[BUG] "Summarize from here" in rewind menu summarizes entire conversation instead of from selected point

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

When using the rewind menu (Esc+Esc) and selecting "Summarize from here" on a message mid-conversation, the feature summarizes the entire conversation into a single summary message, rather than preserving messages before the selected point and only summarizing from that point onward.

What Should Happen?

Per the checkpointing docs:

• Messages before the selected checkpoint should stay intact (verbatim)
• Only the selected message and all subsequent messages should get replaced with an AI-generated summary

Error Messages/Logs

I had a small session and used "Summarize from here" on a message that was a few messages back (intending to only compress the last few messages). Result:

```shell
✻ Conversation compacted (ctrl+o for history)

⏺ Summarized conversation
⎿ Summarized 121 messages from this point
(ctrl+o to expand history)
...
```

• The entire conversation was compressed into a single summary message
• All original messages became diverged branches
• Result was indistinguishable from running /compact on the entire conversation
• Claude confirmed it only had reconstructed message text from the summary — no actual response content or tool outputs from before the selected point survived

Steps to Reproduce

1. Have a conversation with 20+ messages of back-and-forth
2. Press Esc+Esc to open the rewind menu
3. Navigate to a message near the end of the conversation
4. Select "Summarize from here"
5. Observe that the resulting session has a single summary covering the entire conversation, not just from the selected point onward

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.89

Platform

Other

Operating System

macOS

Terminal/Shell

iTerm2

Additional Information

### Impact

This makes "Summarize from here" functionally identical to /compact, removing its primary value: targeted compression of tangential exploration while preserving earlier context.

### Related issues

• #28716 — Feature request for "Summarize before here" (inverse). Describes current behavior as working correctly ("compresses the selected message and everything after it, keeping earlier messages

intact").

• #38796 — Duplicate of #28716, same description of intended behavior.
• #26488 — Describes the internal implementation (ea4 function that splits at selected message index). No bug reports.

No existing bug reports found for this behavior.