`[2026-06-15]` **Memory plane TDD'd + shipped** (commit `cd12951`, v0.17.3). Impl decisions worth keeping: vec0 `distance_metric=cosine` at table creation (`score = 1 − distance`); `search` over-fetches ALL candidates by cosine then scope-filters in Python so `top_k` counts IN-SCOPE hits; idempotency_id = reference 4-tuple `("default",verb,_ctx_actor(ctx),key)` pipe-joined as the SQLite PK, digest = sha256 canonical-JSON; `_ctx_actor` = `job_id|jwt_sub|session_id`. heid-code-review returned zero true drift; optimistic-lock semantics pinned to the reference via an `expected_revisions` parity test.