Building at Subvisual
Co-founder of a product design and engineering studio, fifteen years in and still in the codebase. Elixir and Phoenix where I choose; Rails where history chose for me.
Software engineer · co-founder of Subvisual · Birmingham, UK
Luís
Zamith
Ferreira
Elixir by choice, Rails by history, JavaScript by fate.
Fifteen years building Subvisual, a product design and engineering studio, and refusing to stop writing code. These days I lead our agentic AI practice. This page is laid out like a board game because I couldn't talk myself out of it.
Contents of box
- 1 studio, co-founded
- 1 agentic AI practice, led
- 7 conference talks
- 3 conferences, organised
- 12 products, in progress
- n pitch decks, red-penned
- 3 unfinished essays
- 1 garden, optimistic
Roll for a fact
Sixes are worth more than they look.
The board — you are on space 1 of 5
1 · Now
Current turn · Aug 2026Leading our agentic AI practice
Past the demos: how review changes, who owns the output, which habits deserve to survive.
Organising AlchemyConf
The Elixir conference in Braga. Deliberately small. RubyConf Portugal and MirrorConf before it. I answer the emails.
12 in 12
Twelve products in twelve months, roadmap by public vote. Being wrong on schedule, with witnesses.
2 · Speaking & community
Talks, in the order they happened
2026
Goatmire
Branching Out with Ecto: Crafting a Git Adapter That Nobody Asked For
2025
flatMap Oslo
Winter is coming
2023
CodeDaze
Crystal: the programming language
2019
Functional Conf, India
Umbrella apps: microservices with the infrastructure included
2015
RailsPacific
Testing Rails without hating it
2014
Eurucamp
Refactoring towards boredom
2012
Codebits
Shipping something in 48 hours
Mini-game · which year?
Round 1/5 · 0 right
Which year did I speak where?
Four options, one of them right. No prizes.
Organiser
AlchemyConf, the Elixir conference in Braga, small on purpose. Before it, RubyConf Portugal and MirrorConf. I do the venue, the budget and the schedule that survives contact with reality.
Teaching
Workshops, bootcamps and university courses on web development. Explaining a thing out loud is the fastest way to find the hole in it.
Advising
Early-stage founders, on product strategy and the pitch deck that has to carry it. Mostly I ask the question the room will ask, before the room does.
3 · Projects
Side projects, various states of repair12 in 12
One product a month for a year, roadmap voted on in public. Deadlines you can't quietly move.
git_ecto_adapter
An Ecto adapter that stores your data in a git repository. Nobody asked for it; there is a whole talk about why I wrote it anyway.
crystalshards
A listing of every Crystal shard there is. Built back when the ecosystem was small enough that someone had to index it.
Open source
Elixir libraries and small tools. Some maintained, the rest honest about it.
Campaign track · 12 in 12
One project a month, twelve times over
Each square is a month and a separate product. The community votes on what goes in the empty ones, which means I have handed the roadmap to strangers on purpose.
In progress · month 2
Forge
Forge yourself. Being built now, aimed at July, which is a statement of intent.
Shipped
In progress
Open to votes
Expansion pack · unlocked by rolling three sixes
Things I have quietly abandoned
Two static site generators, one note-taking app, a Portuguese tax calculator, and a board game about the wool trade that got as far as printed prototypes. Every one of them taught me something I have since used in paid work, which is the only defence I have.
4 · Writing
Published, not drafted · 2013 onwards
AI · Engineering
The Lesson Every AI Builder Should Remember
A tool built without a view on how it gets used is not a neutral tool. What the people who build AI owe the people who run it.
Web3 · Solidity
Solidity Spotlight: Populating Arrays
Fixed against dynamic, memory against storage, and which of those choices the compiler will not let you undo.
Product
Your tech stack matters
No stack saves a product, but the wrong one makes it slow to change. Pick for ease of change and for the people who have to live in it.
Elixir · Ecto
Upsert statements with Ecto
Insert or update in one atomic statement, conflict handling and all, instead of three round trips and a race condition.
Craft
Clean Architecture
Entities, interactors and boundaries in a Rails app, so the tests stop waiting on the framework. Thirteen years old and I still argue it.
Archive
Twenty-six posts, back to 2013
Ruby Bits, git tricks, Crystal on Heroku, accessibility, open source Fridays. The whole run on Subvisual's blog.
5 · About
One player, fifteen years
Fifteen years of Subvisual, a product design and engineering studio built from nothing with people I still like. These days I lead its agentic AI practice, advise early-stage founders, and teach web development to anyone who will sit still for it. Portuguese, living in Birmingham. The rest is below.
- Birmingham, UK
- Elixir · Phoenix
- Ruby on Rails
- Agentic AI
- Advising founders
- Teaching
- Padel
- Ultimate frisbee
- Basketball
- Board games
- Economic history