VS Code Codex extension 26.623.31921 causes severe @file mention typing lag on Linux

What version of the IDE extension are you using?

26.623.31921

What subscription do you have?

Plus

Which IDE are you using?

VS Code

What platform is your computer?

Linux 6.17.0-35-generic x86_64 x86_64

What issue are you seeing?

I am seeing severe input lag in the VS Code Codex sidebar composer when typing @file references.

There is no error message. The issue happens before sending any prompt, while typing in the composer.

Example prompt/input:

@log-report

Actual behavior:

• Characters appear very slowly after typing.
• Typing @log-report takes around 8–10 seconds before the text appears.
• The lag happens in every Codex thread, not just one existing thread.
• The lag happens in a clean VS Code profile with only the OpenAI ChatGPT/Codex extension installed.
• VS Code Process Explorer shows window / zygote activity spiking while typing.
• The repository is tiny, so it does not seem related to workspace size.

What steps can reproduce the bug?

1. Open VS Code with a clean profile:

code \
  --user-data-dir /tmp/vscode-codex-test/user \
  --extensions-dir /tmp/vscode-codex-test/ext \
  .

1. Install only the OpenAI ChatGPT / Codex extension:

openai.chatgpt@26.623.31921

1. Open the Codex sidebar.
2. Start a new Codex thread.
3. Type an @file reference in the composer, for example:

@log-report

1. Observe that the typed characters appear with a large delay. In my case, the letters appear around 8–10 seconds later.

What is the expected behavior?

Typing in the Codex sidebar composer, including typing @file references, should be immediate and responsive.

The @file mention/autocomplete UI should not cause noticeable input lag, especially in a tiny repository.

Additional information

I tried the following, and none of them fixed the issue:

code \
  --disable-gpu \
  --user-data-dir /tmp/vscode-codex-test/user \
  --extensions-dir /tmp/vscode-codex-test/ext \
  .

Also tried disabling IME/input method variables:

GTK_IM_MODULE=xim \
QT_IM_MODULE=xim \
XMODIFIERS=@im=none \
code \
  --user-data-dir /tmp/vscode-codex-test/user \
  --extensions-dir /tmp/vscode-codex-test/ext \
  .

The issue still reproduced.

However, downgrading the extension fixes the issue:

Bad: openai.chatgpt@26.623.31921
Good: openai.chatgpt@26.609.30741

So this looks like a regression introduced after 26.609.30741, affecting the Codex sidebar composer / @file mention input path on Linux.