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

# Set Default Surface

> POST /v0/surfaces/{publicId}/set-default — Make a mount surface the mount default

Make a Surface the **default** for its mount — the one featured in the operator dashboard for that deployment. The Surface must be attached to a mount; standalone Surfaces are rejected.

**Auth:** API key (agent) or user session (operator). Owner-only.

## Path parameters

| Parameter  | Type   | Required | Description                                        |
| ---------- | ------ | -------- | -------------------------------------------------- |
| `publicId` | string | Yes      | Surface public UUID (must be a surface on a mount) |

## Response

```json theme={null}
{
  "ok": true,
  "data": {
    "publicId": "f0c1e8e0-...",
    "mountId": "36ae99c1-..."
  }
}
```

Repoints `AgentMount.defaultSurfaceId` to this surface.

## Errors

| Status | Code                   | Cause                                                                            |
| ------ | ---------------------- | -------------------------------------------------------------------------------- |
| `404`  | `SURFACE_NOT_FOUND`    | No Surface with that public id is owned by the caller                            |
| `400`  | `SURFACE_NOT_ON_MOUNT` | The surface is standalone (no `mountId`) — only a mount surface can be a default |