diff --git a/apps/backend/drizzle/0008_extend_messages.sql b/apps/backend/drizzle/0008_extend_messages.sql
new file mode 100644
index 0000000..8156484
--- /dev/null
+++ b/apps/backend/drizzle/0008_extend_messages.sql
@@ -0,0 +1,6 @@
+CREATE TYPE "public"."content_type" AS ENUM('text', 'file', 'image', 'video', 'audio', 'system');--> statement-breakpoint
+ALTER TABLE "messages" ADD COLUMN "content_type" "content_type" NOT NULL DEFAULT 'text';--> statement-breakpoint
+ALTER TABLE "messages" ADD COLUMN "sender_device_id" uuid NOT NULL;--> statement-breakpoint
+ALTER TABLE "messages" ADD COLUMN "sequence_number" bigint NOT NULL;--> statement-breakpoint
+ALTER TABLE "messages" ADD COLUMN "expires_at" timestamp;--> statement-breakpoint
+ALTER TABLE "messages" ADD CONSTRAINT "messages_sender_device_id_user_devices_id_fk" FOREIGN KEY ("sender_device_id") REFERENCES "public"."user_devices"("id") ON DELETE cascade ON UPDATE no action;
diff --git a/apps/backend/drizzle/meta/_journal.json b/apps/backend/drizzle/meta/_journal.json
index 83106f4..6f5a899 100644
--- a/apps/backend/drizzle/meta/_journal.json
+++ b/apps/backend/drizzle/meta/_journal.json
@@ -61,8 +61,8 @@
     {
       "idx": 8,
       "version": "7",
-      "when": 1782653959991,
-      "tag": "0008_keen_sway",
+      "when": 1783000000000,
+      "tag": "0008_extend_messages",
       "breakpoints": true
     }
   ]
diff --git a/apps/backend/src/db/schema.ts b/apps/backend/src/db/schema.ts
index 6a85ca0..988f6cb 100644
--- a/apps/backend/src/db/schema.ts
+++ b/apps/backend/src/db/schema.ts
@@ -8,6 +8,7 @@ import {
   index,
   integer,
   uniqueIndex,
+  bigint,
 } from 'drizzle-orm/pg-core';
 import { relations, sql } from 'drizzle-orm';
 
@@ -42,6 +43,15 @@ export const conversations = pgTable('conversations', {
   createdAt: timestamp('created_at').notNull().defaultNow(),
 });
 
+export const contentTypeEnum = pgEnum('content_type', [
+  'text',
+  'file',
+  'image',
+  'video',
+  'audio',
+  'system',
+]);
+
 export const conversationMembers = pgTable('conversation_members', {
   id: uuid('id').primaryKey().defaultRandom(),
   conversationId: uuid('conversation_id')
@@ -69,6 +79,12 @@ export const messages = pgTable(
       .notNull()
       .references(() => users.id, { onDelete: 'cascade' }),
     content: text('content').notNull(),
+    contentType: contentTypeEnum('content_type').notNull().default('text'),
+    senderDeviceId: uuid('sender_device_id')
+      .notNull()
+      .references(() => userDevices.id, { onDelete: 'cascade' }),
+    sequenceNumber: bigint('sequence_number', { mode: 'bigint' }).notNull(),
+    expiresAt: timestamp('expires_at'),
     createdAt: timestamp('created_at').notNull().defaultNow(),
     deletedAt: timestamp('deleted_at'),
   },
@@ -266,6 +282,10 @@ export const messagesRelations = relations(messages, ({ one }) => ({
     references: [conversations.id],
   }),
   sender: one(users, { fields: [messages.senderId], references: [users.id] }),
+  senderDevice: one(userDevices, {
+    fields: [messages.senderDeviceId],
+    references: [userDevices.id],
+  }),
 }));
 
 export const tokenTransfersRelations = relations(tokenTransfers, ({ one }) => ({
@@ -293,6 +313,11 @@ export const oneTimePreKeysRelations = relations(oneTimePreKeys, ({ one }) => ({
   device: one(devices, { fields: [oneTimePreKeys.deviceId], references: [devices.id] }),
 }));
 
+export const userDevicesRelations = relations(userDevices, ({ one, many }) => ({
+  user: one(users, { fields: [userDevices.userId], references: [users.id] }),
+  messages: many(messages),
+}));
+
 // ─── Types ────────────────────────────────────────────────────────────────────
 
 export type User = typeof users.$inferSelect;
@@ -312,3 +337,5 @@ export type SignedPreKey = typeof signedPreKeys.$inferSelect;
 export type NewSignedPreKey = typeof signedPreKeys.$inferInsert;
 export type OneTimePreKey = typeof oneTimePreKeys.$inferSelect;
 export type NewOneTimePreKey = typeof oneTimePreKeys.$inferInsert;
+export type UserDevice = typeof userDevices.$inferSelect;
+export type NewUserDevice = typeof userDevices.$inferInsert;