Valid question. It's because they have a separate product intended for use with general tools: Their API.

Their subscription plans aren't actually "Claude Code Plans". They're subscription plans for their tool suite, which includes claude code. It's offered at a discount because they know the usage of this customer base.

OpenCode used a private API to imitate Claude Code and connect as if it was an Anthropic product, bypassing the need to pay for the API that was for this purpose.

Anthropic has been consistent on this from the start. The subscription plans were never for general use with other tools. They looked the other way for a while but OpenCode was openly flaunting it, so they started doing detection and blocking.

OpenCode and maintainers have gone on the offense on Twitter with some rather juvenile behavior and now they're trying to cheekily allow a plugin system so they can claim they're not supporting it while very obviously putting work into supporting it.

Most of the anger in this thread comes from people who want their monthly subscription to be usable as a cheaper version of the public API, even though it was never sold as that.

Same reason movie theaters care about you not bringing your own snacks

Because models are quickly moving toward commoditization, whether the big three like it or not. The differentiator now is tooling around those models. By eliminating OpenCode's auth stuff, they prevent leaking customers onto another platform that allows model choice (they will likely lose paying customers to one of the major inference catalogs like OpenRouter once they move from Claude Code to OpenCode).

Why does Netflix care how the movies they stream to you are consumed? Shouldn't your $8/mo allow you to stream any movie to OpenFlix and consume however you like?

Because they're selling discounted tokens to use with their tooling.

If you use Claude through an interface that’s not Claude Code, you’ll only stick with it for as long as it proves itself the best. With other interfaces, you can experiment with multiple models and switch from one to another for different tasks or different periods of time.

Those tokens going to other providers are tokens not going to Anthropic, so they want to lock you in with Claude Code. And it clearly works, since a lot of people swear by it.

because he is giving them at 90% discount in their subscription. they are more than happy if you use the tokens at api pricing, but when subsidized they want you to use their claude code surface.