diff --git a/src/vs/base/common/errors.ts b/src/vs/base/common/errors.ts
index a00d5ebd2ad8b..568a6baee1adb 100644
--- a/src/vs/base/common/errors.ts
+++ b/src/vs/base/common/errors.ts
@@ -168,6 +168,24 @@ export function transformErrorForSerialization(error: any): any {
 	return error;
 }
 
+// see https://github.com/v8/v8/wiki/Stack%20Trace%20API#basic-stack-traces
+export interface V8CallSite {
+	getThis(): any;
+	getTypeName(): string;
+	getFunction(): string;
+	getFunctionName(): string;
+	getMethodName(): string;
+	getFileName(): string;
+	getLineNumber(): number;
+	getColumnNumber(): number;
+	getEvalOrigin(): string;
+	isToplevel(): boolean;
+	isEval(): boolean;
+	isNative(): boolean;
+	isConstructor(): boolean;
+	toString(): string;
+}
+
 const canceledName = 'Canceled';
 
 /**
diff --git a/src/vs/workbench/api/node/extHost.api.impl.ts b/src/vs/workbench/api/node/extHost.api.impl.ts
index 42991687a611c..2fae8ebfbe802 100644
--- a/src/vs/workbench/api/node/extHost.api.impl.ts
+++ b/src/vs/workbench/api/node/extHost.api.impl.ts
@@ -47,7 +47,6 @@ import { ITelemetryService } from 'vs/platform/telemetry/common/telemetry';
 import { CancellationTokenSource } from 'vs/base/common/cancellation';
 import * as vscode from 'vscode';
 import * as paths from 'vs/base/common/paths';
-import { realpath } from 'fs';
 import { MainContext, ExtHostContext, IInitData } from './extHost.protocol';
 import * as languageConfiguration from 'vs/editor/common/modes/languageConfiguration';
 import { TextEditorCursorStyle } from 'vs/editor/common/config/editorOptions';
@@ -621,30 +620,7 @@ class Extension<T> implements vscode.Extension<T> {
 }
 
 export function initializeExtensionApi(extensionService: ExtHostExtensionService, apiFactory: IExtensionApiFactory): TPromise<void> {
-	return createExtensionPathIndex(extensionService).then(trie => defineAPI(apiFactory, trie));
-}
-
-function createExtensionPathIndex(extensionService: ExtHostExtensionService): TPromise<TrieMap<IExtensionDescription>> {
-
-	// create trie to enable fast 'filename -> extension id' look up
-	const trie = new TrieMap<IExtensionDescription>();
-	const extensions = extensionService.getAllExtensionDescriptions().map(ext => {
-		if (!ext.main) {
-			return undefined;
-		}
-		return new TPromise((resolve, reject) => {
-			realpath(ext.extensionFolderPath, (err, path) => {
-				if (err) {
-					reject(err);
-				} else {
-					trie.insert(path, ext);
-					resolve(void 0);
-				}
-			});
-		});
-	});
-
-	return TPromise.join(extensions).then(() => trie);
+	return extensionService.getExtensionPathIndex().then(trie => defineAPI(apiFactory, trie));
 }
 
 function defineAPI(factory: IExtensionApiFactory, extensionPaths: TrieMap<IExtensionDescription>): void {
diff --git a/src/vs/workbench/api/node/extHostExtensionService.ts b/src/vs/workbench/api/node/extHostExtensionService.ts
index d14ff88d23244..e2f327c3efb2d 100644
--- a/src/vs/workbench/api/node/extHostExtensionService.ts
+++ b/src/vs/workbench/api/node/extHostExtensionService.ts
@@ -18,6 +18,8 @@ import { MainContext, MainThreadExtensionServiceShape, IWorkspaceData, IEnvironm
 import { IExtensionMemento, ExtensionsActivator, ActivatedExtension, IExtensionAPI, IExtensionContext, EmptyExtension, IExtensionModule } from "vs/workbench/api/node/extHostExtensionActivator";
 import { Barrier } from "vs/workbench/services/extensions/node/barrier";
 import { ExtHostThreadService } from "vs/workbench/services/thread/node/extHostThreadService";
+import { realpath } from 'fs';
+import { TrieMap } from "vs/base/common/map";
 
 class ExtensionMemento implements IExtensionMemento {
 
@@ -115,7 +117,7 @@ export class ExtHostExtensionService implements ExtHostExtensionServiceShape {
 	private readonly _storagePath: ExtensionStoragePath;
 	private readonly _proxy: MainThreadExtensionServiceShape;
 	private _activator: ExtensionsActivator;
-
+	private _extensionPathIndex: TPromise<TrieMap<IExtensionDescription>>;
 	/**
 	 * This class is constructed manually because it is a service, so it doesn't use any ctor injection
 	 */
@@ -202,6 +204,31 @@ export class ExtHostExtensionService implements ExtHostExtensionServiceShape {
 		}
 	}
 
+	// create trie to enable fast 'filename -> extension id' look up
+	public getExtensionPathIndex(): TPromise<TrieMap<IExtensionDescription>> {
+		if (!this._extensionPathIndex) {
+			const trie = new TrieMap<IExtensionDescription>();
+			const extensions = this.getAllExtensionDescriptions().map(ext => {
+				if (!ext.main) {
+					return undefined;
+				}
+				return new TPromise((resolve, reject) => {
+					realpath(ext.extensionFolderPath, (err, path) => {
+						if (err) {
+							reject(err);
+						} else {
+							trie.insert(path, ext);
+							resolve(void 0);
+						}
+					});
+				});
+			});
+			this._extensionPathIndex = TPromise.join(extensions).then(() => trie);
+		}
+		return this._extensionPathIndex;
+	}
+
+
 	public deactivate(extensionId: string): TPromise<void> {
 		let result: TPromise<void> = TPromise.as(void 0);
 
diff --git a/src/vs/workbench/node/extensionHostMain.ts b/src/vs/workbench/node/extensionHostMain.ts
index 2fcb43ba60c66..62476408f29cb 100644
--- a/src/vs/workbench/node/extensionHostMain.ts
+++ b/src/vs/workbench/node/extensionHostMain.ts
@@ -12,6 +12,7 @@ import { join } from 'path';
 import { RPCProtocol } from 'vs/workbench/services/extensions/node/rpcProtocol';
 import { ExtHostExtensionService } from 'vs/workbench/api/node/extHostExtensionService';
 import { ExtHostThreadService } from 'vs/workbench/services/thread/node/extHostThreadService';
+import { IExtensionDescription } from "vs/platform/extensions/common/extensions";
 import { QueryType, ISearchQuery } from 'vs/platform/search/common/search';
 import { DiskSearch } from 'vs/workbench/services/search/node/searchService';
 import { RemoteTelemetryService } from 'vs/workbench/api/node/extHostTelemetry';
@@ -49,9 +50,27 @@ export class ExtensionHostMain {
 		const telemetryService = new RemoteTelemetryService('pluginHostTelemetry', threadService);
 		this._extensionService = new ExtHostExtensionService(initData, threadService, telemetryService);
 
-		// Error forwarding
+		// error forwarding and stack trace scanning
+		this._extensionService.getExtensionPathIndex().then(map => {
+			(<any>Error).prepareStackTrace = (error: Error, stackTrace: errors.V8CallSite[]) => {
+				let stackTraceMessage = '';
+				let extension: IExtensionDescription;
+				for (const call of stackTrace) {
+					stackTraceMessage += `\n\tat ${call.toString()}`;
+					extension = extension || map.findSubstr(stackTrace[0].getFileName());
+				}
+				let name = error.name || 'Error';
+				if (extension) {
+					name = `[${extension.id}] ${name}`;
+				}
+				return `${name}: ${error.message}${stackTraceMessage}`;
+			};
+		});
 		const mainThreadErrors = threadService.get(MainContext.MainThreadErrors);
-		errors.setUnexpectedErrorHandler(err => mainThreadErrors.$onUnexpectedExtHostError(errors.transformErrorForSerialization(err)));
+		errors.setUnexpectedErrorHandler(err => {
+			const data = errors.transformErrorForSerialization(err);
+			mainThreadErrors.$onUnexpectedExtHostError(data);
+		});
 
 		// Configure the watchdog to kill our process if the JS event loop is unresponsive for more than 10s
 		if (!initData.environment.isExtensionDevelopmentDebug) {