Streamable HTTP endless retry loop

[Shapur1234]

Bug description

When the McpClient with WebClientStreamableHttpTransport is provided a url that does not point to a valid streamable http mcp endpoint, exception io.modelcontextprotocol.spec.McpTransportSessionNotFoundException: Session [missing_session_id] not found on the server is thrown during client initialization, which then leads to initialization being retired... why causes initialization to get stuck in an endless retry loop.

To reproduce:

McpClient.async(
    WebClientStreamableHttpTransport
                                .builder(webClientBuilder)
                                .endpoint("Url to not a streamable http endpoint")
                                .build()
).build().initialize()

[ENE033]

I have same problem:

        WebClient.Builder webClientBuilder = WebClient.builder()
                .baseUrl("http://localhost:8080");

        WebClientStreamableHttpTransport transport = WebClientStreamableHttpTransport
                .builder(webClientBuilder)
                .build();

//        McpClientTransport transport = new WebFluxSseClientTransport(webClientBuilder, new ObjectMapper());

        this.mcpClient = McpClient.async(transport)
                .requestTimeout(Duration.ofSeconds(10))
                .capabilities(McpSchema.ClientCapabilities.builder()
                        .roots(true)
                        .build())
                .loggingConsumer(loggingMessageNotification -> Mono.fromRunnable(() -> logger.info("log: {}", loggingMessageNotification.data())))
                .toolsChangeConsumer(tools -> Mono.fromRunnable(() -> logger.info("Tools updated: {}", tools)))
                .resourcesChangeConsumer(resources -> Mono.fromRunnable(() -> logger.info("Resources updated: {}", resources)))
                .promptsChangeConsumer(prompts -> Mono.fromRunnable(() -> logger.info("Prompts updated: {}", prompts)))
                .build();

when I call

public Mono<Void> initialize() {
    return mcpClient.initialize().then();
}

I got a endless loop

[johnyannj]

HttpClientStreamableHttpTransport +1

when return 400 or 404

will produce McpTransportSessionNotFoundException

and

io.modelcontextprotocol.client.LifecycleInitializer#handleException

will loop