Seed a Managed Agents session with `initial_events` and start the agent loop in one call instead of two
Claude Platform release notes·medium signal
Since July 22, `POST /v1/sessions` accepts an `initial_events` array of up to 50 `user.message` and `user.define_outcome` events; a non-empty list starts the agent loop in the same request, removing the separate send-events round trip that every session previously needed. The same release made the `version` field optional on agent updates — supply it for optimistic concurrency (mismatch returns 409), omit it to apply unconditionally. Both are small API shape changes that remove boilerplate from every session-spawning code path.