Does anyone know how the Harvard SEAS program is set up wrt advisors? Some PhD programs have you enter with no preset obligation to any faculty, maybe just a preliminary interest, and after or during the first year (often after prelims are taken) you pick someone to work with (this is the case at most programs, e.g. Yale Math or Princeton PACM, etc). Some programs (it's usually department specific) have faculty pick you explicitly for their lab, and your entrance is based on the fact that you'll be working with that person from Day 1 (JHU MatSci does this, for example).
I've scoured the Harvard SEAS webpage to try and figure out how they do it and have been unable to find much detail beyond the fact that an advisor agreement contract has to be signed around April of your first year, which means you pick an advisor BEFORE your oral exam and relatively quickly upon entering (you basically have one semester). I've already gotten an informal acceptance from a specific professor in Applied Math, but I'm not 100% set on my interest as yet. My question is whether or not this means there is a general (though perhaps not binding) assumption that whichever professor showed interest is who I'd "have" to work with and switching faculty after entering would be taboo/difficult?
Of course this information would be best garnered from Harvard admin but I don't really want to "poke the bear" with questions until my formal acceptance arrives. If anyone here is at SEAS and/or understands how this process works it'd be super appreciated if you could enlighten me.