diff --git a/changelog/unreleased/930-detect-apiserver-endpoint.md b/changelog/unreleased/930-detect-apiserver-endpoint.md
new file mode 100644
index 000000000..d4eba980c
--- /dev/null
+++ b/changelog/unreleased/930-detect-apiserver-endpoint.md
@@ -0,0 +1,7 @@
+# Agent heartbeats reach a public API server endpoint
+
+The chart's `allow-agent-to-apiserver` and `allow-sentinel-to-apiserver` policies only allowed
+private ranges by default, so on a k3s node with a public IP every agent heartbeat timed out
+and servers stayed "Starting" with no CPU, memory or disk figures. When
+`networkPolicies.apiServerCIDRs` is unset, the chart now also allows the `kubernetes` Service
+addresses it detects at install or upgrade time. [PR #930](https://github.com/GameplanePanel/Gameplane/pull/930)
diff --git a/charts/gameplane/templates/_helpers.tpl b/charts/gameplane/templates/_helpers.tpl
index 44bf31ee3..bb80d1b29 100644
--- a/charts/gameplane/templates/_helpers.tpl
+++ b/charts/gameplane/templates/_helpers.tpl
@@ -189,3 +189,47 @@ mergeOverwrite preserves explicit zero/empty values so validation can reject the
 {{- end -}}
 {{- uniq $namespaces | toJson -}}
 {{- end -}}
+
+{{- /*
+gameplane.apiServerEgressPeers renders the NetworkPolicy `to:` peers of the
+agent and sentinel apiserver egress rules. An explicit
+networkPolicies.apiServerCIDRs list wins. Otherwise it renders the RFC1918 +
+link-local fallback plus every address the live cluster reports for the
+`kubernetes` Service: its ClusterIPs and its EndpointSlice endpoint addresses.
+On k3s and kubeadm single-node installs that endpoint is the node's own IP,
+which is often public and outside the fallback; without it heartbeats time
+out and every server stays "Starting". Offline renders (helm template, client
+dry-run) get empty lookups and keep the plain fallback. Addresses are read at
+install/upgrade time, so re-run helm upgrade if the API endpoint moves.
+*/}}
+{{- define "gameplane.apiServerEgressPeers" -}}
+{{- $cidrs := .Values.networkPolicies.apiServerCIDRs | default (list) -}}
+{{- if not $cidrs -}}
+{{- $cidrs = list "10.0.0.0/8" "172.16.0.0/12" "192.168.0.0/16" "169.254.0.0/16" -}}
+{{- $addrs := list -}}
+{{- $svc := lookup "v1" "Service" "default" "kubernetes" -}}
+{{- range (dig "spec" "clusterIPs" (list) $svc) -}}
+{{- $addrs = append $addrs . -}}
+{{- end -}}
+{{- $slices := lookup "discovery.k8s.io/v1" "EndpointSlice" "default" "" -}}
+{{- range (dig "items" (list) $slices) -}}
+{{- if eq (dig "metadata" "labels" "kubernetes.io/service-name" "" .) "kubernetes" -}}
+{{- range (dig "endpoints" (list) .) -}}
+{{- range (dig "addresses" (list) .) -}}
+{{- $addrs = append $addrs . -}}
+{{- end -}}
+{{- end -}}
+{{- end -}}
+{{- end -}}
+{{- range $addrs -}}
+{{- if contains ":" . -}}
+{{- $cidrs = append $cidrs (printf "%s/128" .) -}}
+{{- else -}}
+{{- $cidrs = append $cidrs (printf "%s/32" .) -}}
+{{- end -}}
+{{- end -}}
+{{- end -}}
+{{- range (uniq $cidrs) }}
+- ipBlock: { cidr: {{ . | quote }} }
+{{- end -}}
+{{- end -}}
diff --git a/charts/gameplane/templates/networkpolicies.yaml b/charts/gameplane/templates/networkpolicies.yaml
index ed2ae0a8a..3d8942297 100644
--- a/charts/gameplane/templates/networkpolicies.yaml
+++ b/charts/gameplane/templates/networkpolicies.yaml
@@ -40,9 +40,10 @@ spec:
 # Allow the agent sidecar to reach the kube-apiserver for its status
 # heartbeat (gameservers/status patches). Service VIP traffic is DNATed
 # to the apiserver endpoint before policy evaluation on most CNIs, so an
-# ipBlock toward the endpoint address is required; like the kubelet
-# probes policy below, default to RFC1918 + link-local and let operators
-# narrow it via networkPolicies.apiServerCIDRs.
+# ipBlock toward the endpoint address is required. Unset
+# networkPolicies.apiServerCIDRs means RFC1918 + link-local plus the
+# kubernetes Service endpoints detected at install time (a k3s node's
+# public IP, for example); set the list to narrow it.
 apiVersion: networking.k8s.io/v1
 kind: NetworkPolicy
 metadata:
@@ -56,17 +57,7 @@ spec:
   policyTypes: [Egress]
   egress:
     - to:
-        {{- $apiCidrs := (.Values.networkPolicies.apiServerCIDRs | default (list)) }}
-        {{- if $apiCidrs }}
-        {{- range $apiCidrs }}
-        - ipBlock: { cidr: {{ . | quote }} }
-        {{- end }}
-        {{- else }}
-        - ipBlock: { cidr: 10.0.0.0/8 }
-        - ipBlock: { cidr: 172.16.0.0/12 }
-        - ipBlock: { cidr: 192.168.0.0/16 }
-        - ipBlock: { cidr: 169.254.0.0/16 }
-        {{- end }}
+        {{- include "gameplane.apiServerEgressPeers" . | trim | nindent 8 }}
       ports:
         - { protocol: TCP, port: 443 }
         - { protocol: TCP, port: 6443 }
@@ -341,17 +332,7 @@ spec:
   policyTypes: [Egress]
   egress:
     - to:
-        {{- $apiCidrs := (.Values.networkPolicies.apiServerCIDRs | default (list)) }}
-        {{- if $apiCidrs }}
-        {{- range $apiCidrs }}
-        - ipBlock: { cidr: {{ . | quote }} }
-        {{- end }}
-        {{- else }}
-        - ipBlock: { cidr: 10.0.0.0/8 }
-        - ipBlock: { cidr: 172.16.0.0/12 }
-        - ipBlock: { cidr: 192.168.0.0/16 }
-        - ipBlock: { cidr: 169.254.0.0/16 }
-        {{- end }}
+        {{- include "gameplane.apiServerEgressPeers" . | trim | nindent 8 }}
       ports:
         - { protocol: TCP, port: 443 }
         - { protocol: TCP, port: 6443 }
diff --git a/charts/gameplane/values.yaml b/charts/gameplane/values.yaml
index f27559e43..3c9b909bb 100644
--- a/charts/gameplane/values.yaml
+++ b/charts/gameplane/values.yaml
@@ -599,8 +599,12 @@ networkPolicies:
   # probe ports, e.g. [{ protocol: TCP, port: 25565 }].
   probePorts: []
   # CIDRs that hold the kube-apiserver endpoint(s) the agent sidecar
-  # patches its status heartbeat through. Same fallback semantics as
-  # kubeletCIDRs: unset means RFC1918 + link-local on TCP 443/6443.
+  # patches its status heartbeat through. Unset means RFC1918 + link-local
+  # plus the kubernetes Service endpoint addresses detected at install or
+  # upgrade time (e.g. a k3s node's public IP), on TCP 443/6443. Offline
+  # renders (helm template, Argo CD) cannot detect them: set the list
+  # explicitly there when the endpoint is public. Re-run helm upgrade if
+  # the API server endpoint changes.
   apiServerCIDRs: []
   # Egress allowance for game pods to reach the public internet. Game
   # servers download their binaries, assets, and mods on first start
diff --git a/docs/install.md b/docs/install.md
index 803bf5085..87b49085d 100644
--- a/docs/install.md
+++ b/docs/install.md
@@ -240,7 +240,7 @@ Top-level knobs (see `values.yaml` for the full list):
   - `networkPolicies.gameIngress` — control ingress to game pods from external sources (players)
     - `gameIngress.enabled` — toggle player-ingress allowance (default `true`)
     - `gameIngress.fromCIDRs` — CIDRs from which player traffic is allowed (default `[0.0.0.0/0]`)
-  - `networkPolicies.apiServerCIDRs` — CIDRs allowed for agent heartbeat to kube-apiserver (defaults to all RFC1918 and link-local addresses on TCP 443/6443; customize to narrow to specific API endpoint(s))
+  - `networkPolicies.apiServerCIDRs` — CIDRs allowed for agent heartbeat to kube-apiserver (defaults to all RFC1918 and link-local addresses plus the `kubernetes` Service endpoints detected at install/upgrade time, on TCP 443/6443; offline renders such as `helm template` or Argo CD cannot detect endpoints, so set this when the API endpoint is public; customize to narrow to specific API endpoint(s))
   - `networkPolicies.gameEgress` — control public-internet egress for game pods (downloads, mod registries)
     - `gameEgress.enabled` — toggle public-egress allowance (default `true`)
     - `gameEgress.ports` — TCP ports for downloads (default 80, 443)
diff --git a/docs/security.md b/docs/security.md
index a67d58424..57b4f1d34 100644
--- a/docs/security.md
+++ b/docs/security.md
@@ -321,8 +321,9 @@ When `networkPolicies.enabled=true` (default) the chart applies:
   for status heartbeat (GameServer status patches). By default permits TCP 443
   and 6443 to all addresses in RFC1918 and link-local ranges (10.0.0.0/8,
   172.16.0.0/12, 192.168.0.0/16, 169.254.0.0/16), not limited to the apiserver
-  endpoint. Customize via `networkPolicies.apiServerCIDRs` to narrow to specific
-  API server addresses.
+  endpoint, plus the `kubernetes` Service ClusterIPs and endpoint addresses
+  the chart detects at install/upgrade time (as /32 or /128). Customize via
+  `networkPolicies.apiServerCIDRs` to narrow to specific API server addresses.
 - `allow-api-to-agent` — allows the API and operator pods (in the
   control-plane namespace) to reach every game pod's agent on TCP port 8090.
   The API proxies console/files/logs/players; the operator calls `/quiesce`