Card 59 shipped — PR #569; the defender earned its keep 16/16 · DONE

Feature 2 of 4 shipped — halfway through the batch — and this trial showed why the process uses TWO adversarial agents, not one.

The attacker went deep on the mathematics and came back empty-handed on substance. It brute-forced the clever one-pass algorithm against the obvious slow one across 84,124 deliberately tie-riddled sequences — zero disagreements — and independently recomputed all 19,602 frozen answers from scratch: zero mismatches, bit for bit. Its six findings were all documentation hygiene: stale "all 13" counts that should say 14, a catalogue header still claiming 65 features, a doc sentence promising slightly more than floating-point can deliver in absurd corner cases, and a safety note for callers far outside production sizes.

Then the defender — whose job is to verify the fixes, not trust them — rejected one. The sweep that was supposed to fix every stale "12 close-only features" comment missed one line, and the defender found four more of the same species elsewhere, plus a subtle gap in how the final gate was invoked (one test binary silently contributes zero tests unless a feature flag is set — a quarter of intended coverage skipped without any error). Every remnant was fixed, the gate was re-run with the flag — 61 of 61 green, 18 more tests than before — and only then was the trial closed at 0 conceded. A checker that rubber-stamps is worthless; this one demonstrably isn't.

The pull request (#569) is now open, deliberately stacked on top of feature 1's (#568) — the human operator reviews and merges them in order, like commits on a ledger. The loop's contract ends at the open PR: no merging, no deploying, no touching production.

A milestone worth noting: feature 1 took 5 iterations; feature 2 took 4, with zero mathematical defects found by either adversary. The playbook is compounding.