Do you mean in Siduction or in a pure Debian Unstable installation? For Siduction check if the metapackage 'linux-headers-siduction-amd64' is installed. For Debian check if the metapackage 'linux-headers-amd64' is installed.
I don't run Siduction, as stated in my signature. linux-headers-amd64, linux-headers-common, and linux-kbuild were installed automatically when I installed Debian Unstable 2-3 years ago. However, a few months ago, none of the packages get updated when there is a new kernel upgrade.
A month or two ago, I checked the status of all three packages and they showed as being manually installed, which I never did. So I marked them as automatically installed, but the no upgrade issue continues. I have to manually install the packages whenever there is a kernel upgrade.
I thought I'd ask here before filing a Debian bug report.
Edit: I just did an
apt show linux-headers-amd64 and the result shows not installed. Interesting...