# ThothII workflow UI contracts

- Pi reasoning arrives as nested `message_update.assistantMessageEvent.type = thinking_delta`.
  The backend maps it to the named SSE event `activity_delta`; the frontend EventSource must
  explicitly subscribe to that name. Model activity is separate from final `text_delta` output.
- Session create/resume must preserve the configured or persisted thinking level. Forcing
  `thinking: off` disables the upstream signal and makes the activity panel legitimately empty.
- A join-only `reviewer_decide` proposal is one complete, atomic join set. The read-only
  `join-review` widget persists every proposed join on Continue; `Other — specify` persists none
  and requires the model to propose the complete corrected set again. Ledger read, sequence
  assignment, and atomic replacement share a per-session cross-process writer lock.
- A v2 phase summary accepts `open_questions?: string[]`. Validate this at the gate boundary and
  normalize legacy malformed entries defensively in the viewer so one object cannot crash React.
- `SqlViewer`'s horizontal/vertical layout control is meaningful only with multiple SQL blocks;
  hide it for the single CTE result shown by `CteResultViewer`.
- A Pi turn is `idle`, `running`, `waiting`, or `failed`. A reviewer gate/request moves it to
  `waiting`; the reviewer response and steering move it back to `running`; provider failures
  remain `failed` after `agent_end` and emit only the fixed sanitized recovery message.
- Resume preserves `running`/`waiting` runtimes. It replaces `idle`/`failed` runtimes, clears the
  old SSE buffer/subscribers before cold resume, and reuses the persisted provider/model/thinking.
- A successful Resume of the already selected session increments the stream generation so React
  closes the old EventSource and opens the same session URL again. Failed Resume must not reconnect.
- SSE endpoints are intentionally keep-alive. Browser cleanup and one-off probes must explicitly
  close the EventSource or cancel/abort the response reader after their terminal event.