sgl-project/sglang · error · ValueError

elements must be int or list; got {type(v[0]).__name__}

Error message

elements must be int or list; got {type(v[0]).__name__}

What it means

The outer value is a non-empty list but its first element is neither an int nor a list, so the validator cannot decide between 1D and 2D shapes and rejects the input.

Source

Thrown at python/sglang/srt/utils/field_validators.py:81

        # Accept None
        return v
    if not isinstance(v, list):
        raise ValueError(f"must be list or null; got {type(v).__name__}")
    if not v:
        # Accept empty list
        return v
    if isinstance(v[0], int):
        # Accept list[int]
        return validate_list_i64_1d(v)
    if isinstance(v[0], list):
        # Accept list[list[int]]
        for i, row in enumerate(v):
            try:
                validate_list_i64_1d(row)
            except ValueError as e:
                raise ValueError(f"row {i}: {e}") from None
        return v
    raise ValueError(f"elements must be int or list; got {type(v[0]).__name__}")

View on GitHub (pinned to 0132848349)

Solutions

1. Convert string elements to int before passing (e.g. [int(x) for x in vals])
2. Remove None/dict/tuple elements
3. If you meant nested rows, wrap each element in a list

Example fix

# before
arg = ['1', '2', '3']
# after
arg = [1, 2, 3]

first = v[0] if v else None
assert first is None or type(first) in (int, list), f'bad first element {first!r}'

def has_homogeneous_first(v) -> TypeGuard[list]:
    return isinstance(v, list) and (not v or type(v[0]) in (int, list))

When it happens

Trigger: Passing ['1','2'], [None], [[1],'2'] style lists, or a list of dicts/tuples where list[int] | list[list[int]] is expected.

Common situations: Parsing CLI input as strings and passing through unparsed, or JSON configs with mixed types.

Related errors

• Invalid component residency assignment: {value!r}
• Invalid component residency assignment: {raw_selector!r}={ra
• must be list or null; got {type(v).__name__}
• Unknown type: {type(other)}
• Invalid threshold_type for topk: {threshold_type}. Choose 'q

AI-assisted analysis of sgl-project/sglang@0132848349 (2026-08-28). Data as JSON: /api/errors/93bc5997b30730d6. Report an issue: GitHub.