diff --git a/src/db-migration.test.ts b/src/db-migration.test.ts
new file mode 100644
index 0000000..e26873d
--- /dev/null
+++ b/src/db-migration.test.ts
@@ -0,0 +1,67 @@
+import Database from 'better-sqlite3';
+import fs from 'fs';
+import os from 'os';
+import path from 'path';
+import { describe, expect, it, vi } from 'vitest';
+
+describe('database migrations', () => {
+  it('defaults Telegram backfill chats to direct messages', async () => {
+    const repoRoot = process.cwd();
+    const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), 'nanoclaw-db-test-'));
+
+    try {
+      process.chdir(tempDir);
+      fs.mkdirSync(path.join(tempDir, 'store'), { recursive: true });
+
+      const dbPath = path.join(tempDir, 'store', 'messages.db');
+      const legacyDb = new Database(dbPath);
+      legacyDb.exec(`
+        CREATE TABLE chats (
+          jid TEXT PRIMARY KEY,
+          name TEXT,
+          last_message_time TEXT
+        );
+      `);
+      legacyDb
+        .prepare(
+          `INSERT INTO chats (jid, name, last_message_time) VALUES (?, ?, ?)`,
+        )
+        .run('tg:12345', 'Telegram DM', '2024-01-01T00:00:00.000Z');
+      legacyDb
+        .prepare(
+          `INSERT INTO chats (jid, name, last_message_time) VALUES (?, ?, ?)`,
+        )
+        .run('tg:-10012345', 'Telegram Group', '2024-01-01T00:00:01.000Z');
+      legacyDb
+        .prepare(
+          `INSERT INTO chats (jid, name, last_message_time) VALUES (?, ?, ?)`,
+        )
+        .run('room@g.us', 'WhatsApp Group', '2024-01-01T00:00:02.000Z');
+      legacyDb.close();
+
+      vi.resetModules();
+      const { initDatabase, getAllChats, _closeDatabase } =
+        await import('./db.js');
+
+      initDatabase();
+
+      const chats = getAllChats();
+      expect(chats.find((chat) => chat.jid === 'tg:12345')).toMatchObject({
+        channel: 'telegram',
+        is_group: 0,
+      });
+      expect(chats.find((chat) => chat.jid === 'tg:-10012345')).toMatchObject({
+        channel: 'telegram',
+        is_group: 0,
+      });
+      expect(chats.find((chat) => chat.jid === 'room@g.us')).toMatchObject({
+        channel: 'whatsapp',
+        is_group: 1,
+      });
+
+      _closeDatabase();
+    } finally {
+      process.chdir(repoRoot);
+    }
+  });
+});
diff --git a/src/db.ts b/src/db.ts
index 87dd941..718bc60 100644
--- a/src/db.ts
+++ b/src/db.ts
@@ -141,7 +141,7 @@ function createSchema(database: Database.Database): void {
       `UPDATE chats SET channel = 'discord', is_group = 1 WHERE jid LIKE 'dc:%'`,
     );
     database.exec(
-      `UPDATE chats SET channel = 'telegram', is_group = 1 WHERE jid LIKE 'tg:%'`,
+      `UPDATE chats SET channel = 'telegram', is_group = 0 WHERE jid LIKE 'tg:%'`,
     );
   } catch {
     /* columns already exist */
@@ -165,6 +165,11 @@ export function _initTestDatabase(): void {
   createSchema(db);
 }
 
+/** @internal - for tests only. */
+export function _closeDatabase(): void {
+  db.close();
+}
+
 /**
  * Store chat metadata only (no message content).
  * Used for all chats to enable group discovery without storing sensitive content.