fix: restore parent task switching and strengthen subtask completion flow (issue #8081)

[Mnehmos]

Most of y'all know me. I dont code, so I'd appreciate a review by an expert as well please. My tests work both manual and automated.

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Related GitHub Issue

Closes: #8081

Roo Code Task Context (Optional)

N/A - Developed using Roo Code's Orchestrator mode with multi-agent collaboration.

Description

This PR fixes a recurring regression where subtasks completing after interruption fail to properly return control to parent agents, leaving the webview stuck displaying the subtask instead of switching to the resumed parent task.

Key Implementation Details:

1. UI Navigation Fix: Added explicit chatButtonClicked action in ClineProvider.finishSubTask() after state posting. The previous implementation only called postStateToWebview() which broadcasts state changes but doesn't trigger UI navigation. This mirrors the pattern used in showTaskWithId() for consistency.

2. Subtask Metadata Persistence: Implemented a new SubtaskMetadata schema (Zod-validated) that stores parent-child relationships in message metadata. This ensures task hierarchy survives VSCode restarts and enables proper parent restoration after interruptions.

3. Enhanced Error Handling: Added verifyParentExists() method to check parent accessibility before completion, gracefully handling orphaned subtasks. Also added race tolerance for resume asks by treating ignored promises as implicit approval.

4. Non-Interactive Injection: Made subtask_result message injection non-interactive to avoid interfering with pending resume asks, preventing timing conflicts.

Reviewers should pay attention to:

• Lines 550-553 in ClineProvider.ts: The UI navigation action that fixes the core regression
• Lines 3071-3112 in Task.ts: Metadata persistence implementation
• Lines 1366-1380 in Task.ts: Resume ask race tolerance handling
• Test mocking changes in ClineProvider.spec.ts (lines 210-224): Proper tuple return from Task.create()

Test Procedure

Automated Testing:

cd src
npx vitest run core/webview/__tests__/ClineProvider.finishSubTask.spec.ts
npx vitest run core/webview/__tests__/ClineProvider.spec.ts
npx vitest run __tests__/subtask-metadata-tracking.test.ts

Test Results:

• ✅ ClineProvider.finishSubTask.spec.ts: 98 tests passing
• ✅ ClineProvider.spec.ts: 92 passed, 6 skipped
• ✅ subtask-metadata-tracking.test.ts: All tests passing

Manual Testing Procedure:

1. Create a parent task with Orchestrator mode
2. Create a subtask from the parent using new_task tool
3. Interrupt the subtask (close VSCode or kill terminal mid-execution)
4. Reopen VSCode and resume the subtask
5. Complete the subtask using attempt_completion
6. Verify: The webview should automatically switch to display the parent task
7. Verify: Parent task should show "Subtask Completed" message
8. Verify: Parent task should be in resume-ask state

Edge Case Testing:

• Test with deleted parent task (should show error message, not crash)
• Test with subtasks created before this PR (backward compatibility)
• Test with multiple nested subtasks (depth > 1) (completed and working)

Pre-Submission Checklist

• Issue Linked: This PR is linked to an approved GitHub Issue (see "Related GitHub Issue" above).
• Scope: My changes are focused on the linked issue (one major feature/fix per PR).
• Self-Review: I have performed a thorough self-review of my code.
• Testing: New and/or updated tests have been added to cover my changes (if applicable).
• Documentation Impact: I have considered if my changes require documentation updates (see "Documentation Updates" section below).
• Contribution Guidelines: I have read and agree to the Contributor Guidelines.

Screenshots / Videos

Before (Bug):

• After subtask completion, webview remains stuck on subtask view
• User must manually click through task history to find resumed parent

After (Fixed):

• Subtask completion automatically switches webview to parent task
• Parent task immediately visible with "Subtask Completed" notification
• Seamless user experience with proper task flow

(https://vimeo.com/1134407282?share=copy&fl=sv&fe=ci)

Documentation Updates

• No documentation updates are required.

Rationale: This is a bug fix that restores expected behavior. The feature (subtask completion returning to parent) already exists and is documented; this PR simply fixes the regression where the UI wasn't properly switching views.

Additional Notes

Backward Compatibility:

• All changes are backward compatible with existing tasks
• Legacy subtasks without metadata are handled gracefully via optional fields
• No breaking changes to public APIs

Performance Impact:

• Minimal: Metadata operations are lightweight and non-blocking
• File system operations use existing infrastructure
• No additional API calls or network requests

Code Quality:

• No superfluous or placeholder code
• Clean error handling with detailed logging
• Follows existing patterns and conventions (e.g., mirrors showTaskWithId() navigation pattern)
• Well-documented with inline comments

Related Changes:

• Fixed Task.create() mock in test suite to return proper tuple structure
• This was necessary to support existing tests after implementation changes

Get in Touch

Discord: @Mnehmos

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Important

Fixes subtask completion flow to ensure UI returns to parent task, adds metadata persistence, and enhances error handling in ClineProvider and Task classes.

• Behavior:
  • Fixes subtask completion flow in ClineProvider.finishSubTask() to ensure UI switches back to parent task.
  • Adds chatButtonClicked action in ClineProvider.finishSubTask() to trigger UI navigation.
  • Implements SubtaskMetadata schema in history.ts for parent-child task tracking.
  • Adds verifyParentExists() in Task.ts to check parent task accessibility.
  • Makes subtask_result injection non-interactive in Task.ts.
• Testing:
  • Adds ClineProvider.finishSubTask.spec.ts to test subtask completion scenarios.
  • Updates ClineProvider.spec.ts to mock Task.create() and test task stack behavior.
• Misc:
  • Updates Task.ts to persist subtask metadata and handle resume ask race conditions.

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[roomote]

Rooviewer   See task on Roo Cloud

Re-review complete. All previously identified issues have been resolved. No new issues found.

Issues Resolved:

• Unhandled promise rejection - createTaskWithHistoryItem promise now has proper error handling
• Race condition in parent verification - TOCTOU race eliminated by removing pre-check and consolidating error handling

Previous reviews

• b5cc86d: Review #1
• 65ba1a7: Review #2
• 22c0a67: Review #3
• db9d2b1: Review #4

_{Mention @roomote in a comment to request specific changes to this pull request or fix all unresolved issues.}

[hannesrudolph]

@Mnehmos
Closing in favor of PR #9090.

Thank you for the work in PR 9086. After comparing both branches, PR 9090 delivers the same delegation resume improvement with a smaller and more focused scope. It keeps the changes limited to the backend, avoids UI and localization updates, and provides a clearer resume path.