fix(task-lifecycle): preserve parent-child link when delegated subtask is interrupted (#560)

[edelauna]

Related GitHub Issue

Closes: #560

Description

When a delegated subtask is interrupted mid-execution (user hits stop), cancelTask immediately severed the parent-child link — parent went from "delegated" → "active" with awaitingChildId cleared. When the user resumed the child and it called attempt_completion, the parent no longer awaited it, so it fell through to the standalone "Start New Task" flow instead of reporting back.

Changes

Core fix — 4 files:

• packages/types/src/history.ts — Add "interrupted" to status enum
• packages/types/src/task.ts / src/core/task/Task.ts / src/core/task-persistence/taskMetadata.ts — Propagate "interrupted" through initialStatus types
• src/core/webview/ClineProvider.ts — cancelTask and removeClineFromStack now mark the child as "interrupted" instead of detaching the parent. Parent stays "delegated" with awaitingChildId intact.
• src/core/tools/AttemptCompletionTool.ts — Accept "interrupted" alongside "active" so resumed children can still delegate back to parent

CLI type sync — 2 files:

• apps/cli/src/ui/types.ts / apps/cli/src/ui/components/autocomplete/triggers/HistoryTrigger.tsx — Add "interrupted" to CLI status types to prevent type drift

Test flake fix — 1 file:

• src/services/mcp/__tests__/McpHub.spec.ts — Replace 20 instances of setTimeout(resolve, 100) with mcpHub.waitUntilReady() to fix a pre-existing timing race that surfaces under thread-pool pressure in the full test suite

How it works

Before: cancel child → parent: delegated→active, awaitingChildId→undefined → child resumes → falls through to standalone
After:  cancel child → child: active→interrupted, parent stays delegated → child resumes → delegates back to parent

Test Procedure

Unit tests (3 files updated, 1 new test added):

• src/__tests__/removeClineFromStack-delegation.spec.ts — Updated to assert child marked interrupted (not parent detached)
• src/core/webview/__tests__/ClineProvider.flicker-free-cancel.spec.ts — Updated for new cancel behavior
• src/core/tools/__tests__/attemptCompletionTool.spec.ts — Added test for interrupted child delegating back to parent; added test for unexpected child status branch

E2E test (1 test updated):

• apps/vscode-e2e/src/suite/subtasks.test.ts — Updated "cancelled child" test to assert the new behavior: interrupted child resumes → reports back to parent → parent completes. Validated locally via xvfb-run.

All tests pass: pnpm exec vitest run (unit), xvfb-run pnpm --filter @roo-code/vscode-e2e test:ci:mock (e2e).

Pre-Submission Checklist

• Issue Linked: Closes fix(task-lifecycle): preserve parent-child link when delegated subtask is interrupted #560
• Scope: Focused on subtask interrupt/resume lifecycle
• Self-Review: Performed
• Testing: Unit tests updated + new test added + e2e test updated
• Documentation Impact: No documentation updates required
• Contribution Guidelines: Read and agreed

Additional Notes

• Filed #612 for broader CLI status type drift (deriving from historyItemSchema instead of independent unions)
• The "abandon subtask" UI action (acceptance criterion from fix(task-lifecycle): preserve parent-child link when delegated subtask is interrupted #560) is deferred — worth tracking as a follow-up
• McpHub test flake fix is included because it was blocking CI; root cause was setTimeout(resolve, 100) timing races under vitest thread-pool pressure

[coderabbitai]

Important

Review skipped

Draft detected.

Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: f61b104c-feef-451d-aacc-ac48202c203b

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch issue/560

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[codecov]

Codecov Report

❌ Patch coverage is 79.41176% with 14 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/core/webview/ClineProvider.ts	80.00%	9 Missing and 3 partials ⚠️
...omponents/autocomplete/triggers/HistoryTrigger.tsx	66.66%	0 Missing and 2 partials ⚠️

📢 Thoughts on this report? Let us know!

[edelauna]

Closing in favor of landing #355 Epic 1+2 foundation first.

The multi-agent code review surfaced 3 blocking concurrency bugs from unserialized delegation-state mutations — a structural problem that the transition guards (Story 2.3, #366) and atomicReadAndUpdate() from #355 are designed to eliminate. See comments on #560 and #559 for the full rationale.

The behavioral design, test coverage (39 unit + 4 E2E tests), and review fixes on this branch are preserved for reuse when interrupted is re-implemented on top of the foundation.