[Windows 26.903.8094.0] Intermediate chat history repeatedly disappears from UI while messages remain in rollout

Environment

• Codex Desktop for Windows
• Installed AppX package: OpenAI.Codex, version 26.903.8094.0
• Observed on September 9, 2026 (UTC+07:00)
• Long-running local conversation with images, code edits and tool output

Problem

Intermediate conversation history repeatedly disappears from the chat UI. The user can still see an older section and a newly sent message immediately after it, while many intervening user and assistant messages are absent. The task itself remains available; this is missing content inside the conversation, not a missing sidebar task.

The user supplied screenshots confirming the visible discontinuity and reported recurrence during the same investigation. The original trigger and a deterministic minimal reproduction are not yet known.

Verified read-only observations

• The affected local rollout JSONL exists and is approximately 957 MiB.
• A bounded scan of normal-sized response_item/message records found 25 user/assistant messages mentioning a topic from the missing interval, spanning September 5–9. This was a content check, not just a file modification-time check.
• A subsequent extraction from a backup recovered 931 text message records and confirmed that the user's latest complaint about the history disappearing again had been saved.
• That extraction omitted tool outputs, image data and records larger than 2,000,000 characters. It is not evidence that every message has been recovered.
• An attempt to read this task through the desktop read_thread interface returned: "Codex app tool request failed" (MCP error -32000). No more specific error was available from that interface.
• The original rollout and application databases were not edited or deleted. A private local backup was created.

The large transcript size may be relevant, but has NOT been established as the cause. We have not inspected projection ordinals or SQLite state and are not claiming an ordinal mismatch.

Observed workflow

1. Continue a local conversation over several days, including image-heavy and tool-assisted work.
2. View the conversation history.
3. Older content is followed directly by a new user message; the intervening history is missing from the UI.
4. Continue interacting: new messages are still saved in the raw rollout, but the user reports the visible gap again.

Restarting/updating were suggested, but successful completion of those steps was not confirmed by the user.

Expected behavior

All persisted conversation messages should remain accessible in the UI. If history projection/loading fails, the app should show a recoverable error and provide a safe per-task rebuild/reindex path without requiring users to edit or delete their transcripts/databases.

Possibly related

• #41566
• #43124

These reports describe a similar symptom. Whether this case shares their underlying cause is unconfirmed.

Privacy

This issue is submitted at the affected user's explicit request. No raw transcript, private conversation text, credentials, local personal paths, or business screenshots are attached. We can collect narrowly scoped, sanitized diagnostics if maintainers specify what is needed.

Start by reproducing the long-running conversation workflow, then compare the affected rollout JSONL and application databases with what the desktop UI projects. Inspect projection ordinals and SQLite state, as suggested by the report, without editing the originals. Done means persisted messages remain visible, or the app provides a recoverable error and safe per-task rebuild path.