diff --git a/frontend/asset-sync-core.js b/frontend/asset-sync-core.js
index 3efa777..1339fdb 100644
--- a/frontend/asset-sync-core.js
+++ b/frontend/asset-sync-core.js
@@ -49,14 +49,13 @@
     return response ? response.json() : null;
   }
 
-  async function status(manifest, cache, { previous, activeLayout } = {}) {
+  async function status(manifest, cache, { previous, activeLayout, offline = true } = {}) {
     const found = await Promise.all(blocking(manifest, previous, activeLayout).map(async path => {
       const response = await cache.match(url(path, manifest.files[path]));
       return !!response && response.headers.get('X-Asset-Hash') === manifest.files[path].h;
     }));
     const missing = found.filter(value => !value).length;
-    const offline = await completeness(manifest, cache);
-    return { ready: missing === 0, missing, version: manifest.buildTag, ...offline };
+    return { ready: missing === 0, missing, version: manifest.buildTag, ...(offline ? await completeness(manifest, cache) : {}) };
   }
 
   // All concurrent messages/layout jobs in this worker share six download slots.
@@ -117,7 +116,7 @@
       }
     }));
     if (failure) throw failure;
-    if (!groups && !all && !(await status(manifest, cache, { previous, activeLayout })).ready) throw new Error('Incomplete blocking assets');
+    if (!groups && !all && !(await status(manifest, cache, { previous, activeLayout, offline: false })).ready) throw new Error('Incomplete blocking assets');
     return { refreshed: count, caches: 1 };
   }
 
@@ -125,12 +124,12 @@
   // Verified cache entries are the durable progress journal. Counters are rebuilt
   // after worker termination or browser eviction; never trust a stored ready bit.
   async function completeness(manifest, cache) {
-    const missingFiles = [];
-    for (const path of paths(manifest)) {
+    const files = paths(manifest);
+    const missingFiles = (await Promise.all(files.map(async path => {
       const response = await cache.match(url(path, manifest.files[path]));
-      if (!response || response.headers.get('X-Asset-Hash') !== manifest.files[path].h) missingFiles.push(path);
-    }
-    const total = paths(manifest).length;
+      return !response || response.headers.get('X-Asset-Hash') !== manifest.files[path].h ? path : null;
+    }))).filter(Boolean);
+    const total = files.length;
     return { offlineReady: missingFiles.length === 0, cached: total - missingFiles.length, total, missingFiles };
   }
 
@@ -167,7 +166,7 @@
 
   async function commit(manifest, cache, { previousClients, activeLayout } = {}) {
     const old = await state(cache);
-    if (!(await status(manifest, cache, { previous: old?.current, activeLayout })).ready) {
+    if (!(await status(manifest, cache, { previous: old?.current, activeLayout, offline: false })).ready) {
       throw new Error('Incomplete blocking assets');
     }
     const sameBuild = old?.current?.buildTag === manifest.buildTag;
diff --git a/frontend/asset-sync-core.test.js b/frontend/asset-sync-core.test.js
index 7eb64ec..371864b 100644
--- a/frontend/asset-sync-core.test.js
+++ b/frontend/asset-sync-core.test.js
@@ -81,3 +81,11 @@ test('overlapping layout and completion jobs share a six-download ceiling',async
  await Promise.all([core.complete(m,{cache:c,fetchFn}),core.syncAssets(m,{cache:c,fetchFn,groups:['extra']})]);
  assert.ok(peak<=6);assert.ok([...calls.values()].every(count=>count===1));
 });
+
+test('blocking commit never waits on an optional file readiness probe',{timeout:1000},async()=>{
+ const c=cache(),m=manifest();m.files['/extra.js']={h:'extra'};m.groups.extra={files:['/extra.js'],background:true,contract:1};
+ await c.put('/a.js?v=a',response('a'));await c.put('/index.html?v=b',response('b'));
+ const match=c.match;let extraProbes=0;c.match=async key=>{if(key==='/extra.js?v=extra'){extraProbes++;return new Promise(()=>{});}return match(key);};
+ await core.commit(m,c);assert.equal(extraProbes,0);assert.equal((await core.state(c)).current.buildTag,m.buildTag);
+ c.match=match;assert.equal((await core.status(m,c)).offlineReady,false);
+});