Jan Haag

A Few Projects

• 2026 – now

  GymTrack

  A training log I built from the database schema and REST API to the web app, sign-in and charts. It runs in a small beta at app.gymtrack.ch. I moved my own history over with a validated CSV import, 106 workouts and 736 sets, with every count checked afterwards. Idempotency keys, transactions and row locks keep two saves at once from clashing.

  Code on GitHub

  

• 2026

  Running it myself

  GymTrack runs on a Linux server I set up and look after. Docker Compose keeps the database and API internal behind a reverse proxy. Prometheus and Grafana watch the services, alerts reach my phone, and encrypted backups leave the machine several times a day. A backup only counts once a restore test has passed.

  

• 2023 – 24

  Reading handwriting

  My Matura thesis, a small neural network in TensorFlow and Keras that recognises handwritten digits. It reached about 97.5% on the MNIST test set. Graded 6.0 out of 6.0.

  Code on GitHub

  

• 2026

  Retrieval, measured

  A Python pipeline that turns PDFs into searchable passages with page references and compares dense, BM25 and hybrid retrieval, with and without retrieved evidence, in a small FastAPI app. Built without a RAG framework, with 63 offline tests. I wrote a 60-question evaluation set, including unanswerable and prompt-injection questions; the live model evaluation is still pending.

  Code on GitHub

  

• 2026 – now

  Tab-List

  A native macOS window switcher in Swift. It lists every window across apps and desktops, not just one per app. Access to the operating system sits behind small adapters, so the logic can be tested, and CI takes care of signing, notarisation and signed updates.

  Code on GitHub