Update app.py

app.py

@@ -31,7 +31,8 @@ except ImportError:
         PDF_SUPPORT = False
 
 # ── Constants ─────────────────────────────────────────────────────────────────
-DEFAULT_MODEL = "mistralai/Mistral-7B-Instruct-v0.3"
+# ── Constants ─────────────────────────────────────────────────────────────────
+DEFAULT_MODEL = "Qwen/Qwen2.5-72B-Instruct"
 FALLBACK_MODEL = "HuggingFaceH4/zephyr-7b-beta"
 MAX_TOKENS = 512
 MAX_HISTORY = 6  # turns to keep in context