Polymarket New Rule Release: How to Build a New Trading Bot

Original Title: How to build a Polymarket bot (after new rules edition)
Original Author: @_dominatos
Translation: Peggy, BlockBeats

Editor's Note: Polymarket unexpectedly removed the 500ms delay and introduced dynamic fees without prior notice, causing a large number of existing bots to become ineffective overnight. This article focuses on this change, systematically outlining the correct way to build trading bots under the new rules, covering fee mechanisms, order signing, market-making logic, and low-latency architecture, providing a clear and actionable path.

The article has received 1.1M views since its publication, sparking widespread discussion. Under Polymarket's new rules, the advantage is shifting from taker arbitrage to a long-term structure centered around market-making and liquidity provision.

The following is the original text:

Polymarket quietly removes the 500ms delay

Explained below: how to build a truly runnable and profitable bot under the new rules

Two days ago, Polymarket removed the 500ms taker quote delay from the crypto market. No announcement, no reminder. Overnight, half of the bots on the platform became obsolete. But at the same time, this also created the biggest opportunity window for new bots since Polymarket's launch.

Today I will explain in detail: how to build a bot that remains effective under the new rules.

Because everything you've seen before February 18th is now outdated.

If you now ask an AI model to help you write Polymarket bot code, what it gives you will definitely still be based on the old rules: REST polling, no fee handling, completely unaware that the 500ms buffer no longer exists

Such a bot will start losing money from the first trade.

Next, I will explain: what has changed and how to redesign bots around these changes.

What Has Changed?

There have been three key changes in the past two months:

1. The 500ms taker delay has been removed (February 18, 2026)

In the past, all taker orders would wait for 500 milliseconds before execution. Market makers relied on this buffer time to cancel their "expired" quotes, which was almost like a free insurance mechanism.

Now things are different. Taker orders are immediately filled without any cancellation window.

2. The Crypto Market Introduces Dynamic Taker Fee (January 2026)

In the 15-minute and 5-minute crypto markets, takers are now being charged a fee based on the formula: Fee = C × 0.25 × (p × (1 - p))²

Fee Peaks: Around 1.56% near a 50% probability

In the extreme probability range (close to 0 or 1), the fee approaches 0

Remember that arbitrage bot that relied on price delays between Binance and Polymarket, making $515,000 in a month with a 99% win rate?

That strategy is now completely dead. This is because the fee alone is now higher than the exploitable spread.

What's the New Meta?

One-liner: Be a maker, not a taker.

The reasons are straightforward:

· Makers don't need to pay any fees

· Makers can receive daily USDC rebates (subsidized by taker fees)

· After the 500ms cancellation delay, maker orders are actually filled faster

Now, the top-tier bots are already profitable solely based on rebates, without even needing to capture the spread. If you are still running a taker bot, you are facing an escalating fee curve. Near a 50% probability, you need at least over a 1.56% advantage to barely break even.

Good luck to you.

So, What's the Strategy for a Truly Viable Bot in 2026?

Here is an architectural design approach for a bot that remains effective in 2026:

Core Components:

1. Use WebSocket Instead of REST

REST polling is completely outdated. By the time your HTTP request completes a round trip, the opportunity is long gone. What you need is a real-time order book data stream based on WebSocket, not intermittent polling.

2. Fee-aware Order Signing

This is a new requirement that didn't exist before. Now, your signed order payload must include the feeRateBps field. If you omit this field, the order will be rejected outright in fee-enabled markets.

3. High-Speed Cancel/Replace Loop

After the 500ms buffer is removed: if your cancel/replace process takes longer than 200ms, you will face "adverse selection." Others will fill your expired order directly before you can update your quote.

How to Set Up

1. Get Your Private Key

Use the same private key you use to log in to Polymarket (EOA/MetaMask/hardware wallet).

export POLYMARKET_PRIVATE_KEY="0xyour_private_key_here"

2. Set Approval (One-time Operation)

Before Polymarket can execute your trades, you need to approve the following contracts: USDC, conditional tokens.

This only needs to be done once per wallet.

3. Connect to CLOB (Central Limit Order Book)

You can directly use the official Python client: pip install py-clob-client

However, there is now a faster option in the Rust ecosystem:

· polyfill-rs (zero-allocation hot path, SIMD JSON parsing, performance improvement around 21%)

·polymarket-client-sdk (Polymarket Official Rust SDK)

·polymarket-hft (Full HFT Framework, integrating CLOB + WebSocket)

The choice of which one is not important; the key is to choose one that you can onboard and run with the fastest.

4. Query Fee Rate Before Each Trade

GET /fee-rate?tokenID={token_id}

Never hardcode the fee.
The fee is subject to market changes, and Polymarket can adjust it at any time.

5. Include Fee Field in Order Signature

When signing an order, the fee field must be included in the payload. Without this, the order will not be accepted in fee-enabled markets.

{
"salt": "...",
"maker": "0x...",
"signer": "0x...",
"taker": "0x...",
"tokenId": "...",
"makerAmount": "50000000",
"takerAmount": "100000000",
"feeRateBps": "150"
}

The CLOB will validate your order signature based on feeRateBps. If the fee rate included in the signature does not match the current actual fee rate, the order will be rejected outright.

If you are using the official SDK (Python or Rust), this logic will be handled automatically. However, if you are implementing the signature logic yourself, you must handle this yourself, or else the order will never be sent out.

6. Place Maker Orders on Both Buy and Sell Sides Simultaneously

Provide liquidity to the market by placing limit orders on both YES and NO tokens; simultaneously place BUY and SELL orders. This is the core way to earn rebates.

7. Run Cancel/Replace Loop

You need to monitor both: an external price feed (e.g., Binance's WebSocket) and your current order book on Polymarket.

Once the price changes: immediately cancel any expired orders and place new orders at the new price. The goal is to keep the entire loop within 100ms.

Special Note About the 5-Minute Market

The 5-minute BTC price movement market is deterministic.

You can directly calculate the specific market based solely on the timestamp:

There are a total of 288 markets each day. Each one is a brand new opportunity.

Currently validated strategy: about 85% of the BTC price movement direction is already determined around T–10 seconds before the window closes, but Polymarket's odds do not fully reflect this information yet.

The operational approach is to: place maker orders at a price of 0.90–0.95 USD on the higher probability side.

If executed: for each contract, you can earn a profit of 0.05–0.10 USD upon settlement; zero fees; and additional rebates.

The real advantage comes from: being quicker than other market makers in determining the direction of BTC and placing orders earlier.

Common Mistakes That Will Get You Liquidated

· Still using REST instead of WebSocket

· Not including feeRateBps in order signatures

· Running a bot on home Wi-Fi (latency above 150ms vs. <5ms on a data center VPS)

· Market-making in a near 50% probability range without considering the risk of adverse selection

· Hardcoding fee rates

· Not consolidating YES/NO positions (resulting in locked funds)

· Still relying on the old taker arbitrage approach from 2025

The Right Way to Leverage AI

The technical section ends here. By now, you have covered: fee-optimized architecture design, computational approach, new market rules

Next, go ahead and open Claude or any other reliable AI model, and give it a clear and specific task description, for example: "This is Polymarket's SDK. Please help me write a maker bot for a 5-minute BTC market: listen to Binance WebSocket to fetch prices on both YES/NO sides simultaneously place maker orders with order signing including feeRateBps use WebSocket to fetch order book data cancel/repost loop control within 100ms."

The correct workflow is: you define the tech stack, infrastructure, and constraints, AI builds specific strategies and implementation logic on top of that.

Of course, even if you describe the bot logic perfectly, testing before deployment is a must. Especially now, with fees starting to substantially erode profit margins, backtesting under real fee curves is a prerequisite before going live.

The bots that can truly win in 2026 are not the fastest takers but the most excellent liquidity providers.

Please build your system in this direction.

[Original Article Link]