LlamaIndex is an ecosystem comprising over 650 Python packages managed within a monorepo on GitHub, with each package having its own pyproject.toml file to define dependencies and other aspects of the package lifecycle. Initially, the team used Poetry for individual package management and Pants for orchestrating testing across the monorepo, but they faced challenges as the system scaled, including slow iterations, complex build maintenance, and difficult debugging processes. To address these issues, LlamaDev was introduced as a new tool to manage monorepos at scale, replacing the previous setup with uv and LlamaDev, resulting in a 20% faster complete test run, clearer logs, and easier local debugging for contributors. LlamaDev enhances the development and contribution experience by simplifying dependency management, reducing reliance on external resources, and improving the overall efficiency and clarity of the build process within the LlamaIndex ecosystem.