Gemini Launches Custom Combos RFQ API for Prediction Markets Beta Testing

Gemini is rolling out a new trading tool that brings Wall Street-style execution mechanics to prediction markets. The exchange’s Custom Combos feature is now live for beta testing in its sandbox environment, allowing market makers to submit sealed bids on multi-leg prediction market contracts through a Request-for-Quote (RFQ) API.

The RFQ process operates on a tight schedule. Market makers have a 1-second window to submit their quotes after a request is made. The requester then has 5 seconds to accept the best bid. Following this, the winning market maker receives a 1-second “last-look” confirmation period to finalize the trade. This entire lifecycle moves through defined states: OPEN, PENDING_ACCEPTANCE, CONFIRMING, and FINALIZING, wrapping up in approximately 7 seconds.

Due to the sealed-bid design, competing market makers cannot view each other’s quotes, with only the winning bid disclosed after the auction concludes. The contracts require at least two legs, enabling traders to construct custom combinations of prediction market positions rather than being limited to single-outcome bets. Production access remains restricted during this controlled beta phase, with developers and market makers only able to integrate and test through the sandbox environment.

Gemini entered the prediction markets space in late 2025, and Custom Combos represent its strategy to stand out in an increasingly competitive field, where similar combo capabilities have been introduced by competitors like Kalshi and Polymarket. However, Gemini’s approach differs in its execution model, utilizing an RFQ system that creates a private marketplace for institutional liquidity providers to compete for flow.