From 69e05fc1883710f3fe8e95d1acb134b1341d8d2e Mon Sep 17 00:00:00 2001
From: Emil Lehre Arnesen <38581916+emilarnesen@users.noreply.github.com>
Date: Tue, 17 Feb 2026 13:49:42 +0100
Subject: [PATCH] Add enableFeatures field to MonitoringStack prometheusConfig

---
 pkg/apis/monitoring/v1alpha1/types.go         | 10 ++++++
 .../v1alpha1/zz_generated.deepcopy.go         |  5 +++
 .../monitoring/monitoring-stack/components.go | 13 +++++++
 .../monitoring-stack/components_test.go       | 36 +++++++++++++++++++
 test/e2e/monitoring_stack_controller_test.go  |  1 +
 5 files changed, 65 insertions(+)

diff --git a/pkg/apis/monitoring/v1alpha1/types.go b/pkg/apis/monitoring/v1alpha1/types.go
index ebb06d4f6..b28c0c179 100644
--- a/pkg/apis/monitoring/v1alpha1/types.go
+++ b/pkg/apis/monitoring/v1alpha1/types.go
@@ -244,6 +244,16 @@ type PrometheusConfig struct {
 	// The resulting endpoint is /api/v1/otlp/v1/metrics.
 	// +optional
 	EnableOtlpHttpReceiver *bool `json:"enableOtlpHttpReceiver,omitempty"`
+	// Enable access to Prometheus feature flags. By default, no features are enabled.
+	// Enabling features which are disabled by default is entirely outside the
+	// scope of what the maintainers will support and by doing so, you accept
+	// that this behaviour may break at any time without notice.
+	//
+	// For more information see https://prometheus.io/docs/prometheus/latest/feature_flags/
+	//
+	// +optional
+	// +kubebuilder:validation:items:MinLength=1
+	EnableFeatures []string `json:"enableFeatures,omitempty"`
 	// Default interval between scrapes.
 	// +optional
 	ScrapeInterval *monv1.Duration `json:"scrapeInterval,omitempty"`
diff --git a/pkg/apis/monitoring/v1alpha1/zz_generated.deepcopy.go b/pkg/apis/monitoring/v1alpha1/zz_generated.deepcopy.go
index 04bfc0e67..fcb18e924 100644
--- a/pkg/apis/monitoring/v1alpha1/zz_generated.deepcopy.go
+++ b/pkg/apis/monitoring/v1alpha1/zz_generated.deepcopy.go
@@ -247,6 +247,11 @@ func (in *PrometheusConfig) DeepCopyInto(out *PrometheusConfig) {
 		*out = new(bool)
 		**out = **in
 	}
+	if in.EnableFeatures != nil {
+		in, out := &in.EnableFeatures, &out.EnableFeatures
+		*out = make([]string, len(*in))
+		copy(*out, *in)
+	}
 	if in.ScrapeInterval != nil {
 		in, out := &in.ScrapeInterval, &out.ScrapeInterval
 		*out = new(monitoringv1.Duration)
diff --git a/pkg/controllers/monitoring/monitoring-stack/components.go b/pkg/controllers/monitoring/monitoring-stack/components.go
index 76514cf9b..9c904ef70 100644
--- a/pkg/controllers/monitoring/monitoring-stack/components.go
+++ b/pkg/controllers/monitoring/monitoring-stack/components.go
@@ -203,6 +203,7 @@ func newPrometheus(
 				ExternalLabels:            config.ExternalLabels,
 				EnableRemoteWriteReceiver: config.EnableRemoteWriteReceiver,
 				EnableOTLPReceiver:        config.EnableOtlpHttpReceiver,
+				EnableFeatures:            toEnableFeatures(config.EnableFeatures),
 			},
 			Retention:             ms.Spec.Retention,
 			RetentionSize:         ms.Spec.RetentionSize,
@@ -565,3 +566,15 @@ func podLabels(component string, msName string) map[string]string {
 		"app.kubernetes.io/part-of":   msName,
 	}
 }
+
+// toEnableFeatures converts a slice of strings to a slice of EnableFeature.
+func toEnableFeatures(features []string) []monv1.EnableFeature {
+	if len(features) == 0 {
+		return nil
+	}
+	result := make([]monv1.EnableFeature, len(features))
+	for i, f := range features {
+		result[i] = monv1.EnableFeature(f)
+	}
+	return result
+}
diff --git a/pkg/controllers/monitoring/monitoring-stack/components_test.go b/pkg/controllers/monitoring/monitoring-stack/components_test.go
index e5feee830..8533524d6 100644
--- a/pkg/controllers/monitoring/monitoring-stack/components_test.go
+++ b/pkg/controllers/monitoring/monitoring-stack/components_test.go
@@ -14,6 +14,42 @@ import (
 	stack "github.com/rhobs/observability-operator/pkg/apis/monitoring/v1alpha1"
 )
 
+func TestToEnableFeatures(t *testing.T) {
+	tt := []struct {
+		name     string
+		input    []string
+		expected []monv1.EnableFeature
+	}{
+		{
+			name:     "nil input returns nil",
+			input:    nil,
+			expected: nil,
+		},
+		{
+			name:     "empty input returns nil",
+			input:    []string{},
+			expected: nil,
+		},
+		{
+			name:     "single feature",
+			input:    []string{"exemplar-storage"},
+			expected: []monv1.EnableFeature{"exemplar-storage"},
+		},
+		{
+			name:     "multiple features",
+			input:    []string{"exemplar-storage", "otlp-write-receiver"},
+			expected: []monv1.EnableFeature{"exemplar-storage", "otlp-write-receiver"},
+		},
+	}
+
+	for _, tc := range tt {
+		t.Run(tc.name, func(t *testing.T) {
+			actual := toEnableFeatures(tc.input)
+			assert.DeepEqual(t, tc.expected, actual)
+		})
+	}
+}
+
 func TestStorageSpec(t *testing.T) {
 	validPVCSpec := &corev1.PersistentVolumeClaimSpec{
 		AccessModes: []corev1.PersistentVolumeAccessMode{corev1.ReadWriteOnce},
diff --git a/test/e2e/monitoring_stack_controller_test.go b/test/e2e/monitoring_stack_controller_test.go
index 717cb5f90..b38fcfa34 100644
--- a/test/e2e/monitoring_stack_controller_test.go
+++ b/test/e2e/monitoring_stack_controller_test.go
@@ -822,6 +822,7 @@ func assertPrometheusManagedFields(t *testing.T) {
 		},
 		EnableRemoteWriteReceiver: true,
 		EnableOtlpHttpReceiver:    func(b bool) *bool { return &b }(true),
+		EnableFeatures:            []string{"exemplar-storage"},
 		WebTLSConfig: &stack.WebTLSConfig{
 			Certificate: stack.SecretKeySelector{
 				Name: "prom-test-managedfields-tls-secret",