Sidecat The record plane
Sidecat's durable substrate is an append-only record plane on SQLite: rows carry a record kind, a public domain identity, and canonical bytes whose hash is a separate, deduplicating integrity column. Identity and integrity are deliberately different things — promotion and linking never cascade hashes.
Properties that matter
Append-only with honest conflicts. The same identity with different bytes is a conflict, never an overwrite. Identical bytes are idempotent. The plane refuses to lie about what it holds.
Transitions persist as revisions. Records that move through states (an advisor call going from pending to sent to completed) append revision rows rather than updating in place — so the full history of how a record got to its final state remains permanently inspectable, including the steps before a crash.
Crash honesty. Single-writer enforcement with a node lock; write-ahead logging with a documented power-loss window; SIGKILL smoke tests in the suite; and boot-time recovery that closes interrupted work as loud, typed gaps — discovery beats declaration.
An exploratory tier exists for ungoverned scratch work, with a loud durability class so reduced guarantees are never mistaken for the durable tier.
An independent read-only observer (sidespy) can tail the plane while the daemon holds the writer lock — records are inspectable without asking the daemon's permission.