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[Bugfix] Fix missing first token in tool calls during reasoning-to-tool transition #30671

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Merged
chaunceyjiang merged 1 commit into from
Dec 15, 2025
+28 −32
Merged

[Bugfix] Fix missing first token in tool calls during reasoning-to-tool transition #30671

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60 changes: 28 additions & 32 deletions vllm/entrypoints/openai/serving_chat.py
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Original file line number Diff line number Diff line change
Expand Up @@ -964,21 +964,9 @@ async def chat_completion_stream_generator(
assert reasoning_end_arr is not None
output_token_ids = as_list(output.token_ids)
if not reasoning_end_arr[i]:
delta_message = (
reasoning_parser.extract_reasoning_streaming(
previous_text,
current_text,
delta_text,
previous_token_ids,
current_token_ids,
output_token_ids,
)
)
# When encountering think end id in prompt_token_ids
# i.e {"enable_thinking": False},
# set reasoning status to end.
# Remove the text and token ids related
# to 'reasoning'.
if (
res.prompt_token_ids
and reasoning_parser.is_reasoning_end(
Expand All @@ -987,30 +975,38 @@ async def chat_completion_stream_generator(
):
reasoning_end_arr[i] = True
current_token_ids = output_token_ids
if delta_message and delta_message.content:
current_text = delta_message.content
delta_message.content = None
else:
current_text = ""
# When encountering think end id in delta_token_ids,
# set reasoning status to end.
# Remove the text and token ids related
# to 'reasoning'.
if reasoning_parser.is_reasoning_end(output_token_ids):
reasoning_end_arr[i] = True
current_token_ids = (
reasoning_parser.extract_content_ids(
output_token_ids
# Don't update current_text, keep it as is from delta
else:
delta_message = (
reasoning_parser.extract_reasoning_streaming(
previous_text,
current_text,
delta_text,
previous_token_ids,
current_token_ids,
output_token_ids,
)
)
if delta_message and delta_message.content:
current_text = delta_message.content
delta_message.content = None
else:
current_text = ""

# When encountering think end id in delta_token_ids,
# set reasoning status to end.
# Remove the text and token ids related
# to 'reasoning'.
if reasoning_parser.is_reasoning_end(output_token_ids):
reasoning_end_arr[i] = True
current_token_ids = (
reasoning_parser.extract_content_ids(
output_token_ids
)
)
if delta_message and delta_message.content:
current_text = delta_message.content
delta_message.content = None
else:
current_text = ""

# handle tool calls only after reasoning is done,
else:
if reasoning_end_arr[i]:
delta_token_ids = output_token_ids
# First time to tool call,
# add the remaining text and token ids
Expand Down