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[IMPROVEMENT] Change MistralReasoningParser behavior (#30391)

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Signed-off-by: juliendenize <julien.denize@mistral.ai>
Signed-off-by: Julien Denize <40604584+juliendenize@users.noreply.github.com>
Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>
This commit is contained in:
Julien Denize 2025-12-11 17:53:26 +01:00 committed by GitHub
parent 305b168a9f
commit aa3c250c48
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GPG Key ID: B5690EEEBB952194
2 changed files with 192 additions and 70 deletions
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157
tests/reasoning/test_mistral_reasoning_parser.py
View File

@ -18,47 +18,53 @@ def mistral_tokenizer():
return mistral_tokenizer
SIMPLE_REASONING = {
INVALID_SIMPLE_REASONING = {
"output": "This is a reasoning section[/THINK]This is the rest",
"reasoning": "This is a reasoning section",
"content": "This is the rest",
"is_reasoning_end": True,
"reasoning": None,
"content": "This is a reasoning sectionThis is the rest",
"is_reasoning_end": False,
}
COMPLETE_REASONING = {
INVALID_COMPLETE_REASONING = {
"output": "This is a reasoning section[/THINK]",
"reasoning": "This is a reasoning section",
"content": None,
"is_reasoning_end": True,
"reasoning": None,
"content": "This is a reasoning section",
"is_reasoning_end": False,
}
NO_CONTENT = {
"output": "This is content",
"reasoning": "This is content",
"output": "[THINK]This is reasoning",
"reasoning": "This is reasoning",
"content": None,
"is_reasoning_end": False,
}
NO_REASONING = {
"output": "This is content",
"reasoning": None,
"content": "This is content",
"is_reasoning_end": False,
}
NO_REASONING_STREAMING = {
"output": "This is a reasoning section",
"reasoning": "This is a reasoning section",
"content": None,
"reasoning": None,
"content": "This is a reasoning section",
"is_reasoning_end": False,
}
MULTIPLE_LINES = {
INVALID_MULTIPLE_LINES = {
"output": "This\nThat[/THINK]This is the rest\nThat",
"reasoning": "This\nThat",
"content": "This is the rest\nThat",
"is_reasoning_end": True,
"reasoning": None,
"content": "This\nThatThis is the rest\nThat",
"is_reasoning_end": False,
}
SHORTEST_REASONING_NO_STREAMING = {
"output": "[/THINK]This is the rest",
"reasoning": "",
"content": "This is the rest",
"is_reasoning_end": True,
}
SHORTEST_REASONING = {
INVALID_SHORTEST_REASONING_NO_STREAMING = {
"output": "[/THINK]This is the rest",
"reasoning": None,
"content": "This is the rest",
"is_reasoning_end": True,
"is_reasoning_end": False,
}
INVALID_SHORTEST_REASONING = {
"output": "[/THINK]This is the rest",
"reasoning": None,
"content": "This is the rest",
"is_reasoning_end": False,
}
REASONING_WITH_THINK = {
"output": "[THINK]This is a reasoning section[/THINK]This is the rest",
@ -78,17 +84,17 @@ MULTIPLE_LINES_WITH_THINK = {
"content": "This is the rest\nThat",
"is_reasoning_end": True,
}
SHORTEST_REASONING_NO_STREAMING_WITH_THINK = {
"output": "[/THINK]This is the rest",
"reasoning": "",
"content": "This is the rest",
"is_reasoning_end": True,
}
SHORTEST_REASONING_WITH_THINK = {
INVALID_SHORTEST_REASONING_NO_STREAMING_WITH_THINK = {
"output": "[/THINK]This is the rest",
"reasoning": None,
"content": "This is the rest",
"is_reasoning_end": True,
"is_reasoning_end": False,
}
INVALID_SHORTEST_REASONING_WITH_THINK = {
"output": "[/THINK]This is the rest",
"reasoning": None,
"content": "This is the rest",
"is_reasoning_end": False,
}
THINK_NO_END = {
"output": "[THINK]This is a reasoning section",
@ -98,8 +104,8 @@ THINK_NO_END = {
}
EMPTY = {
"output": "",
"reasoning": "",
"content": None,
"reasoning": None,
"content": "",
"is_reasoning_end": False,
}
EMPTY_STREAMING = {
@ -109,47 +115,48 @@ EMPTY_STREAMING = {
"is_reasoning_end": False,
}
NEW_LINE = {
"output": "\n[THINK]This is a reasoning section[/THINK]\nThis is the rest",
"output": "Before\n[THINK]This is a reasoning section[/THINK]\nThis is the rest",
"reasoning": "This is a reasoning section",
"content": "\nThis is the rest",
"content": "Before\n\nThis is the rest",
"is_reasoning_end": True,
}
# Streaming cannot handle new lines at the beginning of the output
# because we need to support [THINK]...[/THINK] and [/THINK]...
# We cannot know if the text before [THINK] is reasoning content
# or not.
NEW_LINE_STREAMING = {
"output": "\n[THINK]This is a reasoning section[/THINK]\nThis is the rest",
"reasoning": "\nThis is a reasoning section",
"content": "\nThis is the rest",
"output": "Before\n[THINK]This is a reasoning section[/THINK]\nThis is the rest",
"reasoning": "This is a reasoning section",
"content": "Before\n\nThis is the rest",
"is_reasoning_end": True,
}
TEST_CASES = [
pytest.param(
False,
SIMPLE_REASONING,
id="simple_reasoning",
INVALID_SIMPLE_REASONING,
id="invalid_simple_reasoning",
),
pytest.param(
True,
SIMPLE_REASONING,
id="simple_reasoning_streaming",
INVALID_SIMPLE_REASONING,
id="invalid_simple_reasoning_streaming",
),
pytest.param(
False,
COMPLETE_REASONING,
id="complete_reasoning",
INVALID_COMPLETE_REASONING,
id="invalid_complete_reasoning",
),
pytest.param(
True,
COMPLETE_REASONING,
id="complete_reasoning_streaming",
INVALID_COMPLETE_REASONING,
id="invalid_complete_reasoning_streaming",
),
pytest.param(
False,
NO_CONTENT,
id="no_content_token",
id="no_content",
),
pytest.param(
False,
NO_REASONING,
id="no_reasoning",
),
pytest.param(
True,
@ -158,23 +165,23 @@ TEST_CASES = [
),
pytest.param(
False,
MULTIPLE_LINES,
id="multiple_lines",
INVALID_MULTIPLE_LINES,
id="invalid_multiple_lines",
),
pytest.param(
True,
MULTIPLE_LINES,
id="multiple_lines_streaming",
INVALID_MULTIPLE_LINES,
id="invalid_multiple_lines_streaming",
),
pytest.param(
True,
SHORTEST_REASONING,
id="shortest",
INVALID_SHORTEST_REASONING,
id="invalid_shortest",
),
pytest.param(
False,
SHORTEST_REASONING_NO_STREAMING,
id="shortest_streaming",
INVALID_SHORTEST_REASONING_NO_STREAMING,
id="invalid_shortest_streaming",
),
pytest.param(
False,
@ -208,13 +215,13 @@ TEST_CASES = [
),
pytest.param(
False,
SHORTEST_REASONING_NO_STREAMING_WITH_THINK,
id="shortest_with_think",
INVALID_SHORTEST_REASONING_NO_STREAMING_WITH_THINK,
id="invalid_shortest_with_think",
),
pytest.param(
True,
SHORTEST_REASONING_WITH_THINK,
id="shortest_with_think_streaming",
INVALID_SHORTEST_REASONING_WITH_THINK,
id="invalid_shortest_with_think_streaming",
),
pytest.param(
False,
@ -316,10 +323,26 @@ def test_mistral_reasoning(
# Test extract_content
if param_dict["content"] is not None:
content = parser.extract_content_ids(output_tokens)
assert content == mistral_tokenizer.tokenizer.encode(
param_dict["content"], bos=False, eos=False
# Handle the case where there are tokens outputted before Thinking.
# This should not occur if the model is well trained and prompted.
if "[THINK]" in param_dict["output"] and not param_dict["output"].startswith(
"[THINK]"
):
before_content = param_dict["output"].split("[THINK]")[0]
before_token_ids = mistral_tokenizer.tokenizer.encode(
before_content, bos=False, eos=False
)
left_to_encode = param_dict["content"][len(before_content) :]
# Normal situation.
else:
before_token_ids = []
left_to_encode = param_dict["content"]
content_tokens = parser.extract_content_ids(output_tokens)
expected_token_ids = before_token_ids + mistral_tokenizer.tokenizer.encode(
left_to_encode, bos=False, eos=False
)
assert content_tokens == expected_token_ids
else:
content = parser.extract_content_ids(output_tokens)
assert content == []

105
vllm/reasoning/mistral_reasoning_parser.py
View File

@ -3,20 +3,29 @@
from functools import cached_property
from vllm.entrypoints.openai.protocol import (
ChatCompletionRequest,
ResponsesRequest,
)
from vllm.logger import init_logger
from vllm.reasoning import ReasoningParser
from vllm.reasoning.deepseek_r1_reasoning_parser import DeepSeekR1ReasoningParser
from vllm.reasoning.basic_parsers import BaseThinkingReasoningParser
from vllm.tokenizers import MistralTokenizer
logger = init_logger(__name__)
class MistralReasoningParser(DeepSeekR1ReasoningParser):
class MistralReasoningParser(BaseThinkingReasoningParser):
"""
Reasoning parser for Mistral models.
The Mistral models uses [THINK]...[/THINK] tokens to denote reasoning
The Mistral models uses `[THINK]`...`[/THINK]` tokens to denote reasoning
text. This parser extracts the reasoning content from the model output.
A valid reasoning trace should always start with a `[THINK]` token and end with
a `[/THINK]` token.
If `[THINK]` token is not generated, then this parser only returns content.
"""
def __init__(self, tokenizer: MistralTokenizer, *args, **kwargs):
@ -53,3 +62,93 @@ class MistralReasoningParser(DeepSeekR1ReasoningParser):
from mistral_common.tokens.tokenizers.base import SpecialTokens
return SpecialTokens.end_think
def is_reasoning_end(self, input_ids: list[int]) -> bool:
has_eot_token = False
for id in input_ids[::-1]:
if id == self.start_token_id:
# Reasoning ends only if a BOT token is found before a EOT token.
return has_eot_token
elif id == self.end_token_id:
has_eot_token = True
return False
def extract_content_ids(self, input_ids: list[int]) -> list[int]:
"""
Extract the content
"""
has_bot_token = False
has_eot_token = False
bot_token_index = -1
eot_token_index = -1
# One for loop instead of multiple lookups
for i, token_id in enumerate(input_ids):
# We filter that we have multiple BOT tokens which should not
# happen for a well prompted trained model
if token_id == self.start_token_id and not has_bot_token:
has_bot_token = True
bot_token_index = i
elif token_id == self.end_token_id:
has_eot_token = True
eot_token_index = i
break
# 1. Only BOT has been outputted
if has_bot_token and not has_eot_token:
# Should be = [] if model is well prompted and trained.
return input_ids[:bot_token_index]
# 2. Neither BOT or EOT have been outputted
elif not has_bot_token and not has_eot_token:
return input_ids
# 3. Both BOT and EOT have been outputted.
elif has_bot_token and has_eot_token:
return input_ids[:bot_token_index] + input_ids[eot_token_index + 1 :]
# 4. Only EOT has been outputted => this should not have occured for a model
# well prompted and trained.
else:
return input_ids[:eot_token_index] + input_ids[eot_token_index + 1 :]
def extract_reasoning(
self, model_output: str, request: ChatCompletionRequest | ResponsesRequest
) -> tuple[str | None, str | None]:
"""
Extract reasoning content from the model output.
"""
if not model_output:
return (None, "")
# Check if the start token is present in the model output, remove it
# if it is present.
prev_bot_token, bot_token, post_bot_token = model_output.partition(
self.start_token
)
has_bot_token = bool(bot_token)
# Valid EOT tokens should follow BOT token
has_valid_eot_token = has_bot_token and self.end_token in post_bot_token
# 1. If there is BOT token followed by EOT token
if has_bot_token and has_valid_eot_token:
prev_eot_token, _, post_eot_token = post_bot_token.partition(self.end_token)
# If model is well prompted and trained prev_bot_token should be ""
content = prev_bot_token + post_eot_token
return prev_eot_token, content if content else None
# 2. Only BOT token
elif has_bot_token:
# If model is well prompted and trained prev_bot_token should be ""
return post_bot_token, prev_bot_token if prev_bot_token else None
# 3. EOT token has been outputted without BOT or neither has been outputted
else:
has_non_valid_eot_token = self.end_token in prev_bot_token
# 3.a EOT token has been outputted without BOT
# If model is well prompted and trained `has_non_valid_eot_token` should
# be `False` and the parser outputs all tokens as 'content'
if has_non_valid_eot_token:
prev_eot_token, _, post_eot_token = prev_bot_token.partition(
self.end_token
)
return None, prev_eot_token + post_eot_token
# 3.b neither BOT or EOT have been outputted
else:
return None, prev_bot_token