fix: hang when navigating to about:blank (#31634)

cli/CHANGELOG.md

@@ -10,6 +10,7 @@ _Released 5/6/2025 (PENDING)_
 **Bugfixes:**
 
 - Fixed an issue where the configuration setting `trashAssetsBeforeRuns=false` was ignored for assets in the `videosFolder`. These assets were incorrectly deleted before running tests with `cypress run`. Addresses [#8280](https://github.com/cypress-io/cypress/issues/8280).
+- Fixed a potential hang condition when navigating to `about:blank`. Addressed in [#31634](https://github.com/cypress-io/cypress/pull/31634).
 
 **Misc:**
 

packages/app/src/runner/aut-iframe.ts

@@ -129,8 +129,6 @@ export class AutIframe {
         return
       }
 
-      this.$iframe[0].src = 'about:blank'
-
       this.$iframe.one('load', () => {
         if (testIsolation) {
           this._showTestIsolationBlankPage()
@@ -140,6 +138,8 @@ export class AutIframe {
 
         resolve()
       })
+
+      this.$iframe[0].src = 'about:blank'
     })
   }