diff --git a/packages/libro-language-client/src/common/vscodeAdaptor/diagnosticCollection.ts b/packages/libro-language-client/src/common/vscodeAdaptor/diagnosticCollection.ts
index 5ed3dd8a..a135bde9 100644
--- a/packages/libro-language-client/src/common/vscodeAdaptor/diagnosticCollection.ts
+++ b/packages/libro-language-client/src/common/vscodeAdaptor/diagnosticCollection.ts
@@ -1,12 +1,15 @@
 import { DisposableCollection } from '@difizen/mana-app';
-import type * as monaco from '@difizen/monaco-editor-core';
 import { MarkerSeverity } from '@difizen/monaco-editor-core';
+import * as monaco from '@difizen/monaco-editor-core';
+import type { editor } from '@difizen/monaco-editor-core';
 import type { DiagnosticCollection } from 'vscode';
-import type { Diagnostic, Uri } from 'vscode';
+import type { Diagnostic, Uri, Disposable } from 'vscode';
 import { URI } from 'vscode-uri';
 
-import type { ResourceMap } from './hostTypeUtil.js';
-import type { ProtocolToMonacoConverter } from './monaco-converter.js';
+import * as c2p from '../codeConverter.js';
+
+import { ResourceMap } from './hostTypeUtil.js';
+import { ProtocolToMonacoConverter } from './monaco-converter.js';
 import { DiagnosticSeverity, EventEmitter } from './vscodeAdaptor.js';
 
 export class LibroDiagnosticCollection implements DiagnosticCollection {
@@ -15,9 +18,13 @@ export class LibroDiagnosticCollection implements DiagnosticCollection {
 
   private readonly _maxDiagnosticsPerFile: number = 1000;
   private readonly _maxDiagnosticsTotal: number = 1.1 * this._maxDiagnosticsPerFile;
+  protected readonly c2p: c2p.Converter = c2p.createConverter();
+  protected readonly p2m: ProtocolToMonacoConverter = new ProtocolToMonacoConverter(
+    monaco,
+  );
 
   name: string;
-  readonly #data: ResourceMap<Diagnostic[]>;
+  readonly #data: ResourceMap<Diagnostic[]> = new ResourceMap();
   private _isDisposed = false;
   set(uri: Uri, diagnostics: ReadonlyArray<Diagnostic>): void;
   set(entries: ReadonlyArray<[Uri, ReadonlyArray<Diagnostic>]>): void;
@@ -85,10 +92,10 @@ export class LibroDiagnosticCollection implements DiagnosticCollection {
     // if (!this.#proxy) {
     //   return;
     // }
-    const entries: [URI, IMarkerData[]][] = [];
+    const entries: [URI, editor.IMarkerData[]][] = [];
     let totalMarkerCount = 0;
     for (const uri of toSync) {
-      let marker: IMarkerData[] = [];
+      let marker: editor.IMarkerData[] = [];
       const diagnostics = this.#data.get(uri);
       if (diagnostics) {
         // no more than N diagnostics per file
@@ -103,10 +110,8 @@ export class LibroDiagnosticCollection implements DiagnosticCollection {
           orderLoop: for (let i = 0; i < 4; i++) {
             for (const diagnostic of diagnostics) {
               if (diagnostic.severity === order[i]) {
-                const len = marker.push({
-                  ...converter.Diagnostic.from(diagnostic),
-                  modelVersionId: this._modelVersionIdProvider(uri),
-                });
+                const diag = this.p2m.asDiagnostic(this.c2p.asDiagnostic(diagnostic));
+                const len = marker.push(diag);
                 if (len === this._maxDiagnosticsPerFile) {
                   break orderLoop;
                 }
@@ -117,29 +122,25 @@ export class LibroDiagnosticCollection implements DiagnosticCollection {
           // add 'signal' marker for showing omitted errors/warnings
           marker.push({
             severity: MarkerSeverity.Info,
-            message: localize(
-              {
-                key: 'limitHit',
-                comment: ['amount of errors/warning skipped due to limits'],
-              },
-              'Not showing {0} further errors and warnings.',
-              diagnostics.length - this._maxDiagnosticsPerFile,
-            ),
+            message: `Not showing ${diagnostics.length - this._maxDiagnosticsPerFile} further errors and warnings.`,
             startLineNumber: marker[marker.length - 1].startLineNumber,
             startColumn: marker[marker.length - 1].startColumn,
             endLineNumber: marker[marker.length - 1].endLineNumber,
             endColumn: marker[marker.length - 1].endColumn,
           });
         } else {
-          marker = diagnostics.map((diag) => ({
-            ...converter.Diagnostic.from(diag),
-            modelVersionId: this._modelVersionIdProvider(uri),
-          }));
+          marker = diagnostics.map((diag) => {
+            const mark = this.p2m.asDiagnostic(this.c2p.asDiagnostic(diag));
+            return mark;
+          });
         }
       }
 
       entries.push([uri, marker]);
 
+      // update monaco
+      this.updateModelMarkers(uri, marker);
+
       totalMarkerCount += marker.length;
       if (totalMarkerCount > this._maxDiagnosticsTotal) {
         // ignore markers that are above the limit
@@ -216,6 +217,13 @@ export class LibroDiagnosticCollection implements DiagnosticCollection {
     }
   }
 
+  updateModelMarkers(uri: Uri, markers: editor.IMarkerData[]): void {
+    const model = monaco.editor.getModel(uri);
+    if (model) {
+      monaco.editor.setModelMarkers(model, this.name, markers);
+    }
+  }
+
   dispose(): void {
     if (!this._isDisposed) {
       this.#onDidChangeDiagnostics.fire([...this.#data.keys()]);
@@ -237,6 +245,7 @@ export class MonacoModelDiagnostics implements Disposable {
     diagnostics: Diagnostic[],
     readonly owner: string,
     protected readonly p2m: ProtocolToMonacoConverter,
+    protected readonly c2p: c2p.Converter,
   ) {
     this.uri = this._monaco.Uri.parse(uri);
     this.diagnostics = diagnostics;
@@ -247,8 +256,16 @@ export class MonacoModelDiagnostics implements Disposable {
 
   set diagnostics(diagnostics: Diagnostic[]) {
     this._diagnostics = diagnostics;
-    this._markers = this.p2m.asDiagnostics(diagnostics);
-    this.updateModelMarkers();
+    this.c2p
+      .asDiagnostics(diagnostics)
+      .then((diag) => {
+        this._markers = this.p2m.asDiagnostics(diag);
+        this.updateModelMarkers();
+        return;
+      })
+      .catch(() => {
+        //
+      });
   }
 
   get diagnostics(): Diagnostic[] {
diff --git a/packages/libro-language-client/src/common/vscodeAdaptor/monacoLanguages.ts b/packages/libro-language-client/src/common/vscodeAdaptor/monacoLanguages.ts
index a50e4cea..add23b20 100644
--- a/packages/libro-language-client/src/common/vscodeAdaptor/monacoLanguages.ts
+++ b/packages/libro-language-client/src/common/vscodeAdaptor/monacoLanguages.ts
@@ -42,12 +42,13 @@ import type {
   InlayHintsProvider,
 } from 'vscode';
 
+import { LibroDiagnosticCollection } from './diagnosticCollection.js';
 import { IMonacoLanguages } from './services.js';
 
 @singleton({ token: IMonacoLanguages })
 export class MonacoLanguages implements IMonacoLanguages {
   createDiagnosticCollection(name?: string): DiagnosticCollection {
-    return {} as DiagnosticCollection;
+    return new LibroDiagnosticCollection();
   }
   match(selector: DocumentSelector, document: TextDocument): number {
     // const notebook = extHostDocuments.getDocumentData(document.uri)?.notebook;