An open letter urging the US to support rather than restrict open-weight AI models has received public support from all the major tech companies—except Anthropic. CEO Dario Amodei is now explaining why, suggesting that open AI models could empower attackers more than defenders. "Open models broaden defensive capability, increase transparency, and allow vulnerabilities to be discovered and remediated across many teams,” the letter says. Still, it’s no secret that open models threaten to reduce industry reliance on the top-tier closed models from OpenAI, Anthropic, and Google. The New York Times reports that OpenAI's allies have been quietly lobbying the White House for restrictions on China's open-weight models.