fix: add Protected Resource Metadata endpoint (RFC 9728)

The MCP auth spec (2025-06-18+) requires /.well-known/oauth-protected-resource
in addition to /.well-known/oauth-authorization-server. Claude fetches
the protected resource metadata first after receiving a 401, then discovers
the authorization server from it. Also fixes WWW-Authenticate header to
use absolute URL pointing to the protected resource endpoint.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

check-oauth.sh

@@ -0,0 +1,8 @@
+#!/bin/bash
+docker exec gearbox bun -e "
+const{Database}=require('bun:sqlite');
+const db=new Database('./data/gearbox.db');
+console.log('CLIENTS:', JSON.stringify(db.query('SELECT * FROM oauth_clients ORDER BY id DESC LIMIT 5').all(), null, 2));
+console.log('CODES:', JSON.stringify(db.query('SELECT id,client_id,used,expires_at FROM oauth_codes ORDER BY id DESC LIMIT 5').all(), null, 2));
+console.log('TOKENS:', JSON.stringify(db.query('SELECT id,client_id,expires_at FROM oauth_tokens ORDER BY id DESC LIMIT 5').all(), null, 2));
+"

src/server/mcp/index.ts

@@ -115,10 +115,12 @@ mcpRoutes.use("/*", async (c, next) => {
 		return c.json({ error: "Invalid API key" }, 401);
 	}
 
-	// No auth provided — return 401 with WWW-Authenticate to trigger OAuth flow
+	// No auth provided — return 401 with WWW-Authenticate to trigger OAuth flow (RFC 9728)
+	const baseUrl = (
+		process.env.GEARBOX_URL || new URL(c.req.url).origin
+	).replace(/\/$/, "");
 	return c.text("Unauthorized", 401, {
-		"WWW-Authenticate":
-			'Bearer resource_metadata="/.well-known/oauth-authorization-server"',
+		"WWW-Authenticate": `Bearer resource_metadata="${baseUrl}/.well-known/oauth-protected-resource"`,
 	});
 });
 

src/server/routes/oauth.ts

@@ -84,6 +84,16 @@ function renderLoginForm(params: {
 
 export const wellKnownRoute = new Hono<Env>();
 
+// Protected Resource Metadata (RFC 9728) — Claude fetches this first after 401
+wellKnownRoute.get("/oauth-protected-resource", (c) => {
+	const baseUrl = getBaseUrl(c);
+	return c.json({
+		resource: `${baseUrl}/mcp`,
+		authorization_servers: [baseUrl],
+	});
+});
+
+// OAuth Authorization Server Metadata (RFC 8414) — Claude fetches this second
 wellKnownRoute.get("/oauth-authorization-server", (c) => {
 	const baseUrl = getBaseUrl(c);
 	return c.json({