diff --git a/docs/architecture.md b/docs/architecture.md
index 4463417..6960a91 100644
--- a/docs/architecture.md
+++ b/docs/architecture.md
@@ -615,7 +615,21 @@ Sémantique simulée, chaque point prouvé par `src/test/hookHarness.test.ts` :
 
 Non simulé : le nouveau rendu après un setter ou un dispatch, les enfants (un composant dans l'arbre rendu reste un élément), le DOM, le concurrent, la boucle de mises à jour pendant le rendu (le `render()` suivant la lit).
 
-Utilisateurs : `useOnboardingChecklist.wiring.test.ts`, `UsersSettingsPage.test.tsx`, `BudgetTable.wiring.test.ts`, `BudgetPage.wiring.test.ts`, `AppShell.slot.test.tsx`, `OnboardingStepCard.test.tsx`. Hors périmètre de #409, `useImportWizard.mount.test.ts` et `useImportWizard.executeImport.test.ts` gardent leurs faux non persistants.
+Utilisateurs : `useOnboardingChecklist.wiring.test.ts`, `UsersSettingsPage.test.tsx`, `BudgetTable.wiring.test.ts`, `BudgetPage.wiring.test.ts`, `AppShell.slot.test.tsx`, `OnboardingStepCard.test.tsx`, `PriceFetchConsentToggle.test.tsx` (#389). Hors périmètre de #409, `useImportWizard.mount.test.ts` et `useImportWizard.executeImport.test.ts` gardent leurs faux non persistants.
+
+### Faux `t` marqué — `src/test/i18nMock.ts` (#389)
+
+**Jamais de `t` brut dans un test.** Un faux `t` qui rend la clé telle quelle cache un appel à `t` oublié : un composant qui affiche `license.removeKey.confirmValid` au lieu du texte traduit passe toute la suite. Le seul faux `t` du dépôt est `markedT` : il rend `t(clé)`, ou `t(clé[a=1,b=2])` avec des options, dans l'ordre des options. Motif unique, en tête du fichier de test :
+
+```ts
+vi.mock("react-i18next", async () => (await import("../test/i18nMock")).i18nMock());
+```
+
+Options de la fabrique : `language` (« fr » par défaut ; une fonction est relue à chaque accès, pour un test qui change de langue entre deux rendus : `i18nMock({ language: () => language })`) et `fixture` (valeurs rendues telles quelles pour certaines clés, comme ce que déclare la locale, un objet sous `returnObjects` par exemple ; une valeur lue par la fabrique au chargement du module se déclare par `vi.hoisted`). Une fonction qui prend `t` en paramètre reçoit `markedT` lui-même.
+
+Les assertions qui nomment un texte affiché s'écrivent sous la forme marquée (`toContain(">t(dashboard.title)<")`, `toEqual(["t(onboarding.state.done)"])`) : elles rougissent sur une chaîne qui a sauté `t`. Une assertion par sous-chaîne sur une clé nue reste valide, la clé figurant dans la marque, mais ne prouve pas l'appel à `t`. Dans une expression régulière, échapper les parenthèses et crochets de la marque.
+
+Garde : `src/__integration__/i18n-mock-guard.test.ts` lit tous les `*.test.ts(x)` de `src/` et échoue sur une propriété `useTranslation:` ou `t: (` (ancrées sur une frontière de mot) hors de `src/test/i18nMock.ts`, ou sur un `vi.mock("react-i18next", …)` qui ne passe pas par `i18nMock`.
 
 ## CI/CD
 
diff --git a/src/__integration__/i18n-mock-guard.test.ts b/src/__integration__/i18n-mock-guard.test.ts
new file mode 100644
index 0000000..b167140
--- /dev/null
+++ b/src/__integration__/i18n-mock-guard.test.ts
@@ -0,0 +1,77 @@
+/**
+ * Guard: one fake `t` in the test suite, the marked one of `src/test/i18nMock.ts` (#389).
+ *
+ * A local fake `t` that returns the key as is hides a forgotten call to `t`
+ * (#387 review). The migration moved every test file to `i18nMock`; this guard
+ * keeps it that way. It reads the sources, as `transactions-transfer-icon.test.ts`
+ * does, and fails on any test file (`*.test.ts`, `*.test.tsx`) other than the
+ * module itself that:
+ *   1. declares a `useTranslation:` property (a hand-written `react-i18next` module);
+ *   2. declares a `t: (` property (a hand-written fake `t`);
+ *   3. mocks `react-i18next` without going through `i18nMock`.
+ *
+ * Keywords rather than an analysis of the factory: less fragile. The matches
+ * are anchored on a word boundary, so `useLicenseContext: () =>` or
+ * `get: (target, key)` are not a `t: (`. This file names the patterns only
+ * inside regular expressions and excludes itself.
+ */
+
+import { describe, it, expect } from "vitest";
+import { readdirSync, readFileSync } from "fs";
+import { relative, resolve, sep } from "path";
+
+const SRC = resolve(import.meta.dirname, "..");
+const MODULE = resolve(SRC, "test", "i18nMock.ts");
+const SELF = resolve(import.meta.dirname, "i18n-mock-guard.test.ts");
+
+const LOCAL_MODULE = /\buseTranslation\s*:/;
+const LOCAL_T = /\bt\s*:\s*\(/;
+const MOCKS_I18NEXT = /vi\.mock\(\s*["']react-i18next["']/;
+
+/** The offending lines of one source, as `path:line: text`. */
+function offences(path: string, source: string): string[] {
+  const name = relative(SRC, path).split(sep).join("/");
+  const found = source
+    .split("\n")
+    .flatMap((line, i) =>
+      LOCAL_MODULE.test(line) || LOCAL_T.test(line) ? [`${name}:${i + 1}: ${line.trim()}`] : [],
+    );
+  if (MOCKS_I18NEXT.test(source) && !source.includes("i18nMock")) {
+    found.push(`${name}: mocks react-i18next without i18nMock`);
+  }
+  return found;
+}
+
+const TEST_FILES = (readdirSync(SRC, { recursive: true }) as string[])
+  .filter((entry) => /\.test\.tsx?$/.test(entry))
+  .map((entry) => resolve(SRC, entry))
+  .filter((path) => path !== MODULE && path !== SELF);
+
+describe("i18n mock guard (#389)", () => {
+  it("scans the test files of src, recursively", () => {
+    expect(TEST_FILES.length).toBeGreaterThan(100);
+    expect(TEST_FILES).toContain(resolve(SRC, "components", "settings", "LicenseCard.render.test.tsx"));
+    expect(TEST_FILES).toContain(resolve(SRC, "pages", "settings", "UsersSettingsPage.test.tsx"));
+  });
+
+  it("recognises a local fake, and only that", () => {
+    const local = [
+      'vi.mock("react-i18next", () => ({',
+      "  useTranslation: () => ({ t: (k: string) => k }),",
+      "}));",
+    ].join("\n");
+    expect(offences(resolve(SRC, "x.test.tsx"), local)).toHaveLength(2);
+    expect(offences(resolve(SRC, "x.test.tsx"), 'vi.mock("react-i18next", () => fake);')).toHaveLength(1);
+    const clean = [
+      'vi.mock("react-i18next", async () => (await import("../test/i18nMock")).i18nMock());',
+      "const context = { useLicenseContext: () => ctx, get: (target: object) => target };",
+      "await view.removeKey({ confirm, t: markedT });",
+    ].join("\n");
+    expect(offences(resolve(SRC, "x.test.tsx"), clean)).toEqual([]);
+  });
+
+  it("finds no other fake t than the one of src/test/i18nMock.ts", () => {
+    const found = TEST_FILES.flatMap((path) => offences(path, readFileSync(path, "utf-8")));
+    expect(found, "use i18nMock from src/test/i18nMock.ts").toEqual([]);
+  });
+});
diff --git a/src/components/balance/PriceFetchControl.test.tsx b/src/components/balance/PriceFetchControl.test.tsx
index ad30af2..2090daf 100644
--- a/src/components/balance/PriceFetchControl.test.tsx
+++ b/src/components/balance/PriceFetchControl.test.tsx
@@ -27,19 +27,8 @@ vi.mock("../../services/userPreferenceService", () => ({
   setPreference: vi.fn(),
 }));
 
-// react-i18next: return the key as-is for tests
-vi.mock("react-i18next", () => ({
-  useTranslation: vi.fn(() => ({
-    t: (key: string, opts?: Record<string, unknown>) => {
-      // Include interpolation values in the returned string for assertions
-      if (opts) {
-        return `${key}(${JSON.stringify(opts)})`;
-      }
-      return key;
-    },
-    i18n: { language: "fr" },
-  })),
-}));
+// react-i18next: the shared marked `t` (#389), so a text that skipped `t` fails
+vi.mock("react-i18next", async () => (await import("../../test/i18nMock")).i18nMock());
 
 // lucide-react: return simple stubs
 vi.mock("lucide-react", () => ({
@@ -58,7 +47,8 @@ import {
   getPreference,
   setPreference,
 } from "../../services/userPreferenceService";
-import {
+import { renderToStaticMarkup } from "react-dom/server";
+import PriceFetchControl, {
   __resetBestEffortDismissForTests,
 } from "./PriceFetchControl";
 
@@ -363,3 +353,31 @@ describe("PriceFetchControl — fetchPrice invocation args", () => {
     expect(mockSetPreference).not.toHaveBeenCalled();
   });
 });
+
+// ---------------------------------------------------------------------------
+// Test: what the control displays (#389)
+// ---------------------------------------------------------------------------
+
+describe("PriceFetchControl — displayed texts", () => {
+  beforeEach(() => {
+    __resetBestEffortDismissForTests();
+    vi.resetAllMocks();
+    setPremium(true);
+  });
+
+  it("names the fetch button and the stock best-effort notice through t", () => {
+    const html = renderToStaticMarkup(
+      <PriceFetchControl
+        symbol="AAPL"
+        date="2026-04-25"
+        categoryKind="priced"
+        assetType="stock"
+        onPriceFetched={vi.fn()}
+      />,
+    );
+    expect(html).toContain('aria-label="t(balance.priceFetching.button)"');
+    expect(html).toContain(">t(balance.priceFetching.button)<");
+    expect(html).toContain(">t(balance.priceFetching.bestEffortNotice)<");
+    expect(html).toContain('aria-label="t(common.close)"');
+  });
+});
diff --git a/src/components/budget/BudgetTable.render.test.tsx b/src/components/budget/BudgetTable.render.test.tsx
index f747d00..4650eee 100644
--- a/src/components/budget/BudgetTable.render.test.tsx
+++ b/src/components/budget/BudgetTable.render.test.tsx
@@ -10,9 +10,7 @@ import { renderToStaticMarkup } from "react-dom/server";
 import type { BudgetYearRow } from "../../shared/types";
 import type { CollapseAccessors } from "../../utils/collapsibleRows";
 
-vi.mock("react-i18next", () => ({
-  useTranslation: () => ({ t: (k: string) => `t(${k})`, i18n: { language: "fr" } }),
-}));
+vi.mock("react-i18next", async () => (await import("../../test/i18nMock")).i18nMock());
 
 const harness = vi.hoisted(() => ({
   /** Keys of the open groups (`p:<category id>`): the grid opens collapsed. */
diff --git a/src/components/budget/BudgetTable.wiring.test.ts b/src/components/budget/BudgetTable.wiring.test.ts
index b16be6b..b5a31c2 100644
--- a/src/components/budget/BudgetTable.wiring.test.ts
+++ b/src/components/budget/BudgetTable.wiring.test.ts
@@ -16,9 +16,7 @@ const ctx = vi.hoisted(() => ({
   /** Keys of the open groups (`p:<category id>`): the grid opens collapsed. */
   expanded: new Set<string>(),
 }));
-vi.mock("react-i18next", () => ({
-  useTranslation: () => ({ t: (k: string) => `t(${k})`, i18n: { language: "fr" } }),
-}));
+vi.mock("react-i18next", async () => (await import("../../test/i18nMock")).i18nMock());
 vi.mock("../../hooks/useCollapsibleGroups", async () => {
   const { collapsibleKeys, isCollapsedFor, visibleRows } = await import("../../utils/collapsibleRows");
   return {
diff --git a/src/components/categories/AddKeywordDialog.render.test.tsx b/src/components/categories/AddKeywordDialog.render.test.tsx
index 002351d..e09e897 100644
--- a/src/components/categories/AddKeywordDialog.render.test.tsx
+++ b/src/components/categories/AddKeywordDialog.render.test.tsx
@@ -4,13 +4,7 @@
 import { describe, it, expect, vi } from "vitest";
 import { renderToStaticMarkup } from "react-dom/server";
 
-vi.mock("react-i18next", () => ({
-  useTranslation: () => ({
-    t: (k: string, o?: Record<string, unknown>) =>
-      o ? `${k}[${Object.entries(o).map(([a, b]) => `${a}=${String(b)}`).join(",")}]` : k,
-    i18n: { language: "fr" },
-  }),
-}));
+vi.mock("react-i18next", async () => (await import("../../test/i18nMock")).i18nMock());
 
 vi.mock("./keywordCategory", () => ({
   loadKeywordCategories: vi.fn(() => new Promise(() => undefined)),
@@ -51,12 +45,12 @@ describe("AddKeywordDialog — category field (#423)", () => {
   it("starts empty, with the 'no category' placeholder, until the list is in", () => {
     const [input] = markup(7).match(/<input [^>]*role="combobox"[^>]*>/g) ?? [];
     expect(input).toContain('value=""');
-    expect(input).toContain('placeholder="transactions.table.noCategory"');
+    expect(input).toContain('placeholder="t(transactions.table.noCategory)"');
   });
 
   it("keeps the apply button disabled before the list is in", () => {
     const html = markup(7);
-    const [apply] = html.match(/<button [^>]*>reports\.keyword\.applyAndRecategorize<\/button>/g) ?? [];
+    const [apply] = html.match(/<button [^>]*>t\(reports\.keyword\.applyAndRecategorize\)<\/button>/g) ?? [];
     expect(apply).toBeDefined();
     expect(apply).toContain("disabled");
   });
diff --git a/src/components/categories/CategoryDetailPanel.render.test.tsx b/src/components/categories/CategoryDetailPanel.render.test.tsx
index 434b8f0..3f61bca 100644
--- a/src/components/categories/CategoryDetailPanel.render.test.tsx
+++ b/src/components/categories/CategoryDetailPanel.render.test.tsx
@@ -3,13 +3,7 @@
 import { describe, it, expect, vi } from "vitest";
 import { renderToStaticMarkup } from "react-dom/server";
 
-vi.mock("react-i18next", () => ({
-  useTranslation: () => ({
-    t: (k: string, o?: Record<string, unknown>) =>
-      o ? `${k}[${Object.entries(o).map(([a, b]) => `${a}=${String(b)}`).join(",")}]` : k,
-    i18n: { language: "fr" },
-  }),
-}));
+vi.mock("react-i18next", async () => (await import("../../test/i18nMock")).i18nMock());
 
 vi.mock("./parentOptions", async (importOriginal) => {
   const actual = await importOriginal<typeof import("./parentOptions")>();
@@ -82,3 +76,14 @@ describe("CategoryDetailPanel — editingId wiring (#423)", () => {
     expect(buildParentOptions).toHaveBeenCalledWith(CATEGORIES, { editingId: null, currentParentId: null });
   });
 });
+
+describe("CategoryDetailPanel — displayed texts (#389)", () => {
+  it("titles the edit view and the create view through t", () => {
+    expect(markup(RENT, formOf(RENT), false)).toContain(">t(categories.editCategory)<");
+    expect(markup(null, formOf(node(0, null, "")), true)).toContain(">t(categories.addCategory)<");
+  });
+
+  it("asks for a selection through t when nothing is selected", () => {
+    expect(markup(null, null, false)).toContain(">t(categories.selectCategory)<");
+  });
+});
diff --git a/src/components/categories/CategoryForm.render.test.tsx b/src/components/categories/CategoryForm.render.test.tsx
index 22ba643..e0d5e22 100644
--- a/src/components/categories/CategoryForm.render.test.tsx
+++ b/src/components/categories/CategoryForm.render.test.tsx
@@ -4,13 +4,7 @@
 import { describe, it, expect, vi } from "vitest";
 import { renderToStaticMarkup } from "react-dom/server";
 
-vi.mock("react-i18next", () => ({
-  useTranslation: () => ({
-    t: (k: string, o?: Record<string, unknown>) =>
-      o ? `${k}[${Object.entries(o).map(([a, b]) => `${a}=${String(b)}`).join(",")}]` : k,
-    i18n: { language: "fr" },
-  }),
-}));
+vi.mock("react-i18next", async () => (await import("../../test/i18nMock")).i18nMock());
 
 // Pass-through spy on the pure module, to pin what the form hands it.
 vi.mock("./parentOptions", async (importOriginal) => {
@@ -79,20 +73,20 @@ describe("CategoryForm — parent field (#423)", () => {
   it("renders the parent as a combobox labelled by the field name, with no parent select left", () => {
     const html = markup(form(null));
     const input = comboboxInput(html);
-    expect(input).toContain('aria-label="categories.parent"');
+    expect(input).toContain('aria-label="t(categories.parent)"');
     // Only the type select remains.
     expect(html.match(/<select/g) ?? []).toHaveLength(1);
     expect(html).not.toContain("categories.noParent</option>");
   });
 
   it("shows the 'no parent' option as the value when creating without a parent", () => {
-    expect(comboboxInput(markup(form(null)))).toContain('value="categories.noParent"');
+    expect(comboboxInput(markup(form(null)))).toContain('value="t(categories.noParent)"');
   });
 
   it("shows the parent's translated name as the value when editing a category with a parent", () => {
     // Seed rows translate through their i18n_key with the name as default value.
     expect(comboboxInput(markup(form(1), 10))).toContain(
-      'value="categoriesSeed.housing[defaultValue=Logement]"',
+      'value="t(categoriesSeed.housing[defaultValue=Logement])"',
     );
   });
 
diff --git a/src/components/dashboard/DashboardEmptyState.render.test.tsx b/src/components/dashboard/DashboardEmptyState.render.test.tsx
index 30967e3..4c6adcc 100644
--- a/src/components/dashboard/DashboardEmptyState.render.test.tsx
+++ b/src/components/dashboard/DashboardEmptyState.render.test.tsx
@@ -7,13 +7,7 @@ import type { ReactElement, ReactNode } from "react";
 import { renderToStaticMarkup } from "react-dom/server";
 import { MemoryRouter } from "react-router-dom";
 
-vi.mock("react-i18next", () => ({
-  useTranslation: () => ({
-    t: (k: string, o?: Record<string, unknown>) =>
-      o ? `t(${k}[${Object.entries(o).map(([a, b]) => `${a}=${String(b)}`).join(",")}])` : `t(${k})`,
-    i18n: { language: "fr" },
-  }),
-}));
+vi.mock("react-i18next", async () => (await import("../../test/i18nMock")).i18nMock());
 
 import DashboardEmptyState from "./DashboardEmptyState";
 import OnboardingChecklist from "./OnboardingChecklist";
diff --git a/src/components/dashboard/OnboardingChecklist.test.tsx b/src/components/dashboard/OnboardingChecklist.test.tsx
index 0dd6503..b3b0a40 100644
--- a/src/components/dashboard/OnboardingChecklist.test.tsx
+++ b/src/components/dashboard/OnboardingChecklist.test.tsx
@@ -8,13 +8,7 @@ import { describe, it, expect, vi } from "vitest";
 import { isValidElement, type ReactElement, type ReactNode } from "react";
 import { Link } from "react-router-dom";
 
-vi.mock("react-i18next", () => ({
-  useTranslation: () => ({
-    t: (key: string, o?: Record<string, unknown>) =>
-      o ? `${key}[${Object.entries(o).map(([a, b]) => `${a}=${String(b)}`).join(",")}]` : key,
-    i18n: { language: "fr" },
-  }),
-}));
+vi.mock("react-i18next", async () => (await import("../../test/i18nMock")).i18nMock());
 
 vi.mock("lucide-react", () => ({
   CheckCircle2: () => null,
@@ -106,11 +100,12 @@ describe("OnboardingChecklist", () => {
   it("renders the title, the counter 1 / 6 and the hide button", () => {
     const { element, onHide } = render();
     const text = texts(element);
-    expect(text).toContain("onboarding.checklist.title");
-    expect(text).toContain("onboarding.checklist.counter[done=1,total=6]");
+    expect(text).toContain("t(onboarding.checklist.title)");
+    expect((element as AnyElement).props["aria-label"]).toBe("t(onboarding.checklist.title)");
+    expect(text).toContain("t(onboarding.checklist.counter[done=1,total=6])");
     const [hide] = find(element, (e) => e.type === "button");
     expect(hide.props.type).toBe("button");
-    expect(texts(hide.props.children)).toContain("onboarding.checklist.hide");
+    expect(texts(hide.props.children)).toContain("t(onboarding.checklist.hide)");
     (hide.props.onClick as () => void)();
     expect(onHide).toHaveBeenCalledTimes(1);
   });
@@ -120,7 +115,7 @@ describe("OnboardingChecklist", () => {
     expect(find(element, (e) => e.type === "li")).toHaveLength(6);
     const text = texts(element);
     for (const key of ["profile", "importFolder", "source", "import", "manualCategory", "budget"]) {
-      expect(text).toContain(`onboarding.checklist.items.${key}`);
+      expect(text).toContain(`t(onboarding.checklist.items.${key})`);
     }
   });
 
@@ -154,12 +149,12 @@ describe("OnboardingChecklist", () => {
     const { element } = render({}, ZERO, false);
     const budget = rowOf(element, "budget");
     expect(find(budget, (e) => e.type === Lock)).toHaveLength(1);
-    expect(texts(budget)).toContain("onboarding.checklist.lockedBudget");
+    expect(texts(budget)).toContain("t(onboarding.checklist.lockedBudget)");
     const [link] = find(budget, (e) => e.type === Link);
     expect(link.props.to).toBe("/settings/users");
     // The license card carries no step card: nothing to focus there.
     expect(link.props.state).toBeUndefined();
-    expect(texts(element)).toContain("onboarding.checklist.counter[done=1,total=5]");
+    expect(texts(element)).toContain("t(onboarding.checklist.counter[done=1,total=5])");
   });
 
   it("while the entitlement is unknown, the budget row is neutral and the counter is absent", () => {
@@ -169,35 +164,35 @@ describe("OnboardingChecklist", () => {
     expect(find(budget, (e) => e.type === CheckCircle2)).toHaveLength(0);
     expect(find(budget, (e) => e.type === Circle)).toHaveLength(1);
     expect(find(budget, (e) => e.type === Link)).toHaveLength(0);
-    expect(texts(budget)).not.toContain("onboarding.checklist.lockedBudget");
-    expect(texts(element).some((s) => s.startsWith("onboarding.checklist.counter"))).toBe(false);
+    expect(texts(budget)).not.toContain("t(onboarding.checklist.lockedBudget)");
+    expect(texts(element).some((s) => s.startsWith("t(onboarding.checklist.counter"))).toBe(false);
   });
 });
 
 describe("OnboardingChecklist — states read out (#384, #397)", () => {
   it("reads done, skipped and locked after the label, and nothing for a row still to do", () => {
     const { element } = render({}, ZERO, false, ["source"]);
-    expect(stateTextsOf(rowOf(element, "profile"))).toEqual(["onboarding.state.done"]);
-    expect(stateTextsOf(rowOf(element, "source"))).toEqual(["onboarding.state.skipped"]);
-    expect(stateTextsOf(rowOf(element, "budget"))).toEqual(["onboarding.state.locked"]);
+    expect(stateTextsOf(rowOf(element, "profile"))).toEqual(["t(onboarding.state.done)"]);
+    expect(stateTextsOf(rowOf(element, "source"))).toEqual(["t(onboarding.state.skipped)"]);
+    expect(stateTextsOf(rowOf(element, "budget"))).toEqual(["t(onboarding.state.locked)"]);
     expect(stateTextsOf(rowOf(element, "importFolder"))).toEqual([]);
     expect(stateTextsOf(rowOf(element, "import"))).toEqual([]);
   });
 
   it("reads the budget row as pending while the entitlement is unknown", () => {
     const { element } = render({ budgetReady: false }, ZERO, false);
-    expect(stateTextsOf(rowOf(element, "budget"))).toEqual(["onboarding.state.pending"]);
+    expect(stateTextsOf(rowOf(element, "budget"))).toEqual(["t(onboarding.state.pending)"]);
   });
 
   it("puts the state text right after the label, inside the same element", () => {
     const { element } = render({}, { ...ZERO, sources: 1 });
     const [labelled] = find(
       rowOf(element, "source"),
-      (e) => e.type === "span" && texts(e.props.children).includes("onboarding.checklist.items.source"),
+      (e) => e.type === "span" && texts(e.props.children).includes("t(onboarding.checklist.items.source)"),
     );
     expect(texts(labelled.props.children).map((s) => s.trim()).filter(Boolean)).toEqual([
-      "onboarding.checklist.items.source",
-      "onboarding.state.done",
+      "t(onboarding.checklist.items.source)",
+      "t(onboarding.state.done)",
     ]);
   });
 });
@@ -210,11 +205,11 @@ describe("OnboardingChecklist — skipped rows (#397)", () => {
     expect(find(source, (e) => e.type === Circle)).toHaveLength(0);
     const [badge] = find(
       source,
-      (e) => e.type === "span" && texts(e.props.children).includes("onboarding.checklist.skippedBadge"),
+      (e) => e.type === "span" && texts(e.props.children).includes("t(onboarding.checklist.skippedBadge)"),
     );
     // The hidden "(skipped)" text already says it: the badge is not read twice.
     expect(badge.props["aria-hidden"]).toBe("true");
-    expect(texts(element)).toContain("onboarding.checklist.counter[done=2,total=6]");
+    expect(texts(element)).toContain("t(onboarding.checklist.counter[done=2,total=6])");
   });
 
   it("'Resume' takes the step back, then opens its page with the step's navigation state", () => {
@@ -223,7 +218,7 @@ describe("OnboardingChecklist — skipped rows (#397)", () => {
     // The label is no link: only "Resume" leads to the page, after taking the step back.
     expect(sourceLinks).toHaveLength(1);
     const [resume] = sourceLinks;
-    expect(texts(resume.props.children)).toEqual(["onboarding.checklist.resume"]);
+    expect(texts(resume.props.children)).toEqual(["t(onboarding.checklist.resume)"]);
     expect(resume.props.to).toBe("/import");
     expect(resume.props.state).toEqual({ onboarding: { focus: true } });
     (resume.props.onClick as () => void)();
@@ -242,7 +237,7 @@ describe("OnboardingChecklist — skipped rows (#397)", () => {
     expect(find(source, (e) => e.type === CheckCircle2)).toHaveLength(1);
     expect(find(source, (e) => e.type === SkipForward)).toHaveLength(0);
     expect(find(source, (e) => e.type === Link)).toHaveLength(0);
-    expect(texts(source)).not.toContain("onboarding.checklist.resume");
+    expect(texts(source)).not.toContain("t(onboarding.checklist.resume)");
   });
 
   it("a locked row stays locked even when skipped", () => {
@@ -250,7 +245,7 @@ describe("OnboardingChecklist — skipped rows (#397)", () => {
     const budget = rowOf(element, "budget");
     expect(find(budget, (e) => e.type === Lock)).toHaveLength(1);
     expect(find(budget, (e) => e.type === SkipForward)).toHaveLength(0);
-    expect(texts(budget)).not.toContain("onboarding.checklist.resume");
+    expect(texts(budget)).not.toContain("t(onboarding.checklist.resume)");
     const [link] = find(budget, (e) => e.type === Link);
     expect(link.props.to).toBe("/settings/users");
   });
diff --git a/src/components/import/ImportEmptyState.test.tsx b/src/components/import/ImportEmptyState.test.tsx
index f830a03..42dbb9a 100644
--- a/src/components/import/ImportEmptyState.test.tsx
+++ b/src/components/import/ImportEmptyState.test.tsx
@@ -9,13 +9,7 @@ import { describe, it, expect, vi } from "vitest";
 import { isValidElement, type ReactElement, type ReactNode } from "react";
 import { Link } from "react-router-dom";
 
-vi.mock("react-i18next", () => ({
-  useTranslation: () => ({
-    t: (key: string, o?: Record<string, unknown>) =>
-      o ? `${key}[${Object.entries(o).map(([a, b]) => `${a}=${String(b)}`).join(",")}]` : key,
-    i18n: { language: "fr" },
-  }),
-}));
+vi.mock("react-i18next", async () => (await import("../../test/i18nMock")).i18nMock());
 
 vi.mock("lucide-react", () => ({
   FolderOpen: () => null,
@@ -83,11 +77,11 @@ describe("ImportEmptyState — no folder (#356)", () => {
   it("offers one primary 'choose a folder' button wired to onBrowse, and the guide link", () => {
     const { props, tree, buttons, links } = render({ hasFolder: false });
 
-    expect(texts(tree)).toContain("import.empty.noFolder.title");
-    expect(texts(tree)).toContain("import.empty.noFolder.description");
+    expect(texts(tree)).toContain("t(import.empty.noFolder.title)");
+    expect(texts(tree)).toContain("t(import.empty.noFolder.description)");
 
     expect(buttons).toHaveLength(1);
-    expect(texts(buttons[0].props.children)).toContain("import.empty.noFolder.cta");
+    expect(texts(buttons[0].props.children)).toContain("t(import.empty.noFolder.cta)");
     expect(buttons[0].props.disabled).toBe(false);
     buttons[0].props.onClick();
     expect(props.onBrowse).toHaveBeenCalledTimes(1);
@@ -96,13 +90,13 @@ describe("ImportEmptyState — no folder (#356)", () => {
     expect(links).toHaveLength(1);
     expect(links[0].props.to).toBe(CSV_EXPORT_GUIDE_PATH);
     expect(links[0].props.to).toBe("/settings/users#import-export");
-    expect(texts(links[0].props.children)).toContain("import.empty.guideLink");
+    expect(texts(links[0].props.children)).toContain("t(import.empty.guideLink)");
   });
 
   it("never shows the sample or refresh actions without a folder", () => {
     const { tree } = render({ hasFolder: false });
-    expect(texts(tree)).not.toContain("import.empty.createSample");
-    expect(texts(tree)).not.toContain("import.empty.refresh");
+    expect(texts(tree)).not.toContain("t(import.empty.createSample)");
+    expect(texts(tree)).not.toContain("t(import.empty.refresh)");
   });
 });
 
@@ -110,22 +104,22 @@ describe("ImportEmptyState — folder without sources (#356)", () => {
   it("offers 'create a sample folder' as primary, 'refresh' as secondary, and the guide link", () => {
     const { props, tree, buttons, links } = render({ hasFolder: true, folderName: "Relevés" });
 
-    expect(texts(tree)).toContain("import.empty.noSources.title");
+    expect(texts(tree)).toContain("t(import.empty.noSources.title)");
 
     expect(buttons).toHaveLength(2);
-    expect(texts(buttons[0].props.children)).toContain("import.empty.createSample");
+    expect(texts(buttons[0].props.children)).toContain("t(import.empty.createSample)");
     expect(buttons[0].props.disabled).toBe(false);
     buttons[0].props.onClick();
     expect(props.onCreateSample).toHaveBeenCalledTimes(1);
 
-    expect(texts(buttons[1].props.children)).toContain("import.empty.refresh");
+    expect(texts(buttons[1].props.children)).toContain("t(import.empty.refresh)");
     buttons[1].props.onClick();
     expect(props.onRefresh).toHaveBeenCalledTimes(1);
     expect(props.onBrowse).not.toHaveBeenCalled();
 
     expect(links).toHaveLength(1);
     expect(links[0].props.to).toBe("/settings/users#import-export");
-    expect(texts(links[0].props.children)).toContain("import.empty.guideLink");
+    expect(texts(links[0].props.children)).toContain("t(import.empty.guideLink)");
   });
 
   it("disables the create button while the sample folders are being written", () => {
@@ -138,9 +132,9 @@ describe("ImportEmptyState — folder without sources (#356)", () => {
   it("names the folder in the description, never the full path", () => {
     const folderName = folderNameFromPath("C:\\Users\\max\\Documents\\Relevés");
     const { tree } = render({ hasFolder: true, folderName });
-    const description = texts(tree).find((s) => s.startsWith("import.empty.noSources.description"));
+    const description = texts(tree).find((s) => s.startsWith("t(import.empty.noSources.description"));
 
-    expect(description).toBe("import.empty.noSources.description[folderName=Relevés]");
+    expect(description).toBe("t(import.empty.noSources.description[folderName=Relevés])");
     expect(description).not.toContain("Users");
   });
 });
@@ -154,14 +148,14 @@ describe("ImportEmptyState — getting-started target (#398)", () => {
     const targets = highlighted(tree);
     expect(targets).toHaveLength(1);
     expect(targets[0].type).toBe("button");
-    expect(texts(targets[0].props.children)).toContain("import.empty.noFolder.cta");
+    expect(texts(targets[0].props.children)).toContain("t(import.empty.noFolder.cta)");
   });
 
   it("highlights 'Create a sample folder' in a folder without sources, not 'Refresh'", () => {
     const { tree } = render({ hasFolder: true, folderName: "Relevés", onboardingTarget: true });
     const targets = highlighted(tree);
     expect(targets).toHaveLength(1);
-    expect(texts(targets[0].props.children)).toContain("import.empty.createSample");
+    expect(texts(targets[0].props.children)).toContain("t(import.empty.createSample)");
   });
 
   it("highlights nothing without the property", () => {
diff --git a/src/components/import/SourceList.test.tsx b/src/components/import/SourceList.test.tsx
index ca74242..2ae2bbd 100644
--- a/src/components/import/SourceList.test.tsx
+++ b/src/components/import/SourceList.test.tsx
@@ -4,13 +4,7 @@
 import { describe, it, expect, vi } from "vitest";
 import { renderToStaticMarkup } from "react-dom/server";
 
-vi.mock("react-i18next", () => ({
-  useTranslation: () => ({
-    t: (k: string, o?: Record<string, unknown>) =>
-      o ? `${k}[${Object.entries(o).map(([a, b]) => `${a}=${String(b)}`).join(",")}]` : k,
-    i18n: { language: "fr" },
-  }),
-}));
+vi.mock("react-i18next", async () => (await import("../../test/i18nMock")).i18nMock());
 
 import SourceList from "./SourceList";
 import { SOURCE_CARD_TARGET } from "./SourceCard";
@@ -61,3 +55,27 @@ describe("SourceList — getting-started target (#398)", () => {
     expect(markup(false)).not.toContain("data-onboarding");
   });
 });
+
+describe("SourceList and SourceCard — displayed texts (#389)", () => {
+  it("titles the list and counts each source's files through t", () => {
+    const html = markup();
+    expect(html).toContain(">t(import.sources.title)<");
+    expect(cards(html)[0]).toContain("t(import.sources.fileCount[count=1])");
+  });
+
+  it("marks the files not yet imported through t", () => {
+    const html = renderToStaticMarkup(
+      <SourceList
+        sources={[source("Desjardins")]}
+        configuredSourceNames={new Set()}
+        importedFileNames={new Map([["Desjardins", new Set<string>()]])}
+        onSelectSource={vi.fn()}
+      />,
+    );
+    expect(html).toContain("t(import.sources.new)");
+  });
+
+  it("says the folder is empty through t", () => {
+    expect(markup(false, [])).toContain(">t(import.sources.empty)<");
+  });
+});
diff --git a/src/components/import/WizardNavigation.test.tsx b/src/components/import/WizardNavigation.test.tsx
index a2e4721..73b0174 100644
--- a/src/components/import/WizardNavigation.test.tsx
+++ b/src/components/import/WizardNavigation.test.tsx
@@ -4,9 +4,7 @@
 import { describe, it, expect, vi } from "vitest";
 import { renderToStaticMarkup } from "react-dom/server";
 
-vi.mock("react-i18next", () => ({
-  useTranslation: () => ({ t: (k: string) => k, i18n: { language: "fr" } }),
-}));
+vi.mock("react-i18next", async () => (await import("../../test/i18nMock")).i18nMock());
 
 import WizardNavigation, { WIZARD_NEXT_TARGET } from "./WizardNavigation";
 
@@ -36,9 +34,9 @@ describe("WizardNavigation — getting-started target (#398)", () => {
     expect(next).toContain("NEXT_LABEL");
     expect(next).toContain(HIGHLIGHT);
     expect(next).toContain(`data-onboarding-target="${WIZARD_NEXT_TARGET}"`);
-    expect(cancel).toContain("common.cancel");
+    expect(cancel).toContain("t(common.cancel)");
     expect(cancel).not.toContain("data-onboarding");
-    expect(back).toContain("import.wizard.back");
+    expect(back).toContain("t(import.wizard.back)");
     expect(back).not.toContain("data-onboarding");
   });
 
diff --git a/src/components/layout/AppShell.render.test.tsx b/src/components/layout/AppShell.render.test.tsx
index a3c830f..ddb3f4a 100644
--- a/src/components/layout/AppShell.render.test.tsx
+++ b/src/components/layout/AppShell.render.test.tsx
@@ -13,13 +13,7 @@ import { MemoryRouter, Route, Routes } from "react-router-dom";
 // plugins) and useEntitlement (→ LicenseContext): stub both.
 vi.mock("../../services/db", () => ({ getDb: vi.fn(), withTransaction: vi.fn() }));
 vi.mock("../../contexts/LicenseContext", () => ({ useLicenseContext: vi.fn() }));
-vi.mock("react-i18next", () => ({
-  useTranslation: () => ({
-    t: (k: string, o?: Record<string, unknown>) =>
-      o ? `t(${k}[${Object.entries(o).map(([a, b]) => `${a}=${String(b)}`).join(",")}])` : `t(${k})`,
-    i18n: { language: "fr" },
-  }),
-}));
+vi.mock("react-i18next", async () => (await import("../../test/i18nMock")).i18nMock());
 vi.mock("./Sidebar", () => ({ default: () => <nav>sidebar</nav> }));
 
 let onboarding: OnboardingValue;
diff --git a/src/components/onboarding/OnboardingBanner.render.test.tsx b/src/components/onboarding/OnboardingBanner.render.test.tsx
index fcdda0e..b9f0b98 100644
--- a/src/components/onboarding/OnboardingBanner.render.test.tsx
+++ b/src/components/onboarding/OnboardingBanner.render.test.tsx
@@ -7,15 +7,9 @@ import { isValidElement, type ReactElement, type ReactNode } from "react";
 import { renderToStaticMarkup } from "react-dom/server";
 import { Link, MemoryRouter } from "react-router-dom";
 
-// The fake `t` marks what it translates, `t(key[options])`: a string that
+// The shared fake `t` (src/test/i18nMock.ts) marks what it translates, `t(key[options])`: a string that
 // skipped `t` would show unmarked.
-vi.mock("react-i18next", () => ({
-  useTranslation: () => ({
-    t: (k: string, o?: Record<string, unknown>) =>
-      o ? `t(${k}[${Object.entries(o).map(([a, b]) => `${a}=${String(b)}`).join(",")}])` : `t(${k})`,
-    i18n: { language: "fr" },
-  }),
-}));
+vi.mock("react-i18next", async () => (await import("../../test/i18nMock")).i18nMock());
 
 import OnboardingBanner, {
   GETTING_STARTED_GUIDE,
diff --git a/src/components/onboarding/StepCard.render.test.tsx b/src/components/onboarding/StepCard.render.test.tsx
index 180ae88..d93d4ec 100644
--- a/src/components/onboarding/StepCard.render.test.tsx
+++ b/src/components/onboarding/StepCard.render.test.tsx
@@ -7,15 +7,9 @@ import { createRef, isValidElement, type ReactElement, type ReactNode } from "re
 import { renderToStaticMarkup } from "react-dom/server";
 import { Link, MemoryRouter } from "react-router-dom";
 
-// The fake `t` marks what it translates, `t(key[options])`: a string that
+// The shared fake `t` (src/test/i18nMock.ts) marks what it translates, `t(key[options])`: a string that
 // skipped `t` would show unmarked.
-vi.mock("react-i18next", () => ({
-  useTranslation: () => ({
-    t: (k: string, o?: Record<string, unknown>) =>
-      o ? `t(${k}[${Object.entries(o).map(([a, b]) => `${a}=${String(b)}`).join(",")}])` : `t(${k})`,
-    i18n: { language: "fr" },
-  }),
-}));
+vi.mock("react-i18next", async () => (await import("../../test/i18nMock")).i18nMock());
 
 import StepCard, { type StepCardProps } from "./StepCard";
 import { GETTING_STARTED_GUIDE } from "./OnboardingBanner";
diff --git a/src/components/reports/FilterPanel.test.tsx b/src/components/reports/FilterPanel.test.tsx
index d4f18a9..56abc19 100644
--- a/src/components/reports/FilterPanel.test.tsx
+++ b/src/components/reports/FilterPanel.test.tsx
@@ -12,12 +12,7 @@
 
 import { describe, it, expect, vi } from "vitest";
 
-vi.mock("react-i18next", () => ({
-  useTranslation: vi.fn(() => ({
-    t: (key: string) => key,
-    i18n: { language: "fr" },
-  })),
-}));
+vi.mock("react-i18next", async () => (await import("../../test/i18nMock")).i18nMock());
 
 vi.mock("lucide-react", () => ({
   Inbox: () => null,
@@ -164,8 +159,8 @@ describe("FilterPanel — render", () => {
   it("uses i18n keys for the accounts filter label and hint (never a hardcoded string)", () => {
     const { element } = renderPanel();
     const text = flatten(element);
-    expect(text).toContain("reports.filters.accounts.label");
-    expect(text).toContain("reports.filters.accounts.hint");
+    expect(text).toContain("t(reports.filters.accounts.label)");
+    expect(text).toContain("t(reports.filters.accounts.hint)");
   });
 });
 
diff --git a/src/components/settings/DocsSubsections.test.tsx b/src/components/settings/DocsSubsections.test.tsx
index 0598ea9..3bd5786 100644
--- a/src/components/settings/DocsSubsections.test.tsx
+++ b/src/components/settings/DocsSubsections.test.tsx
@@ -1,13 +1,14 @@
 // DocsSubsections — unit tests (Issue #355).
 //
 // Same approach as FilterPanel.test.tsx: no jsdom in this project, and the
-// component's only hook is `useTranslation` (mocked into a lookup over a
+// component's only hook is `useTranslation` (mocked by `i18nMock` over a
 // fixture), so it is invoked directly as a function and its React-element
 // tree is walked without a renderer.
 
 import { describe, it, expect, vi } from "vitest";
 
-const FIXTURE: Record<string, unknown> = {
+// Hoisted: the factory of `vi.mock` below reads it when the module loads.
+const FIXTURE = vi.hoisted((): Record<string, unknown> => ({
   "docs.import.subsections": [
     {
       id: "import-export",
@@ -22,16 +23,14 @@ const FIXTURE: Record<string, unknown> = {
       steps: ["Expected header"],
     },
   ],
-};
-
-vi.mock("react-i18next", () => ({
-  useTranslation: vi.fn(() => ({
-    // i18next returns the key itself when nothing is declared under it.
-    t: (key: string) => (key in FIXTURE ? FIXTURE[key] : key),
-    i18n: { language: "fr" },
-  })),
 }));
 
+// The fixture stands for what the locale declares; every other key goes
+// through the marked `t` (#389), as i18next returns a string for a missing key.
+vi.mock("react-i18next", async () =>
+  (await import("../../test/i18nMock")).i18nMock({ fixture: FIXTURE }),
+);
+
 import DocsSubsections, { readSubsections } from "./DocsSubsections";
 
 // ---------------------------------------------------------------------------
diff --git a/src/components/settings/LicenseCard.render.test.tsx b/src/components/settings/LicenseCard.render.test.tsx
index 3edc275..6b37a5c 100644
--- a/src/components/settings/LicenseCard.render.test.tsx
+++ b/src/components/settings/LicenseCard.render.test.tsx
@@ -10,16 +10,10 @@ vi.mock("@tauri-apps/api/core", () => ({ invoke: vi.fn() }));
 vi.mock("@tauri-apps/plugin-opener", () => ({ openUrl: vi.fn(() => Promise.resolve()) }));
 
 let language = "fr";
-// The fake `t` marks what it translates, `t(key[options])`: the assertions written in that form
+// The shared fake `t` (src/test/i18nMock.ts) marks what it translates, `t(key[options])`: the assertions written in that form
 // fail on a string that skipped `t` (#387 review). Substring assertions on a bare key still read
 // the key inside the mark.
-vi.mock("react-i18next", () => ({
-  useTranslation: () => ({
-    t: (k: string, o?: Record<string, unknown>) =>
-      o ? `t(${k}[${Object.entries(o).map(([a, b]) => `${a}=${String(b)}`).join(",")}])` : `t(${k})`,
-    i18n: { language },
-  }),
-}));
+vi.mock("react-i18next", async () => (await import("../../test/i18nMock")).i18nMock({ language: () => language }));
 
 let context: Record<string, unknown>;
 vi.mock("../../contexts/LicenseContext", async (importOriginal) => ({
diff --git a/src/components/settings/LicenseKeyForm.render.test.tsx b/src/components/settings/LicenseKeyForm.render.test.tsx
index a3cdcbd..c28ba59 100644
--- a/src/components/settings/LicenseKeyForm.render.test.tsx
+++ b/src/components/settings/LicenseKeyForm.render.test.tsx
@@ -4,12 +4,7 @@ import { describe, it, expect, vi } from "vitest";
 import { renderToStaticMarkup } from "react-dom/server";
 
 vi.mock("@tauri-apps/api/core", () => ({ invoke: vi.fn() }));
-vi.mock("react-i18next", () => ({
-  useTranslation: () => ({
-    t: (k: string, o?: Record<string, unknown>) =>
-      o ? `${k}[${Object.entries(o).map(([a, b]) => `${a}=${String(b)}`).join(",")}]` : k,
-  }),
-}));
+vi.mock("react-i18next", async () => (await import("../../test/i18nMock")).i18nMock());
 
 import LicenseKeyForm from "./LicenseKeyForm";
 
@@ -30,18 +25,18 @@ function render(validationError: string | null, busy = false): string {
 describe("LicenseKeyForm", () => {
   it("names a refused key in the app language", () => {
     const html = render('{"code":"invalid_prefix"}');
-    expect(html).toContain("license.errors.invalidPrefix");
+    expect(html).toContain("t(license.errors.invalidPrefix)");
     expect(html).not.toContain("{&quot;code&quot;");
   });
 
   it("never prints a raw backend string", () => {
     const html = render("License key must start with SR-BASE- or SR-PREMIUM-");
-    expect(html).toContain("license.errors.unknown");
+    expect(html).toContain("t(license.errors.unknown)");
     expect(html).not.toContain("License key must start");
   });
 
   it("shows no error line before a submission is refused", () => {
-    expect(render(null)).not.toContain("license.errors.");
+    expect(render(null)).not.toContain("t(license.errors.");
   });
 
   it("blocks the submission while a machine activation runs", () => {
diff --git a/src/components/settings/PriceFetchConsentToggle.test.tsx b/src/components/settings/PriceFetchConsentToggle.test.tsx
index b5a14bf..73f14ec 100644
--- a/src/components/settings/PriceFetchConsentToggle.test.tsx
+++ b/src/components/settings/PriceFetchConsentToggle.test.tsx
@@ -11,6 +11,10 @@ import { describe, it, expect, vi, beforeEach } from "vitest";
 // Mocks — declared before imports to satisfy vi.mock hoisting
 // ---------------------------------------------------------------------------
 
+// React's hooks from the shared harness (#409): the toggle renders nothing while
+// it loads, so the render test below presets its `loading` slot.
+vi.mock("react", async (orig) => (await import("../../test/hookHarness")).fakeReact(await orig()));
+
 vi.mock("../../hooks/useIsPremium", () => ({
   useIsPremium: vi.fn(),
 }));
@@ -21,16 +25,16 @@ vi.mock("../../services/userPreferenceService", () => ({
   deletePreference: vi.fn(),
 }));
 
-vi.mock("react-i18next", () => ({
-  useTranslation: vi.fn(() => ({
-    t: (key: string) => key,
-  })),
-}));
+vi.mock("react-i18next", async () => (await import("../../test/i18nMock")).i18nMock());
 
 // ---------------------------------------------------------------------------
 // Imports (after mock declarations)
 // ---------------------------------------------------------------------------
 
+import type { ReactNode } from "react";
+import { renderToStaticMarkup } from "react-dom/server";
+import { hookHarness } from "../../test/hookHarness";
+import { PriceFetchConsentToggle } from "./PriceFetchConsentToggle";
 import { useIsPremium } from "../../hooks/useIsPremium";
 import {
   getPreference,
@@ -42,6 +46,7 @@ import {
 // Helpers
 // ---------------------------------------------------------------------------
 
+const harness = hookHarness();
 const mockUseIsPremium = vi.mocked(useIsPremium);
 const mockGetPreference = vi.mocked(getPreference);
 const mockSetPreference = vi.mocked(setPreference);
@@ -210,3 +215,39 @@ describe("PriceFetchConsentToggle — premium guard", () => {
     expect(buttonDisabled).toBe(false);
   });
 });
+
+// ---------------------------------------------------------------------------
+// Test: what the toggle displays (#389)
+// ---------------------------------------------------------------------------
+
+describe("PriceFetchConsentToggle — displayed texts", () => {
+  beforeEach(() => {
+    vi.resetAllMocks();
+    harness.clear();
+  });
+
+  /** One render once loaded: slots by call order, hasConsent, showConfirm, loading. */
+  function markup(premium: boolean, consent: boolean, confirming: boolean): string {
+    setPremium(premium);
+    harness.slots[0] = consent;
+    harness.slots[1] = confirming;
+    harness.slots[2] = false;
+    return renderToStaticMarkup(harness.render(() => PriceFetchConsentToggle() as ReactNode));
+  }
+
+  it("names the section, the consent row and the not-premium tooltip through t", () => {
+    const html = markup(false, false, false);
+    expect(html).toContain(">t(settings.privacy.title)<");
+    expect(html).toContain(">t(settings.privacy.priceFetchConsent.label)<");
+    expect(html).toContain(">t(settings.privacy.priceFetchConsent.description)<");
+    expect(html).toContain('title="t(settings.privacy.priceFetchConsent.notPremium)"');
+  });
+
+  it("names the revoke confirmation through t", () => {
+    const html = markup(true, true, true);
+    expect(html).toContain('aria-label="t(settings.privacy.priceFetchConsent.revokeButton)"');
+    expect(html).toContain(">t(settings.privacy.priceFetchConsent.confirmRevoke)<");
+    expect(html).toContain(">t(common.cancel)<");
+    expect(html).toContain(">t(settings.privacy.priceFetchConsent.revokeButton)<");
+  });
+});
diff --git a/src/components/shared/UpsellCtas.render.test.tsx b/src/components/shared/UpsellCtas.render.test.tsx
index ddf95d5..b1f9d03 100644
--- a/src/components/shared/UpsellCtas.render.test.tsx
+++ b/src/components/shared/UpsellCtas.render.test.tsx
@@ -16,13 +16,7 @@ vi.mock("../../services/logService", async (importOriginal) => ({
 }));
 
 let language = "fr";
-vi.mock("react-i18next", () => ({
-  useTranslation: () => ({
-    t: (k: string, o?: Record<string, unknown>) =>
-      o ? `${k}[${Object.entries(o).map(([a, b]) => `${a}=${String(b)}`).join(",")}]` : k,
-    i18n: { language },
-  }),
-}));
+vi.mock("react-i18next", async () => (await import("../../test/i18nMock")).i18nMock({ language: () => language }));
 
 // The locked screen and the Updates card read one thing from the license context:
 // whether the stored key was revoked (#365).
@@ -69,19 +63,19 @@ describe("UpsellGate with a revoked key (#365)", () => {
     );
 
   it("says nothing about a revocation for a key that is not revoked", () => {
-    expect(gate()).not.toContain("upsell.revoked");
+    expect(gate()).not.toContain("t(upsell.revoked)");
   });
 
   it("names the revocation between the feature description and the CTAs", () => {
     licenseRevoked = true;
     const html = gate();
-    const line = html.indexOf("upsell.revoked");
-    expect(line).toBeGreaterThan(html.indexOf("upsell.features.budget"));
-    expect(line).toBeLessThan(html.indexOf("upsell.ctaGet"));
-    expect(html.split("upsell.revoked")).toHaveLength(2);
+    const line = html.indexOf("t(upsell.revoked)");
+    expect(line).toBeGreaterThan(html.indexOf("t(upsell.features.budget)"));
+    expect(line).toBeLessThan(html.indexOf("t(upsell.ctaGet["));
+    expect(html.split("t(upsell.revoked)")).toHaveLength(2);
     // The way out stays: buying, or entering another key.
-    expect(html).toContain("upsell.ctaGet[tier=license.editions.base]");
-    expect(html).toContain("upsell.ctaHaveKey");
+    expect(html).toContain("t(upsell.ctaGet[tier=t(license.editions.base)])");
+    expect(html).toContain("t(upsell.ctaHaveKey)");
   });
 });
 
@@ -92,10 +86,10 @@ describe("UpsellGate wiring", () => {
         <UpsellGate feature="budget" requiredTier="base" />
       </MemoryRouter>,
     );
-    expect(html).toContain("upsell.ctaGet[tier=license.editions.base]");
+    expect(html).toContain("t(upsell.ctaGet[tier=t(license.editions.base)])");
     expect(html).not.toContain("disabled");
-    expect(html).not.toContain("upsell.premiumNotForSale");
-    expect(html).toContain("upsell.ctaHaveKey");
+    expect(html).not.toContain("t(upsell.premiumNotForSale)");
+    expect(html).toContain("t(upsell.ctaHaveKey)");
   });
 
   it("Premium screen: disabled button with the not-for-sale note", () => {
@@ -105,14 +99,14 @@ describe("UpsellGate wiring", () => {
       </MemoryRouter>,
     );
     expect(html).toContain('disabled=""');
-    expect(html).toContain("upsell.ctaGet[tier=license.editions.premium]");
-    expect(html).toContain("upsell.premiumNotForSale");
+    expect(html).toContain("t(upsell.ctaGet[tier=t(license.editions.premium)])");
+    expect(html).toContain("t(upsell.premiumNotForSale)");
   });
 
   it("outside any router (ProfileSelectionPage, ErrorPage): renders, without I already have a key", () => {
     const html = renderToStaticMarkup(<UpsellGate feature="multi-profile" requiredTier="base" />);
-    expect(html).toContain("upsell.ctaGet");
-    expect(html).not.toContain("upsell.ctaHaveKey");
+    expect(html).toContain("t(upsell.ctaGet[tier=t(license.editions.base)])");
+    expect(html).not.toContain("t(upsell.ctaHaveKey)");
   });
 
   it("forwards onNavigate to I already have a key only", () => {
@@ -157,11 +151,11 @@ describe("UpdateCard in the free edition", () => {
         <UpdateCard />
       </MemoryRouter>,
     );
-    expect(html).toContain("settings.updates.notEntitled");
-    expect(html).toContain("upsell.ctaGet[tier=license.editions.base]");
-    expect(html).toContain("upsell.ctaHaveKey");
-    expect(html).toContain("settings.updates.downloadLatest");
-    expect(html).not.toContain("upsell.revoked");
+    expect(html).toContain("t(settings.updates.notEntitled)");
+    expect(html).toContain("t(upsell.ctaGet[tier=t(license.editions.base)])");
+    expect(html).toContain("t(upsell.ctaHaveKey)");
+    expect(html).toContain("t(settings.updates.downloadLatest)");
+    expect(html).not.toContain("t(upsell.revoked)");
   });
 
   it("names a revoked key between the message and the CTAs (#365)", () => {
@@ -171,9 +165,9 @@ describe("UpdateCard in the free edition", () => {
         <UpdateCard />
       </MemoryRouter>,
     );
-    const line = html.indexOf("upsell.revoked");
-    expect(line).toBeGreaterThan(html.indexOf("settings.updates.notEntitled"));
-    expect(line).toBeLessThan(html.indexOf("upsell.ctaGet"));
-    expect(html.split("upsell.revoked")).toHaveLength(2);
+    const line = html.indexOf("t(upsell.revoked)");
+    expect(line).toBeGreaterThan(html.indexOf("t(settings.updates.notEntitled)"));
+    expect(line).toBeLessThan(html.indexOf("t(upsell.ctaGet["));
+    expect(html.split("t(upsell.revoked)")).toHaveLength(2);
   });
 });
diff --git a/src/components/transactions/TransactionTable.render.test.tsx b/src/components/transactions/TransactionTable.render.test.tsx
index d36696b..266b4f7 100644
--- a/src/components/transactions/TransactionTable.render.test.tsx
+++ b/src/components/transactions/TransactionTable.render.test.tsx
@@ -5,13 +5,7 @@
 import { describe, it, expect, vi } from "vitest";
 import { renderToStaticMarkup } from "react-dom/server";
 
-vi.mock("react-i18next", () => ({
-  useTranslation: () => ({
-    t: (k: string, o?: Record<string, unknown>) =>
-      o ? `${k}[${Object.entries(o).map(([a, b]) => `${a}=${String(b)}`).join(",")}]` : k,
-    i18n: { language: "fr" },
-  }),
-}));
+vi.mock("react-i18next", async () => (await import("../../test/i18nMock")).i18nMock());
 
 import TransactionTable, { TRANSACTION_CATEGORY_TARGET } from "./TransactionTable";
 import type { Category, TransactionRow } from "../../shared/types";
@@ -66,11 +60,11 @@ const markup = (rows: TransactionRow[], onboardingTarget?: boolean) =>
 /** The rows of the table's body, in order. */
 const bodyRows = (html: string) => html.split("<tbody")[1].split("<tr").slice(1);
 
-/** The highlighted wrapper around a closed combobox, whose input shows `value`. */
+/** The highlighted wrapper around a closed combobox, whose input shows `value` (escaped). */
 const ringedCategory = (value: string) =>
   new RegExp(
     `<div class="rounded-lg" data-onboarding-target="${TRANSACTION_CATEGORY_TARGET}" ${HIGHLIGHT}>` +
-      `<div class="relative"><input [^>]*role="combobox"[^>]*value="${value}"[^>]*/></div></div>`,
+      `<div class="relative"><input [^>]*role="combobox"[^>]*value="${value.replace(/[()[\]]/g, "\\$&")}"[^>]*/></div></div>`,
   );
 
 describe("TransactionTable — getting-started target (#399)", () => {
@@ -79,7 +73,7 @@ describe("TransactionTable — getting-started target (#399)", () => {
     expect(count(html, HIGHLIGHT)).toBe(1);
     const [first, ...others] = bodyRows(html);
     expect(first).toContain("IGA 123");
-    expect(first).toMatch(ringedCategory("transactions.table.noCategory"));
+    expect(first).toMatch(ringedCategory("t(transactions.table.noCategory)"));
     expect(others).toHaveLength(2);
     for (const other of others) {
       expect(other).not.toContain("data-onboarding");
@@ -102,7 +96,7 @@ describe("TransactionTable — getting-started target (#399)", () => {
 
   it("highlights nothing without a row: the card stays, without a ring", () => {
     const html = markup([], true);
-    expect(html).toContain("transactions.noTransactions");
+    expect(html).toContain("t(transactions.noTransactions)");
     expect(html).not.toContain("data-onboarding");
   });
 });
diff --git a/src/hooks/useLicenseMachines.test.ts b/src/hooks/useLicenseMachines.test.ts
index 892d3a8..4a7f120 100644
--- a/src/hooks/useLicenseMachines.test.ts
+++ b/src/hooks/useLicenseMachines.test.ts
@@ -35,6 +35,7 @@ import {
   type MachineList,
   type TokenDropped,
 } from "../services/licenseService";
+import { markedT } from "../test/i18nMock";
 
 // The hook itself reads the LicenseContext; the pure functions below never do.
 const context = { refresh: vi.fn(async () => {}), revoked: false };
@@ -640,7 +641,7 @@ describe("useLicenseMachines wiring to the LicenseContext", () => {
     const view = renderHook();
     expect(view.canRemoveKey).toBe(true);
 
-    await view.removeKey({ confirm, t: echo });
+    await view.removeKey({ confirm, t: markedT });
 
     expect(confirm).toHaveBeenCalledWith("t(license.removeKey.confirmRevoked)");
     expect(invoke).toHaveBeenCalledWith("remove_license", { releaseSlot: false });
@@ -652,21 +653,15 @@ describe("useLicenseMachines wiring to the LicenseContext", () => {
     vi.mocked(invoke).mockResolvedValue(null);
     const confirm = vi.fn(() => false);
     const view = renderHook();
-    await view.removeKey({ confirm, t: echo });
+    await view.removeKey({ confirm, t: markedT });
     expect(confirm).toHaveBeenCalledWith("t(license.removeKey.confirmValid)");
     expect(invoke).not.toHaveBeenCalled();
   });
 });
 
-// The removal of the stored key (#370). The fake `t` marks what it translates, `t(key[options])`,
+// The removal of the stored key (#370). `markedT` marks what it translates, `t(key[options])`,
 // so each assertion names the message the user would read, and a string that skipped `t` (a raw
 // key) fails it (#387 review).
-function echo(key: string, options?: Record<string, unknown>): string {
-  const params = options
-    ? `[${Object.entries(options).map(([name, value]) => `${name}=${String(value)}`).join(",")}]`
-    : "";
-  return `t(${key}${params})`;
-}
 
 describe("licenseMachinesReducer — removal of the key", () => {
   it("marks the removal running, clearing the previous failure", () => {
@@ -753,7 +748,7 @@ describe("performRemoveLicense", () => {
         events.push(`confirm ${message}`);
         return confirmations.shift() ?? false;
       }),
-      t: echo,
+      t: markedT,
       removeLicense: vi.fn(async (releaseSlot: boolean) => {
         events.push(`remove(${releaseSlot})`);
         return outcomes.shift() ?? removed;
diff --git a/src/pages/BudgetPage.render.test.tsx b/src/pages/BudgetPage.render.test.tsx
index 0d6d7df..82b3af7 100644
--- a/src/pages/BudgetPage.render.test.tsx
+++ b/src/pages/BudgetPage.render.test.tsx
@@ -11,13 +11,7 @@ import { MemoryRouter } from "react-router-dom";
 
 // The budget, collapse and preference services pull the database: stub the connection.
 vi.mock("../services/db", () => ({ getDb: vi.fn(), withTransaction: vi.fn() }));
-vi.mock("react-i18next", () => ({
-  useTranslation: () => ({
-    t: (k: string, o?: Record<string, unknown>) =>
-      o ? `t(${k}[${Object.entries(o).map(([a, b]) => `${a}=${String(b)}`).join(",")}])` : `t(${k})`,
-    i18n: { language: "fr" },
-  }),
-}));
+vi.mock("react-i18next", async () => (await import("../test/i18nMock")).i18nMock());
 vi.mock("../components/shared/PageHelp", () => ({ PageHelp: () => null }));
 
 const harness = vi.hoisted(() => ({ budget: null as unknown, onboarding: null as unknown }));
diff --git a/src/pages/BudgetPage.wiring.test.ts b/src/pages/BudgetPage.wiring.test.ts
index 9791db7..c2d85c5 100644
--- a/src/pages/BudgetPage.wiring.test.ts
+++ b/src/pages/BudgetPage.wiring.test.ts
@@ -19,9 +19,7 @@ vi.mock("react-router-dom", async (importOriginal) => ({
   ...(await importOriginal<typeof import("react-router-dom")>()),
   useLocation: () => ({ pathname: ctx.pathname }),
 }));
-vi.mock("react-i18next", () => ({
-  useTranslation: () => ({ t: (k: string) => `t(${k})`, i18n: { language: "fr" } }),
-}));
+vi.mock("react-i18next", async () => (await import("../test/i18nMock")).i18nMock());
 // The page's modules pull the database: stub the connection.
 vi.mock("../services/db", () => ({ getDb: vi.fn(), withTransaction: vi.fn() }));
 vi.mock("../contexts/OnboardingContext", () => ({ useOnboarding: () => ctx.onboarding }));
diff --git a/src/pages/DashboardPage.render.test.tsx b/src/pages/DashboardPage.render.test.tsx
index 833dcd6..208835d 100644
--- a/src/pages/DashboardPage.render.test.tsx
+++ b/src/pages/DashboardPage.render.test.tsx
@@ -9,9 +9,7 @@ import { renderToStaticMarkup } from "react-dom/server";
 import { MemoryRouter } from "react-router-dom";
 import type { OnboardingValue } from "../hooks/useOnboardingChecklist";
 
-vi.mock("react-i18next", () => ({
-  useTranslation: () => ({ t: (k: string) => k, i18n: { language: "fr" } }),
-}));
+vi.mock("react-i18next", async () => (await import("../test/i18nMock")).i18nMock());
 
 let onboarding: OnboardingValue;
 vi.mock("../contexts/OnboardingContext", () => ({ useOnboarding: () => onboarding }));
@@ -116,7 +114,7 @@ describe("DashboardPage on the shared path (#352, #396, #397)", () => {
   it("renders only its header while the path first loads", () => {
     onboarding = path({ status: "loading", checklist: null, counters: null });
     const html = render();
-    expect(html).toContain("dashboard.title");
+    expect(html).toContain("t(dashboard.title)");
     expect(html).not.toContain('data-marker="empty-state"');
     expect(html).not.toContain('data-marker="filters"');
   });
diff --git a/src/pages/ImportPage.render.test.tsx b/src/pages/ImportPage.render.test.tsx
index 13ddbaa..a511b16 100644
--- a/src/pages/ImportPage.render.test.tsx
+++ b/src/pages/ImportPage.render.test.tsx
@@ -12,13 +12,7 @@ import { MemoryRouter } from "react-router-dom";
 // Importing the real wizard module (for its initial state) pulls the import
 // services, then the database: stub the connection.
 vi.mock("../services/db", () => ({ getDb: vi.fn(), withTransaction: vi.fn() }));
-vi.mock("react-i18next", () => ({
-  useTranslation: () => ({
-    t: (k: string, o?: Record<string, unknown>) =>
-      o ? `t(${k}[${Object.entries(o).map(([a, b]) => `${a}=${String(b)}`).join(",")}])` : `t(${k})`,
-    i18n: { language: "fr" },
-  }),
-}));
+vi.mock("react-i18next", async () => (await import("../test/i18nMock")).i18nMock());
 
 const harness = vi.hoisted(() => ({ wizard: null as unknown, onboarding: null as unknown }));
 
diff --git a/src/pages/TransactionsPage.render.test.tsx b/src/pages/TransactionsPage.render.test.tsx
index 04ba739..678e360 100644
--- a/src/pages/TransactionsPage.render.test.tsx
+++ b/src/pages/TransactionsPage.render.test.tsx
@@ -12,13 +12,7 @@ import type { TransactionFilters, TransactionRow } from "../shared/types";
 
 // The page's services pull the database: stub the connection.
 vi.mock("../services/db", () => ({ getDb: vi.fn(), withTransaction: vi.fn() }));
-vi.mock("react-i18next", () => ({
-  useTranslation: () => ({
-    t: (k: string, o?: Record<string, unknown>) =>
-      o ? `t(${k}[${Object.entries(o).map(([a, b]) => `${a}=${String(b)}`).join(",")}])` : `t(${k})`,
-    i18n: { language: "fr" },
-  }),
-}));
+vi.mock("react-i18next", async () => (await import("../test/i18nMock")).i18nMock());
 vi.mock("../components/shared/PageHelp", () => ({ PageHelp: () => null }));
 
 const harness = vi.hoisted(() => ({
diff --git a/src/pages/settings/UsersSettingsPage.test.tsx b/src/pages/settings/UsersSettingsPage.test.tsx
index 953b3a0..ab4db00 100644
--- a/src/pages/settings/UsersSettingsPage.test.tsx
+++ b/src/pages/settings/UsersSettingsPage.test.tsx
@@ -11,9 +11,7 @@ import { isValidElement, type ReactElement, type ReactNode } from "react";
 
 vi.mock("react", async (orig) => (await import("../../test/hookHarness")).fakeReact(await orig()));
 const ctx = vi.hoisted(() => ({ onboarding: null as unknown }));
-vi.mock("react-i18next", () => ({
-  useTranslation: () => ({ t: (k: string) => `t(${k})`, i18n: { language: "fr" } }),
-}));
+vi.mock("react-i18next", async () => (await import("../../test/i18nMock")).i18nMock());
 vi.mock("../../contexts/OnboardingContext", () => ({
   useOnboarding: () => ctx.onboarding,
 }));
diff --git a/src/test/i18nMock.test.ts b/src/test/i18nMock.test.ts
new file mode 100644
index 0000000..876c4df
--- /dev/null
+++ b/src/test/i18nMock.test.ts
@@ -0,0 +1,41 @@
+// The shared fake `t` (#389): its mark is the convention every assertion reads.
+import { describe, it, expect } from "vitest";
+import { i18nMock, markedT } from "./i18nMock";
+
+describe("markedT", () => {
+  it("marks a key without options", () => {
+    expect(markedT("license.removeKey.confirmValid")).toBe("t(license.removeKey.confirmValid)");
+  });
+
+  it("marks a key with its options, in their order", () => {
+    expect(markedT("budget.count", { count: 2, name: "x" })).toBe("t(budget.count[count=2,name=x])");
+  });
+
+  it("never returns the bare key", () => {
+    expect(markedT("a.b")).not.toBe("a.b");
+  });
+});
+
+describe("i18nMock", () => {
+  it("hands out the marked t and the French language by default", () => {
+    const { t, i18n } = i18nMock().useTranslation();
+    expect(t("a.b", { n: 1 })).toBe("t(a.b[n=1])");
+    expect(i18n.language).toBe("fr");
+  });
+
+  it("reads a language function at each access", () => {
+    let language = "fr";
+    const { i18n } = i18nMock({ language: () => language }).useTranslation();
+    expect(i18n.language).toBe("fr");
+    language = "en";
+    expect(i18n.language).toBe("en");
+  });
+
+  it("returns the fixture value for a fixture key, the mark for any other", () => {
+    const value = [{ id: "x" }];
+    const { t } = i18nMock({ fixture: { "docs.a.subsections": value } }).useTranslation();
+    expect(t("docs.a.subsections", { returnObjects: true })).toBe(value);
+    expect(t("docs.b.subsections", { returnObjects: true })).toBe("t(docs.b.subsections[returnObjects=true])");
+    expect(t("toString")).toBe("t(toString)");
+  });
+});
diff --git a/src/test/i18nMock.ts b/src/test/i18nMock.ts
new file mode 100644
index 0000000..4738c5f
--- /dev/null
+++ b/src/test/i18nMock.ts
@@ -0,0 +1,58 @@
+// i18nMock — the one fake `t` of the test suite (#389).
+//
+// A fake `t` that returns the key as is hides a forgotten call to `t`: a
+// component that displays `license.removeKey.confirmValid` instead of the
+// translated text passes every test (#387 review, S1). This fake MARKS what it
+// translates, `t(key)` or `t(key[a=1,b=2])`, so an assertion written in that
+// form fails on a string that skipped `t`. A substring assertion on a bare key
+// still reads the key inside the mark.
+//
+// USE — one pattern, at the head of the test module, before the imports of
+// the code under test (the factory of `vi.mock` is hoisted, hence the dynamic
+// import inside it):
+//
+//   vi.mock("react-i18next", async () => (await import("../test/i18nMock")).i18nMock());
+//
+// Options of the factory:
+// - `language`: the `i18n.language` the component reads, "fr" by default. A
+//   function is read at each access, for a test that changes the language
+//   between two renders: `i18nMock({ language: () => language })` with a
+//   `let language` of the test module.
+// - `fixture`: values `t` returns for some keys, as i18next returns what the
+//   locale declares under them (an object with `returnObjects`, for instance).
+//   Every other key goes through `markedT`.
+//
+// A test that calls a function taking `t` as a parameter passes `markedT`
+// itself. `src/__integration__/i18n-mock-guard.test.ts` refuses any other
+// fake `t` in a test file.
+
+/** The marked translation: `t(key)`, or `t(key[a=1,b=2])` with options. */
+export function markedT(key: string, options?: Record<string, unknown>): string {
+  const params = options
+    ? `[${Object.entries(options)
+        .map(([name, value]) => `${name}=${String(value)}`)
+        .join(",")}]`
+    : "";
+  return `t(${key}${params})`;
+}
+
+export interface I18nMockOptions {
+  /** `i18n.language`, "fr" by default; a function is read at each access. */
+  language?: string | (() => string);
+  /** Values returned as is for these keys, instead of the mark. */
+  fixture?: Record<string, unknown>;
+}
+
+/** The module `react-i18next` for `vi.mock`: `useTranslation` with the marked `t`. */
+export function i18nMock({ language = "fr", fixture }: I18nMockOptions = {}) {
+  const t = (key: string, options?: Record<string, unknown>): unknown =>
+    fixture && Object.prototype.hasOwnProperty.call(fixture, key)
+      ? fixture[key]
+      : markedT(key, options);
+  const i18n = {
+    get language(): string {
+      return typeof language === "function" ? language() : language;
+    },
+  };
+  return { useTranslation: () => ({ t, i18n }) };
+}