diff --git a/config/reference.php b/config/reference.php
index a0dc365..1ee83e3 100644
--- a/config/reference.php
+++ b/config/reference.php
@@ -467,7 +467,7 @@ use Symfony\Component\Config\Loader\ParamConfigurator as Param;
  *     },
  *     disallow_search_engine_index?: bool|Param, // Enabled by default when debug is enabled. // Default: true
  *     http_client?: bool|array{ // HTTP Client configuration
- *         enabled?: bool|Param, // Default: false
+ *         enabled?: bool|Param, // Default: true
  *         max_host_connections?: int|Param, // The maximum number of connections to a single host.
  *         default_options?: array{
  *             headers?: array<string, mixed>,
diff --git a/frontend/components/task/TaskModal.vue b/frontend/components/task/TaskModal.vue
index 8cd8d38..9f895ef 100644
--- a/frontend/components/task/TaskModal.vue
+++ b/frontend/components/task/TaskModal.vue
@@ -14,7 +14,7 @@
                     style="max-height: min(90vh, 900px)"
                 >
                     <!-- Header -->
-                    <div class="border-b border-neutral-100 bg-neutral-50/80 px-8 py-5">
+                    <div class="border-b border-neutral-100 bg-neutral-50/80 px-4 py-4 sm:px-8 sm:py-5">
                         <div class="flex items-center justify-between">
                             <div class="flex items-center gap-3">
                                 <span
@@ -38,7 +38,7 @@
                     </div>
 
                     <!-- Body -->
-                    <form @submit.prevent="handleSubmit" class="overflow-y-auto px-8 py-6">
+                    <form @submit.prevent="handleSubmit" class="overflow-y-auto px-4 py-4 sm:px-8 sm:py-6">
                         <!-- Title -->
                         <MalioInputText
                             v-model="form.title"
@@ -49,7 +49,7 @@
                         />
 
                         <!-- Two-column selects -->
-                        <div class="mt-4 grid grid-cols-2 gap-x-6 gap-y-4">
+                        <div class="mt-4 grid grid-cols-1 gap-x-6 gap-y-4 sm:grid-cols-2">
                             <MalioSelect
                                 v-model="form.statusId"
                                 :options="statusOptions"
diff --git a/frontend/components/ui/AppTopNav.vue b/frontend/components/ui/AppTopNav.vue
index 4ccd4d6..e4fdfd5 100644
--- a/frontend/components/ui/AppTopNav.vue
+++ b/frontend/components/ui/AppTopNav.vue
@@ -1,10 +1,16 @@
 <template>
-  <header class="border-b border-neutral-200 bg-primary-500 p-5 text-white">
-    <div class="flex h-full items-center justify-end">
-      <div class="flex gap-12 text-xl text-white">
-        <div class="group relative flex gap-4">
+  <header class="border-b border-neutral-200 bg-primary-500 p-3 text-white sm:p-5">
+    <div class="flex h-full items-center justify-between">
+      <button
+        class="rounded-md p-2 text-white hover:bg-primary-600 transition-colors lg:hidden"
+        @click="ui.openMobileSidebar()"
+      >
+        <Icon name="mdi:menu" size="24" />
+      </button>
+      <div class="ml-auto flex gap-4 text-xl text-white sm:gap-12">
+        <div class="group relative flex gap-2 sm:gap-4">
           <Icon name="mdi:account-circle-outline" class="self-center cursor-pointer" size="36" />
-          <p class="self-center cursor-pointer">{{ user?.username }}</p>
+          <p class="hidden self-center cursor-pointer sm:block">{{ user?.username }}</p>
           <div class="invisible absolute right-0 top-full z-50 mt-2 w-44 rounded-md border border-neutral-200 bg-white py-1 text-sm text-neutral-800 opacity-0 shadow-lg transition-all group-hover:visible group-hover:opacity-100">
             <button
               type="button"
@@ -34,6 +40,7 @@ defineProps<{
 }>()
 
 const auth = useAuthStore()
+const ui = useUiStore()
 
 const handleLogout = async () => {
   await auth.logout()
diff --git a/frontend/components/ui/DataTable.vue b/frontend/components/ui/DataTable.vue
index a6a041d..8367086 100644
--- a/frontend/components/ui/DataTable.vue
+++ b/frontend/components/ui/DataTable.vue
@@ -37,7 +37,7 @@
                             <slot name="actions" :item="item" />
                             <button
                                 v-if="deletable"
-                                class="text-[red-500] hover:text-[red-700]"
+                                class="text-neutral-400 transition-colors hover:text-red-500"
                                 @click.stop="$emit('delete', item)"
                             >
                                 <Icon name="mdi:delete-outline" size="20" />
diff --git a/frontend/components/ui/SidebarTimer.vue b/frontend/components/ui/SidebarTimer.vue
index ca437b3..44b765b 100644
--- a/frontend/components/ui/SidebarTimer.vue
+++ b/frontend/components/ui/SidebarTimer.vue
@@ -1,15 +1,18 @@
 <template>
     <button
-        class="flex w-full items-center justify-center gap-2 rounded-md px-4 py-2 text-sm font-semibold text-white transition"
-        :class="timerStore.isRunning
-            ? 'bg-[#F18619] hover:bg-[#d97314]'
-            : 'bg-primary-500 hover:bg-primary-600'"
+        class="flex w-full items-center justify-center gap-2 rounded-md py-2 text-sm font-semibold text-white transition"
+        :class="[
+            timerStore.isRunning
+                ? 'bg-[#F18619] hover:bg-[#d97314]'
+                : 'bg-primary-500 hover:bg-primary-600',
+            collapsed ? 'px-2' : 'px-4'
+        ]"
         :title="timerStore.isRunning ? 'Arrêter le timer' : 'Démarrer un timer'"
         @click="timerStore.isRunning ? timerStore.stop() : timerStore.start()"
     >
         <Icon
             :name="timerStore.isRunning ? 'mdi:stop' : 'mdi:play'"
-            size="16"
+            :size="collapsed ? '20' : '16'"
         />
         <span v-if="!collapsed" class="font-mono tracking-wide">
             {{ timerStore.elapsedFormatted }}
diff --git a/frontend/layouts/default.vue b/frontend/layouts/default.vue
index 1866c76..1616d11 100644
--- a/frontend/layouts/default.vue
+++ b/frontend/layouts/default.vue
@@ -1,13 +1,25 @@
 <template>
     <div class="h-screen overflow-hidden">
         <div class="flex h-full">
+            <!-- Mobile sidebar overlay -->
+            <Transition name="sidebar-overlay">
+                <div
+                    v-if="ui.sidebarOpen"
+                    class="fixed inset-0 z-40 bg-black/50 lg:hidden"
+                    @click="ui.closeMobileSidebar()"
+                />
+            </Transition>
+
             <aside
-                class="flex h-full flex-shrink-0 flex-col border-r border-neutral-200 bg-tertiary-500 transition-all duration-300"
-                :class="ui.sidebarCollapsed ? 'w-16' : 'w-64'"
+                class="fixed inset-y-0 left-0 z-50 flex h-full flex-shrink-0 flex-col border-r border-neutral-200 bg-tertiary-500 transition-transform duration-300 lg:static lg:z-auto lg:translate-x-0"
+                :class="[
+                    ui.sidebarCollapsed ? 'lg:w-16' : 'lg:w-64',
+                    ui.sidebarOpen ? 'w-64 translate-x-0' : '-translate-x-full',
+                ]"
             >
-                <div class="flex items-center justify-center overflow-hidden" :class="ui.sidebarCollapsed ? 'p-2' : ''">
+                <div class="flex items-center justify-between overflow-hidden" :class="sidebarIsCollapsed ? 'p-2 justify-center' : ''">
                     <img
-                        v-if="!ui.sidebarCollapsed"
+                        v-if="!sidebarIsCollapsed"
                         src="/malio.png"
                         alt="Logo"
                         class="w-auto"
@@ -18,49 +30,61 @@
                         alt="Logo"
                         class="h-8 w-8 object-cover object-left"
                     />
+                    <button
+                        class="mr-2 rounded-md p-2 text-neutral-500 hover:bg-neutral-200 hover:text-neutral-700 transition-colors lg:hidden"
+                        @click="ui.closeMobileSidebar()"
+                    >
+                        <Icon name="mdi:close" size="20" />
+                    </button>
                 </div>
-                <nav class="flex-1 overflow-hidden" :class="ui.sidebarCollapsed ? 'px-1 pb-6' : 'px-4 pb-6'">
+                <nav class="flex-1 overflow-hidden" :class="sidebarIsCollapsed ? 'px-1 pb-6' : 'px-4 pb-6'">
                     <SidebarLink
                         to="/"
                         icon="mdi:view-dashboard-outline"
                         label="Tableau de bord"
-                        :collapsed="ui.sidebarCollapsed"
-                        :class="ui.sidebarCollapsed ? 'mt-4' : 'border-t border-secondary-500 pt-6'"
+                        :collapsed="sidebarIsCollapsed"
+                        :class="sidebarIsCollapsed ? 'mt-4' : 'border-t border-secondary-500 pt-6'"
+                        @click="ui.closeMobileSidebar()"
                     />
                     <SidebarLink
                         to="/my-tasks"
                         icon="mdi:clipboard-check-outline"
                         label="Mes tâches"
-                        :collapsed="ui.sidebarCollapsed"
+                        :collapsed="sidebarIsCollapsed"
+                        @click="ui.closeMobileSidebar()"
                     />
                     <SidebarLink
                         to="/projects"
                         icon="mdi:folder-outline"
                         label="Projets"
-                        :collapsed="ui.sidebarCollapsed"
+                        :collapsed="sidebarIsCollapsed"
+                        @click="ui.closeMobileSidebar()"
                     />
                     <template v-if="currentProjectId">
                         <SidebarLink
                             :to="`/projects/${currentProjectId}`"
                             icon="mdi:view-column-outline"
                             label="Kanban"
-                            :collapsed="ui.sidebarCollapsed"
+                            :collapsed="sidebarIsCollapsed"
                             sub
                             exact
+                            @click="ui.closeMobileSidebar()"
                         />
                         <SidebarLink
                             :to="`/projects/${currentProjectId}/groups`"
                             icon="mdi:tag-multiple-outline"
                             label="Groupes"
-                            :collapsed="ui.sidebarCollapsed"
+                            :collapsed="sidebarIsCollapsed"
                             sub
+                            @click="ui.closeMobileSidebar()"
                         />
                         <SidebarLink
                             :to="`/projects/${currentProjectId}/archives`"
                             icon="mdi:archive-outline"
                             label="Archives"
-                            :collapsed="ui.sidebarCollapsed"
+                            :collapsed="sidebarIsCollapsed"
                             sub
+                            @click="ui.closeMobileSidebar()"
                         />
 
                     </template>
@@ -68,24 +92,26 @@
                         to="/time-tracking"
                         icon="mdi:clock-outline"
                         label="Suivi de temps"
-                        :collapsed="ui.sidebarCollapsed"
+                        :collapsed="sidebarIsCollapsed"
+                        @click="ui.closeMobileSidebar()"
                     />
                     <SidebarLink
                         to="/admin"
                         icon="mdi:cog-outline"
                         label="Administration"
-                        :collapsed="ui.sidebarCollapsed"
+                        :collapsed="sidebarIsCollapsed"
+                        @click="ui.closeMobileSidebar()"
                     />
                 </nav>
 
                 <div class="px-4 py-3">
-                    <SidebarTimer :collapsed="ui.sidebarCollapsed" />
+                    <SidebarTimer :collapsed="sidebarIsCollapsed" />
                 </div>
 
                 <div class="flex flex-col gap-2 items-center p-4">
-                    <p v-if="!ui.sidebarCollapsed" class="font-bold">v {{ version }}</p>
+                    <p v-if="!sidebarIsCollapsed" class="font-bold">v {{ version }}</p>
                     <button
-                        class="flex items-center justify-center rounded-md p-2 text-neutral-500 hover:bg-neutral-200 hover:text-neutral-700 transition-colors"
+                        class="hidden items-center justify-center rounded-md p-2 text-neutral-500 hover:bg-neutral-200 hover:text-neutral-700 transition-colors lg:flex"
                         :title="ui.sidebarCollapsed ? 'Ouvrir le menu' : 'Réduire le menu'"
                         @click="ui.toggleSidebar()"
                     >
@@ -99,8 +125,8 @@
 
             <div class="h-full flex-1 flex flex-col min-h-0">
                 <AppTopNav :user="auth.user" />
-                <main class="flex flex-1 flex-col overflow-y-auto bg-white px-16 pb-24">
-                    <div aria-hidden="true" class="pointer-events-none sticky top-0 z-30 h-12 flex-shrink-0 bg-white" />
+                <main class="flex flex-1 flex-col overflow-y-auto bg-white px-4 pb-24 sm:px-8 lg:px-16">
+                    <div aria-hidden="true" class="pointer-events-none sticky top-0 z-30 h-8 flex-shrink-0 bg-white sm:h-12" />
                     <slot/>
                 </main>
             </div>
@@ -129,6 +155,17 @@ const ui = useUiStore()
 const {version} = useAppVersion()
 const route = useRoute()
 
+// On mobile, sidebar is always expanded (not collapsed icon mode)
+const sidebarIsCollapsed = computed(() => {
+    if (ui.sidebarOpen) return false
+    return ui.sidebarCollapsed
+})
+
+// Close mobile sidebar on route change
+watch(() => route.path, () => {
+    ui.closeMobileSidebar()
+})
+
 const currentProjectId = computed(() => {
     const match = route.path.match(/^\/projects\/(\d+)/)
     return match ? match[1] : null
@@ -211,3 +248,14 @@ const handleLogout = async () => {
     await navigateTo('/login')
 }
 </script>
+
+<style scoped>
+.sidebar-overlay-enter-active,
+.sidebar-overlay-leave-active {
+    transition: opacity 0.3s ease;
+}
+.sidebar-overlay-enter-from,
+.sidebar-overlay-leave-to {
+    opacity: 0;
+}
+</style>
diff --git a/frontend/pages/admin.vue b/frontend/pages/admin.vue
index ffa73c4..90433f4 100644
--- a/frontend/pages/admin.vue
+++ b/frontend/pages/admin.vue
@@ -1,24 +1,26 @@
 <template>
     <div>
-        <h1 class="text-2xl font-bold text-primary-500">Administration</h1>
+        <div class="sticky top-8 z-20 bg-white pb-4 sm:top-12">
+            <h1 class="text-xl font-bold text-primary-500 sm:text-2xl">Administration</h1>
 
-        <div class="mt-6 border-b border-neutral-200">
-            <nav class="flex gap-6">
-                <button
-                    v-for="tab in tabs"
-                    :key="tab.key"
-                    class="px-1 pb-3 text-sm font-semibold transition"
-                    :class="activeTab === tab.key
-                        ? 'border-b-2 border-primary-500 text-primary-500'
-                        : 'text-neutral-500 hover:text-neutral-700'"
-                    @click="activeTab = tab.key"
-                >
-                    {{ tab.label }}
-                </button>
-            </nav>
+            <div class="mt-6 border-b border-neutral-200 overflow-x-auto">
+                <nav class="flex gap-4 sm:gap-6">
+                    <button
+                        v-for="tab in tabs"
+                        :key="tab.key"
+                        class="whitespace-nowrap px-1 pb-3 text-sm font-semibold transition"
+                        :class="activeTab === tab.key
+                            ? 'border-b-2 border-primary-500 text-primary-500'
+                            : 'text-neutral-500 hover:text-neutral-700'"
+                        @click="activeTab = tab.key"
+                    >
+                        {{ tab.label }}
+                    </button>
+                </nav>
+            </div>
         </div>
 
-        <div class="mt-6">
+        <div>
             <AdminClientTab v-if="activeTab === 'clients'" />
             <AdminStatusTab v-if="activeTab === 'statuses'" />
             <AdminEffortTab v-if="activeTab === 'efforts'" />
diff --git a/frontend/pages/index.vue b/frontend/pages/index.vue
index dba6111..c20da94 100644
--- a/frontend/pages/index.vue
+++ b/frontend/pages/index.vue
@@ -492,36 +492,38 @@ const lineOptions = {
 
 <template>
     <div>
-        <h1 class="text-2xl font-bold text-primary-500">{{ $t('dashboard.title') }}</h1>
+        <div class="sticky top-8 z-20 bg-white pb-4 sm:top-12">
+            <h1 class="text-xl font-bold text-primary-500 sm:text-2xl">{{ $t('dashboard.title') }}</h1>
 
-        <!-- Filters -->
-        <div class="mt-4 flex flex-wrap gap-3">
-            <MalioSelect
-                v-model="selectedPeriod"
-                :options="periodOptions"
-                :label="$t('dashboard.filters.period')"
-                min-width="!w-48"
-                text-field="text-sm"
-                text-value="text-sm"
-            />
-            <MalioSelect
-                v-model="selectedProjectId"
-                :options="projectOptions"
-                :label="$t('dashboard.filters.project')"
-                :empty-option-label="$t('dashboard.filters.allProjects')"
-                min-width="!w-40"
-                text-field="text-sm"
-                text-value="text-sm"
-            />
-            <MalioSelect
-                v-model="selectedUserId"
-                :options="userOptions"
-                :label="$t('dashboard.filters.user')"
-                :empty-option-label="$t('dashboard.filters.allUsers')"
-                min-width="!w-40"
-                text-field="text-sm"
-                text-value="text-sm"
-            />
+            <!-- Filters -->
+            <div class="mt-4 flex flex-wrap gap-3">
+                <MalioSelect
+                    v-model="selectedPeriod"
+                    :options="periodOptions"
+                    :label="$t('dashboard.filters.period')"
+                    min-width="!w-48"
+                    text-field="text-sm"
+                    text-value="text-sm"
+                />
+                <MalioSelect
+                    v-model="selectedProjectId"
+                    :options="projectOptions"
+                    :label="$t('dashboard.filters.project')"
+                    :empty-option-label="$t('dashboard.filters.allProjects')"
+                    min-width="!w-40"
+                    text-field="text-sm"
+                    text-value="text-sm"
+                />
+                <MalioSelect
+                    v-model="selectedUserId"
+                    :options="userOptions"
+                    :label="$t('dashboard.filters.user')"
+                    :empty-option-label="$t('dashboard.filters.allUsers')"
+                    min-width="!w-40"
+                    text-field="text-sm"
+                    text-value="text-sm"
+                />
+            </div>
         </div>
 
         <!-- Loading -->
@@ -536,7 +538,7 @@ const lineOptions = {
                     <p class="text-xs font-medium uppercase tracking-wider text-neutral-400">
                         {{ $t('dashboard.stats.hoursPeriod') }}
                     </p>
-                    <p class="mt-2 text-3xl font-bold text-neutral-900">
+                    <p class="mt-2 text-2xl font-bold text-neutral-900 sm:text-3xl">
                         {{ formatHours(totalHoursThisWeek) }}
                     </p>
                 </div>
@@ -544,7 +546,7 @@ const lineOptions = {
                     <p class="text-xs font-medium uppercase tracking-wider text-neutral-400">
                         {{ $t('dashboard.stats.myActiveTasks') }}
                     </p>
-                    <p class="mt-2 text-3xl font-bold text-neutral-900">
+                    <p class="mt-2 text-2xl font-bold text-neutral-900 sm:text-3xl">
                         {{ myTasks.length - myTasksDone.length }}
                     </p>
                     <p class="mt-1 text-xs text-neutral-400">
@@ -555,7 +557,7 @@ const lineOptions = {
                     <p class="text-xs font-medium uppercase tracking-wider text-neutral-400">
                         {{ $t('dashboard.stats.totalTasks') }}
                     </p>
-                    <p class="mt-2 text-3xl font-bold text-neutral-900">
+                    <p class="mt-2 text-2xl font-bold text-neutral-900 sm:text-3xl">
                         {{ tasks.length }}
                     </p>
                     <p class="mt-1 text-xs text-neutral-400">
@@ -566,7 +568,7 @@ const lineOptions = {
                     <p class="text-xs font-medium uppercase tracking-wider text-neutral-400">
                         {{ $t('dashboard.stats.projects') }}
                     </p>
-                    <p class="mt-2 text-3xl font-bold text-neutral-900">
+                    <p class="mt-2 text-2xl font-bold text-neutral-900 sm:text-3xl">
                         {{ projects.length }}
                     </p>
                     <p class="mt-1 text-xs text-neutral-400">
diff --git a/frontend/pages/my-tasks.vue b/frontend/pages/my-tasks.vue
index fef4fcb..e24de7f 100644
--- a/frontend/pages/my-tasks.vue
+++ b/frontend/pages/my-tasks.vue
@@ -230,103 +230,135 @@ onMounted(() => {
 
 <template>
     <div>
-        <!-- Header -->
-        <div class="flex items-center justify-between">
-            <h1 class="text-2xl font-bold text-primary-500">{{ $t('myTasks.title') }}</h1>
-            <div class="flex gap-1">
-                <button
-                    class="rounded-lg p-2 transition-colors"
-                    :class="viewMode === 'kanban' ? 'bg-primary-500 text-white' : 'text-neutral-400 hover:text-primary-500'"
-                    :title="$t('myTasks.viewKanban')"
-                    @click="viewMode = 'kanban'"
-                >
-                    <Icon name="mdi:view-column-outline" size="20" />
-                </button>
-                <button
-                    class="rounded-lg p-2 transition-colors"
-                    :class="viewMode === 'list' ? 'bg-primary-500 text-white' : 'text-neutral-400 hover:text-primary-500'"
-                    :title="$t('myTasks.viewList')"
-                    @click="viewMode = 'list'"
-                >
-                    <Icon name="mdi:view-list-outline" size="20" />
-                </button>
+        <!-- Header + Filters -->
+        <div class="sticky top-8 z-20 bg-white pb-4 sm:top-12">
+            <div class="flex items-center justify-between gap-3">
+                <h1 class="text-xl font-bold text-primary-500 sm:text-2xl">{{ $t('myTasks.title') }}</h1>
+                <div class="flex gap-1">
+                    <button
+                        class="rounded-lg p-2 transition-colors"
+                        :class="viewMode === 'kanban' ? 'bg-primary-500 text-white' : 'text-neutral-400 hover:text-primary-500'"
+                        :title="$t('myTasks.viewKanban')"
+                        @click="viewMode = 'kanban'"
+                    >
+                        <Icon name="mdi:view-column-outline" size="20" />
+                    </button>
+                    <button
+                        class="rounded-lg p-2 transition-colors"
+                        :class="viewMode === 'list' ? 'bg-primary-500 text-white' : 'text-neutral-400 hover:text-primary-500'"
+                        :title="$t('myTasks.viewList')"
+                        @click="viewMode = 'list'"
+                    >
+                        <Icon name="mdi:view-list-outline" size="20" />
+                    </button>
+                </div>
+            </div>
+
+            <div class="mt-4 flex flex-wrap gap-3">
+                <MalioSelect
+                    v-model="selectedProjectId"
+                    :options="projectOptions"
+                    label="Projet"
+                    :empty-option-label="$t('myTasks.allProjects')"
+                    min-width="!w-40"
+                    text-field="text-sm"
+                    text-value="text-sm"
+                />
+                <MalioSelect
+                    v-model="selectedGroupId"
+                    :options="groupOptions"
+                    label="Groupe"
+                    :empty-option-label="$t('myTasks.allGroups')"
+                    min-width="!w-40"
+                    text-field="text-sm"
+                    text-value="text-sm"
+                />
+                <MalioSelect
+                    v-model="selectedTagId"
+                    :options="tagOptions"
+                    label="Type"
+                    :empty-option-label="$t('myTasks.allTypes')"
+                    min-width="!w-40"
+                    text-field="text-sm"
+                    text-value="text-sm"
+                />
+                <MalioSelect
+                    v-model="selectedPriorityId"
+                    :options="priorityOptions"
+                    label="Priorité"
+                    :empty-option-label="$t('myTasks.allPriorities')"
+                    min-width="!w-40"
+                    text-field="text-sm"
+                    text-value="text-sm"
+                />
+                <MalioSelect
+                    v-model="selectedEffortId"
+                    :options="effortOptions"
+                    label="Effort"
+                    :empty-option-label="$t('myTasks.allEfforts')"
+                    min-width="!w-40"
+                    text-field="text-sm"
+                    text-value="text-sm"
+                />
+                <MalioSelect
+                    v-model="selectedAssigneeId"
+                    :options="assigneeOptions"
+                    label="Assigné"
+                    :empty-option-label="$t('myTasks.allAssignees')"
+                    min-width="!w-40"
+                    text-field="text-sm"
+                    text-value="text-sm"
+                />
             </div>
         </div>
 
-        <!-- Filters -->
-        <div class="mt-4 flex flex-wrap gap-3">
-            <MalioSelect
-                v-model="selectedProjectId"
-                :options="projectOptions"
-                label="Projet"
-                :empty-option-label="$t('myTasks.allProjects')"
-                min-width="!w-40"
-                text-field="text-sm"
-                text-value="text-sm"
-            />
-            <MalioSelect
-                v-model="selectedGroupId"
-                :options="groupOptions"
-                label="Groupe"
-                :empty-option-label="$t('myTasks.allGroups')"
-                min-width="!w-40"
-                text-field="text-sm"
-                text-value="text-sm"
-            />
-            <MalioSelect
-                v-model="selectedTagId"
-                :options="tagOptions"
-                label="Type"
-                :empty-option-label="$t('myTasks.allTypes')"
-                min-width="!w-40"
-                text-field="text-sm"
-                text-value="text-sm"
-            />
-            <MalioSelect
-                v-model="selectedPriorityId"
-                :options="priorityOptions"
-                label="Priorité"
-                :empty-option-label="$t('myTasks.allPriorities')"
-                min-width="!w-40"
-                text-field="text-sm"
-                text-value="text-sm"
-            />
-            <MalioSelect
-                v-model="selectedEffortId"
-                :options="effortOptions"
-                label="Effort"
-                :empty-option-label="$t('myTasks.allEfforts')"
-                min-width="!w-40"
-                text-field="text-sm"
-                text-value="text-sm"
-            />
-            <MalioSelect
-                v-model="selectedAssigneeId"
-                :options="assigneeOptions"
-                label="Assigné"
-                :empty-option-label="$t('myTasks.allAssignees')"
-                min-width="!w-40"
-                text-field="text-sm"
-                text-value="text-sm"
-            />
-        </div>
-
         <!-- Kanban View -->
-        <div v-if="viewMode === 'kanban'" class="mt-6 flex gap-4 overflow-x-auto pb-4">
-            <!-- Backlog column (tasks without status) -->
+        <div v-if="viewMode === 'kanban'">
+            <div class="mt-6 flex gap-4 overflow-x-auto pb-4">
+                <div
+                    v-for="status in sortedStatuses"
+                    :key="status.id"
+                    class="flex w-72 shrink-0 flex-col rounded-lg transition-colors"
+                    :class="dragOverStatusId === status.id ? 'bg-neutral-200' : 'bg-neutral-50'"
+                    @dragover.prevent
+                    @dragenter.prevent="onDragEnter(status.id)"
+                    @dragleave="onDragLeave"
+                    @drop.prevent="onDropStatus($event, status)"
+                >
+                    <div
+                        class="rounded-t-lg px-4 py-3 text-sm font-bold text-white"
+                        :style="{ backgroundColor: status.color }"
+                    >
+                        {{ status.label }} ({{ tasksByStatus(status.id).length }})
+                    </div>
+                    <div class="flex flex-col gap-3 p-3">
+                        <TaskCard
+                            v-for="task in tasksByStatus(status.id)"
+                            :key="task.id"
+                            :task="task"
+                            @click="openTaskEdit(task)"
+                        />
+                        <p
+                            v-if="tasksByStatus(status.id).length === 0"
+                            class="py-4 text-center text-xs text-neutral-400"
+                        >
+                            {{ $t('myTasks.noTasks') }}
+                        </p>
+                    </div>
+                </div>
+            </div>
+
+            <!-- Backlog below kanban -->
             <div
-                v-if="backlogTasks.length > 0"
-                class="flex w-72 shrink-0 flex-col rounded-lg transition-colors"
+                class="mt-8 rounded-lg p-4 transition-colors"
                 :class="dragOverStatusId === 0 ? 'bg-neutral-200' : 'bg-neutral-50'"
                 @dragover.prevent
                 @dragenter.prevent="onDragEnter(0)"
                 @dragleave="onDragLeave"
                 @drop.prevent="onDropBacklog($event)"
             >
-                <div class="rounded-t-lg bg-neutral-500 px-4 py-3 text-sm font-bold text-white">
-                    {{ $t('myTasks.backlog') }} ({{ backlogTasks.length }})
-                </div>
-                <div class="flex flex-col gap-3 p-3">
+                <h2 class="text-lg font-bold text-neutral-900">{{ $t('myTasks.backlog') }} ({{ backlogTasks.length }})</h2>
+                <div class="mt-4 grid grid-cols-1 gap-3 sm:grid-cols-2 lg:grid-cols-3 xl:grid-cols-4">
                     <TaskCard
                         v-for="task in backlogTasks"
                         :key="task.id"
@@ -334,39 +366,12 @@ onMounted(() => {
                         @click="openTaskEdit(task)"
                     />
                 </div>
-            </div>
-
-            <!-- Status columns -->
-            <div
-                v-for="status in sortedStatuses"
-                :key="status.id"
-                class="flex w-72 shrink-0 flex-col rounded-lg transition-colors"
-                :class="dragOverStatusId === status.id ? 'bg-neutral-200' : 'bg-neutral-50'"
-                @dragover.prevent
-                @dragenter.prevent="onDragEnter(status.id)"
-                @dragleave="onDragLeave"
-                @drop.prevent="onDropStatus($event, status)"
-            >
-                <div
-                    class="rounded-t-lg px-4 py-3 text-sm font-bold text-white"
-                    :style="{ backgroundColor: status.color }"
+                <p
+                    v-if="backlogTasks.length === 0"
+                    class="py-4 text-center text-xs text-neutral-400"
                 >
-                    {{ status.label }} ({{ tasksByStatus(status.id).length }})
-                </div>
-                <div class="flex flex-col gap-3 p-3">
-                    <TaskCard
-                        v-for="task in tasksByStatus(status.id)"
-                        :key="task.id"
-                        :task="task"
-                        @click="openTaskEdit(task)"
-                    />
-                    <p
-                        v-if="tasksByStatus(status.id).length === 0"
-                        class="py-4 text-center text-xs text-neutral-400"
-                    >
-                        {{ $t('myTasks.noTasks') }}
-                    </p>
-                </div>
+                    {{ $t('myTasks.noTasks') }}
+                </p>
             </div>
         </div>
 
@@ -375,12 +380,12 @@ onMounted(() => {
             <div
                 v-for="task in tasks"
                 :key="task.id"
-                class="flex cursor-pointer items-center justify-between border-b border-neutral-100 px-4 py-3 transition-colors hover:bg-neutral-50"
+                class="flex cursor-pointer items-center justify-between gap-2 border-b border-neutral-100 px-2 py-3 transition-colors hover:bg-neutral-50 sm:px-4"
                 @click="openTaskEdit(task)"
             >
                 <div class="min-w-0 flex-1">
                     <h4 class="text-sm font-semibold text-neutral-900">{{ task.title }}</h4>
-                    <div class="mt-1 flex items-center gap-1.5">
+                    <div class="mt-1 flex flex-wrap items-center gap-1.5">
                         <span
                             v-if="task.priority"
                             class="rounded-full px-2 py-0.5 text-xs font-semibold text-white"
diff --git a/frontend/pages/projects/[id]/archives.vue b/frontend/pages/projects/[id]/archives.vue
index ae0180a..60360ec 100644
--- a/frontend/pages/projects/[id]/archives.vue
+++ b/frontend/pages/projects/[id]/archives.vue
@@ -1,20 +1,22 @@
 <template>
     <div>
-        <div class="flex items-center justify-between">
-            <h1 class="text-2xl font-bold text-primary-500">{{ project?.name ?? '' }} — {{ $t('archive.title') }}</h1>
+        <div class="sticky top-8 z-20 bg-white pb-4 sm:top-12">
+            <div class="flex items-center justify-between">
+                <h1 class="text-xl font-bold text-primary-500 sm:text-2xl">{{ project?.name ?? '' }} — {{ $t('archive.title') }}</h1>
+            </div>
+
+            <div class="mt-4">
+                <MalioSelect
+                    v-model="selectedGroupId"
+                    :options="groupFilterOptions"
+                    label="Groupe"
+                    empty-option-label="Tous les groupes"
+                    min-width="w-64"
+                />
+            </div>
         </div>
 
-        <div class="mt-4">
-            <MalioSelect
-                v-model="selectedGroupId"
-                :options="groupFilterOptions"
-                label="Groupe"
-                empty-option-label="Tous les groupes"
-                min-width="w-64"
-            />
-        </div>
-
-        <div class="mt-6">
+        <div>
             <p v-if="filteredTasks.length === 0" class="text-sm text-neutral-400">
                 {{ $t('archive.empty') }}
             </p>
diff --git a/frontend/pages/projects/[id]/groups.vue b/frontend/pages/projects/[id]/groups.vue
index d148000..ce87026 100644
--- a/frontend/pages/projects/[id]/groups.vue
+++ b/frontend/pages/projects/[id]/groups.vue
@@ -1,10 +1,12 @@
 <template>
     <div>
-        <div class="flex items-center justify-between">
-            <h1 class="text-2xl font-bold text-primary-500">{{ project?.name ?? '' }} — Groupes</h1>
+        <div class="sticky top-8 z-20 bg-white pb-4 sm:top-12">
+            <div class="flex items-center justify-between">
+                <h1 class="text-xl font-bold text-primary-500 sm:text-2xl">{{ project?.name ?? '' }} — Groupes</h1>
+            </div>
         </div>
 
-        <div class="mt-6">
+        <div>
             <ProjectGroupTab :project-id="projectId" />
         </div>
     </div>
diff --git a/frontend/pages/projects/[id]/index.vue b/frontend/pages/projects/[id]/index.vue
index f6c6abb..5bd364d 100644
--- a/frontend/pages/projects/[id]/index.vue
+++ b/frontend/pages/projects/[id]/index.vue
@@ -1,52 +1,55 @@
 <template>
     <div>
-        <div class="flex items-center justify-between">
-            <h1 class="text-2xl font-bold text-primary-500">{{ project?.name ?? '' }}</h1>
-            <button
-                class="rounded-md bg-primary-500 px-4 py-2 text-sm font-semibold text-white hover:bg-secondary-500"
-                @click="openTaskCreate"
-            >
-                + Ajouter un ticket
-            </button>
-        </div>
+        <div class="sticky top-8 z-20 bg-white pb-4 sm:top-12">
+            <div class="flex items-center justify-between gap-3">
+                <h1 class="text-xl font-bold text-primary-500 sm:text-2xl">{{ project?.name ?? '' }}</h1>
+                <button
+                    class="shrink-0 rounded-md bg-primary-500 px-3 py-2 text-xs font-semibold text-white hover:bg-secondary-500 sm:px-4 sm:text-sm"
+                    @click="openTaskCreate"
+                >
+                    <span class="hidden sm:inline">+ Ajouter un ticket</span>
+                    <span class="sm:hidden">+ Ticket</span>
+                </button>
+            </div>
 
-        <div class="mt-4 flex flex-wrap gap-3">
-            <MalioSelect
-                v-model="selectedGroupId"
-                :options="groupFilterOptions"
-                label="Groupe"
-                empty-option-label="Tous les groupes"
-                min-width="!w-40"
-                text-field="text-sm"
-                text-value="text-sm"
-            />
-            <MalioSelect
-                v-model="selectedTagId"
-                :options="tagFilterOptions"
-                label="Tags"
-                empty-option-label="Tous les tags"
-                min-width="!w-40"
-                text-field="text-sm"
-                text-value="text-sm"
-            />
-            <MalioSelect
-                v-model="selectedAssigneeId"
-                :options="userFilterOptions"
-                label="User"
-                empty-option-label="Tous les users"
-                min-width="!w-40"
-                text-field="text-sm"
-                text-value="text-sm"
-            />
-            <MalioSelect
-                v-model="selectedStatusId"
-                :options="statusFilterOptions"
-                label="Status"
-                empty-option-label="Tous les status"
-                min-width="!w-40"
-                text-field="text-sm"
-                text-value="text-sm"
-            />
+            <div class="mt-4 flex flex-wrap gap-3">
+                <MalioSelect
+                    v-model="selectedGroupId"
+                    :options="groupFilterOptions"
+                    label="Groupe"
+                    empty-option-label="Tous les groupes"
+                    min-width="!w-40"
+                    text-field="text-sm"
+                    text-value="text-sm"
+                />
+                <MalioSelect
+                    v-model="selectedTagId"
+                    :options="tagFilterOptions"
+                    label="Tags"
+                    empty-option-label="Tous les tags"
+                    min-width="!w-40"
+                    text-field="text-sm"
+                    text-value="text-sm"
+                />
+                <MalioSelect
+                    v-model="selectedAssigneeId"
+                    :options="userFilterOptions"
+                    label="User"
+                    empty-option-label="Tous les users"
+                    min-width="!w-40"
+                    text-field="text-sm"
+                    text-value="text-sm"
+                />
+                <MalioSelect
+                    v-model="selectedStatusId"
+                    :options="statusFilterOptions"
+                    label="Status"
+                    empty-option-label="Tous les status"
+                    min-width="!w-40"
+                    text-field="text-sm"
+                    text-value="text-sm"
+                />
+            </div>
         </div>
 
         <!-- Kanban -->
@@ -93,55 +96,14 @@
             @dragleave="onDragLeave"
             @drop.prevent="onDropBacklog($event)"
         >
-            <h2 class="text-lg font-bold text-neutral-900">Backlog</h2>
-            <div class="mt-4 grid grid-cols-1 gap-3 md:grid-cols-2">
-                <div
+            <h2 class="text-lg font-bold text-neutral-900">Backlog ({{ backlogTasks.length }})</h2>
+            <div class="mt-4 grid grid-cols-1 gap-3 sm:grid-cols-2 lg:grid-cols-3 xl:grid-cols-4">
+                <TaskCard
                     v-for="task in backlogTasks"
                     :key="task.id"
-                    class="flex cursor-pointer items-center justify-between rounded-lg border border-neutral-200 bg-white px-4 py-3 hover:shadow-sm"
-                    draggable="true"
-                    @dragstart="onBacklogDragStart($event, task)"
-                    @dragend="onBacklogDragEnd"
+                    :task="task"
                     @click="openTaskEdit(task)"
-                >
-                    <span class="text-sm font-semibold text-neutral-900">{{ task.title }}</span>
-                    <div class="flex items-center gap-2">
-                        <span
-                            v-for="tag in task.tags"
-                            :key="tag.id"
-                            class="rounded-full px-2 py-0.5 text-xs font-semibold text-white"
-                            :style="{ backgroundColor: tag.color }"
-                        >
-                            {{ tag.label }}
-                        </span>
-                        <span
-                            v-if="task.priority"
-                            class="rounded-full px-2 py-0.5 text-xs font-semibold text-white"
-                            :style="{ backgroundColor: task.priority.color }"
-                        >
-                            {{ task.priority.label }}
-                        </span>
-                        <span
-                            v-if="task.effort"
-                            class="text-sm font-bold text-neutral-700"
-                        >
-                            {{ task.effort.label }}
-                        </span>
-                        <span
-                            v-if="task.assignee"
-                            class="flex h-5 w-5 items-center justify-center rounded-full bg-primary-500 text-[10px] font-bold text-white"
-                            :title="task.assignee.username"
-                        >
-                            {{ task.assignee.username.substring(0, 2).toUpperCase() }}
-                        </span>
-                        <span
-                            v-else
-                            class="flex h-5 w-5 items-center justify-center rounded-full bg-neutral-200 text-neutral-400"
-                        >
-                            <Icon name="mdi:account-outline" size="14" />
-                        </span>
-                    </div>
-                </div>
+                />
             </div>
         </div>
 
@@ -307,15 +269,6 @@ function onDrop(event: DragEvent) {
     return Number(event.dataTransfer!.getData('text/plain'))
 }
 
-function onBacklogDragStart(event: DragEvent, task: Task) {
-    event.dataTransfer!.effectAllowed = 'move'
-    event.dataTransfer!.setData('text/plain', String(task.id))
-    ;(event.target as HTMLElement).classList.add('opacity-50')
-}
-
-function onBacklogDragEnd(event: DragEvent) {
-    ;(event.target as HTMLElement).classList.remove('opacity-50')
-}
 
 async function onDropStatus(event: DragEvent, status: TaskStatus) {
     const taskId = onDrop(event)
diff --git a/frontend/pages/projects/index.vue b/frontend/pages/projects/index.vue
index 6a94db3..51dcb6c 100644
--- a/frontend/pages/projects/index.vue
+++ b/frontend/pages/projects/index.vue
@@ -1,28 +1,31 @@
 <template>
     <div>
-        <div class="flex items-center justify-between">
-            <h1 class="text-2xl font-bold text-primary-500">Projets</h1>
-            <div class="flex items-center gap-3">
-                <button
-                    class="flex items-center gap-1.5 rounded-md px-3 py-2 text-sm font-medium transition"
-                    :class="showArchived
-                        ? 'bg-amber-100 text-amber-700 hover:bg-amber-200'
-                        : 'text-neutral-500 hover:bg-neutral-100 hover:text-neutral-700'"
-                    @click="toggleArchived"
-                >
-                    <Icon :name="showArchived ? 'mdi:archive-arrow-up-outline' : 'mdi:archive-outline'" size="18" />
-                    {{ showArchived ? $t('projects.hideArchived') : $t('projects.showArchived') }}
-                </button>
-                <button
-                    class="rounded-md bg-primary-500 px-4 py-2 text-sm font-semibold text-white hover:bg-secondary-500"
-                    @click="openCreate"
-                >
-                    + Ajouter un projet
-                </button>
+        <div class="sticky top-8 z-20 bg-white pb-4 sm:top-12">
+            <div class="flex flex-wrap items-center justify-between gap-3">
+                <h1 class="text-xl font-bold text-primary-500 sm:text-2xl">Projets</h1>
+                <div class="flex items-center gap-2 sm:gap-3">
+                    <button
+                        class="flex items-center gap-1.5 rounded-md px-2 py-2 text-sm font-medium transition sm:px-3"
+                        :class="showArchived
+                            ? 'bg-amber-100 text-amber-700 hover:bg-amber-200'
+                            : 'text-neutral-500 hover:bg-neutral-100 hover:text-neutral-700'"
+                        @click="toggleArchived"
+                    >
+                        <Icon :name="showArchived ? 'mdi:archive-arrow-up-outline' : 'mdi:archive-outline'" size="18" />
+                        <span class="hidden sm:inline">{{ showArchived ? $t('projects.hideArchived') : $t('projects.showArchived') }}</span>
+                    </button>
+                    <button
+                        class="shrink-0 rounded-md bg-primary-500 px-3 py-2 text-xs font-semibold text-white hover:bg-secondary-500 sm:px-4 sm:text-sm"
+                        @click="openCreate"
+                    >
+                        <span class="hidden sm:inline">+ Ajouter un projet</span>
+                        <span class="sm:hidden">+ Projet</span>
+                    </button>
+                </div>
             </div>
         </div>
 
-        <div class="mt-6 grid grid-cols-1 gap-6 sm:grid-cols-2 lg:grid-cols-3 xl:grid-cols-4">
+        <div class="grid grid-cols-1 gap-6 sm:grid-cols-2 lg:grid-cols-3 xl:grid-cols-4">
             <div
                 v-for="project in projects"
                 :key="project.id"
diff --git a/frontend/pages/time-tracking.vue b/frontend/pages/time-tracking.vue
index 8de0eb5..8d85976 100644
--- a/frontend/pages/time-tracking.vue
+++ b/frontend/pages/time-tracking.vue
@@ -1,17 +1,18 @@
 <template>
     <div class="flex min-h-0 flex-1 flex-col">
-        <div ref="pageHeaderEl" class="flex-shrink-0 pb-4">
-            <div class="flex items-center justify-between">
-                <h1 class="text-2xl font-bold text-primary-500">Suivi des temps</h1>
+        <div ref="pageHeaderEl" class="sticky top-8 z-20 flex-shrink-0 bg-white pb-4 sm:top-12">
+            <div class="flex items-center justify-between gap-3">
+                <h1 class="text-xl font-bold text-primary-500 sm:text-2xl">Suivi des temps</h1>
                 <button
-                    class="rounded-md bg-primary-500 px-4 py-2 text-sm font-semibold text-white hover:bg-primary-600 transition"
+                    class="shrink-0 rounded-md bg-primary-500 px-3 py-2 text-xs font-semibold text-white hover:bg-primary-600 transition sm:px-4 sm:text-sm"
                     @click="openCreateDrawer()"
                 >
-                    + Ajouter une Activité
+                    <span class="hidden sm:inline">+ Ajouter une Activité</span>
+                    <span class="sm:hidden">+ Activité</span>
                 </button>
             </div>
 
-            <div class="relative z-30 mt-4 flex items-center gap-4">
+            <div class="relative z-30 mt-4 flex flex-wrap items-center gap-3 sm:gap-4">
                 <h2 class="text-lg font-bold text-orange-500">
                     {{ currentMonthLabel }}
                 </h2>
@@ -37,7 +38,7 @@
                 <MalioSelect
                     v-model="selectedUserId"
                     :options="userOptions"
-                    min-width="!w-44"
+                    min-width="!w-36 sm:!w-44"
                     text-field="text-sm"
                     text-value="text-sm"
                     label="User"
@@ -49,7 +50,7 @@
                     :options="projectOptions"
                     empty-option-label="Tous"
                     label="Projet"
-                    min-width="!w-44"
+                    min-width="!w-36 sm:!w-44"
                     text-field="text-sm"
                     text-value="text-sm"
                 />
@@ -59,7 +60,7 @@
                     :options="tagOptions"
                     empty-option-label="Tous"
                     label="Tag"
-                    min-width="!w-44"
+                    min-width="!w-36 sm:!w-44"
                     text-field="text-sm"
                     text-value="text-sm"
                 />
diff --git a/frontend/stores/ui.ts b/frontend/stores/ui.ts
index fc51610..9646556 100644
--- a/frontend/stores/ui.ts
+++ b/frontend/stores/ui.ts
@@ -1,5 +1,6 @@
 export const useUiStore = defineStore('ui', () => {
     const sidebarCollapsed = ref(false)
+    const sidebarOpen = ref(false)
 
     if (import.meta.client) {
         const saved = localStorage.getItem('ui-sidebar-collapsed')
@@ -18,5 +19,13 @@ export const useUiStore = defineStore('ui', () => {
         sidebarCollapsed.value = !sidebarCollapsed.value
     }
 
-    return { sidebarCollapsed, toggleSidebar }
+    function openMobileSidebar() {
+        sidebarOpen.value = true
+    }
+
+    function closeMobileSidebar() {
+        sidebarOpen.value = false
+    }
+
+    return { sidebarCollapsed, sidebarOpen, toggleSidebar, openMobileSidebar, closeMobileSidebar }
 })
diff --git a/src/Service/GiteaApiService.php b/src/Service/GiteaApiService.php
index d20a71e..fa26d8c 100644
--- a/src/Service/GiteaApiService.php
+++ b/src/Service/GiteaApiService.php
@@ -13,6 +13,7 @@ use Symfony\Component\String\Slugger\AsciiSlugger;
 use Symfony\Component\String\Slugger\SluggerInterface;
 use Symfony\Contracts\HttpClient\Exception\ExceptionInterface;
 use Symfony\Contracts\HttpClient\HttpClientInterface;
+use Throwable;
 
 final readonly class GiteaApiService
 {
@@ -203,7 +204,11 @@ final readonly class GiteaApiService
             throw new GiteaApiException('Gitea token is not set.');
         }
 
-        return $this->tokenEncryptor->decrypt($encrypted);
+        try {
+            return $this->tokenEncryptor->decrypt($encrypted);
+        } catch (Throwable $e) {
+            throw new GiteaApiException('Failed to decrypt Gitea token: '.$e->getMessage(), 0, $e);
+        }
     }
 
     private function assertProjectHasRepo(Project $project): void
diff --git a/src/Service/TokenEncryptor.php b/src/Service/TokenEncryptor.php
index bf9b0e9..86be2ae 100644
--- a/src/Service/TokenEncryptor.php
+++ b/src/Service/TokenEncryptor.php
@@ -4,31 +4,51 @@ declare(strict_types=1);
 
 namespace App\Service;
 
-use InvalidArgumentException;
+use App\Exception\GiteaApiException;
 use RuntimeException;
+use SodiumException;
 use Symfony\Component\DependencyInjection\Attribute\Autowire;
 
-final readonly class TokenEncryptor
+final class TokenEncryptor
 {
-    private string $key;
+    private readonly string $key;
+    private readonly bool $configured;
 
     public function __construct(
         #[Autowire('%env(GITEA_ENCRYPTION_KEY)%')]
         string $encryptionKey,
     ) {
         if ('' === $encryptionKey) {
-            throw new InvalidArgumentException('GITEA_ENCRYPTION_KEY environment variable must be set.');
+            $this->key        = '';
+            $this->configured = false;
+
+            return;
         }
 
-        $this->key = sodium_hex2bin($encryptionKey);
+        try {
+            $key = sodium_hex2bin($encryptionKey);
+        } catch (SodiumException) {
+            $this->key        = '';
+            $this->configured = false;
 
-        if (SODIUM_CRYPTO_SECRETBOX_KEYBYTES !== mb_strlen($this->key, '8bit')) {
-            throw new InvalidArgumentException('GITEA_ENCRYPTION_KEY must be a valid sodium secret box key.');
+            return;
         }
+
+        if (SODIUM_CRYPTO_SECRETBOX_KEYBYTES !== mb_strlen($key, '8bit')) {
+            $this->key        = '';
+            $this->configured = false;
+
+            return;
+        }
+
+        $this->key        = $key;
+        $this->configured = true;
     }
 
     public function encrypt(string $plaintext): string
     {
+        $this->assertConfigured();
+
         $nonce      = random_bytes(SODIUM_CRYPTO_SECRETBOX_NONCEBYTES);
         $ciphertext = sodium_crypto_secretbox($plaintext, $nonce, $this->key);
 
@@ -37,6 +57,8 @@ final readonly class TokenEncryptor
 
     public function decrypt(string $encrypted): string
     {
+        $this->assertConfigured();
+
         $decoded    = sodium_hex2bin($encrypted);
         $nonce      = mb_substr($decoded, 0, SODIUM_CRYPTO_SECRETBOX_NONCEBYTES, '8bit');
         $ciphertext = mb_substr($decoded, SODIUM_CRYPTO_SECRETBOX_NONCEBYTES, null, '8bit');
@@ -49,4 +71,11 @@ final readonly class TokenEncryptor
 
         return $plaintext;
     }
+
+    private function assertConfigured(): void
+    {
+        if (!$this->configured) {
+            throw new GiteaApiException('Gitea encryption is not configured. Please set a valid GITEA_ENCRYPTION_KEY.');
+        }
+    }
 }