What is the test for vacating a judgment and remand for resentencing before a different judge?

Given the government's concession and representations, we vacate the judgment and remand for resentencing before a different judge, see, e.g., United States v. Carbone, 739 F.2d 45, 48 (2d Cir.1984) ("Despite the fact that the prosecutor alone breached the plea agreement, 'compliance with the agreement is best insured by requiring resentencing before another district judge.' ") (quoting United States v. Corsentino, 685 F.2d 48, 52 (2d Cir.1982)).