Add WP_ALLOW_COLLABORATION constant

src/wp-admin/options-writing.php

@@ -112,10 +112,14 @@
 <tr>
 <th scope="row"><?php _e( 'Collaboration' ); ?></th>
 <td>
-	<label for="wp_collaboration_enabled">
-		<input name="wp_collaboration_enabled" type="checkbox" id="wp_collaboration_enabled" value="1" <?php checked( '1', (bool) get_option( 'wp_collaboration_enabled' ) ); ?> />
-		<?php _e( 'Enable real-time collaboration' ); ?>
-	</label>
+	<?php if ( ! WP_ALLOW_COLLABORATION ) : ?>
+		<p class="notice notice-warning inline"><?php _e( '<strong>Note:</strong> Real-time collaboration has been disabled.' ); ?></p>
+	<?php else : ?>
+		<label for="wp_collaboration_enabled">
+			<input name="wp_collaboration_enabled" type="checkbox" id="wp_collaboration_enabled" value="1" <?php checked( '1', (bool) get_option( 'wp_collaboration_enabled' ) ); ?> />
+			<?php _e( 'Enable real-time collaboration' ); ?>
+		</label>
+	<?php endif; ?>
 </td>
 </tr>
 <?php

src/wp-includes/collaboration.php

@@ -6,6 +6,25 @@
  * @since 7.0.0
  */
 
+/**
+ * Determines whether real-time collaboration is enabled.
+ *
+ * If the WP_ALLOW_COLLABORATION constant is false,
+ * collaboration is always disabled regardless of the database option.
+ * Otherwise, falls back to the 'wp_collaboration_enabled' option.
+ *
+ * @since 7.0.0
+ *
+ * @return bool Whether real-time collaboration is enabled.
+ */
+function wp_is_collaboration_enabled() {
+	if ( ! defined( 'WP_ALLOW_COLLABORATION' ) || ! WP_ALLOW_COLLABORATION ) {
+		return false;
+	}
+
+	return (bool) get_option( 'wp_collaboration_enabled' );
+}
+
 /**
  * Injects the real-time collaboration setting into a global variable.
  *
@@ -18,7 +37,7 @@
 function wp_collaboration_inject_setting() {
 	global $pagenow;
 
-	if ( ! (bool) get_option( 'wp_collaboration_enabled' ) ) {
+	if ( ! wp_is_collaboration_enabled() ) {
 		return;
 	}
 

src/wp-includes/default-constants.php

@@ -398,6 +398,21 @@ function wp_functionality_constants() {
 	if ( ! defined( 'WP_CRON_LOCK_TIMEOUT' ) ) {
 		define( 'WP_CRON_LOCK_TIMEOUT', MINUTE_IN_SECONDS );
 	}
+
+	/**
+	 * Whether real time collaboration is permitted to be enabled.
+	 *
+	 * @since 7.0.0
+	 */
+	if ( ! defined( 'WP_ALLOW_COLLABORATION' ) ) {
+		$env_value = getenv( 'WP_ALLOW_COLLABORATION' );
+		if ( false !== $env_value ) {
+			define( 'WP_ALLOW_COLLABORATION', 'true' === $env_value );
+		} else {
+			// Environment variable is not defined, default to true.
+			define( 'WP_ALLOW_COLLABORATION', true );
+		}
+	}
 }
 
 /**

src/wp-includes/post.php

@@ -657,7 +657,7 @@ function create_initial_post_types() {
 		)
 	);
 
-	if ( (bool) get_option( 'wp_collaboration_enabled' ) ) {
+	if ( wp_is_collaboration_enabled() ) {
 		register_post_type(
 			'wp_sync_storage',
 			array(
@@ -8672,7 +8672,7 @@ function wp_create_initial_post_meta() {
 		)
 	);
 
-	if ( (bool) get_option( 'wp_collaboration_enabled' ) ) {
+	if ( wp_is_collaboration_enabled() ) {
 		register_meta(
 			'post',
 			'_crdt_document',

src/wp-includes/rest-api.php

@@ -430,7 +430,7 @@ function create_initial_rest_routes() {
 	$icons_controller->register_routes();
 
 	// Collaboration.
-	if ( (bool) get_option( 'wp_collaboration_enabled' ) ) {
+	if ( wp_is_collaboration_enabled() ) {
 		$sync_storage = new WP_Sync_Post_Meta_Storage();
 		$sync_server  = new WP_HTTP_Polling_Sync_Server( $sync_storage );
 		$sync_server->register_routes();

src/wp-includes/rest-api/endpoints/class-wp-rest-autosaves-controller.php

@@ -254,7 +254,7 @@ public function create_item( $request ) {
 		 *   the saved post. This diff is then applied to the in-memory CRDT
 		 *   document, which can lead to duplicate inserts or deletions.
 		 */
-		$is_collaboration_enabled = (bool) get_option( 'wp_collaboration_enabled' );
+		$is_collaboration_enabled = wp_is_collaboration_enabled();
 
 		if ( $is_draft && (int) $post->post_author === $user_id && ! $post_lock && ! $is_collaboration_enabled ) {
 			/*