diff --git a/tests/unit/proxy/proxy_server/test_streaming_helpers.py b/tests/unit/proxy/proxy_server/test_streaming_helpers.py
index 4ae4361cc1a..165f3a14cbe 100644
--- a/tests/unit/proxy/proxy_server/test_streaming_helpers.py
+++ b/tests/unit/proxy/proxy_server/test_streaming_helpers.py
@@ -551,8 +551,6 @@ def test_fast_serialize_simple_model_response_stream_with_usage_returns_none_inv
 
 
 def test_fast_serialize_simple_model_response_stream_with_reasoning_items_returns_none():
-    """``reasoning_items`` carries the provider's encrypted reasoning state, which
-    the fast path cannot emit — it must bail so the slow path serializes it."""
     chunk = _simple_chunk(content="")
     chunk.choices[0].delta.reasoning_items = [
         {"id": "rs_abc", "type": "reasoning", "encrypted_content": "ENCRYPTED-BLOB"}
@@ -584,17 +582,27 @@ def test_serialize_streaming_chunk_simple_uses_fast_path_bytes():
 
 
 def test_serialize_streaming_chunk_preserves_reasoning_items():
-    """End-to-end pin for the bug: a chunk whose only payload beside text is
-    ``reasoning_items`` must still reach the wire with those items. The fast
-    path emits ``role``/``content`` only, so it has to decline this chunk."""
     chunk = _simple_chunk(content="")
     chunk.choices[0].delta.reasoning_items = [
         {"id": "rs_abc", "type": "reasoning", "encrypted_content": "ENCRYPTED-BLOB"}
     ]
-    payload = json.loads(_serialize_streaming_chunk(chunk))
-    assert payload["choices"][0]["delta"]["reasoning_items"] == [
-        {"id": "rs_abc", "type": "reasoning", "encrypted_content": "ENCRYPTED-BLOB"}
-    ]
+    payload: Final = json.loads(_serialize_streaming_chunk(chunk))
+    assert payload == {
+        "id": "chatcmpl-test",
+        "created": 0,
+        "model": "gpt-4",
+        "object": "chat.completion.chunk",
+        "choices": [
+            {
+                "index": 0,
+                "delta": {
+                    "role": "assistant",
+                    "content": "",
+                    "reasoning_items": [{"id": "rs_abc", "type": "reasoning", "encrypted_content": "ENCRYPTED-BLOB"}],
+                },
+            }
+        ],
+    }
 
 
 def test_serialize_streaming_chunk_invalid_input_raises_attribute_error():