Frontier-lab safety governance is being formalized as a four-layer control stack — internal controls monitoring capabilities during training/deployment, dedicated internal safety and alignment teams, independent external auditors/evaluators, and an independent board committee — i.e. safety enforcement is instantiated as an engineering artifact with defined interfaces rather than a policy statement.
If safety is expressed as four distinct, separately-inhabited layers, each layer becomes an interface that can be instrumented, audited, and tested independently — which changes how evaluation harnesses and audit evidence are designed around a model vendor.
Wherever a high-risk capability is shipped, separating 'who builds controls', 'who checks controls internally', 'who checks them externally', and 'who can halt the release' reduces the chance that a single team both grades its own work and holds the kill switch.
The accord includes four layers: internal controls, internal teams, external auditors, and board-level independent committees.