[Solana] `useWallets` incompatible with standard Web3 SDKs (Metaplex Umi / Irys) / `TypeError: t is not iterable`

[tayelroy]

Description:
When using a Privy connected Solana wallet (via useWallets()) as a provider for standard Solana Web3 SDKs like @metaplex-foundation/umi or @irys/sdk, transactions fail with a fatal serialization error (TypeError: t is not iterable).

The Root Cause:
The standard @solana/wallet-adapter-react ecosystem (which Metaplex and Irys rely on) expects signTransaction to accept and return fully constructed @solana/web3.js Transaction or VersionedTransaction objects.

However, Privy's v3 ConnectedStandardSolanaWallet strict implementation expects signTransaction to receive a serialized byte array wrapped in an object: { transaction: Uint8Array }. When an SDK passes an object instead of a byte array, the underlying wallet extension (e.g., Backpack) fails to iterate over it during deserialization, resulting in the crash.

Steps to Reproduce:

1. Retrieve the active Solana wallet via const { wallets } = useWallets().
2. Map it to the standard adapter shape to use as a signer for Metaplex Umi (createSignerFromWalletAdapter) or WebIrys.
3. Trigger an on-chain action (e.g., minting a Metaplex Core Asset).
4. The transaction fails immediately at the serialization layer before reaching the browser extension UI.

Current Workaround:
To bypass the crash, developers are forced to build a custom adapterShim that intercepts the Web3 transaction objects, serializes them to raw bytes for Privy, and then deserializes them back into objects for the SDKs.

// The necessary workaround to bridge Privy to Metaplex Umi / Irys
const activeWallet = solanaWallets[0];

const adapterShim = {
  publicKey: new PublicKey(activeWallet.address),

  signMessage: async (msg: Uint8Array) => {
    const result = await activeWallet.signMessage({ message: msg });
    return new Uint8Array(result.signature);
  },

  signTransaction: async <T extends Transaction | VersionedTransaction>(tx: T): Promise<T> => {
    const isVersioned = 'version' in tx;

    // 1. Serialize to raw bytes for Privy's Wallet Standard interface
    const serialized: Uint8Array = isVersioned
      ? (tx as VersionedTransaction).serialize()
      : (tx as Transaction).serialize({ requireAllSignatures: false });

    // 2. Pass bytes to Privy
    const { signedTransaction } = await activeWallet.signTransaction({ transaction: serialized });

    // 3. Deserialize back to Web3 object for Metaplex/Irys
    return (isVersioned
      ? VersionedTransaction.deserialize(signedTransaction)
      : Transaction.from(signedTransaction)) as T;
  },

  signAllTransactions: async <T extends Transaction | VersionedTransaction>(txs: T[]): Promise<T[]> => {
    return Promise.all(txs.map((tx) => adapterShim.signTransaction(tx)));
  },
};

Expected Behavior:
Ideally, Privy should export an official "Adapter Shim" hook (e.g., useSolanaAdapter()) that automatically handles this byte array serialization/deserialization under the hood, allowing Privy wallets to drop seamlessly into existing @solana/wallet-adapter-react contexts without crashing downstream SDKs.

Environment:

• @privy-io/react-auth: ^3.23.1
• @metaplex-foundation/umi: ^1.5.1
• @irys/sdk: ^0.2.11
• @solana/web3.js: ^1.98.4