fix: encode bytes in SessionAgent/Session.to_dict() for JSON serialization#1899
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fix: encode bytes in SessionAgent/Session.to_dict() for JSON serialization#1899giulio-leone wants to merge 1 commit intostrands-agents:mainfrom
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…ation SessionAgent.to_dict() and Session.to_dict() call asdict() directly without encoding bytes values, while SessionMessage.to_dict() correctly uses encode_bytes_values(). This inconsistency causes S3SessionManager and FileSessionManager to crash with: TypeError: Object of type bytes is not JSON serializable when agent state contains binary content (e.g., inline PDF bytes from multimodal prompts passed through LiteLLM proxy). Fix: Apply encode_bytes_values() in SessionAgent.to_dict() and Session.to_dict() (matching SessionMessage.to_dict()), and add decode_bytes_values() in SessionAgent.from_dict() for round-trip correctness. Added regression tests for bytes serialization in SessionAgent. Fixes strands-agents#1864
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Problem
S3SessionManagerandFileSessionManagercrash withTypeError: Object of type bytes is not JSON serializablewhen agent state contains binary content (e.g., inline PDF bytes from multimodal prompts via LiteLLM proxy).Root Cause
Inconsistent
to_dict()implementations:to_dict()SessionMessageencode_bytes_values(asdict(self))✅SessionAgentasdict(self)❌Sessionasdict(self)❌SessionMessage.to_dict()correctly usesencode_bytes_values()(which convertsbytes→{"__bytes_encoded__": True, "data": "<base64>"}) before JSON serialization. ButSessionAgent.to_dict()andSession.to_dict()skip this encoding, so anybytesvalues in agent state causejson.dumps()to crash.Fix
SessionAgent.to_dict(): Applyencode_bytes_values(asdict(self))— matchingSessionMessageSessionAgent.from_dict(): Applydecode_bytes_values()for round-trip correctness (matchingSessionMessage.from_dict())Session.to_dict(): Applyencode_bytes_values(asdict(self))for consistencyTests
Added two regression tests:
test_session_agent_with_bytes: VerifiesSessionAgentwith binary document content survives JSON round-triptest_session_with_bytes_in_session_type: VerifiesSession.to_dict()is JSON-safeAll 116 existing session tests + 9 type tests continue to pass.
Fixes #1864