La Porte's High Reliability Theory distinguishes technical/physical tight coupling from organizational/social tight coupling

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Todd La Porte's High Reliability Theory (HRT) treats "tight coupling" as having at least two independent axes, not one. La Porte writes: "it is useful to make a distinction between physical, functional, tight-coupling, that is, the degree to which the system is technically 'hard-wired' and the degree to which its working groups are tightly coupled in coordinative relationships. Both technical and social coupling can be structured in a vertical, hierarchical fashion and/or in horizontal tightly-coupled ways."

Perrow's Normal Accident Theory and the vault's own Bit2Watt claim both use "tight coupling" exclusively in the technical/physical sense — process speed and cascade propagation through hardware and infrastructure, without slack for intervention. La Porte's HRT literature treats organizational/social coupling — how tightly an organization's human decision-makers are coordinated with one another — as a separate, independently manageable variable, and identifies it as part of what lets a technically tightly-coupled system (a grid, an aircraft carrier's flight deck, an air-traffic-control sector) still be operated reliably over long periods.

Neither the vault's existing NAT claim nor its Bit2Watt claim currently carries this second axis. A system judged tightly coupled on the technical dimension alone may still vary widely in how tightly its human operators are coordinated, and HRT's account of achieved reliability rests specifically on that second, so-far unaddressed axis being managed well.