OpenAI core product lead Thibault Sottiaux confirmed on social media that the Ultra version of the next flagship model, GPT-5.6 Sol, will be integrated into Codex.
https://twitter.com/thsottiaux/status/2073933490513752151
This comes after users complained that OpenAI made a major mistake by not including GPT-5.5 Pro in Codex, arguing that adding GPT-5.6 Ultra would allow developers to ditch paying for Anthropic's Claude. Sottiaux publicly responded, confirming that the Ultra version is indeed on Codex's roadmap.