[Hat] hat-trail and hat-observe errors

Hi, I'm getting some odd errors running hat under OS X. I'm trying to work with a trivial piece of code to prove that hat is doing sensible things - which at the moment it isn't. When running hat-trail or hat-observe I get the following error:

[host-172-17-2-19:Work/Project/test] tatd100% hat-trail stupid sh: resize: command not found

Fail: user error Reason: Command (resize -u) failed

I originally assumed an incompatibility with my terminal (OS X's Terminal.app), but I receive the same error when using xterm (under Apple's X11 server). I've been searching source files for where they might call the resize command, but can't find it. Any help much appreciated. Thanks Tom Davie