e2e: close the interact-before-hydration race (cold-start flake)

Diagnosis (reproduced by looping cold-server runs): the recurring
"cold start" failures in the auth/follow specs were a hydration race,
not a Vite dep-reload (the server.warmup config already handles that —
no reload events in the logs). FollowButton is an onClick button, and
Playwright considers it actionable (visible + enabled) before React
attaches the handler on a freshly-navigated page. A click in that
window is dropped (or triggers a native form submit), so the expected
state change never happens — e.g. notifications.test.ts:59 clicked
"Request to follow" with no hydration wait and the button never
flipped to "Requested".

The existing waitForHydration guard was applied per-interaction and so
was easy to forget (test 1 had it, test 3 didn't). Fix it at the
navigation instead:

- add gotoHydrated(page, url) = goto + waitForHydration, documented as
  the default for "navigate then interact with a React control"
- use it before every FollowButton interaction in notifications +
  social
- consolidate the setProfileVisibility helper (copy-pasted in three
  specs, two missing the hydration wait) into e2e/helpers/profile.ts,
  built on gotoHydrated

Validation against a fresh Postgres, cold servers: notifications 0/10
failures (was the proven flaker); notifications+social+explore 0/5
(55 tests); planner unaffected (25/25).

Note: two other "cold-start"-attributed flakes are NOT this race and
are out of scope here — planner map-load latency (mitigated by warmup
+ CI retries) and the /explore directory assertion (a local artifact
of the scratch DB accumulating >20 public users; CI's fresh DB stays
under the page size, so it doesn't bite there).

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

e2e/explore.test.ts

@@ -1,15 +1,6 @@
-import { test, expect, waitForHydration, type CDPSession, type Page } from "./fixtures/test";
+import { test, expect, type CDPSession } from "./fixtures/test";
 import { setupVirtualAuthenticator, registerUser } from "./helpers/auth";
-
-async function setProfileVisibility(page: Page, value: "public" | "private") {
-  await page.goto("/settings/profile");
-  // Wait for hydration so the visibility form submits via the fetcher
-  // (and shows the "Profile saved." toast) instead of native-navigating.
-  await waitForHydration(page);
-  await page.locator(`input[type=radio][name=profileVisibility][value=${value}]`).check();
-  await page.getByRole("button", { name: /^Save$/ }).first().click();
-  await expect(page.getByText("Profile saved.")).toBeVisible({ timeout: 10000 });
-}
+import { setProfileVisibility } from "./helpers/profile";
 
 test.describe.configure({ mode: "serial" });
 

e2e/fixtures/test.ts

@@ -98,5 +98,23 @@ export async function waitForHydration(page: import("@playwright/test").Page) {
   );
 }
 
+/**
+ * Navigate and wait for the page to be hydrated before returning.
+ *
+ * Use this (instead of bare `page.goto`) whenever the very next step
+ * interacts with a control whose behaviour lives in a React handler —
+ * notably the onClick-driven FollowButton and the profile-settings
+ * fetcher form. A button is "visible and enabled" per Playwright's
+ * actionability check before React has attached its onClick, so a click
+ * in that window is silently dropped (or triggers a native form submit),
+ * which is the dominant source of the cold-server e2e flake. Waiting for
+ * hydration at the navigation closes that race so individual tests can't
+ * forget it per interaction.
+ */
+export async function gotoHydrated(page: import("@playwright/test").Page, url: string) {
+  await page.goto(url);
+  await waitForHydration(page);
+}
+
 export { expect };
 export type { CDPSession, Page } from "@playwright/test";

e2e/helpers/profile.ts

@@ -0,0 +1,21 @@
+import { expect, gotoHydrated, type Page } from "../fixtures/test";
+
+/**
+ * Set the logged-in user's profile visibility via /settings/profile.
+ * Single source of truth — this was copy-pasted across the explore,
+ * social, and notifications specs, two of which omitted the hydration
+ * wait and so raced the fetcher-backed Save on a cold server.
+ */
+export async function setProfileVisibility(page: Page, value: "public" | "private") {
+  // gotoHydrated so the visibility form submits via the fetcher (and
+  // shows the "Profile saved." toast) instead of native-navigating.
+  await gotoHydrated(page, "/settings/profile");
+  // Target the radio by name+value; getByLabel collides because one
+  // radio's help text mentions the other's word ("public" appears in
+  // the Private radio's helper sentence).
+  await page.locator(`input[type=radio][name=profileVisibility][value=${value}]`).check();
+  await page.getByRole("button", { name: /^Save$/ }).first().click();
+  // SSE keeps the network busy, so don't wait on networkidle — wait for
+  // the explicit save confirmation instead.
+  await expect(page.getByText("Profile saved.")).toBeVisible({ timeout: 10000 });
+}

e2e/notifications.test.ts

@@ -1,15 +1,6 @@
-import { test, expect, waitForHydration, type CDPSession, type Page } from "./fixtures/test";
+import { test, expect, gotoHydrated, type CDPSession } from "./fixtures/test";
 import { setupVirtualAuthenticator, registerUser } from "./helpers/auth";
-
-async function setProfileVisibility(page: Page, value: "public" | "private") {
-  await page.goto("/settings");
-  await page.locator(`input[type=radio][name=profileVisibility][value=${value}]`).check();
-  await page.getByRole("button", { name: /^Save$/ }).first().click();
-  // Don't use waitForLoadState("networkidle") — the SSE connection to
-  // /api/events keeps the network busy indefinitely. Wait for the
-  // explicit save confirmation instead.
-  await expect(page.getByText("Profile saved.")).toBeVisible({ timeout: 10000 });
-}
+import { setProfileVisibility } from "./helpers/profile";
 
 test.describe.configure({ mode: "serial" });
 
@@ -39,8 +30,7 @@ test.describe("Notifications", () => {
     await setProfileVisibility(bPage, "public");
 
     // A follows B (auto-accept).
-    await page.goto(`/users/${bUsername}`);
-    await waitForHydration(page);
+    await gotoHydrated(page, `/users/${bUsername}`);
     await page.getByRole("button", { name: "Follow" }).click();
     await expect(page.getByRole("button", { name: "Unfollow" })).toBeVisible({ timeout: 5000 });
 
@@ -76,7 +66,7 @@ test.describe("Notifications", () => {
     // B stays private (default).
 
     // A requests to follow B.
-    await page.goto(`/users/${bUsername}`);
+    await gotoHydrated(page, `/users/${bUsername}`);
     await page.getByRole("button", { name: /Request to follow/i }).click();
     await expect(page.getByRole("button", { name: /Requested/i })).toBeVisible({ timeout: 5000 });
 

e2e/social.test.ts

@@ -1,16 +1,6 @@
-import { test, expect, waitForHydration, type CDPSession, type Page } from "./fixtures/test";
+import { test, expect, gotoHydrated, type CDPSession } from "./fixtures/test";
 import { setupVirtualAuthenticator, registerUser } from "./helpers/auth";
-
-async function setProfileVisibility(page: Page, value: "public" | "private") {
-  await page.goto("/settings");
-  // Target the radio by name+value; getByLabel collides because the
-  // help text of one radio mentions the other's word ("public" appears
-  // in the Private radio's helper sentence).
-  await page.locator(`input[type=radio][name=profileVisibility][value=${value}]`).check();
-  await page.getByRole("button", { name: /^Save$/ }).first().click();
-  // SSE keeps the network busy; wait for the save confirmation instead.
-  await expect(page.getByText("Profile saved.")).toBeVisible({ timeout: 10000 });
-}
+import { setProfileVisibility } from "./helpers/profile";
 
 // WebAuthn + parallel workers + shared local Postgres race; serialize.
 test.describe.configure({ mode: "serial" });
@@ -71,7 +61,7 @@ test.describe("Social follows + /feed", () => {
     await setProfileVisibility(bPage, "public");
 
     // A visits B's profile and follows.
-    await page.goto(`/users/${bUsername}`);
+    await gotoHydrated(page, `/users/${bUsername}`);
     await expect(page.getByRole("button", { name: "Follow" })).toBeVisible();
     await page.getByRole("button", { name: "Follow" }).click();
     await expect(page.getByRole("button", { name: "Unfollow" })).toBeVisible({ timeout: 5000 });