How to Change the Model in Codex CLI
Type /model and press Enter to change the model in Codex CLI. There is no dedicated key for it — the slash command opens a picker, and that is the only way in.
The thing worth knowing is that /model sets two things at once: which model runs, and how much reasoning effort it spends. Codex treats those as one choice, which is why the picker asks about both.
Reasoning effort has its own keys
You can change reasoning effort without opening the picker at all, and this is the part most write-ups leave out:
| Key | What it does |
|---|---|
| Alt + . | Increase reasoning effort |
| Alt + , | Decrease reasoning effort |
| Shift + Up | Increase — alternate binding |
| Shift + Down | Decrease — alternate binding |
Both pairs are real defaults. Third-party cheat sheets tend to publish one pair or the other and imply the alternative was removed; neither was. The Alt pair is the primary in Codex's own documentation, and the Shift arrows work alongside it — though they drop out if you rebind those arrow keys to something else in your own keymap.
Model and reasoning effort are different dials
It is easy to conflate them, and the failure mode is reaching for the wrong one. A bigger model changes what Codex is capable of. More reasoning effort changes how long it thinks before answering with the model you already have.
If the answers are shallow but the model is right, raise reasoning effort with Alt + . — it is one keystroke and it does not interrupt what you are doing. Opening /model to fix that is the slower path to the same place.
Neither of these is Plan mode
The third setting people mix into this is the collaboration mode, which Shift + Tab cycles. That controls how Codex works with you — whether it plans before acting — and it is independent of both the model and the reasoning effort.
So there are three separate dials, and changing one does not touch the others. If Codex is doing the wrong kind of work rather than doing it badly, Plan mode is the control you want.
The model picker is not the only place models appear
Codex runs on more than one surface, and they do not share a picker. The Codex desktop app has its own model control with its own keyboard shortcut, and the terminal agent's /model only governs the terminal session. Switching in one place does not switch the other.
The rest of the keymap
/model is one entry in a full slash-command catalog, alongside /plan, /new and /resume. On the keyboard side Codex CLI also has Ctrl + J for multi-line prompts, Ctrl + U to clear your input, and Ctrl + C to exit. The Codex CLI cheat sheet has all of it in one printable page.