diff --git a/weed/worker/tasks/ec_vacuum/ec_vacuum_task.go b/weed/worker/tasks/ec_vacuum/ec_vacuum_task.go
index fe4442393..efcf3e987 100644
--- a/weed/worker/tasks/ec_vacuum/ec_vacuum_task.go
+++ b/weed/worker/tasks/ec_vacuum/ec_vacuum_task.go
@@ -9,6 +9,7 @@ import (
 
 	"github.com/seaweedfs/seaweedfs/weed/operation"
 	"github.com/seaweedfs/seaweedfs/weed/pb"
+	"github.com/seaweedfs/seaweedfs/weed/pb/master_pb"
 	"github.com/seaweedfs/seaweedfs/weed/pb/volume_server_pb"
 	"github.com/seaweedfs/seaweedfs/weed/pb/worker_pb"
 	"github.com/seaweedfs/seaweedfs/weed/storage/erasure_coding"
@@ -27,6 +28,7 @@ type EcVacuumTask struct {
 	targetGeneration uint32 // generation to create (G+1)
 	tempDir          string
 	grpcDialOption   grpc.DialOption
+	masterAddress    pb.ServerAddress // master server address for activation RPC
 }
 
 // NewEcVacuumTask creates a new EC vacuum task instance
@@ -78,7 +80,12 @@ func (t *EcVacuumTask) Execute(ctx context.Context, params *worker_pb.TaskParams
 		return fmt.Errorf("failed to distribute new EC shards: %w", err)
 	}
 
-	// Step 6: Clean up old EC shards
+	// Step 6: Activate new generation (atomic switch from G to G+1)
+	if err := t.activateNewGeneration(); err != nil {
+		return fmt.Errorf("failed to activate new generation: %w", err)
+	}
+
+	// Step 7: Clean up old EC shards
 	if err := t.cleanupOldEcShards(); err != nil {
 		t.LogWarning("Failed to clean up old EC shards", map[string]interface{}{
 			"error": err.Error(),
@@ -291,6 +298,42 @@ func (t *EcVacuumTask) distributeNewEcShards(sourceNode pb.ServerAddress) error
 	return nil
 }
 
+// activateNewGeneration atomically switches the master to use the new generation
+func (t *EcVacuumTask) activateNewGeneration() error {
+	t.LogInfo("Activating new generation", map[string]interface{}{
+		"volume_id":         t.volumeID,
+		"source_generation": t.sourceGeneration,
+		"target_generation": t.targetGeneration,
+		"master_address":    t.masterAddress,
+	})
+
+	if t.masterAddress == "" {
+		t.LogWarning("Master address not set - skipping automatic generation activation", map[string]interface{}{
+			"volume_id":         t.volumeID,
+			"target_generation": t.targetGeneration,
+			"note":              "Generation activation must be done manually via master API",
+		})
+		return nil
+	}
+
+	return operation.WithMasterServerClient(false, t.masterAddress, t.grpcDialOption, func(client master_pb.SeaweedClient) error {
+		_, err := client.ActivateEcGeneration(context.Background(), &master_pb.ActivateEcGenerationRequest{
+			VolumeId:   t.volumeID,
+			Collection: t.collection,
+			Generation: t.targetGeneration,
+		})
+		if err != nil {
+			return fmt.Errorf("failed to activate generation %d for volume %d: %w", t.targetGeneration, t.volumeID, err)
+		}
+
+		t.LogInfo("Successfully activated new generation", map[string]interface{}{
+			"volume_id":         t.volumeID,
+			"active_generation": t.targetGeneration,
+		})
+		return nil
+	})
+}
+
 // cleanupOldEcShards removes the original volume after successful vacuum
 func (t *EcVacuumTask) cleanupOldEcShards() error {
 	t.LogInfo("Cleaning up original volume", map[string]interface{}{
@@ -353,3 +396,8 @@ func (t *EcVacuumTask) GetCollection() string {
 func (t *EcVacuumTask) SetGrpcDialOption(option grpc.DialOption) {
 	t.grpcDialOption = option
 }
+
+// SetMasterAddress sets the master server address for generation activation
+func (t *EcVacuumTask) SetMasterAddress(address pb.ServerAddress) {
+	t.masterAddress = address
+}