diff --git a/nix/host-modules/swarm-nats.nix b/nix/host-modules/swarm-nats.nix
index 671c2d8e..5c97dccc 100644
--- a/nix/host-modules/swarm-nats.nix
+++ b/nix/host-modules/swarm-nats.nix
@@ -603,6 +603,27 @@ in
             listenAddress = "127.0.0.1";
             port = cfg.metricsPort;
             url = "http://127.0.0.1:${toString cfg.monitorPort}";
+
+            # ⚠️ NOT optional, despite the name. Upstream renders
+            # `-addr … -port … ${extraFlags} ${url}` and defaults
+            # `extraFlags` to the empty list, but the exporter REFUSES TO
+            # START without at least one collector: it exits 1 with
+            # "no Collectors specified". Shipped without this the unit logs
+            # `Started`, the process is gone milliseconds later, and the
+            # scrape is refused — measured, and invisible to evaluation
+            # because the empty list renders perfectly.
+            #
+            # Which three, and why not more: `varz` is the server itself
+            # (uptime, memory, slow consumers), `connz` is per-connection so
+            # a client that will not stay connected is visible, and `jsz`
+            # covers JetStream, which this swarm relies on for the status
+            # KV. The remaining collectors describe a clustered deployment
+            # this swarm does not have.
+            extraFlags = [
+              "-varz"
+              "-connz"
+              "-jsz=all"
+            ];
           };
 
           # A wrapper that includes upstream's rendered settings verbatim