Had the same question, comment below quotes their docs saying Agent SDK using oAuth token is also not allowed.

The SDK is Claude Code in a harnesss, so it works with your credentials the same way CC does.

But they're stating you can only use your subscription for your personal usage, not someone else's for their usage in your product.

I honestly think they're being short sighted not just giving a "3rd party quota" since they already show users like 4 quotas.

If the fear is 3rd party agents screwing up the math, just make it low enough for entry level usage. I suspect 3rd party token usage is bi-modal where some users just need enough to kick tires, but others are min-maxing for how mamy tokens they can burn as if that's its own reward

I think the subscription pricing exists because it’s a far more palatable way to bill people for day to day personal use.

I used Claude back when API per token pricing was the only option and it was bad for all the usual reasons pay-per-use sucks compared to flat billing: you’re constantly thinking about cost. Like trying to watch a Netflix video with a ticker in the corner counting up the cents you owe them.

I don’t understand your claim that they want people paying per token - the subscription is the opposite of that, and it also has upsides for them as a business since most people don’t saturate the usage limits, and the business gets to stuff a bunch of value-adds on a bundle offering which is generally a more lucrative and enticing consumer pricing model.

It’s been obvious from the start that the $200 point is the free tier

That should be fine, because it's still using their tooling. And this seems like the better way to go. I have a couple of tools that work like this. I think the issue is mostly 3rd party harnesses that seek to do the same as Claude Code. And it seems reasonable that Anthropic decides how you can use the subscription, because it's heavily subsidized. Get a Claude $200 sub and max out the usage limits, then compare that usage to the cost of using their API. The difference is significant, which is why people are getting multiple $200 subs rather than paying for API usage (and I have seen reports where they are cracking down on this as well.)

Yes. You can build third party applications on top of codex app server. All open source. https://developers.openai.com/codex/app-server/

By default, assume no. The lack of any official integration guide should be a clear sign. Even saying that you reverse-engineer Codex for apps to pretend to be Codex makes it clear that this is not an officially endorsed thing to do

Interested to know this too

Why does it matter to the free buffet manager where do you consume the food? We may never know.

They'll own entire pipeline interface, conduit, backend. Interface is what people get habitual to. If I am a regular user of Claude Code, I may not shift to competitor for 10-20% gains in cost.

They must be getting something out of it, because we sure aren't.

They want that sweet vendor lock-in.

Presumably because their flat rate pricing is based off their ability to manage token use via their first-party tools.

A third-party tool may be less efficient in saving costs (I have heard many of them don't hit Anthropic LLMs' caches as well).

Would you be willing to pay more for your plan, to subsidize the use of third-party tools by others?

---

Note, afaik, Anthropic hasn't come out and said this is the reason, but it fits.

Or, it could also just be that the LLM companies view their agent tools as the real moat, since the models themselves aren't.

Read the actual ToS. What you describe is NOT allowed.

Flat rate does not imply unlimited.

Is there a way to legally or even practically prevent this? `claude` CLI execution in a shell is certainly included in the subscription - it’s the product.

https://x.com/thdxr/status/2013010664776683644

I can't find anything official from OpenAI, but they have worked with the OpenCode people to support using your ChatGPT subscription in OpenCode.

From TFA: “OAuth authentication (used with Free, Pro, and Max plans) is intended exclusively for Claude Code and Claude.ai. Using OAuth tokens obtained through Claude Free, Pro, or Max accounts in any other product, tool, or service — including the Agent SDK — is not permitted and constitutes a violation of the Consumer Terms of Service.”