diff --git a/src/vs/sessions/contrib/markdownPreview/browser/markdownPreview.contribution.ts b/src/vs/sessions/contrib/markdownPreview/browser/markdownPreview.contribution.ts
new file mode 100644
index 00000000000..f186d71637d
--- /dev/null
+++ b/src/vs/sessions/contrib/markdownPreview/browser/markdownPreview.contribution.ts
@@ -0,0 +1,24 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { localize } from '../../../../nls.js';
+import { ContextKeyExpr } from '../../../../platform/contextkey/common/contextkey.js';
+import { MenuId, MenuRegistry } from '../../../../platform/actions/common/actions.js';
+import { EditorContextKeys } from '../../../../editor/common/editorContextKeys.js';
+import { IsSessionsWindowContext } from '../../../../workbench/common/contextkeys.js';
+
+// Show a floating "Open Preview" button in the editor content
+// area when editing markdown or related prompt/instructions/chatagent/skill
+// language content in the sessions window.
+MenuRegistry.appendMenuItem(MenuId.EditorContent, {
+	command: {
+		id: 'markdown.showPreviewToSide',
+		title: localize('openPreview', "Open Preview"),
+	},
+	when: ContextKeyExpr.and(
+		IsSessionsWindowContext,
+		ContextKeyExpr.regex(EditorContextKeys.languageId.key, /^(markdown|prompt|instructions|chatagent|skill)$/),
+	),
+});
diff --git a/src/vs/sessions/sessions.desktop.main.ts b/src/vs/sessions/sessions.desktop.main.ts
index 4b35ada8541..17d622826eb 100644
--- a/src/vs/sessions/sessions.desktop.main.ts
+++ b/src/vs/sessions/sessions.desktop.main.ts
@@ -212,6 +212,7 @@ import './contrib/gitSync/browser/gitSync.contribution.js';
 import './contrib/applyCommitsToParentRepo/browser/applyChangesToParentRepo.js';
 import './contrib/fileTreeView/browser/fileTreeView.contribution.js'; // view registration disabled; filesystem provider still needed
 import './contrib/configuration/browser/configuration.contribution.js';
+import './contrib/markdownPreview/browser/markdownPreview.contribution.js';
 
 import './contrib/terminal/browser/sessionsTerminalContribution.js';
 import './contrib/logs/browser/logs.contribution.js';