About Antithesis

We've been quietly reinventing how the world thinks about software reliability, and we're just getting started! At Antithesis, we start at the foundations – we run entire software systems inside a deterministic simulation and break them in every way imaginable. Every issue then comes with a perfect reproduction, so you can identify root causes fast instead of spending days trying to recreate what went wrong.

The rise of AI-generated code has made this work more urgent than ever. Agents can write code faster than any human, but speed doesn't matter much when the output is buggy, stuck in review, or slipping through undetected. The verification bottleneck is real, it's growing, and solving it is one of the most consequential problems in software right now. That's what you'd be working on.

We're well-funded and deeply technical, the kind of place where the hardest problems get the most attention and the best ideas win regardless of who has them. If you want to do work that actually moves the needle on how reliable software can be, keep reading.

About This Role

Antithesis is looking for an IT Engineer to drive and evolve our IT infrastructure as we scale in the UK. You'll be the person our engineers rely on to keep their environments running, their access managed, and their issues resolved quickly. This role sits at the intersection of endpoint management, network infrastructure, and internal tooling, and you'll have real ownership over the systems and processes you build.

Day to day, you'll manage our Mac and Linux fleet using Mosyle and Apple Business Manager, support our network and VPN infrastructure, and serve as our primary escalation point for endpoint and application issues. You'll also help build the documentation and operational foundations that let us move fast without losing institutional knowledge.

This is a hands-on role for someone who likes solving technical problems, working across teams, and building things that last. If you thrive in fast-moving environments and want to have a meaningful impact on how a rapidly growing engineering company operates, we'd love to talk.

What You'll Do

• Manage and support our technology using tools like Mosyle and Apple Business Manager, keeping hardware and software environments running smoothly across the company.

• Maintain network infrastructure including VPNs, DNS, firewalls, and wireless systems, collaborating with engineering and other teams to keep things reliable and secure.

• Serve as Tier 1 and Tier 2 support for endpoint, network, and application issues, tracking and resolving problems through Linear with a focus on fast resolution.

• Own asset management and security compliance, maintaining accurate records in our corporate asset database and ensuring we're meeting relevant compliance frameworks.

• Build and maintain documentation on IT processes, configurations, and architecture so knowledge is shared and the team can scale without losing institutional context.

What We're Looking For

• Hands-on experience in IT systems administration or a similar role, ideally in a fast-paced or high-growth tech environment.

• Strong working knowledge of macOS and Linux (Ubuntu or similar), with familiarity with NixOS and modern endpoint management tools.

• Experience with identity and access management platforms like Google Workspace, Okta, or Azure AD.

• Solid networking fundamentals, including DNS, DHCP, firewalls, VLANs, and wireless infrastructure.

• Clear communicator who documents well, troubleshoots methodically, and takes ownership of problems through to resolution.

Nice to Haves:

• Experience working in a dynamic start-up environment working with complex systems

• Global experience supporting team members in other countries including the US & Asia