Ask HN: Open-source alternatives to enterprise-grade code indexing/RAG systems?

I&#x27;ve been exploring various AI coding assistants (Cursor, GitHub Copilot, Devin, etc.) and noticed they all share a common foundation: sophisticated retrieval-augmented generation (RAG) systems that enable deep understanding of codebases. These systems excel at:<p>- Rapidly indexing entire codebases<p>- Semantic search across code snippets<p>- Contextual ranking of relevant code sections<p>- Integration with LLMs for enhanced code understanding<p>While proprietary solutions are abundant, I&#x27;m looking for open-source alternatives that could provide similar functionality. Specifically:<p>- Tools for building and maintaining code indexes<p>- Systems that can integrate with existing LLMs<p>- Solutions for semantic code search and retrieval<p>- Frameworks for contextual code understanding<p>Has anyone built or worked with open-source tools that could serve as building blocks for such a system? I&#x27;m particularly interested in hearing about:<p>- Real-world implementations<p>- Performance comparisons with commercial solutions<p>- Scalability considerations<p>- Integration challenges<p>The goal is to understand what&#x27;s possible with current open-source technology in this space, and potentially contribute to building more accessible alternatives to proprietary systems.