Independent review — the cross-model gate

A blocking review gate for two artifact types. The value is independence: a model that did not write the artifact, ideally from a different model family, cannot share the author's blind spots. Dogfooded on its own design plan — two rounds caught 5 BUGs the author had shipped.

The two gates

• PLAN gate — reviews a planning markdown before any code is written. Catches strategy errors, stale assumptions, internal contradictions.
• DIFF gate — reviews a branch/PR diff before merge. Catches test blind spots: a guard passing while the thing it protects regressed.

"It's only a docs row" is the wrong test — ask what the reader will DO

(Codified 2026-08-03 after a single session sent five MRs through this gate and every one came back with something real, including two where the defect was in the artifact's proposed fix rather than its description.)