Last month, Garrick Wilhelm joined the rush into prediction market trading, but he soon began to regret it. This user based in British Columbia, Canada, registered on the Polymarket platform and started placing bets on events related to the Middle East situation, with one betting option being whether Israel and Hezbollah could reach a ceasefire agreement.
Wilhelm put in $567 on a losing bet, convinced that the armed group would absolutely not sign a ceasefire agreement, calling it a sure win.
Subsequently, Israel and the Lebanese government reached a truce agreement. Some traders deemed this equivalent to reaching a ceasefire with Hezbollah. After carefully studying the platform rules, Wilhelm firmly disagreed with this determination.
The outcome of this bet involving millions of dollars was not ultimately decided by the Polymarket platform. Wilhelm then learned that the resolution of his trade was to be arbitrated by a loosely organized group holding cryptocurrency tokens.
With a massive influx of new users and explosive growth in trading volume, trading disputes have become an increasingly thorny problem for prediction market platforms like Polymarket. Platforms originally strive to frame betting topics as clear-cut, black-and-white questions, but real-world events are complex, and the line between win and loss is often blurry.
Most other similar prediction market platforms, like Kalshi, resolve controversies and determine final outcomes themselves; but Polymarket chooses to outsource its dispute arbitration business to a third-party service called UMA. When parties to a trade disagree on the payout result, the UMA voting arbitration mechanism is triggered. Voting power is controlled by UMA token holders, with more tokens conferring greater voting weight, and the vast majority of voters remain anonymous.
Polymarket explicitly states in its user agreement that the platform assumes no responsibility for arbitrating disputes related to trading contracts.
Many traders and crypto industry veterans point out that this UMA voting system is highly susceptible to manipulation. Token holders can freely vote on contentious bets in which they have a financial stake, with no institutional constraints.
Analysis by The Wall Street Journal, combining Polymarket trading data and on-chain information, found: Over the past year, at least 60% of active UMA voters could be matched to Polymarket trading accounts; in over 300 dispute cases during the same period, UMA voters were found to hold financial positions in the very bets under dispute.
UMA bills itself as decentralized, but on-chain data shows voting power is highly concentrated among a few "whales." Statistics indicate that in the vast majority of dispute votes, the top ten wallet addresses account for over half the votes.
Nic Carter, founding partner of venture capital firm Castle Island Ventures, bluntly stated that Polymarket shouldn't shirk its dispute resolution responsibilities. "Arbitrating disputes is inherently part of Polymarket's job. It shouldn't be outsourced to this anonymous, unidentified third-party group of token holders."
A Polymarket spokesperson responded that only 0.2% of betting contracts on the platform trigger UMA voting arbitration, and added that UMA disperses adjudication authority into an open market system rather than leaving it to a single entity.
In March of this year, Polymarket founder Shayne Coplan admitted at a Harvard Business School forum that the platform's current dispute resolution mechanism indeed has many flaws. "Related optimization solutions are about to be implemented," he said, but did not reveal specific reform details. It is reported that Polymarket has entered into a data partnership with Dow Jones, the parent company of The Wall Street Journal.
UMA was co-founded by two former Goldman Sachs traders and is managed by the Risk Labs Foundation, registered in the Cayman Islands. Foundation spokesperson James Fry stated that no conclusive evidence has been found to suggest UMA manipulates trades. "Much of the external skepticism is just losing traders looking for excuses."
When disputes arise, UMA token holders debate on the Discord social platform, citing various pieces of evidence to support their views. UMA also has a penalty mechanism that financially penalizes users who vote in the minority, a move the platform says aims to guide voters toward factually correct determinations.
According to statistics from Polymarket's dedicated trading terminal Betmoar, from the beginning of 2026 to now, the platform has seen over 1,150 betting disputes, a number that has already surpassed the total for all of 2025.
A recent popular dispute involved a bet on whether streamer Clavicular would officially announce a pregnancy: the streamer did publicly announce a partner's pregnancy, but many traders argued this announcement didn't meet the contract's requirement of a "formal and valid declaration." Ultimately, UMA voting ruled the announcement was compliant. Additionally, multiple arbitration disagreements have erupted over bets related to the situation in Iran.
Public regulatory filings show that Polymarket initially handled various disputes internally; in early 2022, the platform reached a settlement with the U.S. Commodity Futures Trading Commission over alleged violations of U.S. financial regulations and subsequently handed over all dispute arbitration work to UMA.
This model of adjudication by a dispersed group of token holders also serves as a key basis for Polymarket to argue it is an offshore platform, not subject to U.S. domestic regulation.
However, Polymarket occasionally overturns UMA's final rulings and also proactively adds supplementary clarifications to betting contract details to avoid potential disputes.
The novice trader Wilhelm mentioned earlier ultimately lost his bet related to the ceasefire agreement; 87% of UMA token voters determined that the Israel-Lebanon truce agreement applied to the Hezbollah-related bet. Despite reasoned arguments from Wilhelm and others, they were powerless to change the ruling.
A group of losing traders formed a Discord community called "Whale Hunters," collectively accusing top UMA voting users of suspected backroom dealings.
Traders have pointed fingers at the startup project UMA.rocks, a platform that allows UMA token holders to pool their voting tokens and delegate voting authority to a specialized decision committee. Its votes recently accounted for about 8% in various dispute votes and are also seen by the market as an important indicator of UMA's overall ruling trends.
UMA.rocks founder Lancelot Chardonnet responded: "Many traders' losses are essentially because they didn't seriously read the betting rules, but afterward they shift all the blame to UMA and our platform. We are the easiest targets."
At the end of April, UMA.rocks formally expelled voting committee member Scout, citing his past suspected market manipulation behavior.
Contacted via Discord, Scout denied manipulating the market or deliberately guiding incorrect voting outcomes but readily admitted to participating in Polymarket bets on disputed markets while exercising UMA dispute voting power.
Scout believes that voters with such conflicting interests can actually make rulings more aligned with the facts. "Voters with no skin in the game might spend at most 5 minutes casually looking into the matter; but we, as stakeholders, driven by our own financial interests, will verify the full picture of the event to make an accurate judgment."
He acknowledged the industry faces a dilemma: "Either use traders with conflicting interests in the adjudication, or let complete outsiders with no expertise drive the voting. There's currently no perfect answer."
