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┌─────────────────────────────────────────────────────────────────────────────┐
│  STANDARD BLOCKHASH                                                         │
│                                                                             │
│    ┌──────┐      ┌──────────┐                                               │
│    │ Sign │ ───▶ │  Submit  │     ⏱️ Must happen within ~90 seconds         │
│    └──────┘      └──────────┘                                               │
│       │                                                                     │
│       └─────────  Transaction expires if not submitted in time              │
└─────────────────────────────────────────────────────────────────────────────┘

┌─────────────────────────────────────────────────────────────────────────────┐
│  DURABLE NONCE                                                              │
│                                                                             │
│    ┌──────┐      ┌───────┐       ┌─────────┐      ┌──────────┐              │
│    │ Sign │ ───▶ │ Store │ ───▶  │ Approve │ ───▶ │  Submit  │              │
│    └──────┘      └───────┘       └─────────┘      └──────────┘              │
│                                                                             │
│    Transaction remains valid until you submit it                            │
└─────────────────────────────────────────────────────────────────────────────┘

import { generateKeyPairSigner } from "@solana/kit";
import {
  getNonceSize,
  getCreateAccountInstruction,
  getInitializeNonceAccountInstruction,
  SYSTEM_PROGRAM_ADDRESS
} from "@solana-program/system";

// Generate a keypair for the nonce account address
const nonceKeypair = await generateKeyPairSigner();

// Get required account size for rent calculation
const space = BigInt(getNonceSize());

// 1. Create the account (owned by System Program)
getCreateAccountInstruction({
  payer,
  newAccount: nonceKeypair,
  lamports: rent,
  space,
  programAddress: SYSTEM_PROGRAM_ADDRESS
});

// 2. Initialize as nonce account
getInitializeNonceAccountInstruction({
  nonceAccount: nonceKeypair.address,
  nonceAuthority: authorityAddress // Controls nonce advancement
});

// Assemble and send transaction to the network

import { fetchNonce } from "@solana-program/system";

const nonceAccount = await fetchNonce(rpc, nonceAddress);
const nonceValue = nonceAccount.data.blockhash; // Use this as your "blockhash"

import { setTransactionMessageLifetimeUsingBlockhash } from "@solana/kit";

setTransactionMessageLifetimeUsingBlockhash(
  {
    blockhash: nonceAccount.data.blockhash,
    lastValidBlockHeight: BigInt(2n ** 64n - 1n) // Effectively never expires
  },
  transactionMessage
);

import { getAdvanceNonceAccountInstruction } from "@solana-program/system";

// MUST be the first instruction in your transaction
getAdvanceNonceAccountInstruction({
  nonceAccount: nonceAddress,
  nonceAuthority // Signer that controls the nonce
});

import {
  signTransactionMessageWithSigners,
  getTransactionEncoder,
  getBase64EncodedWireTransaction
} from "@solana/kit";

// Sign the transaction
const signedTx = await signTransactionMessageWithSigners(transactionMessage);

// Serialize for storage (database, file, etc.)
const txBytes = getTransactionEncoder().encode(signedTx);
const serialized = getBase64EncodedWireTransaction(txBytes);

import {
  getBase64Decoder,
  getTransactionDecoder,
  getTransactionEncoder,
  getBase64EncodedWireTransaction
} from "@solana/kit";

// Deserialize the stored transaction
const txBytes = getBase64Decoder().decode(serializedString);
const partiallySignedTx = getTransactionDecoder().decode(txBytes);

// Each approver adds their signature
const fullySignedTx = await newSigner.signTransactions([partiallySignedTx]);

// Serialize again for storage
const txBytes = getTransactionEncoder().encode(fullySignedTx);
const serialized = getBase64EncodedWireTransaction(txBytes);

const signature = await rpc
  .sendTransaction(serializedTransaction, { encoding: "base64" })
  .send();

import { getAdvanceNonceAccountInstruction } from "@solana-program/system";

// Submit this instruction (with a regular blockhash) to invalidate any pending transaction
getAdvanceNonceAccountInstruction({
  nonceAccount: nonceAddress,
  nonceAuthority
});