Darwin Academy · 02

Choose my brain — three ways to power the thinking

I live on your computer, but the thinking itself comes from an AI model you pick — your own API key, a flat-rate subscription you may already pay for, or a free local model that never touches the internet. None of it is locked in: you can switch any time, mid-conversation included.

By Darwin · the voice AI assistant that runs on your own PC

This is the one decision worth two minutes of thought before your first real conversation with me. Here are the three options honestly, with what each one costs and who it suits — followed by the setup for each.

The three options at a glance

My honest advice: start with the API key. If I become part of your working day, move to a flat-rate subscription. Keep the local brain for the private stuff — it's there whenever you want it.

Option 1 — Your own Anthropic API key (start here)

An API key is simply your private password to Anthropic's Claude models — the same family of models behind this website's chat. The usage runs on your own account, so the bill is yours and stays transparent: a normal conversation costs cents.

1. Go to console.anthropic.com and create an account (or sign in).
2. Under Billing, add a small amount of credit — $5 is plenty to start with.
3. Open API Keys and click Create Key. Copy the key immediately — it is shown only once.
4. In Darwin, open Settings → API keys and paste it in. Done — no restart needed.

The key never leaves your computer, and we — the makers of Darwin — never see it. If a key ever leaks, you can revoke it in the console and make a new one in seconds.

Option 2 — Flat rate on a subscription you already pay for

If you already pay for a Claude subscription, I can think with it instead of counting every message. In Darwin, open Settings → Claude Code · flat rate and connect it — this is the brain I reach for when the work gets heavy: long multi-step jobs, reading through whole folders of documents, actual programming.

The same idea works on the other side of the fence: with a ChatGPT subscription, connect Settings → GPT · flat rate and I think with that at no extra cost. You are not choosing a religion here — you can switch brains whenever you like.

Option 3 — The local brain: free, offline, yours

With the local brain I run entirely on your own machine. No internet, no account, no cost — and complete privacy, because nothing leaves your computer. Not to Anthropic, not to OpenAI, not to us.

Two honest caveats: it likes a decent graphics card, and even a strong PC won't match a data centre. For everyday questions it does fine; for the heaviest thinking you'll want a cloud brain. I will always tell you plainly which brain a task really needs.

Switching brains — and keeping the thread

Switching is a setting, not a commitment. And when you switch mid-conversation, the brain-switch bridge (Settings → Conversation memory) hands the new brain a summary of the recent talk, so the thread carries over instead of starting cold. My long-term memory is a separate thing entirely — it stays with me no matter which brain is doing the thinking.

One key, one paste, and I'm thinking. Everything else — the subscription, the local model — can wait until you know how you like to work with me.

What's next

• Make me hear you — the free Groq key, a two-minute video ›
• Give me a real voice — the complete ElevenLabs setup ›
• Curious what else can be set up? Take the guided settings tour ›