Building on the Codex Harness — Dominik Kundel, OpenAI

Why watch

Dominik Kundel from OpenAI demonstrates how to build on the Codex App Server, an open-source JSON-RPC protocol that powers Codex, IDE extensions, and third-party clients. The talk covers customizing agents with developer instructions, dynamic/deferred tools, per-thread settings, shipping binaries, generating bindings, and using the Python SDK. Includes a demo of Codex running inside Doom with game-modifying tools. For developers building AI coding agents or IDE integrations.