fix: use EU subdomain for MCP OAuth routing

src/lib/agent-runner.ts

@@ -132,9 +132,14 @@ export async function runAgentWizard(
   const spinner = clack.spinner();
 
   // Determine MCP URL: CLI flag > env var > production default
+  // Use EU subdomain for EU users to work around Claude Code's OAuth bug
+  // See: https://github.com/anthropics/claude-code/issues/2267
   const mcpUrl = options.localMcp
     ? 'http://localhost:8787/mcp'
-    : process.env.MCP_URL || 'https://mcp.posthog.com/mcp';
+    : process.env.MCP_URL ||
+      (cloudRegion === 'eu'
+        ? 'https://mcp-eu.posthog.com/mcp'
+        : 'https://mcp.posthog.com/mcp');
 
   const agent = initializeAgent(
     {

src/steps/add-mcp-server-to-clients/__tests__/defaults.test.ts

@@ -28,9 +28,9 @@ describe('defaults', () => {
       );
     });
 
-    it('should add region param for EU region', () => {
+    it('should use EU subdomain for EU region', () => {
       const url = buildMCPUrl('streamable-http', undefined, false, 'eu');
-      expect(url).toBe('https://mcp.posthog.com/mcp?region=eu');
+      expect(url).toBe('https://mcp-eu.posthog.com/mcp');
     });
 
     it('should not add region param for US region (default)', () => {
@@ -43,11 +43,9 @@ describe('defaults', () => {
       expect(url).toBe('http://localhost:8787/mcp');
     });
 
-    it('should combine features and region params', () => {
+    it('should combine EU subdomain with features param', () => {
       const url = buildMCPUrl('streamable-http', ['dashboards'], false, 'eu');
-      expect(url).toBe(
-        'https://mcp.posthog.com/mcp?features=dashboards&region=eu',
-      );
+      expect(url).toBe('https://mcp-eu.posthog.com/mcp?features=dashboards');
     });
   });
 
@@ -78,15 +76,15 @@ describe('defaults', () => {
       expect(config).not.toHaveProperty('env');
     });
 
-    it('should include region in URL for EU users in OAuth mode', () => {
+    it('should use EU subdomain for EU users in OAuth mode', () => {
       const config = getDefaultServerConfig(
         undefined,
         'streamable-http',
         undefined,
         false,
         'eu',
       );
-      expect(config.args).toContain('https://mcp.posthog.com/mcp?region=eu');
+      expect(config.args).toContain('https://mcp-eu.posthog.com/mcp');
     });
   });
 
@@ -112,15 +110,15 @@ describe('defaults', () => {
       expect(config).not.toHaveProperty('headers');
     });
 
-    it('should include region in URL for EU users', () => {
+    it('should use EU subdomain for EU users', () => {
       const config = getNativeHTTPServerConfig(
         undefined,
         'streamable-http',
         undefined,
         false,
         'eu',
       );
-      expect(config.url).toBe('https://mcp.posthog.com/mcp?region=eu');
+      expect(config.url).toBe('https://mcp-eu.posthog.com/mcp');
     });
   });
 });

src/steps/add-mcp-server-to-clients/defaults.ts

@@ -77,7 +77,14 @@ export const buildMCPUrl = (
   local?: boolean,
   region?: CloudRegion,
 ) => {
-  const host = local ? 'http://localhost:8787' : 'https://mcp.posthog.com';
+  // Use subdomain for EU to work around Claude Code's OAuth bug where it ignores
+  // the authorization_servers field and fetches /.well-known/oauth-authorization-server
+  // directly from the MCP server hostname. See: https://github.com/anthropics/claude-code/issues/2267
+  const host = local
+    ? 'http://localhost:8787'
+    : region === 'eu'
+    ? 'https://mcp-eu.posthog.com'
+    : 'https://mcp.posthog.com';
   const baseUrl = `${host}/${type === 'sse' ? 'sse' : 'mcp'}`;
 
   const isAllFeaturesSelected =
@@ -96,13 +103,6 @@ export const buildMCPUrl = (
     params.push(`features=${selectedFeatures.join(',')}`);
   }
 
-  // Add region param for non-US regions to route OAuth to the correct authorization server.
-  // US is the default, so we only need to specify region for EU users.
-  // Not needed in local mode since local dev always uses the same auth server.
-  if (region && region !== 'us' && !local) {
-    params.push(`region=${region}`);
-  }
-
   return params.length > 0 ? `${baseUrl}?${params.join('&')}` : baseUrl;
 };