Conversation cache unexpectedly drops to nearly zero during short continuous sessions #21756

Summary

Recently, the conversation/cache indicator sometimes drops almost to zero unexpectedly, even when I continue the same conversation with only a short gap and without closing or restarting Codex.

What I observed

• The cache appears healthy during an ongoing conversation.
• After a short interval, the cache can suddenly be nearly 0.
• This can happen even for back-to-back messages in the same thread.
• I did not quit Codex, reload the session, switch projects, or intentionally clear context/cache.

Expected behavior

The cache should remain available for continuous or short-interval conversations in the same session unless there is an explicit reset, compaction, restart, or other visible reason.

Actual behavior

The reported cache suddenly drops to almost zero, which makes the conversation feel as if context reuse has been lost.

Environment

I'm using Codex with the Chrome extension on macOS. I can provide logs or version details if helpful.