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Set Mcp-Protocol-Version in client requests after init, and warn when it doesn't match negotiated version (it SHOULD match)

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Olivier Chafik 2025-06-10 14:07:10 +01:00
commit 84971c83ea
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1 changed files with 243 additions and 19 deletions
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55
src/server/streamableHttp.ts
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@ -1,6 +1,6 @@
import { IncomingMessage, ServerResponse } from "node:http";
import { Transport } from "../shared/transport.js";
import { isInitializeRequest, isJSONRPCError, isJSONRPCRequest, isJSONRPCResponse, JSONRPCMessage, JSONRPCMessageSchema, RequestId } from "../types.js";
import { isInitializeRequest, isJSONRPCError, isJSONRPCRequest, isJSONRPCResponse, JSONRPCMessage, JSONRPCMessageSchema, RequestId, SUPPORTED_PROTOCOL_VERSIONS } from "../types.js";
import getRawBody from "raw-body";
import contentType from "content-type";
import { randomUUID } from "node:crypto";
@ -110,7 +110,8 @@ export class StreamableHTTPServerTransport implements Transport {
private _eventStore?: EventStore;
private _onsessioninitialized?: (sessionId: string) => void;
sessionId?: string | undefined;
sessionId?: string;
protocolVersion?: string;
onclose?: () => void;
onerror?: (error: Error) => void;
onmessage?: (message: JSONRPCMessage, extra?: { authInfo?: AuthInfo }) => void;
@ -172,6 +173,9 @@ export class StreamableHTTPServerTransport implements Transport {
if (!this.validateSession(req, res)) {
return;
}
if (!this.validateProtocolVersion(req, res)) {
return;
}
// Handle resumability: check for Last-Event-ID header
if (this._eventStore) {
const lastEventId = req.headers['last-event-id'] as string | undefined;
@ -378,11 +382,17 @@ export class StreamableHTTPServerTransport implements Transport {
}
}
// If an Mcp-Session-Id is returned by the server during initialization,
// clients using the Streamable HTTP transport MUST include it
// in the Mcp-Session-Id header on all of their subsequent HTTP requests.
if (!isInitializationRequest && !this.validateSession(req, res)) {
return;
if (!isInitializationRequest) {
// If an Mcp-Session-Id is returned by the server during initialization,
// clients using the Streamable HTTP transport MUST include it
// in the Mcp-Session-Id header on all of their subsequent HTTP requests.
if (!this.validateSession(req, res)) {
return;
}
// Mcp-Protocol-Version header is required for all requests after initialization.
if (!this.validateProtocolVersion(req, res)) {
return;
}
}
@ -457,6 +467,9 @@ export class StreamableHTTPServerTransport implements Transport {
if (!this.validateSession(req, res)) {
return;
}
if (!this.validateProtocolVersion(req, res)) {
return;
}
await this.close();
res.writeHead(200).end();
}
@ -524,6 +537,34 @@ export class StreamableHTTPServerTransport implements Transport {
return true;
}
private validateProtocolVersion(req: IncomingMessage, res: ServerResponse): boolean {
let protocolVersion = req.headers["mcp-protocol-version"];
if (Array.isArray(protocolVersion)) {
protocolVersion = protocolVersion[protocolVersion.length - 1];
}
if (protocolVersion == null || protocolVersion === undefined) {
// If the protocol version is not set, we assume the client supports the implicit protocol version
return true;
}
protocolVersion = String(protocolVersion).trim();
if (this.protocolVersion !== undefined && this.protocolVersion !== protocolVersion) {
console.warn(`Request has header with protocol version ${protocolVersion}, but version previously negotiated is ${this.protocolVersion}.`);
}
if (!SUPPORTED_PROTOCOL_VERSIONS.includes(protocolVersion)) {
res.writeHead(400).end(JSON.stringify({
jsonrpc: "2.0",
error: {
code: -32000,
message: 'Bad Request: Unsupported protocol version'
},
id: null
}));
return false;
}
return true;
}
async close(): Promise<void> {
// Close all SSE connections