Chainlink Data Streams

What is Chainlink?

Chainlink is the world’s most widely adopted decentralized oracle network. It lets smart contracts securely access off-chain data, APIs, and traditional payment systems. Chainlink Data Streams is a pull-based oracle that delivers high-frequency, low-latency market data directly to smart contracts.

What this guide teaches you

This tutorial shows you how to integrate Chainlink Data Streams on Sei to:

Fetch real-time price data with the Chainlink Data Streams SDK
Deploy a smart contract that can verify and decode price reports on-chain
Combine off-chain and on-chain components to create a complete oracle solution
Verify SEI/USDT price feeds as a practical example

By the end of this guide, you will have a working implementation that uses the Chainlink Data Streams SDK. It fetches price data off-chain and verifies it on-chain.

Prerequisites

Before you start this tutorial, make sure that you have:

Technical requirements

Node.js (v18 or higher) and npm installed
Basic knowledge of TypeScript or JavaScript
Solidity development experience (basic to intermediate)
Familiarity with tools to deploy smart contracts, such as Remix or Hardhat

Sei network setup

Sei Testnet:

Sei Testnet RPC: https://evm-rpc-testnet.sei-apis.com
Chain ID: 1328

Sei Mainnet:

Sei Mainnet RPC: https://evm-rpc.sei-apis.com
Chain ID: 1329

Chainlink Data Streams access

Contact Chainlink to get access to the API credentials for Data Streams.

API credentials: Contact Chainlink to get access to Data Streams on Sei Mainnet or Sei Testnet
API Key and User Secret for testnet access
Feed IDs: This guide uses the SEI/USDT feed ID 0x0003dba2d8553dfd7afe35c2bfe217ef5106d7805e5272c04a08940ddb868117
VerifierProxy contract address: 0x60fAa7faC949aF392DFc858F5d97E3EEfa07E9EB. Sei Mainnet and Sei Testnet use the same address. For the current list, see Chainlink’s Stream Addresses page.

Step-by-step tutorial

Step 1: Project setup

Create a new directory and initialize your project:

mkdir chainlink-data-streams-sei
cd chainlink-data-streams-sei
npm init -y

Install the required dependencies:

npm install @chainlink/data-streams-sdk dotenv tsx ethers
npm install -D typescript @types/node

Create a .env file in your project root:

API_KEY=your_chainlink_api_key_here
USER_SECRET=your_chainlink_user_secret_here

Step 2: Fetching price data with TypeScript

Create a file named singleStream.ts with this code:

import { createClient, decodeReport, LogLevel, getReportVersion, formatReport } from '@chainlink/data-streams-sdk';
import 'dotenv/config';

async function main() {
  if (process.argv.length < 3) {
    console.error('Please provide a feed ID as an argument');
    console.error('Example: npx tsx singleStream.ts 0x0003dba2d8553dfd7afe35c2bfe217ef5106d7805e5272c04a08940ddb868117');
    process.exit(1);
  }

  const feedId = process.argv[2];
  const version = getReportVersion(feedId);

  try {
    const config = {
      apiKey: process.env.API_KEY || 'YOUR_API_KEY',
      userSecret: process.env.USER_SECRET || 'YOUR_USER_SECRET',
      endpoint: 'https://api.testnet-dataengine.chain.link',
      wsEndpoint: 'wss://ws.testnet-dataengine.chain.link',
      // Comment to disable SDK logging:
      logging: {
        logger: console,
        logLevel: LogLevel.INFO
      }
    };

    const client = createClient(config);
    console.log(`\nFetching latest report for feed ${feedId} (${version})...\n`);

    // Get raw report data
    const report = await client.getLatestReport(feedId);
    console.log(`Raw Report Blob: ${report.fullReport}`);

    // Decode the report
    const decodedData = decodeReport(report.fullReport, report.feedID);

    // Combine decoded data with report metadata
    const decodedReport = {
      ...decodedData,
      feedID: report.feedID,
      validFromTimestamp: report.validFromTimestamp,
      observationsTimestamp: report.observationsTimestamp
    };
    console.log(formatReport(decodedReport, version));
  } catch (error) {
    if (error instanceof Error) {
      console.error('Error:', error.message);
    } else {
      console.error('Unknown error:', error);
    }
    process.exit(1);
  }
}

main();

This script:

Creates a Data Streams client with your API credentials
Fetches the latest report for a given feed ID
Decodes the raw report into readable price data
Displays both the raw and the formatted data for debugging

Step 3: Smart contract deployment

Create and deploy the verification contract on Sei. Copy this Solidity code into Remix IDE:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

import {Common} from "@chainlink/contracts@1.5.0/src/v0.8/llo-feeds/libraries/Common.sol";
import {IVerifierFeeManager} from "@chainlink/contracts@1.5.0/src/v0.8/llo-feeds/v0.3.0/interfaces/IVerifierFeeManager.sol";
import {IERC20} from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import {SafeERC20} from "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";

using SafeERC20 for IERC20;

/**
 * THIS IS AN EXAMPLE CONTRACT FOR DEMONSTRATION PURPOSES.
 * This contract verifies Chainlink Data Streams reports onchain
 * and handles fee payments automatically.
 */

interface IVerifierProxy {
  function verify(
    bytes calldata payload,
    bytes calldata parameterPayload
  ) external payable returns (bytes memory verifierResponse);

  function s_feeManager() external view returns (IVerifierFeeManager);
}

interface IFeeManager {
  function getFeeAndReward(
    address subscriber,
    bytes memory unverifiedReport,
    address quoteAddress
  ) external returns (Common.Asset memory, Common.Asset memory, uint256);

  function i_linkAddress() external view returns (address);
  function i_rewardManager() external view returns (address);
}

contract ClientReportsVerifier {
  // Errors
  error NothingToWithdraw();
  error NotOwner(address caller);
  error InvalidReportVersion(uint16 version);

  // Report schema v3 (crypto streams)
  struct ReportV3 {
    bytes32 feedId;
    uint32 validFromTimestamp;
    uint32 observationsTimestamp;
    uint192 nativeFee;
    uint192 linkFee;
    uint32 expiresAt;
    int192 price;
    int192 bid;
    int192 ask;
  }

  // Storage
  IVerifierProxy public immutable i_verifierProxy;
  address private immutable i_owner;
  int192 public lastDecodedPrice;

  // Events
  event DecodedPrice(int192 price);

  constructor(address _verifierProxy) {
    i_owner = msg.sender;
    i_verifierProxy = IVerifierProxy(_verifierProxy);
  }

  modifier onlyOwner() {
    if (msg.sender != i_owner) revert NotOwner(msg.sender);
    _;
  }

  /**
   * @notice Verify a Data Streams report and extract price
   * @param unverifiedReport Full payload from Data Streams API
   */
  function verifyReport(bytes memory unverifiedReport) external {
    // Extract report data and version
    (, bytes memory reportData) = abi.decode(unverifiedReport, (bytes32[3], bytes));

    uint16 reportVersion = (uint16(uint8(reportData[0])) << 8) | uint16(uint8(reportData[1]));
    if (reportVersion != 3) {
      revert InvalidReportVersion(reportVersion);
    }

    // Handle fees
    IFeeManager feeManager = IFeeManager(address(i_verifierProxy.s_feeManager()));
    bytes memory parameterPayload;

    if (address(feeManager) != address(0)) {
      address feeToken = feeManager.i_linkAddress();
      (Common.Asset memory fee,,) = feeManager.getFeeAndReward(
        address(this),
        reportData,
        feeToken
      );

      IERC20(feeToken).approve(feeManager.i_rewardManager(), fee.amount);
      parameterPayload = abi.encode(feeToken);
    } else {
      parameterPayload = bytes("");
    }

    // Verify through proxy
    bytes memory verified = i_verifierProxy.verify(unverifiedReport, parameterPayload);

    // Decode and store price
    ReportV3 memory report = abi.decode(verified, (ReportV3));
    lastDecodedPrice = report.price;
    emit DecodedPrice(report.price);
  }

  /**
   * @notice Withdraw ERC-20 tokens from contract
   */
  function withdrawToken(address _beneficiary, address _token) external onlyOwner {
    uint256 amount = IERC20(_token).balanceOf(address(this));
    if (amount == 0) revert NothingToWithdraw();
    IERC20(_token).safeTransfer(_beneficiary, amount);
  }

  /**
   * @notice Get the last decoded price
   */
  function getLastPrice() external view returns (int192) {
    return lastDecodedPrice;
  }
}

Deployment steps in Remix:

Switch to Sei Testnet in MetaMask
Deploy the contract with the VerifierProxy address for Sei Testnet: 0x60fAa7faC949aF392DFc858F5d97E3EEfa07E9EB
Save the contract address for testing

Step 4: Complete integration script

Create verifyOnChain.ts to combine off-chain fetching with on-chain verification:

import { createClient, LogLevel } from '@chainlink/data-streams-sdk';
import 'dotenv/config';

// You'll need to install ethers: npm install ethers
import { ethers } from 'ethers';

async function main() {
  const feedId = '0x0003dba2d8553dfd7afe35c2bfe217ef5106d7805e5272c04a08940ddb868117';

  // 1. Fetch the latest report
  const config = {
    apiKey: process.env.API_KEY!,
    userSecret: process.env.USER_SECRET!,
    endpoint: 'https://api.testnet-dataengine.chain.link',
    wsEndpoint: 'wss://ws.testnet-dataengine.chain.link',
    logging: {
      logger: console,
      logLevel: LogLevel.INFO
    }
  };

  const client = createClient(config);
  console.log('Fetching latest report...');

  const report = await client.getLatestReport(feedId);
  console.log(`Got report: ${report.fullReport}`);

  // 2. Connect to Sei Testnet and your deployed contract
  const provider = new ethers.JsonRpcProvider('https://evm-rpc-testnet.sei-apis.com');
  const wallet = new ethers.Wallet(process.env.PRIVATE_KEY!, provider);

  const contractAddress = 'YOUR_DEPLOYED_CONTRACT_ADDRESS';
  const abi = ['function verifyReport(bytes memory unverifiedReport) external', 'function getLastPrice() external view returns (int192)', 'event DecodedPrice(int192 price)'];

  const contract = new ethers.Contract(contractAddress, abi, wallet);

  // 3. Verify the report on-chain
  console.log('Verifying report on-chain...');
  const tx = await contract.verifyReport(report.fullReport);
  await tx.wait();

  // 4. Get the decoded price
  const price = await contract.getLastPrice();
  console.log(`Price verified on-chain: ${ethers.formatUnits(price.toString(), 18)} SEI/USDT`);
}

main().catch(console.error);

How to run and test

1. Test off-chain data fetching

Run the single-stream script to test off-chain fetching and decoding:

npx tsx singleStream.ts 0x0003dba2d8553dfd7afe35c2bfe217ef5106d7805e5272c04a08940ddb868117

Expected output:

npx tsx singleStream.ts 0x0003dba2d8553dfd7afe35c2bfe217ef5106d7805e5272c04a08940ddb868117
[DataStreams] Data Streams client initialized

Fetching latest report for feed 0x0003dba2d8553dfd7afe35c2bfe217ef5106d7805e5272c04a08940ddb868117 (V3)...

[DataStreams] Request successful: GET https://api.testnet-dataengine.chain.link/api/v1/reports/latest?feedID=0x0003dba2d8553dfd7afe35c2bfe217ef5106d7805e5272c04a08940ddb868117 - 200
Raw Report Blob: 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

Report Metadata:
Feed ID: 0x0003dba2d8553dfd7afe35c2bfe217ef5106d7805e5272c04a08940ddb868117
Valid From: 1762764867
Observations: 1762764867

Decoded Data:
Native Fee: 89051407707956
LINK Fee: 19676218805901927
Expires At: 1765356867
Price: 180009506586149300
Bid Price: 179941088372418000
Ask Price: 180063641553635300

2. Test smart contract deployment

Copy the raw report blob from the Step 1 output (the long hex string that starts with 0x00090d9e...)
Call verifyReport() with the entire blob as the unverifiedReport parameter
Call getLastPrice(). You should see the decoded price (for example, 180009506586149300)

3. Test complete integration

Step 3a: Set up the integration script Add your private key to .env:

API_KEY=your_chainlink_api_key_here
USER_SECRET=your_chainlink_user_secret_here
PRIVATE_KEY=your_sei_testnet_private_key_here

In verifyOnChain.ts, replace YOUR_DEPLOYED_CONTRACT_ADDRESS with the address of your deployed contract. Step 3b: Run the integration test

npx tsx verifyOnChain.ts

Expected output:

npx tsx verifyOnChain.ts
[DataStreams] Data Streams client initialized
Fetching latest report...
[DataStreams] Request successful: GET https://api.testnet-dataengine.chain.link/api/v1/reports/latest?feedID=0x0003dba2d8553dfd7afe35c2bfe217ef5106d7805e5272c04a08940ddb868117 - 200
Got report: 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
Verifying report on-chain...
Price verified on-chain: 0.180009506586149300 SEI/USDT

Resources

Chainlink Data Streams documentation

Overview

Essentials

seid CLI

Frontend Development

Smart Contracts

sei-js Library

Videos

Ecosystem Tutorials

Reference

Hardware Wallets

Chainlink Data Streams

What is Chainlink?

What this guide teaches you

Prerequisites

Technical requirements

Sei network setup

Chainlink Data Streams access

Step-by-step tutorial

Step 1: Project setup

Step 2: Fetching price data with TypeScript

Step 3: Smart contract deployment

Step 4: Complete integration script

How to run and test

1. Test off-chain data fetching

2. Test smart contract deployment

3. Test complete integration

Resources

​What is Chainlink?

​What this guide teaches you

​Prerequisites

​Technical requirements

​Sei network setup

​Chainlink Data Streams access

​Step-by-step tutorial

​Step 1: Project setup

​Step 2: Fetching price data with TypeScript

​Step 3: Smart contract deployment

​Step 4: Complete integration script

​How to run and test

​1. Test off-chain data fetching

​2. Test smart contract deployment

​3. Test complete integration

​Resources

What is Chainlink?

What this guide teaches you

Prerequisites

Technical requirements

Sei network setup

Chainlink Data Streams access

Step-by-step tutorial

Step 1: Project setup

Step 2: Fetching price data with TypeScript

Step 3: Smart contract deployment

Step 4: Complete integration script

How to run and test

1. Test off-chain data fetching

2. Test smart contract deployment

3. Test complete integration

Resources