test(messages): verify metadata dict copy prevents raw_request leak

tests/test_litellm/llms/anthropic/experimental_pass_through/messages/test_metadata_dict_copy.py

@@ -0,0 +1,124 @@
+"""
+Test that metadata dict is shallow-copied in transform_anthropic_messages_request
+to prevent raw_request leak from litellm_params into the Anthropic API request.
+
+Related: PR #24661 (same bug, chat/completions path).
+"""
+
+from litellm.llms.anthropic.experimental_pass_through.messages.transformation import (
+    AnthropicMessagesConfig,
+)
+from litellm.types.router import GenericLiteLLMParams
+
+
+def test_metadata_dict_is_copied_not_shared():
+    """
+    The metadata dict inside optional_params should be a different object
+    after transform_anthropic_messages_request, so mutations to the original
+    (e.g. raw_request injection by the logging layer) don't leak.
+    """
+    config = AnthropicMessagesConfig()
+
+    original_metadata = {"user_id": "test-user-123"}
+    optional_params = {
+        "max_tokens": 100,
+        "metadata": original_metadata,
+    }
+
+    result = config.transform_anthropic_messages_request(
+        model="claude-sonnet-4-20250514",
+        messages=[{"role": "user", "content": "Hello"}],
+        anthropic_messages_optional_request_params=optional_params,
+        litellm_params=GenericLiteLLMParams(),
+        headers={},
+    )
+
+    # The metadata in optional_params should now be a copy, not the same object
+    assert optional_params["metadata"] is not original_metadata
+
+    # The copy should still have the same content
+    assert optional_params["metadata"]["user_id"] == "test-user-123"
+
+    # Mutating the original should not affect the copy in optional_params
+    original_metadata["raw_request"] = "leaked!"
+    assert "raw_request" not in optional_params["metadata"]
+
+
+def test_metadata_dict_copy_preserves_content_in_result():
+    """
+    Verify the copied metadata ends up in the final request dict with
+    correct content.
+    """
+    config = AnthropicMessagesConfig()
+
+    metadata = {"user_id": "u-456"}
+    optional_params = {
+        "max_tokens": 200,
+        "metadata": metadata,
+    }
+
+    result = config.transform_anthropic_messages_request(
+        model="claude-sonnet-4-20250514",
+        messages=[{"role": "user", "content": "Hi"}],
+        anthropic_messages_optional_request_params=optional_params,
+        litellm_params=GenericLiteLLMParams(),
+        headers={},
+    )
+
+    assert result["metadata"]["user_id"] == "u-456"
+
+
+def test_no_metadata_dict_no_error():
+    """
+    When metadata is absent, the copy logic should be a no-op (no KeyError).
+    """
+    config = AnthropicMessagesConfig()
+
+    optional_params = {
+        "max_tokens": 100,
+    }
+
+    result = config.transform_anthropic_messages_request(
+        model="claude-sonnet-4-20250514",
+        messages=[{"role": "user", "content": "Hello"}],
+        anthropic_messages_optional_request_params=optional_params,
+        litellm_params=GenericLiteLLMParams(),
+        headers={},
+    )
+
+    # Should succeed without error; metadata absent from result
+    assert "metadata" not in result or result.get("metadata") is None
+
+
+def test_non_dict_metadata_not_copied():
+    """
+    If metadata is not a dict (e.g. a Pydantic model), the copy guard
+    should skip it without error.
+    """
+    config = AnthropicMessagesConfig()
+
+    class FakeMetadata:
+        user_id = "test"
+
+    fake = FakeMetadata()
+    optional_params = {
+        "max_tokens": 100,
+        "metadata": fake,
+    }
+
+    # Should not raise; the non-dict metadata passes through as-is
+    try:
+        config.transform_anthropic_messages_request(
+            model="claude-sonnet-4-20250514",
+            messages=[{"role": "user", "content": "Hello"}],
+            anthropic_messages_optional_request_params=optional_params,
+            litellm_params=GenericLiteLLMParams(),
+            headers={},
+        )
+    except Exception:
+        # AnthropicMessagesRequest might reject non-dict metadata; that's fine.
+        # The point is the copy logic itself doesn't crash.
+        pass
+
+    # The metadata should still be the same object (not copied)
+    assert optional_params["metadata"] is fake