[Fix] Subtask e2e suite can inherit a cancelled delayed mock stream from the previous test

[zoomote]

Created by Roomote. Follow up by mentioning @zoomote, in the web UI, or in Discord.

Related GitHub Issue

Split out from #835 (test-stabilization portion only; no production telemetry changes). Independent from main — does not depend on any of the other split PRs.

Description

Stabilizes the delayed-stream subtask e2e tests in apps/vscode-e2e, test-only.

The race being prevented: the API-hang child fixture delayed its mocked response with aimock's flat latency: 15_000. aimock applies flat latency to every SSE chunk and never observes client disconnects (writeSSEStream only honors the fixture's own interruption signal). When the test cancels the child's in-flight request, the mock keeps the stream pending server-side for chunks × latency (~75s for this 5-chunk response) and then flushes the remaining chunks to the dead socket. A streamed request opened by the next test can interleave with that late flush — so one test's unfinished delayed request leaked into the next test.

The fix, in two parts:

1. fixtures/subtasks.ts — the fixture now delays only the first chunk via streamingProfile: { ttft: SUBTASK_API_HANG_RESPONSE_LATENCY_MS }. With no flat latency set, chunks after the first get ~0 delay, so the server-side pending window is exactly one named constant instead of an unbounded chunks × latency. Observable pre-cancel behavior is identical (no bytes for 15s), so the test scenario is preserved.
2. suite/subtasks.test.ts — the API-hang test captures the request's aimock journal timestamp (journal entries are stamped when the request is received, before the delayed write begins) and, in finally, drains via waitForDelayedSubtaskStreamDrain: it waits only the remaining time until timestamp + SUBTASK_API_HANG_RESPONSE_LATENCY_MS + 500ms grace.

Why this synchronization point is reliable: the deadline is anchored to the journal timestamp of the exact request this test created (scenario-unique marker + parent-marker exclusion, matched before cancellation, so it can only be the original hung request — never a stale or resumed one). The wait is bounded by one latency window plus grace, so it cannot hide a genuine hang; it no-ops if the delayed request never reached the mock. This replaces the arbitrary fixed sleep(latency) / blanket per-test sleep(1_500) teardown approach with an explicit, bounded drain.

Production files deliberately untouched: all of src/, webview-ui/, packages/ — including every telemetry behavior from #835 (consent, circuit breaker, shutdown, task aggregation, tool attribution, model-cache). bedrock-mock-server.ts was also left untouched: the subtask suite routes through aimock, not the bedrock mock, and aimock's journal already exposes the needed synchronization point.

Test Procedure

• TEST_FILE=subtasks.test.js xvfb-run -a pnpm --filter @roo-code/vscode-e2e test:ci:mock — 11/11 passing, run twice consecutively; the API-hung test completes in a deterministic ~15.8s (one latency window).
• npx tsc -p apps/vscode-e2e/tsconfig.json --noEmit — clean.
• pnpm --dir apps/vscode-e2e exec eslint --prune-suppressions --max-warnings=0 src/fixtures/subtasks.ts src/suite/subtasks.test.ts — clean, no suppression-count increases.
• Full repo pnpm test: zoo-code (src) 7190 passed. One unrelated pre-existing flake in webview-ui (SlashCommandsSettings.spec.tsx › "refreshes commands after creating new command") failed under the full parallel run but passes in isolation; that package is untouched by this diff.

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).
• Visual Snapshot (UI changes only): If a user would notice this change at a glance (layout, theme tokens, brand elements, empty/error states), I've added or updated a *.visual.tsx snapshot in webview-ui/. See webview-ui/AGENTS.md → "When a UI change needs a snapshot".
• 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.

Visual Snapshots

N/A — test-only change, no UI surface.

Videos (interaction / animation only)

N/A.

Documentation Updates

• No documentation updates are required.
• Yes, documentation updates are required. (Please describe what needs to be updated or link to a PR in the docs repository).

Additional Notes

Success criterion: repeated runs of the subtask suite do not inherit delayed mock activity from the preceding test — verified with two consecutive clean mock-mode runs.

Get in Touch

edelauna

[zoomote]

No new code issues found. See task

The one new commit since the last review (2c72188) is docs/comment-only: a new AGENTS.md section on streamingProfile.ttft vs flat latency, moved no-flat-latency invariant notes onto the constant's doc comment, and an explicit Promise<number | undefined> return type that matches the implementation. No behavior changed; the prior review's verified claims still hold.

_{Reviewed 2c72188}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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