diff --git a/litellm/llms/openai/chat/gpt_5_transformation.py b/litellm/llms/openai/chat/gpt_5_transformation.py
index 3f33d6183f..e3b3805023 100644
--- a/litellm/llms/openai/chat/gpt_5_transformation.py
+++ b/litellm/llms/openai/chat/gpt_5_transformation.py
@@ -223,16 +223,6 @@ 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/tests/test_litellm/llms/openai/chat/test_openai_gpt_transformation.py b/tests/test_litellm/llms/openai/chat/test_openai_gpt_transformation.py
index 0f743b1a93..81ffa1aa42 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 7c731e4e00..d954798006 100644
--- a/tests/test_litellm/llms/openai/test_gpt5_transformation.py
+++ b/tests/test_litellm/llms/openai/test_gpt5_transformation.py
@@ -324,11 +324,10 @@ 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.
+def test_gpt5_normalizes_reasoning_effort_dict_to_string(config: OpenAIConfig):
+    """Chat completion API expects reasoning_effort as a string, not a dict.
 
     Config/deployments may pass Responses API format: {'effort': 'high', 'summary': 'detailed'}.
-    We preserve the full dict so it reaches the Responses API transformation.
     """
     params = config.map_openai_params(
         non_default_params={"reasoning_effort": {"effort": "high", "summary": "detailed"}},
@@ -366,10 +365,10 @@ def test_gpt5_xhigh_dict_accepted_for_supported_model(config: OpenAIConfig):
 
 
 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 +377,7 @@ 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"] == {"effort": "none", "summary": "detailed"}
     assert params["tools"] == tools
 
 
@@ -411,10 +410,10 @@ def test_gpt5_preserves_reasoning_effort_dict_with_summary_from_optional_params(
         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):
+def test_gpt5_4_drops_reasoning_effort_when_tools_present(config: OpenAIConfig):
     """gpt-5.4: function calls not supported with reasoning_effort != 'none'. Drop reasoning_effort."""
     tools = [{"type": "function", "function": {"name": "test", "description": "test"}}]
     params = config.map_openai_params(
@@ -438,8 +437,8 @@ 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 +446,7 @@ 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