Build a Reasoning Model (from Scratch)

Reasoning models break problems into steps, producing more reliable answers in math, logic, and code. These improvements aren’t just a curiosity–they’re already integrated into top models like Grok 4 and GPT-5. Build A Reasoning Model (From Scratch) demystifies these complex models with a simple philosophy: the best way to learn how something works is to build it yourself! Large language models can perform strong reasoning tasks, but using them alone is not enough. To build powerful applications, you need to know how to create and customise them. This book guides you to build your own reasoning model. It explains complex ideas in a simple way and shows how to build a model that can reason. Pretrain a large language model for general text generation. Fine-tune the model to improve reasoning tasks. Evaluate model performance using standard benchmarks. Understand the complete, hands-on project of building a reasoning model. Learn to customise the model using your own data. Build a Reasoning Model (From Scratch) is a practical guide to creating your own large language models. The book takes you through a complete hands-on project. You will learn to prepare data, pretrain a model and fine-tune it for reasoning. The author explains each step clearly so that you can build a working model. After reading this book, you will have the skills to build and adapt your own reasoning models. You can move beyond using existing tools and start creating your own intelligent systems. This book is for readers who know Python and have some knowledge of machine learning.