Elon Musk's artificial intelligence company xAI has signed an agreement to allow the military to use its model, Grok, in classified systems, a Defense official confirmed to Axios.Why it matters: Up to now, Anthropic's Claude has been the only model available in the systems on which the military's most sensitive intelligence work, weapons development and battlefield operations take place. But the Pentagon is threatening Anthropic in a dispute over safeguards and may soon need a replacement. Anthr...