fix: propagate CancellationException instead of logging as error (#706)

fixes #242

## How Has This Been Tested?
new and existing tests pass

## Breaking Changes
none 

## Types of changes
- [x] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update

## Checklist
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [x] My code follows the repository's style guidelines
- [x] New and existing tests pass locally
- [x] I have added appropriate error handling
- [x] I have added or updated documentation as needed

kotlin-sdk-client/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/client/SseClientTransport.kt

@@ -24,11 +24,12 @@ import kotlinx.coroutines.CoroutineName
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.ExperimentalCoroutinesApi
 import kotlinx.coroutines.Job
+import kotlinx.coroutines.NonCancellable
 import kotlinx.coroutines.SupervisorJob
 import kotlinx.coroutines.cancel
-import kotlinx.coroutines.cancelAndJoin
 import kotlinx.coroutines.ensureActive
 import kotlinx.coroutines.launch
+import kotlinx.coroutines.withContext
 import kotlinx.serialization.SerializationException
 import kotlin.concurrent.atomics.ExperimentalAtomicApi
 import kotlin.time.Duration
@@ -171,13 +172,15 @@ public class SseClientTransport(
     }
 
     override suspend fun closeResources() {
-        job?.cancelAndJoin()
-        try {
-            if (::session.isInitialized) session.cancel()
-            if (::scope.isInitialized) scope.cancel()
-            endpoint.cancel()
-        } catch (e: Throwable) {
-            _onError(e)
+        withContext(NonCancellable) {
+            job?.cancel()
+            try {
+                if (::session.isInitialized) session.cancel()
+                if (::scope.isInitialized) scope.cancel()
+                endpoint.cancel()
+            } catch (e: Throwable) {
+                _onError(e)
+            }
         }
     }
 }

kotlin-sdk-client/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/client/StdioClientTransport.kt

@@ -21,6 +21,7 @@ import kotlinx.coroutines.CoroutineName
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.Job
+import kotlinx.coroutines.NonCancellable
 import kotlinx.coroutines.SupervisorJob
 import kotlinx.coroutines.cancel
 import kotlinx.coroutines.cancelAndJoin
@@ -31,6 +32,7 @@ import kotlinx.coroutines.channels.consumeEach
 import kotlinx.coroutines.flow.channelFlow
 import kotlinx.coroutines.isActive
 import kotlinx.coroutines.launch
+import kotlinx.coroutines.withContext
 import kotlinx.coroutines.yield
 import kotlinx.io.Buffer
 import kotlinx.io.IOException
@@ -241,8 +243,10 @@ public class StdioClientTransport @JvmOverloads public constructor(
     }
 
     override suspend fun closeResources() {
-        scope.stopProcessing("Closed")
-        scope.coroutineContext[Job]?.join() // Wait for all coroutines to complete
+        withContext(NonCancellable) {
+            scope.stopProcessing("Closed")
+            scope.coroutineContext[Job]?.join() // Wait for all coroutines to complete
+        }
     }
 
     private fun sendOutboundMessage(message: JSONRPCMessage, sink: Sink, mainScope: CoroutineScope) {
@@ -264,6 +268,8 @@ public class StdioClientTransport @JvmOverloads public constructor(
     private suspend fun handleJSONRPCMessage(msg: JSONRPCMessage) {
         try {
             _onMessage.invoke(msg)
+        } catch (e: CancellationException) {
+            throw e
         } catch (e: Throwable) {
             logger.error(e) { "Error processing message." }
             runCatching { _onError.invoke(e) }