diff --git a/src/__tests__/v1341-locale-parity.test.ts b/src/__tests__/v1341-locale-parity.test.ts
new file mode 100644
index 000000000..b1993b23f
--- /dev/null
+++ b/src/__tests__/v1341-locale-parity.test.ts
@@ -0,0 +1,174 @@
+import { readFileSync } from "node:fs";
+import { join } from "node:path";
+
+import { describe, expect, it } from "vitest";
+
+const ROOT = join(__dirname, "../..");
+const LOCALES = ["en", "de", "es", "fr", "it", "pl"] as const;
+
+const REQUIRED_KEYS = [
+  // Security: adding a passkey now requires an existing sign-in factor.
+  "settings.passkeyReauth.title",
+  "settings.passkeyReauth.description",
+  "settings.passkeyReauth.methodLabel",
+  "settings.passkeyReauth.methods.password",
+  "settings.passkeyReauth.methods.totp",
+  "settings.passkeyReauth.methods.passkey",
+  "settings.passkeyReauth.methods.webauthn",
+  "settings.passkeyReauth.currentPassword",
+  "settings.passkeyReauth.authenticatorCode",
+  "settings.passkeyReauth.authenticatorPlaceholder",
+  "settings.passkeyReauth.verifyAndAdd",
+  // Integrations/imports: operator policy and Apple ECG terminal outcome.
+  "settings.nightscoutPrivateOperatorTitle",
+  "settings.nightscoutPrivateOperatorDescription",
+  "settings.sections.export.import.appleHealth.ecgResult",
+  // Existing terminal contracts reused by the final v1.34.1 call sites.
+  "insights.assessmentPreparing",
+  "insights.noAnalysisYet",
+  "insights.noProviderConfigured",
+  "insights.noProviderAction",
+  "common.loadFailed",
+  "common.networkError",
+  "settings.googleHealthSyncResult",
+  "settings.googleHealthSyncFailed",
+  "settings.googleHealthBackfillInProgress",
+  "settings.syncOutcome.empty",
+  "settings.syncOutcome.partial",
+  "settings.syncOutcome.failed",
+  // Retained score, records, and navigation contracts.
+  "insights.healthScore.bandSetter",
+  "insights.healthScore.versionAndNoise",
+  "insights.healthScore.methodVersion",
+  "insights.healthScore.source",
+  "records.profileFacts.save",
+  "records.allergies.add",
+  "records.allergies.addFirst",
+  "records.family.add",
+  "records.family.addFirst",
+  "admin.shell.sectionsNav",
+  "settings.shell.sectionsNav",
+] as const;
+
+const OBSOLETE_KEYS = [
+  "insights.healthScore.algorithmChanged",
+  "insights.healthScore.dismissAlgorithmChanged",
+  "insights.healthScore.method",
+  "insights.healthScore.composition",
+  "documents.detail.summary.regenerate",
+  "records.profileFacts.correct",
+  "settings.nightscoutPrivateHost",
+  "settings.nightscoutPrivateHostHelp",
+] as const;
+
+const NEW_CALL_SITES = {
+  "src/components/settings/security-section/passkey-list-section.tsx": [
+    "settings.passkeyReauth.title",
+    "settings.passkeyReauth.description",
+    "settings.passkeyReauth.methodLabel",
+    "settings.passkeyReauth.methods.password",
+    "settings.passkeyReauth.methods.totp",
+    "settings.passkeyReauth.methods.passkey",
+    "settings.passkeyReauth.methods.webauthn",
+    "settings.passkeyReauth.currentPassword",
+    "settings.passkeyReauth.authenticatorCode",
+    "settings.passkeyReauth.authenticatorPlaceholder",
+    "settings.passkeyReauth.verifyAndAdd",
+  ],
+  "src/components/settings/integrations/nightscout-card.tsx": [
+    "settings.nightscoutPrivateOperatorTitle",
+    "settings.nightscoutPrivateOperatorDescription",
+  ],
+  "src/components/settings/import-panel/apple-health-import-card.tsx": [
+    "settings.sections.export.import.appleHealth.ecgResult",
+  ],
+} as const;
+
+type Catalog = Record<string, unknown>;
+
+function readCatalog(locale: (typeof LOCALES)[number]): Catalog {
+  return JSON.parse(
+    readFileSync(join(ROOT, "messages", `${locale}.json`), "utf8"),
+  ) as Catalog;
+}
+
+function resolveLeaf(catalog: Catalog, dottedKey: string): string | undefined {
+  let value: unknown = catalog;
+  for (const segment of dottedKey.split(".")) {
+    if (
+      typeof value !== "object" ||
+      value === null ||
+      !(segment in value)
+    ) {
+      return undefined;
+    }
+    value = (value as Record<string, unknown>)[segment];
+  }
+  return typeof value === "string" ? value : undefined;
+}
+
+function placeholders(message: string): string[] {
+  return [
+    ...new Set(
+      [...message.matchAll(/\{([A-Za-z_][A-Za-z0-9_]*)\b/g)].map(
+        (match) => match[1],
+      ),
+    ),
+  ].sort();
+}
+
+describe("v1.34.1 locale reconciliation", () => {
+  it("wires every newly introduced user-facing state through a literal t() call", () => {
+    for (const [relativePath, keys] of Object.entries(NEW_CALL_SITES)) {
+      const source = readFileSync(join(ROOT, relativePath), "utf8");
+      for (const key of keys) {
+        expect(source, `${relativePath} must translate ${key}`).toMatch(
+          new RegExp(`\\bt\\(["']${key.replaceAll(".", "\\.")}["']`),
+        );
+      }
+    }
+  });
+
+  it("provides every final contract in all six locales with ICU parity", () => {
+    const catalogs = Object.fromEntries(
+      LOCALES.map((locale) => [locale, readCatalog(locale)]),
+    ) as Record<(typeof LOCALES)[number], Catalog>;
+
+    for (const key of REQUIRED_KEYS) {
+      const english = resolveLeaf(catalogs.en, key);
+      expect(english, `messages/en.json is missing ${key}`).toBeTruthy();
+
+      for (const locale of LOCALES) {
+        const translated = resolveLeaf(catalogs[locale], key);
+        expect(
+          translated,
+          `messages/${locale}.json is missing ${key}`,
+        ).toBeTruthy();
+        expect(
+          placeholders(translated ?? ""),
+          `messages/${locale}.json changed ICU placeholders for ${key}`,
+        ).toEqual(placeholders(english ?? ""));
+      }
+    }
+  });
+
+  it("removes only the v1.34.1 copy proven obsolete after final call-site inventory", () => {
+    for (const locale of LOCALES) {
+      const catalog = readCatalog(locale);
+      for (const key of OBSOLETE_KEYS) {
+        expect(
+          resolveLeaf(catalog, key),
+          `messages/${locale}.json still contains obsolete ${key}`,
+        ).toBeUndefined();
+      }
+    }
+
+    const productionSource = Object.keys(NEW_CALL_SITES)
+      .map((relativePath) => readFileSync(join(ROOT, relativePath), "utf8"))
+      .join("\n");
+    for (const key of OBSOLETE_KEYS) {
+      expect(productionSource).not.toContain(`t("${key}")`);
+      expect(productionSource).not.toContain(`t('${key}')`);
+    }
+  });
+});