diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index eb250e4be..3ce7d49dc 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -1177,8 +1177,7 @@ jobs:
           path: ~/.cache/ms-playwright
           key: playwright-${{ runner.os }}-${{ runner.arch }}-${{ hashFiles('web/package-lock.json') }}
       - name: install chromium
-        # Skips the browser download on a cache hit; still apt-installs deps.
-        run: npx playwright install --with-deps chromium
+        run: bash e2e/install-chromium.sh
       - name: build production dashboard for plain HTTP browser check
         run: npm run build
       - name: TypeScript editor on plain HTTP
@@ -2271,8 +2270,10 @@ jobs:
           path: ~/.cache/ms-playwright
           key: playwright-${{ runner.os }}-${{ runner.arch }}-${{ hashFiles('web/package-lock.json') }}
       - name: install playwright browser
+        working-directory: web
         run: |
-          cd web && npm ci && npx playwright install --with-deps chromium
+          npm ci
+          bash e2e/install-chromium.sh
       - name: i18n catalogs for the live dashboard
         # The live job serves the dashboard with plain vite, which never builds
         # the gitignored language list and catalogs (spec 019 T037).
diff --git a/.github/workflows/visual-diff.yaml b/.github/workflows/visual-diff.yaml
index 18f2f93f2..8d2904751 100644
--- a/.github/workflows/visual-diff.yaml
+++ b/.github/workflows/visual-diff.yaml
@@ -27,6 +27,12 @@ jobs:
   visual-diff:
     name: design vs browser visual diff
     runs-on: ubuntu-latest
+    # Include the same system fonts used by the hosted runner alongside the
+    # complete Playwright font set used for design and clipping comparisons.
+    container: &screenshot_runtime
+      image: mcr.microsoft.com/playwright:v1.65.0-noble@sha256:6e3fb709361521eb27161606e6da6d2674e5e89fa16516cb37d6fdd91372273d
+      volumes:
+        - /usr/share/fonts:/usr/local/share/fonts/runner:ro
     permissions:
       contents: read
     timeout-minutes: 20
@@ -47,16 +53,20 @@ jobs:
       - name: install dependencies
         run: npm ci
 
-      - name: playwright browser cache
-        uses: actions/cache@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
-        with:
-          path: ~/.cache/ms-playwright
-          key: playwright-${{ runner.os }}-${{ runner.arch }}-${{ hashFiles('web/package-lock.json') }}
-          restore-keys: |
-            playwright-${{ runner.os }}-${{ runner.arch }}-
-
-      - name: install chromium
-        run: npx playwright install --with-deps chromium
+      - &verify_screenshot_browser
+        name: verify the locked screenshot browser
+        run: |
+          node --input-type=module <<'JS'
+          import assert from 'node:assert/strict';
+          import { readFileSync } from 'node:fs';
+          const json = path => JSON.parse(readFileSync(path, 'utf8'));
+          assert.equal(
+            json('/ms-playwright/.docker-info').driverVersion,
+            json('node_modules/playwright/package.json').version,
+            'Update the screenshot image digest when upgrading Playwright',
+          );
+          JS
+          bash e2e/install-chromium.sh
 
       - name: capture browser screenshots
         run: npm run screenshots:design
@@ -86,6 +96,7 @@ jobs:
   pseudo-locale:
     name: en-XA screenshots (spec 019)
     runs-on: ubuntu-latest
+    container: *screenshot_runtime
     permissions:
       contents: read
     timeout-minutes: 30
@@ -106,16 +117,7 @@ jobs:
       - name: install dependencies
         run: npm ci
 
-      - name: playwright browser cache
-        uses: actions/cache@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
-        with:
-          path: ~/.cache/ms-playwright
-          key: playwright-${{ runner.os }}-${{ runner.arch }}-${{ hashFiles('web/package-lock.json') }}
-          restore-keys: |
-            playwright-${{ runner.os }}-${{ runner.arch }}-
-
-      - name: install chromium
-        run: npx playwright install --with-deps chromium
+      - *verify_screenshot_browser
 
       - name: capture en-XA screenshots and check clipping
         run: npm run screenshots:pseudo
diff --git a/changelog/unreleased/917-browser-runtime.md b/changelog/unreleased/917-browser-runtime.md
new file mode 100644
index 000000000..006d56d86
--- /dev/null
+++ b/changelog/unreleased/917-browser-runtime.md
@@ -0,0 +1,6 @@
+### Browser checks on hosted runners
+
+The dashboard’s mock, live Kubernetes and screenshot jobs now verify that the
+locked Chromium build can render a screenshot and record video. Runners with a
+working browser skip Ubuntu package installation. If the probe fails, CI
+installs the distribution dependencies and repeats the probe before testing.
diff --git a/web/e2e/install-chromium.sh b/web/e2e/install-chromium.sh
new file mode 100644
index 000000000..46b40b741
--- /dev/null
+++ b/web/e2e/install-chromium.sh
@@ -0,0 +1,37 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Run from web/ after npm ci. Use the browser and FFmpeg from the locked CLI.
+playwright=./node_modules/.bin/playwright
+
+probe_browser() {
+  timeout --kill-after=5s 45s node --input-type=module <<'JS'
+import { stat } from 'node:fs/promises';
+import { tmpdir } from 'node:os';
+import { chromium } from 'playwright';
+
+const browser = await chromium.launch();
+try {
+  const page = await browser.newPage({ recordVideo: { dir: tmpdir() } });
+  await page.setContent('<button>Français</button>');
+  await page.getByRole('button', { name: 'Français' }).screenshot();
+  const video = page.video();
+  await page.close();
+  if ((await stat(await video.path())).size === 0) throw new Error('Chromium recorded an empty video');
+  await video.delete();
+} finally {
+  await browser.close();
+}
+JS
+}
+
+# Hosted runners normally have Chromium's native libraries. Only contact the
+# distro mirrors if the installed browser cannot render and record a page.
+timeout --kill-after=10s 4m "$playwright" install chromium
+if probe_browser; then
+  exit 0
+fi
+
+echo "Chromium's runtime probe failed; installing Playwright's distribution dependencies." >&2
+timeout --kill-after=10s 4m "$playwright" install --with-deps chromium
+probe_browser