[roodboi]

What

tests/python-free-download.test.ts, "bounded cancellation refuses uncertain read-error settlement and preserves the primary failure", hit Bun's 5 s default timeout on hosted macOS shard 1/8 (#853). The next scenario then failed toHaveBeenCalledTimes(1) with 2, and the global-state guard reported globalThis.fetch replaced.

What it was really waiting on

The test drove a fake clock after a single setTimeout(0):

await drain();      // one event-loop turn
clock.advance(5);   // expire the 5 ms cleanup grace

transferAttempt (src/lib/release-transfer.ts) awaits a real open() of the target file before reading. Only after the size failure does settleCancellation arm the 5 ms grace on the fake clock. If open() takes more than one turn (a loaded runner), the advance fires nothing. The grace is armed afterwards at the new time and never expires, so the download never settles. The test then hangs until the 5 s timeout, and its finally { mock.mockRestore() } never runs. The next scenario's spyOn(globalThis, "fetch") reuses the leaked spy, which already has one call: hence 2, and the guard error.

sequenceDiagram
  participant T as test
  participant D as download
  participant C as fake clock
  T->>D: start
  T->>T: one setTimeout(0)
  T->>C: advance(5): nothing armed yet
  D->>D: open() completes (real I/O, late)
  D->>C: arm 5 ms cleanup grace (never advanced)
  Note over T: hangs to the 5 s timeout, finally skipped, fetch spy leaks

Loading

The same assumption (one turn is enough) sat in three sibling tests in this file: "HTTP transfer budget … progress / total" and "five-file … cleanup". They fail the same way when open() is slow.

Fix (test-only)

• until(ready, what) drains in a loop with a 2 s real-time bound, well under the 5 s default. A missed step fails with Fixture step did not happen within 2000 ms: <what> instead of a timeout. within(promise, what) bounds the final settlement the same way.
• Before advancing the 5 ms cleanup grace, the test waits for clock.isArmed(5). FixtureClock now records each timer's delay; the other timers are 30 and 100 ms.
• Before an inactivity tick, the test waits for an actual pending read. The fixture streams use highWaterMark: 0 and flag pull(), which runs only while the download is reading. A file-existence check was not enough: the file exists before open() returns its handle (found in review).
• The five-file spin loops, capped at 100 turns, use the same real-time bound.
• afterEach calls mock.restore(), so a test that fails before its finally cannot leak the fetch spy into the next test. The existing per-test mockRestore() calls stay.

No assertion is weakened or removed.

Validation (Linux, 16 cores)

Check	Before	After
-t "bounded cancellation" under 16-way parallel load	5 of 400 failed, with the hosted signature (5 s timeout, then 2 calls and the guard error)	400 of 400 pass at 5f16f8b
Whole file under 16-way parallel load	2 of 191 failed at an intermediate head (progress/total false stall, found in review)	208 of 208 pass (15/15 each) at 5f16f8b
Preload delaying open() by 50 ms	4 failures, incl. read-error and stalled-read timeouts with the guard error	15/15
Preload delaying open() by 200 ms	—	15/15
Preload delaying after open() creates the file	progress/total fail	15/15

tsc -p packages/cli (it includes tests/) and biome check pass.

Not verified: macOS. The lead runs the 200 on the Mac.

Release signal

test: test-only.

Refs HACK-2250.

🤖 Generated with Claude Code

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[roodboi]

@codex review

[linear-code]

HACK-2250

[chatgpt-codex-connector]

Codex Review Summary: ✅ Completed

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-11-15T02:30:26.436082Z	0c33970	Manual request
🔒 Security Review	✅ Completed 2026-11-15T02:32:32.119223Z	0c33970	Manual request

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[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Delightful!

Reviewed commit: 5f16f8be39

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[chatgpt-codex-connector]

🛡️ Codex Security Review · Automatically triggered

Security review completed. No security issues were found in this pull request.

Reviewed commit: 5f16f8be39

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[roodboi]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. 🎉

Reviewed commit: 0c33970830

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Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[chatgpt-codex-connector]

🛡️ Codex Security Review · Automatically triggered

Security review completed. No security issues were found in this pull request.

Reviewed commit: 0c33970830

View security finding report

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ℹ️ About Codex security reviews in GitHub

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• You comment "@codex security review"
• A regular code review gets triggered (for example, "@codex review" or when a PR is opened), and you’re opted in so security review runs alongside code review

Once complete, Codex will leave suggestions, or a comment if no findings are found.

[roodboi]

Ready for lead: head 0c339708308a79c9db4882a83fe56b2624618c73 (my changes at 5f16f8b, plus a normal merge of next at e47681e; #794 had added one assertion in this file).

Ran (Linux, 16 cores)

• Before the fix, -t "bounded cancellation" with 16 runs in parallel: 5 of 400 runs failed with the hosted signature (read-error 5 s timeout, then toHaveBeenCalledTimes 2 and globalThis.fetch replaced).
• After the fix, same setup at 5f16f8b: 400 of 400 pass. Whole file with 16 in parallel: 208 of 208 pass at 5f16f8b and 208 of 208 at this merge head (15/15 each, no timeouts or guard errors).
• Preloads that delay open() by 50 ms or 200 ms before it opens the file, or by 50 ms after it creates the file: 15/15 at this head. The old test fails every time with the 50 ms delay.
• tsc -p packages/cli (includes tests/) and biome check.
• Hosted CI run 43667984279: success, both required checks pass. The file ran in Linux test shard 8/8. The change scope did not schedule the macOS shards for this test-only PR, so hosted macOS did not run this file here. Earlier runs 43666802013 and 43666807807 were cancelled when a newer run started on the same head, one of them after I edited the PR body; they are not test failures.
• Independent Codex reviewer (same thread as the earlier units). Round 5: one P2 (file existence does not prove a read is pending), fixed with a pull() handshake. CLEAN at 5f16f8b and again at this merge head, including feat(native): guide first-use runtime setup #794's assertion.
• Codex bot: no major issues at 0c33970, and its automatic security review found none. computer pr review-status: CLEAR at 0c33970.

Not verified

• macOS: your 200-run on the Mac.

Also fixed in this file: the same "one event-loop turn is enough" assumption in "HTTP transfer budget … progress/total" and "five-file … cleanup". At an intermediate head these failed 2 of 191 runs under load (false stall), and they fail with the injected delays. Test-only; no assertion weakened.

[roodboi]

Mac result at 0c33970 (Apple silicon): the four "bounded cancellation" tests pass 200 of 200 runs, and the whole file passes 20 of 20. This PR goes into the next combined Mac batch.

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