Installation

Choose the setup that matches your workflow. For the terminal quickstart, you only need the command-line tool. Connect an agent if you want it to write and test programs, or install the library in your application.

Prerequisites

Node.js 24 or newer. node --version prints the version you have.
npm, which comes with Node.js.

The SDK ships under the Eco, Inc. Proprietary License 1.1, the LICENSE.md file in the @eco-incorp/sauce package, which holds its terms. Its Additional Use Grant begins:

Notwithstanding the restrictions in this License, you may do the following, in each case solely to create, compile, test, simulate, and execute programs for use with the Authorized Contracts (the “Licensed Purpose”):

Sauce transactions need no API key. For a use the license does not cover, contact Eco at partners@eco.com.

Install the command

npm install -g @eco-incorp/sauce

Check the install:

sauce --version

@eco-incorp/sauce <version>

Every command takes --help, which lists what the command does and every flag it accepts.

Run it without installing

npx -y @eco-incorp/sauce <command>

npx fetches the package and runs the command. Outside a project that depends on @eco-incorp/sauce, never run a bare npx sauce: npx then fetches an unrelated npm package named sauce.

Install it in a project

npm install @eco-incorp/sauce viem

This installs the TypeScript library. In that project, npx sauce <command> runs the version the project’s package.json pins; a global sauce run there runs the global version. The library’s EVM API takes and returns viem types. TypeScript overview lists the import paths. To create a project with the CLI, run:

sauce init my-app
cd my-app
npm install

sauce init writes these files, then installs the agent skills:

a package.json that pins @eco-incorp/sauce to the version that ran it;
AGENTS.md, plus CLAUDE.md and GEMINI.md that import it;
.gitignore;
sauce.config.example.json;
programs/tsconfig.json, so an editor type-checks the programs in programs/.

See sauce init.

Add the MCP server to your agent

The MCP server lets an agent compile and simulate programs through tools. The agent starts it as a local process and communicates over standard input and output (stdio). You do not need to run that process separately. For a shared project, use project configuration to pin the server version. To configure an individual agent, choose it below:

claude mcp add sauce -- sauce mcp

codex mcp add sauce -- sauce mcp

A project Codex trusts can carry the same server in .codex/config.toml:

[mcp_servers.sauce]
command = "sauce"
args = ["mcp"]

In .cursor/mcp.json in the project, or ~/.cursor/mcp.json for every project:

{
  "mcpServers": {
    "sauce": { "command": "sauce", "args": ["mcp"] }
  }
}

In .vscode/mcp.json, under servers:

{
  "servers": {
    "sauce": { "type": "stdio", "command": "sauce", "args": ["mcp"] }
  }
}

gemini mcp add sauce sauce mcp

Open Settings, then Developer, then Edit Config. Add the server under mcpServers in claude_desktop_config.json, then restart Claude Desktop:

{
  "mcpServers": {
    "sauce": { "command": "sauce", "args": ["mcp"] }
  }
}

A desktop client may not see your shell’s PATH, and then cannot start a sauce installed under nvm or another version manager. sauce is a Node.js script that starts with #!/usr/bin/env node, so the absolute path of sauce alone is not enough: Node must be found too. Give the absolute path that which node prints as the command, and the path that which sauce prints, then mcp, as the args. npx is a Node.js script as well, so the alternative, command npx with args ["-y", "@eco-incorp/sauce", "mcp"], also needs Node on the client’s PATH.

Write the project files for every agent

sauce mcp setup

sauce mcp setup writes the server into each agent’s project file and keeps everything else in that file:

Agent	File
Claude Code	`.mcp.json`
Codex	`.codex/config.toml`
Cursor	`.cursor/mcp.json`
VS Code (Copilot)	`.vscode/mcp.json`
Gemini CLI	`.gemini/settings.json`

These files are shared through version control, so the entry does not depend on a global install. It runs npx -y @eco-incorp/sauce@<version> mcp, where <version> is the exact version of the sauce that ran setup, with no wallet flags: the server serves ~/.sauce/wallets (Agents, wallets and keys). --agent claude,cursor limits it to those agents. --force replaces an existing sauce entry that differs. A file that is not plain JSON stops setup with exit code 2, after the files before it are written. sauce mcp lists every flag.

Runtime packages

The MCP server loads two packages that are optional peer dependencies of @eco-incorp/sauce: the MCP SDK and zod. A Solana simulation in a local copy loads LiteSVM. These packages are resolved in this order:

Your own copies, if they are exactly the versions the package pins.
Otherwise, a runtime folder under ~/.sauce/runtime/. The first use installs it, and so does sauce mcp setup.

To install the folder ahead of time, or to see where each package comes from:

sauce runtime install
sauce runtime

See sauce runtime.

Install the agent skills

sauce skills install

This copies the package’s agent skills into the project:

.claude/skills/ is read by Claude Code;
.agents/skills/ is read by Codex, Cursor, Copilot and Gemini CLI.

sauce skills status reports each directory as up to date, outdated or modified. sauce skills update brings the directories to the installed version. A file you edited is kept unless you pass --force. The MCP server also serves the same skills as tools and resources, so an agent connected to it needs nothing installed in the project. See sauce skills.

Configure endpoints

An RPC endpoint is the connection a command uses to read blockchain state. The CLI uses a built-in public endpoint unless you provide one. Public endpoints can be slow or rate-limited, and each read through one prints a note on stderr. The following commands use the pay.sauce.ts program from the quickstart. To choose an endpoint for one command:

sauce simulate pay.sauce.ts --chain base --owner <address> --rpc-url <url> --args <recipient> 1000000

Or give a file of endpoints, keyed by chain id:

rpc.json

{ "rpcUrls": { "1": "<url>", "8453": "<url>", "1399811149": "<url>" } }

sauce simulate pay.sauce.ts --chain base --owner <address> --config rpc.json --args <recipient> 1000000
sauce mcp --config rpc.json

--offline reads no chain at all, not even through a built-in endpoint. sauce compile works offline. A command that needs the chain refuses:

sauce simulate: --offline reads no chain, and this reads base

Chains, endpoints and fees covers fallback between public endpoints, eth_simulateV1, and Arc’s fees.

Updates

Run sauce update --check to compare your installed version with the latest release. Follow Package updates to update the command, project dependency, agent configuration and skills together.

Troubleshooting

Unsupported Node.js version: check node --version and use Node.js 24 or newer.
Your agent cannot find the command: a desktop app may use a different PATH from your shell. Configure the absolute paths to Node.js and sauce, as described above.
RPC requests fail or are rate-limited: use your own endpoint and check endpoint troubleshooting.
An MCP server fails to start: check MCP setup troubleshooting, including runtime packages and pinned versions.

Next steps

Quickstart: write, compile, simulate and build a program on Base.
AI agents: what an agent does with the server and the skills.
CLI overview: every command.

Start here

Integration guides

Language reference

SauceScript libraries

Runtime and security

Troubleshooting and production

Chains and protocols

@eco-incorp/sauce

@eco-incorp/sauce-compiler

Prerequisites

Install the command

Run it without installing

Install it in a project

Add the MCP server to your agent

Write the project files for every agent

Runtime packages

Install the agent skills

Configure endpoints

Updates

Troubleshooting

Next steps

​Prerequisites

​Install the command

​Run it without installing

​Install it in a project

​Add the MCP server to your agent

​Write the project files for every agent

​Runtime packages

​Install the agent skills

​Configure endpoints

​Updates

​Troubleshooting

​Next steps

Prerequisites

Install the command

Run it without installing

Install it in a project

Add the MCP server to your agent

Write the project files for every agent

Runtime packages

Install the agent skills

Configure endpoints

Updates

Troubleshooting

Next steps