AFAIK, such a beast does not exist where you can stop a transaction from pressing a browsers stop button. Web is stateless, so a stop button on a browser cannot be connected to the servers understanding of finish the request or don't.
Hitting the stop button on the browser at least causes two things: a) stop making further requests (stop loading images etc.) on that page b) reset all open tcp connections from that browser window by sending a RST packet. What we see with that long running process is b), and that is something the server can notice - web is stateless, but a tcp connection is not. That was the point why I tested a similar thing with apache/mod-perl. The process _will_ get stopped when the user presses stop on his browser. Zope just runs on under the same circumstances. cheers, oliver