diff --git a/python/packages/core/agent_framework/_workflows/_agent.py b/python/packages/core/agent_framework/_workflows/_agent.py
index f0b51969c07..01bd70d300d 100644
--- a/python/packages/core/agent_framework/_workflows/_agent.py
+++ b/python/packages/core/agent_framework/_workflows/_agent.py
@@ -64,7 +64,18 @@ def to_dict(self) -> dict[str, Any]:
             return {"request_id": self.request_id, "request_event": self.request_event.to_dict()}
 
         @classmethod
-        def from_dict(cls, payload: dict[str, Any]) -> WorkflowAgent.RequestInfoFunctionArgs:
+        def from_dict(
+            cls,
+            payload: dict[str, Any],
+            *,
+            allowed_types: Mapping[str, type[Any]] | None = None,
+        ) -> WorkflowAgent.RequestInfoFunctionArgs:
+            """Create request-info function arguments from a dictionary.
+
+            Args:
+                payload: Serialized request-info function arguments.
+                allowed_types: Optional exact mapping of serialized names to trusted custom types.
+            """
             if "request_id" not in payload or "request_event" not in payload:
                 raise ValueError(
                     "Invalid payload for RequestInfoFunctionArgs. 'request_id' and 'request_event' are required."
@@ -74,7 +85,10 @@ def from_dict(cls, payload: dict[str, Any]) -> WorkflowAgent.RequestInfoFunction
 
             return cls(
                 request_id=payload.get("request_id", ""),
-                request_event=WorkflowEvent.from_dict(payload.get("request_event", {})),
+                request_event=WorkflowEvent.from_dict(
+                    payload.get("request_event", {}),
+                    allowed_types=allowed_types,
+                ),
             )
 
     def __init__(
diff --git a/python/packages/core/agent_framework/_workflows/_events.py b/python/packages/core/agent_framework/_workflows/_events.py
index 8788599e652..669887a3c29 100644
--- a/python/packages/core/agent_framework/_workflows/_events.py
+++ b/python/packages/core/agent_framework/_workflows/_events.py
@@ -6,7 +6,7 @@
 import sys
 import traceback as _traceback
 import warnings
-from collections.abc import Generator
+from collections.abc import Generator, Mapping
 from contextlib import contextmanager
 from contextvars import ContextVar
 from dataclasses import dataclass
@@ -426,14 +426,24 @@ def to_dict(self) -> dict[str, Any]:
         }
 
     @classmethod
-    def from_dict(cls, data: dict[str, Any]) -> WorkflowEvent[Any]:
-        """Create a REQUEST_INFO event from a dictionary."""
+    def from_dict(
+        cls,
+        data: dict[str, Any],
+        *,
+        allowed_types: Mapping[str, builtins.type[Any]] | None = None,
+    ) -> WorkflowEvent[Any]:
+        """Create a request-info event from a dictionary.
+
+        Args:
+            data: Serialized request-info event fields.
+            allowed_types: Optional exact mapping of serialized names to trusted custom types.
+        """
         for prop in ["data", "request_id", "source_executor_id", "request_type", "response_type"]:
             if prop not in data:
                 raise KeyError(f"Missing '{prop}' field in WorkflowEvent dictionary.")
 
         request_data = data["data"]
-        request_type = deserialize_type(data["request_type"])
+        request_type = deserialize_type(data["request_type"], allowed_types=allowed_types)
 
         if request_type is not type(request_data):
             raise TypeError(
@@ -444,5 +454,5 @@ def from_dict(cls, data: dict[str, Any]) -> WorkflowEvent[Any]:
             request_id=data["request_id"],
             source_executor_id=data["source_executor_id"],
             request_data=cast(Any, request_data),  # type: ignore
-            response_type=deserialize_type(data["response_type"]),
+            response_type=deserialize_type(data["response_type"], allowed_types=allowed_types),
         )
diff --git a/python/packages/core/agent_framework/_workflows/_typing_utils.py b/python/packages/core/agent_framework/_workflows/_typing_utils.py
index 404b83f7092..6dff6ba7a48 100644
--- a/python/packages/core/agent_framework/_workflows/_typing_utils.py
+++ b/python/packages/core/agent_framework/_workflows/_typing_utils.py
@@ -1,7 +1,9 @@
 # Copyright (c) Microsoft. All rights reserved.
 
+import sys
 import typing
-from types import UnionType
+from collections.abc import Mapping
+from types import ModuleType, UnionType
 from typing import Any, TypeGuard, Union, cast, get_args, get_origin
 
 import typing_extensions
@@ -14,6 +16,17 @@
 _TYPEVAR_TYPES: tuple[type, ...] = (type(typing.TypeVar("_T")), type(typing_extensions.TypeVar("_T")))  # pyright: ignore[reportUnknownVariableType]
 
 
+def _is_runtime_type(value: object) -> TypeGuard[type[Any]]:
+    if not isinstance(value, type):
+        return False
+    try:
+        type.__getattribute__(value, "__module__")
+        type.__getattribute__(value, "__qualname__")
+    except TypeError:
+        return False
+    return True
+
+
 def is_typevar(x: Any) -> bool:
     """Check if x is an unresolved TypeVar instance (from typing or typing_extensions).
 
@@ -274,19 +287,46 @@ def serialize_type(t: type) -> str:
     return f"{t.__module__}.{t.__qualname__}"
 
 
-def deserialize_type(serialized_type_string: str) -> type:
+def deserialize_type(
+    serialized_type_string: str,
+    *,
+    allowed_types: Mapping[str, type[Any]] | None = None,
+) -> type:
     """Deserialize a serialized type string.
 
+    Resolution is limited to exact caller-supplied types or types already present
+    in loaded module namespaces. This function never imports a module selected by
+    the serialized value.
+
+    Args:
+        serialized_type_string: Fully qualified serialized type name.
+        allowed_types: Optional exact mapping of serialized names to trusted types.
+
     For example,
 
     deserialize_type("builtins.int") => int
     """
-    import importlib
+    if allowed_types is not None and serialized_type_string in allowed_types:
+        resolved = allowed_types[serialized_type_string]
+        if not _is_runtime_type(resolved):
+            raise TypeError(f"allowed_types entry {serialized_type_string!r} must be a type.")
+        if serialize_type(resolved) != serialized_type_string:
+            raise ValueError(f"allowed_types entry {serialized_type_string!r} does not match the supplied type.")
+        return resolved
 
     module_name, _, type_name = serialized_type_string.rpartition(".")
-    module = importlib.import_module(module_name)
-
-    return cast(type, getattr(module, type_name))
+    module = sys.modules.get(module_name)
+    if not isinstance(module, ModuleType):
+        raise ModuleNotFoundError(f"No module named {module_name!r}", name=module_name)
+
+    namespace = ModuleType.__getattribute__(module, "__dict__")
+    if type_name not in namespace:
+        raise AttributeError(f"{module_name!r} has no attribute {type_name!r}")
+
+    resolved = namespace[type_name]
+    if not _is_runtime_type(resolved):
+        raise TypeError(f"{serialized_type_string!r} does not resolve to a type.")
+    return resolved
 
 
 def is_type_compatible(source_type: type | UnionType | Any, target_type: type | UnionType | Any) -> bool:
diff --git a/python/packages/core/tests/workflow/test_request_info_event_rehydrate.py b/python/packages/core/tests/workflow/test_request_info_event_rehydrate.py
index c05ab66984e..1be0a75f58e 100644
--- a/python/packages/core/tests/workflow/test_request_info_event_rehydrate.py
+++ b/python/packages/core/tests/workflow/test_request_info_event_rehydrate.py
@@ -1,8 +1,12 @@
 # Copyright (c) Microsoft. All rights reserved.
 
 import json
+import sys
 from dataclasses import dataclass, field
 from datetime import datetime, timezone
+from pathlib import Path
+
+import pytest
 
 from agent_framework import (
     FileCheckpointStorage,
@@ -47,6 +51,91 @@ class TimedApproval:
     issued_at: datetime = field(default_factory=lambda: datetime.now(timezone.utc))
 
 
+def test_workflow_event_from_dict_accepts_explicit_allowed_types() -> None:
+    """Request-info reconstruction accepts exact trusted custom types."""
+
+    @dataclass
+    class ExplicitRequest:
+        prompt: str
+
+    class ExplicitResponse:
+        pass
+
+    request_type_name = f"{ExplicitRequest.__module__}.{ExplicitRequest.__qualname__}"
+    response_type_name = f"{ExplicitResponse.__module__}.{ExplicitResponse.__qualname__}"
+    event = WorkflowEvent.from_dict(
+        {
+            "type": "request_info",
+            "data": ExplicitRequest(prompt="Approve?"),
+            "request_id": "request-123",
+            "source_executor_id": "review_gateway",
+            "request_type": request_type_name,
+            "response_type": response_type_name,
+        },
+        allowed_types={
+            request_type_name: ExplicitRequest,
+            response_type_name: ExplicitResponse,
+        },
+    )
+
+    assert type(event.data) is ExplicitRequest
+    assert event.request_type is ExplicitRequest
+    assert event.response_type is ExplicitResponse
+
+
+def _write_observable_type_module(tmp_path: Path, module_name: str) -> Path:
+    marker_path = tmp_path / f"{module_name}.imported"
+    module_path = tmp_path / f"{module_name}.py"
+    module_path.write_text(f"from pathlib import Path\nPath({str(marker_path)!r}).touch()\nclass Attack:\n    pass\n")
+    return marker_path
+
+
+def test_workflow_event_from_dict_does_not_import_request_type(
+    tmp_path: Path,
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """A request-type name cannot cause its module to be imported."""
+    module_name = "_request_info_untrusted_request_type"
+    marker_path = _write_observable_type_module(tmp_path, module_name)
+    monkeypatch.syspath_prepend(str(tmp_path))
+
+    with pytest.raises(ModuleNotFoundError, match=f"No module named '{module_name}'"):
+        WorkflowEvent.from_dict({
+            "type": "request_info",
+            "data": "Approve?",
+            "request_id": "request-123",
+            "source_executor_id": "review_gateway",
+            "request_type": f"{module_name}.Attack",
+            "response_type": "builtins.bool",
+        })
+
+    assert module_name not in sys.modules
+    assert not marker_path.exists()
+
+
+def test_workflow_event_from_dict_does_not_import_response_type(
+    tmp_path: Path,
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """A response-type name cannot cause its module to be imported."""
+    module_name = "_request_info_untrusted_response_type"
+    marker_path = _write_observable_type_module(tmp_path, module_name)
+    monkeypatch.syspath_prepend(str(tmp_path))
+
+    with pytest.raises(ModuleNotFoundError, match=f"No module named '{module_name}'"):
+        WorkflowEvent.from_dict({
+            "type": "request_info",
+            "data": "Approve?",
+            "request_id": "request-123",
+            "source_executor_id": "review_gateway",
+            "request_type": "builtins.str",
+            "response_type": f"{module_name}.Attack",
+        })
+
+    assert module_name not in sys.modules
+    assert not marker_path.exists()
+
+
 async def test_rehydrate_request_info_event() -> None:
     """Rehydration should succeed for valid request info events."""
     request_info_event = WorkflowEvent.request_info(
diff --git a/python/packages/core/tests/workflow/test_typing_utils.py b/python/packages/core/tests/workflow/test_typing_utils.py
index cc3e7bf4ea3..6e54cd64c7c 100644
--- a/python/packages/core/tests/workflow/test_typing_utils.py
+++ b/python/packages/core/tests/workflow/test_typing_utils.py
@@ -1,7 +1,11 @@
 # Copyright (c) Microsoft. All rights reserved.
 
+import importlib
+import sys
 from dataclasses import dataclass
+from types import ModuleType
 from typing import Any, Generic, Optional, TypeVar, Union
+from unittest.mock import Mock
 
 import pytest
 
@@ -337,6 +341,52 @@ def test_deserialize_type_error_handling() -> None:
         deserialize_type("builtins.NonExistentType")
 
 
+def test_deserialize_type_does_not_import_unknown_module(monkeypatch: pytest.MonkeyPatch) -> None:
+    """Unknown serialized types fail without importing payload-selected modules."""
+    imported_modules: list[str] = []
+
+    def fail_import(module_name: str) -> None:
+        imported_modules.append(module_name)
+        raise AssertionError("deserialize_type must not import payload-selected modules")
+
+    monkeypatch.setattr(importlib, "import_module", fail_import)
+
+    with pytest.raises(ModuleNotFoundError, match="No module named 'untrusted_request_info_payload'"):
+        deserialize_type("untrusted_request_info_payload.Attack")
+
+    assert imported_modules == []
+
+
+def test_deserialize_type_accepts_explicit_allowed_type() -> None:
+    """Callers can resolve an exact trusted custom type without importing its module."""
+
+    class ExplicitType:
+        pass
+
+    serialized_name = f"{ExplicitType.__module__}.{ExplicitType.__qualname__}"
+
+    assert deserialize_type(serialized_name, allowed_types={serialized_name: ExplicitType}) is ExplicitType
+
+
+def test_deserialize_type_rejects_spoofed_allowed_type() -> None:
+    """Allowed values must be actual class objects, not objects spoofing ``type``."""
+    spoofed_type = Mock(spec=type)
+
+    with pytest.raises(TypeError, match="must be a type"):
+        deserialize_type("spoofed.Type", allowed_types={"spoofed.Type": spoofed_type})  # type: ignore[dict-item]
+
+
+def test_deserialize_type_rejects_spoofed_loaded_type(monkeypatch: pytest.MonkeyPatch) -> None:
+    """Loaded namespace values must be actual class objects."""
+    module_name = "_spoofed_request_info_type"
+    module = ModuleType(module_name)
+    module.__dict__["Spoofed"] = Mock(spec=type)
+    monkeypatch.setitem(sys.modules, module_name, module)
+
+    with pytest.raises(TypeError, match="does not resolve to a type"):
+        deserialize_type(f"{module_name}.Spoofed")
+
+
 def test_type_compatibility_basic() -> None:
     """Test basic type compatibility scenarios."""
     # Exact type match
diff --git a/python/packages/core/tests/workflow/test_workflow_agent.py b/python/packages/core/tests/workflow/test_workflow_agent.py
index 0cf69aa9414..d5f0c1a6861 100644
--- a/python/packages/core/tests/workflow/test_workflow_agent.py
+++ b/python/packages/core/tests/workflow/test_workflow_agent.py
@@ -335,6 +335,32 @@ def test_request_info_dataclass_arguments_are_serialized_when_content_is_created
         assert deserialized_args.request_event.data == HandoffRequest(target_agent="helper", reason="overflow")
         assert deserialized_args.request_event.response_type is str
 
+    def test_request_info_function_args_from_dict_accepts_explicit_allowed_types(self) -> None:
+        """Envelope reconstruction forwards exact trusted custom types."""
+
+        @dataclass
+        class ExplicitRequest:
+            prompt: str
+
+        serialized_name = f"{ExplicitRequest.__module__}.{ExplicitRequest.__qualname__}"
+        args = WorkflowAgent.RequestInfoFunctionArgs.from_dict(
+            {
+                "request_id": "request-123",
+                "request_event": {
+                    "type": "request_info",
+                    "data": ExplicitRequest(prompt="Approve?"),
+                    "request_id": "request-123",
+                    "source_executor_id": "review_gateway",
+                    "request_type": serialized_name,
+                    "response_type": "builtins.bool",
+                },
+            },
+            allowed_types={serialized_name: ExplicitRequest},
+        )
+
+        assert type(args.request_event.data) is ExplicitRequest
+        assert args.request_event.response_type is bool
+
     def test_process_request_info_event_passes_through_function_approval_request(self) -> None:
         """If the event data is already a function approval request, it is forwarded unchanged.