Is it possible to compile a plugin with a earlier minor build release (ex. 16.0.557) and use it with a later release of the same major version (ex. 16.0.600)? If so, what would one need to include?

Cheers

It is possible but inconsistent between builds:

http://www.sidefx.com/docs/hdk/_h_d_k__intro__compatibility.html [sidefx.com]

We try to avoid too many binary compatibility breaks between builds, but it is often necessary to break binary compatibility in order to fix serious bugs.

If the HDK_API_VERSION value Graham linked to changes, you may or may not still be able to use the plugin built with the old version, depending on what interfaces your plugin uses and what structures or interfaces changed. For example, if the VRAY_PixelFilter structure changes, you wouldn't need to rebuild an HDK SOP, but you would probably need to rebuild an HDK pixel filter. If UT_PageArray changes, (which I think it did a few months ago, to fix a doubling of memory use on Linux in some fluid sims), pretty much every HDK SOP needs to be rebuilt, but if GU_IsoMeta changed, (which probably won't happen until the next major version), only HDK SOPs that use it would need to be rebuilt.

great, thanks guys!
Will try out the HDK_API_VERSION Graham posted.
Cheers