How does Sprite-Lit-Default work with sprite masks?

[valid turret]

So looking into the Sprite-Lit-Default shader I have noticed that it doesn't use Stencil anywhere so I was wondering how sprite masks work if Sprite-Lit never writes or reads to stencil.

[gilded garden]

Unity's pipeline's usually exposes the stencil buffer to manipulate outside of the shader code via rendering assets or custom pipeline scripting. This allows you to modify them (usually via layer) without having to hardcode these values inside of the shader.