# Update Username

Update the authenticated user's username.

## Request Body

**`username`** string required

New username (3-100 characters, lowercase letters/numbers/dots/underscores/hyphens only).

## Returns

Success message with updated username.

## Validation Rules

- 3-100 characters
- Lowercase letters, numbers, dots (`.`), underscores (`_`), hyphens (`-`)
- Must be unique across the system


Request

```bash
curl -X PUT \
  "https://api.aitronos.com/v1/user/username" \
  -H "X-API-Key: $FREDDY_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "username": "johndoe"
  }'
```


```python
import requests

response = requests.put(
    "https://api.aitronos.com/v1/user/username",
    headers={"Authorization": f"Bearer {FREDDY_API_KEY}"},
    json={"username": "johndoe"}
)
```


```javascript
const response = await fetch('https://api.aitronos.com/v1/user/username', {
  method: 'PUT',
  headers: {
    'Authorization': `Bearer ${FREDDY_API_KEY}`,
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({ username: 'johndoe' })
});
```

**Response:**

200 OK

```json
{
  "success": true,
  "message": "Username updated successfully",
  "username": "johndoe"
}
```

409 Conflict

```json
{
  "detail": "Username already taken"
}
```

422 Validation Error

```json
{
  "detail": [
    {
      "loc": ["body", "username"],
      "msg": "Username must be 3-100 characters",
      "type": "value_error"
    }
  ]
}
```