[RossRichardson]

PR2481 routes an ordinary R439 update through two restored dirty payload banks. This contribution uses one: exchange the source into the bank, route it into the target layout, update the target through a charged owned-record scan, reverse the routes and exchange back. Snapshot taps keep their source immutable.

For the exact 303 ordinary events and ten taps, route calls remain 1,232, while exchanges fall 1,232 → 626 and outer packet XOR work falls 4,009 → 2,191 P-record units. The written proof covers arbitrary correlated bit payloads and invertible coordinate permutations under the explicit route/scan contract. The role/direction route multiset is unchanged; equal weighted route work additionally requires context-independent route tariffs. Physical headers, control, private child scratch and complete supplier admission remain open. This is not a bank minimum or new kappa.

The source-bound GL2(Z/9) replay covers all 431,568 family records in each direction, including 422,577 unowned records, all 313 event boundaries, and eight semantic faults. A separately implemented S3 check covers 216 chart triples and 2,592 event boundaries with seven faults, including noncommuting factor order. A separate specialist also reviewed the proof and reran the stable primary verifier under Python 3.14.6; that replay is explicitly distinguished from the independent small implementation.

Validation completed locally:

• Registered CPython 3.12 replay and source/metadata checks.
• All 15 retained and three live source corruptions rejected; changed cost receipt rejected.
• Optimized read-only, Git-free export replay, with unchanged bytes.
• Full PR2481 predecessor payload reproduced; six finite route counters agree in both directions.
• Selected-record integrity check passed; selected cold replay was not run because no selected construction changed.

Only research/r439-one-buffer-packet/ is added. Base canonical main is 0fdd7d82de03e43c9e5a1000dfbcd380d1b687d2, priority revision 4; exact freshness/overlap coverage and limitations are in TASK.json. The canonical claim is Discussion2401.

Credit ywz65's PR2481 (d3ec95362a071e2726c5ff4ce587de80c7d4f984), Ross Richardson's PR2448/2407/2437, Jose Manuel's PR2195, alephnan's PR1627/540, and the retained supplier/exporter lineage. The exchange and conjugation identities are standard; the contribution is the changed schedule, explicit contract/invoice and exact chronological binding. Ross Richardson with substantial OpenAI Codex assistance, including a separate mathematical specialist. Apache-2.0; no independent human review, formal-kernel proof or hosted-CI success claimed.