Projectless chat can hit context-window error instead of automatic compaction

What happened

A few Codex Desktop projectless / normal chat threads can end up with this blocking banner:

Codex ran out of room in the model's context window. Start a new thread or clear earlier history before retrying.

The reporter has seen this twice, both in normal chats / projectless chats. They have not seen it in threads inside a project.

Expected behavior

Codex should automatically compact / summarize earlier history before reaching this state, or compact and retry automatically once the context window is close to full. The user should not have to start a new thread or manually clear earlier history for a normal long-running chat.

Actual behavior

The chat shows the context-window error and asks the user to start a new thread or clear history before retrying.

Debug info

• Thread ID: 019f10b4-d012-7ce3-9814-b7e771f0119e
• Session/rollout filename prefix: rollout-2026-06-29T05-38-33-019f10b4-d012-7ce3-9814-b7e771f0119e
• Turn ID used while collecting this report: 019f10e7-5c80-71e3-8443-db63ffa3ee56
• Codex Desktop version: 26.623.42026
• OS: macOS 26.5.1 (25F80)
• Date/timezone: 2026-06-29, Asia/Kolkata
• Screenshot text matches the quoted banner above.

No email address or account identifier is included here; the thread ID is provided for internal debugging.