diff --git a/scripts/package.json b/scripts/package.json
index 0c563c71..f6894bfe 100644
--- a/scripts/package.json
+++ b/scripts/package.json
@@ -6,6 +6,7 @@
   "scripts": {
     "hello": "tsx ./src/hello.ts",
     "seed": "tsx ./src/seed.ts",
+    "remove-chat": "tsx ./src/remove-chat.ts",
     "typecheck": "tsc -p tsconfig.json --noEmit"
   },
   "dependencies": {
diff --git a/scripts/post-merge.sh b/scripts/post-merge.sh
index 4f0889d6..396547d3 100644
--- a/scripts/post-merge.sh
+++ b/scripts/post-merge.sh
@@ -1,6 +1,11 @@
 #!/bin/bash
 set -e
 pnpm install --frozen-lockfile
+# Task #511: idempotent destructive cleanup of the removed Chat feature
+# (drops chat tables, deletes chat-related notifications, removes the chat
+# app catalog row + link rows). Runs before push so push won't see chat
+# tables in the live DB that aren't in the schema. Safe to run repeatedly.
+pnpm --filter scripts run remove-chat
 pnpm --filter db run push-force
 # Idempotent: ensure the default groups exist and existing users are mapped
 # (Admins, Tx, Everyone). Safe to run repeatedly.
diff --git a/scripts/src/remove-chat.ts b/scripts/src/remove-chat.ts
new file mode 100644
index 00000000..e1c7af03
--- /dev/null
+++ b/scripts/src/remove-chat.ts
@@ -0,0 +1,80 @@
+import { pool } from "@workspace/db";
+
+async function tableExists(table: string): Promise<boolean> {
+  const result = await pool.query(
+    `SELECT 1 FROM information_schema.tables WHERE table_schema = 'public' AND table_name = $1`,
+    [table],
+  );
+  return (result.rowCount ?? 0) > 0;
+}
+
+async function main(): Promise<void> {
+  const client = await pool.connect();
+  try {
+    await client.query("BEGIN");
+
+    for (const table of [
+      "message_reads",
+      "messages",
+      "conversation_participants",
+      "conversations",
+    ]) {
+      if (await tableExists(table)) {
+        await client.query(`DROP TABLE IF EXISTS "${table}" CASCADE`);
+        console.log(`[remove-chat] Dropped table ${table}`);
+      }
+    }
+
+    if (await tableExists("notifications")) {
+      const r = await client.query(
+        `DELETE FROM notifications
+          WHERE related_type = 'conversation' OR type = 'chat'`,
+      );
+      if ((r.rowCount ?? 0) > 0) {
+        console.log(
+          `[remove-chat] Removed ${r.rowCount} chat-related notification row(s)`,
+        );
+      }
+    }
+
+    if (await tableExists("apps")) {
+      const idRes = await client.query(
+        `SELECT id FROM apps WHERE slug = 'chat'`,
+      );
+      const chatAppId = idRes.rows[0]?.id as number | undefined;
+      if (chatAppId !== undefined) {
+        for (const link of [
+          "user_app_orders",
+          "app_opens",
+          "app_permissions",
+          "group_apps",
+        ]) {
+          if (await tableExists(link)) {
+            await client.query(`DELETE FROM "${link}" WHERE app_id = $1`, [
+              chatAppId,
+            ]);
+          }
+        }
+        await client.query(`DELETE FROM apps WHERE id = $1`, [chatAppId]);
+        console.log(
+          `[remove-chat] Removed chat app (id=${chatAppId}) and link rows`,
+        );
+      }
+    }
+
+    await client.query("COMMIT");
+  } catch (err) {
+    await client.query("ROLLBACK");
+    throw err;
+  } finally {
+    client.release();
+  }
+}
+
+main()
+  .then(() => pool.end())
+  .catch(async (err) => {
+    console.error("[remove-chat] failed:", err);
+    await pool.end();
+    process.exit(1);
+  });