diff --git a/tests/e2e/playwright.config.ts b/tests/e2e/playwright.config.ts
index 16f925d..611bffa 100644
--- a/tests/e2e/playwright.config.ts
+++ b/tests/e2e/playwright.config.ts
@@ -29,8 +29,10 @@ export default defineConfig({
       // green suite with a test that does not exist. 17- joined on 2026-09-16
       // (the hermes vhost, whose upstream is a host address rather than a
       // container name, so it needs its own pass condition). 18- joined on
-      // 2026-09-24 (OpenWebUI SSO through authentik).
-      testMatch: /(10|12|13|16|17|18)-.*\.spec\.ts/,
+      // 2026-09-24 (OpenWebUI SSO through authentik). 20- joined on 2026-10-21
+      // (Grafana's OAuth2 relying-party login, which the edge-only 13- never
+      // follows).
+      testMatch: /(10|12|13|16|17|18|20)-.*\.spec\.ts/,
       use: { storageState: ".auth/qa-e2e.json" },
       dependencies: ["setup"],
     },
diff --git a/tests/e2e/specs/20-grafana-sso.spec.ts b/tests/e2e/specs/20-grafana-sso.spec.ts
new file mode 100644
index 0000000..d8c850d
--- /dev/null
+++ b/tests/e2e/specs/20-grafana-sso.spec.ts
@@ -0,0 +1,56 @@
+import { expect, test } from "@playwright/test";
+
+// Grafana (grafana.franksdank.cloud) is an OAuth2 RELYING PARTY, not an
+// outpost-fronted proxy: the guard chain (13-sso) only proves an authenticated
+// session reaches Grafana's login page. The login itself happens through
+// Grafana's own "Sign in with Authentik" button, which the edge test never
+// follows — that is exactly how the RP login could be dead (500 on authorize,
+// or an email-claim gap bouncing back to /login) while 13- still passed green.
+// This spec drives the real RP round-trip and asserts a live Grafana session.
+
+const HOST = "grafana.franksdank.cloud";
+const CHALLENGE = "Making sure you're not a bot";
+
+test("SSO: Grafana relying-party login lands a real session", async ({ page, request }) => {
+  test.setTimeout(180_000);
+
+  // Warm the guard: the vhost runs its own Anubis proof-of-work on first visit.
+  await page.goto(`https://${HOST}/`);
+  await expect
+    .poll(
+      async () => !(await page.locator("body").innerText()).includes(CHALLENGE),
+      { timeout: 90_000 },
+    )
+    .toBe(true);
+
+  // The "Sign in with Authentik" button targets this RP start URL exactly.
+  // Going straight there is the same code path without depending on the SPA's
+  // button markup.
+  await page.goto(`https://${HOST}/login/generic_oauth`);
+
+  // The chain: grafana -> auth (implicit consent, the session is already
+  // there) -> back to grafana with the code -> grafana provisions the user and
+  // redirects to "/". A dead provider/claims config bounces back to /login.
+  await expect
+    .poll(
+      async () => {
+        const u = new URL(page.url());
+        return u.hostname === HOST && u.pathname !== "/login";
+      },
+      { timeout: 90_000 },
+    )
+    .toBe(true);
+
+  const body = await page.locator("body").innerText();
+  expect(body).not.toContain("Login failed");
+  expect(body.toLowerCase()).not.toContain("powered by authentik"); // IdP flow shell
+  expect(body).not.toContain(CHALLENGE);
+
+  // A genuine logged-in session exists: /api/user answers 200 with an email,
+  // not 401. This is the assertion the edge-only spec could never make.
+  const resp = await page.request.get(`https://${HOST}/api/user`);
+  expect(resp.status()).toBe(200);
+  const user = await resp.json();
+  expect(typeof user.email).toBe("string");
+  expect(user.email.length).toBeGreaterThan(0);
+});