Why do you need them to provide a coding agent? Just use their model with any off the shelf coding agent. I happen to prefer Pi, but use whatever works for you.
Yeah, I'm using Pi with their models through an OpenCode Go subscription and it works pretty well. 10 bucks and V4-Flash is virtually infinite.
RL with the harness inputs and outputs of users is one of the primary improvers of model performance, a self perpetuating flywheel.
I probably have an unfounded assumption that whatever coding agent they make will work really well with their models, better than external harnesses. I don't have a good sense for how all the model + harness combinations compare, nor any good way to compare them myself, but generally believe model companies train their models to work best with their own harness.