---
title: "Prepare a passkey second-factor assertion"
method: POST
path: "/identity/sign_in/passkey_assertions"
tags: ["identity", "customer-session", "customer-session-public"]
---

# Prepare a passkey second-factor assertion

`POST /identity/sign_in/passkey_assertions`

## Request

- Base URL: `https://api.stablesea.com` (the document declares no server; this is the origin it was published from)
- URL: `https://api.stablesea.com/identity/sign_in/passkey_assertions`
- Auth: none declared

Requires the live password-proven session_token. A browser assertion with user verification completes this second factor; no cookie is installed here.

## Request body

- IdentitySignInPasskeyInput
  - `session_token` string, required

## Response `200`

OK

- IdentitySignInPasskeyChallenge
  - `ceremony_token` string
  - `webauthn_options` unknown

## Other responses

- `400`: Bad Request
- `401`: Unauthorized
- `403`: Forbidden
- `404`: Not Found
- `429`: Too Many Requests
- `default`: Error response.

## Changes

- **2026-11-02** `772c80d83658`: 1 info
  - endpoint added

[Operation history](https://skmtc.dev/stablesea/apis/stable-sea-backend/changes/identity/sign_in/passkey_assertions/post.md)

---

[API](https://skmtc.dev/stablesea/apis/stable-sea-backend.md) - [All operations](https://skmtc.dev/stablesea/apis/stable-sea-backend/llms.txt) - [OpenAPI document](https://skmtc.dev/stablesea/apis/stable-sea-backend/revisions/772c80d83658?raw)