According to Greg Brockman on X (citing user am.will/LLMJunky), the OpenAI Codex app server enables developers to build agentic applications by exposing unified endpoints for sessions, agents, skills, folders, and prompts, allowing seamless continuity between desktop and mobile experiences. As reported by the same X thread, the community-built Kitty Litter app by @SIGKITTEN demonstrates how developers can plug into the Codex app server instead of building full infrastructure, accelerating time-to-market for custom agent workflows and multi-device chat synchronization. According to the X posts, the server supports using a ChatGPT account across different harnesses, creating a consistent developer experience (DX) and user experience (UX) that lowers integration overhead and encourages third-party app ecosystems.