fix(utils): stop a nested additional_drop_params entry from crashing openai-compatible calls (#42492)

add_provider_specific_params_to_optional_params built the extra_body dropped-key
set as frozenset(additional_drop_params), so one non-string entry raised
TypeError: unhashable type: 'list' and every openai-compatible call carrying one
failed with a 500 before it reached the transport. The set now takes only the
string entries, the element type every other signature in this chain already
declares as list[str].

A list-form entry still drops nothing: is_nested_path() tests a string, so
delete_nested_value() has never applied one on any provider. This removes the
crash only, so a working string path such as "tools[*].function.x" sitting
beside a malformed list entry is applied instead of taking the request down.

litellm/utils.py

@@ -4979,7 +4979,9 @@ def add_provider_specific_params_to_optional_params(
                 **extra_body,
             }
 
-            dropped_keys: Final = EXTRA_BODY_ROUTING_KEYS | frozenset(additional_drop_params or ())
+            dropped_keys: Final = EXTRA_BODY_ROUTING_KEYS | frozenset(
+                param for param in (additional_drop_params or ()) if isinstance(param, str)
+            )
             processed_extra_body: Final = {k: v for k, v in initial_extra_body.items() if k not in dropped_keys}
 
             _ensure_extra_body_is_safe: Final = getattr(sys.modules[__name__], "_ensure_extra_body_is_safe")

tests/test_litellm/test_utils.py

@@ -3042,6 +3042,45 @@ class TestExtraBodyCannotOverrideModel:
 
         assert result["extra_body"] == {"top_k": 5}, result
 
+    def test_nested_drop_paths_do_not_break_extra_body_filtering(self) -> None:
+        from litellm.utils import add_provider_specific_params_to_optional_params
+
+        result = add_provider_specific_params_to_optional_params(
+            optional_params={},
+            passed_params={
+                "model": "hosted_vllm/my-vllm-model",
+                "extra_body": {"model": "hosted_vllm/other", "top_k": 5, "kept": True},
+            },
+            custom_llm_provider="hosted_vllm",
+            openai_params=["model", "temperature"],
+            additional_drop_params=[["tools", "function", "strict"], "top_k"],
+        )
+
+        assert result == {"extra_body": {"kept": True}}, result
+
+    def test_a_list_entry_does_not_break_a_supported_nested_drop_path(self) -> None:
+        def tools() -> list[dict]:
+            return [
+                {
+                    "type": "function",
+                    "function": {"name": "f", "custom_marker": "LEAK", "parameters": {"type": "object"}},
+                }
+            ]
+
+        untouched = litellm.get_optional_params(
+            model="my-vllm-model", custom_llm_provider="hosted_vllm", tools=tools()
+        )
+        assert untouched["tools"][0]["function"]["custom_marker"] == "LEAK", untouched
+
+        result = litellm.get_optional_params(
+            model="my-vllm-model",
+            custom_llm_provider="hosted_vllm",
+            tools=tools(),
+            additional_drop_params=["tools[*].function.custom_marker", ["tools", "function", "custom_marker"]],
+        )
+
+        assert "custom_marker" not in result["tools"][0]["function"], result
+
 
 class TestDropParamsWithPromptCacheKey:
     """