Index sequence assembly and history lookups

docs/roadmap/remediation.md

@@ -222,7 +222,15 @@ mapping is still explicit. Defaults-only overrides keep their existing behavior.
 
 ## 7. Remove new quadratic scans from sequence construction — P2
 
-- [ ] Addressed and behaviorally validated.
+- [x] Addressed and behaviorally validated.
+
+Completion: claims retain encountered immutable nodes; history construction
+groups ranges by source; scope/version projection uses source/path range
+lookups; retained-history traversal and replay use per-application path indexes.
+Ordered slices and detached clone ownership remain intact. Static review confirms
+the listed nested scans are removed. A wide-collection replay/origin/ownership
+regression, the everyday check, and `go test -race ./...` passed. No timing
+threshold or release gate was added.
 
 **Owners:** [compose.go](../../internal/engine/compose.go), especially
 `validateRegisteredSequences` and application construction; range lookups in