If you want your coding harness to be predictable, then use something open source, like Pi:

https://pi.dev/

https://github.com/badlogic/pi-mono/tree/main/packages/codin...

But if you want to use it with Claude models you will have to pay per token (Claude subscriptions are only for use with Claude's own harnesses like claude code, the Claude desktop app, and the Claude Excel/Powerpoint extensions).