Python: Fix core observability unsafe serialization of function-call arguments containing dataclass/framework objects (#6026)

* fix: safely serialize function-call arguments in core observability

Apply make_json_safe() to content.arguments in _to_otel_part() before
building the otel message dict, so that dataclass/framework payloads
(e.g. workflow request_info events) do not cause a TypeError when
_capture_messages() calls json.dumps().

Lift make_json_safe() into agent_framework._serialization (no new
external deps — dataclasses/datetime only) so the core observability
path can use it without a dependency on the ag-ui adapter.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* fix(core): safely serialize workflow request_info payloads in observability (#5733)

- Add make_json_safe() helper to recursively convert non-serializable objects
- Use make_json_safe() in _to_otel_part() for function_call arguments
- Fix CustomPayload test class to use @dataclass (resolves B903 lint error)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* fix(serialization): guard callability and normalize dict keys in make_json_safe (#5733)

- Use callable(getattr(obj, method, None)) instead of hasattr() so that
  non-callable attributes named model_dump/to_dict/dict do not raise
  TypeError at runtime.
- Wrap each call in try/except TypeError to handle callables with
  mandatory arguments gracefully.
- Convert dict keys to str() so that non-string keys (e.g. datetime,
  int) cannot cause json.dumps to raise TypeError.
- Add regression tests for both scenarios.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Address observability serialization review feedback

---------

Co-authored-by: Copilot <copilot@github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

python/packages/core/agent_framework/_serialization.py

@@ -7,6 +7,8 @@ import json
 import logging
 import re
 from collections.abc import Mapping, MutableMapping
+from dataclasses import asdict, is_dataclass
+from datetime import date, datetime
 from typing import Any, ClassVar, Protocol, TypeVar, runtime_checkable
 
 logger = logging.getLogger("agent_framework")
@@ -614,3 +616,46 @@ class SerializationMixin:
         # Fallback and default
         # Convert class name to snake_case
         return _CAMEL_TO_SNAKE_PATTERN.sub("_", cls.__name__).lower()
+
+
+def make_json_safe(obj: Any) -> Any:
+    """Recursively convert an object to a JSON-serializable form.
+
+    Handles dataclasses, Pydantic models, objects with ``to_dict``/``dict``/``__dict__``,
+    datetimes, lists, dicts, and primitives.  Falls back to ``str()`` for any remaining
+    non-serializable value so that ``json.dumps`` never raises a ``TypeError``.
+
+    Args:
+        obj: Object to make JSON safe.
+
+    Returns:
+        A JSON-serializable version of the object.
+    """
+    if obj is None or isinstance(obj, (str, int, float, bool)):
+        return obj
+    if isinstance(obj, (datetime, date)):
+        return obj.isoformat()
+    if is_dataclass(obj) and not isinstance(obj, type):
+        return make_json_safe(asdict(obj))  # type: ignore[arg-type]
+    if callable(getattr(obj, "model_dump", None)):
+        try:
+            return make_json_safe(obj.model_dump())  # type: ignore[no-any-return]
+        except TypeError:
+            pass
+    if callable(getattr(obj, "to_dict", None)):
+        try:
+            return make_json_safe(obj.to_dict())  # type: ignore[no-any-return]
+        except TypeError:
+            pass
+    if callable(getattr(obj, "dict", None)):
+        try:
+            return make_json_safe(obj.dict())  # type: ignore[no-any-return]
+        except TypeError:
+            pass
+    if isinstance(obj, dict):
+        return {str(key): make_json_safe(value) for key, value in obj.items()}  # type: ignore[misc]
+    if isinstance(obj, (list, tuple)):
+        return [make_json_safe(item) for item in obj]  # type: ignore[misc]
+    if hasattr(obj, "__dict__"):
+        return {key: make_json_safe(value) for key, value in vars(obj).items()}  # type: ignore[misc]
+    return str(obj)

python/packages/core/agent_framework/_workflows/_agent.py

@@ -12,6 +12,7 @@ from datetime import datetime, timezone
 from typing import TYPE_CHECKING, Any, ClassVar, Literal, cast, overload
 
 from .._agents import BaseAgent
+from .._serialization import make_json_safe
 from .._sessions import (
     AgentSession,
     ContextProvider,
@@ -61,7 +62,7 @@ class WorkflowAgent(BaseAgent):
         data: Any
 
         def to_dict(self) -> dict[str, Any]:
-            return {"request_id": self.request_id, "data": self.data}
+            return {"request_id": self.request_id, "data": make_json_safe(self.data)}
 
         def to_json(self) -> str:
             return json.dumps(self.to_dict())

python/packages/core/agent_framework/_workflows/_functional.py

@@ -47,6 +47,7 @@ from copy import deepcopy
 from typing import Any, Generic, Literal, TypeVar, overload
 
 from .._feature_stage import ExperimentalFeature, experimental
+from .._serialization import make_json_safe
 from .._types import AgentResponse, AgentResponseUpdate, ResponseStream
 from ..observability import OtelAttr, capture_exception, create_workflow_span
 from ._checkpoint import CheckpointStorage, WorkflowCheckpoint
@@ -1515,7 +1516,7 @@ class FunctionalWorkflowAgent:
         function_call = Content.from_function_call(
             call_id=request_id,
             name=self.REQUEST_INFO_FUNCTION_NAME,
-            arguments={"request_id": request_id, "data": event.data},
+            arguments={"request_id": request_id, "data": make_json_safe(event.data)},
         )
         return Content.from_function_approval_request(
             id=request_id,

python/packages/core/tests/core/test_observability.py

@@ -1691,6 +1691,65 @@ def test_to_otel_part_function_call():
     }
 
 
+def test_to_otel_part_function_call_reuses_prepared_arguments():
+    """Test _to_otel_part does not re-serialize function-call arguments in the observability hot path."""
+    from agent_framework import Content
+    from agent_framework.observability import _to_otel_part
+
+    arguments = {"payload": object()}
+    content = Content(type="function_call", call_id="call_789", name="handoff", arguments=arguments)
+    result = _to_otel_part(content)
+
+    assert result is not None
+    assert result["arguments"] is arguments
+
+
+def test_make_json_safe_non_callable_method_attribute():
+    """Test make_json_safe handles objects where model_dump/to_dict/dict are non-callable attributes."""
+    from agent_framework._serialization import make_json_safe
+
+    class ObjWithNonCallableModelDump:
+        model_dump = 42  # not callable
+
+    obj = ObjWithNonCallableModelDump()
+    result = make_json_safe(obj)
+    assert result == {}
+
+
+def test_make_json_safe_callable_method_type_error_falls_through():
+    """Test make_json_safe falls through when serializer-like methods require arguments."""
+    from agent_framework._serialization import make_json_safe
+
+    class ObjWithRequiredArgModelDump:
+        def __init__(self) -> None:
+            self.value = "fallback"
+
+        def model_dump(self, required: str) -> dict[str, str]:
+            return {"required": required}
+
+    obj = ObjWithRequiredArgModelDump()
+    result = make_json_safe(obj)
+    assert result == {"value": "fallback"}
+
+
+def test_make_json_safe_dict_with_non_string_keys():
+    """Test make_json_safe converts non-primitive dict keys to strings."""
+    import json
+    from datetime import datetime
+
+    from agent_framework._serialization import make_json_safe
+
+    dt_key = datetime(2024, 1, 1)
+    obj = {dt_key: "value", 42: "num_value", "str_key": "normal"}
+    result = make_json_safe(obj)
+    # json.dumps must not raise TypeError
+    serialized = json.dumps(result)
+    parsed = json.loads(serialized)
+    assert parsed[str(dt_key)] == "value"
+    assert parsed["42"] == "num_value"
+    assert parsed["str_key"] == "normal"
+
+
 def test_to_otel_part_function_result():
     """Test _to_otel_part with function_result content."""
     from agent_framework import Content
@@ -3019,6 +3078,49 @@ async def test_system_instructions_preserves_non_ascii_characters(span_exporter:
     assert [msg.get("role") for msg in input_messages] == ["user"]
 
 
+@pytest.mark.parametrize("enable_sensitive_data", [True], indirect=True)
+def test_capture_messages_with_prepared_request_info_function_call_arguments(span_exporter: InMemorySpanExporter):
+    """Test _capture_messages handles request-info function-call arguments prepared at Content creation."""
+    import dataclasses
+    import json
+
+    from opentelemetry import trace
+
+    from agent_framework import WorkflowAgent
+
+    @dataclasses.dataclass
+    class HandoffRequest:
+        target_agent: str
+        reason: str
+
+    arguments = WorkflowAgent.RequestInfoFunctionArgs(
+        request_id="call_dc",
+        data=HandoffRequest(target_agent="helper", reason="overflow"),
+    ).to_dict()
+    msg = Message(
+        role="assistant",
+        contents=[
+            Content(
+                type="function_call",
+                call_id="call_dc",
+                name="request_info",
+                arguments=arguments,
+            )
+        ],
+    )
+    span_exporter.clear()
+    tracer = trace.get_tracer("test")
+    with tracer.start_as_current_span("test_span") as span:
+        _capture_messages(span=span, provider_name="test_provider", messages=[msg])
+
+    spans = span_exporter.get_finished_spans()
+    span = spans[0]
+    input_messages = json.loads(span.attributes[OtelAttr.INPUT_MESSAGES])
+    tool_part = input_messages[0]["parts"][0]
+    assert tool_part["type"] == "tool_call"
+    assert tool_part["arguments"]["data"] == {"target_agent": "helper", "reason": "overflow"}
+
+
 def test_capture_messages_keeps_framework_instructions_out_of_logs_and_span_messages(
     span_exporter: InMemorySpanExporter,
 ):

python/packages/core/tests/workflow/test_functional_workflow.py

@@ -5,6 +5,7 @@
 from __future__ import annotations
 
 import asyncio
+import json
 import logging
 from collections.abc import Iterator
 from contextlib import contextmanager
@@ -1642,6 +1643,37 @@ class TestFunctionalWorkflowAgentHITL:
                     break
         assert approval_found, "expected FunctionApprovalRequestContent in agent response"
 
+    async def test_request_info_dataclass_arguments_are_serialized_for_agent(self):
+        @dataclass
+        class HandoffRequest:
+            target_agent: str
+            reason: str
+
+        @workflow
+        async def wf(x: str, ctx: RunContext) -> str:
+            answer = await ctx.request_info(
+                HandoffRequest(target_agent=x, reason="overflow"),
+                response_type=str,
+                request_id="rid-1",
+            )
+            return f"got:{answer}"
+
+        agent = wf.as_agent()
+        response = await agent.run("helper")
+
+        function_call_arguments = None
+        for message in response.messages:
+            for content in message.contents:
+                if getattr(content, "type", None) == "function_approval_request" and content.function_call is not None:
+                    function_call_arguments = content.function_call.arguments
+                    break
+
+        assert function_call_arguments == {
+            "request_id": "rid-1",
+            "data": {"target_agent": "helper", "reason": "overflow"},
+        }
+        assert json.loads(json.dumps(function_call_arguments)) == function_call_arguments
+
     async def test_resume_via_agent_responses_kwarg(self):
         @workflow
         async def wf(x: str, ctx: RunContext) -> str:

python/packages/core/tests/workflow/test_workflow_agent.py

@@ -1,7 +1,9 @@
 # Copyright (c) Microsoft. All rights reserved.
 
+import json
 import uuid
 from collections.abc import Awaitable, Sequence
+from dataclasses import dataclass
 from typing import Any, Literal, overload
 
 import pytest
@@ -23,6 +25,7 @@ from agent_framework import (
     WorkflowAgent,
     WorkflowBuilder,
     WorkflowContext,
+    WorkflowEvent,
     executor,
     handler,
     response_handler,
@@ -293,6 +296,33 @@ class TestWorkflowAgent:
         # Verify cleanup - pending requests should be cleared after function response handling
         assert len(agent.pending_requests) == 0
 
+    def test_request_info_dataclass_arguments_are_serialized_when_content_is_created(self) -> None:
+        """Test WorkflowAgent prepares request_info arguments before observability captures messages."""
+
+        @dataclass
+        class HandoffRequest:
+            target_agent: str
+            reason: str
+
+        executor = SimpleExecutor(id="executor1", response_text="Response")
+        workflow = WorkflowBuilder(start_executor=executor).build()
+        agent = WorkflowAgent(workflow=workflow, name="Request Test Agent")
+        event = WorkflowEvent.request_info(
+            request_id="request_123",
+            source_executor_id="executor1",
+            request_data=HandoffRequest(target_agent="helper", reason="overflow"),
+            response_type=str,
+        )
+
+        function_call, approval_request = agent._process_request_info_event(event)  # pyright: ignore[reportPrivateUsage]
+
+        assert function_call.arguments == {
+            "request_id": "request_123",
+            "data": {"target_agent": "helper", "reason": "overflow"},
+        }
+        assert approval_request.function_call is function_call
+        assert json.loads(json.dumps(function_call.arguments)) == function_call.arguments
+
     def test_workflow_as_agent_method(self) -> None:
         """Test that Workflow.as_agent() creates a properly configured WorkflowAgent."""
         # Create a simple workflow