Twitter CEO Linda Yaccarino took a not-so-subtle dig at the app’s biggest competitor on Monday. Boasting the “largest usage day since February,” Yaccarino took a shot at Meta’s newly launched Threads. “There’s only ONE Twitter,” she said. “You know it. I know it.” Minutes later, owner Elon Musk was in her replies, where he made a bold proclamation. “I think we may hit an all-time record this week,” he said. Musk has gone after Threads and Meta owner Mark Zuckerberg all week since the launch of the new app, which surpassed 100 million users on Monday—just five days after its public release.