We just released the 0.0.16 google-appengine gem. The big change for JRuby with this release was that app.yaml must now live in the WEB-INF dir. See 1.3.6 Release Post for more information. App Engine Tools updated to version 0.0.16 App Engine SDK updated to version 1.3.6 App Engine APIs updated to version 0.0.19 The appengine-tools will automatically move app.yaml into WEB-INF, but if you have ap