Browser Security Engineer at Kernel (San Francisco, CA)
Kernel· San Francisco, CA·
Role details
Job description
About Kernel
Kernel is crazy fast, open source browser infrastructure for AI agents. We handle autoscaling, observability, and the messy details of web interaction, so developers can focus on what their agents do instead of how they do it.
Teams at Cash App, Framer, and 7000+ others use Kernel for deep research, QA automation, and real-time web analysis. We've raised $22M from Accel, YC, and Vercel.
If you're interested in building critical infrastructure for agents on the web, we'd love to chat.
About the role
We’re hiring a Browser Security Engineer to harden and extend our Chromium-based browser runtime. You’ll work at the intersection of sandboxing, networking, and virtualization — ensuring our browsers run securely and efficiently across thousands of concurrent users.
What you’ll do
Debug, patch, and optimize Chromium builds running inside Kernel’s microVM environments.
- Implement and maintain network isolation, proxy routing, and IP handling for browsers.
- Collaborate with infra engineers on unikernel-based isolation, process scheduling, and kernel security policies.
- Build internal tooling for binary analysis, crash triage, and vulnerability monitoring.
- Support the team in maintaining secure supply chain and reproducible builds for our browser images.
What we’re looking for
- Deep familiarity with Chromium internals, browser sandboxes, or renderer/network stacks.
- Experience with Linux kernel, microVMs (Firecracker, Cloud-Hypervisor, Kata, gVisor, etc.), or container isolation.
- Strong debugging skills with strace, gdb, perf, or similar low-level tools.
- Knowledge of networking fundamentals (DNS, TCP/IP, NAT, proxies, TLS).
- Background in security engineering or browser hardening a plus.
What you can expect as a Kernel
- Industry-competitive salary
- Above market equity
- Premium medical + dental coverage + dependent coverage
- Small, trusting team of senior + staff engineers
- Default async with minimal bureaucracy
- Daily lunches on us
- Unlimited PTO
- 401k + company match
- Relocation assistance
Hiring process
We have a simple process focused on real world collaboration and jointly getting to know each other:
- 30 minute intro calls with one of Kernel’s co-founders
- 45-minute technical interview (virtual)
- Half-day on-site (in-person) working with our team on relevant technical challenges.
- Offer!
Why work at Kernel
- Early-stage impact: Join a well-funded Series A startup (15 employees) backed by top-tier investors – opportunity to shape the product and culture from an early stage
- Founding team pedigree: Work alongside founders who have built and exited a $500M company (Clever) and led engineering at Cash App
- Technical challenges: Build cutting-edge infrastructure for AI agents – browser virtualization, stealth proxies, serverless compute, and observability at scale
- Open-source culture: 61 public repos, active community engagement, and commitment to transparent development
- Work environment: In-office culture based in San Francisco (4 locations in the US), with a focus on well-designed tooling and developer experience
- Perks: Competitive compensation at a well-funded startup; perks and benefits typical of an early-stage YC company (details available on Built In)
- Current openings: Infrastructure Engineer, Product Engineer, Backend Engineer, DevRel Engineer, Solutions Engineer, Customer Engineer – indicating strong growth and diverse team needs