A first-out / last-out (FOLO) split: which piece prices wider and why?

The last-out piece prices wider. In a FOLO unitranche, the first-out tranche is repaid first from enforcement proceeds (lower risk, lower spread — it behaves like senior first-lien), while the last-out tranche is paid only after the first-out is made whole (higher risk, behaves like a junior/second-lien or mezz piece), so it commands a materially higher spread. The blended rate the borrower pays is the weighted average of the two. The interest 'skim' in the Agreement Among Lenders shifts coupon toward the first-out to compensate it, but the last-out still earns the higher all-in return for taking the junior risk.