fix lc streaming (#272)

src/chainlit/langchain/callbacks.py

@@ -119,11 +119,29 @@ def append_to_last_tokens(self, token: str) -> None:
             self.last_tokens.pop(0)
             self.last_tokens_stripped.pop(0)
 
+    def _compare_last_tokens(self, last_tokens: List[str]):
+        if last_tokens == self.answer_prefix_tokens_stripped:
+            # If tokens match perfectly we are done
+            return True
+        else:
+            # Some LLMs will consider all the tokens of the final answer as one token
+            # so we check if any last token contains all answer tokens
+            return any(
+                [
+                    all(
+                        answer_token in last_token
+                        for answer_token in self.answer_prefix_tokens_stripped
+                    )
+                    for last_token in last_tokens
+                ]
+            )
+
     def check_if_answer_reached(self) -> bool:
         if self.strip_tokens:
-            return self.last_tokens_stripped == self.answer_prefix_tokens_stripped
+            return self._compare_last_tokens(self.last_tokens_stripped)
+
         else:
-            return self.last_tokens == self.answer_prefix_tokens
+            return self._compare_last_tokens(self.last_tokens)
 
     def start_stream(self):
         author = self.get_author()