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A3S is an open-source, local-first runtime for agent work. A session names its model, tools, and permissions; work runs through typed contracts; isolation and Cloud stay off until that work needs them.

The product command is a3s. An interactive session is a3s code. Use one install channel.

brew tap a3s-lab/tap https://github.com/A3S-Lab/homebrew-tap
brew install a3s
cd /path/to/project
a3s code

A model-backed session needs an explicit provider:

a3s config init
a3s config validate
a3s model list
a3s model use <provider>/<model>

Prefer a native window? Download A3S Desktop. It is a Tauri workbench over the local Code kernel, not a wrapper around the a3s binary. Other install channels are in Install.

Start with Code. Add another surface only when the job needs that owner.

The host chooses the authority. ACL and Use describe what the work may do. Code, Flow, Runtime, and Box carry it out. Health, digests, revisions, and receipts come back as evidence the owner can inspect. ACL is the Agent Configuration Language. It is not HCL; parse and generate it with a3s-acl.

Four rules keep the parts replaceable:

1. Hosts own policy. Backends do not invent authority.
2. One concern has one owner. Cloud owns desired state, Flow owns durable orchestration, Runtime owns provider-neutral lifecycles, and concrete providers own enforcement.
3. Processes, containers, MicroVMs, and remote providers meet typed contracts. None of them is a hidden default.
4. A digest, a revision, and a receipt are different facts. Installation is not authorization, and authorization is not a completed run.

Support claims live with the component that owns the behavior. This page does not assign one maturity label to the whole system.

Pick one channel and stay on it. A second copy earlier on PATH is the usual reason a3s looks installed but is the wrong binary.

Not shipped for the umbrella CLI: musl/Alpine, Windows ARM, MinGW, or Cygwin. Installers resolve one SemVer, require the platform artifact, verify SHA-256 and a3s --version, and keep the previous install if activation fails. They do not use sudo or UAC.

Installs a3s, a3s-webview, the bundled moli/ runtime, and libzvec.

brew tap a3s-lab/tap https://github.com/A3S-Lab/homebrew-tap
brew install a3s
a3s --version

brew update && brew upgrade a3s
brew uninstall a3s

Do not brew install a3s-code. That formula is the legacy standalone binary and does not provide a3s. Other tap formulae (a3s-box, a3s-search, a3s-power) are separate products.

If an upgrade fails on an a3s-webview symlink, or the old a3s-code formula is still present:

brew uninstall a3s-code 2>/dev/null || true
brew uninstall a3s-webview 2>/dev/null || true
brew uninstall --force a3s 2>/dev/null || true
brew install a3s-lab/tap/a3s

On macOS and glibc Linux, Homebrew is used when it is on PATH. Otherwise the GitHub archive is installed into ~/.local/bin.

curl --proto '=https' --tlsv1.2 -LsSf \
  https://raw.githubusercontent.com/A3S-Lab/a3s/main/install.sh | sh

# Inspect only
curl --proto '=https' --tlsv1.2 -LsSf \
  https://raw.githubusercontent.com/A3S-Lab/a3s/main/install.sh | sh -s -- --dry-run

--channel binary forces the GitHub archive. --channel brew fails if Homebrew is missing. Overrides: A3S_VERSION, A3S_INSTALL_DIR, A3S_CHANNEL, A3S_YES, A3S_DRY_RUN, A3S_GITHUB_TOKEN, A3S_MODIFY_PATH=1.

Update the Homebrew channel with brew upgrade a3s. Update the binary channel with a3s self update or by re-running the installer. Uninstall the binary channel with:

rm -f ~/.local/bin/a3s ~/.local/bin/a3s-webview ~/.local/bin/a3s-code
rm -rf ~/.local/bin/moli

Windows x64 (PowerShell 5.1+) installs into %LOCALAPPDATA%\Programs\a3s\bin:

irm https://raw.githubusercontent.com/A3S-Lab/a3s/main/install.ps1 | iex

Set $env:A3S_MODIFY_PATH = '1' before running to update the user PATH. Re-run the same command to update. Uninstall by closing a3s, removing that directory, and deleting the PATH entry if you added one.

cargo install a3s --locked

Cargo installs the CLI from crates.io. Release companions (a3s-webview, bundled moli/) are not guaranteed. Prefer Homebrew or the installer when you need that layout.

a3s --version
which a3s
a3s code

Uninstalling the binary does not delete ~/.a3s/ (or the Windows equivalent). Remove that directory only if you intend to wipe local config and caches.

A3S_OFFLINE=1 and A3S_NO_AUTO_INSTALL=1 stop runtime component installs and network mutation. They do not turn an online installer into an offline one.

a3s/
├── apps/          Cloud, Desktop, docs, Windhole
├── packages/      Office, Science, UI
├── crates/        hosts, capabilities, runtimes, services
├── compat/        exact revisions and protocol locks
├── use-registry/  pinned signed Use Registry deployment
└── homebrew-tap/  release formulae

Clone the snapshot, not a partial tree:

git clone --recurse-submodules git@github.com:A3S-Lab/a3s.git
cd a3s

For an existing checkout: git submodule update --init --recursive.

The root justfile only orchestrates. Desktop JavaScript dependencies live in apps/desktop/package-lock.json; run cd apps/desktop && npm ci once before desktop recipes.

just desktop
just desktop-check
just code
just docs
just cloud-stack-check

The project directory lists role, stage, and release channel for each project. AGENTS.md is the contributor contract for this root.

• Website
• Desktop download
• CLI reference
• Desktop release
• Cloud compatibility lock
• Discord

This integration repository is MIT. Pinned projects keep the license of their owning repositories.