diff --git a/extensions/vscode-api-tests/src/singlefolder-tests/window.test.ts b/extensions/vscode-api-tests/src/singlefolder-tests/window.test.ts
index ea521f1e66b..91efbf70974 100644
--- a/extensions/vscode-api-tests/src/singlefolder-tests/window.test.ts
+++ b/extensions/vscode-api-tests/src/singlefolder-tests/window.test.ts
@@ -383,9 +383,8 @@ suite('vscode API - window', () => {
 		assert.strictEqual(tabs[1].resource?.toString(), notebookDoc.uri.toString());
 		assert.strictEqual(tabs[2].resource?.toString(), docB.uri.toString());
 		assert.strictEqual(tabs[3].resource?.toString(), docC.uri.toString());
-		const diffResource = tabs[4].resource as { primary?: Uri, secondary?: Uri } | undefined;
-		assert.strictEqual(diffResource?.secondary?.toString(), leftDiff.toString());
-		assert.strictEqual(diffResource?.primary?.toString(), rightDiff.toString());
+		// Diff editor and side by side editor report the right side as the resource
+		assert.strictEqual(tabs[4].resource?.toString(), rightDiff.toString());
 
 		assert.strictEqual(tabs[0].viewColumn, ViewColumn.One);
 		assert.strictEqual(tabs[1].viewColumn, ViewColumn.One);
diff --git a/src/vs/vscode.proposed.d.ts b/src/vs/vscode.proposed.d.ts
index a58df8f7577..0562934cc9d 100644
--- a/src/vs/vscode.proposed.d.ts
+++ b/src/vs/vscode.proposed.d.ts
@@ -2320,17 +2320,15 @@ declare module 'vscode' {
 
 		/**
 		 * The resource represented by the tab if availble.
-		 * If the tab contains more than one resource then primary will represent the right resource, and secondary the left one.
-		 * Note: Not all editor types have a resource associated with them
+		 * Note: Not all tabs have a resource associated with them.
 		 */
-		readonly resource?: Uri | { primary?: Uri, secondary?: Uri };
+		readonly resource?: Uri;
 
 		/**
 		 * The identifier of the editor which the tab should contain, because
 		 * not all tabs represent editors this may be undefined.
 		 * This is equivalent to `viewType` for custom editors and notebooks.
 		 * The built-in text editor has an id of 'default' for all configurations.
-		 * Note: Tabs are not guaranteed to contain editors but this id represents what editor the tab will resolve if available
 		 */
 		readonly editorId?: string;
 
diff --git a/src/vs/workbench/api/browser/mainThreadEditorTabs.ts b/src/vs/workbench/api/browser/mainThreadEditorTabs.ts
index 677d19a1730..8a263c5ecc6 100644
--- a/src/vs/workbench/api/browser/mainThreadEditorTabs.ts
+++ b/src/vs/workbench/api/browser/mainThreadEditorTabs.ts
@@ -45,7 +45,7 @@ export class MainThreadEditorTabs {
 				tabs.push({
 					viewColumn: editorGroupToColumn(this._editorGroupsService, group),
 					label: editor.getName(),
-					resource: editor instanceof SideBySideEditorInput ? EditorResourceAccessor.getCanonicalUri(editor, { supportSideBySide: SideBySideEditor.BOTH }) : EditorResourceAccessor.getCanonicalUri(editor),
+					resource: editor instanceof SideBySideEditorInput ? EditorResourceAccessor.getCanonicalUri(editor, { supportSideBySide: SideBySideEditor.PRIMARY }) : EditorResourceAccessor.getCanonicalUri(editor),
 					editorId: editor.editorId,
 					isActive: (this._editorGroupsService.activeGroup === group) && group.isActive(editor)
 				});
diff --git a/src/vs/workbench/api/common/extHost.protocol.ts b/src/vs/workbench/api/common/extHost.protocol.ts
index ebd05448324..d8fe3a603ed 100644
--- a/src/vs/workbench/api/common/extHost.protocol.ts
+++ b/src/vs/workbench/api/common/extHost.protocol.ts
@@ -642,7 +642,7 @@ export interface MainThreadEditorTabsShape extends IDisposable {
 export interface IEditorTabDto {
 	viewColumn: EditorGroupColumn;
 	label: string;
-	resource?: UriComponents | { primary?: UriComponents, secondary?: UriComponents };
+	resource?: UriComponents;
 	editorId?: string;
 	isActive: boolean;
 }
diff --git a/src/vs/workbench/api/common/extHostEditorTabs.ts b/src/vs/workbench/api/common/extHostEditorTabs.ts
index 879dc99e4ff..e4e61af8543 100644
--- a/src/vs/workbench/api/common/extHostEditorTabs.ts
+++ b/src/vs/workbench/api/common/extHostEditorTabs.ts
@@ -6,7 +6,7 @@
 import type * as vscode from 'vscode';
 import * as typeConverters from 'vs/workbench/api/common/extHostTypeConverters';
 import { IEditorTabDto, IExtHostEditorTabsShape } from 'vs/workbench/api/common/extHost.protocol';
-import { URI, UriComponents } from 'vs/base/common/uri';
+import { URI } from 'vs/base/common/uri';
 import { Emitter, Event } from 'vs/base/common/event';
 import { createDecorator } from 'vs/platform/instantiation/common/instantiation';
 import { ViewColumn } from 'vs/workbench/api/common/extHostTypes';
@@ -14,7 +14,7 @@ import { ViewColumn } from 'vs/workbench/api/common/extHostTypes';
 export interface IEditorTab {
 	label: string;
 	viewColumn: ViewColumn;
-	resource?: vscode.Uri | { primary?: vscode.Uri, secondary?: vscode.Uri };
+	resource?: vscode.Uri;
 	editorId?: string;
 	isActive: boolean;
 }
@@ -55,23 +55,10 @@ export class ExtHostEditorTabs implements IExtHostEditorTabs {
 			if (dto.isActive) {
 				activeIndex = index;
 			}
-			// Resolve resource into the right shape for either normal or side by side
-			let resource = undefined;
-			if (dto.resource) {
-				const resourceAsSidebySide = dto.resource as ({ primary?: UriComponents, secondary?: UriComponents });
-				if (resourceAsSidebySide.primary || resourceAsSidebySide.secondary) {
-					resource = {
-						primary: URI.revive(resourceAsSidebySide.primary),
-						secondary: URI.revive(resourceAsSidebySide.secondary)
-					};
-				} else {
-					resource = URI.revive(dto.resource as UriComponents | undefined);
-				}
-			}
 			return Object.freeze({
 				label: dto.label,
 				viewColumn: typeConverters.ViewColumn.to(dto.viewColumn),
-				resource,
+				resource: URI.revive(dto.resource),
 				editorId: dto.editorId,
 				isActive: dto.isActive
 			});