diff --git a/desktop/src/features/messages/hooks.ts b/desktop/src/features/messages/hooks.ts
index 3d07f40834..478878b939 100644
--- a/desktop/src/features/messages/hooks.ts
+++ b/desktop/src/features/messages/hooks.ts
@@ -38,6 +38,7 @@ import {
   MIN_TOP_LEVEL_ROWS_PER_FETCH,
   pageOlderMessagesUntilRowFloor,
 } from "@/features/messages/lib/pageOlderMessages";
+import { isDuplicateReactionError } from "@/features/pulse/lib/noteActions";
 import {
   KIND_REACTION,
   KIND_STREAM_MESSAGE,
@@ -575,7 +576,18 @@ export function useToggleReactionMutation() {
         emoji,
         queryClient.getQueryData<CustomEmoji[]>(customEmojiQueryKey),
       );
-      await addReaction(eventId, emoji, emojiUrl);
+      try {
+        await addReaction(eventId, emoji, emojiUrl);
+      } catch (error) {
+        // The relay already has this reaction (its `e`-only kind:7 never came
+        // back over the `#h` live sub, so the cache didn't render it and the
+        // user clicked again — Tyler's exact repro). That's idempotent
+        // success: swallow it so onError doesn't roll back the optimistic
+        // write and leave us back at "duplicate but nothing visible".
+        if (!isDuplicateReactionError(error)) {
+          throw error;
+        }
+      }
     },
     onError: (_error, _variables, context) => {
       if (context) {
diff --git a/desktop/src/features/messages/lib/optimisticReaction.test.mjs b/desktop/src/features/messages/lib/optimisticReaction.test.mjs
index a974f31dbd..d4d19b5e4e 100644
--- a/desktop/src/features/messages/lib/optimisticReaction.test.mjs
+++ b/desktop/src/features/messages/lib/optimisticReaction.test.mjs
@@ -4,6 +4,7 @@ import test from "node:test";
 import { createOptimisticReaction } from "./optimisticReaction.ts";
 import { formatTimelineMessages } from "./formatTimelineMessages.ts";
 import { sortMessages } from "./messageQueryKeys.ts";
+import { isDuplicateReactionError } from "@/features/pulse/lib/noteActions";
 import { KIND_REACTION } from "@/shared/constants/kinds";
 
 const CHANNEL_ID = "36411e44-0e2d-4cfe-bd6e-567eb169db9f";
@@ -101,3 +102,24 @@ test("custom-emoji optimistic reaction carries the NIP-30 emoji tag", () => {
   );
   assert.equal(optimistic.content, ":party:");
 });
+
+test("duplicate-on-add is recognized so the optimistic write is kept, not rolled back", () => {
+  // Tyler's exact repro: the relay already holds the reactor's ✅ (it never
+  // came back over the `#h` live sub, so the cache didn't render it). Clicking
+  // again writes the optimistic reaction, then `addReaction` rejects with the
+  // relay's duplicate message. useToggleReactionMutation swallows precisely
+  // this error so onError never runs and the optimistic reaction survives —
+  // turning "duplicate but nothing visible" into a rendered ✅. This pins the
+  // relay error string that swallow depends on; if it drifts, the bug returns.
+  const relayDuplicate = new Error(
+    "relay rejected event: duplicate: reaction already exists",
+  );
+  assert.equal(isDuplicateReactionError(relayDuplicate), true);
+
+  // Any other failure must still propagate (onError rolls back) — we only
+  // treat duplicate-on-add as idempotent success.
+  assert.equal(
+    isDuplicateReactionError(new Error("relay rejected event: rate-limited")),
+    false,
+  );
+});