ADR 0006 — The hash chain is mandatory

Status: accepted · 2026-09-13

Context. An optional chain would lower the bar for new implementations; a mandatory one makes every conformant logbook tamper-evident.

Decision. The chain (SPEC §3) is required for conformance. It is invisible to the person: add computes it, verify checks it, nothing else mentions it.

Consequences. A file that does not chain is not a logbook. Implementations must pass the conformance fixture. Simplicity is delivered by hiding the chain, never by removing it.