Verify Google sign-in for a branded guest

POST /v1/developer/guest-auth/google/verify

Operation ID: verifyDeveloperGuestGoogleAuth

Exchanges a Google authorization code with PKCE and nonce verification on an explicitly configured installation callback, resolves the canonical guest, and returns tokens only to the host BFF. Requires a server credential, CSRF proof and authorized branded origin. TEST and LIVE callbacks are configured separately; unsupported installations fail closed.

Contract status

Field	Value
Maturity	`beta`
Required capability	`guest_auth.write`
Freshness class	`sandbox-write`
Quota cost	`1`

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
`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:

{
  "type": "object",
  "additionalProperties": false,
  "required": [
    "code",
    "codeVerifier",
    "nonce",
    "kidSid"
  ],
  "properties": {
    "code": {
      "type": "string",
      "minLength": 1,
      "maxLength": 4096
    },
    "codeVerifier": {
      "type": "string",
      "pattern": "^[a-zA-Z0-9_-]{43,128}$"
    },
    "nonce": {
      "type": "string",
      "pattern": "^[a-zA-Z0-9_-]{43}$"
    },
    "kidSid": {
      "type": "string",
      "pattern": "^kid_[A-Za-z0-9]{8}$"
    }
  }
}

Minimal example:

{
  "code": "042817",
  "codeVerifier": "string",
  "nonce": "string",
  "kidSid": "kid_Ab12Cd34"
}

cURL

Set KISMET_API_ORIGIN=https://api.ksmt.app and configure KISMET_DEVELOPER_API_KEY in your environment. Run server-credential requests from your backend, not browser code.

Guest access tokens come from the signed-in guest session held by your backend. Forward a CSRF proof only after your same-origin backend validates it. If shown, KISMET_SITE_ORIGIN is the authorized origin of your site. Do not substitute a guest ID or an invented token.

curl --request POST \
  "$KISMET_API_ORIGIN/v1/developer/guest-auth/google/verify" \
  --header "Authorization: Bearer $KISMET_DEVELOPER_API_KEY" \
  --header "Accept: application/json" \
  --header "x-kismet-csrf: $VALIDATED_CSRF_TOKEN" \
  --header "origin: $KISMET_SITE_ORIGIN" \
  --header "Content-Type: application/json" \
  --data '{"code":"042817","codeVerifier":"string","nonce":"string","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.

200 response example

{
  "kidSid": "kid_AbCdEf12",
  "guest": {
    "id": "77777777-7777-4777-8777-777777777777",
    "email": "[email protected]",
    "guestProfileId": "88888888-8888-4888-8888-888888888888"
  },
  "session": {
    "accessToken": "<server-only-access-token>",
    "refreshToken": "<server-only-refresh-token>",
    "expiresAt": "2026-09-17T18:00:00.000Z"
  }
}

200 response schema

Content type: application/json. Required fields, nullable values, and nested structures are defined below.

View complete response schema

{
  "type": "object",
  "additionalProperties": false,
  "required": [
    "kidSid",
    "guest",
    "session"
  ],
  "properties": {
    "kidSid": {
      "type": "string"
    },
    "guest": {
      "type": "object",
      "additionalProperties": false,
      "required": [
        "id",
        "email",
        "guestProfileId"
      ],
      "properties": {
        "id": {
          "type": "string"
        },
        "email": {
          "type": "string"
        },
        "guestProfileId": {
          "type": "string"
        }
      }
    },
    "session": {
      "type": "object",
      "additionalProperties": false,
      "required": [
        "accessToken",
        "refreshToken",
        "expiresAt"
      ],
      "properties": {
        "accessToken": {
          "type": "string"
        },
        "refreshToken": {
          "type": "string"
        },
        "expiresAt": {
          "type": "string",
          "format": "date-time"
        }
      }
    }
  }
}