Wat is Jamshidian decomposition?

The Jamshidian decomposition (1989) writes an option on a coupon bond, in a one-factor model where every bond price at expiry is a decreasing function of the single state $x_T$, as a portfolio of options on its zero-coupon bonds: with $x^\star$ the state at which the coupon bond is worth the strike, each zero-coupon option is struck at that bond’s price at $x^\star$.