Windows desktop 26.903.8094.0: repeated 0xc0000409 crashes immediately after Store update check; recent conversation hidden although JSONL survives

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

Installed Windows package: OpenAI.Codex_26.903.8094.0_x64__2p2nqsd0c76g0 (queried with Get-AppxPackage).
Executable: ChatGPT.exe, file version 152.0.7977.83.
Get-AppxPackage reports Status: Ok.

What subscription do you have?

Not included in this diagnostic report.

What platform is your computer?

Windows x64, OS build 26200.6899, display version 25H2. Local timezone: UTC+08:00.

What issue are you seeing?

The desktop app abruptly exits during ongoing work. After reopening, the user sees older conversation content while recent work/conversation appears missing.

Two Windows Application Error events (Event ID 1000) have the same crash signature. In both sessions, the final app-log line is a Windows Store update check, approximately half a second before the crash event. This is a reproducible temporal correlation across two observed crashes, not a confirmed native root cause.

Local time (UTC+08:00)	Final updater log (UTC)	Manifest build offered
2026-09-17 21:02:01.370	2026-09-17T13:02:00.899Z	26.911.7940.0
2026-09-18 18:19:07.874	2026-09-18T10:19:07.379Z	26.915.3509.0

Both events:

• Faulting application: ChatGPT.exe
• Faulting module: ntdll.dll, version 10.0.26100.6899
• Exception code: 0xc0000409
• Fault offset: 0x000000000009bad8

Sanitized final log lines:

2026-09-17T13:02:00.899Z info [windows-store-updater] Checking Windows Store for package updates buildVersion=26.903.8094.0 manifestBuildVersion=26.911.7940.0 packageIdentity=OpenAI.Codex
2026-09-18T10:19:07.379Z info [windows-store-updater] Checking Windows Store for package updates buildVersion=26.903.8094.0 manifestBuildVersion=26.915.3509.0 packageIdentity=OpenAI.Codex

What steps can reproduce the bug?

No minimal deterministic reproduction yet. Observed sequence:

1. Use the Windows desktop app for a long-running local project/conversation.
2. The Windows Store update check runs with a newer manifest build than the installed build.
3. The app exits abruptly; Windows records Event ID 1000.
4. Reopen the app. The user reports that recent conversation content is no longer visible; older content remains.

The newest observed conversation-display problem also followed a later application restart, but no matching Event 1000 has been established for that later restart. The exact causal link between the native crash and stale conversation display is therefore unconfirmed.

What is the expected behavior?

• A Store update check must not terminate active work, including when Store access or package installation fails.
• Recent persisted conversation content should be reloaded after restart.
• If the conversation view/index cannot be rebuilt, surface an actionable error and preserve the original transcript.

Additional information

Conversation recovery evidence

• The local rollout JSONL file still contains the exact recent user requests and assistant messages.
• The file was approximately 121 MB when inspected; a complete line-by-line JSON parse found no malformed JSON lines.
• The task-list tool returned the current task, but the app-provided recent-turn reader returned older turns despite newer records in the JSONL. This may be a display/index/retrieval mismatch; its cause is not established.
• The corresponding project changes remain on disk and the deployed UI contains them.
• The original JSONL has been backed up and a small visible-message export created. No live session or state database has been edited/reset.

Update state

• Current user remains registered to 26.903.8094.0.
• Get-AppxPackage -AllUsers also shows 26.908.9136.0 as Staged for SYSTEM.
• Windows Store policy inspection: RemoveWindowsStore and RequirePrivateStoreOnly are absent; AutoDownload is 0. No policy changes were made.

Related reports: #27146 and #39621 (Store-updater crashes), #46370 (update staging/registration). This report has a different observed exception/module signature from the access-violation reports, so equivalence is not assumed.

Only sanitized technical excerpts are included here. Full conversation logs contain private project data and credentials and are intentionally not attached. Please investigate both native updater crash handling and recovery of persisted recent conversation content.

Follow-up: official Windows package-manager update attempt

After making a consistent SQLite backup (quick_check: ok) and backing up session/index state, attempted:

winget upgrade --id 9PLM9XGG6VKS --exact --source msstore --silent --disable-interactivity --accept-source-agreements --accept-package-agreements

Result: No available upgrade found. No newer package versions are available from the configured sources.

winget list --id 9PLM9XGG6VKS --exact resolves the installed app as ChatGPT, version 26.903.8094.0. The package remains on 26.903.8094.0 after the attempt. No app reset, uninstall, forced shutdown, or live session/database modification was performed. The update-manifest vs. Store availability discrepancy is additional diagnostic evidence; the crash and conversation-display issue are not yet resolved.

No source file or test is named. Start by correlating the Windows Store updater log with Event ID 1000, then inspect the backed-up JSONL and SQLite state; done means isolating the crash path and separately verifying that recent persisted turns reload after restart without altering live state.