What changed
OpenAI compiled five Codex and three Codex-plus-Claude-Code projects spanning packaging, optimization, language migration and GPU redesign. Contributors repeatedly emphasized external correctness tests, staged changes, representative workloads and long-term stewardship.
Why it matters
The field report makes scientific coding-agent value concrete while showing that domain experts shift from implementation toward specification, verification and maintenance ownership.
What to do
Select one maintenance task with a trusted reference output, stage the migration behind representative workloads and assign a named maintainer before accepting agent-generated code.
Caveat
The eight projects are exploratory, self-selected case studies rather than a controlled productivity study, and contributors' acceleration claims are not independently measured.