harden proxy auth and event ordering

crates/chat_ui/src/lib.rs

@@ -598,16 +598,23 @@ impl ChatPanel {
             return;
         }
 
+        let content = SharedString::from(&event.content);
         let emojis = emojis_from_tags(&event.tags);
+
         let image = Message::reaction_image(&event.content, &emojis)
             .map(|url| SharedUri::from(url.to_string()));
 
         for id in event.tags.event_ids() {
-            self.reactions.entry(id).or_default().push((
-                SharedString::from(&event.content),
-                image.clone(),
-                event.pubkey,
-            ));
+            let entries = self.reactions.entry(id).or_default();
+            // NIP-25: a newer reaction by the same author replaces their previous one
+            if let Some(existing) = entries
+                .iter_mut()
+                .find(|(_, _, author)| *author == event.pubkey)
+            {
+                *existing = (content.clone(), image.clone(), event.pubkey);
+            } else {
+                entries.push((content.clone(), image.clone(), event.pubkey));
+            }
         }
 
         cx.notify();