Before it
Open models were released as final checkpoints with no training history.
The problem
You cannot study how capabilities emerge if you only see the finished model.
What it introduced
Sixteen models across scales, trained on identical data in identical order, with 154 checkpoints each released.
Why it matters
It turned training dynamics into something outsiders could actually study, including memorisation and bias formation.
What modern models inherit
Open checkpoints and data order as research infrastructure.
What came next
OLMo extended the fully-open approach to frontier-adjacent scale.