Editor's Note: Polymarket removed the 500ms delay without prior announcement and introduced dynamic fees, instantly rendering a large number of existing bots obsolete overnight. This article systematically outlines the correct way to build trading bots under these new rules, providing a clear and actionable path—from the fee mechanism and order signing to market-making logic and low-latency architecture.

After publication, the article garnered 1.1M views, sparking widespread discussion. Under Polymarket's new rules, the advantage is shifting from taker arbitrage to long-term structures centered around market making and liquidity provision.

Original text below:

Polymarket Quietly Removed the 500ms Delay

Here’s the clear explanation: How to build a bot that actually runs and makes money under the new rules.

Two days ago, Polymarket removed the 500ms taker quote delay in crypto markets. No announcement, no warning. Overnight, half the bots on the platform stopped working. But at the same time, this created the biggest opportunity window for new bots since Polymarket launched.

Today I will explain in detail: How to build a bot that still works under the new rules.

Because every solution you saw before February 18th is now outdated.

If you ask an AI model to write Polymarket bot code for you right now, it will give you a solution based on the old rules: REST polling, no fee handling, completely unaware the 500ms buffer is gone.

Such a bot will lose money from the very first trade.

Let me explain: What exactly changed, and how to redesign your bot around these changes.

What Changed?

Three key changes happened over the past two months:

1. The 500ms Taker Delay Was Removed (February 18, 2026)

Previously, all taker orders waited 500ms before execution. Market makers relied on this buffer time to cancel "stale" quotes, which was almost like free insurance.

Now it's different. Taker orders execute immediately, with no cancellation window.

2. Dynamic Taker Fees Introduced in Crypto Markets (January 2026)

15-minute and 5-minute crypto markets now charge taker fees. The formula is: Fee = C × 0.25 × (p × (1 - p))²

Peak fee: ~1.56% around 50% probability

Fee approaches 0 in extreme probability ranges (near 0 or 1)

Remember that bot that arbitraged the price delay between Binance and Polymarket, making $515,000 in a month with a 99% win rate?

That strategy is completely dead. Because the fee alone is now higher than the arbitrageable spread.

What is the New Meta?

In one sentence: Be a maker, not a taker.

The reasons are simple:

· Makers pay no fees

· Makers earn daily USDC rebates (subsidized by taker fees)

· With the 500ms delay gone, maker order execution is actually faster

The top bots now profit just from rebates, without even needing the spread. If you're still running a taker bot, you're facing a constantly rising fee curve. Around 50% probability, you need at least a 1.56% edge just to break even.

Good luck.

So, How Should a Truly Viable 2026 Bot Be Built?

Here is a design思路 (design approach) for a bot architecture that remains effective in 2026:

Core Components:

1. Use WebSocket, Not REST

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

2. Fee-Aware Order Signing

This is a new requirement that didn't exist before. Now, the feeRateBps field must be included in the payload of the order you sign. If you omit this field, orders will be outright rejected in markets where fees are enabled.

3. Ultra-Fast Cancel/Replace Loop

With the 500ms buffer removed: If your cancel-replace process takes over 200ms, you will suffer from adverse selection. Others will snatch your stale quotes before you can update them.

How to Build It

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 Up Approvals (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 the CLOB (Central Limit Order Book)

The official Python client can be used directly: pip install py-clob-client

However, there are now faster options in the Rust ecosystem:

· polyfill-rs (Hot path zero-allocation, SIMD JSON parsing, ~21% performance boost)

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

· polymarket-hft (Complete HFT framework, integrates CLOB + WebSocket)

Which one you choose isn't critical; the key is to pick the one you can get up and running the fastest.

4. Query the Fee Rate Before Placing Every Order

GET /fee-rate?tokenID={token_id}

Never hardcode fees.
Fees vary by market, and Polymarket can adjust them at any time.

5. Include the Fee Field in Order Signing

When signing the order, the fee field must be written into the payload. Missing this will cause the order to be rejected 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 in the signature doesn't match the current actual rate, the order will be rejected outright.

If you use the official SDK (Python or Rust), this logic is handled automatically; but if you implement the signing logic yourself, you must handle this, otherwise the order simply won't go through.

6. Place Maker Orders on Both Sides (Bid and Ask)

Provide liquidity to the market by placing limit orders: On both YES and NO tokens; Place both BUY and SELL orders. This is the core way you earn rebates.

7. Run a Cancel/Replace Loop

You need to monitor simultaneously: External price feeds (e.g., Binance WebSocket); Your current open orders on Polymarket.

Once the price changes: Immediately cancel outdated quotes; Re-place orders at the new price. The goal: Keep the entire cycle under 100ms.

Special Note on 5-Minute Markets

The 5-minute cycle BTC up/down markets are deterministic.

You can directly calculate the specific market just from the timestamp:

There are 288 markets per day. Each one is a fresh opportunity.

Currently validated effective strategy: By T–10 seconds before the window closes, the direction of BTC's move is about 85% determined, but the odds on Polymarket haven't fully reflected this information yet.

The method is: On the side with the higher probability; Place maker orders at a price of $0.90–0.95.

If filled: Profit $0.05–0.10 per contract at settlement; Zero fees; Plus you get rebates.

The real advantage comes from: Figuring out BTC's direction faster than other market makers, and getting your orders up sooner.

Common Mistakes That Will Get You Wiped Out

· Still using REST instead of WebSocket

· Not including feeRateBps in order signing

· Running the bot on home Wi-Fi (150ms+ latency, vs. <5ms for datacenter VPS)

· Market making near 50% probability without considering adverse selection risk

· Hardcoding fee rates

· Not merging YES/NO positions (locking up capital)

· Still using 2025's taker arbitrage mindset

The Right Way to Use AI

The technical part ends here. Now you understand: The architecture design, fee calculation method, and new market rules.

Next, you can open Claude or any reliable AI model and give it a sufficiently clear and specific task description, for example: "Here is the Polymarket SDK. Please write a maker bot for the 5-minute BTC market that: Listens to Binance WebSocket for prices; Places maker orders on both YES and NO sides; Includes feeRateBps in order signing; Uses WebSocket for order book data; Keeps the cancel/replace cycle under 100ms."

The correct workflow is: You define the tech stack, infrastructure, and constraints, and the AI generates the specific strategy and implementation logic on top of that.

Of course, no matter how perfectly you describe the bot's logic, you must test it before going live. Especially at this stage, where fees are already materially eroding profit margins, backtesting under the real fee curve is a mandatory step before deployment.

The bots that will truly win in 2026 are not the fastest takers, but the best liquidity providers.

Build your system accordingly.