[Windows][Chat] Reasoning effort is stuck on Instant in newly opened chats; existing chats work

Product

ChatGPT desktop app — regular Chat mode, not ChatGPT Work or Codex.

Environment

• App version: 26.901.1978.0
• Package: OpenAI.Codex_26.901.1978.0_x64
• Subscription: ChatGPT Pro
• OS: Windows 25H2, build 26200.9168, x64
• Date reproduced: September 3, 2026

Summary

In the Windows ChatGPT desktop app, the reasoning-effort selector works normally inside existing regular Chat conversations.

However, when I open a new chat window or enter the New Chat page, the selector cannot retain Medium, High, or Extra High. It remains on or returns to Instant. Pro can still be selected.

This report concerns regular Chat mode, not ChatGPT Work.

Steps to reproduce

1. Launch the ChatGPT desktop app on Windows.
2. Open an existing regular Chat conversation.
3. Open the reasoning-effort selector.
4. Confirm that Medium, High, and Extra High can be selected normally.
5. Open a new chat window or select New Chat.
6. Open the reasoning-effort selector.
7. Attempt to select Medium, High, or Extra High.

Expected behavior

The selected reasoning-effort level should remain selected and be used for the new conversation, just as it is in existing conversations and on chatgpt.com.

Actual behavior

• Existing regular Chat conversations: reasoning-effort selection works.
• Newly opened/empty Chat conversations: the selection remains on or returns to Instant.
• Only Instant and Pro can be selected reliably.
• No usage-limit, permission, or model-availability error is shown.

Control tests

• The same account can select all available reasoning-effort levels normally on chatgpt.com.
• Model and reasoning selection in ChatGPT Work are unaffected.
• Existing regular Chat conversations in the same Windows app are unaffected.
• Therefore, the problem appears limited to initialization of the regular Chat New Chat composer/window.

Troubleshooting already attempted

• Checked Microsoft Store for updates.
• Used Windows Repair.
• Used Windows Reset.
• Uninstalled and reinstalled the app.
• Recreated the app-local package data.
• Restarted the app and Windows.

The issue remains reproducible after all these steps.

Related reports

This may be related to the following new-chat initialization issues:

• #42191 — Windows selector is unclickable on the New Chat page, while it works in existing conversations.
• #20364 — Thinking effort defaults to Low and cannot be changed when starting a new chat.
• #21093 — New-chat reasoning selection does not apply to the initial prompt.

My reproduction differs because it occurs in regular Chat mode on Windows version 26.901.1978.0, and the selector is specifically stuck on Instant while existing Chat conversations work normally.

Additional information

Screenshots are available if needed. They show the same account and application successfully selecting High/Extra High in existing regular Chat conversations, while a newly opened Chat window remains on Instant.

No repository file or test is named. Start by reproducing the issue in the Windows desktop app's regular Chat New Chat composer, then compare its reasoning selector with an existing conversation and chatgpt.com. Done means Medium, High, and Extra High remain selected and apply to the new conversation.