diff --git a/src/vs/workbench/api/electron-browser/mainThreadOutputService.ts b/src/vs/workbench/api/electron-browser/mainThreadOutputService.ts
index 0df0a7c9bfb..a8eed0c7b50 100644
--- a/src/vs/workbench/api/electron-browser/mainThreadOutputService.ts
+++ b/src/vs/workbench/api/electron-browser/mainThreadOutputService.ts
@@ -38,11 +38,13 @@ export class MainThreadOutputService extends Disposable implements MainThreadOut
 
 		this._proxy = extHostContext.getProxy(ExtHostContext.ExtHostOutputService);
 
-		this._register(anyEvent<any>(this._outputService.onActiveOutputChannel, this._panelService.onDidPanelOpen, this._panelService.onDidPanelClose)(() => {
+		const setVisibleChannel = () => {
 			const panel = this._panelService.getActivePanel();
 			const visibleChannel: IOutputChannel = panel && panel.getId() === OUTPUT_PANEL_ID ? this._outputService.getActiveChannel() : null;
 			this._proxy.$setVisibleChannel(visibleChannel ? visibleChannel.id : null);
-		}));
+		};
+		this._register(anyEvent<any>(this._outputService.onActiveOutputChannel, this._panelService.onDidPanelOpen, this._panelService.onDidPanelClose)(() => setVisibleChannel()));
+		setVisibleChannel();
 	}
 
 	public dispose(): void {
@@ -72,10 +74,10 @@ export class MainThreadOutputService extends Disposable implements MainThreadOut
 		return undefined;
 	}
 
-	public $clear(channelId: string): Thenable<void> {
+	public $clear(channelId: string, till: number): Thenable<void> {
 		const channel = this._getChannel(channelId);
 		if (channel) {
-			channel.clear();
+			channel.clear(till);
 		}
 		return undefined;
 	}
diff --git a/src/vs/workbench/api/node/extHost.protocol.ts b/src/vs/workbench/api/node/extHost.protocol.ts
index a7e9ea956cf..e7c980489a8 100644
--- a/src/vs/workbench/api/node/extHost.protocol.ts
+++ b/src/vs/workbench/api/node/extHost.protocol.ts
@@ -305,7 +305,7 @@ export interface MainThreadOutputServiceShape extends IDisposable {
 	$register(label: string, log: boolean, file?: UriComponents): Thenable<string>;
 	$append(channelId: string, value: string): Thenable<void>;
 	$update(channelId: string): Thenable<void>;
-	$clear(channelId: string): Thenable<void>;
+	$clear(channelId: string, till: number): Thenable<void>;
 	$reveal(channelId: string, preserveFocus: boolean): Thenable<void>;
 	$close(channelId: string): Thenable<void>;
 	$dispose(channelId: string): Thenable<void>;
diff --git a/src/vs/workbench/api/node/extHostOutputService.ts b/src/vs/workbench/api/node/extHostOutputService.ts
index 4d5c0f9f8b2..bae23eb8674 100644
--- a/src/vs/workbench/api/node/extHostOutputService.ts
+++ b/src/vs/workbench/api/node/extHostOutputService.ts
@@ -19,6 +19,7 @@ export abstract class AbstractExtHostOutputChannel extends Disposable implements
 	private readonly _name: string;
 	protected readonly _proxy: MainThreadOutputServiceShape;
 	private _disposed: boolean;
+	private _offset: number;
 
 	protected _onDidAppend: Emitter<void> = this._register(new Emitter<void>());
 	get onDidAppend(): Event<void> { return this._onDidAppend.event; }
@@ -29,13 +30,17 @@ export abstract class AbstractExtHostOutputChannel extends Disposable implements
 		this._name = name;
 		this._proxy = proxy;
 		this._id = proxy.$register(this.name, log, file);
+		this._offset = 0;
 	}
 
 	get name(): string {
 		return this._name;
 	}
 
-	abstract append(value: string): void;
+	append(value: string): void {
+		this.validate();
+		this._offset += value ? Buffer.from(value).byteLength : 0;
+	}
 
 	update(): void {
 		this._id.then(id => this._proxy.$update(id));
@@ -48,7 +53,8 @@ export abstract class AbstractExtHostOutputChannel extends Disposable implements
 
 	clear(): void {
 		this.validate();
-		this._id.then(id => this._proxy.$clear(id));
+		const till = this._offset;
+		this._id.then(id => this._proxy.$clear(id, till));
 	}
 
 	show(columnOrPreserveFocus?: vscode.ViewColumn | boolean, preserveFocus?: boolean): void {
@@ -85,7 +91,7 @@ export class ExtHostPushOutputChannel extends AbstractExtHostOutputChannel {
 	}
 
 	append(value: string): void {
-		this.validate();
+		super.append(value);
 		this._id.then(id => this._proxy.$append(id, value));
 		this._onDidAppend.fire();
 	}
@@ -105,7 +111,7 @@ export class ExtHostOutputChannelBackedByFile extends AbstractExtHostOutputChann
 	}
 
 	append(value: string): void {
-		this.validate();
+		super.append(value);
 		this._appender.append(value);
 		this._onDidAppend.fire();
 	}
diff --git a/src/vs/workbench/parts/output/common/output.ts b/src/vs/workbench/parts/output/common/output.ts
index c8709c545a1..aca59d9ff7a 100644
--- a/src/vs/workbench/parts/output/common/output.ts
+++ b/src/vs/workbench/parts/output/common/output.ts
@@ -124,7 +124,7 @@ export interface IOutputChannel {
 	/**
 	 * Clears all received output for this channel.
 	 */
-	clear(): void;
+	clear(till?: number): void;
 
 	/**
 	 * Disposes the output channel.
diff --git a/src/vs/workbench/parts/output/electron-browser/outputServices.ts b/src/vs/workbench/parts/output/electron-browser/outputServices.ts
index bc8fbc58591..8e4d8f4e1f0 100644
--- a/src/vs/workbench/parts/output/electron-browser/outputServices.ts
+++ b/src/vs/workbench/parts/output/electron-browser/outputServices.ts
@@ -113,7 +113,7 @@ abstract class AbstractFileOutputChannel extends Disposable {
 		return this.outputChannelDescriptor.label;
 	}
 
-	clear(): void {
+	clear(till?: number): void {
 		if (this.modelUpdater.isScheduled()) {
 			this.modelUpdater.cancel();
 			this.onUpdateModelCancelled();
@@ -121,6 +121,7 @@ abstract class AbstractFileOutputChannel extends Disposable {
 		if (this.model) {
 			this.model.setValue('');
 		}
+		this.endOffset = isNumber(till) ? till : this.endOffset;
 		this.startOffset = this.endOffset;
 	}
 
@@ -208,8 +209,8 @@ class OutputChannelBackedByFile extends AbstractFileOutputChannel implements Out
 		}
 	}
 
-	clear(): void {
-		super.clear();
+	clear(till?: number): void {
+		super.clear(till);
 		this.appendedMessage = '';
 	}
 
@@ -338,6 +339,7 @@ class FileOutputChannel extends AbstractFileOutputChannel implements OutputChann
 
 	private updateInProgress: boolean = false;
 	private etag: string = '';
+	private loadModelPromise: TPromise<ITextModel> = TPromise.as(null);
 
 	constructor(
 		outputChannelDescriptor: IOutputChannelDescriptor,
@@ -354,12 +356,20 @@ class FileOutputChannel extends AbstractFileOutputChannel implements OutputChann
 	}
 
 	loadModel(): TPromise<ITextModel> {
-		return this.fileService.resolveContent(this.file, { position: this.startOffset, encoding: 'utf8' })
+		this.loadModelPromise = this.fileService.resolveContent(this.file, { position: this.startOffset, encoding: 'utf8' })
 			.then(content => {
 				this.endOffset = this.startOffset + Buffer.from(content.value).byteLength;
 				this.etag = content.etag;
 				return this.createModel(content.value);
 			});
+		return this.loadModelPromise;
+	}
+
+	clear(till?: number): void {
+		this.loadModelPromise.then(() => {
+			super.clear(till);
+			this.update();
+		});
 	}
 
 	append(message: string): void {