[BUG] .session-chain-cache.json feature appears incomplete - files only created during brief deployment window

Summary

The .session-chain-cache.json feature appears to be incomplete - files are only created during a brief deployment window and not maintained for new sessions.

Evidence

I investigated my local Claude Code installation and found:

• 6 out of 54 projects have .session-chain-cache.json files
• All files created within 63-minute window: Jan 10, 2026 01:47-02:50 PST
• No updates since: New sessions in those projects don't update the file
• No files created for new projects: Projects used after Jan 10 don't get the file

File Creation Timestamps

2026-01-10 01:47 cc-skills
2026-01-10 01:47 alpha-forge
2026-01-10 01:49 fork-tools (no longer exists locally)
2026-01-10 01:54 .claude (user config)
2026-01-10 02:33 alpha-forge-data
2026-01-10 02:50 alpha-forge-worktree

File Format

The files contain a well-structured schema with session chain tracking:

{
  "version": 1,
  "currentSessionId": "8e017a43-227e-4b37-b1bb-0d136f894271",
  "chain": [
    {"sessionId": "...", "shortId": "8e017a43", "timestamp": "ISO8601"}
  ],
  "updatedAt": 1768042226189
}

Expected Behavior

Based on the file structure, it appears this feature was intended to:

1. Track current session UUID per project
2. Maintain a chain of previous sessions
3. Enable session continuity and debugging

Actual Behavior

• Feature only worked during initial deployment
• New sessions don't update existing files
• New projects don't get registry files

Related Issues

• #18417 - Request for native session persistence
• #12774 - Session continuity across restarts
• #12052 - Session ID visibility request

System Information

• Claude Code version: Latest (Jan 2026)
• Platform: macOS (darwin/arm64)
• Location: ~/.claude/projects/{encoded-path}/.session-chain-cache.json

Impact

This would be valuable for:

• Debugging across session boundaries
• Correlating sessions with transcript files
• Building tools that need session awareness