The U.S. Commodity Futures Trading Commission is reviewing unusual trading in Kalshi's Ethereum perpetual futures market after nearly one million trades clustered around $5,500 since August, The Wall Street Journal reported. The pattern represented more than $5 billion in volume and raised concerns about potential wash trading, although the regulator had not decided whether to begin a formal enforcement investigation. Kalshi said it has not been contacted by the CFTC and does not believe a formal investigation is underway. The company said hundreds of separate traders participated, that self-trading is mechanically blocked, and that recurring order sizes result from market makers posting fixed resting orders under liquidity programs that reward quoted sizes and spreads rather than volume. Jump Trading and Wintermute were identified among firms involved in rapid trading, while Jump said it trades for its own account, uses self-match prevention tools and does not coordinate with other traders. The scrutiny comes as Kalshi expands its perpetual futures business, which opened to crypto in May, while facing legal disputes over event contracts and enforcement against users who traded contracts tied to themselves.