Runnable Directories: The Solution to the Monorepo vs. Multi-repo Debate

Abstract: Modern software systems increasingly strain traditional codebase organization strategies. Monorepos offer consistency but often suffer from scalability issues and tooling complexity, while multi-repos provide modularity at the cost of coordination and dependency management challenges. As an answer to this trade-off, we present the Causify Dev system, a hybrid approach that integrates key benefits of both. Its central concept is the runnable directory -- a self-contained, independently executable unit with its own development, testing, and deployment lifecycles. Backed by a unified thin environment, shared helper utilities, and containerized Docker-based workflows, runnable directories enable consistent setups, isolated dependencies, and efficient CI/CD processes. The Causify Dev approach provides a practical middle ground between monorepo and multi-repo strategies, improving reliability and maintainability for growing, complex codebases.