diff --git a/libs/partners/anthropic/tests/unit_tests/middleware/test_prompt_caching.py b/libs/partners/anthropic/tests/unit_tests/middleware/test_prompt_caching.py
index f2b2c5cfb2b..789a2eb5192 100644
--- a/libs/partners/anthropic/tests/unit_tests/middleware/test_prompt_caching.py
+++ b/libs/partners/anthropic/tests/unit_tests/middleware/test_prompt_caching.py
@@ -4,7 +4,7 @@ import warnings
 from typing import Any, cast
 
 import pytest
-from langchain.agents.middleware.types import ModelRequest
+from langchain.agents.middleware.types import ModelRequest, ModelResponse
 from langchain_core.callbacks import CallbackManagerForLLMRun
 from langchain_core.language_models import BaseChatModel
 from langchain_core.messages import AIMessage, BaseMessage, HumanMessage
@@ -25,7 +25,7 @@ class FakeToolCallingModel(BaseChatModel):
         **kwargs: Any,
     ) -> ChatResult:
         """Top Level call"""
-        messages_string = "-".join([m.content for m in messages])
+        messages_string = "-".join([str(m.content) for m in messages])
         message = AIMessage(content=messages_string, id="0")
         return ChatResult(generations=[ChatGeneration(message=message)])
 
@@ -62,8 +62,10 @@ def test_anthropic_prompt_caching_middleware_initialization() -> None:
         model_settings={},
     )
 
-    def mock_handler(req: ModelRequest) -> AIMessage:
-        return AIMessage(content="mock response", **req.model_settings)
+    def mock_handler(req: ModelRequest) -> ModelResponse:
+        return ModelResponse(
+            result=[AIMessage(content="mock response")]
+        )
 
     middleware.wrap_model_call(fake_request, mock_handler)
     # Check that model_settings were passed through via the request
@@ -88,8 +90,8 @@ def test_anthropic_prompt_caching_middleware_unsupported_model() -> None:
 
     middleware = AnthropicPromptCachingMiddleware(unsupported_model_behavior="raise")
 
-    def mock_handler(req: ModelRequest) -> AIMessage:
-        return AIMessage(content="mock response")
+    def mock_handler(req: ModelRequest) -> ModelResponse:
+        return ModelResponse(result=[AIMessage(content="mock response")])
 
     # Since we're in the langchain-anthropic package, ChatAnthropic is always
     # available. Test that it raises an error for unsupported model instances
@@ -107,7 +109,7 @@ def test_anthropic_prompt_caching_middleware_unsupported_model() -> None:
     # Test warn behavior for unsupported model instances
     with warnings.catch_warnings(record=True) as w:
         result = middleware.wrap_model_call(fake_request, mock_handler)
-        assert isinstance(result, AIMessage)
+        assert isinstance(result, ModelResponse)
         assert len(w) == 1
         assert (
             "AnthropicPromptCachingMiddleware caching middleware only supports "
@@ -117,4 +119,4 @@ def test_anthropic_prompt_caching_middleware_unsupported_model() -> None:
     # Test ignore behavior
     middleware = AnthropicPromptCachingMiddleware(unsupported_model_behavior="ignore")
     result = middleware.wrap_model_call(fake_request, mock_handler)
-    assert isinstance(result, AIMessage)
+    assert isinstance(result, ModelResponse)