Codex VS Code Extension – Diff view fails to open


## Codex VS Code Extension – Diff view fails to open

**Extension**
- OpenAI Codex (`openai.chatgpt`)
- Version: **26.721.41059**

**VS Code**
- Version: **1.131.0**
- macOS 15.5 (Darwin arm64 25.5.0)
- Apple M4 Pro

### Steps to reproduce

1. Open a repository in VS Code.
2. Use the Codex panel to modify files.
3. Wait until Codex finishes and displays the list of changed files.
4. Click any changed file (e.g. `README.md`) or click **Review**.

### Expected behavior

The full **Codex Diff** view opens and displays the file diff.

### Actual behavior

The **Codex Diff** tab opens but immediately shows:

> **An error occurred**

or

> **Missing diff tool**

The full diff cannot be displayed.

### Additional observations

- Hovering the mouse over a changed file **shows the diff preview correctly**.
- The problem only affects the full **Codex Diff** / **Review** view.
- Native VS Code diff works normally.
- `git`, `diff` and `opendiff` are installed and available.

```
git:      /opt/homebrew/bin/git
diff:     /usr/bin/diff
opendiff: /usr/bin/opendiff
```

### Browser/WebView console

The WebView console reports:

```
Thread context is unavailable for non-thread routes
```

Stack trace points to the React WebView used by the Diff page.

### Notes

This appears to be a regression in the VS Code extension's Diff/Review view rather than an issue with Git, the repository, or the operating system. The diff preview works, but opening the full review page consistently fails.

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Codex VS Code Extension – Diff view fails to open #36016