setup

Walk the user through turning compact-manager on. Be brief — this is two decisions, not a tutorial.

1. Locate the compact-manager CLI. The path in the later steps normally reads as an absolute path (script installs write it in). If it instead still says ${CLAUDE_PLUGIN_ROOT} literally — plugin installs may not substitute command markdown — find the CLI file itself: find ~/.claude/plugins -maxdepth 8 -type f -name compact-manager -path "*/bin/*" 2>/dev/null (this handles versioned cache layouts, where a directory merely NAMED compact-manager has no bin/). If several paths match, use the most recently modified (ls -t).
2. Read the current state: ~/.claude/compact-manager.json (may not exist; mode defaults to off), "${CLAUDE_PLUGIN_ROOT}/bin/compact-manager" overview, and env | grep '^COMPACT_MANAGER_' — environment variables OVERRIDE the file, so if any are set, warn the user that editing the file alone may not change effective behavior in sessions carrying those variables. If a mode is already set, say so and ask whether the user wants to change it before continuing.
3. Explain the choice in about three sentences, then ask which mode they want:
   • advisory — pure hooks, any platform, zero risk: the model is warned crossing 70% of the context window (and again, firmer, at 80% — whichever thresholds are crossed) so it can save its working state, and after any compaction the saved state is injected back so the session resumes oriented. The user still runs /compact themselves.
   • managed — advisory plus a per-session watcher that types /compact into the session's tmux pane at a verified-idle moment. Linux/WSL + tmux only; each session must be attached explicitly.
   • (off stays available — everything inert.)
4. Ask one follow-up: do they run models with a context window other than 1M? The default context_window is 1,000,000 (the Claude 5 standard); smaller/legacy models need a models override, e.g. {"haiku": {"context_window": 200000}} (substring match, longest wins). Getting this wrong is asymmetric: too small warns — and in managed mode compacts — far too early; too large just means advisories never fire.
5. If the user is switching AWAY from managed (to advisory or off): running watchers snapshot their config at spawn and will keep typing /compact regardless of the file change. Check overview for live watchers and stop each one ("${CLAUDE_PLUGIN_ROOT}/bin/compact-manager" stop <session-id>, with the user confirming the list) — or tell the user explicitly that existing watchers stay active until stopped or their session ends.
6. Write ~/.claude/compact-manager.json with the chosen mode (and any overrides). If the file exists, MERGE — show the user the exact final JSON before writing, and never drop keys they already set. The hooks re-read the file each time, so it takes effect immediately.
7. Close with the command map, one line each: managed sessions attach with the attach command (/compact-manager:attach or /compact-manager-attach); …status shows mode, watchers, and per-session usage (or run bin/compact-manager overview directly — no model turn); …detach stops this session's watcher. If they chose managed and this session is in tmux ($TMUX_PANE non-empty), offer to attach right now.