OpenAI opens ChatGPT's 1.2B weekly users to developers

DevDay 2026 brought more than 20 major announcements across ChatGPT, Codex and models, and OpenAI calls it its biggest DevDay yet. The headline change is ChatGPT itself: OpenAI says it's now a shared surface where people and agents work together and developers can launch native experiences straight to 1.2B weekly users, with agents that take on ongoing responsibilities. The recap's intro doesn't list the individual announcements, so it doesn't say whether the Free, Prototype and Accelerate API plans spotted earlier in code strings made the cut.