---
title: "OIDC callback landing — issues session and redirects to SPA"
method: GET
path: "/auth/oidc/callback"
tags: ["Auth"]
---

# OIDC callback landing — issues session and redirects to SPA

`GET /auth/oidc/callback`

## Request

- Base URL: `https://api.mnemom.ai/v1`
- URL: `https://api.mnemom.ai/v1/auth/oidc/callback`
- Auth: none required

B1 PR-B (MNE-1449). Validates the HMAC-signed `state` (double-submitted against the `mnemom_oidc_initiator` cookie), consumes the single-use nonce, exchanges the authorization `code` at the Zitadel token endpoint (PKCE), and issues `mnemom_session` via a 302 to the SPA. Returns 503 unless the cell is configured for Zitadel login.

## Query parameters

- `code` string, required
- `state` string, required

## Other responses

- `302`: Session issued. Redirects to the SPA.
- `400`: Bad request
- `401`: Authentication required
- `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)