Refactor watch-inbox to use platform Monitors primitive (v4.x scope)

[michael-wojcik]

Background

Plugins reference §Monitors (Claude Code v2.1.105+) documents a declarative platform primitive for plugin-managed background monitors. Monitors are declared in monitors/monitors.json (or inline in plugin.json); the harness starts them automatically when the plugin is active and turns each stdout line into a notification.

This overlaps significantly with the inbox-watch mechanism shipped in #603 and #609 (/PACT:watch-inbox + /PACT:unwatch-inbox + wake_lifecycle_emitter PostToolUse hook).

Comparison

Concern	Current PACT (#603/#609)	Platform Monitors
Spawn mechanism	Skill-invoked Monitor via Skill(\"PACT:watch-inbox\")	Declarative `monitors/monitors.json`
Lifecycle	Armed on first-active-task transition; torn down on last-active-task transition	`when: "always"` (session-lifetime) or `when: "on-skill-invoke:"`
Duplicate prevention	Custom logic in skill body	`name` field; "Prevents duplicate processes when the plugin reloads or a skill is invoked again"
Path substitution	None	`${CLAUDE_PLUGIN_ROOT}`, `${CLAUDE_PLUGIN_DATA}`, `${user_config.*}`, `${ENV_VAR}`

Scope

Platform Monitors solve the spawn / lifecycle / duplicate-prevention problem declaratively. They do not solve PACT's task-state-conditional arming logic ("arm only while at least one teammate task is in_progress"), which would still need PACT-side hooks (TaskCreated / TaskCompleted / TeammateIdle) to start and stop a platform-managed monitor.

Suggested refactor:

1. Declare the inbox monitor in `monitors/monitors.json` with `when: "on-skill-invoke:watch-inbox"` (or similar gating)
2. Reduce `/PACT:watch-inbox` to a thin trigger — the heavy lifting (spawn, duplicate-prevention, identity) moves to the platform
3. Keep PACT-side hooks for task-state-conditional teardown
4. Bump plugin's minimum Claude Code version to v2.1.105

Constraints noted in docs

Disabling a plugin mid-session does not stop monitors that are already running. They stop when the session ends.

This differs from current PACT teardown (`/PACT:unwatch-inbox` actively stops the Monitor mid-session). Worth verifying the platform supports active mid-session teardown before refactoring.

Priority

Medium. Net win in code surface area but not blocking. Slot into v4.x backlog after v4.0.0 (orchestrator agent migration) ships.

References

• Add inbox-wake skill (lead-only) + 20/20/60 quiet-window + PostToolUse lifecycle #603 — original inbox-wake skill + 20/20/60 quiet-window + PostToolUse lifecycle
• Register inbox-wake + prune-memory commands in plugin.json (#608) #609 — manifest registration fix
• Plugins reference §Monitors
• Tools reference §Monitor tool