> ## Documentation Index
> Fetch the complete documentation index at: https://usenaive.ai/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Upgrade Plan

> Upgrade to a higher subscription plan

For existing subscribers, returns a billing portal URL for plan change (with automatic proration). For users without an active subscription, creates a new subscription checkout.

### Request Body

| Parameter | Type   | Required | Description        |
| --------- | ------ | -------- | ------------------ |
| `plan`    | string | Yes      | `starter` or `pro` |

### Response (existing subscriber)

```json theme={"theme":"css-variables"}
{
  "portal_url": "https://billing.example.com/p/session/...",
  "hint": "Open the portal URL to manage your subscription and change plans."
}
```

### Response (no subscription)

Same as `POST /v1/billing/subscribe`.