Rider no longer adds/resolves asmdef references for UnityAtoms

Hi,

I'm suddenly blocked by a dependency resolution issue that appeared today (I had no problems working with assembly definitions yesterday).

Setup

• Unity project split into multiple assemblies via Assembly Definitions (Core.asmdef, Systems.asmdef, UI.asmdef, Data.asmdef, etc.).
• UnityAtoms packages added via Package Manager (from Github).
• Types I'm trying to use: AtomEvent, AtomValueList, etc. (from UnityAtoms.UnityAtomsCore.Runtime and related assemblies).
   

What happens

1. I type a UnityAtoms type → Rider offers the usual Alt+Enter → Reference and import. that resolves the dependency (text is no longer red). It seems working, until…
2. I switch focus to the Unity Editor window, and at that point…
3. Back in Rider the symbols become unresolved again.

The Alt+Enter action that used to automatically add the reference to my .asmdef no longer does so (e.g. I except to see a dependency between Data and UnityAtoms.UnityAtomsCore.Runtime, but the Data.asmdef shows none of that).

Even if I manually add the reference in Unity’s Assembly Definition Inspector, Rider still cannot resolve the types reliably. 

It feels like Rider has lost the ability to write/update assembly definitions or assembly definition references.
 

Temporary workaround

Editing the .asmdef file directly inside Rider (adding the reference by  GUID) sometimes makes the symbols resolve again, but only temporarily. What triggers the problem again is a mistery.

My problem sounds similar to: RIDER-94834. I find the conversation confusing to be honest. I don't understand if a proper step-by-step solution or workaround exists. 

What I’ve already tried

• Invalidate Caches / Restart
• Regenerating project files from Unity
• Closing Unity completely, deleting .csproj / .sln files, reopening
• Usual cache / Library folder clean-ups
• Updating both Rider and JetBrains Rider Editor in Unity
• Enabling “Git packages” and “Build-in packages” in the Unity “External Tools” preference menu

Questions 

• Is this a known regression with Rider + Github + asmdefs (especially after the recent Rider update)?
• Is the “Reference and import” action still supposed to work for packages coming from the Package Manager / registry?
• Any recommended way to force Rider to correctly pick up and persist asmdef references for external packages like UnityAtoms?
   

Thanks in advance. I wasted an entire day of work trying to solve this issue and I'm very frustrated. I hope I can get help soon because this is currently blocking my workflow.

P.S.: Maybe it's only me, but