"Cannot serialize value: (couldn't stringify value)" when starting a Codex Worktree chat. Update past 26.1016.51333 or use Local

Error (Codex desktop app, first message of a new chat):

Error starting chat
Cannot serialize value: (couldn't stringify value)

When: Codex app 26.1016.51333 (build 21161), from 21 Oct 2026, on macOS, Windows and Linux. Only chats started with New worktree selected fail; Local chats start normally. The app's own updater reported "up to date" on the broken build.

Cause (from reporters' logs, not confirmed by OpenAI): the app fails while preparing the worktree request (managedWorktrees.pending.create), before any worktree is made. Two reporters traced it to one value, openingPromptForHistory.document.attrs, which the app's serializer refuses.

Fix:

1. Update the app. Reporters confirmed it fixed in 26.1016.61520 on macOS (the issue's author closed it on 22 Oct 2026 after updating) and in 26.1016.62342 on Windows (22 Oct 2026).
2. Until you can update: switch the new chat to Local instead of New worktree. Several reporters confirmed this works on the broken build.

Versions: broken in 26.1016.51333 (Windows package OpenAI.Codex_26.1016.6573.0). Fixed per reporters in 26.1016.61520 (macOS) and 26.1016.62342 (Windows). The previous build named in reports was 26.1013.

Sources:

• https://github.com/openai/codex/issues/55744 (reporter's closing comment, 22 Oct 2026)
• https://github.com/openai/codex/issues/55827 (Windows)
• Codex changelog, checked 28 Oct 2026, has no 26.1016 app entry yet: https://learn.chatgpt.com/docs/changelog

Verified: the error text, the affected build, the Local workaround and the fixed builds, each from several independent reporters. Not verified: OpenAI has not commented or named the fix in its changelog, and it was not run here.