diff --git a/ray-operator/controllers/ray/utils/validation.go b/ray-operator/controllers/ray/utils/validation.go
index 07d4591afc1..b75500b57ea 100644
--- a/ray-operator/controllers/ray/utils/validation.go
+++ b/ray-operator/controllers/ray/utils/validation.go
@@ -194,6 +194,13 @@ func ValidateRayClusterSpec(spec *rayv1.RayClusterSpec, annotations map[string]s
 		}
 	}
 
+	// Validate AutoscalerOptions.IdleTimeoutSeconds (works with both v1 and v2 autoscaler)
+	if spec.AutoscalerOptions != nil && spec.AutoscalerOptions.IdleTimeoutSeconds != nil {
+		if *spec.AutoscalerOptions.IdleTimeoutSeconds < 0 {
+			return fmt.Errorf("autoscalerOptions.idleTimeoutSeconds must be non-negative, got %d", *spec.AutoscalerOptions.IdleTimeoutSeconds)
+		}
+	}
+
 	if IsAuthEnabled(spec) {
 		if spec.RayVersion == "" {
 			return fmt.Errorf("authOptions.mode is 'token' but RayVersion was not specified. Ray version 2.52.0 or later is required")
@@ -603,21 +610,23 @@ func validateLegacyDeletionPolicies(rayJob *rayv1.RayJob) error {
 // validateWorkerGroupIdleTimeout validates the idleTimeoutSeconds field in a worker group spec
 func validateWorkerGroupIdleTimeout(workerGroup rayv1.WorkerGroupSpec, spec *rayv1.RayClusterSpec) error {
 	idleTimeoutSeconds := workerGroup.IdleTimeoutSeconds
-	if idleTimeoutSeconds != nil {
-		if *idleTimeoutSeconds < 0 {
-			return fmt.Errorf("idleTimeoutSeconds must be non-negative, got %d", *idleTimeoutSeconds)
-		}
+	if idleTimeoutSeconds == nil {
+		return nil
+	}
 
-		// idleTimeoutSeconds only allowed on autoscaler v2
-		if IsAutoscalingV2Enabled(spec) {
-			return nil
-		}
-		envVar, exists := EnvVarByName(RAY_ENABLE_AUTOSCALER_V2, spec.HeadGroupSpec.Template.Spec.Containers[RayContainerIndex].Env)
-		if exists && (envVar.Value == "1" || envVar.Value == "true") {
-			return nil
-		}
-		return fmt.Errorf("worker group %s has idleTimeoutSeconds set, but autoscaler v2 is not enabled. Please set .spec.autoscalerOptions.version to 'v2' (or set %s environment variable to 'true' in the head pod if using KubeRay < 1.4.0)", workerGroup.GroupName, RAY_ENABLE_AUTOSCALER_V2)
+	if *idleTimeoutSeconds < 0 {
+		return fmt.Errorf("worker group %s: idleTimeoutSeconds must be non-negative, got %d", workerGroup.GroupName, *idleTimeoutSeconds)
 	}
 
-	return nil
+	// WorkerGroupSpec.idleTimeoutSeconds only allowed on autoscaler v2
+	if IsAutoscalingV2Enabled(spec) {
+		return nil
+	}
+
+	envVar, exists := EnvVarByName(RAY_ENABLE_AUTOSCALER_V2, spec.HeadGroupSpec.Template.Spec.Containers[RayContainerIndex].Env)
+	if exists && (envVar.Value == "1" || envVar.Value == "true") {
+		return nil
+	}
+
+	return fmt.Errorf("worker group %s: idleTimeoutSeconds is set, but autoscaler v2 is not enabled. Please set .spec.autoscalerOptions.version to 'v2' (or set %s environment variable to 'true' in the head pod if using KubeRay < 1.4.0)", workerGroup.GroupName, RAY_ENABLE_AUTOSCALER_V2)
 }
diff --git a/ray-operator/controllers/ray/utils/validation_test.go b/ray-operator/controllers/ray/utils/validation_test.go
index 43fa6af48e9..d575ef9cee3 100644
--- a/ray-operator/controllers/ray/utils/validation_test.go
+++ b/ray-operator/controllers/ray/utils/validation_test.go
@@ -1883,20 +1883,29 @@ func TestValidateClusterUpgradeOptions(t *testing.T) {
 	}
 }
 
-func TestValidateWorkerGroupIdleTimeout(t *testing.T) {
+func TestValidateRayClusterSpec_IdleTimeoutSeconds(t *testing.T) {
+	// Util function to create a RayCluster spec.
+	createSpec := func() rayv1.RayClusterSpec {
+		return rayv1.RayClusterSpec{
+			EnableInTreeAutoscaling: ptr.To(true),
+			HeadGroupSpec: rayv1.HeadGroupSpec{
+				Template: podTemplateSpec(nil, nil),
+			},
+		}
+	}
+
 	tests := map[string]struct {
 		expectedErr string
 		spec        rayv1.RayClusterSpec
 	}{
-		"should accept worker group with valid idleTimeoutSeconds": {
-			spec: rayv1.RayClusterSpec{
-				EnableInTreeAutoscaling: ptr.To(true),
-				HeadGroupSpec: rayv1.HeadGroupSpec{
-					Template: podTemplateSpec([]corev1.EnvVar{
-						{Name: RAY_ENABLE_AUTOSCALER_V2, Value: "1"},
-					}, nil),
-				},
-				WorkerGroupSpecs: []rayv1.WorkerGroupSpec{
+		// Worker group tests
+		"Valid: Worker group with valid idleTimeoutSeconds and v2 spec field": {
+			spec: func() rayv1.RayClusterSpec {
+				s := createSpec()
+				s.AutoscalerOptions = &rayv1.AutoscalerOptions{
+					Version: ptr.To(rayv1.AutoscalerVersionV2),
+				}
+				s.WorkerGroupSpecs = []rayv1.WorkerGroupSpec{
 					{
 						GroupName:          "worker-group-1",
 						Template:           podTemplateSpec(nil, nil),
@@ -1904,39 +1913,37 @@ func TestValidateWorkerGroupIdleTimeout(t *testing.T) {
 						MinReplicas:        ptr.To(int32(0)),
 						MaxReplicas:        ptr.To(int32(10)),
 					},
-				},
-			},
+				}
+				return s
+			}(),
 			expectedErr: "",
 		},
-		"should reject negative idleTimeoutSeconds": {
-			spec: rayv1.RayClusterSpec{
-				EnableInTreeAutoscaling: ptr.To(true),
-				HeadGroupSpec: rayv1.HeadGroupSpec{
-					Template: podTemplateSpec([]corev1.EnvVar{
-						{Name: RAY_ENABLE_AUTOSCALER_V2, Value: "1"},
-					}, nil),
-				},
-				WorkerGroupSpecs: []rayv1.WorkerGroupSpec{
+		"Valid: Worker group with idleTimeoutSeconds and v2 env var": {
+			spec: func() rayv1.RayClusterSpec {
+				s := createSpec()
+				s.HeadGroupSpec.Template = podTemplateSpec([]corev1.EnvVar{
+					{Name: RAY_ENABLE_AUTOSCALER_V2, Value: "1"},
+				}, nil)
+				s.WorkerGroupSpecs = []rayv1.WorkerGroupSpec{
 					{
 						GroupName:          "worker-group-1",
 						Template:           podTemplateSpec(nil, nil),
-						IdleTimeoutSeconds: ptr.To(int32(-10)),
+						IdleTimeoutSeconds: ptr.To(int32(60)),
 						MinReplicas:        ptr.To(int32(0)),
 						MaxReplicas:        ptr.To(int32(10)),
 					},
-				},
-			},
-			expectedErr: "idleTimeoutSeconds must be non-negative, got -10",
+				}
+				return s
+			}(),
+			expectedErr: "",
 		},
-		"should accept zero idleTimeoutSeconds": {
-			spec: rayv1.RayClusterSpec{
-				EnableInTreeAutoscaling: ptr.To(true),
-				HeadGroupSpec: rayv1.HeadGroupSpec{
-					Template: podTemplateSpec([]corev1.EnvVar{
-						{Name: RAY_ENABLE_AUTOSCALER_V2, Value: "1"},
-					}, nil),
-				},
-				WorkerGroupSpecs: []rayv1.WorkerGroupSpec{
+		"Valid: Worker group with zero idleTimeoutSeconds": {
+			spec: func() rayv1.RayClusterSpec {
+				s := createSpec()
+				s.AutoscalerOptions = &rayv1.AutoscalerOptions{
+					Version: ptr.To(rayv1.AutoscalerVersionV2),
+				}
+				s.WorkerGroupSpecs = []rayv1.WorkerGroupSpec{
 					{
 						GroupName:          "worker-group-1",
 						Template:           podTemplateSpec(nil, nil),
@@ -1944,73 +1951,34 @@ func TestValidateWorkerGroupIdleTimeout(t *testing.T) {
 						MinReplicas:        ptr.To(int32(0)),
 						MaxReplicas:        ptr.To(int32(10)),
 					},
-				},
-			},
+				}
+				return s
+			}(),
 			expectedErr: "",
 		},
-		"should reject idleTimeoutSeconds when autoscaler version is not v2": {
-			spec: rayv1.RayClusterSpec{
-				EnableInTreeAutoscaling: ptr.To(true),
-				HeadGroupSpec: rayv1.HeadGroupSpec{
-					Template: podTemplateSpec(nil, nil),
-				},
-				WorkerGroupSpecs: []rayv1.WorkerGroupSpec{
-					{
-						GroupName:          "worker-group-1",
-						Template:           podTemplateSpec(nil, nil),
-						IdleTimeoutSeconds: ptr.To(int32(60)),
-						MinReplicas:        ptr.To(int32(0)),
-						MaxReplicas:        ptr.To(int32(10)),
-					},
-				},
-			},
-			expectedErr: fmt.Sprintf("worker group worker-group-1 has idleTimeoutSeconds set, but autoscaler v2 is not enabled. Please set .spec.autoscalerOptions.version to 'v2' (or set %s environment variable to 'true' in the head pod if using KubeRay < 1.4.0)", RAY_ENABLE_AUTOSCALER_V2),
-		},
-		"should reject idleTimeoutSeconds when autoscaler version is not set": {
-			spec: rayv1.RayClusterSpec{
-				EnableInTreeAutoscaling: ptr.To(true),
-				HeadGroupSpec: rayv1.HeadGroupSpec{
-					Template: podTemplateSpec(nil, nil),
-				},
-				WorkerGroupSpecs: []rayv1.WorkerGroupSpec{
-					{
-						GroupName:          "worker-group-1",
-						Template:           podTemplateSpec(nil, nil),
-						IdleTimeoutSeconds: ptr.To(int32(60)),
-						MinReplicas:        ptr.To(int32(0)),
-						MaxReplicas:        ptr.To(int32(10)),
-					},
-				},
-			},
-			expectedErr: fmt.Sprintf("worker group worker-group-1 has idleTimeoutSeconds set, but autoscaler v2 is not enabled. Please set .spec.autoscalerOptions.version to 'v2' (or set %s environment variable to 'true' in the head pod if using KubeRay < 1.4.0)", RAY_ENABLE_AUTOSCALER_V2),
-		},
-		"should reject idleTimeoutSeconds when AutoscalerOptions is nil": {
-			spec: rayv1.RayClusterSpec{
-				EnableInTreeAutoscaling: ptr.To(true),
-				HeadGroupSpec: rayv1.HeadGroupSpec{
-					Template: podTemplateSpec(nil, nil),
-				},
-				WorkerGroupSpecs: []rayv1.WorkerGroupSpec{
+		"Invalid: Worker group with negative idleTimeoutSeconds": {
+			spec: func() rayv1.RayClusterSpec {
+				s := createSpec()
+				s.AutoscalerOptions = &rayv1.AutoscalerOptions{
+					Version: ptr.To(rayv1.AutoscalerVersionV2),
+				}
+				s.WorkerGroupSpecs = []rayv1.WorkerGroupSpec{
 					{
 						GroupName:          "worker-group-1",
 						Template:           podTemplateSpec(nil, nil),
-						IdleTimeoutSeconds: ptr.To(int32(60)),
+						IdleTimeoutSeconds: ptr.To(int32(-10)),
 						MinReplicas:        ptr.To(int32(0)),
 						MaxReplicas:        ptr.To(int32(10)),
 					},
-				},
-			},
-			expectedErr: fmt.Sprintf("worker group worker-group-1 has idleTimeoutSeconds set, but autoscaler v2 is not enabled. Please set .spec.autoscalerOptions.version to 'v2' (or set %s environment variable to 'true' in the head pod if using KubeRay < 1.4.0)", RAY_ENABLE_AUTOSCALER_V2),
+				}
+				return s
+			}(),
+			expectedErr: "worker group worker-group-1: idleTimeoutSeconds must be non-negative, got -10",
 		},
-		"should reject idleTimeoutSeconds when env var is set to invalid value": {
-			spec: rayv1.RayClusterSpec{
-				EnableInTreeAutoscaling: ptr.To(true),
-				HeadGroupSpec: rayv1.HeadGroupSpec{
-					Template: podTemplateSpec([]corev1.EnvVar{
-						{Name: RAY_ENABLE_AUTOSCALER_V2, Value: "false"},
-					}, nil),
-				},
-				WorkerGroupSpecs: []rayv1.WorkerGroupSpec{
+		"Invalid: Worker group idleTimeoutSeconds without v2": {
+			spec: func() rayv1.RayClusterSpec {
+				s := createSpec()
+				s.WorkerGroupSpecs = []rayv1.WorkerGroupSpec{
 					{
 						GroupName:          "worker-group-1",
 						Template:           podTemplateSpec(nil, nil),
@@ -2018,19 +1986,18 @@ func TestValidateWorkerGroupIdleTimeout(t *testing.T) {
 						MinReplicas:        ptr.To(int32(0)),
 						MaxReplicas:        ptr.To(int32(10)),
 					},
-				},
-			},
-			expectedErr: fmt.Sprintf("worker group worker-group-1 has idleTimeoutSeconds set, but autoscaler v2 is not enabled. Please set .spec.autoscalerOptions.version to 'v2' (or set %s environment variable to 'true' in the head pod if using KubeRay < 1.4.0)", RAY_ENABLE_AUTOSCALER_V2),
+				}
+				return s
+			}(),
+			expectedErr: fmt.Sprintf("worker group worker-group-1: idleTimeoutSeconds is set, but autoscaler v2 is not enabled. Please set .spec.autoscalerOptions.version to 'v2' (or set %s environment variable to 'true' in the head pod if using KubeRay < 1.4.0)", RAY_ENABLE_AUTOSCALER_V2),
 		},
-		"should accept worker group with idleTimeoutSeconds when env var is set to true": {
-			spec: rayv1.RayClusterSpec{
-				EnableInTreeAutoscaling: ptr.To(true),
-				HeadGroupSpec: rayv1.HeadGroupSpec{
-					Template: podTemplateSpec([]corev1.EnvVar{
-						{Name: RAY_ENABLE_AUTOSCALER_V2, Value: "true"},
-					}, nil),
-				},
-				WorkerGroupSpecs: []rayv1.WorkerGroupSpec{
+		"Invalid: Worker group idleTimeoutSeconds with invalid env var": {
+			spec: func() rayv1.RayClusterSpec {
+				s := createSpec()
+				s.HeadGroupSpec.Template = podTemplateSpec([]corev1.EnvVar{
+					{Name: RAY_ENABLE_AUTOSCALER_V2, Value: "false"},
+				}, nil)
+				s.WorkerGroupSpecs = []rayv1.WorkerGroupSpec{
 					{
 						GroupName:          "worker-group-1",
 						Template:           podTemplateSpec(nil, nil),
@@ -2038,25 +2005,96 @@ func TestValidateWorkerGroupIdleTimeout(t *testing.T) {
 						MinReplicas:        ptr.To(int32(0)),
 						MaxReplicas:        ptr.To(int32(10)),
 					},
-				},
-			},
-			expectedErr: "",
+				}
+				return s
+			}(),
+			expectedErr: fmt.Sprintf("worker group worker-group-1: idleTimeoutSeconds is set, but autoscaler v2 is not enabled. Please set .spec.autoscalerOptions.version to 'v2' (or set %s environment variable to 'true' in the head pod if using KubeRay < 1.4.0)", RAY_ENABLE_AUTOSCALER_V2),
 		},
-		"should accept worker group without idleTimeoutSeconds and without autoscaler v2": {
-			spec: rayv1.RayClusterSpec{
-				EnableInTreeAutoscaling: ptr.To(true),
-				HeadGroupSpec: rayv1.HeadGroupSpec{
-					Template: podTemplateSpec(nil, nil),
-				},
-				WorkerGroupSpecs: []rayv1.WorkerGroupSpec{
+		"Valid: Worker group without idleTimeoutSeconds": {
+			spec: func() rayv1.RayClusterSpec {
+				s := createSpec()
+				s.WorkerGroupSpecs = []rayv1.WorkerGroupSpec{
 					{
 						GroupName:   "worker-group-1",
 						Template:    podTemplateSpec(nil, nil),
 						MinReplicas: ptr.To(int32(0)),
 						MaxReplicas: ptr.To(int32(10)),
 					},
-				},
-			},
+				}
+				return s
+			}(),
+			expectedErr: "",
+		},
+
+		// AutoscalerOptions tests (idleTimeoutSeconds works with both v1 and v2)
+		"Valid: AutoscalerOptions with idleTimeoutSeconds and v2": {
+			spec: func() rayv1.RayClusterSpec {
+				s := createSpec()
+				s.AutoscalerOptions = &rayv1.AutoscalerOptions{
+					Version:            ptr.To(rayv1.AutoscalerVersionV2),
+					IdleTimeoutSeconds: ptr.To(int32(120)),
+				}
+				return s
+			}(),
+			expectedErr: "",
+		},
+		"Valid: AutoscalerOptions with idleTimeoutSeconds and v1": {
+			spec: func() rayv1.RayClusterSpec {
+				s := createSpec()
+				s.AutoscalerOptions = &rayv1.AutoscalerOptions{
+					Version:            ptr.To(rayv1.AutoscalerVersionV1),
+					IdleTimeoutSeconds: ptr.To(int32(120)),
+				}
+				return s
+			}(),
+			expectedErr: "",
+		},
+		"Valid: AutoscalerOptions with idleTimeoutSeconds and no version": {
+			spec: func() rayv1.RayClusterSpec {
+				s := createSpec()
+				s.AutoscalerOptions = &rayv1.AutoscalerOptions{
+					IdleTimeoutSeconds: ptr.To(int32(120)),
+				}
+				return s
+			}(),
+			expectedErr: "",
+		},
+		"Valid: AutoscalerOptions with zero idleTimeoutSeconds": {
+			spec: func() rayv1.RayClusterSpec {
+				s := createSpec()
+				s.AutoscalerOptions = &rayv1.AutoscalerOptions{
+					IdleTimeoutSeconds: ptr.To(int32(0)),
+				}
+				return s
+			}(),
+			expectedErr: "",
+		},
+		"Invalid: AutoscalerOptions with negative idleTimeoutSeconds": {
+			spec: func() rayv1.RayClusterSpec {
+				s := createSpec()
+				s.AutoscalerOptions = &rayv1.AutoscalerOptions{
+					IdleTimeoutSeconds: ptr.To(int32(-10)),
+				}
+				return s
+			}(),
+			expectedErr: "autoscalerOptions.idleTimeoutSeconds must be non-negative, got -10",
+		},
+		"Valid: AutoscalerOptions without idleTimeoutSeconds": {
+			spec: func() rayv1.RayClusterSpec {
+				s := createSpec()
+				s.AutoscalerOptions = &rayv1.AutoscalerOptions{
+					Version: ptr.To(rayv1.AutoscalerVersionV1),
+				}
+				return s
+			}(),
+			expectedErr: "",
+		},
+		"Valid: AutoscalerOptions is nil": {
+			spec: func() rayv1.RayClusterSpec {
+				s := createSpec()
+				s.AutoscalerOptions = nil
+				return s
+			}(),
 			expectedErr: "",
 		},
 	}