From 32f86aa7be8b76d66b020396e68f79e42ac7f0e2 Mon Sep 17 00:00:00 2001
From: Ishaan Jaffer <ishaan@berri.ai>
Date: Wed, 6 May 2026 17:06:03 -0700
Subject: [PATCH] test: regression test for #26153 (stream_chunk_builder
 server_tool_use type)

---
 ...streaming_chunk_builder_server_tool_use.py | 130 ++++++++++++++++++
 1 file changed, 130 insertions(+)
 create mode 100644 tests/test_litellm/litellm_core_utils/test_streaming_chunk_builder_server_tool_use.py

diff --git a/tests/test_litellm/litellm_core_utils/test_streaming_chunk_builder_server_tool_use.py b/tests/test_litellm/litellm_core_utils/test_streaming_chunk_builder_server_tool_use.py
new file mode 100644
index 00000000000..4e28d5ba7d2
--- /dev/null
+++ b/tests/test_litellm/litellm_core_utils/test_streaming_chunk_builder_server_tool_use.py
@@ -0,0 +1,130 @@
+"""
+Regression tests for https://github.com/BerriAI/litellm/issues/26153
+
+``stream_chunk_builder`` used to leave ``usage.server_tool_use`` as a plain
+``dict`` when reconstructing a streaming response. Downstream cost-calculation
+code (``StandardBuiltInToolCostTracking.response_object_includes_web_search_call``
+and ``get_cost_for_anthropic_web_search``) accesses
+``usage.server_tool_use.web_search_requests`` as an attribute, which raised
+``AttributeError: 'dict' object has no attribute 'web_search_requests'``.
+
+These tests reconstruct streaming chunks for an Anthropic-style web_search
+response and assert:
+
+1. ``stream_chunk_builder`` returns ``ServerToolUse`` (not ``dict``) for
+   ``usage.server_tool_use``.
+2. ``completion_cost`` runs end-to-end on the rebuilt response without
+   raising ``AttributeError``.
+"""
+
+import os
+import sys
+
+import pytest
+
+sys.path.insert(0, os.path.abspath("../../.."))
+
+from litellm import completion_cost, stream_chunk_builder
+from litellm.types.utils import (
+    Delta,
+    ModelResponseStream,
+    ServerToolUse,
+    StreamingChoices,
+    Usage,
+)
+
+
+def _make_text_chunk(text: str) -> ModelResponseStream:
+    return ModelResponseStream(
+        id="chatcmpl-test-26153",
+        created=1700000000,
+        model="claude-3-haiku-20240307",
+        object="chat.completion.chunk",
+        choices=[
+            StreamingChoices(
+                finish_reason=None,
+                index=0,
+                delta=Delta(role="assistant", content=text),
+            )
+        ],
+    )
+
+
+def _make_finish_chunk_with_usage_dict_server_tool_use() -> ModelResponseStream:
+    """Final chunk where server_tool_use is a *dict* — reproduces the bug shape."""
+    return ModelResponseStream(
+        id="chatcmpl-test-26153",
+        created=1700000000,
+        model="claude-3-haiku-20240307",
+        object="chat.completion.chunk",
+        choices=[
+            StreamingChoices(
+                finish_reason="stop",
+                index=0,
+                delta=Delta(),
+            )
+        ],
+        usage=Usage(
+            prompt_tokens=42,
+            completion_tokens=11,
+            total_tokens=53,
+            # NOTE: passed as a dict on purpose — this is the shape that
+            # historically slipped through stream_chunk_builder unchanged.
+            server_tool_use={"web_search_requests": 3},
+        ),
+    )
+
+
+def test_stream_chunk_builder_coerces_server_tool_use_to_pydantic():
+    """
+    Regression: stream_chunk_builder must produce ServerToolUse, not dict.
+    """
+    chunks = [
+        _make_text_chunk("Otters "),
+        _make_text_chunk("are great."),
+        _make_finish_chunk_with_usage_dict_server_tool_use(),
+    ]
+
+    rebuilt = stream_chunk_builder(chunks)
+
+    assert rebuilt is not None
+    assert rebuilt.usage is not None  # type: ignore[attr-defined]
+    server_tool_use = rebuilt.usage.server_tool_use  # type: ignore[attr-defined]
+
+    assert (
+        server_tool_use is not None
+    ), "server_tool_use should be carried through from the final chunk"
+    assert isinstance(server_tool_use, ServerToolUse), (
+        f"expected ServerToolUse, got {type(server_tool_use).__name__}: "
+        f"{server_tool_use!r}"
+    )
+    # Attribute access must not raise (this is exactly what was broken).
+    assert server_tool_use.web_search_requests == 3
+
+
+def test_completion_cost_does_not_raise_on_streaming_web_search_response():
+    """
+    Regression: completion_cost(...) must not raise AttributeError when the
+    response was reconstructed by stream_chunk_builder from a streaming
+    Anthropic web_search call.
+    """
+    chunks = [
+        _make_text_chunk("hello"),
+        _make_finish_chunk_with_usage_dict_server_tool_use(),
+    ]
+
+    rebuilt = stream_chunk_builder(chunks)
+    assert rebuilt is not None
+
+    # The exact dollar amount depends on the model-pricing table; what matters
+    # for this regression is that it does NOT raise AttributeError on
+    # `dict has no attribute 'web_search_requests'`.
+    try:
+        cost = completion_cost(completion_response=rebuilt)
+    except AttributeError as e:  # pragma: no cover - regression guard
+        pytest.fail(
+            "completion_cost raised AttributeError after stream_chunk_builder "
+            f"(issue #26153 regression): {e}"
+        )
+
+    assert isinstance(cost, (int, float))