Running Rack in debug mode on Mac

It’s been a while since I tried to run in debug mode. Now I can’t figure out how.

I can run Rack and point it at my development directory:

/Applications/Rack.app/Contents/MacOS/Rack -u /my/user/dir

That works just fine. Rack finds and loads my plugin.

When I add the -d flag…

/Applications/Rack.app/Contents/MacOS/Rack -d -u /my/user/dir

… Rack complains on startup that “Rack’s resource directory “./res” does not exist.” It appears that with the -d flag, Rack uses the current working directory as its system directory by default.

When I try to specify a system directory…

/Applications/Rack.app/Contents/MacOS/Rack -d -u /my/usr/dir -s /Applications/Rack.app/Contents/Resources

… Rack launches, complains about a JSON parsing error in some unspecified stream, and loads only Rack’s 11 core plugins.

The last time I successfully ran debug mode (more than a month ago), I was using a special development version of Rack that was released alongside the SDK. I think that worked just fine (though it, too, complained of a JSON parsing error).

Is it possible to run the released version of Rack in debug mode? If so, what am I doing wrong?