# Show HN: Zerostack, an open coding agent optimized for memory footprint

> Source: <https://gi-dellav.github.io/zerostack/>
> Published: 2026-06-04 16:33:07+00:00

## Overview

Minimal coding agent written in Rust — ~16k LoC, 26MB binary, ~16 MB RAM (avg), ~24 MB (peak). Peak RAM ~24 MB vs ~700 MB for JS-based agents. CPU: 0.0% idle, ~1.5% under load.

**Multi-provider**— OpenRouter, OpenAI, Anthropic, Gemini, Ollama, plus custom providers** Standard tools**— all tools exposed to coding agents (as described by opencode)** Permission system**— 5 modes, per-tool patterns, session allowlists** Terminal UI**— crossterm, markdown rendering, mouse support, scrollback** Prompts system**— 10 built-in prompts, switchable at runtime** Session management**— save/load/resume, auto-compaction** MCP support**— connect external tool servers** Ralph Wiggum loops**— iterative coding for long-horizon tasks** Git Worktrees**— branch-per-task workflow** ACP support**(gated) — editor integration (Zed, etc.)** Persistent memory**(gated) — plain-Markdown memory across sessions** Subagents**— parallel, fast codebase exploration** ARCHITECTURE.md**— shared core knowledge for all agents on the same codebase** Sandbox mode**— bubblewrap / zerobox isolation** Exa search**— WebFetch & WebSearch tools

[zerostack-general room](https://app.element.io/#/room/#zerostack-general:matrix.org)on Matrix.

## Prompts

Built-in system prompts that change the agent's behavior and tone — switch at runtime with `/prompt`

:

| Prompt | Description |
|---|---|
`code` | Coding mode with full file & bash access, TDD workflow |
`plan` | Planning-only — explores and produces a plan without code |
`review` | Code review for correctness, design, testing, and impact |
`debug` | Finds root cause before proposing fixes |
`ask` | Read-only mode — no writes or bash |
`brainstorm` | Design-only — explores ideas without code |
`frontend-design` | Distinctive, production-grade UI |
`review-security` | Finds exploitable vulnerabilities |
`simplify` | Refines for clarity without behavior change |
`write-prompt` | Creates and optimizes agent prompts |

Custom prompts can be created by placing markdown files in `$XDG_CONFIG_HOME/zerostack/prompts/`

.

## Permissions

| Mode | CLI | Behavior |
|---|---|---|
restrictive | `-R` | Ask for every operation |
readonly | `--read-only` | Read/grep/list only. Deny writes, edits, bash |
guarded | `--guarded` | Allow reads. Ask for writes, edits, bash |
standard | (default) | Allow path tools within CWD. Safe bash auto-allowed |
yolo | `--yolo` | Allow everything, prompt for destructive commands |

Per-tool granular glob patterns, session allowlists, and doom-loop detection prevent runaway agents. The `--dangerously-skip-permissions`

flag bypasses all checks.

## Commands

**/model**— Switch model

**/thinking**— Set thinking level

**/clear**— Clear conversation

**/session**— List/save/load sessions

**/loop**— Schedule recurring prompts

**/prompt**— List or change system prompt

**/mode**— Set permission mode

**/worktree**— Create git worktree and move into it

**/wt-merge**— Merge worktree branch, push, clean up, return

**/wt-exit**— Return to main repo without merging

**/help**— Show all commands

## Quick Start

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

# Interactive session (default prompt: code)
zerostack

# Monochrome TUI
zerostack --no-color

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

# Continue last session
zerostack -c

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

## Installation

Requires [Cargo](https://rustup.rs/) and git:

```
# Default — MCP, loop, git-worktree, and subagents
cargo install zerostack

# With ACP (Agent Communication Protocol) support for editor integration
cargo install zerostack --features acp

# With Memory support
cargo install zerostack --features memory

# With experimental multi-threaded subagents
cargo install zerostack --features multithread
```

Pre-built binaries are also available on [GitHub Releases](https://github.com/gi-dellav/zerostack/releases).

Once installed, run `/prompt autoconfig`

inside zerostack to configure the tool interactively.

### Optional: Sandbox

```
# Debian/Ubuntu
apt install bubblewrap

# Fedora
dnf install bubblewrap

# Arch
pacman -S bubblewrap
```

## Parallel Agent

Run multiple zerostack agents on the same repository simultaneously without manual git worktree management.

```
zerostack --parallel
```

Each parallel agent operates in a temporary git worktree. Changes are merged and the worktree is removed when the agent exits.

## ACP (Agent Communication Protocol)

With the `acp`

feature, zerostack acts as an ACP Agent server, allowing editors like **Zed** to connect to it as a coding agent backend:

```
# Stdio mode (editor spawns as subprocess)
zerostack --acp

# TCP mode
zerostack --acp --acp-host 0.0.0.0 --acp-port 7243
```

## 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.

## Sessions

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.