diff --git a/docker-compose.proxyless.yml b/docker-compose.proxyless.yml
index ecfec9c..83a6532 100644
--- a/docker-compose.proxyless.yml
+++ b/docker-compose.proxyless.yml
@@ -35,7 +35,7 @@ services:
     container_name: synapsis-app
     restart: unless-stopped
     ports:
-      - "127.0.0.1:${APP_HOST_PORT:-3000}:3000"
+      - "127.0.0.1:${PORT:-3000}:${PORT:-3000}"
     environment:
       DATABASE_URL: postgresql://${DB_USER:-synapsis}:${DB_PASSWORD:-changeme}@postgres:5432/${DB_NAME:-synapsis}
       AUTH_SECRET: ${AUTH_SECRET}
@@ -45,7 +45,7 @@ services:
       ALLOW_LOCALHOST: ${ALLOW_LOCALHOST:-}
       ADMIN_EMAILS: ${ADMIN_EMAILS}
       BOT_MAX_PER_USER: ${BOT_MAX_PER_USER:-5}
-      PORT: "3000"
+      PORT: ${PORT:-3000}
       NODE_ENV: production
     volumes:
       - uploads_data:/app/uploads
@@ -55,7 +55,7 @@ services:
       postgres:
         condition: service_healthy
     healthcheck:
-      test: ["CMD-SHELL", "wget -q --spider http://127.0.0.1:3000/api/health || exit 1"]
+      test: ["CMD-SHELL", "wget -q --spider http://127.0.0.1:${PORT:-3000}/api/health || exit 1"]
       interval: 30s
       timeout: 10s
       retries: 3
diff --git a/docker/.env.example b/docker/.env.example
index f96ee70..94dc042 100644
--- a/docker/.env.example
+++ b/docker/.env.example
@@ -34,14 +34,11 @@ DB_NAME=synapsis
 # OPTIONAL: General Settings
 # ===========================================
 
-# Application port - 'auto' scans 3000-3020 for first available (recommended)
-# Or set a specific port: PORT=3000
+# Application port.
+# Default install (with bundled Caddy): PORT=auto scans 3000-3020 automatically.
+# Existing reverse proxy mode (PROXY=none): use a fixed localhost port, e.g. PORT=3000.
 PORT=auto
 
-# External reverse proxy mode only:
-# Port on localhost to expose Synapsis for nginx/Traefik/Caddy
-# APP_HOST_PORT=3000
-
 # Allow localhost domains in production (set only for local testing)
 # ALLOW_LOCALHOST=1
 
diff --git a/docker/README.md b/docker/README.md
index 73ada1f..5fc4480 100644
--- a/docker/README.md
+++ b/docker/README.md
@@ -49,7 +49,6 @@ Optional (advanced):
 **Port Configuration:**
 - `PORT=auto` (default) — Automatically finds an available port between 3000-3020
 - `PORT=3000` — Use a specific port instead
-- `APP_HOST_PORT=3000` — Only used in advanced `PROXY=none` installs
 
 ---
 
@@ -66,9 +65,11 @@ docker compose up -d
 
 This mode:
 - skips the bundled Caddy service
-- binds Synapsis to `127.0.0.1:${APP_HOST_PORT:-3000}`
+- binds Synapsis to `127.0.0.1:${PORT:-3000}`
 - expects your existing reverse proxy to forward traffic there
 
+In `PROXY=none` mode, `PORT` is the localhost port your reverse proxy should target. The installer automatically changes `PORT=auto` to `PORT=3000` unless you override it.
+
 Example nginx site:
 
 ```nginx
@@ -152,8 +153,8 @@ For the application port itself, `PORT=auto` (default) automatically finds an av
 # Check what's using the port
 sudo netstat -tlnp | grep :3000
 
-# Switch back to auto or choose a different port
-# Edit .env: PORT=auto
+# Choose a different fixed port in /opt/synapsis/.env
+# Example: PORT=3013
 ```
 
 ### Database connection failed
diff --git a/docker/install.sh b/docker/install.sh
index 8265617..231bd69 100644
--- a/docker/install.sh
+++ b/docker/install.sh
@@ -79,13 +79,24 @@ set_env_value() {
     rm -f "${file}.bak"
 }
 
+get_env_value() {
+    file="$1"
+    key="$2"
+
+    if [ ! -f "$file" ]; then
+        return 1
+    fi
+
+    sed -n -E "s/^${key}=(.*)$/\\1/p" "$file" | head -n 1
+}
+
 generate_db_password() {
     openssl rand -base64 24 | tr -d '\n' | tr '/+' '_-' | cut -c1-32
 }
 
-resolve_proxyless_host_port() {
-    if [ -n "${APP_HOST_PORT:-}" ]; then
-        printf '%s\n' "${APP_HOST_PORT}"
+resolve_proxyless_port() {
+    if [ -n "${PORT:-}" ] && [ "${PORT}" != "auto" ]; then
+        printf '%s\n' "${PORT}"
         return
     fi
 
@@ -131,7 +142,7 @@ require_command cp
 
 RAW_BASE="https://raw.githubusercontent.com/${REPO}/${REF}"
 PROXY="$(normalize_proxy_mode "${PROXY}")"
-PROXYLESS_HOST_PORT="$(resolve_proxyless_host_port)"
+PROXYLESS_PORT="$(resolve_proxyless_port)"
 
 echo "========================================"
 echo "  Synapsis Docker Installer"
@@ -182,8 +193,21 @@ if [ ! -f "${INSTALL_DIR}/.env" ]; then
         set_env_value "${INSTALL_DIR}/.env" "ADMIN_EMAILS" "${ADMIN_EMAILS}"
         echo "📧 Set ADMIN_EMAILS=${ADMIN_EMAILS}"
     fi
+
+    if [ "${PROXY}" = "none" ]; then
+        set_env_value "${INSTALL_DIR}/.env" "PORT" "${PROXYLESS_PORT}"
+        echo "📡 Set PORT=${PROXYLESS_PORT} for proxyless mode"
+    fi
 else
     echo "📝 Existing ${INSTALL_DIR}/.env found, leaving it unchanged"
+
+    if [ "${PROXY}" = "none" ]; then
+        current_port="$(get_env_value "${INSTALL_DIR}/.env" "PORT" || true)"
+        if [ -z "${current_port}" ] || [ "${current_port}" = "auto" ]; then
+            set_env_value "${INSTALL_DIR}/.env" "PORT" "${PROXYLESS_PORT}"
+            echo "📡 Updated PORT=${PROXYLESS_PORT} for proxyless mode"
+        fi
+    fi
 fi
 
 echo ""
@@ -196,6 +220,6 @@ else
     echo "  2. Start Synapsis:"
     echo "     cd ${INSTALL_DIR} && docker compose up -d"
     echo "  3. Configure your existing reverse proxy to forward to:"
-    echo "     http://127.0.0.1:${PROXYLESS_HOST_PORT}"
-    echo "     (change APP_HOST_PORT in ${INSTALL_DIR}/.env if you want a different localhost port)"
+    echo "     http://127.0.0.1:${PROXYLESS_PORT}"
+    echo "     (change PORT in ${INSTALL_DIR}/.env if you want a different localhost port)"
 fi