Meta Llama 3.1 405B Review — The First Open-Weight Frontier Model

Meta Llama 3.1 405B launched July 23, 2024 as the first open-weight model to benchmark competitively against GPT-4o and Claude 3.5 Sonnet. A 405-billion-parameter dense Transformer with a 128K context window — 16× wider than its predecessor — it shipped with tool use, multilingual support across 8 languages, and a commercial license. This review covers the architecture, benchmarks, deployment hardware requirements, API pricing, and its place in the history of open-source AI.