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fix: bump SDK to 1.26.0, add session management to tools_call scenario (#134)

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* fix: bump SDK to 1.26.0, add session management to tools_call scenario

SDK 1.26.0 made Protocol.connect() throw if already connected to a
transport. The tools_call scenario was calling server.connect(transport)
on every request with the same Server instance, which now throws.

Fixed by adding proper session management: each initialize request
creates a new Server + Transport pair, and subsequent requests are
routed to the correct transport via the mcp-session-id header.

* fix: return 404 for invalid session IDs in tools_call POST handler

The else branch was returning 400 for both missing-session and
invalid/stale-session cases. The MCP spec requires 404 for invalid
session IDs and 400 only for non-initialization requests without
any session ID.

* refactor: keep tools_call stateless, create fresh server per request

Instead of adding session management, simply create a new Server
instance per request. This preserves the original stateless design
while fixing the SDK 1.26.0 Protocol.connect() restriction.
This commit is contained in:
Paul Carleton 2026-02-05 15:43:21 +00:00 • committed by GitHub
commit 22196ca809
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3 changed files with 46 additions and 26 deletions
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60
package-lock.json generated
View file

@ -9,7 +9,7 @@
"version": "0.1.12", "version": "0.1.12",
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"eventsource-parser": "^3.0.6", "eventsource-parser": "^3.0.6",
"express": "^5.1.0", "express": "^5.1.0",
@ -752,9 +752,9 @@
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@ -855,12 +855,12 @@
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@ -868,14 +868,15 @@
"cross-spawn": "^7.0.5", "cross-spawn": "^7.0.5",
"eventsource": "^3.0.2", "eventsource": "^3.0.2",
"eventsource-parser": "^3.0.0", "eventsource-parser": "^3.0.0",
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"jose": "^6.1.1", "hono": "^4.11.4",
"jose": "^6.1.3",
"json-schema-typed": "^8.0.2", "json-schema-typed": "^8.0.2",
"pkce-challenge": "^5.0.0", "pkce-challenge": "^5.0.0",
"raw-body": "^3.0.0", "raw-body": "^3.0.0",
"zod": "^3.25 || ^4.0", "zod": "^3.25 || ^4.0",
"zod-to-json-schema": "^3.25.0" "zod-to-json-schema": "^3.25.1"
}, },
"engines": { "engines": {
"node": ">=18" "node": ">=18"
@ -3042,17 +3043,19 @@
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}, },
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"license": "MIT",
"dependencies": { "dependencies": {
"accepts": "^2.0.0", "accepts": "^2.0.0",
"body-parser": "^2.2.0", "body-parser": "^2.2.1",
"content-disposition": "^1.0.0", "content-disposition": "^1.0.0",
"content-type": "^1.0.5", "content-type": "^1.0.5",
"cookie": "^0.7.1", "cookie": "^0.7.1",
"cookie-signature": "^1.2.1", "cookie-signature": "^1.2.1",
"debug": "^4.4.0", "debug": "^4.4.0",
"depd": "^2.0.0",
"encodeurl": "^2.0.0", "encodeurl": "^2.0.0",
"escape-html": "^1.0.3", "escape-html": "^1.0.3",
"etag": "^1.8.1", "etag": "^1.8.1",
@ -3083,10 +3086,13 @@
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"dependencies": {
"ip-address": "10.0.1"
},
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}, },
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@ -3556,9 +3570,9 @@
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2
package.json
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@ -45,7 +45,7 @@
"vitest": "^4.0.16" "vitest": "^4.0.16"
}, },
"dependencies": { "dependencies": {
"@modelcontextprotocol/sdk": "^1.25.2", "@modelcontextprotocol/sdk": "^1.26.0",
"commander": "^14.0.2", "commander": "^14.0.2",
"eventsource-parser": "^3.0.6", "eventsource-parser": "^3.0.6",
"express": "^5.1.0", "express": "^5.1.0",

10
src/scenarios/client/tools_call.ts
View file

@ -9,7 +9,7 @@ import express, { Request, Response } from 'express';
import { ScenarioUrls } from '../../types'; import { ScenarioUrls } from '../../types';
import { createRequestLogger } from '../request-logger'; import { createRequestLogger } from '../request-logger';
function createServer(checks: ConformanceCheck[]): express.Application { function createMcpServer(checks: ConformanceCheck[]): Server {
const server = new Server( const server = new Server(
{ {
name: 'add-numbers-server', name: 'add-numbers-server',
@ -84,6 +84,10 @@ function createServer(checks: ConformanceCheck[]): express.Application {
throw new Error(`Unknown tool: ${request.params.name}`); throw new Error(`Unknown tool: ${request.params.name}`);
}); });
return server;
}
function createServerApp(checks: ConformanceCheck[]): express.Application {
const app = express(); const app = express();
app.use(express.json()); app.use(express.json());
@ -96,6 +100,8 @@ function createServer(checks: ConformanceCheck[]): express.Application {
); );
app.post('/mcp', async (req: Request, res: Response) => { app.post('/mcp', async (req: Request, res: Response) => {
// Stateless: create a fresh server and transport per request
const server = createMcpServer(checks);
const transport = new StreamableHTTPServerTransport({ const transport = new StreamableHTTPServerTransport({
sessionIdGenerator: undefined sessionIdGenerator: undefined
}); });
@ -116,7 +122,7 @@ export class ToolsCallScenario implements Scenario {
async start(): Promise<ScenarioUrls> { async start(): Promise<ScenarioUrls> {
this.checks = []; this.checks = [];
this.app = createServer(this.checks); this.app = createServerApp(this.checks);
this.httpServer = this.app.listen(0); this.httpServer = this.app.listen(0);
const port = this.httpServer.address().port; const port = this.httpServer.address().port;
return { serverUrl: `http://localhost:${port}/mcp` }; return { serverUrl: `http://localhost:${port}/mcp` };