Hydra trial not completely removable

I installed the latest hydra trial (october 2019) and found that it still suffers from the necessity to have the same delphi versions for host and plugin.
So I deinstalled it, which seemed to work smoothly.
But now when I start Delphi, I get the errormessage that the file RemObjects.Everwood.RadStudio.XE12.dll could not be found.
There is a checkmark in this message that says ‘remove / deactivate this assembly’.
I set this checkmark but on the next start I got the same error.
How can I avoid this error ?

Gerhard Sachs


Do you have installed other our products like Remoting SDK for Delphi or Data Abstract for Delphi?

The uninstall issue aside, that should not be the case. One of the features of Hydra is that it allows mixing of plugins and hosts written using different versions of Delphi, between Delphi 7 and latest…


@EvgenyK : No, the PC is a Windows10 VM with Delphi 10.3.2. The errormessage did not occur before the Hydra test installation.

@mh : I made a test with one of the demo projects. When I compiled host and plugin using Delphi Rio, it worked as expected. After compiling the plugin in another VM with XE8, they did not work together. I made a similar test in march 2015. At that time I was notified by EvgenyK that this is not yet possible.

Gerhard Sachs

can you check your plugin module? it should export only a HYGetCrossPlatformModule method.

if it exports HYGetModuleController - it means that plugin can only work with the same runtime as host, i.e. both (host and plugin) will require Hydra_VCL_D26.bpl (in your case).

Note: full version of Hydra hasn’t such limitation because it was shipper with sources so host and plugin can be compiled w/o runtime packages.

try again. now it should be possible. at least it works as expected in full version

pls remove RemObjects.Everwood.RadStudio.XE12.dll from HKEY_CURRENT_USER\Software\Embarcadero\BDS\20.0\Known IDE Assemblies with regedit.
I wonder why it wasn’t removed correctly.

I removed the registry entry and it worked.
Thank you for the help.

About different delphi versions :
I think that it makes no sense to invest time in a plugin system that is version dependent.
So I deinstalled Hydra very soon after I found it did not work.
I did not know that the full version of Hydra is different than the demo version in that point.
The question is why do I install a demo version ?
In my case to find if it is version dependent, thats the very basic point.
If a demo version is that much different than the full version there should be at least a clear indication to avoid confusion.
At the moment I am continuing without plugins, I will try Hydra again next time.


Looks like you don’t find a proper sample that demonstrate cross platform features. We will crate a new one that will show this feature.

You mean cross-version, not cross-platform.

No, I mean cross platform one - that will work as cross-version too because plugin will export only HYGetCrossPlatformModule method and won’t HYGetModuleController.
the HYGetModuleController method assumes that this is VCL-compatible plugin as a result, shared VCL packages (like VCL, Hydra_VCL) with host are required