Docs→Connecting API keys (BYOK)

Connecting API keys (BYOK)

Custos AI works on a Bring Your Own Key model. You supply your own API keys — we never charge margin on LLM usage. All costs go directly to the provider.

How BYOK works

When you send a message, Custos AI routes your request to the LLM provider using your API key. The provider charges you directly based on token usage. Custos AI adds no markup. Your API keys are encrypted at rest using AES-256-GCM and are never logged in plaintext.

OpenAI (GPT-4o, GPT-4o mini, o1, o1-mini)

  1. 1Go to platform.openai.com and sign in or create an account.
  2. 2Navigate to API → API Keys and click Create new secret key.
  3. 3Give it a name (e.g. Custos AI) and copy the key — you will only see it once.
  4. 4In Custos AI, go to Settings → API Keys → Add key, select OpenAI, and paste your key.
  5. 5Optionally set a usage limit directly in your OpenAI account under Billing → Usage limits.

Anthropic (Claude Sonnet, Claude Opus)

  1. 1Go to console.anthropic.com and sign in or create an account.
  2. 2Navigate to API Keys and click Create Key.
  3. 3Copy the key — you will only see it once.
  4. 4In Custos AI, go to Settings → API Keys → Add key, select Anthropic, and paste your key.
  5. 5Note: Anthropic API access requires a verified account with a payment method added.

Google (Gemini 2.5 Pro, Gemini 2.0 Flash)

  1. 1Go to aistudio.google.com and sign in with your Google account.
  2. 2Click Get API Key and then Create API key.
  3. 3Copy the key.
  4. 4In Custos AI, go to Settings → API Keys → Add key, select Google, and paste your key.

Mistral AI

  1. 1Go to console.mistral.ai and sign in or create an account.
  2. 2Navigate to API Keys and click Create new key.
  3. 3Copy the key.
  4. 4In Custos AI, go to Settings → API Keys → Add key, select Mistral, and paste your key.

Security

Your API keys are encrypted at rest using AES-256-GCM. They are decrypted in memory only at the moment of use and are never written to logs or exposed in any system output. Custos AI staff cannot read your API keys.

Next: Set budget limits

Protect your team from unexpected LLM costs with monthly spending caps.

Budget limits guide