoad` flag was consumed by whichever tab auto-selected, leaving every other TUI tab one frame of history). Shell sessions instead load a bounded 1 MiB `?tail=` window on every selection: a 100k-line shell capture can be tens of MiB, and automatically parsing it makes tab-switch latency scale with the entire session. Shell full history is therefore explicit-button-only; reaching the top during an ordinary wheel/touch gesture must not reset xterm and replay the multi-megabyte capture on its main thread. Other modes may still re-pull `full=1` at the TOP, and pressing **Load full history** forces the request for any recoverably truncated session (`_maybeRefetchFullHistory`, 4s per-session gesture cooldown, in-flight + tab-switch guards, viewport position held across the replay); Shell full pulls are not retained in the tab cache, so the next switch stays bounded. Chunked replay enqueues 32 KiB pieces across safe yields, appends an xterm parse marker, then releases the live-output gate; output arriving after that release stays ordered behind the snapshot, while the marker callback supplies accurate parse timing without extending the pre-existing queued-event discard window. The route exposes capture/prepare totals in `Server-Timing`, while `[TERMINAL-PERF]` separates TTFB, body/JSON, reset+parse and total time for both selection and on-demand full pulls; parse completion is not a browser compositor/GPU paint measurement. The re-pull exists because xterm's buffer is only a WINDOW onto tmux's history and two things shrink it: tmux coalesces bursty output into pane REPAINTS that overwrite rows instead of emitting linefeeds (measured: a 60-line burst added 1 row of browser scrollback and destroyed 34), and a tab switch replays only the visible frame. tmux's own history is intact throughout — the browser just has to ask for it again. On-demand rather than automatic because at a 100k history limit the capture can be megabytes. ⚠️ **The re-pull must never DOWNGRADE the buffer** (#205 round 2): the same reasoning that makes it a win for a shell pane makes it destructive for a repaint-mode CLI pane, where tmux keeps no history of its own (`history_size≈0` measured for a Claude pane) and the capture is roughly ONE frame while xterm may hold hundreds of rows of replayed frames — `_resetTerminalForReplay()` + rewrite then deletes history mid-scroll ("goes back a bit, repeats blocks, gets worse the further up I go"; measured A/B on a live pane: 341 rows → 42 with the guard off). `_replayWouldShrinkBuffer()` (terminal-ui.js) estimates the capture's rendered rows — escape sequences stripped, `capture-pane -J` re-wrapping accounted for — and the pull is skipped when that is more than one screen short of `buffer.active.length`. The one-screen tolerance matters: both sides are estimates (the buffer length counts trailing blank rows), so only a clear downgrade is refused. A refused session joins `_fullHistoryRepullUseless`, raising its cooldown from 4s to 60s so a hollow pane stops re-fetching megabytes on every scroll-up. Tests: `test/tmux-capture-full-history.test.ts`, `test/tmux-scrollback-eol.test.ts`, `test/terminal-scroll-routing.test.ts`.
+**Full-scrollback replay** (COD-164/#148, reworked for #205): `GET /api/sessions/:id/terminal?full=1` returns the ENTIRE tmux scrollback (capture-pane `-e -S -<lines>` bounded by the configured history limit, explicit `maxBuffer` from the terminal-history config, early byte-cap before normalization, CRLF-normalized for shell panes). On success the capture is returned ALONE (`source='mux-full-history'` — it supersedes the byte buffer; no duplication). The first load of each non-shell TUI session per page requests `full=1` (`_fullHistoryLoaded` Set in app.js — the old one-shot `_initialFullBufferLoad` flag was consumed by whichever tab auto-selected, leaving every other TUI tab one frame of history). Shell sessions instead load a bounded 1 MiB `?tail=` window on every selection and automatic drop recovery: a 100k-line shell capture can be tens of MiB, and automatically parsing it makes tab-switch latency scale with the entire session. Shell full history is explicit-button-only; reaching the top during an ordinary wheel/touch gesture must not reset xterm and replay the multi-megabyte capture on its main thread. Other modes may still re-pull `full=1` at the TOP, and pressing **Load full history** forces the request for any recoverably truncated session (`_maybeRefetchFullHistory`, 4s per-session gesture cooldown, in-flight + tab-switch guards, viewport position held across the replay); Shell full pulls are not retained in the tab cache, so the next switch stays bounded. Chunked replay enqueues 32 KiB pieces across safe yields, appends an xterm parse marker, then releases the live-output gate; output arriving after that release stays ordered behind the snapshot, while the marker callback supplies accurate parse timing without extending the pre-existing queued-event discard window. Live output is separately one-chunk-in-flight: xterm's callback releases each 32/64 KiB write before the next is submitted, keeping the remainder in the app queue where the 128 KiB cap can observe it instead of hiding an unbounded backlog in xterm's private WriteBuffer. While WebSocket owns terminal I/O, parallel SSE terminal/output-recovery events are discarded before JSON parsing; fallback recovery is single-flight per active session so backpressure cannot start overlapping reset+replay cycles. The route exposes capture/prepare totals in `Server-Timing`, while `[TERMINAL-PERF]` separates TTFB, body/JSON, reset+parse and total time for both selection and on-demand full pulls; parse completion is not a browser compositor/GPU paint measurement. The re-pull exists because xterm's buffer is only a WINDOW onto tmux's history and two things shrink it: tmux coalesces bursty output into pane REPAINTS that overwrite rows instead of emitting linefeeds (measured: a 60-line burst added 1 row of browser scrollback and destroyed 34), and a tab switch replays only the visible frame. tmux's own history is intact throughout — the browser just has to ask for it again. On-demand rather than automatic because at a 100k history limit the capture can be megabytes. ⚠️ **The re-pull must never DOWNGRADE the buffer** (#205 round 2): the same reasoning that makes it a win for a shell pane makes it destructive for a repaint-mode CLI pane, where tmux keeps no history of its own (`history_size≈0` measured for a Claude pane) and the capture is roughly ONE frame while xterm may hold hundreds of rows of replayed frames — `_resetTerminalForReplay()` + rewrite then deletes history mid-scroll ("goes back a bit, repeats blocks, gets worse the further up I go"; measured A/B on a live pane: 341 rows → 42 with the guard off). `_replayWouldShrinkBuffer()` (terminal-ui.js) estimates the capture's rendered rows — escape sequences stripped, `capture-pane -J` re-wrapping accounted for — and the pull is skipped when that is more than one screen short of `buffer.active.length`. The one-screen tolerance matters: both sides are estimates (the buffer length counts trailing blank rows), so only a clear downgrade is refused. A refused session joins `_fullHistoryRepullUseless`, raising its cooldown from 4s to 60s so a hollow pane stops re-fetching megabytes on every scroll-up. Tests: `test/tmux-capture-full-history.test.ts`, `test/tmux-scrollback-eol.test.ts`, `test/terminal-scroll-routing.test.ts`, `test/terminal-flush-budget.test.ts`.
 
 ### Terminal scrollback: strip flavors and wheel/touch forwarding
 

docs/wiki/The-Dashboard.md

@@ -136,7 +136,7 @@ Worth knowing:
 - **Scrollback.** Agent/TUI sessions pull their entire tmux scrollback on first open.
   Shell sessions open from a bounded recent tail so a large transcript cannot stall tab
   switching; press **Load full history** to pull the rest explicitly. Ordinary Shell scrolling
-  stays within the bounded browser buffer so dragging upward remains responsive.
+  and automatic output recovery stay within the bounded browser buffer.
 - **Wheel and touch scrolling** are forwarded into Claude's own transcript on recent Claude
   versions, so the wheel scrolls the conversation rather than the terminal. `Shift+Wheel` is
   always local scrollback. Other CLIs scroll locally.