[6.x]: Unable to add matrix blocks within matrix field

[DenyEs]

What happened?

Description

I created a "Body Content" matrix block with a "Body" matrix block, however when I add the first Body Content block, it just keeps spinning and won't let me add any body blocks at all. This breaks only when I choose the View mode to be "blocks", when it's "cards", it works as expected. Unfortunately it doesn't trigger any errors I can see in a console or network tab

Steps to reproduce

1. Create a matrix within a matrix field and set both fields view mode to be "blocks"
2. Add to an entry type
3. Try to add blocks

Expected behavior

Block are added as per Craft 5

Actual behavior

CMS won't let me add any blocks

Craft CMS version

6.0.0-alpha9

PHP version

8.5

Operating system and version

macOS 26.5.1

Database type and version

MySQL 8.4.6

Image driver and version

No response

Installed plugins and versions

[linear-code]

CMS-2243

[brandonkelly]

Are you getting any JavaScript errors or 500 Ajax responses after pressing the button?

If a 500 response, please find the corresponding error in storage/logs and post the full error message and stack trace.

[DenyEs]

I am getting some console errors but I also get these when I am not on an entry type using this field.

The stylesheet https://craft-6.test/vendor/craft/legacy/tailwindreset/dist/tailwind_reset.js?v=6.0.0-alpha.9 was not loaded because its MIME type, “application/javascript”, is not “text/css”.

2 404s for the following
https://craft-6.test/vendor/craft/legacy/prismjs/dist/prism.js?v=6.0.0-alpha.9
https://craft-6.test/vendor/craft/legacy/prismjs/dist/prism.css?v=6.0.0-alpha.9

There's nothing in storage/logs

[brandonkelly]

Try running this command:

php artisan craft:setup:publish

[DenyEs]

Running the command did not fix the issue for me

[brandonkelly]

Craft 6.0.0-alpha.10 is out with a fix for this.

[Fakhri17]

Craft 6.0.0-alpha.10 is out with a fix for this.

in 6.0.0-alpha.11 this still bug

[DenyEs]

The issue still persists for me as well