BIP340 Schnorr specification materially revised during implementation review
A substantial revision to BIP 340 changed parts of the Schnorr-signature design, including tagged hashing and nonce generation, while the proposal was still under implementation review.
In late February, Pieter Wuille circulated significant revisions to the BIP 340 Schnorr specification. The changes altered nonce generation, incorporated the public key and optional auxiliary randomness, and changed tagged-hash domains so implementations of earlier drafts would not accidentally validate against the revised design.
This was a review-stage event rather than a consensus change. The fact that incompatible draft details were still being changed underscored how Bitcoin developers used prolonged public review to harden cryptographic proposals before asking the network to adopt them.