[Windows][26.715.2305.0] Severe UI lag persists across two updates while main process consumes ~1 CPU core

What version of the Codex App are you using (From “About Codex” dialog)?

26.715.2305.0 (Microsoft Store package OpenAI.Codex_26.715.2305.0_x64__2p2nqsd0c76g0)

What subscription do you have?

Unknown (not exposed by the desktop app diagnostics)

What platform is your computer?

Microsoft Windows NT 10.0.26200.0 x64 (Windows 11 Pro for Workstations)

What issue are you seeing?

The Windows Codex app is severely laggy in an existing long-running task. The current build is 26.715.2305.0. The same symptom persisted through updates from 26.707.9981.0 -> 26.707.12708.0 -> 26.715.2305.0.

During a 10-sample capture while the lag was visible:

• Main ChatGPT.exe: average 49.1% CPU, peak 104%.
• C: PhysicalDisk: peak 6% active time; average disk queue length stayed at 0.
• Hardware: Intel Core i5-12500 (6 cores / 12 logical processors), 24 GB RAM.

The UI remains laggy even after persistent SQLite log writes are eliminated:

• RUST_LOG=error
• logs_2.sqlite: logs rows = 0, MAX(id)=NULL, database size = 40 KiB
• WAL = 0 bytes and did not grow during a timed observation
• A local BEFORE INSERT ... RAISE(IGNORE) workaround blocks logs-table inserts

This makes logs_2.sqlite churn unlikely to be the immediate bottleneck in this reproduction.

Based on these measurements, this looks more like main/UI/session-history processing than physical-disk saturation. That is an inference, not a confirmed root cause.

What steps can reproduce the bug?

1. Install or update the Microsoft Store Codex app to 26.715.2305.0.
2. Open an existing long local task in a projectless/non-Git workspace.
3. Continue the task until it contains substantial tool and terminal output, then interact normally with the task.
4. Observe severe UI latency while sampling ChatGPT.exe CPU and Windows physical-disk counters.
5. Repeat after app updates. This remained reproducible on 26.707.9981.0, 26.707.12708.0, and 26.715.2305.0.

Current local session-store metadata:

• 136 rollout JSONL files
• 453.5 MB total
• Largest file: 43.2 MB

The large session history may amplify the issue, but I have not proven it causal. A controlled new/short-task comparison was not completed. No session content or PII is attached; a session ID can be provided privately if maintainers need it.

What is the expected behavior?

Typing, scrolling, switching tasks, and rendering tool output should remain responsive in long tasks without the main process repeatedly consuming about one CPU core. Background persistence or history processing should not block the UI.

Additional information

Current package: OpenAI.Codex_26.715.2305.0_x64__2p2nqsd0c76g0

Related older reports: #20214, #20867, #28109, #28224.

This is a new current-version report because the severe lag persists on 26.715.2305.0 after two intervening updates. It also separates the current UI/high-CPU symptom from the older SQLite log-write problem by measuring CPU, physical disk, database rows, MAX(id), and WAL growth together.