laravel - Lumen deployment error on Heroku / Scalingo -

i created fresh lumen project using composer , try put on heroku/scalingo.

however in both hosting solutions following error:

generating optimized autoload files    [runtimeexception]                                                                                                                                                            not scan classes inside "/build/4a8cf965dc0068e76480b81aa5321cff/vendor/laravel/lumen-framework/src/foundation" not appear file nor folder   

it related composer dont understand how.

thank you

i added exclude /vendor/ folder on .gitignore , solved problem. dont understand looking broke it.