Summary

Closes #3697

Previously /rewind only truncated conversation history — files modified by the assistant remained on disk, requiring manual git checkout to undo. This PR adds a file-copy-based backup system (ported from claude-code's fileHistory) so users can optionally roll back file changes when rewinding.

Core Service (fileHistoryService.ts)

• Snapshot/backup lifecycle: trackEdit() saves a copy of each file before the first tool-initiated write; makeSnapshot() captures per-turn file state at each user turn boundary
• Restore: rewind(promptId) returns RewindResult { filesChanged, filesFailed } — partial failures are surfaced to the caller instead of being silently swallowed
• DiffStats: computes +insertions -deletions for the RewindSelector UI via diff.diffLines
• Version safety: both trackEdit and makeSnapshot use global max-version scan to prevent backup filename collisions after rewind or snapshot eviction
• Backup storage: ~/.qwen/file-history/{sessionId}/{sha256hash}@v{version}

Tool Integration

• edit.ts and write-file.ts call trackEdit() before each file write, wrapped in try/catch so file history never breaks core tool operations
• client.ts calls makeSnapshot() at each UserQuery turn boundary (wrapped in try/catch so file history never breaks the core chat flow)

Config

• New fileCheckpointingEnabled parameter (default: true for interactive, false for SDK mode and non-interactive -p mode)
• Gates on !params.sdkMode && params.interactive !== false
• Lazy-initialized FileHistoryService singleton on Config

RewindSelector UI (3-phase flow)

1. Pick list — select which user turn to rewind to (unchanged)
2. Restore options — NEW: choose what to restore with async diff stats loading
   • "Restore code and conversation" (shown only when file changes exist, with +N -N in M files detail)
   • "Restore conversation only"
   • "Restore code only" (shown only when file changes exist)
   • "Never mind"
3. Loading state — selector stays open during async restore, showing "Restoring..." with all input disabled
4. Legacy confirm — Y/N fallback when fileCheckpointingEnabled is false

Error handling

• rewind() returns RewindResult { filesChanged, filesFailed } — partial failures are reported with file names
• In "both" mode, conversation truncation is skipped when any file fails to restore (prevents inconsistent state)
• handleRewindConfirm uses try/finally to ensure the selector closes on all exit paths (including early returns for compressed turns)

Other changes

• HistoryItemUser.promptId for snapshot lookup during rewind
• handleRewindConfirm accepts RestoreOption, handles file restore before conversation truncation
• i18n strings added for all 9 locales (en, zh, ca, de, fr, ja, pt, ru, zh-TW)

Test plan

Unit tests

npx vitest run packages/core/src/services/fileHistoryService.test.ts

17 tests covering: trackEdit, makeSnapshot, version inheritance, rewind (success/deletion/partial failure/truncateHistory), snapshot eviction, getDiffStats, and disabled service.

Manual verification

1. Build and start

npm run build && npm run start
# or use dev mode:
npm run dev

2. File restoration (golden path)

1. Ask the AI to edit a file: e.g. Add a comment to the top of README.md
2. Ask the AI to edit a second file: e.g. Add a space to the description in package.json
3. Trigger rewind: press Esc Esc or type /rewind
4. Verify the 3-phase UI:
   • Phase 1: pick list to select which turn to rewind to
   • Phase 2: restore options with diff stats (+N -M in K files)
5. Select Restore code and conversation → verify files revert AND conversation truncates
6. Verify files are restored: git diff should show no changes

3. Test each restore option

4. Edge cases

• Esc to go back: Press Esc during restore options phase → should return to pick list
• Loading state: Selector shows "Restoring..." during async restore, input disabled
• New file created then rewind: Ask AI to create a file test-temp.txt, rewind → file should be deleted
• file checkpointing disabled: In SDK mode (fileCheckpointingEnabled: false), rewind should only show Y/N confirm with no file restore options
• /clear then edit: Run /clear, ask AI to edit a file, rewind → should work correctly (session reset)
• Diff loading state: After selecting a turn, should briefly show "Computing file changes..." before options appear
• Compressed turn: Select a compressed turn → should show error, does not crash
• Multiple edits to same file in one turn: Only first pre-edit state is captured, restore is correct

Automated verification results (tmux)

The following scenarios were verified programmatically via tmux send-keys against npm run dev with glm-5 model:

Scenario 1: Restore code and conversation

Scenario 2: Restore conversation only

Scenario 3: Restore code only

Scenario 4: Esc navigation

人工验证视频：

Restore code and conversation:
https://github.com/user-attachments/assets/9425fa1f-5b86-445f-aebd-b5d9dd1cae10

Restore conversation only:
https://github.com/user-attachments/assets/07454200-60e8-4f75-857c-cda34bfe2d7f

Restore code only:
https://github.com/user-attachments/assets/ee6d2a96-dc75-4a8f-aa3d-577d340cb151

🤖 Generated with Qwen Code