FINDING / HANDOFF: selected BIT fixed routes with charged stream lowering

[jmbarrancoml]

FINDING / HANDOFF. Claim released. I completed the scoped fixed-header investigation as @jmbarrancoml. The contribution supplies a conditional physical stream reduction, not a new supplier or exponent.

Public artifact: PR2157, head eb1bf93950e9b14f7fadca7892866e9f29a26ad3. The package includes the proof and full bill, source pins, an IR emitter and registered replay. The implementation remains at 432cd20a; the follow-up corrects attribution to distinguish DreamingOfClouds' PR589 tuning from eumemic's PR555 base word.

I compile the selected nine-stage BIT catalogue: 999 data route types and 124 hosted types covering 126,432 hosted owner occurrences. For each elementary factor, I update complete high fibers using carries from the current low class, then move the whole payload packet through its low-class permutation. Reversed field order uses two charged completed ordinary interchanges. Width one still requires the low permutation.

For hosted slots I choose an isometry by exchanging the two coordinate-set differences. The selected overlapping slot needs one axis swap, and each exterior slot needs eight. The residual subspace projector agrees with PR442's requirement. The resulting maximum is 1,664 ordinary calls per hosted action; the selected data-route maximum is 3,520. The occurrence counts describe one header action per occurrence, not the complete supplier runtime.

I verified exact rational factor products and source/owner bindings, 288 payload additions, 90 scalings, complete GL2 low/high packet movement, and four semantic failure controls. The additions move 2,957,760 bits. Registered Python 3.12 replay and an optimized Python replay pass locally. The physical simulator charges an exact ordinary-callee oracle; the written proof supplies the counter, rewind and cleanup argument. I claim no full machine execution or hosted CI pass.

The open handoff is one data-dependent good-child normalizer with explicit mutable-weight reads on the same stopped GL chart. Full admission also needs bad-residue fallback, COPY/ERASE lifetimes and the complete correlated-helper domain bridge. Fixed rational header words do not establish those interfaces.

I retain predecessor credit for Nick Petalas's PR2140 row-index carry lowering and PR2120 stock analysis, Adam Gall's stock/borrowing boundary, the retained ordered-affine stream lemma, DreamingOfClouds' PR589 tuning of eumemic's PR555 word, the punctured interface and chain, DaysSky's PR442 hosting theorem, Zhihao Chen's geometry, Dylan Crow's Hamming E8 producer and Jacob Sussman's E8/frame interfaces. Prepared with substantial OpenAI Codex assistance; no independent human review.

Scientific base: canonical main 0fdd7d82de03e43c9e5a1000dfbcd380d1b687d2, priority revision 4. I leave the selected frontier and frozen sources unchanged.

I refreshed canonical main at 21:16 UTC. Submission overlap covered 408 open PRs and 831 Discussion records through 21:18 UTC, with complete pagination and no warnings. PR2140 remains at the pinned head. These text checks establish coverage, not novelty.