[Windows Desktop 26.917] Every completed reply hangs UI; reasoning-summary disable ignored after restart #48033

Codex App version

26.917.9434.0 (Windows MSIX package)

Subscription

Not provided; the issue reproduces in the local desktop UI after a completed response.

Platform

Microsoft Windows NT 10.0.26200.0 x64 (Windows 11), 16 GB RAM

What issue are you seeing?

The Codex desktop window repeatedly enters Windows "Not Responding" immediately when an assistant reply completes. It recovers after selecting "Wait for the program to respond." A reply containing only Hi. reproduced it after a full app restart. Other desktop apps remained responsive.

Windows Application log recorded AppHangTransient for ChatGPT.exe at 10:37:35, 13:05:05, 13:16:57, 13:28:49, and 13:41:50 local time on 2026-09-25 (Asia/Kolkata). The Codex log repeatedly records main_thread_jank_snapshot around turn completion, many ResizeObserver loop completed with undelivered notifications errors, and bursts of fs/getMetadata requests, some delayed roughly 12–20 seconds. Those events correlate with hangs; the metadata requests have not been proven causal.

Three full process dumps captured during separate hangs (13:24, 13:28, 13:31) show the same main UI thread JavaScript callback stack in Chromium/V8. A responsive baseline dump shows that thread waiting normally. Chromium private symbols are unavailable, so the exact application JavaScript function is not identified. Dumps and raw logs remain local because they contain private process memory, paths, and task data; I can provide them through a suitable private support channel.

Reproduction steps

1. Open an existing task in Codex Desktop on Windows.
2. Send any short prompt, even Just reply Hi.
3. When the response finishes, the whole Codex window becomes unresponsive and Windows offers "Close the program" or "Wait for the program to respond."
4. Choose Wait; the window eventually recovers. Repeat with another short prompt.

This occurred repeatedly across multiple turns. It also reproduced after explicitly setting [features] concurrent_reasoning_summaries = false in %USERPROFILE%\.codex\config.toml and fully terminating/relaunching the app. The new process log still says Concurrent reasoning summaries feature override resolved featureOverride=true, so this configuration does not disable the feature in this build. The bundled feature list reports its default as false, which is inconsistent with the running desktop override.

Expected behavior

Completing a reply must not block the desktop UI. An explicit local feature disable should take effect, or the app should clearly report why it was overridden.

Additional information

Related: #33996 (same ResizeObserver/freezing pattern, but its suggested configuration workaround fails here); #22655 (Windows end-of-turn hang). No reinstall, cache deletion, GPU change, or memory-pressure diagnosis is claimed as a fix.