A unit's innies pin part of a cage's sum, splitting it into two known cages. hard killer only
The 45-rule pins the marked cells (inside the tinted rows/columns) to 10, splitting the cage into a known inside part and a known outside part; no split assignment allows 2 and 8 in R4C6, R5C6, R6C6.
When a unit's leftover cells (its innies) all belong to one cage, the 45-rule pins their sum, splitting the cage into two virtual cages with known sums. Both halves can then be reasoned about like ordinary cages, and no digit may repeat across the split.