Vercel Open-Sources Bash Tool for Context Retrieval Using Local Filesystems

"The bash-tool exposes three primary operations for use by agents: bash, which interprets and executes Bash scripts; readFile, which reads files from a preloaded filesystem; and writeFile, which updates files. The engine runs on top of just-bash, a TypeScript-based interpreter that avoids spawning separate shell processes or executing arbitrary binaries, and it can operate with either an in-memory filesystem or in an isolated virtual machine."

"In practice, developers can preload a set of files when creating the tool and allow the agent to run commands against those files on demand. For example, a simple agent configuration can pass a JavaScript source file into bash-tool, providing the agent with the ability to search or manipulate the filesystem without including the full file contents in the prompt. The same tool can be used with a Vercel sandbox environment that supports full VM isolation when a real shell and filesystem are required."

bash-tool provides a Bash execution engine for AI agents, enabling filesystem-based commands to retrieve context for model prompts. It allows agents to run shell-style operations such as find, grep, and jq directly against a directory of files to avoid embedding whole files into prompts. The tool exposes three operations: bash, readFile, and writeFile. The engine is built on just-bash, a TypeScript interpreter that avoids spawning separate shell processes or executing arbitrary binaries and supports both in-memory filesystems and isolated virtual machines. Developers can preload files and let agents query them on demand to reduce token usage.

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