diff --git a/.changeset/olive-paws-divide.md b/.changeset/olive-paws-divide.md
new file mode 100644
index 0000000000..688b6025bf
--- /dev/null
+++ b/.changeset/olive-paws-divide.md
@@ -0,0 +1,5 @@
+---
+'@backstage/frontend-app-api': patch
+---
+
+Updated `app.extensions` configuration schema.
diff --git a/packages/frontend-app-api/config.d.ts b/packages/frontend-app-api/config.d.ts
index 9ec020fa56..28355f5376 100644
--- a/packages/frontend-app-api/config.d.ts
+++ b/packages/frontend-app-api/config.d.ts
@@ -34,17 +34,17 @@ export interface Config {
     /**
      * @deepVisibility frontend
      */
-    extensions?:
+    extensions?: Array<
       | string
       | {
           [extensionId: string]:
             | boolean
-            | string
             | {
-                at?: string;
-                extension?: string;
+                attachTo?: { id: string; input: string };
+                disabled?: boolean;
                 config?: unknown;
               };
-        };
+        }
+    >;
   };
 }