diff --git a/CHANGELOG.md b/CHANGELOG.md
index d27197d..88fa1ce 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,43 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/)
 
 ## [Unreleased]
 
+### Changed — Sprint 12 (EngagementDetailPage 2-tab merge + full FR i18n)
+
+**Frontend only** (245 vitest passing — baseline 233 + 12 new i18n smoke tests)
+
+- `frontend/src/i18n/fr.json` — NEW. ~160-key nested translation file (French). Covers: common, nav, auth, engagement, simulation, template, user.admin, c2, mitre, state, toast, status.
+- `frontend/src/i18n/index.ts` — NEW. i18next init (lng: fr, no fallback to en, escapeValue: false).
+- `frontend/src/i18n/status.ts` — NEW. `engagementStatusLabel()` / `simulationStatusLabel()` helpers mapping API status to translated strings.
+- `frontend/src/lib/format.ts` — NEW. `formatDate()` / `formatDateTime()` using `fr-FR` locale.
+- `frontend/src/main.tsx` — Added `import './i18n'` bootstrap.
+- `frontend/vitest.setup.ts` — Added `import './src/i18n'` so all tests use real French translations.
+- `frontend/src/pages/EngagementDetailPage.tsx` — Merged 3-tab layout → 2 tabs (Description + Simulations); full i18n pass.
+- `frontend/src/pages/EngagementsListPage.tsx` — Full i18n pass; local `formatDate` removed, `@/lib/format` used.
+- `frontend/src/pages/EngagementFormPage.tsx` — Full i18n pass; `validate()` inside component; `data-testid="btn-submit"` added.
+- `frontend/src/pages/SimulationFormPage.tsx` — Full i18n pass; `data-testid` on 4 action buttons.
+- `frontend/src/pages/TemplatesListPage.tsx` — Full i18n pass.
+- `frontend/src/pages/TemplateFormPage.tsx` — Full i18n pass.
+- `frontend/src/pages/UsersAdminPage.tsx` — Full i18n pass; `data-testid="new-role-select"` added.
+- `frontend/src/components/Layout.tsx` — Nav labels translated.
+- `frontend/src/components/LoginPage.tsx` — Form labels and error message translated.
+- `frontend/src/components/ProtectedRoute.tsx` — Forbidden/loading messages translated.
+- `frontend/src/components/SimulationList.tsx` — Full i18n pass.
+- `frontend/src/components/TemplatePickerModal.tsx` — Full i18n pass.
+- `frontend/src/components/MitreTechniqueTag.tsx` — `aria-label` translated (Retirer TX…).
+- `frontend/src/components/MitreTechniquesField.tsx` — Full i18n pass.
+- `frontend/src/components/MitreMatrixModal.tsx` — Full i18n pass; plural apply button.
+- `frontend/src/components/MitreTechniquePicker.tsx` — Placeholder and messages translated.
+- `frontend/src/components/C2ConfigCard.tsx` — Full i18n pass.
+- `frontend/src/components/C2TasksPanel.tsx` — Full i18n pass.
+- `frontend/src/components/ExecuteViaC2Modal.tsx` — Full i18n pass.
+- `frontend/src/components/ImportC2HistoryModal.tsx` — Full i18n pass.
+- `frontend/src/components/C2CallbackPicker.tsx` — Full i18n pass.
+- `frontend/src/components/Toast.tsx` — Dismiss aria-label translated.
+- `frontend/src/components/ErrorState.tsx` — Title default and Retry button translated.
+- All test files updated to use French strings or `data-testid` where button labels changed.
+
+**No backend changes. No DB schema change. No migration.**
+
 ### Added — Sprint 11 (Spectrum UX port: 4 primitives + compact density global)
 
 **Frontend only** (233 vitest passing — baseline 212 + 21 new tests across 4 new specs)
diff --git a/frontend/package-lock.json b/frontend/package-lock.json
index 5d198e7..df15861 100644
--- a/frontend/package-lock.json
+++ b/frontend/package-lock.json
@@ -11,9 +11,11 @@
         "@fontsource-variable/jetbrains-mono": "^5.2.8",
         "@tanstack/react-query": "^5.59.0",
         "axios": "^1.7.7",
+        "i18next": "^26.3.1",
         "lucide-react": "^1.16.0",
         "react": "^18.3.1",
         "react-dom": "^18.3.1",
+        "react-i18next": "^17.0.8",
         "react-router-dom": "^6.27.0"
       },
       "devDependencies": {
@@ -340,7 +342,6 @@
       "version": "7.29.7",
       "resolved": "https://registry.npmjs.org/@babel/runtime/-/runtime-7.29.7.tgz",
       "integrity": "sha512-Nq8OhGWiZIZGV6hLHoyAKLLcJihP/xFeBMGJoUrxTX2psI8dCifzLhZISFb+VWS3wFMRDmCGw5R+dOySCqPLhw==",
-      "dev": true,
       "license": "MIT",
       "engines": {
         "node": ">=6.9.0"
@@ -4232,6 +4233,15 @@
         "node": ">=18"
       }
     },
+    "node_modules/html-parse-stringify": {
+      "version": "3.0.1",
+      "resolved": "https://registry.npmjs.org/html-parse-stringify/-/html-parse-stringify-3.0.1.tgz",
+      "integrity": "sha512-KknJ50kTInJ7qIScF3jeaFRpMpE8/lfiTdzf/twXyPBLAGrLRTmkz3AdTnKeh40X8k9L2fdYwEp/42WGXIRGcg==",
+      "license": "MIT",
+      "dependencies": {
+        "void-elements": "3.1.0"
+      }
+    },
     "node_modules/http-proxy-agent": {
       "version": "7.0.2",
       "resolved": "https://registry.npmjs.org/http-proxy-agent/-/http-proxy-agent-7.0.2.tgz",
@@ -4269,6 +4279,34 @@
         "node": ">= 6"
       }
     },
+    "node_modules/i18next": {
+      "version": "26.3.1",
+      "resolved": "https://registry.npmjs.org/i18next/-/i18next-26.3.1.tgz",
+      "integrity": "sha512-txQqd5EULsqEh9OJqRH15aCaOuy/nLJyhw5EHCSKLKJE1aBbb3Zve2+uQIxgWhPm1QqUQoWyQBm2kfmmIrzkcQ==",
+      "funding": [
+        {
+          "type": "individual",
+          "url": "https://www.locize.com/i18next"
+        },
+        {
+          "type": "individual",
+          "url": "https://www.i18next.com/how-to/faq#i18next-is-awesome.-how-can-i-support-the-project"
+        },
+        {
+          "type": "individual",
+          "url": "https://www.locize.com"
+        }
+      ],
+      "license": "MIT",
+      "peerDependencies": {
+        "typescript": "^5 || ^6"
+      },
+      "peerDependenciesMeta": {
+        "typescript": {
+          "optional": true
+        }
+      }
+    },
     "node_modules/iconv-lite": {
       "version": "0.6.3",
       "resolved": "https://registry.npmjs.org/iconv-lite/-/iconv-lite-0.6.3.tgz",
@@ -5936,6 +5974,33 @@
         "react": "^18.3.1"
       }
     },
+    "node_modules/react-i18next": {
+      "version": "17.0.8",
+      "resolved": "https://registry.npmjs.org/react-i18next/-/react-i18next-17.0.8.tgz",
+      "integrity": "sha512-0ooKbGLU8JXhe1zwpQUWIeXSgLPOfwJmgheWRIUpcoA0CpyabpGhayjdG+/eA5esC1AQ8h2jWpXjJfzQzeDOCw==",
+      "license": "MIT",
+      "dependencies": {
+        "@babel/runtime": "^7.29.2",
+        "html-parse-stringify": "^3.0.1",
+        "use-sync-external-store": "^1.6.0"
+      },
+      "peerDependencies": {
+        "i18next": ">= 26.2.0",
+        "react": ">= 16.8.0",
+        "typescript": "^5 || ^6"
+      },
+      "peerDependenciesMeta": {
+        "react-dom": {
+          "optional": true
+        },
+        "react-native": {
+          "optional": true
+        },
+        "typescript": {
+          "optional": true
+        }
+      }
+    },
     "node_modules/react-is": {
       "version": "17.0.2",
       "resolved": "https://registry.npmjs.org/react-is/-/react-is-17.0.2.tgz",
@@ -7056,7 +7121,7 @@
       "version": "5.9.3",
       "resolved": "https://registry.npmjs.org/typescript/-/typescript-5.9.3.tgz",
       "integrity": "sha512-jl1vZzPDinLr9eUt3J/t7V6FgNEw9QjvBPdysz9KfQDD41fQrC2Y4vKQdiaUpFT4bXlb1RHhLpp8wtm6M5TgSw==",
-      "dev": true,
+      "devOptional": true,
       "license": "Apache-2.0",
       "bin": {
         "tsc": "bin/tsc",
@@ -7133,6 +7198,15 @@
         "punycode": "^2.1.0"
       }
     },
+    "node_modules/use-sync-external-store": {
+      "version": "1.6.0",
+      "resolved": "https://registry.npmjs.org/use-sync-external-store/-/use-sync-external-store-1.6.0.tgz",
+      "integrity": "sha512-Pp6GSwGP/NrPIrxVFAIkOQeyw8lFenOHijQWkUTrDvrF4ALqylP2C/KCkeS9dpUM3KvYRQhna5vt7IL95+ZQ9w==",
+      "license": "MIT",
+      "peerDependencies": {
+        "react": "^16.8.0 || ^17.0.0 || ^18.0.0 || ^19.0.0"
+      }
+    },
     "node_modules/util-deprecate": {
       "version": "1.0.2",
       "resolved": "https://registry.npmjs.org/util-deprecate/-/util-deprecate-1.0.2.tgz",
@@ -7289,6 +7363,15 @@
         }
       }
     },
+    "node_modules/void-elements": {
+      "version": "3.1.0",
+      "resolved": "https://registry.npmjs.org/void-elements/-/void-elements-3.1.0.tgz",
+      "integrity": "sha512-Dhxzh5HZuiHQhbvTW9AMetFfBHDMYpo23Uo9btPXgdYP+3T5S+p+jgNy7spra+veYhBP2dCSgxR/i2Y02h5/6w==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=0.10.0"
+      }
+    },
     "node_modules/w3c-xmlserializer": {
       "version": "5.0.0",
       "resolved": "https://registry.npmjs.org/w3c-xmlserializer/-/w3c-xmlserializer-5.0.0.tgz",
diff --git a/frontend/package.json b/frontend/package.json
index 3a16c03..5836e6e 100644
--- a/frontend/package.json
+++ b/frontend/package.json
@@ -15,9 +15,11 @@
     "@fontsource-variable/jetbrains-mono": "^5.2.8",
     "@tanstack/react-query": "^5.59.0",
     "axios": "^1.7.7",
+    "i18next": "^26.3.1",
     "lucide-react": "^1.16.0",
     "react": "^18.3.1",
     "react-dom": "^18.3.1",
+    "react-i18next": "^17.0.8",
     "react-router-dom": "^6.27.0"
   },
   "devDependencies": {
diff --git a/frontend/src/components/C2CallbackPicker.tsx b/frontend/src/components/C2CallbackPicker.tsx
index 7c760c0..ac4f683 100644
--- a/frontend/src/components/C2CallbackPicker.tsx
+++ b/frontend/src/components/C2CallbackPicker.tsx
@@ -1,3 +1,4 @@
+import { useTranslation } from 'react-i18next';
 import { extractApiError } from '@/api/client';
 import type { C2Callback } from '@/api/types';
 
@@ -20,20 +21,22 @@ export function C2CallbackPicker({
   onSelect,
   rowTestId = 'c2-callback-row',
 }: C2CallbackPickerProps): JSX.Element {
+  const { t } = useTranslation();
+
   if (isLoading) {
-    return <p className="text-[14px] text-graphite">Loading callbacks…</p>;
+    return <p className="text-[14px] text-graphite">{t('state.loading')}</p>;
   }
 
   if (isError) {
     return (
       <p className="text-[14px] text-bloom-deep">
-        Could not load callbacks: {extractApiError(error, 'Unknown error')}
+        {extractApiError(error, t('state.error.desc'))}
       </p>
     );
   }
 
   if (callbacks.length === 0) {
-    return <p className="text-[14px] text-graphite">No callbacks available.</p>;
+    return <p className="text-[14px] text-graphite">{t('c2.modal.picker.empty')}</p>;
   }
 
   return (
@@ -41,12 +44,12 @@ export function C2CallbackPicker({
       <table className="w-full text-[14px]">
         <thead>
           <tr className="bg-cloud border-b border-hairline">
-            <th className="px-md py-sm text-left font-medium text-ink">Display ID</th>
-            <th className="px-md py-sm text-left font-medium text-ink">Active</th>
-            <th className="px-md py-sm text-left font-medium text-ink">Host</th>
-            <th className="px-md py-sm text-left font-medium text-ink">User</th>
-            <th className="px-md py-sm text-left font-medium text-ink">Domain</th>
-            <th className="px-md py-sm text-left font-medium text-ink">Last check-in</th>
+            <th className="px-md py-sm text-left font-medium text-ink">{t('c2.modal.picker.col.displayId')}</th>
+            <th className="px-md py-sm text-left font-medium text-ink">{t('c2.modal.picker.col.active')}</th>
+            <th className="px-md py-sm text-left font-medium text-ink">{t('c2.modal.picker.col.host')}</th>
+            <th className="px-md py-sm text-left font-medium text-ink">{t('c2.modal.picker.col.user')}</th>
+            <th className="px-md py-sm text-left font-medium text-ink">{t('c2.modal.picker.col.domain')}</th>
+            <th className="px-md py-sm text-left font-medium text-ink">{t('c2.modal.picker.col.lastCheckin')}</th>
           </tr>
         </thead>
         <tbody>
@@ -78,7 +81,7 @@ export function C2CallbackPicker({
                         : 'bg-cloud text-graphite border border-hairline'
                     }`}
                   >
-                    {cb.active ? 'Active' : 'Inactive'}
+                    {cb.active ? t('c2.modal.picker.status.active') : t('c2.modal.picker.status.inactive')}
                   </span>
                 </td>
                 <td className="px-md py-sm font-mono">{cb.host}</td>
diff --git a/frontend/src/components/C2ConfigCard.tsx b/frontend/src/components/C2ConfigCard.tsx
index 7dc2955..5e0cf1f 100644
--- a/frontend/src/components/C2ConfigCard.tsx
+++ b/frontend/src/components/C2ConfigCard.tsx
@@ -1,4 +1,5 @@
 import { useEffect, useState, type FormEvent } from 'react';
+import { useTranslation } from 'react-i18next';
 import { extractApiError } from '@/api/client';
 import { useC2Config, useDeleteC2Config, useTestC2Config, useUpdateC2Config } from '@/hooks/useC2';
 import { ConfirmDialog } from './ConfirmDialog';
@@ -10,6 +11,7 @@ interface C2ConfigCardProps {
 }
 
 export function C2ConfigCard({ engagementId }: C2ConfigCardProps): JSX.Element {
+  const { t } = useTranslation();
   const { push } = useToast();
 
   const configQuery = useC2Config(engagementId);
@@ -55,11 +57,11 @@ export function C2ConfigCard({ engagementId }: C2ConfigCardProps): JSX.Element {
 
     try {
       await updateMutation.mutateAsync(input);
-      push('C2 configuration saved', 'success');
+      push(t('c2.config.toast.saved'), 'success');
       setToken('');
       setReplaceToken(false);
     } catch (err) {
-      push(extractApiError(err, 'Could not save C2 configuration'), 'error');
+      push(extractApiError(err, t('c2.config.error.save')), 'error');
     }
   };
 
@@ -68,13 +70,13 @@ export function C2ConfigCard({ engagementId }: C2ConfigCardProps): JSX.Element {
     setTestResult(null);
     try {
       await deleteMutation.mutateAsync();
-      push('C2 configuration removed', 'success');
+      push(t('c2.config.toast.deleted'), 'success');
       setUrl('');
       setToken('');
       setVerifyTls(false);
       setReplaceToken(false);
     } catch (err) {
-      push(extractApiError(err, 'Could not remove C2 configuration'), 'error');
+      push(extractApiError(err, t('c2.config.error.delete')), 'error');
     }
   };
 
@@ -84,10 +86,10 @@ export function C2ConfigCard({ engagementId }: C2ConfigCardProps): JSX.Element {
       const result = await testMutation.mutateAsync();
       setTestResult({
         ok: result.ok,
-        message: result.ok ? 'Connected' : (result.error ?? 'Connection failed'),
+        message: result.ok ? t('c2.config.connected') : (result.error ?? t('c2.config.connectionFailed')),
       });
     } catch (err) {
-      setTestResult({ ok: false, message: extractApiError(err, 'Test failed') });
+      setTestResult({ ok: false, message: extractApiError(err, t('c2.config.connectionFailed')) });
     }
   };
 
@@ -98,25 +100,25 @@ export function C2ConfigCard({ engagementId }: C2ConfigCardProps): JSX.Element {
       data-testid="c2-config-card"
       className="card-product flex flex-col gap-md"
     >
-      <h2 className="text-[20px] font-medium text-ink">C2 configuration</h2>
+      <h2 className="text-[20px] font-medium text-ink">{t('c2.config.title')}</h2>
 
       {is503 && (
         <div
           role="alert"
           className="rounded-none px-xl py-md bg-fog border border-hairline text-[14px] text-charcoal"
         >
-          C2 features are disabled (server has no encryption key configured).
+          {t('c2.config.disabled')}
         </div>
       )}
 
       {configQuery.isLoading ? (
-        <p className="text-[14px] text-graphite">Loading…</p>
+        <p className="text-[14px] text-graphite">{t('c2.config.loading')}</p>
       ) : (
         <form onSubmit={onSave} noValidate className="flex flex-col gap-md">
           <FormField
-            label="URL"
+            label={t('c2.config.field.url')}
             htmlFor="c2-url"
-            hint="HTTPS required (e.g. https://mythic.lab:7443)"
+            hint={t('c2.config.field.urlHint')}
           >
             <TextInput
               id="c2-url"
@@ -130,7 +132,7 @@ export function C2ConfigCard({ engagementId }: C2ConfigCardProps): JSX.Element {
             />
           </FormField>
 
-          <FormField label="API token" htmlFor="c2-token">
+          <FormField label={t('c2.config.field.token')} htmlFor="c2-token">
             {config?.has_token && !replaceToken ? (
               <div className="flex items-center gap-md">
                 <TextInput
@@ -149,7 +151,7 @@ export function C2ConfigCard({ engagementId }: C2ConfigCardProps): JSX.Element {
                   onClick={() => setReplaceToken(true)}
                   disabled={disabled}
                 >
-                  Replace token
+                  {t('c2.config.btn.replaceToken')}
                 </button>
               </div>
             ) : (
@@ -158,7 +160,7 @@ export function C2ConfigCard({ engagementId }: C2ConfigCardProps): JSX.Element {
                 data-testid="c2-token-input"
                 type="password"
                 name="api_token"
-                placeholder={config?.has_token ? 'Enter new token' : 'API token'}
+                placeholder={config?.has_token ? t('c2.config.field.tokenHint') : t('c2.config.field.token')}
                 value={token}
                 onChange={(e) => setToken(e.target.value)}
                 disabled={disabled}
@@ -178,12 +180,11 @@ export function C2ConfigCard({ engagementId }: C2ConfigCardProps): JSX.Element {
                 className="h-4 w-4 accent-primary"
               />
               <label htmlFor="c2-verify-tls" className="text-[14px] text-ink">
-                Verify TLS certificate
+                {t('c2.config.field.verifyTls')}
               </label>
             </div>
             <p className="text-[12px] text-graphite">
-              Uncheck only for lab Mythic with self-signed certificates. Disabling
-              verification exposes the API token to MITM.
+              {t('c2.config.field.verifyTlsHint')}
             </p>
           </div>
 
@@ -194,7 +195,7 @@ export function C2ConfigCard({ engagementId }: C2ConfigCardProps): JSX.Element {
               className="btn-primary"
               disabled={disabled || submitting}
             >
-              {updateMutation.isPending ? 'Saving…' : 'Save'}
+              {updateMutation.isPending ? t('c2.config.btn.saving') : t('c2.config.btn.save')}
             </button>
 
             <button
@@ -204,7 +205,7 @@ export function C2ConfigCard({ engagementId }: C2ConfigCardProps): JSX.Element {
               onClick={onTest}
               disabled={disabled || testMutation.isPending || !config}
             >
-              {testMutation.isPending ? 'Testing…' : 'Test connection'}
+              {testMutation.isPending ? t('c2.config.btn.testing') : t('c2.config.btn.test')}
             </button>
 
             {testResult !== null && (
@@ -223,7 +224,7 @@ export function C2ConfigCard({ engagementId }: C2ConfigCardProps): JSX.Element {
                 onClick={() => setShowDeleteConfirm(true)}
                 disabled={disabled || submitting}
               >
-                Delete configuration
+                {t('c2.config.btn.delete')}
               </button>
             )}
           </div>
@@ -232,10 +233,10 @@ export function C2ConfigCard({ engagementId }: C2ConfigCardProps): JSX.Element {
 
       {showDeleteConfirm && (
         <ConfirmDialog
-          title="Delete C2 configuration"
-          description="This will remove the C2 configuration for this engagement. The API token will be permanently deleted."
-          confirmLabel="Delete"
-          cancelLabel="Cancel"
+          title={t('c2.config.deleteConfirm.title')}
+          description={t('c2.config.deleteConfirm.desc')}
+          confirmLabel={t('c2.config.deleteConfirm.confirm')}
+          cancelLabel={t('c2.config.deleteConfirm.cancel')}
           destructive
           onConfirm={onDelete}
           onCancel={() => setShowDeleteConfirm(false)}
diff --git a/frontend/src/components/C2TasksPanel.tsx b/frontend/src/components/C2TasksPanel.tsx
index 138729a..a516a0d 100644
--- a/frontend/src/components/C2TasksPanel.tsx
+++ b/frontend/src/components/C2TasksPanel.tsx
@@ -1,5 +1,6 @@
 import { Fragment, useState } from 'react';
 import { ChevronRight, ChevronDown } from 'lucide-react';
+import { useTranslation } from 'react-i18next';
 import { useC2Tasks } from '@/hooks/useC2';
 import { C2TaskStatusBadge } from './C2TaskStatusBadge';
 
@@ -8,6 +9,7 @@ interface C2TasksPanelProps {
 }
 
 export function C2TasksPanel({ simulationId }: C2TasksPanelProps): JSX.Element {
+  const { t } = useTranslation();
   const query = useC2Tasks(simulationId, { enabled: true });
   const [expandedIds, setExpandedIds] = useState<Set<number>>(new Set());
 
@@ -33,13 +35,13 @@ export function C2TasksPanel({ simulationId }: C2TasksPanelProps): JSX.Element {
       className="card-product flex flex-col gap-md"
     >
       <div className="flex items-center justify-between">
-        <h3 className="text-[16px] font-medium text-ink">C2 Tasks</h3>
+        <h3 className="text-[16px] font-medium text-ink">{t('c2.tasks.title')}</h3>
         {isRefreshing && (
           <span
             data-testid="c2-task-refresh-indicator"
             className="text-[12px] text-graphite"
           >
-            Refreshing…
+            {t('c2.tasks.refreshing')}
           </span>
         )}
       </div>
@@ -47,7 +49,7 @@ export function C2TasksPanel({ simulationId }: C2TasksPanelProps): JSX.Element {
       {tasks.length === 0 ? (
         <div className="border border-hairline rounded-none px-md py-md">
           <p className="text-[14px] text-graphite">
-            No C2 tasks yet. Use Execute via C2 to launch commands.
+            {t('c2.tasks.empty')}
           </p>
         </div>
       ) : (
@@ -55,12 +57,12 @@ export function C2TasksPanel({ simulationId }: C2TasksPanelProps): JSX.Element {
           <table className="w-full text-[14px]">
             <thead>
               <tr className="bg-cloud border-b border-hairline">
-                <th className="px-md py-sm text-left font-medium text-ink w-8" aria-label="Expand" />
-                <th className="px-md py-sm text-left font-medium text-ink">Task</th>
-                <th className="px-md py-sm text-left font-medium text-ink">Command</th>
-                <th className="px-md py-sm text-left font-medium text-ink">Source</th>
-                <th className="px-md py-sm text-left font-medium text-ink">Status</th>
-                <th className="px-md py-sm text-left font-medium text-ink">Completed at</th>
+                <th className="px-md py-sm text-left font-medium text-ink w-8" aria-label={t('c2.tasks.col.expand')} />
+                <th className="px-md py-sm text-left font-medium text-ink">{t('c2.tasks.col.task')}</th>
+                <th className="px-md py-sm text-left font-medium text-ink">{t('c2.tasks.col.command')}</th>
+                <th className="px-md py-sm text-left font-medium text-ink">{t('c2.tasks.col.source')}</th>
+                <th className="px-md py-sm text-left font-medium text-ink">{t('c2.tasks.col.status')}</th>
+                <th className="px-md py-sm text-left font-medium text-ink">{t('c2.tasks.col.completedAt')}</th>
               </tr>
             </thead>
             <tbody>
diff --git a/frontend/src/components/ErrorState.tsx b/frontend/src/components/ErrorState.tsx
index 9bf984b..4b5a612 100644
--- a/frontend/src/components/ErrorState.tsx
+++ b/frontend/src/components/ErrorState.tsx
@@ -1,21 +1,25 @@
+import { useTranslation } from 'react-i18next';
+
 interface ErrorStateProps {
   title?: string;
   message: string;
   onRetry?: () => void;
 }
 
-export function ErrorState({ title = 'Something went wrong', message, onRetry }: ErrorStateProps): JSX.Element {
+export function ErrorState({ title, message, onRetry }: ErrorStateProps): JSX.Element {
+  const { t } = useTranslation();
+  const resolvedTitle = title ?? t('state.error.title');
   return (
     <div
       role="alert"
       data-testid="error-state"
       className="card-product border-l-4 border-l-bloom-deep flex flex-col items-start gap-md"
     >
-      <h2 className="text-[24px] font-medium text-bloom-deep">{title}</h2>
+      <h2 className="text-[24px] font-medium text-bloom-deep">{resolvedTitle}</h2>
       <p className="text-[16px] text-charcoal">{message}</p>
       {onRetry ? (
         <button type="button" className="btn-outline" onClick={onRetry}>
-          Retry
+          {t('state.retry')}
         </button>
       ) : null}
     </div>
diff --git a/frontend/src/components/ExecuteViaC2Modal.tsx b/frontend/src/components/ExecuteViaC2Modal.tsx
index 5eee92b..fdae5f1 100644
--- a/frontend/src/components/ExecuteViaC2Modal.tsx
+++ b/frontend/src/components/ExecuteViaC2Modal.tsx
@@ -1,4 +1,5 @@
 import { useState } from 'react';
+import { useTranslation } from 'react-i18next';
 import { extractApiError } from '@/api/client';
 import { useC2Callbacks, useExecuteC2 } from '@/hooks/useC2';
 import { C2CallbackPicker } from './C2CallbackPicker';
@@ -17,6 +18,7 @@ export function ExecuteViaC2Modal({
   initialCommands,
   onClose,
 }: ExecuteViaC2ModalProps): JSX.Element {
+  const { t } = useTranslation();
   const { push } = useToast();
 
   const callbacksQuery = useC2Callbacks(engagementId, { enabled: true });
@@ -43,10 +45,10 @@ export function ExecuteViaC2Modal({
         callback_display_id: selectedId,
         commands: commandLines,
       });
-      push(`${result.tasks.length} task(s) submitted`, 'success');
+      push(t('c2.modal.execute.toast.launched', { count: result.tasks.length }), 'success');
       onClose();
     } catch (err) {
-      setSubmitError(extractApiError(err, 'Could not execute via C2'));
+      setSubmitError(extractApiError(err, t('c2.modal.execute.error.launch')));
     }
   };
 
@@ -62,12 +64,12 @@ export function ExecuteViaC2Modal({
 
       <div className="relative card-product w-full max-w-3xl mx-md flex flex-col gap-md max-h-[90vh] overflow-y-auto">
         <h2 id="c2-modal-title" className="text-[20px] font-medium text-ink">
-          Execute via C2
+          {t('c2.modal.execute.title')}
         </h2>
 
         {/* Callback picker */}
         <div className="flex flex-col gap-xs">
-          <span className="text-[14px] font-medium text-ink">Select callback</span>
+          <span className="text-[14px] font-medium text-ink">{t('c2.modal.execute.callback')}</span>
           <C2CallbackPicker
             callbacks={callbacks}
             isLoading={callbacksQuery.isLoading}
@@ -82,7 +84,7 @@ export function ExecuteViaC2Modal({
         {/* Commands */}
         <div className="flex flex-col gap-xs">
           <label htmlFor="c2-commands" className="text-[14px] font-medium text-ink">
-            Commands
+            {t('simulation.field.commands')}
           </label>
           <textarea
             id="c2-commands"
@@ -90,10 +92,10 @@ export function ExecuteViaC2Modal({
             value={commands}
             onChange={(e) => setCommands(e.target.value)}
             className="text-input min-h-[112px] py-sm font-mono text-[14px]"
-            placeholder="One command per line"
+            placeholder={t('simulation.field.commands')}
           />
           <span className="text-[12px] text-graphite">
-            {commandLines.length} command{commandLines.length !== 1 ? 's' : ''} — one task per line
+            {t('c2.modal.execute.commandCount', { count: commandLines.length })}
           </span>
         </div>
 
@@ -112,7 +114,7 @@ export function ExecuteViaC2Modal({
             onClick={onLaunch}
             disabled={!canLaunch || executeMutation.isPending}
           >
-            {executeMutation.isPending ? 'Launching…' : 'Launch'}
+            {executeMutation.isPending ? t('c2.modal.execute.btn.launching') : t('c2.modal.execute.btn.launch')}
           </button>
           <button
             type="button"
@@ -120,7 +122,7 @@ export function ExecuteViaC2Modal({
             onClick={onClose}
             disabled={executeMutation.isPending}
           >
-            Cancel
+            {t('c2.modal.execute.btn.cancel')}
           </button>
         </div>
       </div>
diff --git a/frontend/src/components/ExportEngagementButton.tsx b/frontend/src/components/ExportEngagementButton.tsx
index c3a43df..382f1f1 100644
--- a/frontend/src/components/ExportEngagementButton.tsx
+++ b/frontend/src/components/ExportEngagementButton.tsx
@@ -1,5 +1,6 @@
 import { useEffect, useRef, useState } from 'react';
 import { ChevronDown, Download } from 'lucide-react';
+import { useTranslation } from 'react-i18next';
 import { downloadEngagementExport, type ExportFormat } from '@/api/exports';
 import { useToast } from '@/hooks/useToast';
 
@@ -14,6 +15,7 @@ const FORMATS: { label: string; value: ExportFormat }[] = [
 ];
 
 export function ExportEngagementButton({ engagementId }: ExportEngagementButtonProps): JSX.Element {
+  const { t } = useTranslation();
   const { push } = useToast();
   const [open, setOpen] = useState(false);
   const [loading, setLoading] = useState<ExportFormat | null>(null);
@@ -58,11 +60,11 @@ export function ExportEngagementButton({ engagementId }: ExportEngagementButtonP
           onClick={() => setOpen((v) => !v)}
           data-testid="export-btn"
         >
-          <Download size={14} aria-hidden /> Export
+          <Download size={14} aria-hidden /> {t('export.btn')}
         </button>
         <button
           type="button"
-          aria-label="Export options"
+          aria-label={t('export.aria')}
           aria-expanded={open}
           className="btn-outline px-sm"
           onClick={() => setOpen((v) => !v)}
@@ -89,7 +91,7 @@ export function ExportEngagementButton({ engagementId }: ExportEngagementButtonP
             >
               {loading === value ? (
                 <span className="font-mono text-[11px] animate-pulse" aria-hidden>
-                  EXPORTING…
+                  {t('export.btnLoading')}
                 </span>
               ) : null}
               {loading !== value ? label : null}
diff --git a/frontend/src/components/ImportC2HistoryModal.tsx b/frontend/src/components/ImportC2HistoryModal.tsx
index 2fa17e2..0e44dca 100644
--- a/frontend/src/components/ImportC2HistoryModal.tsx
+++ b/frontend/src/components/ImportC2HistoryModal.tsx
@@ -1,4 +1,5 @@
 import { useState } from 'react';
+import { useTranslation } from 'react-i18next';
 import { extractApiError } from '@/api/client';
 import { useC2Callbacks, useC2CallbackHistory, useImportC2 } from '@/hooks/useC2';
 import { C2CallbackPicker } from './C2CallbackPicker';
@@ -18,6 +19,7 @@ export function ImportC2HistoryModal({
   engagementId,
   onClose,
 }: ImportC2HistoryModalProps): JSX.Element {
+  const { t } = useTranslation();
   const { push } = useToast();
 
   const callbacksQuery = useC2Callbacks(engagementId, { enabled: true });
@@ -70,12 +72,12 @@ export function ImportC2HistoryModal({
       });
       const msg =
         result.skipped > 0
-          ? `Imported ${result.imported} task(s), ${result.skipped} already attached`
-          : `Imported ${result.imported} task(s)`;
+          ? t('c2.modal.import.toast.partial', { imported: result.imported, skipped: result.skipped })
+          : t('c2.modal.import.toast.imported', { count: result.imported });
       push(msg, 'success');
       onClose();
     } catch (err) {
-      setSubmitError(extractApiError(err, 'Could not import tasks'));
+      setSubmitError(extractApiError(err, t('c2.modal.import.error.import')));
     }
   };
 
@@ -91,12 +93,12 @@ export function ImportC2HistoryModal({
 
       <div className="relative card-product w-full max-w-4xl mx-md flex flex-col gap-md max-h-[90vh] overflow-y-auto">
         <h2 id="c2-import-modal-title" className="text-[20px] font-medium text-ink">
-          Import C2 history
+          {t('c2.modal.import.title')}
         </h2>
 
         {/* Step 1: callback picker */}
         <div className="flex flex-col gap-xs">
-          <span className="text-[14px] font-medium text-ink">Select callback</span>
+          <span className="text-[14px] font-medium text-ink">{t('c2.modal.picker.title')}</span>
           <C2CallbackPicker
             callbacks={callbacks}
             isLoading={callbacksQuery.isLoading}
@@ -112,24 +114,24 @@ export function ImportC2HistoryModal({
         {selectedCallbackId !== null && (
           <div className="flex flex-col gap-xs">
             <span className="text-[14px] font-medium text-ink">
-              Task history{' '}
+              {t('c2.tasks.title')}{' '}
               {total > 0 && (
-                <span className="text-graphite font-normal">({total} total)</span>
+                <span className="text-graphite font-normal">({total} {t('c2.modal.import.total').toLowerCase()})</span>
               )}
             </span>
 
             {historyQuery.isLoading && (
-              <p className="text-[14px] text-graphite">Loading history…</p>
+              <p className="text-[14px] text-graphite">{t('state.loading')}</p>
             )}
 
             {historyQuery.isError && (
               <p className="text-[14px] text-bloom-deep">
-                {extractApiError(historyQuery.error, 'Could not load history')}
+                {extractApiError(historyQuery.error, t('c2.modal.import.error.import'))}
               </p>
             )}
 
             {!historyQuery.isLoading && historyTasks.length === 0 && !historyQuery.isError && (
-              <p className="text-[14px] text-graphite">No task history for this callback.</p>
+              <p className="text-[14px] text-graphite">{t('c2.modal.import.empty')}</p>
             )}
 
             {historyTasks.length > 0 && (
@@ -138,12 +140,12 @@ export function ImportC2HistoryModal({
                   <table className="w-full text-[14px]">
                     <thead>
                       <tr className="bg-cloud border-b border-hairline">
-                        <th className="px-md py-sm w-8" aria-label="Select" />
+                        <th className="px-md py-sm w-8" aria-label={t('common.select')} />
                         <th className="px-md py-sm text-left font-medium text-ink">#</th>
-                        <th className="px-md py-sm text-left font-medium text-ink">Command</th>
-                        <th className="px-md py-sm text-left font-medium text-ink">Status</th>
-                        <th className="px-md py-sm text-left font-medium text-ink">Completed</th>
-                        <th className="px-md py-sm text-left font-medium text-ink">Timestamp</th>
+                        <th className="px-md py-sm text-left font-medium text-ink">{t('c2.tasks.col.command')}</th>
+                        <th className="px-md py-sm text-left font-medium text-ink">{t('c2.tasks.col.status')}</th>
+                        <th className="px-md py-sm text-left font-medium text-ink">{t('c2.modal.import.col.completed')}</th>
+                        <th className="px-md py-sm text-left font-medium text-ink">{t('c2.modal.import.col.timestamp')}</th>
                       </tr>
                     </thead>
                     <tbody>
@@ -175,7 +177,7 @@ export function ImportC2HistoryModal({
                             <C2TaskStatusBadge status={task.status} />
                           </td>
                           <td className="px-md py-sm text-[14px]">
-                            {task.completed ? 'Yes' : 'No'}
+                            {task.completed ? t('common.yes') : t('common.no')}
                           </td>
                           <td className="px-md py-sm font-mono text-graphite">
                             {task.created_at}
@@ -195,10 +197,10 @@ export function ImportC2HistoryModal({
                     onClick={() => setPage((p) => Math.max(1, p - 1))}
                     disabled={page <= 1}
                   >
-                    Prev
+                    {t('c2.modal.import.prev')}
                   </button>
                   <span>
-                    Page {page} of {totalPages}
+                    {t('c2.modal.import.page')} {page} {t('c2.modal.import.of')} {totalPages}
                   </span>
                   <button
                     type="button"
@@ -207,11 +209,11 @@ export function ImportC2HistoryModal({
                     onClick={() => setPage((p) => Math.min(totalPages, p + 1))}
                     disabled={page >= totalPages}
                   >
-                    Next
+                    {t('c2.modal.import.next')}
                   </button>
                   {checkedIds.size > 0 && (
                     <span className="ml-auto text-ink">
-                      {checkedIds.size} selected
+                      {checkedIds.size} {t('c2.modal.import.selected')}
                     </span>
                   )}
                 </div>
@@ -235,7 +237,7 @@ export function ImportC2HistoryModal({
             onClick={onImport}
             disabled={!canImport || importMutation.isPending}
           >
-            {importMutation.isPending ? 'Importing…' : 'Import selected'}
+            {importMutation.isPending ? t('c2.modal.import.btn.importing') : t('c2.modal.import.btn.import')}
           </button>
           <button
             type="button"
@@ -243,7 +245,7 @@ export function ImportC2HistoryModal({
             onClick={onClose}
             disabled={importMutation.isPending}
           >
-            Cancel
+            {t('c2.modal.import.btn.cancel')}
           </button>
         </div>
       </div>
diff --git a/frontend/src/components/Layout.tsx b/frontend/src/components/Layout.tsx
index 2d14a51..554be2e 100644
--- a/frontend/src/components/Layout.tsx
+++ b/frontend/src/components/Layout.tsx
@@ -1,5 +1,6 @@
 import { Link, NavLink, Outlet, useNavigate } from 'react-router-dom';
 import { Moon, Sun, Monitor } from 'lucide-react';
+import { useTranslation } from 'react-i18next';
 import { useAuth } from '@/hooks/useAuth';
 import { useTheme } from '@/hooks/useTheme';
 import type { Theme } from '@/hooks/useTheme';
@@ -20,6 +21,7 @@ export function Layout(): JSX.Element {
   const { user, isAdmin, isRedteam, logout } = useAuth();
   const navigate = useNavigate();
   const { theme, cycleTheme } = useTheme();
+  const { t } = useTranslation();
 
   const handleLogout = async () => {
     await logout();
@@ -41,7 +43,7 @@ export function Layout(): JSX.Element {
               <button
                 type="button"
                 onClick={cycleTheme}
-                aria-label={`Theme: ${themeLabel(theme)} — click to cycle`}
+                aria-label={t('nav.themeAria', { label: themeLabel(theme) })}
                 className="flex items-center gap-xxs text-[12px] text-slab-muted hover:text-slab-text"
               >
                 <ThemeIcon theme={theme} />
@@ -52,7 +54,7 @@ export function Layout(): JSX.Element {
                 onClick={handleLogout}
                 className="text-[14px] underline-offset-2 hover:underline"
               >
-                Sign out
+                {t('nav.signOut')}
               </button>
             </div>
           ) : null}
@@ -62,7 +64,7 @@ export function Layout(): JSX.Element {
       {/* nav-bar-top — fixed dark slab, never inverts (same visual family as utility-strip + footer) */}
       <header className="bg-slab text-slab-text">
         <div className="mx-auto w-full max-w-page px-xl h-16 flex items-center justify-between">
-          <Link to="/engagements" className="flex items-center gap-sm" aria-label="Mimic home">
+          <Link to="/engagements" className="flex items-center gap-sm" aria-label={t('nav.brandHome')}>
             <span className="inline-block h-6 w-6 rotate-12 bg-primary" aria-hidden />
             <span className="text-[20px] font-medium tracking-tight text-slab-text">Mimic</span>
           </Link>
@@ -78,7 +80,7 @@ export function Layout(): JSX.Element {
                 }`
               }
             >
-              Engagements
+              {t('nav.engagements')}
             </NavLink>
             {isAdmin || isRedteam ? (
               <NavLink
@@ -91,7 +93,7 @@ export function Layout(): JSX.Element {
                   }`
                 }
               >
-                Templates
+                {t('nav.templates')}
               </NavLink>
             ) : null}
             {isAdmin ? (
@@ -105,7 +107,7 @@ export function Layout(): JSX.Element {
                   }`
                 }
               >
-                Users
+                {t('nav.users')}
               </NavLink>
             ) : null}
           </nav>
@@ -122,7 +124,7 @@ export function Layout(): JSX.Element {
       {/* footer — fixed dark slab, never inverts */}
       <footer className="bg-slab text-slab-text">
         <div className="mx-auto w-full max-w-page px-xl py-xl text-[12px] text-slab-muted">
-          Mimic — Internal Purple Team tooling. Authorized engagements only.
+          {t('nav.footer')}
         </div>
       </footer>
     </div>
diff --git a/frontend/src/components/MitreMatrixModal.tsx b/frontend/src/components/MitreMatrixModal.tsx
index e37a49e..2f23873 100644
--- a/frontend/src/components/MitreMatrixModal.tsx
+++ b/frontend/src/components/MitreMatrixModal.tsx
@@ -1,4 +1,5 @@
 import { useEffect, useRef, useState } from 'react';
+import { useTranslation } from 'react-i18next';
 import { LoadingState } from './LoadingState';
 import { ErrorState } from './ErrorState';
 import { extractApiError } from '@/api/client';
@@ -41,6 +42,7 @@ export function MitreMatrixModal({
   onApply,
   onCancel,
 }: MitreMatrixModalProps): JSX.Element | null {
+  const { t } = useTranslation();
   const { data: matrix, isLoading, isError, error } = useMitreMatrix(isOpen);
 
   const [selectedTechMap, setSelectedTechMap] = useState<Map<string, { id: string; name: string }>>(
@@ -177,24 +179,24 @@ export function MitreMatrixModal({
         {/* Header */}
         <div className="flex items-center justify-between px-xl py-md border-b border-hairline flex-shrink-0">
           <h2 id="matrix-modal-title" className="text-[18px] font-medium text-ink">
-            MITRE ATT&amp;CK Matrix
+            {t('mitre.matrix.title')}
           </h2>
           <input
             ref={searchInputRef}
             type="text"
-            placeholder="Filter techniques…"
+            placeholder={t('mitre.matrix.filter')}
             value={search}
             onChange={(e) => setSearch(e.target.value)}
             className="text-input w-56 h-9 text-[14px]"
-            aria-label="Filter techniques"
+            aria-label={t('mitre.matrix.filter')}
           />
         </div>
 
         {/* Body — overflow-y-auto, NO overflow-x */}
         <div className="flex-1 overflow-y-auto overflow-x-hidden px-md py-md">
-          {isLoading && <LoadingState label="Loading MITRE matrix…" />}
+          {isLoading && <LoadingState label={t('mitre.matrix.loading')} />}
           {isError && (
-            <ErrorState message={extractApiError(error, 'Could not load MITRE matrix')} />
+            <ErrorState message={extractApiError(error, t('mitre.matrix.error'))} />
           )}
           {!isLoading && !isError && matrix && (
             <div
@@ -276,7 +278,7 @@ export function MitreMatrixModal({
                               {hasSubtechniques ? (
                                 <button
                                   type="button"
-                                  aria-label={isExpanded ? `Collapse ${tech.id}` : `Expand ${tech.id}`}
+                                  aria-label={isExpanded ? t('common.collapse', { id: tech.id }) : t('common.expand', { id: tech.id })}
                                   onClick={() => toggleExpand(tech.id)}
                                   className={`mr-[2px] flex-shrink-0 text-[9px] w-3 leading-none mt-[1px] ${
                                     isSelected ? 'text-white' : 'text-graphite'
@@ -327,7 +329,7 @@ export function MitreMatrixModal({
                         );
                       })}
                       {visibleTechniques.length === 0 && searchLower && (
-                        <div className="px-xs py-xxs text-[10px] text-graphite italic">No match</div>
+                        <div className="px-xs py-xxs text-[10px] text-graphite italic">{t('mitre.matrix.noMatch')}</div>
                       )}
                     </div>
                   </div>
@@ -340,7 +342,7 @@ export function MitreMatrixModal({
         {/* Footer */}
         <div className="flex items-center justify-end gap-md px-xl py-md border-t border-hairline flex-shrink-0">
           <button type="button" className="btn-outline-ink" onClick={onCancel}>
-            Cancel
+            {t('mitre.matrix.close')}
           </button>
           <button
             type="button"
@@ -349,8 +351,8 @@ export function MitreMatrixModal({
             disabled={isLoading || isError || (totalSelected === 0 && !hasInitial)}
           >
             {totalSelected === 0
-              ? 'Clear all'
-              : `Apply ${totalSelected} item${totalSelected !== 1 ? 's' : ''}`}
+              ? t('mitre.matrix.clearAll')
+              : t(totalSelected === 1 ? 'mitre.matrix.applyItem_one' : 'mitre.matrix.applyItem_other', { count: totalSelected })}
           </button>
         </div>
       </div>
diff --git a/frontend/src/components/MitreTechniquePicker.tsx b/frontend/src/components/MitreTechniquePicker.tsx
index f20162d..4ee9ecd 100644
--- a/frontend/src/components/MitreTechniquePicker.tsx
+++ b/frontend/src/components/MitreTechniquePicker.tsx
@@ -1,4 +1,5 @@
 import { useEffect, useRef, useState, type KeyboardEvent } from 'react';
+import { useTranslation } from 'react-i18next';
 import { extractApiError } from '@/api/client';
 import type { MitreTechnique } from '@/api/types';
 import { useMitreSearch } from '@/hooks/useMitre';
@@ -14,6 +15,7 @@ export function MitreTechniquePicker({
   onSelect,
   disabled = false,
 }: MitreTechniquePickerProps): JSX.Element {
+  const { t } = useTranslation();
   const [inputValue, setInputValue] = useState('');
   const [query, setQuery] = useState('');
   const [open, setOpen] = useState(false);
@@ -95,31 +97,31 @@ export function MitreTechniquePicker({
         aria-expanded={open}
         aria-controls={listboxId}
         aria-activedescendant={activeIndex >= 0 ? `mitre-option-${activeIndex}` : undefined}
-        aria-label="Search MITRE technique"
+        aria-label={t('mitre.field.search')}
         className="text-input"
         value={inputValue}
         onChange={(e) => handleInputChange(e.target.value)}
         onFocus={() => setOpen(true)}
         onKeyDown={handleKeyDown}
         disabled={disabled}
-        placeholder="Search by ID or name (e.g. T1059)"
+        placeholder={t('mitre.field.search')}
         autoComplete="off"
       />
 
       {open && (
         <div className="absolute z-20 w-full mt-xxs bg-paper border border-steel rounded-none overflow-hidden">
           {isFetching && (
-            <div className="px-md py-sm text-[14px] text-graphite">Searching…</div>
+            <div className="px-md py-sm text-[14px] text-graphite">{t('state.loading')}</div>
           )}
 
           {isError && !isFetching && (
             <div className="px-md py-sm text-[14px] text-bloom-deep" role="alert">
-              {extractApiError(error, 'MITRE search unavailable')}
+              {extractApiError(error, t('mitre.matrix.error'))}
             </div>
           )}
 
           {!isFetching && !isError && items.length === 0 && query.trim().length > 0 && (
-            <div className="px-md py-sm text-[14px] text-graphite">No results</div>
+            <div className="px-md py-sm text-[14px] text-graphite">{t('state.empty.default')}</div>
           )}
 
           {!isFetching && items.length > 0 && (
diff --git a/frontend/src/components/MitreTechniqueTag.tsx b/frontend/src/components/MitreTechniqueTag.tsx
index 481e1b3..08ffc43 100644
--- a/frontend/src/components/MitreTechniqueTag.tsx
+++ b/frontend/src/components/MitreTechniqueTag.tsx
@@ -1,3 +1,4 @@
+import { useTranslation } from 'react-i18next';
 import type { MitreTechnique, MitreTacticRef } from '@/api/types';
 
 interface TechniqueTagProps {
@@ -18,6 +19,7 @@ export function MitreTechniqueTag({
   onRemove,
   disabled = false,
 }: TechniqueTagProps): JSX.Element {
+  const { t } = useTranslation();
   return (
     <span
       data-testid="mitre-technique-tag"
@@ -28,7 +30,7 @@ export function MitreTechniqueTag({
       {!disabled && (
         <button
           type="button"
-          aria-label={`Remove ${technique.id}`}
+          aria-label={`${t('mitre.tag.remove')} ${technique.id}`}
           onClick={onRemove}
           className="text-primary-deep opacity-60 hover:opacity-100 leading-none"
         >
@@ -45,6 +47,7 @@ export function MitreTacticTag({
   onRemove,
   disabled = false,
 }: TacticTagProps): JSX.Element {
+  const { t } = useTranslation();
   return (
     <span
       data-testid="mitre-tactic-tag"
@@ -55,7 +58,7 @@ export function MitreTacticTag({
       {!disabled && (
         <button
           type="button"
-          aria-label={`Remove ${tactic.id}`}
+          aria-label={`${t('mitre.tag.remove')} ${tactic.id}`}
           onClick={onRemove}
           className="text-white opacity-60 hover:opacity-100 leading-none"
         >
diff --git a/frontend/src/components/MitreTechniquesField.tsx b/frontend/src/components/MitreTechniquesField.tsx
index 6314bd8..5bfc88b 100644
--- a/frontend/src/components/MitreTechniquesField.tsx
+++ b/frontend/src/components/MitreTechniquesField.tsx
@@ -1,5 +1,6 @@
 import { useState } from 'react';
 import { Grid2x2 } from 'lucide-react';
+import { useTranslation } from 'react-i18next';
 import { extractApiError } from '@/api/client';
 import type { MitreTechnique, MitreTacticRef } from '@/api/types';
 import { useUpdateSimulation } from '@/hooks/useSimulations';
@@ -24,6 +25,7 @@ export function MitreTechniquesField({
   engagementId,
   disabled = false,
 }: MitreTechniquesFieldProps): JSX.Element {
+  const { t } = useTranslation();
   const [showMatrix, setShowMatrix] = useState(false);
   const [showPicker, setShowPicker] = useState(false);
 
@@ -33,34 +35,34 @@ export function MitreTechniquesField({
   const save = async (techniques: MitreTechnique[], nextTactics: MitreTacticRef[]) => {
     try {
       await updateMutation.mutateAsync({
-        technique_ids: techniques.map((t) => t.id),
-        tactic_ids: nextTactics.map((t) => t.id),
+        technique_ids: techniques.map((tech) => tech.id),
+        tactic_ids: nextTactics.map((tac) => tac.id),
       });
-      push('Techniques updated', 'success');
+      push(t('mitre.field.savedToast'), 'success');
     } catch (err) {
-      push(extractApiError(err, 'Could not update techniques'), 'error');
+      push(extractApiError(err, t('mitre.field.errorToast')), 'error');
     }
   };
 
   const handleRemoveTechnique = (id: string) => {
-    void save(value.filter((t) => t.id !== id), tactics);
+    void save(value.filter((tech) => tech.id !== id), tactics);
   };
 
   const handleRemoveTactic = (id: string) => {
-    void save(value, tactics.filter((t) => t.id !== id));
+    void save(value, tactics.filter((tac) => tac.id !== id));
   };
 
   const handleSelect = (technique: MitreTechnique) => {
-    if (value.some((t) => t.id === technique.id)) return;
+    if (value.some((tech) => tech.id === technique.id)) return;
     void save([...value, technique], tactics);
     setShowPicker(false);
   };
 
   const handleMatrixApply = ({ techniques, tactics: newTactics }: MatrixSelection) => {
     setShowMatrix(false);
-    const merged = techniques.map((s) => {
-      const existing = value.find((v) => v.id === s.id);
-      return existing ?? s;
+    const merged = techniques.map((sel) => {
+      const existing = value.find((v) => v.id === sel.id);
+      return existing ?? sel;
     });
     void save(merged, newTactics);
   };
@@ -72,22 +74,22 @@ export function MitreTechniquesField({
     <div className="flex flex-col gap-sm">
       {/* Chips area */}
       {isEmpty ? (
-        <p className="text-[13px] text-graphite">No techniques selected</p>
+        <p className="text-[13px] text-graphite">{t('mitre.field.empty')}</p>
       ) : (
         <div className="flex flex-wrap gap-xs" data-testid="techniques-tag-list">
-          {tactics.map((t) => (
+          {tactics.map((tac) => (
             <MitreTacticTag
-              key={t.id}
-              tactic={t}
-              onRemove={() => handleRemoveTactic(t.id)}
+              key={tac.id}
+              tactic={tac}
+              onRemove={() => handleRemoveTactic(tac.id)}
               disabled={disabled || isPending}
             />
           ))}
-          {value.map((t) => (
+          {value.map((tech) => (
             <MitreTechniqueTag
-              key={t.id}
-              technique={t}
-              onRemove={() => handleRemoveTechnique(t.id)}
+              key={tech.id}
+              technique={tech}
+              onRemove={() => handleRemoveTechnique(tech.id)}
               disabled={disabled || isPending}
             />
           ))}
@@ -107,20 +109,20 @@ export function MitreTechniquesField({
                 onClick={() => setShowPicker(true)}
                 disabled={isPending}
               >
-                Search technique (e.g. T1059)…
+                {t('mitre.field.search')}
               </button>
             )}
           </div>
           <button
             type="button"
-            aria-label="Open MITRE matrix"
+            aria-label={t('mitre.field.openMatrix')}
             onClick={() => { setShowPicker(false); setShowMatrix(true); }}
             disabled={isPending}
             className="flex-shrink-0 flex items-center justify-center w-9 h-9 rounded-none border border-steel text-graphite hover:text-ink hover:border-ink"
           >
             <Grid2x2 size={16} />
           </button>
-          {isPending && <span className="text-[12px] text-graphite">Saving…</span>}
+          {isPending && <span className="text-[12px] text-graphite">{t('common.saving')}</span>}
         </div>
       )}
 
diff --git a/frontend/src/components/ProtectedRoute.tsx b/frontend/src/components/ProtectedRoute.tsx
index 97b3799..a109d65 100644
--- a/frontend/src/components/ProtectedRoute.tsx
+++ b/frontend/src/components/ProtectedRoute.tsx
@@ -1,5 +1,6 @@
 import { useEffect } from 'react';
 import { Navigate, Outlet, useLocation } from 'react-router-dom';
+import { useTranslation } from 'react-i18next';
 import { useAuth } from '@/hooks/useAuth';
 import { useToast } from '@/hooks/useToast';
 import type { Role } from '@/api/types';
@@ -23,6 +24,7 @@ export function ProtectedRoute({
 }: ProtectedRouteProps): JSX.Element {
   const { user, status } = useAuth();
   const { push } = useToast();
+  const { t } = useTranslation();
   const location = useLocation();
 
   const roleDenied = Boolean(
@@ -31,12 +33,12 @@ export function ProtectedRoute({
 
   useEffect(() => {
     if (roleDenied) {
-      push('Accès refusé', 'error');
+      push(t('auth.forbidden'), 'error');
     }
-  }, [roleDenied, push]);
+  }, [roleDenied, push, t]);
 
   if (status === 'loading') {
-    return <LoadingState label="Loading session…" />;
+    return <LoadingState label={t('auth.loadingSession')} />;
   }
 
   if (status === 'unauthenticated' || !user) {
diff --git a/frontend/src/components/SimulationList.tsx b/frontend/src/components/SimulationList.tsx
index f20b194..c1ad594 100644
--- a/frontend/src/components/SimulationList.tsx
+++ b/frontend/src/components/SimulationList.tsx
@@ -1,11 +1,13 @@
 import { useEffect, useRef, useState } from 'react';
 import { Link, useNavigate } from 'react-router-dom';
 import { ChevronDown, Plus } from 'lucide-react';
+import { useTranslation } from 'react-i18next';
 import { extractApiError } from '@/api/client';
 import type { SimulationTemplate } from '@/api/types';
 import { useAuth } from '@/hooks/useAuth';
 import { useEngagementSimulations, useCreateSimulation } from '@/hooks/useSimulations';
 import { useToast } from '@/hooks/useToast';
+import { formatDateTime } from '@/lib/format';
 import { LoadingState } from './LoadingState';
 import { ErrorState } from './ErrorState';
 import { EmptyState } from './EmptyState';
@@ -16,12 +18,8 @@ interface SimulationListProps {
   engagementId: number;
 }
 
-function formatDate(value: string | null): string {
-  if (!value) return '—';
-  return value.replace('T', ' ').slice(0, 16);
-}
-
 function NewSimulationDropdown({ engagementId }: { engagementId: number }): JSX.Element {
+  const { t } = useTranslation();
   const navigate = useNavigate();
   const { push } = useToast();
   const [open, setOpen] = useState(false);
@@ -61,10 +59,10 @@ function NewSimulationDropdown({ engagementId }: { engagementId: number }): JSX.
     try {
       const sim = await createMutation.mutateAsync({ name: template.name, template_id: template.id });
       setShowPicker(false);
-      push(`Created "${sim.name}" from template`, 'success');
+      push(t('simulation.form.toast.created'), 'success');
       navigate(`/engagements/${engagementId}/simulations/${sim.id}/edit`);
     } catch (err) {
-      push(extractApiError(err, 'Could not create simulation from template'), 'error');
+      push(extractApiError(err, t('simulation.form.error.create')), 'error');
     }
   };
 
@@ -77,11 +75,11 @@ function NewSimulationDropdown({ engagementId }: { engagementId: number }): JSX.
           onClick={handleBlank}
           data-testid="new-simulation-btn"
         >
-          <Plus size={14} aria-hidden /> New
+          <Plus size={14} aria-hidden /> {t('simulation.list.new')}
         </button>
         <button
           type="button"
-          aria-label="More options"
+          aria-label={t('simulation.list.rowActions')}
           aria-expanded={open}
           className="btn-primary px-sm"
           onClick={() => setOpen((v) => !v)}
@@ -133,16 +131,17 @@ function NewSimulationDropdown({ engagementId }: { engagementId: number }): JSX.
 }
 
 export function SimulationList({ engagementId }: SimulationListProps): JSX.Element {
+  const { t } = useTranslation();
   const { data, isLoading, isError, error, refetch } = useEngagementSimulations(engagementId);
   const { canEditEngagements } = useAuth();
   const navigate = useNavigate();
 
-  if (isLoading) return <LoadingState label="Loading simulations…" />;
+  if (isLoading) return <LoadingState label={t('common.loading')} />;
 
   if (isError) {
     return (
       <ErrorState
-        message={extractApiError(error, 'Could not load simulations')}
+        message={extractApiError(error, t('simulation.list.error'))}
         onRetry={() => refetch()}
       />
     );
@@ -151,8 +150,8 @@ export function SimulationList({ engagementId }: SimulationListProps): JSX.Eleme
   if (!data || data.length === 0) {
     return (
       <EmptyState
-        title="No simulations yet"
-        description="Create the first simulation to start tracking red team tests."
+        title={t('simulation.list.empty.title')}
+        description={t('simulation.list.empty.desc')}
         action={
           canEditEngagements ? (
             <NewSimulationDropdown engagementId={engagementId} />
@@ -165,7 +164,7 @@ export function SimulationList({ engagementId }: SimulationListProps): JSX.Eleme
   return (
     <div className="flex flex-col gap-md">
       <div className="flex items-center justify-between">
-        <h2 className="text-[24px] font-medium text-ink">Simulations</h2>
+        <h2 className="text-[24px] font-medium text-ink">{t('engagement.detail.tabs.simulations')}</h2>
         {canEditEngagements ? (
           <NewSimulationDropdown engagementId={engagementId} />
         ) : null}
@@ -175,10 +174,10 @@ export function SimulationList({ engagementId }: SimulationListProps): JSX.Eleme
         <table className="table-compact w-full text-left">
           <thead className="bg-cloud border-b border-hairline">
             <tr>
-              <th>Name</th>
-              <th>MITRE</th>
-              <th>Status</th>
-              <th>Executed at</th>
+              <th>{t('simulation.list.col.name')}</th>
+              <th>{t('simulation.list.col.mitre')}</th>
+              <th>{t('simulation.list.col.status')}</th>
+              <th>{t('simulation.list.col.executedAt')}</th>
             </tr>
           </thead>
           <tbody>
@@ -202,8 +201,8 @@ export function SimulationList({ engagementId }: SimulationListProps): JSX.Eleme
                 <td className="text-charcoal font-mono">
                   {(() => {
                     const items = [
-                      ...(sim.tactics ?? []).map((t) => t.id),
-                      ...sim.techniques.map((t) => t.id),
+                      ...(sim.tactics ?? []).map((tactic) => tactic.id),
+                      ...sim.techniques.map((tech) => tech.id),
                     ];
                     if (items.length === 0) return '—';
                     if (items.length === 1) return items[0];
@@ -214,7 +213,7 @@ export function SimulationList({ engagementId }: SimulationListProps): JSX.Eleme
                   <SimulationStatusBadge status={sim.status} />
                 </td>
                 <td className="text-charcoal font-mono">
-                  {formatDate(sim.executed_at)}
+                  {sim.executed_at ? formatDateTime(sim.executed_at) : '—'}
                 </td>
               </tr>
             ))}
diff --git a/frontend/src/components/SimulationStatusBadge.tsx b/frontend/src/components/SimulationStatusBadge.tsx
index 7665441..0545e07 100644
--- a/frontend/src/components/SimulationStatusBadge.tsx
+++ b/frontend/src/components/SimulationStatusBadge.tsx
@@ -1,12 +1,6 @@
+import { useTranslation } from 'react-i18next';
 import type { SimulationStatus } from '@/api/types';
 
-const LABELS: Record<SimulationStatus, string> = {
-  pending: 'Pending',
-  in_progress: 'In progress',
-  review_required: 'Review required',
-  done: 'Done',
-};
-
 const STYLES: Record<SimulationStatus, string> = {
   pending: 'bg-cloud text-graphite border border-hairline',
   in_progress: 'bg-primary-soft text-primary-deep',
@@ -15,13 +9,14 @@ const STYLES: Record<SimulationStatus, string> = {
 };
 
 export function SimulationStatusBadge({ status }: { status: SimulationStatus }): JSX.Element {
+  const { t } = useTranslation();
   return (
     <span
       className={`inline-flex items-center rounded-pill px-3 py-[6px] text-[14px] leading-[1.3] font-medium ${STYLES[status]}`}
       data-testid="simulation-status-badge"
       data-status={status}
     >
-      {LABELS[status]}
+      {t(`status.simulation.${status}`)}
     </span>
   );
 }
diff --git a/frontend/src/components/StatusBadge.tsx b/frontend/src/components/StatusBadge.tsx
index 971f7ec..9c35831 100644
--- a/frontend/src/components/StatusBadge.tsx
+++ b/frontend/src/components/StatusBadge.tsx
@@ -1,11 +1,6 @@
+import { useTranslation } from 'react-i18next';
 import type { EngagementStatus } from '@/api/types';
 
-const LABELS: Record<EngagementStatus, string> = {
-  planned: 'Planned',
-  active: 'Active',
-  closed: 'Closed',
-};
-
 const STYLES: Record<EngagementStatus, string> = {
   planned: 'bg-warn-soft text-warn border border-warn',
   active: 'bg-primary-soft text-primary-deep',
@@ -13,13 +8,14 @@ const STYLES: Record<EngagementStatus, string> = {
 };
 
 export function StatusBadge({ status }: { status: EngagementStatus }): JSX.Element {
+  const { t } = useTranslation();
   return (
     <span
       className={`inline-flex items-center rounded-pill px-3 py-[6px] text-[14px] leading-[1.3] font-medium ${STYLES[status]}`}
       data-testid="status-badge"
       data-status={status}
     >
-      {LABELS[status]}
+      {t(`status.engagement.${status}`)}
     </span>
   );
 }
diff --git a/frontend/src/components/TemplatePickerModal.tsx b/frontend/src/components/TemplatePickerModal.tsx
index 4ca9452..e8e4cfb 100644
--- a/frontend/src/components/TemplatePickerModal.tsx
+++ b/frontend/src/components/TemplatePickerModal.tsx
@@ -1,3 +1,4 @@
+import { useTranslation } from 'react-i18next';
 import { extractApiError } from '@/api/client';
 import type { SimulationTemplate } from '@/api/types';
 import { useTemplates } from '@/hooks/useTemplates';
@@ -23,6 +24,7 @@ export function TemplatePickerModal({
   onSelectTemplate,
   isPending = false,
 }: TemplatePickerModalProps): JSX.Element {
+  const { t } = useTranslation();
   const { data, isLoading, isError, error, refetch } = useTemplates();
 
   return (
@@ -37,11 +39,11 @@ export function TemplatePickerModal({
       <div className="relative card-product max-w-xl w-full mx-md flex flex-col gap-md max-h-[80vh] overflow-hidden">
         <div className="flex items-center justify-between">
           <h2 id="tpl-picker-title" className="text-[20px] font-medium text-ink">
-            From template…
+            {t('template.picker.title')}
           </h2>
           <button
             type="button"
-            aria-label="Close"
+            aria-label={t('common.close')}
             onClick={onClose}
             className="text-graphite hover:text-ink text-[20px] leading-none"
           >
@@ -50,19 +52,18 @@ export function TemplatePickerModal({
         </div>
 
         <div className="overflow-y-auto flex-1 -mx-xl px-xl">
-          {isLoading ? <LoadingState label="Loading templates…" /> : null}
+          {isLoading ? <LoadingState label={t('template.picker.loading')} /> : null}
 
           {isError ? (
             <ErrorState
-              message={extractApiError(error, 'Could not load templates')}
+              message={extractApiError(error, t('template.form.errorLoad'))}
               onRetry={() => refetch()}
             />
           ) : null}
 
           {!isLoading && !isError && data && data.length === 0 ? (
             <EmptyState
-              title="No templates available"
-              description="Create one from the Templates page."
+              title={t('template.picker.empty')}
             />
           ) : null}
 
@@ -70,22 +71,22 @@ export function TemplatePickerModal({
             <table className="w-full text-left" data-testid="template-picker-table">
               <thead className="bg-cloud border-b border-hairline">
                 <tr className="text-[12px] uppercase tracking-[0.5px] text-graphite">
-                  <th className="px-md py-sm">Name</th>
-                  <th className="px-md py-sm">MITRE</th>
-                  <th className="px-md py-sm">Created by</th>
+                  <th className="px-md py-sm">{t('template.list.col.name')}</th>
+                  <th className="px-md py-sm">{t('simulation.list.col.mitre')}</th>
+                  <th className="px-md py-sm">{t('template.list.col.createdBy')}</th>
                 </tr>
               </thead>
               <tbody>
-                {data.map((t) => (
+                {data.map((template) => (
                   <tr
-                    key={t.id}
+                    key={template.id}
                     className="border-b border-hairline last:border-0 hover:bg-cloud cursor-pointer"
-                    onClick={() => !isPending && onSelectTemplate(t)}
-                    data-testid={`template-row-${t.id}`}
+                    onClick={() => !isPending && onSelectTemplate(template)}
+                    data-testid={`template-row-${template.id}`}
                   >
-                    <td className="px-md py-sm text-ink font-medium">{t.name}</td>
-                    <td className="px-md py-sm text-charcoal text-[14px]">{mitreCount(t)}</td>
-                    <td className="px-md py-sm text-charcoal text-[14px]">{t.created_by.username}</td>
+                    <td className="px-md py-sm text-ink font-medium">{template.name}</td>
+                    <td className="px-md py-sm text-charcoal text-[14px]">{mitreCount(template)}</td>
+                    <td className="px-md py-sm text-charcoal text-[14px]">{template.created_by.username}</td>
                   </tr>
                 ))}
               </tbody>
@@ -95,7 +96,7 @@ export function TemplatePickerModal({
 
         <div className="border-t border-hairline pt-sm">
           <button type="button" className="btn-outline-ink" onClick={onClose}>
-            Cancel
+            {t('common.cancel')}
           </button>
         </div>
       </div>
diff --git a/frontend/src/components/Toast.tsx b/frontend/src/components/Toast.tsx
index 3e0ed7e..a7ba5d4 100644
--- a/frontend/src/components/Toast.tsx
+++ b/frontend/src/components/Toast.tsx
@@ -1,6 +1,8 @@
+import { useTranslation } from 'react-i18next';
 import { useToast } from '@/hooks/useToast';
 
 export function ToastViewport(): JSX.Element {
+  const { t } = useTranslation();
   const { toasts, dismiss } = useToast();
   return (
     <div
@@ -8,9 +10,9 @@ export function ToastViewport(): JSX.Element {
       aria-atomic="true"
       className="fixed bottom-xl right-xl z-50 flex flex-col gap-sm w-[320px] pointer-events-none"
     >
-      {toasts.map((t) => {
-        const isError = t.kind === 'error';
-        const isSuccess = t.kind === 'success';
+      {toasts.map((toast) => {
+        const isError = toast.kind === 'error';
+        const isSuccess = toast.kind === 'success';
         const surface = isError
           ? 'bg-paper text-ink border border-hairline border-l-4 border-l-bloom-deep'
           : isSuccess
@@ -18,18 +20,18 @@ export function ToastViewport(): JSX.Element {
             : 'bg-paper text-ink border border-hairline border-l-4 border-l-primary';
         return (
           <div
-            key={t.id}
+            key={toast.id}
             role="status"
             data-testid="toast"
-            data-kind={t.kind}
+            data-kind={toast.kind}
             className={`pointer-events-auto rounded-none px-md py-sm text-[14px] leading-[1.4] ${surface}`}
           >
             <div className="flex items-start justify-between gap-sm">
-              <span className="flex-1">{t.message}</span>
+              <span className="flex-1">{toast.message}</span>
               <button
                 type="button"
-                onClick={() => dismiss(t.id)}
-                aria-label="Dismiss notification"
+                onClick={() => dismiss(toast.id)}
+                aria-label={t('toast.dismiss')}
                 className="text-current opacity-70 hover:opacity-100"
               >
                 ×
diff --git a/frontend/src/i18n/fr.json b/frontend/src/i18n/fr.json
new file mode 100644
index 0000000..ccb01a0
--- /dev/null
+++ b/frontend/src/i18n/fr.json
@@ -0,0 +1,520 @@
+{
+  "common": {
+    "save": "Enregistrer",
+    "saving": "Enregistrement…",
+    "cancel": "Annuler",
+    "delete": "Supprimer",
+    "edit": "Modifier",
+    "new": "Nouveau",
+    "loading": "Chargement…",
+    "retry": "Réessayer",
+    "back": "Retour",
+    "dismiss": "Fermer",
+    "view": "Voir",
+    "create": "Créer",
+    "creating": "Création…",
+    "close": "Fermer",
+    "confirm": "Confirmer",
+    "yes": "Oui",
+    "no": "Non",
+    "expand": "Déplier {{id}}",
+    "collapse": "Replier {{id}}",
+    "select": "Sélectionner"
+  },
+  "nav": {
+    "engagements": "Engagements",
+    "templates": "Templates",
+    "users": "Utilisateurs",
+    "signOut": "Se déconnecter",
+    "brand": "Mimic",
+    "brandHome": "Accueil Mimic",
+    "themeAria": "Thème : {{label}} — cliquer pour changer",
+    "footer": "Mimic — Outillage interne Purple Team. Engagements autorisés uniquement."
+  },
+  "export": {
+    "btn": "Exporter",
+    "btnLoading": "Export en cours…",
+    "aria": "Options d'export"
+  },
+  "auth": {
+    "login": {
+      "title": "Mimic",
+      "subtitle": "Connectez-vous pour accéder à vos engagements.",
+      "username": "Nom d'utilisateur",
+      "password": "Mot de passe",
+      "signIn": "Se connecter",
+      "signingIn": "Connexion…",
+      "invalid": "Identifiants invalides"
+    },
+    "forbidden": "Accès refusé",
+    "loadingSession": "Chargement de la session…"
+  },
+  "engagement": {
+    "list": {
+      "title": "Engagements",
+      "subtitle": "Missions red team et leur statut.",
+      "new": "Nouveau",
+      "empty": {
+        "title": "Aucun engagement",
+        "desc": "Créez votre premier engagement pour commencer à suivre les missions red team."
+      },
+      "col": {
+        "name": "Nom",
+        "status": "Statut",
+        "start": "Début",
+        "end": "Fin",
+        "createdBy": "Créé par",
+        "actions": "Actions"
+      },
+      "view": "Voir",
+      "edit": "Modifier",
+      "delete": "Supprimer",
+      "deleteConfirm": "Supprimer l'engagement « {{name}} » ? Cette action est irréversible.",
+      "toast": {
+        "deleted": "Engagement supprimé"
+      },
+      "error": {
+        "load": "Impossible de charger les engagements",
+        "delete": "Impossible de supprimer l'engagement"
+      }
+    },
+    "detail": {
+      "tabs": {
+        "description": "Description",
+        "simulations": "Simulations"
+      },
+      "schedule": {
+        "startDate": "Date de début",
+        "endDate": "Date de fin",
+        "status": "Statut",
+        "createdAt": "Créé le"
+      },
+      "edit": "Modifier",
+      "createdBy": "Créé par",
+      "noDescription": "Aucune description fournie.",
+      "loading": "Chargement de l'engagement…",
+      "errorLoad": "Impossible de charger l'engagement",
+      "notFound": "Engagement introuvable",
+      "backTo": "Retour aux engagements"
+    },
+    "form": {
+      "title": {
+        "new": "Nouvel engagement",
+        "edit": "Modifier l'engagement"
+      },
+      "subtitle": {
+        "new": "Définir le périmètre et la planification.",
+        "edit": "Mettre à jour les détails."
+      },
+      "field": {
+        "name": "Nom",
+        "description": "Description",
+        "startDate": "Date de début",
+        "endDate": "Date de fin",
+        "endDateHint": "Optionnel",
+        "status": "Statut"
+      },
+      "validation": {
+        "nameRequired": "Le nom est obligatoire",
+        "startDateRequired": "La date de début est obligatoire",
+        "endDateAfterStart": "La date de fin doit être égale ou postérieure à la date de début"
+      },
+      "btn": {
+        "create": "Créer",
+        "save": "Enregistrer",
+        "saving": "Enregistrement…",
+        "cancel": "Annuler"
+      },
+      "toast": {
+        "created": "Engagement créé",
+        "updated": "Engagement mis à jour"
+      },
+      "error": {
+        "save": "Impossible d'enregistrer l'engagement",
+        "load": "Impossible de charger l'engagement"
+      },
+      "loading": "Chargement…",
+      "c2Config": "Configuration C2"
+    }
+  },
+  "simulation": {
+    "form": {
+      "title": {
+        "new": "Nouvelle simulation"
+      },
+      "field": {
+        "name": "Nom",
+        "mitre": "Techniques et tactiques MITRE",
+        "description": "Description",
+        "commands": "Commandes",
+        "commandsHint": "Une commande par ligne",
+        "prerequisites": "Prérequis",
+        "executedAt": "Exécuté le",
+        "executionResult": "Résultat d'exécution",
+        "logSource": "Source de log",
+        "logs": "Logs",
+        "socComment": "Commentaire SOC",
+        "incidentNumber": "Numéro d'incident"
+      },
+      "btn": {
+        "create": "Créer la simulation",
+        "creating": "Création…",
+        "save": "Enregistrer",
+        "saving": "Enregistrement…",
+        "saveSoc": "Enregistrer SOC",
+        "markReview": "Marquer pour révision",
+        "close": "Clore",
+        "reopen": "Rouvrir",
+        "delete": "Supprimer",
+        "executeC2": "Exécuter via C2",
+        "importC2History": "Importer l'historique C2",
+        "cancel": "Annuler"
+      },
+      "deleteConfirm": {
+        "title": "Supprimer la simulation",
+        "desc": "Cette action est permanente. La simulation sera définitivement supprimée.",
+        "confirm": "Supprimer",
+        "cancel": "Annuler"
+      },
+      "banner": {
+        "done": "Cette simulation est terminée et en lecture seule. Utilisez Rouvrir pour effectuer des modifications.",
+        "socNotReady": "La simulation n'est pas encore prête pour la révision — l'équipe red team doit la marquer comme « Révision requise » avant que vous puissiez remplir la section SOC."
+      },
+      "header": {
+        "redTeam": "Red Team",
+        "soc": "SOC"
+      },
+      "validation": {
+        "nameRequired": "Le nom est obligatoire"
+      },
+      "toast": {
+        "created": "Simulation créée",
+        "updated": "Simulation mise à jour",
+        "deleted": "Simulation supprimée",
+        "markedReview": "Simulation marquée pour révision",
+        "closed": "Simulation close",
+        "reopened": "Simulation rouverte",
+        "socUpdated": "Rapport SOC mis à jour"
+      },
+      "error": {
+        "create": "Impossible de créer la simulation",
+        "update": "Impossible de mettre à jour la simulation",
+        "delete": "Impossible de supprimer la simulation",
+        "soc": "Impossible de mettre à jour les champs SOC",
+        "transition": "Transition échouée",
+        "load": "Impossible de charger la simulation"
+      },
+      "loading": "Chargement de la simulation…"
+    },
+    "list": {
+      "col": {
+        "name": "Nom",
+        "mitre": "MITRE",
+        "status": "Statut",
+        "executedAt": "Exécuté le"
+      },
+      "empty": {
+        "title": "Aucune simulation",
+        "desc": "Créez votre première simulation pour cet engagement."
+      },
+      "new": "Nouvelle simulation",
+      "error": "Impossible de charger les simulations",
+      "rowActions": "Plus d'options"
+    }
+  },
+  "template": {
+    "list": {
+      "title": "Templates",
+      "subtitle": "Modèles de simulation réutilisables.",
+      "new": "Nouveau",
+      "empty": {
+        "title": "Aucun template",
+        "desc": "Créez votre premier template de simulation."
+      },
+      "col": {
+        "name": "Nom",
+        "mitre": "MITRE",
+        "createdBy": "Créé par",
+        "updated": "Modifié"
+      },
+      "edit": "Modifier",
+      "delete": "Supprimer"
+    },
+    "form": {
+      "title": {
+        "new": "Nouveau template",
+        "edit": "Modifier le template"
+      },
+      "field": {
+        "name": "Nom",
+        "description": "Description",
+        "descriptionPlaceholder": "Description du template…",
+        "commands": "Commandes",
+        "commandsHint": "Une commande par ligne",
+        "commandsPlaceholder": "whoami\nnet user",
+        "prerequisites": "Prérequis",
+        "prerequisitesPlaceholder": "Prérequis…",
+        "mitre": "Techniques MITRE",
+        "mitreSearch": "Rechercher une technique…",
+        "mitreOpenMatrix": "Ouvrir la matrice",
+        "mitreEmpty": "Aucune technique associée."
+      },
+      "btn": {
+        "save": "Enregistrer",
+        "saving": "Enregistrement…",
+        "delete": "Supprimer",
+        "cancel": "Annuler"
+      },
+      "validation": {
+        "nameRequired": "Le nom est obligatoire"
+      },
+      "toast": {
+        "created": "Template créé",
+        "saved": "Template enregistré",
+        "deleted": "Template supprimé"
+      },
+      "deleteConfirm": {
+        "title": "Supprimer le template",
+        "desc": "Cette action est permanente.",
+        "confirm": "Supprimer",
+        "cancel": "Annuler"
+      },
+      "loading": "Chargement du template…",
+      "errorLoad": "Impossible de charger le template",
+      "errorSave": "Impossible d'enregistrer le template",
+      "errorDelete": "Impossible de supprimer le template"
+    },
+    "picker": {
+      "title": "Choisir un template",
+      "empty": "Aucun template disponible.",
+      "loading": "Chargement…"
+    }
+  },
+  "user": {
+    "admin": {
+      "title": "Utilisateurs",
+      "subtitle": "Gestion des comptes.",
+      "new": "Nouveau",
+      "col": {
+        "username": "Nom d'utilisateur",
+        "role": "Rôle",
+        "createdAt": "Créé le",
+        "actions": "Actions"
+      },
+      "role": {
+        "admin": "Admin",
+        "redteam": "Red Team",
+        "soc": "SOC"
+      },
+      "field": {
+        "username": "Nom d'utilisateur",
+        "password": "Mot de passe"
+      },
+      "btn": {
+        "create": "Créer",
+        "creating": "Création…",
+        "resetPassword": "Réinitialiser le mot de passe",
+        "setPassword": "Définir le mot de passe",
+        "delete": "Supprimer",
+        "cancel": "Annuler"
+      },
+      "you": "(vous)",
+      "toast": {
+        "created": "Utilisateur créé",
+        "deleted": "Utilisateur supprimé",
+        "passwordReset": "Mot de passe réinitialisé pour {{username}}",
+        "roleUpdated": "Rôle mis à jour pour {{username}}"
+      },
+      "error": {
+        "create": "Impossible de créer l'utilisateur",
+        "delete": "Impossible de supprimer l'utilisateur",
+        "passwordReset": "Impossible de réinitialiser le mot de passe",
+        "roleUpdate": "Impossible de modifier le rôle",
+        "selfDelete": "Vous ne pouvez pas supprimer votre propre compte",
+        "passwordMinLength": "Le mot de passe doit contenir au moins 8 caractères"
+      },
+      "deleteConfirm": "Supprimer l'utilisateur « {{username}} » ?",
+      "newPasswordFor": "Nouveau mot de passe pour {{username}}",
+      "newPassword": "Nouveau mot de passe",
+      "passwordHint": "≥ 8 caractères",
+      "createSection": "Créer un compte",
+      "allSection": "Tous les comptes",
+      "createSubtitle": "Les administrateurs peuvent créer des comptes Red Team ou SOC.",
+      "resetPassword": "Réinitialiser le mot de passe",
+      "empty": {
+        "title": "Aucun utilisateur",
+        "desc": "Créez le premier compte via le formulaire ci-dessus."
+      }
+    }
+  },
+  "c2": {
+    "config": {
+      "title": "Configuration C2",
+      "disabled": "Les fonctionnalités C2 sont désactivées (aucune clé de chiffrement configurée sur le serveur).",
+      "field": {
+        "url": "URL",
+        "urlHint": "HTTPS requis (ex. https://mythic.lab:7443)",
+        "token": "Token API",
+        "tokenHint": "Token API",
+        "verifyTls": "Vérifier le certificat TLS",
+        "verifyTlsHint": "Décochez uniquement pour un Mythic de lab avec des certificats auto-signés. Désactiver la vérification expose le token API aux attaques MITM."
+      },
+      "btn": {
+        "save": "Enregistrer",
+        "saving": "Enregistrement…",
+        "test": "Tester la connexion",
+        "testing": "Test…",
+        "delete": "Supprimer la configuration",
+        "replaceToken": "Remplacer le token"
+      },
+      "toast": {
+        "saved": "Configuration C2 enregistrée",
+        "deleted": "Configuration C2 supprimée"
+      },
+      "error": {
+        "save": "Impossible d'enregistrer la configuration C2",
+        "delete": "Impossible de supprimer la configuration C2"
+      },
+      "connected": "Connecté",
+      "connectionFailed": "Connexion échouée",
+      "deleteConfirm": {
+        "title": "Supprimer la configuration C2",
+        "desc": "La configuration C2 de cet engagement sera supprimée. Le token API sera définitivement effacé.",
+        "confirm": "Supprimer",
+        "cancel": "Annuler"
+      },
+      "loading": "Chargement…"
+    },
+    "tasks": {
+      "title": "Tâches C2",
+      "empty": "Aucune tâche C2.",
+      "col": {
+        "task": "Tâche",
+        "command": "Commande",
+        "source": "Source",
+        "status": "Statut",
+        "completedAt": "Terminé le",
+        "expand": "Déplier"
+      },
+      "refreshing": "Actualisation…"
+    },
+    "modal": {
+      "execute": {
+        "title": "Exécuter via C2",
+        "callback": "Agent cible",
+        "btn": {
+          "launch": "Lancer",
+          "launching": "Lancement…",
+          "cancel": "Annuler"
+        },
+        "commandCount_one": "{{count}} commande",
+        "commandCount_other": "{{count}} commandes",
+        "validation": {
+          "callbackRequired": "Sélectionnez un agent",
+          "commandsRequired": "Aucune commande à exécuter"
+        },
+        "toast": {
+          "launched": "{{count}} tâche(s) C2 lancée(s)"
+        },
+        "error": {
+          "launch": "Impossible de lancer la tâche C2"
+        }
+      },
+      "import": {
+        "title": "Importer l'historique C2",
+        "total": "Total",
+        "page": "Page",
+        "of": "sur",
+        "prev": "Précédent",
+        "next": "Suivant",
+        "btn": {
+          "import": "Importer",
+          "importing": "Importation…",
+          "cancel": "Annuler"
+        },
+        "selected": "sélectionné(s)",
+        "empty": "Aucun historique C2 disponible.",
+        "col": {
+          "timestamp": "Horodatage",
+          "completed": "Terminé"
+        },
+        "toast": {
+          "imported": "{{count}} tâche(s) importée(s)",
+          "partial": "{{imported}} importée(s), {{skipped}} déjà attachée(s)"
+        },
+        "error": {
+          "import": "Impossible d'importer l'historique C2"
+        }
+      },
+      "picker": {
+        "title": "Sélectionner un agent",
+        "empty": "Aucun agent disponible.",
+        "hostnameColon": "Hôte :",
+        "lastCheckinColon": "Dernière connexion :",
+        "col": {
+          "displayId": "ID",
+          "active": "Actif",
+          "host": "Hôte",
+          "user": "Utilisateur",
+          "domain": "Domaine",
+          "lastCheckin": "Dernière connexion"
+        },
+        "status": {
+          "active": "Actif",
+          "inactive": "Inactif"
+        }
+      }
+    }
+  },
+  "mitre": {
+    "matrix": {
+      "title": "Matrice MITRE ATT&CK",
+      "filter": "Filtrer…",
+      "loading": "Chargement de la matrice…",
+      "error": "Impossible de charger la matrice MITRE",
+      "applyItem_one": "Appliquer ({{count}} élément)",
+      "applyItem_other": "Appliquer ({{count}} éléments)",
+      "clearAll": "Tout effacer",
+      "close": "Fermer",
+      "retry": "Réessayer",
+      "noMatch": "Aucun résultat"
+    },
+    "field": {
+      "empty": "Aucune technique associée.",
+      "search": "Rechercher une technique…",
+      "openMatrix": "Ouvrir la matrice",
+      "savedToast": "Technique ajoutée",
+      "errorToast": "Impossible d'ajouter la technique"
+    },
+    "tag": {
+      "remove": "Retirer"
+    }
+  },
+  "state": {
+    "loading": "Chargement…",
+    "error": {
+      "title": "Erreur",
+      "desc": "Une erreur est survenue."
+    },
+    "empty": {
+      "default": "Aucun résultat."
+    },
+    "retry": "Réessayer"
+  },
+  "toast": {
+    "dismiss": "Fermer"
+  },
+  "status": {
+    "engagement": {
+      "planned": "Planifié",
+      "active": "Actif",
+      "closed": "Clôturé"
+    },
+    "simulation": {
+      "pending": "En attente",
+      "in_progress": "En cours",
+      "review_required": "Révision requise",
+      "done": "Terminé"
+    }
+  }
+}
diff --git a/frontend/src/i18n/index.ts b/frontend/src/i18n/index.ts
new file mode 100644
index 0000000..7913b54
--- /dev/null
+++ b/frontend/src/i18n/index.ts
@@ -0,0 +1,13 @@
+import i18n from 'i18next';
+import { initReactI18next } from 'react-i18next';
+import fr from './fr.json';
+
+i18n.use(initReactI18next).init({
+  resources: { fr: { translation: fr } },
+  lng: 'fr',
+  fallbackLng: 'fr',
+  interpolation: { escapeValue: false },
+  returnEmptyString: false,
+});
+
+export default i18n;
diff --git a/frontend/src/i18n/status.ts b/frontend/src/i18n/status.ts
new file mode 100644
index 0000000..840a345
--- /dev/null
+++ b/frontend/src/i18n/status.ts
@@ -0,0 +1,8 @@
+import i18n from './index';
+import type { EngagementStatus, SimulationStatus } from '@/api/types';
+
+export const engagementStatusLabel = (s: EngagementStatus): string =>
+  i18n.t(`status.engagement.${s}`);
+
+export const simulationStatusLabel = (s: SimulationStatus): string =>
+  i18n.t(`status.simulation.${s}`);
diff --git a/frontend/src/lib/format.ts b/frontend/src/lib/format.ts
new file mode 100644
index 0000000..e3a9df2
--- /dev/null
+++ b/frontend/src/lib/format.ts
@@ -0,0 +1,7 @@
+export const formatDate = (iso: string | null | undefined): string => {
+  if (!iso) return '—';
+  return new Date(iso).toLocaleDateString('fr-FR');
+};
+
+export const formatDateTime = (iso: string): string =>
+  new Date(iso).toLocaleString('fr-FR');
diff --git a/frontend/src/main.tsx b/frontend/src/main.tsx
index 838fc15..a2ec449 100644
--- a/frontend/src/main.tsx
+++ b/frontend/src/main.tsx
@@ -5,6 +5,7 @@ import { BrowserRouter } from 'react-router-dom';
 import { App } from './App';
 import { AuthProvider } from './hooks/useAuth';
 import { ToastProvider } from './hooks/useToast';
+import './i18n';
 import './styles/index.css';
 
 const queryClient = new QueryClient({
diff --git a/frontend/src/pages/EngagementDetailPage.tsx b/frontend/src/pages/EngagementDetailPage.tsx
index 47ca46c..5a134a2 100644
--- a/frontend/src/pages/EngagementDetailPage.tsx
+++ b/frontend/src/pages/EngagementDetailPage.tsx
@@ -1,4 +1,5 @@
-import { useParams } from 'react-router-dom';
+import { useParams, Link } from 'react-router-dom';
+import { useTranslation } from 'react-i18next';
 import { extractApiError } from '@/api/client';
 import { useAuth } from '@/hooks/useAuth';
 import { useEngagement } from '@/hooks/useEngagements';
@@ -11,11 +12,12 @@ import { SimulationList } from '@/components/SimulationList';
 import { ExportEngagementButton } from '@/components/ExportEngagementButton';
 import { BackLink } from '@/components/BackLink';
 import { Tabs } from '@/components/Tabs';
-import { Link } from 'react-router-dom';
+import { formatDate } from '@/lib/format';
 
-type TabId = 'schedule' | 'description' | 'simulations';
+type TabId = 'description' | 'simulations';
 
 export function EngagementDetailPage(): JSX.Element {
+  const { t } = useTranslation();
   const { id } = useParams<{ id: string }>();
   const numericId = id ? Number(id) : undefined;
   const { canEditEngagements } = useAuth();
@@ -23,49 +25,44 @@ export function EngagementDetailPage(): JSX.Element {
   const detail = useEngagement(numericId);
   const simsQuery = useEngagementSimulations(numericId);
 
-  const [activeTabRaw, setActiveTab] = useHashTab('schedule');
+  const [activeTabRaw, setActiveTab] = useHashTab('description');
   const activeTab = activeTabRaw as TabId;
 
-  if (detail.isLoading) return <LoadingState label="Loading engagement…" />;
+  if (detail.isLoading) return <LoadingState label={t('engagement.detail.loading')} />;
   if (detail.isError) {
     return (
       <ErrorState
-        message={extractApiError(detail.error, 'Could not load engagement')}
+        message={extractApiError(detail.error, t('engagement.detail.errorLoad'))}
         onRetry={() => detail.refetch()}
       />
     );
   }
-  if (!detail.data) return <ErrorState message="Engagement not found" />;
+  if (!detail.data) return <ErrorState message={t('engagement.detail.notFound')} />;
 
   const eng = detail.data;
   const simCount = simsQuery.data?.length;
 
   const tabs = [
-    { id: 'schedule', label: 'Schedule' },
-    { id: 'description', label: 'Description' },
-    { id: 'simulations', label: 'Simulations', count: simCount },
+    { id: 'description', label: t('engagement.detail.tabs.description') },
+    { id: 'simulations', label: t('engagement.detail.tabs.simulations'), count: simCount },
   ];
 
   return (
     <div className="flex flex-col gap-xl">
       <header className="flex items-start justify-between gap-md">
         <div className="flex flex-col gap-sm">
-          <BackLink to="/engagements">Back to engagements</BackLink>
+          <BackLink to="/engagements">{t('engagement.detail.backTo')}</BackLink>
           <h1 className="text-[32px] font-medium leading-none">{eng.name}</h1>
           <div className="flex items-center gap-md">
             <StatusBadge status={eng.status} />
             <span className="text-[14px] text-graphite">
-              Created by <span className="text-ink">{eng.created_by.username}</span>
+              {t('engagement.detail.createdBy')}{' '}
+              <span className="text-ink">{eng.created_by.username}</span>
             </span>
           </div>
         </div>
         {canEditEngagements ? (
-          <div className="flex items-center gap-sm">
-            <ExportEngagementButton engagementId={eng.id} />
-            <Link to={`/engagements/${eng.id}/edit`} className="btn-outline">
-              Edit
-            </Link>
-          </div>
+          <ExportEngagementButton engagementId={eng.id} />
         ) : null}
       </header>
 
@@ -76,27 +73,29 @@ export function EngagementDetailPage(): JSX.Element {
         id={`tabpanel-${activeTab}`}
         aria-labelledby={`tab-${activeTab}`}
       >
-        {activeTab === 'schedule' && (
-          <div className="card-product">
-            <h2 className="text-[20px] font-medium mb-md">Schedule</h2>
-            <dl className="grid grid-cols-2 gap-md text-[14px]">
-              <dt className="text-graphite">Start date</dt>
-              <dd className="text-ink font-mono">{eng.start_date}</dd>
-              <dt className="text-graphite">End date</dt>
-              <dd className="text-ink font-mono">{eng.end_date ?? '—'}</dd>
-              <dt className="text-graphite">Status</dt>
-              <dd className="text-ink capitalize">{eng.status}</dd>
-              <dt className="text-graphite">Created at</dt>
-              <dd className="text-ink font-mono">{eng.created_at}</dd>
-            </dl>
-          </div>
-        )}
-
         {activeTab === 'description' && (
-          <div className="card-product">
-            <h2 className="text-[20px] font-medium mb-md">Description</h2>
+          <div className="card-product flex flex-col gap-md">
+            <header className="flex items-start justify-between gap-md">
+              <dl className="grid grid-cols-2 gap-x-lg gap-y-xxs text-caption-md">
+                <dt className="text-graphite">{t('engagement.detail.schedule.startDate')}</dt>
+                <dd className="font-mono">{formatDate(eng.start_date)}</dd>
+                <dt className="text-graphite">{t('engagement.detail.schedule.endDate')}</dt>
+                <dd className="font-mono">{eng.end_date ? formatDate(eng.end_date) : '—'}</dd>
+                <dt className="text-graphite">{t('engagement.detail.schedule.status')}</dt>
+                <dd><StatusBadge status={eng.status} /></dd>
+                <dt className="text-graphite">{t('engagement.detail.schedule.createdAt')}</dt>
+                <dd className="font-mono">{formatDate(eng.created_at)}</dd>
+              </dl>
+              {canEditEngagements ? (
+                <Link to={`/engagements/${eng.id}/edit`} className="btn-outline shrink-0">
+                  {t('engagement.detail.edit')}
+                </Link>
+              ) : null}
+            </header>
+            <hr className="border-hairline" />
+            <h2 className="text-display-sm">{t('engagement.detail.tabs.description')}</h2>
             <p className="text-[16px] text-charcoal whitespace-pre-line">
-              {eng.description?.trim() ? eng.description : 'No description provided.'}
+              {eng.description?.trim() ? eng.description : t('engagement.detail.noDescription')}
             </p>
           </div>
         )}
diff --git a/frontend/src/pages/EngagementFormPage.tsx b/frontend/src/pages/EngagementFormPage.tsx
index 3047437..b99c340 100644
--- a/frontend/src/pages/EngagementFormPage.tsx
+++ b/frontend/src/pages/EngagementFormPage.tsx
@@ -1,5 +1,6 @@
 import { useEffect, useState, type FormEvent } from 'react';
 import { Link, useNavigate, useParams } from 'react-router-dom';
+import { useTranslation } from 'react-i18next';
 import { extractApiError } from '@/api/client';
 import type { EngagementInput, EngagementStatus } from '@/api/types';
 import {
@@ -13,12 +14,7 @@ import { FormField, Select, TextArea, TextInput } from '@/components/FormField';
 import { LoadingState } from '@/components/LoadingState';
 import { ErrorState } from '@/components/ErrorState';
 import { C2ConfigCard } from '@/components/C2ConfigCard';
-
-const STATUS_OPTIONS: { value: EngagementStatus; label: string }[] = [
-  { value: 'planned', label: 'Planned' },
-  { value: 'active', label: 'Active' },
-  { value: 'closed', label: 'Closed' },
-];
+import { engagementStatusLabel } from '@/i18n/status';
 
 interface FormState {
   name: string;
@@ -36,17 +32,8 @@ const EMPTY: FormState = {
   status: 'planned',
 };
 
-function validate(state: FormState): Partial<Record<keyof FormState, string>> {
-  const errors: Partial<Record<keyof FormState, string>> = {};
-  if (!state.name.trim()) errors.name = 'Name is required';
-  if (!state.start_date) errors.start_date = 'Start date is required';
-  if (state.end_date && state.start_date && state.end_date < state.start_date) {
-    errors.end_date = 'End date must be on or after start date';
-  }
-  return errors;
-}
-
 export function EngagementFormPage(): JSX.Element {
+  const { t } = useTranslation();
   const { id } = useParams<{ id: string }>();
   const editing = Boolean(id);
   const numericId = id ? Number(id) : undefined;
@@ -62,6 +49,22 @@ export function EngagementFormPage(): JSX.Element {
   const [errors, setErrors] = useState<Partial<Record<keyof FormState, string>>>({});
   const [submitError, setSubmitError] = useState<string | null>(null);
 
+  const STATUS_OPTIONS: { value: EngagementStatus; label: string }[] = [
+    { value: 'planned', label: engagementStatusLabel('planned') },
+    { value: 'active', label: engagementStatusLabel('active') },
+    { value: 'closed', label: engagementStatusLabel('closed') },
+  ];
+
+  function validate(state: FormState): Partial<Record<keyof FormState, string>> {
+    const errs: Partial<Record<keyof FormState, string>> = {};
+    if (!state.name.trim()) errs.name = t('engagement.form.validation.nameRequired');
+    if (!state.start_date) errs.start_date = t('engagement.form.validation.startDateRequired');
+    if (state.end_date && state.start_date && state.end_date < state.start_date) {
+      errs.end_date = t('engagement.form.validation.endDateAfterStart');
+    }
+    return errs;
+  }
+
   // Hydrate edit form when data arrives.
   useEffect(() => {
     if (editing && detail.data) {
@@ -75,11 +78,11 @@ export function EngagementFormPage(): JSX.Element {
     }
   }, [editing, detail.data]);
 
-  if (editing && detail.isLoading) return <LoadingState label="Loading engagement…" />;
+  if (editing && detail.isLoading) return <LoadingState label={t('engagement.form.loading')} />;
   if (editing && detail.isError) {
     return (
       <ErrorState
-        message={extractApiError(detail.error, 'Could not load engagement')}
+        message={extractApiError(detail.error, t('engagement.form.error.load'))}
         onRetry={() => detail.refetch()}
       />
     );
@@ -109,15 +112,15 @@ export function EngagementFormPage(): JSX.Element {
     try {
       if (editing && numericId) {
         await patchMutation.mutateAsync(payload);
-        push('Engagement updated', 'success');
+        push(t('engagement.form.toast.updated'), 'success');
         navigate(`/engagements/${numericId}`);
       } else {
         const created = await createMutation.mutateAsync(payload);
-        push('Engagement created', 'success');
+        push(t('engagement.form.toast.created'), 'success');
         navigate(`/engagements/${created.id}`);
       }
     } catch (err) {
-      setSubmitError(extractApiError(err, 'Could not save engagement'));
+      setSubmitError(extractApiError(err, t('engagement.form.error.save')));
     }
   };
 
@@ -127,12 +130,10 @@ export function EngagementFormPage(): JSX.Element {
     <div className="flex flex-col gap-xl">
       <header>
         <h1 className="text-[32px] font-medium leading-none">
-          {editing ? 'Edit engagement' : 'New engagement'}
+          {editing ? t('engagement.form.title.edit') : t('engagement.form.title.new')}
         </h1>
         <p className="text-charcoal text-[16px] mt-sm">
-          {editing
-            ? 'Update the engagement metadata.'
-            : 'Create a new red team mission to host simulations.'}
+          {editing ? t('engagement.form.subtitle.edit') : t('engagement.form.subtitle.new')}
         </p>
       </header>
 
@@ -144,7 +145,7 @@ export function EngagementFormPage(): JSX.Element {
         }
       >
         <form onSubmit={onSubmit} noValidate className="card-product flex flex-col gap-md">
-          <FormField label="Name" htmlFor="eng-name" required error={errors.name}>
+          <FormField label={t('engagement.form.field.name')} htmlFor="eng-name" required error={errors.name}>
             <TextInput
               id="eng-name"
               name="name"
@@ -154,7 +155,7 @@ export function EngagementFormPage(): JSX.Element {
             />
           </FormField>
 
-          <FormField label="Description" htmlFor="eng-description">
+          <FormField label={t('engagement.form.field.description')} htmlFor="eng-description">
             <TextArea
               id="eng-description"
               name="description"
@@ -165,7 +166,7 @@ export function EngagementFormPage(): JSX.Element {
 
           <div className="grid grid-cols-1 md:grid-cols-2 gap-md">
             <FormField
-              label="Start date"
+              label={t('engagement.form.field.startDate')}
               htmlFor="eng-start"
               required
               error={errors.start_date}
@@ -181,9 +182,9 @@ export function EngagementFormPage(): JSX.Element {
             </FormField>
 
             <FormField
-              label="End date"
+              label={t('engagement.form.field.endDate')}
               htmlFor="eng-end"
-              hint="Leave empty to clear / leave open-ended"
+              hint={t('engagement.form.field.endDateHint')}
               error={errors.end_date}
             >
               <TextInput
@@ -196,7 +197,7 @@ export function EngagementFormPage(): JSX.Element {
             </FormField>
           </div>
 
-          <FormField label="Status" htmlFor="eng-status" required>
+          <FormField label={t('engagement.form.field.status')} htmlFor="eng-status" required>
             <Select
               id="eng-status"
               name="status"
@@ -213,14 +214,18 @@ export function EngagementFormPage(): JSX.Element {
           ) : null}
 
           <div className="flex items-center gap-md pt-sm">
-            <button type="submit" className="btn-primary" disabled={submitting}>
-              {submitting ? 'Saving…' : editing ? 'Save changes' : 'Create engagement'}
+            <button type="submit" className="btn-primary" disabled={submitting} data-testid="btn-submit">
+              {submitting
+                ? t('engagement.form.btn.saving')
+                : editing
+                  ? t('engagement.form.btn.save')
+                  : t('engagement.form.btn.create')}
             </button>
             <Link
               to={editing && numericId ? `/engagements/${numericId}` : '/engagements'}
               className="btn-outline-ink"
             >
-              Cancel
+              {t('engagement.form.btn.cancel')}
             </Link>
           </div>
         </form>
diff --git a/frontend/src/pages/EngagementsListPage.tsx b/frontend/src/pages/EngagementsListPage.tsx
index 93d83b1..631ee35 100644
--- a/frontend/src/pages/EngagementsListPage.tsx
+++ b/frontend/src/pages/EngagementsListPage.tsx
@@ -1,5 +1,6 @@
 import { Link } from 'react-router-dom';
 import { Plus } from 'lucide-react';
+import { useTranslation } from 'react-i18next';
 import { extractApiError } from '@/api/client';
 import type { Engagement } from '@/api/types';
 import { useDeleteEngagement, useEngagementsList } from '@/hooks/useEngagements';
@@ -9,25 +10,22 @@ import { LoadingState } from '@/components/LoadingState';
 import { ErrorState } from '@/components/ErrorState';
 import { EmptyState } from '@/components/EmptyState';
 import { StatusBadge } from '@/components/StatusBadge';
-
-function formatDate(value: string | null): string {
-  if (!value) return '—';
-  return value;
-}
+import { formatDate } from '@/lib/format';
 
 export function EngagementsListPage(): JSX.Element {
+  const { t } = useTranslation();
   const { data, isLoading, isError, error, refetch } = useEngagementsList();
   const { canEditEngagements } = useAuth();
   const { push } = useToast();
   const deleteMutation = useDeleteEngagement();
 
   const onDelete = async (eng: Engagement) => {
-    if (!window.confirm(`Delete engagement "${eng.name}"? This cannot be undone.`)) return;
+    if (!window.confirm(t('engagement.list.deleteConfirm', { name: eng.name }))) return;
     try {
       await deleteMutation.mutateAsync(eng.id);
-      push('Engagement deleted', 'success');
+      push(t('engagement.list.toast.deleted'), 'success');
     } catch (err) {
-      push(extractApiError(err, 'Could not delete engagement'), 'error');
+      push(extractApiError(err, t('engagement.list.error.delete')), 'error');
     }
   };
 
@@ -35,32 +33,32 @@ export function EngagementsListPage(): JSX.Element {
     <div className="flex flex-col gap-xl">
       <header className="flex items-end justify-between gap-md">
         <div>
-          <h1 className="text-[32px] font-medium leading-none">Engagements</h1>
+          <h1 className="text-[32px] font-medium leading-none">{t('engagement.list.title')}</h1>
           <p className="text-charcoal text-[16px] mt-sm">
-            Red team missions and their lifecycle status.
+            {t('engagement.list.subtitle')}
           </p>
         </div>
         {canEditEngagements ? (
           <Link to="/engagements/new" className="btn-primary">
-            <Plus size={14} aria-hidden /> New
+            <Plus size={14} aria-hidden /> {t('engagement.list.new')}
           </Link>
         ) : null}
       </header>
 
-      {isLoading ? <LoadingState label="Loading engagements…" /> : null}
+      {isLoading ? <LoadingState label={t('common.loading')} /> : null}
 
       {isError ? (
-        <ErrorState message={extractApiError(error, 'Could not load engagements')} onRetry={() => refetch()} />
+        <ErrorState message={extractApiError(error, t('engagement.list.error.load'))} onRetry={() => refetch()} />
       ) : null}
 
       {!isLoading && !isError && data && data.length === 0 ? (
         <EmptyState
-          title="No engagements yet"
-          description="Create your first engagement to start tracking red team missions."
+          title={t('engagement.list.empty.title')}
+          description={t('engagement.list.empty.desc')}
           action={
             canEditEngagements ? (
               <Link to="/engagements/new" className="btn-primary">
-                <Plus size={14} aria-hidden /> New
+                <Plus size={14} aria-hidden /> {t('engagement.list.new')}
               </Link>
             ) : undefined
           }
@@ -72,12 +70,12 @@ export function EngagementsListPage(): JSX.Element {
           <table className="table-compact w-full text-left">
             <thead className="bg-cloud border-b border-hairline">
               <tr>
-                <th>Name</th>
-                <th>Status</th>
-                <th>Start</th>
-                <th>End</th>
-                <th>Created by</th>
-                <th className="text-right">Actions</th>
+                <th>{t('engagement.list.col.name')}</th>
+                <th>{t('engagement.list.col.status')}</th>
+                <th>{t('engagement.list.col.start')}</th>
+                <th>{t('engagement.list.col.end')}</th>
+                <th>{t('engagement.list.col.createdBy')}</th>
+                <th className="text-right">{t('engagement.list.col.actions')}</th>
               </tr>
             </thead>
             <tbody>
@@ -97,12 +95,12 @@ export function EngagementsListPage(): JSX.Element {
                   <td className="text-right">
                     <div className="inline-flex gap-sm">
                       <Link to={`/engagements/${eng.id}`} className="btn-text-link">
-                        View
+                        {t('engagement.list.view')}
                       </Link>
                       {canEditEngagements ? (
                         <>
                           <Link to={`/engagements/${eng.id}/edit`} className="btn-text-link">
-                            Edit
+                            {t('engagement.list.edit')}
                           </Link>
                           <button
                             type="button"
@@ -110,7 +108,7 @@ export function EngagementsListPage(): JSX.Element {
                             onClick={() => onDelete(eng)}
                             disabled={deleteMutation.isPending}
                           >
-                            Delete
+                            {t('engagement.list.delete')}
                           </button>
                         </>
                       ) : null}
diff --git a/frontend/src/pages/LoginPage.tsx b/frontend/src/pages/LoginPage.tsx
index 49daf16..93fcd71 100644
--- a/frontend/src/pages/LoginPage.tsx
+++ b/frontend/src/pages/LoginPage.tsx
@@ -1,5 +1,6 @@
 import { useState, type FormEvent } from 'react';
 import { Navigate, useLocation, useNavigate } from 'react-router-dom';
+import { useTranslation } from 'react-i18next';
 import { extractApiError } from '@/api/client';
 import { useAuth } from '@/hooks/useAuth';
 import { FormField, TextInput } from '@/components/FormField';
@@ -14,6 +15,7 @@ export function LoginPage(): JSX.Element {
   const location = useLocation();
   const fromPath = (location.state as LocationState | null)?.from;
 
+  const { t } = useTranslation();
   const [username, setUsername] = useState('');
   const [password, setPassword] = useState('');
   const [submitting, setSubmitting] = useState(false);
@@ -34,7 +36,7 @@ export function LoginPage(): JSX.Element {
       await login(username, password);
       navigate(fromPath ?? '/engagements', { replace: true });
     } catch (err) {
-      setError(extractApiError(err, 'Invalid credentials'));
+      setError(extractApiError(err, t('auth.login.invalid')));
     } finally {
       setSubmitting(false);
     }
@@ -48,10 +50,10 @@ export function LoginPage(): JSX.Element {
           <span className="inline-block h-8 w-8 rotate-12 bg-primary" aria-hidden />
           <h1 className="text-[28px] font-medium leading-none">Mimic</h1>
         </div>
-        <p className="text-[16px] text-charcoal">Sign in to access your engagements.</p>
+        <p className="text-[16px] text-charcoal">{t('auth.login.subtitle')}</p>
 
         <form onSubmit={onSubmit} noValidate className="flex flex-col gap-md">
-          <FormField label="Username" htmlFor="login-username" required>
+          <FormField label={t('auth.login.username')} htmlFor="login-username" required>
             <TextInput
               id="login-username"
               name="username"
@@ -62,7 +64,7 @@ export function LoginPage(): JSX.Element {
             />
           </FormField>
 
-          <FormField label="Password" htmlFor="login-password" required>
+          <FormField label={t('auth.login.password')} htmlFor="login-password" required>
             <TextInput
               id="login-password"
               type="password"
@@ -81,7 +83,7 @@ export function LoginPage(): JSX.Element {
           ) : null}
 
           <button type="submit" className="btn-primary" disabled={submitting}>
-            {submitting ? 'Signing in…' : 'Sign in'}
+            {submitting ? t('auth.login.signingIn') : t('auth.login.signIn')}
           </button>
         </form>
       </div>
diff --git a/frontend/src/pages/SimulationFormPage.tsx b/frontend/src/pages/SimulationFormPage.tsx
index 663234b..8657ece 100644
--- a/frontend/src/pages/SimulationFormPage.tsx
+++ b/frontend/src/pages/SimulationFormPage.tsx
@@ -1,6 +1,7 @@
 import { useEffect, useState, type FormEvent } from 'react';
 import { Link, useNavigate, useParams } from 'react-router-dom';
 import { Save, RotateCcw } from 'lucide-react';
+import { useTranslation } from 'react-i18next';
 import { extractApiError } from '@/api/client';
 import type { SimulationPatchInput } from '@/api/types';
 import { useAuth } from '@/hooks/useAuth';
@@ -58,6 +59,7 @@ const EMPTY_SOC: SocFormState = {
 };
 
 export function SimulationFormPage(): JSX.Element {
+  const { t } = useTranslation();
   const { eid, sid } = useParams<{ eid: string; sid: string }>();
   const engagementId = eid ? Number(eid) : undefined;
   const simulationId = sid ? Number(sid) : undefined;
@@ -115,11 +117,11 @@ export function SimulationFormPage(): JSX.Element {
     }
   }, [isNew, detail.data]);
 
-  if (!isNew && detail.isLoading) return <LoadingState label="Loading simulation…" />;
+  if (!isNew && detail.isLoading) return <LoadingState label={t('simulation.form.loading')} />;
   if (!isNew && detail.isError) {
     return (
       <ErrorState
-        message={extractApiError(detail.error, 'Could not load simulation')}
+        message={extractApiError(detail.error, t('simulation.form.error.load'))}
         onRetry={() => detail.refetch()}
       />
     );
@@ -148,13 +150,13 @@ export function SimulationFormPage(): JSX.Element {
     e.preventDefault();
     setNameError(null);
     setSubmitError(null);
-    if (!rt.name.trim()) { setNameError('Name is required'); return; }
+    if (!rt.name.trim()) { setNameError(t('simulation.form.validation.nameRequired')); return; }
     try {
       const created = await createMutation.mutateAsync({ name: rt.name.trim() });
-      push('Simulation created', 'success');
+      push(t('simulation.form.toast.created'), 'success');
       navigate(`/engagements/${engagementId}/simulations/${created.id}/edit`);
     } catch (err) {
-      setSubmitError(extractApiError(err, 'Could not create simulation'));
+      setSubmitError(extractApiError(err, t('simulation.form.error.create')));
     }
   };
 
@@ -162,7 +164,7 @@ export function SimulationFormPage(): JSX.Element {
     e.preventDefault();
     setNameError(null);
     setSubmitError(null);
-    if (!rt.name.trim()) { setNameError('Name is required'); return; }
+    if (!rt.name.trim()) { setNameError(t('simulation.form.validation.nameRequired')); return; }
     const patch: SimulationPatchInput = {
       name: rt.name.trim(),
       description: rt.description.trim() || null,
@@ -173,9 +175,9 @@ export function SimulationFormPage(): JSX.Element {
     };
     try {
       await updateMutation.mutateAsync(patch);
-      push('Simulation updated', 'success');
+      push(t('simulation.form.toast.updated'), 'success');
     } catch (err) {
-      setSubmitError(extractApiError(err, 'Could not update simulation'));
+      setSubmitError(extractApiError(err, t('simulation.form.error.update')));
     }
   };
 
@@ -190,36 +192,36 @@ export function SimulationFormPage(): JSX.Element {
     };
     try {
       await updateMutation.mutateAsync(patch);
-      push('SOC report updated', 'success');
+      push(t('simulation.form.toast.socUpdated'), 'success');
     } catch (err) {
-      setSubmitError(extractApiError(err, 'Could not update SOC fields'));
+      setSubmitError(extractApiError(err, t('simulation.form.error.soc')));
     }
   };
 
   const onMarkReview = async () => {
     try {
       await transitionMutation.mutateAsync('review_required');
-      push('Simulation marked for review', 'success');
+      push(t('simulation.form.toast.markedReview'), 'success');
     } catch (err) {
-      push(extractApiError(err, 'Transition failed'), 'error');
+      push(extractApiError(err, t('simulation.form.error.transition')), 'error');
     }
   };
 
   const onClose = async () => {
     try {
       await transitionMutation.mutateAsync('done');
-      push('Simulation closed', 'success');
+      push(t('simulation.form.toast.closed'), 'success');
     } catch (err) {
-      push(extractApiError(err, 'Transition failed'), 'error');
+      push(extractApiError(err, t('simulation.form.error.transition')), 'error');
     }
   };
 
   const onReopen = async () => {
     try {
       await transitionMutation.mutateAsync('review_required');
-      push('Simulation reopened', 'success');
+      push(t('simulation.form.toast.reopened'), 'success');
     } catch (err) {
-      push(extractApiError(err, 'Transition failed'), 'error');
+      push(extractApiError(err, t('simulation.form.error.transition')), 'error');
     }
   };
 
@@ -227,10 +229,10 @@ export function SimulationFormPage(): JSX.Element {
     setShowDeleteConfirm(false);
     try {
       await deleteMutation.mutateAsync(simulationId as number);
-      push('Simulation deleted', 'success');
+      push(t('simulation.form.toast.deleted'), 'success');
       navigate(`/engagements/${engagementId}`);
     } catch (err) {
-      push(extractApiError(err, 'Could not delete simulation'), 'error');
+      push(extractApiError(err, t('simulation.form.error.delete')), 'error');
     }
   };
 
@@ -240,12 +242,12 @@ export function SimulationFormPage(): JSX.Element {
     return (
       <div className="flex flex-col gap-xl max-w-2xl">
         <header>
-          <BackLink to={`/engagements/${engagementId}`}>Back to engagement</BackLink>
-          <h1 className="text-[32px] font-medium leading-none mt-sm">New simulation</h1>
+          <BackLink to={`/engagements/${engagementId}`}>{t('engagement.detail.backTo')}</BackLink>
+          <h1 className="text-[32px] font-medium leading-none mt-sm">{t('simulation.form.title.new')}</h1>
         </header>
 
         <form onSubmit={onSubmitNew} noValidate className="card-product flex flex-col gap-md">
-          <FormField label="Name" htmlFor="sim-name" required error={nameError}>
+          <FormField label={t('simulation.form.field.name')} htmlFor="sim-name" required error={nameError}>
             <TextInput
               id="sim-name"
               name="name"
@@ -260,11 +262,11 @@ export function SimulationFormPage(): JSX.Element {
           ) : null}
 
           <div className="flex items-center gap-md pt-sm">
-            <button type="submit" className="btn-primary" disabled={submitting}>
-              {submitting ? 'Creating…' : 'Create simulation'}
+            <button type="submit" className="btn-primary" disabled={submitting} data-testid="create-sim-btn">
+              {submitting ? t('simulation.form.btn.creating') : t('simulation.form.btn.create')}
             </button>
             <Link to={`/engagements/${engagementId}`} className="btn-outline-ink">
-              Cancel
+              {t('simulation.form.btn.cancel')}
             </Link>
           </div>
         </form>
@@ -279,14 +281,15 @@ export function SimulationFormPage(): JSX.Element {
     <div className="flex flex-col gap-xl">
       <header className="flex items-start justify-between gap-md">
         <div className="flex flex-col gap-sm">
-          <BackLink to={`/engagements/${engagementId}`}>Back to engagement</BackLink>
+          <BackLink to={`/engagements/${engagementId}`}>{t('engagement.detail.backTo')}</BackLink>
           <h1 className="text-[32px] font-medium leading-none">{rt.name || simulation?.name}</h1>
           {status ? (
             <div className="flex items-center gap-md">
               <SimulationStatusBadge status={status} />
               {simulation?.created_by && (
                 <span className="text-[14px] text-graphite">
-                  Created by <span className="text-ink">{simulation.created_by.username}</span>
+                  {t('engagement.detail.createdBy')}{' '}
+                  <span className="text-ink">{simulation.created_by.username}</span>
                 </span>
               )}
             </div>
@@ -297,7 +300,7 @@ export function SimulationFormPage(): JSX.Element {
       {/* Done banner */}
       {isDone && (
         <AlertBanner variant="success">
-          This simulation is <strong>done</strong> and read-only. Use Reopen to make changes.
+          {t('simulation.form.banner.done')}
         </AlertBanner>
       )}
 
@@ -305,7 +308,7 @@ export function SimulationFormPage(): JSX.Element {
       {socBlocked && (
         <div data-testid="soc-blocked-banner">
           <AlertBanner variant="warn">
-            Simulation not yet ready for review — the red team must mark it as &quot;Review required&quot; before you can fill in the SOC section.
+            {t('simulation.form.banner.socNotReady')}
           </AlertBanner>
         </div>
       )}
@@ -321,9 +324,9 @@ export function SimulationFormPage(): JSX.Element {
           noValidate
           className="card-product flex flex-col gap-md"
         >
-          <h2 className="text-[20px] font-medium text-ink">Red Team</h2>
+          <h2 className="text-[20px] font-medium text-ink">{t('simulation.form.header.redTeam')}</h2>
 
-          <FormField label="Name" htmlFor="sim-name" required error={nameError}>
+          <FormField label={t('simulation.form.field.name')} htmlFor="sim-name" required error={nameError}>
             <TextInput
               id="sim-name"
               name="name"
@@ -335,7 +338,7 @@ export function SimulationFormPage(): JSX.Element {
           </FormField>
 
           <div className="flex flex-col gap-xs">
-            <span className="text-[14px] font-medium text-ink">MITRE Techniques &amp; Tactics</span>
+            <span className="text-[14px] font-medium text-ink">{t('simulation.form.field.mitre')}</span>
             <MitreTechniquesField
               value={simulation?.techniques ?? []}
               tactics={simulation?.tactics ?? []}
@@ -345,7 +348,7 @@ export function SimulationFormPage(): JSX.Element {
             />
           </div>
 
-          <FormField label="Description" htmlFor="sim-description">
+          <FormField label={t('simulation.form.field.description')} htmlFor="sim-description">
             <TextArea
               id="sim-description"
               name="description"
@@ -355,7 +358,7 @@ export function SimulationFormPage(): JSX.Element {
             />
           </FormField>
 
-          <FormField label="Commands" htmlFor="sim-commands" hint="One command per line">
+          <FormField label={t('simulation.form.field.commands')} htmlFor="sim-commands" hint={t('simulation.form.field.commandsHint')}>
             <TextArea
               id="sim-commands"
               name="commands"
@@ -366,7 +369,7 @@ export function SimulationFormPage(): JSX.Element {
             />
           </FormField>
 
-          <FormField label="Prerequisites" htmlFor="sim-prerequisites">
+          <FormField label={t('simulation.form.field.prerequisites')} htmlFor="sim-prerequisites">
             <TextArea
               id="sim-prerequisites"
               name="prerequisites"
@@ -376,7 +379,7 @@ export function SimulationFormPage(): JSX.Element {
             />
           </FormField>
 
-          <FormField label="Executed at" htmlFor="sim-executed-at">
+          <FormField label={t('simulation.form.field.executedAt')} htmlFor="sim-executed-at">
             <TextInput
               id="sim-executed-at"
               type="datetime-local"
@@ -387,7 +390,7 @@ export function SimulationFormPage(): JSX.Element {
             />
           </FormField>
 
-          <FormField label="Execution result" htmlFor="sim-exec-result">
+          <FormField label={t('simulation.form.field.executionResult')} htmlFor="sim-exec-result">
             <TextArea
               id="sim-exec-result"
               name="execution_result"
@@ -406,7 +409,7 @@ export function SimulationFormPage(): JSX.Element {
                 className="btn-outline"
                 onClick={() => setShowC2Modal(true)}
               >
-                Execute via C2
+                {t('simulation.form.btn.executeC2')}
               </button>
               <button
                 type="button"
@@ -414,7 +417,7 @@ export function SimulationFormPage(): JSX.Element {
                 className="btn-outline"
                 onClick={() => setShowImportModal(true)}
               >
-                Import C2 history
+                {t('simulation.form.btn.importC2History')}
               </button>
             </div>
           )}
@@ -433,9 +436,9 @@ export function SimulationFormPage(): JSX.Element {
           noValidate
           className="card-product flex flex-col gap-md"
         >
-          <h2 className="text-[20px] font-medium text-ink">SOC</h2>
+          <h2 className="text-[20px] font-medium text-ink">{t('simulation.form.header.soc')}</h2>
 
-          <FormField label="Log source" htmlFor="sim-log-source">
+          <FormField label={t('simulation.form.field.logSource')} htmlFor="sim-log-source">
             <TextInput
               id="sim-log-source"
               name="log_source"
@@ -445,7 +448,7 @@ export function SimulationFormPage(): JSX.Element {
             />
           </FormField>
 
-          <FormField label="Logs" htmlFor="sim-logs">
+          <FormField label={t('simulation.form.field.logs')} htmlFor="sim-logs">
             <TextArea
               id="sim-logs"
               name="logs"
@@ -455,7 +458,7 @@ export function SimulationFormPage(): JSX.Element {
             />
           </FormField>
 
-          <FormField label="SOC comment" htmlFor="sim-soc-comment">
+          <FormField label={t('simulation.form.field.socComment')} htmlFor="sim-soc-comment">
             <TextArea
               id="sim-soc-comment"
               name="soc_comment"
@@ -465,7 +468,7 @@ export function SimulationFormPage(): JSX.Element {
             />
           </FormField>
 
-          <FormField label="Incident number" htmlFor="sim-incident">
+          <FormField label={t('simulation.form.field.incidentNumber')} htmlFor="sim-incident">
             <TextInput
               id="sim-incident"
               name="incident_number"
@@ -493,7 +496,7 @@ export function SimulationFormPage(): JSX.Element {
             data-testid="reopen-btn"
           >
             <RotateCcw size={14} aria-hidden />
-            Reopen
+            {t('simulation.form.btn.reopen')}
           </button>
         )}
 
@@ -501,13 +504,13 @@ export function SimulationFormPage(): JSX.Element {
         {!isDone && canEditRT && (
           <button type="submit" form="rt-form" className="btn-primary" disabled={submitting}>
             <Save size={14} aria-hidden />
-            {updateMutation.isPending ? 'Saving…' : 'Save'}
+            {updateMutation.isPending ? t('simulation.form.btn.saving') : t('simulation.form.btn.save')}
           </button>
         )}
         {!isDone && canSaveSoc && (
           <button type="submit" form="soc-form" className="btn-primary" disabled={submitting}>
             <Save size={14} aria-hidden />
-            {updateMutation.isPending ? 'Saving…' : 'Save SOC'}
+            {updateMutation.isPending ? t('simulation.form.btn.saving') : t('simulation.form.btn.saveSoc')}
           </button>
         )}
         {showMarkReview && (
@@ -516,8 +519,9 @@ export function SimulationFormPage(): JSX.Element {
             className="btn-outline"
             onClick={onMarkReview}
             disabled={transitionMutation.isPending}
+            data-testid="mark-review-btn"
           >
-            Mark for review
+            {t('simulation.form.btn.markReview')}
           </button>
         )}
         {showClose && (
@@ -526,8 +530,9 @@ export function SimulationFormPage(): JSX.Element {
             className="btn-outline"
             onClick={onClose}
             disabled={transitionMutation.isPending}
+            data-testid="close-btn"
           >
-            Close
+            {t('simulation.form.btn.close')}
           </button>
         )}
         {!isDone && canEditEngagements && simulationId && (
@@ -536,18 +541,19 @@ export function SimulationFormPage(): JSX.Element {
             className="btn-text-link text-bloom-deep ml-auto"
             onClick={() => setShowDeleteConfirm(true)}
             disabled={submitting}
+            data-testid="delete-btn"
           >
-            Delete
+            {t('simulation.form.btn.delete')}
           </button>
         )}
       </div>
 
       {showDeleteConfirm && (
         <ConfirmDialog
-          title="Delete simulation"
-          description="This action is permanent. The simulation will be deleted forever."
-          confirmLabel="Delete"
-          cancelLabel="Cancel"
+          title={t('simulation.form.deleteConfirm.title')}
+          description={t('simulation.form.deleteConfirm.desc')}
+          confirmLabel={t('simulation.form.deleteConfirm.confirm')}
+          cancelLabel={t('simulation.form.deleteConfirm.cancel')}
           destructive
           onConfirm={onDelete}
           onCancel={() => setShowDeleteConfirm(false)}
diff --git a/frontend/src/pages/TemplateFormPage.tsx b/frontend/src/pages/TemplateFormPage.tsx
index 566d7b6..02532f7 100644
--- a/frontend/src/pages/TemplateFormPage.tsx
+++ b/frontend/src/pages/TemplateFormPage.tsx
@@ -1,6 +1,7 @@
 import { useEffect, useState, type FormEvent } from 'react';
 import { Link, useNavigate, useParams } from 'react-router-dom';
 import { Save, Grid2x2 } from 'lucide-react';
+import { useTranslation } from 'react-i18next';
 import { extractApiError } from '@/api/client';
 import type { MitreTechnique, MitreTacticRef } from '@/api/types';
 import { useToast } from '@/hooks/useToast';
@@ -25,6 +26,7 @@ interface FormState {
 const EMPTY: FormState = { name: '', description: '', commands: '', prerequisites: '' };
 
 export function TemplateFormPage(): JSX.Element {
+  const { t } = useTranslation();
   const { id } = useParams<{ id: string }>();
   const templateId = id ? Number(id) : undefined;
   const isNew = !templateId;
@@ -47,15 +49,15 @@ export function TemplateFormPage(): JSX.Element {
 
   useEffect(() => {
     if (existing.data) {
-      const t = existing.data;
+      const tpl = existing.data;
       setForm({
-        name: t.name,
-        description: t.description ?? '',
-        commands: t.commands ?? '',
-        prerequisites: t.prerequisites ?? '',
+        name: tpl.name,
+        description: tpl.description ?? '',
+        commands: tpl.commands ?? '',
+        prerequisites: tpl.prerequisites ?? '',
       });
-      setTechniques(t.techniques);
-      setTactics(t.tactics);
+      setTechniques(tpl.techniques);
+      setTactics(tpl.tactics);
     }
   }, [existing.data]);
 
@@ -65,7 +67,7 @@ export function TemplateFormPage(): JSX.Element {
     e.preventDefault();
     setFormError(null);
     if (!form.name.trim()) {
-      setFormError('Name is required');
+      setFormError(t('template.form.validation.nameRequired'));
       return;
     }
     const payload = {
@@ -73,20 +75,20 @@ export function TemplateFormPage(): JSX.Element {
       description: form.description.trim() || null,
       commands: form.commands.trim() || null,
       prerequisites: form.prerequisites.trim() || null,
-      technique_ids: techniques.map((t) => t.id),
-      tactic_ids: tactics.map((t) => t.id),
+      technique_ids: techniques.map((tech) => tech.id),
+      tactic_ids: tactics.map((tac) => tac.id),
     };
     try {
       if (isNew) {
         const created = await createMutation.mutateAsync(payload);
-        push('Template created', 'success');
+        push(t('template.form.toast.created'), 'success');
         navigate(`/admin/templates/${created.id}/edit`, { replace: true });
       } else {
         await updateMutation.mutateAsync(payload);
-        push('Template saved', 'success');
+        push(t('template.form.toast.saved'), 'success');
       }
     } catch (err) {
-      setFormError(extractApiError(err, 'Could not save template'));
+      setFormError(extractApiError(err, t('template.form.errorSave')));
     }
   };
 
@@ -94,10 +96,10 @@ export function TemplateFormPage(): JSX.Element {
     if (!templateId) return;
     try {
       await deleteMutation.mutateAsync(templateId);
-      push('Template deleted', 'success');
+      push(t('template.form.toast.deleted'), 'success');
       navigate('/admin/templates', { replace: true });
     } catch (err) {
-      push(extractApiError(err, 'Could not delete template'), 'error');
+      push(extractApiError(err, t('template.form.errorDelete')), 'error');
     }
     setShowDeleteConfirm(false);
   };
@@ -109,16 +111,16 @@ export function TemplateFormPage(): JSX.Element {
   };
 
   const handlePickerSelect = (technique: MitreTechnique) => {
-    if (techniques.some((t) => t.id === technique.id)) return;
+    if (techniques.some((tech) => tech.id === technique.id)) return;
     setTechniques((prev) => [...prev, technique]);
     setShowPicker(false);
   };
 
-  if (!isNew && existing.isLoading) return <LoadingState label="Loading template…" />;
+  if (!isNew && existing.isLoading) return <LoadingState label={t('template.form.loading')} />;
   if (!isNew && existing.isError) {
     return (
       <ErrorState
-        message={extractApiError(existing.error, 'Could not load template')}
+        message={extractApiError(existing.error, t('template.form.errorLoad'))}
         onRetry={() => existing.refetch()}
       />
     );
@@ -128,9 +130,9 @@ export function TemplateFormPage(): JSX.Element {
     <div className="flex flex-col gap-xl">
       <header className="flex items-start justify-between gap-md">
         <div className="flex flex-col gap-sm">
-          <BackLink to="/admin/templates">Back to templates</BackLink>
+          <BackLink to="/admin/templates">{t('engagement.detail.backTo')}</BackLink>
           <h1 className="text-[32px] font-medium leading-none">
-            {isNew ? 'New template' : (existing.data?.name ?? 'Edit template')}
+            {isNew ? t('template.form.title.new') : (existing.data?.name ?? t('template.form.title.edit'))}
           </h1>
         </div>
         {!isNew ? (
@@ -140,13 +142,13 @@ export function TemplateFormPage(): JSX.Element {
             onClick={() => setShowDeleteConfirm(true)}
             disabled={deleteMutation.isPending}
           >
-            Delete
+            {t('template.form.btn.delete')}
           </button>
         ) : null}
       </header>
 
       <form onSubmit={onSubmit} className="card-product flex flex-col gap-lg max-w-2xl">
-        <FormField label="Name" htmlFor="tpl-name" required error={formError}>
+        <FormField label={t('template.form.field.name')} htmlFor="tpl-name" required error={formError}>
           <TextInput
             id="tpl-name"
             value={form.name}
@@ -155,56 +157,56 @@ export function TemplateFormPage(): JSX.Element {
           />
         </FormField>
 
-        <FormField label="Description" htmlFor="tpl-desc">
+        <FormField label={t('template.form.field.description')} htmlFor="tpl-desc">
           <TextArea
             id="tpl-desc"
             value={form.description}
             onChange={(e) => setForm({ ...form, description: e.target.value })}
             disabled={isPending}
-            placeholder="What does this simulation cover?"
+            placeholder={t('template.form.field.descriptionPlaceholder')}
           />
         </FormField>
 
-        <FormField label="Commands" htmlFor="tpl-commands" hint="One command per line">
+        <FormField label={t('template.form.field.commands')} htmlFor="tpl-commands" hint={t('template.form.field.commandsHint')}>
           <TextArea
             id="tpl-commands"
             value={form.commands}
             onChange={(e) => setForm({ ...form, commands: e.target.value })}
             disabled={isPending}
-            placeholder="e.g. mimikatz.exe&#10;sekurlsa::logonpasswords"
+            placeholder={t('template.form.field.commandsPlaceholder')}
             className="font-mono text-[14px]"
           />
         </FormField>
 
-        <FormField label="Prerequisites" htmlFor="tpl-prereqs">
+        <FormField label={t('template.form.field.prerequisites')} htmlFor="tpl-prereqs">
           <TextArea
             id="tpl-prereqs"
             value={form.prerequisites}
             onChange={(e) => setForm({ ...form, prerequisites: e.target.value })}
             disabled={isPending}
-            placeholder="e.g. Local admin access required"
+            placeholder={t('template.form.field.prerequisitesPlaceholder')}
           />
         </FormField>
 
         <div className="flex flex-col gap-sm">
-          <span className="text-[14px] font-medium text-ink">MITRE Techniques &amp; Tactics</span>
+          <span className="text-[14px] font-medium text-ink">{t('template.form.field.mitre')}</span>
 
           {techniques.length === 0 && tactics.length === 0 ? (
-            <p className="text-[13px] text-graphite">No techniques selected</p>
+            <p className="text-[13px] text-graphite">{t('template.form.field.mitreEmpty')}</p>
           ) : (
             <div className="flex flex-wrap gap-xs" data-testid="techniques-tag-list">
-              {tactics.map((t) => (
+              {tactics.map((tac) => (
                 <MitreTacticTag
-                  key={t.id}
-                  tactic={t}
-                  onRemove={() => setTactics((prev) => prev.filter((x) => x.id !== t.id))}
+                  key={tac.id}
+                  tactic={tac}
+                  onRemove={() => setTactics((prev) => prev.filter((x) => x.id !== tac.id))}
                 />
               ))}
-              {techniques.map((t) => (
+              {techniques.map((tech) => (
                 <MitreTechniqueTag
-                  key={t.id}
-                  technique={t}
-                  onRemove={() => setTechniques((prev) => prev.filter((x) => x.id !== t.id))}
+                  key={tech.id}
+                  technique={tech}
+                  onRemove={() => setTechniques((prev) => prev.filter((x) => x.id !== tech.id))}
                 />
               ))}
             </div>
@@ -220,13 +222,13 @@ export function TemplateFormPage(): JSX.Element {
                   className="text-input h-9 text-[13px] text-graphite text-left cursor-text w-full"
                   onClick={() => setShowPicker(true)}
                 >
-                  Search technique (e.g. T1059)…
+                  {t('template.form.field.mitreSearch')}
                 </button>
               )}
             </div>
             <button
               type="button"
-              aria-label="Open MITRE matrix"
+              aria-label={t('template.form.field.mitreOpenMatrix')}
               onClick={() => { setShowPicker(false); setShowMatrix(true); }}
               className="flex-shrink-0 flex items-center justify-center w-9 h-9 rounded-none border border-steel text-graphite hover:text-ink hover:border-ink"
             >
@@ -237,10 +239,10 @@ export function TemplateFormPage(): JSX.Element {
 
         <div className="flex items-center gap-md pt-xs border-t border-hairline">
           <button type="submit" className="btn-primary" disabled={isPending}>
-            <Save size={14} aria-hidden /> {isPending ? 'Saving…' : 'Save'}
+            <Save size={14} aria-hidden /> {isPending ? t('template.form.btn.saving') : t('template.form.btn.save')}
           </button>
           <Link to="/admin/templates" className="btn-outline-ink">
-            Cancel
+            {t('template.form.btn.cancel')}
           </Link>
         </div>
       </form>
@@ -255,9 +257,10 @@ export function TemplateFormPage(): JSX.Element {
 
       {showDeleteConfirm ? (
         <ConfirmDialog
-          title="Delete template"
-          description={`Delete "${existing.data?.name ?? 'this template'}"? This cannot be undone. Simulations already created from it are unaffected.`}
-          confirmLabel="Delete"
+          title={t('template.form.deleteConfirm.title')}
+          description={t('template.form.deleteConfirm.desc')}
+          confirmLabel={t('template.form.deleteConfirm.confirm')}
+          cancelLabel={t('template.form.deleteConfirm.cancel')}
           onConfirm={onDelete}
           onCancel={() => setShowDeleteConfirm(false)}
           destructive
diff --git a/frontend/src/pages/TemplatesListPage.tsx b/frontend/src/pages/TemplatesListPage.tsx
index 10455b3..8427a72 100644
--- a/frontend/src/pages/TemplatesListPage.tsx
+++ b/frontend/src/pages/TemplatesListPage.tsx
@@ -1,5 +1,6 @@
 import { Link } from 'react-router-dom';
 import { Plus } from 'lucide-react';
+import { useTranslation } from 'react-i18next';
 import { extractApiError } from '@/api/client';
 import type { SimulationTemplate } from '@/api/types';
 import { useDeleteTemplate, useTemplates } from '@/hooks/useTemplates';
@@ -7,28 +8,25 @@ import { useToast } from '@/hooks/useToast';
 import { LoadingState } from '@/components/LoadingState';
 import { ErrorState } from '@/components/ErrorState';
 import { EmptyState } from '@/components/EmptyState';
+import { formatDate } from '@/lib/format';
 
 function mitreCount(t: SimulationTemplate): number {
   return t.techniques.length + t.tactics.length;
 }
 
-function formatDate(value: string | null): string {
-  if (!value) return '—';
-  return value.slice(0, 10);
-}
-
 export function TemplatesListPage(): JSX.Element {
+  const { t } = useTranslation();
   const { data, isLoading, isError, error, refetch } = useTemplates();
   const deleteMutation = useDeleteTemplate();
   const { push } = useToast();
 
-  const onDelete = async (t: SimulationTemplate) => {
-    if (!window.confirm(`Delete template "${t.name}"? This cannot be undone.`)) return;
+  const onDelete = async (template: SimulationTemplate) => {
+    if (!window.confirm(`${t('template.list.title')} « ${template.name} » ?`)) return;
     try {
-      await deleteMutation.mutateAsync(t.id);
-      push('Template deleted', 'success');
+      await deleteMutation.mutateAsync(template.id);
+      push(t('template.form.toast.deleted'), 'success');
     } catch (err) {
-      push(extractApiError(err, 'Could not delete template'), 'error');
+      push(extractApiError(err, t('template.form.errorDelete')), 'error');
     }
   };
 
@@ -36,32 +34,32 @@ export function TemplatesListPage(): JSX.Element {
     <div className="flex flex-col gap-xl">
       <header className="flex items-end justify-between gap-md">
         <div>
-          <h1 className="text-[32px] font-medium leading-none">Templates</h1>
+          <h1 className="text-[32px] font-medium leading-none">{t('template.list.title')}</h1>
           <p className="text-charcoal text-[16px] mt-sm">
-            Reusable simulation blueprints for red team operations.
+            {t('template.list.subtitle')}
           </p>
         </div>
         <Link to="/admin/templates/new" className="btn-primary">
-          <Plus size={14} aria-hidden /> New
+          <Plus size={14} aria-hidden /> {t('template.list.new')}
         </Link>
       </header>
 
-      {isLoading ? <LoadingState label="Loading templates…" /> : null}
+      {isLoading ? <LoadingState label={t('common.loading')} /> : null}
 
       {isError ? (
         <ErrorState
-          message={extractApiError(error, 'Could not load templates')}
+          message={extractApiError(error, t('template.form.errorLoad'))}
           onRetry={() => refetch()}
         />
       ) : null}
 
       {!isLoading && !isError && data && data.length === 0 ? (
         <EmptyState
-          title="No templates yet"
-          description="Create your first template to speed up simulation setup."
+          title={t('template.list.empty.title')}
+          description={t('template.list.empty.desc')}
           action={
             <Link to="/admin/templates/new" className="btn-primary">
-              <Plus size={14} aria-hidden /> New template
+              <Plus size={14} aria-hidden /> {t('template.list.new')}
             </Link>
           }
         />
@@ -72,41 +70,41 @@ export function TemplatesListPage(): JSX.Element {
           <table className="table-compact w-full text-left">
             <thead className="bg-cloud border-b border-hairline">
               <tr>
-                <th>Name</th>
-                <th>MITRE</th>
-                <th>Created by</th>
-                <th>Updated</th>
-                <th className="text-right">Actions</th>
+                <th>{t('template.list.col.name')}</th>
+                <th>{t('template.list.col.mitre')}</th>
+                <th>{t('template.list.col.createdBy')}</th>
+                <th>{t('template.list.col.updated')}</th>
+                <th className="text-right">{t('engagement.list.col.actions')}</th>
               </tr>
             </thead>
             <tbody>
-              {data.map((t) => (
-                <tr key={t.id}>
+              {data.map((template) => (
+                <tr key={template.id}>
                   <td>
                     <Link
-                      to={`/admin/templates/${t.id}/edit`}
+                      to={`/admin/templates/${template.id}/edit`}
                       className="text-ink font-medium hover:underline"
                     >
-                      {t.name}
+                      {template.name}
                     </Link>
                   </td>
                   <td className="text-charcoal">
-                    {mitreCount(t) === 0 ? '—' : mitreCount(t)}
+                    {mitreCount(template) === 0 ? '—' : mitreCount(template)}
                   </td>
-                  <td className="text-charcoal">{t.created_by.username}</td>
-                  <td className="text-charcoal font-mono">{formatDate(t.updated_at)}</td>
+                  <td className="text-charcoal">{template.created_by.username}</td>
+                  <td className="text-charcoal font-mono">{formatDate(template.updated_at)}</td>
                   <td className="text-right">
                     <div className="inline-flex gap-sm">
-                      <Link to={`/admin/templates/${t.id}/edit`} className="btn-text-link">
-                        Edit
+                      <Link to={`/admin/templates/${template.id}/edit`} className="btn-text-link">
+                        {t('template.list.edit')}
                       </Link>
                       <button
                         type="button"
                         className="btn-text-link text-bloom-deep"
-                        onClick={() => onDelete(t)}
+                        onClick={() => onDelete(template)}
                         disabled={deleteMutation.isPending}
                       >
-                        Delete
+                        {t('template.list.delete')}
                       </button>
                     </div>
                   </td>
diff --git a/frontend/src/pages/UsersAdminPage.tsx b/frontend/src/pages/UsersAdminPage.tsx
index 46e9eb1..bc9b8d1 100644
--- a/frontend/src/pages/UsersAdminPage.tsx
+++ b/frontend/src/pages/UsersAdminPage.tsx
@@ -1,4 +1,6 @@
 import { Fragment, useState, type FormEvent } from 'react';
+import { formatDate } from '@/lib/format';
+import { useTranslation } from 'react-i18next';
 import { extractApiError } from '@/api/client';
 import type { Role, User } from '@/api/types';
 import { useAuth } from '@/hooks/useAuth';
@@ -14,12 +16,6 @@ import { LoadingState } from '@/components/LoadingState';
 import { ErrorState } from '@/components/ErrorState';
 import { EmptyState } from '@/components/EmptyState';
 
-const ROLE_OPTIONS: { value: Role; label: string }[] = [
-  { value: 'admin', label: 'Admin' },
-  { value: 'redteam', label: 'Red Team' },
-  { value: 'soc', label: 'SOC' },
-];
-
 interface CreateFormState {
   username: string;
   password: string;
@@ -29,6 +25,7 @@ interface CreateFormState {
 const EMPTY_CREATE: CreateFormState = { username: '', password: '', role: 'redteam' };
 
 export function UsersAdminPage(): JSX.Element {
+  const { t } = useTranslation();
   const { user: currentUser } = useAuth();
   const { push } = useToast();
   const list = useUsersList();
@@ -36,6 +33,12 @@ export function UsersAdminPage(): JSX.Element {
   const patchMutation = usePatchUser();
   const deleteMutation = useDeleteUser();
 
+  const ROLE_OPTIONS: { value: Role; label: string }[] = [
+    { value: 'admin', label: t('user.admin.role.admin') },
+    { value: 'redteam', label: t('user.admin.role.redteam') },
+    { value: 'soc', label: t('user.admin.role.soc') },
+  ];
+
   const [createForm, setCreateForm] = useState<CreateFormState>(EMPTY_CREATE);
   const [createError, setCreateError] = useState<string | null>(null);
 
@@ -47,15 +50,15 @@ export function UsersAdminPage(): JSX.Element {
     e.preventDefault();
     setCreateError(null);
     if (createForm.password.length < 8) {
-      setCreateError('Password must be at least 8 characters');
+      setCreateError(t('user.admin.error.passwordMinLength'));
       return;
     }
     try {
       await createMutation.mutateAsync(createForm);
       setCreateForm(EMPTY_CREATE);
-      push('User created', 'success');
+      push(t('user.admin.toast.created'), 'success');
     } catch (err) {
-      setCreateError(extractApiError(err, 'Could not create user'));
+      setCreateError(extractApiError(err, t('user.admin.error.create')));
     }
   };
 
@@ -63,53 +66,53 @@ export function UsersAdminPage(): JSX.Element {
     if (u.role === role) return;
     try {
       await patchMutation.mutateAsync({ id: u.id, input: { role } });
-      push(`Role updated for ${u.username}`, 'success');
+      push(t('user.admin.toast.roleUpdated', { username: u.username }), 'success');
     } catch (err) {
-      push(extractApiError(err, 'Could not update role'), 'error');
+      push(extractApiError(err, t('user.admin.error.roleUpdate')), 'error');
     }
   };
 
   const onResetPassword = async (u: User, e: FormEvent) => {
     e.preventDefault();
     if (resetPassword.length < 8) {
-      push('Password must be at least 8 characters', 'error');
+      push(t('user.admin.error.passwordMinLength'), 'error');
       return;
     }
     try {
       await patchMutation.mutateAsync({ id: u.id, input: { password: resetPassword } });
-      push(`Password reset for ${u.username}`, 'success');
+      push(t('user.admin.toast.passwordReset', { username: u.username }), 'success');
       setResetOpen(null);
       setResetPassword('');
     } catch (err) {
-      push(extractApiError(err, 'Could not reset password'), 'error');
+      push(extractApiError(err, t('user.admin.error.passwordReset')), 'error');
     }
   };
 
   const onDelete = async (u: User) => {
     if (currentUser?.id === u.id) {
-      push('You cannot delete your own account', 'error');
+      push(t('user.admin.error.selfDelete'), 'error');
       return;
     }
-    if (!window.confirm(`Delete user "${u.username}"?`)) return;
+    if (!window.confirm(t('user.admin.deleteConfirm', { username: u.username }))) return;
     try {
       await deleteMutation.mutateAsync(u.id);
-      push('User deleted', 'success');
+      push(t('user.admin.toast.deleted'), 'success');
     } catch (err) {
-      push(extractApiError(err, 'Could not delete user'), 'error');
+      push(extractApiError(err, t('user.admin.error.delete')), 'error');
     }
   };
 
   return (
     <div className="flex flex-col gap-xl">
       <header>
-        <h1 className="text-[32px] font-medium leading-none">User accounts</h1>
+        <h1 className="text-[32px] font-medium leading-none">{t('user.admin.title')}</h1>
         <p className="text-charcoal text-[16px] mt-sm">
-          Manage local accounts. Admins can create new red team or SOC analysts.
+          {t('user.admin.createSubtitle')}
         </p>
       </header>
 
       <section className="card-product flex flex-col gap-md">
-        <h2 className="text-[20px] font-medium">Create account</h2>
+        <h2 className="text-[20px] font-medium">{t('user.admin.createSection')}</h2>
         {/*
           Option A structural fix (AC-17.3): labels / inputs / hints in 3 explicit grid rows
           so the browser can never misalign them by collapsing different-height cells.
@@ -121,13 +124,13 @@ export function UsersAdminPage(): JSX.Element {
         >
           {/* Row 1 — labels */}
           <label htmlFor="new-username" className="text-[14px] font-medium text-ink">
-            Username <span className="text-bloom-deep">*</span>
+            {t('user.admin.field.username')} <span className="text-bloom-deep">*</span>
           </label>
           <label htmlFor="new-password" className="text-[14px] font-medium text-ink">
-            Password <span className="text-bloom-deep">*</span>
+            {t('user.admin.field.password')} <span className="text-bloom-deep">*</span>
           </label>
           <label htmlFor="new-role" className="text-[14px] font-medium text-ink">
-            Role <span className="text-bloom-deep">*</span>
+            {t('user.admin.col.role')} <span className="text-bloom-deep">*</span>
           </label>
           <div aria-hidden="true" />
 
@@ -148,17 +151,18 @@ export function UsersAdminPage(): JSX.Element {
           />
           <Select
             id="new-role"
+            data-testid="new-role-select"
             value={createForm.role}
             onChange={(e) => setCreateForm({ ...createForm, role: e.target.value as Role })}
             options={ROLE_OPTIONS}
           />
           <button type="submit" className="btn-primary w-full" disabled={createMutation.isPending}>
-            {createMutation.isPending ? 'Creating…' : 'Create'}
+            {createMutation.isPending ? t('common.creating') : t('user.admin.btn.create')}
           </button>
 
           {/* Row 3 — hints */}
           <div aria-hidden="true" />
-          <span className="text-[12px] text-graphite">≥ 8 characters</span>
+          <span className="text-[12px] text-graphite">{t('user.admin.passwordHint')}</span>
           <div aria-hidden="true" />
           <div aria-hidden="true" />
         </form>
@@ -170,19 +174,19 @@ export function UsersAdminPage(): JSX.Element {
       </section>
 
       <section className="flex flex-col gap-md">
-        <h2 className="text-[20px] font-medium">All accounts</h2>
+        <h2 className="text-[20px] font-medium">{t('user.admin.allSection')}</h2>
 
-        {list.isLoading ? <LoadingState label="Loading users…" /> : null}
+        {list.isLoading ? <LoadingState label={t('state.loading')} /> : null}
         {list.isError ? (
           <ErrorState
-            message={extractApiError(list.error, 'Could not load users')}
+            message={extractApiError(list.error, t('user.admin.error.create'))}
             onRetry={() => list.refetch()}
           />
         ) : null}
         {!list.isLoading && !list.isError && list.data && list.data.length === 0 ? (
           <EmptyState
-            title="No users yet"
-            description="Create the first account using the form above."
+            title={t('user.admin.empty.title')}
+            description={t('user.admin.empty.desc')}
           />
         ) : null}
 
@@ -191,10 +195,10 @@ export function UsersAdminPage(): JSX.Element {
             <table className="table-compact w-full text-left">
               <thead className="bg-cloud border-b border-hairline">
                 <tr>
-                  <th>Username</th>
-                  <th>Role</th>
-                  <th>Created</th>
-                  <th className="text-right">Actions</th>
+                  <th>{t('user.admin.col.username')}</th>
+                  <th>{t('user.admin.col.role')}</th>
+                  <th>{t('user.admin.col.createdAt')}</th>
+                  <th className="text-right">{t('user.admin.col.actions')}</th>
                 </tr>
               </thead>
               <tbody>
@@ -209,7 +213,7 @@ export function UsersAdminPage(): JSX.Element {
                           <span className="font-mono font-medium">{u.username}</span>
                           {isSelf ? (
                             <span className="ml-sm font-sans text-[12px] text-graphite">
-                              (you)
+                              {t('user.admin.you')}
                             </span>
                           ) : null}
                         </td>
@@ -218,11 +222,11 @@ export function UsersAdminPage(): JSX.Element {
                             value={u.role}
                             onChange={(e) => onRoleChange(u, e.target.value as Role)}
                             options={ROLE_OPTIONS}
-                            aria-label={`Change role for ${u.username}`}
+                            aria-label={`${t('user.admin.col.role')} ${u.username}`}
                             disabled={patchMutation.isPending}
                           />
                         </td>
-                        <td className="text-charcoal font-mono">{u.created_at}</td>
+                        <td className="text-charcoal font-mono">{formatDate(u.created_at)}</td>
                         <td className="text-right">
                           <div className="inline-flex gap-sm">
                             <button
@@ -233,7 +237,7 @@ export function UsersAdminPage(): JSX.Element {
                                 setResetPassword('');
                               }}
                             >
-                              Reset password
+                              {t('user.admin.resetPassword')}
                             </button>
                             <button
                               type="button"
@@ -241,7 +245,7 @@ export function UsersAdminPage(): JSX.Element {
                               disabled={isSelf || deleteMutation.isPending}
                               onClick={() => onDelete(u)}
                             >
-                              Delete
+                              {t('user.admin.btn.delete')}
                             </button>
                           </div>
                         </td>
@@ -255,9 +259,9 @@ export function UsersAdminPage(): JSX.Element {
                               className="flex items-end gap-md"
                             >
                               <FormField
-                                label={`New password for ${u.username}`}
+                                label={t('user.admin.newPasswordFor', { username: u.username })}
                                 htmlFor={`reset-${u.id}`}
-                                hint="≥ 8 characters"
+                                hint={t('user.admin.passwordHint')}
                               >
                                 <TextInput
                                   id={`reset-${u.id}`}
@@ -269,7 +273,7 @@ export function UsersAdminPage(): JSX.Element {
                                 />
                               </FormField>
                               <button type="submit" className="btn-primary">
-                                Save password
+                                {t('user.admin.btn.setPassword')}
                               </button>
                               <button
                                 type="button"
@@ -279,7 +283,7 @@ export function UsersAdminPage(): JSX.Element {
                                   setResetPassword('');
                                 }}
                               >
-                                Cancel
+                                {t('user.admin.btn.cancel')}
                               </button>
                             </form>
                           </td>
diff --git a/frontend/tests/EngagementFormPage.test.tsx b/frontend/tests/EngagementFormPage.test.tsx
index 0de3ee5..f8471c9 100644
--- a/frontend/tests/EngagementFormPage.test.tsx
+++ b/frontend/tests/EngagementFormPage.test.tsx
@@ -90,7 +90,7 @@ describe('EngagementFormPage — C2 config card visibility', () => {
       routerProps: { initialEntries: ['/engagements/5/edit'] },
     });
     await waitFor(() => {
-      expect(screen.getByRole('button', { name: /save changes/i })).toBeInTheDocument();
+      expect(screen.getByTestId('btn-submit')).toBeInTheDocument();
     });
     expect(screen.queryByTestId('c2-config-card')).toBeNull();
   });
@@ -101,7 +101,7 @@ describe('EngagementFormPage — C2 config card visibility', () => {
       routerProps: { initialEntries: ['/engagements/new'] },
     });
     await waitFor(() => {
-      expect(screen.getByRole('button', { name: /create engagement/i })).toBeInTheDocument();
+      expect(screen.getByTestId('btn-submit')).toBeInTheDocument();
     });
     expect(screen.queryByTestId('c2-config-card')).toBeNull();
   });
diff --git a/frontend/tests/ExportEngagementButton.test.tsx b/frontend/tests/ExportEngagementButton.test.tsx
index a139ff3..25e677d 100644
--- a/frontend/tests/ExportEngagementButton.test.tsx
+++ b/frontend/tests/ExportEngagementButton.test.tsx
@@ -47,7 +47,7 @@ describe('ExportEngagementButton', () => {
     renderWithProviders(<ExportEngagementButton engagementId={1} />);
     expect(screen.getByTestId('export-btn')).toBeInTheDocument();
     expect(screen.getByTestId('export-dropdown-toggle')).toBeInTheDocument();
-    expect(screen.getByText('Export')).toBeInTheDocument();
+    expect(screen.getByText('Exporter')).toBeInTheDocument();
   });
 
   it('clicking primary opens dropdown with three formats', async () => {
diff --git a/frontend/tests/MitreMatrixModal.test.tsx b/frontend/tests/MitreMatrixModal.test.tsx
index 6d8a851..82f5ea1 100644
--- a/frontend/tests/MitreMatrixModal.test.tsx
+++ b/frontend/tests/MitreMatrixModal.test.tsx
@@ -124,7 +124,7 @@ describe('MitreMatrixModal', () => {
     );
     await user.click(t1078Btn!);
 
-    await user.click(screen.getByRole('button', { name: /Apply/i }));
+    await user.click(screen.getByRole('button', { name: /Appliquer/i }));
 
     expect(onApply).toHaveBeenCalledWith(
       expect.objectContaining({
@@ -148,7 +148,7 @@ describe('MitreMatrixModal', () => {
       />,
     );
 
-    await user.click(screen.getByRole('button', { name: /Cancel/i }));
+    await user.click(screen.getByRole('button', { name: /Fermer/i }));
 
     expect(onCancel).toHaveBeenCalled();
     expect(onApply).not.toHaveBeenCalled();
@@ -202,7 +202,7 @@ describe('MitreMatrixModal', () => {
 
     await waitFor(() => screen.getByText('T1078'));
 
-    const searchInput = screen.getByPlaceholderText(/Filter techniques/i);
+    const searchInput = screen.getByPlaceholderText(/Filtrer/i);
     await user.type(searchInput, 'T1059');
 
     expect(screen.queryByText('T1078')).toBeNull();
@@ -224,7 +224,7 @@ describe('MitreMatrixModal', () => {
     await waitFor(() => screen.getByText('T1078'));
     expect(screen.queryByText(/Default Accounts/)).toBeNull();
 
-    const expandBtn = screen.getByRole('button', { name: /Expand T1078/i });
+    const expandBtn = screen.getByRole('button', { name: /Déplier T1078/i });
     await user.click(expandBtn);
 
     expect(screen.getByText(/Default Accounts/)).toBeInTheDocument();
@@ -242,7 +242,7 @@ describe('MitreMatrixModal', () => {
     );
 
     await waitFor(() => {
-      expect(screen.getByRole('button', { name: /Apply 1 item/i })).toBeInTheDocument();
+      expect(screen.getByRole('button', { name: /Appliquer \(1 élément\)/i })).toBeInTheDocument();
     });
   });
 
@@ -259,11 +259,11 @@ describe('MitreMatrixModal', () => {
 
     await waitFor(() => screen.getByText('T1078'));
 
-    const applyBtn = screen.getByRole('button', { name: /Clear all/i });
+    const applyBtn = screen.getByRole('button', { name: /Tout effacer/i });
     expect(applyBtn).toBeDisabled();
   });
 
-  it('Apply button shows "Clear all" and is enabled when initial selection is deselected', async () => {
+  it('Apply button shows "Tout effacer" and is enabled when initial selection is deselected', async () => {
     const onApply = vi.fn();
     const user = userEvent.setup();
 
@@ -284,7 +284,7 @@ describe('MitreMatrixModal', () => {
     );
     await user.click(t1078Btn!);
 
-    const applyBtn = screen.getByRole('button', { name: /Clear all/i });
+    const applyBtn = screen.getByRole('button', { name: /Tout effacer/i });
     expect(applyBtn).not.toBeDisabled();
     await user.click(applyBtn);
     expect(onApply).toHaveBeenCalledWith(
diff --git a/frontend/tests/MitreTechniquePicker.test.tsx b/frontend/tests/MitreTechniquePicker.test.tsx
index ed75574..248c004 100644
--- a/frontend/tests/MitreTechniquePicker.test.tsx
+++ b/frontend/tests/MitreTechniquePicker.test.tsx
@@ -30,7 +30,7 @@ describe('MitreTechniquePicker', () => {
     vi.useRealTimers();
     renderWithProviders(<MitreTechniquePicker onSelect={vi.fn()} />);
     expect(screen.getByRole('combobox')).toBeInTheDocument();
-    expect(screen.getByPlaceholderText(/Search by ID or name/i)).toBeInTheDocument();
+    expect(screen.getByPlaceholderText(/Rechercher une technique/i)).toBeInTheDocument();
   });
 
   it('is disabled when disabled prop is true', () => {
diff --git a/frontend/tests/MitreTechniqueTag.test.tsx b/frontend/tests/MitreTechniqueTag.test.tsx
index c2b2f99..5cf0926 100644
--- a/frontend/tests/MitreTechniqueTag.test.tsx
+++ b/frontend/tests/MitreTechniqueTag.test.tsx
@@ -23,7 +23,7 @@ describe('MitreTechniqueTag', () => {
     renderWithProviders(
       <MitreTechniqueTag technique={TECHNIQUE} onRemove={vi.fn()} />,
     );
-    expect(screen.getByRole('button', { name: /Remove T1059/i })).toBeInTheDocument();
+    expect(screen.getByRole('button', { name: /Retirer T1059/i })).toBeInTheDocument();
   });
 
   it('clicking × calls onRemove', async () => {
@@ -32,7 +32,7 @@ describe('MitreTechniqueTag', () => {
     renderWithProviders(
       <MitreTechniqueTag technique={TECHNIQUE} onRemove={onRemove} />,
     );
-    await user.click(screen.getByRole('button', { name: /Remove T1059/i }));
+    await user.click(screen.getByRole('button', { name: /Retirer T1059/i }));
     expect(onRemove).toHaveBeenCalledOnce();
   });
 
@@ -40,7 +40,7 @@ describe('MitreTechniqueTag', () => {
     renderWithProviders(
       <MitreTechniqueTag technique={TECHNIQUE} onRemove={vi.fn()} disabled />,
     );
-    expect(screen.queryByRole('button', { name: /Remove/i })).toBeNull();
+    expect(screen.queryByRole('button', { name: /Retirer/i })).toBeNull();
   });
 });
 
@@ -57,7 +57,7 @@ describe('MitreTacticTag', () => {
     renderWithProviders(
       <MitreTacticTag tactic={TACTIC} onRemove={vi.fn()} />,
     );
-    expect(screen.getByRole('button', { name: /Remove TA0007/i })).toBeInTheDocument();
+    expect(screen.getByRole('button', { name: /Retirer TA0007/i })).toBeInTheDocument();
   });
 
   it('clicking × calls onRemove', async () => {
@@ -66,7 +66,7 @@ describe('MitreTacticTag', () => {
     renderWithProviders(
       <MitreTacticTag tactic={TACTIC} onRemove={onRemove} />,
     );
-    await user.click(screen.getByRole('button', { name: /Remove TA0007/i }));
+    await user.click(screen.getByRole('button', { name: /Retirer TA0007/i }));
     expect(onRemove).toHaveBeenCalledOnce();
   });
 
@@ -74,6 +74,6 @@ describe('MitreTacticTag', () => {
     renderWithProviders(
       <MitreTacticTag tactic={TACTIC} onRemove={vi.fn()} disabled />,
     );
-    expect(screen.queryByRole('button', { name: /Remove/i })).toBeNull();
+    expect(screen.queryByRole('button', { name: /Retirer/i })).toBeNull();
   });
 });
diff --git a/frontend/tests/MitreTechniquesField.test.tsx b/frontend/tests/MitreTechniquesField.test.tsx
index b8d5b5d..363b6c2 100644
--- a/frontend/tests/MitreTechniquesField.test.tsx
+++ b/frontend/tests/MitreTechniquesField.test.tsx
@@ -48,7 +48,7 @@ describe('MitreTechniquesField', () => {
     renderWithProviders(
       <MitreTechniquesField value={[]} tactics={[]} simulationId={7} engagementId={42} />,
     );
-    expect(screen.getByText(/No techniques selected/i)).toBeInTheDocument();
+    expect(screen.getByText(/Aucune technique associée/i)).toBeInTheDocument();
   });
 
   it('renders technique tags for each technique', () => {
@@ -72,16 +72,16 @@ describe('MitreTechniquesField', () => {
     renderWithProviders(
       <MitreTechniquesField value={[]} tactics={[]} simulationId={7} engagementId={42} />,
     );
-    expect(screen.getByRole('button', { name: /Open MITRE matrix/i })).toBeInTheDocument();
+    expect(screen.getByRole('button', { name: /Ouvrir la matrice/i })).toBeInTheDocument();
     // The search placeholder button
-    expect(screen.getByRole('button', { name: /Search technique/i })).toBeInTheDocument();
+    expect(screen.getByRole('button', { name: /Rechercher une technique/i })).toBeInTheDocument();
   });
 
   it('hides input row when disabled', () => {
     renderWithProviders(
       <MitreTechniquesField value={[T1059]} tactics={[]} simulationId={7} engagementId={42} disabled />,
     );
-    expect(screen.queryByRole('button', { name: /Open MITRE matrix/i })).toBeNull();
+    expect(screen.queryByRole('button', { name: /Ouvrir la matrice/i })).toBeNull();
   });
 
   it('× button on technique tag calls PATCH with technique removed', async () => {
@@ -94,7 +94,7 @@ describe('MitreTechniquesField', () => {
       <MitreTechniquesField value={[T1059, T1078]} tactics={[]} simulationId={7} engagementId={42} />,
     );
 
-    const removeBtn = screen.getByRole('button', { name: /Remove T1059/i });
+    const removeBtn = screen.getByRole('button', { name: /Retirer T1059/i });
     await user.click(removeBtn);
 
     await waitFor(() => {
@@ -115,7 +115,7 @@ describe('MitreTechniquesField', () => {
       <MitreTechniquesField value={[T1059]} tactics={[TA0007]} simulationId={7} engagementId={42} />,
     );
 
-    const removeBtn = screen.getByRole('button', { name: /Remove TA0007/i });
+    const removeBtn = screen.getByRole('button', { name: /Retirer TA0007/i });
     await user.click(removeBtn);
 
     await waitFor(() => {
@@ -131,7 +131,7 @@ describe('MitreTechniquesField', () => {
     renderWithProviders(
       <MitreTechniquesField value={[]} tactics={[]} simulationId={7} engagementId={42} />,
     );
-    await user.click(screen.getByRole('button', { name: /Search technique/i }));
+    await user.click(screen.getByRole('button', { name: /Rechercher une technique/i }));
     expect(screen.getByRole('combobox')).toBeInTheDocument();
   });
 
@@ -142,7 +142,7 @@ describe('MitreTechniquesField', () => {
       <MitreTechniquesField value={[T1059]} tactics={[]} simulationId={7} engagementId={42} />,
     );
 
-    await user.click(screen.getByRole('button', { name: /Search technique/i }));
+    await user.click(screen.getByRole('button', { name: /Rechercher une technique/i }));
     const combobox = screen.getByRole('combobox');
 
     await user.type(combobox, 'T1059');
@@ -161,7 +161,7 @@ describe('MitreTechniquesField', () => {
     renderWithProviders(
       <MitreTechniquesField value={[]} tactics={[]} simulationId={7} engagementId={42} />,
     );
-    await user.click(screen.getByRole('button', { name: /Open MITRE matrix/i }));
+    await user.click(screen.getByRole('button', { name: /Ouvrir la matrice/i }));
     expect(screen.getByRole('dialog')).toBeInTheDocument();
   });
 });
diff --git a/frontend/tests/SimulationFormPage.test.tsx b/frontend/tests/SimulationFormPage.test.tsx
index cd68ce4..62c9db0 100644
--- a/frontend/tests/SimulationFormPage.test.tsx
+++ b/frontend/tests/SimulationFormPage.test.tsx
@@ -88,12 +88,12 @@ describe('SimulationFormPage — redteam mode (edit existing)', () => {
     });
 
     await waitFor(() => {
-      expect(screen.getByLabelText(/^Name/i)).not.toBeDisabled();
+      expect(screen.getByLabelText(/^Nom/i)).not.toBeDisabled();
     });
 
-    expect(screen.getByLabelText(/Description/i)).not.toBeDisabled();
-    expect(screen.getByLabelText(/Commands/i)).not.toBeDisabled();
-    expect(screen.getByLabelText(/Executed at/i)).not.toBeDisabled();
+    expect(screen.getByLabelText(/^Description/i)).not.toBeDisabled();
+    expect(screen.getByLabelText(/^Commandes/i)).not.toBeDisabled();
+    expect(screen.getByLabelText(/^Exécuté le/i)).not.toBeDisabled();
   });
 
   it('shows "Mark for review" button when status is pending', async () => {
@@ -102,7 +102,7 @@ describe('SimulationFormPage — redteam mode (edit existing)', () => {
     });
 
     await waitFor(() => {
-      expect(screen.getByRole('button', { name: /Mark for review/i })).toBeInTheDocument();
+      expect(screen.getByTestId('mark-review-btn')).toBeInTheDocument();
     });
   });
 
@@ -111,8 +111,8 @@ describe('SimulationFormPage — redteam mode (edit existing)', () => {
       routerProps: { initialEntries: ['/engagements/42/simulations/7/edit'] },
     });
 
-    await waitFor(() => screen.getByRole('button', { name: /Mark for review/i }));
-    expect(screen.queryByRole('button', { name: /^Close$/i })).toBeNull();
+    await waitFor(() => screen.getByTestId('mark-review-btn'));
+    expect(screen.queryByTestId('close-btn')).toBeNull();
   });
 
   it('shows "Mark for review" for in_progress status', async () => {
@@ -122,7 +122,7 @@ describe('SimulationFormPage — redteam mode (edit existing)', () => {
     });
 
     await waitFor(() => {
-      expect(screen.getByRole('button', { name: /Mark for review/i })).toBeInTheDocument();
+      expect(screen.getByTestId('mark-review-btn')).toBeInTheDocument();
     });
   });
 
@@ -133,7 +133,7 @@ describe('SimulationFormPage — redteam mode (edit existing)', () => {
     });
 
     await waitFor(() => {
-      expect(screen.getByRole('button', { name: /^Close$/i })).toBeInTheDocument();
+      expect(screen.getByTestId('close-btn')).toBeInTheDocument();
     });
   });
 
@@ -143,7 +143,7 @@ describe('SimulationFormPage — redteam mode (edit existing)', () => {
     });
 
     await waitFor(() => {
-      expect(screen.getByRole('button', { name: /^Delete$/i })).toBeInTheDocument();
+      expect(screen.getByTestId('delete-btn')).toBeInTheDocument();
     });
   });
 });
@@ -179,10 +179,10 @@ describe('SimulationFormPage — SOC role + pending (blocked)', () => {
     });
 
     await waitFor(() => {
-      expect(screen.getByLabelText(/Log source/i)).toBeDisabled();
+      expect(screen.getByLabelText(/^Source de log/i)).toBeDisabled();
     });
 
-    expect(screen.getByLabelText(/Incident number/i)).toBeDisabled();
+    expect(screen.getByLabelText(/^Numéro d'incident/i)).toBeDisabled();
   });
 
   it('Red Team inputs are disabled for SOC', async () => {
@@ -191,10 +191,10 @@ describe('SimulationFormPage — SOC role + pending (blocked)', () => {
     });
 
     await waitFor(() => {
-      expect(screen.getByLabelText(/^Name/i)).toBeDisabled();
+      expect(screen.getByLabelText(/^Nom/i)).toBeDisabled();
     });
 
-    expect(screen.getByLabelText(/Description/i)).toBeDisabled();
+    expect(screen.getByLabelText(/^Description/i)).toBeDisabled();
   });
 });
 
@@ -218,10 +218,10 @@ describe('SimulationFormPage — SOC role + review_required (can edit SOC fields
     });
 
     await waitFor(() => {
-      expect(screen.getByLabelText(/Log source/i)).not.toBeDisabled();
+      expect(screen.getByLabelText(/^Source de log/i)).not.toBeDisabled();
     });
 
-    expect(screen.getByLabelText(/Incident number/i)).not.toBeDisabled();
+    expect(screen.getByLabelText(/^Numéro d'incident/i)).not.toBeDisabled();
   });
 
   it('Red Team inputs remain disabled for SOC even when review_required', async () => {
@@ -230,7 +230,7 @@ describe('SimulationFormPage — SOC role + review_required (can edit SOC fields
     });
 
     await waitFor(() => {
-      expect(screen.getByLabelText(/^Name/i)).toBeDisabled();
+      expect(screen.getByLabelText(/^Nom/i)).toBeDisabled();
     });
   });
 
@@ -240,7 +240,7 @@ describe('SimulationFormPage — SOC role + review_required (can edit SOC fields
     });
 
     await waitFor(() => {
-      expect(screen.getByLabelText(/Log source/i)).not.toBeDisabled();
+      expect(screen.getByLabelText(/^Source de log/i)).not.toBeDisabled();
     });
 
     expect(screen.queryByTestId('soc-blocked-banner')).toBeNull();
@@ -252,7 +252,7 @@ describe('SimulationFormPage — SOC role + review_required (can edit SOC fields
     });
 
     await waitFor(() => {
-      expect(screen.getByRole('button', { name: /^Close$/i })).toBeInTheDocument();
+      expect(screen.getByTestId('close-btn')).toBeInTheDocument();
     });
   });
 });
@@ -273,8 +273,8 @@ describe('SimulationFormPage — new simulation', () => {
     renderWithProviders(<NewPage />, {
       routerProps: { initialEntries: ['/engagements/42/simulations/new'] },
     });
-    expect(screen.getByLabelText(/^Name/i)).toBeInTheDocument();
-    expect(screen.getByRole('button', { name: /Create simulation/i })).toBeInTheDocument();
+    expect(screen.getByLabelText(/^Nom/i)).toBeInTheDocument();
+    expect(screen.getByTestId('create-sim-btn')).toBeInTheDocument();
   });
 });
 
@@ -311,7 +311,7 @@ describe('SimulationFormPage — Execute via C2 button visibility', () => {
       routerProps: { initialEntries: ['/engagements/42/simulations/7/edit'] },
     });
     await waitFor(() => {
-      expect(screen.getByLabelText(/^Name/i)).not.toBeDisabled();
+      expect(screen.getByLabelText(/^Nom/i)).not.toBeDisabled();
     });
     expect(screen.queryByTestId('c2-execute-btn')).toBeNull();
   });
@@ -369,7 +369,7 @@ describe('SimulationFormPage — C2 tasks panel visibility', () => {
     });
     // Wait for page data to load then confirm no panel
     await waitFor(() => {
-      expect(screen.getByLabelText(/^Name/i)).not.toBeDisabled();
+      expect(screen.getByLabelText(/^Nom/i)).not.toBeDisabled();
     });
     expect(screen.queryByTestId('c2-tasks-panel')).toBeNull();
   });
diff --git a/frontend/tests/SimulationStatusBadge.test.tsx b/frontend/tests/SimulationStatusBadge.test.tsx
index 796d995..fa065de 100644
--- a/frontend/tests/SimulationStatusBadge.test.tsx
+++ b/frontend/tests/SimulationStatusBadge.test.tsx
@@ -4,10 +4,10 @@ import { SimulationStatusBadge } from '@/components/SimulationStatusBadge';
 import type { SimulationStatus } from '@/api/types';
 
 const CASES: { status: SimulationStatus; label: string }[] = [
-  { status: 'pending', label: 'Pending' },
-  { status: 'in_progress', label: 'In progress' },
-  { status: 'review_required', label: 'Review required' },
-  { status: 'done', label: 'Done' },
+  { status: 'pending', label: 'En attente' },
+  { status: 'in_progress', label: 'En cours' },
+  { status: 'review_required', label: 'Révision requise' },
+  { status: 'done', label: 'Terminé' },
 ];
 
 describe('SimulationStatusBadge', () => {
diff --git a/frontend/tests/StatusBadge.test.tsx b/frontend/tests/StatusBadge.test.tsx
index a9e6187..8ebea55 100644
--- a/frontend/tests/StatusBadge.test.tsx
+++ b/frontend/tests/StatusBadge.test.tsx
@@ -2,12 +2,18 @@ import { describe, expect, it } from 'vitest';
 import { render, screen } from '@testing-library/react';
 import { StatusBadge } from '@/components/StatusBadge';
 
+const LABELS: Record<string, string> = {
+  planned: 'Planifié',
+  active: 'Actif',
+  closed: 'Clôturé',
+};
+
 describe('StatusBadge', () => {
   it.each(['planned', 'active', 'closed'] as const)('renders %s label and data attr', (status) => {
     render(<StatusBadge status={status} />);
     const badge = screen.getByTestId('status-badge');
     expect(badge).toHaveAttribute('data-status', status);
-    expect(badge.textContent?.toLowerCase()).toBe(status);
+    expect(badge.textContent).toBe(LABELS[status]);
   });
 
   it('applies warn-soft surface for planned', () => {
diff --git a/frontend/tests/TemplateFormPage.test.tsx b/frontend/tests/TemplateFormPage.test.tsx
index 09cb5dc..c76f19d 100644
--- a/frontend/tests/TemplateFormPage.test.tsx
+++ b/frontend/tests/TemplateFormPage.test.tsx
@@ -92,22 +92,20 @@ describe('TemplateFormPage — new mode', () => {
 
   it('renders the form with name field in empty state', () => {
     renderNew();
-    expect(screen.getByLabelText(/Name/i)).toBeInTheDocument();
-    expect(screen.getByLabelText(/Description/i)).toBeInTheDocument();
-    expect(screen.getByLabelText(/Commands/i)).toBeInTheDocument();
-    expect(screen.getByLabelText(/Prerequisites/i)).toBeInTheDocument();
-    // All inputs should be empty
-    expect(screen.getByLabelText(/Name/i)).toHaveValue('');
+    expect(screen.getByLabelText(/^Nom/i)).toBeInTheDocument();
+    expect(screen.getByLabelText(/^Description/i)).toBeInTheDocument();
+    expect(screen.getByLabelText(/^Commandes/i)).toBeInTheDocument();
+    expect(screen.getByLabelText(/^Prérequis/i)).toBeInTheDocument();
+    expect(screen.getByLabelText(/^Nom/i)).toHaveValue('');
   });
 
   it('shows validation error when name is empty on submit', async () => {
     const user = userEvent.setup();
     renderNew();
-    // Name field is empty by default — click Save directly
-    const saveBtn = screen.getByRole('button', { name: /Save/i });
+    const saveBtn = screen.getByRole('button', { name: /Enregistrer/i });
     await user.click(saveBtn);
     await waitFor(() => {
-      expect(screen.getByText('Name is required')).toBeInTheDocument();
+      expect(screen.getByText('Le nom est obligatoire')).toBeInTheDocument();
     });
   });
 
@@ -115,8 +113,8 @@ describe('TemplateFormPage — new mode', () => {
     mock.onPost('/templates').reply(201, { ...TEMPLATE, id: 99 });
     const user = userEvent.setup();
     renderNew();
-    await user.type(screen.getByLabelText(/Name/i), 'My Template');
-    await user.click(screen.getByRole('button', { name: /Save/i }));
+    await user.type(screen.getByLabelText(/^Nom/i), 'My Template');
+    await user.click(screen.getByRole('button', { name: /Enregistrer/i }));
     await waitFor(() => {
       expect(mock.history.post.length).toBe(1);
     });
@@ -128,8 +126,8 @@ describe('TemplateFormPage — new mode', () => {
     mock.onPost('/templates').reply(409, { error: 'template name already exists' });
     const user = userEvent.setup();
     renderNew();
-    await user.type(screen.getByLabelText(/Name/i), 'Duplicate');
-    await user.click(screen.getByRole('button', { name: /Save/i }));
+    await user.type(screen.getByLabelText(/^Nom/i), 'Duplicate');
+    await user.click(screen.getByRole('button', { name: /Enregistrer/i }));
     await waitFor(() => {
       expect(screen.getByText('template name already exists')).toBeInTheDocument();
     });
@@ -137,7 +135,7 @@ describe('TemplateFormPage — new mode', () => {
 
   it('does not show Delete button in new mode', () => {
     renderNew();
-    expect(screen.queryByText('Delete')).toBeNull();
+    expect(screen.queryByText('Supprimer')).toBeNull();
   });
 });
 
@@ -176,7 +174,7 @@ describe('TemplateFormPage — edit mode', () => {
     await waitFor(() => {
       expect(screen.getByDisplayValue('Mimikatz LSASS Dump')).toBeInTheDocument();
     });
-    expect(screen.getByText('Delete')).toBeInTheDocument();
+    expect(screen.getByText('Supprimer')).toBeInTheDocument();
   });
 
   it('submits PATCH on save', async () => {
@@ -187,7 +185,7 @@ describe('TemplateFormPage — edit mode', () => {
     await waitFor(() => {
       expect(screen.getByDisplayValue('Mimikatz LSASS Dump')).toBeInTheDocument();
     });
-    await user.click(screen.getByRole('button', { name: /Save/i }));
+    await user.click(screen.getByRole('button', { name: /Enregistrer/i }));
     await waitFor(() => {
       expect(mock.history.patch.length).toBe(1);
     });
@@ -201,14 +199,14 @@ describe('TemplateFormPage — edit mode', () => {
     const user = userEvent.setup();
     renderEdit(5);
     await waitFor(() => {
-      expect(screen.getByText('Delete')).toBeInTheDocument();
+      expect(screen.getByText('Supprimer')).toBeInTheDocument();
     });
-    await user.click(screen.getByText('Delete'));
+    await user.click(screen.getByText('Supprimer'));
     await waitFor(() => {
       expect(screen.getByRole('dialog')).toBeInTheDocument();
     });
-    // Click the Delete button inside the dialog
-    const dialogDeleteBtn = screen.getAllByText('Delete').find(
+    // Click the Supprimer button inside the dialog
+    const dialogDeleteBtn = screen.getAllByText('Supprimer').find(
       (el) => el.tagName === 'BUTTON' && el.closest('[role="dialog"]')
     ) as HTMLElement;
     await user.click(dialogDeleteBtn);
diff --git a/frontend/tests/TemplatePickerModal.test.tsx b/frontend/tests/TemplatePickerModal.test.tsx
index f067200..8069d98 100644
--- a/frontend/tests/TemplatePickerModal.test.tsx
+++ b/frontend/tests/TemplatePickerModal.test.tsx
@@ -76,7 +76,7 @@ describe('TemplatePickerModal', () => {
     await waitFor(() => {
       expect(screen.getByTestId('empty-state')).toBeInTheDocument();
     });
-    expect(screen.getByText(/No templates available/i)).toBeInTheDocument();
+    expect(screen.getByText(/Aucun template disponible/i)).toBeInTheDocument();
   });
 
   it('lists templates with name and MITRE count', async () => {
@@ -128,9 +128,9 @@ describe('TemplatePickerModal', () => {
       />
     );
     await waitFor(() => {
-      expect(screen.getByText('Cancel')).toBeInTheDocument();
+      expect(screen.getByText('Annuler')).toBeInTheDocument();
     });
-    await user.click(screen.getByText('Cancel'));
+    await user.click(screen.getByText('Annuler'));
     expect(onClose).toHaveBeenCalledOnce();
   });
 
diff --git a/frontend/tests/TemplatesListPage.test.tsx b/frontend/tests/TemplatesListPage.test.tsx
index e587a05..2169c91 100644
--- a/frontend/tests/TemplatesListPage.test.tsx
+++ b/frontend/tests/TemplatesListPage.test.tsx
@@ -100,7 +100,7 @@ describe('TemplatesListPage', () => {
     await waitFor(() => {
       expect(screen.getByText('Mimikatz LSASS Dump')).toBeInTheDocument();
     });
-    expect(screen.getAllByText(/New/i).length).toBeGreaterThan(0);
+    expect(screen.getAllByText(/Nouveau/i).length).toBeGreaterThan(0);
   });
 
   it('shows Edit and Delete actions', async () => {
@@ -109,8 +109,8 @@ describe('TemplatesListPage', () => {
     await waitFor(() => {
       expect(screen.getByText('Mimikatz LSASS Dump')).toBeInTheDocument();
     });
-    expect(screen.getAllByText('Edit').length).toBe(2);
-    expect(screen.getAllByText('Delete').length).toBe(2);
+    expect(screen.getAllByText('Modifier').length).toBe(2);
+    expect(screen.getAllByText('Supprimer').length).toBe(2);
   });
 
   it('calls delete endpoint on confirm', async () => {
@@ -124,10 +124,10 @@ describe('TemplatesListPage', () => {
 
     renderWithProviders(<TemplatesListPage />);
     await waitFor(() => {
-      expect(screen.getAllByText('Delete')[0]).toBeInTheDocument();
+      expect(screen.getAllByText('Supprimer')[0]).toBeInTheDocument();
     });
 
-    const deleteButtons = screen.getAllByText('Delete');
+    const deleteButtons = screen.getAllByText('Supprimer');
     await user.click(deleteButtons[0]);
 
     await waitFor(() => {
diff --git a/frontend/tests/Toast.test.tsx b/frontend/tests/Toast.test.tsx
index 4195dc8..7e7949d 100644
--- a/frontend/tests/Toast.test.tsx
+++ b/frontend/tests/Toast.test.tsx
@@ -28,7 +28,7 @@ describe('Toast', () => {
     expect(toast).toHaveTextContent('Session expirée');
     expect(toast).toHaveAttribute('data-kind', 'error');
 
-    await user.click(screen.getByRole('button', { name: /dismiss/i }));
+    await user.click(screen.getByRole('button', { name: /fermer/i }));
     await waitFor(() => {
       expect(screen.queryByTestId('toast')).toBeNull();
     });
diff --git a/frontend/tests/UsersAdminPage.test.tsx b/frontend/tests/UsersAdminPage.test.tsx
index deccfc8..cfe82c8 100644
--- a/frontend/tests/UsersAdminPage.test.tsx
+++ b/frontend/tests/UsersAdminPage.test.tsx
@@ -56,15 +56,15 @@ describe('UsersAdminPage', () => {
 
     await screen.findByText('alice');
 
-    await user.type(screen.getByLabelText(/^username/i), 'dan');
-    await user.type(screen.getByLabelText(/^password/i), 'sup3rs4fe!');
+    await user.type(screen.getByLabelText(/^nom d'utilisateur/i), 'dan');
+    await user.type(screen.getByLabelText(/^mot de passe/i), 'sup3rs4fe!');
     // role default is 'redteam'; switch to 'soc' to match newUser
-    await user.selectOptions(screen.getByLabelText(/^role/i), 'soc');
+    await user.selectOptions(screen.getByTestId('new-role-select'), 'soc');
 
     // After POST, hooks invalidate and the list refetches → return the new list
     mock.onGet('/users').reply(200, [...USERS, newUser]);
 
-    await user.click(screen.getByRole('button', { name: /^create$/i }));
+    await user.click(screen.getByRole('button', { name: /^créer$/i }));
 
     await waitFor(() => {
       expect(postSpy).toHaveBeenCalledWith({
@@ -85,12 +85,12 @@ describe('UsersAdminPage', () => {
     // The "Reset password" button for bob lives in bob's row.
     const bobRow = screen.getByText('bob').closest('tr');
     expect(bobRow).not.toBeNull();
-    await user.click(within(bobRow as HTMLElement).getByRole('button', { name: /reset password/i }));
+    await user.click(within(bobRow as HTMLElement).getByRole('button', { name: /réinitialiser le mot de passe/i }));
 
     // The reset form for bob (and bob only) must appear.
-    expect(await screen.findByLabelText(/new password for bob/i)).toBeInTheDocument();
-    expect(screen.queryByLabelText(/new password for carol/i)).toBeNull();
-    expect(screen.queryByLabelText(/new password for alice/i)).toBeNull();
+    expect(await screen.findByLabelText(/nouveau mot de passe pour bob/i)).toBeInTheDocument();
+    expect(screen.queryByLabelText(/nouveau mot de passe pour carol/i)).toBeNull();
+    expect(screen.queryByLabelText(/nouveau mot de passe pour alice/i)).toBeNull();
   });
 
   it('disables the delete button on the current user own row', async () => {
@@ -100,7 +100,7 @@ describe('UsersAdminPage', () => {
     const aliceRow = screen.getByText('alice').closest('tr') as HTMLElement;
     const bobRow = screen.getByText('bob').closest('tr') as HTMLElement;
 
-    expect(within(aliceRow).getByRole('button', { name: /delete/i })).toBeDisabled();
-    expect(within(bobRow).getByRole('button', { name: /delete/i })).toBeEnabled();
+    expect(within(aliceRow).getByRole('button', { name: /supprimer/i })).toBeDisabled();
+    expect(within(bobRow).getByRole('button', { name: /supprimer/i })).toBeEnabled();
   });
 });
diff --git a/frontend/tests/components/C2ConfigCard.test.tsx b/frontend/tests/components/C2ConfigCard.test.tsx
index cc6e349..a8d92c7 100644
--- a/frontend/tests/components/C2ConfigCard.test.tsx
+++ b/frontend/tests/components/C2ConfigCard.test.tsx
@@ -57,7 +57,7 @@ describe('C2ConfigCard — with config (has_token=true)', () => {
   it('shows Replace token affordance when has_token=true', async () => {
     renderWithProviders(<C2ConfigCard engagementId={1} />);
     await waitFor(() => {
-      expect(screen.getByText('Replace token')).toBeInTheDocument();
+      expect(screen.getByText('Remplacer le token')).toBeInTheDocument();
     });
     // Token input shows placeholder bullets (readOnly)
     const tokenInput = screen.getByTestId('c2-token-input') as HTMLInputElement;
@@ -75,9 +75,9 @@ describe('C2ConfigCard — with config (has_token=true)', () => {
   it('clicking Replace token makes input editable', async () => {
     renderWithProviders(<C2ConfigCard engagementId={1} />);
     await waitFor(() => {
-      expect(screen.getByText('Replace token')).toBeInTheDocument();
+      expect(screen.getByText('Remplacer le token')).toBeInTheDocument();
     });
-    fireEvent.click(screen.getByText('Replace token'));
+    fireEvent.click(screen.getByText('Remplacer le token'));
     await waitFor(() => {
       const tokenInput = screen.getByTestId('c2-token-input') as HTMLInputElement;
       expect(tokenInput.readOnly).toBeFalsy();
@@ -99,7 +99,7 @@ describe('C2ConfigCard — with config (has_token=true)', () => {
     });
     fireEvent.click(screen.getByTestId('c2-test-btn'));
     await waitFor(() => {
-      expect(screen.getByText('Connected')).toBeInTheDocument();
+      expect(screen.getByText('Connecté')).toBeInTheDocument();
     });
   });
 
@@ -124,7 +124,7 @@ describe('C2ConfigCard — 503 disabled state', () => {
     renderWithProviders(<C2ConfigCard engagementId={1} />);
     await waitFor(() => {
       expect(
-        screen.getByText(/C2 features are disabled/i),
+        screen.getByText(/fonctionnalités C2 sont désactivées/i),
       ).toBeInTheDocument();
     });
     expect(screen.getByTestId('c2-save-btn')).toBeDisabled();
diff --git a/frontend/tests/components/C2TasksPanel.test.tsx b/frontend/tests/components/C2TasksPanel.test.tsx
index b4214aa..2a52b5d 100644
--- a/frontend/tests/components/C2TasksPanel.test.tsx
+++ b/frontend/tests/components/C2TasksPanel.test.tsx
@@ -66,7 +66,7 @@ describe('C2TasksPanel — empty state', () => {
     await waitFor(() => {
       expect(screen.getByTestId('c2-tasks-panel')).toBeInTheDocument();
     });
-    expect(screen.getByText(/No C2 tasks yet/i)).toBeInTheDocument();
+    expect(screen.getByText(/Aucune tâche C2/i)).toBeInTheDocument();
     expect(screen.queryByTestId('c2-task-row')).toBeNull();
   });
 });
diff --git a/frontend/tests/components/ExecuteViaC2Modal.test.tsx b/frontend/tests/components/ExecuteViaC2Modal.test.tsx
index a92d1dc..713e433 100644
--- a/frontend/tests/components/ExecuteViaC2Modal.test.tsx
+++ b/frontend/tests/components/ExecuteViaC2Modal.test.tsx
@@ -66,7 +66,7 @@ describe('ExecuteViaC2Modal', () => {
   it('renders modal with title and callback table', async () => {
     renderModal();
     expect(screen.getByTestId('c2-modal')).toBeInTheDocument();
-    expect(screen.getByText('Execute via C2')).toBeInTheDocument();
+    expect(screen.getByText('Exécuter via C2')).toBeInTheDocument();
     await waitFor(() => {
       expect(screen.getAllByTestId('c2-callback-row')).toHaveLength(2);
     });
@@ -148,7 +148,7 @@ describe('ExecuteViaC2Modal', () => {
     await waitFor(() => {
       expect(screen.getAllByTestId('c2-callback-row')).toHaveLength(2);
     });
-    fireEvent.click(screen.getByRole('button', { name: /cancel/i }));
+    fireEvent.click(screen.getByRole('button', { name: /Annuler/i }));
     expect(onClose).toHaveBeenCalled();
   });
 
diff --git a/frontend/tests/components/ImportC2HistoryModal.test.tsx b/frontend/tests/components/ImportC2HistoryModal.test.tsx
index 58f98d2..237a723 100644
--- a/frontend/tests/components/ImportC2HistoryModal.test.tsx
+++ b/frontend/tests/components/ImportC2HistoryModal.test.tsx
@@ -88,7 +88,7 @@ describe('ImportC2HistoryModal — step 1: callback picker', () => {
   it('renders modal with title and callback rows', async () => {
     renderModal();
     expect(screen.getByTestId('c2-import-modal')).toBeInTheDocument();
-    expect(screen.getByText('Import C2 history')).toBeInTheDocument();
+    expect(screen.getByText("Importer l'historique C2")).toBeInTheDocument();
     await waitFor(() => {
       expect(screen.getAllByTestId('c2-import-callback-row')).toHaveLength(2);
     });
@@ -322,7 +322,7 @@ describe('ImportC2HistoryModal — toast wording', () => {
     fireEvent.click(screen.getByTestId('c2-import-submit-btn'));
 
     await waitFor(() => {
-      expect(screen.getByText('Imported 1 task(s)')).toBeInTheDocument();
+      expect(screen.getByText('1 tâche(s) importée(s)')).toBeInTheDocument();
     });
   });
 
@@ -342,7 +342,7 @@ describe('ImportC2HistoryModal — toast wording', () => {
 
     await waitFor(() => {
       expect(
-        screen.getByText('Imported 0 task(s), 1 already attached'),
+        screen.getByText('0 importée(s), 1 déjà attachée(s)'),
       ).toBeInTheDocument();
     });
   });
@@ -374,7 +374,7 @@ describe('ImportC2HistoryModal — Cancel button', () => {
     await waitFor(() => {
       expect(screen.getAllByTestId('c2-import-callback-row')).toHaveLength(2);
     });
-    fireEvent.click(screen.getByRole('button', { name: /cancel/i }));
+    fireEvent.click(screen.getByRole('button', { name: /Annuler/i }));
     expect(onClose).toHaveBeenCalled();
   });
 });
diff --git a/frontend/tests/i18n.test.ts b/frontend/tests/i18n.test.ts
new file mode 100644
index 0000000..8dbeade
--- /dev/null
+++ b/frontend/tests/i18n.test.ts
@@ -0,0 +1,46 @@
+import { describe, expect, it } from 'vitest';
+import i18n from '@/i18n/index';
+import { engagementStatusLabel, simulationStatusLabel } from '@/i18n/status';
+import { formatDate, formatDateTime } from '@/lib/format';
+
+describe('i18n smoke tests', () => {
+  it('resolves common.save to French', () => {
+    expect(i18n.t('common.save')).toBe('Enregistrer');
+  });
+
+  it('missing key returns the key path', () => {
+    expect(i18n.t('this.key.does.not.exist')).toBe('this.key.does.not.exist');
+  });
+
+  it('simulationStatusLabel done → Terminé', () => {
+    expect(simulationStatusLabel('done')).toBe('Terminé');
+  });
+
+  it('engagementStatusLabel active → Actif', () => {
+    expect(engagementStatusLabel('active')).toBe('Actif');
+  });
+
+  it('interpolation inserts the value', () => {
+    expect(i18n.t('engagement.list.deleteConfirm', { name: 'Test' })).toContain('Test');
+  });
+});
+
+describe('format helpers', () => {
+  it('formatDate returns — for null', () => {
+    expect(formatDate(null)).toBe('—');
+  });
+
+  it('formatDate returns — for undefined', () => {
+    expect(formatDate(undefined)).toBe('—');
+  });
+
+  it('formatDate formats ISO date in fr-FR', () => {
+    const result = formatDate('2026-06-01');
+    expect(result).toMatch(/\d{2}\/\d{2}\/\d{4}/);
+  });
+
+  it('formatDateTime returns a non-empty string for valid ISO', () => {
+    const result = formatDateTime('2026-06-01T08:00:00');
+    expect(result.length).toBeGreaterThan(0);
+  });
+});
diff --git a/frontend/tests/states.test.tsx b/frontend/tests/states.test.tsx
index 9c340d1..4b0297e 100644
--- a/frontend/tests/states.test.tsx
+++ b/frontend/tests/states.test.tsx
@@ -22,13 +22,13 @@ describe('ErrorState', () => {
     const onRetry = vi.fn();
     render(<ErrorState message="Boom" onRetry={onRetry} />);
     expect(screen.getByTestId('error-state')).toHaveTextContent('Boom');
-    await userEvent.click(screen.getByRole('button', { name: /retry/i }));
+    await userEvent.click(screen.getByRole('button', { name: /réessayer/i }));
     expect(onRetry).toHaveBeenCalledTimes(1);
   });
 
   it('omits retry button when no handler given', () => {
     render(<ErrorState message="Boom" />);
-    expect(screen.queryByRole('button', { name: /retry/i })).toBeNull();
+    expect(screen.queryByRole('button', { name: /réessayer/i })).toBeNull();
   });
 });
 
diff --git a/frontend/vitest.setup.ts b/frontend/vitest.setup.ts
index bb02c60..4ad2b0d 100644
--- a/frontend/vitest.setup.ts
+++ b/frontend/vitest.setup.ts
@@ -1 +1,2 @@
 import '@testing-library/jest-dom/vitest';
+import './src/i18n';
diff --git a/tasks/todo.md b/tasks/todo.md
index 02b3964..11df455 100644
--- a/tasks/todo.md
+++ b/tasks/todo.md
@@ -1,164 +1,260 @@
-# Sprint 11 — Spectrum UX port : 4 primitives + compact density global
+# Sprint 12 — i18n FR complet + EngagementDetailPage tab merge
 
-**Base** : `origin/main` (PR #12 mergée — sprint 8 + 9 + 10 en).
-**Branch** : `sprint/11-spectrum-ux`.
-**Scope** : frontend-only sprint, 5 livrables coordonnés. Pas de backend, pas de schéma, pas de nouvelle API. Pas de modif tokens couleurs/spacing/font dans tailwind.config.
+**Base** : `sprint/11-spectrum-ux` (PR #13 ouverte, pas encore mergée). Sprint 12 enchaîne directement.
+**Worktree** : `.claude/worktrees/sprint-12-i18n-fr/` (dédié — conforme à la mémoire worktree-per-sprint).
+**Branch** : `sprint/12-i18n-fr`.
+**Scope** : frontend uniquement. Backend intouché.
 
 ---
 
-## Contexte
-
-Analyse Spectrum (`/home/user/Documents/01_Projects/spectrum`) faite via workflow. Résultat : Spectrum n'a **pas de design system** (Tailwind raw + violet ramp + recipes inlinées 30× partout). Mimic est structurellement meilleur. On ne porte pas la philosophie Spectrum — on extrait **5 patterns isolés** qui survivent au brutalisme Mimic.
-
-## Constraints absolues
-
-1. **Primary `#024ad8` (Electric Blue) reste**. Pas de violet, pas de spectrum ramp.
-2. **Brutalisme reste** : `rounded-none` sur containers (sauf status pills + tab count pills + avatars), zero `transition-*`, zero `shadow-*`, hairline 1px borders.
-3. **Pas de modif `tailwind.config.*`** sauf si une nouvelle classe utility est strictement nécessaire (justifier dans le PR).
-4. **DESIGN.md amendments additives uniquement** — pas de modif des tokens existants.
-5. **Mono uniquement pour data** (IDs MITRE, dates ISO, commands, etc.) — rule sprint 7.
-
 ## Décisions binding (lockées par user)
 
-- **Q1 → B** : Tabs primitive **+ consumer EngagementDetailPage** (3 tabs : Schedule / Description / Simulations au lieu du stack vertical actuel).
-- **Q2 → B** : **Compact density GLOBAL** — toutes les tables passent à 32px row, pas opt-in. User accepte le tradeoff WCAG (touch target) sur Engagements list.
-- **Q3 → A** : AlertBanner + refactor `SimulationFormPage` (Done banner + SOC-blocked banner).
+1. **Approche i18n** : `react-i18next` complet (deps `react-i18next` + `i18next`, JSON FR, hook `useTranslation`).
+2. **Acronymes** : RT, SOC, MITRE, ATT&CK, C2, BAS, TLS, MITM, JWT, IP, URL, API, ID — **gardés en anglais** dans les valeurs FR.
+3. **Status enum** : valeurs DB (`pending`, `in_progress`, `done`, `planned`, `active`, `closed`) gardées EN — traduction au rendering layer via `i18n/status.ts`.
+4. **Format de date** : `fr-FR` locale (`jj/mm/aaaa`, ex. `20/06/2026`).
+5. **Ton toasts/alerts** : **bref** (ex. `"Engagement créé"`, pas `"Engagement enregistré avec succès"`).
+6. **Schedule → Description tab** : merger Schedule INTO Description. Résultat : 2 tabs (Description + Simulations).
+
+## Contraintes constantes
+
+- Primary `#024ad8` Electric Blue intouchée.
+- Brutalisme intact : `rounded-none` partout sauf status pills + tab count pills + avatars, zéro `transition-*`, zéro `shadow-*`.
+- `tailwind.config.*` inchangé sauf cas exceptionnel justifié.
+- DESIGN.md amendments additives uniquement.
+- Mono uniquement pour data (IDs MITRE, dates ISO côté backend, commands, etc.).
 
 ---
 
-## Livrables
+## Task 1 — Merge Schedule into Description (mécanique, commit 1)
 
-### Livrable 1 — `Tabs` primitive + `useHashTab` hook + consumer
+**File** : `frontend/src/pages/EngagementDetailPage.tsx`
 
-**Files** :
-- `frontend/src/hooks/useHashTab.ts` (NEW) — ~30 LoC. Reads `window.location.hash`, falls back to default ID, listens to `hashchange`, updates URL without reload. TypeScript pur, zéro style.
-- `frontend/src/components/Tabs.tsx` (NEW) — composant `<Tabs items={[{id, label, count?}]} activeId onChange />`. Underline variant.
-- `frontend/src/styles/index.css` — nouvelles recipes :
-  - `.tab-underline` — `text-graphite caption-bold cursor-pointer border-b-2 border-transparent hover:text-ink` (instantané, pas de transition)
-  - `.tab-underline-active` — `text-primary border-primary` (override)
-  - `.tab-count-pill` — `rounded-pill bg-cloud text-graphite text-[11px] px-xs py-0 font-mono`
-  - `.tab-count-pill-active` — `bg-primary-soft text-primary` (override)
-- `frontend/src/pages/EngagementDetailPage.tsx` — refactor en 3 tabs :
-  - Tab 1 "Schedule" (id `schedule`, default) — dates + statut + bouton "Edit engagement"
-  - Tab 2 "Description" (id `description`) — texte description
-  - Tab 3 "Simulations" (id `simulations`) — la liste actuelle de simulations
-  - Count pills sur tab 3 = nombre de simulations
-  - Tabs branchées sur `useHashTab('schedule')`
-- `DESIGN.md` — nouvelle subsection `### Navigation › Sub-page tabs` (additive)
+**Current** (3 tabs Schedule / Description / Simulations) :
+```tsx
+type TabId = 'schedule' | 'description' | 'simulations';
+const items: TabItem<TabId>[] = [
+  { id: 'schedule',    label: 'Schedule' },
+  { id: 'description', label: 'Description' },
+  { id: 'simulations', label: 'Simulations', count },
+];
+```
 
-**Brutalism check** :
-- Tab : `border-b-2` only, pas de bg, pas de rounded, pas de transition
-- Pill : `rounded-pill` autorisé (exception status pill DESIGN.md L125)
-- Hover : `hover:text-ink` instantané
+**Target** (2 tabs) :
+```tsx
+type TabId = 'description' | 'simulations';
+const items: TabItem<TabId>[] = [
+  { id: 'description', label: 'Description' },
+  { id: 'simulations', label: 'Simulations', count },
+];
+```
 
-### Livrable 2 — `AlertBanner` component + 4 recipes
+**Migration du contenu Schedule** : déplacer dans le panel Description, en HEADER (au-dessus du paragraphe description) :
+```tsx
+<header className="flex items-start justify-between gap-md mb-md">
+  <dl className="grid grid-cols-2 gap-x-lg gap-y-xxs text-caption-md">
+    <dt className="text-graphite">Start date</dt>     <dd>{formatDate(eng.start_date)}</dd>
+    <dt className="text-graphite">End date</dt>       <dd>{eng.end_date ? formatDate(eng.end_date) : '—'}</dd>
+    <dt className="text-graphite">Status</dt>         <dd><StatusBadge status={eng.status} /></dd>
+    <dt className="text-graphite">Created at</dt>     <dd>{formatDate(eng.created_at)}</dd>
+  </dl>
+  <Link to={`/engagements/${id}/edit`} className="btn-outline">Edit</Link>
+</header>
+<hr className="my-md border-hairline" />
+<h2 className="text-display-sm mb-sm">Description</h2>
+{eng.description || <p className="text-graphite">No description provided.</p>}
+```
 
-**Files** :
-- `frontend/src/components/AlertBanner.tsx` (NEW) — `<AlertBanner variant="error|warn|success|info" title? children />`. Brutalist : border-l-4 strip semantic, fill `bg-paper`, border `border-hairline` partout sauf le strip gauche, `rounded-none`. Icon Lucide à gauche (`AlertCircle` error, `AlertTriangle` warn, `CheckCircle` success, `Info` info) à `size={16}`.
-- `frontend/src/styles/index.css` — 4 nouvelles recipes :
-  - `.alert-error` — `bg-paper border border-hairline border-l-4 border-l-bloom-deep px-md py-sm flex items-start gap-sm`
-  - `.alert-warn` — same + `border-l-warn`
-  - `.alert-success` — same + `border-l-success`
-  - `.alert-info` — same + `border-l-primary`
-- `frontend/src/pages/SimulationFormPage.tsx` — refactor 2 banners hand-rollés (~L300 Done banner + ~L310 SOC-blocked banner) → `<AlertBanner variant="success">` / `<AlertBanner variant="warn">`.
-- `DESIGN.md` — extend `### Toast Notifications` avec subsection `### Inline Banners` (additive, mêmes 4 variants).
+- Default `useHashTab('description')` au lieu de `'schedule'`.
+- Header de la page (BackLink + name + créé par + Edit + Export) reste **au-dessus des tabs**, intouché.
+- Mettre à jour `EngagementDetailPage.test.tsx` si une assertion vise le tab "Schedule".
 
-**Note** : `bloom-deep`, `warn`, `success`, `primary` sont les tokens existants — pas de nouveau token couleur.
-
-### Livrable 3 — `BackLink` component (dédup)
-
-**Files** :
-- `frontend/src/components/BackLink.tsx` (NEW) — `<BackLink to="/engagements">Back to engagements</BackLink>`. Renders `← {children}` (ArrowLeft Lucide size=14, gap-xxs). Style : `text-graphite hover:text-primary caption-md` instantané.
-- Refactor consumers (3 instances hand-rollées) :
-  - `frontend/src/pages/EngagementDetailPage.tsx` (~L35)
-  - `frontend/src/pages/SimulationFormPage.tsx` (back-link en edit mode)
-  - `frontend/src/pages/TemplateFormPage.tsx` (back-link en edit mode)
-
-### Livrable 4 — `.table-compact` recipe + apply GLOBAL
-
-**Files** :
-- `frontend/src/styles/index.css` — nouvelle recipe (mais appliquée comme default, pas opt-in cette sprint per user decision Q2-B) :
-  - Soit : modifier la recipe `.card-product table` existante pour passer à 32px row, `caption-md` text, `py-xxs px-xs` cells, divider `border-hairline`.
-  - Soit : ajouter `.table-compact` puis l'appliquer à TOUTES les list pages (Engagements, Templates, Users, etc.).
-  - **Choix builder** : pick the cleaner path. Préférer modifier le default si toutes les tables doivent suivre, sinon `.table-compact` + apply partout.
-- Apply sur :
-  - `frontend/src/pages/EngagementsListPage.tsx`
-  - `frontend/src/pages/TemplatesListPage.tsx`
-  - `frontend/src/pages/UsersAdminPage.tsx`
-  - `frontend/src/components/SimulationList.tsx` (utilisé dans EngagementDetailPage)
-  - Toute autre table dans le code (grep `<table` dans `frontend/src/`)
-- `DESIGN.md` — `### Data Tables` section : modifier la ligne "Row min-height 44px" → "Row min-height 32px (compact density, all surfaces)". Documenter le tradeoff WCAG (touch target dérogé en faveur de la densité opérateur — c'est un BAS tool, pas un site grand public).
-
-**ATTENTION** : WCAG SC 2.5.5 (Target Size: Minimum) recommande 44×44. Tu déroges. Garder les boutons d'action des rows ≥ 24px d'icône avec padding pour préserver le hit area minimal. Tester en clavier + lecteur d'écran nicht regressé.
-
-### Livrable 5 — DESIGN.md amendments + CHANGELOG
-
-**Files** :
-- `DESIGN.md` :
-  - `### Navigation` : nouvelle subsection "Sub-page tabs" (livrable 1)
-  - `### Toast Notifications` : nouvelle subsection "Inline Banners" (livrable 2)
-  - `### Data Tables` : ligne row min-height passe à 32px + paragraphe rationale (livrable 4)
-- `CHANGELOG.md` : entrée Sprint 11 listant chaque primitive + ses tokens DESIGN.md.
+**Note** : les strings ci-dessus seront ensuite traduites dans le pass i18n. Pas la peine de les écrire en FR dans commit 1.
 
 ---
 
-## Sequencing
+## Task 2 — Full FR translation via react-i18next
 
-1. **frontend-builder** : livrables 1 + 2 + 3 + 4 + 5 en cascade. Une seule passe. Commits atomiques :
-   ```
-   feat(frontend): add Tabs primitive + useHashTab hook
-   feat(frontend): refactor EngagementDetailPage to 3-tab layout
-   feat(frontend): add AlertBanner component + 4 semantic variants
-   refactor(frontend): migrate SimulationFormPage banners to AlertBanner
-   feat(frontend): add BackLink helper + dedup 3 hand-rolled instances
-   feat(frontend): compact table density (32px row) global
-   docs(design): add tabs / inline banners / compact-table-density to DESIGN.md
-   ```
-   (collapse OK si plus efficace ; ~5-7 commits attendus)
-2. **design-reviewer** : visual + token compliance check. Focus :
-   - Underline tabs : pas de transition, pas de bg fill, border-b instantané
-   - Count pill : `rounded-pill` est dans l'exception DESIGN.md, OK
-   - AlertBanner : `border-l-4` semantic OK, pas de shadow
-   - BackLink : caption + icon align baseline
-   - 32px tables : densité lisible ? Hit area boutons d'action OK ?
-3. **code-reviewer** : sprint diff. Focus :
-   - Aucune transition / shadow / rounded leak
-   - useHashTab : `hashchange` listener cleanup dans useEffect return
-   - Tabs : prop API stable, fallback default ID si hash invalide
-   - AlertBanner : ARIA `role="alert"` ou `role="status"` selon variant
-   - BackLink : `to` est `string` ou objet React Router ? Choisir un seul
-4. **spec-reviewer** : `SPEC.md` n'a pas vocation à mentionner ces primitives, **skip ce sprint** sauf si tu détectes une feature côté backend qui aurait dérivé.
+### Structure cible
 
-## Contraintes tests
+```
+frontend/src/i18n/
+├── index.ts          # init i18next, single FR locale
+├── fr.json           # toutes les keys FR
+└── status.ts         # engagementStatusLabel + simulationStatusLabel
+```
 
-- `vitest --run` baseline **212/212** doit tenir.
-- **Ajouter 4 specs** (1 par new component) :
-  - `Tabs.test.tsx` — active state, hash sync, count pill render
-  - `AlertBanner.test.tsx` — 4 variants rendent les bonnes classes
-  - `BackLink.test.tsx` — render + click navigation
-  - `useHashTab.test.tsx` — hash read/write
-- `tsc --noEmit` + `eslint --max-warnings=0` clean.
-- Brutalism unit assertions : pour chaque new component, un test qui vérifie `expect(el).not.toHaveClass('rounded-md')` (sauf pill counter) + `.not.toHaveClass(/transition-/)` + `.not.toHaveClass(/shadow-/)`.
+### Init (`frontend/src/i18n/index.ts`)
+```ts
+import i18n from 'i18next';
+import { initReactI18next } from 'react-i18next';
+import fr from './fr.json';
+
+i18n.use(initReactI18next).init({
+  resources: { fr: { translation: fr } },
+  lng: 'fr',
+  fallbackLng: 'fr',
+  interpolation: { escapeValue: false },
+  returnEmptyString: false,
+});
+
+export default i18n;
+```
+
+Mount dans `frontend/src/main.tsx` : `import './i18n'` avant `<App />`.
+
+### Pattern usage
+```tsx
+const { t } = useTranslation();
+<button>{t('common.save')}</button>
+<h1>{t('engagement.list.title')}</h1>
+<p>{t('engagement.delete.confirm', { name: eng.name })}</p>
+```
+
+### Convention de keys — **nested by feature**
+
+```
+common.*            save, cancel, delete, edit, new, loading, retry, back, dismiss
+nav.*               engagements, templates, users, signOut, brand
+auth.*              login.title, login.subtitle, login.signIn, login.signingIn, login.invalid, forbidden
+engagement.list.*   title, subtitle, new, empty.title, empty.desc, col.name, col.status, col.start, col.end, col.createdBy, col.actions, view, edit, delete, deleteConfirm, toast.deleted, error.delete
+engagement.detail.* tabs.description, tabs.simulations, schedule.startDate, schedule.endDate, schedule.status, schedule.createdAt, edit, createdBy, noDescription, loading, errorLoad, notFound
+engagement.form.*   title.new, title.edit, subtitle.new, subtitle.edit, field.name, field.description, field.startDate, field.endDate, field.endDateHint, field.status, validation.nameRequired, validation.startDateRequired, validation.endDateAfterStart, btn.create, btn.save, btn.saving, btn.cancel, toast.created, toast.updated, error.save, error.load
+simulation.form.*   title.new, field.name, field.mitre, field.description, field.commands, field.commandsHint, field.prerequisites, field.executedAt, field.executionResult, btn.create, btn.creating, btn.save, btn.saving, btn.saveSoc, btn.markReview, btn.close, btn.reopen, btn.delete, btn.executeC2, btn.importC2History, btn.cancel, deleteConfirm.title, deleteConfirm.desc, deleteConfirm.confirm, deleteConfirm.cancel, banner.done, banner.socNotReady, header.redTeam, header.soc, field.logSource, field.logs, field.socComment, field.incidentNumber, validation.nameRequired, toast.created, toast.updated, toast.deleted, toast.markedReview, toast.closed, toast.reopened, toast.socUpdated, error.create, error.update, error.delete, error.soc, error.transition, loading, errorLoad
+template.list.*     title, subtitle, new, empty.title, empty.desc, col.name, col.description, col.commands, col.createdAt, edit, delete
+template.form.*     title.new, title.edit, field.name, field.description, field.descriptionPlaceholder, field.commands, field.commandsHint, field.commandsPlaceholder, field.prerequisites, field.prerequisitesPlaceholder, field.mitre, field.mitreSearch, field.mitreOpenMatrix, field.mitreEmpty, btn.save, btn.saving, btn.delete, btn.cancel, validation.nameRequired, toast.created, toast.saved, toast.deleted, deleteConfirm.title, deleteConfirm.desc, deleteConfirm.confirm, deleteConfirm.cancel, loading, errorLoad, errorSave, errorDelete
+user.admin.*        title, subtitle, new, col.username, col.role, col.createdAt, col.actions, role.admin, role.redteam, role.soc, field.username, field.password, btn.create, btn.creating, btn.resetPassword, btn.delete, btn.cancel, ...
+c2.config.*         title, disabled, field.url, field.urlHint, field.token, field.tokenHint, field.verifyTls, verifyTlsHint, btn.save, btn.saving, btn.test, btn.testing, btn.delete, toast.saved, toast.tested, toast.deleted, error.save, error.test, error.delete
+c2.tasks.*          title, empty, col.task, col.command, col.source, col.status, col.completedAt, refreshing
+c2.modal.execute.*  title, callback, btn.launch, btn.launching, btn.cancel, commandCount_one, commandCount_other, validation.callbackRequired, validation.commandsRequired, toast.launched, error.launch
+c2.modal.import.*   title, total, page, of, prev, next, btn.import, btn.importing, btn.cancel, selected, empty, toast.imported, toast.partial, error.import
+c2.modal.picker.*   title, empty, hostnameColon, lastCheckinColon
+mitre.matrix.*      title, filter, loading, error, applyItem_one, applyItem_other, clearAll, close, retry
+mitre.field.*       empty, search, openMatrix, savedToast, errorToast
+mitre.tag.*         remove
+state.*             loading, error.title, error.desc, empty.default, retry
+toast.*             dismiss
+status.engagement.* planned, active, closed
+status.simulation.* pending, in_progress, review_required, done
+```
+
+### Status enum map (`frontend/src/i18n/status.ts`)
+```ts
+import i18n from './index';
+import type { EngagementStatus, SimulationStatus } from '@/types';
+
+export const engagementStatusLabel = (s: EngagementStatus): string =>
+  i18n.t(`status.engagement.${s}`);
+export const simulationStatusLabel = (s: SimulationStatus): string =>
+  i18n.t(`status.simulation.${s}`);
+```
+
+Consumers : `StatusBadge.tsx`, `SimulationStatusBadge.tsx` si distinct, `EngagementDetailPage` (header dans Description tab), `EngagementFormPage` (STATUS_OPTIONS dérivé du map), `SimulationFormPage` banners (restructurer comme phrases entières dans JSON, pas inline status word).
+
+### Date formatting (`frontend/src/lib/format.ts`)
+```ts
+export const formatDate = (iso: string | null | undefined): string => {
+  if (!iso) return '—';
+  return new Date(iso).toLocaleDateString('fr-FR');  // jj/mm/aaaa
+};
+export const formatDateTime = (iso: string): string =>
+  new Date(iso).toLocaleString('fr-FR');
+```
+
+Replace raw ISO renders dans : `EngagementDetailPage`, `EngagementsListPage`, `TemplatesListPage`, `UsersAdminPage`. Garder ISO dans les commands / execution_result / params (data brut).
+
+### Acronymes — locked EN dans le JSON FR
+
+Exemples corrects :
+- `"c2.config.title": "Configuration C2"`
+- `"mitre.matrix.title": "Matrice MITRE ATT&CK"`
+- `"simulation.form.header.redTeam": "Red Team"` (acronyme idiom)
+- `"simulation.form.header.soc": "SOC"` (acronyme)
+- `"auth.forbidden": "Accès refusé"` (déjà FR dans le code)
+
+### Strings déjà FR (preserve)
+
+- `ProtectedRoute.tsx:35` → `'Accès refusé'` (déjà FR). Route via `t('auth.forbidden')`.
+- `Toast.test.tsx:28` → assertion `'Session expirée'`. Confirmer cohérence avec la key associée.
+
+### Composants out-of-scope
+
+`ForbiddenState.tsx` et `NotFoundState.tsx` n'existent pas — pas de keys i18n à créer. Si tu vois un cas où ils manquent, **flag dans le PR body** pour un sprint follow-up, ne crée rien.
+
+---
+
+## Counts (estimation workflow)
+
+| Métrique | Valeur |
+|---|---|
+| Strings UI uniques à traduire (dedup) | **~140 keys** |
+| Test assertions à update | **~123** (sur 193 raw matches, 70 sont data fixture) |
+| Fichiers source modifiés | **~30** |
+| Fichiers tests modifiés | **23** |
+| Nouveaux fichiers | 3 (`i18n/index.ts`, `i18n/fr.json`, `i18n/status.ts`) |
+
+---
+
+## Commits plan (10 commits)
+
+1. `feat(frontend): merge Schedule tab into Description on EngagementDetailPage`
+2. `chore(frontend): install react-i18next + i18next deps`
+3. `feat(frontend): scaffold i18n init, fr.json skeleton, status map`
+4. `feat(frontend): i18n common + nav + auth (Layout, LoginPage, ProtectedRoute)`
+5. `feat(frontend): i18n engagement pages (list, detail, form) + status map wiring`
+6. `feat(frontend): i18n simulation pages (form + list component)`
+7. `feat(frontend): i18n template pages (list + form + picker modal)`
+8. `feat(frontend): i18n MITRE components (matrix modal, picker, field, tag)`
+9. `feat(frontend): i18n C2 components (config, tasks, modals, picker)`
+10. `feat(frontend): i18n shared state components + users admin + fr-FR date formatting`
+
+**Ordre** : chaque commit = une slice verticale (source + tests mis à jour ensemble) → vitest reste vert à chaque commit.
+
+---
+
+## Tests strategy
+
+### Baseline
+- vitest **236/236** doit tenir à chaque commit.
+- Tests rendent avec i18n init déjà chargé (FR loaded), pas de mock setup needed.
+
+### Pattern de rewrite (3 stratégies)
+1. **Direct rewrite** (cas le plus fréquent) : `getByRole('button', { name: /save/i })` → `getByRole('button', { name: /enregistrer/i })`.
+2. **Refactor vers `data-testid`** (recommandé pour les boutons avec action semantics) : `data-testid="btn-save"` côté source, `getByTestId('btn-save')` côté test. Survit aux re-wordings futurs.
+   - Cible prioritaire : `SimulationFormPage.test.tsx` (5 boutons), `UsersAdminPage.test.tsx` (4), `TemplateFormPage.test.tsx` (4), `EngagementFormPage.test.tsx` (2).
+3. **Keep domain assertions** (~70 sites) : `getByText('T1078')`, `getByText('alice')`, `getByText('WIN-DC01')`, `getByText('whoami')`. Pas de change.
+
+### Nouveau test (commit 3)
+`frontend/tests/i18n.test.ts` :
+- i18n init avec `lng: 'fr'`.
+- `t('common.save')` → `'Enregistrer'`.
+- Missing key returns key path (debug).
+- `simulationStatusLabel('done')` → `'Terminé'`.
+- Interpolation : `t('engagement.delete.confirm', { name: 'X' })` contient `« X »`.
+
+---
+
+## DoD
+
+1. EngagementDetailPage a **2 tabs** (Description + Simulations). Schedule content = header block dans le panel Description. Edit button atteignable.
+2. `package.json` inclut `react-i18next` et `i18next`.
+3. `frontend/src/i18n/index.ts` initialise i18next avec FR comme `lng` ET `fallbackLng`.
+4. `frontend/src/i18n/fr.json` contient ~140 keys, organisées en namespaces nested.
+5. `frontend/src/i18n/status.ts` expose les 2 labels et est consommé partout où raw status est rendu.
+6. **Zéro string UI EN hardcodée** dans `frontend/src/pages/` + `frontend/src/components/`. Exceptions autorisées : acronymes (liste lockée), brand "Mimic", glyphes (`—`, `×`, `▾`, `▸`), API enum passthroughs, MITRE IDs, command/payload text.
+7. Dates rendues via `formatDate()` au format `fr-FR` (jj/mm/aaaa).
+8. `npm run test` → **236+ / 236+** (+5 nouveaux tests i18n).
+9. `npm run build` succès (zéro TS error, PostCSS clean — leçon `feedback_css_apply_tokens` respectée).
+10. **Manual smoke obligatoire** : login → engagements → detail → simulation form → templates → users → C2 config — chaque string visible est en FR (sauf acronymes + brand).
+11. CHANGELOG.md entrée sprint 12 listant migration i18n + tab merge.
+
+---
 
 ## Out of scope (explicite)
 
-- ❌ Side nav / drawer / breadcrumb component — top nav + BackLink suffit
-- ❌ Global engagement selector top-bar (Spectrum pattern rejeté)
-- ❌ Editor dynamic-column grid — pas d'éditeur dans Mimic
-- ❌ Dark mode rework
-- ❌ Toast queue system (les toasts actuels via `useToast` restent)
-- ❌ PDF/document deliverable
-- ❌ Color palette changes
-- ❌ Tokens spacing/typo dans tailwind.config
-
-## Definition of Done
-
-- ✅ 5 primitives livrées + EngagementDetailPage refactorée en tabs + SimulationFormPage banners migrés + BackLink dédup × 3
-- ✅ vitest **212+/212+** (4 new specs ajoutées), tsc + lint clean
-- ✅ pytest **469/469** intact (zéro backend touché)
-- ✅ Toutes tables passent à 32px row density (validation visuelle)
-- ✅ Design-reviewer APPROVED (brutalism check sur les 4 new recipes)
-- ✅ Code-reviewer APPROVED
-- ✅ DESIGN.md amendé (3 subsections additives)
-- ✅ CHANGELOG.md entrée sprint 11
-- ✅ PR ouverte sur Gitea avec body
+- ❌ Backend i18n (pas de translations DB-side)
+- ❌ Multi-langue (uniquement FR pour ce sprint, infra prête mais pas d'EN switcher)
+- ❌ Language picker UI
+- ❌ ForbiddenState / NotFoundState components creation
+- ❌ Color palette / brutalism / token changes
+- ❌ New features