Codex extension 26.721.30844 fails to load in Antigravity 2.1.1 due to proposed API requirements

What version of the IDE extension are you using?

26.721.30844

Which IDE are you using?

Google Antigravity IDE 2.1.1 on Windows x64
VS Code OSS base: 1.107.0

What issue are you seeing?

After updating the Codex extension to 26.721.30844, the Codex sidebar shows only:

Oops, an error has occurred

The previous extension version, 26.715.61943, works normally on the same machine after rollback.

Antigravity's extension-host logs show that the updated extension requests proposed APIs which Antigravity refuses to grant:

Extension 'openai.chatgpt' CANNOT use API proposal: chatSessionsProvider
Extension 'openai.chatgpt' CANNOT USE these API proposals 'chatSessionsProvider, languageModelProxy'

The Codex log then records an error boundary after a /settings/user request returned HTTP 403.

Steps to reproduce

1. Use Antigravity IDE 2.1.1 on Windows (VS Code OSS 1.107.0).
2. Install or update openai.chatgpt to 26.721.30844.
3. Open the Codex sidebar.
4. Observe the error screen.

Expected behavior

The Codex panel should load normally, as it does with 26.715.61943.

Workaround

Roll back with:

antigravity.cmd --install-extension openai.chatgpt@26.715.61943 --force

Restart Antigravity after installation.

Additional context

Antigravity's UI incorrectly reports that no older versions are available, even though the Marketplace version can be installed through its CLI.