Blob

A reference to an uploaded blob as embedded in a record body.

AT Protocol blobs are stored out-of-band (uploaded via com.atproto.repo.uploadBlob, addressed by CID) and referenced inline from the records that use them. The inline reference shape is:

{
  "$type": "blob",
  "ref":    { "$link": "bafkreig..." },
  "mimeType": "image/jpeg",
  "size":     123456
}

type is a constant "blob" discriminator required by the spec. It's marked EncodeDefault.Mode.ALWAYS so that construction doesn't require repeating the literal at every call site but the wire form still carries it.