You're right that write reordering might cause this (an invalid frame followed by a few valid frames). That shouldn't happen if you use PRAGMA synchronous=FULL

You're right that write reordering might cause this (an invalid frame followed by a few valid frames). That shouldn't happen if you use PRAGMA synchronous=FULL, but in WAL mode it's very common to use NORMAL. Not sure what's the better strategy here, but I'd definitely appreciate a mode that warns me before silently truncating a WAL that has valid frames in it.