sgl-project/sglang · error · ValueError

material URI has an invalid base64 payload

Error message

material URI has an invalid base64 payload

What it means

The material URI's base64 payload is malformed (bad characters or length). Fix the data:...;base64 URI.

Solutions

1. Re-encode with URL-safe alphabet, no padding/newlines: base64.urlsafe_b64encode(data).rstrip(b'=')
2. Strip whitespace/newlines from the payload before embedding
3. If standard base64, translate +/ to -_ before building the URI

Example fix

# before
uri = "data:application/octet-stream;base64," + std_b64  # may contain +/
# after
import base64
safe = base64.urlsafe_b64encode(data).decode().rstrip('=')
uri = "data:application/octet-stream;base64," + safe

import base64
payload = payload_part_of_uri
clean = "".join(payload.split())  # strip whitespace
try:
    base64.b64decode(clean + "=" * (-len(clean) % 4), altchars=b"-_", validate=True)
    ok = True
except Exception:
    ok = False

When it happens

Trigger: Inline base64 material URIs containing whitespace, '+'/'/' instead of '-_'/'_', truncated chunks, or concatenated payload with stray characters, streamed through _stream_base64_material in MINIMAX_H3_BASE64_DECODE_CHUNK_CHARS-sized chunks.

Common situations: Copy-paste corruption, URL-unsafe base64 not translated to the URL-safe alphabet, line-wrapped base64, or truncation from size limits.

Related errors

• material URI has data after base64 padding
• material URI has invalid base64 padding
• condition URI must be a non-empty string
• data URI must use ;base64 encoding
• file URI host must be local, got

AI-assisted analysis of sgl-project/sglang@0132848349 (2026-08-28). Data as JSON: /api/errors/d7c30604e52d14fa. Report an issue: GitHub.

Appendix: source

Thrown at python/sglang/multimodal_gen/runtime/pipelines_core/stages/model_specific_stages/minimax_h3/material_io.py:586

def _material_workdir(batch: Any) -> str:
    registry = batch.extra.setdefault(MINIMAX_H3_TEMP_DIRS_EXTRA_KEY, {})
    material_dirs = registry.get("material")
    if isinstance(material_dirs, list) and material_dirs:
        return str(material_dirs[0])
    return minimax_h3_register_temp_dir(
        batch,
        tempfile.mkdtemp(prefix="minimax_h3_material_"),
        owner="material",
    )


def _decode_base64_chunk(encoded: bytes | bytearray) -> bytes:
    try:
        return base64.b64decode(encoded, altchars=b"-_", validate=True)
    except Exception as exc:
        raise ValueError("material URI has an invalid base64 payload") from exc


def _stream_base64_material(
    batch: Any,
    uri: str,
    *,
    condition_type: str,
    condition_index: int,
) -> str:
    payload_start, media_type = _base64_uri_payload_start(uri)

    output_path, partial_path = _material_output_paths(
        batch,
        condition_type=condition_type,
        condition_index=condition_index,
        media_type=media_type,
    )
    total = 0

View on GitHub (pinned to 0132848349)