bash-tool

bash-tool is an open-source TypeScript package from Vercel Labs that gives AI agents a bash tool, a file-reading tool and a file-writing tool. It is compatible with the AI SDK and runs commands against the just-bash virtual environment by default, or against a full VM sandbox.

What It Is

bash-tool exposes three tools to an agent: bash (runs a command and returns stdout, stderr and exit code), readFile and writeFile (which creates parent directories as needed). A developer calls createBashTool with initial files or a local directory to upload, then passes the resulting tools to an AI SDK agent such as ToolLoopAgent. For analysis agents, the bash tool alone may be enough.

Sandbox Options

By default it pairs with just-bash, a TypeScript bash interpreter with an in-memory filesystem built for AI agents. The just-bash project describes itself as beta software. For full VM support, bash-tool can use @vercel/sandbox or another sandbox product, including reconnecting to an existing sandbox by ID across serverless invocations. Developers can also supply a custom just-bash instance or implement their own sandbox with executeCommand, readFile and writeFiles.

Control and Extensibility

onBeforeBashCall and onAfterBashCall hooks let developers log, rewrite or block commands and modify results. An experimental skills feature discovers directories containing a SKILL.md file, with optional scripts, and exposes them through a skill tool alongside the bash tool.