diff --git a/frontend/package.json b/frontend/package.json
index a1ce7f9..1857eeb 100644
--- a/frontend/package.json
+++ b/frontend/package.json
@@ -17,6 +17,7 @@
   "dependencies": {
     "@fontsource/roboto": "^5.2.10",
     "@mdi/font": "7.4.47",
+    "highlight.js": "^11.11.1",
     "markdown-it": "^14.3.0",
     "pinia": "^3.0.4",
     "vue": "^3.5.30",
diff --git a/frontend/src/components/category/CreateCategoryDialog.vue b/frontend/src/components/category/CreateCategoryDialog.vue
new file mode 100644
index 0000000..1617834
--- /dev/null
+++ b/frontend/src/components/category/CreateCategoryDialog.vue
@@ -0,0 +1,90 @@
+<script lang="ts" setup>
+import {ref, watch} from 'vue'
+import {useCategoryStore} from '@/stores/category'
+
+const props = defineProps<{
+  modelValue: boolean
+  serverId: string
+}>()
+
+const emit = defineEmits<{
+  (e: 'update:modelValue', value: boolean): void
+  (e: 'created', category: any): void
+}>()
+
+const categoryStore = useCategoryStore()
+const name = ref('')
+const isSubmitting = ref(false)
+
+const resetForm = () => {
+  name.value = ''
+}
+
+const handleClose = () => {
+  emit('update:modelValue', false)
+  resetForm()
+}
+
+const handleSubmit = async () => {
+  if (!name.value.trim()) {
+    alert('Category name is required')
+    return
+  }
+
+  isSubmitting.value = true
+  try {
+    const newCategory = await categoryStore.createCategory({
+      name: name.value.trim(),
+      server_id: props.serverId
+    })
+    emit('created', newCategory)
+    handleClose()
+  } catch (error) {
+    console.error('Failed to create category:', error)
+  } finally {
+    isSubmitting.value = false
+  }
+}
+
+watch(
+  () => props.modelValue,
+  (isOpen) => {
+    if (!isOpen) {
+      resetForm()
+    }
+  }
+)
+</script>
+
+<template>
+  <v-dialog :model-value="modelValue" width="400" @update:model-value="handleClose">
+    <v-card>
+      <v-card-title>Create Category</v-card-title>
+      <v-card-text>
+        <v-text-field
+          v-model="name"
+          autofocus
+          density="compact"
+          label="Category Name"
+          outlined
+          @keyup.enter="handleSubmit"
+        />
+      </v-card-text>
+      <v-card-actions>
+        <v-spacer />
+        <v-btn :disabled="isSubmitting" variant="text" @click="handleClose">
+          Cancel
+        </v-btn>
+        <v-btn
+          :disabled="!name.trim()"
+          :loading="isSubmitting"
+          color="primary"
+          variant="tonal"
+          @click="handleSubmit"
+        >
+          Create
+        </v-btn>
+      </v-card-actions>
+    </v-card>
+  </v-dialog>
+</template>
diff --git a/frontend/src/composables/useMarkdown.ts b/frontend/src/composables/useMarkdown.ts
new file mode 100644
index 0000000..d464e68
--- /dev/null
+++ b/frontend/src/composables/useMarkdown.ts
@@ -0,0 +1,30 @@
+import MarkdownIt from 'markdown-it'
+import hljs from 'highlight.js'
+
+// Déclaré hors de la fonction = instancié une seule fois pour toute l'application
+const md = new MarkdownIt({
+  html: false,
+  linkify: true,
+  typographer: true,
+  breaks: true,
+})
+
+md.set({
+  highlight: (str: string, lang: string): string => {
+    if (lang && hljs.getLanguage(lang)) {
+      try {
+        return `<pre class="hljs"><code>${hljs.highlight(str, {
+          language: lang,
+          ignoreIllegals: true
+        }).value}</code></pre>`
+      } catch (__) {
+      }
+    }
+    return `<pre class="hljs"><code>${md.utils.escapeHtml(str)}</code></pre>`
+  }
+})
+
+export function useMarkdown() {
+  const renderMarkdown = (content: string) => md.render(content)
+  return {renderMarkdown}
+}
\ No newline at end of file
diff --git a/frontend/src/pages/server/channel/index.vue b/frontend/src/pages/server/channel/index.vue
index 046f9f5..05c5d77 100644
--- a/frontend/src/pages/server/channel/index.vue
+++ b/frontend/src/pages/server/channel/index.vue
@@ -1,10 +1,11 @@
 <script lang="ts" setup>
-import MarkdownIt from 'markdown-it'
+import 'highlight.js/styles/github-dark.css'
 import {computed, nextTick, onMounted, ref, watch} from 'vue';
 import {useRoute} from 'vue-router';
 import {storeToRefs} from 'pinia';
 import {useMessageStore} from '@/stores/message';
 import {useUserStore} from "@/stores/user.ts";
+import {useMarkdown} from '@/composables/useMarkdown'
 
 const props = defineProps<{
   serverId: string
@@ -16,6 +17,7 @@ const channelId = computed(() => props.channelId);
 const route = useRoute();
 const messageStore = useMessageStore();
 const userStore = useUserStore();
+const {renderMarkdown} = useMarkdown()
 
 // Référence vers l'élément scrollable
 const messageContainer = ref<HTMLElement | null>(null);
@@ -25,15 +27,6 @@ const {messages, loading} = storeToRefs(messageStore);
 
 const newMessage = ref('');
 
-const md = new MarkdownIt({
-  html: false,        // Désactive le HTML pur pour la sécurité
-  linkify: true,      // Convertit automatiquement les URLs en liens
-  typographer: true,
-  breaks: true        // Convertit les retours à la ligne en <br> (comportement type chat)
-})
-const renderMarkdown = (content: string) => {
-  return md.render(content);
-};
 
 const scrollToBottom = async () => {
   await nextTick();
@@ -100,9 +93,9 @@ watch(messages, () => {
             <span class="text-caption text-grey">{{ msg.created_at }}</span>
           </v-list-item-title>
 
-          <v-list-item-subtitle class="text-body-1 text-high-emphasis opacity-100">
+          <div class="text-body-1 text-high-emphasis opacity-100 mt-1">
             <div class="markdown-content" v-html="renderMarkdown(msg.content)"></div>
-          </v-list-item-subtitle>
+          </div>
         </v-list-item>
       </v-list>
     </div>
diff --git a/frontend/src/pages/server/index.vue b/frontend/src/pages/server/index.vue
index 4668289..0ae4045 100644
--- a/frontend/src/pages/server/index.vue
+++ b/frontend/src/pages/server/index.vue
@@ -5,6 +5,7 @@ import {useCategoryStore} from '@/stores/category'
 import {ref, watch} from 'vue'
 import {useRoute} from 'vue-router'
 import CreateChannelDialog from '@/components/channel/CreateChannelDialog.vue'
+import CreateCategoryDialog from '@/components/category/CreateCategoryDialog.vue'
 import {type MenuItem, useContextMenu} from '@/composables/useContextMenu'
 import {useUserStore} from "@/stores/user.ts";
 import {useServerStore} from "@/stores/server.ts";
@@ -33,6 +34,7 @@ const loadServerData = async (targetServerId: string) => {
       userStore.fetchUsers(targetServerId),
       serverStore.fetchServerTree(targetServerId)
     ])
+    syncOpenedCategories()
   } catch (error) {
     console.error('Failed to load server-scoped channels and categories:', error)
   }
@@ -48,7 +50,21 @@ watch(
   {immediate: true}
 )
 
-const showDialog = ref(false)
+const showChannelDialog = ref(false)
+const showCategoryDialog = ref(false)
+const selectedCategoryId = ref<string | null>(null)
+const openedCategories = ref<string[]>([])
+
+function syncOpenedCategories() {
+  openedCategories.value = currentTree.value
+    .filter((item) => 'Category' in item)
+    .map((item) => item.Category[0].id)
+}
+
+async function refreshServerTree() {
+  await serverStore.fetchServerTree(props.serverId)
+  syncOpenedCategories()
+}
 
 // Right click menu (sidebar)
 function onSidebarContextMenu(event: MouseEvent) {
@@ -56,17 +72,34 @@ function onSidebarContextMenu(event: MouseEvent) {
     {
       label: 'Nouveau canal',
       icon: 'mdi-plus',
-      action: () => console.log('Nouveau canal'),
+      action: () => {
+        selectedCategoryId.value = null
+        showChannelDialog.value = true
+      },
     },
     {
       label: 'Nouvelle catégorie',
       icon: 'mdi-folder-plus',
-      action: () => console.log('Nouvelle catégorie'),
+      action: () => { showCategoryDialog.value = true },
     }
   ]
   openContextMenu(event, menuItems);
 }
 
+function onCategoryContextMenu(event: MouseEvent, category: any) {
+  const menuItems: MenuItem[] = [
+    {
+      label: 'Nouveau canal',
+      icon: 'mdi-plus',
+      action: () => {
+        selectedCategoryId.value = category.id
+        showChannelDialog.value = true
+      },
+    },
+  ]
+  openContextMenu(event, menuItems)
+}
+
 // Right click menu (channel)
 async function openEditDialog(channel: any) {
   console.log("edit dialog clicked")
@@ -109,22 +142,16 @@ function onChannelContextMenu(event: MouseEvent, channel: any) {
       width="100%"
     ></v-sheet>
 
-    <v-btn
-      block
-      class="ma-2"
-      prepend-icon="mdi-plus"
-      variant="text"
-      @click="showDialog = true"
-    >
-      New Channel
-    </v-btn>
-
-    <v-list density="compact">
+    <v-list v-model:opened="openedCategories" density="compact">
       <template v-for="(item, index) in currentTree" :key="index">
         <!-- Catégorie et ses canaux enfants -->
         <v-list-group v-if="'Category' in item" :value="item.Category[0].id">
           <template #activator="{ props: groupProps }">
-            <v-list-item :title="item.Category[0].name" v-bind="groupProps"/>
+            <v-list-item
+              :title="item.Category[0].name"
+              v-bind="groupProps"
+              @contextmenu="onCategoryContextMenu($event, item.Category[0])"
+            />
           </template>
 
           <v-list-item
@@ -151,11 +178,19 @@ function onChannelContextMenu(event: MouseEvent, channel: any) {
   </v-navigation-drawer>
 
   <CreateChannelDialog
-    v-model="showDialog"
+    v-model="showChannelDialog"
+    :category-id="selectedCategoryId"
     :server-id="serverId"
+    @created="refreshServerTree"
+  />
+
+  <CreateCategoryDialog
+    v-model="showCategoryDialog"
+    :server-id="serverId"
+    @created="refreshServerTree"
   />
 
   <v-main>
     <router-view/>
   </v-main>
-</template>
\ No newline at end of file
+</template>
diff --git a/frontend/src/stores/category.ts b/frontend/src/stores/category.ts
index 7056eb3..79002e4 100644
--- a/frontend/src/stores/category.ts
+++ b/frontend/src/stores/category.ts
@@ -11,7 +11,9 @@ interface Category {
 
 export const useCategoryStore = defineStore("category", {
   state: () => ({
-    categories: [] as Category[]
+    categories: [] as Category[],
+    loading: false,
+    error: null as string | null
   }),
   actions: {
     async fetchCategories(serverId?: string) {
@@ -23,8 +25,32 @@ export const useCategoryStore = defineStore("category", {
       let response = await api.get(url);
       this.categories = await response.json();
     },
+    async createCategory(payload: { server_id: string; name: string }) {
+      this.loading = true;
+      this.error = null;
+      try {
+        const api = useApi();
+        const response = await api.post("/categories", payload);
+
+        if (!response.ok) {
+          const error = await response.json();
+          throw new Error(error.message || 'Failed to create category');
+        }
+
+        const newCategory = await response.json();
+        this.categories.push(newCategory);
+        return newCategory;
+      } catch (err) {
+        this.error = err instanceof Error ? err.message : 'Unknown error';
+        throw err;
+      } finally {
+        this.loading = false;
+      }
+    },
     reset() {
       this.categories = [];
+      this.loading = false;
+      this.error = null;
     }
   }
-});
\ No newline at end of file
+});
diff --git a/frontend/yarn.lock b/frontend/yarn.lock
index 719dad6..e6a3c82 100644
--- a/frontend/yarn.lock
+++ b/frontend/yarn.lock
@@ -1660,6 +1660,11 @@ has-flag@^4.0.0:
   resolved "https://registry.npmjs.org/has-flag/-/has-flag-4.0.0.tgz"
   integrity sha512-EykJT/Q1KjTWctppgIAgfSO0tKVuZUjhgMr17kqTumMl6Afv3EISleU7qZUzoXDFTAHTDC4NOoG/ZxU3EvlMPQ==
 
+highlight.js@^11.11.1:
+  version "11.11.1"
+  resolved "https://registry.yarnpkg.com/highlight.js/-/highlight.js-11.11.1.tgz#fca06fa0e5aeecf6c4d437239135fabc15213585"
+  integrity sha512-Xwwo44whKBVCYoliBQwaPvtd/2tYFkRQtXDWj1nackaV2JPXx3L0+Jvd8/qCJ2p+ML0/XVkJ2q+Mr+UVdpJK5w==
+
 hookable@^5.5.3:
   version "5.5.3"
   resolved "https://registry.npmjs.org/hookable/-/hookable-5.5.3.tgz"
diff --git a/src/services/category.rs b/src/services/category.rs
index af89a81..6ca8933 100644
--- a/src/services/category.rs
+++ b/src/services/category.rs
@@ -1,6 +1,9 @@
-use crate::services::ServicesContext;
 use crate::models::category;
-use sea_orm::{ActiveModelTrait, ColumnTrait, EntityTrait, QueryFilter, TransactionTrait, Set};
+use crate::models::server_item_order::{self, OrderedResourceType};
+use crate::services::ServicesContext;
+use sea_orm::{
+    ActiveModelTrait, ColumnTrait, EntityTrait, QueryFilter, QuerySelect, Set, TransactionTrait,
+};
 use std::sync::Arc;
 use uuid::Uuid;
 
@@ -22,16 +25,40 @@ impl CategoryService {
         let db = &self.service_context.repositories.server.context.db;
         let event_bus = &self.service_context.event_bus;
 
-        let txn = db.begin().await?;
+        let cat = db
+            .transaction::<_, category::Model, anyhow::Error>(|txn| {
+                Box::pin(async move {
+                    let active = category::ActiveModel {
+                        server_id: Set(server_id),
+                        name: Set(name),
+                        ..Default::default()
+                    };
+                    let cat = active.insert(txn).await?;
 
-        let active = category::ActiveModel {
-            server_id: Set(server_id),
-            name: Set(name),
-            ..Default::default()
-        };
-        let cat = active.insert(&txn).await?;
+                    let max_order: Option<i64> = server_item_order::Entity::find()
+                        .filter(server_item_order::Column::ServerId.eq(server_id))
+                        .filter(server_item_order::Column::ParentCategoryId.is_null())
+                        .select_only()
+                        .column_as(server_item_order::Column::OrderKey.max(), "max_key")
+                        .into_tuple::<Option<i64>>()
+                        .one(txn)
+                        .await?
+                        .flatten();
 
-        txn.commit().await?;
+                    let order_item = server_item_order::ActiveModel {
+                        server_id: Set(server_id),
+                        resource_id: Set(cat.id),
+                        resource_type: Set(OrderedResourceType::Category),
+                        parent_category_id: Set(None),
+                        order_key: Set(max_order.unwrap_or(0) + 1),
+                        ..Default::default()
+                    };
+                    order_item.insert(txn).await?;
+
+                    Ok(cat)
+                })
+            })
+            .await?;
 
         event_bus.emit("category_created", cat.clone());
 
@@ -71,10 +98,14 @@ impl CategoryService {
 
         let txn = db.begin().await?;
 
-        let res = category::Entity::delete_by_id(id)
+        server_item_order::Entity::delete_many()
+            .filter(server_item_order::Column::ResourceId.eq(id))
+            .filter(server_item_order::Column::ResourceType.eq(OrderedResourceType::Category))
             .exec(&txn)
             .await?;
 
+        let res = category::Entity::delete_by_id(id).exec(&txn).await?;
+
         let deleted = res.rows_affected > 0;
 
         txn.commit().await?;