JWT authentication

The SDK supports two authentication modes: API key and JWT. API keys are the default and easiest way to get started. JWTs are an alternative for integrators that need finer-grained control over token lifetime, key rotation, or per-request sponsorship policies.

JWT authentication is experimental. The config option is prefixed with experimental_ and the API may change in future versions.

Why JWTs

JWTs are short-lived, asymmetrically-signed tokens (RS256 or ES256) issued by your backend. Compared to a long-lived API key, they let you:

Cut latency and backend code. Clients hit Rhinestone directly with a bounded access token instead of round-tripping through your server for every SDK call. For sponsored intents, a separate extension token binds your approval to the exact payload — so you stay in control per intent without proxying the submission.
Bound the blast radius of a leaked credential. Access tokens expire on a TTL you choose. An API key stays valid until you notice and rotate it.
Rotate signing keys without downtime. Register a new kid, start minting tokens with it, and tokens signed under the old kid keep verifying until they expire. No coordinated client deploy, no revocation race.

For unsponsored intents, the difference in hops looks like this:

Dashboard setup

Before you can issue JWTs, you need to register a signing key with Rhinestone. Keys are managed per-project from the Dashboard under Auth → JWT Keys.

Viewing your keys

Open the “JWT Keys” tab. If you haven’t added a key yet, the list is empty:

Adding a key

Press ”+ Add Key” to open the key creation modal. There are two ways to add a key: generate a new keypair in the browser, or upload a public JWK you’ve created yourself.

Generate
Upload

The dashboard can generate a keypair directly in your browser. Only the public key is sent to Rhinestone — the private key stays on your machine.

Fill in the form

Integrator ID — identifier for your organisation, emitted as the iss claim in the JWTs you’ll sign. Typically the name of your service.
Key ID — identifier for this specific public key, emitted as the kid JOSE header. Use a stable name you can rotate later (e.g. prod-2026-04).

Press “Add Key” to generate the keypair and register the public half.

Save the private key

The dashboard shows the private key once. Download the .json file and store it somewhere safe — Rhinestone never sees it and it cannot be recovered:

If you lose the private key, you’ll need to register a new one and rotate any clients using the old kid.

Once the key is created, it shows up in the list along with the integrator ID, status, and creation time:

Configuration

Signing a JWT requires five values. Three come from the Dashboard; the other two are free-form labels you pick yourself.

Field	Where from	JWT claim
`privateKey`	Downloaded once when the key was generated (or supplied at registration)	n/a — signs the token
`integratorId`	Dashboard — set when registering the key	`iss`
`keyId`	Dashboard — set when registering the key	`kid` (JOSE header)
`projectId`	Dashboard — shown on the project overview	`sub`
`appId`	You choose	`app_id`

integratorId, keyId, and projectId are verified server-side. The access token’s (iss, kid) must resolve to a registered key, and the token’s sub must equal the project that key was registered against. Mismatches produce a 401 or 403 at verification time — see Troubleshooting. appId is a free-form environment/app label — typically prod, staging, etc. It isn’t registered anywhere. The only server-side check is that the access token’s app_id matches the accompanying intent-extension token’s app_id, so a sponsorship approval issued for one deployment can’t be spent by another. Use it to correlate logs or split rate limits per deployment; if you don’t need that, use the same value everywhere.

keyId and appId are independent axes. keyId rotates on key rotation (same deployment, new signing key). appId rotates on environment changes (same key, new deployment). You can reuse one signing key across multiple environments, or rotate keys within a single environment.

SDK usage

There are two integration patterns depending on where the signing key lives.

Client-server
Same-host

When the SDK runs on the client (browser, mobile) and a separate backend holds the private key, fetch tokens from your backend over HTTP:

const rhinestone = new RhinestoneSDK({
  auth: {
    mode: 'experimental_jwt',
    accessToken: async () => {
      const res = await fetch('/api/auth/access-token')
      const { token } = await res.json()
      return token
    },
    // Only required for sponsored intents:
    getIntentExtensionToken: async (intentInput) => {
      const res = await fetch('/api/auth/extension-token', {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ intentInput }),
      })
      const { token } = await res.json()
      return token
    },
  },
})

Your backend is responsible for issuing the two token types. See Sponsorship signing server for a drop-in implementation.

When the SDK runs server-side with direct access to the private key, use createJwtSigner to sign tokens in-process without an HTTP round-trip:

import { createJwtSigner } from '@rhinestone/sdk/jwt-server'

const signer = createJwtSigner({
  jwt: {
    privateKey: myJwk,
    integratorId: 'int_abc',
    projectId: 'proj_xyz',
    appId: 'app_prod',
    keyId: 'key_1',
  },
})

const rhinestone = new RhinestoneSDK({
  auth: { mode: 'experimental_jwt', ...signer },
})

createJwtSigner returns { accessToken, getIntentExtensionToken } — the two callbacks the auth config expects, so you can spread them in next to the mode field.

Sponsorship signing server

For the client-server pattern, your backend needs two endpoints: one that issues short-lived access tokens, and one that signs an intent extension token for each sponsored intent. The SDK ships ready-made handlers for both.

Web standard handlers

The Web Standard handlers accept a Request and return a Response. They work with Next.js App Router, Hono, SvelteKit, Remix, Deno, Bun, and Cloudflare Workers:

import {
  createAccessTokenHandler,
  createExtensionTokenHandler,
} from '@rhinestone/sdk/jwt-server'

const config = {
  jwt: {
    privateKey: myJwk,
    integratorId: 'int_abc',
    projectId: 'proj_xyz',
    appId: 'app_prod',
    keyId: 'key_1',
  },
}

export const GET = createAccessTokenHandler(config)
export const POST = createExtensionTokenHandler(config)

Express

For Express, use createExpressRouter. It mounts GET /access-token and POST /extension-token:

import express from 'express'
import { createExpressRouter } from '@rhinestone/sdk/jwt-server'

const app = express()
app.use(express.json())
app.use('/api/auth', createExpressRouter(config))

Custom sponsorship policy

By default the signer sponsors any intent your users submit. To restrict this, pass a shouldSponsor filter. Each predicate can be sync or async, and omitted predicates default to true. Filters are AND-composed — the intent must pass all of them to be signed:

import { createJwtSigner } from '@rhinestone/sdk/jwt-server'
import { base, optimism } from 'viem/chains'

const signer = createJwtSigner({
  jwt: { privateKey, integratorId, projectId, appId, keyId },
  shouldSponsor: {
    chain: ({ id }) => [base.id, optimism.id].includes(id),
    account: async (address) => await isKnownUser(address),
    calls: (calls) => calls.every((c) => ALLOWED_CONTRACTS.has(c.to)),
  },
})

The same shouldSponsor config can be passed to the handler factories (createAccessTokenHandler, createExtensionTokenHandler, createExpressRouter). Denied requests throw a SponsorshipDeniedError, which the handlers surface as a 403. When calling the signer directly, the error is instanceof-checkable:

import { SponsorshipDeniedError } from '@rhinestone/sdk/jwt-server'

try {
  await signer.getIntentExtensionToken(intentInput)
} catch (error) {
  if (error instanceof SponsorshipDeniedError) {
    // intent was rejected by your policy
  }
  throw error
}

Troubleshooting

Auth failures surface as HTTP 4xx responses with a message field. The common ones:

Status	Message	Cause	Fix
401	`Unknown integrator key: iss=<x>, kid=<y>`	No registered key matches the `(iss, kid)` pair in the token	Confirm `integratorId` and `keyId` exactly match the values shown in the Dashboard for this key
401	`access_token verification failed: ...`	Signature invalid, token expired, or wrong audience	Check that the private key matches the registered public key, that the system clock isn’t skewed, and that the TTL isn’t too short
401	`Invalid token type: expected "access", got "intent_extension"`	Extension token sent in the `Authorization` header (or vice versa)	Send the access token as `Authorization: Bearer`; send the extension token as `X-Intent-Extension: Bearer`
403	`access_token sub does not match the project bound to signing key`	`projectId` doesn’t match the project this key was registered against	Copy the project ID from the Dashboard project page into your signer config
403	intent-extension binding failure	`iss` / `sub` / `app_id` differ between the access token and the extension token, or the `jti` has already been spent	Sign both tokens from the same config; mint a fresh extension token (new `jti`) when retrying a failed submit

If you’re hitting a 401 seconds after registering or rotating a key, the verification cache may briefly hold the old state — wait a minute and retry, or register under a fresh kid.

Tutorial

Sending intents

Use cases

API guides

Configuration

Why JWTs

Dashboard setup

Viewing your keys

Adding a key

Configuration

SDK usage

Sponsorship signing server

Web standard handlers

Express

Custom sponsorship policy

Troubleshooting

Tutorial

Sending intents

Use cases

API guides

Configuration

​Why JWTs

​Dashboard setup

​Viewing your keys

​Adding a key

​Configuration

​SDK usage

​Sponsorship signing server

​Web standard handlers

​Express

​Custom sponsorship policy

​Troubleshooting

Why JWTs

Dashboard setup

Viewing your keys

Adding a key

Configuration

SDK usage

Sponsorship signing server

Web standard handlers

Express

Custom sponsorship policy

Troubleshooting