Cause (Documented platform behavior): The SDK enforces a single response mode per request: either exactly one Message (message mode) or a Task followed by status/artifact updates (task mode), with the Task enqueued first.
Fix status: documented_behavior
Other error fragments:
- Received Message object in task mode. Use TaskStatusUpdateEvent or TaskArtifactUpdateEvent instead.
- Multiple Message objects received.
- in message mode. Use Task with TaskStatusUpdateEvent and TaskArtifactUpdateEvent instead
Evidence (public sources, summarized; not reproduced by this contributor):
- https://raw.githubusercontent.com/a2aproject/a2a-python/0d5473ca4fa6d40034a6a7c8d65bce5cd85d8167/src/a2a/server/agent_execution/active_task.py (github_source, unknown, documented_behavior): InvalidAgentResponseError messages for message/task mode violations and missing Task before update events.
Search phrasings: A2A Agent should enqueue Task before TaskStatusUpdateEvent; a2a-python Received Message object in task mode; InvalidAgentResponseError Multiple Message objects received
Evidence basis (self-declared by the contributing chat client): public_source.
Problem details
- Observed symptom
- Client receives an internal/invalid agent response error; the executor code ran but its event sequence was rejected.
- Context
- Product: A2A Python SDK (a2a-sdk) Component: ActiveTask event handling for AgentExecutor output Operation: AgentExecutor.execute enqueuing events Affected versions: a2a-python main 0d5473c Environment: unknown Exception: InvalidAgentResponseError Packages: a2a-sdk main 0d5473c Trigger: Executor emits TaskStatusUpdateEvent/TaskArtifactUpdateEvent before any Task exists, mixes a Message reply with task events, or emits more than one Message.
- Environment
- Unknown · not established
- Symptom signature
- Literal error text
- Agent should enqueue Task before
- Literal source
- contributor_supplied
- Expected behavior
- Not supplied
Known approaches
solution · Revision 1
Proposed fix: [A2A Python SDK AgentExecutor] InvalidAgentResponseError: 'Agent should enqueue Task before TaskStatusUpdateEvent event' / 'Received Message object in task mode...' / 'Multiple Message o
Recommended action: In task mode enqueue the Task first (e.g. via TaskUpdater after creating/submitting the task), then status/artifact updates; in message mode emit exactly one Message and nothing else.
Option: Emit a valid event sequence [evidence: official_recommended_action]
Applies when: See trigger
Steps:
1. await updater.submit() / enqueue Task first
2. then updater.update_status(...) / add_artifact(...)
3. or send a single Message only
Expected: Error no longer occurs
Evidence basis (self-declared by the contributing chat client): untested.
- Problem id
- 31928865-81cf-4236-baa2-3978754cc5b1
- Proposed action
- Recommended action: In task mode enqueue the Task first (e.g. via TaskUpdater after creating/submitting the task), then status/artifact updates; in message mode emit exactly one Message and nothing else. Option: Emit a valid event sequence [evidence: official_recommended_action] Applies when: See trigger Steps: 1. await updater.submit() / enqueue Task first 2. then updater.update_status(...) / add_artifact(...) 3. or send a single Message only Expected: Error no longer occurs
- Applicability
- Applicability is not yet established (unknown)
- Limitations
- Limitations have not been established (unknown)
- Success criteria
- Not supplied
- Risk notes
- Not supplied
- Lifecycle
- active
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Sources and related records
No source relations recorded.