shim-cli

shim-cli is an open source command-line tool that runs on your machine next to coding agents such as Claude Code, Codex, Copilot CLI and VS Code. It finds secrets and personal data in what your agent sends, masks them where the client allows it, and shows what each Claude Code session sent and cost. When the agent reads a file or tool result holding a key, an IBAN or an email, the model gets a placeholder instead of the value.

The main uses are a few separate commands. shim install adds a native hook to your agent so sensitive values are masked in every session. shim watch runs a local proxy for one command and reports tokens, spend and every secret or personal value that went past. shim audit reads Claude Code history on your disk and counts what already reached the model, and shim demo shows the detector working on a made-up sentence without installing anything.

shim-cli is published as an open source CLI under the Apache-2.0 licence, and the quickstart says nothing in it needs an account, an API key or a network call to shim, so no price list applies. It needs Python 3.10 or newer and installs with uv or pipx. The company also describes a team view of every AI call, what it cost and what was masked; this profile covers only the CLI.

Check platform and client fit before adopting it. The setup instructions say shim-cli runs on macOS and Linux and tell an agent to stop on Windows outside WSL. It names Claude Code, Codex, Copilot CLI and VS Code as clients and gives Cursor, Windsurf and Gemini CLI as examples it does not support. Masking happens only where the client allows it, Codex needs the shim entry enabled in /hooks, and shim audit reads Claude Code history only.