fix(terminal): gate the row-preserving skips on a capture, not the query flag

Review of the previous commit found the guard inverted: the three skips keyed
on `?full=1`, which is only what the client asked for. When the capture comes
back null — ENOBUFS, a timeout, a vanished pane, or a session with no mux at
all — the reply falls back to the byte history, which IS a stream of
successive frames and still needs stripping. Gating on the request returned it
whole: measured at 82KB against 4KB for the same buffer without `full=1`. A
direct-PTY session takes that path on every first selection, not only during
an outage. The skips now key on `isFullCapture`, meaning a capture arrived.

Three further defects the same review surfaced, all on this path:

Keeping the trailing rows is only sound when a cursor move follows to count
back up from them. On the two branches where the cursor query fails there is
no move, so the caret was left at the bottom of the pane — worse than before.
The cursor is now read first and settles both decisions together.

The move is relative rather than absolute. `CUP` numbers rows from the top of
the browser's screen, so it is only right while the browser's row count equals
the pane's, and `resizeWindow` does not wait for tmux, so a capture can be
taken before a requested resize applies. Measured against real tmux with a
browser four rows shorter than the pane: the absolute move lands on a blank
row, the relative one lands on the caret's row.

An all-blank pane no longer reads as content. Retaining trailing rows and
appending a move made it non-empty, and the caller treats non-empty as "replay
this", so a blank screen would have replaced real history — the downgrade
`_replayWouldShrinkBuffer` refuses, arriving from the server side where that
guard cannot see it.

The documentation claimed one line per screen row. `-J` joins a hard-wrapped
row into its logical line, so that is false whenever any row wrapped: measured
at 10 lines for a 12-row pane. Both entries now say what actually holds, and
the stale "NOT repositioned" contract in the mux interface is updated too.

Tests: the byte-history fallback is stripped, an empty capture leaves history
intact, and the extracted helpers are unit-tested directly rather than through
source-text matching. The slice window in the capture test is bounded at the
next method, having overrun into its neighbours.

CLAUDE.md

@@ -247,7 +247,7 @@ 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 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=1` capture is the rendered pane, one line per screen row, and it ENDS with an absolute cursor move back to the pane's own position** — without it the caret stays where the last character landed, which for an agent CLI is the status line, and every cursor-relative update the CLI sends afterwards is measured from the wrong row. That makes row alignment load-bearing on this path only: no transform that can DELETE A LINE may run over the capture, so it keeps its trailing blank rows and skips redraw-bloat stripping, the banner trim and the leading-whitespace strip. All three stay for the byte-stream and `?tail=` paths, where nothing depends on a row's absolute index. ⚠️ 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)
+**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=1` capture ENDS with a cursor move back to the pane's own caret position**, counted UP from the last replayed row — without it the caret stays where the last character landed, which for an agent CLI is the status line, and every cursor-relative update the CLI sends afterwards is measured from the wrong row. The move is relative, not `CUP`: absolute row addressing is only right while the browser's rows equal the pane's, and `resizeWindow` does not wait for tmux, so a capture can be taken before a requested resize applies. That makes row alignment load-bearing on this path: no transform that can DELETE A LINE may run over the capture, so it keeps its trailing blank rows and skips redraw-bloat stripping, the banner trim and the leading-whitespace strip. ⚠️ Those three skips key on whether a capture actually CAME BACK (`isFullCapture`), never on `?full=1` alone — the fallback to the byte history is a stream of successive frames that must still be stripped, and a session with no mux takes it on every load. A capture holding nothing visible returns '' so the byte history survives instead of a blank screen replacing it. ⚠️ 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`.
 

src/mux-interface.ts

@@ -137,7 +137,12 @@ export interface RespawnPaneOptions {
 
 /** Options for pane buffer capture (COD-47 full-history mode). */
 export interface PaneCaptureOptions {
-  /** Capture the entire tmux scrollback instead of just the visible frame. */
+  /**
+   * Capture the entire scrollback instead of just the visible frame, as linear
+   * text ending with a cursor move back to the pane's caret position. An
+   * implementation returns '' when the pane holds nothing visible, which the
+   * caller reads as "nothing to replay" and keeps its existing history.
+   */
   fullHistory?: boolean;
   /** Bound the full-history capture to this many scrollback lines (`-S -<N>`). */
   historyLimitLines?: number;

src/tmux-manager.ts

@@ -528,6 +528,73 @@ export function normalizeScrollbackEol(buffer: string): string {
   return buffer.replace(/\r?\n/g, '\r\n');
 }
 
+/** Pane geometry and caret position, as `display-message` reports them. */
+interface PaneCursorGeometry {
+  cols: number;
+  rows: number;
+  cursorX: number;
+  cursorY: number;
+}
+
+/**
+ * Read the pane's cursor and size, or null when tmux cannot say.
+ *
+ * Every field is validated together: a caller that gets a value back can place
+ * a caret with it, and one that gets null must not try.
+ */
+export function queryPaneCursor(run: () => string): PaneCursorGeometry | null {
+  let raw: string;
+  try {
+    raw = run().trim();
+  } catch (cursorErr) {
+    console.error('[TmuxManager] Failed to query pane cursor after capture:', cursorErr);
+    return null;
+  }
+  const [cursorX, cursorY, cols, rows] = raw.split(/\s+/).map((value) => parseInt(value, 10));
+  if (
+    !Number.isFinite(cursorX) ||
+    !Number.isFinite(cursorY) ||
+    !Number.isFinite(cols) ||
+    !Number.isFinite(rows) ||
+    cursorX < 0 ||
+    cursorY < 0 ||
+    cols <= 0 ||
+    rows <= 0
+  ) {
+    return null;
+  }
+  return { cols, rows, cursorX, cursorY };
+}
+
+/** SGR attributes, which is all `capture-pane -e` emits. */
+// eslint-disable-next-line no-control-regex
+const CAPTURE_STYLE_SEQUENCE = /\x1b\[[0-9;:]*m/g;
+
+/** Whether a capture holds anything a reader would see, styles discounted. */
+export function hasVisibleContent(capture: string): boolean {
+  return /\S/.test(capture.replace(CAPTURE_STYLE_SEQUENCE, ''));
+}
+
+/**
+ * Put the caret back where the pane has it, counting UP from the bottom of what
+ * was just replayed.
+ *
+ * Relative rather than absolute (`CUP`) on purpose. `\x1b[<row>;<col>H` numbers
+ * rows from the top of the browser's screen, so it only lands correctly while
+ * the browser's row count equals the pane's — and it need not, because
+ * `resizeWindow` fires its tmux resize without waiting, so a capture can be
+ * taken before a requested resize has been applied. Counting up from the last
+ * replayed row is anchored to the content instead, which is the thing both ends
+ * genuinely share.
+ */
+export function formatCursorRestore(geometry: PaneCursorGeometry): string {
+  const up = Math.max(0, geometry.rows - 1 - geometry.cursorY);
+  const right = Math.max(0, geometry.cursorX);
+  // `\r` first so the column is known: the replay leaves the caret wherever the
+  // last row's text ended.
+  return `${up > 0 ? `\x1b[${up}A` : ''}\r${right > 0 ? `\x1b[${right}C` : ''}`;
+}
+
 export function formatPaneSnapshot(
   lines: string[],
   geometry: { cols: number; rows: number; cursorX: number; cursorY: number }
@@ -3199,11 +3266,14 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
    *   the browser xterm reproduces the live frame. Used for fast tab switches.
    * - Full history (`opts.fullHistory`): `capture-pane -p -e -J -S -<N>` grabs
    *   the tmux scrollback (COD-47, bounded to the configured history limit),
-   *   returned as linear scrollback text with SGR codes preserved (NOT
-   *   repositioned — a multi-screen history can't be painted into a single
-   *   visible frame, so the snapshot repaint is skipped). `-J` re-joins lines
-   *   hard-wrapped at the pane width so they reflow in the browser xterm.
-   *   Used for full page reloads so the user gets back their scroll history.
+   *   returned as linear scrollback text with SGR codes preserved. Rows are not
+   *   repainted at absolute positions — a multi-screen history can't be painted
+   *   into a single visible frame — but the capture DOES end with a cursor move
+   *   putting the caret back where the pane has it, counted up from the last
+   *   replayed row. `-J` re-joins lines hard-wrapped at the pane width so they
+   *   reflow in the browser xterm. Used for full page reloads so the user gets
+   *   back their scroll history. Returns '' for a pane holding nothing visible,
+   *   so the caller keeps whatever history it already had.
    *   Caveat: lines tmux has already evicted past its history-limit are gone.
    */
   /**
@@ -3263,57 +3333,40 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
           (opts?.maxCaptureBytes ?? DEFAULT_TERMINAL_BUFFER_MAX_BYTES) + FULL_HISTORY_CAPTURE_SLACK_BYTES;
       }
       const rawCapture = execSync(`${this.tmux()} ${captureFlags} -t ${shellescape(target)}`, execOpts);
-      // The visible path drops every trailing blank row, which is harmless there
-      // because it repaints each row at an absolute position afterwards. The
-      // full-history path replays linearly, so its trailing blank rows are the
-      // real bottom of the screen and dropping them would move every row up and
-      // leave the restored cursor pointing at the wrong line. Take off the last
-      // line terminator only.
-      const buffer = fullHistory ? rawCapture.replace(/\n$/, '') : rawCapture.replace(/\n+$/g, '');
-      // Full-history spans many screens — return it as raw linear scrollback
-      // rather than repainting rows at single-screen absolute positions. tmux
-      // joins scrollback rows with a bare `\n`; normalize to `\r\n` so a fresh
-      // xterm (convertEol:false) starts each replayed line at column 0 instead
-      // of staircasing diagonally (COD-138).
-      try {
-        const cursor = execSync(
+      // Query the cursor BEFORE deciding anything else. On the full-history path
+      // it settles both how the capture is trimmed and whether a cursor move is
+      // appended, and those two have to agree: trailing blank rows are only safe
+      // to keep when a move follows to put the caret back above them.
+      const geometry = queryPaneCursor(() =>
+        execSync(
           `${this.tmux()} display-message -p -t ${shellescape(target)} '#{cursor_x} #{cursor_y} #{pane_width} #{pane_height}'`,
-          {
-            encoding: 'utf-8',
-            timeout: EXEC_TIMEOUT_MS,
-          }
-        ).trim();
-        const [cursorX, cursorY, cols, rows] = cursor.split(/\s+/).map((value) => parseInt(value, 10));
-        // Put the cursor back where the pane has it. A linear replay leaves it
-        // wherever the last character landed, which is the bottom-most row
-        // carrying text — the status line, for an agent CLI. The caret then sits
-        // there until the CLI's next redraw moves it, and every cursor-relative
-        // update the CLI sends until then is measured from the wrong row.
-        // Absolute addressing is safe because the replay ends with the pane's
-        // own last row at the bottom of the viewport.
-        if (fullHistory) {
-          const normalized = normalizeScrollbackEol(buffer);
-          if (Number.isFinite(cursorX) && Number.isFinite(cursorY) && cursorX >= 0 && cursorY >= 0) {
-            return `${normalized}\x1b[${cursorY + 1};${cursorX + 1}H`;
-          }
-          return normalized;
-        }
-        if (
-          Number.isFinite(cursorX) &&
-          Number.isFinite(cursorY) &&
-          Number.isFinite(cols) &&
-          Number.isFinite(rows) &&
-          cursorX >= 0 &&
-          cursorY >= 0 &&
-          cols > 0 &&
-          rows > 0
-        ) {
-          return formatPaneSnapshot(buffer.split('\n'), { cols, rows, cursorX, cursorY });
-        }
-      } catch (cursorErr) {
-        console.error('[TmuxManager] Failed to query pane cursor after capture:', cursorErr);
-        if (fullHistory) return normalizeScrollbackEol(buffer);
+          { encoding: 'utf-8', timeout: EXEC_TIMEOUT_MS }
+        )
+      );
+
+      if (fullHistory) {
+        // Without geometry there is no cursor move, so fall back to the old trim.
+        // Keeping the blank rows here would park the caret at the bottom of the
+        // pane with nothing to correct it — worse than not trying at all.
+        if (!geometry) return normalizeScrollbackEol(rawCapture.replace(/\n+$/g, ''));
+        // Take the line terminator off and nothing else. The trailing blank rows
+        // that remain are the real bottom of the screen, and the cursor move
+        // below counts up from it. tmux joins rows with a bare `\n`; normalize to
+        // `\r\n` so a fresh xterm (convertEol:false) starts each replayed line at
+        // column 0 instead of staircasing diagonally (COD-138).
+        const trimmed = rawCapture.replace(/\n$/, '');
+        // An all-blank pane has to keep reading as "nothing to replay". The caller
+        // treats an empty string as "capture unavailable" and keeps the byte
+        // history; blank rows plus a cursor move are not empty, so without this a
+        // blank pane REPLACES that history with a blank screen — the downgrade
+        // `_replayWouldShrinkBuffer` exists to refuse, arriving from the server
+        // side where that guard cannot see it.
+        if (!hasVisibleContent(trimmed)) return '';
+        return `${normalizeScrollbackEol(trimmed)}${formatCursorRestore(geometry)}`;
       }
+
+      const buffer = rawCapture.replace(/\n+$/g, '');
+      if (geometry) return formatPaneSnapshot(buffer.split('\n'), geometry);
       // Cursor query failed or geometry was invalid, so we skip the absolute-
       // positioned snapshot repaint and fall back to the raw capture. Normalize
       // its bare `\n` line endings to `\r\n` so the replay doesn't staircase

src/web/routes/session-routes.ts

@@ -2603,6 +2603,12 @@ export function registerSessionRoutes(
         ? 'mux-full-history'
         : 'mux-visible'
       : 'history';
+    // What the three row-preserving skips below must key on. `isFullReload` is
+    // only what the CLIENT ASKED FOR: when the capture comes back null — ENOBUFS,
+    // a timeout, a vanished pane, or a session with no mux at all — rawBuffer
+    // falls back to the byte history, which is a stream of successive frames with
+    // no row alignment to protect and every reason to be stripped.
+    const isFullCapture = isFullReload && hasLiveMuxBuffer;
     let rawBuffer: string;
     if (liveMuxBuffer !== null && liveMuxBuffer.length > 0) {
       // Full-history capture is the RENDERED form of everything already in the
@@ -2656,7 +2662,7 @@ export function registerSessionRoutes(
     // border rather than its input line. Redraw-bloat stripping exists for a
     // byte stream of successive frames; a capture holds no successive frames.
     let strippedBuffer =
-      isFullReload || getCli(session.mode)?.capabilities.stripInkBloat === false
+      isFullCapture || getCli(session.mode)?.capabilities.stripInkBloat === false
         ? rawBuffer
         : stripInkRedrawBloat(rawBuffer);
 
@@ -2699,7 +2705,7 @@ export function registerSessionRoutes(
       // Skipped for a full reload: the banner sits at whatever row the pane has
       // it, and cutting to it would drop the blank rows above and move every
       // row up by that many.
-      const claudeMatch = isFullReload ? null : cleanBuffer.match(CLAUDE_BANNER_PATTERN);
+      const claudeMatch = isFullCapture ? null : cleanBuffer.match(CLAUDE_BANNER_PATTERN);
       if (claudeMatch && claudeMatch.index !== undefined && claudeMatch.index > 0) {
         let lineStart = claudeMatch.index;
         while (lineStart > 0 && cleanBuffer[lineStart - 1] !== '\n') {
@@ -2714,7 +2720,7 @@ export function registerSessionRoutes(
     // blank line is the pane's own first row and dropping it shifts every row
     // up by one.
     cleanBuffer = cleanBuffer.replace(CTRL_L_PATTERN, '');
-    if (!isFullReload) cleanBuffer = cleanBuffer.replace(LEADING_WHITESPACE_PATTERN, '');
+    if (!isFullCapture) cleanBuffer = cleanBuffer.replace(LEADING_WHITESPACE_PATTERN, '');
 
     const finishedAt = performance.now();
     reply.header(

test/routes/session-routes.test.ts

@@ -878,6 +878,58 @@ describe('session-routes', () => {
       expect(body.data.terminalBuffer.split('\r\n')).toHaveLength(rendered.split('\r\n').length);
     });
 
+    it('full reload (?full=1) still strips the byte history when no capture came back', async () => {
+      // The row-preserving skips exist for a rendered pane. When the capture is
+      // unavailable the reply IS the byte stream — successive Ink frames, no row
+      // alignment to protect — so keying the skips on the query parameter rather
+      // than on the capture returned it unstripped, which is the whole reason
+      // stripInkRedrawBloat exists. A session with no mux takes this path on
+      // every first selection, not just during an outage.
+      harness.ctx._session.mode = 'claude';
+      // A VPA cluster the stripper will collapse: >= 10 sequences, spanning the
+      // 32KB minimum, with real content after it.
+      const frame = '\x1b[12d' + 'spinner frame '.repeat(240);
+      harness.ctx._session.terminalBuffer = frame.repeat(20) + 'REAL CONTENT AFTER THE BLOAT';
+      (harness.ctx.mux as { captureActivePaneBuffer?: unknown }).captureActivePaneBuffer = vi.fn(() => null);
+
+      const res = await harness.app.inject({
+        method: 'GET',
+        url: `/api/sessions/${harness.ctx._sessionId}/terminal?full=1`,
+      });
+
+      expect(res.statusCode).toBe(200);
+      const body = JSON.parse(res.body);
+      expect(body.data.source).toBe('history');
+      expect(body.data.terminalBuffer).toContain('REAL CONTENT AFTER THE BLOAT');
+      // Stripped, not passed through whole.
+      expect(body.data.terminalBuffer.length).toBeLessThan(harness.ctx._session.terminalBuffer.length);
+    });
+
+    it('full reload (?full=1) keeps the byte history when the capture is empty', async () => {
+      // Pins the contract the capture side relies on: an empty capture means
+      // "nothing to replay" and the byte history survives. capturePaneBuffer
+      // returns '' for an all-blank pane precisely to reach this branch, since
+      // retaining trailing blank rows and appending a cursor move would
+      // otherwise make a blank screen non-empty and replace the history with it.
+      // (The blank-pane decision itself is unit-tested on hasVisibleContent —
+      // capturePaneBuffer short-circuits under IS_TEST_MODE and cannot run here.)
+      harness.ctx._session.mode = 'claude';
+      harness.ctx._session.terminalBuffer = 'a real conversation worth keeping';
+      (harness.ctx.mux as { captureActivePaneBuffer?: unknown }).captureActivePaneBuffer = vi.fn(
+        (_name: string, opts?: { fullHistory?: boolean }) => (opts?.fullHistory ? '' : 'visible frame')
+      );
+
+      const res = await harness.app.inject({
+        method: 'GET',
+        url: `/api/sessions/${harness.ctx._sessionId}/terminal?full=1`,
+      });
+
+      expect(res.statusCode).toBe(200);
+      const body = JSON.parse(res.body);
+      expect(body.data.source).toBe('history');
+      expect(body.data.terminalBuffer).toContain('a real conversation worth keeping');
+    });
+
     it('full reload (?full=1) falls back to the byte history when the capture is unavailable', async () => {
       harness.ctx._session.mode = 'claude';
       harness.ctx._session.terminalBuffer = 'byte history survives';

test/tmux-capture-full-history.test.ts

@@ -11,11 +11,15 @@
 import { readFileSync } from 'node:fs';
 import { resolve } from 'node:path';
 import { describe, expect, it } from 'vitest';
+import { formatCursorRestore, hasVisibleContent } from '../src/tmux-manager.js';
 
 describe('tmux full-history pane capture (COD-47)', () => {
   const source = readFileSync(resolve(import.meta.dirname, '../src/tmux-manager.ts'), 'utf8');
   const methodStart = source.indexOf('capturePaneBuffer(muxName: string');
-  const methodBody = source.slice(methodStart, methodStart + 6500);
+  // Bounded at the next method so `methodBody` really is one method: the
+  // ordering assertions below would otherwise be satisfiable by a neighbour.
+  const methodEnd = source.indexOf('captureActivePaneBuffer(muxName: string', methodStart);
+  const methodBody = source.slice(methodStart, methodEnd);
 
   it('capturePaneBuffer accepts pane-capture options with a fullHistory flag', () => {
     expect(methodStart).toBeGreaterThan(-1);
@@ -42,32 +46,37 @@ describe('tmux full-history pane capture (COD-47)', () => {
   });
 
   it('returns full-history capture as raw scrollback (skips the single-screen repaint)', () => {
-    // When fullHistory, return the normalized buffer BEFORE the
-    // formatPaneSnapshot repaint (which is single-screen and would clip a
-    // multi-screen history).
-    const normalize = methodBody.indexOf('normalizeScrollbackEol(buffer)');
+    // The fullHistory branch returns before the formatPaneSnapshot repaint,
+    // which is single-screen and would clip a multi-screen history.
+    const branch = methodBody.indexOf('if (fullHistory) {\n        // Without geometry');
     const snapshot = methodBody.indexOf('formatPaneSnapshot(');
-    expect(normalize).toBeGreaterThan(-1);
+    expect(branch).toBeGreaterThan(-1);
     expect(snapshot).toBeGreaterThan(-1);
-    expect(normalize).toBeLessThan(snapshot);
+    expect(branch).toBeLessThan(snapshot);
+    // …and what it returns is normalized linear scrollback, not a repaint.
+    expect(methodBody.slice(branch, snapshot)).toContain('normalizeScrollbackEol(');
   });
 
   it('appends the pane cursor to the full-history capture', () => {
     // A linear replay leaves the caret wherever the last character landed — the
     // status line, for an agent CLI — and every cursor-relative update the CLI
     // sends afterwards is then measured from the wrong row.
-    const restore = methodBody.indexOf('return `${normalized}');
+    const restore = methodBody.indexOf('formatCursorRestore(geometry)');
     const snapshot = methodBody.indexOf('formatPaneSnapshot(');
     expect(restore).toBeGreaterThan(-1);
     expect(restore).toBeLessThan(snapshot);
-    expect(methodBody).toContain('cursorY + 1};${cursorX + 1}H');
   });
 
-  it('keeps the trailing rows of a full-history capture', () => {
-    // The visible path drops trailing blank rows because it repaints each row
-    // absolutely afterwards. Dropping them on the linear path would move the
-    // frame up and leave the restored cursor pointing at the wrong line.
-    expect(methodBody).toContain("fullHistory ? rawCapture.replace(/\\n$/, '')");
+  it('keeps the trailing rows only when a cursor move will follow', () => {
+    // Trailing blank rows are the bottom of the screen and the cursor move counts
+    // up from them, so the two decisions travel together: no geometry, no move,
+    // and the old trim applies instead.
+    expect(methodBody).toContain("rawCapture.replace(/\\n$/, '')");
+    expect(methodBody).toContain("if (!geometry) return normalizeScrollbackEol(rawCapture.replace(/\\n+$/g, ''))");
+  });
+
+  it('defers to the byte history when the pane holds nothing visible', () => {
+    expect(methodBody).toContain("if (!hasVisibleContent(trimmed)) return ''");
   });
 
   it('captureActivePaneBuffer forwards the capture options', () => {
@@ -78,3 +87,37 @@ describe('tmux full-history pane capture (COD-47)', () => {
     expect(body).toContain('this.capturePaneBuffer(muxName, target, opts)');
   });
 });
+
+describe('full-history cursor restore', () => {
+  it('counts up from the last replayed row rather than down from the top', () => {
+    // Relative, not `CUP`: absolute row addressing is only correct while the
+    // browser's row count equals the pane's, and resizeWindow does not wait for
+    // tmux, so a capture can be taken before a requested resize has applied.
+    expect(formatCursorRestore({ cols: 80, rows: 24, cursorX: 2, cursorY: 20 })).toBe('\x1b[3A\r\x1b[2C');
+  });
+
+  it('emits no row move when the caret is already on the last row', () => {
+    expect(formatCursorRestore({ cols: 80, rows: 24, cursorX: 5, cursorY: 23 })).toBe('\r\x1b[5C');
+  });
+
+  it('emits no column move for column zero', () => {
+    expect(formatCursorRestore({ cols: 80, rows: 10, cursorX: 0, cursorY: 0 })).toBe('\x1b[9A\r');
+  });
+});
+
+describe('hasVisibleContent', () => {
+  it('is false for a pane of blank rows', () => {
+    expect(hasVisibleContent('\n'.repeat(23))).toBe(false);
+  });
+
+  it('is false for blank rows carrying only SGR attributes', () => {
+    // `capture-pane -e` styles every row, so an all-blank pane is not an empty
+    // string. Treating it as content would replace the byte history with a
+    // blank screen.
+    expect(hasVisibleContent('\x1b[m   \x1b[0m\n\x1b[m   \x1b[0m')).toBe(false);
+  });
+
+  it('is true as soon as one row carries a character', () => {
+    expect(hasVisibleContent('\x1b[m   \x1b[0m\n\x1b[m x \x1b[0m')).toBe(true);
+  });
+});