Renaming variables created with "Promote to variable" in Control Rig breaks rename ability

Development Character & Animation
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When migrating rigs from Unreal 5.6 to 5.8, we lose the ability to use the “Promote to variable”, as we cannot then rename the variable without all instances of it breaking in the graph requiring manual fixing of each node. Oddly enough, variables created manually from the My Blueprint panel can be renamed just fine without breaking, and the “Promote to variable” then rename functionality appears to work just fine when creating a new Control Rig in 5.8 (instead of working in a CR that has been updated from 5.6).

You’ll note in the example file, I don’t really need to construct any sort of rig for this to happen. The graph can essentially be empty before upgrading engine versions.

We are on Linux, but I’ve tested this in both Linux and Windows and the same issue persists.

I have found that recreating the rig by making an empty Control Rig in 5.8.2, then copying everything from one rig over resolves the issue, but this is not a viable solution. I REALLY wish that when you copied over a graph from one CR to another, the variables (even if broken/empty) stuck around. The fact that they disappear and there’s no way to resolve them makes it really challenging to copy functionality. This is a feature in normal Blueprints and I do really wish it existed in control rig as well.

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Steps to Reproduce

  1. Create an Unreal 5.6.1 project, and create a Control Rig
  2. Update the project to Unreal 5.8.2
  3. Open the Control Rig, and create a variable by dragging out an output pin from a node, and selecting “Promote to variable” from the context menu. You’ll notice an error that will go away once you compile. Leave the node in the graph.
  4. Try renaming the variable, then compile the control rig. The existing node in the graph will break with an error "Variable Node [Content removed] or previously created variables they can be renamed just fine.
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Hi, it looks like we’ve also run into this issue and already have a fix, which has been implemented in UE5-Main. The CL with the fix is 57747295 if you want to integrate that. I’ve also attached a patch from release-5.8, again, in case that’s easier.

As extra context, there were several major refactors to control rig/rigvm in the 5.8 release. One of these was to make variables be tracked by GUID rather than name. That’s what broke the behaviour in this case, specifically for legacy blueprint-based control rig assets (another major refactor in 5.8 moved new control rig assets to be non-blueprint-based). It seems we missed the promote to variable workflow when testing the legacy assets. If you run into any other issues like this, please let us know.

Let me know that the patch fixes the bug for you, and I’m also going to look at getting this integrated into the 5.8.4 hotfix. It’s a pretty nasty one and at the moment, it’s only fixed for 5.9.

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Thank you Euan, that context is very helpful and we appreciate the fix!

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Just a quick follow-up to say that I got permission to get this integrated into 5.8.4, so you’ll be able to drop the customizations if/when you upgrade to that version. I’ll close out this thread now we have everything rounded off.

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