OpenAI, Anthropic Skip 25-Firm Open-Weights AI Coalition Letter

The tell in the open-source AI fight this week was not what the letter said, but who did not sign it. Twenty-five companies, including Nvidia, Microsoft, Meta, IBM, Hugging Face, Palantir, Mozilla and the Linux Foundation, published a July 24 letter titled 'Open Weights and American AI Leadership' urging US policymakers not to impose premature restrictions on open-weight AI models, according to CNBC. The names missing from the top were the ones you would notice: OpenAI, Anthropic, Alphabet and Amazon.

OpenAI eventually added its signature after the omission was widely noticed, and Sam Altman reposted a note on X in support of open-source models. Anthropic held out. Dario Amodei has described open source as 'a red herring,' saying he does not think it works the same way in AI as in other areas. The New York Times frames the split as a quieter Washington lobbying push by the two closed-model leaders running underneath Altman's public openness, while their nominal peers line up on the other side of the debate.

The context matters. Moonshot AI's Kimi K3, released in mid-July and backed by Alibaba, is a 2.8-trillion-parameter open model that the company benchmarks as performing neck-and-neck with Anthropic's and OpenAI's proprietary systems on several tasks, at API prices of $3 per million input tokens and $15 per million output tokens, as VentureBeat reported. If a Chinese open-weight model can approximate frontier US capability at meaningfully cheaper inference cost, the commercial ground under closed-API business models shifts. That is the backdrop for David Sacks accusing the closed labs of lobbying to ban open-source rivals in what he calls regulatory capture, and Suhail Doshi arguing that American labs trained on 'humanity's data and didn't pay a cent' before what he calls lobbying to ban open-weight models 'in the name of distillation.'

Take the specifics as reported, not settled. What the coverage does not give you is the actual legislative text or executive order the closed labs are said to be pushing, or a clean read on where the White House lands, since PBS has reported the administration sees no need to restrict open source AI 'for now.' The forward question is whether the open-weights coalition can convert a signed letter into durable policy cover before any distillation or export rule is drafted, which is the moment Nvidia, Meta, Hugging Face and the startups behind Andreessen Horowitz's name on the letter actually need it.