Codex Plan Mode: Reasoning Level and Model Switching Appear Locked

Melvin Vivas · X video post · 2026-09-09 · 0:10 · 3,776 views · Open on X

Topics: AI Dev Tools & Productivity · Level: intermediate

Summary

This is a 10-second clip with no speech. Melvin Vivas asks whether it's a feature or a bug that OpenAI Codex's Plan mode won't let him change the reasoning level or switch models. The post only raises the question and gives no answer, so all you learn is that this limitation was seen in Codex Plan mode around September 2026.

Key points

• The creator saw that in OpenAI Codex's Plan mode he could not change the reasoning setting or switch to a different model.
• The caption mentions "Astra" as where reasoning can't be changed. The post doesn't explain it; it may be a model, profile or mode name.
• It's unclear whether this is intended behavior or a bug. The post asks the question without answering it.
• Practical tip: if you need a different model or reasoning effort, check or set it before entering Plan mode, or leave Plan mode to change it.
• The video has no speech, so the caption is the only information available.

Resources mentioned

• OpenAI Codex · tool · openai.com · paid
  OpenAI's coding agent. In the diagram it writes code, fixes review findings and drives the build loop. The creator also used it to make this video.
  Also in: An agent bot that installs and drives Codex on its own (Melvin Vivas on X · notes), Asking a Coder bot to install Codex (Melvin Vivas on X · notes), Sign in with ChatGPT: Setting Usage Limits for Each App (Melvin Vivas on X · notes), Codex Cloud Environments Must Be Saved & Published Before Use (Melvin Vivas on X · notes) and 240 more