I was helping a friend tonight with a problem they were having getting a tiny web app to run on heroku.

I spent quite some time trying to figure out the issue.

It turns out that Heroku reserves the vendor/ folder for it’s own use, so you can’t delivery files from it. (This is true for PHP applications, at least. We didn’t investigate further).

So, simple rule, don’t use the vendor/ directory in your own app.