diff --git a/SETUP_LOCAL.md b/SETUP_LOCAL.md
index 098179f..274662b 100644
--- a/SETUP_LOCAL.md
+++ b/SETUP_LOCAL.md
@@ -34,12 +34,21 @@ http://localhost/index.html
 
 ### Opsi 3: Gunakan PHP Built-in Server
 
+**Frontend:**
 ```bash
 cd "C:\laragon\www\RETRIBUSI_BAPENDA\retribusi (frontend)\public"
 php -S localhost:8080
 ```
 
-Akses: `http://localhost:8080/index.html`
+**Backend API (PENTING - harus dengan router.php):**
+```bash
+cd "C:\laragon\www\RETRIBUSI_BAPENDA\api-btekno\public"
+php -S localhost:8000 router.php
+```
+
+**Akses:**
+- Frontend: `http://localhost:8080/index.html`
+- Backend API: `http://localhost:8000` (dengan router.php)
 
 ## Konfigurasi API
 
diff --git a/SETUP_LOCAL_FIX.md b/SETUP_LOCAL_FIX.md
new file mode 100644
index 0000000..f8346b2
--- /dev/null
+++ b/SETUP_LOCAL_FIX.md
@@ -0,0 +1,102 @@
+# Fix: Failed to fetch di Localhost
+
+## Masalah
+
+Error: "Failed to fetch" saat mengakses `http://localhost:8080/`
+
+Backend API error:
+```
+[404]: OPTIONS /auth/v1/login - No such file or directory
+```
+
+## Penyebab
+
+PHP built-in server dijalankan **TANPA router.php**, sehingga routing tidak bekerja.
+
+## Solusi
+
+### 1. Jalankan Backend API dengan Router
+
+**SALAH** (yang menyebabkan error):
+```bash
+cd api-btekno
+php -S localhost:8000
+```
+
+**BENAR** (yang harus dilakukan):
+```bash
+cd api-btekno/public
+php -S localhost:8000 router.php
+```
+
+File `router.php` diperlukan untuk handle routing seperti `/auth/v1/login`.
+
+### 2. Jalankan Frontend
+
+```bash
+cd "retribusi (frontend)/public"
+php -S localhost:8080
+```
+
+### 3. Test Backend API
+
+Buka browser dan akses:
+```
+http://localhost:8000/health
+```
+
+Harusnya return: `{"status":"ok","time":...}`
+
+Jika masih 404, berarti router.php tidak bekerja.
+
+### 4. Cek Config Frontend
+
+File `public/dashboard/js/config.js` harus return:
+```javascript
+return 'http://localhost:8000';
+```
+
+## Quick Start Script
+
+Buat file `start-local.bat` di root project:
+
+```batch
+@echo off
+echo Starting Backend API...
+start "Backend API" cmd /k "cd api-btekno\public && php -S localhost:8000 router.php"
+
+timeout /t 2
+
+echo Starting Frontend...
+start "Frontend" cmd /k "cd retribusi (frontend)\public && php -S localhost:8080"
+
+echo.
+echo Backend API: http://localhost:8000
+echo Frontend: http://localhost:8080
+echo.
+pause
+```
+
+Jalankan `start-local.bat` untuk start kedua server sekaligus.
+
+## Troubleshooting
+
+### Masih 404 di Backend?
+
+1. Pastikan menjalankan dari folder `api-btekno/public`
+2. Pastikan menggunakan `router.php`: `php -S localhost:8000 router.php`
+3. Cek file `router.php` ada di `api-btekno/public/router.php`
+
+### Masih "Failed to fetch"?
+
+1. Buka browser console (F12)
+2. Cek log `[API] Request:` - pastikan URL benar
+3. Test backend langsung: `curl http://localhost:8000/health`
+4. Cek CORS - pastikan backend allow origin `http://localhost:8080`
+
+### CORS Error?
+
+Backend sudah ada CORS middleware, tapi pastikan:
+1. Backend running dengan router.php
+2. CORS middleware sudah di-register di `public/index.php`
+