diff --git a/src/components/mental-health/__tests__/check-in-wizard.browser.test.tsx b/src/components/mental-health/__tests__/check-in-wizard.browser.test.tsx
new file mode 100644
index 000000000..69469cf9f
--- /dev/null
+++ b/src/components/mental-health/__tests__/check-in-wizard.browser.test.tsx
@@ -0,0 +1,331 @@
+/**
+ * The questionnaire check-in, driven by clicks and keys in a real browser.
+ *
+ * The step arithmetic is pinned on its own in `check-in-nav.test.ts`; this
+ * suite proves the wizard a person uses: one question at a time in the source
+ * order, Back keeping the answer, the number keys, the review with a way back
+ * to every answer, the optional PHQ-9 follow-up, the note over an unvalidated
+ * translation staying on screen with every question, and the body the page
+ * posts. The questionnaire text loads through the production chunk loader,
+ * not a seeded cache.
+ */
+import { describe, expect, it, vi } from "vitest";
+import { page, userEvent } from "vitest/browser";
+
+import { WORDING } from "@/lib/mental-health/wording";
+import type { Locale } from "@/lib/i18n/config";
+
+import { stubFetch } from "../../../../tests/browser/fetch-stub";
+import { renderWithApp } from "../../../../tests/browser/render";
+import { CheckInWizard } from "../check-in-wizard";
+import { MentalWellbeing } from "../mental-wellbeing";
+import type { CheckInAnswers, InstrumentId } from "../types";
+
+const WHO5 = WORDING.WHO5.en;
+const PHQ9 = WORDING.PHQ9.en;
+
+async function wizard(
+  instrument: InstrumentId,
+  {
+    locale = "en",
+    isError = false,
+  }: { locale?: Locale; isError?: boolean } = {},
+) {
+  const onSubmit = vi.fn<(answers: CheckInAnswers) => void>();
+  const onBack = vi.fn();
+  const { screen } = await renderWithApp(
+    <CheckInWizard
+      instrument={instrument}
+      onSubmit={onSubmit}
+      onBack={onBack}
+      isPending={false}
+      isError={isError}
+    />,
+    { locale },
+  );
+  const heading = screen.getByRole("heading", { level: 2 });
+  /** The step on screen asks `text` (waiting out the language's chunk). */
+  const expectQuestion = (text: string) =>
+    expect.element(heading).toHaveTextContent(text);
+  const answer = (name: string) =>
+    screen.getByRole("radio", { name, exact: true });
+  const button = (name: string) =>
+    screen.getByRole("button", { name, exact: true });
+  return { screen, onSubmit, onBack, expectQuestion, answer, button };
+}
+
+/**
+ * Answer the current step by its position, as a keyboard user does: each new
+ * step focuses its question, so Tab first reaches the answers, then the
+ * number key chooses.
+ */
+async function pressAnswer(position: number) {
+  await userEvent.tab();
+  await userEvent.keyboard(String(position));
+}
+
+describe("<CheckInWizard> steps", () => {
+  it("opens on the first question with the stem and the answers in source order", async () => {
+    const { screen, button } = await wizard("WHO5");
+    await expect.element(screen.getByText(WHO5.items[0])).toBeVisible();
+    await expect.element(screen.getByText(WHO5.stems.period)).toBeVisible();
+    await expect.element(screen.getByText("Question 1 of 5")).toBeVisible();
+    const labels = screen
+      .getByRole("radio")
+      .elements()
+      .map((el) => el.textContent);
+    expect(labels).toEqual([5, 4, 3, 2, 1, 0].map((v) => WHO5.anchors.all[v]));
+    await expect.element(button("Back")).toBeDisabled();
+    await expect.element(button("Next")).toBeDisabled();
+    await expect.element(button("See my result")).not.toBeInTheDocument();
+    // The instrument's own explanation heads the check-in; the landing's
+    // self-test disclaimer does not follow the person into it.
+    await expect
+      .element(
+        screen.getByText(
+          "5-question well-being check. Answer for the last two weeks; higher numbers mean better well-being.",
+        ),
+      )
+      .toBeVisible();
+    await expect
+      .element(screen.getByText(/not a diagnosis/i))
+      .not.toBeInTheDocument();
+    // English is the validated wording: no note, no switch.
+    await expect
+      .element(screen.getByText(/has not been scientifically validated/))
+      .not.toBeInTheDocument();
+  });
+
+  it("gives each SCI item its own answers under its section stem", async () => {
+    const SCI = WORDING.SCI.en;
+    const { screen, expectQuestion } = await wizard("SCI");
+    await expectQuestion(SCI.items[0]);
+    await expect.element(screen.getByText(SCI.stems.night)).toBeVisible();
+    await expect.element(screen.getByText("Question 1 of 8")).toBeVisible();
+    expect(
+      screen
+        .getByRole("radio")
+        .elements()
+        .map((el) => el.textContent),
+    ).toEqual([4, 3, 2, 1, 0].map((v) => SCI.anchors.duration[v]));
+  });
+
+  it("advances on a choice, and Back returns with the answer still chosen", async () => {
+    const { screen, answer, button, expectQuestion } = await wizard("WHO5");
+    await answer(WHO5.anchors.all[3]).click();
+    await expect.element(screen.getByText("Question 2 of 5")).toBeVisible();
+    await expectQuestion(WHO5.items[1]);
+    await expect.element(button("Next")).toBeDisabled();
+
+    await button("Back").click();
+    await expectQuestion(WHO5.items[0]);
+    await expect.element(answer(WHO5.anchors.all[3])).toBeChecked();
+    await button("Next").click();
+    await expectQuestion(WHO5.items[1]);
+  });
+
+  it("chooses by number key, moves with the arrows and focuses each new question", async () => {
+    const { screen, answer } = await wizard("WHO5");
+    await answer(WHO5.anchors.all[5]).click();
+    await expect
+      .element(screen.getByRole("heading", { name: WHO5.items[1] }))
+      .toHaveFocus();
+    await userEvent.tab();
+    await expect.element(answer(WHO5.anchors.all[5])).toHaveFocus();
+    await userEvent.keyboard("{ArrowDown}{ArrowDown}");
+    await expect.element(answer(WHO5.anchors.all[3])).toHaveFocus();
+    await userEvent.keyboard("{End}");
+    await expect.element(answer(WHO5.anchors.all[0])).toHaveFocus();
+
+    // "2" is the second answer as printed, which scores 4 on the WHO-5.
+    await userEvent.keyboard("2");
+    await expect.element(screen.getByText("Question 3 of 5")).toBeVisible();
+    await screen.getByRole("button", { name: "Back", exact: true }).click();
+    await expect.element(answer(WHO5.anchors.all[4])).toBeChecked();
+  });
+
+  it("reviews every answer, changes one and returns to the review", async () => {
+    const { screen, onSubmit, button } = await wizard("WHO5");
+    for (const position of [1, 2, 3, 4, 5]) await pressAnswer(position);
+    await expect
+      .element(screen.getByRole("heading", { name: "Check your answers" }))
+      .toBeVisible();
+    await expect
+      .element(screen.getByText("All 5 questions answered"))
+      .toBeVisible();
+
+    await screen
+      .getByRole("button", { name: "Change the answer to question 3" })
+      .click();
+    await expect.element(screen.getByText("Question 3 of 5")).toBeVisible();
+    await screen
+      .getByRole("radio", { name: WHO5.anchors.all[0], exact: true })
+      .click();
+    await expect
+      .element(screen.getByRole("heading", { name: "Check your answers" }))
+      .toBeVisible();
+
+    await button("See my result").click();
+    expect(onSubmit).toHaveBeenCalledExactlyOnceWith({
+      items: [5, 4, 0, 2, 1],
+      functionalDifficulty: undefined,
+      englishOriginal: false,
+    });
+  });
+
+  it("asks the PHQ-9 follow-up as an optional step that a second press clears", async () => {
+    const { screen, onSubmit, answer, button, expectQuestion } =
+      await wizard("PHQ9");
+    for (let i = 0; i < 9; i++) await pressAnswer(1);
+    await expect
+      .element(screen.getByText("Follow-up question (optional)"))
+      .toBeVisible();
+    await expectQuestion(PHQ9.functional!.title);
+    await expect.element(button("Review answers")).toBeEnabled();
+
+    await answer(PHQ9.functional!.anchors[2]).click();
+    await expect.element(answer(PHQ9.functional!.anchors[2])).toBeChecked();
+    await answer(PHQ9.functional!.anchors[2]).click();
+    await expect.element(answer(PHQ9.functional!.anchors[2])).not.toBeChecked();
+
+    await button("Review answers").click();
+    await expect.element(screen.getByText("Not answered")).toBeVisible();
+    await button("See my result").click();
+    expect(onSubmit).toHaveBeenCalledExactlyOnceWith({
+      items: [0, 0, 0, 0, 0, 0, 0, 0, 0],
+      functionalDifficulty: undefined,
+      englishOriginal: false,
+    });
+  });
+
+  it("returns to the overview and shows a failed submit", async () => {
+    const { screen, onBack } = await wizard("GAD7", { isError: true });
+    await expect
+      .element(screen.getByRole("alert"))
+      .toHaveTextContent("Something went wrong. Please try again.");
+    await screen.getByRole("button", { name: "Overview" }).click();
+    expect(onBack).toHaveBeenCalledOnce();
+  });
+});
+
+describe("<CheckInWizard> in the reader's language", () => {
+  const SCI_DE = WORDING.SCI.de;
+  const NOTE =
+    "Diese Übersetzung ist nicht wissenschaftlich validiert; nimm das Ergebnis als Orientierung.";
+
+  it("keeps the note over an unvalidated translation on screen with every question", async () => {
+    await page.viewport(390, 640);
+    const { screen, expectQuestion } = await wizard("SCI", { locale: "de" });
+    expect(SCI_DE.validated).toBe(false);
+    const note = screen.getByText(NOTE);
+    for (let i = 0; i < 8; i++) {
+      await expectQuestion(SCI_DE.items[i]);
+      await expect.element(note).toBeVisible();
+      const rect = note.element().getBoundingClientRect();
+      expect(rect.top, `step ${i + 1}`).toBeGreaterThanOrEqual(0);
+      expect(rect.bottom, `step ${i + 1}`).toBeLessThanOrEqual(
+        window.innerHeight,
+      );
+      // The first question arrives with the language's chunk, after the
+      // focus move has run, so it is answered by pointer; the rest by key.
+      if (i === 0) await screen.getByRole("radio").first().click();
+      else await pressAnswer(1);
+    }
+    await expect
+      .element(screen.getByRole("heading", { name: "Antworten prüfen" }))
+      .toBeVisible();
+    await expect.element(note).toBeVisible();
+  });
+
+  it("switches to the English original and says so in the answers", async () => {
+    const { screen, onSubmit, expectQuestion } = await wizard("SCI", {
+      locale: "de",
+    });
+    await expectQuestion(SCI_DE.items[0]);
+    await screen
+      .getByRole("button", { name: "Englischen Originaltext zeigen" })
+      .click();
+    await expect
+      .element(screen.getByRole("heading", { name: WORDING.SCI.en.items[0] }))
+      .toHaveAttribute("lang", "en");
+    // The note stays: the reader is still in a language with no validated form.
+    await expect.element(screen.getByText(NOTE)).toBeVisible();
+    await screen.getByRole("radio").first().click();
+    for (let i = 1; i < 8; i++) await pressAnswer(1);
+    await screen
+      .getByRole("button", { name: "Ergebnis ansehen", exact: true })
+      .click();
+    expect(onSubmit).toHaveBeenCalledExactlyOnceWith(
+      expect.objectContaining({ englishOriginal: true }),
+    );
+  });
+
+  it("shows a validated translation with no note and no switch", async () => {
+    const { screen, expectQuestion } = await wizard("PHQ9", { locale: "nl" });
+    await expectQuestion(WORDING.PHQ9.nl.items[0]);
+    await expect
+      .element(screen.getByText(WORDING.PHQ9.nl.stems.period))
+      .toBeVisible();
+    await expect
+      .element(screen.getByRole("button", { name: /English/ }))
+      .not.toBeInTheDocument();
+  });
+});
+
+describe("the check-in from the overview", () => {
+  it("posts the answers with the instrument and the reader's language, then shows the result", async () => {
+    const api = stubFetch().on("GET", "/api/mental-health/assessments", {
+      data: { assessments: [] },
+    });
+    const post = api.deferred("POST", "/api/mental-health/assessments");
+    const { screen } = await renderWithApp(<MentalWellbeing />);
+
+    const start =
+      '[data-instrument="WHO5"] [data-slot="instrument-card-start"]';
+    await expect.poll(() => document.querySelector(start)).toBeTruthy();
+    await page.elementLocator(document.querySelector(start)!).click();
+    await expect.element(screen.getByText(WHO5.items[0])).toBeVisible();
+    await screen.getByRole("radio").nth(1).click();
+    for (const position of [2, 3, 1, 2]) await pressAnswer(position);
+    const submit = screen.getByRole("button", { name: "See my result" });
+    await submit.click();
+
+    await expect
+      .element(screen.getByRole("button", { name: "Saving…" }))
+      .toBeDisabled();
+    expect(api.calls("POST", "/api/mental-health/assessments")).toHaveLength(1);
+    expect(api.calls("POST", "/api/mental-health/assessments")[0].body).toEqual(
+      {
+        instrument: "WHO5",
+        locale: "en",
+        items: [4, 4, 3, 5, 4],
+        englishOriginal: false,
+      },
+    );
+
+    post.release({
+      status: 201,
+      data: {
+        assessment: {
+          id: "a-1",
+          instrument: "WHO5",
+          locale: "en",
+          wording: "validated",
+          totalScore: 80,
+          severityBand: "good",
+          item9Flagged: false,
+          crisisShownAt: null,
+          takenAt: "2026-09-15T10:00:00.000Z",
+        },
+        actionThreshold: 50,
+        crisis: null,
+      },
+    });
+    await expect
+      .element(screen.getByText("80", { exact: true }).first())
+      .toBeVisible();
+    await expect
+      .element(screen.getByRole("button", { name: "See my result" }))
+      .not.toBeInTheDocument();
+  });
+});
diff --git a/src/components/mental-health/__tests__/mental-wellbeing.test.tsx b/src/components/mental-health/__tests__/mental-wellbeing.test.tsx
index f31aff775..dc9925453 100644
--- a/src/components/mental-health/__tests__/mental-wellbeing.test.tsx
+++ b/src/components/mental-health/__tests__/mental-wellbeing.test.tsx
@@ -6,15 +6,14 @@ import { I18nProvider } from "@/lib/i18n/context";
 import { queryKeys } from "@/lib/query-keys";
 import en from "../../../../messages/en.json";
 import nl from "../../../../messages/nl.json";
-import { WORDING } from "@/lib/mental-health/wording";
 import { seedQuestionnaireWording } from "@/__tests__/helpers/questionnaire-wording";
 
 /**
- * Mental-wellbeing surface redesign (v1.25.3). The SSR-only convention
- * (`renderToStaticMarkup`, `environment: "node"`, no `@testing-library/react`)
- * means clicks can't be driven here — the wizard's advance/back grammar is
- * pinned in `check-in-nav.test.ts`. These tests pin the SSR-observable
- * contracts: the disclaimer renders ONLY on the landing (never while testing),
+ * Mental-wellbeing surface redesign (v1.25.3). The check-in wizard itself is
+ * driven in a real browser by `check-in-wizard.browser.test.tsx` (steps,
+ * keys, review, follow-up, the unvalidated-translation note, the posted
+ * body); its step arithmetic is pinned in `check-in-nav.test.ts`. These tests
+ * pin the rendered contracts of the rest of the surface: the disclaimer renders ONLY on the landing (never while testing),
  * a positive item-9 surfaces the crisis card, and (v1.27.9) the landing is
  * intro + instrument cards only — the dated history + trend chart live in the
  * per-instrument detail a card click opens, pinned to one instrument.
@@ -74,52 +73,6 @@ describe("landing chrome (v1.25.5 — disclaimer + heading removed)", () => {
     // …and the lead description still introduces the screeners.
     expect(html).toContain(mh.pageDescription);
   });
-
-  it("does NOT render any disclaimer inside the check-in wizard", () => {
-    const html = withProviders(
-      <CheckInWizard
-        instrument="PHQ9"
-        onSubmit={() => {}}
-        onBack={() => {}}
-        isPending={false}
-        isError={false}
-      />,
-    );
-    expect(html).not.toContain('data-slot="mental-health-disclaimer"');
-    // …but the standardized instrument explanation IS shown.
-    expect(html).toContain(mh.instrumentDescription.phq9);
-  });
-});
-
-describe("check-in wizard scaffolding (v1.27.6 — questions only)", () => {
-  const html = withProviders(
-    <CheckInWizard
-      instrument="PHQ9"
-      onSubmit={() => {}}
-      onBack={() => {}}
-      isPending={false}
-      isError={false}
-    />,
-  );
-
-  it("no longer renders the question-overview strip", () => {
-    expect(html).not.toContain('data-slot="wizard-stepper"');
-  });
-
-  it("no longer renders the review recap or the functional follow-up", () => {
-    expect(html).not.toContain("You have answered");
-    expect(html).not.toContain('data-slot="check-in-submit"');
-  });
-
-  it("opens on the first question with the Back/Next footer", () => {
-    expect(html).toContain(WORDING.PHQ9.en.items[0]);
-    expect(html).toContain('data-slot="check-in-back"');
-    expect(html).toContain('data-slot="check-in-next"');
-    // Back is disabled on the first step.
-    expect(html).toMatch(
-      /data-slot="check-in-back"[^>]*disabled|disabled[^>]*data-slot="check-in-back"/,
-    );
-  });
 });
 
 describe("item-9 crisis surfacing on the result", () => {
@@ -243,49 +196,6 @@ describe("WHO-5 / SCI on the same infrastructure (v1.27.9)", () => {
     expect(html).not.toContain("Rhythmus");
   });
 
-  it("WHO-5 wizard opens on item 1 with the six-point scale in source order and the recall stem", () => {
-    const html = withProviders(
-      <CheckInWizard
-        instrument="WHO5"
-        onSubmit={() => {}}
-        onBack={() => {}}
-        isPending={false}
-        isError={false}
-      />,
-    );
-    expect(html).toContain(WORDING.WHO5.en.items[0]);
-    expect(html).toContain('data-slot="check-in-stem"');
-    expect(html).toContain(WORDING.WHO5.en.stems.period);
-    // Six anchors, 5 → 0 (the WHO form leads with "All of the time").
-    for (const v of [5, 4, 3, 2, 1, 0]) {
-      expect(html).toContain(WORDING.WHO5.en.anchors.all[v]);
-    }
-    // English items are the validated wording for en — no translation note.
-    expect(html).not.toContain('data-slot="check-in-unvalidated-note"');
-    expect(html).not.toContain('data-slot="check-in-wording-toggle"');
-    // No functional follow-up outside the PHQ-9: 5 steps total.
-    expect(html).toContain("Question 1 of 5");
-  });
-
-  it("SCI wizard opens on item 1 with the item-specific duration anchors and section stem", () => {
-    const html = withProviders(
-      <CheckInWizard
-        instrument="SCI"
-        onSubmit={() => {}}
-        onBack={() => {}}
-        isPending={false}
-        isError={false}
-      />,
-    );
-    expect(html).toContain(WORDING.SCI.en.items[0]);
-    expect(html).toContain(WORDING.SCI.en.stems.night);
-    // Item 1 carries the sleep-latency time ranges, 4 → 0.
-    for (const v of [4, 3, 2, 1, 0]) {
-      expect(html).toContain(WORDING.SCI.en.anchors.duration[v]);
-    }
-    expect(html).toContain("Question 1 of 8");
-  });
-
   it("shows the gentle PHQ-9 pointer on a WHO-5 total of 50 or below", () => {
     const result: CreateResponse = {
       assessment: {
@@ -530,23 +440,20 @@ describe("questionnaires in the reader's language", () => {
     );
   }
 
-  function wizard(instrument: "PHQ9" | "SCI") {
-    return (
-      <CheckInWizard
-        instrument={instrument}
-        onSubmit={() => {}}
-        onBack={() => {}}
-        isPending={false}
-        isError={false}
-      />
-    );
-  }
-
+  // Kept here rather than in the browser suite: the frame before the
+  // language's chunk arrives is the one a server render always paints, and a
+  // browser loads the chunk before a test can look.
   it("holds the step's place while the language's text loads", () => {
     const html = renderToStaticMarkup(
       <QueryClientProvider client={new QueryClient()}>
         <I18nProvider initialLocale="nl" initialMessages={nl}>
-          {wizard("SCI")}
+          <CheckInWizard
+            instrument="SCI"
+            onSubmit={() => {}}
+            onBack={() => {}}
+            isPending={false}
+            isError={false}
+          />
         </I18nProvider>
       </QueryClientProvider>,
     );
@@ -555,30 +462,6 @@ describe("questionnaires in the reader's language", () => {
     expect(html).not.toContain('data-slot="check-in-unvalidated-note"');
   });
 
-  it("the PHQ-9 in Dutch is the validated Dutch form, with no note and no switch", () => {
-    const html = renderIn("nl", wizard("PHQ9"));
-    const dutch = WORDING.PHQ9.nl;
-    expect(html).toContain(dutch.stems.period);
-    expect(html).toContain(dutch.items[0]);
-    for (const v of [0, 1, 2, 3]) expect(html).toContain(dutch.anchors.all[v]);
-    expect(html).not.toContain(WORDING.PHQ9.en.items[0]);
-    expect(html).not.toContain('data-slot="check-in-unvalidated-note"');
-    expect(html).not.toContain('data-slot="check-in-wording-toggle"');
-  });
-
-  it("the SCI in Dutch shows the translation under the note, with the switch to the English original", () => {
-    const html = renderIn("nl", wizard("SCI"));
-    const dutch = WORDING.SCI.nl;
-    expect(dutch.validated).toBe(false);
-    expect(html).toContain(dutch.stems.night);
-    expect(html).toContain(dutch.items[0]);
-    expect(html).not.toContain(WORDING.SCI.en.items[0]);
-    expect(html).toContain('data-slot="check-in-unvalidated-note"');
-    expect(html).toContain(nl.mentalHealth.wording.unvalidatedNote);
-    expect(html).toContain('data-slot="check-in-wording-toggle"');
-    expect(html).toContain(nl.mentalHealth.wording.showOriginal);
-  });
-
   it("the result and the history mark an unvalidated translation, and only that", () => {
     const row = (wording: AssessmentRow["wording"]): AssessmentRow => ({
       id: `s-${wording}`,
diff --git a/vitest.config.mts b/vitest.config.mts
index 51fa3430b..995c34e16 100644
--- a/vitest.config.mts
+++ b/vitest.config.mts
@@ -129,6 +129,15 @@ export default defineConfig({
             ),
           },
         },
+        // Next's client modules (`next/link` among them) read
+        // `process.env.*`, which Next's own bundler inlines at build time.
+        // A page has no `process`; this inlines an environment with no
+        // public variables set, as a build without any would.
+        define: {
+          "process.env": JSON.stringify({
+            NODE_ENV: process.env.NODE_ENV ?? "test",
+          }),
+        },
         // Pre-bundle every dependency the browser files reach before the
         // first one loads. Discovered late, a dependency makes Vite re-bundle
         // and reload the page mid-run, which fails the file that was