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

# Begin passkey authentication

> Returns challengeId and WebAuthn request options. Supply an active challengeId for password-login or reauthentication; a signed-in session without one starts reauthentication.

No signed-in session is required. Endpoint-specific tokens, setup secrets or challenges may still be required.

Returns challengeId and WebAuthn request options. Supply an active challengeId for password-login or reauthentication; a signed-in session without one starts reauthentication.

[Request conventions](/api-reference/overview) · [API keys](/api-keys) · [MCP connections](/mcp-connections)


## OpenAPI

````yaml api-reference/openapi.json POST /api/auth/passkeys/authenticate/options
openapi: 3.1.0
info:
  title: Posted HTTP API
  version: 0.2.0
  description: >-
    All registered application, account, OAuth, MCP transport and health
    endpoints. Publishing and draft request schemas come from the shared runtime
    validators. Replace the example server with your installation. Documentation
    uses simple request examples and does not execute live publishing requests.
servers:
  - url: https://posted-api.example.com
security: []
paths:
  /api/auth/passkeys/authenticate/options:
    post:
      tags:
        - Passkeys and recovery
      summary: Begin passkey authentication
      description: >-
        Returns challengeId and WebAuthn request options. Supply an active
        challengeId for password-login or reauthentication; a signed-in session
        without one starts reauthentication.


        No signed-in session is required. Endpoint-specific tokens, setup
        secrets or challenges may still be required.
      operationId: post_api_auth_passkeys_authenticate_options
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              properties:
                challengeId:
                  type: string
                  pattern: ^[A-Za-z0-9_-]{43}$
              additionalProperties: false
      responses:
        '200':
          description: >-
            Successful response. Examples are illustrative; field values vary by
            record.
          content:
            application/json:
              schema:
                type: object
                properties:
                  challengeId:
                    type: string
                  options:
                    type: object
                    properties:
                      challenge:
                        type: string
                      rpId:
                        type: string
                      userVerification:
                        type: string
                    additionalProperties: true
                additionalProperties: true
              example:
                challengeId: example-challenge-token
                options:
                  challenge: example-browser-challenge
                  rpId: posted.example.test
                  userVerification: required
        default:
          description: >-
            Request failure. Inspect code, message and requestId; respect
            Retry-After on HTTP 429.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Error'
      security: []
components:
  schemas:
    Error:
      type: object
      required:
        - error
      properties:
        error:
          type: object
          required:
            - code
            - message
            - requestId
          properties:
            code:
              type: string
            message:
              type: string
            requestId:
              type: string

````

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