Get Codex¶
Codex is OpenAI's agentic coding tool: a terminal CLI (and IDE/cloud variants) that plans, edits multi-file changes, and runs commands in a sandbox on your behalf. Source: github.com/openai/codex.
Install¶
Then, from inside a project folder:
Sign in with your ChatGPT account (Plus/Pro/Team) or an API key. Other ways in: the IDE extension for VS Code/Cursor, or Codex Cloud for background/async tasks. Full docs: developers.openai.com/codex.
IDE extension¶
Install the Codex extension from the VS Code Marketplace (also works in Cursor and Windsurf; Xcode and JetBrains have their own native integrations) if you'd rather stay in an editor than the terminal:
- Sign in with your OpenAI account, then open the Codex sidebar.
- It pulls your open files and selection into the prompt automatically, so you don't have to restate what you're looking at.
- Edits show as an inline, focused diff you review in place, then follow up in the same chat.
- For a task that's going to take a while, hand it off to Codex web (cloud) from the sidebar: it keeps running, and the chat history is there when you come back.
Full docs: learn.chatgpt.com/docs/codex/ide.
Using its agent on a project¶
cdinto your project folder and runcodex.- Paste the project brief from Foundations, Clinical Application, or Basic Science as your first prompt.
- Codex proposes and runs a plan inside its sandbox, asking approval before network access or destructive commands. Review the diff before accepting.
- Ask it to explain any generated code you don't recognize before you build on top of it.