They are both - part of the new source code done in HLSL but you can also run any Shader Action also if you like.
So I hope this is clear - all my shaders are new simple API's but running an external Action will also work.
The only exception to this is a couple of HLSL shaders were too big to work correctly within the C++ source code of CC (shader model 2 limitation) so will only work currently using an Action like the Rain effect and the Aurora effect - all others are fine.
Why this difference exists between internal source code and running an Action is not currently clear to me but I got error messages saying it cant run very long shader code in the source yet somehow works as an Action....