Consider two inventions: X and X+Y. For the sake of argument, assume that X is not patentable (prior art), but the combination of X+Y is patentable.
The problem: In practice X must be sold by itself. However, the intention would be to use X in combination with Y provided by the end user. For example, X could be a device which performs chemical processing, and Y could be raw material to be processed.
The question: If a company starts selling X with the clear intention of using it in combination with Y, is that sufficient to infringe on a patent claim covering X+Y?
I'm mostly interested in the US but would also be interested in other jurisdictions.
(Comment: In reality I probably can write a more narrow claim covering X', which is similar to X but more specialized towards combination with Y, and consequently narrowed to avoid prior art. I believe that the combination of X in general with Y is patentable, but I don't know if it'll be useful as a claim.)