diff --git a/Jakefile.js b/Jakefile.js
index bf20bf29275..2c3f9f3a2fd 100644
--- a/Jakefile.js
+++ b/Jakefile.js
@@ -110,6 +110,12 @@ var serverCoreSources = [
     return path.join(serverDirectory, f);
 });
 
+var cancellationTokenSources = [
+    "cancellationToken.ts"
+].map(function (f) {
+    return path.join(serverDirectory, f);
+});
+
 var serverSources = serverCoreSources.concat(servicesSources);
 
 var languageServiceLibrarySources = [
@@ -517,8 +523,11 @@ compileFile(servicesFile, servicesSources,[builtLocalDirectory, copyright].conca
             });
 
 
+var cancellationTokenFile = path.join(builtLocalDirectory, "cancellationToken.js");
+compileFile(cancellationTokenFile, cancellationTokenSources, [builtLocalDirectory].concat(cancellationTokenSources), /*prefixes*/ [copyright], /*useBuiltCompiler*/ true, { outDir: builtLocalDirectory, noOutFile: true });
+
 var serverFile = path.join(builtLocalDirectory, "tsserver.js");
-compileFile(serverFile, serverSources,[builtLocalDirectory, copyright].concat(serverSources), /*prefixes*/ [copyright], /*useBuiltCompiler*/ true);
+compileFile(serverFile, serverSources,[builtLocalDirectory, copyright, cancellationTokenFile].concat(serverSources), /*prefixes*/ [copyright], /*useBuiltCompiler*/ true);
 
 var tsserverLibraryFile = path.join(builtLocalDirectory, "tsserverlibrary.js");
 var tsserverLibraryDefinitionFile = path.join(builtLocalDirectory, "tsserverlibrary.d.ts");
diff --git a/src/server/cancellationToken.ts b/src/server/cancellationToken.ts
new file mode 100644
index 00000000000..ac5adeab6d7
--- /dev/null
+++ b/src/server/cancellationToken.ts
@@ -0,0 +1,34 @@
+/// <reference path="node.d.ts"/>
+
+
+// TODO: extract services types 
+interface HostCancellationToken {
+    isCancellationRequested(): boolean;
+}
+
+const fs: typeof NodeJS.fs = require("fs");
+
+function createCancellationToken(args: string[]): HostCancellationToken {
+    let cancellationPipeName: string;
+    for (let i = 0; i < args.length - 1; i++) {
+        if (args[i] === "--cancellationPipeName") {
+            cancellationPipeName = args[i + 1];
+            break;
+        }
+    }
+    if (!cancellationPipeName) {
+        return { isCancellationRequested: () => false  };
+    }
+    return {
+        isCancellationRequested() {
+            try {
+                fs.statSync(cancellationPipeName);
+                return true;
+            }
+            catch(e) {
+                return false;
+            }
+        }
+    };
+}
+export = createCancellationToken
\ No newline at end of file
diff --git a/src/server/editorServices.ts b/src/server/editorServices.ts
index f2e5eabb4e3..87ae34ca239 100644
--- a/src/server/editorServices.ts
+++ b/src/server/editorServices.ts
@@ -129,7 +129,7 @@ namespace ts.server {
         private resolvedTypeReferenceDirectives: ts.FileMap<Map<ResolvedTypeReferenceDirectiveWithFailedLookupLocations>>;
         private getCanonicalFileName: (fileName: string) => string;
 
-        constructor(private host: ServerHost, private project: Project) {
+        constructor(private host: ServerHost, private project: Project, private cancellationToken: HostCancellationToken) {
             this.getCanonicalFileName = ts.createGetCanonicalFileName(this.host.useCaseSensitiveFileNames);
             this.resolvedModuleNames = createFileMap<Map<ResolvedModuleWithFailedLookupLocations>>();
             this.resolvedTypeReferenceDirectives = createFileMap<Map<ResolvedTypeReferenceDirectiveWithFailedLookupLocations>>();
@@ -188,6 +188,10 @@ namespace ts.server {
             }
         }
 
+        getCancellationToken() {
+            return this.cancellationToken;
+        }
+
         resolveTypeReferenceDirectives(typeDirectiveNames: string[], containingFile: string): ResolvedTypeReferenceDirective[] {
             return this.resolveNamesWithLocalCache(typeDirectiveNames, containingFile, this.resolvedTypeReferenceDirectives, resolveTypeReferenceDirective, m => m.resolvedTypeReferenceDirective);
         }
@@ -316,7 +320,7 @@ namespace ts.server {
                 compilerOptions.allowNonTsExtensions = true;
             }
 
-            this.lsHost = new LSHost(this.projectService.host, this);
+            this.lsHost = new LSHost(this.projectService.host, this, this.projectService.cancellationToken);
             this.lsHost.setCompilationSettings(compilerOptions);
             this.languageService = ts.createLanguageService(this.lsHost, documentRegistry);
         }
@@ -642,7 +646,10 @@ namespace ts.server {
 
         private documentRegistry: ts.DocumentRegistry;
 
-        constructor(public host: ServerHost, public psLogger: Logger, public eventHandler?: ProjectServiceEventHandler) {
+        constructor(public host: ServerHost,
+            public psLogger: Logger,
+            public cancellationToken: HostCancellationToken,
+            public eventHandler?: ProjectServiceEventHandler) {
             // ts.disableIncrementalParsing = true;
             this.setDefaultHostConfiguration();
             this.documentRegistry = ts.createDocumentRegistry(host.useCaseSensitiveFileNames, host.getCurrentDirectory());
diff --git a/src/server/server.ts b/src/server/server.ts
index efd01741f86..da1996d341f 100644
--- a/src/server/server.ts
+++ b/src/server/server.ts
@@ -92,8 +92,8 @@ namespace ts.server {
     }
 
     class IOSession extends Session {
-        constructor(host: ServerHost, logger: ts.server.Logger) {
-            super(host, Buffer.byteLength, process.hrtime, logger);
+        constructor(host: ServerHost, cancellationToken: HostCancellationToken, logger: ts.server.Logger) {
+            super(host, cancellationToken, Buffer.byteLength, process.hrtime, logger);
         }
 
         exit() {
@@ -294,7 +294,21 @@ namespace ts.server {
     sys.setTimeout = setTimeout;
     sys.clearTimeout = clearTimeout;
 
-    const ioSession = new IOSession(sys, logger);
+    let cancellationToken: HostCancellationToken;
+    try {
+        let cancellationPipeName: string;
+        if (cancellationPipeName) {
+            const factory = require("./cancellationToken");
+            cancellationToken = factory(sys.args);
+        }
+    }
+    catch(e) {
+        cancellationToken = {
+            isCancellationRequested: () => false
+        }
+    }
+
+    const ioSession = new IOSession(sys, cancellationToken, logger);
     process.on("uncaughtException", function(err: Error) {
         ioSession.logError(err, "unknown");
     });
diff --git a/src/server/session.ts b/src/server/session.ts
index b5616ae2bf9..86d8dc0734f 100644
--- a/src/server/session.ts
+++ b/src/server/session.ts
@@ -156,12 +156,12 @@ namespace ts.server {
 
         constructor(
             private host: ServerHost,
+            private cancellationToken: HostCancellationToken,
             private byteLength: (buf: string, encoding?: string) => number,
             private hrtime: (start?: number[]) => number[],
-            private logger: Logger
-        ) {
+            private logger: Logger) {
             this.projectService =
-                new ProjectService(host, logger, (eventName, project, fileName) => {
+                new ProjectService(host, logger, cancellationToken, (eventName, project, fileName) => {
                     this.handleEvent(eventName, project, fileName);
                 });
         }
@@ -1067,6 +1067,10 @@ namespace ts.server {
             return { response, responseRequired: true };
         }
 
+        private canceledResponse() {
+            return { canceled: true, responseRequired: true };
+        }
+
         private handlers: Map<(request: protocol.Request) => { response?: any, responseRequired?: boolean }> = {
             [CommandNames.OpenExternalProject]: (request: protocol.OpenExternalProjectRequest) => {
                 this.projectService.openExternalProject(request.arguments);
@@ -1282,6 +1286,8 @@ namespace ts.server {
             catch (err) {
                 if (err instanceof OperationCanceledException) {
                     // Handle cancellation exceptions
+                    this.output({ canceled: true }, request.command, request.seq);
+                    return;
                 }
                 this.logError(err, message);
                 this.output(