diff --git a/docs/2026-08-15-sales-summary-balance-validation.md b/docs/2026-08-15-sales-summary-balance-validation.md
index bc87b993..6c4a5899 100644
--- a/docs/2026-08-15-sales-summary-balance-validation.md
+++ b/docs/2026-08-15-sales-summary-balance-validation.md
@@ -287,3 +287,27 @@ came to $56.37 across 69 days — identical to the in-memory prediction in Part
 the job path end to end. The 20 contended clients were re-measured in memory after the charge
 repair, because a second full pass through the job would have taken hours for the reason in defect
 2. The two methods agree exactly where both were run.
+
+## Ongoing deduplication, with both clients active again
+
+The re-key is meant to make contention impossible even if a location is configured on two clients
+again. To test that rather than assume it, all 10 twins were **re-activated** — every location
+shared once more — and the import re-run.
+
+**Repeated imports are idempotent.** Three consecutive refund imports for both halves of the
+Concord pair, with both clients live on location `L43Z5GMW72VMG`:
+
+| | run 0 | run 1 | run 2 | run 3 |
+|---|---|---|---|---|
+| NGCC | 127 | 127 | 127 | 127 |
+| NGCD | 1,419 | 1,419 | 1,419 | 1,419 |
+
+Not one entity created or moved. Before the re-key this is the exact configuration that made a
+refund's owner flip every ~20 minutes.
+
+The first import after the migration is the only one that grows anything, and it grows once: NGCD
+gained 100 refunds materialising its own copies, while NGCC — whose refunds already carried its
+own scoped key — gained only the 2 that were genuinely new. After that, steady state.
+
+**State the restore was left in:** twins re-activated, i.e. Phase 0 deliberately undone for this
+test. Re-applying it is the ten-datom retraction recorded above.