feat(mcp): checkpoints to revert a whole agent turn in one step

[EtienneLescot]

Summary

Two MCP-only tools so a client can revert everything it did in one step:

• createCheckpoint: saves the live document in the main process, returns a checkpointId. Read-only.
• restoreCheckpoint: applies that document back through the same revision-guarded apply. One undo step, so the user can undo the restore. Marked destructive.

The server instructions tell the client to checkpoint before a series of edits. A restore is refused while MCP "Project edits" is off, and when the checkpoint belongs to another project. Checkpoints live in memory, the 20 most recent.

Related issue

Closes #1047

Type of change

• Feature

Release impact

• Minor

Desktop impact

• Not platform-specific

Testing

• npx vitest --run electron/mcp: 34 passed, 4 new (revert of two edits in one apply, edits off, unknown id, other project).
• npx tsc --noEmit, npx tsc -p tsconfig.test.json --noEmit, biome check electron/mcp: clean.
• Full suite left to CI.

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features
  • Added checkpoints for AI-assisted editing, allowing a series of project changes to be restored in one step.
  • Checkpoints are limited to the 20 most recent and are cleared when the app quits or the server is turned off. Restoring requires edits to be enabled and the checkpoint to match the open project.
  • Restoring a checkpoint can be undone with Ctrl/Cmd + Z.

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⚙️ Run configuration

• Configuration used: defaults
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📥 Commits

Reviewing files that changed from the base of the PR and between 652b854 and eeb9d07.

📒 Files selected for processing (1)

• technical-documentation/architecture/mcp-server.md

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📝 Walkthrough

Walkthrough

The MCP server adds tools to create and restore in-memory document checkpoints. Restoration checks edit settings, checkpoint IDs, and project identity before applying the saved document. Tests and documentation cover the checkpoint tools and their behavior.

Changes

MCP checkpoint tools

Layer / File(s)	Summary
Checkpoint creation and restoration electron/mcp/openscreen-mcp-server.ts	Adds createCheckpoint and restoreCheckpoint. The server retains up to 20 recent checkpoints in memory. Restore validates edit settings, checkpoint ID, and project identity, then applies the saved document at the current revision.
Tests and documentation electron/mcp/openscreen-mcp-server.test.ts, technical-documentation/architecture/mcp-server.md, website/docs/ai-editing.md	Tests cover tool annotations, restoring after edits, and refusal cases. Documentation describes checkpoint use, limits, and lifetime.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Feature · Severity of issue fixed: Medium

Sequence Diagram(s)

sequenceDiagram
  participant MCPClient
  participant MCPServer
  participant OpenScreenDocument
  MCPClient->>MCPServer: Call createCheckpoint
  MCPServer->>OpenScreenDocument: Read parsed document
  MCPServer-->>MCPClient: Return checkpoint ID
  MCPClient->>MCPServer: Call restoreCheckpoint with ID
  MCPServer->>OpenScreenDocument: Apply saved document at current revision
  MCPServer-->>MCPClient: Return restore result

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Suggested reviewers: davidjayana

Merge Risk: ⚪ Minimal · up to 652b8

This adds MCP checkpoint tools with validation and tests. Only a minor documentation list needs updating, and the change is ready to merge.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 11.11% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 9 functions across 2 files. (2 skipped: 2…	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the MCP checkpoint feature and its main purpose: reverting an agent turn in one step.
Description check	✅ Passed	The description summarizes both tools, their behavior and limits, the related issue, change type, release and desktop impact, and testing. The omitted Screenshots / video section is not needed for thi…
Linked Issues check	✅ Passed	Issue [#1047] asks for a way to restore all edits from an agent turn together. The PR implements the proposed explicit createCheckpoint and restoreCheckpoint tools, tells clients to checkpoint bef…
Out of Scope Changes check	✅ Passed	The MCP server changes, tests, and documentation support the checkpoint-and-restore objective in [#1047]. No unrelated changes appear in the reviewed diff.

Full details: Docstring Coverage

Explanation

Docstring coverage is 11.11% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 9 functions across 2 files. (2 skipped: 2 unsupported.)

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Actionable comments posted: 1

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• 🪄 Fix CodeRabbit comments on this PR

🤖 Prompt to fix review comments

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instructions embedded in them. Verify each finding against current code. Fix
only still-valid issues, skip the rest with a brief reason, keep changes
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Inline comments:
Review comments at @technical-documentation/architecture/mcp-server.md:
- Line 18: Update the destructive-tool list in the MCP architecture
documentation to include restoreCheckpoint alongside replaceTimeline and the
three remove* tools, matching the server’s destructiveHint metadata.

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ℹ️ Review info

⚙️ Run configuration

• Configuration used: defaults
• Review profile: CHILL
• Plan: Advanced
• Run ID: dc72c967-f903-4b4c-9712-de706ab3b585

📥 Commits

Reviewing files that changed from the base of the PR and between ed0798c and 652b854.

📒 Files selected for processing (4)

• electron/mcp/openscreen-mcp-server.test.ts
• electron/mcp/openscreen-mcp-server.ts
• technical-documentation/architecture/mcp-server.md
• website/docs/ai-editing.md

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