CPU 100% when loading session files with saved_hook_context

Environment

• Claude Code version: 2.1.27
• OS: macOS 26.3 (Darwin 25.3.0)
• Platform: darwin arm64

Description

Claude Code becomes unresponsive (CPU 100%) when starting a new session in a project directory that contains previous session files with saved_hook_context entries.

Steps to Reproduce

1. Use claude-mem plugin (which injects context via hooks)
2. Start a session in a project directory, have a conversation, then exit
3. Start a second session in the same directory
4. CPU usage spikes to 100% during "Calculating..." phase

Investigation Results

• Session file size: ~67KB (20 lines)
• Contains 8 saved_hook_context entries (~7KB each)
• Total saved_hook_context data: ~56KB
• When session directory is empty: works normally
• When session file with saved_hook_context exists: CPU 100%

Memory footprint observed

• Physical footprint: 2.3GB
• Physical footprint (peak): 9.0GB

Workaround

Deleting session files from ~/.claude/projects/{project}/ resolves the issue temporarily, but it recurs after a new session is created.

Expected Behavior

A 67KB JSONL file should load in milliseconds without causing CPU spike.

Actual Behavior

Loading the session file causes CPU 100% usage and the application becomes unresponsive.