Windows Desktop 26.1007: UI sluggishness with repeated primary-renderer ResizeObserver errors #52827

Problem

The Codex desktop app on Windows is noticeably sluggish during ordinary chat use. Local diagnostics show repeated primary-renderer errors:

[desktop-notifications][global-error] ResizeObserver loop completed with undelivered notifications.

The user reports sluggishness; the error counts below are locally verified. No controlled performance trace has established that ResizeObserver is the cause.

Environment

• Windows x64, Microsoft Store/MSIX installation
• Desktop product version: 26.1007.21434, build 13901, production channel
• Installed package version: 26.1007.2314.0
• Bundled backend reported by the desktop log: codex-cli 0.162.0-alpha.17.2
• Observation date: October 10, 2026
• The app's configured update check reported up_to_date during this investigation

Verified observations

• One current app-run log contains 124 exact ResizeObserver error-line occurrences across approximately 10 minutes. These are log-line counts, not counts of independent user-visible freezes.
• The error records identify the primary renderer. The forwarded records do not identify the observer callback or include a usable component stack.
• Some occurrences are near reasoning-summary updates or failed optional MCP discovery messages. These are temporal associations, not proof of causation.
• A read-only check using the bundled backend's features list reports concurrent_reasoning_summaries as false. No explicit entry was found in the inspected user configuration. This does not establish the effective desktop experiment or per-request override.
• The same log has three guardianv2.thread_context deprecation notices, although the inspected user config contains neither guardianv2 nor thread_context. The exact live source of that override remains unconfirmed.
• A previously observed unknown code_mode_tool_description_first setting is absent from this current run's log and is not claimed to be currently reproduced.

Reproduction and limits

During ordinary local chat use, the user observes sluggishness and the primary renderer logs the repeated ResizeObserver error above. The exact interaction that triggers each event is not yet isolated. A minimal clean-profile reproduction, source-mapped observer trace, and controlled before/after performance comparison have not been performed.

These observations do not establish a GPU problem, memory leak, database corruption, or a shared cause between the layout error and Guardian warning. No chat deletion, cache reset, or application-bundle patch was performed as part of this report.

Expected behavior / request

Please investigate the primary-renderer layout/state-update path in this build and provide a supported diagnostic or workaround that preserves chats and settings. Please distinguish genuine performance failures from noisy generic renderer error forwarding and include actionable source/stack diagnostics.

Separately, the Guardian notice should identify the configuration layer supplying the obsolete field rather than directing users to remove a key absent from their local file.

Related reports

• [Windows][Desktop 26.810.7004.0] Typing and mouse stutter with repeated ResizeObserver loops #39120: Windows typing and mouse stutter with repeated ResizeObserver loops
• Windows Desktop: concurrent reasoning summaries correlate with ResizeObserver loops and UI freezes #33996: summary-update correlation and later corrections showing multiple possible causes
• macOS Desktop: unfiltered ResizeObserver global errors flood logs under misleading desktop-notifications prefix #42495: generic renderer error forwarding under a misleading notification prefix
• Desktop: Guardian experiment reintroduces deprecated thread_context despite clean config.toml #50526: deprecated Guardian field despite clean local configuration
• Windows Desktop: unknown injected code_mode_tool_description_first and opaque forced-cleanup denial #52747: separate unknown injected session-feature report

Privacy

Prepared by a Codex assistant at the affected user's explicit request. This report includes only product versions, generic error strings, aggregate counts, and bounded diagnostic conclusions. No raw logs, screenshots, chat content, local usernames or paths, account/session identifiers, credentials, private files, or third-party provider details are attached.