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TimeBoost is Arbitrum’s express lane mechanism that gives the winning bidder a 200ms sequencing advantage for each 60-second round. ouroborai includes a TimeBoostBidder that automates round bidding, MEV estimation, and express lane resale.

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How TimeBoost Works

  • Rounds last 60 seconds each
  • Bidding closes 15 seconds before the next round starts
  • Auction is sealed-bid, second-price (you pay the second-highest bid)
  • The winner can submit transactions via timeboost_sendExpressLaneTransaction
  • Express lane access can be resold to other searchers

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Setup

1

Initialize the bidder

Create a TimeBoostBidder instance with your configuration:
import { TimeBoostBidder } from "@arb-agent/timeboost";

const bidder = new TimeBoostBidder({
  privateKey: "0xYOUR_PRIVATE_KEY",
  rpcUrl: "https://arb-mainnet.g.alchemy.com/v2/YOUR_KEY",
  auctioneerUrl: "https://arb1-auctioneer.arbitrum.io/",
  minProfitThresholdWei: 1_000_000_000_000_000n, // 0.001 ETH minimum
});
Configuration options:
OptionTypeDefaultDescription
privateKeyHexrequiredWallet key for signing bids
rpcUrlstringArbitrum public RPCJSON-RPC endpoint
auctioneerUrlstringOfficial auctioneerTimeBoost auctioneer RPC URL
minProfitThresholdWeibigint0nSkip rounds below this expected value
2

Start the bid loop

The bidder continuously monitors round transitions and bids when profitable:
await bidder.start();
The loop runs every 5 seconds and:
  1. Checks if a new round has started
  2. Estimates expected profit using configured strategies
  3. Fetches the average winning bid from the auctioneer
  4. Caps the bid at 90% of the average to avoid overbidding
  5. Submits the bid if profitable
Stop the loop with:
bidder.stop();
3

Listen for events

Register event handlers for round outcomes:
bidder.on("roundWon", (round) => {
  console.log(`Won round ${round} -- executing priority trades`);
  // Submit your time-sensitive transactions here
});

bidder.on("roundLost", (round) => {
  console.log(`Lost round ${round}`);
});

bidder.on("resaleSold", (slot) => {
  console.log(`Sold express lane access to ${slot.buyer}`);
});
4

Manual bidding (optional)

For fine-grained control, bypass the automatic loop and bid manually:
const round = await bidder.getCurrentRound();
const nextRound = round + 1n;
const bidAmount = 2_000_000_000_000_000n; // 0.002 ETH

await bidder.bidForRound(nextRound, bidAmount);
The auctioneer only considers the most recent bid per address per round. Submitting a second bid replaces the first.
5

Send express lane transactions

When you control the express lane, submit transactions with priority sequencing:
if (bidder.isExpressLaneController) {
  const txHash = await bidder.sendExpressLaneTransaction(signedTx);
  console.log(`Express lane tx: ${txHash}`);
}
Express lane transactions use the timeboost_sendExpressLaneTransaction RPC method and bypass the standard sequencer queue.
6

Resell express lane access

Monetize winning rounds by reselling access to other searchers:
const slot = await bidder.resellExpressLane(
  "0xBuyerAddress",
  5_000_000n, // 5 USDC
);
console.log(`Resale valid until: ${slot.validUntilMs}`);
The on-chain TimeBoostVault contract handles USDC collection from buyers. See Contract Methods for the vault’s purchase_express_lane_access function.

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MEV Estimation

The bidder includes a built-in MEV estimator that calculates expected round value based on available strategies.

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Per-Strategy Values

StrategyEstimated ValueRisk
arb~0.002 ETHLow
liquidation~0.005 ETHLow
sandwich~0.0015 ETHHigh
backrun~0.0008 ETHMedium
resale~0.003 ETHLow

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Using the Estimator

const estimatedValue = bidder.estimateRoundValue([
  "arb",
  "liquidation",
  "resale",
]);
console.log(`Expected round value: ${estimatedValue} wei`);
The estimator subtracts estimated gas costs (~0.00002 ETH on Arbitrum) and applies a historical performance multiplier.

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Historical Calibration

Record actual profits after each won round to improve future estimates: 
bidder.recordRoundResult(round, actualProfitWei);
The bidder maintains the last 100 round results. The history multiplier adjusts estimates:
  • Fewer than 5 recorded rounds: neutral (1x)
  • Average profit below zero: reduces estimates to 0.6x
  • Average profit above 0.005 ETH: boosts estimates to 1.2x

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Auctioneer Stats

The bidder periodically fetches aggregate stats from the auctioneer to inform bidding: 
const stats = await bidder.refreshAuctioneerStats();
if (stats) {
  console.log(`Average winning bid: ${stats.avgWinningBidWei} wei`);
  console.log(`Recent rounds tracked: ${stats.recentRounds}`);
}
Stats are cached for 5 minutes to avoid excessive RPC calls.