zerostack - crates.io: Rust Package Registry

zerostack v1.0.0

Minimalistic coding agent written in Rust, optimized for memory footprint and performance

• #ai
• #cli
• #dev

zerostack

Minimal coding agent written in Rust, inspired by pi and opencode.

Features

• Multi-provider: OpenRouter, OpenAI, Anthropic, Gemini, Ollama, plus custom providers
• File tools: read, write, edit (by exact match with diff display), grep, find_files, list_dir
• Bash execution: with permission gating, optional sandboxing for isolation, and doom-loop detection
• Permission system: four configurable modes with per-tool patterns, session allowlists, and external directory policies
• Session management: save/load/resume sessions, auto-compaction to stay within context windows
• Terminal UI: crossterm-based, markdown rendering, mouse selection/copy, scrollback, reasoning visibility toggle
• Prompts system: switch between system prompt modes at runtime (code, plan, review, debug, etc.) to tailor the agent's behavior to the task without having to manage Skills.
• MCP support: connect MCP servers for extended tooling
• Integrated Exa search: allows for WebFetch and WebSearch tools
• Integrated Ralph Wiggum loops: looping capabilities for long-horizon tasks
• Integrated Git Worktrees integration: Use /worktree to move the agent from one worktree to another.

Performance

zerostack is one of the smallest and most performant coding agents on the market.

• Lines of code: ~7k LoC
• Binary size: 8.9MB
• RAM footprint: ~8MB on an empty session, ~12MB when working (vs ~300MB for opencode or other JS-based coding agents)
• CPU usage: 0.0% on idle, ~1.5% when using tools (measured on an Intel i5 7th gen, vs ~2% on idle and ~20% when working for opencode)

Installation

In order to install zerostack, you must have Cargo and git installed. Then, run:

cargo install zerostack

You are now ready to work with a lightweight coding agent!

Optional: sandbox mode

Install bubblewrap for --sandbox, which runs every bash command inside an isolated environment to protect your system from accidental or malicious damage:

# Debian/Ubuntu
apt install bubblewrap

# Fedora
dnf install bubblewrap

# Arch
pacman -S bubblewrap

Quick start

# Set your API key (OpenRouter is default)
export OPENROUTER_API_KEY="[api_key]"

# Interactive session (default prompt: code)
zerostack

# One-shot mode
zerostack -p "Explain this project"

# Continue last session
zerostack -c

# Explicit provider/model
zerostack --provider openrouter --model deepseek/deepseek-v4-flash

Prompts system

zerostack includes a set of built-in system prompts that change the agent's behavior and tone.

The idea is to build a complete suite of prompts that can fully substitute skills like superpower or the Claude's official skills.

You can switch between different prompts or list all registered prompts using /prompt.

Built-in prompts:

Prompt	Description
code (default)	Coding mode with full file and bash tool access, TDD workflow
plan	Planning-only mode — explores and produces a plan without writing code
review	Code review mode — reviews for correctness, design, testing, and impact
debug	Debug mode — finds root cause before proposing fixes
ask	Read-only mode — only read/grep/glob permitted, no writes or bash
brainstorm	Design-only mode — explores ideas and presents designs without code
frontend-design	Frontend design mode — distinctive, production-grade UI
review-security	Security review mode — finds exploitable vulnerabilities
simplify	Code simplification mode — refines for clarity without changing behavior
write-prompt	Prompt writing mode — creates and optimizes agent prompts

You can also create custom prompts by placing markdown files in $XDG_CONFIG_HOME/zerostack/prompts/ and referencing them by name.

Additionally, the agent automatically loads AGENTS.md or CLAUDE.md from the project root or any ancestor directory, injecting their contents into the system prompt. Use -n / --no-context-files to disable this.

Permission system

zerostack has four permission modes, from safest to most permissive:

1. restrictive (-R): every tool action prompts for approval unless explicitly allowed in config
2. standard (default): safe commands (ls, cd, git log, cargo check) are auto-approved; writes and destructive operations ask
3. accept-all (--accept-all): auto-approves all operations inside the working directory; external paths prompt for confirmation
4. yolo (--yolo): auto-approves everything without prompting

Permissions can be configured per-tool with granular glob patterns in the config file. For example, you can allow write **.rs automatically while always asking before writing to other files.

A session allowlist persists approved decisions for the duration of the session, so you don't have to repeatedly confirm the same operation.

Doom-loop detection: identical tool calls repeated 3+ times trigger a warning prompt (or denial depending on your config), preventing runaway agents from spamming destructive operations.

Slash commands

This is a list of the most important slash commands:

• /model — Switch model
• /thinking — Set thinking level
• /clear — Clear conversation
• /session — List/save/load sessions
• /loop — Schedule recurring prompts
• /prompt — List or change the agent's prompt
• /mode — Set the permission system's mode

To see all of the commands, use /help.

Session management

Sessions are saved to $XDG_DATA_HOME/zerostack/sessions/. Use -c to resume the most recent session, -r to browse and select one, or --session <id> to load a specific session.

Loop system

zerostack includes an iterative coding loop for long-horizon tasks. The agent repeatedly reads the task, picks an item from the plan, works on it, runs tests, updates the plan, and loops until the task is complete or the iteration limit is reached.

NOTE The loop system is an experimental feature.

Loop usage

/loop Implement the user authentication system
/loop stop
/loop status

• /loop <prompt> — Start a loop with the given prompt
• /loop stop — Stop the active loop
• /loop status — Show current loop state

Each iteration includes the original task, the evolving LOOP_PLAN.md, a summary of the previous iteration, and any validation output. Non-slash input is blocked while a loop is active.

Headless loops via CLI

zerostack --loop --loop-prompt "Refactor the API" --loop-max 10 --loop-run "cargo test"

Flag	Description
--loop	Enable headless loop mode
--loop-prompt <text>	Prompt for each iteration
--loop-plan <path>	Custom plan file path (default: LOOP_PLAN.md)
--loop-max <N>	Maximum iterations (default: unlimited)
--loop-run <cmd>	Validation command to run after each iteration

Git worktrees integration

zerostack provides a branch-per-task workflow using git worktrees. You can create, work in, merge, and exit worktrees entirely from the chat UI.

NOTE The git worktrees integration is an experimental feature.

Git worktree usage

The worktrees integrations offers 3 slash commands:

Command	Description
/worktree <name>	Create a git worktree on branch <name> and move into it (skips creating it if it already exists)
/wt-merge [branch]	Merge the worktree branch into [branch] (default: main/master), push, clean up, and return to the main repo
/wt-exit	Return to the main repo without merging

Example workflow for git worktrees

1. Create — /worktree feature-x creates a new branch and worktree directory and moves you there.
2. Work — Use zerostack normally; changes stay on the feature branch.
3. Merge — /wt-merge tells the agent to merge the branch, push, clean up, and return to the main repo.
4. Exit — /wt-exit immediately returns to the main repo without merging.

Supported providers

• OpenRouter (default)
• OpenAI-compatible (vLLM, LiteLLM, etc.)
• Anthropic
• Gemini
• Ollama

Custom providers can be configured with any base URL and API key environment variable in $XDG_CONFIG_HOME/zerostack/config.json.

License

GPL-3.0-only

Metadata

Release date:30 days ago

2024 edition

License:GPL-3.0-only

6.7K SLoC

Size:115 KiB

Package URL:pkg:cargo/zerostack@1.0.0

Install

cargo install zerostack@1.0.0 Running the above command will globally install the zerostack binary.

Browse source

docs.rs/crate/zerostack/1.0.0/source

Repository

github.com/gi-dellav/zerostack

Owners

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