fix(responses): only merge repeated Codex tools when drop_params is on (#49112)

Without drop_params, every copy of a tool from additional_tools input items
is forwarded as sent, so a provider that rejects duplicate tools returns its
own 400. Codex keeps the merge because the proxy turns drop_params on for it.

litellm/llms/bedrock_mantle/responses/transformation.py

@@ -22,6 +22,7 @@ import httpx
 
 import litellm
 from litellm._logging import verbose_logger
+from litellm.litellm_core_utils.core_helpers import drops_unsupported_params
 from litellm.litellm_core_utils.url_utils import join_api_base
 from litellm.llms.base_llm.chat.transformation import BaseLLMException
 from litellm.llms.base_llm.responses.codex_compat import drop_unsupported_tools, normalize_codex_input_items
@@ -196,7 +197,9 @@ class BedrockMantleResponsesAPIConfig(BedrockMantleAuthMixin, OpenAIResponsesAPI
         params: Final = cast(  # cast-ok: the base signature leaves the params dict untyped
             "ResponsesAPIOptionalRequestParams", response_api_optional_request_params
         )
-        hoisted: Final = hoist_additional_tools(input, params.get("tools"))
+        hoisted: Final = hoist_additional_tools(
+            input, params.get("tools"), drop_params=drops_unsupported_params(litellm_params.drop_params)
+        )
         normalized_input, rewritten_types = normalize_codex_input_items(hoisted.input)
         if rewritten_types:
             verbose_logger.warning(

litellm/responses/additional_tools.py

@@ -89,6 +89,8 @@ def _unique_tools(tools: Sequence[Mapping[str, object]]) -> tuple[Mapping[str, o
 def hoist_additional_tools(
     input: str | ResponseInputParam,
     tools: Sequence[ALL_RESPONSES_API_TOOL_PARAMS] | None,
+    *,
+    drop_params: bool,
 ) -> HoistedAdditionalTools:
     existing: Final = tuple(tools or ())
     if isinstance(input, str):
@@ -103,6 +105,8 @@ def hoist_additional_tools(
         len(items),
     )
     remaining_input: Final = [item for item in input if not _is_additional_tools_item(item)]
+    if not drop_params:
+        return HoistedAdditionalTools(input=remaining_input, tools=(*existing, *hoisted), hoisted=hoisted)
     unique: Final = tuple(
         cast("ALL_RESPONSES_API_TOOL_PARAMS", tool)  # cast-ok: a merged namespace is rebuilt from the same tool dicts
         for tool in _unique_tools((*existing, *hoisted))

litellm/responses/litellm_completion_transformation/count_request.py

@@ -114,7 +114,7 @@ def with_provider_file_ids(
     }
 
 
-def _with_hoisted_additional_tools(responses_request: Mapping[str, object]) -> Mapping[str, object]:
+def _with_hoisted_additional_tools(responses_request: Mapping[str, object], drop_params: bool) -> Mapping[str, object]:
     responses_input: Final = responses_request.get("input")
     if not isinstance(responses_input, list):
         return responses_request
@@ -122,7 +122,7 @@ def _with_hoisted_additional_tools(responses_request: Mapping[str, object]) -> M
     top_level_tools: Final = cast(  # cast-ok: tools are forwarded as sent, as inference does
         "tuple[ALL_RESPONSES_API_TOOL_PARAMS, ...]", _ITEMS.validate_python(responses_request.get("tools") or ())
     )
-    hoisted: Final = hoist_additional_tools(input_items, top_level_tools)
+    hoisted: Final = hoist_additional_tools(input_items, top_level_tools, drop_params=drop_params)
     if not hoisted.hoisted:
         return responses_request
     return {**responses_request, "input": hoisted.input, "tools": list(hoisted.tools)}
@@ -196,7 +196,7 @@ async def chat_count_request(
         chat_body: Final = await _with_previous_turns(
             responses_batch_body_to_chat_body(
                 _with_compaction_as_summary_text(
-                    _with_emulated_file_search(_with_hoisted_additional_tools(responses_request))
+                    _with_emulated_file_search(_with_hoisted_additional_tools(responses_request, policy.drop_params))
                 ),
                 custom_llm_provider,
                 policy.drop_params,

litellm/responses/litellm_completion_transformation/handler.py

@@ -9,6 +9,7 @@ from typing import Final
 from pydantic import TypeAdapter
 
 import litellm
+from litellm.litellm_core_utils.core_helpers import drops_unsupported_params
 from litellm.responses.additional_tools import HoistedAdditionalTools, hoist_additional_tools
 from litellm.responses.litellm_completion_transformation.client_tool_search import bridge_client_tool_search
 from litellm.responses.litellm_completion_transformation.compaction_items import holds_compaction_summary
@@ -73,7 +74,11 @@ class LiteLLMCompletionTransformationHandler:
         | BaseResponsesAPIStreamingIterator
         | Coroutine[object, object, ResponsesAPIResponse | BaseResponsesAPIStreamingIterator]
     ):
-        hoisted: Final = hoist_additional_tools(input, responses_api_request.get("tools"))
+        hoisted: Final = hoist_additional_tools(
+            input,
+            responses_api_request.get("tools"),
+            drop_params=drops_unsupported_params(_REQUEST_KWARGS_ADAPTER.validate_python(kwargs).get("drop_params")),
+        )
         previous_response_id: Final = responses_api_request.get("previous_response_id")
         if _is_async and previous_response_id and has_client_tool_search(hoisted.tools):
             return self._async_response_api_handler_after_earlier_searches(

tests/integration/providers/test_responses_codex_repeated_additional_tools_wire.py

@@ -70,7 +70,9 @@ def bedrock_converse_peer(request: Request) -> Reply:
     )
 
 
-def send_to_bedrock_converse(gateway: Gateway, history: list[JsonValue]) -> tuple[httpx.Response, tuple[Request, ...]]:
+def send_to_bedrock_converse(
+    gateway: Gateway, history: list[JsonValue], drop_params: bool = True
+) -> tuple[httpx.Response, tuple[Request, ...]]:
     with wire_server(bedrock_converse_peer) as wire, gateway.scenario() as scenario:
         model: Final = scenario.model(
             model=f"bedrock/converse/{BEDROCK_GPT}",
@@ -79,7 +81,15 @@ def send_to_bedrock_converse(gateway: Gateway, history: list[JsonValue]) -> tupl
             aws_bedrock_runtime_endpoint=wire.url,
         )
         response: Final = gateway.request(
-            "POST", "/v1/responses", {"model": model, "input": history, "store": False, "cache": {"no-cache": True}}
+            "POST",
+            "/v1/responses",
+            {
+                "model": model,
+                "input": history,
+                "store": False,
+                "cache": {"no-cache": True},
+                "drop_params": drop_params,
+            },
         )
         return response, wire.drain()
 
@@ -113,6 +123,20 @@ def test_codex_tool_list_repeated_on_every_turn_reaches_bedrock_converse_once(ga
     assert sorted(names) == ["collaboration__followup_task", "exec_command"], names
 
 
+def test_codex_tool_list_repeated_on_every_turn_reaches_bedrock_converse_as_sent_without_drop_params(
+    gateway: Gateway,
+) -> None:
+    marker: Final = uuid.uuid4().hex
+    tools: Final = tool_list_item(function_tool("exec_command"))
+    history: Final[list[JsonValue]] = [tools, user_turn(f"first {marker}"), assistant_turn("ok"), tools]
+
+    response, forwarded = send_to_bedrock_converse(gateway, history, drop_params=False)
+
+    assert response.status_code == 400, response.text
+    assert "already defined" in response.text, response.text
+    assert [str(spec["name"]) for spec in converse_tool_specs(forwarded[0])] == ["exec_command", "exec_command"]
+
+
 def test_newest_copy_of_a_repeated_codex_tool_is_what_bedrock_converse_receives(gateway: Gateway) -> None:
     marker: Final = uuid.uuid4().hex
     history: Final[list[JsonValue]] = [
@@ -195,6 +219,7 @@ def test_codex_tool_list_repeated_on_every_turn_reaches_bedrock_mantle_once(gate
                     user_turn(f"second {marker}"),
                 ],
                 "store": False,
+                "drop_params": True,
             },
         )
         forwarded: Final = wire.drain()

tests/unit/responses/litellm_completion_transformation/test_count_request.py

@@ -95,8 +95,8 @@ async def test_claude_count_request_counts_additional_tools_input_items_as_tools
 
 
 @pytest.mark.asyncio
-async def test_claude_count_request_counts_a_tool_list_repeated_on_every_turn_once() -> None:
-    policy: Final = DropPolicy(drop_params=False, additional_drop_params=frozenset())
+async def test_claude_count_request_counts_a_tool_list_repeated_on_every_turn_once_under_drop_params() -> None:
+    policy: Final = DropPolicy(drop_params=True, additional_drop_params=frozenset())
     tool_list: Final[dict[str, JsonValue]] = {"type": "additional_tools", "tools": [_WEATHER_TOOL]}
 
     repeated: Final = await _claude_count(

tests/unit/responses/test_additional_tools.py

@@ -15,7 +15,7 @@ _USER_MESSAGE = {"type": "message", "role": "user", "content": "Run ls"}
 
 
 def test_string_input_passes_through_with_existing_tools():
-    hoisted = hoist_additional_tools("hello", [_TOP_LEVEL_TOOL])
+    hoisted = hoist_additional_tools("hello", [_TOP_LEVEL_TOOL], drop_params=False)
 
     assert hoisted.input == "hello"
     assert hoisted.tools == (_TOP_LEVEL_TOOL,)
@@ -25,7 +25,7 @@ def test_string_input_passes_through_with_existing_tools():
 def test_input_without_additional_tools_items_is_returned_untouched():
     request_input = [_USER_MESSAGE]
 
-    hoisted = hoist_additional_tools(request_input, None)
+    hoisted = hoist_additional_tools(request_input, None, drop_params=False)
 
     assert hoisted.input is request_input
     assert hoisted.tools == ()
@@ -39,7 +39,7 @@ def test_additional_tools_items_are_stripped_and_appended_after_top_level_tools_
         {"type": "additional_tools", "id": "at_2", "role": "developer", "tools": [_WAIT_TOOL]},
     ]
 
-    hoisted = hoist_additional_tools(request_input, [_TOP_LEVEL_TOOL])
+    hoisted = hoist_additional_tools(request_input, [_TOP_LEVEL_TOOL], drop_params=False)
 
     assert hoisted.input == [_USER_MESSAGE]
     assert hoisted.tools == (_TOP_LEVEL_TOOL, _EXEC_TOOL, _WAIT_TOOL)
@@ -49,7 +49,7 @@ def test_additional_tools_items_are_stripped_and_appended_after_top_level_tools_
 def test_additional_tools_item_without_a_tools_list_is_stripped_and_contributes_nothing():
     request_input = [{"type": "additional_tools", "id": "at_1", "role": "developer", "tools": "exec"}, _USER_MESSAGE]
 
-    hoisted = hoist_additional_tools(request_input, None)
+    hoisted = hoist_additional_tools(request_input, None, drop_params=False)
 
     assert hoisted.input == [_USER_MESSAGE]
     assert hoisted.tools == ()
@@ -77,7 +77,7 @@ def test_tool_list_repeated_on_every_turn_keeps_each_tool_once_with_the_newest_d
         _USER_MESSAGE,
     ]
 
-    hoisted: Final = hoist_additional_tools(request_input, None)
+    hoisted: Final = hoist_additional_tools(request_input, None, drop_params=True)
 
     assert hoisted.tools == (collaboration, _function("exec", "new"))
 
@@ -89,7 +89,7 @@ def test_namespace_sent_in_several_turns_keeps_every_distinct_member_once() -> N
         _tool_list(_namespace("mcp__docs__", _function("fetch", "new"), _function("list"))),
     ]
 
-    hoisted: Final = hoist_additional_tools(request_input, None)
+    hoisted: Final = hoist_additional_tools(request_input, None, drop_params=True)
 
     assert hoisted.tools == (
         _namespace("mcp__docs__", _function("search"), _function("fetch", "new"), _function("list")),
@@ -109,7 +109,7 @@ def test_unnamed_tools_collapse_only_when_identical() -> None:
     }
     request_input: Final = [_tool_list(docs_server, wiki_server), _USER_MESSAGE, _tool_list(docs_server)]
 
-    hoisted: Final = hoist_additional_tools(request_input, None)
+    hoisted: Final = hoist_additional_tools(request_input, None, drop_params=True)
 
     assert hoisted.tools == (docs_server, wiki_server)
 
@@ -117,6 +117,20 @@ def test_unnamed_tools_collapse_only_when_identical() -> None:
 def test_top_level_tool_repeated_in_a_tool_list_item_is_kept_once() -> None:
     request_input: Final = [_tool_list(_TOP_LEVEL_TOOL, _WAIT_TOOL), _USER_MESSAGE]
 
-    hoisted: Final = hoist_additional_tools(request_input, [_TOP_LEVEL_TOOL])
+    hoisted: Final = hoist_additional_tools(request_input, [_TOP_LEVEL_TOOL], drop_params=True)
 
     assert hoisted.tools == (_TOP_LEVEL_TOOL, _WAIT_TOOL)
+
+
+def test_tool_list_repeated_on_every_turn_is_sent_as_is_without_drop_params() -> None:
+    request_input: Final = [
+        _tool_list(_function("exec", "old")),
+        _USER_MESSAGE,
+        _tool_list(_function("exec", "new")),
+        _USER_MESSAGE,
+    ]
+
+    hoisted: Final = hoist_additional_tools(request_input, [_TOP_LEVEL_TOOL], drop_params=False)
+
+    assert hoisted.tools == (_TOP_LEVEL_TOOL, _function("exec", "old"), _function("exec", "new"))
+    assert hoisted.input == [_USER_MESSAGE, _USER_MESSAGE]