I tend to tell claude to research what is already there, and think hard, and that gives me much better per-prompt results.
But you are right that codex does that all by default. I just get frustrated when I ask it something simple and it spends half an hour researching code first.
Some do this by using tools like RepoPrompt to read entire files into GPT-5 Pro, and then using GPT-5 Pro to send the relevant context and work plan to Codex so that it can skip needing to poke around files. If you give it the context, it won't spend that time looking for it. But then you spend time with Pro (which can ingest entire files at once instead of searching through them, and provide a better plan for Codex, though)
But you are right that codex does that all by default. I just get frustrated when I ask it something simple and it spends half an hour researching code first.