Documentation

Read the entropy pool

import { Connection, PublicKey } from "@solana/web3.js";

const connection = new Connection("https://rpc.mainnet.x1.xyz", "confirmed");
const PROGRAM_ID = new PublicKey("BSKTJpgAGHRaSMLA88chYPKuSuD9qbesEcHYmUrBWU7R");

// EntropyPool PDA
const [poolPda] = PublicKey.findProgramAddressSync(
  [Buffer.from("entropy-pool")],
  PROGRAM_ID
);

const info = await connection.getAccountInfo(poolPda, "confirmed");
const d = Buffer.from(info.data);
const entropyHex = d.slice(8, 40).toString("hex");          // 32 bytes @ offset 8
const currentRound = Number(d.readBigUInt64LE(40));
const entropyAvailable = d[48] !== 0;
const lastAggregatedSlot = Number(d.readBigUInt64LE(49));

Build a request_randomness transaction

import { Transaction, TransactionInstruction, SystemProgram } from "@solana/web3.js";

const DISC_REQUEST = Buffer.from([213, 5, 173, 166, 37, 236, 31, 18]);  // sha256("global:request_randomness")[:8]

// Derive PDAs
function u64le(n) {
  const b = Buffer.alloc(8);
  b.writeBigUInt64LE(BigInt(n));
  return b;
}
const [configPda] = PublicKey.findProgramAddressSync([Buffer.from("protocol-config")], PROGRAM_ID);
const [poolPda]   = PublicKey.findProgramAddressSync([Buffer.from("entropy-pool")], PROGRAM_ID);
const [escrowPda] = PublicKey.findProgramAddressSync([Buffer.from("fee-escrow"), u64le(currentRound)], PROGRAM_ID);
const [wrapperRoundPda] = PublicKey.findProgramAddressSync([Buffer.from("wrapper-round"), u64le(currentRound)], PROGRAM_ID);
const [requestPda] = PublicKey.findProgramAddressSync(
  [Buffer.from("request"), requesterPubkey.toBuffer(), seedBytes32],
  PROGRAM_ID
);

const callbackProgram = new PublicKey("11111111111111111111111111111111"); // SystemProgram = no callback
const callbackInstruction = Buffer.alloc(8, 0);
const data = Buffer.concat([DISC_REQUEST, seedBytes32, callbackProgram.toBuffer(), callbackInstruction]);

const SLOT_HASHES = new PublicKey("SysvarS1otHashes111111111111111111111111111");

const ix = new TransactionInstruction({
  programId: PROGRAM_ID,
  keys: [
    { pubkey: requestPda,               isSigner: false, isWritable: true  },
    { pubkey: requesterPubkey,          isSigner: true,  isWritable: true  },
    { pubkey: configPda,                isSigner: false, isWritable: false },
    { pubkey: poolPda,                  isSigner: false, isWritable: true  },
    { pubkey: escrowPda,                isSigner: false, isWritable: true  },
    { pubkey: wrapperRoundPda,          isSigner: false, isWritable: false },
    { pubkey: SLOT_HASHES,              isSigner: false, isWritable: false },
    // dapp_registration: pass SystemProgram as opt-out (no fee override)
    { pubkey: SystemProgram.programId,  isSigner: false, isWritable: false },
    { pubkey: SystemProgram.programId,  isSigner: false, isWritable: false },
  ],
  data,
});

Poll for fulfillment (RequestState.fulfilled @ offset 152)

async function pollFulfillment(requestPda, connection, maxAttempts = 60) {
  for (let i = 0; i < maxAttempts; i++) {
    await new Promise(r => setTimeout(r, 2000));
    const info = await connection.getAccountInfo(requestPda, "confirmed");
    if (!info || info.data.length < 202) continue;
    const d = Buffer.from(info.data);
    if (d[152]) {  // fulfilled = true
      const output = d.slice(153, 185).toString("hex");
      return output;
    }
  }
  return null;
}