Senior Software Engineer, Agentic Harness Quality and Performance

You will join Paddington, our AI-native product line inside Goodnotes, and work directly with Steven, our founder, and a small team shipping new products. Engineers own the full cycle: they design, build, test, ship, and operate what they ship. Coding agents write the product code, and the engineer who merges it owns what lands.

You will ship product changes with a squad and build the harness around those agents: guides and automated checks that catch defects and performance regressions before the code merges. When a defect reaches users, or a user-facing path gets slower, you change the product code or the check and show the measurement. You'll be an individual contributor reporting to the Engineering Manager. We hire at Senior level and welcome Staff-level candidates.

• This role will be required to work on-site, 5 days per week in our London Paddington office
• This is a permanent role