diff --git a/Viewer/features/core.js b/Viewer/features/core.js
index 01303338..f974149c 100755
--- a/Viewer/features/core.js
+++ b/Viewer/features/core.js
@@ -2746,25 +2746,29 @@ function(title, func){
 	return object.mixin(
 		action = Queued(function(items, ...args){
 			var that = this
+			var inputs = [...arguments]
 
 			// sync start...
-			if(arguments[0] == 'sync' || arguments[0] == 'async'){
-				var [sync, items, ...args] = arguments }
+			if(inputs[0] == 'sync' || inputs[0] == 'async'){
+				var [sync, [items, ...args]] = [inputs.shift(), inputs] }
 
+			// XXX see arg_handler(..) note below...
 			var q
-			var inputs = [items, ...args]
 
-			// pre-process args...
+			// pre-process args (sync)...
 			arg_handler
 				&& (inputs = arg_handler.call(this, 
 					sync == 'sync' ? 
 						sync 
+						// XXX should this be a queue???
+						// 		...seems like this is either 'sync' or 
+						// 		undefined but never a queue at this stage...
 						: q, 
 					...inputs))
 			// special-case: empty inputs -- no need to handle anything...
 			if(inputs instanceof Array 
-					&& inputs[0] 
-					&& inputs[0].length == 0){
+					&& (inputs.length == 0
+						|| (inputs[0] || []).length == 0)){
 				return Promise.resolve(inputs) }
 
 			// Define the runner and prepare...
diff --git a/Viewer/features/filesystem.js b/Viewer/features/filesystem.js
index 5bb24d7c..9bf55962 100755
--- a/Viewer/features/filesystem.js
+++ b/Viewer/features/filesystem.js
@@ -858,14 +858,11 @@ var FileSystemLoaderActions = actions.Actions({
 	_checkIndex: ['File/Check index consistency',
 		// XXX technically this can be a non-session queue, but we'll 
 		// 		need to save the check results...
-		// XXX update handlers... 
+		// XXX update .handlers to maintain .changes via promise... 
 		core.sessionQueueHandler('checkIndex',
 			function(queue, ...args){
 				// no index loaded...
 				if(!this.location.loaded){
-					// XXX should this throw or resolve???
-					//throw new Error('.checkIndex(): no index to fix.') }
-					// XXX test...
 					return [] }
 				// merged index...
 				// XXX can we remove this restriction -- i.e. check each index...
@@ -873,7 +870,6 @@ var FileSystemLoaderActions = actions.Actions({
 					throw new Error('.checkIndex(): combined indexes not supported.') }
 				// get the data...
 				return [Object.entries(this.images), ...args] },
-			// XXX test...
 			function([gid, image], ...args){
 				var updated = false
 				// image .previews...
@@ -883,7 +879,6 @@ var FileSystemLoaderActions = actions.Actions({
 						!fse.existsSync(image.base_path +'/'+ p[1])
 							&& (updated = true)
 							&& (delete previews[p[0]]) })
-				// XXX do we need this???
 				Object.keys(previews).length == 0
 					&& (delete image.preview)
 				// image .path...