diff --git a/sdks/python/agenta/sdk/engines/running/handlers.py b/sdks/python/agenta/sdk/engines/running/handlers.py
index fbc515674a..ac1174c9ad 100644
--- a/sdks/python/agenta/sdk/engines/running/handlers.py
+++ b/sdks/python/agenta/sdk/engines/running/handlers.py
@@ -2220,7 +2220,10 @@ async def chat_v0(
 
     message = response.choices[0].message  # type: ignore
 
-    return message.model_dump(exclude_none=True)  # type: ignore
+    # Normalize to the canonical Message shape (drops provider-specific fields).
+    return Message.model_validate(message.model_dump(exclude_none=True)).model_dump(
+        exclude_none=True
+    )
 
 
 @instrument(ignore_inputs=["parameters"])