Add SDK status bar item

README.md

@@ -29,6 +29,11 @@ The extension relies on the Python extension for locating your Python
 environment. In some cases, this appears to default to your globally-installed
 environment, even when a virtual environment exists.
 
+When the extension detects a Mojo project (a workspace containing `.mojo`
+files, or with a `.mojo` file open), the SDK status appears in the bottom-left
+status bar, showing details of the detected SDK or a clickable notice if no
+SDK was detected.
+
 If the Mojo extension cannot find your SDK installation, try invoking the
 `Python: Select Interpreter` command and selecting your virtual
 environment.

extension/extension.ts

@@ -25,6 +25,7 @@ import { RpcServer } from './server/RpcServer';
 import { Mutex } from 'async-mutex';
 import { TelemetryReporter } from './telemetry';
 import { PythonEnvironmentManager } from './pyenv';
+import { SDKStatusBar } from './statusBar';
 
 /**
  * This class provides an entry point for the Mojo extension, managing the
@@ -72,6 +73,30 @@ Activating the Mojo Extension
       this.pushSubscription(this.pyenvManager);
       await this.pyenvManager.init();
 
+      // Set up the SDK status bar.
+      const showOutputCommand = 'mojo.showOutput';
+      this.pushSubscription(
+        vscode.commands.registerCommand(showOutputCommand, () => {
+          this.logger.main.show();
+        }),
+      );
+      const statusBar = new SDKStatusBar(showOutputCommand);
+      this.pushSubscription(statusBar);
+
+      const updateStatusBar = async () => {
+        statusBar.showLoading();
+        const sdk = await this.pyenvManager!.findActiveSDK();
+        statusBar.update(sdk);
+      };
+
+      this.pushSubscription(
+        statusBar.onRefreshRequested(() => updateStatusBar()),
+      );
+      this.pushSubscription(
+        this.pyenvManager.onEnvironmentChange(() => updateStatusBar()),
+      );
+      await statusBar.checkVisibility();
+
       this.pushSubscription(
         await configWatcher.activate({
           settings: ['SDK.additionalSDKs'],

extension/statusBar.ts

@@ -0,0 +1,127 @@
+//===----------------------------------------------------------------------===//
+// Copyright (c) 2026, Modular Inc. All rights reserved.
+//
+// Licensed under the Apache License v2.0 with LLVM Exceptions:
+// https://llvm.org/LICENSE.txt
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//===----------------------------------------------------------------------===//
+
+import * as vscode from 'vscode';
+import { SDK, SDKKind } from './pyenv';
+
+const SDK_KIND_LABELS: Record<SDKKind, string> = {
+  [SDKKind.Environment]: 'env',
+  [SDKKind.Custom]: 'custom',
+  [SDKKind.Internal]: 'dev',
+};
+
+function editorHasMojoFile(): boolean {
+  return vscode.window.visibleTextEditors.some(
+    (editor) => editor.document.languageId === 'mojo',
+  );
+}
+
+export class SDKStatusBar implements vscode.Disposable {
+  private statusBarItem: vscode.StatusBarItem;
+  private disposables: vscode.Disposable[] = [];
+  private visible = false;
+  private workspaceHasMojo: boolean | undefined = undefined;
+  private onShouldRefresh: vscode.EventEmitter<void> =
+    new vscode.EventEmitter();
+  readonly onRefreshRequested: vscode.Event<void> = this.onShouldRefresh.event;
+
+  constructor(showOutputCommand: string) {
+    this.statusBarItem = vscode.window.createStatusBarItem(
+      'mojo-sdk-status',
+      vscode.StatusBarAlignment.Left,
+      50,
+    );
+    this.statusBarItem.name = 'Mojo SDK';
+    this.statusBarItem.command = showOutputCommand;
+
+    // Watch for mojo files being opened.
+    this.disposables.push(
+      vscode.window.onDidChangeVisibleTextEditors(() => this.checkVisibility()),
+    );
+
+    // Watch for mojo files being created/deleted in the workspace.
+    const watcher = vscode.workspace.createFileSystemWatcher('**/*.mojo');
+    this.disposables.push(watcher);
+    this.disposables.push(
+      watcher.onDidCreate(() => {
+        this.workspaceHasMojo = true;
+        this.checkVisibility();
+      }),
+    );
+    this.disposables.push(
+      watcher.onDidDelete(() => {
+        this.workspaceHasMojo = undefined; // invalidate cache
+        this.checkVisibility();
+      }),
+    );
+  }
+
+  async checkVisibility() {
+    if (editorHasMojoFile()) {
+      this.show();
+      return;
+    }
+
+    if (this.workspaceHasMojo === undefined) {
+      const results = await vscode.workspace.findFiles('**/*.mojo', null, 1);
+      this.workspaceHasMojo = results.length > 0;
+    }
+
+    if (this.workspaceHasMojo) {
+      this.show();
+    } else if (this.visible) {
+      this.visible = false;
+      this.statusBarItem.hide();
+    }
+  }
+
+  private show() {
+    if (!this.visible) {
+      this.visible = true;
+      this.statusBarItem.show();
+      this.onShouldRefresh.fire();
+    }
+  }
+
+  showLoading() {
+    this.statusBarItem.text = '$(loading~spin) Mojo';
+    this.statusBarItem.tooltip = 'Detecting Mojo SDK...';
+    this.statusBarItem.backgroundColor = undefined;
+  }
+
+  update(sdk: SDK | undefined) {
+    if (sdk) {
+      const version = sdk.version.replace(/^mojo\s*/i, '').trim();
+      const kindLabel = SDK_KIND_LABELS[sdk.kind];
+      this.statusBarItem.text = `$(check) Mojo ${version} (${kindLabel})`;
+      this.statusBarItem.tooltip = new vscode.MarkdownString(
+        `**Mojo SDK** (${kindLabel})\n\nVersion: ${version}\n\nPath: ${sdk.mojoPath}`,
+      );
+      this.statusBarItem.backgroundColor = undefined;
+    } else {
+      this.statusBarItem.text = '$(warning) Mojo: No SDK';
+      this.statusBarItem.tooltip = 'No Mojo SDK detected. Click to view logs.';
+      this.statusBarItem.backgroundColor = new vscode.ThemeColor(
+        'statusBarItem.warningBackground',
+      );
+    }
+  }
+
+  dispose() {
+    this.statusBarItem.dispose();
+    this.onShouldRefresh.dispose();
+    for (const d of this.disposables) {
+      d.dispose();
+    }
+  }
+}