Very standard in all coding harnesses/models I've worked with, with the bonus that everything listed in the "What doesn't work in Portal by Spotify" section still works. I've been watching Opus spin off work to Fable and Sonnet as appropriate all day.
Do you have specific instructions that cause this or did it come out of the box? Is it also when using normal prompting or only when you set a goal?
In codex I don’t see this behaviour despite having added the instructions to do so to my agents file. I also let that agents file be reviewed by Sol to come up with the right phrasing but no luck so far.
Can you name some harnesses?