The data model leaves the hash and Meadowcap leaves the signatures as parameters; Willow'25 fixes them (Ed25519, WILLIAM3, 4096, ChaCha20-Poly1305, a Noise-style XX handshake the authors call Nose) so implementations interoperate; not a new protocol, and no new set until a primitive breaks.

"Which Willow" is answered by this unit.

The data model does not say which hash to use. Meadowcap does not say which signatures. Those are parameters. Each app could choose its own.

Willow twenty five fills the slots. Not a new protocol. The same protocol with its blanks filled in. Ed25519 keys and signatures. WILLIAM3 hashes, from the Bab tree hash.

Path limits: four thousand ninety six parts, four thousand ninety six bytes each, four thousand ninety six bytes in all.

ChaCha twenty Poly thirteen oh five for encryption. A Noise style XX handshake, with those same primitives. The authors call it Nose.

One set, so that implementations interoperate. The authors intend no new set until one of these primitives is broken.

Check yourself. Which hash function does Willow'25 use, and where is it defined?