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Slashy writes with Claude Sonnet by default. To use Claude Opus for harder drafts, you bring your own Anthropic API key — Slashy doesn’t bill for Opus usage, Anthropic does. This guide walks through creating that key and adding it to Slashy.
You only need this if you want Opus. Sonnet works on every account with no key and no setup. See AI models in Slashy.

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Create the key

1

Sign in to the Anthropic Console

Go to console.anthropic.com and sign in, or create an account if you don’t have one. This is Anthropic’s developer console — separate from your Claude.ai chat account.
2

Add billing

API usage is pay-as-you-go and billed by Anthropic, so the console asks you to add a payment method and some credit before keys will work. Open Billing (or Plans & Billing) and add a card or buy credits.
3

Open API Keys

Go to Settings → API Keys (at console.anthropic.com/settings/keys).
4

Create a key

Click Create Key, give it a name you’ll recognize later (e.g. Slashy), and create it.
5

Copy it now

Copy the key the moment it’s shown — it starts with sk-ant-. Anthropic only displays the full key once; if you lose it, you’ll have to create a new one.
Treat the key like a password. Anyone with it can spend against your Anthropic account. Don’t paste it into chats, screenshots, or shared docs.

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Add the key to Slashy

The first time you select Opus, Slashy prompts for the key inline in the compose window — paste it there.
1

Open the model picker

Click the model name above the compose box.
2

Select Opus

Choose Opus from the dropdown.
3

Paste your key

A prompt appears asking for an Anthropic API key. Paste the sk-ant- key and confirm. It’s stored on your account only.
You can also add, rotate, or remove the key any time under Settings → AI. See AI models in Slashy for managing it and setting Opus as your default.

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Costs and limits

  • You pay Anthropic directly. Opus usage is billed to the Anthropic account that owns the key, at Anthropic’s published per-token rates. Slashy adds nothing on top.
  • Watch your usage in the Anthropic Console under Usage. You can set spend limits there to cap monthly cost.
  • New accounts sometimes start with a low rate limit. If Opus drafts fail with a rate-limit error, raise your limit in the console or add more credit.

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Troubleshooting

SymptomFix
”Invalid API key”Re-copy the key from the console — it must start with sk-ant- and have no extra spaces. Create a fresh key if unsure.
Opus fails but Sonnet worksThe key is missing, wrong, or out of credit. Check Settings → AI in Slashy and Billing in the Anthropic Console.
Rate-limit errorsRaise your usage tier or add credit in the Anthropic Console.

AI models in Slashy

When to use Sonnet vs Opus, and managing your key.

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Use Slashy’s tools from Claude and other AI clients.