# US02-04 — Expose Job APIs and Activity Events

Epic: [E02](../E02-unified-workflow-shell.md)

As a frontend client, I want versioned job commands, status APIs, and activity events
so the browser can operate workflows without HTML responses or internal imports.

## Acceptance criteria

- `/api/v1` exposes typed job start, status, cancel, blocker, and event contracts.
- Operational endpoints return JSON; the event endpoint returns SSE with resumable IDs.
- SSE reconnects without duplicate/lost durable events and polling is sufficient as a
  fallback.
- Errors use the shared JSON envelope and correct status codes, including `409`.

## Automated tests

- OpenAPI/contract tests validate schemas, status codes, errors, and content types.
- Black-box tests cover SSE disconnect/reconnect, polling, idempotency, and cancellation.

## Dependencies

- US02-02, US02-03