Privy on Solana mobile

Privy owns the user: a durable account identifier and a JWT a backend can verify. Mobile Wallet Adapter owns the keys. Privy signs nothing in this setup — every signature still comes from the wallet app.

Sign-In-With-Solana joins the two. Privy generates a message, MWA signs it, Privy exchanges the signature for a session.

Reach for this when an app needs a stable user record across devices, a server-verifiable session, or login methods beyond a wallet. An app that only needs a connected address does not need Privy — use the solana-mobile-wallet skill alone.

Android only, and a development build only. MWA has no iOS support and does not run in Expo Go, which caps the whole integration.

Before you start

Step 1: create the Privy app

Do this first. Two of these values are compile-time environment variables, and one dashboard toggle decides whether login works at all.

1. Sign in at https://dashboard.privy.io and click New app on the organization overview
2. Name it, select Mobile app, create it, and save the App ID
3. Under User management > Authentication, in the External wallets card, enable SVM (Solana) wallets
4. Under App settings > Clients, set the app identifier to the expo.android.package value from app.json, and save the Client ID

The SVM wallets toggle is the one that is easy to skip and expensive to debug — while it is off, login rejects every SIWS attempt even though the wallet signed correctly. The app identifier matters because Privy checks the calling app's package name against the client.

EXPO_PUBLIC_PRIVY_APP_ID=your-privy-app-id
EXPO_PUBLIC_PRIVY_CLIENT_ID=your-privy-client-id

Both are public client-side identifiers, so EXPO_PUBLIC_ is correct. The Privy app secret never belongs in a mobile app — anything prefixed EXPO_PUBLIC_ is readable in the shipped bundle. The secret is for server code only.

Step 2: install and configure

npx expo install @privy-io/expo @privy-io/expo-native-extensions

@privy-io/expo carries a long peer dependency list that shifts between releases — passkeys, secure store, web browser, crypto, viem. Install what the version you picked asks for rather than copying a list from anywhere, including from here.

Three pieces of native wiring are required, and the SDK fails in a different place for each:

• Crypto and text-encoding polyfills, loaded from the entry module before anything else
• expo-secure-store and expo-web-browser in app.json plugins
• A Metro resolver override so jose resolves to its browser build

Full contents for each, and how to confirm they took: references/setup.md. Rebuild natively (npx expo run:android) after this step — a JS reload will not pick up the new native modules.

Step 3: mount the providers

import { PrivyProvider } from '@privy-io/expo'
import { QueryClient, QueryClientProvider } from '@tanstack/react-query'
import { type AppIdentity, createSolanaDevnet, MobileWalletProvider } from '@wallet-ui/react-native-kit'
import type { ReactNode } from 'react'

const cluster = createSolanaDevnet()
const identity: AppIdentity = { name: 'My App', uri: 'myapp://myapp' }
const privyAppId = process.env.EXPO_PUBLIC_PRIVY_APP_ID
const privyClientId = process.env.EXPO_PUBLIC_PRIVY_CLIENT_ID
const queryClient = new QueryClient()

export function AppProviders({ children }: { children: ReactNode }) {
  if (!privyAppId || !privyClientId) {
    throw new Error('Missing Privy environment variables')
  }

  return (
    <QueryClientProvider client={queryClient}>
      <PrivyProvider appId={privyAppId} clientId={privyClientId}>
        <MobileWalletProvider cluster={cluster} identity={identity}>
          {children}
        </MobileWalletProvider>
      </PrivyProvider>
    </QueryClientProvider>
  )
}

PrivyProvider and MobileWalletProvider do not depend on each other, so their relative nesting is free — but both must sit above every screen, and QueryClientProvider above both if the hooks below are queries and mutations.

Throwing on missing environment variables is deliberate. Undefined values reach Privy as a malformed app ID and surface much later as an opaque initialization error.

clientId is typed optional in PrivyProviderProps, which is misleading here: Privy's mobile documentation treats it as required, and the dashboard issues one per mobile client. Pass it.

Step 4: wait for isReady

usePrivy() returns state that is meaningless until the SDK finishes reading stored tokens:

const { error, isReady, user } = usePrivy()

if (!isReady) return <Loading />
if (error) return <ErrorCard message={error.message} />

Rendering a signed-out state while isReady is false makes an already-authenticated user flash through a login screen on every cold start.

Step 5: sign in with SIWS

The whole integration is this one sequence: generate, sign, exchange.

import { useLoginWithSiws } from '@privy-io/expo'
import type { Address } from '@solana/kit'
import { useMutation } from '@tanstack/react-query'
import { fromUint8Array, useMobileWallet } from '@wallet-ui/react-native-kit'

const siwsDomain = 'myapp.com'
const siwsUri = 'myapp://privy-login'

export function usePrivySignInMutation(address: Address) {
  const { generateMessage, login } = useLoginWithSiws()
  const { signMessages } = useMobileWallet()

  return useMutation({
    mutationFn: async () => {
      const { message } = await generateMessage({
        from: { domain: siwsDomain, uri: siwsUri },
        wallet: { address: address.toString() },
      })

      const signedPayload = await signMessages(new TextEncoder().encode(message))

      await login({ message, signature: fromUint8Array(signedPayload) })
    },
  })
}

Call it only once a wallet is connected — useMobileWallet().account must be defined, since signMessages triggers its own authorization otherwise.

Three encoding details decide whether this works:

1. Pass account.address, which is base58. account.addressBase64 also exists; it is MWA's wire format and Privy will not accept it. Privy's own recipe spends three lines converting base64 to base58 because it drives the raw protocol — @wallet-ui/react-native-kit has already done that conversion for you.
2. fromUint8Array produces base64, not base58. It is a re-export of js-base64. Privy wants the base64 string here; base58 fails verification.
3. Do not slice the bytes. signMessages resolves to MWA's signed payload, not a bare 64-byte signature. Base64-encode it whole and hand it over — the template and Privy's recipe both do exactly this.

from.domain is an RFC 3986 authority: a bare host, no scheme and no path. from.uri is a full URI and is normally your app's deep link. Keep both stable — they are embedded in the signed message the user sees in their wallet.

Linking a wallet to an account that already exists, and verifying the session on a server: references/siws.md.

Step 6: sign out of both

const { logout } = usePrivy()
const { disconnect } = useMobileWallet()

await logout()
await disconnect()

Doing one without the other leaves the app in a half-signed-out state. disconnect() alone keeps a live Privy session with no wallet behind it; logout() alone leaves the wallet authorized and re-signs in silently on the next attempt.

Which side owns what

There is no Privy signer in this setup. A user is signed in to Privy and connected over MWA as two independent facts, and the UI has to handle every combination — most usefully "connected but not signed in", which is where the sign-in button belongs.

Reference material

• references/setup.md — polyfills, Metro config, app.json plugins, environment variables, and how to verify each one landed
• references/siws.md — the SIWS exchange in depth, linking additional wallets, server-side token verification, and the raw-protocol variant without Wallet UI
• references/troubleshooting.md — Privy-specific failures and their causes

The patterns here follow expo-kit-privy, a complete working app. Read it when this file is ambiguous:

npx solana-mobile@latest create /tmp/reference-app --template expo-kit-privy --skip-install

Related skills

• solana-mobile-wallet — MWA connection, signing, and sending, which this builds on
• solana-mobile — development builds, emulators, toolchain checks
• seeker-genesis-token — SIWS verified server-side without Privy, when a JWT is overkill

Links

• Privy Solana MWA recipe: https://docs.privy.io/recipes/solana/adding-solana-mwa
• Privy Expo SIWS login: https://docs.privy.io/guide/expo/authentication/siws
• Privy dashboard: https://dashboard.privy.io