C
content-length headers 
Crequest.body it will upload successfullyCnew ReadableStream manually, it'll throw the error.
KC
ReadableStream?KKrequest.bodyCrequest.body for the instruction description. The latter part of body is data as parameters for the instruction.Cfetch with the instruction body and the second fetch with data?
M
Content-Length header on the requestC
ReadableStream without the headers.Mrequest.body? Could you read that length, then subtract N for the data stream?C
content-lengthrequest.bodyrequest.bodyrequest.bodyrequest.bodynew ReadableStreamReadableStreamReadableStreamfetchfetchContent-Length