Scoped negative result: restored sharing cannot reach the selected R439 copy path (no new kappa)

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Finite word-level barrier note on the selected PR 589 R439 bit word (PR 799 X4 assembly). No construction proposed, no kappa claimed, no selected-frontier or supplier file edited.

Three priced avenues for the restored-temporary sharing mechanism of merged PR 708:

• Decoder totals are vacuous: 27 source reads across 18 late A gates (3 per total), pairwise disjoint source sets.
• Frame-zero D section is arithmetically rich (41,404 positive oriented pairs over 430 helper operands, best 65, seed-42 greedy 205 pairs / 6,231 ADDs) but interface-blocked: the unchanged lemma's H2 requires every D gate to write a target. Control C1 shows the full helper-temp wrap is scalar-valid yet H2-rejected; control C2 shows target-written temps are H2-legal but cost exactly +2 with no saving (no target appears in any D source set).
• Same-frame A groups total 1 greedy ADD at frame 506 (mini-node region covered by other work).

Reproduce (standard library only):

python research/r439-copy-path-sharing-barrier/verify.py

Expected final line:

PASS_R439_COPY_PATH_SHARING_BARRIER totals_reads=27 d_positive=41404 d_best=65 a_sameframe=1 controls=3 no_new_kappa

The script reruns the full baseline H1-H5 check through the unchanged xcheck_p checker, recomputes all censuses, runs three variant controls (including an unrestored-temp rejection), and compares the full report against CERTIFICATE.json. A tampered certificate fails with 'certificate mismatch' (checked locally).

Scope: inherits all selected-review assumptions. Greedy matchings are not optimal; R420 and open PR 686 (different word/checker) are explicitly out of scope. Overlap refreshed against 200 open PRs: R439 miners (PR 728/PR 792/PR 843/PR 844) work disjoint regions.

Base: f567884. Assignment seed 42, structural decoder research. Credit: eumemic (PR 543/PR 555, xcheck lineage), DreamingOfClouds (PR 589), Sagar Thakrar (PR 708 mechanism as priced hypothesis), mikhailramalho (related open PR 686). Prepared with substantial AI assistance (via OpenCode); no independent human review claimed. Apache-2.0.