diff --git a/canon/architecture/adr-007-workplan-identity-and-repo-worker-topology.md b/canon/architecture/adr-007-workplan-identity-and-repo-worker-topology.md
index c5b8796..bab998c 100644
--- a/canon/architecture/adr-007-workplan-identity-and-repo-worker-topology.md
+++ b/canon/architecture/adr-007-workplan-identity-and-repo-worker-topology.md
@@ -152,6 +152,34 @@ being retired under `STATE-WP-0079`.
 Migration scope for C2: **758 workplan files** across the fleet currently carry
 these fields.
 
+> **Amended 2026-08-21 — derivation scope for C2.** `ADR-011` decision 7 keys
+> derivation on `(namespace, identifier)`, which separates *forks*. It does not
+> separate collisions inside one namespace, and the ecosystem's posture is `N1`
+> — a single implied namespace. A fleet scan on 2026-08-21 found **20 reused
+> identifiers across 48 files**, all within that one namespace, so the
+> prerequisite above is not satisfied by `ADR-011` alone.
+>
+> Ruled: **C2 derives only for live records; archived records keep their minted
+> identifiers, frozen.** This is what reconciles § Migration option 2 — under
+> which historical files keep colliding identifiers — with the uniqueness
+> derivation requires. Of the 20, only **five** collide among live files, so the
+> remediation surface is 11 files rather than 48.
+>
+> Two consequences follow, and both are load-bearing:
+>
+> 1. **Un-archiving a record with a frozen identifier is a collision hazard.**
+>    A record returning to live status must be checked against the live
+>    namespace before it is re-derived, and renumbered if it clashes.
+> 2. **Derivation is not retroactive.** Existing live records keep their minted
+>    UUIDs until they are re-derived deliberately; C2 changes provenance for new
+>    and re-registered records, not the whole corpus at once.
+>
+> Rejected: treating a *repository* as the namespace. That would make the
+> collisions vanish by construction, but it redefines the term `ADR-011`
+> decision 1 fixes as "a fleet instance, a client deployment, an autonomous
+> domain", and `ADR-011` decision 9 warns specifically against reading N-plane
+> movement into claims it does not support.
+
 **3. Lifecycle status is not automatically promoted.** An automated
 normalization pass may report drift; it may not move a workplan from `proposed`
 to `active`. `proposed` means awaiting human review, and an automation that