# Jarle Mathiesen

> Senior software engineer in Oslo, Norway. I build products in product teams, use AI to raise the quality and scope of the work, and have shipped AI-powered products to real users.

I’m a senior software engineer in Oslo. I do my best work in product teams, close to the users and the problem, taking ideas all the way to something people rely on every day.

For eight years I’ve built systems where the numbers have to be right: pension premium calculation for Norway’s largest public pension provider, and reporting and invoicing at Posten Bring.

I use AI to raise both the quality and the scope of what I build, and I’ve shipped products with AI at the core: SummYT, a video summarizer with more than 200,000 registered users, and an assistant that analyses Posten Bring customers’ reports and invoices.

Currently: Senior consultant at Knowit, on the Analytics team at Posten Bring. Our department owns Mybring, the self-service platform for Posten Bring’s business customers, and my team works on its reporting and invoicing. Outside work I maintain open-source projects around AdonisJS.

## About

- [CV](https://mathiesen.dev/cv): Full work history, projects, skills and education. Markdown: https://mathiesen.dev/cv.md
- [SummYT](https://summyt.app): AI summaries of YouTube videos, as a web app and a browser extension. Launched in 2023 as YouTube Summarized. Full stack, built and run by me.
- Mybring AI assistant: An assistant that helps Mybring’s business customers work with their reports and invoices. Domain-specific tools let it run aggregations and analysis on their actual data, not just answer questions.
- [Matstack](https://matstack.dev): react-adonisjs: full-stack React Router apps on AdonisJS 6, with ORM, auth and dependency injection built in.
- Talk: “Your Service Layer Is a Mess (Here’s a Simple Fix)” (Lightning talk, JavaZone 2026) https://2026.javazone.no/program/6f24def7-8a7a-4316-b20e-f5a1ddc801b9: Service layer patterns for backend applications. The fix ships as installable agent skills alongside the slides.

## Writing

- [Cognitive Debt](https://mathiesen.dev/writing/cognitive-debt.md): If agents write more of our systems, what happens to the human understanding required to operate, change, and trust those systems over time?
- [Understanding Email Under the Hood](https://mathiesen.dev/writing/understanding-email-under-the-hood.md): A developer's guide to how email actually works, from MIME and MX records to SMTP, SPF, DKIM, and DMARC.

## Elsewhere

- [Email](mailto:jarle@mathiesen.dev)
- [GitHub](https://github.com/jarle)
- [LinkedIn](https://www.linkedin.com/in/jarle-mathiesen)
- [X](https://x.com/jarlemathiesen)
- [RSS](https://mathiesen.dev/rss.xml)