Stabilize flaky test: McpCompletionTests.testCompletionErrorOnMissingContext

McpCompletionTests.testCompletionErrorOnMissingContext is sometimes failing and recovers after simple build restart.
**Error:** Session not found: <sessionId>

Likely causes:
The server removes the session when SSE connection closes, but the client still has pending requests in flight. This is a race condition between:

• SSE connection closing → server removes session
• Client sending next request → "Session not found"

2026-02-09 23:31:09 [HttpClient-1-Worker-0] WARN  i.m.c.t.HttpClientSseClientTransport - SSE stream observed an error
java.io.IOException: chunked transfer encoding, state: READING_LENGTH
	at java.net.http/jdk.internal.net.http.common.Utils.wrapWithExtraDetail(Utils.java:375)
	at java.net.http/jdk.internal.net.http.Http1Response$BodyReader.onReadError(Http1Response.java:660)
	at java.net.http/jdk.internal.net.http.Http1AsyncReceiver.checkForErrors(Http1AsyncReceiver.java:302)
	at java.net.http/jdk.internal.net.http.Http1AsyncReceiver.flush(Http1AsyncReceiver.java:268)
	at java.net.http/jdk.internal.net.http.common.SequentialScheduler$LockingRestartableTask.run(SequentialScheduler.java:205)
	at java.net.http/jdk.internal.net.http.common.SequentialScheduler$CompleteRestartableTask.run(SequentialScheduler.java:149)
	at java.net.http/jdk.internal.net.http.common.SequentialScheduler$SchedulableTask.run(SequentialScheduler.java:230)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
	at java.base/java.lang.Thread.run(Thread.java:840)
Caused by: java.io.EOFException: EOF reached while reading
	at java.net.http/jdk.internal.net.http.Http1AsyncReceiver$Http1TubeSubscriber.onComplete(Http1AsyncReceiver.java:597)
	at java.net.http/jdk.internal.net.http.SocketTube$InternalReadPublisher$ReadSubscription.signalCompletion(SocketTube.java:648)
	at java.net.http/jdk.internal.net.http.SocketTube$InternalReadPublisher$InternalReadSubscription.read(SocketTube.java:853)
	at java.net.http/jdk.internal.net.http.SocketTube$SocketFlowTask.run(SocketTube.java:181)
	at java.net.http/jdk.internal.net.http.common.SequentialScheduler$SchedulableTask.run(SequentialScheduler.java:230)
	at java.net.http/jdk.internal.net.http.common.SequentialScheduler.runOrSchedule(SequentialScheduler.java:303)
	at java.net.http/jdk.internal.net.http.common.SequentialScheduler.runOrSchedule(SequentialScheduler.java:256)
	at java.net.http/jdk.internal.net.http.SocketTube$InternalReadPublisher$InternalReadSubscription.signalReadable(SocketTube.java:782)
	at java.net.http/jdk.internal.net.http.SocketTube$InternalReadPublisher$ReadEvent.signalEvent(SocketTube.java:965)
	at java.net.http/jdk.internal.net.http.SocketTube$SocketFlowEvent.handle(SocketTube.java:253)
	at java.net.http/jdk.internal.net.http.HttpClientImpl$SelectorManager.handleEvent(HttpClientImpl.java:1402)
	at java.net.http/jdk.internal.net.http.HttpClientImpl$SelectorManager.lambda$run$3(HttpClientImpl.java:1347)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
	at java.net.http/jdk.internal.net.http.HttpClientImpl$SelectorManager.run(HttpClientImpl.java:1347)
2026-02-09 23:31:09 [ForkJoinPool.commonPool-worker-1] ERROR i.m.c.t.HttpClientSseClientTransport - Error sending message: Sending message failed with a non-OK HTTP code: 404 - {"cause":null,"jsonRpcError":null,"localizedMessage":"Session not found: 7a9438d6-5965-456a-99af-26523f108d68","message":"Session not found: 7a9438d6-5965-456a-99af-26523f108d68","stackTrace":

https://github.com/modelcontextprotocol/java-sdk/actions/runs/21845041347/job/63038831474#step:4:15277

Bắt đầu với McpCompletionTests.testCompletionErrorOnMissingContext và nhật ký lỗi liên kết của GitHub Actions, sau đó kiểm tra vòng đời phiên của client/server SSE xung quanh việc đóng kết nối và các yêu cầu đang chờ xử lý. Hoàn thành khi bài kiểm thử vẫn đáng tin cậy qua các bản build và không còn thất bại với lỗi 404 Session not found trong race bị ảnh hưởng.