Senior Full Stack Engineer - AI Harness
XeroXero, the New Zealand cloud software company, is looking for a Senior Full Stack Engineer to join the MyXero Ghostbusters squad within the Identity and Platform group. This role focuses on AI harnesses and automated verification to help software agents implement changes safely, supporting the platform that underpins every organisation and user record while handling hundreds of millions of daily requests. It’s a chance for someone who enjoys turning ambiguous platform challenges into solid architectural solutions and who’s happy to mentor teammates along the way.
The position is based in New Zealand with a flexible, remote-first setup and optional office access in Wellington or Auckland. If you prefer collaboration at a distance and value thoughtful, written communication, this could be a good fit. The team looks for people who like contributing to a steady pace of delivery while staying curious and open to learning together.
As part of the MyXero team, you’ll help modernise a massive system by turning it into decoupled domain services without upsetting downstream products. You’ll build automated verification loops and robust testing harnesses to reduce manual checks and boost reliability, while guiding teammates and shaping how engineering practices evolve when working with intelligent tooling.
Shaping AI harnesses for safer software
In this role you own a critical delivery stream on MyXero, taking ambiguous platform challenges from problem framing to durable architectural solutions. You’ll design the specifications, verification harnesses, and AI guardrails that enable software agents to perform implementations safely.
Your work supports the modernisation of the platform into decoupled domain services without disrupting dependent products. By engineering automated verification loops and robust testing harnesses, you’ll raise reliability, mentor team members, and influence how engineering practices operate with intelligent tools.
What you’ll need to bring
Strong full-stack or backend engineering experience with typed languages, ideally including exposure to C# and the .NET ecosystem.
Hands-on work with AI harnesses, coding agents, or automated verification pipelines in either a personal or professional setting.
Practical familiarity with distributed systems architecture, API design, data modelling, and managing complex relational database migrations.
Proven ability to take ambiguous technical problems from concept to production delivery.
Clear written communication to articulate system trade-offs through design records and technical documentation.
A collaborative mindset with a track record of sharing learnings, lifting team capabilities, and contributing to production support rotations.
Nice-to-have bonuses
Experience migrating legacy .NET Framework endpoints and SQL Server-based services toward modern APIs.
Hands-on familiarity with building cloud agent tooling and collaborative workflows that support an automated development lifecycle.
Comfort working in a remote-first team, using design records, paired kick-offs, and blameless reviews to stay aligned.
Mentoring or coaching experience to help uplift teammates beyond core project work.
Where and how you’ll work
The role is open to candidates based in New Zealand, offering a flexible remote-first setup with office access in Wellington or Auckland. The team prioritises async communication and balanced collaboration, so you’ll have time to focus on meaningful work while staying connected with colleagues across the country.
Advice for applicants
Lead with the parts of your background that line up most closely with the must-haves: highlight your typed-language experience and any direct C# or .NET work, plus a project where you helped shape a large platform.
Provide concrete examples that prove the must-have skills. Describe a time you built or contributed to an automated verification pipeline or AI harness, and quantify the impact you achieved, such as reduced toil or improved reliability.
Be ready to talk through how you turned an unclear technical idea into a durable architecture. Bring design records or other technical documentation that demonstrates your ability to frame problems, outline trade-offs, and gain alignment in a remote, written-first environment.
Ask a targeted question about the team’s approach to safety and collaboration. For example: how design records and blameless reviews shape decision-making, or how AI guardrails are implemented in practice and how you measure their effectiveness in production.