diff --git a/core/http/react-ui/e2e/addons-fixtures.js b/core/http/react-ui/e2e/addons-fixtures.js
index 7ba7a20b4..87cc580fb 100644
--- a/core/http/react-ui/e2e/addons-fixtures.js
+++ b/core/http/react-ui/e2e/addons-fixtures.js
@@ -44,6 +44,22 @@ export function sessionFor(user, permissions = {}) {
 const ok = (payload) => ({ status: 200, contentType: 'application/json', body: JSON.stringify({ payload }) })
 const fail = (status, type, extra = {}) => ({ status, contentType: 'application/json', body: JSON.stringify({ error: { type, message: type, ...extra } }) })
 
+// Specs that draw add-on pages need add-ons on. With no add-on owner running,
+// the server reports add-ons off and answers 5xx on the pin routes, and the
+// browser logs each failed request. These stubs answer the add-on pages with an
+// empty set. They live on the context, which Playwright matches after the
+// page's own routes: a spec that sets its own features, builtin or pin list
+// still gets it.
+export async function stubAddonRoutes(page) {
+  // The real flags, with add-ons on: the other switches keep what the server says.
+  await page.context().route('**/api/features', async route => {
+    const real = await (await route.fetch()).json()
+    return route.fulfill({ json: { ...real, addons: true } })
+  })
+  await page.context().route('**/api/addons/builtin', route => route.fulfill({ json: { builtin: [] } }))
+  await page.context().route('**/api/addons/pins', route => route.fulfill({ json: [] }))
+}
+
 // Installs the routes and returns the mutable state the spec reads and edits.
 export async function mockAddons(page, options = {}) {
   const state = {
@@ -62,6 +78,7 @@ export async function mockAddons(page, options = {}) {
     dispatch: options.dispatch || null,
   }
 
+  await stubAddonRoutes(page)
   await page.route(/\/api\/addons\/apps\/[^/]+\/icon/, route => route.fulfill({ status: 200, contentType: 'image/png', body: PNG }))
   await page.route(/\/api\/addons\/apps$/, route => {
     state.log.appsList += 1
diff --git a/core/http/react-ui/e2e/not-found.spec.js b/core/http/react-ui/e2e/not-found.spec.js
index 2ee6f85a6..59ae829b6 100644
--- a/core/http/react-ui/e2e/not-found.spec.js
+++ b/core/http/react-ui/e2e/not-found.spec.js
@@ -1,8 +1,10 @@
 import { test, expect } from './coverage-fixtures.js'
 import { mockAccess } from './access-fixtures.js'
+import { stubAddonRoutes } from './addons-fixtures.js'
 
 test.describe('404', () => {
   test('names the address, offers a way home and lists the places the viewer can go', async ({ page }) => {
+    await stubAddonRoutes(page)
     await page.goto('/app/no-such-page')
     const nf = page.getByTestId('not-found')
     await expect(nf.getByRole('heading', { level: 1 })).toHaveText('This page does not exist')
diff --git a/core/http/react-ui/e2e/studio-addon.js b/core/http/react-ui/e2e/studio-addon.js
index 3565355e9..4ce7e098f 100644
--- a/core/http/react-ui/e2e/studio-addon.js
+++ b/core/http/react-ui/e2e/studio-addon.js
@@ -6,7 +6,7 @@
 import fs from 'node:fs'
 import path from 'node:path'
 import { fileURLToPath } from 'node:url'
-import { app, mockAddons } from './addons-fixtures.js'
+import { app, mockAddons, stubAddonRoutes } from './addons-fixtures.js'
 
 const addons = path.resolve(path.dirname(fileURLToPath(import.meta.url)), '../../../../addons')
 const DIGEST = 'e'.repeat(64)
@@ -55,6 +55,7 @@ export function packagedApp(id, over = {}) {
 // Returns the state of mockAddons.
 export async function installStudioAddons(page, { ids = ['studio', 'talk'], ...options } = {}) {
   const dirs = await Promise.all(ids.map(build))
+  await stubAddonRoutes(page)
   await page.route(/\/api\/addons\/(studio|talk|voice)\/assets\//, route => {
     const parts = new URL(route.request().url()).pathname.split('/')
     const id = parts[3]
diff --git a/core/http/react-ui/e2e/studio-addons.spec.js b/core/http/react-ui/e2e/studio-addons.spec.js
index 46347b3e1..3e56c0424 100644
--- a/core/http/react-ui/e2e/studio-addons.spec.js
+++ b/core/http/react-ui/e2e/studio-addons.spec.js
@@ -1,5 +1,6 @@
 import { test, expect } from './coverage-fixtures.js'
 import { installStudioAddons } from './studio-addon.js'
+import { stubAddonRoutes } from './addons-fixtures.js'
 import { mockStudio } from './studio-fixtures.js'
 import { fakeRealtime } from './chat-fixtures.js'
 
@@ -66,6 +67,7 @@ test.describe('Studio add-on', () => {
   })
 
   test('the old Studio addresses say so plainly when the add-on is not installed', async ({ page }) => {
+    await stubAddonRoutes(page)
     for (const address of ['/app/studio', '/app/studio/tts', '/app/image', '/app/talk']) {
       await page.goto(address)
       await expect(page.getByTestId('addon-unavailable')).toBeVisible({ timeout: 15_000 })