Update app.py

app.py

@@ -61,7 +61,7 @@ class BasicAgent:
     # ---- Low‑level LLM call
     def _call_llm(self, prompt: str, max_tokens: int = 256) -> str:
         resp = self.llm.chat.completions.create(
-            model="gpt-4o-mini",
+            model="gpt-3.5-turbo",
             messages=[
                 {"role": "system", "content": "You are a careful reasoning assistant."},
                 {"role": "user", "content": prompt},