Desktop: launch crash ("Something went wrong") caused by a persisted composer @-mention draft — at-mention-list TypeError reading 'match'

Environment

• Codex App version: 26.616.51431 (build 4212)
• Platform: macOS 26.5.1 — Darwin 25.5.0 arm64 arm
• Subscription: ChatGPT Pro

What happens

On launch, Codex Desktop immediately shows the full-screen "Something went wrong" / "糟糕，出错了" error and is completely unusable — clicking Retry just throws again. It started right after the app auto-updated to 26.616.51431, so this is a regression (the previous version was fine).

How to reproduce

1. In the composer (the message box of a new conversation), type @ followed by a letter — e.g. @r — to start an @-mention. Don't pick anything from the popup and don't send the message; just leave @r sitting in the box.
2. Quit Codex while that unsent text is still in the composer.
3. Reopen Codex.

➡️ It comes straight up to the "Something went wrong" screen and never loads the UI.

In short: any half-typed @-mention left in the composer when you quit will brick the app on the next launch.

Screenshot

<img width="1100" height="500" alt="Image" src="https://github.com/user-attachments/assets/a1f95f29-59b4-48da-9fa8-651fe56a2956" />

Workaround

Since the app won't open, you can't clear it from the UI. Quit Codex, then in ~/.codex/.codex-global-state.json set electron-persisted-atom-state.composer-prompt-drafts-v1 to {} (that's where the unsent composer draft is stored — mine held {"new-conversation":"@r"}). Back up the file first, then relaunch.

Technical details (for maintainers)

Renderer error, caught by the top-level AppRoutes error boundary:

TypeError: Cannot read properties of undefined (reading 'match')

React component stack (leaf first): at-mention-list → composer-top-menu-chrome → composer. On launch the saved draft is restored, the @-mention list re-renders for that query, and something on that code path calls .match() on an undefined value — which throws through the top-level error boundary and takes down the whole app.

Notes:

• Reproduces with a clean --user-data-dir, so it isn't Chromium profile/cache corruption.
• Independent of remote SSH hosts (crashes whether or not a remote connects).
• An @r draft in an otherwise-empty CODEX_HOME doesn't crash on its own — it needs normal workspace/session data present so the @-mention list has items to render.

Expected behavior

A leftover/partial @-mention draft should render normally (or simply be ignored). It must never throw through the top-level error boundary and make the entire app unlaunchable — the @-mention list should guard the undefined value instead of calling .match() on it.