How many output may have a shader?

hi. i have a quite complexe project with one camera, and a lot of calculation of effects thruth many shaders and contour.
i m fighting on this project the probleme of siding fx freeframes and renderers as preview.

to be more confortable, i was asking myself if a shader could handle 2 or more outputs, this to split my video signal as there is fight in keeping the hand on the signal between shaders and contour.

with shaders a simple S node with the video as a texture works great and enables multiple renderers ( preview, work of differents effects …) but everything becomes to have many problem when using contour.
i suppose this conflict to be manly because of freeframe structure…

having 2 or 3 layer output from a shader: i m not sure this is possible.