Properly propagate errors in NetworkTransport receive stream

Changes AsyncStream to AsyncThrowingStream to ensure network errors are correctly propagated to callers. Updates receive() to handle errors from the underlying message stream.

Author: mattt

Sources/MCP/Base/Transports.swift

@@ -180,8 +180,8 @@ public actor StdioTransport: Transport {
         public nonisolated let logger: Logger
 
         private var isConnected = false
-        private let messageStream: AsyncStream<String>
-        private let messageContinuation: AsyncStream<String>.Continuation
+        private let messageStream: AsyncThrowingStream<String, Swift.Error>
+        private let messageContinuation: AsyncThrowingStream<String, Swift.Error>.Continuation
 
         // Track connection state for continuations
         private var connectionContinuationResumed = false
@@ -196,8 +196,8 @@ public actor StdioTransport: Transport {
                 )
 
             // Create message stream
-            var continuation: AsyncStream<String>.Continuation!
-            self.messageStream = AsyncStream { continuation = $0 }
+            var continuation: AsyncThrowingStream<String, Swift.Error>.Continuation!
+            self.messageStream = AsyncThrowingStream { continuation = $0 }
             self.messageContinuation = continuation
         }
 
@@ -330,10 +330,14 @@ public actor StdioTransport: Transport {
         public func receive() -> AsyncThrowingStream<String, Swift.Error> {
             return AsyncThrowingStream { continuation in
                 Task {
-                    for await message in messageStream {
-                        continuation.yield(message)
+                    do {
+                        for try await message in messageStream {
+                            continuation.yield(message)
+                        }
+                        continuation.finish()
+                    } catch {
+                        continuation.finish(throwing: error)
                     }
-                    continuation.finish()
                 }
             }
         }
@@ -361,6 +365,7 @@ public actor StdioTransport: Transport {
                 } catch {
                     if !Task.isCancelled {
                         logger.error("Receive error: \(error)")
+                        messageContinuation.finish(throwing: error)
                     }
                     break
                 }