That would be the published mechanism.
Orita, Akihiro; Fukudome, Masato; Ohe, Kouichi; Murai, Shinji
Journal of Organic Chemistry, 1994 , vol. 59, # 2 p. 477 - 481
This one came up on our mechanism board a while ago and four different people each got four different pathways, each of them arguing passionately for their own. I figgured this might be a fun one to send to the internet then.
Personally I like the electrocyclization pathway best too, but i figured it would be best to ask for an answer here where I can give a solid reference.
Well done Rory!