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Python: [Bug]: make_json_safe() raises RecursionError on a plain Enum member #9194
Description
Description
agent_framework._serialization.make_json_safe() is documented to fall back to str() "so that json.dumps never raises". A plain Enum member breaks that. It is not a scalar and has no to_dict() or model_dump(), so it reaches the vars(obj) fallback. Among its attributes is __objclass__, the enum class itself, and walking the class leads back to its members, so the call recurses until RecursionError.
Members of enums with a str or int mixin are not affected, because they take the scalar branch.
It shows up wherever arbitrary values pass through make_json_safe(). In AG-UI, for example, _safe_serialize_session_continuation_state() catches the error and saves the snapshot with session_state=None, so the session state is dropped without an error reaching the caller. Marimo (@SuperMarimoBros) ran into it in discussion #9189.
Code Sample
from enum import Enum
from agent_framework._serialization import make_json_safe
class Color(Enum):
RED = 1
make_json_safe({"color": Color.RED})Error Messages / Stack Traces
File ".../agent_framework/_serialization.py", line 779, in make_json_safe
return {key: make_json_safe(value) for key, value in vars(obj).items()}
RecursionError: maximum recursion depth exceeded
Package Versions
agent-framework-core: 1.20.0 (main at 3d0bde5)
Python Version
Python 3.12
Additional Context
A fix that keeps every current output: an Enum branch right after the scalar check that returns make_json_safe(obj.value). Mixin enums still return through the scalar branch unchanged, and .value is what json.dumps already writes for IntEnum and StrEnum. I have it ready with tests and can open the PR.
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github-actions commentedon Oct 8, 2026
🤖 Automated triage reproduction notes (agent-authored — trust but verify)
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Repro:
python/packages/core/agent_framework/_serialization.py::make_json_safeat lines 756 and 779 recursively traverses a plainEnummember untilRecursionError. Minimal repro: defineColor(Enum)withRED = 1, then callmake_json_safe({"color": Color.RED}).python/packages/core/tests/core/test_observability.py1.20.01.20.0Python: make_json_safe serializes plain Enum members by value instead…