diff --git a/temporalio/contrib/openai_agents/__init__.py b/temporalio/contrib/openai_agents/__init__.py
index aedf6eb85..d2969e509 100644
--- a/temporalio/contrib/openai_agents/__init__.py
+++ b/temporalio/contrib/openai_agents/__init__.py
@@ -8,6 +8,12 @@
     Use with caution in production environments.
 """
 
+import importlib
+import inspect
+import pkgutil
+
+from pydantic import BaseModel
+
 from temporalio.contrib.openai_agents._invoke_model_activity import ModelActivity
 from temporalio.contrib.openai_agents._model_parameters import ModelActivityParameters
 from temporalio.contrib.openai_agents._trace_interceptor import (
@@ -30,3 +36,23 @@
     "TestModel",
     "TestModelProvider",
 ]
+
+
+def _reload_models(module_name: str) -> None:
+    """Recursively walk through modules and rebuild BaseModel classes."""
+    module = importlib.import_module(module_name)
+
+    # Process classes in the current module
+    for _, obj in inspect.getmembers(module, inspect.isclass):
+        if issubclass(obj, BaseModel) and obj is not BaseModel:
+            obj.model_rebuild()
+
+    # Recursively process submodules
+    if hasattr(module, "__path__"):
+        for _, submodule_name, _ in pkgutil.iter_modules(module.__path__):
+            full_submodule_name = f"{module_name}.{submodule_name}"
+            _reload_models(full_submodule_name)
+
+
+# Recursively call model_rebuild() on all BaseModel classes in openai.types
+_reload_models("openai.types")
diff --git a/temporalio/contrib/openai_agents/_invoke_model_activity.py b/temporalio/contrib/openai_agents/_invoke_model_activity.py
index 069ea001e..6b365902a 100644
--- a/temporalio/contrib/openai_agents/_invoke_model_activity.py
+++ b/temporalio/contrib/openai_agents/_invoke_model_activity.py
@@ -5,7 +5,6 @@
 
 import enum
 import json
-from dataclasses import dataclass
 from typing import Any, Optional, Union, cast
 
 from agents import (
@@ -24,6 +23,7 @@
     WebSearchTool,
 )
 from agents.models.multi_provider import MultiProvider
+from pydantic.dataclasses import dataclass
 from typing_extensions import Required, TypedDict
 
 from temporalio import activity
diff --git a/tests/contrib/openai_agents/test_openai.py b/tests/contrib/openai_agents/test_openai.py
index 57dc5c252..484e4d61a 100644
--- a/tests/contrib/openai_agents/test_openai.py
+++ b/tests/contrib/openai_agents/test_openai.py
@@ -45,7 +45,7 @@
 )
 from openai.types.responses.response_function_web_search import ActionSearch
 from openai.types.responses.response_prompt_param import ResponsePromptParam
-from pydantic import ConfigDict, Field
+from pydantic import ConfigDict, Field, TypeAdapter
 
 from temporalio import activity, workflow
 from temporalio.client import Client, WorkflowFailureError, WorkflowHandle
@@ -1778,3 +1778,22 @@ async def test_workflow_method_tools(client: Client):
                 execution_timeout=timedelta(seconds=10),
             )
             await workflow_handle.result()
+
+
+async def test_response_serialization():
+    import json
+
+    from openai.types.responses.response_output_item import ImageGenerationCall
+
+    data = json.loads(
+        b'{"id": "msg_68757ec43348819d86709f0fcb70316301a1194a3e05b38c","type": "image_generation_call","status": "completed"}'
+    )
+    call = TypeAdapter(ImageGenerationCall).validate_python(data)
+    model_response = ModelResponse(
+        output=[
+            call,
+        ],
+        usage=Usage(),
+        response_id="",
+    )
+    encoded = await pydantic_data_converter.encode([model_response])
diff --git a/uv.lock b/uv.lock
index 638b7a118..6cf32b17e 100644
--- a/uv.lock
+++ b/uv.lock
@@ -1091,7 +1091,7 @@ wheels = [
 
 [[package]]
 name = "openai"
-version = "1.92.3"
+version = "1.96.0"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
     { name = "anyio" },
@@ -1103,9 +1103,9 @@ dependencies = [
     { name = "tqdm" },
     { name = "typing-extensions" },
 ]
-sdist = { url = "https://files.pythonhosted.org/packages/8b/bd/6c123e53d6727dc39086346df1161c8b6bb50e4cc0f2e9075cae909049b6/openai-1.92.3.tar.gz", hash = "sha256:6b707bc926a9fffab262dbd1eb4be29c36d627b9012633a66ccdbe2d615a9532", size = 485647, upload-time = "2025-06-27T17:06:55.96Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/47/7d/dbc636786f8bf029600abdbf89da74706bdde37c4fe1471ce78834a7ecaa/openai-1.96.0.tar.gz", hash = "sha256:36e34b5aa2c9c0380c1934fa16ba53b3b3c6462450b4c008b98859b9b6424cf7", size = 488898, upload-time = "2025-07-15T15:56:52.853Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/ea/60/4956baa677a569a247336c7edff4b3b6aab7a54119e2342d391d1d370446/openai-1.92.3-py3-none-any.whl", hash = "sha256:979f00c097d023a28f22c63373a646a675e4b9e1fad586e2424bf7274a2689f2", size = 753350, upload-time = "2025-06-27T17:06:53.547Z" },
+    { url = "https://files.pythonhosted.org/packages/dc/63/e29319a52449b7ac4c3a13a1448a9fa326aa1263478eb4c4a9bcbbe95648/openai-1.96.0-py3-none-any.whl", hash = "sha256:4dee023520f8a70ddeaa9f4d6fb247e6dcafd79d2ebb415e3f85932d95aa64a0", size = 757092, upload-time = "2025-07-15T15:56:50.387Z" },
 ]
 
 [[package]]