sgl-project/sglang · error · ValueError

reasoning_effort must not be a boolean

Error message

reasoning_effort must not be a boolean

What it means

Chat completion request validator explicitly rejects booleans for reasoning_effort (bool is a subclass of int in Python, so this guard runs before enum checks).

Source

Thrown at python/sglang/srt/entrypoints/openai/protocol.py:980

        return _migrate_deprecated_dp_rank(values)

    @model_validator(mode="before")
    @classmethod
    def set_tool_choice_default(cls, values):
        if values.get("tool_choice") is None:
            if values.get("tools") is None and not _has_message_level_tools(
                values.get("messages")
            ):
                values["tool_choice"] = "none"
            else:
                values["tool_choice"] = "auto"
        return values

    @field_validator("reasoning_effort", mode="before")
    @classmethod
    def validate_reasoning_effort_type(cls, value):
        if isinstance(value, bool):
            raise ValueError("reasoning_effort must not be a boolean")
        return value

    @model_validator(mode="before")
    @classmethod
    def normalize_reasoning_inputs(cls, values: Dict):
        r = values.get("reasoning")
        thinking = None

        if r is not None and isinstance(r, dict):
            effort = r.get("effort")
            if effort is None:
                effort = r.get("reasoning_effort")
            if isinstance(effort, str) and effort in {
                "none",
                "minimal",
                "low",
                "medium",
                "high",

View on GitHub (pinned to 0132848349)

Solutions

1. Set reasoning_effort to a valid string like 'low'/'medium'/'high' or omit it.
2. Audit config templating so booleans never land in reasoning_effort.

Example fix

# before
{"reasoning_effort": true}
# after
{"reasoning_effort": "high"}

if reasoning_effort is not None:
    assert not isinstance(reasoning_effort,bool) and isinstance(reasoning_effort,str)

def valid_effort(v): return v is None or (isinstance(v,str) and not isinstance(v,bool))

When it happens

Trigger: reasoning_effort=true/false or True/False in the request JSON.

Common situations: Config templating that substitutes booleans; YAML/JSON configs where effort level was toggled to a bool; dynamic kwargs passing unchecked flags.

Related errors

• 'role' must be a string
• Inkling reasoning_effort must be a number
• spt must be a bool when provided
• Unknown type: {type(other)}
• Invalid value: {other}

AI-assisted analysis of sgl-project/sglang@0132848349 (2026-08-28). Data as JSON: /api/errors/7f5ca2fb44bbf2ac. Report an issue: GitHub.