Exploring the frontiers of language models, agents, and software design.

A collection of notes, essays, and technical deep dives by Ivan Leo.

Currently building general agents for knowledge work at Manus.

Featured Series

Building an Agent

A comprehensive series on building AI coding agents from scratch, covering everything from basic tool integration to advanced features like agentic search and subagents.

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1 PartsIn Progress

LLMs From Scratch

Working through Stanford's CS336 and documenting what I learn at each step — from tokenization to training.

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Latest Articles

Reversing Chinese Poetry

Creating our first RL Pipeline with Verifiers

Jan 2, 2026·Reinforcement Learning From Scratch

Three Lessons I've Learned at Manus

Lessons learnt from going from zero to $100M ARR in 8 months

Dec 22, 2025

Implementing BPE

Building a Byte-Pair Encoding tokenizer from scratch

Nov 30, 2025·LLMs From Scratch

Spinning Up RL

Getting started with reinforcement learning

Nov 9, 2025·Reinforcement Learning From Scratch

Agentic Search

Models can't do much without the right context, agentic search does just that

Oct 11, 2025·Building an Agent

Building your own AI SDK

Switch between models with your own custom router

Oct 9, 2025·Building an Agent

Building a Coding CLI with React Ink

Migrating Our Coding Agent to React Ink

Jul 17, 2025·Building an Agent

Building An Agent

Implementing a coding agent in around 200 lines of Javascript code

Jul 16, 2025·Building an Agent