diff --git a/src/vs/workbench/api/common/extHostEditorTabs.ts b/src/vs/workbench/api/common/extHostEditorTabs.ts
index 292cd429c3f..6fe404878bb 100644
--- a/src/vs/workbench/api/common/extHostEditorTabs.ts
+++ b/src/vs/workbench/api/common/extHostEditorTabs.ts
@@ -321,26 +321,26 @@ export class ExtHostEditorTabs implements IExtHostEditorTabs {
 		// Construct the tab change event based on the operation
 		switch (operation.kind) {
 			case TabModelOperationKind.TAB_OPEN:
-				this._onDidChangeTabs.fire({
-					added: [tab.apiObject],
-					removed: [],
+				this._onDidChangeTabs.fire(Object.freeze({
+					opened: [tab.apiObject],
+					closed: [],
 					changed: []
-				});
+				}));
 				return;
 			case TabModelOperationKind.TAB_CLOSE:
-				this._onDidChangeTabs.fire({
-					added: [],
-					removed: [tab.apiObject],
+				this._onDidChangeTabs.fire(Object.freeze({
+					opened: [],
+					closed: [tab.apiObject],
 					changed: []
-				});
+				}));
 				return;
 			case TabModelOperationKind.TAB_MOVE:
 			case TabModelOperationKind.TAB_UPDATE:
-				this._onDidChangeTabs.fire({
-					added: [],
-					removed: [],
+				this._onDidChangeTabs.fire(Object.freeze({
+					opened: [],
+					closed: [],
 					changed: [tab.apiObject]
-				});
+				}));
 				return;
 		}
 	}
diff --git a/src/vscode-dts/vscode.proposed.tabs.d.ts b/src/vscode-dts/vscode.proposed.tabs.d.ts
index 381506507b6..1029de92ac1 100644
--- a/src/vscode-dts/vscode.proposed.tabs.d.ts
+++ b/src/vscode-dts/vscode.proposed.tabs.d.ts
@@ -154,10 +154,18 @@ declare module 'vscode' {
 	}
 
 	export interface TabChangeEvent {
-		// TODO@API consider: opened
-		readonly added: readonly Tab[];
-		// TODO@API consider: closed (aligns with TabGroups.close(...))
-		readonly removed: readonly Tab[];
+		/**
+		 * The tabs that have been opened
+		 */
+		readonly opened: readonly Tab[];
+		/**
+		 * The tabs that have been closed
+		 */
+		readonly closed: readonly Tab[];
+		/**
+		 * Tabs that have changed, e.g have changed
+		 * their {@link Tab.isActive active} state.
+		 */
 		readonly changed: readonly Tab[];
 	}