Before it
Open weights trailed the closed frontier by a clear margin.
The problem
Nobody had released a model that could stand beside GPT-4 class systems.
What it introduced
405B parameters, 128K context, a candid 90-page account of the training, and a licence permitting distillation from outputs.
Why it matters
Open weights reached the frontier, and the distillation clause seeded a generation of smaller models.
What modern models inherit
The expectation that open weights compete at the frontier, now contested.
What came next
Llama 4's MoE in 2025, then Meta's pivot to closed models in 2026.