Cross reference from DSL to EMF Ecore model not working in LSP setup

Question

I have a DSL language where we need to cross-refer EAttribute that are defined in a separate file. This works fine in the eclipse plugin setup but it is not working in the LSP setup based on Vscode/Theia client.

Grammar Snippet -

Atomic returns Expression:
    {IntConstant} value=INT |
    {StringConstant} value=STRING |
    {BoolConstant} value=('true' | 'false') |
    {VariableRef} variable=[ecore::EAttribute|QualifiedName];

Example -

1. DSL file - test.mexpression

  iota=1

2. iota is a variable which is defined in a separate file - variables.ecore

<?xml version="1.0" encoding="UTF-8"?>
<ecore:EPackage xmi:version="2.0" xmlns:xmi="http://www.omg.org/XMI" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:ecore="http://www.eclipse.org/emf/2002/Ecore" name="vari" nsURI="vvvv" nsPrefix="var">
<eClassifiers xsi:type="ecore:EClass" name="Variables">
<eStructuralFeatures xsi:type="ecore:EAttribute" name="iota" eType="ecore:EDataType 
 http://www.eclipse.org/emf/2002/Ecore#//EBoolean"/>
<eStructuralFeatures xsi:type="ecore:EAttribute" name="Cars" eType="ecore:EDataType 
http://www.eclipse.org/emf/2002/Ecore#//EString"
    defaultValueLiteral=""/>
</eClassifiers>
<eClassifiers xsi:type="ecore:EClass" name="Car">
<eStructuralFeatures xsi:type="ecore:EAttribute" name="Model" eType="ecore:EDataType 
http://www.eclipse.org/emf/2002/Ecore#//EString"/>
</eClassifiers>
</ecore:EPackage>

Language client Snippet -

 export function activate(context: ExtensionContext) {
     // The server is a started as a separate app and listens on port 5007
     let connectionInfo = {
         port: 5008
     };
     let serverOptions = () => {
         // Connect to language server via socket
         let socket = net.connect(connectionInfo);
         let result: StreamInfo = {
             writer: socket,
             reader: socket
         };
         return Promise.resolve(result);
     };
     
     let clientOptions: LanguageClientOptions = {
         documentSelector: ['mexpression','ecore'],
         synchronize: {
             fileEvents: workspace.createFileSystemWatcher('**/*.*')
         }
     };
     
     // Create the language client and start the client.
     let lc = new LanguageClient('Xtext Server', serverOptions, clientOptions);

Am I missing something here ? or We have to create a standalone setup for variable file & register it via service providers to make it work in LSP environment.