What?

In Code Editor (text) mode, meta boxes at the bottom of the post editor become invisible and unreachable once the content field grows taller than the viewport. This is a regression since WP 7.0.

Closes #78637

Why?

The split-view meta boxes layout (introduced in #69958) applies flex constraints to .editor-visual-editor to keep it from pushing the meta box panel out of view. No equivalent rule existed for .editor-text-editor.

When the react-autosize-textarea grows with content, the text editor expands beyond the viewport, pushing MetaBoxesMain outside the scrollable area and making it unreachable.

How?

• Add a single SCSS parent rule targeting the split‑view context and apply shared sizing to both editors, then set per‑editor overflow:
  • .editor-visual-editor: overflow: hidden (existing behavior).
  • .editor-text-editor: overflow: auto (keeps code area scrollable while meta boxes remain docked).

Testing Instructions

1. Open a post/page for editing.
2. Activate a plugin that registers meta boxes (e.g. any plugin with add_meta_box()).
3. Switch to Code Editor view (⋮ → Code editor).
4. Paste/type enough content that the textarea grows taller than the viewport.
5. Expected: Meta box panel remains visible and docked at the bottom; code area scrolls internally.
6. Previously: Meta box panel disappeared below the viewport and could not be scrolled to.

add_action( 'add_meta_boxes', function() {
    add_meta_box(
        'test_meta_normal',
        'Test Meta (Normal)',
        function( $post ) {
            echo '<label>Custom Field 1: <input type="text" name="test_field_1" value="' 
                . esc_attr( get_post_meta( $post->ID, 'test_field_1', true ) ) . '"></label><br><br>';
            echo '<label>Custom Field 2: <input type="text" name="test_field_2" value="' 
                . esc_attr( get_post_meta( $post->ID, 'test_field_2', true ) ) . '"></label>';
        },
        [ 'post', 'page' ],
        'normal'
    );
    add_meta_box(
        'test_meta_advanced',
        'Test Meta (Advanced)',
        function( $post ) {
            echo '<label>SEO Title: <input type="text" name="seo_title" value="' 
                . esc_attr( get_post_meta( $post->ID, 'seo_title', true ) ) . '"></label><br><br>';
            echo '<label>SEO Description: <textarea name="seo_desc" rows="3" style="width:100%">' 
                . esc_textarea( get_post_meta( $post->ID, 'seo_desc', true ) ) . '</textarea></label>';
        },
        [ 'post', 'page' ],
        'advanced'
    );
} );

Screenshots or screencast

Before	After