Description

What?

Custom block with core/navigation as parent cannot be inserted with WordPress 6.9 (works with 6.8).

Expected behavior:

I expect the block to be inserted (like in WordPress 6.8). See an example bellow with 6.8:

Step-by-step reproduction instructions

• Create a custom block (I used @wordpress/create-block default block).
• In block.json, add "parent": [ "core/navigation" ].
• Activate a block theme (TwentyTwentyFive in my case).
• Visit "Appearance" => "Editor" => "Navigation".
• Edit the Navigation.
• Add the custom block.
• See "Block "Foo" can't be inserted" notice and no block added (see a screenshot bellow).

Screenshots, screen recording, code snippet

With WordPress 6.9:

With WordPRess 6.8:

Environment info

• WordPress 6.9
• PHP 8.4
• TwentyTwentyFive 1.4

{
	"$schema": "https://schemas.wp.org/trunk/block.json",
	"apiVersion": 3,
	"name": "create-block/foo",
	"version": "0.1.0",
	"title": "Foo",
	"category": "design",
	"icon": "smiley",
	"description": "Example block scaffolded with Create Block tool.",
	"example": {},
	"parent": [ "core/navigation" ],
	"supports": {
		"html": false
	},
	"textdomain": "foo",
	"editorScript": "file:./index.js",
	"editorStyle": "file:./index.css",
	"style": "file:./style-index.css",
	"viewScript": "file:./view.js"
}

Please confirm that you have searched existing issues in the repo.

• Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

• Yes

Please confirm which theme type you used for testing.

• Block
• Classic
• Hybrid (e.g. classic with theme.json)
• Not sure