From 7e5cf0f21a4ff04786051a39254ffe0cb6304708 Mon Sep 17 00:00:00 2001
From: Raphael Fakhri <153192858+RaphaelFakhri@users.noreply.github.com>
Date: Mon, 2 Nov 2026 23:17:47 +0000
Subject: [PATCH] fix: accept ListTasks responses with fewer tasks than
 pageSize

The A2A specification defines the response pageSize as the page size
used for the response, and a server may return fewer tasks than that.
ListTasksResult rejected any response where pageSize differed from the
number of tasks, so clients failed with InvalidParamsError on every
partial page.

Fixes #1260
---
 .../common/wrappers/ListTasksResult.java      |  5 +--
 .../sdk/grpc/utils/JSONRPCUtilsTest.java      | 33 +++++++++++++++++++
 2 files changed, 34 insertions(+), 4 deletions(-)

diff --git a/jsonrpc-common/src/main/java/org/a2aproject/sdk/jsonrpc/common/wrappers/ListTasksResult.java b/jsonrpc-common/src/main/java/org/a2aproject/sdk/jsonrpc/common/wrappers/ListTasksResult.java
index 7844547dd..4f4e1d8e5 100644
--- a/jsonrpc-common/src/main/java/org/a2aproject/sdk/jsonrpc/common/wrappers/ListTasksResult.java
+++ b/jsonrpc-common/src/main/java/org/a2aproject/sdk/jsonrpc/common/wrappers/ListTasksResult.java
@@ -12,7 +12,7 @@
  * @param tasks Array of tasks matching the specified criteria
  * @param totalSize Total number of matching tasks across all pages, after any applicable authorization
  *                  filtering
- * @param pageSize Number of tasks returned in this response
+ * @param pageSize The page size used for this response; may be greater than the number of tasks returned
  * @param nextPageToken Token for retrieving the next page of results (null if no more results)
  */
 public record ListTasksResult(
@@ -39,9 +39,6 @@ public record ListTasksResult(
         if (pageSize < 0) {
             throw new IllegalArgumentException("pageSize must be non-negative");
         }
-        if (pageSize != tasks.size()) {
-            throw new IllegalArgumentException("pageSize must be equal to the number of tasks in the list. Got " + pageSize + ", but list has " + tasks.size() + " tasks.");
-        }
         // Make defensive copy
         tasks = List.copyOf(tasks);
     }
diff --git a/spec-grpc/src/test/java/org/a2aproject/sdk/grpc/utils/JSONRPCUtilsTest.java b/spec-grpc/src/test/java/org/a2aproject/sdk/grpc/utils/JSONRPCUtilsTest.java
index 300a2802a..fcead19af 100644
--- a/spec-grpc/src/test/java/org/a2aproject/sdk/grpc/utils/JSONRPCUtilsTest.java
+++ b/spec-grpc/src/test/java/org/a2aproject/sdk/grpc/utils/JSONRPCUtilsTest.java
@@ -39,6 +39,8 @@
 import org.a2aproject.sdk.jsonrpc.common.wrappers.GetTaskPushNotificationConfigResponse;
 import org.a2aproject.sdk.jsonrpc.common.wrappers.GetTaskResponse;
 import org.a2aproject.sdk.jsonrpc.common.wrappers.ListTasksRequest;
+import org.a2aproject.sdk.jsonrpc.common.wrappers.ListTasksResponse;
+import org.a2aproject.sdk.jsonrpc.common.wrappers.ListTasksResult;
 import org.a2aproject.sdk.jsonrpc.common.wrappers.SendMessageRequest;
 import org.a2aproject.sdk.spec.DataPart;
 import org.a2aproject.sdk.spec.InvalidParamsError;
@@ -142,6 +144,37 @@ public void testGetTask_WithNestedNulls_RoundTrips() throws JsonProcessingExcept
         assertEquals(task, roundTripped.getResult());
     }
 
+    @Test
+    public void testListTasksResponse_PageSizeLargerThanReturnedTasks() throws JsonProcessingException {
+        String json = """
+                {
+                  "jsonrpc": "2.0",
+                  "id": "1",
+                  "result": {
+                    "tasks": [{
+                      "id": "task-1",
+                      "contextId": "context-1",
+                      "status": {
+                        "state": "TASK_STATE_COMPLETED"
+                      }
+                    }],
+                    "nextPageToken": "",
+                    "pageSize": 10,
+                    "totalSize": 1
+                  }
+                }
+                """;
+
+        ListTasksResponse response = assertInstanceOf(ListTasksResponse.class,
+                JSONRPCUtils.parseResponseBody(json, LIST_TASK_METHOD));
+        ListTasksResult result = response.getResult();
+        assertNotNull(result);
+        assertEquals(1, result.tasks().size());
+        assertEquals(10, result.pageSize());
+        assertEquals(1, result.totalSize());
+        assertFalse(result.hasMoreResults());
+    }
+
     @Test
     public void testParseCreateTaskPushNotificationConfigRequest_ValidProtoFormat() throws JsonProcessingException {
         String validRequest = """