Fix deserialization in read buffer

kotlin-sdk-core/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/shared/ReadBuffer.kt

@@ -1,5 +1,6 @@
 package io.modelcontextprotocol.kotlin.sdk.shared
 
+import io.github.oshai.kotlinlogging.KotlinLogging
 import io.modelcontextprotocol.kotlin.sdk.JSONRPCMessage
 import kotlinx.io.Buffer
 import kotlinx.io.indexOf
@@ -9,6 +10,9 @@ import kotlinx.io.readString
  * Buffers a continuous stdio stream into discrete JSON-RPC messages.
  */
 public class ReadBuffer {
+
+    private val logger = KotlinLogging.logger { }
+
     private val buffer: Buffer = Buffer()
 
     public fun append(chunk: ByteArray) {
@@ -37,7 +41,13 @@ public class ReadBuffer {
                 string
             }
         }
-        return deserializeMessage(line)
+        try {
+            return deserializeMessage(line)
+        } catch (e: Exception) {
+            logger.error(e) { "Failed to deserialize message from line: $line\nSkipping..." }
+        }
+
+        return null
     }
 
     public fun clear() {

kotlin-sdk-test/src/jvmTest/kotlin/io/modelcontextprotocol/kotlin/sdk/client/StdioClientTransportTest.kt

@@ -45,4 +45,24 @@ class StdioClientTransportTest : BaseTransportTest() {
         process.waitFor()
         process.destroy()
     }
+
+    @Test
+    fun `should ignore first output messages`() = runTest {
+        val processBuilder = ProcessBuilder("/usr/bin/tee")
+        val process = processBuilder.start()
+        process.outputStream.write("Stdio server started".toByteArray())
+
+        val input = process.inputStream.asSource().buffered()
+        val output = process.outputStream.asSink().buffered()
+
+        val client = StdioClientTransport(
+            input = input,
+            output = output,
+        )
+
+        testClientRead(client)
+
+        process.waitFor()
+        process.destroy()
+    }
 }