No. You can use OS3 without an API key at all: new accounts start on rabbit-hosted model with free usage, and rabbit-hosted model then needs a monthly plan. See OS3 plans and pricing.
If you choose custom model and bring your own key instead, rabbit does not charge for model usage. Many AI providers do, but there are a few ways to use a custom model without paying for it.
An API key itself is not something you pay for — it is just a credential. What can cost money is the model usage behind it, and that depends on the provider and model you choose. Some providers offer models you can use for free, within limits they set.
openrouter's free models
OpenRouter, one of the aggregator providers OS3 supports, offers a selection of free models. Which models are free changes over time, so check OpenRouter's current free models rather than relying on any specific list. Register your OpenRouter key in settings → api keys, then choose one of its free models for a tier the same way you would choose any other model.
google gemini's free tier
Google offers a free tier for the Gemini API, with its own usage limits. Create a key in Google AI Studio, register it under Google Gemini in settings → api keys, and choose a Gemini model that falls within the free tier. See Gemini API pricing for what is included at no cost.
running a model locally
OS3 also supports running a compatible model on a computer you have already connected with rabbit agent, instead of through a cloud provider. This avoids provider charges entirely, but needs hardware capable of running the model you choose. See how to bring your own key for how to set up a Local model connection.
good to know
- Free tiers, limits and available models are set by each provider, not by rabbit, and can change at any time.
- Not every provider or model is free. Anthropic, OpenAI, xAI, Moonshot, MiniMax and Z.ai bill for usage, Z.ai Coding Plan and OpenCode Go need a subscription, and some OpenRouter and Gemini models fall outside their free tiers.
- Free access does not necessarily cover every OS3 feature or model — check the provider's own terms for what is included.
common questions
do I have to pay to use OS3 itself?
With custom model, no: rabbit does not charge for model usage, any cost comes from the model provider you choose, and the options above are ways to avoid that cost. With rabbit-hosted model, you start with free usage and then choose a monthly plan. See OS3 plans and pricing.
can I mix a free model with a paid one?
Yes. OS3 splits its work into a small and a standard tier, and each can use a different saved key. You could, for example, run the small tier on a free model and keep a paid model for standard work.
which providers can I use with OS3?
See how to bring your own key for the full list of supported providers.