diff --git a/local-tool/server/internal/api/handlers/system_driver_windows.go b/local-tool/server/internal/api/handlers/system_driver_windows.go
index faf6e2d..db40ba7 100644
--- a/local-tool/server/internal/api/handlers/system_driver_windows.go
+++ b/local-tool/server/internal/api/handlers/system_driver_windows.go
@@ -28,30 +28,60 @@ func installKneronWinUSBDriverHandler(pythonBin string) error {
 	// venv 根目錄
 	venvRoot := filepath.Dir(filepath.Dir(pythonBin))
 
+	// Python script:
+	//  1. 對三種 PID 呼叫 kp.core.install_driver_for_windows
+	//  2. 安裝完立刻 scan_devices() 驗證，看 SDK 能不能開 handle
+	//  3. 不 swallow exception — 把 traceback 完整寫到 result 檔
 	pyScript := fmt.Sprintf(`
-import sys, os
+import sys, os, traceback
 result_path = r'%s'
+lines = []
+def out(msg):
+    lines.append(str(msg))
+    try:
+        sys.stdout.write(str(msg) + '\n'); sys.stdout.flush()
+    except Exception:
+        pass
 try:
     kp_lib = os.path.join(r'%s', 'Lib', 'site-packages', 'kp', 'lib')
     if os.path.isdir(kp_lib):
         os.environ['PATH'] = kp_lib + ';' + os.environ.get('PATH', '')
-        os.add_dll_directory(kp_lib)
+        try:
+            os.add_dll_directory(kp_lib)
+        except Exception as dle:
+            out(f"WARN: add_dll_directory failed: {dle}")
     import kp
-    results = []
+    out(f"kp module imported: {kp.__file__}")
     for pid in [kp.ProductId.KP_DEVICE_KL520, kp.ProductId.KP_DEVICE_KL720, kp.ProductId.KP_DEVICE_KL720_LEGACY]:
         try:
+            out(f"Installing driver for {pid.name} (value={pid.value})...")
             kp.core.install_driver_for_windows(pid)
-            results.append(f"OK: {pid.name}")
+            out(f"  OK: {pid.name}")
         except Exception as e:
-            results.append(f"SKIP: {pid.name}: {e}")
-    with open(result_path, 'w') as f:
-        f.write('\n'.join(results) + '\nDONE\n')
+            out(f"  SKIP: {pid.name}: {type(e).__name__}: {e}")
+    # 驗證：裝完立刻 scan + 印 is_connectable
+    out("Verifying with scan_devices()...")
+    try:
+        descs = kp.core.scan_devices()
+        out(f"  found {descs.device_descriptor_number} Kneron device(s)")
+        for i in range(descs.device_descriptor_number):
+            d = descs.device_descriptor_list[i]
+            out(f"  [{i}] pid=0x{d.product_id:04X} usb_port={d.usb_port_id} connectable={d.is_connectable} fw={d.firmware}")
+    except Exception as se:
+        out(f"  scan_devices failed: {type(se).__name__}: {se}")
+    out("DONE")
 except ImportError as e:
-    with open(result_path, 'w') as f:
-        f.write(f'ERROR: kp module not available: {e}\n')
+    out(f"ERROR: kp module not available: {e}")
+    out(traceback.format_exc())
 except Exception as e:
-    with open(result_path, 'w') as f:
-        f.write(f'ERROR: {e}\n')
+    out(f"ERROR: {type(e).__name__}: {e}")
+    out(traceback.format_exc())
+finally:
+    try:
+        with open(result_path, 'w', encoding='utf-8') as f:
+            f.write('\n'.join(lines))
+    except Exception:
+        pass
 `, resultPath, venvRoot)
 
 	scriptPath := filepath.Join(os.TempDir(), "visiona-local-install-usb-driver.py")
@@ -77,9 +107,32 @@ except Exception as e:
 	}
 
 	result := strings.TrimSpace(string(resultData))
+	// 把完整結果印到 server stderr 方便使用者 / 我們 debug
+	fmt.Fprintln(os.Stderr, "=== Kneron driver install result ===")
+	fmt.Fprintln(os.Stderr, result)
+	fmt.Fprintln(os.Stderr, "=== end ===")
+
 	if strings.Contains(result, "ERROR:") {
-		return fmt.Errorf("driver 安裝失敗：%s", result)
+		return fmt.Errorf("driver 安裝失敗（完整訊息見 server.stderr.log）：%s", firstLines(result, 6))
+	}
+
+	// 檢查 DONE 標記 + 至少一個 OK
+	if !strings.Contains(result, "DONE") {
+		return fmt.Errorf("driver 安裝未完成（沒有 DONE 標記，見 server.stderr.log）：%s", firstLines(result, 6))
+	}
+	if !strings.Contains(result, "OK:") {
+		return fmt.Errorf("driver 安裝全部失敗，沒有任何 PID 成功（見 server.stderr.log）：%s", firstLines(result, 10))
 	}
 
 	return nil
 }
+
+// firstLines 取結果的前 n 行，避免 error message 過長
+func firstLines(s string, n int) string {
+	lines := strings.Split(s, "\n")
+	if len(lines) > n {
+		lines = lines[:n]
+		lines = append(lines, "...")
+	}
+	return strings.Join(lines, " | ")
+}