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NeilandBrennan
bc319abfbe
Root-cause follow-up to #15559, which stopped a CPR overtaking a deferred colour reply but left the deferral itself in place. Orca answers terminal queries by writing to the PTY master, which a line discipline in ECHO copies straight back out as junk on a cooked prompt (#12112). The guard was to withhold the write until an `stty` subprocess proved ECHO clear — and forking is what forced the decision to be async. Any deferral, however short, lets a reply written later in the same turn overtake this one, so the async probe was the bug's root cause. Read the bit synchronously instead. Linux and the BSDs redirect a master's mode ioctls to the slave, so a `tcgetattr` on the master fd node-pty already owns answers for the slave with no fork: measured 0.26us against 2403us for the subprocess. With a verdict available inline, a querying program that already cleared ECHO — every raw-mode prober, including the colour probe behind the `gh auth login` report — is answered in its own turn and can never be reordered. The deferral stays for the genuinely cooked case, and the ordering guarantee stays underneath it: hosts whose node-pty predates this patch get no sync probe and fall back to the deferred path, which mixed client/host versions make a live production path. Reply routing is all-or-nothing: a payload needing neither containment nor ordering stays on the host's own path, so a CPR answered during shell startup cannot pass the daemon's post-ready flush gate and splice into the buffered startup command. Native side is fail-safe: a kernel that did not redirect would answer from the master's own termios, whose ECHO defaults set, so the degraded verdict is "echoing" — never a false "quiet". The JS half ships in the pnpm patch while the binding needs a source build, so ORCA_REQUIRE_NODE_PTY_ECHO_STATE=1 makes CI fail rather than silently skip when it is handed an upstream prebuild. Co-authored-by: Brennan <brennanb2025@users.noreply.github.com>