Unify to Verify: A Monorepo Approach for Hardware and Software using Bazel, Cocotb and Verilator

“Software is Software, and Hardware is Hardware, and never the twain shall meet” — Rudyard Kipling (possibly apocryphal) Bringing software and hardware teams into a shared development flow has long felt out of reach — siloed tools, incompatible languages, and divergent workflows stand in the way. But with the right infrastructure and open source tooling, it's now possible to unify these disciplines in a single, cohesive environment. At Fractile, we've embraced a monorepo model — a single repository that holds everything from RTL and verification code to software models, device drivers, and architecture specs. This unified codebase, built on Bazel, enables consistent builds, scalable dependency management, and tight integration between hardware and software development. By leveraging Cocotb and Verilator, we’ve built a verification flow that aligns with our software teams’ tooling and culture. Python-based testbenches allow us to reuse existing software components, and shared infrastructure enables co-development against a Single Source of Truth (SSoT). Our verification workloads are part of the same Continuous Integration pipeline as software — fully automated, continuously tested. This talk will explore the challenges we encountered adopting this approach, how we overcame them, and why this model may be valuable to teams considering how verification can take advantage of modern development practices.

Will Keen has 12 years of experience in pre-silicon verification, spanning SoC, CPU, and unit-level work across both simulation and formal methodologies. He is currently working at Fractile, where the team applies modern, software-inspired methods to tackle complex hardware challenges. His guiding philosophy is: “solving hardware problems with a software mindset.”