vllm/vllm/entrypoints/openai/chat_completion/protocol.py

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

# Adapted from
# https://github.com/lm-sys/FastChat/blob/168ccc29d3f7edc50823016105c024fe2282732a/fastchat/protocol/openai_api_protocol.py
import json
import time
from typing import Annotated, Any, ClassVar, Literal

import torch
from openai.types.chat.chat_completion_audio import (
    ChatCompletionAudio as OpenAIChatCompletionAudio,
)
from openai.types.chat.chat_completion_message import Annotation as OpenAIAnnotation
from pydantic import Field, model_validator

from vllm.config import ModelConfig
from vllm.config.utils import replace
from vllm.entrypoints.chat_utils import (
    ChatCompletionMessageParam,
    ChatTemplateContentFormatOption,
)
from vllm.entrypoints.openai.engine.protocol import (
    AnyResponseFormat,
    DeltaMessage,
    FunctionCall,
    FunctionDefinition,
    LegacyStructuralTagResponseFormat,
    OpenAIBaseModel,
    StreamOptions,
    StructuralTagResponseFormat,
    ToolCall,
    UsageInfo,
)
from vllm.exceptions import VLLMValidationError
from vllm.logger import init_logger
from vllm.logprobs import Logprob
from vllm.renderers import ChatParams, TokenizeParams, merge_kwargs
from vllm.sampling_params import (
    BeamSearchParams,
    RequestOutputKind,
    SamplingParams,
    StructuredOutputsParams,
)
from vllm.utils import random_uuid

logger = init_logger(__name__)


_LONG_INFO = torch.iinfo(torch.long)


class ChatMessage(OpenAIBaseModel):
    role: str
    content: str | None = None
    refusal: str | None = None
    annotations: OpenAIAnnotation | None = None
    audio: OpenAIChatCompletionAudio | None = None
    function_call: FunctionCall | None = None
    tool_calls: list[ToolCall] = Field(default_factory=list)

    # vLLM-specific fields that are not in OpenAI spec
    reasoning: str | None = None


class ChatCompletionLogProb(OpenAIBaseModel):
    token: str
    logprob: float = -9999.0
    bytes: list[int] | None = None


class ChatCompletionLogProbsContent(ChatCompletionLogProb):
    # Workaround: redefine fields name cache so that it's not
    # shared with the super class.
    field_names: ClassVar[set[str] | None] = None
    top_logprobs: list[ChatCompletionLogProb] = Field(default_factory=list)


class ChatCompletionLogProbs(OpenAIBaseModel):
    content: list[ChatCompletionLogProbsContent] | None = None


class ChatCompletionResponseChoice(OpenAIBaseModel):
    index: int
    message: ChatMessage
    logprobs: ChatCompletionLogProbs | None = None
    # per OpenAI spec this is the default
    finish_reason: str | None = "stop"
    # not part of the OpenAI spec but included in vLLM for legacy reasons
    stop_reason: int | str | None = None
    # not part of the OpenAI spec but is useful for tracing the tokens
    # in agent scenarios
    token_ids: list[int] | None = None


class ChatCompletionResponse(OpenAIBaseModel):
    id: str = Field(default_factory=lambda: f"chatcmpl-{random_uuid()}")
    object: Literal["chat.completion"] = "chat.completion"
    created: int = Field(default_factory=lambda: int(time.time()))
    model: str
    choices: list[ChatCompletionResponseChoice]
    service_tier: Literal["auto", "default", "flex", "scale", "priority"] | None = None
    system_fingerprint: str | None = None
    usage: UsageInfo

    # vLLM-specific fields that are not in OpenAI spec
    prompt_logprobs: list[dict[int, Logprob] | None] | None = None
    prompt_token_ids: list[int] | None = None
    kv_transfer_params: dict[str, Any] | None = Field(
        default=None, description="KVTransfer parameters."
    )


class ChatCompletionResponseStreamChoice(OpenAIBaseModel):
    index: int
    delta: DeltaMessage
    logprobs: ChatCompletionLogProbs | None = None
    finish_reason: str | None = None
    stop_reason: int | str | None = None
    # not part of the OpenAI spec but for tracing the tokens
    token_ids: list[int] | None = None


class ChatCompletionStreamResponse(OpenAIBaseModel):
    id: str = Field(default_factory=lambda: f"chatcmpl-{random_uuid()}")
    object: Literal["chat.completion.chunk"] = "chat.completion.chunk"
    created: int = Field(default_factory=lambda: int(time.time()))
    model: str
    choices: list[ChatCompletionResponseStreamChoice]
    usage: UsageInfo | None = Field(default=None)
    # not part of the OpenAI spec but for tracing the tokens
    prompt_token_ids: list[int] | None = None


class ChatCompletionToolsParam(OpenAIBaseModel):
    type: Literal["function"] = "function"
    function: FunctionDefinition


class ChatCompletionNamedFunction(OpenAIBaseModel):
    name: str


class ChatCompletionNamedToolChoiceParam(OpenAIBaseModel):
    function: ChatCompletionNamedFunction
    type: Literal["function"] = "function"


class ChatCompletionRequest(OpenAIBaseModel):
    # Ordered by official OpenAI API documentation
    # https://platform.openai.com/docs/api-reference/chat/create
    messages: list[ChatCompletionMessageParam]
    model: str | None = None
    frequency_penalty: float | None = 0.0
    logit_bias: dict[str, float] | None = None
    logprobs: bool | None = False
    top_logprobs: int | None = 0
    max_tokens: int | None = Field(
        default=None,
        deprecated="max_tokens is deprecated in favor of "
        "the max_completion_tokens field",
    )
    max_completion_tokens: int | None = None
    n: int | None = 1
    presence_penalty: float | None = 0.0
    response_format: AnyResponseFormat | None = None
    seed: int | None = Field(None, ge=_LONG_INFO.min, le=_LONG_INFO.max)
    stop: str | list[str] | None = []
    stream: bool | None = False
    stream_options: StreamOptions | None = None
    temperature: float | None = None
    top_p: float | None = None
    tools: list[ChatCompletionToolsParam] | None = None
    tool_choice: (
        Literal["none"]
        | Literal["auto"]
        | Literal["required"]
        | ChatCompletionNamedToolChoiceParam
        | None
    ) = "none"
    reasoning_effort: Literal["low", "medium", "high"] | None = None
    include_reasoning: bool = True
    parallel_tool_calls: bool | None = True

    # NOTE this will be ignored by vLLM
    user: str | None = None

    # --8<-- [start:chat-completion-sampling-params]
    use_beam_search: bool = False
    top_k: int | None = None
    min_p: float | None = None
    repetition_penalty: float | None = None
    length_penalty: float = 1.0
    stop_token_ids: list[int] | None = []
    include_stop_str_in_output: bool = False
    ignore_eos: bool = False
    min_tokens: int = 0
    skip_special_tokens: bool = True
    spaces_between_special_tokens: bool = True
    truncate_prompt_tokens: Annotated[int, Field(ge=-1, le=_LONG_INFO.max)] | None = (
        None
    )
    prompt_logprobs: int | None = None
    allowed_token_ids: list[int] | None = None
    bad_words: list[str] = Field(default_factory=list)
    # --8<-- [end:chat-completion-sampling-params]

    # --8<-- [start:chat-completion-extra-params]
    echo: bool = Field(
        default=False,
        description=(
            "If true, the new message will be prepended with the last message "
            "if they belong to the same role."
        ),
    )
    add_generation_prompt: bool = Field(
        default=True,
        description=(
            "If true, the generation prompt will be added to the chat template. "
            "This is a parameter used by chat template in tokenizer config of the "
            "model."
        ),
    )
    continue_final_message: bool = Field(
        default=False,
        description=(
            "If this is set, the chat will be formatted so that the final "
            "message in the chat is open-ended, without any EOS tokens. The "
            "model will continue this message rather than starting a new one. "
            'This allows you to "prefill" part of the model\'s response for it. '
            "Cannot be used at the same time as `add_generation_prompt`."
        ),
    )
    add_special_tokens: bool = Field(
        default=False,
        description=(
            "If true, special tokens (e.g. BOS) will be added to the prompt "
            "on top of what is added by the chat template. "
            "For most models, the chat template takes care of adding the "
            "special tokens so this should be set to false (as is the "
            "default)."
        ),
    )
    documents: list[dict[str, str]] | None = Field(
        default=None,
        description=(
            "A list of dicts representing documents that will be accessible to "
            "the model if it is performing RAG (retrieval-augmented generation)."
            " If the template does not support RAG, this argument will have no "
            "effect. We recommend that each document should be a dict containing "
            '"title" and "text" keys.'
        ),
    )
    chat_template: str | None = Field(
        default=None,
        description=(
            "A Jinja template to use for this conversion. "
            "As of transformers v4.44, default chat template is no longer "
            "allowed, so you must provide a chat template if the tokenizer "
            "does not define one."
        ),
    )
    chat_template_kwargs: dict[str, Any] | None = Field(
        default=None,
        description=(
            "Additional keyword args to pass to the template renderer. "
            "Will be accessible by the chat template."
        ),
    )
    mm_processor_kwargs: dict[str, Any] | None = Field(
        default=None,
        description=("Additional kwargs to pass to the HF processor."),
    )
    structured_outputs: StructuredOutputsParams | None = Field(
        default=None,
        description="Additional kwargs for structured outputs",
    )
    priority: int = Field(
        default=0,
        description=(
            "The priority of the request (lower means earlier handling; "
            "default: 0). Any priority other than 0 will raise an error "
            "if the served model does not use priority scheduling."
        ),
    )
    request_id: str = Field(
        default_factory=random_uuid,
        description=(
            "The request_id related to this request. If the caller does "
            "not set it, a random_uuid will be generated. This id is used "
            "through out the inference process and return in response."
        ),
    )

    return_tokens_as_token_ids: bool | None = Field(
        default=None,
        description=(
            "If specified with 'logprobs', tokens are represented "
            " as strings of the form 'token_id:{token_id}' so that tokens "
            "that are not JSON-encodable can be identified."
        ),
    )
    return_token_ids: bool | None = Field(
        default=None,
        description=(
            "If specified, the result will include token IDs alongside the "
            "generated text. In streaming mode, prompt_token_ids is included "
            "only in the first chunk, and token_ids contains the delta tokens "
            "for each chunk. This is useful for debugging or when you "
            "need to map generated text back to input tokens."
        ),
    )

    cache_salt: str | None = Field(
        default=None,
        description=(
            "If specified, the prefix cache will be salted with the provided "
            "string to prevent an attacker to guess prompts in multi-user "
            "environments. The salt should be random, protected from "
            "access by 3rd parties, and long enough to be "
            "unpredictable (e.g., 43 characters base64-encoded, corresponding "
            "to 256 bit)."
        ),
    )

    kv_transfer_params: dict[str, Any] | None = Field(
        default=None,
        description="KVTransfer parameters used for disaggregated serving.",
    )

    vllm_xargs: dict[str, str | int | float | list[str | int | float]] | None = Field(
        default=None,
        description=(
            "Additional request parameters with (list of) string or "
            "numeric values, used by custom extensions."
        ),
    )

    # --8<-- [end:chat-completion-extra-params]

    def build_chat_params(
        self,
        default_template: str | None,
        default_template_content_format: ChatTemplateContentFormatOption,
    ) -> ChatParams:
        return ChatParams(
            chat_template=self.chat_template or default_template,
            chat_template_content_format=default_template_content_format,
            chat_template_kwargs=merge_kwargs(
                self.chat_template_kwargs,
                dict(
                    add_generation_prompt=self.add_generation_prompt,
                    continue_final_message=self.continue_final_message,
                    documents=self.documents,
                    reasoning_effort=self.reasoning_effort,
                ),
            ),
        )

    def build_tok_params(self, model_config: ModelConfig) -> TokenizeParams:
        if self.max_completion_tokens is not None:
            max_output_tokens: int | None = self.max_completion_tokens
            max_output_tokens_param = "max_completion_tokens"
        else:
            max_output_tokens = self.max_tokens
            max_output_tokens_param = "max_tokens"

        return TokenizeParams(
            max_total_tokens=model_config.max_model_len,
            max_output_tokens=max_output_tokens or 0,
            truncate_prompt_tokens=self.truncate_prompt_tokens,
            add_special_tokens=self.add_special_tokens,
            needs_detokenization=bool(self.echo and not self.return_token_ids),
            max_total_tokens_param="max_model_len",
            max_output_tokens_param=max_output_tokens_param,
        )

    # Default sampling parameters for chat completion requests
    _DEFAULT_SAMPLING_PARAMS: dict = {
        "repetition_penalty": 1.0,
        "temperature": 1.0,
        "top_p": 1.0,
        "top_k": 0,
        "min_p": 0.0,
    }

    def to_beam_search_params(
        self, max_tokens: int, default_sampling_params: dict
    ) -> BeamSearchParams:
        n = self.n if self.n is not None else 1
        if (temperature := self.temperature) is None:
            temperature = default_sampling_params.get(
                "temperature", self._DEFAULT_SAMPLING_PARAMS["temperature"]
            )

        return BeamSearchParams(
            beam_width=n,
            max_tokens=max_tokens,
            ignore_eos=self.ignore_eos,
            temperature=temperature,
            length_penalty=self.length_penalty,
            include_stop_str_in_output=self.include_stop_str_in_output,
        )

    def to_sampling_params(
        self,
        max_tokens: int,
        default_sampling_params: dict,
    ) -> SamplingParams:
        # Default parameters
        if (repetition_penalty := self.repetition_penalty) is None:
            repetition_penalty = default_sampling_params.get(
                "repetition_penalty",
                self._DEFAULT_SAMPLING_PARAMS["repetition_penalty"],
            )
        if (temperature := self.temperature) is None:
            temperature = default_sampling_params.get(
                "temperature", self._DEFAULT_SAMPLING_PARAMS["temperature"]
            )
        if (top_p := self.top_p) is None:
            top_p = default_sampling_params.get(
                "top_p", self._DEFAULT_SAMPLING_PARAMS["top_p"]
            )
        if (top_k := self.top_k) is None:
            top_k = default_sampling_params.get(
                "top_k", self._DEFAULT_SAMPLING_PARAMS["top_k"]
            )
        if (min_p := self.min_p) is None:
            min_p = default_sampling_params.get(
                "min_p", self._DEFAULT_SAMPLING_PARAMS["min_p"]
            )

        prompt_logprobs = self.prompt_logprobs
        if prompt_logprobs is None and self.echo:
            prompt_logprobs = self.top_logprobs

        response_format = self.response_format
        if response_format is not None:
            structured_outputs_kwargs = dict[str, Any]()

            # Set structured output params for response format
            if response_format.type == "json_object":
                structured_outputs_kwargs["json_object"] = True
            elif response_format.type == "json_schema":
                json_schema = response_format.json_schema
                assert json_schema is not None
                structured_outputs_kwargs["json"] = json_schema.json_schema
            elif response_format.type == "structural_tag":
                structural_tag = response_format
                assert structural_tag is not None and isinstance(
                    structural_tag,
                    (
                        LegacyStructuralTagResponseFormat,
                        StructuralTagResponseFormat,
                    ),
                )
                s_tag_obj = structural_tag.model_dump(by_alias=True)
                structured_outputs_kwargs["structural_tag"] = json.dumps(s_tag_obj)

            # If structured outputs wasn't already enabled,
            # we must enable it for these features to work
            if len(structured_outputs_kwargs) > 0:
                self.structured_outputs = (
                    StructuredOutputsParams(**structured_outputs_kwargs)
                    if self.structured_outputs is None
                    else replace(self.structured_outputs, **structured_outputs_kwargs)
                )

        extra_args: dict[str, Any] = self.vllm_xargs if self.vllm_xargs else {}
        if self.kv_transfer_params:
            # Pass in kv_transfer_params via extra_args
            extra_args["kv_transfer_params"] = self.kv_transfer_params
        return SamplingParams.from_optional(
            n=self.n,
            presence_penalty=self.presence_penalty,
            frequency_penalty=self.frequency_penalty,
            repetition_penalty=repetition_penalty,
            temperature=temperature,
            top_p=top_p,
            top_k=top_k,
            min_p=min_p,
            seed=self.seed,
            stop=self.stop,
            stop_token_ids=self.stop_token_ids,
            logprobs=self.top_logprobs if self.logprobs else None,
            prompt_logprobs=prompt_logprobs,
            ignore_eos=self.ignore_eos,
            max_tokens=max_tokens,
            min_tokens=self.min_tokens,
            skip_special_tokens=self.skip_special_tokens,
            spaces_between_special_tokens=self.spaces_between_special_tokens,
            include_stop_str_in_output=self.include_stop_str_in_output,
            truncate_prompt_tokens=self.truncate_prompt_tokens,
            output_kind=RequestOutputKind.DELTA
            if self.stream
            else RequestOutputKind.FINAL_ONLY,
            structured_outputs=self.structured_outputs,
            logit_bias=self.logit_bias,
            bad_words=self.bad_words,
            allowed_token_ids=self.allowed_token_ids,
            extra_args=extra_args or None,
            skip_clone=True,  # Created fresh per request, safe to skip clone
        )

    @model_validator(mode="before")
    @classmethod
    def validate_stream_options(cls, data):
        if data.get("stream_options") and not data.get("stream"):
            raise VLLMValidationError(
                "Stream options can only be defined when `stream=True`.",
                parameter="stream_options",
            )

        return data

    @model_validator(mode="before")
    @classmethod
    def check_logprobs(cls, data):
        if (prompt_logprobs := data.get("prompt_logprobs")) is not None:
            if data.get("stream") and (prompt_logprobs > 0 or prompt_logprobs == -1):
                raise VLLMValidationError(
                    "`prompt_logprobs` are not available when `stream=True`.",
                    parameter="prompt_logprobs",
                )

            if prompt_logprobs < 0 and prompt_logprobs != -1:
                raise VLLMValidationError(
                    "`prompt_logprobs` must be a positive value or -1.",
                    parameter="prompt_logprobs",
                    value=prompt_logprobs,
                )
        if (top_logprobs := data.get("top_logprobs")) is not None:
            if top_logprobs < 0 and top_logprobs != -1:
                raise VLLMValidationError(
                    "`top_logprobs` must be a positive value or -1.",
                    parameter="top_logprobs",
                    value=top_logprobs,
                )

            if (top_logprobs == -1 or top_logprobs > 0) and not data.get("logprobs"):
                raise VLLMValidationError(
                    "when using `top_logprobs`, `logprobs` must be set to true.",
                    parameter="top_logprobs",
                )

        return data

    @model_validator(mode="before")
    @classmethod
    def check_structured_outputs_count(cls, data):
        if isinstance(data, ValueError):
            raise data

        if data.get("structured_outputs", None) is None:
            return data

        structured_outputs_kwargs = data["structured_outputs"]
        count = sum(
            structured_outputs_kwargs.get(k) is not None
            for k in ("json", "regex", "choice")
        )
        # you can only use one kind of constraints for structured outputs
        if count > 1:
            raise ValueError(
                "You can only use one kind of constraints for structured "
                "outputs ('json', 'regex' or 'choice')."
            )
        # you can only either use structured outputs or tools, not both
        if count > 1 and data.get("tool_choice", "none") not in (
            "none",
            "auto",
            "required",
        ):
            raise ValueError(
                "You can only either use constraints for structured outputs "
                "or tools, not both."
            )
        return data

    @model_validator(mode="before")
    @classmethod
    def check_tool_usage(cls, data):
        # if "tool_choice" is not specified but tools are provided,
        # default to "auto" tool_choice
        if "tool_choice" not in data and data.get("tools"):
            data["tool_choice"] = "auto"

        # if "tool_choice" is "none" -- no validation is needed for tools
        if "tool_choice" in data and data["tool_choice"] == "none":
            return data

        # if "tool_choice" is specified -- validation
        if "tool_choice" in data and data["tool_choice"] is not None:
            # ensure that if "tool choice" is specified, tools are present
            if "tools" not in data or data["tools"] is None:
                raise ValueError("When using `tool_choice`, `tools` must be set.")

            # make sure that tool choice is either a named tool
            # OR that it's set to "auto" or "required"
            if data["tool_choice"] not in ["auto", "required"] and not isinstance(
                data["tool_choice"], dict
            ):
                raise ValueError(
                    f"Invalid value for `tool_choice`: {data['tool_choice']}! "
                    'Only named tools, "none", "auto" or "required" '
                    "are supported."
                )

            # if tool_choice is "required" but the "tools" list is empty,
            # override the data to behave like "none" to align with
            # OpenAI’s behavior.
            if (
                data["tool_choice"] == "required"
                and isinstance(data["tools"], list)
                and len(data["tools"]) == 0
            ):
                data["tool_choice"] = "none"
                del data["tools"]
                return data

            # ensure that if "tool_choice" is specified as an object,
            # it matches a valid tool
            correct_usage_message = (
                'Correct usage: `{"type": "function",'
                ' "function": {"name": "my_function"}}`'
            )
            if isinstance(data["tool_choice"], dict):
                valid_tool = False
                function = data["tool_choice"].get("function")
                if not isinstance(function, dict):
                    raise ValueError(
                        f"Invalid value for `function`: `{function}` in "
                        f"`tool_choice`! {correct_usage_message}"
                    )
                if "name" not in function:
                    raise ValueError(
                        f"Expected field `name` in `function` in "
                        f"`tool_choice`! {correct_usage_message}"
                    )
                function_name = function["name"]
                if not isinstance(function_name, str) or len(function_name) == 0:
                    raise ValueError(
                        f"Invalid `name` in `function`: `{function_name}`"
                        f" in `tool_choice`! {correct_usage_message}"
                    )
                for tool in data["tools"]:
                    if tool["function"]["name"] == function_name:
                        valid_tool = True
                        break
                if not valid_tool:
                    raise ValueError(
                        "The tool specified in `tool_choice` does not match any"
                        " of the specified `tools`"
                    )
        return data

    @model_validator(mode="before")
    @classmethod
    def check_generation_prompt(cls, data):
        if data.get("continue_final_message") and data.get("add_generation_prompt"):
            raise ValueError(
                "Cannot set both `continue_final_message` and "
                "`add_generation_prompt` to True."
            )
        return data

    @model_validator(mode="before")
    @classmethod
    def check_cache_salt_support(cls, data):
        if data.get("cache_salt") is not None and (
            not isinstance(data["cache_salt"], str) or not data["cache_salt"]
        ):
            raise ValueError(
                "Parameter 'cache_salt' must be a non-empty string if provided."
            )
        return data

    @model_validator(mode="before")
    @classmethod
    def check_system_message_content_type(cls, data):
        """Warn if system messages contain non-text content.

        According to OpenAI API spec, system messages can only be of type
        'text'. We log a warning instead of rejecting to avoid breaking
        users who intentionally send multimodal system messages.
        See: https://platform.openai.com/docs/api-reference/chat/create#chat_create-messages-system_message
        """
        if not isinstance(data, dict):
            return data
        messages = data.get("messages", [])
        for msg in messages:
            # Check if this is a system message
            if isinstance(msg, dict) and msg.get("role") == "system":
                content = msg.get("content")

                # If content is a list (multimodal format)
                if isinstance(content, list):
                    for part in content:
                        if isinstance(part, dict):
                            part_type = part.get("type")
                            # Infer type when 'type' field is not explicit
                            if part_type is None:
                                if "image_url" in part or "image_pil" in part:
                                    part_type = "image_url"
                                elif "image_embeds" in part:
                                    part_type = "image_embeds"
                                elif "audio_url" in part:
                                    part_type = "audio_url"
                                elif "input_audio" in part:
                                    part_type = "input_audio"
                                elif "audio_embeds" in part:
                                    part_type = "audio_embeds"
                                elif "video_url" in part:
                                    part_type = "video_url"

                            # Warn about non-text content in system messages
                            if part_type and part_type != "text":
                                logger.warning_once(
                                    "System messages should only contain text "
                                    "content according to the OpenAI API spec. "
                                    "Found content type: '%s'.",
                                    part_type,
                                )

        return data