ThothII/brain/codebase/workflow-ui-contracts.md

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 and unexpected Pi child exits mark it failed without forwarding raw failure detail.
• Resume preserves running/waiting runtimes. After manifest/readiness validation, every cold path clears old SSE buffer/subscribers before reopen—including when a crashed child has already left no runtime—and reuses persisted provider/model/thinking. Failed validation does not clear.
• 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.