diff --git a/pkg/features/kube_features.go b/pkg/features/kube_features.go
index 09c7fd3e60b..fa04622bdb5 100644
--- a/pkg/features/kube_features.go
+++ b/pkg/features/kube_features.go
@@ -376,6 +376,14 @@ const (
 	// Add support for distributed tracing in the kubelet
 	KubeletTracing featuregate.Feature = "KubeletTracing"
 
+	// owner: @gjkim42
+	//
+	// Enable legacy code path in pkg/kubelet/kuberuntime that predates the
+	// SidecarContainers feature. This temporary feature gate is disabled by
+	// default and intended to safely remove the redundant code path. This is
+	// only available in v1.33 and will be removed in v1.34.
+	LegacySidecarContainers featuregate.Feature = "LegacySidecarContainers"
+
 	// owner: @RobertKrawitz
 	//
 	// Allow use of filesystems for ephemeral storage monitoring.
diff --git a/pkg/features/versioned_kube_features.go b/pkg/features/versioned_kube_features.go
index 322467a4f5c..11190d05740 100644
--- a/pkg/features/versioned_kube_features.go
+++ b/pkg/features/versioned_kube_features.go
@@ -485,6 +485,11 @@ var defaultVersionedKubernetesFeatureGates = map[featuregate.Feature]featuregate
 		{Version: version.MustParse("1.27"), Default: true, PreRelease: featuregate.Beta},
 	},
 
+	LegacySidecarContainers: {
+		{Version: version.MustParse("1.0"), Default: true, PreRelease: featuregate.GA},
+		{Version: version.MustParse("1.33"), Default: false, PreRelease: featuregate.Deprecated},
+	},
+
 	LoadBalancerIPMode: {
 		{Version: version.MustParse("1.29"), Default: false, PreRelease: featuregate.Alpha},
 		{Version: version.MustParse("1.30"), Default: true, PreRelease: featuregate.Beta},
diff --git a/pkg/kubelet/kuberuntime/kuberuntime_manager.go b/pkg/kubelet/kuberuntime/kuberuntime_manager.go
index 46b53805452..ab63cd6e1ff 100644
--- a/pkg/kubelet/kuberuntime/kuberuntime_manager.go
+++ b/pkg/kubelet/kuberuntime/kuberuntime_manager.go
@@ -915,7 +915,9 @@ func (m *kubeGenericRuntimeManager) computePodActions(ctx context.Context, pod *
 		ContainersToKill:  make(map[kubecontainer.ContainerID]containerToKillInfo),
 	}
 
-	handleRestartableInitContainers := types.HasRestartableInitContainer(pod)
+	// TODO: Remove handleRestartableInitContainers value with the
+	// LegacySidecarContainers feature gate.
+	handleRestartableInitContainers := types.HasRestartableInitContainer(pod) || !utilfeature.DefaultFeatureGate.Enabled(features.LegacySidecarContainers)
 
 	// If we need to (re-)create the pod sandbox, everything will need to be
 	// killed and recreated, and init containers should be purged.
@@ -1375,7 +1377,7 @@ func (m *kubeGenericRuntimeManager) SyncPod(ctx context.Context, pod *v1.Pod, po
 
 	// TODO: Remove this code path as logically it is the subset of the next
 	// code path.
-	if !types.HasRestartableInitContainer(pod) {
+	if !types.HasRestartableInitContainer(pod) && utilfeature.DefaultFeatureGate.Enabled(features.LegacySidecarContainers) {
 		// Step 6: start the init container.
 		if container := podContainerChanges.NextInitContainerToStart; container != nil {
 			// Start the next init container.
diff --git a/pkg/kubelet/kuberuntime/kuberuntime_manager_test.go b/pkg/kubelet/kuberuntime/kuberuntime_manager_test.go
index a60ee64c5a9..f834ff34b40 100644
--- a/pkg/kubelet/kuberuntime/kuberuntime_manager_test.go
+++ b/pkg/kubelet/kuberuntime/kuberuntime_manager_test.go
@@ -1280,6 +1280,224 @@ func TestComputePodActionsWithInitContainers(t *testing.T) {
 		ContainersToKill:  map[kubecontainer.ContainerID]containerToKillInfo{},
 	}
 
+	for desc, test := range map[string]struct {
+		mutatePodFn    func(*v1.Pod)
+		mutateStatusFn func(*kubecontainer.PodStatus)
+		actions        podActions
+	}{
+		"initialization completed; start all containers": {
+			actions: podActions{
+				SandboxID:         baseStatus.SandboxStatuses[0].Id,
+				ContainersToStart: []int{0, 1, 2},
+				ContainersToKill:  getKillMapWithInitContainers(basePod, baseStatus, []int{}),
+			},
+		},
+		"no init containers have been started; start the first one": {
+			mutateStatusFn: func(status *kubecontainer.PodStatus) {
+				status.ContainerStatuses = nil
+			},
+			actions: podActions{
+				SandboxID:             baseStatus.SandboxStatuses[0].Id,
+				InitContainersToStart: []int{0},
+				ContainersToStart:     []int{},
+				ContainersToKill:      getKillMapWithInitContainers(basePod, baseStatus, []int{}),
+			},
+		},
+		"initialization in progress; do nothing": {
+			mutatePodFn: func(pod *v1.Pod) { pod.Spec.RestartPolicy = v1.RestartPolicyAlways },
+			mutateStatusFn: func(status *kubecontainer.PodStatus) {
+				status.ContainerStatuses[2].State = kubecontainer.ContainerStateRunning
+			},
+			actions: noAction,
+		},
+		"Kill pod and restart the first init container if the pod sandbox is dead": {
+			mutatePodFn: func(pod *v1.Pod) { pod.Spec.RestartPolicy = v1.RestartPolicyAlways },
+			mutateStatusFn: func(status *kubecontainer.PodStatus) {
+				status.SandboxStatuses[0].State = runtimeapi.PodSandboxState_SANDBOX_NOTREADY
+			},
+			actions: podActions{
+				KillPod:               true,
+				CreateSandbox:         true,
+				SandboxID:             baseStatus.SandboxStatuses[0].Id,
+				Attempt:               uint32(1),
+				InitContainersToStart: []int{0},
+				ContainersToStart:     []int{},
+				ContainersToKill:      getKillMapWithInitContainers(basePod, baseStatus, []int{}),
+			},
+		},
+		"initialization failed; restart the last init container if RestartPolicy == Always": {
+			mutatePodFn: func(pod *v1.Pod) { pod.Spec.RestartPolicy = v1.RestartPolicyAlways },
+			mutateStatusFn: func(status *kubecontainer.PodStatus) {
+				status.ContainerStatuses[2].ExitCode = 137
+			},
+			actions: podActions{
+				SandboxID:             baseStatus.SandboxStatuses[0].Id,
+				InitContainersToStart: []int{2},
+				ContainersToStart:     []int{},
+				ContainersToKill:      getKillMapWithInitContainers(basePod, baseStatus, []int{}),
+			},
+		},
+		"initialization failed; restart the last init container if RestartPolicy == OnFailure": {
+			mutatePodFn: func(pod *v1.Pod) { pod.Spec.RestartPolicy = v1.RestartPolicyOnFailure },
+			mutateStatusFn: func(status *kubecontainer.PodStatus) {
+				status.ContainerStatuses[2].ExitCode = 137
+			},
+			actions: podActions{
+				SandboxID:             baseStatus.SandboxStatuses[0].Id,
+				InitContainersToStart: []int{2},
+				ContainersToStart:     []int{},
+				ContainersToKill:      getKillMapWithInitContainers(basePod, baseStatus, []int{}),
+			},
+		},
+		"initialization failed; kill pod if RestartPolicy == Never": {
+			mutatePodFn: func(pod *v1.Pod) { pod.Spec.RestartPolicy = v1.RestartPolicyNever },
+			mutateStatusFn: func(status *kubecontainer.PodStatus) {
+				status.ContainerStatuses[2].ExitCode = 137
+			},
+			actions: podActions{
+				KillPod:           true,
+				SandboxID:         baseStatus.SandboxStatuses[0].Id,
+				ContainersToStart: []int{},
+				ContainersToKill:  getKillMapWithInitContainers(basePod, baseStatus, []int{}),
+			},
+		},
+		"init container state unknown; kill and recreate the last init container if RestartPolicy == Always": {
+			mutatePodFn: func(pod *v1.Pod) { pod.Spec.RestartPolicy = v1.RestartPolicyAlways },
+			mutateStatusFn: func(status *kubecontainer.PodStatus) {
+				status.ContainerStatuses[2].State = kubecontainer.ContainerStateUnknown
+			},
+			actions: podActions{
+				SandboxID:             baseStatus.SandboxStatuses[0].Id,
+				InitContainersToStart: []int{2},
+				ContainersToStart:     []int{},
+				ContainersToKill:      getKillMapWithInitContainers(basePod, baseStatus, []int{2}),
+			},
+		},
+		"init container state unknown; kill and recreate the last init container if RestartPolicy == OnFailure": {
+			mutatePodFn: func(pod *v1.Pod) { pod.Spec.RestartPolicy = v1.RestartPolicyOnFailure },
+			mutateStatusFn: func(status *kubecontainer.PodStatus) {
+				status.ContainerStatuses[2].State = kubecontainer.ContainerStateUnknown
+			},
+			actions: podActions{
+				SandboxID:             baseStatus.SandboxStatuses[0].Id,
+				InitContainersToStart: []int{2},
+				ContainersToStart:     []int{},
+				ContainersToKill:      getKillMapWithInitContainers(basePod, baseStatus, []int{2}),
+			},
+		},
+		"init container state unknown; kill pod if RestartPolicy == Never": {
+			mutatePodFn: func(pod *v1.Pod) { pod.Spec.RestartPolicy = v1.RestartPolicyNever },
+			mutateStatusFn: func(status *kubecontainer.PodStatus) {
+				status.ContainerStatuses[2].State = kubecontainer.ContainerStateUnknown
+			},
+			actions: podActions{
+				KillPod:           true,
+				SandboxID:         baseStatus.SandboxStatuses[0].Id,
+				ContainersToStart: []int{},
+				ContainersToKill:  getKillMapWithInitContainers(basePod, baseStatus, []int{}),
+			},
+		},
+		"Pod sandbox not ready, init container failed, but RestartPolicy == Never; kill pod only": {
+			mutatePodFn: func(pod *v1.Pod) { pod.Spec.RestartPolicy = v1.RestartPolicyNever },
+			mutateStatusFn: func(status *kubecontainer.PodStatus) {
+				status.SandboxStatuses[0].State = runtimeapi.PodSandboxState_SANDBOX_NOTREADY
+			},
+			actions: podActions{
+				KillPod:           true,
+				CreateSandbox:     false,
+				SandboxID:         baseStatus.SandboxStatuses[0].Id,
+				Attempt:           uint32(1),
+				ContainersToStart: []int{},
+				ContainersToKill:  getKillMapWithInitContainers(basePod, baseStatus, []int{}),
+			},
+		},
+		"Pod sandbox not ready, and RestartPolicy == Never, but no visible init containers;  create a new pod sandbox": {
+			mutatePodFn: func(pod *v1.Pod) { pod.Spec.RestartPolicy = v1.RestartPolicyNever },
+			mutateStatusFn: func(status *kubecontainer.PodStatus) {
+				status.SandboxStatuses[0].State = runtimeapi.PodSandboxState_SANDBOX_NOTREADY
+				status.ContainerStatuses = []*kubecontainer.Status{}
+			},
+			actions: podActions{
+				KillPod:               true,
+				CreateSandbox:         true,
+				SandboxID:             baseStatus.SandboxStatuses[0].Id,
+				Attempt:               uint32(1),
+				InitContainersToStart: []int{0},
+				ContainersToStart:     []int{},
+				ContainersToKill:      getKillMapWithInitContainers(basePod, baseStatus, []int{}),
+			},
+		},
+		"Pod sandbox not ready, init container failed, and RestartPolicy == OnFailure; create a new pod sandbox": {
+			mutatePodFn: func(pod *v1.Pod) { pod.Spec.RestartPolicy = v1.RestartPolicyOnFailure },
+			mutateStatusFn: func(status *kubecontainer.PodStatus) {
+				status.SandboxStatuses[0].State = runtimeapi.PodSandboxState_SANDBOX_NOTREADY
+				status.ContainerStatuses[2].ExitCode = 137
+			},
+			actions: podActions{
+				KillPod:               true,
+				CreateSandbox:         true,
+				SandboxID:             baseStatus.SandboxStatuses[0].Id,
+				Attempt:               uint32(1),
+				InitContainersToStart: []int{0},
+				ContainersToStart:     []int{},
+				ContainersToKill:      getKillMapWithInitContainers(basePod, baseStatus, []int{}),
+			},
+		},
+		"some of the init container statuses are missing but the last init container is running, don't restart preceding ones": {
+			mutatePodFn: func(pod *v1.Pod) { pod.Spec.RestartPolicy = v1.RestartPolicyAlways },
+			mutateStatusFn: func(status *kubecontainer.PodStatus) {
+				status.ContainerStatuses[2].State = kubecontainer.ContainerStateRunning
+				status.ContainerStatuses = status.ContainerStatuses[2:]
+			},
+			actions: podActions{
+				KillPod:           false,
+				SandboxID:         baseStatus.SandboxStatuses[0].Id,
+				ContainersToStart: []int{},
+				ContainersToKill:  getKillMapWithInitContainers(basePod, baseStatus, []int{}),
+			},
+		},
+		"an init container is in the created state due to an unknown error when starting container; restart it": {
+			mutatePodFn: func(pod *v1.Pod) { pod.Spec.RestartPolicy = v1.RestartPolicyAlways },
+			mutateStatusFn: func(status *kubecontainer.PodStatus) {
+				status.ContainerStatuses[2].State = kubecontainer.ContainerStateCreated
+			},
+			actions: podActions{
+				KillPod:               false,
+				SandboxID:             baseStatus.SandboxStatuses[0].Id,
+				InitContainersToStart: []int{2},
+				ContainersToStart:     []int{},
+				ContainersToKill:      getKillMapWithInitContainers(basePod, baseStatus, []int{}),
+			},
+		},
+	} {
+		t.Run(desc, func(t *testing.T) {
+			pod, status := makeBasePodAndStatusWithInitContainers()
+			if test.mutatePodFn != nil {
+				test.mutatePodFn(pod)
+			}
+			if test.mutateStatusFn != nil {
+				test.mutateStatusFn(status)
+			}
+			ctx := context.Background()
+			actions := m.computePodActions(ctx, pod, status)
+			verifyActions(t, &test.actions, &actions, desc)
+		})
+	}
+}
+
+func TestComputePodActionsWithInitContainersWithLegacySidecarContainers(t *testing.T) {
+	_, _, m, err := createTestRuntimeManager()
+	require.NoError(t, err)
+
+	// Creating a pair reference pod and status for the test cases to refer
+	// the specific fields.
+	basePod, baseStatus := makeBasePodAndStatusWithInitContainers()
+	noAction := podActions{
+		SandboxID:         baseStatus.SandboxStatuses[0].Id,
+		ContainersToStart: []int{},
+		ContainersToKill:  map[kubecontainer.ContainerID]containerToKillInfo{},
+	}
+
 	for desc, test := range map[string]struct {
 		mutatePodFn    func(*v1.Pod)
 		mutateStatusFn func(*kubecontainer.PodStatus)
@@ -1479,28 +1697,31 @@ func TestComputePodActionsWithInitContainers(t *testing.T) {
 			},
 		},
 	} {
-		pod, status := makeBasePodAndStatusWithInitContainers()
-		if test.mutatePodFn != nil {
-			test.mutatePodFn(pod)
-		}
-		if test.mutateStatusFn != nil {
-			test.mutateStatusFn(status)
-		}
-		ctx := context.Background()
-		actions := m.computePodActions(ctx, pod, status)
-		handleRestartableInitContainers := kubelettypes.HasRestartableInitContainer(pod)
-		if !handleRestartableInitContainers {
-			// If sidecar containers are disabled or the pod does not have any
-			// restartable init container, we should not see any
-			// InitContainersToStart in the actions.
-			test.actions.InitContainersToStart = nil
-		} else {
-			// If sidecar containers are enabled and the pod has any
-			// restartable init container, we should not see any
-			// NextInitContainerToStart in the actions.
-			test.actions.NextInitContainerToStart = nil
-		}
-		verifyActions(t, &test.actions, &actions, desc)
+		t.Run(desc, func(t *testing.T) {
+			featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, features.LegacySidecarContainers, true)
+			pod, status := makeBasePodAndStatusWithInitContainers()
+			if test.mutatePodFn != nil {
+				test.mutatePodFn(pod)
+			}
+			if test.mutateStatusFn != nil {
+				test.mutateStatusFn(status)
+			}
+			ctx := context.Background()
+			actions := m.computePodActions(ctx, pod, status)
+			handleRestartableInitContainers := kubelettypes.HasRestartableInitContainer(pod)
+			if !handleRestartableInitContainers {
+				// If sidecar containers are disabled or the pod does not have any
+				// restartable init container, we should not see any
+				// InitContainersToStart in the actions.
+				test.actions.InitContainersToStart = nil
+			} else {
+				// If sidecar containers are enabled and the pod has any
+				// restartable init container, we should not see any
+				// NextInitContainerToStart in the actions.
+				test.actions.NextInitContainerToStart = nil
+			}
+			verifyActions(t, &test.actions, &actions, desc)
+		})
 	}
 }
 
@@ -1972,6 +2193,153 @@ func TestComputePodActionsWithInitAndEphemeralContainers(t *testing.T) {
 		ContainersToKill:  map[kubecontainer.ContainerID]containerToKillInfo{},
 	}
 
+	for desc, test := range map[string]struct {
+		mutatePodFn    func(*v1.Pod)
+		mutateStatusFn func(*kubecontainer.PodStatus)
+		actions        podActions
+	}{
+		"steady state; do nothing; ignore ephemeral container": {
+			actions: noAction,
+		},
+		"No ephemeral containers running; start one": {
+			mutateStatusFn: func(status *kubecontainer.PodStatus) {
+				status.ContainerStatuses = status.ContainerStatuses[:4]
+			},
+			actions: podActions{
+				SandboxID:                  baseStatus.SandboxStatuses[0].Id,
+				ContainersToStart:          []int{},
+				ContainersToKill:           map[kubecontainer.ContainerID]containerToKillInfo{},
+				EphemeralContainersToStart: []int{0},
+			},
+		},
+		"Start second ephemeral container": {
+			mutatePodFn: func(pod *v1.Pod) {
+				pod.Spec.EphemeralContainers = append(pod.Spec.EphemeralContainers, v1.EphemeralContainer{
+					EphemeralContainerCommon: v1.EphemeralContainerCommon{
+						Name:  "debug2",
+						Image: "busybox",
+					},
+				})
+			},
+			actions: podActions{
+				SandboxID:                  baseStatus.SandboxStatuses[0].Id,
+				ContainersToStart:          []int{},
+				ContainersToKill:           map[kubecontainer.ContainerID]containerToKillInfo{},
+				EphemeralContainersToStart: []int{1},
+			},
+		},
+		"Ephemeral container exited; do not restart": {
+			mutatePodFn: func(pod *v1.Pod) { pod.Spec.RestartPolicy = v1.RestartPolicyAlways },
+			mutateStatusFn: func(status *kubecontainer.PodStatus) {
+				status.ContainerStatuses[4].State = kubecontainer.ContainerStateExited
+			},
+			actions: podActions{
+				SandboxID:         baseStatus.SandboxStatuses[0].Id,
+				ContainersToStart: []int{},
+				ContainersToKill:  map[kubecontainer.ContainerID]containerToKillInfo{},
+			},
+		},
+		"initialization in progress; start ephemeral container": {
+			mutateStatusFn: func(status *kubecontainer.PodStatus) {
+				status.ContainerStatuses[3].State = kubecontainer.ContainerStateRunning
+				status.ContainerStatuses = status.ContainerStatuses[:4]
+			},
+			actions: podActions{
+				SandboxID:                  baseStatus.SandboxStatuses[0].Id,
+				ContainersToStart:          []int{},
+				ContainersToKill:           map[kubecontainer.ContainerID]containerToKillInfo{},
+				EphemeralContainersToStart: []int{0},
+			},
+		},
+		"Create a new pod sandbox if the pod sandbox is dead, init container failed and RestartPolicy == OnFailure": {
+			mutatePodFn: func(pod *v1.Pod) { pod.Spec.RestartPolicy = v1.RestartPolicyOnFailure },
+			mutateStatusFn: func(status *kubecontainer.PodStatus) {
+				status.SandboxStatuses[0].State = runtimeapi.PodSandboxState_SANDBOX_NOTREADY
+				status.ContainerStatuses = status.ContainerStatuses[3:]
+				status.ContainerStatuses[0].ExitCode = 137
+			},
+			actions: podActions{
+				KillPod:               true,
+				CreateSandbox:         true,
+				SandboxID:             baseStatus.SandboxStatuses[0].Id,
+				Attempt:               uint32(1),
+				InitContainersToStart: []int{0},
+				ContainersToStart:     []int{},
+				ContainersToKill:      getKillMapWithInitContainers(basePod, baseStatus, []int{}),
+			},
+		},
+		"Kill pod and do not restart ephemeral container if the pod sandbox is dead": {
+			mutatePodFn: func(pod *v1.Pod) { pod.Spec.RestartPolicy = v1.RestartPolicyAlways },
+			mutateStatusFn: func(status *kubecontainer.PodStatus) {
+				status.SandboxStatuses[0].State = runtimeapi.PodSandboxState_SANDBOX_NOTREADY
+			},
+			actions: podActions{
+				KillPod:               true,
+				CreateSandbox:         true,
+				SandboxID:             baseStatus.SandboxStatuses[0].Id,
+				Attempt:               uint32(1),
+				InitContainersToStart: []int{0},
+				ContainersToStart:     []int{},
+				ContainersToKill:      getKillMapWithInitContainers(basePod, baseStatus, []int{}),
+			},
+		},
+		"Kill pod if all containers exited except ephemeral container": {
+			mutatePodFn: func(pod *v1.Pod) {
+				pod.Spec.RestartPolicy = v1.RestartPolicyNever
+			},
+			mutateStatusFn: func(status *kubecontainer.PodStatus) {
+				// all regular containers exited
+				for i := 0; i < 3; i++ {
+					status.ContainerStatuses[i].State = kubecontainer.ContainerStateExited
+					status.ContainerStatuses[i].ExitCode = 0
+				}
+			},
+			actions: podActions{
+				SandboxID:         baseStatus.SandboxStatuses[0].Id,
+				CreateSandbox:     false,
+				KillPod:           true,
+				ContainersToStart: []int{},
+				ContainersToKill:  map[kubecontainer.ContainerID]containerToKillInfo{},
+			},
+		},
+		"Ephemeral container is in unknown state; leave it alone": {
+			mutatePodFn: func(pod *v1.Pod) { pod.Spec.RestartPolicy = v1.RestartPolicyNever },
+			mutateStatusFn: func(status *kubecontainer.PodStatus) {
+				status.ContainerStatuses[4].State = kubecontainer.ContainerStateUnknown
+			},
+			actions: noAction,
+		},
+	} {
+		t.Run(desc, func(t *testing.T) {
+			pod, status := makeBasePodAndStatusWithInitAndEphemeralContainers()
+			if test.mutatePodFn != nil {
+				test.mutatePodFn(pod)
+			}
+			if test.mutateStatusFn != nil {
+				test.mutateStatusFn(status)
+			}
+			ctx := context.Background()
+			actions := m.computePodActions(ctx, pod, status)
+			verifyActions(t, &test.actions, &actions, desc)
+		})
+	}
+}
+
+func TestComputePodActionsWithInitAndEphemeralContainersWithLegacySidecarContainers(t *testing.T) {
+	// Make sure existing test cases pass with feature enabled
+	TestComputePodActions(t)
+	TestComputePodActionsWithInitContainersWithLegacySidecarContainers(t)
+
+	_, _, m, err := createTestRuntimeManager()
+	require.NoError(t, err)
+
+	basePod, baseStatus := makeBasePodAndStatusWithInitAndEphemeralContainers()
+	noAction := podActions{
+		SandboxID:         baseStatus.SandboxStatuses[0].Id,
+		ContainersToStart: []int{},
+		ContainersToKill:  map[kubecontainer.ContainerID]containerToKillInfo{},
+	}
+
 	for desc, test := range map[string]struct {
 		mutatePodFn    func(*v1.Pod)
 		mutateStatusFn func(*kubecontainer.PodStatus)
@@ -2091,28 +2459,31 @@ func TestComputePodActionsWithInitAndEphemeralContainers(t *testing.T) {
 			actions: noAction,
 		},
 	} {
-		pod, status := makeBasePodAndStatusWithInitAndEphemeralContainers()
-		if test.mutatePodFn != nil {
-			test.mutatePodFn(pod)
-		}
-		if test.mutateStatusFn != nil {
-			test.mutateStatusFn(status)
-		}
-		ctx := context.Background()
-		actions := m.computePodActions(ctx, pod, status)
-		handleRestartableInitContainers := kubelettypes.HasRestartableInitContainer(pod)
-		if !handleRestartableInitContainers {
-			// If sidecar containers are disabled or the pod does not have any
-			// restartable init container, we should not see any
-			// InitContainersToStart in the actions.
-			test.actions.InitContainersToStart = nil
-		} else {
-			// If sidecar containers are enabled and the pod has any
-			// restartable init container, we should not see any
-			// NextInitContainerToStart in the actions.
-			test.actions.NextInitContainerToStart = nil
-		}
-		verifyActions(t, &test.actions, &actions, desc)
+		t.Run(desc, func(t *testing.T) {
+			featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, features.LegacySidecarContainers, true)
+			pod, status := makeBasePodAndStatusWithInitAndEphemeralContainers()
+			if test.mutatePodFn != nil {
+				test.mutatePodFn(pod)
+			}
+			if test.mutateStatusFn != nil {
+				test.mutateStatusFn(status)
+			}
+			ctx := context.Background()
+			actions := m.computePodActions(ctx, pod, status)
+			handleRestartableInitContainers := kubelettypes.HasRestartableInitContainer(pod)
+			if !handleRestartableInitContainers {
+				// If sidecar containers are disabled or the pod does not have any
+				// restartable init container, we should not see any
+				// InitContainersToStart in the actions.
+				test.actions.InitContainersToStart = nil
+			} else {
+				// If sidecar containers are enabled and the pod has any
+				// restartable init container, we should not see any
+				// NextInitContainerToStart in the actions.
+				test.actions.NextInitContainerToStart = nil
+			}
+			verifyActions(t, &test.actions, &actions, desc)
+		})
 	}
 }
 
diff --git a/test/featuregates_linter/test_data/versioned_feature_list.yaml b/test/featuregates_linter/test_data/versioned_feature_list.yaml
index 9c3f6e48d7c..2ca394de5d4 100644
--- a/test/featuregates_linter/test_data/versioned_feature_list.yaml
+++ b/test/featuregates_linter/test_data/versioned_feature_list.yaml
@@ -712,6 +712,16 @@
     lockToDefault: false
     preRelease: Beta
     version: "1.27"
+- name: LegacySidecarContainers
+  versionedSpecs:
+  - default: true
+    lockToDefault: false
+    preRelease: GA
+    version: "1.0"
+  - default: false
+    lockToDefault: false
+    preRelease: Deprecated
+    version: "1.33"
 - name: LoadBalancerIPMode
   versionedSpecs:
   - default: false