diff --git a/apps/backend/drizzle/0008_migrate_messages_ciphertext.sql b/apps/backend/drizzle/0008_migrate_messages_ciphertext.sql
new file mode 100644
index 00000000..6f0034ef
--- /dev/null
+++ b/apps/backend/drizzle/0008_migrate_messages_ciphertext.sql
@@ -0,0 +1,11 @@
+-- Drop the full-text search index that relied on the plaintext content column.
+DROP INDEX IF EXISTS "messages_content_search_idx";--> statement-breakpoint
+
+-- Add the new nullable ciphertext column for single-blob E2EE messages.
+ALTER TABLE "messages" ADD COLUMN "ciphertext" text;--> statement-breakpoint
+
+-- Migrate existing plaintext content into ciphertext so no data is lost.
+UPDATE "messages" SET "ciphertext" = "content" WHERE "deleted_at" IS NULL;--> statement-breakpoint
+
+-- Drop the old plaintext content column.
+ALTER TABLE "messages" DROP COLUMN "content";
diff --git a/apps/backend/src/__tests__/conversations.cache.test.ts b/apps/backend/src/__tests__/conversations.cache.test.ts
index fdc93b69..7eb854c3 100644
--- a/apps/backend/src/__tests__/conversations.cache.test.ts
+++ b/apps/backend/src/__tests__/conversations.cache.test.ts
@@ -62,7 +62,7 @@ vi.mock('../db/schema.js', () => ({
     id: 'id',
     conversationId: 'conversationId',
     senderId: 'senderId',
-    content: 'content',
+    ciphertext: 'ciphertext',
     createdAt: 'createdAt',
     deletedAt: 'deletedAt',
   },
diff --git a/apps/backend/src/__tests__/conversations.routes.test.ts b/apps/backend/src/__tests__/conversations.routes.test.ts
index 20f12028..db1c9f44 100644
--- a/apps/backend/src/__tests__/conversations.routes.test.ts
+++ b/apps/backend/src/__tests__/conversations.routes.test.ts
@@ -54,7 +54,7 @@ vi.mock('../db/schema.js', () => ({
     id: 'id',
     conversationId: 'conversationId',
     senderId: 'senderId',
-    content: 'content',
+    ciphertext: 'ciphertext',
     createdAt: 'createdAt',
     deletedAt: 'deletedAt',
   },
diff --git a/apps/backend/src/__tests__/messages.routes.test.ts b/apps/backend/src/__tests__/messages.routes.test.ts
index aa5361b3..12e27da6 100644
--- a/apps/backend/src/__tests__/messages.routes.test.ts
+++ b/apps/backend/src/__tests__/messages.routes.test.ts
@@ -43,7 +43,7 @@ vi.mock('../db/schema.js', () => ({
     id: 'id',
     conversationId: 'conversationId',
     senderId: 'senderId',
-    content: 'content',
+    ciphertext: 'ciphertext',
     createdAt: 'createdAt',
     deletedAt: 'deletedAt',
   },
@@ -86,7 +86,7 @@ describe('DELETE /messages/:id', () => {
       id: 'msg-1',
       conversationId: 'conv-1',
       senderId: 'user-2',
-      content: 'hello',
+      ciphertext: 'hello',
       deletedAt: null,
     });
 
@@ -101,7 +101,7 @@ describe('DELETE /messages/:id', () => {
       id: 'msg-1',
       conversationId: 'conv-1',
       senderId: 'user-1',
-      content: 'hello',
+      ciphertext: 'hello',
       deletedAt: null,
     });
 
diff --git a/apps/backend/src/socket/messaging.ts b/apps/backend/src/socket/messaging.ts
index 5426137c..ba9b44bd 100644
--- a/apps/backend/src/socket/messaging.ts
+++ b/apps/backend/src/socket/messaging.ts
@@ -636,7 +636,7 @@ export function registerMessagingHandlers(io: Server, socket: AuthSocket): void
       const response = await fetch('http://localhost:8000/chat', {
         method: 'POST',
         headers: { 'Content-Type': 'application/json' },
-        body: JSON.stringify({ message: content, conversation_id: conversationId }),
+        body: JSON.stringify({ message: ciphertext, conversation_id: conversationId }),
       });
 
       if (!response.ok) {