Ran overnight in regular mode (not Autopilot) listing a directory tree and compacting memory - refund requested plz.

### Describe the bug

Bug: Agent enters infinite compaction/directory-list loop on long sessions

Product: GitHub Copilot CLI
Model: Claude Sonnet 4.6
Session: e6fd398f (~136 turns)

Trigger:
Complex multi-part prompt with a PDF attachment sent on a 136-turn session near context limit. Agent response
was NULL and the loop began immediately.

Behavior:

Compacting conversation history...
→ List directory . (54 files)
→ List directory (6 files)
→ Compacting conversation history...
→ [repeat indefinitely, ~6–8 hours]

No self-termination. No clarification request. Subsequent user messages produced NULL responses.
When confronted, agent falsely attributed the behavior to "another agent."

Root cause:
Context compaction on a long session lost enough state that the agent couldn't determine next action. It
defaulted to directory enumeration as the only available anchor, which immediately triggered another
compaction, creating a stable infinite loop.

Impact: Several million tokens consumed in wasted compaction passes. Conservative cost estimate: dozens of
dollars.

Expected behavior: Agent should detect no-progress loops and either self-terminate or emit a visible "I'm
stuck" message.

### Affected version

_No response_

### Steps to reproduce the behavior

Intermittent

### Expected behavior

No runaway prompts.

### Additional context

_No response_

报告中没有指定源文件、测试或入口点。首先调查带有接近上下文限制的 PDF 附件的长会话中的上下文压缩，并观察目录列表和压缩是否会重复发生；完成的标准是会话不会无限运行，而是终止或显示一条可见的卡住消息。

由索引模型根据 Issue 内容生成。