diff --git a/build.gradle b/build.gradle
index 065224a6..e9a3cae2 100644
--- a/build.gradle
+++ b/build.gradle
@@ -28,7 +28,7 @@ subprojects {
     ext {
         otelVersion = '1.30.1'
         otelVersionAlpha = "${otelVersion}-alpha"
-        javaSDKVersion = '1.25.0'
+        javaSDKVersion = '1.26.0'
         camelVersion = '3.22.1'
         jarVersion = '1.0.0'
     }
diff --git a/core/build.gradle b/core/build.gradle
index c73ce227..b4653f82 100644
--- a/core/build.gradle
+++ b/core/build.gradle
@@ -28,6 +28,7 @@ dependencies {
     implementation group: 'io.cloudevents', name: 'cloudevents-api', version: '4.0.1'
     implementation group: 'io.cloudevents', name: 'cloudevents-json-jackson', version: '3.0.0'
     implementation group: 'net.thisptr', name: 'jackson-jq', version: '1.0.0-preview.20240207'
+    implementation group: 'commons-cli', name: 'commons-cli', version: '1.9.0'
 
     // we don't update it to 2.1.0 because 2.1.0 requires Java 11
     implementation 'com.codingrodent:jackson-json-crypto:1.1.0'
diff --git a/core/src/main/java/io/temporal/samples/nexus/README.MD b/core/src/main/java/io/temporal/samples/nexus/README.MD
new file mode 100644
index 00000000..2483a8b3
--- /dev/null
+++ b/core/src/main/java/io/temporal/samples/nexus/README.MD
@@ -0,0 +1,103 @@
+# Nexus
+
+Temporal Nexus is a new feature of the Temporal platform designed to connect durable executions across team, namespace,
+region, and cloud boundaries. It promotes a more modular architecture for sharing a subset of your team’s capabilities
+via well-defined service API contracts for other teams to use, that abstract underlying Temporal primitives, like
+Workflows, or execute arbitrary code.
+
+Learn more at [temporal.io/nexus](https://temporal.io/nexus).
+
+This sample shows how to use Temporal for authoring a Nexus service and call it from a workflow.
+
+### Sample directory structure
+
+- [service](./service) - shared service definition
+- [caller](./caller) - caller workflows, worker, and starter
+- [handler](./handler) - handler workflow, operations, and worker
+- [options](./options) - command line argument parsing utility
+
+## Getting started locally
+
+### Get `temporal` CLI to enable local development
+
+1. Follow the instructions on the [docs
+   site](https://learn.temporal.io/getting_started/go/dev_environment/#set-up-a-local-temporal-service-for-development-with-temporal-cli)
+   to install Temporal CLI.
+
+> NOTE: Required version is at least v1.1.0.
+
+### Spin up environment
+
+#### Start temporal server
+
+> HTTP port is required for Nexus communications
+
+```
+temporal server start-dev --http-port 7243 --dynamic-config-value system.enableNexus=true
+```
+
+### Initialize environment
+
+In a separate terminal window
+
+#### Create caller and target namespaces
+
+```
+temporal operator namespace create --namespace my-target-namespace
+temporal operator namespace create --namespace my-caller-namespace
+```
+
+#### Create Nexus endpoint
+
+```
+temporal operator nexus endpoint create \
+  --name my-nexus-endpoint-name \
+  --target-namespace my-target-namespace \
+  --target-task-queue my-handler-task-queue \
+  --description-file ./service/description.md
+```
+
+## Getting started with a self-hosted service or Temporal Cloud
+
+Nexus is currently available as
+[Public Preview](https://docs.temporal.io/evaluate/development-production-features/release-stages).
+
+Self hosted users can [try Nexus
+out](https://github.com/temporalio/temporal/blob/main/docs/architecture/nexus.md#trying-nexus-out) in single cluster
+deployments with server version 1.25.0.
+
+### Make Nexus calls across namespace boundaries
+
+> Instructions apply for local development, for Temporal Cloud or a self-hosted setups, supply the relevant [CLI
+> flags](./options/ClientOptions.java) to properly set up the connection.
+
+In separate terminal windows:
+
+### Nexus handler worker
+
+```
+./gradlew -q execute -PmainClass=io.temporal.samples.nexus.handler.HandlerWorker \
+    --args="-target-host localhost:7233 -namespace my-target-namespace"
+```
+
+### Nexus caller worker
+
+```
+./gradlew -q execute -PmainClass=io.temporal.samples.nexus.caller.CallerWorker \
+    --args="-target-host localhost:7233 -namespace my-caller-namespace"
+```
+
+### Start caller workflow
+
+```
+./gradlew -q execute -PmainClass=io.temporal.samples.nexus.caller.CallerStarter \
+    --args="-target-host localhost:7233 -namespace my-caller-namespace"
+```
+
+### Output
+
+which should result in:
+```
+[main] INFO  i.t.s.nexus.caller.CallerStarter - Workflow result: Nexus Echo 👋 
+[main] INFO  i.t.s.nexus.caller.CallerStarter - Workflow result: ¡Hola! Nexus 👋  
+```
diff --git a/core/src/main/java/io/temporal/samples/nexus/caller/CallerStarter.java b/core/src/main/java/io/temporal/samples/nexus/caller/CallerStarter.java
new file mode 100644
index 00000000..23dd0f5e
--- /dev/null
+++ b/core/src/main/java/io/temporal/samples/nexus/caller/CallerStarter.java
@@ -0,0 +1,53 @@
+/*
+ *  Copyright (c) 2020 Temporal Technologies, Inc. All Rights Reserved
+ *
+ *  Copyright 2012-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ *  Modifications copyright (C) 2017 Uber Technologies, Inc.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"). You may not
+ *  use this file except in compliance with the License. A copy of the License is
+ *  located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ *  or in the "license" file accompanying this file. This file is distributed on
+ *  an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ *  express or implied. See the License for the specific language governing
+ *  permissions and limitations under the License.
+ */
+
+package io.temporal.samples.nexus.caller;
+
+import io.temporal.client.WorkflowClient;
+import io.temporal.client.WorkflowOptions;
+import io.temporal.client.WorkflowStub;
+import io.temporal.samples.nexus.options.ClientOptions;
+import io.temporal.samples.nexus.service.NexusService;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class CallerStarter {
+  private static final Logger logger = LoggerFactory.getLogger(CallerStarter.class);
+
+  public static void main(String[] args) {
+    WorkflowClient client = ClientOptions.getWorkflowClient(args);
+
+    WorkflowOptions workflowOptions =
+        WorkflowOptions.newBuilder().setTaskQueue(CallerWorker.DEFAULT_TASK_QUEUE_NAME).build();
+    EchoCallerWorkflow echoWorkflow =
+        client.newWorkflowStub(EchoCallerWorkflow.class, workflowOptions);
+    logger.info("Workflow result: {}", echoWorkflow.echo("Nexus Echo 👋"));
+    logger.info(
+        "Started workflow workflowId: {} runId: {}",
+        WorkflowStub.fromTyped(echoWorkflow).getExecution().getWorkflowId(),
+        WorkflowStub.fromTyped(echoWorkflow).getExecution().getRunId());
+    HelloCallerWorkflow helloWorkflow =
+        client.newWorkflowStub(HelloCallerWorkflow.class, workflowOptions);
+    logger.info("Workflow result: {}", helloWorkflow.hello("Nexus", NexusService.Language.ES));
+    logger.info(
+        "Started workflow workflowId: {} runId: {}",
+        WorkflowStub.fromTyped(helloWorkflow).getExecution().getWorkflowId(),
+        WorkflowStub.fromTyped(helloWorkflow).getExecution().getRunId());
+  }
+}
diff --git a/core/src/main/java/io/temporal/samples/nexus/caller/CallerWorker.java b/core/src/main/java/io/temporal/samples/nexus/caller/CallerWorker.java
new file mode 100644
index 00000000..e7be0ae4
--- /dev/null
+++ b/core/src/main/java/io/temporal/samples/nexus/caller/CallerWorker.java
@@ -0,0 +1,51 @@
+/*
+ *  Copyright (c) 2020 Temporal Technologies, Inc. All Rights Reserved
+ *
+ *  Copyright 2012-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ *  Modifications copyright (C) 2017 Uber Technologies, Inc.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"). You may not
+ *  use this file except in compliance with the License. A copy of the License is
+ *  located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ *  or in the "license" file accompanying this file. This file is distributed on
+ *  an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ *  express or implied. See the License for the specific language governing
+ *  permissions and limitations under the License.
+ */
+
+package io.temporal.samples.nexus.caller;
+
+import io.temporal.client.WorkflowClient;
+import io.temporal.samples.nexus.options.ClientOptions;
+import io.temporal.worker.Worker;
+import io.temporal.worker.WorkerFactory;
+import io.temporal.worker.WorkflowImplementationOptions;
+import io.temporal.workflow.NexusServiceOptions;
+import java.util.Collections;
+
+public class CallerWorker {
+  public static final String DEFAULT_TASK_QUEUE_NAME = "my-caller-workflow-task-queue";
+
+  public static void main(String[] args) {
+    WorkflowClient client = ClientOptions.getWorkflowClient(args);
+
+    WorkerFactory factory = WorkerFactory.newInstance(client);
+
+    Worker worker = factory.newWorker(DEFAULT_TASK_QUEUE_NAME);
+    worker.registerWorkflowImplementationTypes(
+        WorkflowImplementationOptions.newBuilder()
+            .setNexusServiceOptions(
+                Collections.singletonMap(
+                    "NexusService",
+                    NexusServiceOptions.newBuilder().setEndpoint("my-nexus-endpoint-name").build()))
+            .build(),
+        EchoCallerWorkflowImpl.class,
+        HelloCallerWorkflowImpl.class);
+
+    factory.start();
+  }
+}
diff --git a/core/src/main/java/io/temporal/samples/nexus/caller/EchoCallerWorkflow.java b/core/src/main/java/io/temporal/samples/nexus/caller/EchoCallerWorkflow.java
new file mode 100644
index 00000000..5f830855
--- /dev/null
+++ b/core/src/main/java/io/temporal/samples/nexus/caller/EchoCallerWorkflow.java
@@ -0,0 +1,29 @@
+/*
+ *  Copyright (c) 2020 Temporal Technologies, Inc. All Rights Reserved
+ *
+ *  Copyright 2012-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ *  Modifications copyright (C) 2017 Uber Technologies, Inc.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"). You may not
+ *  use this file except in compliance with the License. A copy of the License is
+ *  located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ *  or in the "license" file accompanying this file. This file is distributed on
+ *  an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ *  express or implied. See the License for the specific language governing
+ *  permissions and limitations under the License.
+ */
+
+package io.temporal.samples.nexus.caller;
+
+import io.temporal.workflow.WorkflowInterface;
+import io.temporal.workflow.WorkflowMethod;
+
+@WorkflowInterface
+public interface EchoCallerWorkflow {
+  @WorkflowMethod
+  String echo(String message);
+}
diff --git a/core/src/main/java/io/temporal/samples/nexus/caller/EchoCallerWorkflowImpl.java b/core/src/main/java/io/temporal/samples/nexus/caller/EchoCallerWorkflowImpl.java
new file mode 100644
index 00000000..7c5d5f78
--- /dev/null
+++ b/core/src/main/java/io/temporal/samples/nexus/caller/EchoCallerWorkflowImpl.java
@@ -0,0 +1,43 @@
+/*
+ *  Copyright (c) 2020 Temporal Technologies, Inc. All Rights Reserved
+ *
+ *  Copyright 2012-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ *  Modifications copyright (C) 2017 Uber Technologies, Inc.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"). You may not
+ *  use this file except in compliance with the License. A copy of the License is
+ *  located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ *  or in the "license" file accompanying this file. This file is distributed on
+ *  an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ *  express or implied. See the License for the specific language governing
+ *  permissions and limitations under the License.
+ */
+
+package io.temporal.samples.nexus.caller;
+
+import io.temporal.samples.nexus.service.NexusService;
+import io.temporal.workflow.NexusOperationOptions;
+import io.temporal.workflow.NexusServiceOptions;
+import io.temporal.workflow.Workflow;
+import java.time.Duration;
+
+public class EchoCallerWorkflowImpl implements EchoCallerWorkflow {
+  NexusService nexusService =
+      Workflow.newNexusServiceStub(
+          NexusService.class,
+          NexusServiceOptions.newBuilder()
+              .setOperationOptions(
+                  NexusOperationOptions.newBuilder()
+                      .setScheduleToCloseTimeout(Duration.ofSeconds(10))
+                      .build())
+              .build());
+
+  @Override
+  public String echo(String message) {
+    return nexusService.echo(new NexusService.EchoInput(message)).getMessage();
+  }
+}
diff --git a/core/src/main/java/io/temporal/samples/nexus/caller/HelloCallerWorkflow.java b/core/src/main/java/io/temporal/samples/nexus/caller/HelloCallerWorkflow.java
new file mode 100644
index 00000000..6e943c17
--- /dev/null
+++ b/core/src/main/java/io/temporal/samples/nexus/caller/HelloCallerWorkflow.java
@@ -0,0 +1,30 @@
+/*
+ *  Copyright (c) 2020 Temporal Technologies, Inc. All Rights Reserved
+ *
+ *  Copyright 2012-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ *  Modifications copyright (C) 2017 Uber Technologies, Inc.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"). You may not
+ *  use this file except in compliance with the License. A copy of the License is
+ *  located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ *  or in the "license" file accompanying this file. This file is distributed on
+ *  an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ *  express or implied. See the License for the specific language governing
+ *  permissions and limitations under the License.
+ */
+
+package io.temporal.samples.nexus.caller;
+
+import io.temporal.samples.nexus.service.NexusService;
+import io.temporal.workflow.WorkflowInterface;
+import io.temporal.workflow.WorkflowMethod;
+
+@WorkflowInterface
+public interface HelloCallerWorkflow {
+  @WorkflowMethod
+  String hello(String message, NexusService.Language language);
+}
diff --git a/core/src/main/java/io/temporal/samples/nexus/caller/HelloCallerWorkflowImpl.java b/core/src/main/java/io/temporal/samples/nexus/caller/HelloCallerWorkflowImpl.java
new file mode 100644
index 00000000..dcc8d1a0
--- /dev/null
+++ b/core/src/main/java/io/temporal/samples/nexus/caller/HelloCallerWorkflowImpl.java
@@ -0,0 +1,50 @@
+/*
+ *  Copyright (c) 2020 Temporal Technologies, Inc. All Rights Reserved
+ *
+ *  Copyright 2012-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ *  Modifications copyright (C) 2017 Uber Technologies, Inc.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"). You may not
+ *  use this file except in compliance with the License. A copy of the License is
+ *  located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ *  or in the "license" file accompanying this file. This file is distributed on
+ *  an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ *  express or implied. See the License for the specific language governing
+ *  permissions and limitations under the License.
+ */
+
+package io.temporal.samples.nexus.caller;
+
+import io.temporal.samples.nexus.service.NexusService;
+import io.temporal.workflow.NexusOperationHandle;
+import io.temporal.workflow.NexusOperationOptions;
+import io.temporal.workflow.NexusServiceOptions;
+import io.temporal.workflow.Workflow;
+import java.time.Duration;
+
+public class HelloCallerWorkflowImpl implements HelloCallerWorkflow {
+  NexusService nexusService =
+      Workflow.newNexusServiceStub(
+          NexusService.class,
+          NexusServiceOptions.newBuilder()
+              .setOperationOptions(
+                  NexusOperationOptions.newBuilder()
+                      .setScheduleToCloseTimeout(Duration.ofSeconds(10))
+                      .build())
+              .build());
+
+  @Override
+  public String hello(String message, NexusService.Language language) {
+    NexusOperationHandle<NexusService.HelloOutput> handle =
+        Workflow.startNexusOperation(
+            nexusService::hello, new NexusService.HelloInput(message, language));
+    // Optionally wait for the operation to be started. NexusOperationExecution will contain the
+    // operation ID in case this operation is asynchronous.
+    handle.getExecution().get();
+    return handle.getResult().get().getMessage();
+  }
+}
diff --git a/core/src/main/java/io/temporal/samples/nexus/handler/HandlerWorker.java b/core/src/main/java/io/temporal/samples/nexus/handler/HandlerWorker.java
new file mode 100644
index 00000000..71a78f91
--- /dev/null
+++ b/core/src/main/java/io/temporal/samples/nexus/handler/HandlerWorker.java
@@ -0,0 +1,41 @@
+/*
+ *  Copyright (c) 2020 Temporal Technologies, Inc. All Rights Reserved
+ *
+ *  Copyright 2012-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ *  Modifications copyright (C) 2017 Uber Technologies, Inc.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"). You may not
+ *  use this file except in compliance with the License. A copy of the License is
+ *  located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ *  or in the "license" file accompanying this file. This file is distributed on
+ *  an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ *  express or implied. See the License for the specific language governing
+ *  permissions and limitations under the License.
+ */
+
+package io.temporal.samples.nexus.handler;
+
+import io.temporal.client.WorkflowClient;
+import io.temporal.samples.nexus.options.ClientOptions;
+import io.temporal.worker.Worker;
+import io.temporal.worker.WorkerFactory;
+
+public class HandlerWorker {
+  public static final String DEFAULT_TASK_QUEUE_NAME = "my-handler-task-queue";
+
+  public static void main(String[] args) {
+    WorkflowClient client = ClientOptions.getWorkflowClient(args);
+
+    WorkerFactory factory = WorkerFactory.newInstance(client);
+
+    Worker worker = factory.newWorker(DEFAULT_TASK_QUEUE_NAME);
+    worker.registerWorkflowImplementationTypes(HelloHandlerWorkflowImpl.class);
+    worker.registerNexusServiceImplementation(new NexusServiceImpl());
+
+    factory.start();
+  }
+}
diff --git a/core/src/main/java/io/temporal/samples/nexus/handler/HelloHandlerWorkflow.java b/core/src/main/java/io/temporal/samples/nexus/handler/HelloHandlerWorkflow.java
new file mode 100644
index 00000000..caa34d98
--- /dev/null
+++ b/core/src/main/java/io/temporal/samples/nexus/handler/HelloHandlerWorkflow.java
@@ -0,0 +1,30 @@
+/*
+ *  Copyright (c) 2020 Temporal Technologies, Inc. All Rights Reserved
+ *
+ *  Copyright 2012-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ *  Modifications copyright (C) 2017 Uber Technologies, Inc.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"). You may not
+ *  use this file except in compliance with the License. A copy of the License is
+ *  located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ *  or in the "license" file accompanying this file. This file is distributed on
+ *  an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ *  express or implied. See the License for the specific language governing
+ *  permissions and limitations under the License.
+ */
+
+package io.temporal.samples.nexus.handler;
+
+import io.temporal.samples.nexus.service.NexusService;
+import io.temporal.workflow.WorkflowInterface;
+import io.temporal.workflow.WorkflowMethod;
+
+@WorkflowInterface
+public interface HelloHandlerWorkflow {
+  @WorkflowMethod
+  NexusService.HelloOutput hello(NexusService.HelloInput input);
+}
diff --git a/core/src/main/java/io/temporal/samples/nexus/handler/HelloHandlerWorkflowImpl.java b/core/src/main/java/io/temporal/samples/nexus/handler/HelloHandlerWorkflowImpl.java
new file mode 100644
index 00000000..ea5203eb
--- /dev/null
+++ b/core/src/main/java/io/temporal/samples/nexus/handler/HelloHandlerWorkflowImpl.java
@@ -0,0 +1,43 @@
+/*
+ *  Copyright (c) 2020 Temporal Technologies, Inc. All Rights Reserved
+ *
+ *  Copyright 2012-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ *  Modifications copyright (C) 2017 Uber Technologies, Inc.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"). You may not
+ *  use this file except in compliance with the License. A copy of the License is
+ *  located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ *  or in the "license" file accompanying this file. This file is distributed on
+ *  an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ *  express or implied. See the License for the specific language governing
+ *  permissions and limitations under the License.
+ */
+
+package io.temporal.samples.nexus.handler;
+
+import io.temporal.failure.ApplicationFailure;
+import io.temporal.samples.nexus.service.NexusService;
+
+public class HelloHandlerWorkflowImpl implements HelloHandlerWorkflow {
+  @Override
+  public NexusService.HelloOutput hello(NexusService.HelloInput input) {
+    switch (input.getLanguage()) {
+      case EN:
+        return new NexusService.HelloOutput("Hello " + input.getName() + " 👋");
+      case FR:
+        return new NexusService.HelloOutput("Bonjour " + input.getName() + " 👋");
+      case DE:
+        return new NexusService.HelloOutput("Hallo " + input.getName() + " 👋");
+      case ES:
+        return new NexusService.HelloOutput("¡Hola! " + input.getName() + " 👋");
+      case TR:
+        return new NexusService.HelloOutput("Merhaba " + input.getName() + " 👋");
+    }
+    throw ApplicationFailure.newFailure(
+        "Unsupported language: " + input.getLanguage(), "UNSUPPORTED_LANGUAGE");
+  }
+}
diff --git a/core/src/main/java/io/temporal/samples/nexus/handler/NexusServiceImpl.java b/core/src/main/java/io/temporal/samples/nexus/handler/NexusServiceImpl.java
new file mode 100644
index 00000000..4d6cb3ca
--- /dev/null
+++ b/core/src/main/java/io/temporal/samples/nexus/handler/NexusServiceImpl.java
@@ -0,0 +1,65 @@
+/*
+ *  Copyright (c) 2020 Temporal Technologies, Inc. All Rights Reserved
+ *
+ *  Copyright 2012-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ *  Modifications copyright (C) 2017 Uber Technologies, Inc.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"). You may not
+ *  use this file except in compliance with the License. A copy of the License is
+ *  located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ *  or in the "license" file accompanying this file. This file is distributed on
+ *  an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ *  express or implied. See the License for the specific language governing
+ *  permissions and limitations under the License.
+ */
+
+package io.temporal.samples.nexus.handler;
+
+import io.nexusrpc.handler.OperationHandler;
+import io.nexusrpc.handler.OperationImpl;
+import io.nexusrpc.handler.ServiceImpl;
+import io.temporal.client.WorkflowOptions;
+import io.temporal.nexus.WorkflowClientOperationHandlers;
+import io.temporal.samples.nexus.service.NexusService;
+
+// To create a service implementation, annotate the class with @ServiceImpl and provide the
+// interface that the service implements. The service implementation class should have methods that
+// return OperationHandler that correspond to the operations defined in the service interface.
+@ServiceImpl(service = NexusService.class)
+public class NexusServiceImpl {
+  @OperationImpl
+  public OperationHandler<NexusService.EchoInput, NexusService.EchoOutput> echo() {
+    // WorkflowClientOperationHandlers.sync is a meant for exposing simple RPC handlers.
+    return WorkflowClientOperationHandlers.sync(
+        // The method is provided with an SDK client that can be used for arbitrary calls such as
+        // signaling, querying,
+        // and listing workflows but implementations are free to make arbitrary calls to other
+        // services or databases, or
+        // perform simple computations such as this one.
+        (ctx, details, client, input) -> new NexusService.EchoOutput(input.getMessage()));
+  }
+
+  @OperationImpl
+  public OperationHandler<NexusService.HelloInput, NexusService.HelloOutput> hello() {
+    // Use the WorkflowClientOperationHandlers.fromWorkflowMethod constructor, which is the easiest
+    // way to expose a workflow as an operation.
+    return WorkflowClientOperationHandlers.fromWorkflowMethod(
+        (ctx, details, client, input) ->
+            client.newWorkflowStub(
+                    HelloHandlerWorkflow.class,
+                    // Workflow IDs should typically be business meaningful IDs and are used to
+                    // dedupe workflow starts.
+                    // For this example, we're using the request ID allocated by Temporal when the
+                    // caller workflow schedules
+                    // the operation, this ID is guaranteed to be stable across retries of this
+                    // operation.
+                    //
+                    // Task queue defaults to the task queue this operation is handled on.
+                    WorkflowOptions.newBuilder().setWorkflowId(details.getRequestId()).build())
+                ::hello);
+  }
+}
diff --git a/core/src/main/java/io/temporal/samples/nexus/options/ClientOptions.java b/core/src/main/java/io/temporal/samples/nexus/options/ClientOptions.java
new file mode 100644
index 00000000..49d0dde2
--- /dev/null
+++ b/core/src/main/java/io/temporal/samples/nexus/options/ClientOptions.java
@@ -0,0 +1,125 @@
+/*
+ *  Copyright (c) 2020 Temporal Technologies, Inc. All Rights Reserved
+ *
+ *  Copyright 2012-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ *  Modifications copyright (C) 2017 Uber Technologies, Inc.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"). You may not
+ *  use this file except in compliance with the License. A copy of the License is
+ *  located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ *  or in the "license" file accompanying this file. This file is distributed on
+ *  an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ *  express or implied. See the License for the specific language governing
+ *  permissions and limitations under the License.
+ */
+
+package io.temporal.samples.nexus.options;
+
+import io.grpc.netty.shaded.io.netty.handler.ssl.SslContextBuilder;
+import io.grpc.netty.shaded.io.netty.handler.ssl.util.InsecureTrustManagerFactory;
+import io.temporal.client.WorkflowClient;
+import io.temporal.client.WorkflowClientOptions;
+import io.temporal.serviceclient.WorkflowServiceStubs;
+import io.temporal.serviceclient.WorkflowServiceStubsOptions;
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
+import java.util.Arrays;
+import javax.net.ssl.SSLException;
+import org.apache.commons.cli.*;
+
+public class ClientOptions {
+  public static WorkflowClient getWorkflowClient(String[] args) {
+    System.out.println(Arrays.toString(args));
+    Options options = new Options();
+    Option targetHostOption = new Option("target-host", true, "Host:port for the Temporal service");
+    targetHostOption.setRequired(false);
+    options.addOption(targetHostOption);
+
+    Option namespaceOption = new Option("namespace", true, "Namespace to connect to");
+    namespaceOption.setRequired(false);
+    options.addOption(namespaceOption);
+
+    Option serverRootCaOption =
+        new Option("server-root-ca-cert", true, "Optional path to root server CA cert");
+    serverRootCaOption.setRequired(false);
+    options.addOption(serverRootCaOption);
+
+    Option clientCertOption = new Option("client-cert", true, "Optional path to client cert");
+    clientCertOption.setRequired(false);
+    options.addOption(clientCertOption);
+
+    Option clientKeyOption = new Option("client-key", true, "Optional path to client key");
+    clientKeyOption.setRequired(false);
+    options.addOption(clientKeyOption);
+
+    Option serverNameOption =
+        new Option(
+            "server-name", true, "Server name to use for verifying the server's certificate");
+    serverNameOption.setRequired(false);
+    options.addOption(serverNameOption);
+
+    Option insercureSkipVerifyOption =
+        new Option(
+            "insecure-skip-verify",
+            false,
+            "Skip verification of the server's certificate and host name");
+    insercureSkipVerifyOption.setRequired(false);
+    options.addOption(insercureSkipVerifyOption);
+
+    CommandLineParser parser = new DefaultParser();
+    HelpFormatter formatter = new HelpFormatter();
+    CommandLine cmd = null;
+
+    try {
+      cmd = parser.parse(options, args);
+    } catch (ParseException e) {
+      System.out.println(e.getMessage());
+      formatter.printHelp("utility-name", options);
+
+      System.exit(1);
+    }
+
+    String targetHost = cmd.getOptionValue("target-host", "localhost:7233");
+    String namespace = cmd.getOptionValue("namespace", "default");
+    String serverRootCaCert = cmd.getOptionValue("server-root-ca-cert", "");
+    String clientCert = cmd.getOptionValue("client-cert", "");
+    String clientKey = cmd.getOptionValue("client-key", "");
+    String serverName = cmd.getOptionValue("server-name", "");
+    boolean insecureSkipVerify = cmd.hasOption("insecure-skip-verify");
+
+    WorkflowServiceStubsOptions.Builder serviceStubOptionsBuilder =
+        WorkflowServiceStubsOptions.newBuilder().setTarget(targetHost);
+    if (!clientCert.isEmpty() || !clientKey.isEmpty()) {
+      if (clientCert.isEmpty() || clientKey.isEmpty()) {
+        throw new IllegalArgumentException("Both client-cert and client-key must be provided");
+      }
+      try {
+        SslContextBuilder sslContext =
+            SslContextBuilder.forClient()
+                .keyManager(new FileInputStream(clientCert), new FileInputStream(clientKey));
+        if (serverRootCaCert != null && !serverRootCaCert.isEmpty()) {
+          sslContext.trustManager(new FileInputStream(serverRootCaCert));
+        }
+        if (insecureSkipVerify) {
+          sslContext.trustManager(InsecureTrustManagerFactory.INSTANCE);
+        }
+        serviceStubOptionsBuilder.setSslContext(sslContext.build());
+      } catch (SSLException e) {
+        throw new RuntimeException(e);
+      } catch (FileNotFoundException e) {
+        throw new RuntimeException(e);
+      }
+    }
+    if (serverName != null && !serverName.isEmpty()) {
+      serviceStubOptionsBuilder.setChannelInitializer(c -> c.overrideAuthority(serverName));
+    }
+    WorkflowServiceStubs service =
+        WorkflowServiceStubs.newServiceStubs(serviceStubOptionsBuilder.build());
+    return WorkflowClient.newInstance(
+        service, WorkflowClientOptions.newBuilder().setNamespace(namespace).build());
+  }
+}
diff --git a/core/src/main/java/io/temporal/samples/nexus/service/NexusService.java b/core/src/main/java/io/temporal/samples/nexus/service/NexusService.java
new file mode 100644
index 00000000..e12dcbe9
--- /dev/null
+++ b/core/src/main/java/io/temporal/samples/nexus/service/NexusService.java
@@ -0,0 +1,106 @@
+/*
+ *  Copyright (c) 2020 Temporal Technologies, Inc. All Rights Reserved
+ *
+ *  Copyright 2012-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ *  Modifications copyright (C) 2017 Uber Technologies, Inc.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"). You may not
+ *  use this file except in compliance with the License. A copy of the License is
+ *  located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ *  or in the "license" file accompanying this file. This file is distributed on
+ *  an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ *  express or implied. See the License for the specific language governing
+ *  permissions and limitations under the License.
+ */
+
+package io.temporal.samples.nexus.service;
+
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import io.nexusrpc.Operation;
+import io.nexusrpc.Service;
+
+@Service
+public interface NexusService {
+  enum Language {
+    EN,
+    FR,
+    DE,
+    ES,
+    TR
+  }
+
+  class HelloInput {
+    private final String name;
+    private final Language language;
+
+    @JsonCreator(mode = JsonCreator.Mode.PROPERTIES)
+    public HelloInput(
+        @JsonProperty("name") String name, @JsonProperty("language") Language language) {
+      this.name = name;
+      this.language = language;
+    }
+
+    @JsonProperty("name")
+    public String getName() {
+      return name;
+    }
+
+    @JsonProperty("language")
+    public Language getLanguage() {
+      return language;
+    }
+  }
+
+  class HelloOutput {
+    private final String message;
+
+    @JsonCreator(mode = JsonCreator.Mode.PROPERTIES)
+    public HelloOutput(@JsonProperty("message") String message) {
+      this.message = message;
+    }
+
+    @JsonProperty("message")
+    public String getMessage() {
+      return message;
+    }
+  }
+
+  class EchoInput {
+    private final String message;
+
+    @JsonCreator(mode = JsonCreator.Mode.PROPERTIES)
+    public EchoInput(@JsonProperty("message") String message) {
+      this.message = message;
+    }
+
+    @JsonProperty("message")
+    public String getMessage() {
+      return message;
+    }
+  }
+
+  class EchoOutput {
+    private final String message;
+
+    @JsonCreator(mode = JsonCreator.Mode.PROPERTIES)
+    public EchoOutput(@JsonProperty("message") String message) {
+      this.message = message;
+    }
+
+    @JsonProperty("message")
+    public String getMessage() {
+      return message;
+    }
+  }
+
+  @Operation
+  HelloOutput hello(HelloInput input);
+
+  @Operation
+  EchoOutput echo(EchoInput input);
+}
diff --git a/core/src/main/java/io/temporal/samples/nexus/service/description.md b/core/src/main/java/io/temporal/samples/nexus/service/description.md
new file mode 100644
index 00000000..74eb4d88
--- /dev/null
+++ b/core/src/main/java/io/temporal/samples/nexus/service/description.md
@@ -0,0 +1,8 @@
+Service Name:
+my-hello-service
+Operation Names:
+echo
+say-hello
+
+Input / Output arguments are in the following repository:
+https://github.com/temporalio/samples-java/core/src/main/java/io/temporal/samples/nexus/service/NexusService.java
diff --git a/core/src/test/java/io/temporal/samples/nexus/caller/CallerWorkflowTest.java b/core/src/test/java/io/temporal/samples/nexus/caller/CallerWorkflowTest.java
new file mode 100644
index 00000000..ba1bba46
--- /dev/null
+++ b/core/src/test/java/io/temporal/samples/nexus/caller/CallerWorkflowTest.java
@@ -0,0 +1,109 @@
+/*
+ *  Copyright (c) 2020 Temporal Technologies, Inc. All Rights Reserved
+ *
+ *  Copyright 2012-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ *  Modifications copyright (C) 2017 Uber Technologies, Inc.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"). You may not
+ *  use this file except in compliance with the License. A copy of the License is
+ *  located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ *  or in the "license" file accompanying this file. This file is distributed on
+ *  an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ *  express or implied. See the License for the specific language governing
+ *  permissions and limitations under the License.
+ */
+
+package io.temporal.samples.nexus.caller;
+
+import static org.junit.Assert.assertEquals;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+import io.temporal.client.WorkflowOptions;
+import io.temporal.samples.nexus.handler.HelloHandlerWorkflow;
+import io.temporal.samples.nexus.handler.NexusServiceImpl;
+import io.temporal.samples.nexus.service.NexusService;
+import io.temporal.testing.TestWorkflowRule;
+import io.temporal.worker.WorkflowImplementationOptions;
+import io.temporal.workflow.NexusServiceOptions;
+import java.util.Collections;
+import org.junit.Rule;
+import org.junit.Test;
+
+public class CallerWorkflowTest {
+
+  @Rule
+  public TestWorkflowRule testWorkflowRule =
+      TestWorkflowRule.newBuilder()
+          // If a Nexus service is registered as part of the test, the TestWorkflowRule will ,by
+          // default, automatically create a Nexus service endpoint and workflows registered as part
+          // of the TestWorkflowRule will automatically inherit the endpoint if none is set.
+          .setNexusServiceImplementation(new NexusServiceImpl())
+          .setWorkflowTypes(HelloCallerWorkflowImpl.class)
+          // Disable automatic worker startup as we are going to register some workflows manually
+          // per test
+          .setDoNotStart(true)
+          .build();
+
+  @Test
+  public void testHelloWorkflow() {
+    testWorkflowRule
+        .getWorker()
+        // Workflows started by a Nexus service can be mocked just like any other workflow
+        .registerWorkflowImplementationFactory(
+            HelloHandlerWorkflow.class,
+            () -> {
+              HelloHandlerWorkflow wf = mock(HelloHandlerWorkflow.class);
+              when(wf.hello(any())).thenReturn(new NexusService.HelloOutput("Hello World 👋"));
+              return wf;
+            });
+    testWorkflowRule.getTestEnvironment().start();
+
+    HelloCallerWorkflow workflow =
+        testWorkflowRule
+            .getWorkflowClient()
+            .newWorkflowStub(
+                HelloCallerWorkflow.class,
+                WorkflowOptions.newBuilder().setTaskQueue(testWorkflowRule.getTaskQueue()).build());
+    String greeting = workflow.hello("World", NexusService.Language.EN);
+    assertEquals("Hello World 👋", greeting);
+
+    testWorkflowRule.getTestEnvironment().shutdown();
+  }
+
+  @Test
+  public void testEchoWorkflow() {
+    // If Workflows are registered later than the endpoint can be set manually
+    // either by setting the endpoint in the NexusServiceOptions in the Workflow implementation or
+    // by setting the NexusServiceOptions on the WorkflowImplementationOptions when registering the
+    // Workflow.
+    testWorkflowRule
+        .getWorker()
+        .registerWorkflowImplementationTypes(
+            WorkflowImplementationOptions.newBuilder()
+                .setNexusServiceOptions(
+                    Collections.singletonMap(
+                        "NexusService",
+                        NexusServiceOptions.newBuilder()
+                            .setEndpoint(testWorkflowRule.getNexusEndpoint().getSpec().getName())
+                            .build()))
+                .build(),
+            EchoCallerWorkflowImpl.class);
+    testWorkflowRule.getTestEnvironment().start();
+
+    EchoCallerWorkflow workflow =
+        testWorkflowRule
+            .getWorkflowClient()
+            .newWorkflowStub(
+                EchoCallerWorkflow.class,
+                WorkflowOptions.newBuilder().setTaskQueue(testWorkflowRule.getTaskQueue()).build());
+    String greeting = workflow.echo("Hello");
+    assertEquals("Hello", greeting);
+    testWorkflowRule.getTestEnvironment().shutdown();
+  }
+}