Add your Claude key

The agent runs on Claude with your own API key. Add the key once and every Space's agent can use it. Tern itself stays free: Anthropic bills you for what the agent uses.

Get a key

Keys come from the Claude Console, Anthropic's site for its API.

1. Open the Claude Console.Go to console.anthropic.com and sign in. Tern's Get a key links take you to the right page.
2. Create a key and copy it.A Claude API key starts with sk-ant-.

Add it to Tern

You can add the key in any of three places. They all do the same thing.

• When you first set Tern up, turn on the agent and paste the key.
• In the agent: press ⌘J, paste the key and click Save key.
• In Settings: choose Tern › Settings › Agents, paste the key under Claude and click Save. It then says API key connected.

The key is kept in your Mac's Keychain and sent only to Anthropic, with each request the agent makes. Tern only reads it when the agent needs it, and there's no Tern server in between. Without a key Tern is a browser on its own, and you can add one any time.

Choose a model

Each Space's agent can run on a different Claude, so you can use the most capable one for work and a cheaper one for quick lookups.

• Claude Opus 5.5 is the most capable, best for long or careful tasks. It costs the most per task.
• Claude Sonnet 5.5 is fast and capable, for everyday tasks, at about half the cost of Opus. Tern suggests it when you set up.
• Claude Haiku 5.5 is the quickest and cheapest, for simple lookups, at a fraction of the cost.

To change a Space's model, open the agent with ⌘J and choose from the model menu at the top, or go to Settings › Agents › Model for each Space. Model for new Spaces sets the one a new Space starts with. You can change the model when the agent isn't working, and the change applies from the next request.

Quick answers

When a Space runs on Opus, a short question is answered by Sonnet, which is faster and costs less. If answering means doing more than reading, such as clicking or filling in a page, Opus takes it from there before anything is done. A quick answer says so under it, with Ask Claude Opus 5.5 to ask the same question again on Opus. To turn quick answers off, go to Settings › Agents › Quick answers.

What it costs

Anthropic charges by the amount of text the agent sends and receives, counted in tokens. Tern works out its estimates from these prices, in US dollars per million tokens:

Haiku's price is for requests up to 100,000 tokens; longer ones cost more. Once a conversation has cost about a cent, the model menu at the top of the agent shows roughly how much it has cost so far, such as Claude Sonnet 5.5 · about $0.12. Your bill from Anthropic is the final word. Repeating tasks and watches use your key on every run too. See Repeat and watch.