Different render than preview in cycles

Hi everyone!
My cube reflected from inside of hemisphere looks different in preview (shift+z) and render.
What am I doing wrong? I try to work with reflections and need genuine preview.

diffrent_results.blend (470 KB)

//Edit: Seems like the second answer is way more useful and correct.

So it seems to me that smooth shading in cycles is calculated differently in the viewport than in the full render, which makes sense, when the viewport has to be sown with higher performance.

I really don’t know, where the difference comes from, but it’s gone when I use quads with subdivision surface modifier instead of triangles. In the image you can see the strange pattern that triangles produce, maybe cycles uses a similar technique for rendering, but another one for preview, that’s a lot faster.

So if you need consistency more that triangles, consider using quads, or wait until someone posts a real solution.

You have unapplied, non-uniform scale on the hemiphere. Select it in Object mode and hit Ctrl-A > Scale.
Final render and rendered viewport seem to be consistent now.

Not exactly sure why this solves the issue, though.

Thaks. Very exact solution.