OpenAI has released major model updates on varying schedules—GPT-4 in March 2023, GPT-4 Turbo in November 2023, and ongoing point releases throughout 2024 and 2025. GPT-5.5 would represent an intermediate minor version rather than a major numbered release, a common pattern in AI model development cycles. As of mid-April 2026, the market currently prices an April 29 release at just 1% YES odds, indicating traders view this date as highly improbable. This low probability likely reflects broader expectations about OpenAI's historical release patterns, which have not typically clustered around late April timeframes. The market is straightforward to resolve: OpenAI must officially announce and make GPT-5.5 publicly available through their website, API, or ChatGPT interface by 11:59 PM UTC on April 29, 2026. Without an official, publicly accessible release by that deadline, the market resolves NO. Traders assessing this market are evaluating the timing of a specific model release, using OpenAI's historical development cadence and public statements about their roadmap as reference points for their probability estimates.