diff --git a/python/packages/core/agent_framework/_serialization.py b/python/packages/core/agent_framework/_serialization.py
index 8dffdc0ce6..550b8bf384 100644
--- a/python/packages/core/agent_framework/_serialization.py
+++ b/python/packages/core/agent_framework/_serialization.py
@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+import copy
 import json
 import logging
 import re
@@ -263,6 +264,26 @@ def __init__(self, **kwargs):
 
     DEFAULT_EXCLUDE: ClassVar[set[str]] = set()
     INJECTABLE: ClassVar[set[str]] = set()
+    _SHALLOW_COPY_FIELDS: ClassVar[set[str]] = {"raw_representation"}
+
+    def __deepcopy__(self, memo: dict[int, Any]) -> SerializationMixin:
+        """Create a deep copy, preserving ``_SHALLOW_COPY_FIELDS`` by reference.
+
+        Fields listed in ``_SHALLOW_COPY_FIELDS`` may contain LLM SDK objects
+        (e.g., proto/gRPC responses) that are not safe to deep-copy.  They are
+        kept as shallow references in the copy; all other attributes are
+        deep-copied normally.
+        """
+        cls = type(self)
+        result = cls.__new__(cls)
+        memo[id(self)] = result
+        shallow = cls._SHALLOW_COPY_FIELDS
+        for k, v in self.__dict__.items():
+            if k in shallow:
+                object.__setattr__(result, k, v)
+            else:
+                object.__setattr__(result, k, copy.deepcopy(v, memo))
+        return result
 
     def to_dict(self, *, exclude: set[str] | None = None, exclude_none: bool = True) -> dict[str, Any]:
         """Convert the instance and any nested objects to a dictionary.
diff --git a/python/packages/core/agent_framework/_types.py b/python/packages/core/agent_framework/_types.py
index 7ae9dbaa3d..f058fc14c1 100644
--- a/python/packages/core/agent_framework/_types.py
+++ b/python/packages/core/agent_framework/_types.py
@@ -445,6 +445,8 @@ class Content:
     `Content.from_uri()`, etc. to create instances.
     """
 
+    _SHALLOW_COPY_FIELDS: ClassVar[set[str]] = {"raw_representation"}
+
     def __init__(
         self,
         type: ContentType,
@@ -546,6 +548,23 @@ def __init__(
         self.approved = approved
         self.consent_link = consent_link
 
+    def __deepcopy__(self, memo: dict[int, Any]) -> Content:
+        """Create a deep copy, preserving ``_SHALLOW_COPY_FIELDS`` by reference.
+
+        Fields listed in ``_SHALLOW_COPY_FIELDS`` may contain LLM SDK objects
+        (e.g., proto/gRPC responses) that are not safe to deep-copy.
+        """
+        cls = type(self)
+        result = cls.__new__(cls)
+        memo[id(self)] = result
+        shallow = cls._SHALLOW_COPY_FIELDS
+        for k, v in self.__dict__.items():
+            if k in shallow:
+                object.__setattr__(result, k, v)
+            else:
+                object.__setattr__(result, k, deepcopy(v, memo))
+        return result
+
     @classmethod
     def from_text(
         cls: type[ContentT],
diff --git a/python/packages/core/tests/core/test_serializable_mixin.py b/python/packages/core/tests/core/test_serializable_mixin.py
index 05ece1072b..8134e14680 100644
--- a/python/packages/core/tests/core/test_serializable_mixin.py
+++ b/python/packages/core/tests/core/test_serializable_mixin.py
@@ -427,3 +427,103 @@ def __init__(self, value: str, options: dict | None = None):
 
         assert obj.options["existing"] == "value"
         assert obj.options["injected"] == "option"
+
+    def test_deepcopy_preserves_shallow_copy_fields_by_reference(self):
+        """Test that deepcopy keeps _SHALLOW_COPY_FIELDS fields as shallow references."""
+        import copy
+
+        class NonCopyable:
+            def __deepcopy__(self, memo):
+                raise TypeError("cannot deepcopy")
+
+        class TestClass(SerializationMixin):
+            _SHALLOW_COPY_FIELDS = {"raw_representation", "other_opaque"}
+
+            def __init__(self, items: list, raw_representation: Any = None, other_opaque: Any = None):
+                self.items = items
+                self.raw_representation = raw_representation
+                self.other_opaque = other_opaque
+
+        raw = NonCopyable()
+        opaque = NonCopyable()
+        original_items = ["a", "b"]
+        obj = TestClass(items=original_items, raw_representation=raw, other_opaque=opaque)
+        cloned = copy.deepcopy(obj)
+
+        # _SHALLOW_COPY_FIELDS fields should be the same object (shallow copy)
+        assert cloned.raw_representation is raw
+        assert cloned.other_opaque is opaque
+        # Normal attributes should be independent copies
+        assert cloned.items is not original_items
+        assert cloned.items == ["a", "b"]
+
+    def test_deepcopy_deep_copies_non_shallow_copy_fields(self):
+        """Test that deepcopy fully copies fields not in _SHALLOW_COPY_FIELDS."""
+        import copy
+
+        class TestClass(SerializationMixin):
+            _SHALLOW_COPY_FIELDS = {"raw_representation"}
+
+            def __init__(self, items: list, raw_representation: Any = None):
+                self.items = items
+                self.raw_representation = raw_representation
+
+        original_list = ["a", "b"]
+        obj = TestClass(items=original_list, raw_representation="raw")
+        cloned = copy.deepcopy(obj)
+
+        # list should be a new object
+        assert cloned.items is not original_list
+        assert cloned.items == ["a", "b"]
+        # raw_representation should be the same object
+        assert cloned.raw_representation is obj.raw_representation
+
+    def test_deepcopy_deep_copies_default_exclude_fields(self):
+        """Test that DEFAULT_EXCLUDE fields are deep-copied unless also in _SHALLOW_COPY_FIELDS."""
+        import copy
+
+        class TestClass(SerializationMixin):
+            DEFAULT_EXCLUDE = {"additional_properties"}
+
+            def __init__(self, items: list, additional_properties: dict | None = None):
+                self.items = items
+                self.additional_properties = additional_properties or {}
+
+        original_props = {"key": "value"}
+        obj = TestClass(items=["a"], additional_properties=original_props)
+        cloned = copy.deepcopy(obj)
+
+        # DEFAULT_EXCLUDE field should be deep-copied (independent copy)
+        assert cloned.additional_properties is not original_props
+        assert cloned.additional_properties == {"key": "value"}
+
+    def test_deepcopy_shallow_copy_fields_override_default_exclude(self):
+        """Test that _SHALLOW_COPY_FIELDS controls deepcopy independently of DEFAULT_EXCLUDE."""
+        import copy
+
+        class NonCopyable:
+            def __deepcopy__(self, memo):
+                raise TypeError("cannot deepcopy")
+
+        class TestClass(SerializationMixin):
+            DEFAULT_EXCLUDE = {"opaque", "additional_properties"}
+            _SHALLOW_COPY_FIELDS = {"opaque"}
+
+            def __init__(self, items: list, opaque: Any = None, additional_properties: dict | None = None):
+                self.items = items
+                self.opaque = opaque
+                self.additional_properties = additional_properties or {}
+
+        opaque = NonCopyable()
+        original_props = {"key": "value"}
+        obj = TestClass(items=["a"], opaque=opaque, additional_properties=original_props)
+        cloned = copy.deepcopy(obj)
+
+        # Field in both DEFAULT_EXCLUDE and _SHALLOW_COPY_FIELDS: shallow-copied
+        assert cloned.opaque is opaque
+        # Field in DEFAULT_EXCLUDE only: deep-copied
+        assert cloned.additional_properties is not original_props
+        assert cloned.additional_properties == {"key": "value"}
+        # Normal field: deep-copied
+        assert cloned.items is not obj.items
+        assert cloned.items == ["a"]
diff --git a/python/packages/core/tests/core/test_types.py b/python/packages/core/tests/core/test_types.py
index 0d314c1aa5..bdbe869394 100644
--- a/python/packages/core/tests/core/test_types.py
+++ b/python/packages/core/tests/core/test_types.py
@@ -1860,6 +1860,170 @@ def test_agent_run_response_update_all_content_types():
     assert update_str.role == "user"
 
 
+# region DeepCopy
+
+
+class _NonCopyableRaw:
+    """Simulates an LLM SDK response object that cannot be deep-copied (e.g., proto/gRPC)."""
+
+    def __deepcopy__(self, memo: dict) -> Any:
+        raise TypeError("Cannot deepcopy this object")
+
+
+def test_content_deepcopy_preserves_raw_representation():
+    """Test that deepcopy of Content keeps raw_representation by reference."""
+    import copy
+
+    raw = _NonCopyableRaw()
+    content = Content.from_text("hello", raw_representation=raw)
+
+    cloned = copy.deepcopy(content)
+
+    assert cloned.text == "hello"
+    assert cloned.raw_representation is raw
+    assert cloned.additional_properties is not content.additional_properties
+
+
+def test_message_deepcopy_preserves_raw_representation():
+    """Test that deepcopy of Message keeps raw_representation by reference."""
+    import copy
+
+    raw = _NonCopyableRaw()
+    msg = Message("assistant", ["hello"], raw_representation=raw)
+
+    cloned = copy.deepcopy(msg)
+
+    assert cloned.text == "hello"
+    assert cloned.raw_representation is raw
+    assert cloned.contents is not msg.contents
+
+
+def test_agent_response_deepcopy_preserves_raw_representation():
+    """Test that deepcopy of AgentResponse keeps raw_representation by reference."""
+    import copy
+
+    raw = _NonCopyableRaw()
+    response = AgentResponse(
+        messages=[Message("assistant", ["test"])],
+        raw_representation=raw,
+    )
+
+    cloned = copy.deepcopy(response)
+
+    assert cloned.text == "test"
+    assert cloned.raw_representation is raw
+    assert cloned.messages is not response.messages
+
+
+def test_chat_response_deepcopy_preserves_raw_representation():
+    """Test that deepcopy of ChatResponse keeps raw_representation by reference."""
+    import copy
+
+    raw = _NonCopyableRaw()
+    response = ChatResponse(
+        messages=[Message("assistant", ["test"])],
+        raw_representation=raw,
+    )
+
+    cloned = copy.deepcopy(response)
+
+    assert cloned.text == "test"
+    assert cloned.raw_representation is raw
+    assert cloned.messages is not response.messages
+
+
+def test_chat_response_update_deepcopy_preserves_raw_representation():
+    """Test that deepcopy of ChatResponseUpdate keeps raw_representation by reference."""
+    import copy
+
+    raw = _NonCopyableRaw()
+    update = ChatResponseUpdate(
+        contents=[Content.from_text("hello")],
+        role="assistant",
+        raw_representation=raw,
+    )
+
+    cloned = copy.deepcopy(update)
+
+    assert cloned.text == "hello"
+    assert cloned.raw_representation is raw
+    assert cloned.contents is not update.contents
+
+
+def test_agent_response_update_deepcopy_preserves_raw_representation():
+    """Test that deepcopy of AgentResponseUpdate keeps raw_representation by reference."""
+    import copy
+
+    raw = _NonCopyableRaw()
+    update = AgentResponseUpdate(
+        contents=[Content.from_text("hello")],
+        role="assistant",
+        raw_representation=raw,
+    )
+
+    cloned = copy.deepcopy(update)
+
+    assert cloned.text == "hello"
+    assert cloned.raw_representation is raw
+    assert cloned.contents is not update.contents
+
+
+def test_nested_deepcopy_preserves_raw_representation():
+    """Test that deepcopy of an AgentResponse with nested Message raw_representations works."""
+    import copy
+
+    raw_msg = _NonCopyableRaw()
+    raw_response = _NonCopyableRaw()
+    response = AgentResponse(
+        messages=[Message("assistant", ["hello"], raw_representation=raw_msg)],
+        raw_representation=raw_response,
+    )
+
+    cloned = copy.deepcopy(response)
+
+    assert cloned.raw_representation is raw_response
+    assert cloned.messages[0].raw_representation is raw_msg
+    assert cloned.messages is not response.messages
+    assert cloned.text == "hello"
+
+
+def test_content_deepcopy_shallow_copy_fields_identity():
+    """Test that Content._SHALLOW_COPY_FIELDS fields are identity-preserved while others are deep-copied."""
+    import copy
+
+    raw = _NonCopyableRaw()
+    content = Content.from_text("hello", raw_representation=raw)
+    content.additional_properties["key"] = "value"
+
+    cloned = copy.deepcopy(content)
+
+    # _SHALLOW_COPY_FIELDS (raw_representation) should be same object
+    assert cloned.raw_representation is raw
+    # Non-shallow fields should be independent deep copies
+    assert cloned.additional_properties is not content.additional_properties
+    assert cloned.additional_properties == {"key": "value"}
+
+
+def test_chat_response_deepcopy_deep_copies_additional_properties():
+    """Test that ChatResponse deepcopy deep-copies additional_properties despite it being in DEFAULT_EXCLUDE."""
+    import copy
+
+    response = ChatResponse(
+        messages=[Message("assistant", ["test"])],
+        additional_properties={"key": [1, 2, 3]},
+    )
+
+    cloned = copy.deepcopy(response)
+
+    # additional_properties is in DEFAULT_EXCLUDE for serialization but not in _SHALLOW_COPY_FIELDS,
+    # so it should be deep-copied (independent copy)
+    assert cloned.additional_properties is not response.additional_properties
+    assert cloned.additional_properties == {"key": [1, 2, 3]}
+
+
+# endregion
+
+
 # region Serialization
 
 
diff --git a/python/packages/core/tests/workflow/test_agent_executor.py b/python/packages/core/tests/workflow/test_agent_executor.py
index 599e62d635..059e683745 100644
--- a/python/packages/core/tests/workflow/test_agent_executor.py
+++ b/python/packages/core/tests/workflow/test_agent_executor.py
@@ -383,3 +383,60 @@ async def test_agent_executor_run_with_messages_kwarg_does_not_raise() -> None:
     result = await workflow.run("hello", messages=["stale"])
     assert result is not None
     assert agent.call_count == 1
+
+
+class _NonCopyableRaw:
+    """Simulates an LLM SDK response object that cannot be deep-copied (e.g., proto/gRPC)."""
+
+    def __deepcopy__(self, memo: dict) -> Any:
+        raise TypeError("Cannot deepcopy this object")
+
+
+class _AgentWithRawRepr(BaseAgent):
+    """Agent that returns responses with a non-copyable raw_representation."""
+
+    def __init__(self, raw: Any, **kwargs: Any):
+        super().__init__(**kwargs)
+        self._raw = raw
+
+    def run(
+        self,
+        messages: str | Message | list[str] | list[Message] | None = None,
+        *,
+        stream: bool = False,
+        session: AgentSession | None = None,
+        **kwargs: Any,
+    ) -> Awaitable[AgentResponse] | ResponseStream[AgentResponseUpdate, AgentResponse]:
+        async def _run() -> AgentResponse:
+            return AgentResponse(
+                messages=[Message("assistant", [f"reply from {self.name}"])],
+                raw_representation=self._raw,
+            )
+
+        return _run()
+
+
+async def test_agent_executor_workflow_with_non_copyable_raw_representation() -> None:
+    """Workflow should complete when AgentResponse contains a raw_representation that cannot be deep-copied."""
+    raw = _NonCopyableRaw()
+
+    agent_a = _AgentWithRawRepr(raw=raw, id="a", name="AgentA")
+    agent_b = _CountingAgent(id="b", name="AgentB")
+
+    exec_a = AgentExecutor(agent_a, id="exec_a")
+    exec_b = AgentExecutor(agent_b, id="exec_b")
+
+    workflow = SequentialBuilder(participants=[exec_a, exec_b]).build()
+    events = await workflow.run("hello")
+
+    completed = [e for e in events if isinstance(e, WorkflowEvent) and e.type == "executor_completed"]
+    completed_a = [e for e in completed if e.executor_id == "exec_a"]
+
+    assert len(completed_a) == 1
+    assert completed_a[0].data is not None
+
+    # The yielded AgentResponse should preserve its raw_representation reference
+    agent_responses = [d for d in completed_a[0].data if isinstance(d, AgentResponse)]
+    assert len(agent_responses) > 0
+    assert agent_responses[0].text == "reply from AgentA"
+    assert agent_responses[0].raw_representation is raw