diff --git a/nix/host-modules/hive-matrix.nix b/nix/host-modules/hive-matrix.nix
index 35c2bbdb..f737c9fb 100644
--- a/nix/host-modules/hive-matrix.nix
+++ b/nix/host-modules/hive-matrix.nix
@@ -99,12 +99,19 @@ in
   options.services.hyperhive.swarm.matrix = {
     enable = lib.mkOption {
       type = lib.types.bool;
-      default = false;
+      default = config.services.hyperhive.swarm.enableRequiredServices;
+      defaultText = lib.literalExpression "services.hyperhive.swarm.enableRequiredServices";
       description = ''
         Run hive-matrix — a private matrix-tuwunel homeserver (in a
-        nixos-container) for hyperhive agents. Off by default while
-        the integration phases in; flip to `true` once the operator
-        has set `services.hyperhive.domain` and is ready to onboard agents.
+        nixos-container) for hyperhive agents.
+
+        Matrix is a swarm-wide service — one homeserver, not one per
+        hive — so this defaults from
+        `services.hyperhive.swarm.enableRequiredServices`, which says
+        the swarm's shared services live on this host. That is off by
+        default, so this is off by default, as before. Set it directly
+        to run the homeserver somewhere other than the host that holds
+        the rest of the swarm's services.
       '';
     };