Midnight upgraded its privacy chain on mainnet before its test network. The docs arrive in a few weeks.
Ledger 9 hard-forked onto Midnight mainnet Nov. 6, skipping the usual Preprod run and soak period. The team says that path is used when security fixes need a more controlled release. Preprod is still on Ledger 8; Preview was relaunched as a fresh chain the next day.
New: contract-to-contract calls, Ethereum-style ECDSA and Keccak support for custodians and bridged stablecoins, and public events. Phase one of calls and events covers unshielded data only.
Known issue, no workaround yet: a contract that spends a shielded coin it already holds and writes back the change gets rejected for running out of gas.
The privacy chain's big upgrade is public announcements. The private part is phase two.