[BUG] Sessions >500MB not resumable despite frequent compacting #19963

Preflight Checklist

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

What's Wrong?

Description:

Session grew to 568MB despite 48 manual compacts. Now it can't be resumed - /resume says "Session not found" even though the file exists.

Steps to reproduce:

1. Long-running session with many file reads/edits
2. Compact regularly with /compact
3. Session still grows (tool_result content not pruned)
4. Eventually session can't be resumed

Evidence:

• File exists: b9c96563-...jsonl (568MB)
• Session ID in file matches filename
• Index rebuilds but doesn't include the session
• Smaller sessions (<16MB) index and resume fine

Analysis:
48 compact boundaries in file
534 MB of user messages
532 MB of tool_result content

Compacting appears to summarize conversation but retains tool results, causing unbounded growth.

Expected: Compacting should prune old tool results OR large sessions should still be resumable.

Version: Claude Code 2.1.14

What Should Happen?

Compacting should prune old tool results OR large sessions should still be resumable.

Error Messages/Logs

Evidence:
- File exists: b9c96563-...jsonl (568MB)
- Session ID in file matches filename
- Index rebuilds but doesn't include the session
- Smaller sessions (<16MB) index and resume fine

Steps to Reproduce

Steps to reproduce:

1. Long-running session with many file reads/edits
2. Compact regularly with /compact
3. Session still grows (tool_result content not pruned)
4. Eventually session can't be resumed

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

No response

Claude Code Version

Claude Code 2.1.14

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

WSL (Windows Subsystem for Linux)

Additional Information

No response