Reproducing rare bugs found during fuzz testing is hard because software can run slightly differently every time. Bedrock is a hypervisor that controls that randomness, so given the same inputs a program runs identically on every execution.

Niklas outlines an approach and a solution, bedrock, for this problem of determinism. He focuses on the challenge of emulating time and pausing a VM at an exact instruction count, something CPUs aren't designed to do.
https://brink.dev/blog/2026/06/25/bedrock-deterministic-hypervisor/

The result is an open source tool, bedrock: an experimental hypervisor purpose-built for deterministic software testing.
https://github.com/oss-garage/bedrock