Claude Code hangs indefinitely during context compaction #19567

Summary

Claude Code becomes completely unresponsive when attempting to compact/summarize a large context. The terminal freezes, Ctrl+C doesn't work, and the process becomes orphaned consuming excessive resources indefinitely.

Environment

• Claude Code version: 2.1.12
• OS: macOS 26.2 (Build 25C56)
• Architecture: Apple Silicon (arm64, M3 Max)
• Shell: zsh

Steps to Reproduce

1. Start a Claude Code session
2. Work on a complex task that generates a large context (multiple tool calls, large file reads, spawning subagents)
3. Continue until the session approaches context limits (~23+ MB session file)
4. When compaction/summarization is triggered, the terminal becomes completely unresponsive

Expected Behavior

• Compaction should complete within a reasonable timeout
• If compaction fails, Claude Code should gracefully handle the error
• Ctrl+C should be able to interrupt the process
• The process should not become orphaned

Actual Behavior

• Terminal goes completely blank/unresponsive
• Ctrl+C has no effect
• User must close the terminal window entirely
• The Claude process becomes orphaned (PPID=1) and continues running
• Orphaned process consumes excessive resources:
  • CPU: 277%
  • RAM: 11.8 GB (31% of system memory)
  • Runtime: 26+ hours until manually killed

Diagnostic Information

Orphaned process details:

PID   PPID STAT STARTED     ELAPSED        ARGS
34461    1 R    Mon01PM     01-02:45:16    claude --dangerously-skip-permissions

Process was holding these files (no active session file):

stats-cache.json
cc-hud.json
secondbrain.json
settings.json
cc-statusline.json
history.jsonl

Session that likely triggered the hang:

• Workspace: secondbrain
• Session file size: 23.6 MB
• Session had already been compacted once (started with summary)
• Topic: "CampusIQ Tools Sync & Update Manager"

Impact

• Data loss: Any unsaved work in the session is lost
• Resource exhaustion: Orphaned process consumes ~12 GB RAM until manually killed
• User disruption: Must force-close terminal and hunt for zombie processes

Suggested Fixes

1. Add timeout for compaction API calls - If summarization takes longer than X seconds, abort gracefully
2. Preserve Ctrl+C handling - Ensure signal handlers remain active during compaction
3. Add compaction progress indicator - Show user that compaction is in progress
4. Graceful degradation - If compaction fails, offer to start a new session with a brief summary rather than hanging
5. Session size warnings - Warn user when session file exceeds a threshold (e.g., 15 MB) before hitting critical limits

Workaround

Users experiencing this issue should:

1. Check for orphaned processes: ps aux | grep claude | grep -v grep
2. Look for processes with PPID=1 and high resource usage
3. Kill orphaned processes: kill -9 <PID>