Via an Anonymous Source, Posted by Warner Music Group

Glassjaw has apparently called it a day. On their website, the band has announced their breakup, though no explanation is given. Beyond the "RIP Glassjaw," the band has also cancelled their December dates which had been scheduled with a temporary lineup.

Update: In light of the lack of details, I've changed this to 'apparently' rather than 'officially' until a statement from the band arrives.