Open-source tools and small sites I have built, most of them around public data or things I use every day. I built most of them with the coding agents Claude Code and OpenAI Codex, and in Google Antigravity, an agent-first development environment.
A local dashboard for everything Claude Code loads when you start working in a project folder: the instructions files, the settings and permissions, the plugins, servers, skills, subagents, hooks and memory notes, each with the file that decided it, how much it adds at startup, a switch to turn it off and an editor to change it.
A guide to what the independent and repertory cinemas of Buenos Aires are showing today and over the next week. Agents read the listings of some thirty venues, and the site merges those readings into one schedule and rebuilds itself every day.
An R package for the citizen complaints and requests (SUACI) that the Buenos Aires city government publishes as open data. It downloads any year from 2011 onward, harmonizes the column names, which change from year to year, and repairs the coordinates, which in the source files come mis-scaled, in a local metric system, or missing.
A macOS app that plays the same audio through two output devices at once, in any combination of Bluetooth and wired. It installs a virtual output device called Dual Audio, and whatever is sent there goes to both devices you pick, each with its own volume.
A chess game that trains you on real mistakes. You give it a Lichess or Chess.com username, and it serves positions from that player's recent games where the move played lost the most, scoring your answer against Stockfish, which runs in the browser. One player alone, or two taking turns on the same device.
A search engine for the job listings of EURAXESS, the European Union's research jobs portal. It crawls the postings into a local database and searches them by meaning as well as by keyword, so it finds jobs that describe the same work in different words. Everything runs on your own machine.