Key points
- The "Open Weights and American AI Leadership" letter grew from 25 signatories on July 24 to 35 the next day.
- OpenAI added its name after skipping the launch. Anthropic has not signed and declined to comment.
- Google and Amazon did not sign, though Google CEO Sundar Pichai posted his support. Nvidia (NVDA), Microsoft (MSFT) and Meta (META) signed at launch.
- Update, July 27, 2026: the list now carries 133 names. Google and Amazon (AMZN) both signed after this article published. Anthropic still has not.
Update, July 27, 2026: The signatory list has since grown to 133 names on the copy hosted by Microsoft. Google and Amazon (AMZN) have both signed, along with AMD, Intel (INTC), SpaceX, CoreWeave (CRWV), Databricks, SAP, Siemens, Comcast (CMCSA) and Uber (UBER). Anthropic and xAI are the notable absences. Anthropic chief executive Dario Amodei published the company's position on July 27, writing that Anthropic "has never advocated for a ban on open-weights models." We covered what he does want here.
OpenAI has signed the open-weights letter it was absent from a day earlier. The letter, titled "Open Weights and American AI Leadership," was published July 24 with 25 signatories. Ten more organizations have since joined, bringing the total to 35.
Anthropic has not signed. The company declined to comment on the letter.
Nvidia (NVDA) chief executive Jensen Huang shared the letter in his first post on X on July 24. Microsoft (MSFT) chief executive Satya Nadella posted it nine minutes later. We covered the original 25 signatories and what the letter says here.
OpenAI added its name after the launch
Sam Altman posted on X before his company signed. "i want the US to win in AI both in open source and proprietary models, and i am glad to see this," the OpenAI chief executive wrote.
Journalist Tae Kim reported the signature. "OpenAI tells me they signed the Nvidia-Microsoft open-source/open-weights AI model letter today," Kim wrote.
OpenAI president Greg Brockman has said open-weight access "is something that really needs to be democratized."
Accounts differ on the exact timing. Some reports place OpenAI's signature on the afternoon of Friday, July 24. Others date it to July 25.
Amodei has argued against open-source scaling
Anthropic chief executive Dario Amodei has told Congress that "the scaling of open source models, I think it's going down a very dangerous path." He has separately described open source as "a red herring."
OpenAI and Anthropic both warned officials this year that China's open-source ecosystem threatens American AI leadership. OpenAI has now signed a letter opposing restrictions on open models. Anthropic has not.
Anthropic sells access to closed frontier models as its core business. Its most recent private valuation was near $965 billion, and the company has been reported to lead OpenAI in enterprise adoption. Three of the letter's signatories, Meta, Mistral and Hugging Face, publish open-weight models that anyone can download at no cost.
Where the largest AI companies stand
| Company | Status |
|---|---|
| Nvidia (NVDA) | Signed July 24 |
| Microsoft (MSFT) | Signed July 24 |
| Meta (META) | Signed July 24 |
| Palantir (PLTR) | Signed July 24 |
| OpenAI | Signed after the launch |
| Google (GOOGL) | Not signed at the time, added by July 27 |
| Amazon (AMZN) | Not signed at the time, added by July 27 |
| Anthropic | Not signed, declined to comment |
Google, a unit of Alphabet (GOOGL), and Amazon (AMZN) are not on the signatory list. Google chief executive Sundar Pichai posted his backing for the letter on X on July 25 without the company adding its name.
Very happy to support this on behalf of Google. We have long benefited from open source, are big contributors to open source and in fact have consistently made open weights models with Gemma available from @GoogleDeepMind @demishassabis.
See Sundar Pichai's post on X
Gemma is Google's family of open-weight models, released by Google DeepMind. xAI has also been reported to support the letter without signing it.
The original 25 signatories included Meta (META), Palantir (PLTR), IBM, Dell Technologies (DELL), CrowdStrike (CRWD), ServiceNow (NOW) and Box (BOX), along with Mistral, Mozilla, Hugging Face, Perplexity, the Linux Foundation, Andreessen Horowitz and Y Combinator.
Ten organizations were added to the letter after the launch. They are OpenAI, Cisco (CSCO), Palo Alto Networks (PANW), DoorDash (DASH), GitHub, Cohere, Fireworks AI, Nous Research, OpenClaw and Prime Intellect. GitHub is owned by Microsoft, which signed at launch.
What the letter asks for
The letter asks policymakers to expand computing access for startups and researchers and to avoid "premature restrictions on open models that stifle competition or drive innovation overseas."
It also states: "Our AI leadership will be judged not by one frontier AI model, but by whether the United States builds a strong, open ecosystem that diffuses into every sector."
The letter defines open-weight models as "AI models that anyone can download, inspect, modify, and run on their own infrastructure." Closed models are reachable only through the developer's own service.
We wrote on July 24 that OpenAI and Anthropic had both stayed off the letter. That is no longer the case for OpenAI. Nvidia reports fiscal second-quarter results on August 26.
Sources
- "Open Weights and American AI Leadership," dated July 24, 2026, and its published signatory list
- Posts by Jensen Huang, Satya Nadella and Sam Altman on X, July 24, 2026
- Tae Kim's reporting on OpenAI's signature
- Dario Amodei's congressional testimony and public remarks on open-source models
- Anthropic declined to comment
