Most AI agents ask for a pay-per-token API key, even when you already pay for Claude, ChatGPT or Gemini every month. That means two bills for the same models. goose, the open source agent now run under the Linux Foundation's Agentic AI Foundation, has a way around it: its README says you can use your existing Claude, ChatGPT or Gemini subscription through ACP providers instead of API keys.
This is the short version of how to set that up, plus what to check before you trust it.
goose is a general-purpose agent that runs on your machine. It ships as a native desktop app (macOS, Linux, Windows), a CLI, and an API. It is written in Rust, works with 15+ providers (Anthropic, OpenAI, Google, Ollama, OpenRouter, Azure, Bedrock and more), and connects to 70+ extensions through the Model Context Protocol. It is not only for code: research, writing, automation and data analysis are all in scope.
Either download the desktop app from the installation page, or install the CLI with the command from the README:
curl -fsSL https://github.com/aaif-goose/goose/releases/download/stable/download_cli.sh | bash
As with any piped script, read it first if you are cautious. It is the official release script from the repo, but it is still a remote script running on your machine.
Open the ACP providers guide linked from the README (goose-docs.ai, under guides, ACP providers). ACP is the protocol goose uses to talk to a provider that you are already logged into. The idea is that goose drives your existing Claude, ChatGPT or Gemini plan instead of billing API tokens.
Connect the provider you pay for, following the guide for that one. The exact flow differs per provider, so I will not guess at flags here. Use the guide as the source of truth, and check the repo for newer instructions, since this part moves fast.
Do not start with a big job. Give goose something short and checkable, for example:
Research three open source tools that do X, and give me a table with name, licence, and last release date.
Confirm two things: the task completes, and your provider's usage page shows the usage against your plan rather than a new API charge. If you see an API charge, you are on the wrong provider entry.
Because goose supports many providers, you can swap models without changing how you work. That is the practical win: try Claude for one task, Gemini for the next, or a local Ollama model when you are offline, all from the same interface.
The full card, with the steps and a ready agent prompt, is on Deduped: Use goose with your existing subscription. If you want other agents that work with the tools you already have, browse AI use cases for Claude Code.
Source repo: aaif-goose/goose.
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