diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b29e14a..85dc38d 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -44,11 +44,20 @@ jobs:
       - run: npm ci
       - run: npm run test:lo
 
-  # Production build booted in headless Chromium — catches bundling and boot
-  # regressions the jsdom suite cannot see.
-  smoke:
-    runs-on: ubuntu-latest
-    timeout-minutes: 20
+  # Production build booted in the three engines behind the supported browsers
+  # (vite build.target). WebKit runs on macOS: its text shaping there is Safari's.
+  browser:
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - { browser: chromium, os: ubuntu-latest }
+          - { browser: firefox, os: ubuntu-latest }
+          - { browser: webkit, os: macos-latest }
+    runs-on: ${{ matrix.os }}
+    timeout-minutes: 30
+    env:
+      BROWSER: ${{ matrix.browser }}
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4
@@ -56,6 +65,7 @@ jobs:
           node-version: 20
           cache: npm
       - run: npm ci
-      - run: npx playwright-core install chromium
+      - run: npx playwright-core install --with-deps ${{ matrix.browser }}
       - run: npm run build
       - run: npm run test:smoke
+      - run: npm run test:dom
diff --git a/CLAUDE.md b/CLAUDE.md
index 9a64c84..bc73c84 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -16,8 +16,8 @@ npm run check    # svelte-check type-check (svelte + ts)
 npm test         # Vitest suite once (tests/**/*.test.ts)
 npm run test:watch   # Vitest in watch mode
 npm run test:lo      # LibreOffice legs: round trip + ODT/DOCX render consistency (needs `soffice`)
-npm run test:smoke   # boots the dist/ build in headless Chromium (tests/smoke/run.mjs)
-npm run test:dom     # pagination + editing in the real browser (tests/dom/run.mjs)
+npm run test:smoke   # boots the dist/ build headless (tests/smoke/run.mjs); BROWSER=firefox|webkit
+npm run test:dom     # pagination + editing in the real browser (tests/dom/run.mjs); same BROWSER
 npm run test:coverage  # vitest + v8 coverage over src/ → coverage/index.html
 npm run test:parity  # render parity vs LibreOffice (tests/render-parity/README.md)
 node scripts/make-thesaurus.mjs   # re-vendor public/thesaurus/ from LibreOffice's MyThes data
@@ -64,10 +64,9 @@ silently lands in every imported document as direct formatting. The defaults fol
 `components/Editor.svelte` and `styles/editor.css` (`PAGE_HEIGHT` 1123px, `PAGE_GAP` 20px, the
 `--user-page-*`/`--user-margin-*` custom properties) — details in `docs/architecture/pagination.md`.
 
-**Headless browser testing** — this container is linux **arm64**. Never `puppeteer` /
-`@puppeteer/browsers`: they fetch an x86-64 Chrome that cannot run here. Use `playwright-core` +
-its Chromium; full recipe in `docs/headless-testing.md`. Driving the live app is the only way to
-verify rendering, layout or NodeView behaviour — there is no DOM test suite for it.
+**Headless browser testing** — `playwright-core` with its own engines, never `puppeteer` (it
+fetches an x86-64 Chrome that cannot run on arm64). Recipe and the three-engine CI matrix in
+`docs/headless-testing.md`; driving the live app is the only way to verify rendering or NodeViews.
 
 **Naming** — components `PascalCase.svelte`, every `.ts` module `camelCase`; extension files are
 named by feature (`image.ts`, `indent.ts`), not `XyzExtension.ts`.
diff --git a/docs/headless-testing.md b/docs/headless-testing.md
index d37c3b4..3069505 100644
--- a/docs/headless-testing.md
+++ b/docs/headless-testing.md
@@ -12,10 +12,17 @@ For PDF-export repros specifically: replicate `pdf.ts`'s clone + `html2canvas(..
 ## The two committed browser runs
 
 `npm run test:smoke` and `npm run test:dom` are these probes made permanent: both boot
-`dist/` in headless Chromium through `tests/browser.mjs` (preview server, checklist,
-`pageerror` collector) and fail on any uncaught page error. The DOM run keeps the
-pagination invariants of pass 4 below — one page count through a settle, a reload, a
-zoom, a page break and its undo — which is the only test `src/lib/components/**` has.
+`dist/` headless through `tests/browser.mjs` (preview server, checklist, `pageerror`
+collector) and fail on any uncaught page error. The DOM run keeps the pagination
+invariants of pass 4 below — one page count through a settle, a reload, a zoom, a page
+break and its undo — which is the only test `src/lib/components/**` has.
+
+`BROWSER=chromium|firefox|webkit` picks the engine (Chromium by default; the others via
+`npx playwright-core install firefox webkit`). CI runs both on all three, one per matrix
+leg, WebKit on macOS because only there its text shaping is Safari's. The engines are
+the ones behind `build.target` in `vite.config.ts`; a browser older than that target
+fails to parse the bundle and no run reaches it. Playwright's WebKit is the engine, not
+Safari: storage eviction, the install prompt and iOS input are outside the matrix.
 
 ## Hunting for bugs the suite cannot see
 
diff --git a/tests/browser.mjs b/tests/browser.mjs
index a7b6125..cad6b7a 100644
--- a/tests/browser.mjs
+++ b/tests/browser.mjs
@@ -4,7 +4,7 @@ import { spawn, execSync } from 'node:child_process';
 import { existsSync } from 'node:fs';
 import { join, resolve, dirname } from 'node:path';
 import { fileURLToPath } from 'node:url';
-import { chromium } from 'playwright-core';
+import * as playwright from 'playwright-core';
 
 export const ROOT = resolve(dirname(fileURLToPath(import.meta.url)), '..');
 export const MOD = process.platform === 'darwin' ? 'Meta' : 'Control';
@@ -34,9 +34,15 @@ export async function previewServer(port) {
   throw new Error('preview server did not start');
 }
 
-// Fixed locale, so the UI labels a test clicks are deterministic across machines.
+// BROWSER=chromium|firefox|webkit picks the engine (Chromium by default). Fixed locale,
+// so the UI labels a test clicks are deterministic across machines.
 export async function openApp(port) {
-  const browser = await chromium.launch({ executablePath: chromium.executablePath(), args: ['--no-sandbox'] });
+  const name = process.env.BROWSER ?? 'chromium';
+  const engine = playwright[name];
+  if (!engine) throw new Error(`unknown BROWSER "${name}": chromium, firefox or webkit`);
+  const args = name === 'chromium' ? ['--no-sandbox'] : [];
+  const browser = await engine.launch({ executablePath: engine.executablePath(), args });
+  console.log(`engine: ${name} ${browser.version()}`);
   const page = await browser.newPage({ viewport: { width: 1400, height: 1000 }, locale: 'en-US' });
   const pageErrors = [];
   page.on('pageerror', (err) => pageErrors.push(String(err)));
diff --git a/vite.config.ts b/vite.config.ts
index 82d30ea..827c2cc 100644
--- a/vite.config.ts
+++ b/vite.config.ts
@@ -21,6 +21,9 @@ export default defineConfig({
   // subpath (GitHub Pages project site). sw.js and the manifest are relative too.
   base: './',
   plugins: [svelte()],
+  // The browsers the bundle promises to parse in; the CI browser matrix runs the
+  // engines behind them (docs/headless-testing.md).
+  build: { target: 'baseline-widely-available' },
   define: {
     __APP_VERSION__: JSON.stringify(commit ? `${pkg.version} (${commit})` : pkg.version),
   },