Size a Fibre upload for Celestia's JSON-RPC request limit

A blob can fit the Fibre protocol and still exceed the node's JSON-RPC request limit after Base64 encoding. Measure the serialized request body for the actual transport.

Include Base64 expansion

An exactly 12 MiB binary payload expands to 16 MiB of Base64 before the method name, JSON punctuation and other arguments. Against the documented 16 MiB node limit, that request is already too large. Count bytes of the final UTF-8 JSON body instead of comparing the file size with the request limit.

payload length = 12 × 2^20 bytes
base64 length = 4 × ceil(payload length / 3) = 16 × 2^20
JSON envelope adds more bytes

Choose the transport deliberately

Use a supported direct upload path for larger payloads or split at application-defined boundaries and retain an ordered manifest. Test gateway and proxy limits separately. A protocol maximum describes a valid blob size and cannot guarantee that every RPC deployment accepts the corresponding HTTP request.

Sources