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

# POST /api/auth/register

> Create a new user account with username, email, and password.

Creates a user row. The password is hashed with `bcryptjs` (cost 10) before insertion.

## Request

```http theme={null}
POST /api/auth/register
Content-Type: application/json
```

### Body

```json theme={null}
{
  "username": "example_user",
  "email": "user@example.com",
  "password": "a-strong-password"
}
```

| Field      | Type   | Constraint                                                   |
| ---------- | ------ | ------------------------------------------------------------ |
| `username` | string | Validated by `registerInput` (see `src/lib/auth/schemas.ts`) |
| `email`    | string | Valid email                                                  |
| `password` | string | Minimum length enforced by schema                            |

## Responses

### 201 Created

```json theme={null}
{
  "user": {
    "id": "00000000-0000-0000-0000-000000000000",
    "username": "example_user",
    "email": "user@example.com"
  }
}
```

The `hashed_password` column is **never** returned.

### 400 Bad Request - invalid JSON

```json theme={null}
{ "error": "Invalid JSON body" }
```

### 400 Bad Request - validation failure

```json theme={null}
{
  "error": "Validation failed",
  "details": {
    "fieldErrors": {
      "email": ["Invalid email"]
    },
    "formErrors": []
  }
}
```

### 409 Conflict - duplicate

When the email or username already exists. Two possible bodies depending on which check tripped:

```json theme={null}
{ "error": "A user with this email already exists" }
```

```json theme={null}
{ "error": "A user with this username already exists" }
```

```json theme={null}
{ "error": "Email or username already exists" }
```

The third is the fallback for a race between the pre-check and the `INSERT` - the route translates Postgres `unique_violation` (`23505`) to `409` rather than leaking `500`.

## cURL

```bash theme={null}
curl -X POST https://probot.vercel.app/api/auth/register \
  -H 'Content-Type: application/json' \
  -d '{
    "username": "example_user",
    "email": "user@example.com",
    "password": "a-strong-password"
  }'
```

## After registering

You're not logged in yet. Use the NextAuth credentials sign-in flow (the `/login` page in the app), or `POST /api/auth/callback/credentials` directly. See [the NextAuth REST API docs](https://next-auth.js.org/getting-started/rest-api).