Research: present-head flag 43 hosts its tail before its head (no new kappa)

[VictorLiwentao]

Change and scope

One-flag follow-up under priority revision 6, card p104-side-correction. Completes the present-head class (0,1,9,43) chronology outside the flag-0 coefficient cascade: #3349 names the class; #3392 pins absent-head flag 2; #3443 pins flag 9; #3451 pins flag 1 with span method. This package pins flag 43 (X21 → Y59, basis head 15).

On the published 4,058-event word:

• the head enters Y59 (listed and in GF(2) span) only at the terminal rank-3 transport after-frame at event 3525
• all 15 Y59 adds (last at event 3364) run in head-free charts (head_free_target_updates=15/15); ten run in the empty chart
• X21's literal drop at event 570 keeps 15 in span (3 ^ 4 ^ 8); source_span_drops=0
• new on this flag: updates 3231 and 3364 already span non-head basis vectors {32} then {6, 18, 32}, co-hosted with X21's live rank-9 frame (tail_cohosting_updates=2) — endpoints share part of the flag basis while the target is still updated; only the head is missing
• preterminal_hosting=0 and preterminal_span_hosting=0; zero joint endpoint events; frames unrestored

Chronological dirty restoration therefore cannot use co-hosted basis-head geometry on this word. Drop/arrive/gap 570/3525/2955 differs from flag 1 (591/3473/2882) and flag 9 (500/3489/2989); scanners refuse equal prior tuples.

Scoped obstruction. No new kappa. Selected κ stays 0.001672660197076918. Coefficient delivery (flag-0 cascade on Y34) is outside this package; open #3363's 208-flag relay census is cited only as leave-alone context.

Result

Package: research/p104-present-head-flag43-audit/.
Tip: d29a0834ff1705e320d828a0fe538e1efc7ddfdf.
Content tip: 5889fe1591f689c3003e2f92c9258d79c97bdee3.
Base: 6f100d4bb5083f8c35d96fd95a539811c62f245c.

Validation

python3.12 -I -B research/p104-present-head-flag43-audit/verify.py
python3.12 -I -O -Werror -B research/p104-present-head-flag43-audit/verify.py
python3.12 -I -O -Werror -B research/p104-present-head-flag43-audit/independent.py
python3.12 -I -O -Werror -B research/p104-present-head-flag43-audit/test_package.py
python3.12 -B scripts/research_package.py --package research/p104-present-head-flag43-audit

Expected:

PASS_P104_PRESENT_HEAD_FLAG43 flag=43 head=15 preterminal_hosting=0 preterminal_span_hosting=0 drop_event=570 arrive_event=3525 source_span_drops=0 head_free_target_updates=15/15 tail_cohosting_updates=2 no_new_kappa
PASS_P104_PRESENT_HEAD_FLAG43_INDEPENDENT flag=43 head=15 preterminal_hosting=0 preterminal_span_hosting=0 drop_event=570 arrive_event=3525 source_span_drops=0 head_free_target_updates=15/15 tail_cohosting_updates=2 no_new_kappa
PASS_P104_PRESENT_HEAD_FLAG43_TESTS groups=7
PASS_REGISTERED_RESEARCH_PACKAGE research/p104-present-head-flag43-audit outcome=completed

Default verify is read-only. Admission uses need() and still fires under -O.

Overlap and credit

Closest priors: #3451 (flag 1 span method), #3443 (flag 9), #3349, #3392, merged #3242. Does not reopen those packages, #3441/#3436/#3421/#3411, deferred V45/rho=0, or the merged readout series through #2883. Soft-overlap checked against open #3363/#3365/#3371/#3372: this package recomputes no coefficient and says nothing about Y34.

Credit Nick Petalas / #2981, jwr404 / #3242, #3349, #3392, #3443, and #3451. Prepared by Wentao Li (VictorLiwentao, @Is__Victor) with substantial AI assistance, under Apache-2.0.