Shown for context, without a threshold: the short end is a three-month interbank lending rate, not a bill yield, and the OECD publishes no live short-tenor government yield for China.
The ten-year Chinese government bond yield minus the three-month interbank rate, both monthly averages from the OECD's financial-market indicators. The ten-year series starts in 2014.
An interbank rate carries a credit and liquidity premium that a bill yield does not, so the spread sits lower than a true curve: it was below zero in most months from 2014 to 2025, which is why no inversion threshold is applied. Chinese bond yields are managed, and monthly averages show a turn a month or two late.