fix(ag-ui): resolve the subagents agent URL against <base href>

cockpit/ag-ui/subagents was the only ag-ui app configuring a root-absolute
`provideAgent({ url: '/agent' })`; the other six build the URL relative to
document.baseURI.

scripts/assemble-examples.ts rewrites each app's <base href> to
/ag-ui/<topic>/, and the Vercel route table only proxies
^/ag-ui/([^/]+)/agent(/.*)?$ to the Railway runtime. The literal therefore
requested https://examples.threadplane.ai/agent, which matches no route,
fell through the filesystem handle and landed on the 404 catch-all.

Local dev hid it: dev serves <base href="/">, so both forms resolve to
/agent and proxy.conf.mjs forwards either one.

Add a static guard covering every registered ag-ui capability. Production
smoke cannot see this class of bug — the page still serves a healthy 200
index.html — so the assertion has to be made against the source.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: blove

apps/cockpit/ag-ui-agent-url.spec.ts

@@ -0,0 +1,65 @@
+import { readFileSync } from 'node:fs';
+import { dirname, join, resolve } from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { capabilities } from './scripts/capability-registry';
+
+/**
+ * Guard for a failure mode production smoke cannot see.
+ *
+ * `scripts/assemble-examples.ts` rewrites each cockpit app's `<base href>` to
+ * `/<product>/<topic>/`, and the Vercel route table only proxies
+ * `^/ag-ui/([^/]+)/agent(/.*)?$` to the Railway runtime. An app that hardcodes
+ * a root-absolute `'/agent'` therefore requests `https://<host>/agent`, which
+ * matches no route, falls through the filesystem handle and lands on the 404
+ * catch-all — while still serving a perfectly healthy 200 index.html, so every
+ * page-reachability assertion keeps passing.
+ *
+ * Local dev is not a safety net either: dev serves with `<base href="/">`, so
+ * the literal and the base-relative form resolve identically to `/agent` and
+ * proxy.conf.mjs forwards both.
+ *
+ * The base-relative form is the only one that survives the base-href rewrite.
+ */
+const AGENT_URL_EXPR = "new URL('agent', document.baseURI).pathname";
+
+const repoRoot = resolve(dirname(fileURLToPath(import.meta.url)), '../..');
+
+/**
+ * Both products are served by the same aggregated AG-UI runtime and both get
+ * their <base href> rewritten at assemble time, so both are exposed to this.
+ */
+const agentBackedCapabilities = capabilities.filter(
+  (c) => c.product === 'ag-ui' || c.product === 'runtimes'
+);
+
+describe('ag-ui agent URL is resolved against <base href>', () => {
+  it('covers every registered agent-backed capability', () => {
+    expect(agentBackedCapabilities.length).toBeGreaterThan(0);
+  });
+
+  for (const cap of agentBackedCapabilities) {
+    it(`${cap.product}/${cap.topic} resolves its agent URL relative to the base href`, () => {
+      const configPath = join(
+        repoRoot,
+        'cockpit',
+        cap.product,
+        cap.topic,
+        'angular/src/app/app.config.ts'
+      );
+      const source = readFileSync(configPath, 'utf8');
+
+      expect(
+        source,
+        `${configPath} must build the agent URL with ${AGENT_URL_EXPR} so it ` +
+          `resolves under the deployed <base href="/${cap.product}/${cap.topic}/">`
+      ).toContain(AGENT_URL_EXPR);
+
+      // A root-absolute literal silently 404s in production; see the note above.
+      expect(
+        source,
+        `${configPath} hardcodes a root-absolute agent URL, which does not ` +
+          `survive the <base href> rewrite in scripts/assemble-examples.ts`
+      ).not.toMatch(/url:\s*['"`]\/agent/);
+    });
+  }
+});

cockpit/ag-ui/subagents/angular/src/app/app.config.ts

@@ -5,7 +5,7 @@ import { provideChat } from '@threadplane/chat';
 
 export const appConfig: ApplicationConfig = {
   providers: [
-    provideAgent({ url: '/agent' }),
+    provideAgent({ url: new URL('agent', document.baseURI).pathname }),
     provideChat({}),
   ],
 };