What it does
Context-OS is an open-source tool for Claude Code that aims to make the first turn open the right file instead of searching for it. A short Python hook builds a static graph of the repository from symbols, imports and recently changed files, then injects ranked file and line candidates into the prompt before Claude's first turn. The page says it uses no embeddings, no server and no model call. A second hook intercepts reads of large files and returns an outline of symbols with their line ranges, so Claude re-reads only the slice it needs. A third hook records estimated savings, which you can view with a /savings command and in the status line. The page says everything stays local, with no telemetry. The page reports a 40.9% token reduction in a cold-cache A/B test of 36 calls on one repository, and it is open about caveats: warm interactive sessions save less, symbol extraction covers Python, TypeScript/JavaScript, Rust and Go, and other languages fall back to path-only ranking. A versioned GitHub Action scores a repository for cost leaks and takes a maximum score, so teams using Claude Code, Codex or Cursor can gate changes in CI. It installs with a setup script, per project or globally. The page says it is compatible with Claude Code on macOS and Linux and needs Python 3. The maker also sells a private audit of agent costs, separate from the free open-source tool.
Capabilities
- Static repository graph of symbols, imports and recently changed files
- Ranked file and line hints injected before Claude's first turn
- Outlines in place of whole-file reads for large files
- Savings receipts through a /savings command and status line
- GitHub Action that scores agent cost leaks and can gate CI
- Runs locally with no server or telemetry
When to use it
- You use Claude Code on a sizeable repository and want fewer exploratory search steps
- Your team wants a CI check on coding-agent cost leaks
- You want to measure token savings against your own session history
