[Windows] Local thread archiving fails with thread-store os error 2

Summary

On the Windows Codex desktop app, archiving a completed local thread fails with a thread-store file-not-found error. The thread remains unarchived.

Environment

• Product: Codex Desktop
• Platform: Windows x64
• App package: OpenAI.Codex_26.814.5167.0_x64__2p2nqsd0c76g0
• Local project thread

Error

The archive request returns:

failed to archive session: thread-store internal error:
failed to archive thread: The system cannot find the file. (os error 2)

The desktop UI reports that the archive failed.

Steps to reproduce

1. Open a completed local Codex thread in the Windows desktop app.
2. Attempt to archive it from the thread/project UI.
3. Observe the archive failure.
4. Restart the desktop app and retry.

Actual behavior

• The first archive attempt shuts down the active thread instance but does not persist the archive.
• A second attempt after the thread is stopped fails with the same os error 2.
• The thread remains visible and its archive state remains archived=0.
• The rollout JSONL file exists on disk, and the archived_sessions directory also exists.
• The affected rollout path uses a Windows extended-length path prefix (\\?\\C:\\...), which may be mishandled by the archive path-move logic.

Expected behavior

A completed local thread should be archived successfully, moved to the archived-session store, marked as archived, and removed from the active thread list.

Related issues

• #36289 — Windows archive fails with a thread-store file-move error (os error 17)
• #26012 — Windows archive/restore path inconsistency with os error 2
• #25713 — Archiving the active Windows thread causes resume/archive state problems

No raw logs, private paths, credentials, or conversation contents are attached.

Start by tracing the desktop archive request into the thread-store file-move logic, focusing on the Windows extended-length path prefix described here; compare the behavior with related issues #36289, #26012, and #25713. Done means a completed local Windows thread moves to archived-session storage, is marked archived, and disappears from the active list without os error 2.