Sandboxing untrusted agent code with gVisor costs ~200ms per cold start. Blocking syscalls instead of emulating them costs ~8ms

Short summary

zviz is a lightweight, OCI-compatible container runtime that sandboxes untrusted agent code by selectively denying dangerous syscalls via BPF filtering instead of emulation. It achieves ~8ms cold starts vs gVisor's ~200ms, blocks 19/19 escape attempts, and runs a 124-instruction seccomp policy small enough to audit manually. The trade-off: no ptrace, nested containers, or build tools like Bazel; the payoff is native-speed allowed syscalls and practical security for agent execution.

• •zviz uses BPF-filtered syscalls (8ms cold start) vs gVisor's emulation (200ms), cutting startup by 25x
• •Blocks 19/19 real escape tests; 124-instruction policy is auditable by humans
• •Trades compatibility (no ptrace/nested containers) for speed and simplicity—ideal for agents, not POSIX-heavy workloads

Generated with AI, which can make mistakes.