zerostack

About

zerostack began as an argument about budgets: if a coding agent mostly shells out and edits text, it should not need hundreds of megabytes of RAM. Written in Rust in roughly two weeks and inspired by pi and opencode, it delivers the standard agent toolbox — editing, execution, session management with auto-compaction, web fetch and search — in a 26MB binary that idles near zero CPU. The crossterm TUI renders markdown, supports mouse selection, and can display model reasoning inline. Capability is modular: MCP support, hooks, persistent memory, an advisor model for second opinions, multimodal input, ACP server mode for Zed, and sandboxing (bubblewrap on Linux, zerobox on macOS) are compile-time features a user includes or excludes, keeping the default binary lean. Behavior is shaped by switchable system-prompt modes (code, plan, review, debug, brainstorm, refactor) and a chaining mechanism that runs them in sequence, plus parallel git-worktree workflows for concurrent agent runs and a permission system with five modes, per-tool globs, and doom-loop detection. Hook compatibility with Claude Code's settings schema lets existing hook configurations carry over. Distributed under GPL-3.0 via install script, cargo, Homebrew, and Nix, it suits developers on constrained machines or those who want their agent's entire ~30k-line source readable.