SPFx webpart cannot be added to the local workbench

[MSF-SP-Yasar]

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 version; latest
• SPFx version: 1.18.2

Describe the bug / error

It started on 02.10.2025 (last week), the local workbench page (/_layouts/15/workbench.aspx) does not work properly. 'Add a new web part' (+) button does not appear, just a button for adding sections.

And sometimes I can see the adding webpart button, but this time I cannot select the local or any webparts, even appear in the webpart list.

I can call 'manifests.js', but there is no workbench.html.

Steps to reproduce

1. gulp serve

Expected behavior

I can create a package and deploy, it works properly, But, cannot test and debug SPFx webparts locally.

[Ashlesha-MSFT]

Hello @MSF-SP-Yasar,
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.

[Ashlesha-MSFT]

Hello @MSF-SP-Yasar,
I tested this on my end using the same setup and was able to successfully load the local workbench and add the SPFx web part without issues.

SPFx Version: 1.18.2
Node.js Version: 18.20.4
Commands Used: gulp serve and npm run serve
Browser Tested: Microsoft Edge (latest)

It might help to try the following steps on your end:

• Ensure you're running the correct Node.js version (≥18.17.1 as required by SPFx 1.18.2)
• Clear the browser cache or try incognito mode

[gretchunkim]

I ran into a similar issue, and manually trusting http://localhost:4321 resolved it for me.

[Ashlesha-MSFT]

@MSF-SP-Yasar,
Just following up on issue. Were you able to resolve the issue on your end?

[MSF-SP-Yasar]

Hi,

I upgraded my SPFx to 1.12.1 and Node versions to v22.20 but still has the same issue. @gretchunkim thanks for your advice but it did not work for me.

[Ashlesha-MSFT]

@MSF-SP-Yasar,
Thanks for the update and for trying the suggestions.
Since you're still encountering the issue, could you please try the following steps:

• After running gulp serve, open the local workbench.
• Once it's loaded, try clicking on the “Preview” button (top-right corner) and then “Edit” again.
• Sometimes this triggers the proper loading of the web part toolbox and resolves the issue temporarily.
• Also, try doing a hard refresh (Ctrl + F5) to clear any cached scripts that might be interfering.

Let us know if this helps, or if the issue persists.