test(sdk): capture the child stderr these tests deliberately provoke (#156)

[kjgbot]

Addresses #156 — but not as filed.

The reported cause does not hold

#156 read the intermittent ENOENT ... .relayflow/backlog-picker-entry.json as a relative path racing under vitest parallelism. Every caller of the flow's steps already runs in its own mkdtempSync directory with an explicit cwd — backlog-picker.test.ts, backlog-picker-flow.test.ts, work-package-consumer.test.ts. There is no shared working directory to race over.

What is actually happening

Several tests here assert a step fails — select-entry refusing an unactionable backlog, emit-package with no entry to read. execFileSync echoes a failing child's stderr into the parent's, so a completely green run prints a full ENOENT stack trace and looks broken.

Measured over six consecutive full suites on main before changing anything: 662 passed, 3 skipped every time, and the ENOENT text present every time. Never a failure, always the noise.

So the defect is the noise

It is what got misdiagnosed, and it will misdiagnose the next person reading a CI log. Child stderr is now captured rather than echoed; the text remains on the thrown error for any test that wants to assert on it.

	result
with the change, 3 consecutive runs	662 passed | 3 skipped — ENOENT lines: 0 each time
with the stdio line reverted	662 passed | 3 skipped — ENOENT lines: 2

Tests pass either way. That is exactly why this was read as a flake: the only signal was output that looked like a failure and was not.

What I am not claiming

I have not closed #156 as invalid. Its first run genuinely showed Test Files 1 failed, so something failed then. The suite has changed substantially since (#153 widened it from four files to all of them, and several fixes have landed). I could not reproduce it in six runs, and I would rather say that than declare a bug I never observed to be absent.

Signoff: local 3-lens preswarm, maintainability / history / structure all REVIEW_PASSED.

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https://claude.ai/code/session_01FtQSAcGDta5VH9xiZFT4sR

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📥 Commits

Reviewing files that changed from the base of the PR and between c6ee55c and 7758814.

📒 Files selected for processing (2)

• sdk/tests/backlog-picker-flow.test.ts
• sdk/tests/work-package-consumer.test.ts

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