fix: filter non-serializable objects from stream events in prepare()#1941
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Exploreunive wants to merge 1 commit intostrands-agents:mainfrom
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fix: filter non-serializable objects from stream events in prepare()#1941Exploreunive wants to merge 1 commit intostrands-agents:mainfrom
Exploreunive wants to merge 1 commit intostrands-agents:mainfrom
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Non-serializable objects (Agent instances, OpenTelemetry Spans, etc.) from invocation_state were being merged into event dicts via prepare(), causing JSON serialization failures when consumers attempt to serialize yielded events. Added _is_json_serializable() and _sanitize_invocation_state() helpers to dynamically filter non-serializable values before merging. This approach is more robust than maintaining a hardcoded blocklist. Fixes strands-agents#1928
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Problem
ModelStreamEvent.prepare()merges the entireinvocation_statedict into yielded event dicts.invocation_statecontains non-serializable objects likeAgentinstances, OpenTelemetrySpans, andTraceobjects. When consumers (e.g., AgentCore SSE streaming) attempt to serialize these events, it fails withTypeErrorand potentially dumps >100MB of object repr data.Related issue: #1928
Solution
Added
_is_json_serializable()and_sanitize_invocation_state()helpers to dynamically filter out non-serializable values before merging inprepare(). This approach is:json.loads(json.dumps(v))Changes
src/strands/types/_events.py: Added_is_json_serializable()and_sanitize_invocation_state(), updatedModelStreamEvent.prepare()tests/strands/agent/hooks/test_agent_events.py: Updatedany_propsto remove filtered fieldstests/strands/agent/test_agent.py: Updated stream test expectationTesting
agent,event_loop_cycle_span,event_loop_cycle_traceare properly filtered from stream events