Microsoft's Phi family of small models trained for strong reasoning at low cost.
Phi is Microsoft's family of small language models, built on the idea that carefully curated training data can give a small model reasoning ability well beyond its parameter count.
The result is models that run cheaply yet handle reasoning and coding tasks surprisingly well, released under a permissive MIT license.
Where it's ideally used
A fit when you need genuine reasoning from a small, cheap-to-run model with a permissive license.
Where it doesn't fit
A small model still has limits — broad world knowledge and the hardest tasks favour a larger one.