diff --git a/deploy/litestream.yml b/deploy/litestream.yml
index 402a143..93b3b5c 100644
--- a/deploy/litestream.yml
+++ b/deploy/litestream.yml
@@ -16,3 +16,22 @@ dbs:
         sync-interval: 60s
         retention: 720h
         snapshot-interval: 24h
+
+  # Contributor registry: a complementary seed list for rebuilding from PDSes.
+  - path: /var/lib/lichen/registry.db
+    replicas:
+      - type: file
+        path: /var/lib/lichen/backups-registry
+        sync-interval: 10s
+        retention: 2160h
+        snapshot-interval: 24h
+
+      - type: s3
+        bucket: lichen-backups
+        path: registry
+        endpoint: https://${LITESTREAM_R2_ACCOUNT_ID}.r2.cloudflarestorage.com
+        access-key-id: ${LITESTREAM_R2_ACCESS_KEY_ID}
+        secret-access-key: ${LITESTREAM_R2_SECRET_ACCESS_KEY}
+        sync-interval: 60s
+        retention: 720h
+        snapshot-interval: 24h
diff --git a/src/lib/orchestrators/bookmark.ts b/src/lib/orchestrators/bookmark.ts
index 67f6e52..a462fa9 100644
--- a/src/lib/orchestrators/bookmark.ts
+++ b/src/lib/orchestrators/bookmark.ts
@@ -15,6 +15,9 @@ export async function addBookmarkAction(
 	wikiAtUri: string,
 	session: Session | null,
 ): Promise<void> {
+	// Idempotent: never mint a second record for an already-bookmarked wiki.
+	if (getBookmarkAtUri(did, wikiAtUri)) return;
+
 	const now = new Date().toISOString();
 	const tid = TID.now();
 	const atUri = `at://${did}/${COLLECTIONS.bookmark}/${tid}`;
diff --git a/src/lib/orchestrators/membership.ts b/src/lib/orchestrators/membership.ts
index ce3e205..4b56ffc 100644
--- a/src/lib/orchestrators/membership.ts
+++ b/src/lib/orchestrators/membership.ts
@@ -10,6 +10,7 @@ import {
 	deleteRequest,
 	getMembership,
 	getMembershipAtUri,
+	getRequest,
 	upsertMembership,
 	upsertRequest,
 } from "../../server/db/queries/index.ts";
@@ -28,6 +29,10 @@ export async function requestAccessAction(
 	}
 
 	const session = ctx.session;
+
+	// Idempotent: never mint a second record for an already-pending request.
+	if (getRequest(ctx.wiki.at_uri, session.did)) return;
+
 	const now = new Date().toISOString();
 	const tid = TID.now();
 	const atUri = `at://${session.did}/wiki.lichen.memberRequest/${tid}`;
diff --git a/tests/lib/orchestrators/bookmark.test.ts b/tests/lib/orchestrators/bookmark.test.ts
index 97d0f41..751001d 100644
--- a/tests/lib/orchestrators/bookmark.test.ts
+++ b/tests/lib/orchestrators/bookmark.test.ts
@@ -73,6 +73,18 @@ describe("addBookmarkAction", () => {
 		).rejects.toBeInstanceOf(PdsWriteError);
 		expect(isBookmarked(USER_DID, WIKI_AT_URI)).toBe(false);
 	});
+
+	test("re-adding an already-bookmarked wiki writes no second PDS record", async () => {
+		const db = getDb();
+		db.run("DELETE FROM bookmarks WHERE did = ?", [USER_DID]);
+		mockWriteBookmarkRecord.mockClear();
+
+		await addBookmarkAction(USER_DID, WIKI_AT_URI, session);
+		await addBookmarkAction(USER_DID, WIKI_AT_URI, session);
+
+		expect(mockWriteBookmarkRecord).toHaveBeenCalledTimes(1);
+		expect(isBookmarked(USER_DID, WIKI_AT_URI)).toBe(true);
+	});
 });
 
 describe("deleteBookmarkAction", () => {
diff --git a/tests/lib/orchestrators/membership.test.ts b/tests/lib/orchestrators/membership.test.ts
index e47aa58..e3d50df 100644
--- a/tests/lib/orchestrators/membership.test.ts
+++ b/tests/lib/orchestrators/membership.test.ts
@@ -148,6 +148,21 @@ describe("requestAccessAction", () => {
 			PdsWriteError,
 		);
 	});
+
+	test("re-requesting access writes no second PDS record", async () => {
+		mockWriteMemberRequestRecord.mockClear();
+
+		const ctx = makeCtx({
+			session: { did: "did:plc:dup-requester", handle: "dup.bsky.social" },
+			did: "did:plc:dup-requester",
+			access: "none",
+		});
+
+		await requestAccessAction(ctx);
+		await requestAccessAction(ctx);
+
+		expect(mockWriteMemberRequestRecord).toHaveBeenCalledTimes(1);
+	});
 });
 
 describe("approveMemberAction", () => {