vLLM/vllm/tool_parsers/gemma4_engine_tool_parser.py

# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project

from openai.types.responses import ToolChoiceCustom, ToolChoiceFunction

from vllm.entrypoints.openai.chat_completion.protocol import (
    ChatCompletionNamedToolChoiceParam,
    ChatCompletionRequest,
)
from vllm.entrypoints.openai.responses.protocol import ResponsesRequest
from vllm.parser.engine.registered_adapters import Gemma4ParserToolAdapter


class Gemma4EngineToolParser(Gemma4ParserToolAdapter):  # type: ignore[valid-type, misc]
    supports_required_and_named = False

    def adjust_request(
        self, request: ChatCompletionRequest | ResponsesRequest
    ) -> ChatCompletionRequest | ResponsesRequest:
        """Skip structured-output JSON for required/named tool choice.

        Gemma4 emits its native ``<|tool_call>call:...`` syntax, which the
        parser extracts directly. The base ``ToolParser.adjust_request`` would
        set ``structured_outputs`` for required/named and force JSON via guided
        decoding, conflicting with that native syntax (it leaks as content and
        crashes EngineCore under speculative decoding). Skip it so the model
        emits its native format (mirrors the GLM4 parser).
        """
        if request.tools:
            tc = request.tool_choice
            if tc == "required" or isinstance(
                tc,
                (
                    ChatCompletionNamedToolChoiceParam,
                    ToolChoiceFunction,
                    ToolChoiceCustom,
                ),
            ):
                request.skip_special_tokens = False
                return request
        return super().adjust_request(request)