diff --git a/labsim/labsim-k8s-etcd.sh b/labsim/labsim-k8s-etcd.sh
index 53819e0..839741d 100755
--- a/labsim/labsim-k8s-etcd.sh
+++ b/labsim/labsim-k8s-etcd.sh
@@ -170,7 +170,17 @@ runcmd:
     # INSTALL_K3S_EXEC=server (bare) -- everything else comes from config.yaml,
     # exactly as production. The token is passed via env for the join; on node 1
     # it seeds the cluster token.
-    curl -sfL https://get.k3s.io | INSTALL_K3S_EXEC="server" K3S_TOKEN="$TOKEN" sh -
+    #
+    # The etcd-arg tuning is LAB-ONLY and deliberately NOT in the production
+    # config.yaml/k3s-config.ts: three embedded-etcd servers on a busy labsim
+    # host starve etcd of CPU, and stock etcd timers (100ms heartbeat / 1s
+    # election) then trigger a constant leader-re-election storm that never
+    # settles ("storage is (re)initializing", k3s stuck activating). Relaxing
+    # the timers lets etcd tolerate the lab's scheduling latency. It changes
+    # NOTHING the dual-stack conversion exercises (config.yaml CIDR handling,
+    # ServiceCIDR pickup, quorum across a restart) -- it just keeps etcd alive
+    # under nested-virt jitter. See dualstack-evidence/etcd-harness-2026-09-07.md.
+    curl -sfL https://get.k3s.io | INSTALL_K3S_EXEC="server --etcd-arg=heartbeat-interval=500 --etcd-arg=election-timeout=5000" K3S_TOKEN="$TOKEN" sh -
 EOF
 
   # Guard the generated YAML before building the ISO -- a bad indent in the