---
title: "Verify a branded guest authentication challenge"
description: "Consumes a single-use challenge only from a branded host authorized through Collection.authorizedDomains, binds the proven Guest and canonical GuestProfile to the same `kidSid`, and returns guest session tokens to the host BFF. The BFF must set its own branded HttpOnly cookie; Kismet credentials and tokens must never enter browser JavaScript."
---

`POST /v1/developer/guest-auth/challenges/{challengeId}/verify`

**Operation ID:** `verifyDeveloperGuestAuth`

Consumes a single-use challenge only from a branded host authorized through Collection.authorizedDomains, binds the proven Guest and canonical GuestProfile to the same `kidSid`, and returns guest session tokens to the host BFF. The BFF must set its own branded HttpOnly cookie; Kismet credentials and tokens must never enter browser JavaScript.

## Contract status

| Field | Value |
| --- | --- |
| Maturity | `beta` |
| Required capability | `guest_auth.write` |
| Freshness class | `sandbox-write` |
| Quota cost | `1` |
| Operational owner | Identity + Developer Experience |

All operations require a Kismet Developer Bearer credential. Collection and resource authority is resolved from the credential's installation grants; identifiers in the URL never grant access.

## Request parameters

| Name | In | Type | Required | Description |
| --- | --- | --- | --- | --- |
| `challengeId` | path | string | yes |  |
| `x-kismet-csrf` | header | string | yes | Opaque CSRF proof validated by the same-origin host BFF before it calls Kismet. Never a Kismet credential. |
| `origin` | header | string | no | Original branded browser origin forwarded by the same-origin BFF. Must match Collection.authorizedDomains. |
| `x-forwarded-host` | header | string | no | Original branded host fallback for server route handlers that do not forward Origin. Must match Collection.authorizedDomains. |

## Request body

The request body is JSON. The canonical schema is:

```json
{
  "type": "object",
  "additionalProperties": false,
  "required": [
    "code",
    "kidSid"
  ],
  "properties": {
    "code": {
      "type": "string",
      "pattern": "^\\d{6}$"
    },
    "kidSid": {
      "type": "string",
      "pattern": "^kid_[A-Za-z0-9]{8}$"
    }
  }
}
```

Minimal example:

```json
{
  "code": "042817",
  "kidSid": "kid_Ab12Cd34"
}
```

## cURL

```sh
curl --request POST \
  "$KISMET_API_ORIGIN/v1/developer/guest-auth/challenges/CHALLENGE_ID/verify" \
  --header "Authorization: Bearer $KISMET_DEVELOPER_API_KEY" \
  --header "Accept: application/json" \
  --header "Content-Type: application/json" \
  --data '{"code":"042817","kidSid":"kid_Ab12Cd34"}'
```

## Responses

| Status | Meaning |
| --- | --- |
| 200 | Success. |
| 400 | Invalid request parameters or body. |
| 401 | Missing, invalid, expired, or inappropriate credential/session. |
| 403 | Credential lacks the required grant/capability, or an origin/CSRF check failed. |
| 409 | Request conflicts with the installation environment or current state. |
| 410 | The single-use authentication challenge is no longer valid. |
| 429 | Rate limit or quota exceeded; inspect response metadata before retrying. |
| 503 | A required Kismet dependency is temporarily unavailable. |

### Success example

```json
{
  "kidSid": "kid_AbCdEf12",
  "guest": {
    "id": "77777777-7777-4777-8777-777777777777",
    "email": "developer-test@example.com",
    "guestProfileId": "88888888-8888-4888-8888-888888888888"
  },
  "session": {
    "accessToken": "<server-only-access-token>",
    "refreshToken": "<server-only-refresh-token>",
    "expiresAt": "2026-09-17T18:00:00.000Z"
  }
}
```

## Machine-readable sources

- [This page as Markdown](/api/reference/verify-developer-guest-auth.md)
- [Developer API OpenAPI v0.7.0](/openapi.json)