---
title: "Issue a challenge for a TOTP factor"
method: POST
path: "/auth/mfa/challenge"
tags: ["Auth"]
---

# Issue a challenge for a TOTP factor

`POST /auth/mfa/challenge`

## Request

- Base URL: `https://api.mnemom.ai/v1`
- URL: `https://api.mnemom.ai/v1/auth/mfa/challenge`
- Auth: API key in cookie `mnemom_session`

Called during the sign-in MFA step-up flow (using the `mnemom_mfa_pending` cookie) or during enrollment verification (using the existing `mnemom_session`). Returns a `challenge_id` to pass to `/auth/mfa/verify`.

## Request body

- object
  - `factor_id` string, required

## Response `200`

Challenge issued.

- object
  - `challenge_id` string, required

## Other responses

- `400`: Bad request
- `401`: Authentication required
- `403`: Cross-origin write refused (`cross_origin_rejected`). A state-changing request that carries the browser session cookie must come from a first-party origin (`Origin`, or failing that `Referer`) and must not send a form-style body (text/plain, urlencoded, multipart) the operation does not declare. Bearer and API-key callers are never subject to this check.
- `422`: Request was well-formed but semantically invalid (e.g., business-rule validation failure, malformed YAML inside a JSON payload).
- `429`: Rate-limit exceeded. The global per-IP limiter (100 requests/minute, applied to every `/v1/*` route) rejected this request. Back off until the window resets — `Retry-After` carries the cooldown in seconds and `X-RateLimit-Reset` the absolute reset time.
- `500`: Server error — request was well-formed but the server failed to fulfill it. Typically a downstream dependency (DB / RPC / external API) returned an unexpected error.
- `503`: An upstream dependency is currently unavailable. The request was not processed; retry after the cooldown window.

---

[API](https://skmtc.dev/mnemom/apis/mnemom-api.md) · [All operations](https://skmtc.dev/mnemom/apis/mnemom-api/llms.txt) · [OpenAPI document](https://skmtc.dev/mnemom/apis/mnemom-api/revisions/274b7a6ea182?raw)