Quick answer: Unity custom Roslyn analyzer not catching new diagnostics after a package update? Analyzer DLL cached - delete Library/ScriptAssemblies and reimport.
Updated a custom analyzer package. New rules ship; editor still warns on the old set.
Force re-import
Right-click the asmdef using the analyzer; Reimport. Library/ScriptAssemblies regenerates.
Delete Library/ScriptAssemblies
Heavy-handed but reliable. Forces full recompile; analyzers reload.
Verify analyzer version
Project Settings > Player > Roslyn Analyzers. Lists active analyzers and versions; mismatch with package indicates the cache problem.
“Analyzer DLLs are aggressively cached. Updates require explicit invalidation.”
If you ship analyzers, document the cache-bust step in your package README. Users hit this once; the workaround is one command.