sgl-project/sglang · error · ValueError

Cosmos3 action generation requires --domain-id or --domain-n

Error message

Cosmos3 action generation requires --domain-id or --domain-name.

What it means

Action generation needs an embodiment domain to embed actions correctly. If neither sampling_params.domain_id nor domain_name is provided, _resolve_domain_id raises immediately when action_mode is active.

Source

Thrown at python/sglang/multimodal_gen/runtime/pipelines_core/stages/model_specific_stages/cosmos3.py:646

    @staticmethod
    def _resolve_domain_id(batch: Req) -> int:
        """Resolve action embodiment domain ID; required for action generation."""
        domain_id = getattr(batch.sampling_params, "domain_id", None)
        if domain_id is not None:
            domain_id = int(domain_id)
            if domain_id < 0:
                raise ValueError(f"domain_id must be non-negative, got {domain_id}")
            return domain_id
        domain_name = getattr(batch.sampling_params, "domain_name", None)
        if domain_name:
            key = str(domain_name).strip().lower()
            if key not in EMBODIMENT_TO_DOMAIN_ID:
                raise ValueError(
                    f"Unknown action domain name {domain_name!r}. "
                    f"Valid names: {sorted(EMBODIMENT_TO_DOMAIN_ID)}"
                )
            return EMBODIMENT_TO_DOMAIN_ID[key]
        raise ValueError(
            "Cosmos3 action generation requires --domain-id or --domain-name."
        )

    def _prepare_action_latents(
        self,
        batch: Req,
        generator,
        device: torch.device,
        dtype: torch.dtype,
    ) -> None:
        """Prepare action latents and conditioning, writing them onto ``batch``.

        Action tokens run at frame rate (no temporal compression), so the chunk
        length is ``num_frames - 1`` with ``start_frame_offset=1`` so each action
        aligns with the frame it drives.

        Three modes:
        - ``forward_dynamics``: the user supplies the action; all tokens are

View on GitHub (pinned to 0132848349)

Solutions

1. Set domain_id to a valid non-negative integer
2. Or set domain_name to a valid embodiment name
3. Make domain params required in your request builder when action_mode is used

Example fix

# before
sp.action_mode = 'policy'

# after
sp.action_mode = 'policy'
sp.domain_id = 0  # or sp.domain_name = 'franka_arm'

if sp.action_mode is not None:
    assert sp.domain_id is not None or sp.domain_name, 'action generation requires a domain'

def has_domain(sp) -> bool:
    return sp.domain_id is not None or bool(getattr(sp, 'domain_name', None))

When it happens

Trigger: Enabling action_mode without setting either domain_id or domain_name on sampling params; both attributes missing/None/empty.

Common situations: Copy-pasting an action example while dropping the domain flags, or CLI users forgetting --domain-id/--domain-name as the message suggests.

Understand the failure class

Background: Missing required parameter errors: what 'X is required' and 'the required X param is missing' mean, and how to fix them — this error's family across 27 libraries.

Related errors

• domain_id must be non-negative, got {domain_id}
• action_mode='forward_dynamics' requires an 'action' array (l
• Cosmos3 action generation does not support sequence parallel
• action_mode is set but the loaded Cosmos3 checkpoint has no
• Unknown action domain name {domain_name!r}. Valid names: {so

AI-assisted analysis of sgl-project/sglang@0132848349 (2026-08-28). Data as JSON: /api/errors/a1a8b6700bf22cb6. Report an issue: GitHub.