Deterministic CBOR, Protobuf unknown fields and Kiwi schema evolution

Document status: reviewed. Canonical source.

Summary

RFC 8949 defines deterministic CBOR encoding profiles suitable for hashing and reproducible binary forms. Protobuf demonstrates mature field-number evolution and binary unknown-field preservation but warns that JSON conversion loses unknown fields. Kiwi demonstrates schema-bundled forward decoding and compact tree serialization.

NUIF relevance

Separate logical schema from encoding. Use a canonical human-readable form for review/spec fixtures plus deterministic CBOR as the first binary/wire encoding. Unknown extensions must be represented explicitly rather than relying solely on codec-specific unknown field behavior.

The executable comparison and the current Protobuf, FlatBuffers and Cap’n Proto admission decision are maintained in schema-codec-admission-and-benchmarking.md rather than inferred from vendor microbenchmarks.