Polymarket shifts to TWAP pricing after suspected settlement manipulation
Polymarket is replacing the single-price snapshot used to settle short-dated prediction markets with time-weighted average price (TWAP) to address widespread complaints about settlement manipulation.
After onchain researchers reviewed roughly two months of five-minute bitcoin contracts, they reported 821 accounts generated about $8.2 million in “likely manipulated” settlement windows. The study found unusually large Binance trades in the final seconds before settlement, followed by quick BTC price reversals. While the paper did not prove traders’ intent, it said that after excluding market makers, 93% of losses in windows classified as manipulated fell on retail traders. In effect, a bet the market treated as near-certain was overturned about once in three.
Polymarket said the “vulnerability is structural” and that it is updating how crypto up/down markets resolve. The new mechanism uses short TWAP windows—30 seconds for five-minute markets and 60 seconds for 15-minute and four-hour markets—and delivers the data via Chainlink Data Streams. Polymarket also added $1M in liquidity rewards across impacted markets through August.
The article contrasts Polymarket with rival Kalshi, which says it uses a regulated CF Benchmarks price index and a 60-second moving average, making brief price distortions harder and more costly.
For traders, the key change is that Polymarket’s settlement method should reduce the profitability of “last-second” price pushes on BTC around settlement—potentially lowering short-term manipulation risk while keeping the market’s trading activity more robust over time.
Neutral
This is unlikely to be broadly bullish or bearish for crypto spot markets. It is mainly a market-structure and settlement-risk update inside Polymarket. By moving from a single-price snapshot to TWAP, Polymarket is directly targeting the specific “last-second” manipulation pattern highlighted by researchers—so the most immediate effect should be improved fairness and reduced micro-time distortions around settlement.
Historically, similar responses to detected settlement vulnerabilities in derivatives or event-driven markets tend to reduce arbitrage/manipulation intensity in the short term (fewer outsized, fast reversals right at expiry), but they don’t usually change the overall direction of BTC/ETH because they don’t alter macro liquidity or fundamentals. In the long run, traders may shift toward more consistent execution strategies (less reliance on capturing single-window price spikes), and volume/liquidity can improve if confidence rises.
Net: neutral for the broader market, with a localized positive effect on Polymarket’s integrity and traders’ execution expectations.