Linear pathways joined by documented handoffs

A route and a pathway are one linear causal chain from one source to one output, and stay so. A system joins two or more of them through a residual stream — a gas turbine's exhaust heat sourcing a steam cycle — that no linear route can express. Each member keeps its own route and its eight checks; the system records the handoff, the outputs and its own performance, and is never run through the checks itself. Systems are not part of the candidate frontier.

1. commercial · 2 members · 1 handoff (demonstrated)
   Natural-gas combined-cycle plant

   Combustion gas-turbine plant (topping-cycle) · Steam Rankine plant (bottoming-cycle)

2. commercial · 2 members · 1 handoff (demonstrated)
   Pressurised-water reactor steam plant

   PWR primary heat delivery (primary-heat-loop) · Steam Rankine plant (secondary-steam-cycle)