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Does New Foundations set theory NF admit a natural well-ordering of its universe that is provable within NF itself, and if so what is the proof-theoretic ordinal of NF?

Related: Holmes consistency proof of NF, Specker theorem on the negation of Choice in NF, Bachmann-Howard ordinal as proof-theoretic ordinal of KP

New Foundations, Quine's alternative set theory based on stratified comprehension, was proven consistent by Randall Holmes in a 2010 manuscript that is still undergoing verification. Even granting consistency, the precise proof-theoretic ordinal of NF remains completely unknown. Unlike ZF or its subsystems, NF does not obviously support ordinal analysis via standard techniques because its universe lacks a cumulative hierarchy, making it deeply unclear how to assign a canonical measure of its logical strength. The recent direct proof of the axiom of Infinity in the fragment NF-0 shows that nontrivial combinatorial structure can be extracted from stratification conditions alone, which reopens the question of what ordinals and well-orderings NF can itself produce or describe internally. The problem asks whether NF proves the existence of a definable well-ordering of some canonical large class of its sets, and whether this can be leveraged to compute a proof-theoretic ordinal in the sense of ordinal analysis.

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