How Does the Concept of a “Soft Fork” Relate to Consensus Mechanism Changes like Adopting PoA?

A soft fork is a backwards-compatible change to a cryptocurrency's protocol. Adopting a major consensus mechanism change like PoA, if implemented as a soft fork, would mean older nodes that haven't upgraded would still see the new PoA blocks as valid, though they might not fully understand the new rules.

However, transitioning to a hybrid model like PoA usually requires a more disruptive hard fork to change fundamental block validation rules.