diff --git a/litellm/llms/openai/chat/gpt_5_transformation.py b/litellm/llms/openai/chat/gpt_5_transformation.py
index 3f33d6183f3..bb5783011a3 100644
--- a/litellm/llms/openai/chat/gpt_5_transformation.py
+++ b/litellm/llms/openai/chat/gpt_5_transformation.py
@@ -188,11 +188,9 @@ class OpenAIGPT5Config(OpenAIGPTConfig):
         ) or optional_params.get("reasoning_effort")
         effective_effort = _get_effort_level(raw_reasoning_effort)
 
-        # Normalize to string for Chat Completions API when dict has only "effort".
-        # Preserve full dict (e.g. {"effort": "high", "summary": "detailed"}) for Responses API.
-        if isinstance(raw_reasoning_effort, dict) and set(
-            raw_reasoning_effort.keys()
-        ) <= {"effort"}:
+        # Normalize dict reasoning_effort to string for Chat Completions API.
+        # Example: {"effort": "high", "summary": "detailed"} -> "high"
+        if isinstance(raw_reasoning_effort, dict) and "effort" in raw_reasoning_effort:
             normalized = _normalize_reasoning_effort_for_chat_completion(
                 raw_reasoning_effort
             )
@@ -223,16 +221,6 @@ class OpenAIGPT5Config(OpenAIGPTConfig):
                 "max_tokens"
             )
 
-        # gpt-5.4: reasoning_effort + tools is only supported in the Responses API
-        # Drop reasoning_effort when tools are present in chat completions
-        if self.is_model_gpt_5_4_model(model):
-            has_tools = bool(
-                non_default_params.get("tools") or optional_params.get("tools")
-            )
-            if has_tools and effective_effort is not None:
-                non_default_params.pop("reasoning_effort", None)
-                optional_params.pop("reasoning_effort", None)
-
         # gpt-5.1/5.2 support logprobs, top_p, top_logprobs only when reasoning_effort="none"
         supports_none = self._supports_reasoning_effort_level(model, "none")
         if supports_none:
diff --git a/litellm/main.py b/litellm/main.py
index 569a9133d2f..722b4a7aaec 100644
--- a/litellm/main.py
+++ b/litellm/main.py
@@ -99,6 +99,7 @@ from litellm.llms.base_llm.base_model_iterator import (
 from litellm.llms.bedrock.common_utils import BedrockModelInfo
 from litellm.llms.cohere.common_utils import CohereModelInfo
 from litellm.llms.custom_httpx.http_handler import AsyncHTTPHandler, HTTPHandler
+from litellm.llms.openai.chat.gpt_5_transformation import OpenAIGPT5Config
 from litellm.llms.openai_like.json_loader import JSONProviderRegistry
 from litellm.llms.vertex_ai.common_utils import (
     VertexAIModelRoute,
@@ -934,6 +935,8 @@ def responses_api_bridge_check(
     model: str,
     custom_llm_provider: str,
     web_search_options: Optional[OpenAIWebSearchOptions] = None,
+    tools: Optional[List[Any]] = None,
+    reasoning_effort: Optional[Any] = None,
 ) -> Tuple[dict, str]:
     model_info: Dict[str, Any] = {}
     try:
@@ -951,6 +954,17 @@ def responses_api_bridge_check(
         if web_search_options is not None and custom_llm_provider == "xai":
             model_info["mode"] = "responses"
             model = model.replace("responses/", "")
+
+        # OpenAI gpt-5.4+ chat-completions calls with both tools + reasoning_effort
+        # must be bridged to Responses API.
+        if (
+            custom_llm_provider == "openai"
+            and OpenAIGPT5Config.is_model_gpt_5_4_plus_model(model)
+            and tools
+            and reasoning_effort is not None
+        ):
+            model_info["mode"] = "responses"
+            model = model.replace("responses/", "")
     except Exception as e:
         verbose_logger.debug("Error getting model info: {}".format(e))
 
@@ -1596,11 +1610,17 @@ def completion(  # type: ignore # noqa: PLR0915
             model=model,
             custom_llm_provider=custom_llm_provider,
             web_search_options=web_search_options,
+            tools=tools,
+            reasoning_effort=reasoning_effort,
         )
 
         if model_info.get("mode") == "responses":
             from litellm.completion_extras import responses_api_bridge
 
+            if isinstance(reasoning_effort, dict) and "summary" in reasoning_effort:
+                optional_params = dict(optional_params)
+                optional_params["reasoning_effort"] = reasoning_effort
+
             return responses_api_bridge.completion(
                 model=model,
                 messages=messages,
diff --git a/tests/test_litellm/llms/openai/chat/test_openai_gpt_transformation.py b/tests/test_litellm/llms/openai/chat/test_openai_gpt_transformation.py
index 0f743b1a93b..81ffa1aa428 100644
--- a/tests/test_litellm/llms/openai/chat/test_openai_gpt_transformation.py
+++ b/tests/test_litellm/llms/openai/chat/test_openai_gpt_transformation.py
@@ -9,6 +9,7 @@ import pytest
 
 sys.path.insert(0, os.path.abspath("../../../../.."))
 
+from litellm.llms.openai.chat.gpt_5_transformation import OpenAIGPT5Config
 from litellm.llms.openai.chat.gpt_transformation import (
     OpenAIChatCompletionStreamingHandler,
     OpenAIGPTConfig,
diff --git a/tests/test_litellm/llms/openai/test_gpt5_transformation.py b/tests/test_litellm/llms/openai/test_gpt5_transformation.py
index 7c731e4e00a..47ae3c44c9e 100644
--- a/tests/test_litellm/llms/openai/test_gpt5_transformation.py
+++ b/tests/test_litellm/llms/openai/test_gpt5_transformation.py
@@ -324,19 +324,15 @@ def test_gpt5_4_pro_allows_reasoning_effort_xhigh(config: OpenAIConfig):
     assert params["reasoning_effort"] == "xhigh"
 
 
-def test_gpt5_preserves_reasoning_effort_dict_with_summary(config: OpenAIConfig):
-    """Dict with summary/generate_summary is preserved for Responses API.
-
-    Config/deployments may pass Responses API format: {'effort': 'high', 'summary': 'detailed'}.
-    We preserve the full dict so it reaches the Responses API transformation.
-    """
+def test_gpt5_normalizes_reasoning_effort_dict_with_summary(config: OpenAIConfig):
+    """Dict with summary/generate_summary is normalized for chat completions."""
     params = config.map_openai_params(
         non_default_params={"reasoning_effort": {"effort": "high", "summary": "detailed"}},
         optional_params={},
         model="gpt-5.4",
         drop_params=False,
     )
-    assert params["reasoning_effort"] == {"effort": "high", "summary": "detailed"}
+    assert params["reasoning_effort"] == "high"
 
 
 def test_gpt5_xhigh_dict_triggers_validation(config: OpenAIConfig):
@@ -362,14 +358,14 @@ def test_gpt5_xhigh_dict_accepted_for_supported_model(config: OpenAIConfig):
         model="gpt-5.4",
         drop_params=False,
     )
-    assert params["reasoning_effort"] == {"effort": "xhigh", "summary": "detailed"}
+    assert params["reasoning_effort"] == "xhigh"
 
 
 def test_gpt5_none_dict_with_tools_no_tool_drop(config: OpenAIConfig):
-    """Dict with effort='none' and tools: reasoning_effort dropped for gpt-5.4.
+    """Dict with effort='none' and tools: no tool-drop, reasoning_effort preserved.
 
-    gpt-5.4 drops all reasoning_effort when tools are present,
-    since that combination is only supported in the Responses API.
+    Regression: effective_effort='none' must be used for tool-drop guard so
+    {"effort": "none", "summary": "detailed"} is not incorrectly treated as non-none.
     """
     tools = [{"type": "function", "function": {"name": "test", "description": "test"}}]
     params = config.map_openai_params(
@@ -378,7 +374,7 @@ def test_gpt5_none_dict_with_tools_no_tool_drop(config: OpenAIConfig):
         model="gpt-5.4",
         drop_params=False,
     )
-    assert "reasoning_effort" not in params
+    assert params["reasoning_effort"] == "none"
     assert params["tools"] == tools
 
 
@@ -398,24 +394,28 @@ def test_gpt5_none_dict_with_sampling_params_allowed(config: OpenAIConfig):
         model="gpt-5.1",
         drop_params=False,
     )
-    assert params["reasoning_effort"] == {"effort": "none", "summary": "detailed"}
+    assert params["reasoning_effort"] == "none"
     assert params["logprobs"] is True
     assert params["top_p"] == 0.9
 
 
-def test_gpt5_preserves_reasoning_effort_dict_with_summary_from_optional_params(config: OpenAIConfig):
-    """reasoning_effort dict with summary in optional_params is preserved."""
+def test_gpt5_normalizes_reasoning_effort_dict_with_summary_from_optional_params(config: OpenAIConfig):
+    """reasoning_effort dict with summary in optional_params is normalized."""
     params = config.map_openai_params(
         non_default_params={},
         optional_params={"reasoning_effort": {"effort": "medium", "summary": "detailed"}},
         model="gpt-5.4",
         drop_params=False,
     )
-    assert params["reasoning_effort"] == {"effort": "medium", "summary": "detailed"}
+    assert params["reasoning_effort"] == "medium"
 
 
-def test_gpt5_4_drops_reasoning_effort_when_user_sends_reasoning_and_tools(config: OpenAIConfig):
-    """gpt-5.4: function calls not supported with reasoning_effort != 'none'. Drop reasoning_effort."""
+def test_gpt5_4_passes_through_reasoning_effort_with_tools(config: OpenAIConfig):
+    """gpt-5.4 with tools + reasoning_effort: map_openai_params passes through both.
+
+    Routing to Responses API (which supports tools + reasoning) happens at completion()
+    level (responses_api_bridge_check). See test_responses_api_bridge_check_gpt_5_4_tools_plus_reasoning_routes_to_responses.
+    """
     tools = [{"type": "function", "function": {"name": "test", "description": "test"}}]
     params = config.map_openai_params(
         non_default_params={"reasoning_effort": "high", "tools": tools},
@@ -423,7 +423,7 @@ def test_gpt5_4_drops_reasoning_effort_when_user_sends_reasoning_and_tools(confi
         model="gpt-5.4",
         drop_params=False,
     )
-    assert "reasoning_effort" not in params
+    assert params["reasoning_effort"] == "high"
     assert params["tools"] == tools
 
 
@@ -438,8 +438,8 @@ def test_gpt5_4_keeps_reasoning_effort_when_no_tools(config: OpenAIConfig):
     assert params["reasoning_effort"] == "high"
 
 
-def test_gpt5_4_drops_reasoning_effort_none_with_tools(config: OpenAIConfig):
-    """reasoning_effort='none' is also dropped when tools are present for gpt-5.4."""
+def test_gpt5_4_keeps_reasoning_effort_none_with_tools(config: OpenAIConfig):
+    """reasoning_effort='none' is kept when tools are present."""
     tools = [{"type": "function", "function": {"name": "test", "description": "test"}}]
     params = config.map_openai_params(
         non_default_params={"reasoning_effort": "none", "tools": tools},
@@ -447,7 +447,7 @@ def test_gpt5_4_drops_reasoning_effort_none_with_tools(config: OpenAIConfig):
         model="gpt-5.4",
         drop_params=False,
     )
-    assert "reasoning_effort" not in params
+    assert params["reasoning_effort"] == "none"
     assert params["tools"] == tools
 
 
diff --git a/tests/test_litellm/test_main.py b/tests/test_litellm/test_main.py
index 3a43b1229de..6ac988b2c21 100644
--- a/tests/test_litellm/test_main.py
+++ b/tests/test_litellm/test_main.py
@@ -627,6 +627,94 @@ def test_responses_api_bridge_check_gpt_5_4_pro():
         )
 
 
+def test_responses_api_bridge_check_gpt_5_4_tools_plus_reasoning_routes_to_responses():
+    """gpt-5.4 with both tools and reasoning_effort should route to Responses API."""
+    from litellm.main import responses_api_bridge_check
+
+    with patch("litellm.main._get_model_info_helper") as mock_get_model_info:
+        mock_get_model_info.return_value = {"max_tokens": 128000}
+        model_info, model = responses_api_bridge_check(
+            model="gpt-5.4",
+            custom_llm_provider="openai",
+            tools=[{"type": "function", "function": {"name": "get_capital"}}],
+            reasoning_effort="xhigh",
+        )
+
+    assert model == "gpt-5.4"
+    assert model_info.get("mode") == "responses"
+
+
+def test_responses_api_bridge_check_gpt_5_5_tools_plus_reasoning_routes_to_responses():
+    """gpt-5.5+ with both tools and reasoning_effort should route to Responses API."""
+    from litellm.main import responses_api_bridge_check
+
+    with patch("litellm.main._get_model_info_helper") as mock_get_model_info:
+        mock_get_model_info.return_value = {"max_tokens": 128000}
+        model_info, model = responses_api_bridge_check(
+            model="gpt-5.5-pro",
+            custom_llm_provider="openai",
+            tools=[{"type": "function", "function": {"name": "get_capital"}}],
+            reasoning_effort="xhigh",
+        )
+
+    assert model == "gpt-5.5-pro"
+    assert model_info.get("mode") == "responses"
+
+
+def test_responses_api_bridge_check_gpt_5_4_tools_without_reasoning_stays_chat():
+    """gpt-5.4 with tools only should not be force-routed to Responses API."""
+    from litellm.main import responses_api_bridge_check
+
+    with patch("litellm.main._get_model_info_helper") as mock_get_model_info:
+        mock_get_model_info.return_value = {"max_tokens": 128000}
+        model_info, model = responses_api_bridge_check(
+            model="gpt-5.4",
+            custom_llm_provider="openai",
+            tools=[{"type": "function", "function": {"name": "get_capital"}}],
+            reasoning_effort=None,
+        )
+
+    assert model == "gpt-5.4"
+    assert model_info.get("mode") != "responses"
+
+
+@patch("litellm.completion_extras.responses_api_bridge.completion")
+def test_gpt_5_4_responses_bridge_preserves_reasoning_summary_dict(
+    mock_responses_completion,
+):
+    """When routed to Responses, preserve reasoning_effort summary dict."""
+    mock_responses_completion.return_value = MagicMock()
+
+    import litellm
+
+    litellm.completion(
+        model="gpt-5.4",
+        messages=[{"role": "user", "content": "What is the capital of France?"}],
+        tools=[
+            {
+                "type": "function",
+                "function": {
+                    "name": "get_capital",
+                    "description": "Get the capital of a country",
+                    "parameters": {
+                        "type": "object",
+                        "properties": {"country": {"type": "string"}},
+                    },
+                },
+            }
+        ],
+        reasoning_effort={"effort": "xhigh", "summary": "detailed"},
+        api_key="fake-key",
+    )
+
+    assert mock_responses_completion.called is True
+    optional_params = mock_responses_completion.call_args.kwargs["optional_params"]
+    assert optional_params["reasoning_effort"] == {
+        "effort": "xhigh",
+        "summary": "detailed",
+    }
+
+
 def test_responses_api_bridge_check_handles_exception():
     """Test that responses_api_bridge_check handles exceptions and still processes responses/ models."""
     from litellm.main import responses_api_bridge_check