VS Code extension: Chat/Agent mode selector disappeared after model switch and does not return

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

Codex — OpenAI’s coding agent (openai.chatgpt) v0.4.71

What subscription do you have?

ChatGPT Plus

What issue are you seeing?

The Chat/Agent mode selector disappeared in the Codex VS Code extension and does not come back.

This happened after setting model = "gpt-5.3-codex" in ~/.codex/config.toml. Reverting to gpt-5.2-codex or removing model did not restore the selector.

Current config:
model_reasoning_effort = "medium"

Reproduces on two machines (one clean install from scratch), so this does not look like local profile corruption.

UI now shows Local and Default permission, but no visible mode selector.

Relevant logs include repeated:

• [IpcClient] Initialize failed (error(name=Error))
• [CodexMcpConnection] CLI: string(len=224) (and 239/449/674/719)

What steps can reproduce the bug?

1. Install VS Code extension "Codex — OpenAI’s coding agent" (openai.chatgpt).
2. Sign in with ChatGPT Plus account.
3. Confirm mode selector is/was available.
4. Set model = "gpt-5.3-codex" in ~/.codex/config.toml.
5. Reload VS Code window.
6. Observe mode selector disappears.
7. Revert config to gpt-5.2-codex or remove model entirely.
8. Reload/restart VS Code.
9. Selector still does not return.

Also reproduced on a second machine with a clean install.

What is the expected behavior?

Mode selector (Chat/Agent, or equivalent explicit mode control) should remain visible for supported Codex IDE workflows, and should return after reverting model config.
Mode selector is missing permanently after the model switch event, even after revert/restart and on clean install.

Additional information

VS Code 1.109.0 (user setup)
Commit: bdd88df003631aaa0bcbe057cb0a940b80a476fa
Date: 2026-02-04T02:01:38.288Z
Electron: 39.3.0
Chromium: 142.0.7444.265
Node.js: 22.21.1
OS: Windows_NT x64 10.0.19045