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Neil b33d1972bc docs(relay): correct why the ConPTY teardown asset diverges from the desktop patch (#18636)
The divergence pinned by #18601 is real and worth keeping, but its stated reason
was wrong. It claimed the desktop patch carries the early conin placement "and
therefore the +2 File / +1 Process regression, measured against its exact
installed tree" -- i.e. that the shipped desktop app leaks because of its own
leak fix.

It does not, for any terminal a user opens. node-pty defaults `_useConptyDll` to
false. Every desktop site that opens a pane sets it true (`local-pty-utils.ts`
twice, `native-pty-spawn.ts`), as does the `windows-conpty-warmup.ts` warm-up, so
they take the `else` branch, where upstream already destroys the input socket. The
relay passes no such option (`src/relay/pty-handler.ts`) and takes the
`!useConptyDll` branch -- the one both this asset and the desktop patch edit.

The desktop is not entirely off that branch, though: the hidden rate-limit probes
in `src/main/rate-limits/claude-pty.ts` and `codex-pty-rate-limit-probe.ts` omit
the option, recur, and tear down through `kill()`, so the hunk is live there --
just never for a visible pane. Whether the early placement costs the same +2 File
/ +1 Process across a probe's lifecycle is unmeasured; the numbers in this comment
were taken on relay-style spawn/kill cycles, and the comment now says so. What is
settled is the replaced claim: not every Windows user, and not every terminal.

Those two probes were missed three enumerations running because they use
`await import('node-pty')`, which no static-import grep finds. The comment now
tells the next reader to grep for `node-pty` instead.

The measurement that produced the wrong claim was taken by a standalone harness
that passed no `useConptyDll` and so defaulted into the branch it was not trying
to measure -- the same standalone-is-not-the-real-host trap #18601's own body
warns about, one level down.

Also refreshes the self-exit paragraph, which #18635 made stale. That leak is now
fixed for the desktop, and the note records why the fix cannot reach a Windows
relay. The fix is mostly native (`src/win/conpty.cc`) and this asset only rewrites
`lib/*.js`, and all three delivery paths stop short of Windows: pnpm patches do
not cross the SSH boundary; `MATRIX_SLOTS` in `build-orcad-prebuilds.mjs` has no
win32 entry; and the one relay asset that does patch native source and rebuild on
the host (`node-pty-1.1.0-master-cloexec-patch.cjs`) returns
`skipped:unsupported-platform` for anything but linux/darwin. #18635's flat self-exit relay numbers were measured
against a locally rebuilt binary, so they describe the relay code path on a
patched tree, not the tree a relay host installs -- the note says so explicitly
rather than leaving the next reader to conflate them.

Assertion and hashes unchanged: the relay must still release conin after the
console-list fork, and a patch sync must still not copy the early placement onto
the relay's branch, where it does cost +2 File and +1 Process per terminal. Only
the justification changes, plus the test name, which said "like the desktop
patch" where it meant "unlike the desktop patch placement".
2026-09-04 22:40:38 -07:00
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