agentauth

OAuth in 3 lines for AI agents. Device flow + localhost callback, multi-provider, file-backed token storage with auto-refresh. Built for the contexts where browser-redirect OAuth doesn't fit: CLIs, MCP servers, desktop agents, anything running locally on a user's machine.

import { AgentAuth } from "@oauthkit/agentauth"
import { github } from "@oauthkit/agentauth/providers/github"

const auth = new AgentAuth({ providers: [github({ clientId: "Iv1.abcd1234" })] })
const { token } = await auth.authorize("github", { scopes: ["repo"] })
// → use token.accessToken in your API calls

That's the entire user-facing surface. No server. No redirect URLs. No Express middleware. Cached tokens are reused on subsequent calls; expired ones refresh in the background.

Why this exists

Every OAuth library on npm assumes the same shape: your app is a web server, the user's browser does a redirect, you handle a callback at /auth/callback. That works great for SaaS — and is wrong for AI agents, which usually run as:

• A CLI the user just npx'd
• An MCP server spawned by Claude Desktop / Cline / Cursor
• A desktop app with no public URL
• A background process in CI that needs to refresh a token

These contexts need different OAuth flows: device flow (where the user sees a code and types it on any browser) or loopback flow (where a localhost server briefly opens to catch the callback). agentauth does both, with a multi-provider plugin shape so you can BYO any service.

Install

npm install @oauthkit/agentauth
# or
bun add @oauthkit/agentauth

Node 18+ required (uses native fetch).

Built-in providers

Provider	Default flow	OAuth setup
github	Device	https://github.com/settings/developers → New OAuth App → ✅ Enable Device Flow
slack	Loopback	https://api.slack.com/apps → New App → OAuth & Permissions → Redirect URLs: http://127.0.0.1:8765/callback
notion	Loopback	https://www.notion.so/my-integrations → New integration → Redirect URIs: http://127.0.0.1:8766/callback

More providers landing soon: Linear, Google, Atlassian, Discord. Want one prioritized? Open an issue with the service name.

You can also write your own — see Custom providers.

import { AgentAuth } from "@oauthkit/agentauth"
import { github } from "@oauthkit/agentauth/providers/github"
import { slack } from "@oauthkit/agentauth/providers/slack"
import { notion } from "@oauthkit/agentauth/providers/notion"

const auth = new AgentAuth({
  providers: [
    github({ clientId: process.env.GH_CLIENT_ID! }),
    slack({ clientId: process.env.SLACK_CLIENT_ID!, clientSecret: process.env.SLACK_CLIENT_SECRET! }),
    notion({ clientId: process.env.NOTION_CLIENT_ID!, clientSecret: process.env.NOTION_CLIENT_SECRET! }),
  ],
})

const gh = await auth.authorize("github", { scopes: ["repo"] })
const sl = await auth.authorize("slack", { scopes: ["channels:read", "chat:write"] })
const nt = await auth.authorize("notion")

Common patterns

Token reuse (the default)

authorize() returns a cached token if a valid one exists. Repeated calls in the same process — or across process restarts — don't re-prompt the user.

const auth = new AgentAuth({ providers: [github({ clientId })] })
const { token, isNew } = await auth.authorize("github", { scopes: ["repo"] })
// First run:  isNew === true   (browser opens, user consents)
// Later runs: isNew === false  (returned from ~/.agentauth/tokens.json)

Force a fresh consent

await auth.authorize("github", { scopes: ["repo"], force: true })

Multiple accounts (work + personal)

const work = await auth.authorize("github", { account: "work" })
const personal = await auth.authorize("github", { account: "personal" })
// Two distinct tokens cached side by side.

Logout

await auth.logout("github")          // forget the default account
await auth.logout("github", "work")  // forget a specific account

Custom token storage

Default is FileTokenStorage at ~/.agentauth/tokens.json (mode 0600). Want OS keychain, Vault, an in-memory map, your own SQLite — implement TokenStorage:

import type { TokenStorage } from "@oauthkit/agentauth"

const myStorage: TokenStorage = {
  async get(key) { /* ... */ },
  async set(key, token) { /* ... */ },
  async delete(key) { /* ... */ },
}

const auth = new AgentAuth({ storage: myStorage, providers: [...] })

Or use the in-memory store for tests:

import { MemoryTokenStorage } from "@oauthkit/agentauth"
const auth = new AgentAuth({ storage: new MemoryTokenStorage(), providers: [...] })

Silence the "open this URL..." prompts

const auth = new AgentAuth({ log: false, providers: [...] })
// or pipe to your own logger:
const auth = new AgentAuth({ log: (msg) => myLogger.info(msg), providers: [...] })

Custom providers

A provider is a tiny object with one or both of authorizeDevice / authorizeLoopback. Here's the shape — full TypeScript types in src/types.ts:

import type { Provider, ProviderFlowContext, Token } from "@oauthkit/agentauth"

export const myService: Provider = {
  id: "myservice",
  name: "My Service",
  defaultFlow: "device",

  async authorizeDevice(ctx: ProviderFlowContext): Promise<Token> {
    // 1. POST to your /device/code endpoint
    // 2. ctx.log("Open ${url}, enter ${code}") + ctx.openBrowser(url)
    // 3. Poll your /token endpoint until consent or timeout
    // 4. return a Token
  },

  // optional — for refresh-token-supporting providers
  async refresh(token: Token): Promise<Token> {
    // POST to your /token endpoint with refresh_token grant
  },
}

src/providers/github.ts is a fully-worked reference (~200 lines).

What it does NOT try to be

• ❌ A full IAM platform. Use Okta / Auth0 / Clerk for that.
• ❌ A server-side OAuth library. Use @octokit/auth-oauth-app or openid-client for that.
• ❌ A token vault for sharing across multiple users. This is single-user-on-their-own-machine.
• ❌ An OS-keychain wrapper. keytar requires native bindings that break npx-style usage on Bun / minimal containers / CI. Files at mode 0600 are good enough for the default; bring your own keychain backend if you want one.

License

MIT.

Contributing

Bug reports + provider PRs welcome. The bar:

1. New providers must include a small test file that exercises the happy path with mocked fetch. See tests/core.test.ts for patterns.
2. bun test and bun run typecheck pass.
3. The provider's OAuth setup (where to register the app, which scopes mean what) is documented in the file header.

If your service has weird OAuth (PKCE-only, custom grant types, non-standard error codes), the Provider interface accommodates it — the library doesn't try to enforce a single shape.