What changed
Five coordinated additions to Claude Managed Agents landed today: (1) effort level on the agent model configuration object at creation time; (2) webhooks covering environment.* (four types) and memory_store.* (three types) lifecycle events; (3) session seeding with initial_events β up to 50 user.message and user.define_outcome events at POST /v1/sessions, starting the agent loop in the same call; (4) thread-level event stream deltas on GET /v1/sessions/{session_id}/threads/{thread_id}/stream via the event_deltas[] query parameter; (5) version field now optional on agent updates. Anthropic SDK Python v0.118.0 ships all five.
TL;DR
Claude Managed Agents now supports per-agent effort-level control, environment and memory store lifecycle webhooks, session pre-seeding with up to 50 events at creation (agent loop starts immediately), per-thread delta streaming of subagent text, and unconditional agent updates β all live today, supported in Python SDK v0.118.0.
Developer signal
Five changes, each targeting a distinct integration gap:
(1) Effort on model config β Pass effort inside the model object when you create an agent (POST /v1/agents). This sets a default effort level for that agent's sessions. Previously, effort control required per-call configuration. Now you can define separate agents for high-quality vs. throughput-focused workloads and let the agent definition carry the effort setting. See Effort levels.
(2) Environment and memory_store webhooks β Four environment.* event types and three memory_store.* event types now available in the webhooks subscription. Previously, knowing when a sandbox environment was ready or a memory store updated required polling the status endpoint. Subscribe via Subscribe to webhooks. This closes a polling gap in event-driven agent orchestration.
(3) Session seeding with initial_events β Pass initial_events (array of user.message and/or user.define_outcome events, up to 50) on POST /v1/sessions. If the list is non-empty, the agent loop starts immediately in the same call β no separate send-events request needed to kick off work. This reduces round-trips for initialization-heavy agents: you can deliver user context, task state, and an outcome definition in a single API call and receive the session ID with the agent already running. See Seed the session with initial events.
(4) Thread stream event deltas β GET /v1/sessions/{session_id}/threads/{thread_id}/stream now accepts event_deltas[] with the same options as the session-level stream. Preview a subagent's text as it generates, before the complete agent.message event arrives. Migration note: the delta type is content_delta, not content_block_delta β accumulator code written for the Messages API streaming does not carry over unchanged. Rewite any accumulator that handles these events. See Preview session thread events.
(5) Version field optional on agent update β Supply version to PATCH /v1/agents/{id} for optimistic concurrency (409 on mismatch), or omit it to apply the update unconditionally. Previously required; now opt-in. See Update semantics.
SDK: pip install --upgrade anthropic (v0.118.0) for all five additions.