MCP server Error state [CLOSE_CONNECTION_NOW] reported while processing request (SSE+HTTP)

Bug description
I'm using the following versions:
spring-ai-starter-mcp-server-webmvc:1.0.0 (MPC server)
spring-ai-starter-mcp-client:1.0.0 (MPC client)
The client successfully sends requests and generates responses. However, most of the time, the client does not wait for the server's full response and instead returns prematurely with a default output.
As a result,The connection between the client and server is aborted.

Server throws the following exception:
java.io.EOFException: null at org.apache.tomcat.util.net.NioEndpoint$NioSocketWrapper.fillReadBuffer(NioEndpoint.java:1295) ~[tomcat-embed-core-10.1.41.jar:10.1.41] at org.apache.tomcat.util.net.NioEndpoint$NioSocketWrapper.read(NioEndpoint.java:1183) ~[tomcat-embed-core-10.1.41.jar:10.1.41]

025-08-03T12:15:41.002+10:00 DEBUG 20823 --- [sse-mcp-server-demo] [nio-8080-exec-2] o.apache.coyote.http11.Http11Processor : Error state [CLOSE_CONNECTION_NOW] reported while processing request

2025-08-03T12:15:41.002+10:00 DEBUG 20823 --- [sse-mcp-server-demo] [nio-8080-exec-2] o.apache.coyote.http11.Http11Processor : Socket: [org.apache.tomcat.util.net.NioEndpoint$NioSocketWrapper@7514622d:org.apache.tomcat.util.net.NioChannel@7bd392ff:java.nio.channels.SocketChannel[connected local=/[127.0.0.1:8080](http://127.0.0.1:8080/) remote=/127.0.0.1:65117]], Status in: [OPEN_READ], State out: [CLOSED]

2025-08-03T12:21:46.570+10:00 DEBUG 20823 --- [sse-mcp-server-demo] [ SIGINT handler] java.lang.Runtime : Runtime.exit() called with status: 130

However request header is not massive, printed in server logs
connection: Upgrade, HTTP2-Settings content-length: 69 host: localhost:8080 http2-settings: AAEAAEAAAAIAAAAAAAMAAAAAAAQBAAAAAAUAAEAAAAYABgAA upgrade: h2c user-agent: Java-http-client/21.0.8 accept: text/event-stream cache-control: no-cache content-type: application/json

Environment
Spring AI version: 1.0.0
Java version: 21
Running in local host

Steps to reproduce

1. Start the server.
2. Start the client.
3. Observe the logs — they indicate that the client and server are communicating initially.
4. The server responds to one or two messages, then throws the error mentioned above.
5. The client continues running but returns a default response, stating that no tool is defined.
   Client responds before server returns with
   2025-08-03T12:15:18.586+10:00 INFO 20994 --- [nio-8081-exec-1] mcp_client.ClientController : User message: get all stores
2025-08-03T12:15:18.586+10:00 INFO 20994 --- [nio-8081-exec-1] mcp_client.ClientController : AI response: To get all stores, you can use the following function:
python stores = spring_ai_mcp_client_server1_getAllStores()

Expected behavior
The client should wait for the server's response and return that response, rather than falling back to a default message.

Minimal Complete Reproducible example
This is server application.yaml
spring: application: name: sse-mcp-server-demo ai: mcp: server: enabled: true stdio: false name: sse-mcp-server-demo version: 1.0.0 resource-change-notification: true tool-change-notification: true prompt-change-notification: true sse-endpoint: /api/v1/sse sse-message-endpoint: /api/v1/mcp type: sync capabilities: completion: true prompt: true resource: true tool: true server: error: include-message: always max-http-request-header-size: 640

This is client application.yaml
server: port: 8081 spring: application: ollama: base-url: http://localhost:11434/ timeout: 300s chat: enabled: true options: model: qwen3:8b ai: mcp: client: enabled: true name: spring-ai-mcp-client version: 1.0.0 initialized: true request-timeout: 300s type: sync root-change-notification: true toolcallback.enabled: true sse: connections: server1: url: http://localhost:8080/ sse-endpoint: /api/v1/sse

Client is using chat client
@Bean fun chatClient(builder: ChatClient.Builder, toolCallbackProvider: ToolCallbackProvider): ChatClient { return builder .defaultToolCallbacks(toolCallbackProvider) .defaultAdvisors( MessageChatMemoryAdvisor.builder( MessageWindowChatMemory.builder().build() ) .build() ) .build(); }

Service using chat client to prompt
@Service class AiServiceImpl(val chatClient: ChatClient) : AiService { override fun complete(message: String): String? { return chatClient.prompt() .user(message) .call() .content(); } }

No repository files or tests are named. Start by running the supplied server and client configuration, then trace the ChatClient service call against the MCP SSE and message endpoints to determine why the client completes before the server response; done means the client waits for and returns the server response without the premature fallback or connection error.