You may not know that most of our test harnesses are now outputting structured logs (thanks in large part to :chmanchester’s tireless work). Saying a log is structured simply means that it is in a machine readable format, in our case each log line is a JSON object. When streamed to a terminal or treeherder log, these JSON objects are first formatted into something that is human readable, aka the same log format you’re already familiar with (which is why you may not have noticed this).