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Set up Anthropic so Cyrus can use Claude to reason about code changes, plans, and tasks. You can connect via an API Key or a Subscription. Once configured, you can make Claude your default model provider.

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Open the Anthropic configuration

1

Go to Integrations

Navigate to app.atcyrus.com/settings/integrations.
2

Open the configuration modal

Find the Claude tile, click the dropdown on the right side of the tile, and select Configure.
3

Choose your authentication method

At the top of the configuration modal you’ll see a dropdown — pick API Key or Subscription depending on how you’d like to authenticate.

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Supported models

Cyrus supports the following Claude models. Use the alias as a Linear label or in a [model=...] description tag — see Default Model Provider for syntax. If no model label is set, Cyrus uses opus and falls back to sonnet on retry. When fable is selected, Cyrus runs claude-fable-5 and automatically falls back to opus, then sonnet. Claude Fable 5 is Anthropic’s most capable Claude model. You can make it your team’s default Claude model in Behaviours settings, or try it on a single issue by adding the fable label before assigning the issue to Cyrus. You can also pass a fully-qualified Anthropic model ID (e.g. claude-fable-5 or claude-opus-4-8) in a [model=...] tag.

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API key setup

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Option A: use claude setup-token

You can generate a token through the CLI:
This command will output a token. Copy it, then paste it into the Cyrus Claude configuration modal (with API Key selected).
Be careful to remove any extra whitespace or newlines from the token before pasting — trailing spaces or line breaks can cause “bad key” errors.

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Option B: create a key via the Anthropic Console

1

Sign in to Anthropic

Go to console.anthropic.com and sign in. If you don’t have an account, create one first.
2

Open the API Keys page

Click API Keys in the left sidebar, or go directly to console.anthropic.com/settings/keys.
3

Create a new key

Click Create Key. Give it a name like cyrus to identify it later.
4

Copy the key

Your key will be shown once. Copy it immediately — you won’t be able to view it again after closing the dialog.
5

Paste it into Cyrus

Back in the Cyrus Anthropic configuration modal (with API Key selected), paste your key and save.
If you lose your API key, you’ll need to generate a new one. Anthropic does not allow you to view existing keys after creation.

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Add billing

Anthropic API keys require a billing method. If you haven’t set one up:
  1. Go to console.anthropic.com/settings/billing
  2. Add a payment method
  3. Optionally configure spend limits

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Troubleshooting

“Invalid Claude API key” error
  • Make sure you copied the full key (it starts with sk-ant-)
  • Verify the key hasn’t been disabled in the Anthropic console
“Insufficient credits” error

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Next steps

To make Claude the provider Cyrus uses for every issue, see Default Model Provider.
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