examples: web-standard twin of the bearer-auth story (#2424)

examples/bearer-auth-web/README.md

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+# bearer-auth-web
+
+The web-standard twin of [`bearer-auth`](../bearer-auth/): the same minimal
+Resource-Server-only story built entirely from `@modelcontextprotocol/server`
+exports, with no framework.
+
+Host and origin validation plus `requireBearerAuth` gate `createMcpHandler`,
+composed as one `fetch(request)` handler. On Cloudflare Workers, Deno, or Bun
+that handler is the whole server; `toNodeHandler` bridges it onto `node:http`
+so the story runs in this repo's example matrix.
+
+No Authorization Server and no discovery documents here, matching the sibling
+— see [`oauth`](../oauth/) for the full RS + AS dance.
+
+```sh
+pnpm --filter @mcp-examples/bearer-auth-web server -- --http --port 3000
+pnpm --filter @mcp-examples/bearer-auth-web client -- --http http://127.0.0.1:3000/mcp
+```

examples/bearer-auth-web/client.ts

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+/**
+ * Asserts a bare request is `401` with a `WWW-Authenticate` challenge (parsed
+ * with the SDK's `extractWWWAuthenticateParams`), and that a request with
+ * `Authorization: Bearer demo-token` reaches the `whoami` tool with the
+ * verified `authInfo`.
+ */
+import { check, parseExampleArgs } from '@mcp-examples/shared';
+import { Client, extractWWWAuthenticateParams, StreamableHTTPClientTransport } from '@modelcontextprotocol/client';
+
+const { url, era } = parseExampleArgs();
+
+// Unauthenticated → 401 + WWW-Authenticate.
+const unauth = await fetch(url, {
+    method: 'POST',
+    headers: { 'content-type': 'application/json', accept: 'application/json, text/event-stream' },
+    body: JSON.stringify({ jsonrpc: '2.0', id: 1, method: 'ping' })
+});
+check.equal(unauth.status, 401);
+check.equal(extractWWWAuthenticateParams(unauth).error, 'invalid_token');
+
+// Authenticated → 200 and the tool sees the authInfo. Bearer auth is
+// HTTP-layer and era-agnostic; the client honours `--legacy` via `era`.
+const client = new Client(
+    { name: 'bearer-auth-web-example-client', version: '1.0.0' },
+    { versionNegotiation: { mode: era === 'modern' ? 'auto' : 'legacy' } }
+);
+await client.connect(new StreamableHTTPClientTransport(new URL(url), { authProvider: { token: async () => 'demo-token' } }));
+
+const result = await client.callTool({ name: 'whoami', arguments: {} });
+check.equal(result.content?.[0]?.type === 'text' ? result.content[0].text : '', 'client=demo-client');
+
+await client.close();

examples/bearer-auth-web/package.json

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+{
+    "name": "@mcp-examples/bearer-auth-web",
+    "private": true,
+    "type": "module",
+    "scripts": {
+        "server": "tsx server.ts",
+        "client": "tsx client.ts"
+    },
+    "dependencies": {
+        "@mcp-examples/shared": "workspace:*",
+        "@modelcontextprotocol/client": "workspace:*",
+        "@modelcontextprotocol/node": "workspace:*",
+        "@modelcontextprotocol/server": "workspace:*",
+        "zod": "catalog:runtimeShared"
+    },
+    "devDependencies": {
+        "tsx": "catalog:devTools"
+    },
+    "example": {
+        "transports": [
+            "http"
+        ],
+        "era": "dual",
+        "path": "/mcp",
+        "//": "The web-standard twin of bearer-auth: requireBearerAuth from @modelcontextprotocol/server composed as one fetch handler (toNodeHandler bridges for the matrix); era-agnostic like its sibling."
+    }
+}

examples/bearer-auth-web/server.ts

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+/**
+ * The web-standard counterpart of `examples/bearer-auth`: the same
+ * Resource-Server-only auth built entirely from `@modelcontextprotocol/server`
+ * exports — `requireBearerAuth` gating the MCP handler, behind the same
+ * DNS-rebinding guards the Express sibling gets from `createMcpExpressApp` —
+ * composed as one `fetch(request)` handler.
+ *
+ * On Cloudflare Workers, Deno, or Bun that handler is the whole server
+ * (`export default { fetch: fetchHandler }`); on Node, `toNodeHandler` bridges
+ * it onto `node:http`. HTTP-only by definition.
+ */
+import { createServer } from 'node:http';
+
+import { parseExampleArgs } from '@mcp-examples/shared';
+import { toNodeHandler } from '@modelcontextprotocol/node';
+import type { AuthInfo, McpServerFactory, OAuthTokenVerifier } from '@modelcontextprotocol/server';
+import {
+    createMcpHandler,
+    hostHeaderValidationResponse,
+    localhostAllowedHostnames,
+    localhostAllowedOrigins,
+    McpServer,
+    OAuthError,
+    OAuthErrorCode,
+    originValidationResponse,
+    requireBearerAuth
+} from '@modelcontextprotocol/server';
+import * as z from 'zod/v4';
+
+const buildServer: McpServerFactory = ctx => {
+    const server = new McpServer({ name: 'bearer-auth-web-example', version: '1.0.0' });
+    server.registerTool('whoami', { description: 'Returns the authenticated subject.', inputSchema: z.object({}) }, async () => ({
+        content: [{ type: 'text', text: `client=${ctx.authInfo?.clientId ?? 'anon'}` }]
+    }));
+    return server;
+};
+
+const { port } = parseExampleArgs();
+
+// Replace with JWT verification, RFC 7662 introspection, etc.
+const staticTokenVerifier: OAuthTokenVerifier = {
+    async verifyAccessToken(token): Promise<AuthInfo> {
+        if (token !== 'demo-token') {
+            throw new OAuthError(OAuthErrorCode.InvalidToken, 'unknown token');
+        }
+        return { token, clientId: 'demo-client', scopes: ['mcp'], expiresAt: Math.floor(Date.now() / 1000) + 3600 };
+    }
+};
+
+const gate = requireBearerAuth({ verifier: staticTokenVerifier, requiredScopes: ['mcp'] });
+const handler = createMcpHandler(buildServer);
+
+async function fetchHandler(request: Request): Promise<Response> {
+    const rejected =
+        hostHeaderValidationResponse(request, localhostAllowedHostnames()) ?? originValidationResponse(request, localhostAllowedOrigins());
+    if (rejected) {
+        return rejected;
+    }
+    const auth = await gate(request);
+    if (auth instanceof Response) {
+        return auth;
+    }
+    return handler.fetch(request, { authInfo: auth });
+}
+
+// On a web-standard runtime the composition above is the whole server;
+// `toNodeHandler` accepts any `{ fetch }` shape and bridges it onto node:http.
+createServer(toNodeHandler({ fetch: fetchHandler })).listen(port, () => {
+    console.error(`[server] listening on http://127.0.0.1:${port}/mcp`);
+});