Name: Felix Cumarav Subject: Building things that work Time allowed: all night
Hire Felix.
Problem 0. Prove that one person can be a full-stack developer, an AI engineer and an ML engineer. Show your work.
- Full-stack developer
- AI engineer
- ML engineer
- Kaggle competitor
- Math Olympiad
Face not included.
Beat three thousand teams.
Kaggle is where thousands of ML engineers fight over the fourth decimal place of a leaderboard. I like it there. My last competition ended 13th out of more than 3000 teams, and I keep entering.
- Kaggle Playground S6E8: Predicting Smartphone AddictionFive-fold-honest stacking pipeline on 691k rows, with a shared out-of-fold ecosystem. Best public leaderboard ROC AUC 0.97128.
- Gemma 4 Developer Agent (Google DeepMind)Post-training Gemma 4 31B into an offline agent that fixes real repository issues, SWE-Bench style. 1500+ teams in the main track, plus a paper track.
Do the maths. Then the AI.
I go to the Math Olympiad, where the problems have no tutorial and the answer is a proof. That habit is why my models get debugged, not just retrained.
Math Olympiad
Competition mathematics. Proofs, combinatorics and a high tolerance for being stuck.
Czech AI Olympiad 2026
Team notokens. Regional round Prague, then the national final. We built an AI legal cofounder for public administration.
Hackathons
Build something that works in a weekend, then keep the parts that survive.
Show that it ships.
Everything I have built so far: shipped products, agents, hardware, client work and a few things I made just to see if they would work. Filter it, or scroll through it all.
What is on my desk right now.
Websites and apps for real clients. I send the offers, then build them.
- Poker appFull product offer sent
- Honza PiblWebsite audit and offer sent
- JL groupWebsite and 2026 marketing plan
- More under NDA██████ ████
Given the following tools.
Full stack
- React
- Next.js
- TypeScript
- Node.js
- Java
- Spring Boot
- PostgreSQL
- Redis
- Prisma
- Docker
- Linux
- Expo
AI engineering
- LLM agents
- RAG
- Embeddings
- Prompt engineering
- Fine-tuning
- LoRA
- Voice agents
- OpenAI API
- Anthropic API
- LangChain
Machine learning
- Python
- Gradient boosting
- CatBoost
- Stacking and blending
- Cross-validation
- PyTorch
- Keras
- GPU and TPU training
Short answers.
Who is Felix Cumarav?
Felix Cumarav is a full-stack developer, AI engineer and ML engineer based in Prague, Czechia. He builds web and mobile products, LLM agents and machine learning pipelines, and works with clients remotely.
How did Felix Cumarav place on Kaggle?
His latest Kaggle competition ended 13th out of more than 3000 teams. In Kaggle Playground S6E8 he built a five-fold stacking pipeline on 691k rows with a best public leaderboard ROC AUC of 0.97128.
What has Felix Cumarav built?
Products include Připojto (a trailer rental platform with an Expo app, Next.js admin, Stripe and smart locks), Virlya (an AI content SaaS), SPNDR (an AI finance tracker) and Forksy (a nutrition app). He also built the Kestrel and LAI autonomous agent, the JARVIS voice agent and a 20-DOF humanoid robot.
Which technologies does Felix Cumarav use?
React, Next.js, TypeScript, Node.js, Java, Spring Boot, PostgreSQL, Redis, Prisma, Docker and Expo for products. LLM agents, RAG, LoRA fine-tuning and voice agents for AI. Python, PyTorch and CatBoost for machine learning.
Is Felix Cumarav available for work?
Yes. He takes on websites, apps and AI projects for clients, and is fine with remote work. Contact: [email protected].
Passed with distinction.
Full-stack, AI and ML in one person, based in Prague and fine with remote. If you have a hard problem, I would like to see it.