[kitlangton]

Problem

Triggering a compaction (e.g. /compact) leaves the session stuck "running" in the TUI forever — it looks like the compaction never stops.

Two root causes:

1. TUI never returns to idle. session.next.compaction.started sets the session status to running (data.tsx), but session.next.compaction.ended only appends the compaction message. For manual compaction there is no runner step, so no step.ended/step.failed ever arrives to reset the status.
2. Failed compactions have no terminal event at all. SessionCompaction.compact publishes Compaction.Started, then returns false on summarization failure (provider error / empty summary) without publishing anything, so every client that reacted to Started waits forever.

Fix

• schema: add live-only SessionEvent.Compaction.Failed (session.next.compaction.failed). A failed compaction produces no durable message, so it is not added to DurableDefinitions (same live-only classification as Compaction.Delta).
• core: publish Compaction.Failed on the summarization failure path after Started; no-op handler in the message updater.
• tui: set session status to idle on compaction.ended and compaction.failed. Mid-run auto compaction is immediately followed by step events that set running again.
• Regenerated packages/client/src/generated (bun run generate) and the legacy JS SDK (packages/sdk/js/script/build.ts). Note: the legacy SDK regeneration also picked up the previously-unregenerated session.synthetic route/metadata surface that was already on v2.

Tests

• Core: manual compaction failure publishes a terminal failed event — asserts Compaction.Failed is observed live, no compaction message is projected, and only Started is durably recorded.
• TUI: extended tracks session status from active sessions and execution events with compaction started -> ended -> idle and started -> failed -> idle transitions.
• Schema: updated the event-manifest count expectations. These were already failing on v2 (expected 63, received 65) from earlier unregenerated event additions; the new counts (66/97/97) reflect the actual current surface including this event.

Note: packages/client exposes every standard HTTP API group also fails on the base branch (pre-existing, unrelated).

[kitlangton]

Closing because this behavior has been absorbed into the current V2 compaction architecture, including terminal session.compaction.ended and session.compaction.failed events and the corresponding TUI handling.