fix(sync): auto-regenerate thumbnail sizes left stale after an image edit

php/class-media.php

@@ -1693,6 +1693,44 @@ public function has_public_id( $attachment_id ) {
 		return ! empty( $new_id ) || ! empty( $id );
 	}
 
+	/**
+	 * Check if an attachment's registered sizes reference files that no longer exist on disk.
+	 *
+	 * This happens when an image is edited (e.g. cropped) via the WordPress image editor: the main file gets
+	 * renamed (an `-e{timestamp}` suffix is added), but the `sizes` metadata can be left pointing at the
+	 * pre-edit filenames, leaving no local file matching that size record.
+	 *
+	 * This intentionally checks file existence rather than filename prefix: WordPress core has valid states
+	 * where a size's filename legitimately keeps the pre-edit base (e.g. editing with "all sizes except
+	 * thumbnail" deliberately preserves the thumbnail, or a size too small to regenerate from the edited
+	 * image is left as-is). A prefix-only check would misflag those as broken and overwrite valid files.
+	 *
+	 * @param int $attachment_id The Attachment ID.
+	 *
+	 * @return bool
+	 */
+	public function has_outdated_sizes( $attachment_id ) {
+		$metadata = wp_get_attachment_metadata( $attachment_id );
+		$path     = get_attached_file( $attachment_id );
+
+		// Also covers cloud-only storage mode, which intentionally removes every local file (see
+		// Storage::remove_local_assets()) without updating the stored metadata: if the main file itself
+		// is gone, there is nothing to regenerate from, so this is not "outdated", it's expected.
+		if ( empty( $metadata['file'] ) || empty( $metadata['sizes'] ) || empty( $path ) || ! file_exists( $path ) ) {
+			return false;
+		}
+
+		$dir = dirname( $path );
+
+		foreach ( $metadata['sizes'] as $size ) {
+			if ( empty( $size['file'] ) || ! file_exists( path_join( $dir, $size['file'] ) ) ) {
+				return true;
+			}
+		}
+
+		return false;
+	}
+
 	/**
 	 * Get a Cloudinary ID which includes the file format extension.
 	 *

php/class-sync.php

@@ -568,6 +568,18 @@ public function setup_sync_base_struct() {
 				'required' => false, // Required to complete URL render flag.
 				'realtime' => true,
 			),
+			'sizes'        => array(
+				'generate' => array( $this, 'generate_sizes_signature' ),
+				'priority' => 5.25,
+				'sync'     => array( $this->managers['upload'], 'regenerate_sizes' ),
+				'validate' => function ( $attachment_id ) {
+					return $this->managers['media']->has_outdated_sizes( $attachment_id );
+				},
+				'state'    => 'info syncing',
+				'note'     => __( 'Regenerating thumbnail sizes', 'cloudinary' ),
+				'required' => false,
+				'realtime' => true,
+			),
 			'folder'       => array(
 				'generate' => array( $this->managers['media'], 'get_cloudinary_folder' ),
 				'validate' => array( $this->managers['media'], 'is_folder_synced' ),
@@ -1389,4 +1401,19 @@ public function generate_edit_signature( $attachment_id ) {
 
 		return $str;
 	}
+
+	/**
+	 * Generate a signature for an attachment's thumbnail sizes.
+	 *
+	 * @param int $attachment_id The attachment ID.
+	 *
+	 * @return string
+	 */
+	public function generate_sizes_signature( $attachment_id ) {
+		$metadata = wp_get_attachment_metadata( $attachment_id );
+		$file     = ! empty( $metadata['file'] ) ? wp_basename( $metadata['file'] ) : '';
+		$sizes    = ! empty( $metadata['sizes'] ) ? wp_json_encode( $metadata['sizes'] ) : '';
+
+		return $file . $sizes;
+	}
 }

php/sync/class-upload-sync.php

@@ -277,6 +277,65 @@ public function edit_upload( $attachment_id ) {
 		return $this->upload_asset( $attachment_id, 'edit' );
 	}
 
+	/**
+	 * Regenerate an attachment's thumbnail sizes when they no longer match the current attached file.
+	 *
+	 * @param int $attachment_id The attachment ID.
+	 *
+	 * @return array|\WP_Error
+	 */
+	public function regenerate_sizes( $attachment_id ) {
+		if ( ! function_exists( '_wp_make_subsizes' ) ) {
+			require_once ABSPATH . 'wp-admin/includes/image.php';
+		}
+
+		$metadata = wp_get_attachment_metadata( $attachment_id );
+		$file     = get_attached_file( $attachment_id );
+
+		if ( empty( $metadata['sizes'] ) || empty( $file ) || ! file_exists( $file ) ) {
+			return new \WP_Error( 'cloudinary_regenerate_sizes_failed', __( 'Could not regenerate attachment sizes.', 'cloudinary' ) );
+		}
+
+		// Only the sizes whose backing file is actually missing get regenerated -- every other size,
+		// including one a user deliberately kept (e.g. editing with "all sizes except thumbnail"), is
+		// left completely untouched. The missing entries are removed from $metadata first so
+		// _wp_make_subsizes() treats them as new sizes to create rather than skipping them as already
+		// present (it only checks whether the size *name* already has an entry, not whether the file
+		// behind it still exists).
+		$dir     = dirname( $file );
+		$missing = array();
+		foreach ( $metadata['sizes'] as $size_name => $size_data ) {
+			if ( ! empty( $size_data['file'] ) && file_exists( path_join( $dir, $size_data['file'] ) ) ) {
+				continue;
+			}
+			unset( $metadata['sizes'][ $size_name ] );
+			$missing[ $size_name ] = true;
+		}
+
+		if ( empty( $missing ) ) {
+			return $metadata;
+		}
+
+		$registered = wp_get_registered_image_subsizes();
+		/** This filter is documented in wp-admin/includes/image.php */
+		$registered = apply_filters( 'intermediate_image_sizes_advanced', $registered, $metadata, $attachment_id );
+		$new_sizes  = array_intersect_key( $registered, $missing );
+
+		// _wp_make_subsizes() is WP core's own low-level size-creation step (used internally by
+		// wp_create_image_subsizes()). Unlike wp_generate_attachment_metadata(), it builds on the
+		// $metadata we pass in rather than a fresh array, so unrelated keys (original_image,
+		// third-party plugin data) are never at risk of being dropped. It also silently leaves a size
+		// out of the result if the image is too small for it, rather than erroring, so that case never
+		// reaches the sync-error path below.
+		$metadata = _wp_make_subsizes( $new_sizes, $file, $metadata, $attachment_id );
+
+		wp_update_attachment_metadata( $attachment_id, $metadata );
+		// Persist the new signature, otherwise this would re-trigger on every subsequent render.
+		$this->sync->set_signature_item( $attachment_id, 'sizes' );
+
+		return $metadata;
+	}
+
 	/**
 	 * Upload an asset to Cloudinary.
 	 *