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vllm.reasoning.poolside_v1_reasoning_parser

Laguna reasoning parser.

DeepSeekV3ReasoningParser.is_reasoning_end walks the entire token sequence backwards and returns True on the first </think> it sees. When called on prompt_token_ids that mistakes any stray </think> in conversation history, few-shot examples or tool descriptions for a template-injected "thinking already ended" marker. In the streaming path (see vllm/entrypoints/openai/chat_completion/serving.py, prompt_is_reasoning_end_arr) that false positive short-circuits the reasoning parser for the whole response, so any <think>...</think> the model emits itself ends up in the content field instead of the reasoning field.

As we have more flexible templates, we instead scope the backward search to the current assistant turn: the walk terminates as soon as we hit the <assistant> start-of-message token. A </think> in a prior user turn or few-shot example is no longer visible.

Classes:

PoolsideV1ReasoningParser

Bases: DeepSeekV3ReasoningParser

Drop-in replacement for deepseek_v3 that tolerates </think> tokens appearing anywhere in the prompt other than the generation prefix.

Source code in vllm/reasoning/poolside_v1_reasoning_parser.py 
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class PoolsideV1ReasoningParser(DeepSeekV3ReasoningParser):
    """Drop-in replacement for ``deepseek_v3`` that tolerates ``</think>``
    tokens appearing anywhere in the prompt other than the generation prefix.
    """

    _start_of_assistant_message = "<assistant>"

    def __init__(self, tokenizer: PreTrainedTokenizerBase, *args, **kwargs):
        super().__init__(tokenizer, *args, **kwargs)

        if self._start_of_assistant_message not in self.vocab:
            raise ValueError(
                f"Tokenizer must contain {self._start_of_assistant_message!r} token"
            )
        self._start_of_assistant_message_token_id = self.vocab[
            self._start_of_assistant_message
        ]

    def is_reasoning_end(self, input_ids: Sequence[int]) -> bool:
        # IdentityReasoningParser always returns True: no reasoning to parse.
        if isinstance(self._parser, IdentityReasoningParser):
            return True

        assert isinstance(self._parser, DeepSeekR1ReasoningParser)
        for tok_id in reversed(input_ids):
            # <think>: reasoning is not yet ended.
            if tok_id == self._parser.start_token_id:
                return False
            # </think>: reasoning has ended.
            if tok_id == self._parser.end_token_id:
                return True
            # <assistant>: reached the start of the current assistant turn
            # without seeing either marker. Anything further back belongs to
            # the prior conversation and should be ignored.
            if tok_id == self._start_of_assistant_message_token_id:
                return False
        return False