diff --git a/nix/modules/hive-gateway.nix b/nix/modules/hive-gateway.nix
index bd461f4f..f051fe0d 100644
--- a/nix/modules/hive-gateway.nix
+++ b/nix/modules/hive-gateway.nix
@@ -168,39 +168,6 @@ in
                     '';
                   };
                 }
-                //
-                  # `.well-known/matrix/*` auto-discovery (#660): when
-                  # `services.hyperhive.matrix.enable` is on and the
-                  # operator's set a hive domain, the gateway serves
-                  # the matrix-spec discovery JSON at the canonical
-                  # location so clients pointed at `${hyperhive.domain}`
-                  # resolve through to the actual tuwunel endpoint
-                  # without needing a `matrix.` subdomain.
-                  #
-                  # `m.homeserver.base_url` advertises the client-server
-                  # API. `m.server` advertises the federation
-                  # `host:port` (tuwunel serves both client + federation
-                  # on the same `httpPort` — see hive-matrix.nix).
-                  #
-                  # CORS `*` on the client endpoint per the matrix spec
-                  # (https://spec.matrix.org/v1.15/client-server-api/#getwell-knownmatrixclient).
-                  # No-op until the operator turns matrix on; until then
-                  # there's no homeserver to advertise.
-                  lib.optionalAttrs (matrixCfg.enable && hyperhiveDomain != null) {
-                    "= /.well-known/matrix/client" = {
-                      extraConfig = ''
-                        default_type application/json;
-                        add_header Access-Control-Allow-Origin *;
-                        return 200 '{"m.homeserver":{"base_url":"http://${hyperhiveDomain}:${toString matrixCfg.httpPort}"}}';
-                      '';
-                    };
-                    "= /.well-known/matrix/server" = {
-                      extraConfig = ''
-                        default_type application/json;
-                        return 200 '{"m.server":"${hyperhiveDomain}:${toString matrixCfg.httpPort}"}';
-                      '';
-                    };
-                  }
                 // {
                   # Everything else proxies to hive-c0re. Upgrade
                   # headers stay set so SSE (`/dashboard/stream`,
diff --git a/nix/modules/hive-matrix.nix b/nix/modules/hive-matrix.nix
index c1575d9e..89198081 100644
--- a/nix/modules/hive-matrix.nix
+++ b/nix/modules/hive-matrix.nix
@@ -7,7 +7,8 @@
 let
   cfg = config.services.hyperhive.matrix;
   hyperhiveDomain = config.services.hyperhive.domain;
-  effectiveServerName = if cfg.serverName != null then cfg.serverName else hyperhiveDomain;
+  effectiveServerName =
+    if cfg.serverName != null then cfg.serverName else "matrix.${hyperhiveDomain}";
 in
 {
   # Private Matrix homeserver (matrix-tuwunel — the official conduwuit
@@ -76,21 +77,10 @@ in
         (`@argus:<server_name>`) and room ID minted on this
         homeserver. CRITICAL: must be stable from day one because
         it's embedded irrevocably in the identifiers. Defaults to
-        `services.hyperhive.domain` (the bare hive domain — per mara
-        on #660). Combined with the `.well-known/matrix/{client,server}`
-        routes the hive-gateway serves at that domain (also #660),
-        clients auto-discover the actual matrix endpoint without
-        needing a subdomain. Override here only if you need a
-        different server_name shape (e.g. `matrix.<domain>` if you
-        want the subdomain split, or `chat.example.org` for a
-        bespoke hostname).
-
-        **Breaking change as of #660**: this used to default to
-        `matrix.''${services.hyperhive.domain}`. matrix IDs embed
-        the server_name irrevocably, so existing homeservers must
-        set `services.hyperhive.matrix.serverName = "matrix.''${services.hyperhive.domain}";`
-        explicitly to preserve their pre-#660 user / room IDs
-        before rebuilding.
+        `matrix.''${services.hyperhive.domain}` (always a subdomain — keeps
+        the root domain free for the dashboard or forge). Override
+        here only if you need a name that doesn't follow the
+        `matrix.<domain>` shape.
       '';
     };