Before it
A model trained at 2K tokens broke down badly past that length.
The problem
Retraining from scratch at longer context is prohibitively expensive.
What it introduced
Scale RoPE position indices down to fit the trained range, then fine-tune briefly. 32K context from a 2K model in a thousand steps.
Why it matters
It made long context an affordable post-hoc upgrade rather than a training-time commitment.
What modern models inherit
Context extension as a cheap fine-tuning step.
What came next
YaRN and LongRoPE refined it; nearly every long-context open model uses some variant.