The [plan-specific collaboration state](../../.agents/notes/implemented/simplification/2026-07-22-plan-specific-collaboration-state.md) decision records the family design.
The subsystem reference — the `plan/mode` fold, the step-boundary flush, configuration, the exit tool — is [docs/subsystems/plan.md](../../docs/subsystems/plan.md); design in [plan-specific collaboration state](../../.agents/notes/implemented/simplification/2026-07-22-plan-specific-collaboration-state.md).