Supported library reference. Rust, Node.js, Python and Go remain supported in a separate workspace. This chapter can contain historical version or installation text; use the current package guide. Extended CLI examples use jacs-compat in 0.15. See the current MCP guide for actual runtime profiles and the release inventory for published versions.

Installation

This guide covers installing the JACS Rust CLI and library.

Requirements

Rust: Version 1.97 or later (Edition 2024)
Cargo: Included with Rust installation

Verify Rust Version

rustc --version
# Should show rustc 1.97.0 or later

If you need to update Rust:

rustup update stable

Installing the CLI

From crates.io (Recommended)

cargo install jacs-cli

At the 2026-07-09 shipped-artifact snapshot, crates.io resolves jacs-cli 0.11.3; the documentation source is 0.13.0. Check the resolved version instead of assuming the source branch has already been published.

From Homebrew (macOS)

brew tap HumanAssisted/homebrew-jacs
brew install jacs

From Source

git clone https://github.com/HumanAssisted/JACS
cd JACS
cargo install --path jacs-cli

Verify Installation

jacs --help

MCP Server

The MCP server is built into the jacs binary. No separate install step needed.

# Start the MCP server (stdio transport)
JACS_CONFIG="$PWD/jacs.config.json" jacs mcp

Using as a Library

Add JACS to your Cargo.toml:

[dependencies]
jacs = "0.11.3"

0.11.3 is the published crate recorded in release/shipped-artifacts.json; source checkout 0.13.0 is not installable from crates.io until its release completes.

With Optional Features

JACS supports several optional features for observability and integrations:

[dependencies]
# Basic library usage
jacs = "0.11.3"

# With OpenTelemetry logging
jacs = { version = "0.11.3", features = ["otlp-logs"] }

# With OpenTelemetry metrics
jacs = { version = "0.11.3", features = ["otlp-metrics"] }

# With OpenTelemetry tracing
jacs = { version = "0.11.3", features = ["otlp-tracing"] }

# With all observability features
jacs = { version = "0.11.3", features = ["otlp-logs", "otlp-metrics", "otlp-tracing"] }

Available Features

Feature	Description
`cli`	(Deprecated -- use `cargo install jacs-cli` instead)
`otlp-logs`	OpenTelemetry Protocol logging backend
`otlp-metrics`	OpenTelemetry Protocol metrics backend
`otlp-tracing`	OpenTelemetry Protocol distributed tracing
`sqlite`	Lightweight sync SQLite backend (default)
`sqlx-sqlite`	Async SQLite backend via sqlx (requires tokio)
`s3`	AWS S3 storage; opt-in because it adds cloud HTTP/XML dependencies
`agreements`	Agreement lifecycle support
`a2a`	Agent-to-Agent protocol support
`attestation`	Attestation support

Platform Support

The Rust crate and the CLI have different distribution models. The jacs crate is source compiled by Cargo; a successful build depends on the Rust target, linker, and system dependencies available to the consumer. The CLI is also published as platform archives.

Observed public artifacts on 2026-07-09:

Surface	Version	Prebuilt targets	Test evidence
Rust library crate	`jacs 0.11.3`	None; crates.io distributes source	Full source suites run in release CI on Ubuntu and macOS. This does not imply every Rust-supported target.
CLI crate	`jacs-cli 0.11.3`	`cargo install` builds from source	Source compilation follows the consumer's Rust target and native dependencies.
CLI archives	`jacs-cli 0.11.3`	macOS arm64/x86_64; glibc Linux arm64/x86_64; Windows x86_64	The release job builds each target and executes `jacs --version` on its runner. Full feature suites are not run separately on every archive target.
Browser WASM	source `0.13.0` only	No published `@jacs/wasm` package	Source CI runs Firefox `wasm-pack` tests and a Chromium/Playwright package smoke on Ubuntu.

There is no basis for a blanket “full support” claim across operating systems. In particular, the Windows x86_64 CLI archive does not imply Windows wheels or native modules for Python, Node, or Go. See Deployment Compatibility for the exact cross-language, architecture, and libc matrix.

WebAssembly Notes

The source-built jacs-wasm package supports both Ed25519 and post-quantum pq2025 signing and verification. The previous claim that WebAssembly lacked post-quantum support was incorrect.

The WASM surface remains browser-specific and omits native filesystem storage, DNS resolution, MCP, and the CLI. It uses encrypted browser persistence, and its private keys live in JavaScript-visible WebAssembly memory. Most importantly for installation, @jacs/wasm was not published to npm at the shipped-artifact observation date; build it from source rather than running the unqualified npm install command until a registry version exists.

Configuration

After installation, initialize JACS:

# Create configuration and agent in one step
jacs init

This creates:

./jacs.config.json - Configuration file
Cryptographic keys for your agent
Initial agent document

Manual Configuration

Alternatively, create configuration and agent separately:

# Create configuration only
jacs config create

# Create agent with keys
jacs agent create --create-keys true

Environment Variables

JACS respects the following environment variables:

Variable	Description	Default
`JACS_CONFIG_PATH`	Path to configuration file	`./jacs.config.json`
`JACS_USE_SECURITY`	Enable/disable security features	`true`
`JACS_DATA_DIRECTORY`	Directory for document storage	`./jacs_data`
`JACS_KEY_DIRECTORY`	Directory for cryptographic keys	`./jacs_keys`
`JACS_DEFAULT_STORAGE`	Storage backend (`fs`, `memory`)	`fs`
`JACS_AGENT_KEY_ALGORITHM`	Key algorithm (`ed25519`, `pq2025`; legacy alias `ring-Ed25519`)	`pq2025`
`JACS_ALLOW_LEGACY_SIGNATURE_CONTENT`	Explicitly allow payload-only verification of legacy v1 signatures; signer/version/time metadata stays untrusted and empty	`false`
`JACS_REJECT_LEGACY_SIGNATURE_CONTENT`	Force legacy-v1 rejection even if compatibility was requested	`false`
`JACS_PAYLOAD_MAX_REPLAY_SECONDS`	Freshness/nonce retention window for HTTP/RPC payload proofs	`300`
`JACS_REQUIRE_SHARED_REPLAY_STORE`	Fail closed unless an application-installed `ReplayStore` is shared across replicas	`false`

Troubleshooting

Build Errors

"edition 2024 is required" Update Rust to version 1.97 or later:

rustup update stable

Missing dependencies on Linux Install build essentials:

# Debian/Ubuntu
sudo apt-get install build-essential pkg-config libssl-dev

# Fedora
sudo dnf install gcc openssl-devel

Runtime Errors

"Configuration file not found" Run jacs init or set JACS_CONFIG_PATH environment variable.

"Key directory does not exist" Create the key directory or run jacs init:

mkdir -p ./jacs_keys

"Permission denied" Ensure you have write permissions to the data and key directories.

Next Steps

CLI Usage - Learn CLI commands
Creating an Agent - Create your first agent
Rust Library API - Use JACS as a library

Keyboard shortcuts

JACS Usage Documentation