Here's an item that stands out in the list of behavior changes to watch out for when targeting Andriod 12 for the first time:

"Toast redesign", specifically the new limit to two lines of text in a toast. We use react-native-simple-toast, which uses the native toast on Android.

One of our longer toast messages without a variable-length component (like a file name, server error, group-PM participants, etc.) looks like this:

Here's how something longer gets cut off:

Things to fix:

• For group-PM messages, there isn't always room in message headers (in the message list) to print all the participants' names. So we offer a toast that's meant to show all the names. That toast will be much worse at its job after this change. We shouldn't just be using full names anyway; sometimes I need more than that to verify that I'm talking to the person I think I am. I may want to see an avatar, email address, and so on. I think we should just link to the group-PM participants screen, which offers a nice scrollable list of user items, where each item has the user's full name, email, and avatar, and it's tappable to get to the full profile.
• Uploading {fileName} failed. should become something like Failed to upload file: {fileName}. The "failed" part is really important, and we can't have it get cut off just because a file name is very long.
• (We sometimes put server errors in toasts. I'm not sure how long those can get...probably servers should convey what's most important in a few words at the start of the message?)