From 2ee67c953e00458983fdbae374304cccd62da54d Mon Sep 17 00:00:00 2001
From: subhash polisetti <subhashr161347@gmail.com>
Date: Thu, 22 Oct 2026 16:31:26 -0700
Subject: [PATCH] Fix listRoots() pagination on an empty nextCursor

McpAsyncServerExchange#listRoots() kept following nextCursor when a client
returned "" instead of omitting it, sending roots/list again with an empty
cursor. Apply the same guard the client list methods already use.
---
 .../server/McpAsyncServerExchange.java        |  6 ++--
 .../server/McpAsyncServerExchangeTests.java   | 28 +++++++++++++++++++
 2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/mcp-core/src/main/java/io/modelcontextprotocol/server/McpAsyncServerExchange.java b/mcp-core/src/main/java/io/modelcontextprotocol/server/McpAsyncServerExchange.java
index 280a3c87a..4f70fa3ad 100644
--- a/mcp-core/src/main/java/io/modelcontextprotocol/server/McpAsyncServerExchange.java
+++ b/mcp-core/src/main/java/io/modelcontextprotocol/server/McpAsyncServerExchange.java
@@ -207,8 +207,10 @@ public Mono<McpSchema.ListRootsResult> listRoots() {
 
 		// @formatter:off
 		return this.listRoots(McpSchema.FIRST_PAGE)
-			.expand(result -> (result.nextCursor() != null) ?
-					this.listRoots(result.nextCursor()) : Mono.empty())
+			.expand(result -> {
+				String next = result.nextCursor();
+				return (next != null && !next.isEmpty()) ? this.listRoots(next) : Mono.empty();
+			})
 			.reduceWith(() -> McpSchema.ListRootsResult.builder(new ArrayList<>()).build(),
 				(allRootsResult, result) -> {
 					allRootsResult.roots().addAll(result.roots());
diff --git a/mcp-core/src/test/java/io/modelcontextprotocol/server/McpAsyncServerExchangeTests.java b/mcp-core/src/test/java/io/modelcontextprotocol/server/McpAsyncServerExchangeTests.java
index d56829a74..80a69c12e 100644
--- a/mcp-core/src/test/java/io/modelcontextprotocol/server/McpAsyncServerExchangeTests.java
+++ b/mcp-core/src/test/java/io/modelcontextprotocol/server/McpAsyncServerExchangeTests.java
@@ -160,6 +160,34 @@ void testListRootsWithEmptyResult() {
 		}).verifyComplete();
 	}
 
+	@Test
+	void testListRootsStopsOnEmptyNextCursor() {
+
+		List<McpSchema.Root> page1Roots = Arrays
+			.asList(McpSchema.Root.builder("file:///home/user/project1").name("Project 1").build());
+		List<McpSchema.Root> page2Roots = Arrays
+			.asList(McpSchema.Root.builder("file:///home/user/project2").name("Project 2").build());
+
+		McpSchema.ListRootsResult page1Result = McpSchema.ListRootsResult.builder(page1Roots).nextCursor("").build();
+		McpSchema.ListRootsResult page2Result = McpSchema.ListRootsResult.builder(page2Roots).build();
+
+		when(mockSession.sendRequest(eq(McpSchema.METHOD_ROOTS_LIST), eq(new McpSchema.PaginatedRequest()),
+				any(TypeRef.class)))
+			.thenReturn(Mono.just(page1Result));
+
+		when(mockSession.sendRequest(eq(McpSchema.METHOD_ROOTS_LIST), eq(new McpSchema.PaginatedRequest("")),
+				any(TypeRef.class)))
+			.thenReturn(Mono.just(page2Result));
+
+		StepVerifier.create(exchange.listRoots()).assertNext(result -> {
+			assertThat(result.roots()).extracting(McpSchema.Root::uri).containsExactly("file:///home/user/project1");
+			assertThat(result.nextCursor()).isNull();
+		}).verifyComplete();
+
+		verify(mockSession, times(1)).sendRequest(eq(McpSchema.METHOD_ROOTS_LIST),
+				any(McpSchema.PaginatedRequest.class), any(TypeRef.class));
+	}
+
 	@Test
 	void testListRootsWithSpecificCursor() {