[jaredLunde]

Fixes serve audit defect #4 (HANG).

do_compact! selected only on the checkpoint channel and the compaction future. compaction_cancel was never cancelled, and input_rx and shutdown were never polled. So abort, get_state and SIGTERM all waited for the summary call, which can take up to the 600 s stream idle timeout. In the audit's repro, get_state and abort sent 700 ms in were answered only after the compact response, SIGTERM was honoured 7 s later, and get_state reported is_compacting:false throughout. A deferred compact (one that runs after the prompt it arrived during) behaved the same way.

Change. The compaction now runs inside a select shaped like the host-bash loop:

• abort cancels compaction_cancel. The compaction ends unapplied and nothing on disk changes. The abort ack is sent after the compact response, the way a mid-run abort is acknowledged.
• Shutdown and stdin EOF cancel the compaction and end the session. The macro now evaluates to whether the session goes on, and both call sites (idle and deferred) act on that.
• get_state (is_compacting: true, message_count as it stands until the compaction lands), get_session_stats and get_messages are answered from a snapshot taken before the compaction starts.
• MCP Events injections are deferred, mcp_events_* commands are dispatched, and every other command is refused as busy.

The macro moved below the shutdown/deferred_events/dispatch_events declarations it now uses. It keeps #265's BusyGuard: now that EOF cancels a compaction, the guard is what stops a reap or drain from cutting one short. Docs are updated in serve.rs's module doc and ARCHITECTURE.md (the is_compacting passage and the MCP Events deferral note).

Tests. crates/agent/tests/serve_compact_cancellable.rs (new). The summary call stalls 20 s:

• abort_cancels_a_manual_compact_and_reads_are_answered_meanwhile: get_state is answered before compact with is_compacting:true. set_session_name gets a busy refusal. abort cancels the compaction in well under 5 s, and the transcript on disk is unchanged.
• sigterm_ends_a_manual_compact_promptly: the process exits within 3 s of SIGTERM.

Both tests fail on the old code. #265's reaper_spares_a_detached_compact still passes. The agent and agent-core suites, clippy -D warnings, fmt and dprint all pass.

Side note, not changed here: the busy prompt loop's get_messages arm reads since from the prompt's cmd instead of the incoming c.

🤖 Generated with Claude Code

https://claude.ai/code/session_01JimHGjsfk2Ktm5GxyZJKKk