Why Pi is my AI coding harness

I want to experiment with AI models without rebuilding my coding workflow every time I switch. Pi has become the stable layer around those experiments.
By “harness”, I mean the command-line environment, tools, extensions, and instructions around the model.
I have been experimenting with AI models and coding tools quite a lot lately. At the moment, I pay $20/month for ChatGPT Plus and $20/month for Claude Pro. I get GitHub Copilot Pro for free as an open-source maintainer, and I sometimes use OpenCode Zen to try the models it offers for free.