How Codex ran OpenAI DevDay 2025

This post details how Codex, OpenAI's AI coding assistant, was instrumental in building and executing OpenAI DevDay 2025. It showcases specific use cases where Codex was employed to: control physical hardware (cameras via VISCA protocol, venue lighting MCP server), develop complex user interfaces (beat pad for ChatGPT demo), generate game assets and implementations (ArcadeGPT), migrate applications from Streamlit to FastAPI/Next.js, create booth demos with AI-generated SVGs and refactored architectures, assist in reviewing and fixing bugs in SDKs (Guardrails, Agents), manage multiple independent coding tasks concurrently, organize and convert fragmented documentation into MDX, and rapidly implement a new 404 page. The post highlights the efficiency gains and problem-solving capabilities provided by Codex CLI, IDE extension, and Codex Cloud in accelerating development and enabling engineers to multitask effectively.