Hi guys,
there is a bug in code bootstrap.js in code, which decides, whether to add .json suffix to manifest name.

            run: function() {
                var manifest = Ext.manifest;

                if (typeof manifest === "string") {
                    var extension = ".json",
                        url = manifest.indexOf(extension) === manifest.length - extension.length
                            ? manifest
                            : manifest + ".json",
                        key = getStorageKey(url),
                        content = LocalStorage.retrieveAsset(key);
The highlighted test should return true when manifest already contains .json extension. But it fails for 4 letter manifests, for example gray .

Btw. is this the proper place to report ExtJS bugs?

Found in extjs