transparent background in gpu mode arnold c4d

[chandan1nift]

how can i get a transparent background while using arnold gpu render, in transparent areas i get a black background. if i switch it go arnold cpu mode then it works fine. since cpu is slow so i want to use gpu mode. i am using arnold version 7.3.6 with cinema 4d 2025

[Stephen.Blair]

There's black in both, and they are rendered from different camera angles, so I can't tell what's going on. What's the background?
My own simple test scene works ok with the latest Arnold.

[chandan1nift]

Here you can see the difference, the angle is same in both. But see the difference in the alpha and final render. i am getting black where i supposed to get transparent background like in the cpu mode. i also attached the c4d file. have a look and if possible send it with the solution. you can also see the final renders.