t type code
The integer discriminator at the top of every proof bundle and inside each cx entry, drawn from a frozen registry namespaced by decade (10-19 block-like, 20-29 item, 30-39 entropy, 40-49 commitment chains); never renumbered or reused, and bound into the signed payload.
Overview
The t type code is the integer discriminator at the top of every proof bundle (the top-level t key) and inside each external commitment entry (cx[].t), drawn from one unified registry namespaced by decade: 10-19 block-like subjects (10 block, 11 beacon), 20-29 item subjects (20 item), 30-39 entropy sources (30 NIST, 31 Stellar, 32 Bitcoin), 40-49 external commitment chains (40 Stellar, 41 Bitcoin), and 50 and above reserved. The codes are a long-lived contract: never renumbered, never reused, never renamed; new types claim the next unused integer in their category. The code is also bound verbatim into the signed payload as a big-endian 16-bit integer, so changing t in a bundle breaks its signature; this is what makes a beacon proof cryptographically distinct from a plain block proof over the same block. The registry table and the signed payload layout live in the proof bundle wire format.