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How to run other apps on your Claude or ChatGPT plan instead of an API key

Connect Claude Code to your Pro or Max plan and Codex to your ChatGPT plan, then check an app bills your subscription and not a separate API key.

By BringYourSubs2 min read

Many AI apps resell model usage on top of their own fee. A growing number let you sign in with a subscription you already pay for instead, so the AI work comes out of your plan's included usage. Most of them do it the same way: they drive Claude Code or Codex on your machine, and those two tools are signed in to your plan. Get that sign-in right once and every app built on top of it follows.

Connect Claude Code to your Pro or Max plan

Anthropic's own steps are short:

  1. Have an active Claude Pro or Max subscription.
  2. Install Claude Code from the Claude Code docs.
  3. When it asks you to authenticate, log in with the same account you use for Claude. That connects the plan to Claude Code.

If you were already signed in with a pay-as-you-go Console account, run /login inside Claude Code and pick your subscription instead.

Your plan also covers Claude Code inside supported editors, including VS Code, Cursor and JetBrains IDEs, and that usage counts toward the same limits as Claude on the web and in the terminal.

The API key trap

Anthropic warns that if an ANTHROPIC_API_KEY environment variable is set, Claude Code uses it instead of your subscription, and you pay API rates. If an app asks you to paste an Anthropic API key, it is not running on your plan.

Connect Codex to your ChatGPT plan

OpenAI's Codex documentation lists two ways to sign in: Sign in with ChatGPT for subscription access, or an API key for usage-based billing.

  • In the Codex CLI, run codex login and finish the browser sign-in. This is the default when no session exists.
  • In the IDE extension or the ChatGPT desktop app, choose Sign in with ChatGPT on the signed-out screen.
  • Codex cloud only works with a ChatGPT sign-in.

Signing in with ChatGPT also means your workspace's permissions and data settings apply, rather than an API organization's.

How to tell whether an app really uses your plan

Before you trust an app with your subscription, check three things:

  1. Where it asks you to connect. A real bring-your-own-plan app sends you to Claude Code's login, codex login or a Sign in with ChatGPT screen. A field asking for an API key means separate, metered billing.
  2. What its own docs say. Every listing in this directory links the page where the maker says the app accepts your plan, and quotes the sentence.
  3. Which plan it names. Some apps accept only Claude, some only ChatGPT, a few work through Cursor. The Claude apps and ChatGPT and Codex apps pages list each group.

Once Claude Code or Codex is signed in to your plan, an app built on top of it adds its own features, not a second meter for the model.

Questions people ask

Why does Claude Code still charge my API account after I subscribed?
If an ANTHROPIC_API_KEY environment variable is set, Claude Code uses that key instead of your Pro or Max plan, so the usage is billed to the API. Remove the variable and run /login to switch to your subscription.
Does Codex cloud work with an API key?
No. OpenAI's Codex documentation says Codex cloud requires signing in with ChatGPT. The CLI, the IDE extension and the desktop app accept either a ChatGPT sign-in or an API key.
Do Claude and Claude Code have separate limits?
No. Anthropic says Pro and Max usage limits are shared across Claude and Claude Code, so work in one counts against the same limits as the other.

Sources

  1. Using Claude Code with your Pro or Max plan, Anthropic, 2026-10-03
  2. Codex authentication, OpenAI, 2026-10-03