diff --git a/docs/operations/github.md b/docs/operations/github.md
index 8194be7..3903fa8 100644
--- a/docs/operations/github.md
+++ b/docs/operations/github.md
@@ -114,6 +114,15 @@ publishing. The [release-source policy](../standards/versioning.md#release-sourc
 owns provenance, selection and quota limits. The first public release passed
 complete matching Server and three-platform App mirror download acceptance.
 
+Release postflight applies the [two-version mirror retention policy](../standards/versioning.md#release-sources).
+After verifying the latest mirror and its fallback against GitHub, inventory
+older releases with `/releases/{id}/attach_files`, verify their GitHub originals,
+then remove only the reviewed attachments through
+`DELETE /releases/{id}/attach_files/{attachment_id}`. Recheck both retained
+versions and the anonymous `download/latest` links afterward. Keep deletion
+inventories and verification results with operator release records, not source
+history. The upload script does not itself delete older attachments.
+
 ## Platform References
 
 - [Protected branch availability](https://docs.github.com/en/repositories/configuring-branches-and-merges-in-your-repository/managing-protected-branches/about-protected-branches)
diff --git a/docs/standards/versioning.md b/docs/standards/versioning.md
index 9a1031f..cf2a475 100644
--- a/docs/standards/versioning.md
+++ b/docs/standards/versioning.md
@@ -271,8 +271,16 @@ an up-to-date result, does not consult the mirror.
 
 Gitee currently documents 100 MB per attachment and 1 GB total repository
 attachments for ordinary projects. The mirror rejects files above 100,000,000
-bytes before writing. Check aggregate capacity before each release; exhausted
-storage leaves a pending preview rather than deleting older downloads.
+bytes before writing. GitHub retains published history; Gitee retains package
+attachments for the latest stable version and one preceding verified stable
+version. Order by semantic version, not update time; a preview cannot displace
+the fallback. Verify the new mirror completely before retiring older attachments,
+and verify that the fallback's packages remain downloadable and match GitHub.
+Delete only older mirror attachments with verified GitHub originals; retain
+release descriptions and tags. Unknown files or provenance require review.
+Check capacity before upload. Cleanup may reclaim versions outside the two
+retained stable versions; never delete either retained version to make an
+unverified replacement fit. Exhausted storage leaves a pending preview.
 Target authentication, uploads, anonymous metadata/CORS and the complete matching
 Server/three-platform App downloads and SHA-256 checks passed for the public release.
 Use API metadata in the Browser; ordinary asset-link redirects are not guaranteed