Whilst working on 27680 I discovered that we do not catch exceptions that are thrown at the point of render.

I failed to resolve the problem there so have moved this piece to it's own bug.

The tests added catch the 500 responses and those responses are the HTML rendered Mojo::Exception templates..

I'll attach the patches I came up with that are not working as expected :(.

I've also tried using

$self->helper( 'reply.exception' => sub { my ($page, $c, $e) = @_; # Custom error page handling here } );

and

$self->before_render => sub {

  my ($c, $args) = @_;

  # Make sure we are rendering the exception template
  return unless my $template = $args->{template};
  return unless $template eq 'exception';

  # Switch to JSON rendering if content negotiation allows it
  return unless $c->accepts('json');
  $args->{json} = {exception => $c->stash('exception')};
};

and neither appeared to work :(