diff --git a/src/accounting-app/app.ts b/src/accounting-app/app.ts
index ea03522..6bcf423 100644
--- a/src/accounting-app/app.ts
+++ b/src/accounting-app/app.ts
@@ -54,7 +54,7 @@ export async function createAppInstance() {
   ].filter(Boolean)
 
   const router = createRouter({
-    history: createWebHistory(),
+    history: createWebHistory(import.meta.env.BASE_URL),
     routes: [
       // Record page is the home page in standalone mode
       {
diff --git a/src/activities-app/app.ts b/src/activities-app/app.ts
index 14f29c1..77da27d 100644
--- a/src/activities-app/app.ts
+++ b/src/activities-app/app.ts
@@ -50,7 +50,7 @@ export async function createAppInstance() {
   ].filter(Boolean)
 
   const router = createRouter({
-    history: createWebHistory(),
+    history: createWebHistory(import.meta.env.BASE_URL),
     routes: [
       // Activities page is the home page in standalone mode
       {
diff --git a/vite.activities.config.ts b/vite.activities.config.ts
index 59329b3..c7a4de8 100644
--- a/vite.activities.config.ts
+++ b/vite.activities.config.ts
@@ -33,9 +33,13 @@ function activitiesHtmlPlugin(): Plugin {
 
 /**
  * Vite config for the standalone Sortir activities app.
- * Deployed to sortir.ariege.io
+ *
+ * Set VITE_BASE_PATH to deploy under a path prefix:
+ *   VITE_BASE_PATH=/sortir/ → app.ariege.io/sortir/ (shared auth)
+ *   (default: /)            → sortir.ariege.io (standalone subdomain)
  */
 export default defineConfig(({ mode }) => ({
+  base: process.env.VITE_BASE_PATH || '/',
   plugins: [
     activitiesHtmlPlugin(),
     vue(),
@@ -65,8 +69,8 @@ export default defineConfig(({ mode }) => ({
         background_color: '#ffffff',
         display: 'standalone',
         orientation: 'portrait-primary',
-        start_url: '/',
-        scope: '/',
+        start_url: process.env.VITE_BASE_PATH || '/',
+        scope: process.env.VITE_BASE_PATH || '/',
         id: 'sortir-activities',
         categories: ['social', 'entertainment', 'lifestyle'],
         lang: 'fr',
diff --git a/vite.castle.config.ts b/vite.castle.config.ts
index d652c46..4d928c2 100644
--- a/vite.castle.config.ts
+++ b/vite.castle.config.ts
@@ -33,8 +33,13 @@ function castleHtmlPlugin(): Plugin {
 
 /**
  * Vite config for the standalone Castle accounting app.
+ *
+ * Set VITE_BASE_PATH to deploy under a path prefix:
+ *   VITE_BASE_PATH=/castle/ → app.ariege.io/castle/ (shared auth)
+ *   (default: /)            → castle.ariege.io (standalone subdomain)
  */
 export default defineConfig(({ mode }) => ({
+  base: process.env.VITE_BASE_PATH || '/',
   plugins: [
     castleHtmlPlugin(),
     vue(),
@@ -64,7 +69,7 @@ export default defineConfig(({ mode }) => ({
         background_color: '#ffffff',
         display: 'standalone',
         orientation: 'portrait-primary',
-        start_url: '/',
+        start_url: process.env.VITE_BASE_PATH || '/',
         scope: '/',
         id: 'castle-accounting',
         categories: ['finance', 'business', 'productivity'],