diff --git a/docker-compose.metrics.yml b/docker-compose.metrics.yml
index e3eb21d..1dcb633 100644
--- a/docker-compose.metrics.yml
+++ b/docker-compose.metrics.yml
@@ -1,25 +1,17 @@
 services:
-  collector:
-    image: otel/opentelemetry-collector-contrib:0.136.0
-    command: ["--config=/etc/otelcol/config.yaml"]
-    volumes:
-      - ./examples/otel-collector.yaml:/etc/otelcol/config.yaml:ro
-    ports:
-      - "4317:4317"   # OTLP gRPC in
-      - "8889:8889"   # Prometheus scrape out
+  # Recommended Variant A: Direct Prometheus scrape of Newt (/metrics)
+  # Optional: You may add the Collector service and enable OTLP export, but do NOT
+  # scrape both Newt and the Collector for the same process.
 
   newt:
     build: .
     image: newt:dev
-    env_file: 
-    - .env
+    env_file:
+      - .env
     environment:
       OTEL_SERVICE_NAME: newt
       NEWT_METRICS_PROMETHEUS_ENABLED: "true"
-      NEWT_METRICS_OTLP_ENABLED: "true"
-      OTEL_EXPORTER_OTLP_ENDPOINT: "collector:4317"
-      OTEL_EXPORTER_OTLP_INSECURE: "true"
-      OTEL_EXPORTER_OTLP_METRICS_TEMPORALITY_PREFERENCE: "cumulative"
+      NEWT_METRICS_OTLP_ENABLED: "false"   # avoid double-scrape by default
       NEWT_ADMIN_ADDR: ":2112"
       # Base NEWT configuration
       PANGOLIN_ENDPOINT: ${PANGOLIN_ENDPOINT}
@@ -28,8 +20,16 @@ services:
       LOG_LEVEL: "DEBUG"
     ports:
       - "2112:2112"
-    depends_on:
-      - collector
+
+  # Optional Variant B: Enable the Collector and switch Prometheus scrape to it.
+  # collector:
+  #   image: otel/opentelemetry-collector-contrib:0.136.0
+  #   command: ["--config=/etc/otelcol/config.yaml"]
+  #   volumes:
+  #     - ./examples/otel-collector.yaml:/etc/otelcol/config.yaml:ro
+  #   ports:
+  #     - "4317:4317"   # OTLP gRPC in
+  #     - "8889:8889"   # Prometheus scrape out
 
   prometheus:
     image: prom/prometheus:v3.6.0
diff --git a/docs/observability.md b/docs/observability.md
index cf8de79..bae5fb7 100644
--- a/docs/observability.md
+++ b/docs/observability.md
@@ -49,8 +49,8 @@ Metric catalog (initial)
 
 Conventions
 
-- Durations in seconds, names end with _seconds
-- Sizes in bytes, names end with _bytes
+- Durations in seconds (unit: s), names end with _seconds
+- Sizes in bytes (unit: By), names end with _bytes
 - Counters end with _total
 - Labels must be low-cardinality and stable
 
@@ -163,6 +163,7 @@ Compatibility notes
 
 - Gauges do not use the _total suffix (e.g., newt_tunnel_sessions).
 - site_id is emitted as both resource attribute and metric label on all newt_* series; region is included as a metric label only when set. tunnel_id is a metric label (WireGuard public key). Never expose secrets in labels.
+- NEWT_METRICS_INCLUDE_TUNNEL_ID (default: true) toggles whether tunnel_id is included as a label on bytes/sessions/proxy/reconnect metrics. Disable in high-cardinality environments.
 - Avoid double-scraping: scrape either Newt (/metrics) or the Collector's Prometheus exporter, not both.
 - Prometheus does not accept remote_write; use Mimir/Cortex/VM/Thanos-Receive for remote_write.
 - No free text in labels; use only the enumerated constants for reason, protocol (tcp|udp), and transport (e.g., websocket|wireguard).
diff --git a/examples/prometheus.yml b/examples/prometheus.yml
index c3018a5..89e82b4 100644
--- a/examples/prometheus.yml
+++ b/examples/prometheus.yml
@@ -2,9 +2,20 @@ global:
   scrape_interval: 15s
 
 scrape_configs:
-  - job_name: newt
+  - job_name: 'newt'
+    scrape_interval: 15s
     static_configs:
-      - targets: ["newt:2112"]
-  - job_name: otel-collector
-    static_configs:
-      - targets: ["collector:8889"]
+      - targets: ['newt:2112']  # /metrics
+    relabel_configs:
+      # optional: tunnel_id droppen
+      - action: labeldrop
+        regex: 'tunnel_id'
+      # optional: nur bestimmte sites zulassen
+      - action: keep
+        source_labels: [site_id]
+        regex: '(site-a|site-b)'
+
+  # WARNING: Do not enable this together with the 'newt' job above or you will double-count.
+  # - job_name: 'otel-collector'
+  #   static_configs:
+  #     - targets: ['collector:8889']
diff --git a/internal/telemetry/metrics.go b/internal/telemetry/metrics.go
index 84c0f27..2571379 100644
--- a/internal/telemetry/metrics.go
+++ b/internal/telemetry/metrics.go
@@ -248,10 +248,13 @@ func IncSiteRegistration(ctx context.Context, result string) {
 }
 
 func AddTunnelBytes(ctx context.Context, tunnelID, direction string, n int64) {
-	mTunnelBytes.Add(ctx, n, metric.WithAttributes(attrsWithSite(
-		attribute.String("tunnel_id", tunnelID),
+	attrs := []attribute.KeyValue{
 		attribute.String("direction", direction),
-	)...))
+	}
+	if ShouldIncludeTunnelID() && tunnelID != "" {
+		attrs = append(attrs, attribute.String("tunnel_id", tunnelID))
+	}
+	mTunnelBytes.Add(ctx, n, metric.WithAttributes(attrsWithSite(attrs...)...))
 }
 
 // AddTunnelBytesSet adds bytes using a pre-built attribute.Set to avoid per-call allocations.
@@ -316,18 +319,24 @@ func IncCertRotation(ctx context.Context, result string) {
 }
 
 func ObserveTunnelLatency(ctx context.Context, tunnelID, transport string, seconds float64) {
-	mTunnelLatency.Record(ctx, seconds, metric.WithAttributes(attrsWithSite(
-		attribute.String("tunnel_id", tunnelID),
+	attrs := []attribute.KeyValue{
 		attribute.String("transport", transport),
-	)...))
+	}
+	if ShouldIncludeTunnelID() && tunnelID != "" {
+		attrs = append(attrs, attribute.String("tunnel_id", tunnelID))
+	}
+	mTunnelLatency.Record(ctx, seconds, metric.WithAttributes(attrsWithSite(attrs...)...))
 }
 
 func IncReconnect(ctx context.Context, tunnelID, initiator, reason string) {
-	mReconnects.Add(ctx, 1, metric.WithAttributes(attrsWithSite(
-		attribute.String("tunnel_id", tunnelID),
+	attrs := []attribute.KeyValue{
 		attribute.String("initiator", initiator),
 		attribute.String("reason", reason),
-	)...))
+	}
+	if ShouldIncludeTunnelID() && tunnelID != "" {
+		attrs = append(attrs, attribute.String("tunnel_id", tunnelID))
+	}
+	mReconnects.Add(ctx, 1, metric.WithAttributes(attrsWithSite(attrs...)...))
 }
 
 func IncConnAttempt(ctx context.Context, transport, result string) {
diff --git a/internal/telemetry/telemetry.go b/internal/telemetry/telemetry.go
index 7e3b819..8eb0927 100644
--- a/internal/telemetry/telemetry.go
+++ b/internal/telemetry/telemetry.go
@@ -112,6 +112,12 @@ type Setup struct {
 // installs recommended histogram views for *_latency_seconds, and returns a Setup with
 // a Shutdown method to flush exporters.
 func Init(ctx context.Context, cfg Config) (*Setup, error) {
+	// Configure tunnel_id label inclusion from env (default true)
+	if getenv("NEWT_METRICS_INCLUDE_TUNNEL_ID", "true") == "true" {
+		includeTunnelIDVal.Store(true)
+	} else {
+		includeTunnelIDVal.Store(false)
+	}
 	// Build resource with required attributes and only include optional ones when non-empty
 	attrs := []attribute.KeyValue{
 		semconv.ServiceName(cfg.ServiceName),
@@ -294,6 +300,7 @@ func parseResourceAttributes(s string) map[string]string {
 // Global site/region used to enrich metric labels.
 var siteIDVal atomic.Value
 var regionVal atomic.Value
+var includeTunnelIDVal atomic.Value // bool; default true
 
 // UpdateSiteInfo updates the global site_id and region used for metric labels.
 // Thread-safe via atomic.Value: subsequent metric emissions will include
@@ -336,6 +343,14 @@ func siteAttrs() []attribute.KeyValue {
 // SiteLabelKVs exposes site label KVs for other packages (e.g., proxy manager).
 func SiteLabelKVs() []attribute.KeyValue { return siteAttrs() }
 
+// ShouldIncludeTunnelID returns whether tunnel_id labels should be emitted.
+func ShouldIncludeTunnelID() bool {
+	if v, ok := includeTunnelIDVal.Load().(bool); ok {
+		return v
+	}
+	return true
+}
+
 func getenv(k, d string) string {
 	if v := os.Getenv(k); v != "" {
 		return v
diff --git a/proxy/manager.go b/proxy/manager.go
index cf15c66..3052f56 100644
--- a/proxy/manager.go
+++ b/proxy/manager.go
@@ -117,26 +117,29 @@ func (pm *ProxyManager) SetTunnelID(id string) {
 	e := pm.tunnels[id]
 	// include site labels if available
 	site := telemetry.SiteLabelKVs()
-	e.attrInTCP = attribute.NewSet(append(site,
-		attribute.String("tunnel_id", id),
+	build := func(base []attribute.KeyValue) attribute.Set {
+		if telemetry.ShouldIncludeTunnelID() {
+			base = append([]attribute.KeyValue{attribute.String("tunnel_id", id)}, base...)
+		}
+		base = append(site, base...)
+		return attribute.NewSet(base...)
+	}
+	e.attrInTCP = build([]attribute.KeyValue{
 		attribute.String("direction", "ingress"),
 		attribute.String("protocol", "tcp"),
-	)...)
-	e.attrOutTCP = attribute.NewSet(append(site,
-		attribute.String("tunnel_id", id),
+	})
+	e.attrOutTCP = build([]attribute.KeyValue{
 		attribute.String("direction", "egress"),
 		attribute.String("protocol", "tcp"),
-	)...)
-	e.attrInUDP = attribute.NewSet(append(site,
-		attribute.String("tunnel_id", id),
+	})
+	e.attrInUDP = build([]attribute.KeyValue{
 		attribute.String("direction", "ingress"),
 		attribute.String("protocol", "udp"),
-	)...)
-	e.attrOutUDP = attribute.NewSet(append(site,
-		attribute.String("tunnel_id", id),
+	})
+	e.attrOutUDP = build([]attribute.KeyValue{
 		attribute.String("direction", "egress"),
 		attribute.String("protocol", "udp"),
-	)...)
+	})
 }
 
 // ClearTunnelID clears cached attribute sets for the current tunnel.
diff --git a/scripts/smoke-metrics.sh b/scripts/smoke-metrics.sh
index e0eac32..d2eb11f 100644
--- a/scripts/smoke-metrics.sh
+++ b/scripts/smoke-metrics.sh
@@ -26,6 +26,16 @@ probe "last_heartbeat with site_id" "^newt_site_last_heartbeat_seconds\{.*site_i
 probe "tunnel bytes ingress" "^newt_tunnel_bytes_total\{.*direction=\"ingress\".*protocol=\"(tcp|udp)\"" || true
 probe "tunnel bytes egress" "^newt_tunnel_bytes_total\{.*direction=\"egress\".*protocol=\"(tcp|udp)\"" || true
 
+# Optional: verify absence/presence of tunnel_id based on EXPECT_TUNNEL_ID (default true)
+EXPECT_TUNNEL_ID=${EXPECT_TUNNEL_ID:-true}
+if [ "$EXPECT_TUNNEL_ID" = "false" ]; then
+  echo "[probe] ensure tunnel_id label is absent when NEWT_METRICS_INCLUDE_TUNNEL_ID=false"
+  ! curl -sf "${METRICS_URL}" | grep -q "tunnel_id=\"" || { echo "[fail] tunnel_id present but EXPECT_TUNNEL_ID=false"; exit 1; }
+else
+  echo "[probe] ensure tunnel_id label is present (default)"
+  curl -sf "${METRICS_URL}" | grep -q "tunnel_id=\"" || { echo "[warn] tunnel_id not found (may be expected if no tunnel is active)"; }
+fi
+
 # WebSocket metrics (when OTLP/WS used)
 probe "websocket connect latency buckets" "^newt_websocket_connect_latency_seconds_bucket" || true
 probe "websocket messages total" "^newt_websocket_messages_total\{.*(direction|msg_type)=" || true