gating

# gating A gate is a check that blocks. Its only job is to go red when it should. The characteristic failure is not a wrong check — a wrong check gets noticed. It is a check that **cannot fail**, which reports PASS forever and is indistinguishable from a working one from the outside. That is what makes this different from ordinary testing: the object under suspicion is the check. ## The three obligations Every gate owes these. A gate missing any of them is not yet a gate. **1. An anchor outside your own code.** Something the check compares against that your implementation did not produce: a published constant, a closed-form answer, a conservation law, a degenerate case with a known result, an independent implementation. A check that compares this run to the last run only ever tells you the code still does what it did. See `references/anchors.md`. **2. A known-bad it demonstrably rejects.** Break the subject the way it would plausibly break, run the gate, confirm red. Until you have done this you have not shown the gate works — you have shown it runs. This is the obligation people skip, because a passing gate feels like evidence. Two things about known-bads that are easy to get wrong: - **Validate it at the configuration it will run in.** A case tuned on a small or fast setting can stop being bad at full size. An "untrained" grid built from one Lloyd iteration was genuinely zero-gain at m=2/K=16 and earned a real +0.10 dB at m=8/K=65536, where one iteration reloc...