it's base64 chars, but that's a limitation of the underlying in the gRPC layer , or atleast the 4M matches what i think is the default limit.
For our internal networking we ended up disabling grpc size lengths (I think that brings it up to 100MB for a single message) by setting rpc.max_send_message_length, grpc.max_receive_message_length to -1.
For arize we just chunk the page for now, it's not a definitive solution as i'm sure you might now want host arbitrary binary blobs for us but we have a short term milestone coming up.
