From da151c13ed3879b6c8c4154253d1ea912c62a82d Mon Sep 17 00:00:00 2001
From: Nell <nell@devpanel.fr>
Date: Sat, 22 Aug 2026 20:34:43 +0200
Subject: [PATCH] init

---
 frontend/src/pages/index.vue                | 83 +++++++++++++++++--
 frontend/src/pages/server/channel/index.vue | 49 +++++++++++-
 frontend/src/pages/server/index.vue         |  3 +-
 frontend/src/router/index.ts                |  8 ++
 frontend/src/stores/conversation.ts         | 48 +++++++++++
 src/domain/dto/conversation.rs              | 31 ++++++++
 src/domain/dto/mod.rs                       |  1 +
 src/routes/channel/handlers.rs              | 24 +++---
 src/routes/conversation/handlers.rs         | 88 +++++++++++++++++++++
 src/routes/conversation/mod.rs              |  2 +
 src/routes/conversation/routes.rs           |  9 +++
 src/routes/message/handlers.rs              | 32 ++++++++
 src/routes/mod.rs                           |  2 +
 src/routes/openapi.rs                       |  7 ++
 14 files changed, 366 insertions(+), 21 deletions(-)
 create mode 100644 frontend/src/stores/conversation.ts
 create mode 100644 src/domain/dto/conversation.rs
 create mode 100644 src/routes/conversation/handlers.rs
 create mode 100644 src/routes/conversation/mod.rs
 create mode 100644 src/routes/conversation/routes.rs

diff --git a/frontend/src/pages/index.vue b/frontend/src/pages/index.vue
index fd71d59..b7d949c 100644
--- a/frontend/src/pages/index.vue
+++ b/frontend/src/pages/index.vue
@@ -1,9 +1,82 @@
 <script lang="ts" setup>
+import { computed, onMounted, ref } from 'vue'
+import { storeToRefs } from 'pinia'
+import { useRouter } from 'vue-router'
+import { useConversationStore } from '@/stores/conversation'
+import { useUserStore } from '@/stores/user'
+import { useAuthStore } from '@/stores/auth'
+
+const router = useRouter()
+const conversationStore = useConversationStore()
+const userStore = useUserStore()
+const authStore = useAuthStore()
+const { conversations } = storeToRefs(conversationStore)
+const showCreateDialog = ref(false)
+const selectedUserIds = ref<string[]>([])
+const submitting = ref(false)
+const users = computed(() => userStore.users.filter(user => user.id !== authStore.currentUser?.id))
+
+onMounted(async () => {
+  await Promise.all([userStore.fetchUsers(), conversationStore.fetchConversations()])
+})
+
+const createConversation = async () => {
+  if (!selectedUserIds.value.length) return
+  submitting.value = true
+  try {
+    const conversation = await conversationStore.createConversation(selectedUserIds.value)
+    showCreateDialog.value = false
+    selectedUserIds.value = []
+    await router.push(`/conversation/${conversation.id}`)
+  } finally { submitting.value = false }
+}
 </script>
 
-
 <template>
-  <div>
-    Hello
-  </div>
-</template>
\ No newline at end of file
+  <v-navigation-drawer permanent width="280" color="grey-lighten-5">
+    <div class="d-flex align-center px-4 py-4">
+      <span class="text-h6 font-weight-medium">Messages</span>
+      <v-spacer />
+      <v-btn icon="mdi-square-edit-outline" size="small" variant="text" aria-label="Nouvelle discussion" @click="showCreateDialog = true" />
+    </div>
+    <v-divider />
+    <v-list density="comfortable" nav>
+      <v-list-item
+        v-for="conversation in conversations"
+        :key="conversation.id"
+        :to="`/conversation/${conversation.id}`"
+        :title="conversation.title"
+        :subtitle="conversation.last_message ?? 'Aucun message'"
+        :class="{ 'font-weight-bold': conversation.unread_count > 0 }"
+        rounded="lg"
+      >
+        <template #prepend><v-avatar color="primary" size="34"><v-icon icon="mdi-account-multiple-outline" /></v-avatar></template>
+        <template #append><v-chip v-if="conversation.unread_count > 0" color="primary" size="small">{{ conversation.unread_count }}</v-chip></template>
+      </v-list-item>
+      <v-list-item v-if="!conversationStore.loading && !conversations.length" class="text-medium-emphasis" title="Aucune discussion" subtitle="Commencez une conversation" />
+    </v-list>
+  </v-navigation-drawer>
+
+  <v-main class="conversation-main">
+    <router-view />
+    <div v-if="!$route.params.channelId" class="empty-state">
+      <v-icon icon="mdi-message-text-outline" size="64" color="grey" />
+      <div class="text-h6 mt-4">Vos discussions</div>
+      <div class="text-body-2 text-medium-emphasis">Sélectionnez une discussion ou commencez-en une nouvelle.</div>
+      <v-btn class="mt-4" color="primary" prepend-icon="mdi-plus" @click="showCreateDialog = true">Nouvelle discussion</v-btn>
+    </div>
+  </v-main>
+
+  <v-dialog v-model="showCreateDialog" width="420">
+    <v-card>
+      <v-card-title>Nouvelle discussion</v-card-title>
+      <v-card-text><v-select v-model="selectedUserIds" :items="users" item-title="username" item-value="id" label="Participants" multiple chips closable-chips /></v-card-text>
+      <v-card-actions><v-spacer /><v-btn @click="showCreateDialog = false">Annuler</v-btn><v-btn color="primary" :loading="submitting" :disabled="!selectedUserIds.length" @click="createConversation">Créer</v-btn></v-card-actions>
+    </v-card>
+  </v-dialog>
+</template>
+
+<style scoped>
+.conversation-main { height: 100%; position: relative; }
+.empty-state { position: absolute; inset: 0; display: flex; flex-direction: column; align-items: center; justify-content: center; text-align: center; }
+</style>
diff --git a/frontend/src/pages/server/channel/index.vue b/frontend/src/pages/server/channel/index.vue
index ebf547e..3c2e34b 100644
--- a/frontend/src/pages/server/channel/index.vue
+++ b/frontend/src/pages/server/channel/index.vue
@@ -10,9 +10,11 @@ import {onReloadAll} from '@/plugins/events.ts'
 import EmojiPicker from '@/components/EmojiPicker.vue'
 import {useEmojiStore, type Emoji} from '@/stores/emoji.ts'
 import {useAuthStore} from '@/stores/auth.ts'
+import {useConversationStore} from '@/stores/conversation'
+import {useRoute, useRouter} from 'vue-router'
 
 const props = defineProps<{
-  serverId: string
+  serverId?: string
   channelId: string
 }>();
 
@@ -22,6 +24,9 @@ const serverStore = useServerStore();
 const userStore = useUserStore();
 const emojiStore = useEmojiStore();
 const authStore = useAuthStore();
+const conversationStore = useConversationStore()
+const route = useRoute()
+const router = useRouter()
 const {renderMarkdown} = useMarkdown()
 
 const messageContainer = ref<HTMLElement | null>(null);
@@ -35,6 +40,16 @@ const paginationLockScrollTop = ref(0);
 const lastScrollTop = ref(0);
 const markedMessageByChannel = new Map<string, string>();
 const reactionPending = ref(new Set<string>());
+const isConversation = computed(() => route.name === 'home-conversation')
+const addParticipantDialog = ref(false)
+const selectedParticipantIds = ref<string[]>([])
+const addingParticipants = ref(false)
+const currentConversation = computed(() => conversationStore.conversations.find(item => item.id === channelId.value))
+const availableParticipants = computed(() => userStore.users.filter(user =>
+  user.id !== authStore.currentUser?.id &&
+  !currentConversation.value?.participants.some(participant => participant.id === user.id) &&
+  !selectedParticipantIds.value.includes(user.id),
+))
 
 const markCurrentChannelRead = async (targetChannelId: string) => {
   if (messageStore.activeChannelId !== targetChannelId || !newestId.value) return;
@@ -47,12 +62,24 @@ const markCurrentChannelRead = async (targetChannelId: string) => {
     if (messageStore.activeChannelId !== targetChannelId) return;
 
     markedMessageByChannel.set(targetChannelId, messageId);
-    serverStore.applyChannelReadState(props.serverId, targetChannelId, readState.unread_count);
+    if (isConversation.value) conversationStore.applyReadState(targetChannelId, readState.unread_count)
+    else if (props.serverId) serverStore.applyChannelReadState(props.serverId, targetChannelId, readState.unread_count);
   } catch (error) {
     console.error('Erreur lors de la mise à jour de la lecture:', error);
   }
 };
 
+const forkConversation = async () => {
+  if (!selectedParticipantIds.value.length) return
+  addingParticipants.value = true
+  try {
+    const conversation = await conversationStore.forkConversation(channelId.value, selectedParticipantIds.value)
+    addParticipantDialog.value = false
+    selectedParticipantIds.value = []
+    await router.push(`/conversation/${conversation.id}`)
+  } finally { addingParticipants.value = false }
+}
+
 const showRecentMessagesButton = computed(() =>
   !loading.value && (hasMoreAfter.value || !isAtBottom.value),
 );
@@ -247,7 +274,7 @@ watch(isAtBottom, async (atBottom) => {
 
 watch(channelId, async (newChannelId) => {
   if (newChannelId) {
-    await emojiStore.fetchEmojis(props.serverId);
+    if (props.serverId) await emojiStore.fetchEmojis(props.serverId);
     await messageStore.fetchMessages(newChannelId);
     await scrollToBottom();
     await markCurrentChannelRead(newChannelId);
@@ -261,6 +288,12 @@ watch(() => props.serverId, (newServerId) => {
 
 <template>
   <v-container class="pa-0 fill-height d-flex flex-column channel-layout" fluid>
+    <v-sheet v-if="isConversation" class="px-4 py-2 d-flex align-center" border>
+      <v-icon class="mr-3" icon="mdi-account-multiple-outline" />
+      <span class="font-weight-medium">{{ currentConversation?.title ?? 'Discussion' }}</span>
+      <v-spacer />
+      <v-btn prepend-icon="mdi-account-plus" variant="text" @click="addParticipantDialog = true">Ajouter</v-btn>
+    </v-sheet>
     <div
       ref="messageContainer"
       class="flex-grow-1 overflow-y-auto w-100 message-container"
@@ -372,6 +405,16 @@ watch(() => props.serverId, (newServerId) => {
       </v-textarea>
     </v-sheet>
   </v-container>
+
+  <v-dialog v-model="addParticipantDialog" width="420">
+    <v-card>
+      <v-card-title>Nouvelle discussion de groupe</v-card-title>
+      <v-card-text>
+        <v-select v-model="selectedParticipantIds" :items="availableParticipants" item-title="username" item-value="id" label="Ajouter des participants" multiple chips closable-chips />
+      </v-card-text>
+      <v-card-actions><v-spacer /><v-btn @click="addParticipantDialog = false">Annuler</v-btn><v-btn color="primary" :loading="addingParticipants" :disabled="!selectedParticipantIds.length" @click="forkConversation">Créer</v-btn></v-card-actions>
+    </v-card>
+  </v-dialog>
 </template>
 
 <style scoped>
diff --git a/frontend/src/pages/server/index.vue b/frontend/src/pages/server/index.vue
index f9e1773..90e9207 100644
--- a/frontend/src/pages/server/index.vue
+++ b/frontend/src/pages/server/index.vue
@@ -167,7 +167,7 @@ function onChannelContextMenu(event: MouseEvent, channel: any) {
       <v-btn block variant="text" prepend-icon="mdi-cog" @click="showServerSettings = true">Gérer le serveur</v-btn>
     </v-sheet>
 
-    <v-list
+  <v-list
       v-model:opened="openedCategories"
       open-strategy="multiple"
       density="compact"
@@ -230,6 +230,7 @@ function onChannelContextMenu(event: MouseEvent, channel: any) {
         </v-list-item>
       </template>
     </v-list>
+
   </v-navigation-drawer>
 
   <CreateChannelDialog
diff --git a/frontend/src/router/index.ts b/frontend/src/router/index.ts
index 0a25a82..dca3bc8 100644
--- a/frontend/src/router/index.ts
+++ b/frontend/src/router/index.ts
@@ -45,6 +45,14 @@ const router = createRouter({
           path: '',
           name: 'home',
           component: () => import('@/pages/index.vue'),
+          children: [
+            {
+              path: 'conversation/:channelId(default|[0-9a-fA-F-]{36})',
+              name: 'home-conversation',
+              component: () => import('@/pages/server/channel/index.vue'),
+              props: true,
+            },
+          ],
         },
         {
           path: 'server/:serverId(default|[0-9a-fA-F-]{36})',
diff --git a/frontend/src/stores/conversation.ts b/frontend/src/stores/conversation.ts
new file mode 100644
index 0000000..f81ce43
--- /dev/null
+++ b/frontend/src/stores/conversation.ts
@@ -0,0 +1,48 @@
+import { defineStore } from 'pinia'
+import { useApi } from '@/composables/useApi'
+
+export interface ConversationParticipant { id: string; username: string }
+export interface Conversation {
+  id: string
+  title: string
+  participants: ConversationParticipant[]
+  last_message: string | null
+  unread_count: number
+  created_at: string
+  updated_at: string
+}
+
+export const useConversationStore = defineStore('conversation', {
+  state: () => ({ conversations: [] as Conversation[], loading: false }),
+  actions: {
+    async fetchConversations() {
+      this.loading = true
+      try {
+        const response = await useApi().get('/conversations')
+        if (!response.ok) throw new Error(`Conversation loading failed (${response.status})`)
+        this.conversations = await response.json()
+      } finally { this.loading = false }
+    },
+    async createConversation(userIds: string[]) {
+      const response = await useApi().post('/conversations', { user_ids: userIds })
+      if (!response.ok) throw new Error(`Conversation creation failed (${response.status})`)
+      const conversation = await response.json() as Conversation
+      const index = this.conversations.findIndex(item => item.id === conversation.id)
+      if (index >= 0) this.conversations[index] = conversation
+      else this.conversations.unshift(conversation)
+      return conversation
+    },
+    async forkConversation(id: string, userIds: string[]) {
+      const response = await useApi().post(`/conversations/${id}/fork`, { user_ids: userIds })
+      if (!response.ok) throw new Error(`Conversation fork failed (${response.status})`)
+      const conversation = await response.json() as Conversation
+      this.conversations.unshift(conversation)
+      return conversation
+    },
+    applyReadState(id: string, unreadCount: number) {
+      const conversation = this.conversations.find(item => item.id === id)
+      if (conversation) conversation.unread_count = unreadCount
+    },
+    reset() { this.conversations = []; this.loading = false }
+  }
+})
diff --git a/src/domain/dto/conversation.rs b/src/domain/dto/conversation.rs
new file mode 100644
index 0000000..a987e37
--- /dev/null
+++ b/src/domain/dto/conversation.rs
@@ -0,0 +1,31 @@
+use chrono::{DateTime, Utc};
+use serde::{Deserialize, Serialize};
+use utoipa::ToSchema;
+use uuid::Uuid;
+
+#[derive(Debug, Serialize, Deserialize, ToSchema)]
+pub struct ConversationParticipantResponse {
+    pub id: Uuid,
+    pub username: String,
+}
+
+#[derive(Debug, Serialize, ToSchema)]
+pub struct ConversationResponse {
+    pub id: Uuid,
+    pub title: String,
+    pub participants: Vec<ConversationParticipantResponse>,
+    pub last_message: Option<String>,
+    pub unread_count: u64,
+    pub created_at: DateTime<Utc>,
+    pub updated_at: DateTime<Utc>,
+}
+
+#[derive(Debug, Deserialize, ToSchema)]
+pub struct CreateConversationRequest {
+    pub user_ids: Vec<Uuid>,
+}
+
+#[derive(Debug, Deserialize, ToSchema)]
+pub struct ForkConversationRequest {
+    pub user_ids: Vec<Uuid>,
+}
diff --git a/src/domain/dto/mod.rs b/src/domain/dto/mod.rs
index 76b3e0b..16badc0 100644
--- a/src/domain/dto/mod.rs
+++ b/src/domain/dto/mod.rs
@@ -2,6 +2,7 @@ pub mod attachment;
 pub mod auth;
 pub mod category;
 pub mod channel;
+pub mod conversation;
 pub mod core;
 pub mod emoji;
 pub mod message;
diff --git a/src/routes/channel/handlers.rs b/src/routes/channel/handlers.rs
index 7750292..fd1b78e 100644
--- a/src/routes/channel/handlers.rs
+++ b/src/routes/channel/handlers.rs
@@ -6,6 +6,7 @@ use crate::domain::dto::channel::{
 };
 use crate::http::context::{CurrentUser, Superuser};
 use crate::http::error::HTTPError;
+use crate::models::{channel, channel_user};
 use crate::routes::channel::mapper;
 use axum::{
     Json,
@@ -13,6 +14,15 @@ use axum::{
     http::StatusCode,
 };
 use uuid::Uuid;
+use sea_orm::{ColumnTrait, EntityTrait, QueryFilter};
+
+async fn require_channel_member(state: &AppState, channel_id: Uuid, user_id: Uuid) -> Result<(), HTTPError> {
+    let channel = state.repositories.channel.get_by_id(channel_id).await?.ok_or(HTTPError::NotFound)?;
+    if channel.channel_type == channel::ChannelType::DM
+        && channel_user::Entity::find().filter(channel_user::Column::ChannelId.eq(channel_id)).filter(channel_user::Column::UserId.eq(user_id)).one(&state.db).await?.is_none()
+    { return Err(HTTPError::Forbidden); }
+    Ok(())
+}
 
 /// Liste tous les channels
 #[utoipa::path(
@@ -54,12 +64,7 @@ pub async fn get_read_state(
     State(state): State<AppState>,
     Path(channel_id): Path<Uuid>,
 ) -> Result<Json<ReadStateResponse>, HTTPError> {
-    state
-        .repositories
-        .channel
-        .get_by_id(channel_id)
-        .await?
-        .ok_or(HTTPError::NotFound)?;
+    require_channel_member(&state, channel_id, user.id).await?;
     let read_state = state
         .repositories
         .read_state
@@ -99,12 +104,7 @@ pub async fn set_read_state(
     Path(channel_id): Path<Uuid>,
     Json(payload): Json<SetReadStateRequest>,
 ) -> Result<Json<ReadStateResponse>, HTTPError> {
-    state
-        .repositories
-        .channel
-        .get_by_id(channel_id)
-        .await?
-        .ok_or(HTTPError::NotFound)?;
+    require_channel_member(&state, channel_id, user.id).await?;
 
     if let Some(message_id) = payload.last_read_message_id {
         let message = state
diff --git a/src/routes/conversation/handlers.rs b/src/routes/conversation/handlers.rs
new file mode 100644
index 0000000..32ef342
--- /dev/null
+++ b/src/routes/conversation/handlers.rs
@@ -0,0 +1,88 @@
+use crate::core::state::AppState;
+use crate::domain::dto::conversation::{
+    ConversationParticipantResponse, ConversationResponse, CreateConversationRequest,
+    ForkConversationRequest,
+};
+use crate::http::context::CurrentUser;
+use crate::http::error::HTTPError;
+use crate::models::{channel, channel_user, message, user};
+use axum::{Json, extract::{Path, State}};
+use chrono::Utc;
+use sea_orm::{ActiveModelTrait, ColumnTrait, EntityTrait, QueryFilter, QueryOrder, Set, TransactionTrait};
+use std::collections::HashSet;
+use uuid::Uuid;
+
+async fn member_ids(state: &AppState, channel_id: Uuid) -> Result<Vec<Uuid>, HTTPError> {
+    Ok(channel_user::Entity::find()
+        .filter(channel_user::Column::ChannelId.eq(channel_id))
+        .all(&state.db).await?.into_iter().map(|m| m.user_id).collect())
+}
+
+async fn response(state: &AppState, current_user_id: Uuid, channel: channel::Model) -> Result<ConversationResponse, HTTPError> {
+    let ids = member_ids(state, channel.id).await?;
+    let users = user::Entity::find().filter(user::Column::Id.is_in(ids.clone())).all(&state.db).await?;
+    let mut participants: Vec<_> = users.into_iter().map(|u| ConversationParticipantResponse { id: u.id, username: u.username }).collect();
+    participants.sort_by(|a, b| a.username.to_lowercase().cmp(&b.username.to_lowercase()));
+    let title = participants.iter().filter(|p| p.id != current_user_id).map(|p| p.username.clone()).collect::<Vec<_>>().join(", ");
+    let last_message = message::Entity::find().filter(message::Column::ChannelId.eq(channel.id)).order_by_desc(message::Column::Id).one(&state.db).await?.map(|m| m.content);
+    let unread_count = state.repositories.read_state.unread_counts(&[channel.id], current_user_id).await?.get(&channel.id).copied().unwrap_or(0);
+    Ok(ConversationResponse { id: channel.id, title: if title.is_empty() { "Discussion".into() } else { title }, participants, last_message, unread_count, created_at: channel.created_at, updated_at: channel.updated_at })
+}
+
+async fn create_channel(state: &AppState, ids: &[Uuid]) -> Result<channel::Model, HTTPError> {
+    let txn = state.db.begin().await?;
+    let channel = channel::ActiveModel { server_id: Set(None), category_id: Set(None), channel_type: Set(channel::ChannelType::DM), name: Set(None), ..Default::default() }.insert(&txn).await?;
+    for user_id in ids {
+        channel_user::ActiveModel { channel_id: Set(channel.id), user_id: Set(*user_id), role: Set("member".into()), joined_at: Set(Utc::now()), ..Default::default() }.insert(&txn).await?;
+    }
+    txn.commit().await?;
+    state.event_bus.emit("channel_created", channel.clone());
+    Ok(channel)
+}
+
+async fn validate_ids(state: &AppState, ids: &[Uuid]) -> Result<(), HTTPError> {
+    if ids.is_empty() { return Err(HTTPError::BadRequest("At least one participant is required".into())); }
+    let found = user::Entity::find().filter(user::Column::Id.is_in(ids.to_vec())).all(&state.db).await?;
+    if found.len() != ids.iter().collect::<HashSet<_>>().len() { return Err(HTTPError::BadRequest("Unknown participant".into())); }
+    Ok(())
+}
+
+#[utoipa::path(get, path = "/conversations", responses((status = 200, body = [ConversationResponse])), tag = "Conversations", security(("bearerAuth" = [])))]
+pub async fn list(user: CurrentUser, State(state): State<AppState>) -> Result<Json<Vec<ConversationResponse>>, HTTPError> {
+    let memberships = channel_user::Entity::find().filter(channel_user::Column::UserId.eq(user.id)).all(&state.db).await?;
+    let ids: Vec<_> = memberships.into_iter().map(|m| m.channel_id).collect();
+    if ids.is_empty() { return Ok(Json(Vec::new())); }
+    let channels = channel::Entity::find().filter(channel::Column::Id.is_in(ids)).filter(channel::Column::ChannelType.eq(channel::ChannelType::DM)).order_by_desc(channel::Column::UpdatedAt).all(&state.db).await?;
+    let mut result = Vec::with_capacity(channels.len());
+    for channel in channels { result.push(response(&state, user.id, channel).await?); }
+    Ok(Json(result))
+}
+
+#[utoipa::path(post, path = "/conversations", request_body = CreateConversationRequest, responses((status = 200, body = ConversationResponse)), tag = "Conversations", security(("bearerAuth" = [])))]
+pub async fn create(user: CurrentUser, State(state): State<AppState>, Json(payload): Json<CreateConversationRequest>) -> Result<Json<ConversationResponse>, HTTPError> {
+    let mut ids = payload.user_ids;
+    ids.push(user.id);
+    ids.sort_unstable(); ids.dedup();
+    validate_ids(&state, &ids).await?;
+    let channels = channel_user::Entity::find().filter(channel_user::Column::UserId.eq(user.id)).all(&state.db).await?;
+    for membership in channels {
+        if let Some(channel) = channel::Entity::find_by_id(membership.channel_id).filter(channel::Column::ChannelType.eq(channel::ChannelType::DM)).one(&state.db).await? {
+            let existing: HashSet<_> = member_ids(&state, channel.id).await?.into_iter().collect();
+            if existing == ids.iter().copied().collect() { return Ok(Json(response(&state, user.id, channel).await?)); }
+        }
+    }
+    let channel = create_channel(&state, &ids).await?;
+    Ok(Json(response(&state, user.id, channel).await?))
+}
+
+#[utoipa::path(post, path = "/conversations/{id}/fork", request_body = ForkConversationRequest, params(("id" = Uuid, Path)), responses((status = 200, body = ConversationResponse)), tag = "Conversations", security(("bearerAuth" = [])))]
+pub async fn fork(user: CurrentUser, State(state): State<AppState>, Path(id): Path<Uuid>, Json(payload): Json<ForkConversationRequest>) -> Result<Json<ConversationResponse>, HTTPError> {
+    let source = channel::Entity::find_by_id(id).one(&state.db).await?.ok_or(HTTPError::NotFound)?;
+    if source.channel_type != channel::ChannelType::DM || !member_ids(&state, id).await?.contains(&user.id) { return Err(HTTPError::Forbidden); }
+    let mut ids = member_ids(&state, id).await?;
+    ids.extend(payload.user_ids);
+    ids.sort_unstable(); ids.dedup();
+    validate_ids(&state, &ids).await?;
+    let channel = create_channel(&state, &ids).await?;
+    Ok(Json(response(&state, user.id, channel).await?))
+}
diff --git a/src/routes/conversation/mod.rs b/src/routes/conversation/mod.rs
new file mode 100644
index 0000000..c0c696a
--- /dev/null
+++ b/src/routes/conversation/mod.rs
@@ -0,0 +1,2 @@
+pub mod handlers;
+pub mod routes;
diff --git a/src/routes/conversation/routes.rs b/src/routes/conversation/routes.rs
new file mode 100644
index 0000000..2d7d916
--- /dev/null
+++ b/src/routes/conversation/routes.rs
@@ -0,0 +1,9 @@
+use super::handlers;
+use crate::core::state::AppState;
+use axum::{routing::{get, post}, Router};
+
+pub fn router() -> Router<AppState> {
+    Router::new()
+        .route("/conversations", get(handlers::list).post(handlers::create))
+        .route("/conversations/{id}/fork", post(handlers::fork))
+}
diff --git a/src/routes/message/handlers.rs b/src/routes/message/handlers.rs
index c1aaec4..23899da 100644
--- a/src/routes/message/handlers.rs
+++ b/src/routes/message/handlers.rs
@@ -6,6 +6,7 @@ use crate::domain::dto::message::{
 use crate::domain::dto::reaction::{CreateReactionRequest, DeleteReactionQuery, ReactionResponse};
 use crate::http::context::CurrentUser;
 use crate::http::error::HTTPError;
+use crate::models::{channel, channel_user};
 use crate::routes::message::mapper;
 use axum::{
     Json,
@@ -13,6 +14,20 @@ use axum::{
     http::StatusCode,
 };
 use uuid::Uuid;
+use sea_orm::{ColumnTrait, EntityTrait, QueryFilter};
+
+pub(crate) async fn can_access(state: &AppState, channel_id: Uuid, user_id: Uuid) -> Result<bool, HTTPError> {
+    let Some(channel) = channel::Entity::find_by_id(channel_id).one(&state.db).await? else {
+        return Ok(false);
+    };
+    if channel.channel_type != channel::ChannelType::DM {
+        return Ok(true);
+    }
+    Ok(channel_user::Entity::find()
+        .filter(channel_user::Column::ChannelId.eq(channel_id))
+        .filter(channel_user::Column::UserId.eq(user_id))
+        .one(&state.db).await?.is_some())
+}
 
 /// Liste une fenêtre paginée de messages
 #[utoipa::path(
@@ -29,6 +44,7 @@ use uuid::Uuid;
     tag = "Messages"
 )]
 pub async fn get_all(
+    user: CurrentUser,
     State(state): State<AppState>,
     Query(filters): Query<MessageQueryParams>,
 ) -> Result<Json<MessagePageResponse>, HTTPError> {
@@ -39,6 +55,11 @@ pub async fn get_all(
     }
 
     let params = mapper::query_params_to_message_filter(filters);
+    if let Some(channel_id) = params.channel_id {
+        if !can_access(&state, channel_id, user.id).await? {
+            return Err(HTTPError::Forbidden);
+        }
+    }
     let page = state.repositories.message.filter(params).await?;
     let message_ids: Vec<_> = page.messages.iter().map(|message| message.id).collect();
     let mut reactions = state
@@ -80,6 +101,7 @@ pub async fn get_all(
     tag = "Messages"
 )]
 pub async fn get_by_id(
+    user: CurrentUser,
     State(state): State<AppState>,
     Path(id): Path<Uuid>,
 ) -> Result<Json<MessageResponse>, HTTPError> {
@@ -89,6 +111,9 @@ pub async fn get_by_id(
         .get_by_id(id)
         .await?
         .ok_or(HTTPError::NotFound)?;
+    if !can_access(&state, message.channel_id, user.id).await? {
+        return Err(HTTPError::Forbidden);
+    }
 
     let reactions = state
         .services
@@ -130,6 +155,9 @@ pub async fn create(
         .get_by_id(payload.channel_id)
         .await?
         .ok_or(HTTPError::BadRequest("Channel not found".to_string()))?;
+    if !can_access(&state, channel.id, user.id).await? {
+        return Err(HTTPError::Forbidden);
+    }
 
     // Optionnel: vérifier reply_to_id
     if let Some(reply_id) = payload.reply_to_id {
@@ -233,6 +261,8 @@ pub async fn add_reaction(
     Path(message_id): Path<Uuid>,
     Json(payload): Json<CreateReactionRequest>,
 ) -> Result<(StatusCode, Json<ReactionResponse>), HTTPError> {
+    let message = state.repositories.message.get_by_id(message_id).await?.ok_or(HTTPError::NotFound)?;
+    if !can_access(&state, message.channel_id, user.id).await? { return Err(HTTPError::Forbidden); }
     let (reaction, created) = state
         .services
         .message_reaction
@@ -270,6 +300,8 @@ pub async fn remove_reaction(
     Path((message_id, emoji_id)): Path<(Uuid, Uuid)>,
     Query(query): Query<DeleteReactionQuery>,
 ) -> Result<StatusCode, HTTPError> {
+    let message = state.repositories.message.get_by_id(message_id).await?.ok_or(HTTPError::NotFound)?;
+    if !can_access(&state, message.channel_id, user.id).await? { return Err(HTTPError::Forbidden); }
     state
         .services
         .message_reaction
diff --git a/src/routes/mod.rs b/src/routes/mod.rs
index f4aabdd..5809a18 100644
--- a/src/routes/mod.rs
+++ b/src/routes/mod.rs
@@ -8,6 +8,7 @@ pub mod attachment;
 pub mod auth;
 pub mod category;
 pub mod channel;
+pub mod conversation;
 pub mod core;
 pub mod emoji;
 pub mod gateway;
@@ -23,6 +24,7 @@ pub fn router() -> OxRouter {
         .merge(server::routes::router())
         .merge(category::routes::router())
         .merge(channel::routes::router())
+        .merge(conversation::routes::router())
         .merge(role::routes::router())
         .merge(message::routes::router())
         .merge(user::routes::router())
diff --git a/src/routes/openapi.rs b/src/routes/openapi.rs
index 432aed2..c494e6f 100644
--- a/src/routes/openapi.rs
+++ b/src/routes/openapi.rs
@@ -31,6 +31,9 @@ use utoipa::{Modify, OpenApi};
         channel::handlers::create,
         channel::handlers::update,
         channel::handlers::delete,
+        conversation::handlers::list,
+        conversation::handlers::create,
+        conversation::handlers::fork,
         role::handlers::get_all,
         role::handlers::get_by_id,
         role::handlers::create,
@@ -69,6 +72,10 @@ use utoipa::{Modify, OpenApi};
             crate::domain::dto::channel::UpdateChannelRequest,
             crate::domain::dto::channel::ReadStateResponse,
             crate::domain::dto::channel::SetReadStateRequest,
+            crate::domain::dto::conversation::ConversationParticipantResponse,
+            crate::domain::dto::conversation::ConversationResponse,
+            crate::domain::dto::conversation::CreateConversationRequest,
+            crate::domain::dto::conversation::ForkConversationRequest,
             crate::domain::dto::role::RoleResponse,
             crate::domain::dto::role::CreateRoleRequest,
             crate::domain::dto::role::UpdateRoleRequest,