OpenAI chief scientist Jakub Pachocki’s internal memo, reported June 11, described GPT-5.6 as a meaningful improvement over the GPT-5.5 model released April 23, shifting trader focus toward late June and supporting the 75% market-implied odds for a June 22–28 release. Codex backend leaks earlier in May and a fast post-GPT-5.5 iteration cadence have reinforced expectations of imminent availability, while the absence of an official announcement or model card keeps the 16% probability on “not released by June 28” alive. Competitive pressure from rivals and the model’s rumored efficiency and context-window gains further anchor sentiment around the coming week as the most likely window.