diff --git a/plugins/org.eclipse.xtext.ide/.classpath b/plugins/org.eclipse.xtext.ide/.classpath
index 5b8856395..428337e56 100644
--- a/plugins/org.eclipse.xtext.ide/.classpath
+++ b/plugins/org.eclipse.xtext.ide/.classpath
@@ -1,8 +1,8 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <classpath>
+	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.8"/>
 	<classpathentry kind="con" path="org.eclipse.pde.core.requiredPlugins"/>
 	<classpathentry kind="src" path="src"/>
 	<classpathentry kind="src" path="xtend-gen"/>
-	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.8"/>
 	<classpathentry kind="output" path="bin"/>
 </classpath>
diff --git a/plugins/org.eclipse.xtext.ide/META-INF/MANIFEST.MF b/plugins/org.eclipse.xtext.ide/META-INF/MANIFEST.MF
index 291f1ad88..21f074642 100644
--- a/plugins/org.eclipse.xtext.ide/META-INF/MANIFEST.MF
+++ b/plugins/org.eclipse.xtext.ide/META-INF/MANIFEST.MF
@@ -10,7 +10,8 @@ Bundle-Vendor: %providerName
 Require-Bundle: org.eclipse.xtext;visibility:=reexport,
  org.eclipse.xtend.lib,
  org.eclipse.core.runtime;bundle-version="3.6.0",
- io.typefox.lsapi;bundle-version="0.1.0";resolution:=optional
+ io.typefox.lsapi;resolution:=optional,
+ io.typefox.lsapi.services
 Import-Package: org.apache.log4j;version="1.2.15"
 Export-Package: org.eclipse.xtext.ide;x-friends:="org.eclipse.xtend.ide",
  org.eclipse.xtext.ide.editor.bracketmatching;x-friends:="org.eclipse.xtend.ide.common,org.eclipse.xtend.ide",
diff --git a/plugins/org.eclipse.xtext.ide/src/org/eclipse/xtext/ide/server/LanguageServerImpl.xtend b/plugins/org.eclipse.xtext.ide/src/org/eclipse/xtext/ide/server/LanguageServerImpl.xtend
index 2b9e21595..7f532f2f4 100644
--- a/plugins/org.eclipse.xtext.ide/src/org/eclipse/xtext/ide/server/LanguageServerImpl.xtend
+++ b/plugins/org.eclipse.xtext.ide/src/org/eclipse/xtext/ide/server/LanguageServerImpl.xtend
@@ -14,6 +14,8 @@ import io.typefox.lsapi.CodeLens
 import io.typefox.lsapi.CodeLensParams
 import io.typefox.lsapi.CompletionItem
 import io.typefox.lsapi.CompletionItemImpl
+import io.typefox.lsapi.CompletionList
+import io.typefox.lsapi.CompletionListImpl
 import io.typefox.lsapi.CompletionOptionsImpl
 import io.typefox.lsapi.Diagnostic
 import io.typefox.lsapi.DiagnosticImpl
@@ -31,10 +33,8 @@ import io.typefox.lsapi.FileEvent
 import io.typefox.lsapi.InitializeParams
 import io.typefox.lsapi.InitializeResult
 import io.typefox.lsapi.InitializeResultImpl
-import io.typefox.lsapi.LanguageServer
 import io.typefox.lsapi.Location
 import io.typefox.lsapi.MessageParams
-import io.typefox.lsapi.NotificationCallback
 import io.typefox.lsapi.PublishDiagnosticsParams
 import io.typefox.lsapi.PublishDiagnosticsParamsImpl
 import io.typefox.lsapi.RangeImpl
@@ -45,11 +45,14 @@ import io.typefox.lsapi.ServerCapabilitiesImpl
 import io.typefox.lsapi.ShowMessageRequestParams
 import io.typefox.lsapi.SymbolInformation
 import io.typefox.lsapi.TextDocumentPositionParams
-import io.typefox.lsapi.TextDocumentService
-import io.typefox.lsapi.WindowService
-import io.typefox.lsapi.WorkspaceService
 import io.typefox.lsapi.WorkspaceSymbolParams
+import io.typefox.lsapi.services.LanguageServer
+import io.typefox.lsapi.services.TextDocumentService
+import io.typefox.lsapi.services.WindowService
+import io.typefox.lsapi.services.WorkspaceService
 import java.util.List
+import java.util.concurrent.CompletableFuture
+import java.util.function.Consumer
 import org.eclipse.emf.common.util.URI
 import org.eclipse.xtend.lib.annotations.Accessors
 import org.eclipse.xtext.ide.editor.contentassist.ContentAssistEntry
@@ -78,7 +81,7 @@ import static io.typefox.lsapi.util.LsapiFactories.*
 	@Inject extension UriExtensions
 	@Inject extension IResourceServiceProvider.Registry languagesRegistry
 
-	override InitializeResult initialize(InitializeParams params) {
+	override CompletableFuture<InitializeResult> initialize(InitializeParams params) {
 		if (params.rootPath === null) {
 			throw new IllegalArgumentException("Bad initialization request. rootPath must not be null.")
 		}
@@ -103,7 +106,7 @@ import static io.typefox.lsapi.util.LsapiFactories.*
 			workspaceManager.initialize(rootURI, [this.publishDiagnostics($0, $1)], cancelIndicator)
 		], CancellableIndicator.NullImpl)
 
-		return result
+		return CompletableFuture.completedFuture(result)
 	}
 
 	override exit() {
@@ -112,28 +115,28 @@ import static io.typefox.lsapi.util.LsapiFactories.*
 	override void shutdown() {
 	}
 
-	override getTextDocumentService() {
-		this
+	override TextDocumentService getTextDocumentService() {
+		return this
 	}
 
-	override getWorkspaceService() {
-		this
+	override WorkspaceService getWorkspaceService() {
+		return this
 	}
 
-	override getWindowService() {
-		this
+	override WindowService getWindowService() {
+		return this
 	}
 
 	// notification callbacks
-	override onShowMessage(NotificationCallback<MessageParams> callback) {
+	override onShowMessage(Consumer<MessageParams> callback) {
 		// TODO: auto-generated method stub
 	}
 
-	override onShowMessageRequest(NotificationCallback<ShowMessageRequestParams> callback) {
+	override onShowMessageRequest(Consumer<ShowMessageRequestParams> callback) {
 		// TODO: auto-generated method stub
 	}
 
-	override onLogMessage(NotificationCallback<MessageParams> callback) {
+	override onLogMessage(Consumer<MessageParams> callback) {
 		// TODO: auto-generated method stub
 	}
 
@@ -182,11 +185,11 @@ import static io.typefox.lsapi.util.LsapiFactories.*
 
 	// end file/content change events
 	// validation stuff
-	private List<NotificationCallback<PublishDiagnosticsParams>> diagnosticListeners = newArrayList()
+	private List<Consumer<PublishDiagnosticsParams>> diagnosticListeners = newArrayList()
     
     WorkspaceResourceAccess resourceAccess
 
-	override onPublishDiagnostics(NotificationCallback<PublishDiagnosticsParams> callback) {
+	override onPublishDiagnostics(Consumer<PublishDiagnosticsParams> callback) {
 		diagnosticListeners.add(callback)
 	}
 
@@ -196,7 +199,7 @@ import static io.typefox.lsapi.util.LsapiFactories.*
 			it.diagnostics = issues.map[toDiagnostic].toList
 		]
 		for (diagnosticsCallback : diagnosticListeners) {
-			diagnosticsCallback.call(diagnostics)
+			diagnosticsCallback.accept(diagnostics)
 		}
 	}
 
@@ -219,23 +222,25 @@ import static io.typefox.lsapi.util.LsapiFactories.*
 
 	// end validation stuff
 	// completion stuff
-	override completion(TextDocumentPositionParams params) {
+	override CompletableFuture<CompletionList> completion(TextDocumentPositionParams params) {
 		return requestManager.runRead[ cancelIndicator |
 			val uri = params.textDocument.uri.toUri
 			val resourceServiceProvider = uri.resourceServiceProvider
 			val contentAssistService = resourceServiceProvider?.get(ContentAssistService)
+			val result = new CompletionListImpl
 			if (contentAssistService === null)
-				return emptyList
+				return result
 	
 			val entries = workspaceManager.doRead(uri) [ document, resource |
 				val offset = document.getOffSet(params.position)
 				return contentAssistService.createProposals(document.contents, offset, resource, cancelIndicator)
 			]
-			return entries.map[toCompletionItem].toList
-		].get
+			result.items = entries.map[toCompletionItem].toList 
+			return result
+		]
 	}
 
-	protected def CompletionItem toCompletionItem(ContentAssistEntry entry) {
+	protected def CompletionItemImpl toCompletionItem(ContentAssistEntry entry) {
 		val completionItem = new CompletionItemImpl
 		completionItem.label = entry.label ?: entry.proposal
 		completionItem.detail = entry.description
@@ -258,7 +263,7 @@ import static io.typefox.lsapi.util.LsapiFactories.*
 				return documentSymbolService.getDefinitions(resource, offset, resourceAccess, cancelIndicator)
 			]
 			return definitions
-		].get
+		]
 	}
 
 	override references(ReferenceParams params) {
@@ -282,7 +287,7 @@ import static io.typefox.lsapi.util.LsapiFactories.*
 				val result = definitions + references
 				return result.toList
 			]
-		].get
+		]
 	}
 
 	override documentSymbol(DocumentSymbolParams params) {
@@ -296,7 +301,7 @@ import static io.typefox.lsapi.util.LsapiFactories.*
 			return workspaceManager.doRead(uri) [ document, resource |
 				return documentSymbolService.getSymbols(resource, cancelIndicator)
 			]
-		].get
+		]
 	}
 
 	// end symbols
@@ -309,7 +314,7 @@ import static io.typefox.lsapi.util.LsapiFactories.*
 	}
 
 	override resolveCompletionItem(CompletionItem unresolved) {
-		return unresolved
+		return CompletableFuture.completedFuture(unresolved)
 	}
 
 	override hover(TextDocumentPositionParams position) {
@@ -333,7 +338,7 @@ import static io.typefox.lsapi.util.LsapiFactories.*
 	}
 
 	override resolveCodeLens(CodeLens unresolved) {
-		return unresolved
+		return CompletableFuture.completedFuture(unresolved)
 	}
 
 	override formatting(DocumentFormattingParams params) {
diff --git a/plugins/org.eclipse.xtext.ide/src/org/eclipse/xtext/ide/server/ServerLauncher.xtend b/plugins/org.eclipse.xtext.ide/src/org/eclipse/xtext/ide/server/ServerLauncher.xtend
index 11a96dfae..794d9423a 100644
--- a/plugins/org.eclipse.xtext.ide/src/org/eclipse/xtext/ide/server/ServerLauncher.xtend
+++ b/plugins/org.eclipse.xtext.ide/src/org/eclipse/xtext/ide/server/ServerLauncher.xtend
@@ -10,13 +10,13 @@ package org.eclipse.xtext.ide.server
 import com.google.inject.Guice
 import com.google.inject.Inject
 import io.typefox.lsapi.NotificationMessage
-import io.typefox.lsapi.json.LanguageServerToJsonAdapter
-import io.typefox.lsapi.json.MessageMethods
+import io.typefox.lsapi.services.json.LanguageServerToJsonAdapter
+import io.typefox.lsapi.services.json.MessageMethods
 import java.io.ByteArrayInputStream
+import java.io.ByteArrayOutputStream
 import java.io.FileOutputStream
 import java.io.PrintStream
 import java.util.concurrent.atomic.AtomicBoolean
-import java.io.ByteArrayOutputStream
 
 /**
  * @author Sven Efftinge - Initial contribution and API
diff --git a/plugins/org.eclipse.xtext.ide/src/org/eclipse/xtext/ide/server/ServerModule.xtend b/plugins/org.eclipse.xtext.ide/src/org/eclipse/xtext/ide/server/ServerModule.xtend
index 16cd3d8aa..f46405cd2 100644
--- a/plugins/org.eclipse.xtext.ide/src/org/eclipse/xtext/ide/server/ServerModule.xtend
+++ b/plugins/org.eclipse.xtext.ide/src/org/eclipse/xtext/ide/server/ServerModule.xtend
@@ -9,7 +9,7 @@ package org.eclipse.xtext.ide.server
 
 import com.google.inject.AbstractModule
 import com.google.inject.name.Names
-import io.typefox.lsapi.LanguageServer
+import io.typefox.lsapi.services.LanguageServer
 import java.util.concurrent.ExecutorService
 import java.util.concurrent.Executors
 import org.eclipse.xtext.ide.server.concurrent.RequestManager
diff --git a/tests/org.eclipse.xtext.ide.tests/META-INF/MANIFEST.MF b/tests/org.eclipse.xtext.ide.tests/META-INF/MANIFEST.MF
index 730e11585..c59810306 100644
--- a/tests/org.eclipse.xtext.ide.tests/META-INF/MANIFEST.MF
+++ b/tests/org.eclipse.xtext.ide.tests/META-INF/MANIFEST.MF
@@ -12,5 +12,6 @@ Require-Bundle: org.eclipse.xtext;visibility:=reexport,
  org.eclipse.core.runtime;bundle-version="3.6.0",
  org.eclipse.xtext.ide,
  org.junit;bundle-version="4.11.0",
- io.typefox.lsapi;bundle-version="0.1.0"
+ io.typefox.lsapi,
+ io.typefox.lsapi.services
 Import-Package: org.apache.log4j;version="1.2.15"
diff --git a/tests/org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/AbstractLanguageServerTest.xtend b/tests/org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/AbstractLanguageServerTest.xtend
index 4e6dc2ff6..270fcfded 100644
--- a/tests/org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/AbstractLanguageServerTest.xtend
+++ b/tests/org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/AbstractLanguageServerTest.xtend
@@ -15,7 +15,6 @@ import io.typefox.lsapi.DidOpenTextDocumentParamsImpl
 import io.typefox.lsapi.InitializeParamsImpl
 import io.typefox.lsapi.InitializeResult
 import io.typefox.lsapi.Location
-import io.typefox.lsapi.NotificationCallback
 import io.typefox.lsapi.Position
 import io.typefox.lsapi.PublishDiagnosticsParams
 import io.typefox.lsapi.Range
@@ -29,6 +28,7 @@ import java.nio.file.Path
 import java.nio.file.Paths
 import java.util.List
 import java.util.Map
+import java.util.concurrent.CompletableFuture
 import org.eclipse.xtext.ide.server.LanguageServerImpl
 import org.eclipse.xtext.ide.server.ServerModule
 import org.eclipse.xtext.ide.server.UriExtensions
@@ -39,12 +39,12 @@ import org.eclipse.xtext.util.Modules2
 import org.junit.Before
 
 import static io.typefox.lsapi.util.LsapiFactories.*
-import java.util.concurrent.CompletableFuture
+import java.util.function.Consumer
 
 /**
  * @author Sven Efftinge - Initial contribution and API
  */
-class AbstractLanguageServerTest implements NotificationCallback<PublishDiagnosticsParams> {
+class AbstractLanguageServerTest implements Consumer<PublishDiagnosticsParams> {
 
 	@Before
 	def void setup() {
@@ -70,7 +70,7 @@ class AbstractLanguageServerTest implements NotificationCallback<PublishDiagnost
 		val injector = Guice.createInjector(module)
 		injector.injectMembers(this)
 		// register notification callbacks
-		languageServer.getTextDocumentService.onPublishDiagnostics(this)
+		languageServer.getTextDocumentService().onPublishDiagnostics(this)
 
 		// create workingdir
 		root = new File("./test-data/test-project")
@@ -103,7 +103,7 @@ class AbstractLanguageServerTest implements NotificationCallback<PublishDiagnost
 		val params = new InitializeParamsImpl
 		params.rootPath = rootPath.toString
 		initializer?.apply(params)
-		return languageServer.initialize(params)
+		return languageServer.initialize(params).get
 	}
 
 	protected def void open(String fileUri, String model) {
@@ -128,7 +128,7 @@ class AbstractLanguageServerTest implements NotificationCallback<PublishDiagnost
 		return file.toURI.normalize.toPath
 	}
 
-	override call(PublishDiagnosticsParams t) {
+	override accept(PublishDiagnosticsParams t) {
 		diagnostics.put(t.uri, t.diagnostics)
 	}
 
diff --git a/tests/org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/CompletionTest.xtend b/tests/org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/CompletionTest.xtend
index f2b109264..09a6d4e59 100644
--- a/tests/org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/CompletionTest.xtend
+++ b/tests/org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/CompletionTest.xtend
@@ -69,7 +69,7 @@ class CompletionTest extends AbstractLanguageServerTest {
 
 		val completionItems = languageServer.completion(newPosition(fileUri, line, column))
 
-		val actualCompletionItems = completionItems.toExpectation
+		val actualCompletionItems = completionItems.get.items.toExpectation
 		assertEquals(expectedCompletionItems, actualCompletionItems)
 	}
 
diff --git a/tests/org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/DefinitionTest.xtend b/tests/org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/DefinitionTest.xtend
index a8aa3a29d..385663605 100644
--- a/tests/org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/DefinitionTest.xtend
+++ b/tests/org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/DefinitionTest.xtend
@@ -44,7 +44,7 @@ class DefinitionTest extends AbstractLanguageServerTest {
 		open(fileUri, model)
 
 		val definitions = languageServer.definition(newPosition(fileUri, line, column))
-		val actualDefinitions = definitions.toExpectation
+		val actualDefinitions = definitions.get.toExpectation
 		assertEquals(expectedDefinitions, actualDefinitions)
 	}
 
diff --git a/tests/org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/DocumentSymbolTest.xtend b/tests/org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/DocumentSymbolTest.xtend
index c92bfe756..8348734bc 100644
--- a/tests/org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/DocumentSymbolTest.xtend
+++ b/tests/org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/DocumentSymbolTest.xtend
@@ -69,7 +69,7 @@ class DocumentSymbolTest extends AbstractLanguageServerTest {
 		val symbols = languageServer.documentSymbol(new DocumentSymbolParamsImpl => [
 			textDocument = fileUri.newIdentifier
 		])
-		val String actualSymbols = symbols.toExpectation
+		val String actualSymbols = symbols.get.toExpectation
 		assertEquals(expectedSymbols, actualSymbols)
 	}
 
diff --git a/tests/org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/ReferenceTest.xtend b/tests/org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/ReferenceTest.xtend
index 872198397..ca6099af2 100644
--- a/tests/org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/ReferenceTest.xtend
+++ b/tests/org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/ReferenceTest.xtend
@@ -71,7 +71,7 @@ class ReferenceTest extends AbstractLanguageServerTest {
 			position = newPosition(line, column)
 			context = referenceContext
 		])
-		val actualDefinitions = definitions.toExpectation
+		val actualDefinitions = definitions.get.toExpectation
 		assertEquals(expectedReferences, actualDefinitions)
 	}
 
diff --git a/tests/org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/ServerLauncherTest.xtend b/tests/org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/ServerLauncherTest.xtend
index 3db82c6cb..3ec89a492 100644
--- a/tests/org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/ServerLauncherTest.xtend
+++ b/tests/org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/ServerLauncherTest.xtend
@@ -8,7 +8,7 @@
 package org.eclipse.xtext.ide.tests.server
 
 import io.typefox.lsapi.InitializeParamsImpl
-import io.typefox.lsapi.json.JsonBasedLanguageServer
+import io.typefox.lsapi.services.json.JsonBasedLanguageServer
 import java.lang.ProcessBuilder.Redirect
 import org.eclipse.xtext.ide.server.ServerLauncher
 import org.junit.After