Fee Authorization

Fee authorization applies when staking BTC to Ethereum Mainnet or Sepolia. The SDK requests an EIP-712 signature to authorize the network fee via the authorize() step.

EVM Destinations (Ethereum Mainnet)

For Ethereum-based destinations, the workflow moves through:

IDLE → NEEDS_FEE_AUTHORIZATION → READY → ADDRESS_READY

The prepare() method initiates this sequence, followed by authorize() to obtain the necessary signature.

Signature Reusability

Previously stored fee signatures can be reused. When calling prepare() again, if a valid signature exists from a previous operation, prepare() will skip directly to READY. This eliminates redundant user prompts.

Non-EVM Destinations

Non-EVM destinations (Base, Solana, Sui, etc.) follow a different pattern using address confirmation rather than fee authorization:

IDLE → NEEDS_ADDRESS_CONFIRMATION → READY → ADDRESS_READY

This involves signing a message confirming the destination chain identifier instead of authorizing network fees.

Implementation

Check the returned status after prepare() to determine whether fee authorization is necessary:

const stake = sdk.chain.btc.stake({
  destChain: Chain.ETHEREUM,
  assetOut: AssetId.LBTC,
});
 
await stake.prepare({
  amount: '0.1',
  recipient: '0x1234...',
});
 
// Check if authorization is needed
if (stake.status === BtcActionStatus.NEEDS_FEE_AUTHORIZATION) {
  await stake.authorize();
}
 
// Now ready to generate deposit address
const address = await stake.generateDepositAddress();