diff --git a/setup/migrate-v2/db.ts b/setup/migrate-v2/db.ts
index fb15ab0..da2bab7 100644
--- a/setup/migrate-v2/db.ts
+++ b/setup/migrate-v2/db.ts
@@ -29,6 +29,7 @@ import { readEnvFile } from '../../src/env.js';
 import { buildDiscordResolver, type DiscordResolver } from './discord-resolver.js';
 import {
   generateId,
+  inferIsGroup,
   parseJid,
   triggerToEngage,
   v2PlatformId,
@@ -148,7 +149,7 @@ async function main(): Promise<void> {
           channel_type: channelType,
           platform_id: platformId,
           name: g.name || null,
-          is_group: 1,
+          is_group: inferIsGroup(channelType, platformId),
           unknown_sender_policy: 'public',
           created_at: createdAt,
         });
diff --git a/setup/migrate-v2/shared.ts b/setup/migrate-v2/shared.ts
index ff219df..58c0b16 100644
--- a/setup/migrate-v2/shared.ts
+++ b/setup/migrate-v2/shared.ts
@@ -74,6 +74,27 @@ export function v2PlatformId(channelType: string, jid: string): string {
   return id.startsWith(`${channelType}:`) ? id : `${channelType}:${id}`;
 }
 
+/**
+ * Infer messaging_groups.is_group from a v2 platform_id, given a channel type.
+ *
+ * v1 didn't track is_group, but most channels encode it in the JID/id format:
+ *   - whatsapp: `<id>@g.us` is a group, `<id>@s.whatsapp.net` / `@lid` is a DM
+ *   - telegram: negative chat IDs are groups, positive are DMs
+ *   - everything else: default to 1 (group/channel) — least-surprising guess
+ *     for chats v1 chose to register, where DM auto-create paths weren't used
+ */
+export function inferIsGroup(channelType: string, platformId: string): number {
+  if (channelType === 'whatsapp') {
+    return platformId.endsWith('@g.us') ? 1 : 0;
+  }
+  if (channelType === 'telegram') {
+    // platform_id is `telegram:<chatId>` — negative chatId means group/channel.
+    const chatId = platformId.replace(/^telegram:/, '');
+    return chatId.startsWith('-') ? 1 : 0;
+  }
+  return 1;
+}
+
 // ── Trigger mapping ─────────────────────────────────────────────────────
 
 /**