[robobun]

Problem

• A socket.write(chunk, cb) that waits for the socket runs its callback, 'drain' and 'finish' with the AsyncLocalStorage store of connect() or listen(). Node 26.3 uses the write's store. On a keep-alive connection that is another request's.
• The write slot in src/js/node/net.ts (kwriteCallback) kept the bare callback. Socket events complete it, in the context that opened the socket (src/runtime/socket/Handlers.rs:173).

Fix

• _write binds the waiting callback to its own async context (waitedWrite). What is queued behind that write completes there too, as in Node.
• The same rule covers TLS end() before the handshake, 'upgrade' and CONNECT sockets, and ServerResponse.
• 'close' stays where the socket's events run.
• Verified: nine fixtures under Node and Bun (66 rows fail on main), net-syscall-fault.test.ts, module-graph-net-write.test.ts. Self-reviewed: 36 concerns raised, 33 addressed.

Background

• The write slot holds the callback of a write that the kernel took part of. Socket events call it.
• runInSameGraph never installs a context of another Bun.ModuleGraph than the socket's. Those cases behave as on main.
• Considered a { callback, frame } record: every reader of the slot changes. A native write request adds a branch per drain on every socket.

Downsides

• A waiting write costs one bound function (96 B). A socket whose write completed in another context keeps 160 B. Binary: +4.6 KB.
• A reset or a bad TLS record that fails a waiting write reports 'error' in the write's store. Main used the socket's.
• ClientRequest 'drain' runs in the write's store. 1.4.0 to 1.4.3 used the request's.

Notes

The rule. A write that waits for its handle completes in the async context in which _write handed it to the handle. The stream issues a queued write from the completion of the write before it, so a queued or corked write, an end() callback and 'finish' complete in the context of the write they are behind. A write issued while the socket connects is issued from 'connect'. This is what Node's write request does (lib/internal/stream_base_commons.js, createWriteWrap and onWriteComplete). All of it was measured against Node v26.3.0. The fixtures also pass on Node 24.22.0 and 26.12.0.

Rows against Node 26.3 (Linux x64, debug build, main's builtins against this branch's).

Probes	Rows	Differ on main	Differ on this branch
node:net and node:tls sockets (12 scripts)	147	78	9
ServerResponse, 12 write and end orders, listen()	36	29	0
ServerResponse, same orders, emit("connection")	36	34	0
ClientRequest on a reused keep-alive connection	36	23	0
Teardown with a write waiting, 8 orders, client reconnects from 'close'	75	4	0
The same over TLS, 4 orders	32	2	0

No row of these that equals Node on main differs on this branch. The 9 rows that remain are the same on main: 'close' after an explicit destroy() runs where destroy() was called (4 rows, Node: where the socket was opened), the events of an accepted socket run in the store of listen() (2), a TLS handshake that fails under a write reports 'error' before the write callback and where the socket was opened (2), and 'close' after a small end() behind the peer's FIN (1).

Two cases outside these probes move off main's value. Both are the 'error' of a waiting write that fails for a reason the socket read, and both follow from the write callback being what destroys the socket:

• A peer's reset with no 'error' listener: the uncaught exception carries the store of the write. Node gives the store of the socket when the socket was reading, and the store of the write when it was not.
• A TLS record that cannot be decrypted: 'error' runs in the store of the write. Node reports it where the socket's events run and does not fail the write.

What changes, by file.

• net.ts: waitedWrite at the three places where _write leaves the callback in the slot. The slot still holds a function, and every reader of the slot calls it as before, in the same order. A write that a TLS wrap holds until its handle is attached goes to the handle in the context of the write. When a write that waited completes in another context than the socket's events, the socket keeps the context of its events (kEventFrame), and a private AsyncLocalStorage holds that record while the completion runs. A destroy() of that socket that the completion leads to (a failed write, an end() behind it) schedules 'close' in the context of the events (scheduleClose). Another socket that the callback destroys, and a destroy() that comes after the write, emit 'close' where destroy() was called, as on main. The socket keeps no context of a write. SocketHandlers.error returns after a failed write destroyed the socket, so an adopted fd emits one 'error' (the repro of node:net: emit 'error' once when a buffered write on an adopted fd fails #43038).
• tls.ts: a _final that waits for the handshake runs in the context of end().
• _http_server.ts: the tunnel socket of 'upgrade' and CONNECT binds its waiting callback. A ServerResponse keeps the context of the first write that reported backpressure (kWaitingWrite). 'drain', the write callbacks, the 'finish' of an end() behind it, and their failure at close run there. Node corks a response for the rest of the tick, so an end() in the tick of that write takes its place. On the 36 rows of the default path, main had 7 right and this branch has 36.
• _http_client.ts, http1_server_fallback.ts: the re-entry of a saved context for 'drain' is removed, because the socket's 'drain' now carries the write. It stays for a socket of another Bun.ModuleGraph. The fallback fails the callbacks that wait, at close, through the same kWaitingWrite rule as the native path.

Bun.ModuleGraph. A context of another graph than the socket's is never installed by this change. The stream's own work (the next write, the shutdown, 'close') would go with a graph that only wrote, and a disposed graph drops it: a host socket then never closes, and a host http.Agent never serves its next request. So those cases run exactly as on main. Where main entered the request's or the response's context for 'drain', it still does when the socket is another graph's. This rule (runInSameGraph, isInAnotherGraph in internal/async_context_frame.ts) is new and needs a yes from the owner of Bun.ModuleGraph.

Measurements.

• A write that completes in the call: the text of _write up to the park is the same, apart from the branch for a send that the kernel rejects and the branch for a write held by a TLS wrap. 80,000 echo writes park 0 times.
• Per socket that never parks, or whose writes complete in the context of its events: no new property. Out-of-line slots are 16/16 (client), 17/32 (accepted), 46/64 (TLS client) on both builds.
• Per socket whose write completed in another context: one record of 32 B and one property (a client socket goes from 16/16 to 17/32 out-of-line slots, +128 B). The record holds the context of the socket's events, not of the write.
• Per parked write: +1 bound function while it waits (heap +96 B to +100 B per parked write over 1,000 parked writes) and nothing after it completes. Main: +0.
• Per completion in another context than the event's: one AsyncLocalStorage.run() and 2 host calls of the graph check. 0 host calls without AsyncLocalStorage or when the write and the socket have one context. internal/async_context_frame is not loaded by a program that uses node:net without AsyncLocalStorage.
• Per socket close: one read of a module variable, which is unset until a write has completed in another context. After that, one getStore().
• How often a write parks: 16 of 1,024 writes (64 MiB in 64 KiB chunks), 0 of 600 after connect, the same on both builds.
• Socket calls (LD_PRELOAD counter): 4,000 send for 2,000 echo round trips and 400 send for 200 parked writes, on both builds.
• Bundled builtins (release): six modules, +4,574 B, measured before main removed the http2 allowHTTP1 proxy (a seventh module, +162 B more then). Release binaries (--lto=off) of the first revision: text 101,811,313 B to 101,815,686 B (+4,373 B) for +4,357 B of bundle, file 102,463,288 B to 102,467,384 B.
• Wall clock, release builds of the first revision, 24 interleaved runs each: 200,000 echo round trips, median 1,658.6 ms on main and 1,669.8 ms here (+0.7%, minimum 1,487.0 and 1,464.1 ms). 256 MiB in 64 KiB chunks, median 263.4 ms and 259.3 ms. Both are inside the run-to-run spread.
• perf, valgrind and strace are not installed in the build container, so there is no instruction count.

Tests.

• Fixtures in test/js/node/async_hooks/async-context/, which AsyncLocalStorage-tracking.test.ts runs under Node and Bun on every lane: net-socket-write-waits, tls-socket-write, tls-wrap-socket-write (STARTTLS), http-upgrade-socket-write, http-connect-socket-write, http-clientrequest-write, http-serverresponse-write (both listen() and emit("connection")), http2-allowhttp1-socket-write. Each checks that its write waited, and fails by name if its socket reports an error or closes early. net-socket-write is as on main.
• net-syscall-fault.test.ts (debug and ASAN builds): the cases that need an injected short or failed send, and the Bun-only rows of 'close' (another socket, a later destroy(), a peer's reset on an accepted socket).
• test/js/bun/module-graph/module-graph-net-write.test.ts: the Bun.ModuleGraph cases.
• 23 mutations, each of which reverts one clause of the change in the bundled builtins: the fixtures and tests catch all 23 (run before the last two rebases).
• Also ran, with no failure that main's builtins do not show: node-http-backpressure, node-net, node-net-server, node-tls-server, node-tls-connect, tls-syscall-fault, node-http, node-https-server, node-http-connect, node-http-upgrade-body, node-http-with-ws, node-http-server-close-drain, node-http-server-socket-end-drain, node-http-agent-free-socket, node-http-syscall-fault, node-http2-upgrade, module-graph-io, module-graph-callbacks, AsyncLocalStorage, async_hooks.node, and 25 of Node's test-net-*, test-tls-* and test-http-* tests.
• Windows takes a write of any size at once, so no write waits for its socket there. The two fixtures that only test such writes (net-socket-write-waits after its first scenario, http-serverresponse-write) do nothing on Windows. macOS was not run locally.

Self-review, not changed.

• A TLS handshake that fails under a waiting write: Node fails the write first, so 'error' runs in the context of the write. Here 'error' still comes first and runs where the socket was opened, as on main. The write callback now runs in the context of the write, and the TLS fixture pins that row. The order is a separate defect.
• The TLS cases that need an injected fault stay in net-syscall-fault.test.ts, next to the slot they test. The cases that need no fault moved to the fixtures.
• A callback that throws: the exception of a parked write's callback still leaves through the socket's error handler, as on main. Node reports it as an uncaught exception and keeps the socket open.

Still different from Node, and not part of this change.

• node:http2 stream writes: the write callback and 'drain' see no store.
• child.stdin (an fs.WriteStream, no write slot), a dgram send that the kernel refused, session.settings(cb), and an IPC send(cb) that did not fit the pipe.
• Listeners on req.socket of a reused http.Agent connection run in the store of the first request.
• request.socket.end() with a response write waiting, on the default server path: the connection never closes (Bun 1.4.3 too). The fixture runs that scenario for emit("connection") only.
• The tunnel socket of 'upgrade' and CONNECT emits a second 'drain' from its native drain event, as on main. The first one, from the stream, now runs in the context of the write. The draft node:http: gate 'drain' on the bytes of the handle, give write callbacks to the stream #46014 removes the second one.
• A response whose first write of a tick is taken at once and whose next write in that tick waits: Node uses the context of the first write (it corks both), this branch and main use the context of the write that waited.
• A response write that takes the backlog of an earlier write with it, before the drain event: the callback of the earlier write runs in the context of the later write, as on main. Node runs it in the context of the earlier write.

Open PRs that touch the same lines. #43250, #43392, #43026 and #43877 read or write the write slot: the slot still holds a function, so their calls stay correct. #43038 is covered by the one-line guard in SocketHandlers.error. The draft #46014 rewrites #onDrain of the tunnel socket, which this change leaves as on main.

---

no test proof · iteration 1 · platform-specific test(s) that do not run on this machine, deferring to CI, which covers all platforms: test/js/node/net/net-syscall-fault.test.ts, test/js/bun/module-graph/module-graph-net-write.test.ts

[robobun]

^{Updated 8:31 AM PT - Oct 22nd, 2026}

✅ @robobun, your commit 842835946b6f59d02c5b17ac466068c563beba6d passed in Build #130928! 🎉

---

🧪   To try this PR locally:

bunx bun-pr 46141

That installs a local version of the PR into your bun-46141 executable, so you can run:

bun-46141 --bun

[robobun]

Status: ready for review.

Reproduction. The script from the report: a 32 MiB socket.write(chunk, cb) to a peer that does not read, issued inside AsyncLocalStorage.run(), with a 'drain' listener. On main and on Bun 1.4.3 the callback and the listener see no store. Node 26.3 gives them the store of the write, and so does this branch. A small write keeps its store on every build.

PR: #46141

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• src/js/internal/async_context_frame.ts
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• src/js/node/_http_client.ts
• src/js/node/_http_server.ts
• src/js/node/net.ts
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Walkthrough

The change captures async-context frames for deferred socket writes and uses them for write callbacks, drain, close, and finish handling across net, HTTP, and TLS paths. It adds module-graph-aware frame helpers and regression tests for backpressure, errors, connection teardown, and graph disposal.

Changes

Socket write async context

Layer / File(s)	Summary
Async-context helpers and socket writes src/js/internal/async_context_frame.ts, src/js/node/net.ts, test/js/node/async_hooks/async-context/async-context-net-socket-write-waits.js, test/js/node/net/net-syscall-fault.test.ts	AsyncContextFrame adds frame and module-graph checks. Socket write completion, failure, and close paths dispatch callbacks in the relevant context. Tests cover delayed writes, errors, resets, and destruction.
HTTP response write waits src/js/internal/http.ts, src/js/internal/http1_server_fallback.ts, src/js/node/_http_server.ts, test/js/node/async_hooks/async-context/async-context-http-serverresponse-write.js	HTTP response handling records the context for waiting writes and uses it for deferred callbacks, drain, finish, and failure handling. The HTTP/1 pipeline exposes the write-wait context hook.
HTTP client, upgrade, and module-graph writes src/js/node/_http_client.ts, test/js/bun/module-graph/module-graph-net-write.test.ts, test/js/node/async_hooks/async-context/async-context-http-clientrequest-write.js, test/js/node/async_hooks/async-context/async-context-http-connect-socket-write.js, test/js/node/async_hooks/async-context/async-context-http-upgrade-socket-write.js, test/js/node/async_hooks/async-context/async-context-http2-allowhttp1-socket-write.js	HTTP client drain handling checks module-graph context before dispatch. Tests cover HTTP requests, CONNECT and upgraded sockets, HTTP/2 with allowHTTP1, and graph-owned or host-owned writes.
TLS write and finalization paths src/js/node/tls.ts, test/js/node/async_hooks/async-context/async-context-tls-socket-write.js, test/js/node/async_hooks/async-context/async-context-tls-wrap-socket-write.js, test/js/node/net/net-syscall-fault.test.ts	TLS finalization uses the captured frame after handshake completion. Tests cover pre-handshake writes, wrapped sockets, and TLS write completion and error paths.

Possibly related issues

• node:net, node:tls: socket teardown events that still differ from Node (spurious 'end', ERR_SOCKET_CLOSED in place of the real error) #43381 — Covers pending writes, callbacks, TLS handshake failures, and transport teardown; this change updates async-context handling across those write and teardown paths.

Suggested reviewers: dylan-conway

Priority: ➖ Normal

Merge Risk: ⚪ Minimal · up to 84283

This change makes socket write callbacks, drain and finish events run in the async context of the write that waited. The two earlier concerns, a type error and a cross-socket close-context leak, are fixed at the current head. No concrete merge-blocking risk remains, and CI results for the latest commit should be confirmed as usual.

Pre-merge checks: 4

Check name	Status	Explanation
Title check		The title clearly identifies the main change: completing socket writes that waited for capacity in the async context of the write.
Description check		The description is detailed and covers the problem, implementation, scope, verification, performance impact, limitations, and remaining differences. It does not use the exact template headings, but it…
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.

Full details: Description check

Explanation

The description is detailed and covers the problem, implementation, scope, verification, performance impact, limitations, and remaining differences. It does not use the exact template headings, but it provides the required information and is substantially complete.

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Actionable comments posted: 1

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Inline comments:
Review comments at @src/js/node/_http_server.ts:
- Around line 2232-2237: Annotate the #pendingCallback field in the relevant
server class as a nullable callback accepting an optional Error or null and
returning void, so the bound AsyncContextFrame.runInSameGraph assignment
type-checks. Remove the now-unnecessary Function casts at the existing
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• src/js/internal/async_context_frame.ts
• src/js/internal/http1_server_fallback.ts
• src/js/node/_http2_upgrade.ts
• src/js/node/_http_client.ts
• src/js/node/_http_server.ts
• src/js/node/net.ts
• src/js/node/tls.ts
• test/js/bun/module-graph/module-graph-net-write.test.ts
• test/js/node/async_hooks/async-context/async-context-http-clientrequest-write.js
• test/js/node/async_hooks/async-context/async-context-http-connect-socket-write.js
• test/js/node/async_hooks/async-context/async-context-http-serverresponse-write.js
• test/js/node/async_hooks/async-context/async-context-http-upgrade-socket-write.js
• test/js/node/async_hooks/async-context/async-context-http2-allowhttp1-socket-write.js
• test/js/node/async_hooks/async-context/async-context-net-socket-write-waits.js
• test/js/node/async_hooks/async-context/async-context-tls-socket-write.js
• test/js/node/async_hooks/async-context/async-context-tls-wrap-socket-write.js
• test/js/node/net/net-syscall-fault.test.ts

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[claude]

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 — CONNECT and 'upgrade' tunnel sockets emit 'drain' twice per backpressure episode, and after this change the two events run in different AsyncLocalStorage contexts. #onDrain at _http_server.ts:1782 invokes the parked Writable callback, which makes afterWrite emit 'drain' when needDrain is set, then _http_server.ts:1784 emits 'drain' again. The callback is now bound at _http_server.ts:2232 to the write's frame, so the first 'drain' carries the write's store and the second carries the native event's. Fix: drop the explicit this.emit("drain") at _http_server.ts:1784 and let the stream emit it, or guard on needDrain so one 'drain' is emitted, in the write's frame.

  Why this was flagged

  Trigger: a streaming-mode server socket (CONNECT tunnel or 'upgrade') whose write returns false from handle.write at _http_server.ts:2227, with the chunk at or above the stream's highWaterMark so Writable sets needDrain. Entry: the native drain callback calls #onDrain (_http_server.ts:1778). Line 1782 runs the stored callback, which is Writable's onwrite; afterWrite (writable.ts) emits 'drain' when needDrain && length === 0. Line 1784 then emits 'drain' a second time. The base branch had the same double emission, but both events ran in the same frame. With this change the callback is wrapped by runInSameGraph.bind at _http_server.ts:2232, so the first 'drain' runs in the write's frame and the second in the native frame; a listener keyed on the ALS store (per-request logging, metrics) now sees one event with the store and one without, and any listener that resumes a piped source resumes it twice. Population: every proxy or WebSocket-style server that pipes through a tunnel socket under backpressure. Remedy: emit 'drain' once, from the stream's own afterWrite, in the write's frame.

  Verification: Pre-existing. Trigger: a CONNECT/'upgrade' tunnel socket whose handle.write returns false at src/js/node/_http_server.ts:2227. #onDrain calls the wrapped callback, and afterWrite emits 'drain' inside the write's frame; line 1784 this.emit("drain") emits a second 'drain' in the native event's frame. The base has the identical #onDrain; the fixture only uses once('drain') so it never observes the second.

[robobun]

On the second 'drain' of the tunnel socket ('upgrade' and CONNECT): that is #onDrain as it is on main, and this change does not touch it. The first 'drain' comes from the stream and now runs in the context of the write. The second comes from the native drain event and runs where it ran before. The draft #46014 removes the second one. The description lists this under what still differs from Node.

[coderabbitai]

Actionable comments posted: 1

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Inline comments:
Review comments at @src/js/node/net.ts:
- Around line 374-387: Replace the module-wide completingEventFrame
AsyncLocalStorage in completeWithEventFrame and setCloseImmediate with
per-socket or per-write state. Ensure only the socket whose write completion
causes destruction retains the event frame, prevent callback continuations from
affecting other sockets, and clear the stored frame when that socket’s close is
scheduled, including deferred write-failure paths.

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• src/js/internal/http.ts
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• src/js/node/_http_server.ts
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• test/js/bun/module-graph/module-graph-net-write.test.ts
• test/js/node/async_hooks/async-context/async-context-http-serverresponse-write.js
• test/js/node/async_hooks/async-context/async-context-net-socket-write-waits.js
• test/js/node/net/net-syscall-fault.test.ts

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[claude]

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/net.ts — Servers using AsyncLocalStorage get 'close' of an accepted or adopted-fd socket in the backpressured write's store instead of the socket's when the peer resets. ServerHandlers.close at net.ts:1290 nulls _handle before SocketEmitEndNT fails the parked write, so the destroy() that completion causes takes _destroy's handle-less branch, whose process.nextTick(emitCloseNT) at net.ts:2582 is never routed through the completing event's frame. Fix: emit 'close' in the completing event's frame on every destroy path reached from a waited write's completion, including net.ts:2588-2589, as setCloseImmediate already does for the handle paths. Base and Node run it where the socket's events run. [also at: src/js/node/net.ts:2582 - Servers using AsyncLocalStorage get a 'close' listener run in the parked write's store, not the socket's, when the peer closes an accepted or fd-adopted socket under backpressure.]

  Why this was flagged

  A net.createServer or tls.createServer accepted socket (ServerHandlers), or a socket over an adopted fd (SocketHandlers), has a write parked in [kwriteCallback] via waitedWrite (src/js/node/net.ts:3139) under store A, with no 'error' listener and a write callback like `err => { if (err)…

  Verification: ServerHandlers.close and SocketHandlers.close null _handle before SocketEmitEndNT fails the parked write inside the write's frame, so Socket.prototype._destroy takes the handle-less branch and process.nextTick(emitCloseNT) at src/js/node/net.ts:2582 captures the write's frame; only the _handle branches use setCloseImmediate. On base 'close' stayed in the socket's frame.

• 🟡 src/js/node/net.ts — TLS users with per-connection AsyncLocalStorage now get a handle-reported 'error' (bad record, peer reset under a parked write) in the write's store instead of the socket's, which main and Node give. SocketHandlers.error at src/js/node/net.ts:918 runs the parked callback in the write's frame; the stream's errorOrDestroy destroys there and queues the only 'error' in that frame, and src/js/node/net.ts:920 then skips the socket-frame emit. Fix: when the failure comes from the handle's own error event rather than the write's completion, emit the single 'error' in the event's frame (for example destroy in the event frame before failing the callback, or emit from the handler and mark errorEmitted) at the three handler sites, keeping one emit. …

  Why this was flagged

  A tls socket with a write parked in [kwriteCallback] (src/js/node/net.ts:3139) receives a record it cannot decrypt, or a reset while reading; the native error arrives through SocketHandlers.error at src/js/node/net.ts:909. The callback stored by waitedWrite enters the write's frame…

  Verification: A socket with a write parked in kwriteCallback under a different AsyncLocalStorage store than its events gets a handle error. In SocketHandlers.error (src/js/node/net.ts:902-917) the callback at line 911 destroys the stream in the write's frame, and line 913 if (self.destroyed) return; skips the socket-frame emit, so the only 'error' runs in the write's store, not the socket's as on the base.

[robobun]

On the two findings outside the diff of 807d367:

• The destroy path of a socket whose handle is already detached (an accepted socket that the peer closed): fixed in 219f700. That path goes through scheduleClose too, so 'close' runs where the socket's events run. net-syscall-fault.test.ts has the case for a client and for an accepted socket, with a peer's reset and a write callback that destroys the socket.
• The 'error' of a waiting write that a bad TLS record or a peer's reset fails: not changed. The write is called back first, and the stream destroys the socket from inside that callback, so 'error' runs in the context of the write. To report it first, in the context of the event, the socket must be destroyed before the callback runs. Then a callback that destroys the socket no longer suppresses 'error', which is the crash the earlier review found. The description lists this under Downsides.

[claude]

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

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

• 🟣 src/js/node/_http_server.ts — pre-existing: a response write callback that waited for backpressure runs in a later write's AsyncLocalStorage store when that later write flushes the backlog itself. ServerResponse.prototype.write at src/js/node/_http_server.ts:3813 calls _callPendingCallbacks in the current frame and never consults the kWaitingWrite record this PR adds for exactly those callbacks. Fix: complete the parked callbacks in the first waiting write's frame on every completion path, including a later write's synchronous flush, by routing the :3813 call through runWhereWriteWaited (and keeping the 'drain' at :4208 in that same frame). Node completes them with the first write request, so they see that write's store.

  Why this was flagged

  A handler does res.write(big, cbA) inside als.run("A"); handle.write reports backpressure (NodeHTTPResponse.rs:2192-2204), so src/js/node/_http_server.ts:3804 records kWaitingWrite = A and :3808 pushes cbA. Later, inside als.run("B"), the handler does res.write(chunk, cbB) after the peer has read: uWS AsyncSocket::write first flushes the buffered backlog and then takes the chunk (packages/bun-uws/src/AsyncSocket.h:320-328), so handle.write returns WantMore, result >= 0, and :3813 runs this._callPendingCallbacks(), which process.nextTick's cbA in the current frame, store "B". The owed drain stays armed, so allowWritesToContinue later emits 'drain' in frame A via :4208, and the callback and the 'drain' of the same write disagree. In Node cbA completes with the first write request in A. The base branch runs :3813 the same way; the kWaitingWrite record is not a safeguard here because :3813 never reads it.

  Verification: pre-existing. A response write parks under store A (src/js/node/_http_server.ts:3803-3808 pushes cbA), then a later res.write is issued under store B after the peer has read; NodeHTTPResponse.rs:2187-2190 returns WantMore, and line 3813 this._callPendingCallbacks() nextTicks cbA in the current frame, so cbA runs with store B, never through runWhereWriteWaited.

[robobun]

The description lists "the events of an accepted socket run in the store of listen()" as a remaining difference. I took that row as a separate change. It should land on top of this PR, not alone on main. These notes are for that follow-up.

What Node does

• A net.Server gives the store of listen() to its own events ('listening', 'connection').
• The 'data', 'end', 'error' and 'close' of a socket it accepts run in no store. Node 22.23.3, 24.22.0, 26.3.0 and 26.12.0 agree.
• tls.Server is different. It makes the TLS socket in 'connection', so that socket's events keep the store of listen(). Only 'close' has none.

Tests, ready to carry over (27ba6d9 on robobun/7c4ff86d/net-accepted-socket-async-context)

• async-context-net-server-accepted-socket.js: TCP, a path and pauseOnConnect, with a clean close and a peer reset.
• async-context-http-server-from-net-connection.js: an http.Server that gets the socket through emit("connection").
• async-context-tls-server-accepted-socket.js: a guard for the tls.Server rows. It passes on main.
• Two tests in test/js/node/net/node-net-server.test.ts. One is a guard that Bun.listen handlers keep the store of the call that gave them.
• The fixtures pass under the four Node versions above. On main the first two print 15 and 9 failing rows. With this PR alone they print the same.

A change that passes them on top of this PR

listenForServer in net.ts (+21 -4, no native change)

--- a/src/js/node/net.ts
+++ b/src/js/node/net.ts
@@ -288,6 +288,8 @@
 // Write-only by design: the onconnection write is a GC edge keeping the
 // native Listener reachable via accepted socket handles (see a93d2fa48e).
 const kServerSocket = Symbol("kServerSocket");
+// On a listening handle: the async context of listen(), when Bun.listen() was called outside of it (listenForServer).
+const kListenFrame = Symbol("kListenFrame");
 const kBytesWritten = Symbol("kBytesWritten");
 const bunTLSConnectOptions = Symbol.for("::buntlsconnectoptions::");
 // tls.Server exposes its native SecureContext constructor through this key so
@@ -1308,7 +1310,9 @@
     // before the ClientHello ever arrives.
     const handle = self._handle || socket.listener;
     if (handle && typeof handle.onconnection === "function") {
-      handle.onconnection(0, socket);
+      const frame = handle[kListenFrame];
+      if (frame === undefined) handle.onconnection(0, socket);
+      else require("internal/async_context_frame").runInSameGraph(frame, handle.onconnection, handle, 0, socket);
     }
   },
   handshake(socket: Socket<TLSSocketInstance>, success, verifyError) {
@@ -1876,6 +1880,19 @@
 const { serverName: _snOnly, ...ServerHandlersALPNOnly } = ServerHandlers;
 const { alpnCallback: _acOnly, ...ServerHandlersSNIOnly } = ServerHandlers;
 
+// Bun.listen() for a net.Server. As in Node, the events of a plain socket it accepts continue no async context, and
+// 'connection' continues listen(): https://github.com/nodejs/node/blob/v26.3.0/src/connection_wrap.cc#L50-L73
+// So the handlers are given in the Bun.ModuleGraph's context alone, and ServerHandlers.open enters listen()'s.
+// A tls.Server makes each TLS socket in 'connection': the events of its sockets continue listen().
+function listenForServer(options) {
+  const frame = $getInternalField($asyncContext, 0);
+  if (frame === undefined || options.tls) return Bun.listen(options);
+  const AsyncContextFrame = require("internal/async_context_frame");
+  const handle = AsyncContextFrame.run(AsyncContextFrame.currentGraphFrame(), Bun.listen, Bun, options);
+  handle[kListenFrame] = frame;
+  return handle;
+}
+
 /** The handler table for a listen config: the full table only when a
  *  per-connection callback is configured, so other servers never pay a JS
  *  round-trip from inside the handshake. */
@@ -4159,7 +4176,7 @@
     exclusive = false;
   }
   if (path) {
-    this._handle = Bun.listen({
+    this._handle = listenForServer({
       unix: path,
       tls,
       // Accepted sockets are always half-open natively; the stream layer
@@ -4193,7 +4210,7 @@
       }
     }
   } else if (fd != null) {
-    this._handle = Bun.listen({
+    this._handle = listenForServer({
       fd,
       hostname,
       tls,
@@ -4206,7 +4223,7 @@
       pauseOnConnect: this.pauseOnConnect,
     });
   } else {
-    this._handle = Bun.listen({
+    this._handle = listenForServer({
       port,
       hostname,
       tls,

• It calls Bun.listen outside the stores and keeps the frame of listen() on the handle. ServerHandlers.open enters that frame for 'connection'. A TLS listener is left as it is.
• I ran it with this PR's builtins, rebased onto main by hand, on the native binary of main at 9b4284f. The fallback hunk of the second commit on that branch was applied too.
• Rows equal to Node v26.3.0 over 43 probe runs (378 rows): main 195, this PR 207, this PR with the change 329. No row moves away from Node.

What has to go with it

• The HTTP/1 path for emit("connection") (http1_server_fallback.ts) has to run its parser in the async context of that call. Without that, 'request' loses the store of listen() that it has today. node:http: stop reading a connection served from JS while the request buffer is full #45841 and node:http, node:http2: give emit('connection') and allowHTTP1 connections the server's timers and error path #46185 edit the same listener.
  • Node frames what the parser reports. For a stream without a handle, what follows execute() ('upgrade', 'connect', a parse error) runs in the stream's 'data'. The hunk on that branch frames the whole 'data' listener. That is wrong for such a stream. 'upgrade' on a duplexPair() side then runs in the hand-over store. Node and main use the writer's store.
  • Node does not frame the socket's 'end'. The 'clientError' of a message cut short runs in no store.
• The server-side close: "opened" expectations of net-syscall-fault.test.ts here should become undefined, because 'close' of an accepted socket then runs in no store. I did not run that file.
• 'close' after a local destroy() still runs where destroy() ran. Node uses no store for an accepted socket. scheduleClose is the place for that rule.

Why not alone on main

• Alone it has to keep the native drain in the store of listen(), because a parked write has no context of its own there. The callback of a waiting write from 'connection' that fails on a peer reset then runs in no store. On main and in Node it runs in the store of listen().
• 98e4070 is a native form of the rule: a wrap policy in Handlers.rs behind a private doListen. Alone on main it moves 195 to 313 rows. domain: route fs callback throws to uncaughtException, unblocking 4 tests (domain 88%→96%) #34661 adds the same doListen and an owner flag on Handlers, so a native form should build on that PR.

[robobun]

On the response write that takes the backlog of an earlier write with it (_callPendingCallbacks in ServerResponse.prototype.write): not changed here, and the same as on main. That call runs on every write that the handle takes, so a lookup of the waiting context there is a cost for every response. The case also needs a later write to arrive between the moment the kernel has room and the drain event, which a test cannot arrange without a fault in the handle. The description lists it under what still differs from Node.

The branch is rebased on main (one conflict in closeSocketHandle, which main changed to pass arguments in place of a closure) and is one commit again.

[claude]

I reviewed the new push and found no bugs; the restructured design (callback-first error path, the completion-scoped completingSocket store instead of a retained write frame, runWhereWriteWaited shared by the native and fallback close paths) addresses the points raised on earlier pushes, but a human look is still worthwhile given how many async-context paths this touches and the new runInSameGraph/isInAnotherGraph Bun.ModuleGraph rule that the description itself flags for its owner.

What was reviewed:

• net.ts: the three waitedWrite sites, scheduleClose routing in _destroy/closeSocketHandle, and the early return in SocketHandlers.error after a callback-destroyed socket.
• _http_server.ts/http1_server_fallback.ts: kWaitingWrite first-write-wins with the same-tick end() override, and the fallback's settleWaiting now entering a frame only for another graph.
• Checked 'close' of a stream-engine TLSSocket wrapped outside any store: it now runs in the waited write's store rather than undefined — a minor divergence, not a correctness bug.
• New fixtures match the glob-driven pattern in AsyncLocalStorage-tracking.test.ts.

Extended reasoning...

The single commit changes how AsyncLocalStorage frames propagate through write completion, drain, finish and close in the JS node:net, node:tls, node:http (server, client, CONNECT/upgrade, http2 allowHTTP1 proxy) and the http1 fallback, adding two helpers to internal/async_context_frame.ts that refuse to install a frame from another Bun.ModuleGraph. It touches no auth, crypto or injection surface. The push substantively redesigned the mechanism compared with the earlier versions this bot commented on, and the hunt ran dry with no findings. It is deferred rather than approved because the change is large and intricate (many ordering-sensitive async-context paths with Node-timing contracts) and introduces a new cross-cutting ModuleGraph rule that needs a maintainer's judgment.

[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.