Compaction happens at low context usage (e.g. 20%) and don't get reported as an actual checkpoint?

Describe the bug

I keep seeing gpt-5.6 sol getting compacted at like 20% context usage. It shows a message like this and if I run /session checkpoints like it says in the message it says no checkpoints. Well, which is it, did you just add a checkpoint to the session or not?

Affected version

1.0.81

Steps to reproduce the behavior

1. Use GPT-5.6 Sol for awhile and see it auto-decide to compact
2. See the session compact message
3. Type /session checkpoints

Expected behavior

What's the point of having 80% available context when you force compaction at 20%.
I also expect that if you do a compaction it shows up in the list instead of this gaslighting message about there being a checkpoint and then doing the exact recommended command shows nothing.

Additional context

Windows Terminal on x64 win11

首先使用 GPT-5.6 Sol 复现该行为：观察自动压缩消息，然后按描述运行 /session checkpoints。跟踪压缩和检查点报告的入口，并在压缩阈值与消息保持一致且生成的检查点出现在列表中时，认为该 issue 已完成。