diff --git a/docs/INTEROP.md b/docs/INTEROP.md
index 68b269f..199bb54 100644
--- a/docs/INTEROP.md
+++ b/docs/INTEROP.md
@@ -333,6 +333,11 @@ Firefish is dead (its site has answered 410 since February 2025).
 
 A new Misskey 2026 starts with `federation: none`.
 
+Misskey never lowers a post's `renoteCount` when a renote is deleted, so a remote boost undone with `Undo{Announce}`
+still counts there (G-0005; its `NoteDeleteService` lowers only `repliesCount`). Sharkey lowers it. It also counted a
+boost twice when the same `Announce` reached it twice at once, which PrivaPub no longer does: a boost goes to the
+author's server once, through its shared inbox.
+
 **Pasture evidence (2026-10-03, Sharkey 2025.4.7, `tools/pasture/scenarios/sharkey.sh`):** 40 checks pass, the whole
 Misskey scenario under Sharkey's name and then what only Sharkey does:
 - its edits arrive as edits, and ours reach it;
diff --git a/tools/pasture/town/gaps.json b/tools/pasture/town/gaps.json
index d716a7f..ab84ca2 100644
--- a/tools/pasture/town/gaps.json
+++ b/tools/pasture/town/gaps.json
@@ -58,5 +58,19 @@
 		"opened": "2026-10-05",
 		"status": "open",
 		"note": "seen in the jobs table: the Create's pre-deliver job has recipientIds [] for every visibility, through the Mastodon and the native API; the Update of the same note lists the mentioned account and reaches PrivaPub"
+	},
+	{
+		"id": "G-0005",
+		"title": "Misskey keeps a post's renote count when a remote Undo{Announce} deletes the renote, so an undone boost still counts",
+		"match": {
+			"feature": "client\\.action\\.boost",
+			"origin": "misskey"
+		},
+		"kind": "peer",
+		"phase": "upstream",
+		"code": "misskey-dev/misskey packages/backend/src/core/NoteDeleteService.ts: only repliesCount is decremented on delete",
+		"opened": "2026-10-05",
+		"status": "open",
+		"note": "the renote row is gone after our Undo (checked in its database); renoteCount stays up. Sharkey decrements it."
 	}
 ]