Can I set spending limits on my LLM API account?
Provider-native limits
OpenAI allows you to set a monthly budget in your account settings; once reached, API requests are blocked until the next month or until you raise the limit. Anthropic offers usage limits that you can configure per API key. Google Cloud and Azure let you set budgets and alerts through their billing consoles.
These limits are usually soft in the sense that they apply to the billing account, not individual projects, unless you use separate accounts. Check your provider's documentation for exact behavior.
Using a proxy for granular limits
If your provider doesn't offer per-key or per-user limits, a proxy like LiteLLM or Helicone can enforce them. You can set a budget for each API key, user, or team, and the proxy will reject requests once the limit is hit.
This is especially useful for multi-tenant apps where you want to prevent one customer from burning through your entire budget. You can also set rate limits (requests per minute) to avoid runaway costs from bugs.
- OpenAI: monthly budget in billing settings
- Anthropic: usage limits per API key
- Azure OpenAI: budgets and alerts in Cost Management
- Google Cloud: budgets in Cloud Billing
- Proxies: per-key, per-user, per-feature budgets
What happens when you hit a limit?
Typically, further API calls will fail with an error until the limit is reset or increased. Some providers send email alerts before cutting you off. Make sure your app handles these errors gracefully—e.g., by falling back to a cheaper model or showing a friendly message.
If you're in production, consider setting the limit slightly above your expected spend to avoid downtime, and monitor closely.
Common mistakes
- Assuming spending limits are per API key when they're often per billing account.
- Setting a limit too low and causing production outages when the limit is hit.
- Not realizing that some providers only offer soft alerts, not hard caps.
