diff --git a/CHANGELOG.md b/CHANGELOG.md
index 72adb0ff..ef48ee50 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,7 @@
 - Go to definition now goes to real file if such presented, or opens from the server
 - Basic syntax highlighting for CSP files, only as HTML
 - Added some snippets for class
+- View subclasses for current class
 
 ## [0.7.7]
 
diff --git a/api/index.ts b/api/index.ts
index 52921d66..f6e23a06 100644
--- a/api/index.ts
+++ b/api/index.ts
@@ -146,7 +146,7 @@ export class AtelierAPI {
     type?: string;
     filter?: string;
   }): Promise<any> {
-    return this.request('GET', `v2/${this.ns}/docnames/${category}/${type}`, {
+    return this.request('GET', `v3/${this.ns}/docnames/${category}/${type}`, {
       filter,
       generated
     });
@@ -159,20 +159,37 @@ export class AtelierAPI {
         format
       };
     }
-    return this.request('GET', `v2/${this.ns}/doc/${name}`, params);
+    return this.request('GET', `v3/${this.ns}/doc/${name}`, params);
   }
 
   putDoc(name: string, data: { enc: boolean; content: string[] }, ignoreConflict?: boolean): Promise<any> {
     let params = { ignoreConflict };
-    return this.request('PUT', `v2/${this.ns}/doc/${name}`, params, {}, data);
+    return this.request('PUT', `v3/${this.ns}/doc/${name}`, params, {}, data);
   }
 
   actionIndex(docs: string[]): Promise<any> {
-    return this.request('POST', `v2/${this.ns}/action/index`, {}, {}, docs);
+    return this.request('POST', `v3/${this.ns}/action/index`, {}, {}, docs);
+  }
+
+  actionSearch(params: { query: string; files?: string; sys?: boolean; gen?: boolean; max?: number }): Promise<any> {
+    return this.request('GET', `v3/${this.ns}/action/search`, params, {});
+  }
+
+  actionQuery(query: string, parameters: string[]): Promise<any> {
+    return this.request(
+      'POST',
+      `v3/${this.ns}/action/query`,
+      {},
+      {},
+      {
+        query,
+        parameters
+      }
+    );
   }
 
   actionCompile(docs: string[], flags?: string, source = false): Promise<any> {
-    return this.request('POST', `v2/${this.ns}/action/compile`, { flags, source }, {}, docs);
+    return this.request('POST', `v3/${this.ns}/action/compile`, { flags, source }, {}, docs);
   }
 
   cvtXmlUdl(source: string): Promise<any> {
diff --git a/commands/subclass.ts b/commands/subclass.ts
new file mode 100644
index 00000000..4c8ebfdd
--- /dev/null
+++ b/commands/subclass.ts
@@ -0,0 +1,38 @@
+import * as vscode from 'vscode';
+import { config } from '../extension';
+import { AtelierAPI } from '../api';
+import { currentFile } from '../utils';
+import { DocumentContentProvider } from '../providers/DocumentContentProvider';
+
+export async function subclass(): Promise<void> {
+  const file = currentFile();
+  if (!file || !file.name.toLowerCase().endsWith('.cls')) {
+    return;
+  }
+  let className = file.name
+    .split('.')
+    .slice(0, -1)
+    .join('.');
+  if (!config('conn').active) {
+    return;
+  }
+
+  const open = item => {
+    let uri = DocumentContentProvider.getUri(item + '.cls');
+    vscode.window.showTextDocument(uri);
+  };
+
+  const api = new AtelierAPI();
+  return api
+    .actionQuery('CALL %Dictionary.ClassDefinitionQuery_SubclassOf(?)', [className])
+    .then(data => {
+      const list = data.result.content || [];
+      if (!list.length) {
+        return;
+      }
+      vscode.window.showQuickPick(list.map(el => el.Name)).then(item => {
+        open(item);
+      });
+    })
+    .catch(err => console.error(err));
+}
diff --git a/commands/viewOthers.ts b/commands/viewOthers.ts
index 29b3d585..5c6cf580 100644
--- a/commands/viewOthers.ts
+++ b/commands/viewOthers.ts
@@ -5,7 +5,6 @@ import { currentFile } from '../utils';
 import { DocumentContentProvider } from '../providers/DocumentContentProvider';
 
 export async function viewOthers(): Promise<void> {
-  const api = new AtelierAPI();
   const file = currentFile();
   if (!file) {
     return;
@@ -22,6 +21,7 @@ export async function viewOthers(): Promise<void> {
   const getOthers = info => {
     return info.result.content[0].others;
   };
+  const api = new AtelierAPI();
   return api
     .actionIndex([file.name])
     .then(info => {
diff --git a/extension.ts b/extension.ts
index bd0e549f..4edded7c 100644
--- a/extension.ts
+++ b/extension.ts
@@ -7,6 +7,7 @@ import { viewOthers } from './commands/viewOthers';
 import { importAndCompile } from './commands/compile';
 import { exportAll, exportExplorerItem } from './commands/export';
 import { xml2doc } from './commands/xml2doc';
+import { subclass } from './commands/subclass';
 
 import { ObjectScriptClassSymbolProvider } from './providers/ObjectScriptClassSymbolProvider';
 import { ObjectScriptRoutineSymbolProvider } from './providers/ObjectScriptRoutineSymbolProvider';
@@ -128,6 +129,7 @@ export async function activate(context: vscode.ExtensionContext): Promise<void>
     vscode.commands.registerCommand('vscode-objectscript.compileWithFlags', () => importAndCompile(true)),
     vscode.commands.registerCommand('vscode-objectscript.export', exportAll),
     vscode.commands.registerCommand('vscode-objectscript.viewOthers', viewOthers),
+    vscode.commands.registerCommand('vscode-objectscript.subclass', subclass),
     vscode.commands.registerCommand('vscode-objectscript.touchBar.viewOthers', viewOthers),
     vscode.commands.registerCommand('vscode-objectscript.explorer.refresh', () => explorerProvider.refresh()),
     vscode.commands.registerCommand('vscode-objectscript.explorer.openClass', vscode.window.showTextDocument),
diff --git a/package.json b/package.json
index 692c2c1f..fcc89d08 100644
--- a/package.json
+++ b/package.json
@@ -82,6 +82,10 @@
           "command": "vscode-objectscript.viewOthers",
           "when": "vscode-objectscript.connectActive"
         },
+        {
+          "command": "vscode-objectscript.subclass",
+          "when": "vscode-objectscript.connectActive"
+        },
         {
           "command": "vscode-objectscript.previewXml",
           "when": "vscode-objectscript.connectActive"
@@ -278,6 +282,11 @@
         "command": "vscode-objectscript.viewOthers",
         "title": "View other"
       },
+      {
+        "category": "ObjectScript",
+        "command": "vscode-objectscript.subclass",
+        "title": "View subclasses"
+      },
       {
         "command": "vscode-objectscript.touchBar.compile",
         "title": "➾¹₀⁰₁¹₀"