diff --git a/litellm/llms/openai/chat/gpt_5_transformation.py b/litellm/llms/openai/chat/gpt_5_transformation.py
index 0223be300b0..bfaf396c7fb 100644
--- a/litellm/llms/openai/chat/gpt_5_transformation.py
+++ b/litellm/llms/openai/chat/gpt_5_transformation.py
@@ -156,6 +156,15 @@ class OpenAIGPT5Config(OpenAIGPTConfig):
             key=f"supports_{level}_reasoning_effort",
         )
 
+    @classmethod
+    def is_reasoning_effort_unsupported(cls, model: str, level: str | None) -> bool:
+        """Return whether GPT-5 capability metadata rejects this effort level."""
+        if level == "xhigh":
+            return not cls._supports_reasoning_effort_level(model, level)
+        if level in ("minimal", "low"):
+            return cls._is_reasoning_effort_level_explicitly_disabled(model, level)
+        return False
+
     @classmethod
     def effort_resolves_to_none(cls, model: str, effective_effort: str | None) -> bool:
         """Whether this request's reasoning effort ends up as "none", which is the single
diff --git a/litellm/llms/openai/responses/transformation.py b/litellm/llms/openai/responses/transformation.py
index 54ce6a366e6..8dd8b574ee8 100644
--- a/litellm/llms/openai/responses/transformation.py
+++ b/litellm/llms/openai/responses/transformation.py
@@ -84,17 +84,9 @@ class OpenAIResponsesAPIConfig(BaseResponsesAPIConfig):
     @staticmethod
     def _is_unsupported_reasoning_effort(model: str, effort: str | None) -> bool:
         """Apply the GPT-5 reasoning-effort capability flags used by chat completions."""
-        from litellm.router_utils.reasoning_effort_capability import (
-            declared_reasoning_efforts_for_model,
-        )
+        from litellm.llms.openai.chat.gpt_5_transformation import OpenAIGPT5Config
 
-        lookup_model: Final = model.removeprefix("openai/")
-        declared: Final = declared_reasoning_efforts_for_model(lookup_model, "openai")
-        if effort == "xhigh":
-            return declared is None or effort not in declared
-        if effort in ("minimal", "low"):
-            return declared is not None and effort not in declared
-        return False
+        return OpenAIGPT5Config.is_reasoning_effort_unsupported(model, effort)
 
     @staticmethod
     def _enforce_min_max_output_tokens(max_output_tokens: "int | None") -> "int | None":