Fix #929

llama_cpp/llama.py

@@ -1323,7 +1323,9 @@ class Llama:
 
         completion_id: str = f"cmpl-{str(uuid.uuid4())}"
         created: int = int(time.time())
-        completion_tokens: List[int] = []
+        # If prompt is empty, initialize completion with BOS token to avoid
+        # detokenization including a space at the beginning of the completion
+        completion_tokens: List[int] = [] if len(prompt) > 0 else [self.token_bos()]
         # Add blank space to start of prompt to match OG llama tokenizer
         prompt_tokens: List[int] = (
             (
@@ -1459,6 +1461,8 @@ class Llama:
                     # not sure how to handle this branch when dealing
                     # with CJK output, so keep it unchanged
                     for token in remaining_tokens:
+                        if token == self.token_bos():
+                            continue
                         token_end_position += len(self.detokenize([token]))
                         # Check if stop sequence is in the token
                         if token_end_position > (
@@ -1582,6 +1586,8 @@ class Llama:
 
                 logprobs_or_none: Optional[CompletionLogprobs] = None
                 if logprobs is not None:
+                    if token == self.token_bos():
+                        continue
                     token_str = self.detokenize([token]).decode(
                         "utf-8", errors="ignore"
                     )
@@ -1709,6 +1715,8 @@ class Llama:
             for token, token_str, logprobs_token in zip(
                 all_tokens, all_token_strs, all_logprobs
             ):
+                if token == self.token_bos():
+                    continue
                 text_offsets.append(text_offset)
                 text_offset += len(token_str)
                 tokens.append(token_str)