Pi is a good harness (I finally gave it a try w/ abliterated GLM), but not with Anthropic subscription, and there are multiple reasons to avoid alternative harnesses with their models in general (imho):

1. Potential ban due to ToS violation;

2. It doesn't follow all Anthropic's communication mechanisms out-of-the-box, they heavily use custom headers, hidden flags, and undocumented API features that affect models' behavior;

3. Compact is better in CC (significantly);

4. Cache related nuances (I mean, A\ regularly messes up with cache even in CC, their caching is non-trivial);

5. It's almost unavoidable to use Pi's extensions, and I wouldn't trust my oauth token to anything third-party (take a look at regular reddit/X posts where people getting banned due to such leaks and abuse) -> it takes enormous amount of hacking on top of Pi to get closer to CC abilities.

CC has hooks and mods, even ui_* (undocumented) protocol if you need some big customization, those are enough to implement whatever you want on top of CC.

Also, I'm working with CC from the very first versions, as for me - it's the best harness (as-is) on the market. I have zero clue what problems people are talking about (except known big issues, 3-4 over the years, I've never had serious problems, at all). Seamless and smooth experience, optimized for Anthropic models.

P.S. You can consider this as Stockholm syndrome effect, but... you have close to zero chances to get unbanned with Anthropic, and it's the best coding model(s) available today.

Most harnesses are not designed with conversations to be append-only from the start, which causes us all endless pain when caching is concerned.

When making a harness, it is so, so easy to do the "web thing" and have your system prompt be a template where you dynamically inject variables like the current date or the contents of the current working directory, and then just re-render that template on every request. THis is a bad, doubleplusungood, terrible, awful idea, and you should never do this under any circumstances. Anthropic will soon force you not to by literally refusing conversations that "break continuity" in this way and do anything but append new user messages at the end, but other providers at least appear to work.

I've only used CC and Pi and the point of pi is to use extensions. Luckily you can write them yourself pretty easily.

I cannot get behind CC is the best harness. Once u switched to pi I knew I was never going back and occasionally I need to use CC for my subscription and find it unpleasant. CC is just this incoherent hodge podge of functionality that seems to have no vision. Subjective, of course.

I've been using claude-bridge [0] and pi-vcc [1] for compaction and it has been a complete life changer. I'm slowly phasing out my Anthropic use for Mistral but I've used it for months without issues.

[0]: https://pi.dev/packages/pi-claude-bridge?name=claude-bridge [1]: https://pi.dev/packages/@sting8k/pi-vcc?name=pi-vcc

> Potential ban due to ToS violation

Anthropic gives monthly API credits for Max and higher subscriptions, equivalent to the subscription cost (so you pay $100 for the Max plan, and you get the normal subscription usage, plus $100 worth of API credits each month). My understanding is you can use those credits with any harness because they are normal API credits that you can use with an API key.

They won't last as long as the subscription itself (they are spent at API prices) but you can use at least use pi.dev with Anthropic models without violating the ToS.

I just want to point out that you’re allowed to use Claude-* models that aren’t a part of your subscription. For example, the ones hosted on openrouter.

Anthropic insists your use of models hosted by them just go through API billing, which is more expensive.

Don’t do sketchy things to use you sub with pi. That’ll get you banned.

Claude models work fine on pi. I’m a happy user.

6. A\ reduce model usage for non-CC client. https://github.com/anthropics/claude-code/issues/97074

I agree. They are probably solving problems we don’t know are problems, beyond UX (like caching). That’s one of the reasons I prefer CC over Pi. Codex is pretty nice too, with respect to UX.

> 4. Cache related nuances (I mean, A\ regularly messes up with cache even in CC, their caching is non-trivial);

I'd be curious to know the background around this. At work, I've used @anthropic/Opus 5.5 through Portkey with Pi, and ended up with $10 within less than 10 message exchanges, on a fairly trivial topic. OTOH, when using Claude Code directly with Opus 5.5, I basically spent $30 for a good back-and-forth across a full chat, reaching the point where CC kicked off compaction.

You can write your own compaction function for Pi, and you can even have different, domain specific compaction logic if you want. The default one is dumb, I agree.

Regarding credentials, my base instructions shared across all agents and all harnesses is that all credentials are accessed through a specific powershell script and should never be shown or written to file. This seems to work with pi, opencode.

Using the Agent SDK to connect to Anthropic is an officially supported method and does not risk a ban.

I use a cheap deepseek model for compaction on purpose since it costs a penny or two and does not use any of my Anthropic quota.

> they heavily use custom headers, hidden flags, and undocumented API features that affect models' behavior;

This is exactly why you'd want to use Pi. All these flags and updates to claude code break so many workflows and give a different experience every time you use it. It's highly inconsistent and very annoying.

this is also my fear, after seeing anthropic yank access to openclaw users, they could just as easily restrict users from third party harnesses