diff --git a/tests/test_litellm/litellm_core_utils/test_streaming_chunk_builder_utils.py b/tests/test_litellm/litellm_core_utils/test_streaming_chunk_builder_utils.py
index e40a0817fd9..35aca525f6c 100644
--- a/tests/test_litellm/litellm_core_utils/test_streaming_chunk_builder_utils.py
+++ b/tests/test_litellm/litellm_core_utils/test_streaming_chunk_builder_utils.py
@@ -520,7 +520,10 @@ def test_stream_chunk_builder_anthropic_web_search():
     assert usage.prompt_tokens == 50
     assert usage.completion_tokens == 27
     assert usage.total_tokens == 77
-    assert usage.server_tool_use["web_search_requests"] == 2
+    # server_tool_use must be a ServerToolUse pydantic so downstream cost-calc
+    # (which uses attribute access) works. See issue #26153.
+    assert isinstance(usage.server_tool_use, ServerToolUse)
+    assert usage.server_tool_use.web_search_requests == 2
 
 
 def test_sort_chunks_handles_dict_hidden_params_created_at():