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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Non initialized McpServerSession hangs and timesout instead of providing helpful error message","articleBody":"This issue is closely related to #274 and could be considered as a follow up to that, but I decided to split it for convenience and readability.\n\nCalling `McpServerSession#handle(JSonRPCMessage)` on an instance that hasn't yet received the `notifications/initialized` notification results in a Mono that never completes until a Timeout is raised.\n\nThis happens because the `io.modelcontextprotocol.spec.McpServerSession#exchangeSink` will never emit any value until such notification is received, and thus the `this.exchangeSink.asMono().flatMap(exchange -\u003e handler.handle(exchange, request.params()));` in `McpServerSession#225` will never complete. \n\nPutting the considerations of #274 aside, it is fair for a non intiailized session to not handle messages, but it should do it by quickly returning a `Mono.error` instead of hanging and returning an unspecified timeout. \n\n","author":{"url":"https://github.com/marianogonzalez","@type":"Person","name":"marianogonzalez"},"datePublished":"2025-05-28T16:23:22.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/275/java-sdk/issues/275"}