fix(grpc): avoid NPE when listTasks is called without a tenant

client/transport/jsonrpc/src/test/java/org/a2aproject/sdk/client/transport/jsonrpc/JSONRPCTransportTest.java

@@ -37,6 +37,10 @@
 import java.util.List;
 import java.util.Map;
 
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParser;
+
+import org.a2aproject.sdk.jsonrpc.common.wrappers.ListTasksResult;
 import org.a2aproject.sdk.spec.A2AClientException;
 import org.a2aproject.sdk.spec.A2AClientHTTPError;
 import org.a2aproject.sdk.spec.AgentCard;
@@ -54,6 +58,7 @@
 import org.a2aproject.sdk.spec.FileWithUri;
 import org.a2aproject.sdk.spec.GetExtendedAgentCardParams;
 import org.a2aproject.sdk.spec.GetTaskPushNotificationConfigParams;
+import org.a2aproject.sdk.spec.ListTasksParams;
 import org.a2aproject.sdk.spec.Message;
 import org.a2aproject.sdk.spec.MessageSendConfiguration;
 import org.a2aproject.sdk.spec.MessageSendParams;
@@ -88,6 +93,50 @@ public void tearDown() {
         server.stop();
     }
 
+    @Test
+    public void testListTasksWithDefaultBuilder() throws Exception {
+        JsonObject params = listTasksAndGetRequestParams(ListTasksParams.builder().build());
+
+        assertEquals("", params.get("tenant").getAsString());
+    }
+
+    @Test
+    public void testListTasksWithDefaultConstructor() throws Exception {
+        JsonObject params = listTasksAndGetRequestParams(new ListTasksParams());
+
+        assertEquals("", params.get("tenant").getAsString());
+    }
+
+    @Test
+    public void testListTasksWithTenant() throws Exception {
+        JsonObject params = listTasksAndGetRequestParams(ListTasksParams.builder().tenant("tenant-123").build());
+
+        assertEquals("tenant-123", params.get("tenant").getAsString());
+    }
+
+    private JsonObject listTasksAndGetRequestParams(ListTasksParams params) throws Exception {
+        String body = """
+                {
+                  "jsonrpc": "2.0",
+                  "id": "list-tasks",
+                  "result": {"tasks": [], "totalSize": 0, "pageSize": 0}
+                }
+                """;
+        server.when(request().withMethod("POST").withPath("/"))
+                .respond(response().withStatusCode(200).withBody(body));
+
+        ListTasksResult result = new JSONRPCTransport("http://localhost:4001").listTasks(params, null);
+
+        assertTrue(result.tasks().isEmpty());
+        assertEquals(0, result.totalSize());
+        assertEquals(0, result.pageSize());
+        var requests = server.retrieveRecordedRequests(request().withMethod("POST").withPath("/"));
+        assertEquals(1, requests.length);
+        JsonObject json = JsonParser.parseString(requests[0].getBodyAsString()).getAsJsonObject();
+        assertEquals("ListTasks", json.get("method").getAsString());
+        return json.getAsJsonObject("params");
+    }
+
     @Test
     public void testA2AClientSendMessage() throws Exception {
         this.server.when(

spec-grpc/src/main/java/org/a2aproject/sdk/grpc/mapper/ListTasksParamsMapper.java

@@ -28,6 +28,7 @@ public interface ListTasksParamsMapper {
     @Mapping(target = "historyLength", source = "historyLength", conditionExpression = "java(params.historyLength() != null)")
     @Mapping(target = "statusTimestampAfter", source = "statusTimestampAfter", qualifiedByName = "instantToProtoTimestamp")
     @Mapping(target = "includeArtifacts", source = "includeArtifacts", conditionExpression = "java(params.includeArtifacts() != null)")
+    @Mapping(target = "tenant", source = "tenant", conditionExpression = "java(params.tenant() != null)")
     ListTasksRequest toProto(org.a2aproject.sdk.spec.ListTasksParams params);
 
     /**
@@ -45,5 +46,6 @@ public interface ListTasksParamsMapper {
     @Mapping(target = "historyLength", expression = "java(request.hasHistoryLength() ? request.getHistoryLength() : null)")
     @Mapping(target = "statusTimestampAfter", source = "statusTimestampAfter", qualifiedByName = "protoTimestampToInstant")
     @Mapping(target = "includeArtifacts", source = "includeArtifacts", qualifiedByName = "falseToNull")
+    @Mapping(target = "tenant", source = "tenant", qualifiedByName = "emptyToNull")
     org.a2aproject.sdk.spec.ListTasksParams fromProto(ListTasksRequest request);
 }

spec-grpc/src/test/java/org/a2aproject/sdk/grpc/mapper/ListTasksParamsMapperTest.java

@@ -0,0 +1,56 @@
+package org.a2aproject.sdk.grpc.mapper;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+import org.a2aproject.sdk.grpc.ListTasksRequest;
+import org.a2aproject.sdk.spec.ListTasksParams;
+import org.junit.jupiter.api.Test;
+
+public class ListTasksParamsMapperTest {
+
+    @Test
+    void toProtoWithDefaultBuilder() {
+        ListTasksRequest request = ListTasksParamsMapper.INSTANCE.toProto(ListTasksParams.builder().build());
+
+        assertEquals("", request.getTenant());
+    }
+
+    @Test
+    void toProtoWithDefaultConstructor() {
+        ListTasksRequest request = ListTasksParamsMapper.INSTANCE.toProto(new ListTasksParams());
+
+        assertEquals("", request.getTenant());
+    }
+
+    @Test
+    void toProtoWithTenant() {
+        ListTasksRequest request = ListTasksParamsMapper.INSTANCE.toProto(
+                ListTasksParams.builder().tenant("tenant-123").build());
+
+        assertEquals("tenant-123", request.getTenant());
+    }
+
+    @Test
+    void fromProtoWithoutTenant() {
+        ListTasksParams params = ListTasksParamsMapper.INSTANCE.fromProto(ListTasksRequest.newBuilder().build());
+
+        assertNull(params.tenant());
+    }
+
+    @Test
+    void fromProtoWithTenant() {
+        ListTasksParams params = ListTasksParamsMapper.INSTANCE.fromProto(
+                ListTasksRequest.newBuilder().setTenant("tenant-123").build());
+
+        assertEquals("tenant-123", params.tenant());
+    }
+
+    @Test
+    void nullTenantRoundTrip() {
+        ListTasksRequest request = ListTasksParamsMapper.INSTANCE.toProto(ListTasksParams.builder().build());
+        ListTasksParams params = ListTasksParamsMapper.INSTANCE.fromProto(request);
+
+        assertNull(params.tenant());
+    }
+}