Self-stopping criterion for ·b33b (proved, conditional): G(n) ≤ n always; G(n)=n iff all v<n are option values; cancellation splits (t,t,c) of the opposite-parity remainders n-1, n-4 realize every non-exceptional value; a two-high-bits construction (Lemma 4) realizes any remaining value whenever t=(m-v)/2 has two set bits above log2(max E), and a bit-transplant lemma reduces the degenerate-t cases to a finite table. Consequence: if computation to horizon N ≥ max(E) + 2^(floor(log2 max E)+3) + 8 shows no exceptions beyond max(E) (plus the finite table checks), then E is complete and ·b33b is arithmetic-periodic with period 1, saltus 1. At the current horizon the hypothesis fails (needed: 1266003; cascade alive), so ·b33b remains open; the criterion also bounds successive-exception ratios by ≈5, matching the observed 1.3-3.0.