diff --git a/src/components/NoteCard.tsx b/src/components/NoteCard.tsx
index 831588bd..530b0109 100644
--- a/src/components/NoteCard.tsx
+++ b/src/components/NoteCard.tsx
@@ -226,14 +226,14 @@ export function NoteCard({ event, className, repostedBy, compact, threaded, thre
     const pTags = event.tags.filter(([name, , , marker]) => name === 'p' && marker !== 'mention');
     
     if (pTags.length > 0) {
-      // Remove duplicates and return pubkeys
-      return [...new Set(pTags.map(([, pubkey]) => pubkey))];
+      // Remove duplicates and filter out undefined/empty pubkeys
+      return [...new Set(pTags.map(([, pubkey]) => pubkey).filter(Boolean))] as string[];
     }
     
     // Fallback: if all p tags are mentions, use all p tags anyway
     const allPTags = event.tags.filter(([name]) => name === 'p');
     if (allPTags.length > 0) {
-      return [...new Set(allPTags.map(([, pubkey]) => pubkey))];
+      return [...new Set(allPTags.map(([, pubkey]) => pubkey).filter(Boolean))] as string[];
     }
 
     // Self-reply fallback: when replying to own post, no p tags are added (the
diff --git a/src/components/ReplyContext.tsx b/src/components/ReplyContext.tsx
index e1d1b085..6bce81e2 100644
--- a/src/components/ReplyContext.tsx
+++ b/src/components/ReplyContext.tsx
@@ -21,8 +21,10 @@ interface ReplyContextProps {
  * Used consistently across NoteCard and notification views.
  */
 export function ReplyContext({ pubkeys, parentEventId, className }: ReplyContextProps) {
+  // Filter out any undefined/empty pubkeys defensively
+  const validPubkeys = pubkeys.filter(Boolean);
   // Show max 2 authors for cleaner UI
-  const displayPubkeys = pubkeys.slice(0, 2);
+  const displayPubkeys = validPubkeys.slice(0, 2);
 
   const replyingToLabel = parentEventId ? (
     <HoverCard openDelay={300} closeDelay={150}>
@@ -52,9 +54,9 @@ export function ReplyContext({ pubkeys, parentEventId, className }: ReplyContext
           {index < displayPubkeys.length - 1 && <span className="shrink-0">and</span>}
         </span>
       ))}
-      {pubkeys.length > 2 && (
+      {validPubkeys.length > 2 && (
         <span className="text-muted-foreground shrink-0">
-          and {pubkeys.length - 2} other{pubkeys.length - 2 !== 1 ? 's' : ''}
+          and {validPubkeys.length - 2} other{validPubkeys.length - 2 !== 1 ? 's' : ''}
         </span>
       )}
     </div>