CS – indexless code search that understands code, comments and strings
I initially built cs (codespelunker) as a way to answer the question, can BM25 relevance search work without building an index? Turns out it can, and so I iterated on the idea, building it into a full CLI tool. Recently I wanted to improve it by adding relevance of tools like Sourcegraph or Zoekt but again without adding an index. cs uses scc https://github.com/boyter/scc to understand the structure of the file on the fly. As such it can filter searches to code, comments or strings. It also applies a weighted BM25 algorithm where matches in actual code rank higher than…
In plain words
CS is a command-line code search tool that performs BM25 relevance searches without requiring a pre-built index. It understands code structure on-the-fly to filter searches across code, comments, or strings separately. The tool applies weighted ranking so matches in actual code rank higher than comments, and uses cyclomatic complexity to prioritize complex implementations over simpler interfaces. Built for developers who need fast, targeted code searches across codebases.
written from the facts on this page · September 2026
From the sources
In the maker’s words, at launch
I initially built cs (codespelunker) as a way to answer the question, can BM25 relevance search work without building an index? Turns out it can, and so I iterated on the idea, building it into a full CLI tool. Recently I wanted to improve it by adding relevance of tools like Sourcegraph or Zoekt but again without adding an index. cs uses scc https://github.com/boyter/scc to understand the structure of the file on the fly. As such it can filter searches to code, comments or strings. It also applies a weighted BM25 algorithm where matches in actual code rank higher than matches in comments (by default). I also added a complexity gravity weight using the cyclomatic complexity output from scc as it scans. So if you're searching for a function, the implementation should rank higher than the interface. cs "authenticate" --gravity=brain # Find the complex implementation, not the interface cs "FIXME OR TODO OR HACK" --only-comments # Search only in comments, not code or strings cs "error" --only-strings # Find where error messages are defined cs "handleRequest" --only-usages # Find every call site, skip the definition v3.0.0 adds a new ranker, along with a interactive TUI, HTTP mode, and MCP support for use with LLMs (Claude Code/Cursor). Since it's doing analysis and complexity math on the fly, it's slower than any grep. However, on an M1 Mac, it can scan and rank the entire 40M+ line Linux kernel in ~6 seconds. Live demo (running over its own source code in HTTP mode): https://codespelunker.boyter.org/ GitHub: https://github.com/boyter/cs
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