test(worker_threads): run worker_threads.test.ts concurrently and tighten its subprocess assertions

[robobun]

Problem

• test/js/node/worker_threads/worker_threads.test.ts is one of the slowest serial files in CI: 25.1s for 132 tests on the debian 13 x64-asan lane (build 97275; about 6.6s on the non-ASAN x64 lane, where the same file is dominated by the same tests).
• The file starts a worker or a bun subprocess per test (37 spawns, ~60 in-process workers) and ran every one of them one after another, so its time is startup latency multiplied by volume. Locally (bun bd test, debug+ASAN, on a loaded box) it took 350s; the tests that dominated were eval does not leak source code (46s: six eval workers whose 100 MiB source was pure whitespace, lexed a character at a time), terminate with work in flight (three tests starting 8+4+4 workers one at a time, 40s together), environmentData > is deeply inherited (12s), worker name survives ... (11s), and the SHARE_ENV / execArgv / stdio fixture subprocesses (3 to 9s each).
• Many subprocess tests only checked the exit code, or checked it before reading output, so a failing child reported as "exit code 1" or as a JSON parse error instead of showing what it printed.

Fix

• Every test that owns its Worker / MessageChannel / subprocess outright is now test.concurrent (or lives in a describe.concurrent), so the startup latency overlaps. The two tests that hook process-wide state (process.once("worker"), a replaced process.emit) stay serial and move to the top of the file, where they run before any other test has created a Worker. No test was removed or skipped: 132 -> 133 tests (379 -> 374 expect() calls: a number of two- and three-call sequences became one toEqual over stdout, stderr and the exit code, and the new test adds four).
• The only other serial tests are the three in-process ones in terminate with work in flight (transpile / SubtleCrypto digest / zlib job), which are unchanged from main. Each worker posts go the moment its job is queued and terminate() must reach it while the job, which takes milliseconds, is still running; the first CI run of this PR had them concurrent and they failed on every non-ASAN lane (and once on ASAN) with terminate() resolving 0: the parent was busy with other tests, and the workers had finished and exited on their own first. With an idle parent (serial, as on main) the reaction is sub-millisecond. The describe's comment records this; its three subprocess tests are concurrent.
• eval-source-leak-fixture.js: the 100 MiB source is built once and is a block comment instead of whitespace, and the fixture reports { eachSizeMiB, iterations, deltaMiB } instead of throwing; the assertion moves into the test, which prints the measured number when it fails. Same sizes and iterations (the per-worker Blob copy, which is what gets measured, is unchanged); 45s -> 28s standalone on the debug build here.
• The bound on that measurement moves from eachSizeMiB * iterations (500 MiB) to half of it. The old bound was the leak's own nominal size, and the leaking case does not reliably read above it: simulating the leak by stubbing out URL.revokeObjectURL (the only thing that releases the copies) on a release build reads 481 to 500 MiB with this fixture shape (15 runs; 14 of them would have passed the old bound) and 500.2 to 511.8 with main's shape (12 runs, several within 1 MiB of the bound; the original fixture's comment itself recorded about 503 on macOS). A healthy run reads about 0: -52 to 0 over 15 release runs, and occasionally one copy that is still being torn down at a reading (a later release run here read 115); 7 on debug+ASAN (where the leaking case reads 517). The fixture also rejects a worker that exits nonzero, so a run whose workers never evaluated the source (and so never made the copies) cannot read as healthy. 250 MiB is at least 135 MiB from every reading on either side. Found by self-review of the first revision; the comments in both files now describe this gap instead of claiming the growth is "at least" the leak size.
• A new in-process test next to it checks the release mechanism exactly, with node:buffer's resolveObjectURL: the blob: URL serving an eval worker's source resolves to a Blob of the source's size while the worker runs and to undefined once it has exited. It stays in this PR as the deterministic half of the leak coverage, given how coarse the RSS reading turned out to be; its node:buffer import is the one line that will need a trivial merge against worker_threads: don't build the process object's lazy properties during worker startup #38987, which also edits the imports.
• Two spawns whose assertions do not depend on anything process-level moved in-process: terminating a worker stops the workers it spawned (now also asserts the first heartbeat, terminate() resolving 1 and no error events) and workerData is not unwrapped for a non-node globalThis.Worker. The remaining spawns are needed: they observe process exit or "the process does not hang", worker uncaught exceptions and unhandled rejections (which bun test intercepts in-process, so the exit-code-1 paths are only visible in a child), clobbered prototypes, SHARE_ENV founding (it replaces the founding thread's process.env), a parent with a known non-empty execArgv, or the RSS of a fresh process.
• Assertions on spawned processes: stdout and stderr are read before the exit code and compared in one toEqual with the exit code (execArgv, both environmentData fixtures, emit-non-function, worker name survives, the two tampered-prototype tests, a collected port, ref()/onmessage, debugPort, the SHARE_ENV child-process cases and Bun.env case, SHARE_ENV founding thread); stderr is now asserted empty where it used to be dropped; JSON.parse is guarded so an empty stdout shows the child's stderr and exit code. emit-non-function-fixture.js and environmentdata-empty-fixture.js print what they observed (the uncaught exception's name and message; the value the grandchild thread read) so the test compares the payload instead of relying on an internal assert plus "no stderr". environmentData > is deeply inherited and execArgv read the pipes before waiting on exit. Spawns use await using.
• Timeouts: the two 9999999 per-test timeouts are gone (they were a 2.7 hour ceiling on a sync test and a worker round trip). The 60s and 30s outliers keep their values, which is why the slow-plugin test joins the other Bun.build cancellation test in a describe and the dns test joins VM teardown ordering (a test.concurrent(name, fn, timeout) call is not a test call to prettier and gets its whole body re-indented). The file's default becomes isASAN || isDebug ? 90_000 : 10_000 (it was isDebug ? ..., which left CI's ASAN lane on 10s; test-changed.test.ts and isolation.test.ts scale on isASAN the same way). It is not shortened: startup is several times slower under ASAN, and with tests overlapping, an individual test's wall time now includes waiting on the others, so it goes up, not down; on the release lanes the 10s is still stricter than the runner's own 90s. Nothing came near either value in the CI runs so far. Five test names were shortened by a few words so the test.concurrent( header still fits in 120 columns for the same reason.
• worker stop ordering: running the file repeatedly turned up a pre-existing flake in these two tests, independent of concurrency (1 failure in 40 runs of the unmodified tests with another test run going on beside them; received [12, 0], i.e. ready plus an empty entry). The worker's 1ms interval logged a tag on every tick, and put() reserves a slot with Atomics.add before storing the tag, so a tick that terminate() cut off between the two calls left a reserved, never-written slot that the parent read back as 0; the ticks were filtered out of the result anyway, and on a busy parent they would also have filled the 255-entry log before the tags that matter. The interval now stays (a timer that is firing when the stop arrives) but logs nothing, which is what the concurrency here needs (nothing fills the log while the parent is busy). 60 further runs of the two tests under the same load: no failures. worker_threads test: make the stop-ordering fixture's log termination-safe #38194 (open, 5 lines) fixes the same torn write from the other side, by making put() write the slot before publishing the count; its analysis is right (a put() that a termination lands inside necessarily started before the stop was requested, so it is never a violation), and the two changes are complementary. This PR deliberately leaves put() alone, so worker_threads test: make the stop-ordering fixture's log termination-safe #38194 applies unchanged before or after it, and the interval's comment here does not depend on which logger put() is.
• Not changed: the setImmediate round trips in the MessagePort tests are loop-turn waits for negative assertions (message delivery is FIFO on the loop, so other tests' activity cannot reorder them); the remaining setTimeouts are part of what is being tested (a watchdog, the "after startup GC timers" delay, the S3 retry window, the fuzzing sleeps in the slow-plugin test), not waits for a condition.
• Verification, locally: bun bd test test/js/node/worker_threads/worker_threads.test.ts (debug+ASAN, which caps concurrency at 5, on a heavily loaded box): 350.7s before (132 pass); 131.8s to 153.9s after across the revisions of this branch (133 pass; the last of those runs is the serial work-in-flight shape, in which those three tests took 21s + 10s + 13s on their own), plus nine more full runs of the built binary between 78s and 159s depending on the box's load. The only failures in any of these were the pre-existing stop-ordering torn write above (before it was fixed; 60 runs of those two tests under load after the fix passed) and two ENOSPCs from the box's shared disk filling up, which passed on re-run. The fixtures were also run directly; the leak fixture's readings with and without the revoke stubbed out are in the bound bullet above. After the bound change, -t "eval|worker stop ordering" (11 tests) passes on the debug build.
• Verification, CI (build 98250, revision 07cf294, which has the final test structure; the last commit only changes the leak bound and comments): 133 pass, 0 fail on every lane. File time: debian 13 x64-asan 12.2s (25.1s before), debian 13 x64 3.7s (6.6s before), windows 2019 x64 4.1s and windows 11 aarch64 4.0s (about 9s before), ubuntu 25.04 x64 5.5s, alpine 3.23 x64 4.8s, the three linux aarch64 lanes 3.3s to 3.5s. For comparison, the first revision, with the three work-in-flight tests concurrent as well, measured 10.05s on the ASAN lane before failing, so keeping them serial costs about 2s there.

Background

• test.concurrent in bun test: consecutive concurrent tests form a group that runs together (up to --max-concurrency, 20 by default and 5 in ASAN builds); a plain test between them is a barrier that waits for the group to drain and runs alone. That is why the process-global tests sit at the top, why long names were shortened rather than leaving tests serial for formatting reasons, and what the three work-in-flight tests rely on: when a barrier test runs, nothing else is using the parent's event loop.
• eval: true workers get their source through a blob: URL: the parent copies the source into a Blob, registers it with URL.createObjectURL, and the worker imports that URL as its entry; the parent revokes it in its exit handler. require("node:buffer").resolveObjectURL(url) returns the registered Blob or undefined, which is what the new test uses. The RSS fixture catches the copies being retained whatever holds them, at the resolution described in the bound bullet; the new test catches the revoke on exit itself being skipped, which the fixture cannot see because the module's GC-driven fallback (a FinalizationRegistry on the worker) would eventually free the copies anyway.
• Related open PRs: worker_threads test: make the stop-ordering fixture's log termination-safe #38194 (see the stop-ordering bullet) and worker_threads: preserve error own properties, surface parse diagnostics, report exit code 1 on terminate() #32867, an older worker_threads PR that also swaps the leak fixture's " ".repeat for Buffer.alloc in passing; this PR's rewrite of the fixture covers that hunk, noted there.

---

[stamp-90s] gate passed · iteration 0 · 4 files touched

passes on PR (with fix)

Test-only change.

Debug/ASAN (expected pass):
$ bun bd test 'test/js/node/worker_threads/worker_threads.test.ts'
$ BUN_DEBUG_QUIET_LOGS=1 bun scripts/build.ts --profile=debug --quiet test test/js/node/worker_threads/worker_threads.test.ts
bun test v1.4.0 (81b7c3f37)

test/js/node/worker_threads/worker_threads.test.ts:
(pass) worker event > is emitted on the next tick with the right value [305.54ms]
(pass) worker event > uses an overridden process.emit function [50.68ms]
(pass) all worker_threads module properties are present [93.43ms]
(pass) markAsUncloneable and markAsUntransferable markers are private, unforgeable, and permanent [84.81ms]
(pass) all worker_threads worker instance properties are present [1233.88ms]
(pass) receiveMessageOnPort works as FIFO [39.10ms]
(pass) threadId module and worker property is consistent [2008.08ms]
(pass) support eval in worker [10243.04ms]
(pass) receiveMessageOnPort works across threads [10107.08ms]
(pass) you can override globalThis.postMessage [9426.33ms]
(pass) support require in eval [9236.17ms]
(pass) worker event > throws if process.emit is not a function [14515.88ms]
(pass) support require in eval for a file that doesnt exist [6742.91ms]
(pass) support worker eval that throws [6465.50ms]
(pass) support require in eval for a file [7426.97ms]
(pass) eval: the blob: URL holding the source is revoked when the worker exits [5227.55ms]
(pass) execArgv option > inherits the parent's execArgv when falsy or unspecified [14291.61ms]
(pass) execArgv option > provides empty execArgv when passed an empty array [11805.26ms]
(pass) captured stdio backpressure > stdout write completion is withheld until the parent reads [7360.63ms]
(pass) execArgv option > can specify an array of strings [12986.67ms]
(pass) captured stdio backpressure > large stdout survives writev batching and repeated acks [9963.03ms]
(pass) stdio is flushed when the worker exits synchronously > captured stdout: console + raw write, then process.exit(0) [10459.86ms]
(pass) captured stdio backpressure > captured stdio that is never consumed does not prevent exit [
... (truncated)
Exit: 0

diff hotspot

.../worker_threads/emit-non-function-fixture.js    |  19 +-
 .../environmentdata-empty-fixture.js               |  22 +-
 .../worker_threads/eval-source-leak-fixture.js     |  27 +-
 test/js/node/worker_threads/worker_threads.test.ts | 766 +++++++++++----------
 4 files changed, 436 insertions(+), 398 deletions(-)

gate history · 1 passed · 0 rejected · iteration 0

evidence per changed file

file                                                      reads  edits  tests
test/js/node/worker_threads/emit-non-function-fixture.js      2      3      0
…js/node/worker_threads/environmentdata-empty-fixture.js      1      1      0
test/js/node/worker_threads/eval-source-leak-fixture.js       3      4      0
test/js/node/worker_threads/worker_threads.test.ts           27     48      0

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📥 Commits

Reviewing files that changed from the base of the PR and between 929043d and 96c74b0.

📒 Files selected for processing (2)

• test/js/node/worker_threads/eval-source-leak-fixture.js
• test/js/node/worker_threads/worker_threads.test.ts

Walkthrough

The pull request updates worker-thread fixtures and expands worker_threads.test.ts. Most tests now run concurrently. Subprocess checks validate stdout, stderr, exit codes, and signals. New coverage exercises worker resources, messaging, startup, teardown, cancellation, and eval-source lifecycle.

Changes

Worker Threads Test Suite

Layer / File(s)	Summary
Worker fixtures and eval validation test/js/node/worker_threads/*fixture.js, test/js/node/worker_threads/worker_threads.test.ts	Fixtures now serialize errors, relay environment data, and measure shared eval-source allocation. Tests validate eval URL revocation and subprocess results.
Worker resources and message semantics test/js/node/worker_threads/worker_threads.test.ts	Concurrent tests cover stdio, FileHandle, MessagePort, environment data, transfers, listeners, closure, and subprocess output.
Worker lifecycle and cancellation coverage test/js/node/worker_threads/worker_threads.test.ts	Concurrent tests cover startup, teardown, termination, IPC, async cancellation, VM and DNS cancellation, and stop ordering. Selected teardown tests remain serial.

Possibly related PRs

• oven-sh/bun#38066: Expands overlapping MessagePort lifecycle coverage.
• oven-sh/bun#38194: Modifies related worker termination and stop-ordering tests.
• oven-sh/bun#38229: Adds overlapping worker stdio flush and exit coverage.

Suggested reviewers: jarred-sumner

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly summarizes the primary changes: concurrent worker_threads tests and stronger subprocess assertions.
Description check	✅ Passed	The description thoroughly explains the changes, rationale, scope, and verification results, although it does not use the template headings exactly.

---

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[robobun]

Status: test-only change, ready for review at 81b7c3f (CI for it is running; it differs from 07cf294, whose full run is below, only in the eval leak bound, the file's default timeout now also scaling on ASAN, the leak fixture rejecting a nonzero worker exit, and comments).

• Baseline (build 97275, unmodified file, 132 tests): 25.1s on debian 13 x64-asan, about 6.6s on debian 13 x64, about 9s on the Windows lanes.
• Build 98250 (07cf294, the final test structure; 133 tests): 133 pass, 0 fail on every lane. debian 13 x64-asan 12.2s, debian 13 x64 3.7s, ubuntu 25.04 x64 5.5s, alpine 3.23 x64 4.8s, windows 2019 x64 4.1s, windows 11 aarch64 4.0s, linux aarch64 lanes 3.3s to 3.5s. (The first revision, build 98139, had the three in-process terminate with work in flight tests concurrent too; it measured 10.05s on ASAN but those tests raced the workers' natural exit and failed on the release lanes, so they are serial again, as on main.)
• Self-review of the first revision found that the eval leak fixture's bound sat at the leak's nominal size, which the leaking case often reads slightly under; 929043d moves it to half, with the measurements in the PR body; 81b7c3f picks up the two review suggestions (ASAN-scaled default timeout, fixture rejects a nonzero worker exit), and both threads are resolved. It also found worker_threads test: make the stop-ordering fixture's log termination-safe #38194 (complementary stop-ordering logger fix, left applicable) and worker_threads: preserve error own properties, surface parse diagnostics, report exit code 1 on terminate() #32867 (overlapping fixture hunk); both are cross-referenced.
• Locally (bun bd test, debug+ASAN, concurrency capped at 5 there): 350.7s before; 131.8s to 153.9s after, 133 passing; nine further full runs of the built binary passed; 60 runs of the two worker stop ordering tests under load passed.
• The retried failures in builds 98139 and 98250 (bun-lock, napi, shell-pipe-read-fault, child-process-exec, pnpm-migration, hoist, bake/deinitialization, inspect-error-leak, isolated-relink, stack, bun-lockb, bun-patch, build-codegen-declared-outputs, dlopen-duplicate-load, the node-napi builds and node parallel tests on Windows aarch64, and a few more) all passed on retry and do not involve this file.

[claude]

I reviewed this PR and the bug hunting system found no issues. Because it's a large test refactor (~800 lines) that changes concurrency semantics across ~130 tests, converts two subprocess tests to in-process, and reworks the terminate with work in flight tests from serial to parallel worker creation, a human look and green CI across all lanes would still be worthwhile.

What was reviewed:

• Checked that the two tests hooking process-wide state (process.once("worker"), replaced process.emit) stay serial and run before any concurrent test creates a Worker.
• Checked setEnvironmentData("foo", ...) in the concurrent environmentData describe — it mutates main-thread state, but no other concurrent test reads that key, so no cross-talk.
• Verified tmpdirSync uses mkdtempSync (unique dirs), so the seven concurrent worker-fh-transfer tests don't collide.
• Confirmed the fixture rewrites preserve the same thresholds/invariants and move assertions to the test file (strictly stronger: stderr now asserted, JSON.parse guarded).

Extended reasoning...

Overview

This PR refactors test/js/node/worker_threads/worker_threads.test.ts (one of the slowest CI files) and three of its fixtures. The changes fall into: (1) converting ~130 tests from serial test to test.concurrent/describe.concurrent; (2) consolidating subprocess assertions into single {stdout, stderr, exitCode} toEqual calls with stderr now asserted and JSON.parse guarded; (3) rewriting three fixtures to print observed data rather than throw, so the test file owns the assertion; (4) converting two subprocess tests to in-process; (5) reworking terminate with work in flight from serial to parallel worker creation via a shared terminateEach helper; (6) fixing a pre-existing torn-write flake in worker stop ordering by making the 1ms interval a no-op instead of logging; (7) adding one new test for blob: URL revocation on eval-worker exit. No runtime code is touched.

Security risks

None. Test-only changes with no auth, crypto, or permission surface.

Level of scrutiny

Medium-high. While test-only, the concurrency conversion requires per-test judgment that no shared process state leaks between tests. The author explicitly identified and isolated the two process.emit/process.on("worker") tests, and I spot-checked setEnvironmentData (benign — only one test writes, on a key no other test reads) and tmpdirSync (unique via mkdtempSync). The terminate with work in flight change alters what states terminate() races against (author argues this is better coverage), and two subprocess→in-process conversions change what the test can observe (author justifies each). The worker stop ordering interval-tick removal is well-argued (the tag was already filtered out and its torn write caused the flake), but it does change the fixture. These are all reasonable, but each is a judgment call rather than a mechanical transform.

Other factors

The PR description is unusually thorough — 11+ full local runs under debug+ASAN, a root-caused flake fix with 60 verification runs, and explicit reasoning for every non-mechanical change. The bug hunting system found nothing. The assertion tightening (stderr checked, pipes drained before exit, await using on spawns) strictly improves diagnostics per REVIEW.md's subprocess-test guidance. However, at ~800 diff lines with several semantic test changes and a new test relying on __filename being the blob: URL inside an eval worker, this exceeds the bar for auto-approval without a human confirming CI is green across platforms (particularly Windows and the ASAN lanes where concurrency caps differ).

[robobun]

Thanks. The first CI run (build 98139) did turn up a problem with exactly the part called out here: the terminate with work in flight rework. Starting the 8/4/4 workers together inside a concurrent group let the parent fall behind; the pool jobs only take milliseconds, so on the release lanes (and once on ASAN and on Windows) some workers had already exited on their own by the time terminate() was called, and it resolved 0 instead of 1. Those three tests are going back to their original serial loops in a plain describe (so they run alone, with an idle parent, as on main), with only the three subprocess tests in that describe marked concurrent; a comment in the describe records why. The rest of the diff is unchanged. Even with that describe serial, the same run measured the file at 10.05s on debian 13 x64-asan (25.1s before) and 3.27s on Windows 11 aarch64 (about 9s before); updated numbers will follow once the fixed revision has run.

The other failures in that run (bun-lock, shell-pipe-read-fault, napi, child-process-exec, pnpm-migration, hoist, bake/deinitialization, inspect-error-leak) all passed on retry and are unrelated to this file.

[robobun]

^{Updated 12:14 PM PT - Aug 15th, 2026}

@robobun, your commit 96c74b0 is building: #98589

[claude]

I reviewed this PR and didn't find any bugs. Because it's a large concurrency conversion (~130 tests moved to test.concurrent, two subprocess tests moved in-process, three fixtures reworked, and a de-flake of the stop-ordering log), and the final revision's CI run isn't reflected in the thread yet, a human look would still be worthwhile.

What was reviewed:

• The two process-global tests (process.once("worker"), overridden process.emit) stay serial and run first; the terminate with work in flight in-process trio stays serial per the follow-up commit — no other tests I checked share process-wide state that would break under concurrency.
• The fixture changes preserve the same thresholds/assertions (leak bound is still eachSizeMiB * iterations; emit-non-function and environmentdata-empty now report their observation instead of asserting internally, and the test compares the payload).
• The stop-ordering de-flake: the 1ms interval no longer writes to the shared log, so terminate() cutting between Atomics.add and Atomics.store no longer leaves a torn 0 entry; the filter it used to need is removed with it.
• Subprocess assertion tightening: stdout/stderr are read concurrently with proc.exited and compared in one toEqual, with JSON.parse guarded on empty stdout so a crashing child shows its stderr.

Extended reasoning...

Overview

Test-only change to test/js/node/worker_threads/worker_threads.test.ts (~700 diff lines) plus three fixture files. Converts nearly every test to test.concurrent / describe.concurrent to overlap worker/subprocess startup latency, tightens subprocess assertions to the repo's {stdout, stderr, exitCode} shape, moves two subprocess tests in-process, adds one new test (resolveObjectURL on an eval worker's blob: URL), and de-flakes the worker stop ordering shared-log torn-write. No production code is touched.

Security risks

None. All changes are to tests and test fixtures; no auth/crypto/permissions paths, no new external inputs.

Level of scrutiny

Medium-high for a test-only change. The correctness question is not "does the code work" but "do any of the ~130 newly-concurrent tests share process-global state that serial execution used to hide". The PR description reasons through this carefully (the process.on('worker') listeners and process.emit override are kept serial at the top; the three latency-sensitive terminate with work in flight tests were reverted to serial after the first CI run caught them racing), and I did not find any remaining shared state — setEnvironmentData in the environmentData describe writes a key no other test reads, the FileHandle/MessageChannel tests each own their resources, and the moved-in-process tests own their workers.

Other factors

• The first CI run (build 98139, commit 2c11bfb) failed on 6 lanes due to the work-in-flight tests going concurrent; commit 07cf294 reverts those three to serial with a comment explaining why. The timeline does not yet show CI results for 07cf294, so I cannot confirm the final revision is green across all lanes.
• The stop-ordering de-flake removes the interval's put() call rather than fixing put() itself — a torn write from a once-fired teardown handler is still theoretically possible, but far less likely than from a 1ms interval, and the PR reports 60 clean runs under load after the change.
• The diff is large and the concurrency reasoning is subtle enough (already one round of CI-discovered flakiness) that a maintainer sign-off is appropriate before merging, even though I found nothing wrong.

[robobun]

On the remaining theoretical torn write in worker stop ordering: it cannot produce a false failure, which is why put() itself was left alone. In the process.exit() variant nothing interrupts the worker (the parent only posts go and waits), so the ready and exit-handler entries are always complete. In the terminate() variant, ready is written before the worker posts ready, so it is complete before the parent can even call terminate(); the only put() that terminate() can cut off is one from a handler running after the stop was requested, and that handler running at all is the bug the test exists to catch. A torn entry from it still bumps the count, so the test still fails, just with a 0 in place of the tag saying which handler it was. Leaving put() as add-then-store keeps that detection: the publish-after-write variant would instead drop a cut-off violation silently.

CI for 07cf294 is still running; the status comment above will carry its per-lane numbers when it finishes.

[robobun]

Correction to my earlier note on put(): a put() that terminate() lands inside necessarily started before the stop was requested (the termination is only delivered at the next trap check), so it can never be a handler that ran after the request, and there is no detection to preserve by keeping the count-first order. #38194 (open) makes that argument and hardens put() itself; this PR leaves put() untouched so that #38194 applies either way, and only stops the interval from logging, which is what the concurrency here needs regardless. The PR body's stop-ordering bullet now says this.

929043d also moves the eval leak bound to half the nominal leak size: with the leak simulated (URL.revokeObjectURL stubbed out) a release build reads 481 to 500 MiB of growth with this fixture shape, so the old 500 MiB bound would have let it pass; a healthy run reads about 0. Numbers are in the PR body.

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Inline comments:
In `@test/js/node/worker_threads/eval-source-leak-fixture.js`:
- Around line 18-24: Update the test function’s Worker "exit" handler to resolve
only when the exit code is zero and reject nonzero exits, while preserving
rejection through the existing "error" handler. This ensures the leak
measurement proceeds only after workers successfully evaluate and run the
supplied source.

In `@test/js/node/worker_threads/worker_threads.test.ts`:
- Around line 28-30: Update the timeout setup near setDefaultTimeout to import
isASAN from harness and use the extended 90-second timeout when either isDebug
or isASAN is true; retain the 10-second timeout for other builds.

🪄 Autofix

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

Plan: Pro

Run ID: 050238c6-88f1-49c6-835d-e16e3f3c984f

📥 Commits

Reviewing files that changed from the base of the PR and between 88a6398 and 929043d.

📒 Files selected for processing (4)

• test/js/node/worker_threads/emit-non-function-fixture.js
• test/js/node/worker_threads/environmentdata-empty-fixture.js
• test/js/node/worker_threads/eval-source-leak-fixture.js
• test/js/node/worker_threads/worker_threads.test.ts

[claude]

I reviewed this PR and didn't find any bugs. Because it's a large test-concurrency conversion (~130 tests, plus fixture semantics changes, two spawned→in-process moves, a halved leak bound, and the stop-ordering interval change that interacts with #38194), a human look would still be worthwhile.

What was reviewed:

• The two process-global tests (process.once("worker"), replaced process.emit) correctly stay serial and run first, before any concurrent test creates a Worker.
• The three in-process terminate with work in flight tests stay serial with a comment explaining why; the first CI revision's failure on release lanes when they were concurrent is accounted for.
• Subprocess assertions now read stdout/stderr before the exit code and compare as one object; JSON.parse calls are guarded so an empty stdout still shows stderr and the exit code.
• The stop-ordering interval no longer logs (avoiding torn writes and log overflow under a busy parent); put() itself is untouched so #38194 still applies cleanly.

Extended reasoning...

Overview

This PR converts test/js/node/worker_threads/worker_threads.test.ts (132→133 tests) from serial to mostly-concurrent execution, roughly halving its CI wall time on the ASAN lane (25.1s → 12.2s). The diff touches ~800 lines across the test file and three fixtures. Most hunks are mechanical (test( → test.concurrent(, describe( → describe.concurrent(), but there are several non-mechanical changes: two tests move from spawned subprocess to in-process, two tests are regrouped into new describe.concurrent blocks to preserve their per-test timeouts under prettier, three fixtures now report observations via stdout (JSON) instead of asserting internally, the eval-leak bound is halved based on empirical measurement of the leaking case, one new test is added for blob-URL revocation on worker exit, and the stop-ordering interval stops logging to avoid a pre-existing torn-write flake.

Security risks

None. This is test-only; no production code, auth, crypto, or permissions are touched.

Level of scrutiny

Medium-high. Although test-only, this file runs on every CI lane, and concurrency conversions have subtle failure modes — the first revision of this PR itself had to revert the three terminate with work in flight in-process tests to serial after they raced the workers' natural exit on release lanes. The author's analysis is unusually thorough (per-test rationale for serial vs. concurrent, measured leak bounds with the revoke stubbed out, 60-run flake verification of the stop-ordering fix, cross-referenced open PRs #38194 and #32867), and CI build 98250 passed on all lanes. But the sheer volume of tests converted, combined with the judgment calls (which tests stay serial, where the leak bound sits, the stop-ordering change's interaction with #38194), means a maintainer familiar with this file's flake history should confirm the concurrency choices.

Other factors

• Both CodeRabbit suggestions (reject nonzero worker exit in the leak fixture; scale the default timeout on isASAN too) were addressed in 81b7c3f and marked resolved.
• The bug hunting system found nothing.
• No test was removed or skipped; assertion count went from 379 to 374 because several two/three-call sequences collapsed into one toEqual over {stdout, stderr, exitCode}.
• The workerData is not unwrapped test's move from spawned to in-process changes what it observes slightly (it now runs inside the test process rather than a fresh one), but the assertion — that a web globalThis.Worker does not unwrap the node-worker envelope — is process-local and does not depend on a fresh main thread.
• The PR body notes a trivial merge with #38987 on the node:buffer import line.

[claude]

I reviewed this PR and the bug-hunting pass found no issues. The change is test-only, well-verified across CI lanes, and both CodeRabbit threads are addressed. That said, it's an ~800-line diff that reworks concurrency across ~130 tests, rewrites two subprocess tests as in-process, changes the eval-leak bound, adds a new blob:-URL revocation test, and adjusts the stop-ordering logger — enough moving parts that a human familiar with the worker_threads suite should confirm the concurrency partitioning before merge.

What was reviewed:

• Concurrency partitioning: the two process.emit/process.on('worker') tests are serial and run first; the three in-process terminate with work in flight tests stay serial with a comment explaining why; setEnvironmentData in the concurrent describe does not conflict with any other test's assertions.
• Fixture rewrites emit structured JSON that the test asserts on; the leak fixture rejects nonzero worker exits so a broken worker cannot read as healthy.
• The leak bound at eachSizeMiB * iterations / 2 (250 MiB) sits between the measured healthy (~0) and leaking (~480–515) readings; the old bound at 500 was not usable.
• Stop-ordering interval no longer logs, removing the torn-put() slot the filter used to hide; the intervalTick filter and TAG entry are both removed.

Extended reasoning...

Overview

Test-only change to test/js/node/worker_threads/worker_threads.test.ts (766 lines changed) plus three fixture files. Converts nearly every test to test.concurrent/describe.concurrent to overlap worker/subprocess startup; tightens subprocess assertions to a single {stdout, stderr, exitCode} toEqual; moves the two process-global tests (process.emit override, process.on('worker')) to the top of the file so they run before any other test has created a Worker; keeps the three in-process terminate with work in flight tests serial after the first CI revision showed them racing worker natural exit on release lanes. Adds one new test (blob: URL revocation on eval-worker exit via resolveObjectURL). Reworks eval-source-leak-fixture.js to build one 100 MiB block-comment source, report {eachSizeMiB, iterations, deltaMiB} as JSON, and reject nonzero worker exits; the test now asserts deltaMiB < 250 instead of < 500. Two subprocess tests (terminating a worker stops the workers it spawned, workerData is not unwrapped for a non-node globalThis.Worker) become in-process. The stop-ordering interval stops logging so a busy parent cannot fill the shared log or leave a torn put() slot.

Security risks

None. Test-only; no runtime code touched. Fixtures do not read untrusted input.

Level of scrutiny

Medium-high. It is test-only and CI-green on every lane (build 98250: 133 pass), but marking ~100 tests concurrent in a file that mixes in-process Workers, MessageChannels, and process-global state (process.emit, setEnvironmentData, process.on('worker')) is exactly the kind of change where a missed shared-state dependency shows up as a rare flake weeks later rather than in the PR's own runs. The author has been careful — the process-global tests are explicitly serial and first, the work-in-flight serial revert came from real CI feedback, and 60 local runs of the stop-ordering pair under load passed — but the sheer number of tests re-partitioned, plus several substantive rewrites (in-process conversions, leak-bound halving, new test, fixture-output restructuring), warrants a maintainer sign-off.

Other factors

• Both CodeRabbit suggestions (reject nonzero worker exit in the leak fixture; scale timeout on isASAN) are applied in 81b7c3f and the threads are resolved.
• The PR description documents interaction with two open PRs (#38194, #32867) and leaves put() untouched so #38194 applies cleanly.
• No prior claude[bot] review on this PR.
• Test count 132 → 133; expect count 379 → 374 (multi-assert sequences collapsed into single toEqual objects).
• File wall time on the ASAN lane: 25.1s → 12.2s.