Bring your own key
Connect your own Anthropic or OpenAI API key to unlock Claude and GPT on any plan, billed by your provider instead of Clusy.
If you already have an Anthropic or OpenAI API key, you can hand it to Clusy and run the agent on it. The models you unlock this way sit in the picker next to the rest, but they bill your provider account, not Clusy, and they consume no Clusy allowance at all.
This also means they ignore your plan. Bring your own key and you can run Claude Opus on the free tier. That's the honest answer to "can I use Claude without upgrading": yes, if you pay Anthropic for it directly.
Every call goes to your key — including the work you never see. Clusy's meter stays at zero.Connecting a key
Go to Settings → Integrations and paste your key into the Anthropic or OpenAI card. That's the whole setup. You can disconnect it from the same place.
What each key unlocks:
| Provider | Models it adds |
|---|---|
| Anthropic | Sonnet 5 and Opus 4.8, on your Anthropic API key. |
| OpenAI | GPT-5.6, on your OpenAI API key. |
GPT-5.6 is only available this way. Clusy's own hosted GPT is GPT-5.5, so if you want the newer one, a key is the route.
Connecting a key also switches your default model to that provider's flagship: an Anthropic key moves you to Sonnet 5, an OpenAI key to GPT-5.6, along with that model's default reasoning effort. Sessions where you'd already picked a specific model keep it. If you later disconnect the key, any selection pointing at those models drops back to your plan's default, so nothing is left pointing at a model you can no longer run.
What it costs
Nothing, from Clusy's side. A turn on a BYOK model is never metered, on any plan, and it doesn't touch your monthly allowance. Your provider bills you for the tokens at their own rates.
The rest of the platform still bills the way it always does. Cells run in a Clusy sandbox, so GPU time is metered as usual, the agent's metered web tools still count, and on the free tier even CPU sandbox time draws down the allowance. A key covers the model, and only the model.
Your key runs everything the turn does
A turn is more than one model call. When it's running on your key, the calls the agent makes along the way — the chat itself, its self-verification, the sub-agents it spawns, what it extracts to remember later — all resolve to the same key. Clusy doesn't quietly hand part of the work to a house model. The flip side: everything the turn does shows up on your provider's bill.
What this changes about the picker
- Plan gating stops applying to these models. They're gated on the connected key instead. That includes the free tier, which is otherwise locked to Auto.
- They're normal picker rows. Same effort control, same per-message switching, marked with a Your key badge so you can see which lane a message is about to go down.
- BYOK Sonnet 5 exposes deeper reasoning than the hosted one. The plan-gated Sonnet stops at High; on your own key it also offers Extended. The picker always shows exactly which effort levels each model supports.
- Your key is used for your session and nothing else. It's resolved per turn, held in memory for the turn, and never logged.
The other way to do this
If what you have is a Claude or ChatGPT subscription rather than an API key, the equivalent route is the local runner: pair your own machine and Clusy drives the claude or codex CLI you already have installed. Same result on the bill (no Clusy credits), different credential, and a different set of trade-offs.