JavaScript Quickstart

Run a script that asks Jan a question and prints its answer as it arrives.

You need Node.js 20+ and access to a model provider. No Git checkout, Jan Desktop, Rust toolchain or TypeScript build step is needed.

⚠️

The ADK is a preview and is not published to npm yet: npm install @janhq/adk does not work. Install the nightly package below instead. The runtime is a separate, prebuilt download.

Install the ADK and runtime

In a new directory, install the latest nightly ADK package:


mkdir jan-js-demo && cd jan-js-demo
npm init -y
npm install "$(node -e "fetch('https://delta.jan.ai/adk-nightly/manifest.json').then(r => r.json()).then(m => console.log(m.packages.javascript.url))")"

The command looks up the current build and installs its versioned package URL, so package.json pins that exact build. The download page (opens in a new tab) shows the same command with the URL written out.

Install the jan runtime:


curl -fsSL https://delta.jan.ai/jan-cli/install-jan-agent.sh | bash
export PATH="$HOME/.local/bin:$PATH"


jan cli agent rpc --help

If you already have a current Jan runtime, skip its installation.

Connect a model


jan login

Or configure your own provider. Both the CLI and ADK use Jan's provider configuration. If you have already configured Jan, skip this step.

Save and run the script

Save this complete example as hello.mjs in jan-js-demo:


import { JanRuntime } from '@janhq/adk'
const runtime = await JanRuntime.start()
try {
  const session = await runtime.createSession({ ephemeral: true, builtins: false })
  const turn = await session.prompt('Explain what a mutex is in one sentence.')
  for await (const event of turn) {
    if (event.type === 'token') process.stdout.write(event.text)
  }
  const result = await turn.result()
  if (result.stopReason === 'error') throw new Error(result.error)
  console.log(`\nFinished: ${result.stopReason}`)
} finally {
  await runtime.close()
}


node hello.mjs

The answer depends on your model. A successful run prints answer text followed by Finished: completed.

What just happened?

start() launched the Jan runtime and checked its protocol version.
createSession() created a conversation. ephemeral: true avoids saving it; builtins: false disables built-in and external tool sources, so this first example only answers a question.
prompt() started a turn. Each token event contains another piece of the answer.
result() returned the final status. close() ended the process, even if the script failed.

Send another prompt on the same session to continue the conversation. To select a specific configured model, add model: 'provider/model-id' to createSession().

TypeScript uses the same API; the installed package includes type declarations.

If it fails

Problem	What to do
Cannot find `@janhq/adk`	Run the `npm install` command above in `jan-js-demo`, and keep `hello.mjs` there.
The package download fails	No nightly is available right now. Use the source install.
Cannot start `jan`	Add it to PATH, or pass its absolute path as `JanRuntime.start({ bin: '/path/to/jan' })`.
Unknown `rpc` command or protocol mismatch	Run `jan update`, then retry startup.
No model, authentication error, or provider error	Run `jan login` or fix the provider configuration. A model override must name a model that provider serves.

See Process & failures for error handling in an application.

Next: give the agent a function

The first script cannot act on your app. Add a host tool when you want it to read application data or perform an action.

Nightly ADK Installation Python Quickstart