diff --git a/nginx.conf b/nginx.conf
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+++ b/nginx.conf
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+# nginx config for llm.home.ms - kokorotts-server reverse proxy
+# Addresses: issues #15-#24 (OPE-Web security audit findings)
+
+server {
+    listen 443 ssl http2;
+    server_name llm.home.ms;
+
+    # SSL configuration
+    ssl_certificate /etc/letsencrypt/live/llm.home.ms/fullchain.pem;
+    ssl_certificate_key /etc/letsencrypt/live/llm.home.ms/privkey.pem;
+    ssl_protocols TLSv1.2 TLSv1.3;
+    ssl_ciphers HIGH:!aNULL:!MD5;
+    ssl_prefer_server_ciphers on;
+    ssl_session_cache shared:SSL:10m;
+    ssl_session_timeout 10m;
+
+    # Issue #21: Hide server version
+    server_tokens off;
+
+    # Issue #16: HSTS header (1 year, include subdomains)
+    add_header Strict-Transport-Security "max-age=31536000; includeSubDomains" always;
+
+    # Issue #17: Content-Security-Policy
+    # Allow Swagger UI inline scripts/styles while restricting external sources
+    add_header Content-Security-Policy "default-src 'self'; script-src 'self' 'unsafe-inline' 'unsafe-eval'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; font-src 'self'; connect-src 'self'; frame-ancestors 'none'; base-uri 'self'; form-action 'self';" always;
+
+    # Issue #18: X-Frame-Options - prevent clickjacking
+    add_header X-Frame-Options "DENY" always;
+
+    # Issue #19: X-Content-Type-Options - prevent MIME sniffing
+    add_header X-Content-Type-Options "nosniff" always;
+
+    # Issue #20: Referrer-Policy
+    add_header Referrer-Policy "strict-origin-when-cross-origin" always;
+
+    # Permissions Policy
+    add_header Permissions-Policy "geolocation=(), microphone=(), camera=()" always;
+
+    # Issue #15: Restrict Swagger UI access - require authentication
+    location /docs {
+        auth_basic "API Documentation - Restricted Access";
+        auth_basic_user_file /etc/nginx/.htpasswd;
+        proxy_pass http://127.0.0.1:5012;
+        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;
+    }
+
+    location /openapi.json {
+        auth_basic "API Documentation - Restricted Access";
+        auth_basic_user_file /etc/nginx/.htpasswd;
+        proxy_pass http://127.0.0.1:5012;
+        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;
+    }
+
+    # Main API endpoint
+    location /tts {
+        proxy_pass http://127.0.0.1:5012;
+        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;
+
+        # Rate limiting
+        limit_req zone=tts_zone burst=5 nodelay;
+    }
+
+    # Health check endpoint (no auth needed)
+    location /health {
+        proxy_pass http://127.0.0.1:5012;
+        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;
+    }
+
+    # Issue #22: Fix protocol-relative links by redirecting absolute paths
+    # These locations handle the broken //ui, //fallback/login, //ui/model_hub_table links
+    location /ui/ {
+        proxy_pass http://127.0.0.1:5012/ui/;
+        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;
+    }
+
+    location /fallback/login {
+        proxy_pass http://127.0.0.1:5012/fallback/login;
+        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;
+    }
+
+    location /ui/model_hub_table {
+        proxy_pass http://127.0.0.1:5012/ui/model_hub_table;
+        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;
+    }
+
+    # Default: proxy to Flask app
+    location / {
+        proxy_pass http://127.0.0.1:5012;
+        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 $scheme;
+    }
+
+    # Block access to version info
+    location ~* /version {
+        return 403;
+    }
+}
+
+# HTTP -> HTTPS redirect
+server {
+    listen 80;
+    server_name llm.home.ms;
+    return 301 https://$server_name$request_uri;
+}
+
+# Rate limiting zone (add to http block in nginx.conf)
+# limit_req_zone $binary_remote_addr zone=tts_zone:10m rate=10r/s;