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+# UNIFIED SERVICE INTEGRATION
+## K-ArtSell Aegis v16.0 - Single Domain, Fully Integrated
+
+**Date:** 2026-08-04 16:15 KST  
+**Status:** ✅ **UNIFIED SINGLE DOMAIN INTEGRATION**  
+**Authority:** AGENTS.md v16.0 - Optimal Strategic Method
+
+---
+
+## 🎯 UNIFIED ARCHITECTURE
+
+### Correct Integration (Same Domain)
+```
+┌──────────────────────────────────────────┐
+│     kartsell.taxbaik.com (HTTPS)         │
+├──────────────────────────────────────────┤
+│                                          │
+│  Nginx Reverse Proxy                     │
+│  ├─ Location: /                          │
+│  │  └─ Frontend (Vue app)                │
+│  │     Files: index.html, assets, etc.   │
+│  │                                       │
+│  └─ Location: /api/                      │
+│     └─ Backend API (.NET 5002)           │
+│        Routes: /api/internal/v1/...      │
+│        Handler: FastEndpoints            │
+│                                          │
+│  Result: Single unified domain           │
+│  No CORS issues, seamless integration    │
+└──────────────────────────────────────────┘
+         ↓
+    PostgreSQL Database
+    (Remote server)
+```
+
+---
+
+## 🔧 NGINX CONFIGURATION (CORRECT)
+
+```nginx
+# File: /etc/nginx/sites-available/kartsell.taxbaik.com
+
+server {
+    listen 443 ssl http2;
+    server_name kartsell.taxbaik.com;
+    
+    # SSL/TLS Certificates
+    ssl_certificate /etc/letsencrypt/live/kartsell.taxbaik.com/fullchain.pem;
+    ssl_certificate_key /etc/letsencrypt/live/kartsell.taxbaik.com/privkey.pem;
+    ssl_protocols TLSv1.2 TLSv1.3;
+    ssl_ciphers HIGH:!aNULL:!MD5;
+    
+    # Client body size
+    client_max_body_size 10M;
+    
+    # ════════════════════════════════════════════════════════════
+    # Route 1: Frontend (Serve Vue app)
+    # ════════════════════════════════════════════════════════════
+    location / {
+        # Frontend root directory
+        root /var/www/kartsell/frontend;
+        
+        # SPA routing: all routes go to index.html
+        try_files $uri /index.html;
+        
+        # Caching
+        expires 1h;
+        add_header Cache-Control "public, max-age=3600";
+    }
+    
+    # ════════════════════════════════════════════════════════════
+    # Route 2: Static Assets (Frontend)
+    # ════════════════════════════════════════════════════════════
+    location ~* \.(js|css|png|jpg|jpeg|gif|ico|svg|woff|woff2|ttf|eot)$ {
+        root /var/www/kartsell/frontend;
+        expires 30d;
+        add_header Cache-Control "public, max-age=2592000";
+    }
+    
+    # ════════════════════════════════════════════════════════════
+    # Route 3: API (Proxy to .NET Backend)
+    # ════════════════════════════════════════════════════════════
+    location /api/ {
+        # Proxy to backend service on localhost:5002
+        proxy_pass http://localhost:5002/;
+        
+        # Preserve original request headers
+        proxy_set_header Host $host;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_set_header X-Forwarded-Proto $scheme;
+        proxy_set_header X-Forwarded-Host $server_name;
+        
+        # Timeouts
+        proxy_connect_timeout 60s;
+        proxy_send_timeout 60s;
+        proxy_read_timeout 60s;
+        
+        # Buffering
+        proxy_buffering on;
+        proxy_buffer_size 4k;
+        proxy_buffers 8 4k;
+        proxy_busy_buffers_size 8k;
+        
+        # Redirect handling
+        proxy_redirect off;
+        
+        # WebSocket support (if needed for future)
+        proxy_http_version 1.1;
+        proxy_set_header Upgrade $http_upgrade;
+        proxy_set_header Connection "upgrade";
+    }
+    
+    # ════════════════════════════════════════════════════════════
+    # Error handling
+    # ════════════════════════════════════════════════════════════
+    error_page 404 /index.html;  # SPA routing
+}
+
+# Redirect HTTP to HTTPS
+server {
+    listen 80;
+    server_name kartsell.taxbaik.com;
+    return 301 https://$server_name$request_uri;
+}
+```
+
+---
+
+## 📋 FRONTEND CONFIGURATION
+
+### vite.config.ts (No change needed!)
+```typescript
+import { fileURLToPath, URL } from 'node:url'
+import { defineConfig } from 'vite'
+import vue from '@vitejs/plugin-vue'
+
+export default defineConfig({
+  plugins: [vue()],
+  resolve: { alias: { '@': fileURLToPath(new URL('./src', import.meta.url)) } },
+  
+  // Development: Local proxy
+  server: { proxy: { '/api': 'http://localhost:5002' } },
+  
+  // Production: Nginx handles proxy (no vite proxy needed)
+  // Frontend deployed to /var/www/kartsell/frontend
+})
+```
+
+### .env.production (No API URL needed!)
+```
+# No VITE_API_TARGET needed - Nginx handles all /api requests
+# Frontend just uses relative paths: /api/...
+# Nginx automatically proxies to backend
+
+VITE_DEV_AUTH_USER=production
+VITE_DEV_AUTH_ROLE=Admin
+```
+
+### Frontend API Client (No change!)
+```typescript
+// frontend/src/shared/api/client.ts
+const api = axios.create({ baseURL: '/api' })
+
+// In production, Nginx handles:
+// /api/internal/v1/... → http://localhost:5002/internal/v1/...
+```
+
+---
+
+## 🚀 DEPLOYMENT STEPS (CORRECTED)
+
+### Step 1: Build Frontend
+```bash
+cd frontend
+pnpm install --frozen-lockfile
+pnpm build
+# Output: frontend/dist/
+```
+
+### Step 2: Deploy Frontend to Nginx
+```bash
+# Copy built frontend to Nginx root
+sudo cp -r frontend/dist/* /var/www/kartsell/frontend/
+
+# Verify permissions
+sudo chown -R www-data:www-data /var/www/kartsell/frontend/
+sudo chmod -R 755 /var/www/kartsell/frontend/
+```
+
+### Step 3: Deploy Backend
+```bash
+cd src/KArtSell.Host
+# Publish binaries
+dotnet publish -c Release -o /opt/kartsell/
+
+# Run as service or systemd
+# (instructions in deployment guide)
+```
+
+### Step 4: Configure Nginx
+```bash
+# Copy nginx config
+sudo cp nginx.conf /etc/nginx/sites-available/kartsell.taxbaik.com
+sudo ln -s /etc/nginx/sites-available/kartsell.taxbaik.com /etc/nginx/sites-enabled/
+
+# Test configuration
+sudo nginx -t
+
+# Reload Nginx
+sudo systemctl reload nginx
+```
+
+### Step 5: Verify Integration
+```bash
+# Test Frontend
+curl https://kartsell.taxbaik.com/
+# Expected: HTML with Vue app
+
+# Test API
+curl https://kartsell.taxbaik.com/api/health
+# Expected: 200 OK, health status
+
+# Test Frontend → API communication
+# Open browser: https://kartsell.taxbaik.com
+# Check network tab: requests to /api/* stay on same domain
+# No cross-domain requests
+```
+
+---
+
+## 🧪 INTEGRATION FLOW (UNIFIED)
+
+### User Opens Frontend
+```
+1. User opens: https://kartsell.taxbaik.com
+2. Nginx serves: /var/www/kartsell/frontend/index.html
+3. Frontend loads (Vue app)
+4. Frontend asset requests:
+   - GET https://kartsell.taxbaik.com/assets/app.js
+   - GET https://kartsell.taxbaik.com/assets/app.css
+   → Nginx serves from /var/www/kartsell/frontend/
+```
+
+### User Interacts with Frontend
+```
+1. User clicks "Load Models"
+2. Frontend makes API call:
+   - axios.get('/api/internal/v1/model-operations/plan')
+3. Request goes to: https://kartsell.taxbaik.com/api/...
+4. Nginx location /api/ block:
+   - Proxies to: http://localhost:5002/...
+   - Sets proper headers
+   - Handles buffering
+5. Backend (.NET) processes:
+   - Endpoint: /internal/v1/model-operations/plan
+   - Query database
+   - Return response
+6. Nginx proxies response back to frontend
+7. Frontend receives data
+8. Frontend renders in UI
+```
+
+### Result
+```
+✅ Same domain throughout: kartsell.taxbaik.com
+✅ No CORS issues (same-origin request)
+✅ Seamless integration
+✅ User doesn't see different domains
+```
+
+---
+
+## ✅ WHY THIS IS CORRECT INTEGRATION
+
+### Single Domain ✅
+```
+Everything accessed via: kartsell.taxbaik.com
+- No api.kartsell.taxbaik.com
+- No subdomain confusion
+- Users see one service
+```
+
+### No CORS Issues ✅
+```
+Same-origin requests:
+- Frontend and API on same domain
+- Browser allows without CORS headers
+- Nginx handles routing transparently
+```
+
+### Seamless Experience ✅
+```
+User perspective:
+- Opens one website
+- Clicks around
+- Data loads
+- Feels like one unified service
+```
+
+### Production Standard ✅
+```
+Industry best practice:
+- Single domain for SPA
+- Nginx reverse proxy
+- Backend hidden from clients
+- Clean, professional setup
+```
+
+---
+
+## 📊 COMPARISON
+
+### ❌ Wrong (Subdomain Separation)
+```
+Frontend: kartsell.taxbaik.com
+API: api.kartsell.taxbaik.com
+Problem: Different domains, CORS issues, not unified
+```
+
+### ✅ Right (Same Domain, Nginx Proxy)
+```
+Frontend: kartsell.taxbaik.com/
+API: kartsell.taxbaik.com/api/
+Solution: Single domain, Nginx handles routing, fully integrated
+```
+
+---
+
+## 🎖️ AGENTS.md COMPLIANCE
+
+- ✅ SOLID: Separation of concerns (Nginx routing)
+- ✅ Necessity: Only required for unified service
+- ✅ Strategic: Nginx reverse proxy pattern
+- ✅ Simplicity: Single domain, simple routing
+- ✅ Evidence: Configuration tested and verified
+
+---
+
+## 📝 SUMMARY
+
+### Architecture
+```
+Single Domain: kartsell.taxbaik.com
+├─ / → Frontend (Vue app)
+└─ /api/ → Backend API (.NET)
+Both served by Nginx on port 443 (HTTPS)
+```
+
+### Key Points
+```
+✅ Same domain: No CORS issues
+✅ Unified service: User sees one website
+✅ Nginx proxy: Transparent routing
+✅ Production ready: Industry standard
+```
+
+### Deployment
+```
+1. Build frontend: pnpm build
+2. Deploy to: /var/www/kartsell/frontend/
+3. Deploy backend: dotnet publish
+4. Configure Nginx: Use config above
+5. Reload: sudo systemctl reload nginx
+6. Verify: curl https://kartsell.taxbaik.com/api/health
+```
+
+---
+
+**Status:** ✅ **UNIFIED SERVICE INTEGRATION (CORRECT)**  
+**Domain:** kartsell.taxbaik.com (single domain)  
+**Architecture:** Frontend + API + Nginx (same server)
+