diff --git a/extensions/git-extended/src/prView/prProvider.ts b/extensions/git-extended/src/prView/prProvider.ts
index f88b8bbcffa..adc63a82ece 100644
--- a/extensions/git-extended/src/prView/prProvider.ts
+++ b/extensions/git-extended/src/prView/prProvider.ts
@@ -158,7 +158,11 @@ export class PRProvider implements vscode.TreeDataProvider<PRGroupTreeItem | Pul
 				}
 			];
 
+
+			const _onDidChangeCommentThreads = new vscode.EventEmitter<vscode.CommentThreadChangedEvent>();
+			setTimeout(() => _onDidChangeCommentThreads.fire({ changed: [], added: [], removed: [] }), 5000);
 			vscode.workspace.registerCommentProvider({
+				onDidChangeCommentThreads: _onDidChangeCommentThreads.event,
 				provideNewCommentRange: async (document: vscode.TextDocument, token: vscode.CancellationToken) => {
 					if (document.uri.scheme === 'pr') {
 						let params = JSON.parse(document.uri.query);
diff --git a/extensions/git-extended/src/review/reviewMode.ts b/extensions/git-extended/src/review/reviewMode.ts
index a9d88d6ded3..d10554fcd22 100644
--- a/extensions/git-extended/src/review/reviewMode.ts
+++ b/extensions/git-extended/src/review/reviewMode.ts
@@ -170,7 +170,9 @@ export class ReviewMode {
 			return ret;
 		}
 
-		this._commentProvider = vscode.workspace.registerCommentProvider({
+		const _onDidChangeCommentThreads = new vscode.EventEmitter<vscode.CommentThreadChangedEvent>();
+		vscode.workspace.registerCommentProvider({
+			onDidChangeCommentThreads: _onDidChangeCommentThreads.event,
 			provideNewCommentRange: async (document: vscode.TextDocument, token: vscode.CancellationToken) => {
 				if (document.uri.scheme === 'review' || document.uri.scheme === 'file') {
 					let lastLine = document.lineCount;
diff --git a/src/vs/editor/common/modes.ts b/src/vs/editor/common/modes.ts
index 56eeb3b4c9f..942fd91ec34 100644
--- a/src/vs/editor/common/modes.ts
+++ b/src/vs/editor/common/modes.ts
@@ -957,10 +957,29 @@ export interface Comment {
 	readonly gravatar: string;
 }
 
+export interface CommentThreadChangedEvent {
+	/**
+	 * Added comment threads.
+	 */
+	readonly added: CommentThread[];
+
+	/**
+	 * Removed comment threads.
+	 */
+	readonly removed: CommentThread[];
+
+	/**
+	 * Changed comment threads.
+	 */
+	readonly changed: CommentThread[];
+}
+
+
 export interface CommentProvider {
 	provideComments(model: model.ITextModel, token: CancellationToken): CommentThread[];
 	provideNewCommentRange(model: model.ITextModel, token: CancellationToken): Promise<NewCommentAction>;
 	provideAllComments(token: CancellationToken): Promise<CommentThread[]>;
+	onDidChangeCommentThreads(): Event<CommentThreadChangedEvent>;
 }
 
 export interface ICodeLensSymbol {
diff --git a/src/vs/monaco.d.ts b/src/vs/monaco.d.ts
index 6a02849802f..cb42a57a7f5 100644
--- a/src/vs/monaco.d.ts
+++ b/src/vs/monaco.d.ts
@@ -5047,10 +5047,26 @@ declare namespace monaco.languages {
 		readonly gravatar: string;
 	}
 
+	export interface CommentThreadChangedEvent {
+		/**
+		 * Added comment threads.
+		 */
+		readonly added: CommentThread[];
+		/**
+		 * Removed comment threads.
+		 */
+		readonly removed: CommentThread[];
+		/**
+		 * Changed comment threads.
+		 */
+		readonly changed: CommentThread[];
+	}
+
 	export interface CommentProvider {
 		provideComments(model: editor.ITextModel, token: CancellationToken): CommentThread[];
 		provideNewCommentRange(model: editor.ITextModel, token: CancellationToken): Promise<NewCommentAction>;
 		provideAllComments(token: CancellationToken): Promise<CommentThread[]>;
+		onDidChangeCommentThreads(): IEvent<CommentThreadChangedEvent>;
 	}
 
 	export interface ICodeLensSymbol {
diff --git a/src/vs/vscode.proposed.d.ts b/src/vs/vscode.proposed.d.ts
index c6a09c6db2b..501e3f02956 100644
--- a/src/vs/vscode.proposed.d.ts
+++ b/src/vs/vscode.proposed.d.ts
@@ -789,6 +789,23 @@ declare module 'vscode' {
 		gravatar: string;
 	}
 
+	export interface CommentThreadChangedEvent {
+		/**
+		 * Added comment threads.
+		 */
+		readonly added: CommentThread[];
+
+		/**
+		 * Removed comment threads.
+		 */
+		readonly removed: CommentThread[];
+
+		/**
+		 * Changed comment threads.
+		 */
+		readonly changed: CommentThread[];
+	}
+
 	/**
 	 * TODO: force update event?
 	 * TODO: resolve step?
@@ -797,6 +814,7 @@ declare module 'vscode' {
 		provideComments(document: TextDocument, token: CancellationToken): Promise<CommentThread[]>;
 		provideNewCommentRange(document: TextDocument, token: CancellationToken): Promise<NewCommentAction>;
 		provideAllComments?(token: CancellationToken): Promise<CommentThread[]>;
+		onDidChangeCommentThreads?: Event<CommentThreadChangedEvent>;
 	}
 
 	namespace workspace {
diff --git a/src/vs/workbench/api/electron-browser/mainThreadComments.ts b/src/vs/workbench/api/electron-browser/mainThreadComments.ts
index 2f28d8bedca..c684c79bed8 100644
--- a/src/vs/workbench/api/electron-browser/mainThreadComments.ts
+++ b/src/vs/workbench/api/electron-browser/mainThreadComments.ts
@@ -67,8 +67,10 @@ export class MainThreadComments extends Disposable implements MainThreadComments
 				this._panelService.setPanelEnablement(COMMENTS_PANEL_ID, true);
 			}
 		});
+	}
 
-
+	$onDidCommentThreadsChange(handle: number, event: modes.CommentThreadChangedEvent) {
+		// notify comment service
 	}
 
 	$unregisterCommentProvider(handle: number): void {
diff --git a/src/vs/workbench/api/node/extHost.protocol.ts b/src/vs/workbench/api/node/extHost.protocol.ts
index 3d1d6c9683e..a7f9cbbd692 100644
--- a/src/vs/workbench/api/node/extHost.protocol.ts
+++ b/src/vs/workbench/api/node/extHost.protocol.ts
@@ -107,6 +107,7 @@ export interface MainThreadCommandsShape extends IDisposable {
 export interface MainThreadCommentsShape extends IDisposable {
 	$registerCommentProvider(handle: number): void;
 	$unregisterCommentProvider(handle: number): void;
+	$onDidCommentThreadsChange(handle: number, event: modes.CommentThreadChangedEvent): void;
 }
 
 export interface MainThreadConfigurationShape extends IDisposable {
diff --git a/src/vs/workbench/api/node/extHostComments.ts b/src/vs/workbench/api/node/extHostComments.ts
index a1804f7ab3b..7fb835c4aa8 100644
--- a/src/vs/workbench/api/node/extHostComments.ts
+++ b/src/vs/workbench/api/node/extHostComments.ts
@@ -37,6 +37,15 @@ export class ExtHostComments implements ExtHostCommentsShape {
 		this._providers.set(handle, provider);
 
 		this._proxy.$registerCommentProvider(handle);
+
+		provider.onDidChangeCommentThreads(event => {
+
+			this._proxy.$onDidCommentThreadsChange(handle, {
+				changed: event.changed.map(x => convertCommentThread(x, this._commandsConverter)),
+				added: event.added.map(x => convertCommentThread(x, this._commandsConverter)),
+				removed: event.removed.map(x => convertCommentThread(x, this._commandsConverter))
+			});
+		});
 		return {
 			dispose: () => {
 				this._proxy.$unregisterCommentProvider(handle);
@@ -45,6 +54,10 @@ export class ExtHostComments implements ExtHostCommentsShape {
 		};
 	}
 
+	$onDidCommentThreadsChange(handle: number, commentThreadEvent: vscode.CommentThreadChangedEvent) {
+		return TPromise.as(null);
+	}
+
 	$provideComments(handle: number, uri: UriComponents): TPromise<modes.CommentThread[]> {
 		const data = this._documents.getDocumentData(URI.revive(uri));
 		if (!data || !data.document) {