I’m Omar U. Espejel. I work on AI and crypto at Starknet Foundation. Before that I worked on crypto at StarkWare and machine learning engineering at Hugging Face.
Here I write notes and essays about AI engineering, crypto, proof systems, and product work. A lot of the pieces start as research in progress. I try to make the idea clear enough that someone else can inspect it, reproduce it, or disagree with it.
Open-source AI
40,297
downloads of models and datasets I publish
18 models, 8 datasets and 85 followers on Hugging Face, publishing there since 2022
All-time figures, read when this page is built. Downloads are the sum of downloadsAllTime over every
public repository, so check the numbers yourself:
models,
datasets,
profile.
Teaching
I teach 4 courses on Platzi, in Spanish: 94 classes and about 14 hours of recorded material, rated 4.8 out of 5 across 472 student reviews.
| Course | Classes | Rating | Reviews |
|---|---|---|---|
| Curso de LangChain | 37 | 4.8 | 192 |
| Curso de Transfer Learning con Hugging Face | 17 | 4.8 | 114 |
| Curso de Redes Neuronales con PyTorch | 24 | 4.7 | 93 |
| Curso de Experimentación en Machine Learning con Hugging Face | 16 | 4.8 | 73 |
Course figures read from the public Platzi course pages on 2026-08-17.
Podcast
I host Hacia Afuera, a Spanish-language deep tech podcast: 85 episodes and 76 hours of conversation since 2021, with researchers and builders in AI, quantum computing, cryptography and neurotechnology. It is on Spotify, Apple Podcasts and Deezer.
Recent essays
- 18 min
418,665 AI Agents, and 145 With a Review a Bot Didn't Write
- agents
- ethereum
- onchain-data
I read all 558,094 reputation events ever written to ERC-8004. 300,692 of them (53.9%) are about one agent: a mining coordinator, rated by the 57 wallets that mine for it, score 1 every time. It stopped writing them on 17 August 2026. On Ethereum, 145 agents out of 50,127 have a review from anything that is not a crawler. I wrote the Starknet integration for this standard, so this is a post-mortem of something I shipped on.
- 7 min
The Environment Contract Is Part of the Product
- agents
- engineering
A postmortem on an auth flag regression in an agent-built app, and the deploy contract that stops stale environments from becoming releases.
- 11 min
What a Proof Is Allowed to Mean
- verifiable ai
- proof systems
A guide to the missing receipt around proof artifacts: how proof bytes, statement meaning, verifier domain, and replay assumptions become one accepted object.
- 13 min
Proof Validity Is Not Statement Validity
- verifiable ai
- proof systems
A proof can verify while the AI claim around it is still relabelable. In a local EZKL-style receipt test, the proof-only path rejected 1 / 7 relabels; the statement-envelope path rejected 7 / 7.