fix(mcp): add RFC 9728 PRM, RFC 8707 audience binding, and collab sub-feature gating

Root cause: claude.ai's MCP connector (spec 2025-06-18) requires the resource server
to publish Protected Resource Metadata and return WWW-Authenticate on 401s to bind
the /mcp endpoint to its AS. Without these, it silently shows no tools after OAuth.

- Add /.well-known/oauth-protected-resource (RFC 9728) with addon gating
- Emit WWW-Authenticate: Bearer resource_metadata=... on 401/auth-failure 403s
- Open CORS (origin: *) on both .well-known/* endpoints per RFC 8414/9728
- Accept resource parameter at authorize + token endpoints (RFC 8707)
- Store audience on oauth_tokens; validate on every MCP request
- Refresh tokens inherit audience; add resource_parameter_supported to AS metadata
- DB migration: ADD COLUMN audience TEXT to oauth_tokens
- Gate collab MCP tools/resources by chat/notes/polls sub-features individually
- Invalidate MCP sessions when collab sub-features are toggled in admin
- Update test mocks and MCP.md

server/src/app.ts

@@ -77,6 +77,11 @@ export function createApp(): express.Application {
 
   const shouldForceHttps = process.env.FORCE_HTTPS === 'true';
 
+  // RFC 8414 / RFC 9728: discovery docs are world-readable — open CORS regardless of deployment config
+  app.use(
+    ['/.well-known/oauth-authorization-server', '/.well-known/oauth-protected-resource'],
+    cors({ origin: '*', credentials: false }),
+  );
   app.use(cors({ origin: corsOrigin, credentials: true }));
   app.use(helmet({
     contentSecurityPolicy: {

server/src/db/migrations.ts

@@ -1767,6 +1767,11 @@ function runMigrations(db: Database.Database): void {
         if (!err.message?.includes('no such table') && !err.message?.includes('FOREIGN KEY')) throw err;
       }
     },
+    // Migration: RFC 8707 resource indicators — audience-bind OAuth tokens to /mcp
+    () => {
+      try { db.exec('ALTER TABLE oauth_tokens ADD COLUMN audience TEXT'); }
+      catch (err: any) { if (!err.message?.includes('duplicate column name')) throw err; }
+    },
   ];
 
   if (currentVersion < migrations.length) {

server/src/mcp/index.ts

@@ -11,6 +11,7 @@ import { registerResources } from './resources';
 import { registerTools } from './tools';
 import { McpSession, sessions, revokeUserSessions, revokeUserSessionsForClient } from './sessionManager';
 import { writeAudit, getClientIp } from '../services/auditLog';
+import { getAppUrl } from '../services/oidcService';
 
 export { revokeUserSessions, revokeUserSessionsForClient };
 
@@ -151,6 +152,12 @@ const sessionSweepInterval = setInterval(() => {
 // Prevent the interval from keeping the process alive if nothing else is running
 sessionSweepInterval.unref();
 
+function setAuthChallenge(res: Response, error = 'invalid_token'): void {
+  const base = (getAppUrl() || '').replace(/\/+$/, '');
+  res.set('WWW-Authenticate',
+    `Bearer realm="TREK MCP", resource_metadata="${base}/.well-known/oauth-protected-resource", error="${error}"`);
+}
+
 interface VerifyTokenResult {
   user: User;
   /** null = full access (static token or JWT); string[] = OAuth 2.1 scoped access */
@@ -173,6 +180,11 @@ function verifyToken(authHeader: string | undefined): VerifyTokenResult | null {
   if (token.startsWith('trekoa_')) {
     const result = getUserByAccessToken(token);
     if (!result) return null;
+    // RFC 8707: if the token carries an audience, it must match this resource endpoint
+    if (result.audience !== null) {
+      const expected = `${(getAppUrl() || '').replace(/\/+$/, '')}/mcp`;
+      if (result.audience !== expected) return null;
+    }
     return { user: result.user, scopes: result.scopes, clientId: result.clientId, isStaticToken: false };
   }
 
@@ -211,6 +223,7 @@ export async function mcpHandler(req: Request, res: Response): Promise<void> {
 
   const tokenResult = verifyToken(req.headers['authorization']);
   if (!tokenResult) {
+    setAuthChallenge(res);
     res.status(401).json({ error: 'Access token required' });
     return;
   }
@@ -231,10 +244,12 @@ export async function mcpHandler(req: Request, res: Response): Promise<void> {
       return;
     }
     if (session.userId !== user.id) {
+      setAuthChallenge(res);
       res.status(403).json({ error: 'Session belongs to a different user' });
       return;
     }
     if (session.clientId !== clientId) {
+      setAuthChallenge(res);
       res.status(403).json({ error: 'Session was created with a different OAuth client' });
       return;
     }

server/src/mcp/resources.ts

@@ -13,7 +13,7 @@ import { listCategories } from '../services/categoryService';
 import { listBucketList, listVisitedCountries, getStats as getAtlasStats, listManuallyVisitedRegions } from '../services/atlasService';
 import { getNotifications } from '../services/inAppNotifications';
 import { getActivePlanId, getActivePlan, getPlanData, getEntries as getVacayEntries, getHolidays } from '../services/vacayService';
-import { isAddonEnabled } from '../services/adminService';
+import { isAddonEnabled, getCollabFeatures } from '../services/adminService';
 import { ADDON_IDS } from '../addons';
 import { canAccessJourney, getJourneyFull, listEntries, listJourneys } from '../services/journeyService';
 import { canRead, canReadTrips } from './scopes';
@@ -188,7 +188,8 @@ export function registerResources(server: McpServer, userId: number, scopes: str
   );
 
   // Collab notes for a trip
-  if (isAddonEnabled(ADDON_IDS.COLLAB) && canRead(scopes, 'collab')) server.registerResource(
+  const collabFeatures = isAddonEnabled(ADDON_IDS.COLLAB) ? getCollabFeatures() : null;
+  if (collabFeatures?.notes && canRead(scopes, 'collab')) server.registerResource(
     'trip-collab-notes',
     new ResourceTemplate('trek://trips/{tripId}/collab-notes', { list: undefined }),
     { description: 'Shared collaborative notes for a trip', mimeType: 'application/json' },
@@ -319,8 +320,8 @@ export function registerResources(server: McpServer, userId: number, scopes: str
     );
   }
 
-  // Collab polls & messages (addon-gated)
-  if (isAddonEnabled(ADDON_IDS.COLLAB) && canRead(scopes, 'collab')) {
+  // Collab polls (addon + sub-feature gated)
+  if (collabFeatures?.polls && canRead(scopes, 'collab')) {
     server.registerResource(
       'trip-collab-polls',
       new ResourceTemplate('trek://trips/{tripId}/collab/polls', { list: undefined }),
@@ -332,7 +333,10 @@ export function registerResources(server: McpServer, userId: number, scopes: str
         return jsonContent(uri.href, polls);
       }
     );
+  }
 
+  // Collab messages (addon + sub-feature gated)
+  if (collabFeatures?.chat && canRead(scopes, 'collab')) {
     server.registerResource(
       'trip-collab-messages',
       new ResourceTemplate('trek://trips/{tripId}/collab/messages', { list: undefined }),

server/src/mcp/tools/collab.ts

@@ -7,7 +7,7 @@ import {
   listPolls, createPoll, votePoll, closePoll, deletePoll,
   listMessages, createMessage, deleteMessage, addOrRemoveReaction,
 } from '../../services/collabService';
-import { isAddonEnabled } from '../../services/adminService';
+import { isAddonEnabled, getCollabFeatures } from '../../services/adminService';
 import { ADDON_IDS } from '../../addons';
 import {
   safeBroadcast, TOOL_ANNOTATIONS_WRITE, TOOL_ANNOTATIONS_DELETE,
@@ -22,9 +22,11 @@ export function registerCollabTools(server: McpServer, userId: number, scopes: s
 
   if (!isAddonEnabled(ADDON_IDS.COLLAB)) return;
 
+  const features = getCollabFeatures();
+
   // --- COLLAB NOTES ---
 
-  if (W) server.registerTool(
+  if (features.notes && W) server.registerTool(
     'create_collab_note',
     {
       description: 'Create a shared collaborative note on a trip (visible to all trip members in the Collab tab).',
@@ -47,7 +49,7 @@ export function registerCollabTools(server: McpServer, userId: number, scopes: s
     }
   );
 
-  if (W) server.registerTool(
+  if (features.notes && W) server.registerTool(
     'update_collab_note',
     {
       description: 'Edit an existing collaborative note on a trip.',
@@ -72,7 +74,7 @@ export function registerCollabTools(server: McpServer, userId: number, scopes: s
     }
   );
 
-  if (W) server.registerTool(
+  if (features.notes && W) server.registerTool(
     'delete_collab_note',
     {
       description: 'Delete a collaborative note from a trip.',
@@ -94,7 +96,7 @@ export function registerCollabTools(server: McpServer, userId: number, scopes: s
 
   // --- COLLAB POLLS & CHAT ---
 
-  if (R) server.registerTool(
+  if (features.polls && R) server.registerTool(
     'list_collab_polls',
       {
         description: 'List all polls for a trip.',
@@ -110,7 +112,7 @@ export function registerCollabTools(server: McpServer, userId: number, scopes: s
       }
     );
 
-    if (W) server.registerTool(
+    if (features.polls && W) server.registerTool(
       'create_collab_poll',
       {
         description: 'Create a new poll in the collab panel.',
@@ -132,7 +134,7 @@ export function registerCollabTools(server: McpServer, userId: number, scopes: s
       }
     );
 
-    if (W) server.registerTool(
+    if (features.polls && W) server.registerTool(
       'vote_collab_poll',
       {
         description: 'Vote on a poll option (or remove vote if already voted for that option).',
@@ -152,7 +154,7 @@ export function registerCollabTools(server: McpServer, userId: number, scopes: s
       }
     );
 
-    if (W) server.registerTool(
+    if (features.polls && W) server.registerTool(
       'close_collab_poll',
       {
         description: 'Close a poll so no more votes can be cast.',
@@ -172,7 +174,7 @@ export function registerCollabTools(server: McpServer, userId: number, scopes: s
       }
     );
 
-    if (W) server.registerTool(
+    if (features.polls && W) server.registerTool(
       'delete_collab_poll',
       {
         description: 'Delete a poll and all its votes.',
@@ -192,7 +194,7 @@ export function registerCollabTools(server: McpServer, userId: number, scopes: s
       }
     );
 
-    if (R) server.registerTool(
+    if (features.chat && R) server.registerTool(
       'list_collab_messages',
       {
         description: 'List chat messages for a trip (most recent 100, oldest-first).',
@@ -209,7 +211,7 @@ export function registerCollabTools(server: McpServer, userId: number, scopes: s
       }
     );
 
-    if (W) server.registerTool(
+    if (features.chat && W) server.registerTool(
       'send_collab_message',
       {
         description: "Send a chat message to a trip's collab channel.",
@@ -230,7 +232,7 @@ export function registerCollabTools(server: McpServer, userId: number, scopes: s
       }
     );
 
-    if (W) server.registerTool(
+    if (features.chat && W) server.registerTool(
       'delete_collab_message',
       {
         description: 'Delete a chat message (only the message owner can delete their own messages).',
@@ -250,7 +252,7 @@ export function registerCollabTools(server: McpServer, userId: number, scopes: s
       }
     );
 
-    if (W) server.registerTool(
+    if (features.chat && W) server.registerTool(
       'react_collab_message',
       {
         description: 'Toggle a reaction emoji on a chat message (adds if not present, removes if already reacted).',

server/src/mcp/tools/trips.ts

@@ -12,7 +12,7 @@ import {
 import {
   createOrUpdateShareLink, getShareLink, deleteShareLink,
 } from '../../services/shareService';
-import { isAddonEnabled } from '../../services/adminService';
+import { isAddonEnabled, getCollabFeatures } from '../../services/adminService';
 import { ADDON_IDS } from '../../addons';
 import { countMessages, listPolls } from '../../services/collabService';
 import {
@@ -161,6 +161,7 @@ export function registerTripTools(server: McpServer, userId: number, scopes: str
       const packingEnabled = isAddonEnabled(ADDON_IDS.PACKING);
       const budgetEnabled  = isAddonEnabled(ADDON_IDS.BUDGET);
       const collabEnabled  = isAddonEnabled(ADDON_IDS.COLLAB);
+      const collabFeatures = collabEnabled ? getCollabFeatures() : null;
       // Scope gates — sections not covered by the client's OAuth scopes are omitted.
       // Core trip data (metadata, days, members, accommodations) is always included
       // because this tool is always registered and needed for navigation.
@@ -173,16 +174,16 @@ export function registerTripTools(server: McpServer, userId: number, scopes: str
       let pollCount = 0;
       let messageCount = 0;
       if (canReadCollab) {
-        pollCount    = listPolls(tripId).length;
-        messageCount = countMessages(tripId);
+        if (collabFeatures?.polls) pollCount    = listPolls(tripId).length;
+        if (collabFeatures?.chat)  messageCount = countMessages(tripId);
       }
       const notice = getDeprecationNotice();
-      const data = {
+      const summaryData = {
         ...summary,
-        reservations:  canReadRes     ? summary.reservations  : undefined,
-        packing:       canReadPacking ? summary.packing        : undefined,
-        budget:        canReadBudget  ? summary.budget         : undefined,
-        collab_notes:  canReadCollab  ? summary.collab_notes   : [],
+        reservations:  canReadRes                                    ? summary.reservations : undefined,
+        packing:       canReadPacking                                ? summary.packing      : undefined,
+        budget:        canReadBudget                                 ? summary.budget       : undefined,
+        collab_notes:  canReadCollab && collabFeatures?.notes        ? summary.collab_notes : [],
         todos,
         pollCount,
         messageCount,
@@ -191,19 +192,10 @@ export function registerTripTools(server: McpServer, userId: number, scopes: str
         isError: true as const,
         content: [
           { type: 'text' as const, text: notice },
-          { type: 'text' as const, text: JSON.stringify(data, null, 2) },
+          { type: 'text' as const, text: JSON.stringify(summaryData, null, 2) },
         ],
       };
-      return ok({
-        ...summary,
-        reservations:  canReadRes     ? summary.reservations  : undefined,
-        packing:       canReadPacking ? summary.packing        : undefined,
-        budget:        canReadBudget  ? summary.budget         : undefined,
-        collab_notes:  canReadCollab  ? summary.collab_notes   : [],
-        todos,
-        pollCount,
-        messageCount,
-      });
+      return ok(summaryData);
     }
   );
 

server/src/routes/admin.ts

@@ -266,6 +266,7 @@ router.get('/collab-features', (_req: Request, res: Response) => {
 
 router.put('/collab-features', (req: Request, res: Response) => {
   const result = svc.updateCollabFeatures(req.body);
+  invalidateMcpSessions();
   const authReq = req as AuthRequest;
   writeAudit({
     userId: authReq.user.id,

server/src/routes/oauth.ts

@@ -87,6 +87,20 @@ oauthPublicRouter.get('/.well-known/oauth-authorization-server', (req: Request,
     scope_descriptions:                    Object.fromEntries(
       ALL_SCOPES.map(s => [s, SCOPE_INFO[s].label])
     ),
+    resource_parameter_supported:          true,
+  });
+});
+
+// RFC 9728 Protected Resource Metadata
+oauthPublicRouter.get('/.well-known/oauth-protected-resource', (_req: Request, res: Response) => {
+  if (!isAddonEnabled(ADDON_IDS.MCP)) return res.status(404).end();
+  const base = (getAppUrl() || '').replace(/\/+$/, '');
+  res.json({
+    resource:                 `${base}/mcp`,
+    authorization_servers:    [base],
+    bearer_methods_supported: ['header'],
+    scopes_supported:         ALL_SCOPES,
+    resource_name:            'TREK MCP',
   });
 });
 
@@ -98,7 +112,7 @@ oauthPublicRouter.post('/oauth/token', tokenLimiter, (req: Request, res: Respons
 
   // Accept both JSON and application/x-www-form-urlencoded
   const body: Record<string, string> = typeof req.body === 'object' ? req.body : {};
-  const { grant_type, code, redirect_uri, client_id, client_secret, code_verifier, refresh_token } = body;
+  const { grant_type, code, redirect_uri, client_id, client_secret, code_verifier, refresh_token, resource } = body;
   const ip = getClientIp(req);
 
   if (!isAddonEnabled(ADDON_IDS.MCP)) {
@@ -133,6 +147,12 @@ oauthPublicRouter.post('/oauth/token', tokenLimiter, (req: Request, res: Respons
       return res.status(400).json({ error: 'invalid_grant', error_description: 'Authorization grant is invalid.' });
     }
 
+    // RFC 8707: if the auth code was bound to a resource, the token request must present the same value
+    if (pending.resource && resource && pending.resource !== resource.replace(/\/+$/, '')) {
+      writeAudit({ userId: pending.userId, action: 'oauth.token.grant_failed', details: { client_id, reason: 'resource_mismatch' }, ip });
+      return res.status(400).json({ error: 'invalid_grant', error_description: 'Authorization grant is invalid.' });
+    }
+
     // Verify client secret
     if (!authenticateClient(client_id, client_secret)) {
       logWarn(`[OAuth] Invalid client credentials for client_id=${client_id} ip=${ip ?? '-'}`);
@@ -146,8 +166,8 @@ oauthPublicRouter.post('/oauth/token', tokenLimiter, (req: Request, res: Respons
       return res.status(400).json({ error: 'invalid_grant', error_description: 'Authorization grant is invalid.' });
     }
 
-    const tokens = issueTokens(client_id, pending.userId, pending.scopes);
-    writeAudit({ userId: pending.userId, action: 'oauth.token.issue', details: { client_id, scopes: pending.scopes }, ip });
+    const tokens = issueTokens(client_id, pending.userId, pending.scopes, null, pending.resource ?? null);
+    writeAudit({ userId: pending.userId, action: 'oauth.token.issue', details: { client_id, scopes: pending.scopes, audience: pending.resource ?? null }, ip });
     return res.json(tokens);
   }
 
@@ -275,6 +295,7 @@ oauthApiRouter.get('/authorize/validate', validateLimiter, optionalAuth, (req: R
       state:                  params.state,
       code_challenge:         params.code_challenge || '',
       code_challenge_method:  params.code_challenge_method || '',
+      resource:               typeof params.resource === 'string' ? params.resource : undefined,
     },
     userId,
   );
@@ -298,7 +319,7 @@ oauthApiRouter.post('/authorize', requireCookieAuth, (req: Request, res: Respons
   const { user } = req as AuthRequest;
   const {
     client_id, redirect_uri, scope, state,
-    code_challenge, code_challenge_method, approved,
+    code_challenge, code_challenge_method, approved, resource,
   } = req.body as {
     client_id: string;
     redirect_uri: string;
@@ -307,6 +328,7 @@ oauthApiRouter.post('/authorize', requireCookieAuth, (req: Request, res: Respons
     code_challenge: string;
     code_challenge_method: string;
     approved: boolean;
+    resource?: string;
   };
   const ip = getClientIp(req);
 
@@ -332,6 +354,7 @@ oauthApiRouter.post('/authorize', requireCookieAuth, (req: Request, res: Respons
     state,
     code_challenge,
     code_challenge_method,
+    resource,
   };
 
   const validation = validateAuthorizeRequest(params, user.id);
@@ -350,6 +373,7 @@ oauthApiRouter.post('/authorize', requireCookieAuth, (req: Request, res: Respons
     userId: user.id,
     redirectUri: redirect_uri,
     scopes,
+    resource: validation.resource ?? null,
     codeChallenge: code_challenge,
     codeChallengeMethod: 'S256',
   });

server/src/services/oauthService.ts

@@ -6,6 +6,7 @@ import { ADDON_IDS } from '../addons';
 import { User } from '../types';
 import { writeAudit, logWarn } from './auditLog';
 import { revokeUserSessionsForClient } from '../mcp/sessionManager';
+import { getAppUrl } from './oidcService';
 
 // ---------------------------------------------------------------------------
 // Constants
@@ -28,6 +29,7 @@ interface PendingCode {
   userId: number;
   redirectUri: string;
   scopes: string[];
+  resource: string | null;
   codeChallenge: string;
   codeChallengeMethod: 'S256';
   expiresAt: number;
@@ -67,6 +69,7 @@ interface OAuthTokenRow {
   access_token_hash: string;
   refresh_token_hash: string;
   scopes: string;           // JSON array
+  audience: string | null;
   access_token_expires_at: string;
   refresh_token_expires_at: string;
   revoked_at: string | null;
@@ -243,6 +246,7 @@ export function createAuthCode(params: {
   userId: number;
   redirectUri: string;
   scopes: string[];
+  resource: string | null;
   codeChallenge: string;
   codeChallengeMethod: 'S256';
 }): string | null {
@@ -294,6 +298,7 @@ export function issueTokens(
   userId: number,
   scopes: string[],
   parentTokenId: number | null = null,
+  audience: string | null = null,
 ): {
   access_token: string;
   refresh_token: string;
@@ -312,9 +317,9 @@ export function issueTokens(
 
   db.prepare(`
     INSERT INTO oauth_tokens
-      (client_id, user_id, access_token_hash, refresh_token_hash, scopes, access_token_expires_at, refresh_token_expires_at, parent_token_id)
-    VALUES (?, ?, ?, ?, ?, ?, ?, ?)
-  `).run(clientId, userId, accessHash, refreshHash, JSON.stringify(scopes), accessExpiry.toISOString(), refreshExpiry.toISOString(), parentTokenId);
+      (client_id, user_id, access_token_hash, refresh_token_hash, scopes, audience, access_token_expires_at, refresh_token_expires_at, parent_token_id)
+    VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)
+  `).run(clientId, userId, accessHash, refreshHash, JSON.stringify(scopes), audience, accessExpiry.toISOString(), refreshExpiry.toISOString(), parentTokenId);
 
   return {
     access_token:  rawAccess,
@@ -333,12 +338,13 @@ export interface OAuthTokenInfo {
   user: User;
   scopes: string[];
   clientId: string;
+  audience: string | null;
 }
 
 export function getUserByAccessToken(rawToken: string): OAuthTokenInfo | null {
   const hash = hashToken(rawToken);
   const row = db.prepare(`
-    SELECT ot.scopes, ot.revoked_at, ot.access_token_expires_at,
+    SELECT ot.scopes, ot.audience, ot.revoked_at, ot.access_token_expires_at,
            ot.user_id, ot.client_id, u.username, u.email, u.role
     FROM oauth_tokens ot
     JOIN users u ON ot.user_id = u.id
@@ -353,6 +359,7 @@ export function getUserByAccessToken(rawToken: string): OAuthTokenInfo | null {
     user: { id: row.user_id, username: row.username, email: row.email, role: row.role as 'admin' | 'user' },
     scopes: JSON.parse(row.scopes),
     clientId: row.client_id,
+    audience: row.audience ?? null,
   };
 }
 
@@ -406,7 +413,7 @@ export function refreshTokens(
 
   const hash = hashToken(rawRefreshToken);
   const row = db.prepare(`
-    SELECT id, client_id, user_id, scopes, refresh_token_expires_at, revoked_at, parent_token_id
+    SELECT id, client_id, user_id, scopes, audience, refresh_token_expires_at, revoked_at, parent_token_id
     FROM oauth_tokens WHERE refresh_token_hash = ?
   `).get(hash) as OAuthTokenRow | undefined;
 
@@ -442,7 +449,7 @@ export function refreshTokens(
 
   revokeUserSessionsForClient(row.user_id, clientId);
 
-  const tokens = issueTokens(clientId, row.user_id, JSON.parse(row.scopes), row.id);
+  const tokens = issueTokens(clientId, row.user_id, JSON.parse(row.scopes), row.id, row.audience ?? null);
   writeAudit({ userId: row.user_id, action: 'oauth.token.refresh', details: { client_id: clientId }, ip });
 
   return { tokens };
@@ -522,6 +529,7 @@ export interface AuthorizeParams {
   state?: string;
   code_challenge: string;
   code_challenge_method: string;
+  resource?: string;
 }
 
 export interface ValidateAuthorizeResult {
@@ -530,6 +538,7 @@ export interface ValidateAuthorizeResult {
   error_description?: string;
   client?: { name: string; allowed_scopes: string[] };
   scopes?: string[];
+  resource?: string | null;
   /** true when user is logged in but consent UI must be shown */
   consentRequired?: boolean;
   /** true when the request is valid but user is not authenticated */
@@ -573,6 +582,13 @@ export function validateAuthorizeRequest(
     return { valid: false, error: 'invalid_redirect_uri', error_description: 'redirect_uri does not match any registered URI' };
   }
 
+  // RFC 8707 resource indicator: if provided, must identify the TREK MCP endpoint exactly
+  const mcpResource = `${(getAppUrl() || '').replace(/\/+$/, '')}/mcp`;
+  const resource = params.resource ? params.resource.replace(/\/+$/, '') : null;
+  if (resource !== null && resource !== mcpResource) {
+    return { valid: false, error: 'invalid_target', error_description: 'Requested resource must be the TREK MCP endpoint' };
+  }
+
   const requestedScopes = (params.scope || '').split(' ').filter(Boolean);
   if (requestedScopes.length === 0) {
     return { valid: false, error: 'invalid_scope', error_description: 'At least one scope is required' };
@@ -599,6 +615,7 @@ export function validateAuthorizeRequest(
     valid: true,
     client: { name: client.name, allowed_scopes: allowedScopes },
     scopes: grantedScopes,
+    resource: resource ?? mcpResource,
     consentRequired,
     scopeSelectable: client.created_via === 'dcr',
   };