diff --git a/backend/internal/handler/admin/system_handler.go b/backend/internal/handler/admin/system_handler.go
index ae6613a3..cd145e52 100644
--- a/backend/internal/handler/admin/system_handler.go
+++ b/backend/internal/handler/admin/system_handler.go
@@ -2,8 +2,10 @@ package admin
 
 import (
 	"net/http"
+	"time"
 
 	"sub2api/internal/pkg/response"
+	"sub2api/internal/pkg/sysutil"
 	"sub2api/internal/service"
 
 	"github.com/gin-gonic/gin"
@@ -72,10 +74,14 @@ func (h *SystemHandler) Rollback(c *gin.Context) {
 // RestartService restarts the systemd service
 // POST /api/v1/admin/system/restart
 func (h *SystemHandler) RestartService(c *gin.Context) {
-	if err := h.updateSvc.RestartService(); err != nil {
-		response.Error(c, http.StatusInternalServerError, err.Error())
-		return
-	}
+	// Schedule service restart in background after sending response
+	// This ensures the client receives the success response before the service restarts
+	go func() {
+		// Wait a moment to ensure the response is sent
+		time.Sleep(500 * time.Millisecond)
+		sysutil.RestartServiceAsync()
+	}()
+
 	response.Success(c, gin.H{
 		"message": "Service restart initiated",
 	})
diff --git a/backend/internal/pkg/sysutil/restart.go b/backend/internal/pkg/sysutil/restart.go
new file mode 100644
index 00000000..aadf4aa7
--- /dev/null
+++ b/backend/internal/pkg/sysutil/restart.go
@@ -0,0 +1,51 @@
+package sysutil
+
+import (
+	"fmt"
+	"log"
+	"os/exec"
+	"runtime"
+)
+
+const serviceName = "sub2api"
+
+// RestartService triggers a service restart via systemd.
+//
+// IMPORTANT: This function initiates the restart and returns immediately.
+// The actual restart happens asynchronously - the current process will be killed
+// by systemd and a new process will be started.
+//
+// We use Start() instead of Run() because:
+//   - systemctl restart will kill the current process first
+//   - Run() waits for completion, but the process dies before completion
+//   - Start() spawns the command independently, allowing systemd to handle the full cycle
+//
+// Prerequisites:
+//   - Linux OS with systemd
+//   - NOPASSWD sudo access configured (install.sh creates /etc/sudoers.d/sub2api)
+func RestartService() error {
+	if runtime.GOOS != "linux" {
+		return fmt.Errorf("systemd restart only available on Linux")
+	}
+
+	log.Println("Initiating service restart...")
+
+	// The sub2api user has NOPASSWD sudo access for systemctl commands
+	// (configured by install.sh in /etc/sudoers.d/sub2api).
+	cmd := exec.Command("sudo", "systemctl", "restart", serviceName)
+	if err := cmd.Start(); err != nil {
+		return fmt.Errorf("failed to initiate service restart: %w", err)
+	}
+
+	log.Println("Service restart initiated successfully")
+	return nil
+}
+
+// RestartServiceAsync is a fire-and-forget version of RestartService.
+// It logs errors instead of returning them, suitable for goroutine usage.
+func RestartServiceAsync() {
+	if err := RestartService(); err != nil {
+		log.Printf("Service restart failed: %v", err)
+		log.Println("Please restart the service manually: sudo systemctl restart sub2api")
+	}
+}
diff --git a/backend/internal/service/update_service.go b/backend/internal/service/update_service.go
index 54c0fd16..b25bd87e 100644
--- a/backend/internal/service/update_service.go
+++ b/backend/internal/service/update_service.go
@@ -13,7 +13,6 @@ import (
 	"net/http"
 	"net/url"
 	"os"
-	"os/exec"
 	"path/filepath"
 	"runtime"
 	"strings"
@@ -244,23 +243,6 @@ func (s *UpdateService) Rollback() error {
 	return nil
 }
 
-// RestartService triggers a service restart via systemd
-func (s *UpdateService) RestartService() error {
-	if runtime.GOOS != "linux" {
-		return fmt.Errorf("systemd restart only available on Linux")
-	}
-
-	// Try direct systemctl first (works if running as root or with proper permissions)
-	cmd := exec.Command("systemctl", "restart", "sub2api")
-	if err := cmd.Run(); err != nil {
-		// Try with sudo (requires NOPASSWD sudoers entry)
-		sudoCmd := exec.Command("sudo", "systemctl", "restart", "sub2api")
-		if sudoErr := sudoCmd.Run(); sudoErr != nil {
-			return fmt.Errorf("systemctl restart failed: %w (sudo also failed: %v)", err, sudoErr)
-		}
-	}
-	return nil
-}
 
 func (s *UpdateService) fetchLatestRelease(ctx context.Context) (*UpdateInfo, error) {
 	url := fmt.Sprintf("https://api.github.com/repos/%s/releases/latest", githubRepo)
diff --git a/backend/internal/setup/handler.go b/backend/internal/setup/handler.go
index a8e73a03..ebd02ed5 100644
--- a/backend/internal/setup/handler.go
+++ b/backend/internal/setup/handler.go
@@ -2,17 +2,15 @@ package setup
 
 import (
 	"fmt"
-	"log"
 	"net/http"
 	"net/mail"
-	"os/exec"
 	"regexp"
-	"runtime"
 	"strings"
 	"sync"
 	"time"
 
 	"sub2api/internal/pkg/response"
+	"sub2api/internal/pkg/sysutil"
 
 	"github.com/gin-gonic/gin"
 )
@@ -346,7 +344,7 @@ func install(c *gin.Context) {
 	go func() {
 		// Wait a moment to ensure the response is sent
 		time.Sleep(500 * time.Millisecond)
-		triggerServiceRestart()
+		sysutil.RestartServiceAsync()
 	}()
 
 	response.Success(c, gin.H{
@@ -355,27 +353,3 @@ func install(c *gin.Context) {
 	})
 }
 
-// triggerServiceRestart attempts to restart the service via systemd
-// This is called after setup completes to switch from setup mode to normal mode
-func triggerServiceRestart() {
-	if runtime.GOOS != "linux" {
-		log.Println("Service restart: not on Linux, manual restart required")
-		return
-	}
-
-	log.Println("Setup completed, triggering service restart...")
-
-	// Try direct systemctl first (works if running as root or with proper permissions)
-	cmd := exec.Command("systemctl", "restart", "sub2api")
-	if err := cmd.Run(); err != nil {
-		// Try with sudo (requires NOPASSWD sudoers entry)
-		sudoCmd := exec.Command("sudo", "systemctl", "restart", "sub2api")
-		if sudoErr := sudoCmd.Run(); sudoErr != nil {
-			log.Printf("Service restart failed: %v (sudo also failed: %v)", err, sudoErr)
-			log.Println("Please restart the service manually: sudo systemctl restart sub2api")
-			return
-		}
-	}
-
-	log.Println("Service restart initiated successfully")
-}