Ah sorry - I misunderstood. Thanks for explaining it. Have not heard of Paseo nor Kepler, and have never tried Zed. Yeah I too assumed if I'm to try use OpenAI subscription outside Codex, or Anthropic subscription outside Claude Code - I'd get my account banned it's agains their rules. So I have never looked how using the whole harness from outside looks like either (except for 'claude -p'). Interesting. BTW I see now https://docs.z.ai/devpack/tool/codex Zai added OpenAI compatible end point.
My current view on things:
Paseo had a really nice UI/UX, except sometimes sub-agents within OpenCode sessions would hang. Still, quite pleasant if you want something like the Codex or Claude Code desktop apps, but across various providers.
Kepler integrates with issue trackers like GitHub, you can just create a worktree from a ticket and let it churn, seemed like the second most polished option I tried, but there are obvious gaps - like moving cards manually, some missing UI options etc., which I'd chalk up to either the software just being that new or maybe being a little bit vibe-codey. Either way, one of the more promising options if you want something like Kanban board for agents.
Zed is mostly just a (really nice) text editor with some AI integrations, though it seems like they're also building a more agentic product as well - https://delta.dev/ haven't used that one much and am not in circumstances where I'd collaborate with people that closely, but there was a pretty cool podcast episode with the creators recently and it seems like it works pretty nicely for them! As an editor though, it succeeded where Fleet failed and has mostly replaced Visual Studio Code for me. Nothing against VSC, Zed just does most of the stuff I actually need out of the box.
Some of those tools interacting with Claude Code instead of trying to replace it is more or less the way to get Anthropic's models in other tools while still on a subscription (at least for now). How it works under the hood, go figure, there's ACP https://agentcommunicationprotocol.dev/introduction/welcome but also any number of hacky approaches.
To be fair, you can use Anthropic's models in many other harnesses directly, it's just that it then counts against API billing instead of your subscription, which ends up being way more expensive for individuals, but is kinda what you're supposed to do as a company.