node:tls: send the FIN when end() runs before the TLS handle is attached

[robobun]

Problem

• end() or destroySoon() on a TLSSocket with no native handle yet emits 'finish' at once and never sends the FIN. Node v26.3.0 sends it (Node parity, no user report). Shapes: tls.connect({ socket }) over an unconnected net.Socket, and new tls.TLSSocket(socket, { isServer: true }) ended in the same tick.
• Cause: TLSSocket.prototype._final (src/js/node/tls.ts:900) starts with if (!this._handle) return callback();. The client path assigns the handle in the transport's 'connect' listener (src/js/node/net.ts:2076), the server wrap one tick later (net.ts:2413).

Fix

• Both paths set kUpgradePending until they assign the handle, then emit kUpgradeAttached. _final waits for it, then shutdown() sends the FIN and 'finish' fires. Other no-handle states call back at once.
• No wait lasts forever. A transport that closes before it connects destroys the TLS socket, as node's _wrapHandle does. connectError destroys a wrap whose engine fails before it opens.
• drain (net.ts:1321) sets kPreHandshakeWrite for a write parked while the transport connected, so the FIN of end("") follows the handshake, as in node. From node:tls: send the FIN when end() runs before a TLSSocket wrap's native handle attaches #42367, which this PR replaces.
• Verified: eight new tests in test/js/node/tls/node-tls-connect.test.ts (five fail on main, four also run under node v26.3.0), test/js/node/tls/, vendored test-tls-*, test-https-*. Self-reviewed twice: 11 concerns, 7 addressed, 4 already on main (Notes).

Background

• _final is the writable side's shutdown hook. 'finish' fires when its callback does. destroySoon() is end() plus destroy() on 'finish'.
• Bun adopts the transport's file descriptor into a native TLS handle. That needs a connected socket, and the server wrap waits one tick for bytes already read.
• kPreHandshakeWrite marks a write that reached the TLS engine during the handshake. _final then holds the FIN until the handshake settles (tls: end() and destroySoon() before the handshake completes now send the FIN #42181).
• Node has its handle from the constructor and defers _final on connecting (wrap.js, net.js).

Notes

Not a regression: bun 1.4.3 behaves the same. Found while working on #42330, which covers a different path (new tls.TLSSocket(stream) without isServer, where _handle is the wrapped stream, not null). #42181 listed the server shape as out of scope. Reach: a write() or an end(data) in the same window is already parked until the handle attaches, so only a bare end(), end("") or destroySoon() reaches the early 'finish'.

This PR also carries the parts of #42367 that it did not have. #42367 fixed the same gap and is closed in favor of this PR. Carried over at db37e4b: the kPreHandshakeWrite line in drain, the end-over-connecting-socket fixture mode with its test, and the in-process test for a server-side wrap whose native handle was closed directly. Not carried over: the server-end-same-tick fixture mode, because server-same-tick here asserts the same shape for end() and destroySoon().

Repros

The client shape, no certificates needed. The peer is a plain TCP server that never answers:

const net = require("net"), tls = require("tls");
const log = [];
const srv = net.createServer({ allowHalfOpen: true }, c => {
  c.on("data", () => log.push("peer: data"));
  c.on("end", () => log.push("peer: got FIN"));
  c.on("error", () => {});
});
srv.listen(0, "127.0.0.1", () => {
  const raw = net.connect(srv.address().port, "127.0.0.1");
  raw.on("connect", () => log.push("raw connect"));
  const s = tls.connect({ socket: raw, rejectUnauthorized: false });
  s.on("error", e => log.push("tls error:" + (e.code || e.message)));
  s.on("finish", () => log.push("tls finish"));
  s.end();
  setTimeout(() => { console.log(log.join("\n")); process.exit(0); }, 800);
});

runtime	output
node v26.3.0	raw connect, tls finish, peer: data, peer: got FIN
bun 1.4.3 and main	tls finish, raw connect, peer: data
this branch	raw connect, tls finish, peer: data, peer: got FIN

The server shape: a net server whose 'connection' handler does new tls.TLSSocket(sock, { isServer: true, key, cert }).end(), with a tls.connect client.

	server events	client events
node v26.3.0	finish, end, close	end, error:ECONNRESET, close
main (a749e0a, debug build)	finish, secure (connection stays open)	secureConnect
this branch	finish, close	end, error:ECONNRESET, close

The missing 'end' on the server side in the last row is a separate regression on main since #42265. It also shows with setImmediate(() => socket.end()), a shape that this change does not touch: bun at 6a92015 (before #42265) reports finish, end, close there, main reports finish, close. It has its own report. The tests here do not subscribe to 'end'.

tls.connect({ socket: net.connect(port) }) followed by end("") before the connect, against a live TLS server:

	client events	server events
node v26.3.0	connect, secureConnect, finish, end, close	secureConnection, end, close
main	finish, secureConnect (connection stays open)	secureConnection
this branch without the drain line	FIN in the middle of the handshake	tlsClientError: ECONNRESET
this branch	secureConnect, finish, end, close	secureConnection, end, close

The empty write completes inside the native open callback, which runs inside upgradeTLSDeferred, before _handle is assigned. _final runs from that write callback, finds kUpgradePending, and waits for kUpgradeAttached. On its second run it finds kPreHandshakeWrite and waits for the handshake. The missing 'connect' in the last row is a separate gap (#42340). A non-empty end(data) was already correct: the engine holds the plaintext until the handshake ends, so the write callback and _final run after it.

Other shapes compared with node v26.3.0 on this branch, all with the same event lists: the client shape against a live TLS server (tlsClientError: ECONNRESET on the server, then end and close on the client), the server shape against a TLS client that sends its ClientHello, write(); end() in the same tick in both shapes (the data still arrives before the close), and end(cb); end(cb) while the upgrade is pending.

Why a flag

The flag is reset at the top of connect() with the other per-connection TLS state. One helper, upgradeAttached, clears it and emits kUpgradeAttached at the three places that assign the handle. Each other exit of the deferred callbacks destroys the socket, and a destroyed stream never runs _final. An upgrade that throws inside the client's 'connect' callback leaves the flag set, but the callback keeps its 'close' listener on the transport until the upgrade has installed its own. Bun routes that exception to the transport's error handler, the transport closes, and the listener destroys the TLS socket. The destroyed on connect shapes in the fixture cover the reachable case: a 'connect' listener that ran first destroyed the transport. A second reachable case is a transport that two TLS sockets wrap: the second upgrade gets no result and throws Invalid socket.

A flag, and not the _write condition (!handle && kupgraded && !destroyed), marks the wait. That condition stays true after an attached handle closes and detaches (socket._handle.close()), so #42367 needed an extra kclosed check to keep end() from waiting forever there. The flag is already clear at that point. The test "a server-side TLSSocket wrap finishes and closes after its native handle was closed" pins this. It passes on main too: it guards the wait, it does not reproduce the bug.

What stays different from node, all of it present before this change:

• The TLSSocket does not emit 'connect' when its transport connects. That is why _final waits on an internal signal here.
• Only the writable side's shutdown waits for the handle. ref(), unref(), setTimeout() and _read() in the same window still act on no handle, as on main. Example: unref() in the wrap tick keeps the process alive on bun, node exits. They are out of scope here.
• A transport whose connect fails: node also emits the transport's 'error' on the TLSSocket. Bun does not yet (node:tls: report a wrapped socket's connect failure on the TLSSocket #38122). This branch closes the TLSSocket with the transport, so a pending end() or destroySoon() ends in 'close' as in node. Before this change end() reported 'finish' and the TLSSocket stayed open.
• A net.Socket transport that takes the stream-level engine at wrap time (a connected named pipe, an outer TLSSocket) stays connecting until the engine opens, so its _final waits for a 'connect' that is never emitted (node:tls: clear connecting on a TLSSocket that wraps a connected socket #42343, node:tls: emit 'connect' on a TLSSocket that wraps a connecting socket #42340). Checked on Windows: tls.connect({ socket: net.connect(pipe) }).end() behaves the same before and after this change.
• end("") in the wrap tick on a server-side wrap waits for the handshake (secure, finish, end, close). Node sends the FIN at once. This is the zero-length write rule that tls: end() and destroySoon() before the handshake completes now send the FIN #42181 describes.
• new tls.TLSSocket(socket, { isServer: true }) over a socket that is still connecting keeps the early 'finish' (see the second self-review below).

One difference that this change introduces: end() on a server wrap followed by raw.destroy() in the same tick. Node reports 'finish' and then 'close', because its cancelled shutdown request still completes. Bun did the same by accident, because 'finish' fired early. This branch reports 'close' only. No FIN can be sent in that case on either runtime.

Same as node: a transport that is already destroyed when tls.connect({ socket }) takes it. Node v26.3.0 keeps the TLSSocket connecting, with no 'finish' and no 'close', because raw.connect() can connect a destroyed net.Socket again. A later raw.connect() completes the pending end() on node and on this branch (raw connect, tls finish, peer: data, peer: got FIN). So the TLSSocket is not destroyed for a transport that is destroyed at wrap time.

Tests and node

Four tests run one fixture (tls-shutdown-before-handshake-fixture.mjs) under bun and under node v26.3.0 and assert the same report: pending-transport, closed-transport, end-over-connecting-socket, server-same-tick. The shape where a 'connect' listener destroys the transport first is part of closed-transport. Node runs its shutdown on the closed handle there and reports close, finish, error:EINVAL. Bun reports close. The shared report is readyState: "closed", destroyed: true, transportDestroyed: true.

Four in-process tests pin paths that only bun's deferred upgrade has. They do not run under node. Node's output for the same scripts:

• end() with plaintext still queued on a connecting transport: node reports transport connect, error:EPIPE, finish, close and the peer gets the FIN. This branch reports transport connect, finish. main reports finish before transport connect. The stream-level engine sends no FIN before it starts (tls: end the wrapped Duplex on end(), also before the handshake completes #42350).
• A stream-level engine that gets a string chunk before it starts (setEncoding("utf8") on the transport): node aborts in TLSWrap::Receive (Assertion failed: buf->IsSharedArrayBuffer()). main and this branch report 'error' and 'close'.
• end() in the wrap tick with a 32 MB plain write queued on the connection: node emits no 'finish' until the plain write drains. main and this branch emit 'finish'. The test guards the upgradeAttached call on that path: without it end() never finishes.
• A server-side wrap whose native handle was closed directly: node reports secure, close, bun reports secure, end, finish, close.

Self-reviews

First version, 5 concerns:

• Addressed (0931c21): TLSSocket.prototype._final first sent every no-handle case to net.Socket's _final. A TLS socket whose upgrade fails synchronously in connect() (for example a second tls.connect({ socket }) over a transport that is already wrapped, Invalid socket) has no handle and still reports connecting. Its end() then waited for a 'connect' that never comes. main reports 'finish' at once there. Now only a pending upgrade takes the new path, and that case behaves as on main again.
• Addressed (481fd60): when the transport connects and the upgrade takes the stream-level engine (plaintext still queued on the transport, or a named pipe that was dialed after the wrap), the handle is attached but the socket stayed connecting until the engine opened on a later task. The second run of _final then waited for a 'connect' that is never emitted, where bun 1.4.2 reported 'finish' at once. The deferred callback now clears connecting once it has the handle, as node does on the transport's 'connect'. 'finish' fires after the transport connects and destroySoon() closes. That sub-path still sends no FIN, because shutdown() is a no-op before the engine starts (tls: end the wrapped Duplex on end(), also before the handshake completes #42350).
• Not changed: node also emits the pending transport's 'error' on the TLS socket (node:tls: report a wrapped socket's connect failure on the TLSSocket #38122).
• Not changed: a TLSSocket that is destroyed while its upgrade is pending and then connected again keeps the listeners of its first life. That is already wrong on main, where the first transport's 'connect' still upgrades the socket that was connected again.
• Not changed then, see below: a server-side wrap over a transport that is still connecting (node:tls: use the stream engine for server-side wraps the native upgrade cannot adopt #38076).

Combined diff at db37e4b, 6 concerns. The verdict was to merge after changes. Changes are in f111176:

• Addressed: after 481fd60 a stream-level engine that failed before it opened was dropped. connectError handed it to afterConnect, which returns when nothing is connecting. main reports 'error' and 'close' there, the branch reported nothing and the socket stayed open. connectError now destroys an upgraded socket itself. These are the same five lines as in node:tls: clear connecting on a TLSSocket that wraps a connected socket #42343, which fixes the same drop for Duplex and TLS-in-TLS transports on main.
• Addressed: new tls.TLSSocket(socket, { isServer: true }) over a net.Socket that is still connecting, then a bare end() or destroySoon(). The native upgrade adopts that handle before it is connected. With the wait, _final then ran shutdown() on it, and the close underflowed the native connection count: panic: attempt to subtract with overflow in Handlers::mark_inactive (src/runtime/socket/Handlers.rs:244) on a debug build, a silent wrap of the counter on a release build. main only reports the early 'finish' there. The server wrap no longer sets kUpgradePending over a connecting socket, so that shape behaves as on main. In a 36-cell matrix (9 operations, 4 kinds of peer) the branch now aborts in the same 7 cells as main and in no other. Those 7 are a bug on main: the same wrap aborts when it is destroyed while its peer never answers, with or without end(). node:tls: use the stream engine for server-side wraps the native upgrade cannot adopt #38076 adopts such a socket only after 'connect' and can remove the exclusion.
• Addressed: the three places that assign the handle each cleared the flag and emitted the event by hand. A rebase of an open PR that dropped one clear would hang every end() on that path. One helper does both now, and each of the three places has a test that hangs without the call.
• Addressed: tests. The bar on tls: end() and destroySoon() before the handshake completes now send the FIN #42181 was that new tests pass under node v26.3.0 too. The 'connect'-listener shape moved into the fixture. The bun-only tests are grouped and node's output for them is listed above.
• Addressed in this description: the merge order below, and the reach of the bug.
• Not changed: ref(), unref(), setTimeout() and _read() in the same window (listed above). They need their own handling of the missing handle, not the _final wait.

Merge order with the open PRs on the same lines

This PR is the narrow fix and can go first.

• node:tls: send the FIN when end() runs before a TLSSocket wrap's native handle attaches #42367: closed, replaced by this PR.
• node:tls: emit 'connect' on a TLSSocket that wraps a connecting socket #42340 emits 'connect' on a TLSSocket whose transport connects. Rebase onto this PR: keep its net.ts part, with onUpgradedConnect(this, connection) next to upgradeAttached(this). Drop its tls.ts hunk. That hunk deletes the no-handle check in _final, and the server shape has no 'connect' to wait for.
• node:tls: clear connecting on a TLSSocket that wraps a connected socket #42343 clears connecting on a wrap of a connected socket. Independent. Its connectError lines are identical to the ones here, so git merges them in either order.
• node:tls: use the stream engine for server-side wraps the native upgrade cannot adopt #38076 uses the stream engine for server-side wraps that the native upgrade cannot adopt, and rewrites ::bunUpgradeServerTLS::. On rebase its two emit(kUpgradeAttached) calls become upgradeAttached(self), and each new exit has to clear the flag or destroy the socket. It can then set kUpgradePending over a connecting socket as well.
• node:tls: destroy the wrapped net.Socket when a TLS wrap is destroyed #38028 destroys the wrapped net.Socket with the TLS wrap. It edits the same deferred 'connect' listener. Line-level conflicts only: keep the named onConnect and onClose pair.
• node:tls: shut the wrapped stream down when a client-side TLSSocket wrap ends or is destroyed #42330 changes the first lines of TLSSocket.prototype._final for new tls.TLSSocket(stream) without isServer, where _handle is the stream. Small conflict, both checks stay.
• net: stop surfacing TLS traffic on the socket that tls.connect({ socket }) / new TLSSocket(socket) took over #36534 reworks the whole upgrade in native code and makes _final wait through _parent. It is large and has conflicts. If it lands, it replaces this mechanism.

Suites, debug build of f111176 (this branch with main at a749e0a merged in):

• test/js/node/tls/node-tls-connect.test.ts: 67 pass, 0 fail. With net.ts, tls.ts and symbols.ts from main: 62 pass, 5 fail (the four fixture tests in their bun variant, and the queued-plaintext test).
• All seven fixture modes give the same report under node v26.3.0 and under this branch.
• test/js/node/tls/: 328 pass, 2 fail. "SNICallback runs even when the requested servername matches the bind hostname" needs an IPv4 localhost and fails the same way on the release binary without this change. "concurrent Workers all see the same CA certificate lists" takes 4.1 to 4.9 s of its 5 s limit on this machine. It passes alone and passed in the run before.
• Vendored parallel/ and sequential/ test-tls-* and test-https-* scripts: 250 of 252 exit 0. test-tls-client-allow-partial-trust-chain.js is a node:test file and needs bun test. test-https-timeout.js hangs on the debug build with and without this change and passes on the release binary.
• test/js/node/http2/node-http2-upgrade.test.mts and node-http2-client-close.test.ts: 84 pass.
• At db37e4b: test/js/node/net/, 266 pass, 11 fail. Ten fail the same way with main's files (net.Socket read, unref should exit, #13126: public DNS or an IPv4 localhost). The eleventh, "should not leak when connect({path}) fails synchronously on a reused handle", is a plain net.Socket test with a 60 s limit. Here it takes 58 s with main's files and runs past the limit with this branch's. No line of this change is on that path, and the script alone takes 48 s on this branch and reports delta: 0.
• Before the merge of node:tls: send the FIN when end() runs before a TLSSocket wrap's native handle attaches #42367's parts, at ed6872e and 5ab7559: also test/js/bun/net/, test/js/node/http2/, the vendored test-net-* and test-http2-* scripts (619 of 621 exit 0 over all four groups), and the new tests on Windows x64 with a local debug build.

---

[human-review] gate passed · iteration 1 · 5 files touched

fails on main (without fix)

ASAN without fix: 5 failed, 18 skipped
$ BUN_DEBUG_QUIET_LOGS=1 bun scripts/build.ts --profile=debug --quiet test "--reporter=junit" "--reporter-outfile=/tmp/pr_gate.xml" test/js/node/tls/node-tls-connect.test.ts
bun test v1.4.3 (6a92015fc)

test/js/node/tls/node-tls-connect.test.ts:
(pass) should have checkServerIdentity [3.89ms]
(pass) should thow ECONNRESET if FIN is received before handshake [355.82ms]
(pass) initializes authorizationError to null in the TLSSocket constructor [8.10ms]
(pass) setMaxSendFragment mirrors OpenSSL's [512, 16384] acceptance without throwing [108.40ms]
(pass) should be able to grab the JSStreamSocket constructor [13.90ms]
(skip) tls.connect > should work with alpnProtocols
(pass) tls.connect > Bun.serve() should work with tls and Bun.file() [81.69ms]
(pass) tls.connect > should have peer certificate when using self asign certificate [88.36ms]
(skip) tls.connect > should have peer certificate
(skip) tls.connect > getCipher, getProtocol, getEphemeralKeyInfo, getSharedSigalgs, getSession, exportKeyingMaterial and isSessionReused should work
(skip) tls.connect > should process options correctly when connect is called with only options
(skip) tls.connect > should process port an
... (truncated)

release without fix: 18 skipped
bun test v1.4.3-canary.1 (f11117648)

test/js/node/tls/node-tls-connect.test.ts:
(pass) should have checkServerIdentity [0.06ms]
(pass) should thow ECONNRESET if FIN is received before handshake [9.87ms]
(pass) initializes authorizationError to null in the TLSSocket constructor [0.30ms]
(pass) setMaxSendFragment mirrors OpenSSL's [512, 16384] acceptance without throwing [5.08ms]
(pass) should be able to grab the JSStreamSocket constructor [0.41ms]
(skip) tls.connect > should work with alpnProtocols
(pass) tls.connect > Bun.serve() should work with tls and Bun.file() [7.02ms]
(pass) tls.connect > should have peer certificate when using self asign certificate [6.14ms]
(skip) tls.connect > should have peer certificate
(skip) tls.connect > getCipher, getProtocol, getEphemeralKeyInfo, getSharedSigalgs, getSession, exportKeyingMaterial and isSessionReused should work
(skip) tls.connect > should process options correctly when connect is called with only options
(skip) tls.connect > should process port and host correctly
(skip) tls.connect > should process port, host, and callback correctly
(skip) tls.connect > should handle the absence of a callback gracefully
(skip) tls.c
... (truncated)

passes on PR (with fix)

ASAN with fix: 18 skipped
$ BUN_DEBUG_QUIET_LOGS=1 bun scripts/build.ts --profile=debug --quiet test "--reporter=junit" "--reporter-outfile=/tmp/pr_gate.xml" test/js/node/tls/node-tls-connect.test.ts
bun test v1.4.3 (6a92015fc)

test/js/node/tls/node-tls-connect.test.ts:
(pass) should have checkServerIdentity [3.72ms]
(pass) should thow ECONNRESET if FIN is received before handshake [369.20ms]
(pass) initializes authorizationError to null in the TLSSocket constructor [8.92ms]
(pass) setMaxSendFragment mirrors OpenSSL's [512, 16384] acceptance without throwing [112.73ms]
(pass) should be able to grab the JSStreamSocket constructor [18.56ms]
(skip) tls.connect > should work with alpnProtocols
(pass) tls.connect > Bun.serve() should work with tls and Bun.file() [85.64ms]
(pass) tls.connect > should have peer certificate when using self asign certificate [94.41ms]
(skip) tls.connect > should have peer certificate
(skip) tls.connect > getCipher, getProtocol, getEphemeralKeyInfo, getSharedSigalgs, getSession, exportKeyingMaterial and isSessionReused should work
(skip) tls.connect > should process options correctly when connect is called with only options
(skip) tls.connect > should process port an
... (truncated)

release with fix: 18 skipped
$ bun scripts/build.ts --profile=release
[configured] bun-profile → bun (stripped) in 630ms (unchanged)
ninja: Entering directory `/workspace/bun/build/release'
[1/126] gen generated_host_exports.rs
generated_host_exports.rs: 122 exports (host=5, lazy=10, generic=107, rust=0); 243 extern-C blocks audited
[2/126] gen cpp.rs (cppbind)
[3/126] gen BunProcess.lut.h
Generating /workspace/bun/build/release/codegen/BunProcess.lut.h from /workspace/bun/src/jsc/bindings/BunProcess.cpp
[4/126] gen JS modules (bundle-modules)
Preprocess modules (7529ms)
Bundle modules (49ms)
Postprocesss modules (205ms)
Bundle Functions (476ms)
Generate Code (39ms)

[8.31s] Bundled "src/js" for production
  2601 kb
  197 internal modules
  13 native modules
  50 internal functions across 16 files
[4/125] cargo bun_runtime → libbun_runtime.a
�[1m�[92m   Compiling�[0m bun_core v0.0.0 (/workspace/bun/src/bun_core)
�[1m�[92m   Compiling�[0m bun_errno v0.0.0 (/workspace/bun/src/errno)
�[1m�[92m   Compiling�[0m bun_ptr v0.0.0 (/workspace/bun/src/ptr)
�[1m�[92m   Compiling�[0m bun_boringssl_sys v0.0.0 (/workspace/bun/src/boringssl_sys)
�[1m�[92m   Compiling�[0m bun_safety v0.0.0 (/workspace/bun/s
... (truncated)

diff hotspot

src/js/internal/net/symbols.ts                     |   2 +
 src/js/node/net.ts                                 |  41 ++++-
 src/js/node/tls.ts                                 |  14 +-
 test/js/node/tls/node-tls-connect.test.ts          | 194 +++++++++++++++++++++
 .../tls/tls-shutdown-before-handshake-fixture.mjs  | 149 ++++++++++++++++
 5 files changed, 394 insertions(+), 6 deletions(-)

gate history · 6 passed · 0 rejected · iteration 1

evidence per changed file

file                                                      reads  edits  tests
src/js/internal/net/symbols.ts                                1      1     39
src/js/node/net.ts                                           16     14     39
src/js/node/tls.ts                                            1      1     39
test/js/node/tls/node-tls-connect.test.ts                     5      6     39
…t/js/node/tls/tls-shutdown-before-handshake-fixture.mjs      3      5     48

[robobun]

Status of the local verification (Linux x64 container, debug build of this branch at f111176):

• Reproduced on main and on bun 1.4.3 with the script in the description: node v26.3.0 prints peer: got FIN, bun does not.
• test/js/node/tls/node-tls-connect.test.ts passes as a whole (67 pass, 0 fail). It has eight new tests. Five fail on main, and four also run under node v26.3.0 and assert the same report there.
• The new fixture tests also passed on Windows x64 with a local debug build (at 8534dd8).
• Vendored node scripts (parallel/ and sequential/ test-tls-*, test-https-*, test-net-*, test-http2-*), each run as a plain script with a 120 s limit: 619 of 621 exit 0 at ed6872e. The ones that wrap a socket were run again after each later change to src/ and all exit 0. The two that do not:
  • parallel/test-tls-client-allow-partial-trust-chain.js is a node:test file (Cannot use describe outside of the test runner). Under bun test it passes.
  • parallel/test-https-timeout.js hangs on the debug build with and without this change (3 of 3 runs with origin/main's net.ts and tls.ts). It passes on the 1.4.3 release binary.

Review state: all review threads are resolved. The description lists what each review round changed, what stays different from node, and how this PR relates to #42340, #42343, #42330, #42350 and #36534. #42367 is closed, and its drain fix and tests are in this PR.

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---

Walkthrough

TLS upgrade paths now track pending transport-handle attachment and defer socket finalization until attachment completes. TLS finalization delegates handle-less sockets to the base implementation. Tests cover pending, closed, and same-tick server-side shutdown.

Changes

TLS pending-upgrade shutdown

Layer / File(s)	Summary
Track TLS handle attachment src/js/internal/net/symbols.ts, src/js/node/net.ts	Client and server TLS upgrades track pending handle attachment, clear the state after installation, and emit kUpgradeAttached.
Defer shutdown until attachment src/js/node/net.ts, src/js/node/tls.ts	_final() waits for pending attachment. Handle-less TLS sockets use base socket finalization.
Validate concurrent TLS shutdown test/js/node/tls/node-tls-connect.test.ts, test/js/node/tls/tls-shutdown-before-handshake-fixture.mjs	Tests cover end() and destroySoon() for pending, closed, and same-tick server-side TLS transports.

Suggested reviewers: cirospaciari

Priority: ➖ Normal

Merge Risk: ⚪ Minimal · up to 8534d

The pending TLS shutdown paths are covered by the added tests, with no reachable merge-blocking issue identified.

🚥 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 and concisely describes the main change: sending the FIN when TLSSocket.end() runs before the TLS handle attaches.
Description check	✅ Passed	The description explains the problem, root cause, fix, scope, compatibility considerations, and verification results. It does not use the exact template headings, but it provides the required content …

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Actionable comments posted: 1

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Inline comments:
In `@src/js/node/net.ts`:
- Around line 2287-2289: Update the pending-transport branch in
Socket.prototype._final to handle an already-destroyed supplied connection and
one-shot error/close events in addition to kUpgradeAttached. On terminal
transport failure, remove the pending connect listener, settle _final with the
transport error or closed-before-connection error, and destroy the TLS socket;
add a regression test covering a refused transport.

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[claude]

I reviewed this PR and didn't find any bugs. Because it changes _final ordering in the TLS socket lifecycle and the PR itself enumerates several remaining Node divergences and interactions with other open work, a human look would still be worthwhile.

What was reviewed:

• Every path that sets kUpgradePending either clears it and emits kUpgradeAttached, or destroys the socket (client once("connect") early-return, server nextTick destroyed/!handle/!result exits) — a destroyed stream never re-enters _final, so no listener is left hanging on a live socket.
• TLSSocket.prototype._final's new no-handle delegation preserves the old immediate-callback() behavior when nothing is pending (net's _final falls through to if (!socket) return callback()), and the deferred this._final.bind(this, callback) re-dispatches through TLSSocket.prototype._final so the secureConnecting/kPreHandshakeWrite gate still applies on the second run.
• this[kUpgradePending] is undefined on plain net.Sockets, so the new Socket.prototype._final guard is a no-op for non-TLS sockets.
• Tests: added to the existing file/fixture, port: 0, await real events (no sleeps), describe.concurrent, whole-object .toEqual, pipes drained via Promise.all, and pinned against Node via the existing describe.each([bun, node]) harness.

Extended reasoning...

Overview

The PR fixes end()/destroySoon() on a TLSSocket that has no native handle yet: previously TLSSocket.prototype._final short-circuited with callback() when !this._handle, so 'finish' fired immediately and no FIN was sent. The fix introduces a kUpgradePending flag on Socket covering the two windows where a TLS socket is waiting to adopt a handle — the client-side tls.connect({ socket }) transport-not-yet-connected case (src/js/node/net.ts:2077) and the server-side new TLSSocket(raw, { isServer: true }) next-tick wrap (net.ts:2420). Socket.prototype._final now defers via once(kUpgradeAttached, ...) while the flag is set, and TLSSocket.prototype._final delegates the no-handle case to NetSocket.prototype._final instead of finishing at once. Both upgrade paths clear the flag and emit kUpgradeAttached once _handle is assigned. Two new fixture modes exercise end()/destroySoon() across connecting/unconnected transports and same-tick server wraps under both Bun and Node.

Security risks

TLS socket lifecycle is security-adjacent, but this change only defers when the writable-side shutdown callback fires; it does not touch handshake, certificate verification, rejectUnauthorized, or any credential path. The new flag is an internal Symbol, not user-reachable. I don't see a way for this to weaken a security check or leave a connection in a more-open state than before — the change makes the FIN actually get sent where it previously wasn't.

Level of scrutiny

Medium-high. The mechanical change is small and mirrors the existing kUpgradeAttached pattern that _write already uses for the server wrap, but _final timing is contract in Node streams and the PR description itself lists several edge cases that remain divergent from Node (transport connect failure leaving a pending end(), raw.destroy() in the same tick as a server wrap, named-pipe/Duplex transports). Those are pre-existing and out of scope here, but a maintainer familiar with the TLS upgrade model (and the overlapping #36534 rework) should confirm this narrow fix doesn't conflict with the direction of that work.

Other factors

I traced every exit of the deferred callbacks: each either sets _handle and emits kUpgradeAttached, or destroys the socket. The one throw new Error("Invalid socket") inside the client once("connect") handler (line 2123) would skip the clear/emit, but that throw is pre-existing code and already broken independently of this PR. The delegation in tls.ts uses .$call per the builtin-module tamper-proofing convention, and the re-run via this._final.bind(this, callback) correctly dispatches through the TLSSocket override so the post-attach secureConnecting && kPreHandshakeWrite gate still applies. Tests follow repo conventions closely (existing file, existing run helper, event-awaited with no sleeps, describe.concurrent, whole-object .toEqual, run against Node to pin the expected report). The bug hunt exited on dry_streak with no findings.

[robobun]

^{Updated 4:10 PM PT - Sep 12th, 2026}

✅ @robobun, your commit 8ca4c0a6c4e373fe3f264ef695d7eebeee64051c passed in Build #114884! 🎉

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Inline comments:
In `@src/js/node/net.ts`:
- Around line 2077-2082: Update the TLS upgrade flow around the onConnect
callback and kUpgradePending so an already-destroyed connection is detected
before registering pending listeners; immediately destroy the TLS socket when
connection.destroyed is true, ensuring end() and destroySoon() do not wait for
kUpgradeAttached. Preserve the existing connect and close handling for live
connections.

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[robobun]

Two pushes after the first reviews:

• 5ab7559: a tls.connect({ socket }) transport that closes before it connects now destroys the TLS socket, as node's _wrapHandle does. A pending end() or destroySoon() ends in 'close'. New fixture mode closed-transport (refused transport, and transport destroyed before it connects).
• eb98f06: the kUpgradePending comment is one line now.

Not changed: a transport that is already destroyed at wrap time keeps the TLS socket waiting. Node v26.3.0 does the same, and a later raw.connect() completes the pending end() on both runtimes. The details are in the review thread. The transport's 'error' on the TLS socket stays with #38122.

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⚠️ Outside diff range comments (1)

src/js/node/net.ts (1)

2092-2093: 🩺 Stability & Availability | 🟠 Major | ⚡ Quick win

Handle failures from the deferred upgrade callback.

When upgradeTLSDeferred() returns no result, onConnect throws "Invalid socket" outside the surrounding try block. The callback then skips kUpgradePending = false and kUpgradeAttached. Catch upgrade failures in onConnect, clear the pending state, and use the existing error-and-close path.

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In `@src/js/node/net.ts` around lines 2092 - 2093, Update onConnect in the
upgradeTLSDeferred flow to catch failures, including a missing result that
currently throws “Invalid socket,” within the surrounding error handling. On
failure, clear kUpgradePending, preserve the kUpgradeAttached cleanup, and route
the error through the existing error-and-close path.

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Outside diff comments:
In `@src/js/node/net.ts`:
- Around line 2092-2093: Update onConnect in the upgradeTLSDeferred flow to
catch failures, including a missing result that currently throws “Invalid
socket,” within the surrounding error handling. On failure, clear
kUpgradePending, preserve the kUpgradeAttached cleanup, and route the error
through the existing error-and-close path.

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[robobun]

On the finding outside the diff (an upgrade that fails inside the deferred 'connect' callback): addressed in f6436a2, in a smaller form than suggested.

• What happens on a throw there: the callback runs inside the transport's 'connect' emit, which the native open handler drives. Bun routes an exception from that handler to the transport's error handler. The transport is destroyed with the error (or the error is dropped when the transport is already destroyed). Nothing reaches uncaughtException.
• The gap was that the callback removed its pending 'close' listener first. After a throw, nothing closed the TLS socket, and a pending end() stayed pending. The listener now stays until the upgrade has installed its own close hook, so the transport's 'close' still destroys the TLS socket.
• Reachable case, now a test: a 'connect' listener that was registered before tls.connect({ socket }) destroys the transport. upgradeTLSDeferred then gets no handle and throws. On main the TLS socket stays open forever. On this branch it closes (raw close, tls close) for no call, end() and destroySoon().

I did not add a try/catch that reports the failure as the TLS socket's 'error'. That changes how upgrade failures are reported in this path, and it belongs with the transport error reporting in #38122. The explicit throw new Error("Invalid socket") is not reachable here: upgradeTLSDeferred returns nothing only for a handle that is already TLS, and such a transport takes the stream-level path.

[claude]

Code review found no issues

No high-confidence issues detected in this change.

[robobun]

One more push after a review of my own: 0931c21.

• TLSSocket.prototype._final sent every no-handle case to net.Socket's _final. One state behaved worse than on main: a TLS socket whose upgrade fails synchronously in connect() has no handle and still reports connecting. A second tls.connect({ socket }) over a transport that is already wrapped gets there (Invalid socket). Its end() waited for a 'connect' that never comes. main reports 'finish' at once.
• Now only a pending upgrade takes the new path. kUpgradePending moved to internal/net/symbols so that tls.ts can read it. Every other no-handle state calls back at once, as on main. Checked with the double wrap: error: Invalid socket, close, finish again, and destroySoon() closes.

A correction to my comment above: I wrote that the explicit throw new Error("Invalid socket") cannot be reached from the deferred 'connect' callback. A transport that two TLS sockets wrap while it is still connecting does reach it, from the second socket's callback. The outcome is the one described there: the exception goes to the transport's error handler, and the 'close' listener destroys the TLS socket when the transport closes.

The description now lists what the review found and did not change, and how this PR overlaps with #42340, #42367, #42330 and #36534.

[claude]

This pull request has been reviewed before and this review found new issues. Where they share a root cause, one fix may close them together.

[claude]

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

[claude]

Code review found no issues

No high-confidence issues detected in this change.

[claude]

Code review found no issues

No high-confidence issues detected in this change.

[robobun]

Two pushes from the consolidation with #42367, which is closed in favor of this PR:

• db37e4b merges main and adds the parts that only node:tls: send the FIN when end() runs before a TLSSocket wrap's native handle attaches #42367 had: the kPreHandshakeWrite line in drain (end("") over a connecting transport now follows the handshake), its fixture mode and test, and the test for a server-side wrap whose native handle was closed directly.
• f111176 addresses a review of the combined diff. connectError destroys a wrap whose engine fails before it opens (the same lines as in node:tls: clear connecting on a TLSSocket that wraps a connected socket #42343). A server-side wrap of a socket that is still connecting keeps the behavior of main, because a shutdown of that adopted handle aborts in Handlers::mark_inactive on a debug build. One helper now clears the flag and emits kUpgradeAttached. The test for a 'connect' listener that destroys the transport moved into the fixture, so it runs under node v26.3.0 too.

The description is updated. It has a merge order for #42340, #42343, #38076, #38028 and #42330.

[claude]

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

[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.

[Jarred-Sumner]

Superseded by #44618, which consolidates the open TLS pull requests. This fix and its tests are in there, either as written, rewritten smaller, or merged with the other PRs that patched the same cause (see the "By area" list in that PR). Closing in favor of it.