API keys / Claude

The Claude key

One Claude API key runs Supercomputer, the chat beside a project that plans a film with you and writes the take prompts. Four steps, about five minutes. This is the API, not claude.ai: a Claude subscription does not pay for it.

Two of the steps are where people stop. They are marked.

1. 1

   Sign in to the Claude Console

   platform.claude.com ↗

   Your claude.ai email works, or a new one. The API is billed on its own: a Pro or Max subscription covers none of it.

2. 2

   Add credits

   Billing ↗

   Anthropic bills in advance, from $5. Without credits every reply is refused.

3. 3

   Create the key

   API keys ↗ · Create Key

   Any name, the default workspace. The key is shown once — copy it before closing the window. It starts with sk-ant-api: an Admin key (sk-ant-admin…) and a token from Claude Code or claude.ai (sk-ant-oat…) will not work.

4. 4

   Paste the key and ask Supercomputer

   Studio ↗ · account menu → API keys → Claude

   The studio checks the key with Anthropic as you save it, so a wrong one is turned away right there. Supercomputer — the chat beside a project, which comes with the subscription — runs on Claude Sonnet 5.5 by default: $2 per million tokens in, $10 out. Above the chat you can start a conversation on Opus 5.5, Fable 5.2 or Haiku 5.5 instead and set how hard it thinks. An ordinary reply on Sonnet costs a few cents, and every reply is counted in your spend.

When something doesn't work

“Anthropic did not accept this key”

A deleted key, a key with a character missing, or not an API key at all. Copy it again from API keys — it starts with sk-ant-; the studio checks it the moment you save.

“This is an Admin key”

An Admin key (sk-ant-admin…) manages the organization and cannot run Claude. Create an ordinary key — step 3.

“This is a Claude subscription token”

A token from Claude Code or claude.ai (sk-ant-oat…) belongs to the subscription. The API takes its own key, billed apart from it — step 3.

“Your Anthropic balance is empty”

The prepaid credits ran out. Top up in Billing — step 2.

“Your Anthropic account hit its rate limit”

A new account starts with low limits. Wait a minute and send again; the limits grow as the account spends.

“Anthropic did not let this key use the model”

The key is valid, but its workspace limits the models or the spend. Check the workspace of the key in the Console.