diff --git a/graphiti_core/llm_client/openai_client.py b/graphiti_core/llm_client/openai_client.py
index 4cb1c810..d7a70502 100644
--- a/graphiti_core/llm_client/openai_client.py
+++ b/graphiti_core/llm_client/openai_client.py
@@ -73,13 +73,16 @@ class OpenAIClient(BaseOpenAIClient):
         verbosity: str | None = None,
     ):
         """Create a structured completion using OpenAI's beta parse API."""
+        # Only pass reasoning parameter for reasoning models (gpt-5 family: o1, o3-mini, o3, gpt-5-*)
+        is_reasoning_model = model.startswith('gpt-5') or model.startswith('o1') or model.startswith('o3')
+
         response = await self.client.responses.parse(
             model=model,
             input=messages,  # type: ignore
             temperature=temperature,
             max_output_tokens=max_tokens,
             text_format=response_model,  # type: ignore
-            reasoning={'effort': reasoning} if reasoning is not None else None,  # type: ignore
+            reasoning={'effort': reasoning} if reasoning is not None and is_reasoning_model else None,  # type: ignore
             text={'verbosity': verbosity} if verbosity is not None else None,  # type: ignore
         )