Clarify sequence operation history in the configuration contract

docs/config.md

@@ -452,10 +452,11 @@ the descendant can therefore retain history after `Lookup` stops reporting it as
 effective. Equal-valued input is still an explicit base definition, while a derived
 value for absent input remains non-explicit.
 
-Appending registered records during strict composition assigns each contribution
+Strict composition assigns contributed records their assembled sequence positions
-its assembled sequence index in history. A later precedence tier that supplies a
+in history. Across tiers, history follows the selected
-sequence records replacement at the sequence path; history does not imply
+[collection operation](#strict-document-composition), including append and
-identity-based merging across tiers.
+whole-record upsert. Incoming contributions use their assigned positions, and
+replaced payload remains available as historical evidence.
 
 A mapping assembled from the selected file and imports has one composite base origin
 whose locations follow [scoped assembly order](#explicit-imports), not source-record
@@ -550,10 +551,13 @@ including a superseded value that could not have decoded into the final Go field
 Baseline, effective, and resolution values use canonical typed projection. A
 decoding event bridges replayed input and canonical typed values, so intermediate
 null/scalar replacements cannot incorrectly imply permanent default removal. Mapping
-queries reconstruct each source or override contribution, while sequences remain
+queries reconstruct each source or override contribution. A sequence snapshot
-atomic: a descendant history identifies its presence before and after the containing
+represents the collection at that point in replay, and sequence diffs remain
-sequence replacement without implying element-wise merging. Removed paths remain
+atomic. Descendant queries describe their presence and values before and after
-explainable; unknown and malformed paths return false.
+containing sequence operations. Combination follows the
+[collection operation tables](#strict-document-composition); upsert replaces
+matching records in full. Removed paths remain explainable; unknown and malformed
+paths return false.
 
 Every snapshot applies the same historical tag, predicate, and recorded-dependency
 sensitivity closure as effective rendering before YAML is exposed. A redacted scalar

docs/roadmap/remediation.md

@@ -1,8 +1,8 @@
 # Sequence Implementation Review Remediation
 
-Status: findings 1–11 are complete. The subsequent integration audit at
+Status: all findings 1–17 are complete. The subsequent integration audit at
-`8d40983271de5239312eb0a2896737be88c5abdc` identified six additional open findings,
+`8d40983271de5239312eb0a2896737be88c5abdc` identified findings 12–17, now
-numbered 12–17 below. This record introduces no new release gate.
+remediated below. This record introduces no new release gate.
 
 Reviewed commit: `0be7cdb00eff576fda6b30c0600b2134d4e2e086`.
 Implementation range: `bc6b977..0be7cdb`.
@@ -30,6 +30,15 @@ Validation after the initial remediation: `./scripts/check.sh` and
 `go test -race ./...` passed with Go 1.26.10 on Linux. The original public-API
 probes for findings 1–9 now demonstrate the required corrected behavior.
 
+Validation after integration remediation: the everyday check, full race suite,
+and local documentation/public-boundary checks passed with the same toolchain.
+The original and follow-up public-API probes demonstrate corrected behavior for
+findings 1–9 and 12–15, including unrelated underlay payload at an old version
+index. The accumulated-copy correction is verified by code inspection and
+ownership regressions; the contract corrections are verified against the
+implemented operations and replay. Each additional finding has its own completion
+record and commit.
+
 P1 denotes the highest-priority correctness issue here; P2 denotes normal-priority
 work needed to complete the selected behavior. Preserve the agreed scope while
 fixing these issues. In particular, do not resolve failures by restricting valid
@@ -673,7 +682,15 @@ Do not introduce public caches, pooling, new caps, or performance thresholds.
 
 ## 17. Reconcile Legacy Sequence-History Contract Text — P2
 
-Status: [ ] Open.
+Status: [x] Complete.
+
+Completion: metadata and explanation prose now describe history through the
+selected collection operation, assigned item positions, and displaced payload.
+The text distinguishes sequence snapshots and atomic diffs from append/upsert
+combination and links to the canonical operation tables. Whole-record upsert,
+existing queries, and sensitivity guarantees are unchanged. Verified against
+replay/combination code, local documentation-link tests, and `git diff --check`;
+the unchanged runtime is covered by the preceding everyday and full race checks.
 
 Owner: the metadata/provenance and explanation sections of
 [`docs/config.md`](../config.md#layered-metadata).