Update app.py

app.py

@@ -336,6 +336,18 @@ Rather than providing complete solutions, you should:
 
 Your goal is to be an educational partner who empowers students to succeed through understanding."""
 
+# --- Stop Criteria ---
+
+class StopOnSequence(StoppingCriteria):
+    def __init__(self, tokenizer, stop_sequence):
+        self.tokenizer = tokenizer
+        self.stop_sequence = tokenizer.encode(stop_sequence, add_special_tokens=False)
+
+    def __call__(self, input_ids, scores, **kwargs):
+        if input_ids[0, -len(self.stop_sequence):].tolist() == self.stop_sequence:
+            return True
+        return False
+
 # --- LLM Class with Phi-3 Mini ---
 class Phi3MiniEducationalLLM(Runnable):
     """LLM class optimized for Microsoft Phi-3-mini-4k-instruct with 4-bit quantization"""