Reality2byte · pull · Aug 7, 2026 · Aug 7, 2026 · Aug 7, 2026 · Aug 7, 2026
diff --git a/mcp-core/src/main/java/io/modelcontextprotocol/client/McpAsyncClient.java b/mcp-core/src/main/java/io/modelcontextprotocol/client/McpAsyncClient.java
@@ -818,13 +818,13 @@ private NotificationHandler asyncToolsChangeNotificationHandler(
 	 * @see #readResource(McpSchema.Resource)
 	 */
 	public Mono<McpSchema.ListResourcesResult> listResources() {
-		return this.listResources(McpSchema.FIRST_PAGE)
-			.expand(result -> (result.nextCursor() != null) ? this.listResources(result.nextCursor()) : Mono.empty())
-			.reduce(new ArrayList<McpSchema.Resource>(), (accumulated, result) -> {
-				accumulated.addAll(result.resources());
-				return accumulated;
-			})
-			.map(all -> McpSchema.ListResourcesResult.builder(Collections.unmodifiableList(all)).build());
+		return this.listResources(McpSchema.FIRST_PAGE).expand(result -> {
+			String next = result.nextCursor();
+			return (next != null && !next.isEmpty()) ? this.listResources(next) : Mono.empty();
+		}).reduce(new ArrayList<McpSchema.Resource>(), (accumulated, result) -> {
+			accumulated.addAll(result.resources());
+			return accumulated;
+		}).map(all -> McpSchema.ListResourcesResult.builder(Collections.unmodifiableList(all)).build());
 	}
 
 	/**
@@ -904,14 +904,13 @@ public Mono<McpSchema.ReadResourceResult> readResource(McpSchema.ReadResourceReq
 	 * @see McpSchema.ListResourceTemplatesResult
 	 */
 	public Mono<McpSchema.ListResourceTemplatesResult> listResourceTemplates() {
-		return this.listResourceTemplates(McpSchema.FIRST_PAGE)
-			.expand(result -> (result.nextCursor() != null) ? this.listResourceTemplates(result.nextCursor())
-					: Mono.empty())
-			.reduce(new ArrayList<McpSchema.ResourceTemplate>(), (accumulated, result) -> {
-				accumulated.addAll(result.resourceTemplates());
-				return accumulated;
-			})
-			.map(all -> McpSchema.ListResourceTemplatesResult.builder(Collections.unmodifiableList(all)).build());
+		return this.listResourceTemplates(McpSchema.FIRST_PAGE).expand(result -> {
+			String next = result.nextCursor();
+			return (next != null && !next.isEmpty()) ? this.listResourceTemplates(next) : Mono.empty();
+		}).reduce(new ArrayList<McpSchema.ResourceTemplate>(), (accumulated, result) -> {
+			accumulated.addAll(result.resourceTemplates());
+			return accumulated;
+		}).map(all -> McpSchema.ListResourceTemplatesResult.builder(Collections.unmodifiableList(all)).build());
 	}
 
 	/**
@@ -1024,13 +1023,13 @@ private NotificationHandler asyncResourcesUpdatedNotificationHandler(
 	 * @see #getPrompt(GetPromptRequest)
 	 */
 	public Mono<ListPromptsResult> listPrompts() {
-		return this.listPrompts(McpSchema.FIRST_PAGE)
-			.expand(result -> (result.nextCursor() != null) ? this.listPrompts(result.nextCursor()) : Mono.empty())
-			.reduce(new ArrayList<McpSchema.Prompt>(), (accumulated, result) -> {
-				accumulated.addAll(result.prompts());
-				return accumulated;
-			})
-			.map(all -> McpSchema.ListPromptsResult.builder(Collections.unmodifiableList(all)).build());
+		return this.listPrompts(McpSchema.FIRST_PAGE).expand(result -> {
+			String next = result.nextCursor();
+			return (next != null && !next.isEmpty()) ? this.listPrompts(next) : Mono.empty();
+		}).reduce(new ArrayList<McpSchema.Prompt>(), (accumulated, result) -> {
+			accumulated.addAll(result.prompts());
+			return accumulated;
+		}).map(all -> McpSchema.ListPromptsResult.builder(Collections.unmodifiableList(all)).build());
 	}
 
 	/**

diff --git a/...main/java/io/modelcontextprotocol/client/transport/HttpClientStreamableHttpTransport.java b/...main/java/io/modelcontextprotocol/client/transport/HttpClientStreamableHttpTransport.java
@@ -114,6 +114,29 @@ public class HttpClientStreamableHttpTransport implements McpClientTransport {
 
 	public static int BAD_REQUEST = 400;
 
+	/**
+	 * Determines whether an SSE event should be treated as a "message" event carrying a
+	 * JSON-RPC payload.
+	 *
+	 * <p>
+	 * Per the <a href=
+	 * "https://html.spec.whatwg.org/multipage/server-sent-events.html#event-stream-interpretation">
+	 * SSE specification (WHATWG HTML Living Standard §9.2.6)</a>, an event with no
+	 * explicit {@code event:} field MUST be dispatched as a {@code message} event by
+	 * default. This method applies that rule by treating {@code null} or empty event
+	 * names as equivalent to {@link #MESSAGE_EVENT_TYPE}.
+	 *
+	 * <p>
+	 * This alignment ensures interoperability with MCP servers that emit bare
+	 * {@code data:} frames without an accompanying {@code event:} line, which are valid
+	 * per the SSE spec.
+	 * @param eventName the SSE event name, which may be {@code null} or empty
+	 * @return {@code true} if the event should be parsed as a JSON-RPC message
+	 */
+	static boolean isMessageEvent(String eventName) {
+		return eventName == null || eventName.isEmpty() || MESSAGE_EVENT_TYPE.equals(eventName);
+	}
+
 	private final McpJsonMapper jsonMapper;
 
 	private final URI baseUri;
@@ -323,7 +346,7 @@ else if (statusCode == METHOD_NOT_ALLOWED) {
 											+ statusCode));
 						}
 						else if (statusCode >= 200 && statusCode < 300) {
-							if (MESSAGE_EVENT_TYPE.equals(sseResponseEvent.sseEvent().event())) {
+							if (isMessageEvent(sseResponseEvent.sseEvent().event())) {
 								String data = sseResponseEvent.sseEvent().data();
 								// Per 2025-11-25 spec (SEP-1699), servers may
 								// send SSE events

diff --git a/mcp-core/src/main/java/io/modelcontextprotocol/common/DefaultMcpTransportContext.java b/mcp-core/src/main/java/io/modelcontextprotocol/common/DefaultMcpTransportContext.java
@@ -20,7 +20,7 @@ class DefaultMcpTransportContext implements McpTransportContext {
 
 	DefaultMcpTransportContext(Map<String, Object> metadata) {
 		Assert.notNull(metadata, "The metadata cannot be null");
-		this.metadata = metadata;
+		this.metadata = Map.copyOf(metadata);
 	}
 
 	@Override

diff --git a/...elcontextprotocol/client/transport/HttpClientStreamableHttpTransportSseEventTypeTest.java b/...elcontextprotocol/client/transport/HttpClientStreamableHttpTransportSseEventTypeTest.java
@@ -0,0 +1,51 @@
+/*
+ * Copyright 2024-2026 the original author or authors.
+ */
+
+package io.modelcontextprotocol.client.transport;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.NullAndEmptySource;
+import org.junit.jupiter.params.provider.ValueSource;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Unit tests for {@link HttpClientStreamableHttpTransport#isMessageEvent(String)}.
+ *
+ * <p>
+ * Verifies that SSE event classification follows the <a href=
+ * "https://html.spec.whatwg.org/multipage/server-sent-events.html#event-stream-interpretation">
+ * WHATWG HTML Living Standard §9.2.6</a>: an event without an explicit {@code event:}
+ * field must be dispatched as a {@code message} event.
+ *
+ * @author jiajingda
+ * @see <a href="https://github.com/modelcontextprotocol/java-sdk/issues/885">#885</a>
+ */
+class HttpClientStreamableHttpTransportSseEventTypeTest {
+
+	@ParameterizedTest
+	@NullAndEmptySource
+	void shouldTreatNullOrEmptyEventAsMessage(String eventName) {
+		assertThat(HttpClientStreamableHttpTransport.isMessageEvent(eventName))
+			.as("SSE frame with null/empty event field must be treated as a 'message' event per SSE spec")
+			.isTrue();
+	}
+
+	@Test
+	void shouldTreatExplicitMessageEventAsMessage() {
+		assertThat(HttpClientStreamableHttpTransport.isMessageEvent("message"))
+			.as("Explicit 'message' event must be parsed as a JSON-RPC message")
+			.isTrue();
+	}
+
+	@ParameterizedTest
+	@ValueSource(strings = { "ping", "error", "notification", "MESSAGE", "Message", "custom-event" })
+	void shouldNotTreatOtherEventsAsMessage(String eventName) {
+		assertThat(HttpClientStreamableHttpTransport.isMessageEvent(eventName))
+			.as("Non-'message' SSE event '%s' must not be parsed as a JSON-RPC message", eventName)
+			.isFalse();
+	}
+
+}
diff --git a/mcp-core/src/test/java/io/modelcontextprotocol/common/McpTransportContextTests.java b/mcp-core/src/test/java/io/modelcontextprotocol/common/McpTransportContextTests.java
@@ -0,0 +1,89 @@
+/*
+ * Copyright 2026-2026 the original author or authors.
+ */
+
+package io.modelcontextprotocol.common;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link McpTransportContext#create(Map)}, which is documented to return an
+ * unmodifiable context.
+ */
+class McpTransportContextTests {
+
+	@Test
+	void createdContextShouldNotSeeLaterWritesToTheSourceMap() {
+		Map<String, Object> metadata = new HashMap<>();
+		metadata.put("tenant", "acme");
+
+		McpTransportContext context = McpTransportContext.create(metadata);
+		metadata.put("tenant", "other");
+
+		assertThat(context.get("tenant")).isEqualTo("acme");
+	}
+
+	@Test
+	void createdContextShouldNotSeeLaterAdditionsToTheSourceMap() {
+		Map<String, Object> metadata = new HashMap<>();
+		metadata.put("tenant", "acme");
+
+		McpTransportContext context = McpTransportContext.create(metadata);
+		metadata.put("added-after-the-fact", "surprise");
+
+		assertThat(context.get("added-after-the-fact")).isNull();
+	}
+
+	@Test
+	void createdContextShouldNotBeEmptiedByClearingTheSourceMap() {
+		Map<String, Object> metadata = new HashMap<>();
+		metadata.put("tenant", "acme");
+
+		McpTransportContext context = McpTransportContext.create(metadata);
+		metadata.clear();
+
+		assertThat(context.get("tenant")).isEqualTo("acme");
+	}
+
+	@Test
+	void createdContextShouldRemainUsableAsAMapKey() {
+		Map<String, Object> metadata = new HashMap<>();
+		metadata.put("tenant", "acme");
+		McpTransportContext context = McpTransportContext.create(metadata);
+
+		Map<McpTransportContext, String> byContext = new HashMap<>();
+		byContext.put(context, "value");
+		metadata.put("tenant", "other");
+
+		assertThat(byContext.get(context)).isEqualTo("value");
+	}
+
+	@Test
+	void twoContextsCreatedFromEqualMapsShouldStayEqual() {
+		Map<String, Object> first = new HashMap<>();
+		first.put("tenant", "acme");
+		Map<String, Object> second = new HashMap<>();
+		second.put("tenant", "acme");
+
+		McpTransportContext firstContext = McpTransportContext.create(first);
+		McpTransportContext secondContext = McpTransportContext.create(second);
+		assertThat(firstContext).isEqualTo(secondContext);
+
+		first.put("tenant", "other");
+
+		assertThat(firstContext).isEqualTo(secondContext);
+	}
+
+	@Test
+	void createdContextFromAnImmutableMapIsAlreadyCorrect() {
+		McpTransportContext context = McpTransportContext.create(Map.of("tenant", "acme"));
+
+		assertThat(context.get("tenant")).isEqualTo("acme");
+	}
+
+}
diff --git a/mcp-test/src/test/java/io/modelcontextprotocol/client/McpAsyncClientTests.java b/mcp-test/src/test/java/io/modelcontextprotocol/client/McpAsyncClientTests.java
@@ -8,6 +8,7 @@
 import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
+import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.Function;
 import java.util.stream.Collectors;
@@ -298,6 +299,42 @@ void testListPromptsWithCursorAndMeta() {
 
 	}
 
+	@Test
+	void listResourcesStopsOnEmptyNextCursor() {
+		var transport = new EmptyCursorTestMcpClientTransport(McpSchema.METHOD_RESOURCES_LIST);
+		McpAsyncClient client = McpClient.async(transport).build();
+
+		McpSchema.ListResourcesResult result = client.listResources().block();
+
+		assertThat(result).isNotNull();
+		assertThat(result.resources()).extracting(McpSchema.Resource::name).containsExactly("test.txt");
+		assertThat(transport.getRequestCount()).isEqualTo(1);
+	}
+
+	@Test
+	void listResourceTemplatesStopsOnEmptyNextCursor() {
+		var transport = new EmptyCursorTestMcpClientTransport(McpSchema.METHOD_RESOURCES_TEMPLATES_LIST);
+		McpAsyncClient client = McpClient.async(transport).build();
+
+		McpSchema.ListResourceTemplatesResult result = client.listResourceTemplates().block();
+
+		assertThat(result).isNotNull();
+		assertThat(result.resourceTemplates()).extracting(McpSchema.ResourceTemplate::name).containsExactly("template");
+		assertThat(transport.getRequestCount()).isEqualTo(1);
+	}
+
+	@Test
+	void listPromptsStopsOnEmptyNextCursor() {
+		var transport = new EmptyCursorTestMcpClientTransport(McpSchema.METHOD_PROMPT_LIST);
+		McpAsyncClient client = McpClient.async(transport).build();
+
+		McpSchema.ListPromptsResult result = client.listPrompts().block();
+
+		assertThat(result).isNotNull();
+		assertThat(result.prompts()).extracting(McpSchema.Prompt::name).containsExactly("test-prompt");
+		assertThat(transport.getRequestCount()).isEqualTo(1);
+	}
+
 	static class TestMcpClientTransport implements McpClientTransport {
 
 		private Function<Mono<McpSchema.JSONRPCMessage>, Mono<McpSchema.JSONRPCMessage>> handler;
@@ -397,4 +434,90 @@ public McpSchema.PaginatedRequest getCapturedRequest() {
 
 	}
 
+	static class EmptyCursorTestMcpClientTransport implements McpClientTransport {
+
+		private final String listMethod;
+
+		private final AtomicInteger requestCount = new AtomicInteger();
+
+		private Function<Mono<McpSchema.JSONRPCMessage>, Mono<McpSchema.JSONRPCMessage>> handler;
+
+		EmptyCursorTestMcpClientTransport(String listMethod) {
+			this.listMethod = listMethod;
+		}
+
+		@Override
+		public Mono<Void> connect(Function<Mono<McpSchema.JSONRPCMessage>, Mono<McpSchema.JSONRPCMessage>> handler) {
+			this.handler = handler;
+			return Mono.empty();
+		}
+
+		@Override
+		public Mono<Void> closeGracefully() {
+			return Mono.empty();
+		}
+
+		@Override
+		public Mono<Void> sendMessage(McpSchema.JSONRPCMessage message) {
+			if (!(message instanceof McpSchema.JSONRPCRequest request)) {
+				return Mono.empty();
+			}
+
+			McpSchema.JSONRPCResponse response;
+			if (McpSchema.METHOD_INITIALIZE.equals(request.method())) {
+				McpSchema.ServerCapabilities caps = McpSchema.ServerCapabilities.builder()
+					.prompts(false)
+					.resources(false, false)
+					.tools(false)
+					.build();
+
+				McpSchema.InitializeResult initResult = McpSchema.InitializeResult
+					.builder(ProtocolVersions.MCP_2024_11_05, caps, MOCK_SERVER_INFO)
+					.build();
+				response = McpSchema.JSONRPCResponse.result(request.id(), initResult);
+			}
+			else if (this.listMethod.equals(request.method())) {
+				this.requestCount.incrementAndGet();
+				response = McpSchema.JSONRPCResponse.result(request.id(), resultForMethod(request.method()));
+			}
+			else {
+				return Mono.empty();
+			}
+
+			return this.handler.apply(Mono.just(response)).then();
+		}
+
+		private Object resultForMethod(String method) {
+			if (McpSchema.METHOD_RESOURCES_LIST.equals(method)) {
+				McpSchema.Resource resource = McpSchema.Resource.builder("file:///test.txt", "test.txt").build();
+				return McpSchema.ListResourcesResult.builder(List.of(resource)).nextCursor("").build();
+			}
+			if (McpSchema.METHOD_RESOURCES_TEMPLATES_LIST.equals(method)) {
+				McpSchema.ResourceTemplate template = McpSchema.ResourceTemplate.builder("file:///{name}", "template")
+					.build();
+				return McpSchema.ListResourceTemplatesResult.builder(List.of(template)).nextCursor("").build();
+			}
+			if (McpSchema.METHOD_PROMPT_LIST.equals(method)) {
+				McpSchema.Prompt prompt = McpSchema.Prompt.builder("test-prompt").build();
+				return McpSchema.ListPromptsResult.builder(List.of(prompt)).nextCursor("").build();
+			}
+			throw new IllegalArgumentException("Unsupported method: " + method);
+		}
+
+		@Override
+		public <T> T unmarshalFrom(Object data, TypeRef<T> typeRef) {
+			return JSON_MAPPER.convertValue(data, new TypeRef<>() {
+				@Override
+				public java.lang.reflect.Type getType() {
+					return typeRef.getType();
+				}
+			});
+		}
+
+		int getRequestCount() {
+			return this.requestCount.get();
+		}
+
+	}
+
 }