The release of the Android 6 Marshmallow factory images for Nexus phones and tablets has a lot of people flashing and wiping and Marshmallow-ing today, but there are a few questions we're getting from folks using Project Fi.
The word is that there will be one unified software build for all models of the Nexus 6 — including the T-Mobile version and the Project Fi version — which have historically had separate builds for network operability. We're trying to verify this with Google, but for now we have to go with what the fine folks at Project Fi support have to say.
I spoke with John from the Fi support team, who tells me that if you have a Nexus 6 that is already Project Fi activated, you should be able to flash the new Marshmallow factory images and everything will work. If you haven't yet activated Project Fi on your Nexus 6, they can't guarantee that everything will go smoothly.
This sounds a bit like they are hedging in case things go wrong (which is understandable), but it also makes sense. We know there are changes coming to the Project Fi SIM card — with new Nexus 5X and 6P owners getting fresh cards — so changes to the activation process sound reasonable.
For what it's worth, I went ahead and flashed the new Android 6 image on my Project Fi Nexus 6. Everything seems to be working after a reboot to get the network connected, though I had a few hiccups sending SMS on Wifi while things were settling in.
Our advice right now is to hold off on your manual updating via factory image until we get an official word from the Nexus team. That is, unless you're comfortable with flashing and wiping and flashing again. It looks like things are working well, but looks can be deceiving.