feat(billing): add direct Stripe billing portal access

Replace dashboard redirect with Stripe Customer Portal session for the
"Manage in Stripe" button, so users go directly to Stripe to manage
invoices, payment methods, and billing details.

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

apps/x/apps/main/src/ipc.ts

@@ -40,7 +40,7 @@ import { triggerRun as triggerAgentScheduleRun } from '@x/core/dist/agent-schedu
 import { search } from '@x/core/dist/search/search.js';
 import { versionHistory, voice } from '@x/core';
 import { classifySchedule, processRowboatInstruction } from '@x/core/dist/knowledge/inline_tasks.js';
-import { getBillingInfo } from '@x/core/dist/billing/billing.js';
+import { getBillingInfo, getBillingPortalUrl } from '@x/core/dist/billing/billing.js';
 import { summarizeMeeting } from '@x/core/dist/knowledge/summarize_meeting.js';
 import { getAccessToken } from '@x/core/dist/auth/tokens.js';
 import { getRowboatConfig } from '@x/core/dist/config/rowboat.js';
@@ -759,5 +759,9 @@ export function setupIpcHandlers() {
     'billing:getInfo': async () => {
       return await getBillingInfo();
     },
+    'billing:getPortalUrl': async () => {
+      const url = await getBillingPortalUrl();
+      return { url };
+    },
   });
 }

apps/x/apps/renderer/src/components/settings/account-settings.tsx

@@ -179,8 +179,8 @@ export function AccountSettings({ dialogOpen }: AccountSettingsProps) {
                   <p className="text-xs text-muted-foreground">Subscribe to access AI features</p>
                 )}
               </div>
-              <Button variant="outline" size="sm" onClick={() => appUrl && window.open(`${appUrl}?intent=upgrade`)}>
+              <Button variant="outline" size="sm" onClick={() => appUrl && window.open(appUrl)}>
-                {!billing.subscriptionPlan ? 'Subscribe' : 'Change plan'}
+                View plan
               </Button>
             </div>
           </div>
@@ -204,7 +204,14 @@ export function AccountSettings({ dialogOpen }: AccountSettingsProps) {
           variant="outline"
           size="sm"
           disabled={!billing?.subscriptionPlan}
-          onClick={() => appUrl && window.open(appUrl)}
+          onClick={async () => {
+            try {
+              const { url } = await window.ipc.invoke('billing:getPortalUrl', null);
+              window.open(url);
+            } catch {
+              toast.error('Failed to open billing portal');
+            }
+          }}
           className="gap-1.5"
         >
           <ExternalLink className="size-3" />

apps/x/packages/core/src/billing/billing.ts

@@ -11,6 +11,19 @@ export interface BillingInfo {
   availableCredits: number;
 }
 
+export async function getBillingPortalUrl(): Promise<string> {
+  const accessToken = await getAccessToken();
+  const response = await fetch(`${API_URL}/v1/billing/portal-session`, {
+    method: 'POST',
+    headers: { Authorization: `Bearer ${accessToken}` },
+  });
+  if (!response.ok) {
+    throw new Error(`Portal session failed: ${response.status}`);
+  }
+  const body = await response.json() as { url: string };
+  return body.url;
+}
+
 export async function getBillingInfo(): Promise<BillingInfo> {
   const accessToken = await getAccessToken();
   const response = await fetch(`${API_URL}/v1/me`, {

apps/x/packages/shared/src/ipc.ts

@@ -572,6 +572,12 @@ const ipcSchemas = {
       availableCredits: z.number(),
     }),
   },
+  'billing:getPortalUrl': {
+    req: z.null(),
+    res: z.object({
+      url: z.string(),
+    }),
+  },
 } as const;
 
 // ============================================================================