Problem

.caveman-active is single global file. When multiple Claude Code sessions run simultaneously with different caveman levels, they clobber each other.

Session A sets ultra → writes ~/.claude/.caveman-active = "ultra"
Session B starts → overwrites file = "full"
Session A statusline now shows wrong mode.

Both caveman-activate.js (SessionStart) and caveman-mode-tracker.js (UserPromptSubmit) write to same global path.

Fix

Use session_id from hook stdin JSON to write per-session flag files:

~/.claude/.caveman-active-{session_id}

session_id is available in:

• Hook stdin JSON (data.session_id)
• Statusline stdin JSON (.session_id)

Changes needed

1. caveman-activate.js — parse stdin for session_id, write ~/.claude/.caveman-active-{session_id}, cleanup stale files >24h
2. caveman-mode-tracker.js — extract session_id from already-parsed stdin, write per-session file
3. caveman-statusline.sh — extract session_id via jq, read per-session file, fallback to global

Environment

• macOS, Claude Code CLI
• Multiple terminal sessions with different caveman levels