diff --git a/docs/auth.md b/docs/auth.md
index 0faef0072..31f6056c2 100644
--- a/docs/auth.md
+++ b/docs/auth.md
@@ -153,9 +153,7 @@ If you need a session the browser cannot read, use Firebase's [session cookies](
 
 #### `beforeAuthStateChanged` from `firebase/auth`
 
-One import in the code above is deliberately different from the rest of this guide. `beforeAuthStateChanged` comes from `firebase/auth` rather than `@angular/fire/auth`. AngularFire's version keeps the app marked as busy until its callback first runs, and this callback only runs when someone signs in or out.
-
-Importing it from `@angular/fire/auth` makes `ng build` hang during route extraction and fail with a timeout. That is a bug on our side, tracked in [#3748](https://github.com/angular/angularfire/issues/3748). Once the fix lands, this can be imported from `@angular/fire/auth` like everything else.
+One import in the code above is deliberately different from the rest of this guide. `beforeAuthStateChanged` comes from `firebase/auth` rather than `@angular/fire/auth`. In AngularFire 21.0.0-rc.1 and earlier, AngularFire's version keeps the app marked as busy until its callback first runs, and this callback only runs when someone signs in or out ([#3748](https://github.com/angular/angularfire/issues/3748)).
 
 ### 3. Pass the cookie into the render
 
diff --git a/src/auth/firebase.ts b/src/auth/firebase.ts
index 743ca90d8..5d359e54d 100644
--- a/src/auth/firebase.ts
+++ b/src/auth/firebase.ts
@@ -58,7 +58,7 @@ import {
 } from 'firebase/auth';
 
 export const applyActionCode = ɵzoneWrap(_applyActionCode, true);
-export const beforeAuthStateChanged = ɵzoneWrap(_beforeAuthStateChanged, true);
+export const beforeAuthStateChanged = ɵzoneWrap(_beforeAuthStateChanged, false);
 export const checkActionCode = ɵzoneWrap(_checkActionCode, true);
 export const confirmPasswordReset = ɵzoneWrap(_confirmPasswordReset, true, 2);
 export const connectAuthEmulator = ɵzoneWrap(_connectAuthEmulator, true);
diff --git a/tools/build.ts b/tools/build.ts
index 2e5b2964f..46a1ed370 100644
--- a/tools/build.ts
+++ b/tools/build.ts
@@ -177,6 +177,8 @@ ${exportedZoneWrappedFns}
       indexedDBLocalPersistence: null,
       prodErrorMap: null,
       multiFactor: null,
+      // Its callback fires only on a sign-in or sign-out, so blocking would keep `ApplicationRef.isStable` false.
+      beforeAuthStateChanged: { blockUntilFirst: false },
       linkWithCredential: { logLevel: LogLevel.VERBOSE },
       linkWithPhoneNumber: { logLevel: LogLevel.VERBOSE },
       linkWithPopup: { logLevel: LogLevel.VERBOSE },