(triggers): after /compact, a chain step's Enter becomes a line break and the step is logged as sent

[devsuitup]

After a /compact chain, step 1 ("Reprise après compaction : …") lands in the composer but its Enter becomes a line break; the message sits unsent while main.log says Chain step 1 sent (e.g. 2026-10-01 22:15:49 on 7615734f, step 0 at 22:13:52). Recurring.

What the code shows (at 4608df0)

• submitToPty (trigger-watcher.js ~154-161) writes the text in one write, waits DEFAULT_SUBMIT_ENTER_DELAY_MS = 50 ms, then writes \r alone. No bracketed paste, no multi-line.
• The "sent" log is emitted after submitWithVerify whatever happened. The verify (pollForBusyObserved ~316-338) is a level probe: any _cliBusy=true within 2 s passes, and _cliBusy comes from OSC titles / OSC 9;4 — so the spinner that ends a compaction satisfies it and the recovery Enter is never armed.
• .ai/contexts/trigger-watcher.md (~741-752) already records the 0.0.64 case where even a lone retry \r, seconds later, was absorbed as a newline: the CLI's post-compaction state, not the 50 ms timing, eats the Enter. fix(triggers): close two false-confirm gaps in chain submission verify #185 (settle), fix(triggers): make waitForBusyFall wait for the busy rise #190 (busy-rise wait) and the midBusy gate did not touch that.

Proposal

• Readiness: before a step that follows /compact, wait for the CLI's own descriptor (~/.claude/sessions/<pid>.json) to say status: "idle" with a statusUpdatedAt after the compact step (read at CLI 2.1.286: idle = at the prompt, waiting = a dialog is open, busy = working), bounded.
• Proof of submission: an edge, not a level — the descriptor going idle→busy after our write, or the transcript gaining the user line; otherwise one recovery Enter, and if that still does not submit, log a warning that names it instead of "sent".

Deciding measurement (isolated instance, real CLI): /compact → text with SWITCHBOARD_SUBMIT_ENTER_DELAY_MS 50 / 500 / 3000, with and without waiting for the descriptor's idle.

[jbr-sekoia]

Another occurrence, on a step that does not follow /compact — for the v0.0.86 check of #410.

Running app: 0.0.85 (without #410). Session 2a633039, main.log:

16:08:40.921–.924  [subagent-spawn] 3 × reviewer-adversarial
16:09:09.632       [subagent-spawn] implementer
16:09:10.935       [subagent-complete] one of the reviewers
16:09:36.268       [trigger-watcher] Chain step 0 sent to 2a633039-…: Write the resume note now — …

Step 0 of a compact-now.sh chain (the resume-note prompt) landed in the composer, and its Enter became a line break. The log still says sent. Four background subagents had been started less than a minute before; three were still running.

Against #410:

• The descriptor edge proof and the not confirmed submitted warning apply to every step, so this case would no longer be logged as sent.
• The readiness wait only runs before a step that follows /compact. Nothing waits before step 0, including while background agents are running.
• Whether the recovery \r submits here is not measured. .ai/contexts/trigger-watcher.md records a lone \r, sent seconds later, absorbed as a newline as well.

Measurement worth adding to the one in the issue: step 0 sent while a background agent is running (no /compact before it), with the descriptor's status and statusUpdatedAt recorded at the write and at the Enter.