sgl-project/sglang · error · ValueError

k_mode must not be empty

Error message

k_mode must not be empty

What it means

Raised by preprocess_dots_video when k_mode is an empty string. k_mode selects the model's key/mode preset for video preprocessing (default 'eval_ek') and cannot be blank.

Source

Thrown at python/sglang/srt/multimodal/processors/dots_note_omni.py:136

    if last < len(user_value):
        content.append({"type": "text", "text": user_value[last:]})
    return content


def preprocess_dots_video(
    raw_video,
    question: str,
    *,
    tokenizer,
    seq: int = 131072,
    audio_cap: float = 1.0,
    audio_sr: int = 16000,
    k_mode: str = "eval_ek",
    max_new_tokens: int = 0,
) -> list[dict[str, Any]]:
    """Return in-memory timestamp/image/audio content using the server tokenizer."""
    if not k_mode:
        raise ValueError("k_mode must not be empty")
    video_bytes, video_id = _video_payload(raw_video)
    cfg = _build_video_cfg(
        seq=seq,
        audio_cap=audio_cap,
        audio_sr=audio_sr,
        max_new_tokens=max_new_tokens,
    )
    from sglang.srt.multimodal.processors.dots_note_omni_video_core import (
        flatten_runner,
    )
    from sglang.srt.multimodal.processors.dots_note_omni_video_core import (
        preprocess as pp,
    )

    video_b64 = base64.b64encode(video_bytes).decode()
    sample = {
        "meta": {"video_0": video_b64},
        "conversations": [{"from": "user", "value": f"<video_0>{question}"}],

View on GitHub (pinned to 0132848349)

Solutions

1. Omit k_mode from video_config to use the default 'eval_ek'
2. Or set a valid mode string such as 'eval_ek'
3. Sanitize config dicts to drop empty-string values before sending

Example fix

// before
video_config = {"k_mode": k_mode or ""}
// after
video_config = {"k_mode": k_mode} if k_mode else {}

cfg = {k: v for k, v in cfg.items() if v != ''}  # drop empty strings
if 'k_mode' in cfg:
    assert cfg['k_mode'], 'k_mode must be a non-empty string'

def valid_k_mode(cfg: dict) -> bool:
    km = cfg.get('k_mode', 'eval_ek')
    return isinstance(km, str) and len(km) > 0

When it happens

Trigger: Passing video_config={"k_mode": ""} (explicitly empty) in a video request; None falls back to the default, only '' fails the falsy check.

Common situations: Config templating code injects an empty string for an unset key (e.g. k_mode from an env var or YAML field left blank) instead of omitting it.

Related errors

• seq must be positive, got {seq}
• audio_cap must be non-negative, got {audio_cap}
• Video placeholder count does not match video_data: {len(vide
• Unsupported video input type: {type(video_file)}
• Attention backend '{selected_backend}' is not supported by t

AI-assisted analysis of sgl-project/sglang@0132848349 (2026-08-28). Data as JSON: /api/errors/6546d31ffa73cdc8. Report an issue: GitHub.