Compiling IR to NFA
Turn regex IR into a graph-based automaton for fast next-step lookup
Feb 9, 2026·Structured Outputs From Scratch
Exploring the frontiers of language models, agents, and software design.
A collection of notes, essays, and technical deep dives by Ivan Leo.
Previously built general agents for knowledge work at Manus (acq by Meta). Embarking on a new adventure soon.
Featured Series
View all series4 PartsIn Progress
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.
Start Reading
1 PartsIn Progress
LLMs From Scratch
Working through Stanford's CS336 and documenting what I learn at each step — from tokenization to training.
Start Reading
Latest Articles
ArchiveBuilding our FSM
Going beyond a simple regex to an FSM for quick lookups
Feb 8, 2026·Structured Outputs From Scratch
Pydantic to Regex: Compiling JSON Schemas for Structured Outputs
Build a recursive JSON Schema-to-regex compiler from first principles
Feb 2, 2026·Structured Outputs From Scratch
Know when to let the model cook
Taste is all that matters.
Jan 18, 2026
How I Broke Into AI Without a Roadmap
The messy, fast-changing path that took me from front-end engineering to LLMs.
Jan 12, 2026
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