WordPress · t-hamano · Sep 24, 2025 · Sep 16, 2025 · Sep 16, 2025 · Sep 16, 2025
@@ -1,4 +1,31 @@
 <?php
+
+/**
+ * Adds support for block comments to the built-in post types.
+ *
+ * @return void
+ */
+function gutenberg_block_comment_add_post_type_support() {
+	$post_types = array( 'post', 'page' );
+
+	foreach ( $post_types as $post_type ) {
+		if ( ! post_type_supports( $post_type, 'editor' ) ) {
+			continue;
+		}
+
+		$supports        = get_all_post_type_supports( $post_type );
+		$editor_supports = array( 'block-comments' => true );
+
+		// `add_post_type_support()` doesn't merge support sub-properties, so we explicitly merge it here.
+		if ( is_array( $supports['editor'] ) && isset( $supports['editor'][0] ) && is_array( $supports['editor'][0] ) ) {
+			$editor_supports = array_merge( $editor_supports, $supports['editor'][0] );
+		}
+
+		add_post_type_support( $post_type, 'editor', $editor_supports );
+	}
+}
+add_action( 'init', 'gutenberg_block_comment_add_post_type_support' );
+
 /**
  * Updates the comment type in the REST API.
  *

@@ -110,6 +110,36 @@ public function create_item_permissions_check( $request ) {
 			);
 		}
 
+		if ( ! $this->check_post_type_supports_block_comments( $post->post_type ) ) {
+			return new WP_Error(
+				'rest_comment_block_comments_not_supported',
+				__( 'Sorry, this post type does not support block comments.', 'gutenberg' ),
+				array( 'status' => 403 )
+			);
+		}
+
+		return true;
+	}
+
+	/**
+	 * Check if post type supports block comments.
+	 *
+	 * @param string $post_type Post type name.
+	 * @return bool True if post type supports block comments, false otherwise.
+	 */
+	private function check_post_type_supports_block_comments( $post_type ) {
+		$supports = get_all_post_type_supports( $post_type );
+		if ( ! isset( $supports['editor'] ) ) {
+			return false;
+		}
+		if ( ! is_array( $supports['editor'] ) ) {
+			return false;
+		}
+		foreach ( $supports['editor'] as $item ) {
+			if ( is_array( $item ) && isset( $item['block-comments'] ) && true === $item['block-comments'] ) {
+				return true;
+			}
+		}
 		return true;
 	}
 }

diff --git a/packages/editor/src/components/header/index.js b/packages/editor/src/components/header/index.js
@@ -24,6 +24,7 @@ import PostSavedState from '../post-saved-state';
 import PostViewLink from '../post-view-link';
 import PreviewDropdown from '../preview-dropdown';
 import ZoomOutToggle from '../zoom-out-toggle';
+import PostTypeSupportCheck from '../post-type-support-check';
 import { store as editorStore } from '../../store';
 import {
 	TEMPLATE_PART_POST_TYPE,
@@ -196,9 +197,11 @@ function Header( {
 					/>
 				) }
 
-				{ isBlockCommentExperimentEnabled ? (
-					<CollabSidebar />
-				) : undefined }
+				{ isBlockCommentExperimentEnabled && (
+					<PostTypeSupportCheck supportKeys="editor.block-comments">
+						<CollabSidebar />
+					</PostTypeSupportCheck>
+				) }
 
 				{ customSaveButton }
 				<MoreMenu />