diff --git a/apps/desktop/src/hooks/useSoundboardSync.ts b/apps/desktop/src/hooks/useSoundboardSync.ts
new file mode 100644
index 0000000..512b8dc
--- /dev/null
+++ b/apps/desktop/src/hooks/useSoundboardSync.ts
@@ -0,0 +1,276 @@
+import { useEffect, useRef, useState } from 'react';
+
+import { getCryptoBackend } from '@chat-app/shared/crypto';
+import {
+  decryptSoundEnvelope,
+  downloadSoundCiphertext,
+  encryptSoundBlob,
+  listOwnSounds,
+  type RemoteSound,
+  upsertSound,
+  uploadSoundCiphertext,
+} from '@chat-app/shared/chat';
+
+import { useAuth } from '../context/AuthContext';
+import {
+  deleteRawStoredSound,
+  getRawStoredSound,
+  listSounds,
+  putRawStoredSound,
+  type SoundboardEntry,
+  subscribeSoundboardChanges,
+} from '../lib/soundboardStorage';
+import { supabase } from '../lib/supabase';
+import { cachedUserKey } from '../lib/userIdentity';
+
+export type SyncBadge = 'synced' | 'uploading' | 'downloading' | 'error';
+
+const PUSH_DEBOUNCE_MS = 500;
+const DELETE_GRACE_MS = 5000;
+
+function storagePathFor(userId: string, soundId: string): string {
+  return userId + '/' + soundId + '.bin';
+}
+
+export function useSoundboardSync(): {
+  badges: Map<string, SyncBadge>;
+  initialPullDone: boolean;
+} {
+  const { session } = useAuth();
+  const userId = session?.user.id ?? null;
+  const [badges, setBadges] = useState<Map<string, SyncBadge>>(new Map());
+  const [initialPullDone, setInitialPullDone] = useState(false);
+  const debounceRef = useRef<number | null>(null);
+
+  function setBadge(id: string, badge: SyncBadge): void {
+    setBadges((cur) => {
+      const next = new Map(cur);
+      next.set(id, badge);
+      return next;
+    });
+  }
+
+  useEffect(() => {
+    if (!userId) {
+      setInitialPullDone(false);
+      setBadges(new Map());
+      return;
+    }
+    let cancelled = false;
+    let teardown: (() => void) | null = null;
+
+    const init = async () => {
+      const priv = await cachedUserKey(userId);
+      if (!priv) return;
+      const pub = getCryptoBackend().scalarMultBase(priv);
+
+      try {
+        await runDiff(userId, priv, pub);
+      } catch (err) {
+        console.error('soundboard initial diff failed', err);
+      }
+      if (cancelled) return;
+      setInitialPullDone(true);
+
+      const unsubLocal = subscribeSoundboardChanges(() => {
+        if (debounceRef.current !== null) window.clearTimeout(debounceRef.current);
+        debounceRef.current = window.setTimeout(() => {
+          debounceRef.current = null;
+          void runDiff(userId, priv, pub).catch((err) => {
+            console.error('soundboard push diff failed', err);
+          });
+        }, PUSH_DEBOUNCE_MS);
+      });
+
+      const channel = supabase
+        .channel('soundboards:' + userId)
+        .on(
+          'postgres_changes',
+          {
+            event: '*',
+            schema: 'public',
+            table: 'user_soundboards',
+            filter: 'user_id=eq.' + userId,
+          },
+          () => {
+            void runDiff(userId, priv, pub).catch((err) => {
+              console.error('soundboard realtime pull failed', err);
+            });
+          },
+        )
+        .subscribe();
+
+      teardown = () => {
+        unsubLocal();
+        void supabase.removeChannel(channel);
+        if (debounceRef.current !== null) {
+          window.clearTimeout(debounceRef.current);
+          debounceRef.current = null;
+        }
+      };
+    };
+
+    void init();
+    return () => {
+      cancelled = true;
+      teardown?.();
+    };
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [userId]);
+
+  async function runDiff(uid: string, priv: Uint8Array, pub: Uint8Array): Promise<void> {
+    const [localList, remoteList] = await Promise.all([
+      listSounds(),
+      listOwnSounds(supabase),
+    ]);
+    const remoteById = new Map<string, RemoteSound>();
+    for (const r of remoteList) remoteById.set(r.id, r);
+    const localById = new Map<string, SoundboardEntry>();
+    for (const l of localList) localById.set(l.id, l);
+
+    // Push pass
+    for (const local of localList) {
+      const remote = remoteById.get(local.id);
+      const localIso = new Date(local.updatedAt).toISOString();
+      if (!remote) {
+        await uploadAndUpsert(local, uid, priv, pub, localIso);
+      } else {
+        const remoteMs = Date.parse(remote.updatedAt);
+        if (local.updatedAt > remoteMs) {
+          await upsertMetadataOnly(local, remote, localIso);
+        }
+      }
+    }
+
+    // Pull pass
+    for (const remote of remoteList) {
+      const local = localById.get(remote.id);
+      const remoteMs = Date.parse(remote.updatedAt);
+      if (!local) {
+        await pullAndStore(remote, priv, pub);
+      } else if (remoteMs > local.updatedAt) {
+        const stored = await getRawStoredSound(remote.id);
+        if (stored) {
+          await putRawStoredSound({
+            ...stored,
+            name: remote.name,
+            mime: remote.mime,
+            size: remote.size,
+            category: remote.category,
+            hotkey: remote.hotkey,
+            gain: remote.gain,
+            order: remote.sortOrder,
+            updatedAt: remoteMs,
+          });
+          setBadge(remote.id, 'synced');
+        }
+      } else {
+        setBadge(remote.id, 'synced');
+      }
+    }
+
+    // Remote-absence → local delete (with grace window for fresh adds).
+    const now = Date.now();
+    for (const local of localList) {
+      if (!remoteById.has(local.id) && now - local.updatedAt > DELETE_GRACE_MS) {
+        await deleteRawStoredSound(local.id);
+      }
+    }
+  }
+
+  async function uploadAndUpsert(
+    local: SoundboardEntry,
+    uid: string,
+    priv: Uint8Array,
+    pub: Uint8Array,
+    localIso: string,
+  ): Promise<void> {
+    setBadge(local.id, 'uploading');
+    try {
+      const stored = await getRawStoredSound(local.id);
+      if (!stored) return;
+      const ciphertext = await encryptSoundBlob(stored.blob, pub, priv);
+      const path = storagePathFor(uid, local.id);
+      await uploadSoundCiphertext(supabase, path, ciphertext);
+      await upsertSound(supabase, {
+        id: local.id,
+        name: local.name,
+        mime: local.mime,
+        size: local.size,
+        category: local.category,
+        hotkey: local.hotkey,
+        gain: local.gain,
+        sortOrder: local.order,
+        storagePath: path,
+        updatedAtIso: localIso,
+      });
+      setBadge(local.id, 'synced');
+    } catch (err) {
+      console.error('soundboard upload failed', err);
+      setBadge(local.id, 'error');
+    }
+  }
+
+  async function upsertMetadataOnly(
+    local: SoundboardEntry,
+    remote: RemoteSound,
+    localIso: string,
+  ): Promise<void> {
+    setBadge(local.id, 'uploading');
+    try {
+      await upsertSound(supabase, {
+        id: local.id,
+        name: local.name,
+        mime: local.mime,
+        size: local.size,
+        category: local.category,
+        hotkey: local.hotkey,
+        gain: local.gain,
+        sortOrder: local.order,
+        storagePath: remote.storagePath,
+        updatedAtIso: localIso,
+      });
+      setBadge(local.id, 'synced');
+    } catch (err) {
+      console.error('soundboard metadata upload failed', err);
+      setBadge(local.id, 'error');
+    }
+  }
+
+  async function pullAndStore(
+    remote: RemoteSound,
+    priv: Uint8Array,
+    pub: Uint8Array,
+  ): Promise<void> {
+    setBadge(remote.id, 'downloading');
+    try {
+      const envelope = await downloadSoundCiphertext(supabase, remote.storagePath);
+      const plain = await decryptSoundEnvelope(envelope, pub, priv);
+      // Copy into a fresh ArrayBuffer so Blob accepts it across TS lib variants
+      // (mirrors the pattern in @chat-app/shared/chat/attachments.ts).
+      const copy = new Uint8Array(plain.byteLength);
+      copy.set(plain);
+      const blob = new Blob([copy.buffer], { type: remote.mime });
+      const ms = Date.parse(remote.updatedAt);
+      await putRawStoredSound({
+        id: remote.id,
+        name: remote.name,
+        mime: remote.mime,
+        size: remote.size,
+        category: remote.category,
+        hotkey: remote.hotkey,
+        gain: remote.gain,
+        order: remote.sortOrder,
+        createdAt: Date.parse(remote.createdAt),
+        updatedAt: ms,
+        blob,
+      });
+      setBadge(remote.id, 'synced');
+    } catch (err) {
+      console.error('soundboard pull failed', err);
+      setBadge(remote.id, 'error');
+    }
+  }
+
+  return { badges, initialPullDone };
+}
diff --git a/apps/desktop/src/lib/soundboardStorage.ts b/apps/desktop/src/lib/soundboardStorage.ts
index d4a028d..fae6d52 100644
--- a/apps/desktop/src/lib/soundboardStorage.ts
+++ b/apps/desktop/src/lib/soundboardStorage.ts
@@ -369,3 +369,52 @@ export async function isHotkeyTaken(
   }
   return false;
 }
+
+// --- Sync-engine bypass helpers ------------------------------------------
+// Used by useSoundboardSync to write/delete IndexedDB rows without firing
+// notifyChange — pulls and remote-driven deletes are not "edits". If they
+// triggered notifyChange the engine would loop:
+//   push debounce → upsert → realtime → pull → notifyChange → push debounce → ...
+
+export async function putRawStoredSound(stored: {
+  id: string;
+  name: string;
+  mime: string;
+  size: number;
+  category: string | null;
+  hotkey: string | null;
+  gain: number;
+  order: number;
+  createdAt: number;
+  updatedAt: number;
+  blob: Blob;
+}): Promise<void> {
+  await tx(SOUNDS_STORE, 'readwrite', (s) => s.put(stored));
+}
+
+export async function deleteRawStoredSound(id: string): Promise<void> {
+  await tx(SOUNDS_STORE, 'readwrite', (s) => s.delete(id));
+}
+
+export async function getRawStoredSound(id: string): Promise<{
+  id: string;
+  name: string;
+  mime: string;
+  size: number;
+  category: string | null;
+  hotkey: string | null;
+  gain: number;
+  order: number;
+  createdAt: number;
+  updatedAt: number;
+  blob: Blob;
+} | null> {
+  const db = await openDb();
+  return new Promise((resolve, reject) => {
+    const t = db.transaction(SOUNDS_STORE, 'readonly');
+    const s = t.objectStore(SOUNDS_STORE);
+    const req = s.get(id);
+    req.onsuccess = () => resolve((req.result as any) ?? null);
+    req.onerror = () => reject(req.error);
+  });
+}