Infrastructure Engineer

Zag is building the platform for AI review agents. As coding agents produce more changes than humans can review, every team will need custom review agents, tailored to their codebase and their standards, running on every proposed change. We're building the infrastructure that makes that possible.

Review agents need real environments to do useful work. They need to build code, run tests, boot applications, and interact with them. Zag provisions these environments as ephemeral sessions on dedicated Apple Silicon that boot in seconds from pre-warmed snapshots. Every session exposes a durable, replayable stream. Getting this right, fast, reliable, and seamless for the teams that depend on it, is the core infrastructure challenge at Zag.

As a founding infrastructure engineer, you'll own the systems that make this work. That includes macOS virtualization and session lifecycle, compute provisioning and scheduling, the streaming and observability layer, and the integration points between Zag's orchestration engine and the sandboxed environments where agents run.

You should be comfortable working across the stack. On a given week you might be optimizing VM boot times, building out the session streaming protocol, debugging an Xcode build failure inside an agent environment, or designing how we scale from managed Apple Silicon to our own bare-metal fleet.

This is a foundational role. The infrastructure you build will define what Zag's agents can do and how fast they can do it. You'll work directly with the founders, ship to production daily, and have real ownership over the platform from day one.

What we're looking for:

• Strong systems engineering background. You've built and operated infrastructure that other engineers depend on.
• Experience with virtualization, containers, or sandboxed compute environments. macOS virtualization experience (Tart, Anka, or similar) is a plus but not required.
• Comfort with low-level systems work: networking, file systems, process management, performance optimization.
• Proficiency in at least two of: TypeScript, Go, Swift, Rust.
• Familiarity with Apple's build toolchain (Xcode, xcrun, simulators, codesigning) is a strong plus.
• You care about reliability and you care about speed. The engineers and agents using Zag's infrastructure need both.