From 2bfdb0de6db65f4fac46bde8bb921a2cbef63a04 Mon Sep 17 00:00:00 2001
From: Olivier 'reivilibre <oliverw@matrix.org>
Date: Fri, 20 Feb 2026 11:04:55 +0000
Subject: [PATCH] Add 404 to /auth_metadata

---
 data/api/client-server/oauth_server_metadata.yaml | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/data/api/client-server/oauth_server_metadata.yaml b/data/api/client-server/oauth_server_metadata.yaml
index 719a1e16..e5533271 100644
--- a/data/api/client-server/oauth_server_metadata.yaml
+++ b/data/api/client-server/oauth_server_metadata.yaml
@@ -195,6 +195,21 @@ paths:
                     "org.matrix.cross_signing_reset",
                   ],
                 }
+        "404":
+          description: |-
+            With `M_UNRECOGNIZED`: the homeserver does not support the OAuth 2.0 API.
+            (See [Authentication API discovery](/client-server-api/#authentication-api-discovery).)
+          content:
+            application/json:
+              schema:
+                $ref: definitions/errors/error.yaml
+              examples:
+                response:
+                  value:
+                    {
+                      "errcode": "M_UNRECOGNIZED",
+                      "error": "Legacy authentication is in use on this homeserver.",
+                    }
       tags:
         - Session management
 servers: