The active state is a pure function of the session log, so resume and fork restore it without extra machinery. The deployment supplies plan instructions through Cordis config, while `exit_plan_mode` stays registered when planning is inactive to keep the request tool catalog stable. Interactive adapters use the plugin-owned `/plan` command; sandbox mode and approval policy remain independent enforcement settings. Design: [plan-specific collaboration state](../../.agents/notes/implemented/simplification/2026-07-22-plan-specific-collaboration-state.md).