diff --git a/src/harness/fourslash.ts b/src/harness/fourslash.ts
index ebf1b1d1814..6cc1eaea3b5 100644
--- a/src/harness/fourslash.ts
+++ b/src/harness/fourslash.ts
@@ -1883,7 +1883,7 @@ module FourSlash {
                     );
                 assert.equal(
                     expected.join(","),
-                    actual.fileNameList.map( file => {
+                    actual.fileNames.map( file => {
                         return file.replace(this.basePath + "/", "");
                         }).join(",")
                     );
@@ -2808,4 +2808,4 @@ module FourSlash {
             fileName: fileName
         };
     }
-}
\ No newline at end of file
+}
diff --git a/src/server/client.ts b/src/server/client.ts
index cc89349b442..f938d478246 100644
--- a/src/server/client.ts
+++ b/src/server/client.ts
@@ -183,7 +183,7 @@ namespace ts.server {
 
             return {
                 configFileName: response.body.configFileName,
-                fileNameList: response.body.fileNameList
+                fileNames: response.body.fileNames
             };
         }
         
diff --git a/src/server/editorServices.ts b/src/server/editorServices.ts
index 64ec600783a..7eaf944e916 100644
--- a/src/server/editorServices.ts
+++ b/src/server/editorServices.ts
@@ -304,7 +304,7 @@ namespace ts.server {
             return this.projectService.openFile(filename, false);
         }
 
-        getFileNameList() {
+        getFileNames() {
             let sourceFiles = this.program.getSourceFiles();
             return sourceFiles.map(sourceFile => sourceFile.fileName);
         }
diff --git a/src/server/protocol.d.ts b/src/server/protocol.d.ts
index 837bce4f99d..99008770bba 100644
--- a/src/server/protocol.d.ts
+++ b/src/server/protocol.d.ts
@@ -116,7 +116,7 @@ declare namespace ts.server.protocol {
         /**
           * The list of normalized file name in the project, including 'lib.d.ts'
           */
-        fileNameList?: string[];
+        fileNames?: string[];
     }
 
     /** 
@@ -894,6 +894,31 @@ declare namespace ts.server.protocol {
     export interface SignatureHelpResponse extends Response {
         body?: SignatureHelpItems;
     }
+
+    /**
+    * Arguments for GeterrForProject request.
+    */
+    export interface GeterrForProjectRequestArgs {
+        /**
+          * the file requesting project error list
+          */
+        file: string;
+
+        /**
+          * Delay in milliseconds to wait before starting to compute
+          * errors for the files in the file list
+          */
+        delay: number;
+    }
+
+    /**
+      * GeterrForProjectRequest request; value of command field is 
+      * "geterrForProject". It works similarly with 'Geterr', only 
+      * it request for every file in this project.
+      */
+    export interface GeterrForProjectRequest extends Request {
+        arguments: GeterrForProjectRequestArgs
+    }
     
     /**
       * Arguments for geterr messages.
diff --git a/src/server/session.ts b/src/server/session.ts
index 54e4423d382..108cf4726dc 100644
--- a/src/server/session.ts
+++ b/src/server/session.ts
@@ -86,6 +86,7 @@ namespace ts.server {
         export const Format = "format";
         export const Formatonkey = "formatonkey";
         export const Geterr = "geterr";
+        export const GeterrForProject = "geterrForProject";
         export const NavBar = "navbar";
         export const Navto = "navto";
         export const Occurrences = "occurrences";
@@ -235,7 +236,7 @@ namespace ts.server {
         }
 
         private updateErrorCheck(checkList: PendingErrorCheck[], seq: number,
-            matchSeq: (seq: number) => boolean, ms = 1500, followMs = 200) {
+            matchSeq: (seq: number) => boolean, ms = 1500, followMs = 200, requireOpen = true) {
             if (followMs > ms) {
                 followMs = ms;
             }
@@ -250,7 +251,7 @@ namespace ts.server {
             var checkOne = () => {
                 if (matchSeq(seq)) {
                     var checkSpec = checkList[index++];
-                    if (checkSpec.project.getSourceFileFromName(checkSpec.fileName, true)) {
+                    if (checkSpec.project.getSourceFileFromName(checkSpec.fileName, requireOpen)) {
                         this.syntacticCheck(checkSpec.fileName, checkSpec.project);
                         this.immediateId = setImmediate(() => {
                             this.semanticCheck(checkSpec.fileName, checkSpec.project);
@@ -389,7 +390,7 @@ namespace ts.server {
             }
 
             if (needFileNameList) {
-                projectInfo.fileNameList = project.getFileNameList();
+                projectInfo.fileNames = project.getFileNames();
             }
 
             return projectInfo;
@@ -873,7 +874,53 @@ namespace ts.server {
             }));
         }
 
-        public exit() {
+        getDiagnosticsForProject(delay: number, fileName: string) {
+            let { configFileName, fileNames: fileNamesInProject } = this.getProjectInfo(fileName, true);
+            // No need to analyze lib.d.ts
+            fileNamesInProject = fileNamesInProject.filter((value, index, array) => value.indexOf("lib.d.ts") < 0);
+
+            // Sort the file name list to make the recently touched files come first
+            let highPriorityFiles: string[] = [];
+            let mediumPriorityFiles: string[] = [];
+            let lowPriorityFiles: string[] = [];
+            let veryLowPriorityFiles: string[] = [];
+            let normalizedFileName = ts.normalizePath(fileName);
+            let project = this.projectService.getProjectForFile(normalizedFileName);
+            for (let fileNameInProject of fileNamesInProject) {
+                if (this.getCanonicalFileName(fileNameInProject) == this.getCanonicalFileName(fileName))
+                    highPriorityFiles.push(fileNameInProject);
+                else {
+                    let info = this.projectService.getScriptInfo(fileNameInProject);
+                    if (!info.isOpen) {
+                        if (fileNameInProject.indexOf(".d.ts") > 0)
+                            veryLowPriorityFiles.push(fileNameInProject);
+                        else
+                            lowPriorityFiles.push(fileNameInProject);
+                    }
+                    else
+                        mediumPriorityFiles.push(fileNameInProject);
+                }
+            }
+
+            fileNamesInProject = highPriorityFiles.concat(mediumPriorityFiles).concat(lowPriorityFiles).concat(veryLowPriorityFiles);
+
+            if (fileNamesInProject.length > 0) {
+                let checkList = fileNamesInProject.map<PendingErrorCheck>((fileName: string) => {
+                    let normalizedFileName = ts.normalizePath(fileName);
+                    return { fileName: normalizedFileName, project };
+                });
+                // Project level error analysis runs on background files too, therefore
+                // doesn't require the file to be opened
+                this.updateErrorCheck(checkList, this.changeSeq, (n) => n == this.changeSeq, delay, 200, /*requireOpen*/ false);
+            }
+        }
+
+        getCanonicalFileName(fileName: string) {
+            let name = this.host.useCaseSensitiveFileNames ? fileName : fileName.toLowerCase();
+            return ts.normalizePath(name);
+        }
+
+        exit() {
         }
 
         private handlers : Map<(request: protocol.Request) => {response?: any, responseRequired?: boolean}> = {
@@ -931,6 +978,10 @@ namespace ts.server {
                 var geterrArgs = <protocol.GeterrRequestArgs>request.arguments;
                 return {response: this.getDiagnostics(geterrArgs.delay, geterrArgs.files), responseRequired: false};
             },
+            [CommandNames.GeterrForProject]: (request: protocol.Request) => {
+                let { file, delay } = <protocol.GeterrForProjectRequestArgs>request.arguments;
+                return {response: this.getDiagnosticsForProject(delay, file), responseRequired: false};
+            },
             [CommandNames.Change]: (request: protocol.Request) => {
                 var changeArgs = <protocol.ChangeRequestArgs>request.arguments;
                 this.change(changeArgs.line, changeArgs.offset, changeArgs.endLine, changeArgs.endOffset,