sgl-project/sglang · error · ValueError

invalid action segment {segment!r}; expected '<keys>-<frames

Error message

invalid action segment {segment!r}; expected '<keys>-<frames>'

What it means

Raised by parse_sana_wm_action_string when a comma-separated segment is empty or contains no '-' separator. Each segment must follow '<keys>-<frames>', e.g. 'ab-4'.

Source

Thrown at python/sglang/multimodal_gen/runtime/pipelines_core/stages/model_specific_stages/sana_wm/base.py:128

    if not isinstance(payload, list):
        raise ValueError(f"{error_label} must be list[list[str]]")
    out: list[list[str]] = []
    for frame_actions in payload:
        if not isinstance(frame_actions, list):
            raise ValueError(f"{error_label} must be list[list[str]]")
        out.append([str(key).lower() for key in frame_actions])
    return out


def parse_sana_wm_action_string(action: str) -> list[list[str]]:
    cleaned = "".join(action.replace("，", ",").split())
    if not cleaned:
        raise ValueError("action string is empty")

    per_frame: list[list[str]] = []
    for segment in cleaned.split(","):
        if not segment or "-" not in segment:
            raise ValueError(
                f"invalid action segment {segment!r}; expected '<keys>-<frames>'"
            )
        keys_part, duration = segment.rsplit("-", 1)
        if not duration.isdigit() or int(duration) <= 0:
            raise ValueError(f"invalid duration in action segment {segment!r}")

        if keys_part.lower() == "none":
            keys: list[str] = []
        else:
            bad = sorted(
                {
                    char
                    for char in keys_part.lower()
                    if char not in _SANA_WM_ALLOWED_ACTION_KEYS
                }
            )
            if bad:
                raise ValueError(

View on GitHub (pinned to 0132848349)

Solutions

1. Fix the segment to '<keys>-<frames>' form, e.g. 'ab-4'
2. Strip trailing/duplicate commas before parsing: ','.join(s for s in cleaned.split(',') if s)
3. Validate the format with a regex before handing to the pipeline

Example fix

// before
action = 'forward-4,,left-2,'
// after
action = 'forward-4,left-2'

import re
assert all(re.fullmatch(r'.+-.+', seg) for seg in cleaned.split(',') if seg)

def segments_wellformed(s: str) -> bool:
    return all('-' in seg and seg for seg in ''.join(s.replace('，', ',')).split(','))

When it happens

Trigger: Action strings like 'ab4' (missing dash), 'ab-4,,cd-2' (empty segment from trailing/double comma), or 'ab-' / '-4' style malformed segments (though those fail the dash check only when no '-' exists at all).

Common situations: User-typed camera action strings missing the dash; trailing commas in config; LLM-generated action strings omitting the duration suffix.

Related errors

• action string is empty
• invalid duration in action segment {segment!r}
• unknown action keys {bad}; allowed keys are {sorted(_SANA_WM
• plucker_emb token count {plucker_emb.shape[1]} != latent tok
• chunk_size must be > 0, got {chunk_size}.

AI-assisted analysis of sgl-project/sglang@0132848349 (2026-08-28). Data as JSON: /api/errors/28e11e7a5de0d409. Report an issue: GitHub.