fix(coding-agent): run extension slash commands immediately during active turns

[code-yeongyu]

Problem

Typing an extension slash command (e.g. /todo) while the agent is mid-turn showed its output only after the turn ended.

AgentSession.prompt() dispatched extension commands below the settled-session-work gate:

• interactive-mode.ts:3566 routes Enter-submitted commands to session.prompt(text) with no streamingBehavior.
• agent-session.ts:2580-2588 then awaits _waitForSettledSessionWork() before reaching the command dispatch.
• _scheduleContinuationAfterCurrentEvent() (agent-session.ts:4904) holds the SessionWorkBarrier for an entire continued run, so in goal-armed sessions every turn deferred commands to turn end. The same happened during compaction.

Two asymmetries showed this was unintended: the Alt+Enter path passes streamingBehavior, hits the canQueueWhileStreaming exemption, and already ran commands immediately; and builtin TUI commands (/model, /fork, …) were always immediate. The in-code comments claimed "extension commands execute immediately" — false for exactly these cases.

Change

1. Hoist the dispatch above the prompt-start bookkeeping and the settled-work gate. A synchronous getCommand() lookup runs first, so ordinary /-leading text gains no new await; a dedicated catch mirrors the existing preflightResult(false) + rethrow contract. Fixes every caller at once — TUI Enter path, the compaction path, RPC, print mode.
2. Guard /ir. Immediate dispatch newly exposes handlers to running turns and active compaction. An audit of all 23 registered command handlers found /ir alone unsafe (it aborts + disposes the live session; during compaction the fire-and-forget abortCompaction() races dispose()). Both ctx.isIdle() and ctx.isCompacting?.() are needed — isIdle() is true during compaction without streaming. Every other handler is safe or already reachable mid-turn via Alt+Enter.
3. Corrected comments in onSubmit / handleFollowUp. Note handleFollowUp is bound directly to app.message.followUp and never traverses onSubmit, so its command check is genuinely reachable.

Verification

Regression tests (test/suite/regressions/extension-command-immediate-dispatch.test.ts, TDD — RED captured before the fix, plus a mutation proof that reverting the hoist re-reds all three):

• Case A barrier-held continuation run · Case B blocked session_before_compact compaction · Case C idle with a held barrier
• Each asserts dispatch resolves before the held work is released, the run/compaction completes intact, no slash-command user message is appended, and preflightResult(true) / promptDisposition("handled") fire.

Pinned contracts stay green: 2023-queued-slash-command-followup, goal-continuation-streaming-prompt-trap, agent-session-prompt, agent-session-queue (queueing semantics untouched).

Scoped run: 9 files, 67/67 passing. npm run check: exit 0.

Full suite: 11 files fail on this branch — a strict subset of the 12 that fail on the base commit ec17cfc8a (rpc, stdout-cleanliness, session-*, mcp oauth-race, fswatch flakes). Zero new failures; footer-data-provider fails on base but passes here.

Real-CLI QA (senpi-qa tool-serve mock + tmux driver, hermetic sandbox, zero tokens) — captured ordering from the live TUI:

event	index in capture
/todo append notify	49879
/todo markdown - [ ] Qa item	54694
final assistant text	77335

The mid-turn screenshot shows the rendered todo widget while the status line still reads ● Working (16s • esc to interrupt). Pre-fix both outputs appeared only after index 77335. Teardown receipt recorded: tmux session killed, serve process dead, sandbox removed, real auth.json sha256 unchanged.

Plan: .omo/plans/immediate-extension-commands.md

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Summary by cubic

Run extension slash commands immediately during active turns and compaction by hoisting dispatch in AgentSession.prompt(). Also block /ir while the agent is busy to prevent unsafe session switches, and update comments/docs to match.

• Bug Fixes
  • Slash commands typed mid-turn (or during compaction) now execute immediately; they were previously delayed by the session-work barrier.
  • Dispatch occurs before the settled-work gate; unknown “/”-leading text is unaffected. Handled commands still call promptDisposition("handled") and preflightResult(true) with no user message added.
  • Guarded /ir: warn and return when streaming or compacting to avoid replacing the live session mid-run.
  • Updated comments in interactive mode and the /ir handler (now pointing to extensions/builtin/changes.md), and added a CHANGELOG.md entry.

^{Written for commit 846e074. Summary will update on new commits.}