Can you expand on this? Is there a way to use Claude subscription but not their harness?

No but you can use bb or t3codes etc with it. Not perfect but allows orchestration between harnesses.

I don't use this myself but I believe they enabled Claude Code recently with explicit permission from Anthropic: https://github.com/anomalyco/opencode/pull/58782#issuecommen...

Can I use my max subscription with Pi without Anthropic banning my account?

I used a claude subscription with omp for 6 months earlier this year, before switching to chatGPT which Im also using with it. Claude even has a splash screen on their login page saying logged in with oh-my-pi so I very much doubt they are trying to ban people for using other harnesses.

They definitely did ban people who used their auth token with other harnesses for a bit. Hence my hesitance.