A Base model is a pretrained starting point and is not required to follow instructions. An Instruct model has already been aligned for conversation and instruction following. Reasoning is not always a mutually exclusive class: a model can be both reasoning-capable and instruct-tuned.

For a narrow, structured domain adapter, Instruct is the default. Use RAG for frequently changing knowledge and constrained decoding when output shape must be guaranteed.

First thought

Use Instruct below 300 rows and Base above 1,000 rows.

Correction

There is no universal row threshold; task, quality, token volume, and starting capabilities must be evaluated together.

Decision rule

Narrow, structured assistant task → start from an Instruct checkpoint.

Base, Instruct, and Reasoning