Unable to test application customizer

[pfrowe]

Target SharePoint environment

SharePoint Online

What SharePoint development model, framework, SDK or API is this about?

💥 SharePoint Framework

Developer environment

Windows

What browser(s) / client(s) have you tested

• 💥 Internet Explorer
• 💥 Microsoft Edge
• 💥 Google Chrome
• 💥 FireFox
• 💥 Safari
• mobile (iOS/iPadOS)
• mobile (Android)
• not applicable
• other (enter in the "Additional environment details" area below)

Additional environment details

Browser versions

• Chrome: 146.0.7680.80 (Official Build) (64-bit)
• Edge: 146.0.3856.62 (Official build) (64-bit)
• Firefox: 148.0.2 (64-bit)

Framework versions

• I originally encountered this issue debugging an application customizer with:
  • SPFx 1.21.1
  • Node 22.21.1
• I downloaded the latest version of Yeoman and the SharePoint Generator and created a new application customizer with:
  • SPFx 1.22.2
  • Node 22.22.1

Describe the bug / error

Chrome and Edge do not load my application customizer when I execute gulp serve (SPFx 1.21.1) or heft start (SPFx 1.22.2). I get an error message in the console that reads Custom action component ids are specified by query parameters but matching manifests cannot be found. Ids: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx (where xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx is the GUID found in my package-solution.json file).

Initially, when I loaded the page in Firefox (which I haven't used in a while), it presented me with the dialog asking whether I wanted to load the debug manifest files. Edge was doing that last week (13 Mar 2026) but never prompted me to do that today (16 Mar 2026). After I clicked the button confirming that I wanted to load the debug manifest files, I was immediately redirected to an error page. When I went back to the debugging page, I was no longer presented with the dialog and Firefox started behaving as Chrome and Edge: not attempting to load the manifests.js file from localhost, not presenting the dialog, and reporting the error quoted above.

Steps to reproduce

1. Walk the steps to create a new SharePoint application customizer extension.
2. Execute npm run start in the VS Code console.

Expected behavior

• I expect to be presented with the dialog confirming that I want to load the debug manifest files.
• I expect to see a network request for the manifests.js file served from localhost.
• I expect to see my code in the Sources tab of the DevTools window.
• I expect to see my application customizer displayed where appropriate.

[Ashlesha-MSFT]

Hello @pfrowe ,
Thank you for bringing this issue to our attention. We will look into it and get back to you shortly.
If you don’t receive a reply within two working days, please use this escalation form to escalate.

[mariafredrikson]

I have exactly the same problem (using heft start).

[mike-kube]

I had the same issue. It was working fine a few days ago, but then it suddenly stopped working.
heft 1.1.2
spfx 1.22.2
node 22

[Ashlesha-MSFT]

@pfrowe,
We have successfully reproduced this issue on our environment using SPFx 1.21.1 / 1.22.2 with Node 22.x on Windows and macOS.
The application customizer / debug manifests fail to load across multiple browsers, consistent with the reported behavior.
We acknowledge this appears to be the same underlying bug confirmed in #10715.

[VesaJuvonen]

We will be providing updates on this at the #10715 as this is a duplicate. Let's keep this still open as the title is good catcher for the situation. Far from optimal situation for sure.

We'll provide updates as we can on this. If you have any option to raise "Premier Support" tickets on this through Microsoft channels - please do as that helps on moving things forward faster and ensures higher visibility for the issues - which helps on prioritization.

[VesaJuvonen]

Issue should be now resolved as concluded in the #10715 with confirmed comments. I'll close this and keep the other open for a while.