Tech Giants Sign Open Weights Letter, Anthropic Holds Out

Recently, an open letter titled "Open Weight and US AI Leadership," championed by Nvidia and Microsoft, has been signed by numerous AI giants and startups. However, Anthropic has yet to join, making its absence a focal point in the industry.

Confirmed

Google, Meta, OpenAI, Amazon, AMD, Cisco, Cloudflare, along with startups like Bolt and Agno, have all signed the letter. The core argument is that US AI leadership should rely on an open ecosystem rather than just a single frontier model. The letter defines "open weight" as downloadable and auditable models, viewing this as the next step in a long-term bet on open source. Signatories like Amazon stated the move aims to support customers' freedom to choose between AI models, maintaining a coexistence of open and closed source.

Unconfirmed

Anthropic currently remains one of the few prominent AI labs that has not signed the letter. The specific official reasons for its refusal to join remain unclear.

Why it matters

This joint letter is more than just a statement on technical approaches; it represents a broad alignment of industry stances. According to analysis by @basedalexandoor, Anthropic's absence has turned into a game of brand positioning, and its strategy of "holding its ground" continues to generate visibility and controversy.

2026-07-27 ~ 2026-07-28 · 8 related posts

Primary sources

Amazon signs the open-weights letter, backing open and closed models as complements — firstadopter · 2026-07-28 07:46 (UTC+08:00)
Google, Meta and OpenAI sign open AI coalition letter as Anthropic stays out — FinanceYF5 · 2026-07-28 15:19 (UTC+08:00)
Open Weights letter argues U.S. AI leadership needs a broad open ecosystem — tomchapin · 2026-07-28 03:18 (UTC+08:00)

Anthropic's choice on an industry sign-on list turns into branding theater — basedalexandoor · 2026-07-27
Agno backs the open-weights letter alongside a long list of AI companies — pritisinghhhh · 2026-07-27
Bolt signs open-weights letter as it doubles down on open source — damianplayer · 2026-07-28
[source] Open Weights letter argues U.S. AI leadership needs a broad open ecosystem — tomchapin · 2026-07-28
[source] Amazon signs the open-weights letter, backing open and closed models as complements — firstadopter · 2026-07-28
[source] Google, Meta and OpenAI sign open AI coalition letter as Anthropic stays out — FinanceYF5 · 2026-07-28

2 near-duplicate retellings: pritisinghhhh · rohanpaul_ai