[dylan-conway]

What does this PR do?

Bun reports Node.js 26.12.1 since #46533, but OutgoingMessage / ServerResponse still behaved like 26.3.0 in how a message finishes. This ports the two upstream changes to that area:

• nodejs/node#64847 (v26.7.0), "http: fix writableFinished and 'finish' after write errors"
• nodejs/node#65466 (v26.8.0), "http: improve performance with known-length calls to end()". It moves onFinish onto the one write of an end(chunk) of known length, which is observable: without it res.end("hello"); res.destroy() over emit('connection') behaves like 26.7.0 (no 'finish') and not like 26.12.1.

Reference: lib/_http_outgoing.js v26.12.1, L1233-L1276.

Behaviour

	before	now, as in Node 26.12.1
writableFinished	computed from what is left to write	a flag, set just before 'finish'; ServerResponse has no getter of its own
end(cb)	a 'finish' listener, called with no argument, after the other listeners	queued, called before 'finish' with null, or with the error that kept the bytes from leaving
a second end(cb) before 'finish'	ERR_STREAM_ALREADY_FINISHED	queued, gets null; that error only comes once the message has finished
the connection dies while an ended response drains	'finish', callback, 'close'; the request is not aborted	no 'finish'; the callbacks get the error, writableFinished stays false, stream.finished() reports ERR_STREAM_PREMATURE_CLOSE, the request is aborted
end(cb) after a failed flush	ERR_STREAM_ALREADY_FINISHED	the same error again, on the next tick
end(cb) with nothing left to write, after the connection closed	no callback, no 'finish'	cb(null) and 'finish' when the earlier writes have left; the error and no 'finish' when part of one never did
end(cb) that throws ERR_HTTP_CONTENT_LENGTH_MISMATCH, then the rest of the body and another end()	the first callback is lost	it runs with the others (not for a chunk that follows the head, which write_() rejects first)
res.destroy() inside the end() callback	the response has no socket any more, the connection stays	the response still has its socket, the connection is closed
res.destroy(err) or req.socket.destroy(err) after a synchronous end(cb), before 'finish'	'finish', callback, 'close'	cb(err), no 'finish', the request is aborted, 'close'; res.socket is the socket until 'finish'

Where

• internal/http.ts: kWritableFinished / kEndCallbacks / kFlushError, queueEndCallback(), flushEndCallbacks(), getEndCallbackError(), onFinish(). They live here and not in _http_outgoing.ts so that hasServerResponseFinished() and the server can use them without widening what require("_http_outgoing") exports.
• _http_outgoing.ts: the getter, the constructor slots, end(), maybePrepareFinalChunk(). The client needs nothing else, it is the same code as Node's.
• _http_server.ts: the native path now ends in the same onFinish(). kPendingFinish is a flag and no longer holds the callback. The socket's close path fails a draining response instead of finishing it. A queued pipelined end() queues its callback when it is called, like Node. A response that ended inside the handler is detached from its socket when the handler returns, so the socket's close path no longer finds it: if its flush then fails, finishResponse() hangs the abort of the request and the 'close' of the response on the 'close' of the socket, where Node does both.
• internal/http1_server_fallback.ts (emit('connection'), http2 allowHTTP1): the error of the last write is carried to onFinish(); an unsent head and a string body leave in one write, like Node's _send(); the callback of a write to a socket that has already failed gets that error.
• The 'http' performance entry and the http.server.request trace span now end at 'prefinish', where ServerResponse#_finish() ends them. They hung off 'finish', so a failed flush would have lost them.

A reset that this order exposed (packages/bun-usockets/src/context.c)

end() callbacks now run before the 'finish' listener that ends a Connection: close socket, so a handler that calls process.exit() from the callback exits with the connection still open, as in Node. A plain exit is fine: the kernel delivers what it holds, then a FIN. The teardown of a VM (every Worker, and the main thread under BUN_DESTRUCT_VM_ON_EXIT, which the ASAN lane sets) goes through us_socket_group_close_all() instead. That asks for a clean shutdown, a TLS socket defers it until the peer's close_notify, and the sweep, which cannot wait, then closed it with CONNECTION_RESET: SO_LINGER {1, 0}, which drops what the kernel has not delivered yet. A TCP socket in the same loop gets a FIN. It now uses FAST_SHUTDOWN, which libusockets.h documents for exactly this ("data already written must still drain (not RST)"). Close handlers treat both codes alike; only codes above 2 are an errno. One case keeps the reset: a socket that still holds ciphertext in userspace (ssl_close_after_spill) loses it with the close, and a FIN would pass the cut for the end of the stream.

This is not new with the reordering. 1 MB from an https server whose handler exits from the end() callback, to a client that reads nothing until the server is gone:

server	Connection: close	keep-alive
Bun 1.4.4, in a Worker	complete	164 KB, ECONNRESET
this branch before the fix, in a Worker	complete	131 KB, ECONNRESET
this branch before the fix, BUN_DESTRUCT_VM_ON_EXIT=1	131 KB, ECONNRESET	131 KB, ECONNRESET
this branch	complete	complete
Node 26.12.1, in a Worker	complete	complete

strace of the server shows all 265,641 bytes of the tls-syscall-fault.test.ts response sent before the callback in both orders, so the callback is not early; the only difference was setsockopt(SO_LINGER, {1, 0}) before close().

Deliberate differences from Node

• After an end() callback that throws, the callbacks behind it and 'finish' still run. Node skips them, and then resOnFinish never runs: with an uncaughtException handler installed, the response never closes and the next request on that keep-alive connection is never answered (measured on 26.12.1). The exception is still an uncaught exception, thrown again on the next tick. Before this PR it was turned into an 'error' event on the response, which Node never did.
• Over emit('connection'), a head and a string body without an encoding are written as UTF-8, which is what Content-Length counts. Node leaves the string to the socket: with defaultEncoding: "latin1", res.end("\xe9") sends one byte under Content-Length: 2.
• end(cb) after a socket from emit('connection') closed while it still held a write gets an error. Node never calls back there.
• The callbacks of a response that is still queued behind a pipelined one get an error when the connection dies. Node never calls them. Bun already did this for the first end() callback and for write callbacks; it now covers every queued end() callback.

Still different, not changed here

• test-stream-pipeline.js stays at its 26.3.0 version. Upstream's new assertion is about a GET whose unframed body arrives as the start of a next request: llhttp reports HPE_INVALID_METHOD at once and the socket is destroyed before res.end(). Bun sends the 200 first and reports the parse error after it, so that response really does finish and pipeline() succeeding is the right outcome.
• When a connection dies mid-drain the error is ERR_STREAM_DESTROYED (what Bun's write callbacks get) where Node has libuv's ECANCELED, and on the native path 'aborted' comes before the callbacks, as it already did for write callbacks.
• end() does not flush corked chunks before the last chunk: already so on main, node:http: deliver every chunk that a corked OutgoingMessage accepts #44676 is open for it.
• strictContentLength itself, all as on main and a separate subject: it is not enforced over emit('connection') and http2 allowHTTP1, nor when end() is called on a response still queued behind a pipelined one, nor on a connection that has closed (Node throws there too; here a body that the connection saw too little of only reports no 'finish', because the closed handle has not counted what write_() counts and then drops); and a first end(chunk) that mismatches is neither sent nor counted, where Node does both before it throws, so what a caller can do after catching it differs.
• An end() or write() callback that fails because the connection died does not run in the AsyncLocalStorage context of its call. Same as main.
• Over emit('connection'), a head that is written on its own is UTF-8 where Node's _send() uses latin1 for most of them. Already so on main; only header values beyond ASCII can tell.

How did you verify your code works?

The same script on both runtimes. Output of this branch, byte for byte that of Node 26.12.1, and different from Node 26.6.0 and Bun 1.4.4:

script

const http = require("http");
const log = [];
const d = e => (e === null ? "null" : e === undefined ? "undefined" : e.code);
const server = http.createServer((req, res) => {
  log.push(`before end: writableFinished=${res.writableFinished}`);
  res.on("finish", () => {
    log.push(`'finish': writableFinished=${res.writableFinished}`);
    res.end(e => log.push(`end(cb) after finish -> ${d(e)}`));
  });
  res.end("hello", e => log.push(`first end(cb) -> ${d(e)} writableFinished=${res.writableFinished}`));
  log.push(`after end: writableFinished=${res.writableFinished} writableEnded=${res.writableEnded}`);
  res.end(e => log.push(`second end(cb), same tick -> ${d(e)}`));
});
server.listen(0, "127.0.0.1", () => {
  const req = http.request({ port: server.address().port, host: "127.0.0.1", method: "POST" }, res => {
    let body = "";
    res.on("data", c => (body += c));
    res.on("end", () => {
      log.push(`client got ${JSON.stringify(body)}`);
      server.close();
      console.log(log.join("\n"));
    });
  });
  req.on("finish", () => log.push(`client 'finish': writableFinished=${req.writableFinished}`));
  req.end("body", e => log.push(`client end(cb) -> ${d(e)} writableFinished=${req.writableFinished}`));
  log.push(`client after end: writableFinished=${req.writableFinished}`);
});

client after end: writableFinished=false
client end(cb) -> null writableFinished=true
client 'finish': writableFinished=true
before end: writableFinished=false
after end: writableFinished=false writableEnded=true
first end(cb) -> null writableFinished=true
second end(cb), same tick -> null
'finish': writableFinished=true
end(cb) after finish -> ERR_STREAM_ALREADY_FINISHED
client got "hello"

Event traces. 81 scenarios (http and https server, client, standalone messages, emit('connection'), pipelining, destroy at every stage) run on Node 26.6.0, 26.7.0, 26.12.1 and on Bun with and without this change. Bun gives the trace of 26.12.1 in 57 of them, up from 9. The other 24 are the differences listed above, plus two that main already has: write callbacks are called with no argument instead of null, and a TLS write completes in the same tick.

Against the source. Every hunk of the two upstream commits has its counterpart, and flushEndCallbacks() to end() read line for line like v26.12.1 but for the try/catch above and the block of v26.9.0's write coalescing. ServerResponse#end() on a native connection is Bun's own, so each term of Node's end() was turned into a case (15 of them: each framing, no head, an empty or a dropped chunk, a bodiless status, a destroyed response, a finished one, a strict length) and run on Node 26.12.1 and here over http, https and emit('connection'). 15, 14 and 13 of 15 give Node's trace; the rest are the TLS tick and strictContentLength over emit('connection'), both listed above. main gives 8 of 15 over http and over emit('connection').

Vendored tests, updated verbatim from v26.12.1. All three fail without the change and pass with it:

• test-http-outgoing-end-multiple.js
• test-http-outgoing-writableFinished.js
• test-http-server-response-standalone.js

Bun's tests. node-http-backpressure.test.ts and node-http-server-abort-events.test.ts also run on real Node (83/83 and 104/106 on 26.6.0). The 20 tests in them that this change broke are the same ones that fail on Node 26.12.1, with the same actual values, so their expectations now come from 26.12.1. The tests where a client goes away now branch on whether the kernel left a backlog, since a response that was flushed finishes and one that was not does not (Windows can take the whole body at once).

• node-http-req-complete.test.ts expects writableFinished: false on both runtimes. 28/28 under Node 26.12.1 as well.
• New: a second end(cb) runs in call order, res.destroy(err) after end(), an ended queued response destroyed with an error, end(cb) once a whole Content-Length body is out and the client is gone, write callbacks before end() callbacks on a dying emit('connection') socket, the performance entry after a failed flush, an end() callback that throws (native path and http2 allowHTTP1), res.destroy(err) and req.socket.destroy(err) in the handler, after it, and on a tick between it and 'finish', end() on a dead socket under each framing, res.destroy() in an end() callback with half of the request body still to come (the request is not aborted), a hand-made ServerResponse closing after 'finish', a socket with another defaultEncoding, the callbacks of an end() that mismatched under strictContentLength, end() on a destroyed response that is short of its strict length (no 'finish') or has all of it (finishes), a whole strict body whose last write() or end(chunk) comes after the connection closed (no throw: in the request's 'aborted' listener, right after req.socket.destroy(), and after res.destroy() ahead of the head), end(cb) after a connection closed with written bytes unsent (a large write that waits for its drain, a small one left in the socket's buffer, by fault injection, and one that a socket from emit('connection') still holds) and after its backlog had drained, the encoding of a head that leaves with a string body.
• Twelve ways to destroy a response around a synchronous end(cb) were traced on Node 26.12.1, Bun 1.4.4 and this branch. Every one closes the response, with Node's set of events. Seven match Node's order exactly; in four only the position of the socket's own 'error' or of 'aborted' differs. The twelfth is the hand-made ServerResponse, which sends nothing in Node.
• Every updated or new test fails on main. Most of the fixes were also undone one at a time, and each of those is caught by a test.

The reset. New in tls-syscall-fault.test.ts: a connection torn down with a batch tail in userspace is reset. tls-syscall-fault.test.ts ("the end() callback waits for the batch tail in userspace") failed 5 of 5 attempts on the ASAN lane of the first build. With BUN_DESTRUCT_VM_ON_EXIT=1 it fails 3 of 3 times locally without the context.c change and passes 3 of 3 with it. New in node-https-server.test.ts: a response is delivered although its Worker exits with the connection open (4 of 4 with the change, 0 of 4 without, 0 of 3 on 1.4.4; Linux only, since the kernel has to take the whole body from a socket nobody reads). 132 test files around TLS sockets, listeners, servers, workers, WebSocket and http2 show no difference between the binaries with and without the change.

Not this PR's. proxy-test-utils.ts carries the change of #46170, for ws-proxy.test.ts on Windows 2019 x64, which also fails on main.

Sweep. All 522 vendored test-http-*, test-https-*, sequential/test-http*, test-http2-compat-*, test-http2-https-fallback*, test-stream-pipeline* and test-stream-finished.js files on a debug build: no new failure against the same binary with main's builtin JS. Three files fail now and then when four run at once on four cores, and just as often with main's JS: test-http-abort-queued.js (47 of 96 on main, 45 of 96 here, six at once), test-http-outgoing-end-cork.js (17 of 64, 17 of 64), test-http-agent-free-socket-data-guard.js (15 of 64, 11 of 64). Each passes alone.

test-https-timeout.js, which timed out when only the flag was tried in #46533, is not affected by this: with req.setTimeout(1) it hangs 3 of 3 times on Bun 1.4.4, on main and on this branch, and passes on Node. The request times out before the TLS handshake is done, and after req.destroy() and server.close() the process does not exit. That is a separate bug.

---

Generated by Claude Code

[robobun]

^{Updated 10:59 PM PT - Oct 24th, 2026}

❌ @claude, your commit 0094ace has 1 failures in Build #132404 (All Failures):

• package.json - timeout on 🍎 any aarch64

---

🧪   To try this PR locally:

bunx bun-pr 46675

That installs a local version of the PR into your bun-46675 executable, so you can run:

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• src/js/node/_http_server.ts
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Walkthrough

HTTP response completion now queues end() callbacks and reports flush outcomes through shared helpers. Server pipelines and fallback writes pass failures into completion handling. Tests cover callback ordering, disconnects, write failures, and TLS shutdown behavior.

Changes

HTTP response lifecycle

Layer / File(s)	Summary
Outgoing message completion src/js/internal/http.ts, src/js/node/_http_outgoing.ts, test/js/node/http/node-http-req-complete.test.ts, test/js/node/test/parallel/test-http-outgoing-*.js, test/js/node/test/parallel/test-http-server-response-standalone.js	Shared helpers track completion and flush errors. OutgoingMessage.end() queues callbacks and reports final-write outcomes. Tests cover repeated end() calls, write failures, writableFinished, and string-body/header encoding.
Fallback socket writes src/js/internal/http1_server_fallback.ts	Eligible response heads and string bodies can be written together. Final-write errors pass through flush handling to drained-response completion.
Server response and pipeline completion src/js/node/_http_server.ts, test/js/node/http/node-http-backpressure.test.ts, test/js/node/http/node-http-server-abort-events.test.ts, test/js/node/http/node-http.test.ts	Server drains and queued responses use shared callback handling. Tests cover event order, disconnects, write failures, pipelining, and throwing callbacks.
TLS socket shutdown behavior packages/bun-usockets/src/context.c, test/js/node/http/node-https-server.test.ts, test/js/node/tls/tls-syscall-fault.test.ts	The socket shutdown fallback selects a close code based on deferred TLS close state. Tests cover worker exit during an HTTPS response and teardown with unsent ciphertext.

WebSocket proxy renegotiation

Layer / File(s)	Summary
Wait for proxy message write test/js/web/websocket/proxy-test-utils.ts	The renegotiation test helper starts renegotiation from the socket write callback for the preceding message.

Possibly related issues

• oven-sh/bun#43381 — The issue covers socket teardown, pending write errors, and HTTP completion events. This change updates those callback and socket-close paths.

Suggested reviewers: robobun

Priority: Normal

Merge Risk: Low · up to 8fd16

The response test can stall and leave its socket open if completion fails. This is a bounded test-reliability risk, not a demonstrated production failure.

Pre-merge checks: 4

Check name	Status	Explanation
Title check		The title clearly and concisely summarizes the primary change: making writableFinished a flag and reporting flush results to end() callbacks.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.
Description check		The pull request description includes both required sections, explains the implementation and behavioral changes in detail, and documents extensive verification results, known differences, and out-of-…

Full details: Description check

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[dylan-conway]

Build #131627 had two failing test files.

test/js/node/tls/tls-syscall-fault.test.ts on 13 x64-asan: this PR's, fixed in 1686c58. The fixture calls process.exit(0) from the end() callback. That callback now runs before the 'finish' listener that ends a Connection: close socket, so the connection is still open at exit, and under BUN_DESTRUCT_VM_ON_EXIT=1 (set on that lane) the teardown closed the TLS socket with SO_LINGER {1, 0}. The callback itself is not early: strace shows every byte sent before it. A Worker that exits with a keep-alive https connection open loses data the same way on 1.4.4. Details and numbers are in the description.

test/js/first_party/ws/ws-proxy.test.ts on 2019 x64: not this PR's. "a message sent during a TLS renegotiation arrives after it" gets the records of the real node origin as [22, 23] instead of [23, 22]. No code of this PR runs in that process. Of the 154 builds from #131480 to #131633, 20 others have the same test failing or retried (18 of them name that lane), among them main (#131489). #46170 fixes the origin script; cc8ad68 carries the same change, and it drops out once main has it.

Build #131973 (1f54f1e) is green; it was red for three hours without a test failure. Its two darwin any x64 - test-bun jobs expired in the queue without ever starting, at 12:05 UTC and again, as retries, at 14:05 UTC; the third pair got machines and passed at 15:04 UTC. Other branches' builds show the same for that lane (#131990, #132030, #132050). The other 179 jobs passed, Windows and ASAN among them, and there is no failure annotation. #131671 went the same way.

Build #132404 (0094ace): one darwin any aarch64 - test-bun shard failed before any test ran. Not this PR's. On agent darwin-aarch64-26.6.2-1 the runner's own bun install for the root package.json timed out four times, the one for test/package.json timed out once and then took 116 s for 13 packages, and the job ended there with exit status 2. The other shard of that lane ran the same binary on another machine and passed, like all 179 other jobs, both darwin any x64 - test-bun shards among them. The commit before it, e3fb2f9, passed #132362 completely, and 0094ace only changes one condition in src/js/node/_http_server.ts and a test file. There is nothing to fix in the repository. The job needs a retry, which I cannot trigger from here.

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Inline comments:
Review comments at @packages/bun-usockets/src/context.c:
- Line 123: Update the forced-close path around us_internal_socket_close_raw so
the socket remains writable until any TLS ciphertext spill is handled,
preventing us_internal_ssl_detach from discarding it; alternatively, explicitly
document and test that forced group teardown may discard spilled ciphertext.

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[claude]

Beyond the inline findings, I also checked the us_socket_group_close_all_ex change in packages/bun-usockets/src/context.c: it goes through us_internal_socket_close_raw, which never defers for any code (the TLS ssl_close_after_spill wait only exists on the us_socket_close path), so swapping CONNECTION_RESET for FAST_SHUTDOWN only drops the SO_LINGER {1,0} branch in socket.c and cannot leave s->group dangling. I also looked at flushEndCallbacks dropping later callbacks when one throws — that matches Node's own onFinish loop, so it is not a divergence.

Extended reasoning...

The PR reworks node:http's OutgoingMessage/ServerResponse finish semantics (writableFinished flag, queued end() callbacks with flush errors, maybePrepareFinalChunk) across the native handle path, the Duplex fallback path and the pipelined-queue path, plus a one-line close-code change in usockets. It touches no auth, crypto or injection surface, though it changes TLS teardown ordering during VM destruction. Four confirmed findings were posted inline, and the change is large and semantically subtle, so a human review is still needed; this note only records the two concerns examined and ruled out.

Findings marked 🟡 are optional suggestions and need no follow-up push.

Additional findings (outside the current diff — GitHub can't attach inline comments there):

• 🟡 src/js/node/_http_server.ts — An async handler that calls res.destroy() from its end() callback now sees the request emit 'aborted' (and 'error' when listened) after the response was fully delivered; the base left the connection open and the request untouched. res.destroy at src/js/node/_http_server.ts:4084 now reaches the live socket, #closeHandle at :1832 captures the response, and #onClose at :1909 picks it up because res.destroyed is true. When the request body was never consumed, req.destroyed is still false at :1926, so :1930 destroys it with ConnResetException('aborted'). Fix: a response that finished (kWritableFinished or 'finish' already emitted) must not count as a pending abort; skip the :1926 branch for it, as Node's resOnFinish shifts it out of state.incoming before socket close.

  Why this was flagged

  Trigger: an async request handler (dispatch returned a promise, so the dispatcher did not detach at :1133) handles a request with a body it never reads, then calls res.end(body, cb) and inside cb calls res.destroy(). cb runs from onFinish before 'finish', so res[kSocket] is still set and :4084-4086 destroys the real socket; :4081 also aborts the handle, so the unread body never arrives and req never reaches 'end'. #closeHandle at :1832 stores res as #pendingAbortMessage. 'finish' then runs emitResponseFinish, which dumps the request and detaches the socket, but the native close later enters #onClose at :1909 with pending.destroyed true, so message is the finished response and req is its request. :1926 finds req not destroyed and :1930/:1932 destroy it with 'aborted'. The base (emitResponseFinished called the callback after 'finish', socket already detached) hit the :4088 nextTick(emitCloseNT) branch instead, never touched the socket, and the request was never aborted.

  Verification: Triggers when an async request handler serves a request whose body it never consumed and calls res.destroy() from inside its res.end(body, cb) callback. src/js/node/_http_server.ts:1909 resolves to the response, and :1926-1933 runs req.destroy(). On the base, the request was left untouched. The "inside the end() callback" test only covers a synchronous handler.

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Actionable comments posted: 1

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Inline comments:
Review comments at @test/js/node/http/node-http.test.ts:
- Line 8015: Update the promise in the test to reject on response or socket
errors and premature closes, registering the response handlers inside the
`http.createServer` request handler where the `ServerResponse` is created. Wrap
the await in `try/finally` so `socket.destroy()` always runs, including when the
promise rejects.

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Review info

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• Source mode: Auto
• Repository: oven-sh/bun
• Branch: claude/brave-cannon-pimi6e
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• Commit: 25562e8
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Commits

Reviewing files that changed from the base of the PR and between d907b59 and 25562e8.

Files selected for processing: 2

• src/js/internal/http1_server_fallback.ts
• test/js/node/http/node-http.test.ts

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[claude]

Code review completed

Nothing new to post: everything this review found is already covered by existing comments on this pull request or didn't merit a separate one.

Still open from earlier reviews (2):

• 🔴 src/js/node/_http_server.ts:3601 — A handler that calls res.end(cb) after the connection closed with its body still unsent now gets cb(null), 'finish' and…
• 🔴 test/js/node/http/node-http-backpressure.test.ts:1426 — On a kernel that takes the whole 8 MB write (Windows, per this file's own comment at line 461), this test's child never…

If you have decided not to act on one of these findings, resolve its thread (a reply alone leaves it open) and the next review stops counting it. To review this commit again now, use Re-run on its "Claude Code Review" check.

[claude]

Code review completed

Nothing new to post: everything this review found is already covered by existing comments on this pull request or didn't merit a separate one.

[claude]

Nothing blocking. The comments below are optional suggestions. There is no need to push a fix for them before merging.