fix(daemon): restore previously recoverable scrollback from durable history

src/main/daemon/daemon-checkpoint-file.ts

@@ -20,5 +20,7 @@ export type TerminalCheckpointFile = {
   /** Ties this checkpoint to the output.log whose header carries the same
    *  generation. Absent on checkpoints written before incremental logs. */
   generation?: number
+  /** Last daemon pending-output batch included in this checkpoint. */
+  pendingOutputSeq?: number
   checkpointedAt: string
 }

src/main/daemon/daemon-durable-history-snapshot.ts

@@ -0,0 +1,159 @@
+import { ColdRestoreReplayWriter } from './cold-restore-replay-writer'
+import { DAEMON_RESTORE_SCROLLBACK_ROWS } from './daemon-restore-scrollback-depth'
+import { HeadlessEmulator } from './headless-emulator'
+import { isValidTerminalHistorySize } from './terminal-history-dimensions'
+import type { ColdRestoreInfo } from './terminal-history-cold-restore-info'
+import type { PendingOutputRecord, TerminalSnapshot } from './types'
+
+type RestoreBase = {
+  scrollbackAnsi: string
+  rehydrateSequences: string
+  snapshotAnsi: string
+  pendingEscapeTailAnsi?: string
+  oscLinks?: TerminalSnapshot['oscLinks']
+  lastTitle?: string
+  cwd: string | null
+  cols: number
+  rows: number
+}
+
+export function terminalSnapshotFromColdRestore(
+  info: ColdRestoreInfo,
+  opts?: { outputSequence?: number; frameRestoreAnsi?: string }
+): TerminalSnapshot {
+  return {
+    snapshotAnsi: info.snapshotAnsi,
+    scrollbackAnsi: info.modes.alternateScreen ? info.scrollbackAnsi : '',
+    oscLinks: info.oscLinks,
+    rehydrateSequences: info.rehydrateSequences,
+    ...(info.pendingEscapeTailAnsi ? { pendingEscapeTailAnsi: info.pendingEscapeTailAnsi } : {}),
+    ...(opts?.frameRestoreAnsi ? { frameRestoreAnsi: opts.frameRestoreAnsi } : {}),
+    cwd: info.cwd,
+    modes: info.modes,
+    cols: info.cols,
+    rows: info.rows,
+    scrollbackLines:
+      info.scrollbackLines ?? Math.max(0, countAnsiRows(info.scrollbackAnsi) - info.rows),
+    ...(info.lastTitle ? { lastTitle: info.lastTitle } : {}),
+    ...(opts?.outputSequence !== undefined ? { outputSequence: opts.outputSequence } : {})
+  }
+}
+
+export async function buildDurableCheckpointSnapshot(opts: {
+  liveSnapshot: TerminalSnapshot
+  restoreInfo: ColdRestoreInfo | null
+  pendingRecords?: readonly PendingOutputRecord[]
+  scrollbackRows?: number
+}): Promise<TerminalSnapshot> {
+  const pendingRecords = opts.pendingRecords ?? []
+  if (!opts.restoreInfo && pendingRecords.length === 0) {
+    return opts.liveSnapshot
+  }
+  if (
+    opts.restoreInfo &&
+    pendingRecords.length === 0 &&
+    (opts.scrollbackRows === undefined || opts.scrollbackRows >= DAEMON_RESTORE_SCROLLBACK_ROWS)
+  ) {
+    return terminalSnapshotFromColdRestore(opts.restoreInfo, {
+      outputSequence: opts.liveSnapshot.outputSequence,
+      frameRestoreAnsi: opts.liveSnapshot.frameRestoreAnsi
+    })
+  }
+
+  const emulator = new HeadlessEmulator({
+    cols: opts.restoreInfo?.cols ?? opts.liveSnapshot.cols,
+    rows: opts.restoreInfo?.rows ?? opts.liveSnapshot.rows,
+    scrollback: Math.min(
+      opts.scrollbackRows ?? DAEMON_RESTORE_SCROLLBACK_ROWS,
+      DAEMON_RESTORE_SCROLLBACK_ROWS
+    )
+  })
+  const replay = new ColdRestoreReplayWriter(emulator)
+  try {
+    // Why not seed the live window when there is no disk history: pending records
+    // are the raw stream. Replaying them on top of the already-truncated live
+    // snapshot would duplicate the newest rows and evict the older recoverable ones.
+    if (opts.restoreInfo) {
+      const base = restoreBaseFrom(opts.restoreInfo)
+      for (const segment of [
+        base.scrollbackAnsi,
+        base.rehydrateSequences,
+        base.snapshotAnsi,
+        base.pendingEscapeTailAnsi ?? ''
+      ]) {
+        if (!(await replay.write(segment))) {
+          return opts.liveSnapshot
+        }
+      }
+      emulator.setRestoredOscLinks(base.oscLinks)
+      if (base.lastTitle) {
+        emulator.setLastTitle(base.lastTitle)
+      }
+      emulator.setCwd(base.cwd)
+    }
+    if (!(await replayPendingRecords(replay, pendingRecords))) {
+      return opts.liveSnapshot
+    }
+    const snapshot = emulator.getSnapshot()
+    return {
+      ...snapshot,
+      ...(opts.liveSnapshot.outputSequence !== undefined
+        ? { outputSequence: opts.liveSnapshot.outputSequence }
+        : {}),
+      ...(opts.liveSnapshot.frameRestoreAnsi && !snapshot.frameRestoreAnsi
+        ? { frameRestoreAnsi: opts.liveSnapshot.frameRestoreAnsi }
+        : {})
+    }
+  } catch (error) {
+    console.warn('[history] durable snapshot rebuild failed:', error)
+    return opts.liveSnapshot
+  } finally {
+    emulator.dispose()
+  }
+}
+
+function restoreBaseFrom(restoreInfo: ColdRestoreInfo): RestoreBase {
+  return {
+    scrollbackAnsi: restoreInfo.modes.alternateScreen ? restoreInfo.scrollbackAnsi : '',
+    rehydrateSequences: restoreInfo.rehydrateSequences,
+    snapshotAnsi: restoreInfo.snapshotAnsi,
+    ...(restoreInfo.pendingEscapeTailAnsi
+      ? { pendingEscapeTailAnsi: restoreInfo.pendingEscapeTailAnsi }
+      : {}),
+    oscLinks: restoreInfo.oscLinks,
+    lastTitle: restoreInfo.lastTitle,
+    cwd: restoreInfo.cwd,
+    cols: restoreInfo.cols,
+    rows: restoreInfo.rows
+  }
+}
+
+async function replayPendingRecords(
+  replay: ColdRestoreReplayWriter,
+  records: readonly PendingOutputRecord[]
+): Promise<boolean> {
+  for (const record of records) {
+    if (record.kind === 'output') {
+      if (!(await replay.write(record.data))) {
+        return false
+      }
+      continue
+    }
+    if (record.kind === 'resize') {
+      if (!isValidTerminalHistorySize(record.cols, record.rows)) {
+        return false
+      }
+      await replay.resize(record.cols, record.rows)
+      continue
+    }
+    await replay.clearScrollback()
+  }
+  return true
+}
+
+function countAnsiRows(ansi: string): number {
+  if (ansi.length === 0) {
+    return 0
+  }
+  return ansi.split(/\r\n|\n|\r/).filter((row) => row.length > 0).length
+}

src/main/daemon/daemon-pty-adapter.test.ts

@@ -2717,7 +2717,8 @@ describe('DaemonPtyAdapter (IPtyProvider)', () => {
 
         expect(checkpointSpy).toHaveBeenCalledWith(
           id,
-          expect.objectContaining({ snapshotAnsi: expect.stringContaining('latest before sleep') })
+          expect.objectContaining({ snapshotAnsi: expect.stringContaining('latest before sleep') }),
+          { pendingOutputSeq: expect.any(Number) }
         )
         expect(existsSync(join(historyDir, getHistorySessionDirName(id)))).toBe(true)
 
@@ -2850,7 +2851,8 @@ describe('DaemonPtyAdapter (IPtyProvider)', () => {
 
       expect(checkpointSpy).toHaveBeenCalledWith(
         id,
-        expect.objectContaining({ snapshotAnsi: expect.stringContaining('fresh output') })
+        expect.objectContaining({ snapshotAnsi: expect.stringContaining('fresh output') }),
+        { pendingOutputSeq: expect.any(Number) }
       )
       expect(existsSync(join(historyDir, getHistorySessionDirName(id)))).toBe(true)
     })
@@ -2866,14 +2868,18 @@ describe('DaemonPtyAdapter (IPtyProvider)', () => {
         env: { SHELL: '/bin/zsh' },
         sessionId: 'sleep-checkpoint-tail'
       })
-      const appendSpy = vi.spyOn(historyAdapter.getHistoryManager()!, 'appendIncrements')
+      const checkpointSpy = vi.spyOn(historyAdapter.getHistoryManager()!, 'checkpoint')
 
       lastSubprocess._simulateData('\x1b]777;orca-shell-ready')
       await historyAdapter.shutdown(id, { immediate: true, keepHistory: true })
 
-      expect(appendSpy).toHaveBeenCalledWith(id, expect.any(Number), [
-        { kind: 'output', data: '\x1b]777;orca-shell-ready' }
-      ])
+      expect(checkpointSpy).toHaveBeenCalledWith(
+        id,
+        expect.objectContaining({
+          pendingEscapeTailAnsi: expect.stringContaining('\x1b]777;orca-shell-ready')
+        }),
+        { pendingOutputSeq: expect.any(Number) }
+      )
     })
 
     it('returns cold restore data when disk history has unclean shutdown', async () => {
@@ -3261,7 +3267,8 @@ describe('DaemonPtyAdapter (IPtyProvider)', () => {
         expect(appendSpy).not.toHaveBeenCalled()
         expect(checkpointSpy).toHaveBeenCalledWith(
           sessionId,
-          expect.objectContaining({ snapshotAnsi: expect.stringContaining('revived session') })
+          expect.objectContaining({ snapshotAnsi: expect.stringContaining('revived session') }),
+          { pendingOutputSeq: expect.any(Number) }
         )
 
         // Subsequent ticks return to incremental appends.
@@ -3320,8 +3327,8 @@ describe('DaemonPtyAdapter (IPtyProvider)', () => {
       }
       const result = await historyAdapter.spawn({ cols: 80, rows: 24, sessionId })
       expect(result.isReattach).toBe(true)
-      expect(internals.sessionsNeedingFullCheckpoint.has(sessionId)).toBe(true)
-      expect(internals.lastFullCheckpointAt.has(sessionId)).toBe(false)
+      expect(internals.sessionsNeedingFullCheckpoint.has(sessionId)).toBe(false)
+      expect(internals.lastFullCheckpointAt.has(sessionId)).toBe(true)
     })
 
     it('skips the cold-restore replay when the daemon session is still alive', async () => {
@@ -3332,20 +3339,17 @@ describe('DaemonPtyAdapter (IPtyProvider)', () => {
       await first.disconnectOnly()
 
       historyAdapter = new DaemonPtyAdapter({ socketPath, tokenPath, historyPath: historyDir })
-      const reader = (historyAdapter as unknown as { historyReader: HistoryReader }).historyReader
-      const detectSpy = vi.spyOn(reader, 'detectColdRestore')
       const result = await historyAdapter.spawn({ cols: 80, rows: 24, sessionId })
 
       expect(result.isReattach).toBe(true)
       expect(result.coldRestore).toBeUndefined()
-      expect(detectSpy).not.toHaveBeenCalled()
-      // The unmanaged-reattach re-anchor must survive the skipped detect.
+      // The unmanaged-reattach re-anchor must survive a live remount overlay.
       const internals = historyAdapter as unknown as {
         sessionsNeedingFullCheckpoint: Set<string>
         lastFullCheckpointAt: Map<string, number>
       }
-      expect(internals.sessionsNeedingFullCheckpoint.has(sessionId)).toBe(true)
-      expect(internals.lastFullCheckpointAt.has(sessionId)).toBe(false)
+      expect(internals.sessionsNeedingFullCheckpoint.has(sessionId)).toBe(false)
+      expect(internals.lastFullCheckpointAt.has(sessionId)).toBe(true)
     })
 
     it('does not probe session aliveness when there is no restorable history', async () => {