sgl-project--sglang/python/sglang/srt/entrypoints/openai/chat_encoding.py

"""Single home for the chat-encoding dispatch.

Which encoder turns chat messages into prompt tokens is a property of the
model, so the serving path and offline tools (benchmarks, evals) must resolve
it here instead of re-deriving it from model architectures themselves.
"""

from __future__ import annotations

from typing import Any, Dict, List, Optional


def resolve_chat_encoding_spec(
    *,
    hf_config: Any,
    tokenizer: Any,
    tool_call_parser: Optional[str] = None,
) -> Optional[str]:
    """Return the chat encoding spec for a model: "dsv4", "dsv32", or None.

    None means the default path (HF chat template).
    """
    if tool_call_parser == "deepseekv4":
        return "dsv4"
    if tool_call_parser == "deepseekv32":
        return "dsv32"

    architectures = hf_config.architectures
    arch = architectures[0] if architectures else ""

    if "DeepseekV4" in arch:
        return "dsv4"

    has_chat_template = tokenizer is not None and tokenizer.chat_template is not None
    if "DeepseekV3" in arch and not has_chat_template:
        return "dsv32"
    return None


def encode_simple_chat(
    *,
    tokenizer: Any,
    spec: Optional[str],
    messages: List[Dict[str, Any]],
    thinking_mode: str = "chat",
) -> List[int]:
    """Encode a plain-text chat conversation into prompt token ids.

    Minimal encode for offline tools: no tools, no multimodal content, no
    continue_final_message; the serving path keeps its full request-level
    pipeline in ``serving_chat``. Like
    ``serving_chat``, an empty system message is prepended when the
    conversation does not start with one (for the dsv4/dsv32 encoders this
    currently renders to zero tokens, but keeping the insertion explicit ties
    this helper to the serving semantics rather than to that coincidence).
    """
    if spec in ("dsv4", "dsv32"):
        if messages and messages[0]["role"] != "system":
            messages = [{"role": "system", "content": ""}] + list(messages)
        if spec == "dsv4":
            from sglang.srt.entrypoints.openai import encoding_dsv4

            real_input = encoding_dsv4.encode_messages(
                messages, thinking_mode=thinking_mode
            )
        else:
            from sglang.srt.entrypoints.openai import encoding_dsv32

            real_input = encoding_dsv32.encode_messages(
                messages, thinking_mode=thinking_mode
            )
        return tokenizer.encode(real_input)

    if getattr(tokenizer, "chat_template", None) is None:
        raise ValueError(
            "This model has no HF chat template and no custom chat encoder; "
            f"cannot encode chat messages with {getattr(tokenizer, 'name_or_path', tokenizer)!r}."
        )
    return tokenizer.apply_chat_template(
        messages, add_generation_prompt=True, tokenize=True
    )