test(conformance): port auth/pre-registration scenario from v1.x

Forward-ports PR #1545 from v1.x. The SDK already skips DCR when
clientInformation() returns pre-populated credentials; only the
conformance adapter wiring was missing.

- withOAuthRetry: accept optional existingProvider
- everythingClient: register auth/pre-registration handler
- expected-failures: drop now-passing scenario

Author: felixweinberger

test/conformance/expected-failures.yaml

@@ -2,5 +2,4 @@
 # CI exits 0 if only these fail, exits 1 on unexpected failures or stale entries.
 
 client:
-    - auth/pre-registration
     - auth/cross-app-access-complete-flow

test/conformance/src/everythingClient.ts

@@ -15,6 +15,7 @@
 import { Client, ClientCredentialsProvider, PrivateKeyJwtProvider, StreamableHTTPClientTransport } from '@modelcontextprotocol/client';
 import * as z from 'zod/v4';
 
+import { ConformanceOAuthProvider } from './helpers/conformanceOAuthProvider.js';
 import { logger } from './helpers/logger.js';
 import { handle401, withOAuthRetry } from './helpers/withOAuthRetry.js';
 
@@ -42,6 +43,11 @@ const ClientConformanceContextSchema = z.discriminatedUnion('name', [
         name: z.literal('auth/client-credentials-basic'),
         client_id: z.string(),
         client_secret: z.string()
+    }),
+    z.object({
+        name: z.literal('auth/pre-registration'),
+        client_id: z.string(),
+        client_secret: z.string()
     })
 ]);
 
@@ -240,6 +246,43 @@ async function runClientCredentialsBasic(serverUrl: string): Promise<void> {
 
 registerScenario('auth/client-credentials-basic', runClientCredentialsBasic);
 
+// ============================================================================
+// Pre-registration scenario (no dynamic client registration)
+// ============================================================================
+
+async function runPreRegistrationClient(serverUrl: string): Promise<void> {
+    const ctx = parseContext();
+    if (ctx.name !== 'auth/pre-registration') {
+        throw new Error(`Expected pre-registration context, got ${ctx.name}`);
+    }
+
+    // Create a provider pre-populated with registered credentials,
+    // so the SDK skips dynamic client registration.
+    const provider = new ConformanceOAuthProvider('http://localhost:3000/callback', {
+        client_name: 'conformance-pre-registration',
+        redirect_uris: ['http://localhost:3000/callback']
+    });
+    provider.saveClientInformation({
+        client_id: ctx.client_id,
+        client_secret: ctx.client_secret,
+        redirect_uris: ['http://localhost:3000/callback']
+    });
+
+    const oauthFetch = withOAuthRetry('conformance-pre-registration', new URL(serverUrl), handle401, undefined, provider)(fetch);
+
+    const client = new Client({ name: 'conformance-pre-registration', version: '1.0.0' }, { capabilities: {} });
+    const transport = new StreamableHTTPClientTransport(new URL(serverUrl), {
+        fetch: oauthFetch
+    });
+
+    await client.connect(transport);
+    await client.listTools();
+    await client.callTool({ name: 'test-tool', arguments: {} });
+    await transport.close();
+}
+
+registerScenario('auth/pre-registration', runPreRegistrationClient);
+
 // ============================================================================
 // Elicitation defaults scenario
 // ============================================================================

test/conformance/src/helpers/withOAuthRetry.ts

@@ -55,16 +55,19 @@ export const withOAuthRetry = (
     clientName: string,
     baseUrl?: string | URL,
     handle401Fn: typeof handle401 = handle401,
-    clientMetadataUrl?: string
+    clientMetadataUrl?: string,
+    existingProvider?: ConformanceOAuthProvider
 ): Middleware => {
-    const provider = new ConformanceOAuthProvider(
-        'http://localhost:3000/callback',
-        {
-            client_name: clientName,
-            redirect_uris: ['http://localhost:3000/callback']
-        },
-        clientMetadataUrl
-    );
+    const provider =
+        existingProvider ??
+        new ConformanceOAuthProvider(
+            'http://localhost:3000/callback',
+            {
+                client_name: clientName,
+                redirect_uris: ['http://localhost:3000/callback']
+            },
+            clientMetadataUrl
+        );
     return (next: FetchLike) => {
         return async (input: string | URL, init?: RequestInit): Promise<Response> => {
             const makeRequest = async (): Promise<Response> => {