Class Task

spec/src/main/java/org/a2aproject/sdk/spec/Task.java:46–265

Represents a single, stateful operation or conversation between a client and an agent in the A2A Protocol. A Task encapsulates the complete lifecycle of an agent interaction, from submission through completion, cancellation, or failure. It maintains the current state, accumulated artifacts (resp

 * @see <a href="https://a2a-protocol.org/latest/">A2A Protocol Specification</a>
 */
public record Task(String id, String contextId, TaskStatus status, @Nullable List<Artifact> artifacts,
        @Nullable List<Message> history, @Nullable Map<String, Object> metadata) implements EventKind, StreamingEventKind {

    /**
     * The identifier when used in streaming responses
     */
    public static final String STREAMING_EVENT_ID = "task";

    /**
     * Compact constructor with validation and defensive copying.
     *
     * @param id the task identifier
     * @param contextId the context identifier
     * @param status the task status
     * @param artifacts the list of artifacts produced by the task
     * @param history the message history for this task
     * @param metadata additional metadata for the task
     * @throws IllegalArgumentException if id, contextId, or status is null
     */
    public Task {
        Assert.checkNotNullParam("id", id);
        Assert.checkNotNullParam("contextId", contextId);
        Assert.checkNotNullParam("status", status);
        artifacts = artifacts != null ? List.copyOf(artifacts) : List.of();
        history = history != null ? List.copyOf(history) : List.of();
        metadata = (metadata != null) ? Map.copyOf(metadata) : null;
    }

    @Override
    public String kind() {
        return STREAMING_EVENT_ID;
    }

    /**
     * Creates a new Builder for constructing Task instances.
     *
     * @return a new Task.Builder instance
     */
    public static Builder builder() {
        return new Builder();
    }

    /**
     * Creates a new Builder initialized with values from an existing Task.
     * <p>
     * This constructor allows for creating a modified copy of an existing Task
     * by copying all fields and then selectively updating specific values.
     *
     * @param task the Task to copy values from
     * @return a new Builder instance initialized with the task's values
     */
    public static Builder builder(Task task) {
        return new Builder(task);
    }

    /**
     * Builder for constructing immutable {@link Task} instances.
     * <p>