Reasoning level doesn't change for new 'Chat' threads

What version of the Codex App are you using (From “About Codex” dialog)?

Version 26.415.30602 (1773)

What subscription do you have?

ChatGPT Pro

What platform is your computer?

MacOS Darwin 25.4.0 arm64 arm

What issue are you seeing?

Whenever I create a new Chat thread, it defaults the last used reasoning level to the thread. If I attempt to change it, the dropdown opens, I can select a different reasoning level, but it doesn't show the new reasoning level when the dropdown closes.

Feedback ID: d162698b-b968-49b1-8305-4b5deabc5051

<img width="766" height="292" alt="Image" src="https://github.com/user-attachments/assets/4910d146-6867-4abc-a2eb-1ebf4a4baf5b" />

In the above image you can see that the current reasoning level when the new chat thread popped up was 'Extra High' and I am attempting to select 'Medium'

<img width="771" height="285" alt="Image" src="https://github.com/user-attachments/assets/4560c767-e93b-4ad1-b711-8df67945a6c0" />

After selecting medium the dropdown closes but the "selected" reasoning level stays at 'Extra High'.

What steps can reproduce the bug?

Uploaded thread: d162698b-b968-49b1-8305-4b5deabc5051

• Click New Chat (Opt + Cmd + N)
• Before submitting a prompt attempt to change the reasoning level
• Once the dropdown dissapears, the reasoning level will not change

What is the expected behavior?

Upon selecting a new reasoning level from the new chat's dropdown, the reasoning level will change to the selected reasoning level

Additional information

_No response_