Start branded email-code guest authentication

POST /v1/developer/guest-auth/challenges

Operation ID: challengeDeveloperGuestAuth

Creates an email OTP challenge bound to this installation, collection, exact Kismet identity anchor (kidSid), and a branded host authorized through Collection.authorizedDomains. Requires a server (sk_) credential and a same-origin BFF CSRF proof. The response includes child-brand auth presentation with missing fields inherited only from the nearest cycle-safe SUB_BRAND parent. TEST installations never send email: registered test recipients receive a deterministic verification code in this authenticated server response; all other addresses receive the same accepted response without a usable code.

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
`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": [
    "email",
    "kidSid"
  ],
  "properties": {
    "email": {
      "type": "string",
      "minLength": 3,
      "maxLength": 254
    },
    "kidSid": {
      "type": "string",
      "pattern": "^kid_[A-Za-z0-9]{8}$"
    }
  }
}

Minimal example:

{
  "email": "developer-test@example.com",
  "kidSid": "kid_Ab12Cd34"
}

cURL

curl --request POST \
  "$KISMET_API_ORIGIN/v1/developer/guest-auth/challenges" \
  --header "Authorization: Bearer $KISMET_DEVELOPER_API_KEY" \
  --header "Accept: application/json" \
  --header "Content-Type: application/json" \
  --data '{"email":"developer-test@example.com","kidSid":"kid_Ab12Cd34"}'

Responses

Status	Meaning
202	Accepted without revealing whether the identity is registered.
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.
429	Rate limit or quota exceeded; inspect response metadata before retrying.
503	A required Kismet dependency is temporarily unavailable.

Success example

{
  "accepted": true,
  "challengeId": "66666666-6666-4666-8666-666666666666",
  "expiresAt": "2026-08-18T18:05:00.000Z",
  "testVerificationCode": "042817",
  "branding": {
    "displayName": "Sandbox Vacation Rentals",
    "logoUrl": "https://cdn.kismet.travel/sandbox/logo.svg",
    "faviconUrl": "https://cdn.kismet.travel/sandbox/favicon.ico",
    "supportEmail": "support@example.invalid",
    "policyLinks": {
      "termsUrl": "https://example.invalid/terms",
      "privacyUrl": "https://example.invalid/privacy"
    },
    "accountProvider": "Kismet"
  }
}