diff --git a/kotlin-sdk-client/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/client/StreamableHttpClientTransport.kt b/kotlin-sdk-client/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/client/StreamableHttpClientTransport.kt index a63c1d2..6df352a 100644 --- a/kotlin-sdk-client/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/client/StreamableHttpClientTransport.kt +++ b/kotlin-sdk-client/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/client/StreamableHttpClientTransport.kt @@ -43,6 +43,10 @@ import kotlinx.coroutines.cancelAndJoin import kotlinx.coroutines.delay import kotlinx.coroutines.isActive import kotlinx.coroutines.launch +import kotlinx.serialization.json.JsonObject +import kotlinx.serialization.json.JsonPrimitive +import kotlin.io.encoding.Base64 +import kotlin.io.encoding.ExperimentalEncodingApi import kotlin.math.pow import kotlin.time.Duration import kotlin.time.Duration.Companion.milliseconds @@ -51,6 +55,10 @@ import kotlin.time.Duration.Companion.seconds private const val MCP_SESSION_ID_HEADER = "mcp-session-id" private const val MCP_PROTOCOL_VERSION_HEADER = "mcp-protocol-version" private const val MCP_RESUMPTION_TOKEN_HEADER = "Last-Event-ID" +private const val MCP_METHOD_HEADER = "Mcp-Method" +private const val MCP_NAME_HEADER = "Mcp-Name" +private const val MCP_BASE64_PREFIX = "=?base64?" +private const val MCP_BASE64_SUFFIX = "?=" /** * Default maximum size, in characters, of a single inline SSE event assembled from a POST response. @@ -167,6 +175,7 @@ public class StreamableHttpClientTransport( val jsonBody = McpJson.encodeToString(message) val response = client.post(url) { applyCommonHeaders(this) + applyStandardPostHeaders(this, message) headers.append(HttpHeaders.Accept, "${ContentType.Application.Json}, ${ContentType.Text.EventStream}") contentType(ContentType.Application.Json) setBody(jsonBody) @@ -390,6 +399,36 @@ public class StreamableHttpClientTransport( } } + private fun applyStandardPostHeaders(builder: HttpRequestBuilder, message: JSONRPCMessage) { + val (method, params) = when (message) { + is JSONRPCRequest -> message.method to message.params + is JSONRPCNotification -> message.method to message.params + else -> return + } + + builder.headers { + append(MCP_METHOD_HEADER, method) + + val paramsObject = params as? JsonObject ?: return@headers + val mcpName = paramsObject.stringValue("name") ?: paramsObject.stringValue("uri") + mcpName?.let { append(MCP_NAME_HEADER, it.encodeMcpHeaderValue()) } + } + } + + private fun JsonObject.stringValue(key: String): String? = + (get(key) as? JsonPrimitive)?.takeIf { it.isString }?.content + + @OptIn(ExperimentalEncodingApi::class) + private fun String.encodeMcpHeaderValue(): String { + val containsUnsafeCharacters = any { it != '\t' && it.code !in 0x20..0x7e } + val hasEdgeWhitespace = firstOrNull()?.isWhitespace() == true || lastOrNull()?.isWhitespace() == true + val matchesBase64Sentinel = startsWith(MCP_BASE64_PREFIX) && endsWith(MCP_BASE64_SUFFIX) + + if (!containsUnsafeCharacters && !hasEdgeWhitespace && !matchesBase64Sentinel) return this + + return "$MCP_BASE64_PREFIX${Base64.Default.encode(encodeToByteArray())}$MCP_BASE64_SUFFIX" + } + private suspend fun collectSse( session: ClientSSESession, replayMessageId: RequestId?, diff --git a/kotlin-sdk-client/src/commonTest/kotlin/io/modelcontextprotocol/kotlin/sdk/client/streamable/http/StreamableHttpClientTransportTest.kt b/kotlin-sdk-client/src/commonTest/kotlin/io/modelcontextprotocol/kotlin/sdk/client/streamable/http/StreamableHttpClientTransportTest.kt index ef55867..d9aaf7a 100644 --- a/kotlin-sdk-client/src/commonTest/kotlin/io/modelcontextprotocol/kotlin/sdk/client/streamable/http/StreamableHttpClientTransportTest.kt +++ b/kotlin-sdk-client/src/commonTest/kotlin/io/modelcontextprotocol/kotlin/sdk/client/streamable/http/StreamableHttpClientTransportTest.kt @@ -246,6 +246,100 @@ class StreamableHttpClientTransportTest { transport.close() } + @Test + fun `should send MCP method and name headers from name`() = runTest { + val transport = createTransport { request -> + assertEquals("tools/call", request.headers["Mcp-Method"]) + assertEquals("read_file", request.headers["Mcp-Name"]) + respond(content = "", status = HttpStatusCode.Accepted) + } + + transport.start() + transport.send( + JSONRPCRequest( + id = "test-id", + method = "tools/call", + params = buildJsonObject { + put("name", JsonPrimitive("read_file")) + put("arguments", buildJsonObject { put("path", JsonPrimitive("README.md")) }) + }, + ), + ) + transport.close() + } + + @Test + fun `should send MCP name header from URI`() = runTest { + val transport = createTransport { request -> + assertEquals("resources/read", request.headers["Mcp-Method"]) + assertEquals("file:///README.md", request.headers["Mcp-Name"]) + respond(content = "", status = HttpStatusCode.Accepted) + } + + transport.start() + transport.send( + JSONRPCRequest( + id = "test-id", + method = "resources/read", + params = buildJsonObject { put("uri", JsonPrimitive("file:///README.md")) }, + ), + ) + transport.close() + } + + @Test + fun `should encode MCP name header values when required`() = runTest { + val cases = listOf( + "Hello, 世界" to "=?base64?SGVsbG8sIOS4lueVjA==?=", + " padded " to "=?base64?IHBhZGRlZCA=?=", + "line1\nline2" to "=?base64?bGluZTEKbGluZTI=?=", + "=?base64?literal?=" to "=?base64?PT9iYXNlNjQ/bGl0ZXJhbD89?=", + ) + + cases.forEachIndexed { index, (name, expectedHeader) -> + val transport = createTransport { request -> + assertEquals(expectedHeader, request.headers["Mcp-Name"]) + respond(content = "", status = HttpStatusCode.Accepted) + } + + transport.start() + transport.send( + JSONRPCRequest( + id = "test-id-$index", + method = "tools/call", + params = buildJsonObject { put("name", JsonPrimitive(name)) }, + ), + ) + transport.close() + } + } + + @Test + fun `should send MCP method header for notifications`() = runTest { + val transport = createTransport { request -> + assertEquals("notifications/tools/list_changed", request.headers["Mcp-Method"]) + assertNull(request.headers["Mcp-Name"]) + respond(content = "", status = HttpStatusCode.Accepted) + } + + transport.start() + transport.send(JSONRPCNotification(method = "notifications/tools/list_changed")) + transport.close() + } + + @Test + fun `should omit MCP standard headers for responses`() = runTest { + val transport = createTransport { request -> + assertNull(request.headers["Mcp-Method"]) + assertNull(request.headers["Mcp-Name"]) + respond(content = "", status = HttpStatusCode.Accepted) + } + + transport.start() + transport.send(JSONRPCResponse(id = RequestId.StringId("test-id"))) + transport.close() + } + // Engine doesn't support SSECapability: https://youtrack.jetbrains.com/issue/KTOR-8177/MockEngine-Add-SSE-support @Ignore @Test