diff --git a/src/vs/workbench/api/electron-browser/mainThreadFileSystem.ts b/src/vs/workbench/api/electron-browser/mainThreadFileSystem.ts
index acc5872827c927a68eb56910792bd8b84d2c1809..52d0da373826216a7cbaf0c19b7f9aac2ee772dc 100644
--- a/src/vs/workbench/api/electron-browser/mainThreadFileSystem.ts
+++ b/src/vs/workbench/api/electron-browser/mainThreadFileSystem.ts
@@ -53,8 +53,8 @@ export class MainThreadFileSystem implements MainThreadFileSystemShape {
 		this._provider.get(handle).$onFileSystemChange(changes);
 	}
 
-	$reportFileChunk(handle: number, data: UriComponents, chunk: number[]): void {
-		this._provider.get(handle).reportFileChunk(URI.revive(data), chunk);
+	$reportFileChunk(handle: number, session: number, chunk: number[]): void {
+		this._provider.get(handle).reportFileChunk(session, chunk);
 	}
 
 	// --- search
@@ -64,10 +64,22 @@ export class MainThreadFileSystem implements MainThreadFileSystemShape {
 	}
 }
 
+class FileReadOperation {
+
+	private static _idPool = 0;
+
+	constructor(
+		readonly progress: IProgress<Uint8Array>,
+		readonly id: number = ++FileReadOperation._idPool
+	) {
+		//
+	}
+}
+
 class RemoteFileSystemProvider implements IFileSystemProvider, ISearchResultProvider {
 
 	private readonly _onDidChange = new Emitter<IFileChange[]>();
-	private readonly _reads = new Map<string, IProgress<Uint8Array>>();
+	private readonly _reads = new Map<number, FileReadOperation>();
 	private readonly _registrations: IDisposable[];
 
 	readonly onDidChange: Event<IFileChange[]> = this._onDidChange.event;
@@ -104,11 +116,12 @@ class RemoteFileSystemProvider implements IFileSystemProvider, ISearchResultProv
 		return this._proxy.$stat(this._handle, resource);
 	}
 	read(resource: URI, offset: number, count: number, progress: IProgress<Uint8Array>): TPromise<number, any> {
-		this._reads.set(resource.toString(), progress);
-		return this._proxy.$read(this._handle, offset, count, resource);
+		const read = new FileReadOperation(progress);
+		this._reads.set(read.id, read);
+		return this._proxy.$read(this._handle, read.id, offset, count, resource);
 	}
-	reportFileChunk(resource: URI, chunk: number[]): void {
-		this._reads.get(resource.toString()).report(Buffer.from(chunk));
+	reportFileChunk(session: number, chunk: number[]): void {
+		this._reads.get(session).progress.report(Buffer.from(chunk));
 	}
 	write(resource: URI, content: Uint8Array): TPromise<void, any> {
 		return this._proxy.$write(this._handle, resource, [].slice.call(content));
@@ -143,7 +156,7 @@ class RemoteFileSystemProvider implements IFileSystemProvider, ISearchResultProv
 		const id = ++this._searchesIdPool;
 		const matches: IFileMatch[] = [];
 		return new PPromise((resolve, reject, report) => {
-			this._proxy.$fileFiles(this._handle, id, query.filePattern).then(() => {
+			this._proxy.$findFiles(this._handle, id, query.filePattern).then(() => {
 				this._searches.delete(id);
 				resolve({
 					results: matches,
diff --git a/src/vs/workbench/api/node/extHost.protocol.ts b/src/vs/workbench/api/node/extHost.protocol.ts
index 9ec2422972fa314e1c348679a8b9175ed401d580..d189f463f6bdb2b30272d1b0ca1768a6b155fa68 100644
--- a/src/vs/workbench/api/node/extHost.protocol.ts
+++ b/src/vs/workbench/api/node/extHost.protocol.ts
@@ -371,7 +371,7 @@ export interface MainThreadFileSystemShape extends IDisposable {
 
 	$onDidAddFileSystemRoot(root: UriComponents): void;
 	$onFileSystemChange(handle: number, resource: IFileChange[]): void;
-	$reportFileChunk(handle: number, resource: UriComponents, chunk: number[] | null): void;
+	$reportFileChunk(handle: number, session: number, chunk: number[] | null): void;
 
 	$handleSearchProgress(handle: number, session: number, resource: UriComponents): void;
 }
@@ -535,14 +535,14 @@ export interface ExtHostWorkspaceShape {
 export interface ExtHostFileSystemShape {
 	$utimes(handle: number, resource: UriComponents, mtime: number, atime: number): TPromise<IStat>;
 	$stat(handle: number, resource: UriComponents): TPromise<IStat>;
-	$read(handle: number, offset: number, count: number, resource: UriComponents): TPromise<number>;
+	$read(handle: number, session: number, offset: number, count: number, resource: UriComponents): TPromise<number>;
 	$write(handle: number, resource: UriComponents, content: number[]): TPromise<void>;
 	$unlink(handle: number, resource: UriComponents): TPromise<void>;
 	$move(handle: number, resource: UriComponents, target: UriComponents): TPromise<IStat>;
 	$mkdir(handle: number, resource: UriComponents): TPromise<IStat>;
 	$readdir(handle: number, resource: UriComponents): TPromise<[UriComponents, IStat][]>;
 	$rmdir(handle: number, resource: UriComponents): TPromise<void>;
-	$fileFiles(handle: number, session: number, query: string): TPromise<void>;
+	$findFiles(handle: number, session: number, query: string): TPromise<void>;
 }
 
 export interface ExtHostExtensionServiceShape {
diff --git a/src/vs/workbench/api/node/extHostFileSystem.ts b/src/vs/workbench/api/node/extHostFileSystem.ts
index 3cdd834d7a712e7c19b7d958cedd9d841612da7f..c2ad87af99017134d1a4f8d4c6bdb41d6e78508e 100644
--- a/src/vs/workbench/api/node/extHostFileSystem.ts
+++ b/src/vs/workbench/api/node/extHostFileSystem.ts
@@ -48,10 +48,10 @@ export class ExtHostFileSystem implements ExtHostFileSystemShape {
 	$stat(handle: number, resource: UriComponents): TPromise<IStat, any> {
 		return asWinJsPromise(token => this._provider.get(handle).stat(URI.revive(resource)));
 	}
-	$read(handle: number, offset: number, count: number, resource: UriComponents): TPromise<number> {
+	$read(handle: number, session: number, offset: number, count: number, resource: UriComponents): TPromise<number> {
 		const progress = {
 			report: chunk => {
-				this._proxy.$reportFileChunk(handle, resource, [].slice.call(chunk));
+				this._proxy.$reportFileChunk(handle, session, [].slice.call(chunk));
 			}
 		};
 		return asWinJsPromise(token => this._provider.get(handle).read(URI.revive(resource), offset, count, progress));
@@ -74,7 +74,7 @@ export class ExtHostFileSystem implements ExtHostFileSystemShape {
 	$rmdir(handle: number, resource: UriComponents): TPromise<void, any> {
 		return asWinJsPromise(token => this._provider.get(handle).rmdir(URI.revive(resource)));
 	}
-	$fileFiles(handle: number, session: number, query: string): TPromise<void> {
+	$findFiles(handle: number, session: number, query: string): TPromise<void> {
 		const provider = this._provider.get(handle);
 		if (!provider.findFiles) {
 			return TPromise.as(undefined);