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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.
AliasModelNotes
fableClaude Fable 5Highest capability. Falls back to Opus, then Sonnet.
opusClaude Opus 4.8Default.
sonnetClaude Sonnet 4.6Balanced quality and speed.
haikuClaude Haiku 4.5Fast and cost-efficient.
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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