diff --git a/src/components/CommunityDetailPage.tsx b/src/components/CommunityDetailPage.tsx
index e89d9d51..5d6894c5 100644
--- a/src/components/CommunityDetailPage.tsx
+++ b/src/components/CommunityDetailPage.tsx
@@ -176,7 +176,7 @@ export function CommunityDetailPage({ event }: { event: NostrEvent }) {
   } = useCommunityBookmarks();
   const bookmarked = !!communityATag && isCommunityBookmarked(communityATag);
   const handleToggleBookmark = useCallback(() => {
-    if (!user || !communityATag) return;
+    if (!user || !communityATag || toggleCommunityBookmark.isPending) return;
     toggleCommunityBookmark.mutate({ aTag: communityATag });
   }, [user, communityATag, toggleCommunityBookmark]);
 
@@ -376,10 +376,12 @@ export function CommunityDetailPage({ event }: { event: NostrEvent }) {
         )}
         {user && communityATag && (
           <button
-            className="p-2 rounded-full hover:bg-secondary/60 transition-colors"
+            className="p-2 rounded-full hover:bg-secondary/60 transition-colors disabled:opacity-50 disabled:pointer-events-none"
             onClick={handleToggleBookmark}
+            disabled={toggleCommunityBookmark.isPending}
             aria-label={bookmarked ? 'Remove community bookmark' : 'Bookmark community'}
             aria-pressed={bookmarked}
+            aria-busy={toggleCommunityBookmark.isPending}
           >
             <Bookmark className={cn('size-5', bookmarked && 'fill-current')} />
           </button>
diff --git a/src/hooks/useCommunityBookmarks.ts b/src/hooks/useCommunityBookmarks.ts
index c0d18a7e..07f3001e 100644
--- a/src/hooks/useCommunityBookmarks.ts
+++ b/src/hooks/useCommunityBookmarks.ts
@@ -5,11 +5,22 @@ import { useCurrentUser } from './useCurrentUser';
 import { useNostrPublish } from './useNostrPublish';
 import { fetchFreshEvent } from '@/lib/fetchFreshEvent';
 import { COMMUNITY_DEFINITION_KIND } from '@/lib/communityUtils';
+import { parseATagCoordinate } from '@/lib/nostrEvents';
 import { toast } from '@/hooks/useToast';
 
 /** NIP-51 Communities list — kind 10004. */
 export const COMMUNITIES_LIST_KIND = 10004;
 
+const HEX_PUBKEY_RE = /^[0-9a-f]{64}$/i;
+
+/** Parse and validate a NIP-51 community list coordinate. */
+export function parseCommunityBookmarkATag(aTag: string): { pubkey: string; dTag: string } | undefined {
+  const coord = parseATagCoordinate(aTag);
+  if (!coord || coord.kind !== COMMUNITY_DEFINITION_KIND) return undefined;
+  if (!HEX_PUBKEY_RE.test(coord.pubkey) || !coord.identifier) return undefined;
+  return { pubkey: coord.pubkey, dTag: coord.identifier };
+}
+
 /**
  * Hook to manage the user's NIP-51 Communities list (kind 10004).
  *
@@ -42,7 +53,7 @@ export function useCommunityBookmarks() {
   // Extract bookmarked community a-tags (only `34550:` coordinates)
   const bookmarkedATags: string[] = (listQuery.data?.tags ?? [])
     .filter(([name, value]) =>
-      name === 'a' && typeof value === 'string' && value.startsWith(`${COMMUNITY_DEFINITION_KIND}:`),
+      name === 'a' && typeof value === 'string' && !!parseCommunityBookmarkATag(value),
     )
     .map(([, value]) => value);
 
diff --git a/src/hooks/useMyCommunities.ts b/src/hooks/useMyCommunities.ts
index 22430196..7ff047c2 100644
--- a/src/hooks/useMyCommunities.ts
+++ b/src/hooks/useMyCommunities.ts
@@ -3,7 +3,7 @@ import { useNostr } from '@nostrify/react';
 import { useQuery } from '@tanstack/react-query';
 
 import { useCurrentUser } from './useCurrentUser';
-import { COMMUNITIES_LIST_KIND } from './useCommunityBookmarks';
+import { COMMUNITIES_LIST_KIND, parseCommunityBookmarkATag } from './useCommunityBookmarks';
 import {
   COMMUNITY_DEFINITION_KIND,
   BADGE_AWARD_KIND,
@@ -108,44 +108,34 @@ export function useMyCommunities() {
         .filter(([n, v]) =>
           n === 'a'
           && typeof v === 'string'
-          && v.startsWith(`${COMMUNITY_DEFINITION_KIND}:`),
+          && !!parseCommunityBookmarkATag(v),
         )
         .map(([, v]) => v);
 
       // Group bookmarked coords by author pubkey: author -> Set<d-tag>
       const coordsByAuthor = new Map<string, Set<string>>();
       for (const coord of bookmarkedCoords) {
-        // Format: "34550:<pubkey>:<d-tag>" -- d-tag may itself contain ":"
-        const firstColon = coord.indexOf(':');
-        const secondColon = coord.indexOf(':', firstColon + 1);
-        if (firstColon === -1 || secondColon === -1) continue;
-        const authorPubkey = coord.slice(firstColon + 1, secondColon);
-        const dTag = coord.slice(secondColon + 1);
-        if (!authorPubkey || !dTag) continue;
-        const existing = coordsByAuthor.get(authorPubkey);
+        const parsed = parseCommunityBookmarkATag(coord);
+        if (!parsed) continue;
+        const existing = coordsByAuthor.get(parsed.pubkey);
         if (existing) {
-          existing.add(dTag);
+          existing.add(parsed.dTag);
         } else {
-          coordsByAuthor.set(authorPubkey, new Set([dTag]));
+          coordsByAuthor.set(parsed.pubkey, new Set([parsed.dTag]));
         }
       }
 
       let bookmarkedCommunityEvents: NostrEvent[] = [];
       if (coordsByAuthor.size > 0) {
-        const bookmarkQueries = await Promise.all(
-          Array.from(coordsByAuthor.entries()).map(([authorPubkey, dTags]) =>
-            nostr.query(
-              [{
-                kinds: [COMMUNITY_DEFINITION_KIND],
-                authors: [authorPubkey],
-                '#d': [...dTags],
-                limit: dTags.size,
-              }],
-              { signal: combinedSignal },
-            ),
-          ),
+        bookmarkedCommunityEvents = await nostr.query(
+          Array.from(coordsByAuthor.entries()).map(([authorPubkey, dTags]) => ({
+            kinds: [COMMUNITY_DEFINITION_KIND],
+            authors: [authorPubkey],
+            '#d': [...dTags],
+            limit: dTags.size,
+          })),
+          { signal: combinedSignal },
         );
-        bookmarkedCommunityEvents = bookmarkQueries.flat();
       }
 
       const bookmarkedATagSet = new Set(bookmarkedCoords);