[buf0-bot]

Automated fix-PR from pr-bug-scan for parent #7310.

Fixer status: FIXED_WITH_CODE_PROOF
Summary: Cold-restore branch now clears screen+scrollback before writing daemon scrollback B, gated on the restored-viewport marker that signals saved buffer A was written — blocking A+B duplication.
Blocked proof link: pty-connection.ts:5274 — writeReplayData(connectResult.coldRestore.scrollback) is now preceded by a marker-gated writeReplayData('\x1b[2J\x1b[3J\x1b[H') at pty-connection.ts:5278-5280, which erases buffer A (written by restoreScrollbackBuffers at use-terminal-pane-lifecycle.ts:1412) before B is written, so the newline-scroll blanking at :5300 no longer preserves both copies.
Typecheck: skipped

Proof (from validator)

• C1 — proof_type: code_analysis
  • trigger: App restart with the daemon session lost (e.g. full machine reboot): the persisted layout has both buffersByLeafId (saved xterm scrollback) and ptyIdsByLeafId for the same leaf, and the daemon cold-restores a fresh shell for that reattach.
  • observable: The pane's scrollback contains the previous session's content twice (saved xterm buffer A followed by overlapping cold-restore scrollback B); the fresh prompt is clean in the viewport but scrolling up shows duplicated history.
  • path:
    • use-terminal-pane-lifecycle.ts:1409 — restoreScrollbackBuffers(manager, restoredBuffers, restoredPaneByLeafId, replayingPanesRef, restoredViewportBlankingPanesRef) runs during mount whenever buffersByLeafId is present, with no gating on ptyIdsByLeafId
    • layout-serialization.ts:248 — replayIntoTerminal(pane, replayingPanesRef, buf) writes the saved SerializeAddon buffer (content A) into the pane's xterm scrollback for the restored leaf
    • layout-serialization.ts:254 — restoredViewportBlankingPanesRef.current.add(pane.id) marks the same pane
    • pty-connection.ts:5159 — the deferred connect resolves into handleReattachResult for deps.restoredLeafId (== pane.leafId), the same pane restoreScrollbackBuffers wrote to
    • pty-connection.ts:5269 — connectResult.coldRestore branch is taken (daemon lost the session, spawned a fresh shell)
    • pty-connection.ts:5274 — writeReplayData(connectResult.coldRestore.scrollback) appends the daemon's disk-recorded scrollback of the same session (content B) below content A, with no preceding clear

Reproduction

pnpm exec vitest run --config config/vitest.config.ts src/renderer/src/components/terminal-pane/pty-connection.test.ts -t "clears restored scrollback before cold-restore"

• before fix: No clear emitted before cold TUI scrollback; rendered scrollback contains both saved buffer A and cold-restore B (duplicated history).
• after fix: Clear '\x1b[2J\x1b[3J\x1b[H' precedes cold-restore B; only B survives in scrollback, saved A is erased.

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Generated by pr-bug-scan (proof-machine architecture). Human approval required before merge.

ELI5

Automated fix: cold-restoring a terminal could duplicate scrollback (A+B). The screen is cleared before writing daemon scrollback when a restore marker is present.