Codex

Codex is OpenAI's coding agent, and the notable part of its design is that it is not tied to one surface. The same agent is reachable from the terminal, an IDE extension and the web, so a task started in one place can be inspected in another. Work runs in an isolated environment and comes back as a diff you review, which suits delegating well-scoped changes — implement this function, fix this failing suite — more than open-ended exploration. Running several independent tasks concurrently is where the model pays off.