sgl-project/sglang · error · ValueError

material URI decoded payload is empty

Error message

material URI decoded payload is empty

What it means

After decoding, the computed decoded size ((encoded_size*3)//4 - padding) is zero or negative, meaning the payload carried no actual bytes (e.g. only padding like '====' slipped through earlier checks).

Source

Thrown at python/sglang/multimodal_gen/runtime/pipelines_core/stages/model_specific_stages/minimax_h3/material_io.py:637

                    raise ValueError("material URI has data after base64 padding")
                encoded_chunk.append(value)
                if len(encoded_chunk) == MINIMAX_H3_BASE64_DECODE_CHUNK_CHARS:
                    decoded_chunk = _decode_base64_chunk(encoded_chunk)
                    total += len(decoded_chunk)
                    output.write(decoded_chunk)
                    encoded_chunk.clear()
            if encoded_size == 0:
                raise ValueError("material URI base64 payload is empty")
            if encoded_size % 4 == 1 or (padding and encoded_size % 4):
                raise ValueError("material URI has an invalid base64 payload length")
            if encoded_chunk:
                encoded_chunk.extend(b"=" * (-len(encoded_chunk) % 4))
                decoded_chunk = _decode_base64_chunk(encoded_chunk)
                total += len(decoded_chunk)
                output.write(decoded_chunk)
        decoded_size = (encoded_size * 3) // 4 - padding
        if decoded_size <= 0:
            raise ValueError("material URI decoded payload is empty")
        if total != decoded_size:
            raise ValueError(
                f"MiniMax H3 base64 decoded size {total} != expected {decoded_size}"
            )
        partial_path.replace(output_path)
    except Exception:
        partial_path.unlink(missing_ok=True)
        output_path.unlink(missing_ok=True)
        raise
    return str(output_path)


def _stream_tar_member_material(
    batch: Any,
    uri: str,
    *,
    condition_type: str,
    condition_index: int,

View on GitHub (pinned to 0132848349)

Solutions

1. Regenerate the data URI from the real asset
2. Validate decoded length > 0 before submission
3. Check for double-encoding bugs that strip content but keep padding

decoded = base64.b64decode(payload + '=' * (-len(payload) % 4))
assert decoded, 'decodes to empty'

When it happens

Trigger: A payload consisting solely of '=' characters, or encoded_size so small relative to padding that decoded_size <= 0.

Common situations: Corrupted data URI where the real payload was lost but padding remains; test fixtures with placeholder base64.

Related errors

• data URI must use ;base64 encoding
• material URI base64 payload must be ASCII
• material URI has an invalid base64 character {character!r}
• tar material URI has an invalid encoded header
• material URI has an invalid base64 payload

AI-assisted analysis of sgl-project/sglang@0132848349 (2026-08-28). Data as JSON: /api/errors/5d2207403d12efeb. Report an issue: GitHub.