server.servlet.context-path not properly factoring into SSE MCP server path

[jorge-trujillo]

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Bug description
When using the MCP Server Starter, one of the supported protocols is SSE. If you are setting a custom context path using the property server.servlet.context-path, the relevant paths for MCP will change, but the path given when you look at the /sse endpoint will not. Therefore MCP clients will break. This was tested with Cursor MCP.

Environment
JVM: OpenJDK Runtime Environment Temurin-21.0.5+11 (build 21.0.5+11-LTS)
Spring AI version: "1.0.0-M6" (Used BOM)

Application was written in Kotlin but that shouldn't be relevant here.

Steps to reproduce

• Create any MCP server application that uses SSE
• Connect it to an MCP client, should work fine (I used /sse as the path in Cursor)
• Set the server.servlet.context-path, say to "/v1"
• Attempt to update your setup in your MCP client, it will always fail

If you look at the output of the /sse endpoint, the reason is that the path provided by the endpoint is incorrect. It will match what you set in spring.ai.mcp.server.sse-message-endpoint but it will not include the context path.

Expected behavior
In my opinion, this would be fixed if the endpoint that is returned in the call to the /sse endpoint also prepended the context path.

Minimal Complete Reproducible example
Please provide a failing test or a minimal complete verifiable example that reproduces the issue.
Bug reports that are reproducible will take priority in resolution over reports that are not reproducible.

[mlmw92]

Same problem

[rod2k2]

same problem, how to solve it if have to add server.servelt.context-path ?

[HollisChen1]

I think there should be an issue of org.springframework.ai.mcp.server.autoconfigure.McpWebMvcServerAutoConfiguration(the same as McpWebFluxServerAutoConfiguration)
by adding bean in our config class like below, using another constructor of WebMvcSseServerTransportProvider, make sure your servlet context path was added to spring.ai.mcp.server.base-url

@Bean
public WebMvcSseServerTransportProvider webMvcSseServerTransportProvider(
        ObjectProvider<ObjectMapper> objectMapperProvider, McpServerProperties serverProperties) {
    ObjectMapper objectMapper = objectMapperProvider.getIfAvailable(ObjectMapper::new);
    return new WebMvcSseServerTransportProvider(objectMapper,serverProperties.getBaseUrl(), serverProperties.getSseMessageEndpoint(), serverProperties.getSseEndpoint());
}


@Bean
public RouterFunction<ServerResponse> mvcMcpRouterFunction(WebMvcSseServerTransportProvider transportProvider) {
    return transportProvider.getRouterFunction();
}

[GregoireW]

@HollisChen1 you mention:

make sure your servlet context path was added to spring.ai.mcp.server.base-url

But setting:

spring:
  ai:
    mcp:
      server:
        base-url: /myapp/
        sse-endpoint: /sse
        sse-message-endpoint: /mcp/message

on spring-ai 1.0.0-M7, I get on curl http://localhost:8080/sse a response containing: data:/mcp/message?sessio... so the base-url is not taken either I think

[GregoireW]

I will answer myself: those beans are initialized with default configuration (base url and sseEndpoint (the /sse ) ) a small change to add the 2 others parameter should fix the issue

spring-ai/auto-configurations/mcp/spring-ai-autoconfigure-mcp-server/src/main/java/org/springframework/ai/mcp/server/autoconfigure/McpWebMvcServerAutoConfiguration.java

Line 75 in 687dea5

return new WebMvcSseServerTransportProvider(objectMapper, serverProperties.getSseMessageEndpoint());

spring-ai/auto-configurations/mcp/spring-ai-autoconfigure-mcp-server/src/main/java/org/springframework/ai/mcp/server/autoconfigure/McpWebFluxServerAutoConfiguration.java

Line 80 in 687dea5

return new WebFluxSseServerTransportProvider(objectMapper, serverProperties.getSseMessageEndpoint());

[GregoireW]

looking for this issue, I found a related one: #2841