Most of the time means that any tool written with Test2 in mind, or directly on Test2 will work as expected, this should include most methods on Test::Builder itself. However cpan tools written against old Test::Builder that do not use Test2's 'Context' system may still call $tb->ok and $tb->diag separately, in which case the diag will still be lost.

In Test2 you would do this:

    sub mytool {
      my $ctx = context();
      $ctx->ok(...);
      $ctx->diag(...);
      $ctx->release; # This is where the bail-on-fail is triggered
    }
[download]

The TB version:

    sub mytool {
      $tb->ok(...); # BailOnFail is triggered here
      $tb->diag(...); # Lost
    }
[download]

$tb methods do acquire context's, but each of those methods has to acquire it's own. That said the diagnostics TB itself generates in a failed-ok (like line number) will make the output, it is just extra diags are lost.

That is unfortunately a fundamental, and not-fixable limitation of Test::Builder that Test2 avoided with the context system. Test2 was specifically designed to overcome this and many other TB limitations.