Software Engineer, Sandboxing

About the Role

Our models and agents increasingly need to run code, use tools, and take actions in the world - safely, reliably, and at scale. The Core Services team builds the sandboxing infrastructure that makes this possible: the isolated execution environments where models write and run code, browse, and interact with tools, both for our researchers during training and for external users building on Tinker.

We're hiring a software engineer to help design, build, and operate this sandboxing platform. You'll work on the systems that isolate and constrain untrusted, model-generated code, and that scale to support thousands of concurrent executions across the company. This is foundational infrastructure: every research experiment and every product surface that lets a model take action depends on it being fast, secure, and dependable.

What You'll Do

• Design, build, and operate sandboxed execution environments for running untrusted, model-generated code and tool calls at scale.
• Improve isolation boundaries using technologies such as containers, microVMs, or gVisor-style kernels, balancing security against startup latency and throughput.
• Build the scheduling, resource-management, and lifecycle systems that provision, reuse, and tear down sandboxes efficiently under heavy concurrent load.
• Partner with researchers and Tinker's product team to expose sandboxing primitives that are simple to use and hard to misuse.
• Instrument sandboxes for observability and abuse detection, and respond to novel escape or exploitation attempts as they're discovered.
• Own reliability and performance of the sandboxing platform end-to-end, from API design down to the underlying virtualization layer.

Minimum Qualifications

• Bachelor's degree or equivalent experience in computer science, engineering, or similar.
• Proficiency in at least one backend language (we use Python or Rust).
• Experience building or operating isolation or virtualization technology, such as containers, microVMs (e.g. Firecracker, Cloud Hypervisor), or sandboxed runtimes (e.g. gVisor, Kata Containers).
• Solid grounding in Linux internals relevant to isolation: namespaces, cgroups, seccomp, capabilities, and networking.
• Comfort operating across the stack and owning projects end-to-end.
• Thrive in a highly collaborative environment involving many, different cross-functional partners and subject matter experts.

Preferred Qualifications

• Experience securing systems that execute untrusted or adversarial code, including threat modeling and hardening against sandbox escapes.
• Familiarity with running large-scale, multi-tenant infrastructure on Kubernetes or similar orchestration systems.
• Experience with performance-sensitive systems programming and reducing cold-start latency for ephemeral compute.
• Track record of contributing to open-source infrastructure or security tooling.
• Interest in how AI agents use tools and code execution, and how that shapes the design of safe execution environments.

Logistics

• Location: This role is based in San Francisco, CA.
• Compensation: Depending on background, skills and experience, the expected annual salary range for this position is $300,000 - $400,000 USD.
• Visa sponsorship: We sponsor visas. While we can't guarantee success for every candidate or role, if you're the right fit, we're committed to working through the visa process together.
• Benefits: Thinking Machines offers generous health, dental, and vision benefits, unlimited PTO, paid parental leave, and relocation support as needed.