diff --git a/mem0/llms/base.py b/mem0/llms/base.py
index 8812122a5f..d7315c52c6 100644
--- a/mem0/llms/base.py
+++ b/mem0/llms/base.py
@@ -51,7 +51,7 @@ def _is_reasoning_model(self, model: str) -> bool:
             bool: True if the model is a reasoning model or GPT-5 series
         """
         reasoning_models = {
-            "o1", "o1-preview", "o3-mini", "o3",
+            "o1", "o1-preview", "o3", "o3-mini", "o4", "o4-mini",
             "gpt-5", "gpt-5o", "gpt-5o-mini", "gpt-5o-micro",
         }
 
@@ -62,9 +62,11 @@ def _is_reasoning_model(self, model: str) -> bool:
         if base_model in reasoning_models:
             return True
 
-        # Match o1/o3 family with prefixes (o1-2024-12-17, o3-2025-04-16)
-        # but NOT gpt-5.x variants (gpt-5.4-mini supports temperature)
-        if any(base_model.startswith(prefix) for prefix in ["o1-", "o1.", "o3-", "o3."]):
+        # Match dated Azure/OpenAI subversions:
+        #   o1-2024-12-17, o3-2025-04-16, o4-mini-2025-04-16
+        #   gpt-5-2025-06-15, gpt-5.4-2025-07-15, gpt-5.4-mini-2025-07-15
+        reasoning_prefixes = ("o1-", "o1.", "o3-", "o3.", "o4-", "o4.", "gpt-5-", "gpt-5.")
+        if any(base_model.startswith(prefix) for prefix in reasoning_prefixes):
             return True
 
         return False