sgl-project/sglang · error · ValueError

rollout_sde_type must be one of {_VALID_ROLLOUT_SDE_TYPES},

Error message

rollout_sde_type must be one of {_VALID_ROLLOUT_SDE_TYPES}, got {self.rollout_sde_type!r}

What it means

rollout_sde_type selects the SDE discretization/scheme used during RL rollouts and must be one of the entries in _VALID_ROLLOUT_SDE_TYPES. Any other string (or wrong case, or typo) is rejected at validation time.

Source

Thrown at python/sglang/multimodal_gen/configs/post_training/rl_rollout.py:37

    """Rollout (log-prob trajectory) options used by SamplingParams and APIs."""

    rollout: bool = False
    rollout_sde_type: str = "sde"
    rollout_noise_level: float = 0.7
    rollout_log_prob_no_const: bool = False
    rollout_debug_mode: bool = False

    def validate(self) -> None:
        noise = self.rollout_noise_level
        if isinstance(noise, bool) or not isinstance(noise, (int, float)):
            raise ValueError(f"rollout_noise_level must be a number, got {noise!r}")
        if not math.isfinite(float(noise)):
            raise ValueError(f"rollout_noise_level must be finite, got {noise!r}")
        if float(noise) < 0.0:
            raise ValueError(f"rollout_noise_level must be non-negative, got {noise!r}")

        if self.rollout_sde_type not in _VALID_ROLLOUT_SDE_TYPES:
            raise ValueError(
                f"rollout_sde_type must be one of {_VALID_ROLLOUT_SDE_TYPES}, "
                f"got {self.rollout_sde_type!r}"
            )

    @classmethod
    def validate_sampling_params(cls, params: Any) -> None:
        """Validate rollout fields on a duck-typed object (e.g. ``SamplingParams``).

        Mirrors how ``ServerArgs`` runs ``NunchakuSVDQuantArgs.validate()`` from
        ``_adjust_quant_config`` instead of inlining checks in a large validator.
        """
        cls(
            rollout=params.rollout,
            rollout_sde_type=params.rollout_sde_type,
            rollout_noise_level=params.rollout_noise_level,
            rollout_log_prob_no_const=params.rollout_log_prob_no_const,
            rollout_debug_mode=params.rollout_debug_mode,
        ).validate()

View on GitHub (pinned to 0132848349)

Solutions

Check the allowed set in the error/config module (_VALID_ROLLOUT_SDE_TYPES) and use one of those exact strings
Fix casing/typos, e.g. the canonical spellings listed in _VALID_ROLLOUT_SDE_TYPES
After upgrading sglang, re-verify the valid SDE type list — names may have changed

Example fix

# before
params.rollout_sde_type = "Euler"  # wrong case

# after
from sglang.multimodal_gen.configs.post_training.rl_rollout import _VALID_ROLLOUT_SDE_TYPES
params.rollout_sde_type = next(iter(_VALID_ROLLOUT_SDE_TYPES))  # or a valid literal

Defensive patterns

Strategy: validation

Validate before calling

from sglang.multimodal_gen.configs.post_training.rl_rollout import _VALID_ROLLOUT_SDE_TYPES
assert params.rollout_sde_type in _VALID_ROLLOUT_SDE_TYPES, f"valid: {_VALID_ROLLOUT_SDE_TYPES}"

Type guard

def is_valid_sde_type(v, valid) -> bool:
    return v in valid

Prevention

Import the valid set and validate configs against it, not hardcoded strings
Re-check the valid set after sglang upgrades
Use exact casing from the constants module

When it happens

Trigger: Passing an unrecognized string as rollout_sde_type (e.g. 'euler', 'Euler', 'DDIM' when not in the allowed set) in sampling params; raised from validate() via validate_sampling_params.

Common situations: Typos or wrong casing; copying a scheme name from a different library (diffusers/eulerancestral) into this config; version changes that rename or remove supported SDE types.

Related errors

AI-assisted analysis of sgl-project/sglang@0132848349 (2026-08-28). Data as JSON: /api/errors/ad93a97b95fc6609. Report an issue: GitHub.