I build the boring parts of magic.

I'm Mateus Coutinho Marim, a software engineer based in Juiz de Fora, Brazil. For the last four years I've worked full-time at TrainWithMe across the stack — backend services in Python and Java, native Android in Kotlin, and a specialty thread in agent systems and browser automation. On the side I run my own self-hosted infrastructure — a small homelab.

My background is computer science at UFJF, where I spent several years contributing to research across machine learning systems, applied ML for network traffic analysis, computational linguistics with FrameNetBrasil, and IoT cryptography — six co-authored publications and contributions to UFJF-MLTK, a C++ machine learning toolkit.

Today I spend most of my time on production code. The agent framework I'm proudest of escalates across four representations of a web page — DOM, accessibility tree, vision pixels, with a supervisor on top — and is in production at TrainWithMe.

What I like working on, in plain terms: agent systems with honest cost models; browser automation that knows when to use which lens; small self-hosted production stacks where I own every layer; and the long, unglamorous middle of taking a system from prototype to something that runs unattended for a year.