The paragraph claimed later child output reaches only the scrollback. Output
after a settle still reaches the scrollback and whichever send is active when
it arrives — appendOutput writes both (session.ts:302-307), and settleActive
clears `active` rather than suppressing delivery. Only the settled operation
stops receiving it, which is what the timing bound protects.
master already stabilized the raw-mode SIGINT scenario in 65e0ffe03 and
3be090f1d with wider scenario-owned bounds and deliberately delayed child
readiness, so the merge takes master's test implementation. What this branch
keeps is the contract that explains why those bounds are required: the note
paragraph on the settle boundary in PtySendOperation.append, and the
waitForOutput comment recording that raising its deadline alone cannot
recover output the send never collected.
The Agent Note paragraph recorded test-specific timing advice, which
docs/AGENTS.md excludes from implemented notes. The durable half of it —
LocalSendOperation.append drops output after settle, so it survives only in
the scrollback — now documents append itself.
The local PTY readiness poll held its inferred_idle fallback for exactly
one pollIntervalMs after a prompt marker, so a bash foreground handoff
that lands on the silence boundary only wins the exact stdin_read
attribution when the kernel publishes it inside that single poll. On a
slow or loaded host it does not, and the attribution flips.
handoffGraceMs replaces the hardcoded one-poll window as a validated,
deployment-owned config field defaulting to 500ms, rejected at load when
it cannot contain one readiness poll. Real-shell tests that interrupt a
send now assert the session is usable again rather than which readiness
tier observed the handoff, because no fixed grace removes the race.
The darwin-parity job failed intermittently on the SIGINT test with the
operation buffer holding only the echoed command line, never RAW_READY. The
harness sets idleSilenceMs to 250, so when a cold python3 start stays silent
past that bound the send settles as inferred_idle; PtySendOperation.append then
drops all later output, and the marker reaches only the scrollback.
Give the harness per-test idleSilenceMs/timeoutMs overrides and let this
scenario raise both above interpreter startup latency, so the readiness marker
lands inside the send it belongs to. waitForOutput's own deadline and the test
timeout grow to match the new bounds.
The product timings are unchanged; the pty Agent Note records why a test that
waits on an operation must outlast the child's startup.
