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‎_data/authors.yaml‎

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@@ -618,4 +618,4 @@ maeste:
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emailhash: "c97a0cf6b2f42295f8bfa8670ada8f63"
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job_title: "Senior Engineering Manager"
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twitter: "maeste"
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bio: "Senior Engineering Manager at Red Hat / IBM"
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bio: "Senior Engineering Manager at Red Hat / IBM with an old passion for Open Source and more recent one for AI Engineering."

‎_posts/2025-06-27-a2a-project-lanunches-java-sdk.adoc‎

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2020

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=== A New Era Under Linux Foundation Stewardship
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The [A2A](https://a2aproject.github.io/A2A/latest/specification) protocol’s transition to the Linux Foundation represents more
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The https://a2aproject.github.io/A2A/latest/specification[A2A] protocol’s transition to the Linux Foundation represents more
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than just a change of governance: it’s a commitment to vendor-neutral,
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community-driven innovation. Similar how WildFly and Quarkus both recently joined CommonHaus fouundation. This ensures A2A as a critical interoperability
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standard remains open and accessible to all. With more than 100
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Python, JavaScript, or any A2A-compatible language +
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well-tested enterprise capabilities (including observability, security...)
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Want to see this interoperability in action? Explore our
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And you know what? Writing agents in Java is now as easy as writing
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==== 1. A class that creates an A2A Agent Card
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[source,java]
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----
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import io.a2a.spec.AgentCapabilities;
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import io.a2a.spec.AgentCard;
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import io.a2a.spec.AgentSkill;
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import io.a2a.spec.PublicAgentCard;
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...
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@ApplicationScoped
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public class WeatherAgentCardProducer {
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@Produces
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@PublicAgentCard
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public AgentCard agentCard() {
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return new AgentCard.Builder()
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.name("Weather Agent")
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.description("Helps with weather")
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.url("http://localhost:10001")
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.version("1.0.0")
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.capabilities(new AgentCapabilities.Builder()
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.streaming(true)
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.pushNotifications(false)
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.stateTransitionHistory(false)
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.build())
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.defaultInputModes(Collections.singletonList("text"))
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.defaultOutputModes(Collections.singletonList("text"))
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.skills(Collections.singletonList(new AgentSkill.Builder()
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.id("weather_search")
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.name("Search weather")
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.description("Helps with weather in city, or states")
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.tags(Collections.singletonList("weather"))
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.examples(List.of("weather in LA, CA"))
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.build()))
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.build();
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}
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}
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----
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==== 2. A class that creates an A2A Agent Executor
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[source,java]
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----
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import io.a2a.server.agentexecution.AgentExecutor;
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import io.a2a.server.agentexecution.RequestContext;
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import io.a2a.server.events.EventQueue;
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import io.a2a.server.tasks.TaskUpdater;
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import io.a2a.spec.JSONRPCError;
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import io.a2a.spec.Message;
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import io.a2a.spec.Part;
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import io.a2a.spec.Task;
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import io.a2a.spec.TaskNotCancelableError;
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import io.a2a.spec.TaskState;
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import io.a2a.spec.TextPart;
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...
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@ApplicationScoped
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public class WeatherAgentExecutorProducer {
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@Inject
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WeatherAgent weatherAgent;
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@Produces
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public AgentExecutor agentExecutor() {
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return new WeatherAgentExecutor(weatherAgent);
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}
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private static class WeatherAgentExecutor implements AgentExecutor {
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private final WeatherAgent weatherAgent;
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public WeatherAgentExecutor(WeatherAgent weatherAgent) {
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this.weatherAgent = weatherAgent;
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}
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@Override
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public void execute(RequestContext context, EventQueue eventQueue) throws JSONRPCError {
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TaskUpdater updater = new TaskUpdater(context, eventQueue);
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// mark the task as submitted and start working on it
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if (context.getTask() == null) {
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updater.submit();
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}
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updater.startWork();
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// extract the text from the message
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String userMessage = extractTextFromMessage(context.getMessage());
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// call the weather agent with the user's message
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String response = weatherAgent.chat(userMessage);
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// create the response part
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TextPart responsePart = new TextPart(response, null);
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List<Part<?>> parts = List.of(responsePart);
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// add the response as an artifact and complete the task
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updater.addArtifact(parts, null, null, null);
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updater.complete();
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}
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@Override
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public void cancel(RequestContext context, EventQueue eventQueue) throws JSONRPCError {
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Task task = context.getTask();
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if (task.getStatus().state() == TaskState.CANCELED) {
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// task already cancelled
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throw new TaskNotCancelableError();
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}
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if (task.getStatus().state() == TaskState.COMPLETED) {
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// task already completed
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throw new TaskNotCancelableError();
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}
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// cancel the task
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TaskUpdater updater = new TaskUpdater(context, eventQueue);
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updater.cancel();
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}
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private String extractTextFromMessage(Message message) {
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StringBuilder textBuilder = new StringBuilder();
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if (message.getParts() != null) {
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for (Part part : message.getParts()) {
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if (part instanceof TextPart textPart) {
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textBuilder.append(textPart.getText());
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}
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}
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}
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return textBuilder.toString();
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}
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}
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}
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----
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Pretty straightforward, right? The SDK provides all the necessary
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components to create agent cards, handle agent execution, and manage
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communication between agents.
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And when it comes to client-side development, it's even easier. The SDK
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includes a simple HTTP client that allows you to interact with A2A agents
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using the A2A protocol. This client abstracts away the complexities of
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the protocol, making it easy to send messages, receive responses, and
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manage agent interactions. Creating an A2A client in Java is as simple as:
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==== 1. Create an A2A client
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[source,java]
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----
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// Create an A2AClient (the URL specified is the server agent's URL, be sure to replace it with the actual URL of the A2A server you want to connect to)
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A2AClient client = new A2AClient("http://localhost:1234");
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----
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==== 2. Send a message to the A2A server agent
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[source,java]
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----
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// Send a text message to the A2A server agent
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Message message = A2A.toUserMessage("tell me a joke"); // the message ID will be automatically generated for you
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MessageSendParams params = new MessageSendParams.Builder()
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.message(message)
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.build();
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SendMessageResponse response = client.sendMessage(params);
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----
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Note that `+A2A#toUserMessage+` will automatically generate a message ID
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for you when creating the `+Message+` if you don’t specify it. You can
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also explicitly specify a message ID like this:
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[source,java]
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----
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Message message = A2A.toUserMessage("tell me a joke", "message-1234"); // messageId is message-1234
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----
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And the SDK also provides a convenient way to handle task management,
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allowing you to create, get gurrent state, and cancel tasks with ease. This is
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especially useful for managing long-running operations or coordinating
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complex workflows between multiple agents. You can find more details
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about task management and many other features in the *https://github.com/a2aproject/a2a-java[A2A Java SDK]* repository's.
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You just want more code? Are you interested to see interoperability in action? Explore our
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https://github.com/a2aproject/a2a-samples/tree/main/samples/multi_language/python_and_java_multiagent[multi-language
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sample implementation&#44;] which demonstrates how Python and Java
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agents collaborate seamlessly.
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agents collaborate seamlessly. See this picture for a bird-eye overview,
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and checkout the code for more insights
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image::A2A_multi_agent.png[scaledwidth=100%]
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And if you need your agent to be reactive, don't worry about the dependencies you are adding, because
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the Java SDK leverages *mutiny-zero* as its reactive foundation, a
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decision that reflects our commitment to framework-agnostic excellence.
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[Mutiny Zero](https://smallrye.io/smallrye-mutiny-zero/latest/) is a minimal API for creating reactive streams-compliant
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https://smallrye.io/smallrye-mutiny-zero/latest/[Mutiny Zero] is a minimal API for creating reactive streams-compliant
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publishers that weighs less than 50K and have **zero** external dependencies
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beyond the Reactive Streams API. This architecture delivers several
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compelling advantages:

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