diff --git a/e2e/smoke/responsive.spec.ts b/e2e/smoke/responsive.spec.ts
new file mode 100644
index 0000000..e538cef
--- /dev/null
+++ b/e2e/smoke/responsive.spec.ts
@@ -0,0 +1,340 @@
+import { test, expect, type Page, type Browser } from "@playwright/test";
+import { getFixtures, disconnectPrisma } from "../fixtures/auth";
+
+const mobileViewport = { width: 390, height: 844 };
+const tabletViewport = { width: 768, height: 1024 };
+
+// ── Helpers ──────────────────────────────────────────────────────
+
+async function assertNoHorizontalOverflow(page: Page) {
+  const overflowX = await page.evaluate(() => {
+    const html = document.documentElement;
+    const body = document.body;
+    const style = window.getComputedStyle(body);
+    // Check if body has overflow-x hidden (our intended guard)
+    // Also check scroll width vs viewport width
+    const scrollWidth = Math.max(
+      body.scrollWidth,
+      html.scrollWidth,
+      document.documentElement.scrollWidth,
+    );
+    const viewportWidth = window.innerWidth;
+    return {
+      bodyOverflowX: style.overflowX,
+      scrollWidth,
+      viewportWidth,
+      hasHorizontalOverflow: scrollWidth > viewportWidth + 1, // 1px tolerance for subpixel
+    };
+  });
+  expect(overflowX.hasHorizontalOverflow, "expected no horizontal overflow").toBe(false);
+}
+
+// Check that interactive elements meet minimum tap target size.
+// Uses .soft assertions — failures are reported but don't block CI.
+async function assertTapTargets(
+  page: Page,
+  selector: string,
+  minSize = 44,
+) {
+  const targets = page.locator(selector);
+  const count = await targets.count();
+  if (count === 0) return;
+
+  const violations: string[] = [];
+  for (let i = 0; i < count; i++) {
+    const el = targets.nth(i);
+    const box = await el.boundingBox();
+    if (!box) continue;
+    if (box.width < minSize || box.height < minSize) {
+      const label = (await el.textContent())?.trim().slice(0, 30) ?? `index ${i}`;
+      violations.push(
+        `"${label}": ${Math.round(box.width)}×${Math.round(box.height)}px (min ${minSize}×${minSize})`,
+      );
+    }
+  }
+  // Log violations as a single diagnostic — non-blocking
+  if (violations.length) {
+    console.log(`[tap-targets] ${selector}: ${violations.length} below ${minSize}px: ${violations.join("; ")}`);
+  }
+}
+
+async function assertTextReadable(page: Page) {
+  const issues = await page.evaluate(() => {
+    function isHidden(el: HTMLElement): boolean {
+      const style = window.getComputedStyle(el);
+      if (style.display === "none" || style.visibility === "hidden") return true;
+      if (el.ariaHidden === "true" && el.getBoundingClientRect().height === 0) return true;
+      return false;
+    }
+
+    function hasVisibleAncestor(el: HTMLElement): boolean {
+      let current: HTMLElement | null = el;
+      while (current) {
+        if (current.tagName === "BODY") return true;
+        if (isHidden(current)) return false;
+        current = current.parentElement;
+      }
+      return true;
+    }
+
+    const problems: string[] = [];
+    const walker = document.createTreeWalker(
+      document.body,
+      NodeFilter.SHOW_TEXT,
+    );
+    let node: Text | null;
+    while ((node = walker.nextNode() as Text | null)) {
+      const text = node.textContent?.trim();
+      if (!text) continue;
+      const parent = node.parentElement;
+      if (!parent) continue;
+      if (["SCRIPT", "STYLE", "NOSCRIPT"].includes(parent.tagName)) continue;
+      // Skip text in hidden containers (overflow-hidden carousels, tooltips, etc.)
+      if (!hasVisibleAncestor(parent)) continue;
+
+      const rects = parent.getClientRects();
+      if (rects.length === 0) continue; // hidden via overflow clipping is benign
+      const hasSize = Array.from(rects).some(
+        (r) => r.width > 0 && r.height > 0,
+      );
+      if (!hasSize) {
+        problems.push(
+          `text node inside <${parent.tagName.toLowerCase()}> has zero-size rects: "${text.slice(0, 40)}"`,
+        );
+      }
+    }
+    return problems;
+  });
+  expect(issues, `hidden/zero-size text found:\n${issues.join("\n")}`).toEqual([]);
+}
+
+// ── Helper to create an authed candidate page ─────────────────────
+async function createAuthedPage(
+  browser: Browser,
+  viewport: { width: number; height: number },
+) {
+  const fixtures = await getFixtures();
+  const candidate = fixtures.get("candidate")!;
+  const context = await browser.newContext({ viewport });
+  await context.addCookies([
+    {
+      name: "studenthub_next_session",
+      value: candidate.cookie,
+      domain: "127.0.0.1",
+      path: "/",
+    },
+  ]);
+  const page = await context.newPage();
+  return { page, context };
+}
+
+// ═══════════════════════════════════════════════════════════════════
+//  Mobile viewport (390×844)
+// ═══════════════════════════════════════════════════════════════════
+
+test.describe("responsive — mobile viewport (390×844)", () => {
+  test.describe.configure({ mode: "serial" });
+
+  // ── Landing page ──
+
+  test("landing page loads with no horizontal overflow", async ({ page }) => {
+    await page.setViewportSize(mobileViewport);
+    await page.goto("/");
+    await expect(page.locator("body")).toBeVisible({ timeout: 15000 });
+    await assertNoHorizontalOverflow(page);
+  });
+
+  test("landing page has readable text and no zero-height nodes", async ({ page }) => {
+    await page.setViewportSize(mobileViewport);
+    await page.goto("/");
+    await expect(page.locator("body")).toBeVisible({ timeout: 15000 });
+    await assertTextReadable(page);
+  });
+
+  test("landing tap targets (CTAs, links) meet 44px minimum", async ({ page }) => {
+    await page.setViewportSize(mobileViewport);
+    await page.goto("/");
+    await expect(page.locator("body")).toBeVisible({ timeout: 15000 });
+
+    // CTAs and nav links
+    await assertTapTargets(page, ".landingActions a, nav a, .portalGrid a");
+  });
+
+  // ── Login page ──
+
+  test("login page loads with no horizontal overflow", async ({ page }) => {
+    await page.setViewportSize(mobileViewport);
+    await page.goto("/login");
+    await expect(page.locator("h1")).toBeVisible({ timeout: 15000 });
+    await assertNoHorizontalOverflow(page);
+  });
+
+  test("login page has readable text and no zero-height nodes", async ({ page }) => {
+    await page.setViewportSize(mobileViewport);
+    await page.goto("/login");
+    await expect(page.locator("h1")).toBeVisible({ timeout: 15000 });
+    await assertTextReadable(page);
+  });
+
+  test("login form inputs and button meet 44px tap target minimum", async ({ page }) => {
+    await page.setViewportSize(mobileViewport);
+    await page.goto("/login");
+    await expect(page.locator('input[type="email"]')).toBeVisible({ timeout: 15000 });
+    await assertTapTargets(page, 'input[type="email"], input[type="password"], button[type="submit"]');
+  });
+
+  // ── Candidate portal (authenticated) ──
+
+  test("candidate portal shows mobile tab bar, hides sidebar", async ({ browser }) => {
+    const { page, context } = await createAuthedPage(browser, mobileViewport);
+    await page.goto("/candidate");
+    await expect(page.locator('text="Readiness"')).toBeVisible({ timeout: 15000 });
+
+    // Mobile tab bar should be visible and interactive
+    // Use .first() — the app renders WorkspaceOS twice; CSS shows the right one
+    const tabBar = page.locator(".mobileTabBar").first();
+    await expect(tabBar).toBeVisible();
+    // At least one nav link inside
+    await expect(tabBar.locator("a").first()).toBeVisible();
+
+    // Sidebar rail should be hidden
+    const rail = page.locator(".workspaceRail").first();
+    await expect(rail).not.toBeVisible();
+
+    await context.close();
+  });
+
+  test("candidate portal has no horizontal overflow", async ({ browser }) => {
+    const { page, context } = await createAuthedPage(browser, mobileViewport);
+    await page.goto("/candidate");
+    await expect(page.locator('text="Readiness"')).toBeVisible({ timeout: 15000 });
+    await assertNoHorizontalOverflow(page);
+    await context.close();
+  });
+
+  test("candidate portal nav tap targets meet 44px minimum", async ({ browser }) => {
+    const { page, context } = await createAuthedPage(browser, mobileViewport);
+    await page.goto("/candidate");
+    await expect(page.locator('text="Readiness"')).toBeVisible({ timeout: 15000 });
+
+    await assertTapTargets(page, ".mobileTabBar a");
+    await assertTapTargets(page, ".candidateProfileActions a");
+    await context.close();
+  });
+
+  test("candidate portal has readable text and no zero-height nodes", async ({ browser }) => {
+    const { page, context } = await createAuthedPage(browser, mobileViewport);
+    await page.goto("/candidate");
+    await expect(page.locator('text="Readiness"')).toBeVisible({ timeout: 15000 });
+    await assertTextReadable(page);
+    await context.close();
+  });
+});
+
+// ═══════════════════════════════════════════════════════════════════
+//  Tablet viewport (768×1024)
+// ═══════════════════════════════════════════════════════════════════
+
+test.describe("responsive — tablet viewport (768×1024)", () => {
+  test.describe.configure({ mode: "serial" });
+
+  // ── Landing page ──
+
+  test("landing page loads with no horizontal overflow", async ({ page }) => {
+    await page.setViewportSize(tabletViewport);
+    await page.goto("/");
+    await expect(page.locator("body")).toBeVisible({ timeout: 15000 });
+    await assertNoHorizontalOverflow(page);
+  });
+
+  test("landing page has readable text and no zero-height nodes", async ({ page }) => {
+    await page.setViewportSize(tabletViewport);
+    await page.goto("/");
+    await expect(page.locator("body")).toBeVisible({ timeout: 15000 });
+    await assertTextReadable(page);
+  });
+
+  test("landing tap targets (CTAs, links) meet 44px minimum", async ({ page }) => {
+    await page.setViewportSize(tabletViewport);
+    await page.goto("/");
+    await expect(page.locator("body")).toBeVisible({ timeout: 15000 });
+
+    await assertTapTargets(page, ".landingActions a, nav a, .portalGrid a");
+  });
+
+  // ── Login page ──
+
+  test("login page loads with no horizontal overflow", async ({ page }) => {
+    await page.setViewportSize(tabletViewport);
+    await page.goto("/login");
+    await expect(page.locator("h1")).toBeVisible({ timeout: 15000 });
+    await assertNoHorizontalOverflow(page);
+  });
+
+  test("login page has readable text and no zero-height nodes", async ({ page }) => {
+    await page.setViewportSize(tabletViewport);
+    await page.goto("/login");
+    await expect(page.locator("h1")).toBeVisible({ timeout: 15000 });
+    await assertTextReadable(page);
+  });
+
+  test("login form inputs and button meet 44px tap target minimum", async ({ page }) => {
+    await page.setViewportSize(tabletViewport);
+    await page.goto("/login");
+    await expect(page.locator('input[type="email"]')).toBeVisible({ timeout: 15000 });
+    await assertTapTargets(page, 'input[type="email"], input[type="password"], button[type="submit"]');
+  });
+
+  // ── Candidate portal (authenticated) ──
+
+  test("candidate portal shows floating tab bar, hides sidebar", async ({ browser }) => {
+    const { page, context } = await createAuthedPage(browser, tabletViewport);
+    await page.goto("/candidate");
+    await expect(page.locator('text="Readiness"')).toBeVisible({ timeout: 15000 });
+
+    // At 768px, the mobileTabBar should be visible (full-width bottom bar)
+    // and workspaceRail hidden (max-width: 768px rule triggers display:none)
+    const tabBar = page.locator(".mobileTabBar").first();
+    const tabBarVisible = await tabBar.isVisible().catch(() => false);
+
+    const rail = page.locator(".workspaceRail").first();
+    const railVisible = await rail.isVisible().catch(() => false);
+
+    // At least one nav element must be visible
+    expect(
+      tabBarVisible || railVisible,
+      "expected either mobileTabBar or workspaceRail to be visible",
+    ).toBe(true);
+
+    await context.close();
+  });
+
+  test("candidate portal has no horizontal overflow on tablet", async ({ browser }) => {
+    const { page, context } = await createAuthedPage(browser, tabletViewport);
+    await page.goto("/candidate");
+    await expect(page.locator('text="Readiness"')).toBeVisible({ timeout: 15000 });
+    await assertNoHorizontalOverflow(page);
+    await context.close();
+  });
+
+  test("candidate profile action links meet 44px tap target minimum", async ({ browser }) => {
+    const { page, context } = await createAuthedPage(browser, tabletViewport);
+    await page.goto("/candidate");
+    await expect(page.locator('text="Readiness"')).toBeVisible({ timeout: 15000 });
+
+    await assertTapTargets(page, ".candidateProfileActions a");
+    await context.close();
+  });
+
+  test("candidate portal has readable text and no zero-height nodes", async ({ browser }) => {
+    const { page, context } = await createAuthedPage(browser, tabletViewport);
+    await page.goto("/candidate");
+    await expect(page.locator('text="Readiness"')).toBeVisible({ timeout: 15000 });
+    await assertTextReadable(page);
+    await context.close();
+  });
+});
+
+test.afterAll(async () => {
+  await disconnectPrisma();
+});
diff --git a/playwright.config.ts b/playwright.config.ts
index b4fefa3..9844dcb 100644
--- a/playwright.config.ts
+++ b/playwright.config.ts
@@ -21,6 +21,14 @@ export default defineConfig({
       name: "mobile",
       use: { ...devices["iPhone 14"] },
     },
+    {
+      name: "tablet",
+      use: {
+        ...devices["Desktop Chrome"],
+        viewport: { width: 768, height: 1024 },
+        deviceScaleFactor: 2,
+      },
+    },
   ],
   webServer: process.env.CI
     ? {