diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index f269214d..1a7e1fa2 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -64,5 +64,9 @@ jobs:
         uses: actions/upload-artifact@v4
         with:
           name: playwright-report
-          path: runner/playwright-report/
+          # playwright-report/ holds the html report, test-results/ the traces.
+          path: |
+            runner/playwright-report/
+            runner/test-results/
           retention-days: 7
+          if-no-files-found: warn
diff --git a/.github/workflows/e2e-live.yml b/.github/workflows/e2e-live.yml
index d2b5f55b..b2677605 100644
--- a/.github/workflows/e2e-live.yml
+++ b/.github/workflows/e2e-live.yml
@@ -123,5 +123,9 @@ jobs:
         uses: actions/upload-artifact@v4
         with:
           name: playwright-report-live
-          path: runner/playwright-report/
+          # playwright-report/ holds the html report, test-results/ the traces.
+          path: |
+            runner/playwright-report/
+            runner/test-results/
           retention-days: 7
+          if-no-files-found: warn
diff --git a/runner/e2e/helpers.ts b/runner/e2e/helpers.ts
new file mode 100644
index 00000000..b8b4c5f7
--- /dev/null
+++ b/runner/e2e/helpers.ts
@@ -0,0 +1,135 @@
+import { expect, type APIRequestContext, type Page } from "@playwright/test";
+
+// Shared helpers for the e2e suite (DEV-2203).
+//
+// Everything here existed first as copy-paste: `stubShell` and `signIn` were
+// declared verbatim in nine specs, the session-cleanup pattern in two, the
+// noise filter in one. New specs import from here; existing specs keep their
+// local copies and migrate opportunistically — a mass rewrite would churn
+// thousands of spec lines for zero behaviour change.
+//
+// The file is not matched by `*.spec.ts`, so Playwright never collects it.
+
+export const EMAIL = "dev@handsontable.com";
+
+/**
+ * The deterministic-shell recipe: a stubbed version list, both Sandpack hosts
+ * aborted (no external bundler, no grid — the shell renders fine without one),
+ * and the login redirect neutered so a stray click cannot leave the app.
+ */
+export async function stubShell(page: Page) {
+  await page.route("**/api/versions", (route) =>
+    route.fulfill({ json: { latest: "18.0.0", next: "19.0.0-next.1", versions: ["18.0.0", "17.1.0"] } }),
+  );
+  await page.route("https://sandpack.codesandbox.io/**", (route) => route.abort());
+  await page.route("https://sandpack-bundler.codesandbox.io/**", (route) => route.abort());
+  await page.route("**/broker/login**", (route) => route.abort());
+}
+
+/**
+ * Sign-in faked at the token layer — the app reads `sessionStorage.hot_token`
+ * and asks the broker who that is. Faking here rather than via `VITE_DEV_USER`
+ * keeps the production auth path in play (see sidebar-crud.spec.ts for the full
+ * argument). Never add storage *clears* to an init script: it runs on
+ * `page.reload()` too and silently defeats persistence tests (AGENTS.md).
+ */
+export async function signIn(page: Page, email: string = EMAIL) {
+  await page.addInitScript(() => sessionStorage.setItem("hot_token", "e2e-token"));
+  await page.route("**/broker/userinfo", (route) => route.fulfill({ json: { email } }));
+}
+
+/**
+ * The visible editor pane. Scoped since T12 (DEV-2169): every open tab keeps
+ * its own CodeMirror instance mounted, so a bare `.cm-content` trips strict
+ * mode as soon as a test opens a second file.
+ *
+ * For *reading file contents*, prefer `workspaceFiles()` — CodeMirror
+ * virtualises long documents, so `.cm-content` only holds the lines on screen.
+ */
+export function activeEditor(page: Page) {
+  return page.locator('[data-pane-active="true"] .cm-content');
+}
+
+/**
+ * The workspace files, via the `window.__HOT_FILES__` test contract
+ * (apps/authoring/src/App.tsx). Poll with `expect(...).toPass()` when the
+ * write you are waiting for rides the Style panel's 250 ms debounce.
+ */
+export function workspaceFiles(page: Page): Promise<Record<string, string>> {
+  return page.evaluate(() => {
+    const hook = (window as unknown as { __HOT_FILES__?: () => Record<string, string> }).__HOT_FILES__;
+    if (!hook) throw new Error("window.__HOT_FILES__ is not installed — is the app older than DEV-2203?");
+    return hook();
+  });
+}
+
+/**
+ * The version and framework pickers are custom listboxes in the preview bar
+ * (T2, DEV-2156) — `selectOption` does not apply. Open the trigger, click the
+ * option.
+ */
+export async function pickFromMenu(page: Page, menu: "Handsontable version" | "Framework", option: string) {
+  await page.getByRole("button", { name: menu, exact: true }).click();
+  await page.getByRole("option", { name: option, exact: true }).click();
+}
+
+/**
+ * Wait for the preview to declare itself ready. Readiness comes off
+ * `data-preview-status` on the preview section (PreviewPane.tsx — a documented
+ * test contract), never off visible text. For containers, "ready" only means
+ * the dev server responded; follow up with `expectGridRendered` before
+ * asserting anything about the demo itself.
+ */
+export async function previewReady(page: Page, engine: "sandpack" | "container" = "sandpack") {
+  await expect(page.locator('section[aria-label="Preview"]')).toHaveAttribute("data-preview-status", "ready", {
+    timeout: engine === "container" ? 240_000 : 120_000,
+  });
+}
+
+/** The rendered grid inside the preview frame — the real functional check. */
+export function gridCells(page: Page) {
+  return page.frameLocator('iframe[title="Demo preview"]').locator(".handsontable .htCore td");
+}
+
+export async function expectGridRendered(page: Page) {
+  await expect
+    .poll(async () => gridCells(page).count().catch(() => 0), { timeout: 60_000, intervals: [1_000] })
+    .toBeGreaterThan(0);
+}
+
+// Console/page noise that isn't a real break. Extend as live runs surface new
+// false positives (same list as starter-matrix.spec.ts).
+export const NOISE = [
+  /non-commercial|evaluation license/i,
+  /Download the React DevTools/i,
+  /favicon\.ico/i,
+  /\[vite\] (connecting|connected)/i,
+  /ERR_BLOCKED_BY_CLIENT|third-party cookie/i,
+];
+export const isKnownNoise = (message: string) => NOISE.some((re) => re.test(message));
+
+/**
+ * Track Tier-2 sessions a test creates so they can be torn down even when the
+ * test fails: the container pool holds five global slots shared with real
+ * traffic, and a leaked session squats one for its whole idle window.
+ *
+ *   const tracked = trackSessions(page);
+ *   try { ... } finally { await tracked.cleanup(request); }
+ */
+export function trackSessions(page: Page) {
+  const sessions: { id: string; apiBase: string }[] = [];
+  page.on("response", async (res) => {
+    if (res.request().method() === "POST" && /\/api\/session$/.test(res.url()) && res.ok()) {
+      const body = (await res.json().catch(() => null)) as { sessionId?: string } | null;
+      if (body?.sessionId) sessions.push({ id: body.sessionId, apiBase: new URL(res.url()).origin });
+    }
+  });
+  return {
+    sessions,
+    async cleanup(request: APIRequestContext) {
+      for (const { id, apiBase } of sessions) {
+        await request.delete(`${apiBase}/api/session/${id}`).catch(() => {});
+      }
+    },
+  };
+}
diff --git a/runner/package.json b/runner/package.json
index b39717c8..62b57a8d 100644
--- a/runner/package.json
+++ b/runner/package.json
@@ -22,7 +22,8 @@
   },
   "devDependencies": {
     "@playwright/test": "^1.48.0",
-    "acorn": "^8.18.0",
+"acorn": "^8.18.0",
+    "fflate": "^0.8.2",
     "typescript": "~5.6.0"
   }
 }
diff --git a/runner/playwright.config.ts b/runner/playwright.config.ts
index e2d056c8..819e858b 100644
--- a/runner/playwright.config.ts
+++ b/runner/playwright.config.ts
@@ -12,7 +12,10 @@ export default defineConfig({
   expect: { timeout: 15_000 },
   fullyParallel: true,
   retries: process.env.CI ? 2 : 0,
-  reporter: process.env.CI ? "github" : "list",
+  // In CI, "github" alone leaves `playwright-report/` empty — the workflows
+  // upload that directory on failure, and until DEV-2203 the artifact was a
+  // no-op. The html reporter fills it; traces land in `test-results/`.
+  reporter: process.env.CI ? [["list"], ["github"], ["html", { open: "never" }]] : "list",
   use: { baseURL, trace: "on-first-retry" },
   projects: [{ name: "chromium", use: { ...devices["Desktop Chrome"] } }],
   // Start a local preview only when not pointing at an external URL.
diff --git a/runner/pnpm-lock.yaml b/runner/pnpm-lock.yaml
index 948101b6..76b44544 100644
--- a/runner/pnpm-lock.yaml
+++ b/runner/pnpm-lock.yaml
@@ -14,6 +14,9 @@ importers:
       acorn:
         specifier: ^8.18.0
         version: 8.18.0
+      fflate:
+        specifier: ^0.8.2
+        version: 0.8.3
       typescript:
         specifier: ~5.6.0
         version: 5.6.3