Fwiw I was shocked when I saw the t/f T/F kluge when I went to work on
jsonlogging. That's the kind of dead-end short-sighted hack that just
lays traps and barriers for future hackers to have to clean up before
they can do the work they want to do.
Please just put a "format" field (or "channel" field -- the logging
daemon doesn't really care what format) with a list of defined formats
that can easily be extended in the future. If you want to steal the
high bit for "is last" and only allow 128 values instead of 256 so be
it.