CREATE TABLE IF NOT EXISTS `chat_messages` (
  `id` INT AUTO_INCREMENT PRIMARY KEY,
  `session_id` INT NOT NULL,
  `sender` ENUM('user', 'assistant') NOT NULL,
  `message` TEXT NOT NULL,
  `sources` TEXT,
  `created_at` TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
  FOREIGN KEY (`session_id`) REFERENCES `chat_sessions`(`id`) ON DELETE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;