There are so many cool harnesses I could use if I didn't have an outrageously subsidized Claude subscription
Try them anyway. Tell your employer about all the principles of freedoms that free, self hosted AI enable. It does not have to dwarf other costs.
Do not worry about vendor lock-in. Standing against big corporations was never easier in this century.
Do it. You know you can.
I just built my own tools and then just drive claude with 'claude -p' through them. Works great for controlling claude from my own android app.
But you can still use Claude code with a gui layer on top (if it's still calling claude code under the hood, not using the APIs directly).
At least that's what I'm using in https://beolis.com (so, you can use the actual harness you like and just have a proper UI to manage agents over it).