Llama 3.1 405B: the first frontier-class open-weights model
Confirmed
Importance: major (4 of 5)The takeaway
Meta released Llama 3.1 including a 405B-parameter model with 128K context, which Meta said was competitive with GPT-4o and Claude 3.5 Sonnet — the first openly downloadable model at the frontier.
Status
- Claim
Confirmed
- Our reporting
- High confidence
- Importance
- Major (4 of 5)
- Last verified
- 29 September 2026
Your AI and this story
- GPT-6 AstraIn its training data
- Claude Opus 5.5In its training data
- Gemini 4 HydrogenIn its training data
- Grok 4.7In its training data
It happened before the cutoffs of all four assistants, so it can be in their training data.
Key facts
- Released 23 July 2024
- Sizes: 8B, 70B, 405B; 128K context
- 405B trained on over 15T tokens using more than 16,000 H100 GPUs
- Mark Zuckerberg published ‘Open Source AI Is the Path Forward’ alongside
What happened
Meta released open weights for a dense 405B model along with a detailed technical report.
Why it matters
Narrowed the open–closed gap to months; open frontier weights reshaped policy debates and enabled wide distillation.
Sources
2 sources from 2 sites. Numbers match the chips in the text.
2 sources: 2 primary
Primary
- Introducing Llama 3.1 (Meta AI)ai.meta.com, official
- The Llama 3 Herd of Models (arXiv)arxiv.org, paper
Changes
- Filed