From 09fd877a1d0866c8d635cebc49bbe332685df840 Mon Sep 17 00:00:00 2001
From: Jayme Klein <jaymerebula04@gmail.com>
Date: Thu, 13 Aug 2026 17:15:57 -0300
Subject: [PATCH] feat(ui): internationalize the console with i18next (en +
 pt-BR)

Adds react-i18next + i18next with browser-locale detection, a LanguageSwitcher,
and en/pt-BR translation bundles, wiring the auth screens, pages, and shared
components through t().
---
 ui/package-lock.json                          |  77 +-
 ui/package.json                               |   2 +
 ui/src/auth/ChangePasswordForm.tsx            |  21 +-
 ui/src/auth/ChangePasswordModal.tsx           |   8 +-
 ui/src/auth/ChangePasswordScreen.tsx          |  16 +-
 ui/src/auth/LoginScreen.tsx                   |  28 +-
 ui/src/auth/UnlockScreen.tsx                  |  35 +-
 ui/src/components/Pager.tsx                   |  18 +-
 .../collections/CollectionFormModal.tsx       |  20 +-
 .../components/documents/DocumentFilters.tsx  |  44 +-
 ui/src/components/documents/UploadZone.tsx    |  10 +-
 ui/src/components/graph/GraphCanvas.tsx       |  13 +-
 ui/src/components/layout/ErrorBoundary.tsx    |  35 +-
 ui/src/components/layout/LanguageSwitcher.tsx |  37 +
 ui/src/components/layout/Sidebar.tsx          |  34 +-
 ui/src/components/layout/Topbar.tsx           |  21 +-
 ui/src/components/search/ResultCard.tsx       |  10 +-
 ui/src/components/search/SearchResults.tsx    |  60 +-
 ui/src/components/search/WorkspaceTree.tsx    |  24 +-
 ui/src/components/settings/ConfigPanel.tsx    | 240 +++---
 ui/src/components/settings/McpPanel.tsx       |  86 +-
 ui/src/components/tags/TagChip.tsx            |   4 +-
 ui/src/components/tags/TagFilterBar.tsx       |  16 +-
 ui/src/components/tags/TagPicker.tsx          |  28 +-
 ui/src/components/ui/ConfirmDialog.tsx        |   8 +-
 ui/src/components/ui/CopyButton.tsx           |   8 +-
 ui/src/components/ui/Modal.tsx                |   4 +-
 ui/src/components/ui/QueryError.tsx           |   8 +-
 ui/src/components/ui/StatusBadge.tsx          |  25 +-
 ui/src/components/ui/Toast.tsx                |  18 +-
 ui/src/components/users/PermissionsModal.tsx  | 122 +--
 ui/src/components/users/RevealOncePanel.tsx   |   6 +-
 ui/src/components/users/UserFormModal.tsx     |  36 +-
 ui/src/components/users/UserKeyModal.tsx      |  42 +-
 .../workspaces/WorkspaceFormModal.tsx         |  20 +-
 ui/src/i18n/apiError.ts                       |  34 +
 ui/src/i18n/detect.ts                         |  57 ++
 ui/src/i18n/i18next.d.ts                      |  15 +
 ui/src/i18n/index.ts                          |  45 +
 ui/src/i18n/locales/en/translation.json       | 782 ++++++++++++++++++
 ui/src/i18n/locales/pt-BR/translation.json    | 782 ++++++++++++++++++
 ui/src/i18n/parity.ts                         |  16 +
 ui/src/lib/format.ts                          |  36 +-
 ui/src/main.tsx                               |   1 +
 ui/src/pages/Collections.tsx                  |  69 +-
 ui/src/pages/Dashboard.tsx                    |  49 +-
 ui/src/pages/Documents.tsx                    | 101 +--
 ui/src/pages/Graph.tsx                        |  52 +-
 ui/src/pages/Indexing.tsx                     |  45 +-
 ui/src/pages/IngestionQueue.tsx               | 112 +--
 ui/src/pages/Search.tsx                       |  52 +-
 ui/src/pages/Settings.tsx                     |  65 +-
 ui/src/pages/Tags.tsx                         | 112 +--
 ui/src/pages/Users.tsx                        |  84 +-
 ui/src/pages/Workspaces.tsx                   |  53 +-
 55 files changed, 2904 insertions(+), 842 deletions(-)
 create mode 100644 ui/src/components/layout/LanguageSwitcher.tsx
 create mode 100644 ui/src/i18n/apiError.ts
 create mode 100644 ui/src/i18n/detect.ts
 create mode 100644 ui/src/i18n/i18next.d.ts
 create mode 100644 ui/src/i18n/index.ts
 create mode 100644 ui/src/i18n/locales/en/translation.json
 create mode 100644 ui/src/i18n/locales/pt-BR/translation.json
 create mode 100644 ui/src/i18n/parity.ts

diff --git a/ui/package-lock.json b/ui/package-lock.json
index ae8ec9a..3730f92 100644
--- a/ui/package-lock.json
+++ b/ui/package-lock.json
@@ -12,9 +12,11 @@
         "@fontsource-variable/jetbrains-mono": "^5.1.1",
         "@fontsource-variable/public-sans": "^5.1.0",
         "@tanstack/react-query": "^5.51.1",
+        "i18next": "^26.3.6",
         "lucide-react": "^0.408.0",
         "react": "^18.3.1",
         "react-dom": "^18.3.1",
+        "react-i18next": "^17.0.11",
         "react-router-dom": "^6.24.0"
       },
       "devDependencies": {
@@ -2556,6 +2558,15 @@
         "node": ">= 0.4"
       }
     },
+    "node_modules/html-parse-stringify": {
+      "version": "4.0.1",
+      "resolved": "https://registry.npmjs.org/html-parse-stringify/-/html-parse-stringify-4.0.1.tgz",
+      "integrity": "sha512-0zHsZJrK7S3K2aucXWL6ycoYJ/iNtIcFHC/nYQgFklPtrv5LpJctIiSCroWZWeuoXvuyFdzp6KzjJQ+OT5MfFw==",
+      "license": "MIT",
+      "funding": {
+        "url": "https://locize.com"
+      }
+    },
     "node_modules/html2canvas": {
       "version": "1.4.1",
       "resolved": "https://registry.npmjs.org/html2canvas/-/html2canvas-1.4.1.tgz",
@@ -2569,6 +2580,34 @@
         "node": ">=8.0.0"
       }
     },
+    "node_modules/i18next": {
+      "version": "26.3.6",
+      "resolved": "https://registry.npmjs.org/i18next/-/i18next-26.3.6.tgz",
+      "integrity": "sha512-Bu5Z2nAXgfVyM8xvW3jk9EKRIuX37PudsrBViThNFx7CR7aaYTpP01cxNB/E4c4UUzTDiAZRstEhsRfPOL/8xA==",
+      "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 || ^7"
+      },
+      "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",
@@ -3160,6 +3199,33 @@
         "react": "^18.3.1"
       }
     },
+    "node_modules/react-i18next": {
+      "version": "17.0.11",
+      "resolved": "https://registry.npmjs.org/react-i18next/-/react-i18next-17.0.11.tgz",
+      "integrity": "sha512-cDtkXgxjuFTWUH6V+aQn1Ve5vDiUztCNPWW5GtSHDccsgRXO1nE6QFWCEmc1KAutrb3OUv87wFShJL5RhUwPXg==",
+      "license": "MIT",
+      "dependencies": {
+        "@babel/runtime": "^7.29.2",
+        "html-parse-stringify": "^4.0.1",
+        "use-sync-external-store": "^1.6.0"
+      },
+      "peerDependencies": {
+        "i18next": ">= 26.2.0",
+        "react": ">= 16.8.0",
+        "typescript": "^5 || ^6 || ^7"
+      },
+      "peerDependenciesMeta": {
+        "react-dom": {
+          "optional": true
+        },
+        "react-native": {
+          "optional": true
+        },
+        "typescript": {
+          "optional": true
+        }
+      }
+    },
     "node_modules/react-refresh": {
       "version": "0.17.0",
       "resolved": "https://registry.npmjs.org/react-refresh/-/react-refresh-0.17.0.tgz",
@@ -3567,7 +3633,7 @@
       "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",
@@ -3608,6 +3674,15 @@
         "browserslist": ">= 4.21.0"
       }
     },
+    "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",
diff --git a/ui/package.json b/ui/package.json
index 9ced4db..77990bb 100644
--- a/ui/package.json
+++ b/ui/package.json
@@ -14,9 +14,11 @@
     "@fontsource-variable/jetbrains-mono": "^5.1.1",
     "@fontsource-variable/public-sans": "^5.1.0",
     "@tanstack/react-query": "^5.51.1",
+    "i18next": "^26.3.6",
     "lucide-react": "^0.408.0",
     "react": "^18.3.1",
     "react-dom": "^18.3.1",
+    "react-i18next": "^17.0.11",
     "react-router-dom": "^6.24.0"
   },
   "devDependencies": {
diff --git a/ui/src/auth/ChangePasswordForm.tsx b/ui/src/auth/ChangePasswordForm.tsx
index 87d630c..9b4c90c 100644
--- a/ui/src/auth/ChangePasswordForm.tsx
+++ b/ui/src/auth/ChangePasswordForm.tsx
@@ -1,5 +1,7 @@
 import { useState, type FormEvent } from 'react'
+import { useTranslation } from 'react-i18next'
 import { ApiError } from '../api/client'
+import { apiErrorMessage } from '../i18n/apiError'
 import { Button, Field, Input } from '../components/ui'
 import { useAuth } from './AuthContext'
 
@@ -11,12 +13,13 @@ const MIN_LENGTH = 12
  * and the voluntary change modal.
  */
 export function ChangePasswordForm({
-  submitLabel = 'Update password',
+  submitLabel,
   onSuccess,
 }: {
   submitLabel?: string
   onSuccess?: () => void
 }) {
+  const { t } = useTranslation()
   const { changePassword } = useAuth()
   const [current, setCurrent] = useState('')
   const [next, setNext] = useState('')
@@ -37,14 +40,14 @@ export function ChangePasswordForm({
       await changePassword(current, next)
       onSuccess?.()
     } catch (err) {
-      setError(err instanceof ApiError ? err.message : 'Could not change the password.')
+      setError(err instanceof ApiError ? apiErrorMessage(err, t) : t('auth.password.failed'))
       setBusy(false)
     }
   }
 
   return (
     <form onSubmit={onSubmit} className="flex flex-col gap-4">
-      <Field label="Current password" htmlFor="cp-current">
+      <Field label={t('auth.password.current')} htmlFor="cp-current">
         <Input
           id="cp-current"
           type="password"
@@ -55,10 +58,10 @@ export function ChangePasswordForm({
         />
       </Field>
       <Field
-        label="New password"
+        label={t('auth.password.new')}
         htmlFor="cp-new"
-        hint={`At least ${MIN_LENGTH} characters.`}
-        error={tooShort ? `Use at least ${MIN_LENGTH} characters.` : undefined}
+        hint={t('auth.password.hint', { min: MIN_LENGTH })}
+        error={tooShort ? t('auth.password.tooShort', { min: MIN_LENGTH }) : undefined}
       >
         <Input
           id="cp-new"
@@ -69,9 +72,9 @@ export function ChangePasswordForm({
         />
       </Field>
       <Field
-        label="Confirm new password"
+        label={t('auth.password.confirm')}
         htmlFor="cp-confirm"
-        error={mismatch ? 'Passwords do not match.' : undefined}
+        error={mismatch ? t('auth.password.mismatch') : undefined}
       >
         <Input
           id="cp-confirm"
@@ -87,7 +90,7 @@ export function ChangePasswordForm({
         </p>
       )}
       <Button type="submit" loading={busy} disabled={!canSubmit} className="w-full">
-        {busy ? 'Saving…' : submitLabel}
+        {busy ? t('common.saving') : (submitLabel ?? t('auth.password.update'))}
       </Button>
     </form>
   )
diff --git a/ui/src/auth/ChangePasswordModal.tsx b/ui/src/auth/ChangePasswordModal.tsx
index ee854e4..5bb4d54 100644
--- a/ui/src/auth/ChangePasswordModal.tsx
+++ b/ui/src/auth/ChangePasswordModal.tsx
@@ -1,15 +1,17 @@
+import { useTranslation } from 'react-i18next'
 import { Modal, useToast } from '../components/ui'
 import { ChangePasswordForm } from './ChangePasswordForm'
 
 /** Voluntary password change, launched from the Topbar (dismissable, unlike the forced screen). */
 export function ChangePasswordModal({ open, onClose }: { open: boolean; onClose: () => void }) {
+  const { t } = useTranslation()
   const toast = useToast()
   return (
-    <Modal open={open} onClose={onClose} title="Change password">
+    <Modal open={open} onClose={onClose} title={t('auth.password.changeTitle')}>
       <ChangePasswordForm
-        submitLabel="Update password"
+        submitLabel={t('auth.password.update')}
         onSuccess={() => {
-          toast.success('Password updated.')
+          toast.success(t('auth.password.updated'))
           onClose()
         }}
       />
diff --git a/ui/src/auth/ChangePasswordScreen.tsx b/ui/src/auth/ChangePasswordScreen.tsx
index b09f50b..ee42389 100644
--- a/ui/src/auth/ChangePasswordScreen.tsx
+++ b/ui/src/auth/ChangePasswordScreen.tsx
@@ -1,4 +1,5 @@
 import { KeyRound } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
 import { ChangePasswordForm } from './ChangePasswordForm'
 import { useAuth } from './AuthContext'
 
@@ -8,6 +9,7 @@ import { useAuth } from './AuthContext'
  * `changePassword` clears the flag and the app renders.
  */
 export function ChangePasswordScreen() {
+  const { t } = useTranslation()
   const { currentUser, logout } = useAuth()
   return (
     <div className="flex min-h-screen items-center justify-center bg-canvas px-4">
@@ -16,19 +18,23 @@ export function ChangePasswordScreen() {
           <div className="mb-4 flex h-11 w-11 items-center justify-center rounded-card bg-accent-weak text-accent">
             <KeyRound className="h-6 w-6" />
           </div>
-          <h1 className="text-lg font-semibold tracking-tight text-ink">Set a new password</h1>
+          <h1 className="text-lg font-semibold tracking-tight text-ink">
+            {t('auth.password.setTitle')}
+          </h1>
           <p className="mt-1 text-[13px] text-ink-muted">
-            {currentUser?.username ? `Signed in as ${currentUser.username}. ` : ''}
-            Choose a new password to finish signing in.
+            {currentUser?.username
+              ? t('auth.password.signedInAs', { name: currentUser.username })
+              : ''}
+            {t('auth.password.chooseNew')}
           </p>
         </div>
-        <ChangePasswordForm submitLabel="Set password & continue" />
+        <ChangePasswordForm submitLabel={t('auth.password.setContinue')} />
         <button
           type="button"
           onClick={logout}
           className="mt-4 w-full text-center text-xs text-ink-faint hover:text-ink-muted"
         >
-          Sign out
+          {t('topbar.signOut')}
         </button>
       </div>
     </div>
diff --git a/ui/src/auth/LoginScreen.tsx b/ui/src/auth/LoginScreen.tsx
index 0977ccf..b86aefb 100644
--- a/ui/src/auth/LoginScreen.tsx
+++ b/ui/src/auth/LoginScreen.tsx
@@ -1,17 +1,18 @@
 import { useEffect, useRef, useState, type FormEvent } from 'react'
 import { LogIn } from 'lucide-react'
+import type { TFunction } from 'i18next'
+import { useTranslation } from 'react-i18next'
 import { ApiError } from '../api/client'
+import { apiErrorMessage } from '../i18n/apiError'
 import { Button } from '../components/ui/Button'
 import { Input } from '../components/ui/Input'
 import { useAuth } from './AuthContext'
 import { ApiReachLine, UnlockScreen, useApiReach } from './UnlockScreen'
 
 /** Maps a login failure to a coarse, credential-safe message. */
-function loginError(err: unknown): string {
-  if (err instanceof ApiError) {
-    return err.status === 401 ? 'Invalid username or password.' : err.message
-  }
-  return 'Could not reach the API. Is the stack running?'
+function loginError(err: unknown, t: TFunction): string {
+  if (err instanceof ApiError && err.status === 401) return t('auth.login.invalid')
+  return apiErrorMessage(err, t)
 }
 
 /**
@@ -19,6 +20,7 @@ function loginError(err: unknown): string {
  * swaps in the bootstrap {@link UnlockScreen} (break-glass admin access).
  */
 export function LoginScreen() {
+  const { t } = useTranslation()
   const { login } = useAuth()
   const { reach, health } = useApiReach()
   const [useMaster, setUseMaster] = useState(false)
@@ -42,7 +44,7 @@ export function LoginScreen() {
     try {
       await login(username.trim(), password)
     } catch (err) {
-      setError(loginError(err))
+      setError(loginError(err, t))
       setBusy(false)
     }
   }
@@ -55,23 +57,23 @@ export function LoginScreen() {
             <LogIn className="h-6 w-6" />
           </div>
           <h1 className="text-lg font-semibold tracking-tight text-ink">EmbedBase</h1>
-          <p className="mt-1 text-[13px] text-ink-muted">Sign in to your account.</p>
+          <p className="mt-1 text-[13px] text-ink-muted">{t('auth.login.subtitle')}</p>
         </div>
 
         <form onSubmit={onSubmit} className="flex flex-col gap-3">
           <Input
             ref={inputRef}
             autoComplete="username"
-            placeholder="Username"
-            aria-label="Username"
+            placeholder={t('auth.field.username')}
+            aria-label={t('auth.field.username')}
             value={username}
             onChange={(e) => setUsername(e.target.value)}
           />
           <Input
             type="password"
             autoComplete="current-password"
-            placeholder="Password"
-            aria-label="Password"
+            placeholder={t('auth.field.password')}
+            aria-label={t('auth.field.password')}
             aria-invalid={error != null}
             value={password}
             onChange={(e) => setPassword(e.target.value)}
@@ -87,7 +89,7 @@ export function LoginScreen() {
             disabled={!username.trim() || !password}
             className="w-full"
           >
-            {busy ? 'Signing in…' : 'Sign in'}
+            {busy ? t('auth.login.submitting') : t('auth.login.submit')}
           </Button>
         </form>
 
@@ -96,7 +98,7 @@ export function LoginScreen() {
           onClick={() => setUseMaster(true)}
           className="mt-4 w-full text-center text-xs text-ink-faint hover:text-ink-muted"
         >
-          Use master key instead
+          {t('auth.login.useMaster')}
         </button>
 
         <ApiReachLine reach={reach} health={health} />
diff --git a/ui/src/auth/UnlockScreen.tsx b/ui/src/auth/UnlockScreen.tsx
index 380ea42..edd55b4 100644
--- a/ui/src/auth/UnlockScreen.tsx
+++ b/ui/src/auth/UnlockScreen.tsx
@@ -1,6 +1,9 @@
 import { useEffect, useRef, useState, type FormEvent } from 'react'
 import { KeyRound, Loader2, ShieldCheck, ShieldAlert } from 'lucide-react'
+import type { TFunction } from 'i18next'
+import { useTranslation } from 'react-i18next'
 import { api, ApiError } from '../api/client'
+import { apiErrorMessage } from '../i18n/apiError'
 import type { Health } from '../api/types'
 import { useAuth } from './AuthContext'
 import { Button } from '../components/ui/Button'
@@ -26,13 +29,9 @@ export function useApiReach(): { reach: ApiReach; health: Health | null } {
 }
 
 /** Maps an unlock failure to a key-safe message (never echoes the key). */
-function unlockError(err: unknown): string {
-  if (err instanceof ApiError) {
-    return err.status === 401
-      ? 'That key was rejected. Check it and try again.'
-      : err.message
-  }
-  return 'Could not reach the API. Is the stack running?'
+function unlockError(err: unknown, t: TFunction): string {
+  if (err instanceof ApiError && err.status === 401) return t('auth.unlock.rejected')
+  return apiErrorMessage(err, t)
 }
 
 /**
@@ -41,6 +40,7 @@ function unlockError(err: unknown): string {
  * toggle. Submitting verifies the key against `/workspaces`.
  */
 export function UnlockScreen({ onBack }: { onBack?: () => void }) {
+  const { t } = useTranslation()
   const { unlock } = useAuth()
   const { reach, health } = useApiReach()
   const [key, setKey] = useState('')
@@ -60,7 +60,7 @@ export function UnlockScreen({ onBack }: { onBack?: () => void }) {
     try {
       await unlock(key.trim())
     } catch (err) {
-      setError(unlockError(err))
+      setError(unlockError(err, t))
       setBusy(false)
     }
   }
@@ -73,9 +73,7 @@ export function UnlockScreen({ onBack }: { onBack?: () => void }) {
             <KeyRound className="h-6 w-6" />
           </div>
           <h1 className="text-lg font-semibold tracking-tight text-ink">EmbedBase</h1>
-          <p className="mt-1 text-[13px] text-ink-muted">
-            Enter your master key to unlock the console.
-          </p>
+          <p className="mt-1 text-[13px] text-ink-muted">{t('auth.unlock.subtitle')}</p>
         </div>
 
         <form onSubmit={onSubmit} className="flex flex-col gap-3">
@@ -84,8 +82,8 @@ export function UnlockScreen({ onBack }: { onBack?: () => void }) {
             type="password"
             autoComplete="off"
             spellCheck={false}
-            placeholder="Master key"
-            aria-label="Master key"
+            placeholder={t('auth.unlock.masterKey')}
+            aria-label={t('auth.unlock.masterKey')}
             aria-invalid={error != null}
             value={key}
             onChange={(e) => setKey(e.target.value)}
@@ -97,7 +95,7 @@ export function UnlockScreen({ onBack }: { onBack?: () => void }) {
             </p>
           )}
           <Button type="submit" loading={busy} disabled={!key.trim()} className="w-full">
-            {busy ? 'Verifying…' : 'Unlock'}
+            {busy ? t('auth.unlock.submitting') : t('auth.unlock.submit')}
           </Button>
         </form>
 
@@ -107,7 +105,7 @@ export function UnlockScreen({ onBack }: { onBack?: () => void }) {
             onClick={onBack}
             className="mt-4 w-full text-center text-xs text-ink-faint hover:text-ink-muted"
           >
-            Back to sign in
+            {t('auth.unlock.back')}
           </button>
         )}
 
@@ -119,11 +117,12 @@ export function UnlockScreen({ onBack }: { onBack?: () => void }) {
 
 /** Subtle API-reachability footer beneath the unlock/login form. */
 export function ApiReachLine({ reach, health }: { reach: ApiReach; health: Health | null }) {
+  const { t } = useTranslation()
   if (reach === 'checking') {
     return (
       <p className="mt-6 flex items-center justify-center gap-1.5 text-xs text-ink-faint">
         <Loader2 className="h-3.5 w-3.5 animate-spin" />
-        Checking API…
+        {t('auth.api.checking')}
       </p>
     )
   }
@@ -131,14 +130,14 @@ export function ApiReachLine({ reach, health }: { reach: ApiReach; health: Healt
     return (
       <p className="mt-6 flex items-center justify-center gap-1.5 text-xs text-err">
         <ShieldAlert className="h-3.5 w-3.5" />
-        API unreachable
+        {t('auth.api.unreachable')}
       </p>
     )
   }
   return (
     <p className="mt-6 flex items-center justify-center gap-1.5 text-xs text-ink-faint">
       <ShieldCheck className="h-3.5 w-3.5 text-ok" />
-      API ready · {health?.embedding_model ?? 'model'}
+      {t('auth.api.ready', { model: health?.embedding_model ?? t('auth.api.modelFallback') })}
     </p>
   )
 }
diff --git a/ui/src/components/Pager.tsx b/ui/src/components/Pager.tsx
index cb37343..a8c60c8 100644
--- a/ui/src/components/Pager.tsx
+++ b/ui/src/components/Pager.tsx
@@ -1,3 +1,4 @@
+import { useTranslation } from 'react-i18next'
 import { cn } from '../lib/cn'
 import { Button } from './ui'
 
@@ -21,6 +22,7 @@ export function Pager({
    *  end of it first. Assumes the page gutter both callers share (see the class note below). */
   sticky?: boolean
 }) {
+  const { t } = useTranslation()
   if (total === 0) return null
   const start = page * pageSize + 1
   const end = Math.min((page + 1) * pageSize, total)
@@ -34,13 +36,7 @@ export function Pager({
         sticky && 'sticky bottom-0 z-10 -mx-8 border-t border-border bg-canvas px-8 py-3',
       )}
     >
-      <span>
-        Showing{' '}
-        <span className="tabular-nums text-ink">
-          {start}–{end}
-        </span>{' '}
-        of <span className="tabular-nums text-ink">{total}</span>
-      </span>
+      <span className="tabular-nums">{t('ui.pager.range', { from: start, to: end, total })}</span>
       <div className="flex items-center gap-2">
         <Button
           variant="ghost"
@@ -48,18 +44,16 @@ export function Pager({
           disabled={page === 0 || loading}
           onClick={() => onPage(page - 1)}
         >
-          Previous
+          {t('ui.pager.previous')}
         </Button>
-        <span className="tabular-nums">
-          Page {page + 1} of {lastPage + 1}
-        </span>
+        <span className="tabular-nums">{t('ui.pager.page', { page: page + 1, pages: lastPage + 1 })}</span>
         <Button
           variant="ghost"
           size="sm"
           disabled={page >= lastPage || loading}
           onClick={() => onPage(page + 1)}
         >
-          Next
+          {t('ui.pager.next')}
         </Button>
       </div>
     </div>
diff --git a/ui/src/components/collections/CollectionFormModal.tsx b/ui/src/components/collections/CollectionFormModal.tsx
index dbca492..d1c7c41 100644
--- a/ui/src/components/collections/CollectionFormModal.tsx
+++ b/ui/src/components/collections/CollectionFormModal.tsx
@@ -1,4 +1,5 @@
 import { useEffect, useState } from 'react'
+import { useTranslation } from 'react-i18next'
 import type { Collection } from '../../api/types'
 import {
   Button,
@@ -54,6 +55,7 @@ export function CollectionFormModal({
   onSubmit: (values: CollectionFormValues) => void
   onClose: () => void
 }) {
+  const { t } = useTranslation()
   const [values, setValues] = useState<CollectionFormValues>(DEFAULTS)
 
   // Reseed every time the modal opens so stale edits never leak between rows.
@@ -75,20 +77,20 @@ export function CollectionFormModal({
     <Modal
       open={open}
       onClose={onClose}
-      title={editing ? 'Edit collection' : 'New collection'}
+      title={editing ? t('collections.editTitle') : t('collections.new')}
       footer={
         <>
           <Button variant="secondary" onClick={onClose} disabled={submitting}>
-            Cancel
+            {t('common.cancel')}
           </Button>
           <Button onClick={submit} loading={submitting} disabled={!name}>
-            {editing ? 'Save changes' : 'Create'}
+            {editing ? t('common.saveChanges') : t('common.create')}
           </Button>
         </>
       }
     >
       <div className="flex flex-col gap-4">
-        <Field label="Name" htmlFor="col-name">
+        <Field label={t('common.name')} htmlFor="col-name">
           <Input
             id="col-name"
             autoFocus
@@ -97,21 +99,21 @@ export function CollectionFormModal({
             onKeyDown={(e) => {
               if (e.key === 'Enter') submit()
             }}
-            placeholder="e.g. Q3 Reports"
+            placeholder={t('collections.namePlaceholder')}
           />
         </Field>
-        <Field label="Description" htmlFor="col-desc" hint="Optional — what this collection holds.">
+        <Field label={t('common.description')} htmlFor="col-desc" hint={t('collections.descHint')}>
           <Textarea
             id="col-desc"
             value={values.description}
             onChange={(e) => set('description', e.target.value)}
-            placeholder="Optional"
+            placeholder={t('common.optional')}
           />
         </Field>
-        <Field label="Color">
+        <Field label={t('common.color')}>
           <ColorPicker value={values.color} onChange={(c) => set('color', c)} />
         </Field>
-        <Field label="Icon">
+        <Field label={t('common.icon')}>
           <IconPicker value={values.icon} onChange={(i) => set('icon', i)} />
         </Field>
       </div>
diff --git a/ui/src/components/documents/DocumentFilters.tsx b/ui/src/components/documents/DocumentFilters.tsx
index 24b40f0..f088283 100644
--- a/ui/src/components/documents/DocumentFilters.tsx
+++ b/ui/src/components/documents/DocumentFilters.tsx
@@ -1,5 +1,6 @@
 import { useState } from 'react'
 import { Search, SlidersHorizontal, X } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
 import {
   FILE_TYPES,
   filterInputCls as inputCls,
@@ -33,6 +34,7 @@ export function DocumentFilters({
   value: DocumentFilterValues
   onChange: (next: DocumentFilterValues) => void
 }) {
+  const { t } = useTranslation()
   const [expanded, setExpanded] = useState(false)
   const set = <K extends keyof DocumentFilterValues>(key: K, v: DocumentFilterValues[K]) =>
     onChange({ ...value, [key]: v })
@@ -46,48 +48,48 @@ export function DocumentFilters({
           <Search className="pointer-events-none absolute left-2.5 top-1/2 h-4 w-4 -translate-y-1/2 text-ink-faint" />
           <input
             className={`${inputCls} w-full pl-8`}
-            placeholder="Search filenames…"
+            placeholder={t('documents.filters.searchPlaceholder')}
             value={value.filename ?? ''}
             onChange={(e) => set('filename', text(e.target.value))}
           />
         </div>
         <select
           className={inputCls}
-          aria-label="Status"
+          aria-label={t('documents.filters.statusAria')}
           value={value.status ?? ''}
           onChange={(e) => set('status', text(e.target.value))}
         >
-          <option value="">Any status</option>
+          <option value="">{t('documents.filters.anyStatus')}</option>
           {STATUSES.map((s) => (
             <option key={s} value={s}>
-              {s}
+              {t(`status.${s}`)}
             </option>
           ))}
         </select>
         <select
           className={inputCls}
-          aria-label="File type"
+          aria-label={t('documents.filters.typeAria')}
           value={value.file_type ?? ''}
           onChange={(e) => set('file_type', text(e.target.value))}
         >
-          <option value="">Any type</option>
-          {FILE_TYPES.map((t) => (
-            <option key={t} value={t}>
-              {t}
+          <option value="">{t('documents.filters.anyType')}</option>
+          {FILE_TYPES.map((ft) => (
+            <option key={ft} value={ft}>
+              {ft}
             </option>
           ))}
         </select>
         <select
           className={inputCls}
-          aria-label="Indexed"
+          aria-label={t('documents.filters.indexedAria')}
           value={value.indexed === undefined ? '' : String(value.indexed)}
           onChange={(e) =>
             set('indexed', e.target.value === '' ? undefined : e.target.value === 'true')
           }
         >
-          <option value="">Indexed: any</option>
-          <option value="true">Indexed</option>
-          <option value="false">Not indexed</option>
+          <option value="">{t('documents.filters.indexedAny')}</option>
+          <option value="true">{t('documents.filters.indexed')}</option>
+          <option value="false">{t('documents.filters.notIndexed')}</option>
         </select>
         <button
           type="button"
@@ -97,7 +99,7 @@ export function DocumentFilters({
           }`}
         >
           <SlidersHorizontal className="h-4 w-4" />
-          More
+          {t('common.more')}
         </button>
         {active && (
           <button
@@ -106,7 +108,7 @@ export function DocumentFilters({
             className="inline-flex h-9 items-center gap-1 rounded-control px-2 text-[13px] text-ink-muted hover:text-ink"
           >
             <X className="h-4 w-4" />
-            Clear
+            {t('common.clear')}
           </button>
         )}
       </div>
@@ -115,23 +117,23 @@ export function DocumentFilters({
         <div className="flex flex-wrap items-center gap-x-3 gap-y-2 rounded-control border border-border/60 bg-canvas/50 p-2.5">
           <input
             className={inputCls}
-            placeholder="Storage backend"
+            placeholder={t('documents.filters.storageBackend')}
             value={value.storage_backend ?? ''}
             onChange={(e) => set('storage_backend', text(e.target.value))}
           />
           <input
             className={inputCls}
-            placeholder="Embedding model"
+            placeholder={t('documents.filters.embeddingModel')}
             value={value.embedding_model ?? ''}
             onChange={(e) => set('embedding_model', text(e.target.value))}
           />
           <label className="flex items-center gap-1.5 text-xs text-ink-muted">
-            Size (bytes)
+            {t('documents.filters.size')}
             <input
               type="number"
               min={0}
               className={`${inputCls} w-24`}
-              placeholder="min"
+              placeholder={t('common.min')}
               value={value.min_size ?? ''}
               onChange={(e) => set('min_size', num(e.target.value))}
             />
@@ -140,13 +142,13 @@ export function DocumentFilters({
               type="number"
               min={0}
               className={`${inputCls} w-24`}
-              placeholder="max"
+              placeholder={t('common.max')}
               value={value.max_size ?? ''}
               onChange={(e) => set('max_size', num(e.target.value))}
             />
           </label>
           <label className="flex items-center gap-1.5 text-xs text-ink-muted">
-            Created
+            {t('documents.filters.created')}
             <input
               type="date"
               className={`${inputCls} w-40`}
diff --git a/ui/src/components/documents/UploadZone.tsx b/ui/src/components/documents/UploadZone.tsx
index 1477830..4e348c3 100644
--- a/ui/src/components/documents/UploadZone.tsx
+++ b/ui/src/components/documents/UploadZone.tsx
@@ -1,5 +1,6 @@
 import { useRef, useState, type DragEvent } from 'react'
 import { UploadCloud } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
 import { cn } from '../../lib/cn'
 import { Spinner } from '../ui'
 
@@ -20,6 +21,7 @@ export function UploadZone({
   busy: boolean
   maxSizeMb: number
 }) {
+  const { t } = useTranslation()
   const inputRef = useRef<HTMLInputElement>(null)
   const [dragging, setDragging] = useState(false)
 
@@ -63,20 +65,18 @@ export function UploadZone({
         <UploadCloud className="h-7 w-7 text-ink-faint" />
       )}
       <p className="text-[13px] text-ink">
-        {busy ? 'Uploading…' : 'Drag files here, or '}
+        {busy ? t('documents.upload.uploading') : t('documents.upload.drag')}
         {!busy && (
           <button
             type="button"
             onClick={() => inputRef.current?.click()}
             className="font-medium text-accent hover:underline"
           >
-            browse
+            {t('documents.upload.browse')}
           </button>
         )}
       </p>
-      <p className="text-xs text-ink-faint">
-        PDF, text, Markdown · DOCX/PPTX with docling · up to {maxSizeMb} MB each
-      </p>
+      <p className="text-xs text-ink-faint">{t('documents.upload.hint', { max: maxSizeMb })}</p>
     </div>
   )
 }
diff --git a/ui/src/components/graph/GraphCanvas.tsx b/ui/src/components/graph/GraphCanvas.tsx
index 19a7cd4..d9165d8 100644
--- a/ui/src/components/graph/GraphCanvas.tsx
+++ b/ui/src/components/graph/GraphCanvas.tsx
@@ -1,6 +1,7 @@
 import { useEffect, useRef, useState, type ReactNode } from 'react'
 import { Graph } from '@antv/g6'
 import { Magnet, Maximize2, ZoomIn, ZoomOut } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
 import type { GraphResponse } from '../../api/types'
 import { toG6 } from '../../lib/toG6'
 import { Button } from '../ui'
@@ -100,6 +101,7 @@ export function GraphCanvas({
   selected?: string | null
   fitNonce?: number
 }) {
+  const { t } = useTranslation()
   const containerRef = useRef<HTMLDivElement>(null)
   const graphRef = useRef<Graph | null>(null)
   // Keep the latest onSelect without forcing a graph rebuild on identity change.
@@ -200,13 +202,13 @@ export function GraphCanvas({
       <div className="absolute bottom-3 right-3 flex flex-col items-end gap-2">
         <RepelControl value={repel} onChange={setRepel} onCommit={applyRepel} />
         <div className="flex flex-col gap-1.5">
-          <ControlButton label="Zoom in" onClick={() => void graphRef.current?.zoomBy(1.2, anim)}>
+          <ControlButton label={t('graph.zoomIn')} onClick={() => void graphRef.current?.zoomBy(1.2, anim)}>
             <ZoomIn className="h-6 w-6" />
           </ControlButton>
-          <ControlButton label="Zoom out" onClick={() => void graphRef.current?.zoomBy(0.8, anim)}>
+          <ControlButton label={t('graph.zoomOut')} onClick={() => void graphRef.current?.zoomBy(0.8, anim)}>
             <ZoomOut className="h-6 w-6" />
           </ControlButton>
-          <ControlButton label="Fit to view" onClick={() => void graphRef.current?.fitView()}>
+          <ControlButton label={t('graph.fitToView')} onClick={() => void graphRef.current?.fitView()}>
             <Maximize2 className="h-6 w-6" />
           </ControlButton>
         </div>
@@ -226,10 +228,11 @@ function RepelControl({
   onChange: (v: number) => void
   onCommit: (v: number) => void
 }) {
+  const { t } = useTranslation()
   return (
     <div
       className="flex items-center gap-2 rounded-control border border-border bg-surface/90 px-2.5 py-1.5 shadow-overlay backdrop-blur"
-      title="Repel force — how strongly nodes push each other apart"
+      title={t('graph.repel.title')}
     >
       <Magnet className="h-5 w-5 shrink-0 text-ink-muted" />
       <input
@@ -237,7 +240,7 @@ function RepelControl({
         min={MIN_REPEL}
         max={MAX_REPEL}
         value={value}
-        aria-label="Repel force"
+        aria-label={t('graph.repel.aria')}
         onChange={(e) => onChange(Number(e.target.value))}
         onPointerUp={() => onCommit(value)}
         onKeyUp={() => onCommit(value)}
diff --git a/ui/src/components/layout/ErrorBoundary.tsx b/ui/src/components/layout/ErrorBoundary.tsx
index 5dfe10e..59c8033 100644
--- a/ui/src/components/layout/ErrorBoundary.tsx
+++ b/ui/src/components/layout/ErrorBoundary.tsx
@@ -1,4 +1,5 @@
 import { Component, type ErrorInfo, type ReactNode } from 'react'
+import { useTranslation } from 'react-i18next'
 
 interface Props {
   children: ReactNode
@@ -8,6 +9,27 @@ interface State {
   error: Error | null
 }
 
+/**
+ * Fallback UI for a caught render error. Split out as a function component so it can
+ * localize its labels via `useTranslation` — a hook the class boundary itself can't use.
+ * The raw `error.message` is shown untranslated: it's the caught JS error's own text.
+ */
+function ErrorFallback({ error, onReset }: { error: Error; onReset: () => void }): ReactNode {
+  const { t } = useTranslation()
+  return (
+    <div className="flex h-screen flex-col items-center justify-center gap-3 bg-canvas px-6 text-center">
+      <h1 className="text-lg font-semibold text-ink">{t('ui.errorBoundary.title')}</h1>
+      <p className="max-w-md text-[13px] text-ink-muted">{error.message}</p>
+      <button
+        onClick={onReset}
+        className="rounded-control border border-border bg-surface px-4 py-2 text-sm font-medium text-ink transition-colors hover:bg-canvas"
+      >
+        {t('common.retry')}
+      </button>
+    </div>
+  )
+}
+
 /** Catches render-time errors and shows a recoverable fallback. */
 export class ErrorBoundary extends Component<Props, State> {
   state: State = { error: null }
@@ -24,18 +46,7 @@ export class ErrorBoundary extends Component<Props, State> {
   render(): ReactNode {
     const { error } = this.state
     if (error) {
-      return (
-        <div className="flex h-screen flex-col items-center justify-center gap-3 bg-canvas px-6 text-center">
-          <h1 className="text-lg font-semibold text-ink">Something went wrong</h1>
-          <p className="max-w-md text-[13px] text-ink-muted">{error.message}</p>
-          <button
-            onClick={() => this.setState({ error: null })}
-            className="rounded-control border border-border bg-surface px-4 py-2 text-sm font-medium text-ink transition-colors hover:bg-canvas"
-          >
-            Try again
-          </button>
-        </div>
-      )
+      return <ErrorFallback error={error} onReset={() => this.setState({ error: null })} />
     }
     return this.props.children
   }
diff --git a/ui/src/components/layout/LanguageSwitcher.tsx b/ui/src/components/layout/LanguageSwitcher.tsx
new file mode 100644
index 0000000..f087191
--- /dev/null
+++ b/ui/src/components/layout/LanguageSwitcher.tsx
@@ -0,0 +1,37 @@
+import { Check, Languages } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
+import { DropdownItem, DropdownMenu } from '../ui/DropdownMenu'
+import { setLanguage } from '../../i18n'
+import { SUPPORTED, type Lang } from '../../i18n/detect'
+
+/** Endonyms — a language is always named in its own tongue, so never translated. */
+const LANG_LABELS: Record<Lang, string> = {
+  en: 'English',
+  'pt-BR': 'Português (BR)',
+}
+
+/**
+ * Topbar control to switch the console language between the supported locales.
+ * Persistence + `<html lang>` / date-locale syncing are handled by the i18n layer
+ * (`i18n/index.ts`), so this only has to call `changeLanguage`.
+ */
+export function LanguageSwitcher() {
+  const { i18n, t } = useTranslation()
+  const active = i18n.resolvedLanguage
+  return (
+    <DropdownMenu
+      triggerAriaLabel={t('topbar.language')}
+      triggerIcon={<Languages className="h-4 w-4" />}
+    >
+      {SUPPORTED.map((lang) => (
+        <DropdownItem
+          key={lang}
+          icon={active === lang ? <Check className="h-4 w-4" /> : undefined}
+          onSelect={() => setLanguage(lang)}
+        >
+          {LANG_LABELS[lang]}
+        </DropdownItem>
+      ))}
+    </DropdownMenu>
+  )
+}
diff --git a/ui/src/components/layout/Sidebar.tsx b/ui/src/components/layout/Sidebar.tsx
index 5a8203d..57c8631 100644
--- a/ui/src/components/layout/Sidebar.tsx
+++ b/ui/src/components/layout/Sidebar.tsx
@@ -1,11 +1,15 @@
 import { NavLink } from 'react-router-dom'
 import { DatabaseZap, FolderKanban, LayoutDashboard, ListChecks, Search, Settings, Users, Workflow, type LucideIcon } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
 import { cn } from '../../lib/cn'
 import { useAuth } from '../../auth/AuthContext'
 
+/** The nav labels are translation keys under `nav.*`, resolved at render. */
+type NavLabelKey = `nav.${'dashboard' | 'workspaces' | 'graph' | 'search' | 'indexing' | 'ingestionQueue' | 'users' | 'settings'}`
+
 interface NavItem {
   to: string
-  label: string
+  labelKey: NavLabelKey
   icon: LucideIcon
   end?: boolean
 }
@@ -13,31 +17,32 @@ interface NavItem {
 // Admins see the full console; a non-admin sees only the data plane they're scoped
 // to (browse their permitted workspaces + search + the ingestion views below).
 const ADMIN_MAIN: NavItem[] = [
-  { to: '/', label: 'Dashboard', icon: LayoutDashboard, end: true },
-  { to: '/workspaces', label: 'Workspaces', icon: FolderKanban },
-  { to: '/graph', label: 'Graph', icon: Workflow },
-  { to: '/search', label: 'Search', icon: Search },
+  { to: '/', labelKey: 'nav.dashboard', icon: LayoutDashboard, end: true },
+  { to: '/workspaces', labelKey: 'nav.workspaces', icon: FolderKanban },
+  { to: '/graph', labelKey: 'nav.graph', icon: Workflow },
+  { to: '/search', labelKey: 'nav.search', icon: Search },
 ]
 
 const USER_MAIN: NavItem[] = [
-  { to: '/workspaces', label: 'Workspaces', icon: FolderKanban },
-  { to: '/search', label: 'Search', icon: Search },
+  { to: '/workspaces', labelKey: 'nav.workspaces', icon: FolderKanban },
+  { to: '/search', labelKey: 'nav.search', icon: Search },
 ]
 
 // Ingestion views — everyone sees them; the backend scopes their contents to the
 // caller's grants (a non-admin sees only their permitted collections' jobs/coverage).
 const INGESTION_ITEMS: NavItem[] = [
-  { to: '/indexing', label: 'Indexing', icon: DatabaseZap },
-  { to: '/ingestion-queue', label: 'Ingestion Queue', icon: ListChecks },
+  { to: '/indexing', labelKey: 'nav.indexing', icon: DatabaseZap },
+  { to: '/ingestion-queue', labelKey: 'nav.ingestionQueue', icon: ListChecks },
 ]
 
 // Grouped under the "Admin" heading in the sidebar (admins only).
 const ADMIN_ITEMS: NavItem[] = [
-  { to: '/users', label: 'Users', icon: Users },
-  { to: '/settings', label: 'Settings', icon: Settings },
+  { to: '/users', labelKey: 'nav.users', icon: Users },
+  { to: '/settings', labelKey: 'nav.settings', icon: Settings },
 ]
 
-function NavItemLink({ to, label, icon: Icon, end }: NavItem) {
+function NavItemLink({ to, labelKey, icon: Icon, end }: NavItem) {
+  const { t } = useTranslation()
   return (
     <NavLink
       to={to}
@@ -52,12 +57,13 @@ function NavItemLink({ to, label, icon: Icon, end }: NavItem) {
       }
     >
       <Icon className="h-5 w-5" />
-      {label}
+      {t(labelKey)}
     </NavLink>
   )
 }
 
 export function Sidebar() {
+  const { t } = useTranslation()
   const { isAdmin } = useAuth()
   const mainItems = [...(isAdmin ? ADMIN_MAIN : USER_MAIN), ...INGESTION_ITEMS]
   return (
@@ -75,7 +81,7 @@ export function Sidebar() {
         {isAdmin && (
           <>
             <div className="mt-4 px-3 pb-1 text-xs font-semibold uppercase tracking-wide text-ink-faint">
-              Admin
+              {t('nav.admin')}
             </div>
             {ADMIN_ITEMS.map((item) => (
               <NavItemLink key={item.to} {...item} />
diff --git a/ui/src/components/layout/Topbar.tsx b/ui/src/components/layout/Topbar.tsx
index 7ead544..376a678 100644
--- a/ui/src/components/layout/Topbar.tsx
+++ b/ui/src/components/layout/Topbar.tsx
@@ -1,13 +1,17 @@
 import { KeyRound, LogOut } from 'lucide-react'
 import { useState, type ReactNode } from 'react'
+import { useTranslation } from 'react-i18next'
 import { useAuth } from '../../auth/AuthContext'
 import { ChangePasswordModal } from '../../auth/ChangePasswordModal'
+import { LanguageSwitcher } from './LanguageSwitcher'
 
 /**
- * Top bar with a breadcrumb slot and the account controls: who's signed in, an
- * optional change-password action (session users only), and Sign out.
+ * Top bar with a breadcrumb slot and the account controls: the language switcher,
+ * who's signed in, an optional change-password action (session users only), and
+ * Sign out.
  */
 export function Topbar({ children }: { children?: ReactNode }) {
+  const { t } = useTranslation()
   const { currentUser, isAdmin, logout } = useAuth()
   const [changing, setChanging] = useState(false)
 
@@ -15,29 +19,30 @@ export function Topbar({ children }: { children?: ReactNode }) {
     <header className="flex h-14 shrink-0 items-center justify-between border-b border-border bg-surface px-6">
       <div className="flex items-center gap-2 text-[13px] text-ink-muted">{children}</div>
       <div className="flex items-center gap-2">
+        <LanguageSwitcher />
         <span className="text-xs text-ink-faint" title={currentUser?.email ?? undefined}>
-          {currentUser ? currentUser.username : 'Master key'}
-          {isAdmin ? ' · admin' : ''}
+          {currentUser ? currentUser.username : t('topbar.masterKey')}
+          {isAdmin ? t('topbar.adminSuffix') : ''}
         </span>
         {currentUser && (
           <button
             type="button"
             onClick={() => setChanging(true)}
-            title="Change your password"
+            title={t('topbar.changePasswordTitle')}
             className="flex items-center gap-1.5 rounded-full border border-border bg-canvas px-3 py-1 text-xs font-medium text-ink-muted transition-colors hover:border-ink-faint hover:text-ink"
           >
             <KeyRound className="h-3.5 w-3.5" />
-            Change password
+            {t('topbar.changePassword')}
           </button>
         )}
         <button
           type="button"
           onClick={logout}
-          title="Sign out and clear your session"
+          title={t('topbar.signOutTitle')}
           className="flex items-center gap-1.5 rounded-full border border-border bg-canvas px-3 py-1 text-xs font-medium text-ink-muted transition-colors hover:border-ink-faint hover:text-ink"
         >
           <LogOut className="h-3.5 w-3.5" />
-          Sign out
+          {t('topbar.signOut')}
         </button>
       </div>
       <ChangePasswordModal open={changing} onClose={() => setChanging(false)} />
diff --git a/ui/src/components/search/ResultCard.tsx b/ui/src/components/search/ResultCard.tsx
index c31ab1b..e36a2ad 100644
--- a/ui/src/components/search/ResultCard.tsx
+++ b/ui/src/components/search/ResultCard.tsx
@@ -1,5 +1,6 @@
 import type { ReactNode } from 'react'
 import { FileText, Layers } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
 import type { SearchResult } from '../../api/types'
 import { Badge, Card } from '../ui'
 
@@ -33,6 +34,7 @@ function highlight(text: string, query: string): ReactNode {
 
 /** A single ranked search hit: rank, score, provenance, and emphasized text. */
 export function ResultCard({ result, query }: { result: SearchResult; query: string }) {
+  const { t } = useTranslation()
   const src = result.source
   return (
     <Card className="p-4">
@@ -49,20 +51,20 @@ export function ResultCard({ result, query }: { result: SearchResult; query: str
             <span className="truncate text-xs text-ink-faint">{src.workspace_name}</span>
           )}
         </div>
-        <span className="shrink-0 font-mono text-xs text-accent" title="Relevance score">
+        <span className="shrink-0 font-mono text-xs text-accent" title={t('search.relevanceScore')}>
           {result.score.toFixed(3)}
         </span>
       </div>
       {src && (src.filename || src.page_number !== null || src.page_range) && (
         <p className="mb-2 flex items-center gap-1.5 text-xs text-ink-muted">
           <FileText className="h-3.5 w-3.5 shrink-0" />
-          <span className="truncate">{src.filename ?? 'Unknown file'}</span>
+          <span className="truncate">{src.filename ?? t('search.unknownFile')}</span>
           {/* A span merged across pages advertises its full range; a single hit shows its page. */}
           {src.page_range ? (
-            <span className="text-ink-faint">· pp.{src.page_range}</span>
+            <span className="text-ink-faint">{t('search.pages', { range: src.page_range })}</span>
           ) : (
             src.page_number !== null && (
-              <span className="text-ink-faint">· p.{src.page_number}</span>
+              <span className="text-ink-faint">{t('search.page', { page: src.page_number })}</span>
             )
           )}
         </p>
diff --git a/ui/src/components/search/SearchResults.tsx b/ui/src/components/search/SearchResults.tsx
index 8f97dcc..b31a581 100644
--- a/ui/src/components/search/SearchResults.tsx
+++ b/ui/src/components/search/SearchResults.tsx
@@ -1,18 +1,18 @@
 import type { UseMutationResult } from '@tanstack/react-query'
 import { AlertTriangle, SearchX, Telescope } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
 import type { CollectionStat, SearchMode, SearchRequest, SearchResponse } from '../../api/types'
 import { Card, EmptyState, QueryError, Skeleton } from '../ui'
+import { apiErrorMessage } from '../../i18n/apiError'
 import { ResultCard } from './ResultCard'
 
-const MODE: Record<SearchMode, { label: string; cls: string; hint: string }> = {
-  hybrid: { label: 'Hybrid', cls: 'border-accent/40 text-accent', hint: 'BM25 + semantic' },
-  semantic: { label: 'Semantic', cls: 'border-border text-ink-muted', hint: 'Vector similarity' },
-  bm25: { label: 'BM25', cls: 'border-border text-ink-muted', hint: 'Keyword ranking' },
-  semantic_only: {
-    label: 'Semantic only',
-    cls: 'border-warn/40 text-warn',
-    hint: 'BM25 index unavailable — fell back to semantic',
-  },
+/** Per-mode chip styling; the label and hint are resolved from `search.mode.*` /
+ *  `search.modeHint.*` at render time. */
+const MODE_CLS: Record<SearchMode, string> = {
+  hybrid: 'border-accent/40 text-accent',
+  semantic: 'border-border text-ink-muted',
+  bm25: 'border-border text-ink-muted',
+  semantic_only: 'border-warn/40 text-warn',
 }
 
 /** Results pane: drives off the search mutation across all of its states. */
@@ -21,6 +21,7 @@ export function SearchResults({
 }: {
   mutation: UseMutationResult<SearchResponse, Error, SearchRequest>
 }) {
+  const { t } = useTranslation()
   if (mutation.isPending) {
     return (
       <div className="flex flex-col gap-3">
@@ -31,15 +32,15 @@ export function SearchResults({
     )
   }
   if (mutation.isError) {
-    return <QueryError title="Search failed" message={mutation.error.message} />
+    return <QueryError title={t('search.failed')} message={apiErrorMessage(mutation.error, t)} />
   }
   const res = mutation.data
   if (!res) {
     return (
       <EmptyState
         icon={<Telescope className="h-7 w-7" />}
-        title="Search your collections"
-        description="Pick one or more collections on the left, type a query, and run it."
+        title={t('search.empty.title')}
+        description={t('search.empty.description')}
       />
     )
   }
@@ -51,8 +52,8 @@ export function SearchResults({
       {res.results.length === 0 ? (
         <EmptyState
           icon={<SearchX className="h-7 w-7" />}
-          title="No matches"
-          description="No chunks matched this query in the selected collections. Try broadening the query or relaxing filters."
+          title={t('search.noMatches.title')}
+          description={t('search.noMatches.description')}
         />
       ) : (
         res.results.map((r) => <ResultCard key={r.chunk_id} result={r} query={query} />)
@@ -64,17 +65,23 @@ export function SearchResults({
 
 /** Mode chip + millisecond timing line. */
 function ResultsHeader({ res }: { res: SearchResponse }) {
-  const mode = MODE[res.search_mode] ?? MODE.semantic
+  const { t } = useTranslation()
+  const mode = res.search_mode
+  const cls = MODE_CLS[mode] ?? MODE_CLS.semantic
   return (
     <div className="flex items-center justify-between gap-3">
       <span
-        className={`inline-flex items-center gap-1.5 rounded-full border px-2 py-0.5 text-xs font-medium ${mode.cls}`}
-        title={mode.hint}
+        className={`inline-flex items-center gap-1.5 rounded-full border px-2 py-0.5 text-xs font-medium ${cls}`}
+        title={t(`search.modeHint.${mode}`)}
       >
-        {mode.label}
+        {t(`search.mode.${mode}`)}
       </span>
       <span className="font-mono text-xs text-ink-faint">
-        embed {res.query_embedding_ms}ms · search {res.search_ms}ms · total {res.total_ms}ms
+        {t('search.timing', {
+          embed: res.query_embedding_ms,
+          search: res.search_ms,
+          total: res.total_ms,
+        })}
       </span>
     </div>
   )
@@ -82,12 +89,14 @@ function ResultsHeader({ res }: { res: SearchResponse }) {
 
 /** Warns that filters or available matches starved the requested `top_k`. */
 function UnderDeliveredBanner({ topK }: { topK?: number }) {
+  const { t } = useTranslation()
   return (
     <div className="flex items-start gap-2 rounded-card border border-warn/30 bg-warn/5 px-3.5 py-3">
       <AlertTriangle className="mt-0.5 h-5 w-5 shrink-0 text-warn" />
       <p className="text-[13px] text-ink-muted">
-        Fewer results than requested{topK ? ` (top_k ${topK})` : ''}. A selective filter or a small
-        candidate pool left some slots unfilled.
+        {topK
+          ? t('search.underDelivered.withTopK', { topK })
+          : t('search.underDelivered.noTopK')}
       </p>
     </div>
   )
@@ -95,12 +104,13 @@ function UnderDeliveredBanner({ topK }: { topK?: number }) {
 
 /** Per-collection retrieved / returned / contributed breakdown. */
 function CollectionStatsPanel({ stats }: { stats: Record<string, CollectionStat> }) {
+  const { t } = useTranslation()
   const entries = Object.values(stats)
   if (entries.length === 0) return null
   return (
     <Card className="p-4">
       <h3 className="mb-3 text-xs font-semibold uppercase tracking-wide text-ink-faint">
-        Per-collection breakdown
+        {t('search.breakdown.title')}
       </h3>
       <div className="flex flex-col gap-2">
         {entries.map((s) => (
@@ -110,7 +120,11 @@ function CollectionStatsPanel({ stats }: { stats: Record<string, CollectionStat>
               <span className="ml-1 text-ink-faint">· {s.workspace_name}</span>
             </span>
             <span className="shrink-0 font-mono text-xs text-ink-muted">
-              {s.retrieved_before_filter} → {s.returned_after_filter} · {s.contributed_to_top_k} in top-k
+              {t('search.breakdown.stats', {
+                retrieved: s.retrieved_before_filter,
+                returned: s.returned_after_filter,
+                contributed: s.contributed_to_top_k,
+              })}
             </span>
           </div>
         ))}
diff --git a/ui/src/components/search/WorkspaceTree.tsx b/ui/src/components/search/WorkspaceTree.tsx
index 7a7a539..42599de 100644
--- a/ui/src/components/search/WorkspaceTree.tsx
+++ b/ui/src/components/search/WorkspaceTree.tsx
@@ -1,8 +1,10 @@
 import { useState } from 'react'
 import { ChevronDown, ChevronRight } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
 import { useCollections, useWorkspaces } from '../../api/hooks'
 import type { Collection, Workspace } from '../../api/types'
 import { EntityIcon, QueryError, Skeleton } from '../ui'
+import { apiErrorMessage } from '../../i18n/apiError'
 
 /** Selection callbacks shared down the tree. */
 interface TreeActions {
@@ -17,6 +19,7 @@ interface TreeActions {
  * select-all toggle.
  */
 export function WorkspaceTree(actions: TreeActions) {
+  const { t } = useTranslation()
   const { data, isLoading, isError, error, refetch } = useWorkspaces()
   if (isLoading) {
     return (
@@ -28,10 +31,16 @@ export function WorkspaceTree(actions: TreeActions) {
     )
   }
   if (isError) {
-    return <QueryError title="Could not load workspaces" message={error?.message} onRetry={() => void refetch()} />
+    return (
+      <QueryError
+        title={t('workspaces.error')}
+        message={error ? apiErrorMessage(error, t) : undefined}
+        onRetry={() => void refetch()}
+      />
+    )
   }
   if (!data || data.length === 0) {
-    return <p className="px-1 text-xs text-ink-faint">No workspaces yet.</p>
+    return <p className="px-1 text-xs text-ink-faint">{t('search.tree.noWorkspaces')}</p>
   }
   return (
     <div className="flex flex-col gap-0.5">
@@ -44,6 +53,7 @@ export function WorkspaceTree(actions: TreeActions) {
 
 /** One workspace and its collections, collapsible, with a select-all control. */
 function WorkspaceNode({ ws, selected, onToggle, onToggleMany }: { ws: Workspace } & TreeActions) {
+  const { t } = useTranslation()
   const { data, isLoading } = useCollections(ws.id)
   const [open, setOpen] = useState(true)
   const cols = data ?? []
@@ -57,7 +67,11 @@ function WorkspaceNode({ ws, selected, onToggle, onToggleMany }: { ws: Workspace
           type="button"
           onClick={() => setOpen((o) => !o)}
           className="text-ink-faint transition-colors hover:text-ink"
-          aria-label={open ? `Collapse ${ws.name}` : `Expand ${ws.name}`}
+          aria-label={
+            open
+              ? t('search.tree.collapse', { name: ws.name })
+              : t('search.tree.expand', { name: ws.name })
+          }
         >
           {open ? <ChevronDown className="h-4 w-4" /> : <ChevronRight className="h-4 w-4" />}
         </button>
@@ -71,7 +85,7 @@ function WorkspaceNode({ ws, selected, onToggle, onToggleMany }: { ws: Workspace
             onClick={() => onToggleMany(ids, !allSelected)}
             className="text-xs text-accent hover:underline"
           >
-            {allSelected ? 'Clear' : 'All'}
+            {allSelected ? t('common.clear') : t('search.tree.all')}
           </button>
         )}
       </div>
@@ -80,7 +94,7 @@ function WorkspaceNode({ ws, selected, onToggle, onToggleMany }: { ws: Workspace
           {isLoading ? (
             <Skeleton className="ml-2 h-6 w-32 rounded-control" />
           ) : cols.length === 0 ? (
-            <p className="px-2 py-1 text-xs text-ink-faint">No collections</p>
+            <p className="px-2 py-1 text-xs text-ink-faint">{t('search.tree.noCollections')}</p>
           ) : (
             cols.map((col) => (
               <CollectionCheckbox
diff --git a/ui/src/components/settings/ConfigPanel.tsx b/ui/src/components/settings/ConfigPanel.tsx
index a94311b..cb9a828 100644
--- a/ui/src/components/settings/ConfigPanel.tsx
+++ b/ui/src/components/settings/ConfigPanel.tsx
@@ -1,5 +1,6 @@
 import { useEffect, useState, type ReactNode } from 'react'
 import { AlertTriangle, Cpu, Info, Zap } from 'lucide-react'
+import { Trans, useTranslation } from 'react-i18next'
 import {
   SECRET_MASK,
   useAccelerator,
@@ -15,15 +16,17 @@ import type {
   SearchConfig,
 } from '../../api/types'
 import { Button, Card, Field, Input, QueryError, Select, Skeleton, useToast } from '../ui'
+import { apiErrorMessage } from '../../i18n/apiError'
 
 /** Runtime config — every section below applies live (API + workers reload). */
 export function ConfigPanel() {
+  const { t } = useTranslation()
   const { data, isLoading, isError, error, refetch } = useConfig()
   if (isLoading) return <Skeleton className="h-72 w-full rounded-card" />
   if (isError || !data) {
     return (
       <QueryError
-        title="Could not load configuration"
+        title={t('settings.config.loadError')}
         message={error?.message}
         onRetry={() => void refetch()}
       />
@@ -48,6 +51,7 @@ export function ConfigPanel() {
  * no longer read by any upload path, so the panel no longer offers it.
  */
 function StorageForm({ config }: { config: AppConfig }) {
+  const { t } = useTranslation()
   const storage = config.storage
   const activeName = storage.default
   const activeType = storage.backends?.[activeName]?.type
@@ -57,15 +61,15 @@ function StorageForm({ config }: { config: AppConfig }) {
       <div className="flex items-start gap-2 rounded-control border border-accent/30 bg-accent-weak px-3 py-2.5">
         <Info className="mt-0.5 h-5 w-5 shrink-0 text-accent" />
         <p className="text-[13px] text-ink-muted">
-          Where uploaded files are stored. The active backend is chosen in{' '}
-          <code>config.yaml</code> / <code>.env</code>. Retention is set{' '}
-          <strong>per upload</strong> (1–30 days, or kept permanently) on the Documents page —
-          there's no global retention setting.
+          <Trans
+            i18nKey="settings.storage.blurb"
+            components={{ code: <code />, strong: <strong /> }}
+          />
         </p>
       </div>
 
-      <Section title="Object storage">
-        <Field label="Active backend" htmlFor="storage-backend">
+      <Section title={t('settings.storage.title')}>
+        <Field label={t('settings.storage.activeBackend')} htmlFor="storage-backend">
           <Input
             id="storage-backend"
             value={activeType ? `${activeName} (${activeType})` : activeName}
@@ -84,6 +88,7 @@ function StorageForm({ config }: { config: AppConfig }) {
  * unwarned on a compatible (Ampere+) GPU; warned and PyMuPDF-preferred otherwise.
  */
 function ParserForm({ config }: { config: AppConfig }) {
+  const { t } = useTranslation()
   const toast = useToast()
   const update = useUpdateConfig()
   const accel = useAccelerator()
@@ -106,20 +111,21 @@ function ParserForm({ config }: { config: AppConfig }) {
     update.mutate(
       { ...config, parsers: { ...config.parsers, pdf_backend: backend } },
       {
-        onSuccess: () => toast.success('PDF backend saved. Services are reloading.'),
-        onError: (e) => toast.error(e.message),
+        onSuccess: () => toast.success(t('settings.toast.pdfSaved')),
+        onError: (e) => toast.error(apiErrorMessage(e, t)),
       },
     )
   }
 
   return (
     <Card className="flex flex-col gap-5 p-5">
-      <Section title="PDF parsing">
-        <Field label="Backend" htmlFor="pdf-backend">
+      <Section title={t('settings.parser.title')}>
+        <Field label={t('settings.parser.backend')} htmlFor="pdf-backend">
           <Select id="pdf-backend" value={backend} onChange={(e) => setBackend(e.target.value)}>
-            <option value="pymupdf">PyMuPDF — fast, one chunk per page</option>
+            <option value="pymupdf">{t('settings.parser.optionPymupdf')}</option>
             <option value="docling">
-              docling — section-aware + tables/OCR{compatible ? '' : ' (needs a GPU)'}
+              {t('settings.parser.optionDocling')}
+              {compatible ? '' : t('settings.parser.needsGpuSuffix')}
             </option>
           </Select>
         </Field>
@@ -131,17 +137,19 @@ function ParserForm({ config }: { config: AppConfig }) {
           <AlertTriangle className="mt-0.5 h-5 w-5 shrink-0 text-warn" />
           <p className="text-[13px] text-ink-muted">
             {accel.data?.device === 'cuda'
-              ? `Your GPU (${accel.data?.name}, capability ${accel.data?.capability}) is older than Ampere — `
-              : 'No GPU detected — '}
-            docling runs on CPU and is <strong>very slow</strong> (minutes per document, and large
-            PDFs can hit the ingestion time limit). PyMuPDF is recommended on this hardware.
+              ? t('settings.parser.gpuOlderThanAmpere', {
+                  name: accel.data?.name,
+                  capability: accel.data?.capability,
+                })
+              : t('settings.parser.noGpuDetected')}
+            <Trans i18nKey="settings.parser.doclingCpuWarn" components={{ strong: <strong /> }} />
           </p>
         </div>
       )}
 
       <div className="flex justify-end">
         <Button onClick={save} disabled={update.isPending}>
-          {update.isPending ? 'Saving…' : 'Save PDF backend'}
+          {update.isPending ? t('common.saving') : t('settings.parser.save')}
         </Button>
       </div>
     </Card>
@@ -156,8 +164,13 @@ function AcceleratorNote({
   accel: ReturnType<typeof useAccelerator>
   recommended: string
 }) {
+  const { t } = useTranslation()
   if (accel.isLoading) {
-    return <p className="text-[13px] text-ink-faint sm:col-span-2">Detecting GPU…</p>
+    return (
+      <p className="text-[13px] text-ink-faint sm:col-span-2">
+        {t('settings.parser.detectingGpu')}
+      </p>
+    )
   }
   const compatible = accel.data?.compatible ?? false
   return (
@@ -168,17 +181,25 @@ function AcceleratorNote({
         <Cpu className="h-4 w-4 shrink-0 text-ink-faint" />
       )}
       {compatible
-        ? `Compatible GPU detected (${accel.data?.name}, capability ${accel.data?.capability}).`
+        ? t('settings.parser.compatibleGpu', {
+            name: accel.data?.name,
+            capability: accel.data?.capability,
+          })
         : accel.data?.device === 'cuda'
-          ? `GPU ${accel.data?.name} (capability ${accel.data?.capability}) is below Ampere.`
-          : 'No compatible GPU detected.'}{' '}
-      Recommended: <strong className="ml-1">{recommended}</strong>.
+          ? t('settings.parser.gpuBelowAmpere', {
+              name: accel.data?.name,
+              capability: accel.data?.capability,
+            })
+          : t('settings.parser.noCompatibleGpu')}{' '}
+      {t('settings.parser.recommendedLabel')}{' '}
+      <strong className="ml-1">{recommended}</strong>.
     </p>
   )
 }
 
 /** Editable form for the embedding section; every other config section round-trips. */
 function EmbeddingForm({ config }: { config: AppConfig }) {
+  const { t } = useTranslation()
   const toast = useToast()
   const update = useUpdateConfig()
   const emb = config.embedding
@@ -225,8 +246,8 @@ function EmbeddingForm({ config }: { config: AppConfig }) {
     update.mutate(
       { ...config, embedding },
       {
-        onSuccess: () => toast.success('Embedding config saved. Services are reloading.'),
-        onError: (e) => toast.error(e.message),
+        onSuccess: () => toast.success(t('settings.toast.embeddingSaved')),
+        onError: (e) => toast.error(apiErrorMessage(e, t)),
       },
     )
   }
@@ -236,28 +257,28 @@ function EmbeddingForm({ config }: { config: AppConfig }) {
       <div className="flex items-start gap-2 rounded-control border border-warn/40 bg-warn/10 px-3 py-2.5">
         <AlertTriangle className="mt-0.5 h-5 w-5 shrink-0 text-warn" />
         <p className="text-[13px] text-ink-muted">
-          The embedding model turns documents into vectors. <strong>Changing the provider,
-            model, or output dimensions changes the vector size</strong> — existing collections
-          must be re-indexed or search will break. Changing only an API key is safe.
+          <Trans i18nKey="settings.embedding.blurb" components={{ strong: <strong /> }} />
         </p>
       </div>
 
-      <Section title="Embedding model">
-        <Field label="Provider" htmlFor="emb-provider">
+      <Section title={t('settings.embedding.title')}>
+        <Field label={t('settings.field.provider')} htmlFor="emb-provider">
           <Select id="emb-provider" value={provider} onChange={(e) => changeProvider(e.target.value)}>
-            <option value="ollama">Ollama (local)</option>
-            <option value="sentence_transformers">Sentence-Transformers (in-process)</option>
-            <option value="openai_compat">OpenAI-compatible</option>
-            <option value="gemini">Google Gemini</option>
+            <option value="ollama">{t('settings.provider.ollamaLocal')}</option>
+            <option value="sentence_transformers">
+              {t('settings.provider.sentenceTransformers')}
+            </option>
+            <option value="openai_compat">{t('settings.provider.openaiCompat')}</option>
+            <option value="gemini">{t('settings.provider.gemini')}</option>
           </Select>
         </Field>
         {provider === 'ollama' ? (
           <OllamaModelField id="emb-model" model={model} setModel={setModel} baseUrl={baseUrl} />
         ) : (
           <Field
-            label="Model"
+            label={t('settings.field.model')}
             htmlFor="emb-model"
-            hint={isGemini ? 'e.g. gemini-embedding-001' : 'the exact model id on this server'}
+            hint={isGemini ? t('settings.embedding.modelHintGemini') : t('settings.embedding.modelHint')}
           >
             <Input
               id="emb-model"
@@ -269,12 +290,12 @@ function EmbeddingForm({ config }: { config: AppConfig }) {
         )}
         {needsBaseUrl && (
           <Field
-            label="Base URL"
+            label={t('settings.field.baseUrl')}
             htmlFor="emb-base-url"
             hint={
               provider === 'openai_compat'
-                ? 'required — e.g. https://openrouter.ai/api'
-                : 'blank uses the Ollama default'
+                ? t('settings.field.baseUrlRequiredOpenrouter')
+                : t('settings.field.baseUrlOllamaDefault')
             }
           >
             <Input
@@ -290,23 +311,31 @@ function EmbeddingForm({ config }: { config: AppConfig }) {
           </Field>
         )}
         {needsKey && (
-          <Field label="API key" htmlFor="emb-api-key" hint="Write-only; never shown after saving.">
+          <Field
+            label={t('settings.field.apiKey')}
+            htmlFor="emb-api-key"
+            hint={t('settings.field.apiKeyHint')}
+          >
             <Input
               id="emb-api-key"
               type="password"
               value={apiKey}
               onChange={(e) => setApiKey(e.target.value)}
               placeholder={
-                keyIsSet ? 'key set — leave blank to keep' : isGemini ? 'AI Studio key' : 'API key'
+                keyIsSet
+                  ? t('settings.field.keySetPlaceholder')
+                  : isGemini
+                    ? t('settings.field.aiStudioKey')
+                    : t('settings.field.apiKey')
               }
             />
           </Field>
         )}
         {isGemini && (
           <Field
-            label="Output dimensions"
+            label={t('settings.embedding.outputDim')}
             htmlFor="emb-output-dim"
-            hint="optional; blank = full 3072"
+            hint={t('settings.embedding.outputDimHint')}
           >
             <Input
               id="emb-output-dim"
@@ -320,9 +349,9 @@ function EmbeddingForm({ config }: { config: AppConfig }) {
         )}
         {provider !== 'sentence_transformers' && (
           <Field
-            label="Max requests / min"
+            label={t('settings.embedding.maxRpm')}
             htmlFor="emb-max-rpm"
-            hint="throttle embeds so bulk ingestion stays under the provider's quota (each text = one request); blank or 0 = unlimited"
+            hint={t('settings.embedding.maxRpmHint')}
           >
             <Input
               id="emb-max-rpm"
@@ -330,7 +359,7 @@ function EmbeddingForm({ config }: { config: AppConfig }) {
               min="0"
               value={maxRpm}
               onChange={(e) => setMaxRpm(e.target.value)}
-              placeholder="0 (unlimited)"
+              placeholder={t('settings.embedding.maxRpmPlaceholder')}
             />
           </Field>
         )}
@@ -340,11 +369,11 @@ function EmbeddingForm({ config }: { config: AppConfig }) {
         {changesDimensions && (
           <span className="flex items-center gap-1.5 text-[13px] text-warn">
             <AlertTriangle className="h-4 w-4" />
-            Re-index required after saving
+            {t('settings.embedding.reindexRequired')}
           </span>
         )}
         <Button onClick={save} disabled={update.isPending}>
-          {update.isPending ? 'Saving…' : 'Save embedding config'}
+          {update.isPending ? t('common.saving') : t('settings.embedding.save')}
         </Button>
       </div>
     </Card>
@@ -358,6 +387,7 @@ function EmbeddingForm({ config }: { config: AppConfig }) {
  * Optional + graceful: a load or remote failure degrades to RRF-only ranking, never a 500.
  */
 function RerankerForm({ config }: { config: AppConfig }) {
+  const { t } = useTranslation()
   const toast = useToast()
   const update = useUpdateConfig()
   const rr = config.reranker
@@ -404,8 +434,8 @@ function RerankerForm({ config }: { config: AppConfig }) {
     update.mutate(
       { ...config, reranker },
       {
-        onSuccess: () => toast.success('Reranker config saved. Services are reloading.'),
-        onError: (e) => toast.error(e.message),
+        onSuccess: () => toast.success(t('settings.toast.rerankerSaved')),
+        onError: (e) => toast.error(apiErrorMessage(e, t)),
       },
     )
   }
@@ -415,13 +445,11 @@ function RerankerForm({ config }: { config: AppConfig }) {
       <div className="flex items-start gap-2 rounded-control border border-accent/30 bg-accent-weak px-3 py-2.5">
         <Info className="mt-0.5 h-5 w-5 shrink-0 text-accent" />
         <p className="text-[13px] text-ink-muted">
-          The reranker reorders retrieved chunks by true query relevance before the final cut — the
-          biggest precision win. It's <strong>optional and safe</strong>: if the model or a remote
-          provider is unavailable, search falls back to its normal ranking.
+          <Trans i18nKey="settings.reranker.blurb" components={{ strong: <strong /> }} />
         </p>
       </div>
 
-      <Section title="Reranker">
+      <Section title={t('settings.reranker.title')}>
         <label className="flex items-center gap-2 text-[13px] text-ink sm:col-span-2">
           <input
             type="checkbox"
@@ -429,25 +457,25 @@ function RerankerForm({ config }: { config: AppConfig }) {
             onChange={(e) => setEnabled(e.target.checked)}
             className="h-5 w-5 accent-accent"
           />
-          Enable reranking
+          {t('settings.reranker.enable')}
         </label>
-        <Field label="Provider" htmlFor="rr-provider">
+        <Field label={t('settings.field.provider')} htmlFor="rr-provider">
           <Select id="rr-provider" value={provider} onChange={(e) => changeProvider(e.target.value)}>
-            <option value="cross_encoder">Cross-encoder (local, no key)</option>
-            <option value="rerank_api">Hosted rerank API (Cohere / Jina / Voyage)</option>
-            <option value="llm">LLM-as-reranker</option>
+            <option value="cross_encoder">{t('settings.reranker.providerCrossEncoder')}</option>
+            <option value="rerank_api">{t('settings.reranker.providerRerankApi')}</option>
+            <option value="llm">{t('settings.reranker.providerLlm')}</option>
           </Select>
         </Field>
         {isLlm && (
-          <Field label="LLM provider" htmlFor="rr-llm-provider">
+          <Field label={t('settings.reranker.llmProvider')} htmlFor="rr-llm-provider">
             <Select
               id="rr-llm-provider"
               value={llmProvider}
               onChange={(e) => setLlmProvider(e.target.value)}
             >
-              <option value="gemini">Google Gemini (AI Studio)</option>
-              <option value="openai_compat">OpenAI-compatible</option>
-              <option value="ollama">Ollama (local)</option>
+              <option value="gemini">{t('settings.provider.geminiAiStudio')}</option>
+              <option value="openai_compat">{t('settings.provider.openaiCompat')}</option>
+              <option value="ollama">{t('settings.provider.ollamaLocal')}</option>
             </Select>
           </Field>
         )}
@@ -455,16 +483,16 @@ function RerankerForm({ config }: { config: AppConfig }) {
           <OllamaModelField id="rr-model" model={model} setModel={setModel} baseUrl={baseUrl} />
         ) : (
           <Field
-            label="Model"
+            label={t('settings.field.model')}
             htmlFor="rr-model"
             hint={
               isRerankApi
-                ? 'e.g. rerank-v3.5 (Cohere), jina-reranker-v2 (Jina)'
+                ? t('settings.reranker.modelHintRerankApi')
                 : isLlm
                   ? isLlmGemini
-                    ? 'e.g. gemini-2.5-flash'
-                    : 'the exact chat model id'
-                  : 'a HuggingFace cross-encoder id; the baked default is offline-safe'
+                    ? t('settings.reranker.modelHintGemini')
+                    : t('settings.reranker.modelHintLlm')
+                  : t('settings.reranker.modelHintCrossEncoder')
             }
           >
             <Input
@@ -477,7 +505,7 @@ function RerankerForm({ config }: { config: AppConfig }) {
                   : isLlm
                     ? isLlmGemini
                       ? 'gemini-2.5-flash'
-                      : 'model id'
+                      : t('settings.field.modelIdPlaceholder')
                     : 'cross-encoder/ms-marco-MiniLM-L6-v2'
               }
             />
@@ -485,14 +513,14 @@ function RerankerForm({ config }: { config: AppConfig }) {
         )}
         {needsBaseUrl && (
           <Field
-            label="Base URL"
+            label={t('settings.field.baseUrl')}
             htmlFor="rr-base-url"
             hint={
               isRerankApi
-                ? 'required — the full /rerank endpoint'
+                ? t('settings.reranker.baseUrlHintRerankApi')
                 : llmProvider === 'openai_compat'
-                  ? 'required — e.g. https://openrouter.ai/api'
-                  : 'blank uses the Ollama default'
+                  ? t('settings.field.baseUrlRequiredOpenrouter')
+                  : t('settings.field.baseUrlOllamaDefault')
             }
           >
             <Input
@@ -510,22 +538,30 @@ function RerankerForm({ config }: { config: AppConfig }) {
           </Field>
         )}
         {needsKey && (
-          <Field label="API key" htmlFor="rr-api-key" hint="Write-only; never shown after saving.">
+          <Field
+            label={t('settings.field.apiKey')}
+            htmlFor="rr-api-key"
+            hint={t('settings.field.apiKeyHint')}
+          >
             <Input
               id="rr-api-key"
               type="password"
               value={apiKey}
               onChange={(e) => setApiKey(e.target.value)}
               placeholder={
-                keyIsSet ? 'key set — leave blank to keep' : isLlmGemini ? 'AI Studio key' : 'API key'
+                keyIsSet
+                  ? t('settings.field.keySetPlaceholder')
+                  : isLlmGemini
+                    ? t('settings.field.aiStudioKey')
+                    : t('settings.field.apiKey')
               }
             />
           </Field>
         )}
         <Field
-          label="Candidates scored (top_n)"
+          label={t('settings.reranker.topN')}
           htmlFor="rr-top-n"
-          hint="max candidates the reranker scores per collection"
+          hint={t('settings.reranker.topNHint')}
         >
           <Input
             id="rr-top-n"
@@ -539,7 +575,7 @@ function RerankerForm({ config }: { config: AppConfig }) {
 
       <div className="flex justify-end">
         <Button onClick={save} disabled={update.isPending}>
-          {update.isPending ? 'Saving…' : 'Save reranker config'}
+          {update.isPending ? t('common.saving') : t('settings.reranker.save')}
         </Button>
       </div>
     </Card>
@@ -552,6 +588,7 @@ function RerankerForm({ config }: { config: AppConfig }) {
  * top_k onto the next page(s) comes back whole. 0 disables it; the other search knobs round-trip.
  */
 function SearchForm({ config }: { config: AppConfig }) {
+  const { t } = useTranslation()
   const toast = useToast()
   const update = useUpdateConfig()
   const search = config.search
@@ -567,8 +604,8 @@ function SearchForm({ config }: { config: AppConfig }) {
     update.mutate(
       { ...config, search: next },
       {
-        onSuccess: () => toast.success('Search config saved. Services are reloading.'),
-        onError: (e) => toast.error(e.message),
+        onSuccess: () => toast.success(t('settings.toast.searchSaved')),
+        onError: (e) => toast.error(apiErrorMessage(e, t)),
       },
     )
   }
@@ -578,18 +615,15 @@ function SearchForm({ config }: { config: AppConfig }) {
       <div className="flex items-start gap-2 rounded-control border border-accent/30 bg-accent-weak px-3 py-2.5">
         <Info className="mt-0.5 h-5 w-5 shrink-0 text-accent" />
         <p className="text-[13px] text-ink-muted">
-          Adjacency expansion pulls the chunks next to each result and merges them into one span, so
-          a section that runs across pages comes back whole instead of cut at the top-K boundary.
-          It's a plain lookup — no extra model calls — and <strong>safe</strong>: if it can't fetch,
-          search returns the un-expanded results.
+          <Trans i18nKey="settings.search.blurb" components={{ strong: <strong /> }} />
         </p>
       </div>
 
-      <Section title="Retrieval">
+      <Section title={t('settings.search.title')}>
         <Field
-          label="Adjacency expansion (neighbours)"
+          label={t('settings.search.expand')}
           htmlFor="search-expand"
-          hint={`chunks pulled on each side of a hit; 0 = off, max ${search.max_expand_neighbors}`}
+          hint={t('settings.search.expandHint', { max: search.max_expand_neighbors })}
         >
           <Input
             id="search-expand"
@@ -604,7 +638,7 @@ function SearchForm({ config }: { config: AppConfig }) {
 
       <div className="flex justify-end">
         <Button onClick={save} disabled={update.isPending}>
-          {update.isPending ? 'Saving…' : 'Save search config'}
+          {update.isPending ? t('common.saving') : t('settings.search.save')}
         </Button>
       </div>
     </Card>
@@ -618,6 +652,7 @@ function SearchForm({ config }: { config: AppConfig }) {
  * so a save binds from the next MCP call. `enabled` and `max_results` round-trip untouched.
  */
 function MCPForm({ config }: { config: AppConfig }) {
+  const { t } = useTranslation()
   const toast = useToast()
   const update = useUpdateConfig()
   const mcp = config.mcp
@@ -638,8 +673,8 @@ function MCPForm({ config }: { config: AppConfig }) {
     update.mutate(
       { ...config, mcp: next },
       {
-        onSuccess: () => toast.success('MCP config saved. Services are reloading.'),
-        onError: (e) => toast.error(e.message),
+        onSuccess: () => toast.success(t('settings.toast.mcpSaved')),
+        onError: (e) => toast.error(apiErrorMessage(e, t)),
       },
     )
   }
@@ -649,17 +684,15 @@ function MCPForm({ config }: { config: AppConfig }) {
       <div className="flex items-start gap-2 rounded-control border border-accent/30 bg-accent-weak px-3 py-2.5">
         <Info className="mt-0.5 h-5 w-5 shrink-0 text-accent" />
         <p className="text-[13px] text-ink-muted">
-          The MCP endpoint (<code>/api/mcp</code>) throttles each API key to this many requests per
-          minute; the next request in the same minute returns <code>429</code>. Each key gets its own
-          budget, and the new limit <strong>applies to the next MCP request</strong>
+          <Trans i18nKey="settings.mcp.blurb" components={{ code: <code />, strong: <strong /> }} />
         </p>
       </div>
 
-      <Section title="MCP server">
+      <Section title={t('settings.mcp.title')}>
         <Field
-          label="Rate limit (requests / min per key)"
+          label={t('settings.mcp.rateLimit')}
           htmlFor="mcp-rpm"
-          hint="per API key on /api/mcp; the next request in the same minute returns 429"
+          hint={t('settings.mcp.rateLimitHint')}
         >
           <Input
             id="mcp-rpm"
@@ -673,7 +706,7 @@ function MCPForm({ config }: { config: AppConfig }) {
 
       <div className="flex justify-end">
         <Button onClick={save} disabled={update.isPending}>
-          {update.isPending ? 'Saving…' : 'Save MCP config'}
+          {update.isPending ? t('common.saving') : t('settings.mcp.save')}
         </Button>
       </div>
     </Card>
@@ -696,6 +729,7 @@ function OllamaModelField({
   setModel: (m: string) => void
   baseUrl: string
 }) {
+  const { t } = useTranslation()
   const { data: models, isLoading, isError, error, refetch } = useOllamaModels(baseUrl, true)
 
   useEffect(() => {
@@ -703,12 +737,14 @@ function OllamaModelField({
   }, [models, model, setModel])
 
   return (
-    <Field label="Model" htmlFor={id} hint="Installed Ollama models">
+    <Field label={t('settings.field.model')} htmlFor={id} hint={t('settings.field.ollamaModelsHint')}>
       {isError ? (
         <div className="flex items-center gap-2">
-          <p className="text-[13px] text-danger">{error?.message ?? 'Could not reach Ollama'}</p>
+          <p className="text-[13px] text-danger">
+            {error?.message ?? t('settings.field.ollamaUnreachable')}
+          </p>
           <Button variant="ghost" onClick={() => void refetch()}>
-            Retry
+            {t('common.retry')}
           </Button>
         </div>
       ) : (
@@ -718,8 +754,8 @@ function OllamaModelField({
           onChange={(e) => setModel(e.target.value)}
           disabled={isLoading || !models?.length}
         >
-          {isLoading && <option>Loading models…</option>}
-          {!isLoading && !models?.length && <option>No models installed</option>}
+          {isLoading && <option>{t('settings.field.loadingModels')}</option>}
+          {!isLoading && !models?.length && <option>{t('settings.field.noModelsInstalled')}</option>}
           {models?.map((m) => (
             <option key={m} value={m}>
               {m}
diff --git a/ui/src/components/settings/McpPanel.tsx b/ui/src/components/settings/McpPanel.tsx
index dd074c9..da903e3 100644
--- a/ui/src/components/settings/McpPanel.tsx
+++ b/ui/src/components/settings/McpPanel.tsx
@@ -1,5 +1,6 @@
 import { useEffect, useState } from 'react'
 import { Download, ExternalLink } from 'lucide-react'
+import { Trans, useTranslation } from 'react-i18next'
 import { api } from '../../api/client'
 import { useMcpTools } from '../../api/hooks'
 import type { McpToolGroup } from '../../api/types'
@@ -191,6 +192,7 @@ ${TAGS_NOTE}
 
 /** A labelled monospace value row with a copy button. */
 function ValueRow({ label, value }: { label: string; value: string }) {
+  const { t } = useTranslation()
   return (
     <div className="flex flex-col gap-1">
       <span className="text-xs text-ink-faint">{label}</span>
@@ -198,7 +200,7 @@ function ValueRow({ label, value }: { label: string; value: string }) {
         <code className="flex-1 truncate rounded-control bg-canvas px-2 py-1.5 font-mono text-[13px] text-ink">
           {value}
         </code>
-        <CopyButton text={value} label="Copy" />
+        <CopyButton text={value} label={t('common.copy')} />
       </div>
     </div>
   )
@@ -212,6 +214,7 @@ function ValueRow({ label, value }: { label: string; value: string }) {
  * they track the registered tools automatically.
  */
 export function McpPanel() {
+  const { t } = useTranslation()
   // Address an MCP client uses to reach this server. Defaults to how the console
   // was reached; when that's localhost it only works on this machine, so we swap
   // in the LAN IP the server reports (same protocol/port) — reachable by other
@@ -247,16 +250,12 @@ export function McpPanel() {
   return (
     <div className="space-y-8">
       <section className="space-y-3">
-        <h2 className="text-sm font-semibold text-ink">Connection</h2>
+        <h2 className="text-sm font-semibold text-ink">{t('mcp.connection.title')}</h2>
         <Card className="flex flex-col gap-4 p-5">
           <Field
-            label="Server address"
+            label={t('mcp.connection.address')}
             htmlFor="mcp-address"
-            hint={
-              isLocal
-                ? "This address only works on this machine; the server couldn't determine a LAN IP for other devices to use."
-                : 'Auto-detected from the server. Used to build the endpoint and snippets below.'
-            }
+            hint={isLocal ? t('mcp.connection.addressHintLocal') : t('mcp.connection.addressHint')}
           >
             <Input
               id="mcp-address"
@@ -265,58 +264,58 @@ export function McpPanel() {
               spellCheck={false}
             />
           </Field>
-          <ValueRow label="Endpoint" value={`${address}/api/mcp/`} />
+          <ValueRow label={t('mcp.connection.endpoint')} value={`${address}/api/mcp/`} />
           <div className="grid grid-cols-1 gap-4 sm:grid-cols-2">
             <div className="flex flex-col gap-1">
-              <span className="text-xs text-ink-faint">Transport</span>
+              <span className="text-xs text-ink-faint">{t('mcp.connection.transport')}</span>
               <span className="font-mono text-[13px] text-ink">HTTP (streamable)</span>
             </div>
             <div className="flex flex-col gap-1">
-              <span className="text-xs text-ink-faint">Auth header</span>
+              <span className="text-xs text-ink-faint">{t('mcp.connection.authHeader')}</span>
               <span className="font-mono text-[13px] text-ink">Authorization: Bearer …</span>
             </div>
           </div>
           <p className="text-xs text-ink-muted">
-            Send an <strong>API key</strong> on every request as{' '}
-            <code className="font-mono">Authorization: Bearer &lt;key&gt;</code> or{' '}
-            <code className="font-mono">X-API-Key: &lt;key&gt;</code> — the master key, or a{' '}
-            <strong>per-user key</strong> for scoped access (each tool respects that user's
-            read/write grants). Substitute your own in the snippets below; nothing is embedded here.
+            <Trans
+              i18nKey="mcp.connection.authNote"
+              components={{
+                strong: <strong />,
+                authcode: <code className="font-mono">Authorization: Bearer &lt;key&gt;</code>,
+                apikeycode: <code className="font-mono">X-API-Key: &lt;key&gt;</code>,
+              }}
+            />
           </p>
         </Card>
       </section>
 
       <section className="space-y-3">
-        <h2 className="text-sm font-semibold text-ink">Client setup</h2>
+        <h2 className="text-sm font-semibold text-ink">{t('mcp.clientSetup.title')}</h2>
         <Card className="flex flex-col gap-3 p-5">
-          <p className="text-[13px] text-ink-muted">
-            Add this to your MCP client's server config (replace the placeholder key):
-          </p>
+          <p className="text-[13px] text-ink-muted">{t('mcp.clientSetup.instructions')}</p>
           <CodeBlock text={config} />
           <div className="flex justify-end">
-            <CopyButton text={config} label="Copy config" />
+            <CopyButton text={config} label={t('mcp.clientSetup.copyConfig')} />
           </div>
         </Card>
       </section>
 
       <section className="space-y-3">
         <div className="flex items-center justify-between gap-2">
-          <h2 className="text-sm font-semibold text-ink">Agent skill</h2>
+          <h2 className="text-sm font-semibold text-ink">{t('mcp.skill.title')}</h2>
           {skill && (
             <div className="flex gap-2">
               <Button variant="secondary" size="sm" onClick={downloadSkill}>
                 <Download className="h-4 w-4" />
-                Download .zip
+                {t('mcp.skill.download')}
               </Button>
             </div>
           )}
         </div>
         <p className="text-[13px] text-ink-muted">
-          A small skill folder (<code className="font-mono">SKILL.md</code> +{' '}
-          <code className="font-mono">references/</code>). Unzip it into your agent's skills directory
-          (e.g. <code className="font-mono">.claude/skills/embedbase/</code>) — the agent loads{' '}
-          <code className="font-mono">SKILL.md</code> up front and opens a reference file only when the
-          task needs it, so a read-only session never pulls in the upload rules.
+          <Trans
+            i18nKey="mcp.skill.folderNote"
+            components={{ code: <code className="font-mono" /> }}
+          />
         </p>
         {toolsQuery.isLoading ? (
           <Skeleton className="h-96 w-full rounded-card" />
@@ -326,7 +325,7 @@ export function McpPanel() {
               <CodeBlock text={skill} className="max-h-96" />
             </Card>
             <p className="text-xs text-ink-faint">
-              Bundled:{' '}
+              {t('mcp.skill.bundled')}{' '}
               {bundle
                 .filter((f) => f.name !== 'SKILL.md')
                 .map((f) => f.name)
@@ -334,24 +333,22 @@ export function McpPanel() {
             </p>
           </>
         ) : (
-          <p className="text-xs text-ink-muted">
-            The skill is unavailable — the tool catalogue could not be loaded.
-          </p>
+          <p className="text-xs text-ink-muted">{t('mcp.skill.unavailable')}</p>
         )}
       </section>
 
       <section className="space-y-3">
         <div className="flex items-center justify-between gap-2">
-          <h2 className="text-sm font-semibold text-ink">Tools</h2>
+          <h2 className="text-sm font-semibold text-ink">{t('mcp.tools.title')}</h2>
           {groups.length > 0 && (
             <span className="text-xs text-ink-faint">
-              {groups.reduce((n, g) => n + g.tools.length, 0)} tools · each respects your grants
+              {t('mcp.tools.count', { count: groups.reduce((n, g) => n + g.tools.length, 0) })}
             </span>
           )}
         </div>
         {toolsQuery.isError ? (
           <QueryError
-            title="Could not load the tool catalogue"
+            title={t('mcp.tools.loadError')}
             message={(toolsQuery.error as Error)?.message}
             onRetry={() => void toolsQuery.refetch()}
           />
@@ -366,31 +363,28 @@ export function McpPanel() {
                     {g.group}
                   </p>
                   <div className="space-y-3">
-                    {g.tools.map((t) => (
-                      <div key={t.name}>
+                    {g.tools.map((tool) => (
+                      <div key={tool.name}>
                         <p className="font-mono text-[13px] text-ink">
-                          {t.name}
-                          <span className="text-ink-faint">{t.signature}</span>
+                          {tool.name}
+                          <span className="text-ink-faint">{tool.signature}</span>
                         </p>
-                        <p className="mt-0.5 text-xs text-ink-muted">{t.summary}</p>
+                        <p className="mt-0.5 text-xs text-ink-muted">{tool.summary}</p>
                       </div>
                     ))}
                   </div>
                 </div>
               ))}
             </Card>
-            <p className="text-xs text-ink-muted">{TAGS_NOTE}</p>
+            <p className="text-xs text-ink-muted">{t('mcp.tagsNote')}</p>
           </>
         )}
       </section>
 
       <section className="space-y-3">
-        <h2 className="text-sm font-semibold text-ink">REST API reference</h2>
+        <h2 className="text-sm font-semibold text-ink">{t('mcp.rest.title')}</h2>
         <Card className="flex flex-wrap items-center justify-between gap-3 p-5">
-          <p className="text-[13px] text-ink-muted">
-            A standalone OpenAPI reference of just the integration endpoints — search and
-            workspace/collection/document access — for the AI to read as the API standard.
-          </p>
+          <p className="text-[13px] text-ink-muted">{t('mcp.rest.blurb')}</p>
           <div className="flex gap-2">
             <a href="/api/reference" target="_blank" rel="noreferrer">
               <Button variant="secondary" size="sm">
diff --git a/ui/src/components/tags/TagChip.tsx b/ui/src/components/tags/TagChip.tsx
index dd4eadb..19f5052 100644
--- a/ui/src/components/tags/TagChip.tsx
+++ b/ui/src/components/tags/TagChip.tsx
@@ -1,4 +1,5 @@
 import { X } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
 import { cn } from '../../lib/cn'
 
 const DEFAULT_COLOR = '#5B6B7A'
@@ -18,6 +19,7 @@ export function TagChip({
   onRemove?: () => void
   className?: string
 }) {
+  const { t } = useTranslation()
   const c = color || DEFAULT_COLOR
   return (
     <span
@@ -32,7 +34,7 @@ export function TagChip({
         <button
           type="button"
           onClick={onRemove}
-          aria-label={`Remove ${name}`}
+          aria-label={t('common.removeAria', { name })}
           className="rounded-full transition-opacity hover:opacity-70"
         >
           <X className="h-3.5 w-3.5" />
diff --git a/ui/src/components/tags/TagFilterBar.tsx b/ui/src/components/tags/TagFilterBar.tsx
index 852c36b..a6693a8 100644
--- a/ui/src/components/tags/TagFilterBar.tsx
+++ b/ui/src/components/tags/TagFilterBar.tsx
@@ -1,3 +1,4 @@
+import { useTranslation } from 'react-i18next'
 import type { TagRef } from '../../api/types'
 import { cn } from '../../lib/cn'
 
@@ -27,19 +28,20 @@ export function TagFilterBar({
   selected: string[]
   onToggle: (name: string) => void
 }) {
+  const { t } = useTranslation()
   if (tags.length === 0) return null
 
   return (
     <div className="flex flex-wrap items-center gap-1.5">
-      <span className="text-xs text-ink-faint">Filter by tag:</span>
-      {tags.map((t) => {
-        const on = selected.includes(t.name)
-        const c = t.color || '#5B6B7A'
+      <span className="text-xs text-ink-faint">{t('tags.filterByTag')}</span>
+      {tags.map((tag) => {
+        const on = selected.includes(tag.name)
+        const c = tag.color || '#5B6B7A'
         return (
           <button
-            key={t.id}
+            key={tag.id}
             type="button"
-            onClick={() => onToggle(t.name)}
+            onClick={() => onToggle(tag.name)}
             aria-pressed={on}
             className={cn(
               'rounded-full px-2 py-0.5 text-xs font-medium transition-colors',
@@ -47,7 +49,7 @@ export function TagFilterBar({
             )}
             style={on ? { backgroundColor: c } : undefined}
           >
-            {t.name}
+            {tag.name}
           </button>
         )
       })}
diff --git a/ui/src/components/tags/TagPicker.tsx b/ui/src/components/tags/TagPicker.tsx
index 9084b45..32e9c4a 100644
--- a/ui/src/components/tags/TagPicker.tsx
+++ b/ui/src/components/tags/TagPicker.tsx
@@ -1,5 +1,6 @@
 import { useState } from 'react'
 import { Check, Plus } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
 import { useTags } from '../../api/hooks'
 import type { TagRef } from '../../api/types'
 import { Input } from '../ui'
@@ -33,14 +34,15 @@ export function TagPicker({
   onCreate: (name: string) => void
   busy?: boolean
 }) {
+  const { t } = useTranslation()
   const [open, setOpen] = useState(false)
   const [query, setQuery] = useState('')
   const { data: tags } = useTags(wsId)
 
-  const assignedIds = new Set(assigned.map((t) => t.id))
+  const assignedIds = new Set(assigned.map((tag) => tag.id))
   const q = normalize(query)
-  const candidates = (tags ?? []).filter((t) => !q || t.name.includes(q))
-  const exists = (tags ?? []).some((t) => t.name === q)
+  const candidates = (tags ?? []).filter((tag) => !q || tag.name.includes(q))
+  const exists = (tags ?? []).some((tag) => tag.name === q)
 
   const close = () => {
     setOpen(false)
@@ -55,7 +57,7 @@ export function TagPicker({
         className="inline-flex items-center gap-1 rounded-full border border-dashed border-border px-2 py-0.5 text-xs text-ink-muted transition-colors hover:border-accent hover:text-ink"
       >
         <Plus className="h-3.5 w-3.5" />
-        Tag
+        {t('tags.picker.add')}
       </button>
 
       {open && (
@@ -66,26 +68,26 @@ export function TagPicker({
               autoFocus
               value={query}
               onChange={(e) => setQuery(e.target.value)}
-              placeholder="Filter or create…"
+              placeholder={t('tags.picker.placeholder')}
               className="h-8 text-[13px]"
             />
             <div className="mt-2 max-h-48 overflow-y-auto">
-              {candidates.map((t) => {
-                const on = assignedIds.has(t.id)
+              {candidates.map((tag) => {
+                const on = assignedIds.has(tag.id)
                 return (
                   <button
-                    key={t.id}
+                    key={tag.id}
                     type="button"
                     disabled={busy}
-                    onClick={() => (on ? onUnassign(t.id) : onAssign(t.id))}
+                    onClick={() => (on ? onUnassign(tag.id) : onAssign(tag.id))}
                     className="flex w-full items-center justify-between gap-2 rounded-control px-2 py-1.5 text-[13px] text-ink transition-colors hover:bg-canvas disabled:opacity-50"
                   >
                     <span className="flex items-center gap-2 truncate">
                       <span
                         className="h-2.5 w-2.5 shrink-0 rounded-full"
-                        style={{ backgroundColor: t.color || '#5B6B7A' }}
+                        style={{ backgroundColor: tag.color || '#5B6B7A' }}
                       />
-                      <span className="truncate">{t.name}</span>
+                      <span className="truncate">{tag.name}</span>
                     </span>
                     {on && <Check className="h-4 w-4 shrink-0 text-accent" />}
                   </button>
@@ -105,11 +107,11 @@ export function TagPicker({
                   )}
                 >
                   <Plus className="h-4 w-4 shrink-0" />
-                  Create “{q}”
+                  {t('tags.picker.create', { name: q })}
                 </button>
               )}
               {candidates.length === 0 && !q && (
-                <p className="px-2 py-1.5 text-xs text-ink-faint">No tags yet.</p>
+                <p className="px-2 py-1.5 text-xs text-ink-faint">{t('tags.picker.empty')}</p>
               )}
             </div>
           </div>
diff --git a/ui/src/components/ui/ConfirmDialog.tsx b/ui/src/components/ui/ConfirmDialog.tsx
index 9d97540..2a0f6a9 100644
--- a/ui/src/components/ui/ConfirmDialog.tsx
+++ b/ui/src/components/ui/ConfirmDialog.tsx
@@ -1,3 +1,4 @@
+import { useTranslation } from 'react-i18next'
 import { Modal } from './Modal'
 import { Button } from './Button'
 
@@ -6,7 +7,7 @@ export function ConfirmDialog({
   open,
   title,
   message,
-  confirmLabel = 'Delete',
+  confirmLabel,
   loading,
   onConfirm,
   onClose,
@@ -19,6 +20,7 @@ export function ConfirmDialog({
   onConfirm: () => void
   onClose: () => void
 }) {
+  const { t } = useTranslation()
   return (
     <Modal
       open={open}
@@ -27,10 +29,10 @@ export function ConfirmDialog({
       footer={
         <>
           <Button variant="secondary" onClick={onClose} disabled={loading}>
-            Cancel
+            {t('common.cancel')}
           </Button>
           <Button variant="danger" onClick={onConfirm} loading={loading}>
-            {confirmLabel}
+            {confirmLabel ?? t('common.confirm')}
           </Button>
         </>
       }
diff --git a/ui/src/components/ui/CopyButton.tsx b/ui/src/components/ui/CopyButton.tsx
index 507d11a..353b902 100644
--- a/ui/src/components/ui/CopyButton.tsx
+++ b/ui/src/components/ui/CopyButton.tsx
@@ -1,5 +1,6 @@
 import { useState } from 'react'
 import { Check, Copy } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
 import { cn } from '../../lib/cn'
 import { Button, type ButtonProps } from './Button'
 import { useToast } from './Toast'
@@ -23,6 +24,7 @@ export function CopyButton({
   iconClassName?: string
 }) {
   const [copied, setCopied] = useState(false)
+  const { t } = useTranslation()
   const toast = useToast()
   const copy = async () => {
     try {
@@ -30,7 +32,7 @@ export function CopyButton({
       setCopied(true)
       window.setTimeout(() => setCopied(false), 2000)
     } catch {
-      toast.error('Copy failed — select it and copy manually.')
+      toast.error(t('ui.copyButton.failed'))
     }
   }
   return (
@@ -38,7 +40,7 @@ export function CopyButton({
       type="button"
       variant={variant}
       size={size}
-      aria-label={label ?? 'Copy'}
+      aria-label={label ?? t('common.copy')}
       {...props}
       onClick={copy}
     >
@@ -47,7 +49,7 @@ export function CopyButton({
       ) : (
         <Copy className={iconClassName} />
       )}
-      {label != null && <span>{copied ? 'Copied' : label}</span>}
+      {label != null && <span>{copied ? t('common.copied') : label}</span>}
     </Button>
   )
 }
diff --git a/ui/src/components/ui/Modal.tsx b/ui/src/components/ui/Modal.tsx
index 76e27bb..e2cd143 100644
--- a/ui/src/components/ui/Modal.tsx
+++ b/ui/src/components/ui/Modal.tsx
@@ -1,6 +1,7 @@
 import { useEffect, type ReactNode } from 'react'
 import { createPortal } from 'react-dom'
 import { X } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
 import { cn } from '../../lib/cn'
 
 export interface ModalProps {
@@ -14,6 +15,7 @@ export interface ModalProps {
 
 /** Centered overlay dialog. Closes on Esc and backdrop click; locks body scroll. */
 export function Modal({ open, onClose, title, children, footer, className }: ModalProps) {
+  const { t } = useTranslation()
   useEffect(() => {
     if (!open) return
     const { body } = document
@@ -49,7 +51,7 @@ export function Modal({ open, onClose, title, children, footer, className }: Mod
             <button
               onClick={onClose}
               className="text-ink-faint transition-colors hover:text-ink"
-              aria-label="Close"
+              aria-label={t('common.close')}
             >
               <X className="h-5 w-5" />
             </button>
diff --git a/ui/src/components/ui/QueryError.tsx b/ui/src/components/ui/QueryError.tsx
index d957a69..45303d4 100644
--- a/ui/src/components/ui/QueryError.tsx
+++ b/ui/src/components/ui/QueryError.tsx
@@ -1,9 +1,10 @@
 import { AlertTriangle } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
 import { Button } from './Button'
 
 /** Inline error surface for a failed query, with an optional retry action. */
 export function QueryError({
-  title = 'Could not load this',
+  title,
   message,
   onRetry,
 }: {
@@ -11,14 +12,15 @@ export function QueryError({
   message?: string
   onRetry?: () => void
 }) {
+  const { t } = useTranslation()
   return (
     <div className="flex flex-col items-center justify-center gap-2 rounded-card border border-dashed border-err/40 bg-surface px-6 py-10 text-center">
       <AlertTriangle className="h-7 w-7 text-err" />
-      <h3 className="text-sm font-semibold text-ink">{title}</h3>
+      <h3 className="text-sm font-semibold text-ink">{title ?? t('ui.queryError.title')}</h3>
       {message && <p className="max-w-sm text-[13px] text-ink-muted">{message}</p>}
       {onRetry && (
         <Button variant="secondary" size="sm" onClick={onRetry} className="mt-2">
-          Try again
+          {t('common.retry')}
         </Button>
       )}
     </div>
diff --git a/ui/src/components/ui/StatusBadge.tsx b/ui/src/components/ui/StatusBadge.tsx
index 846efcd..44fc4c4 100644
--- a/ui/src/components/ui/StatusBadge.tsx
+++ b/ui/src/components/ui/StatusBadge.tsx
@@ -1,3 +1,4 @@
+import { useTranslation } from 'react-i18next'
 import { cn } from '../../lib/cn'
 
 export type DocStatus = 'uploading' | 'pending' | 'processing' | 'done' | 'failed' | 'deleting'
@@ -5,23 +6,27 @@ export type DocStatus = 'uploading' | 'pending' | 'processing' | 'done' | 'faile
 /** Document states plus `rate_limited` — a job-only pause the ingestion queue surfaces. */
 export type BadgeStatus = DocStatus | 'rate_limited'
 
-const MAP: Record<BadgeStatus, { label: string; dot: string; text: string }> = {
-  uploading: { label: 'Uploading', dot: 'bg-accent animate-pulse', text: 'text-accent' },
-  pending: { label: 'Pending', dot: 'bg-pending', text: 'text-ink-muted' },
-  processing: { label: 'Processing', dot: 'bg-warn animate-pulse', text: 'text-warn' },
-  done: { label: 'Done', dot: 'bg-ok', text: 'text-ok' },
-  failed: { label: 'Failed', dot: 'bg-err', text: 'text-err' },
-  deleting: { label: 'Deleting', dot: 'bg-warn animate-pulse', text: 'text-warn' },
-  rate_limited: { label: 'Rate limited', dot: 'bg-warn animate-pulse', text: 'text-warn' },
+// Presentation only — the human label is resolved from `status.<token>` at render
+// so it follows the active language (a module-const label never would).
+const STYLE: Record<BadgeStatus, { dot: string; text: string }> = {
+  uploading: { dot: 'bg-accent animate-pulse', text: 'text-accent' },
+  pending: { dot: 'bg-pending', text: 'text-ink-muted' },
+  processing: { dot: 'bg-warn animate-pulse', text: 'text-warn' },
+  done: { dot: 'bg-ok', text: 'text-ok' },
+  failed: { dot: 'bg-err', text: 'text-err' },
+  deleting: { dot: 'bg-warn animate-pulse', text: 'text-warn' },
+  rate_limited: { dot: 'bg-warn animate-pulse', text: 'text-warn' },
 }
 
 /** Ingestion status pill with a semantic color dot. */
 export function StatusBadge({ status }: { status: BadgeStatus }) {
-  const s = MAP[status] ?? MAP.pending
+  const { t } = useTranslation()
+  const safe: BadgeStatus = status in STYLE ? status : 'pending'
+  const s = STYLE[safe]
   return (
     <span className="inline-flex items-center gap-1.5 rounded-full border border-border bg-surface px-2 py-0.5 text-xs font-medium">
       <span className={cn('h-1.5 w-1.5 rounded-full', s.dot)} />
-      <span className={s.text}>{s.label}</span>
+      <span className={s.text}>{t(`status.${safe}`)}</span>
     </span>
   )
 }
diff --git a/ui/src/components/ui/Toast.tsx b/ui/src/components/ui/Toast.tsx
index 74f7031..2f31f9b 100644
--- a/ui/src/components/ui/Toast.tsx
+++ b/ui/src/components/ui/Toast.tsx
@@ -8,6 +8,7 @@ import {
 } from 'react'
 import { createPortal } from 'react-dom'
 import { AlertCircle, CheckCircle2, X } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
 import { cn } from '../../lib/cn'
 
 type ToastKind = 'success' | 'error'
@@ -33,10 +34,11 @@ export function useToast(): ToastApi {
 }
 
 export function ToastProvider({ children }: { children: ReactNode }) {
+  const { t } = useTranslation()
   const [toasts, setToasts] = useState<ToastItem[]>([])
 
   const remove = useCallback((id: number) => {
-    setToasts((list) => list.filter((t) => t.id !== id))
+    setToasts((list) => list.filter((item) => item.id !== id))
   }, [])
 
   const push = useCallback(
@@ -61,24 +63,24 @@ export function ToastProvider({ children }: { children: ReactNode }) {
       {children}
       {createPortal(
         <div className="fixed bottom-4 right-4 z-[60] flex w-80 flex-col gap-2">
-          {toasts.map((t) => (
+          {toasts.map((item) => (
             <div
-              key={t.id}
+              key={item.id}
               className={cn(
                 'flex animate-fade-in items-start gap-2 rounded-card border bg-surface px-3.5 py-3 shadow-overlay',
-                t.kind === 'success' ? 'border-ok/30' : 'border-err/30',
+                item.kind === 'success' ? 'border-ok/30' : 'border-err/30',
               )}
             >
-              {t.kind === 'success' ? (
+              {item.kind === 'success' ? (
                 <CheckCircle2 className="mt-0.5 h-5 w-5 shrink-0 text-ok" />
               ) : (
                 <AlertCircle className="mt-0.5 h-5 w-5 shrink-0 text-err" />
               )}
-              <p className="flex-1 text-[13px] text-ink">{t.message}</p>
+              <p className="flex-1 text-[13px] text-ink">{item.message}</p>
               <button
-                onClick={() => remove(t.id)}
+                onClick={() => remove(item.id)}
                 className="text-ink-faint transition-colors hover:text-ink"
-                aria-label="Dismiss"
+                aria-label={t('common.dismiss')}
               >
                 <X className="h-4 w-4" />
               </button>
diff --git a/ui/src/components/users/PermissionsModal.tsx b/ui/src/components/users/PermissionsModal.tsx
index 1e51ba8..4c327a1 100644
--- a/ui/src/components/users/PermissionsModal.tsx
+++ b/ui/src/components/users/PermissionsModal.tsx
@@ -1,5 +1,6 @@
 import { useState } from 'react'
 import { Plus, ShieldCheck, Trash2 } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
 import {
   useCollections,
   useGrantPermission,
@@ -21,21 +22,13 @@ import {
   Skeleton,
   useToast,
 } from '../ui'
+import { apiErrorMessage } from '../../i18n/apiError'
 
 /** Grantable capabilities — privileges not tied to a resource (backend `_CAPABILITIES`).
- *  The `id` must match the backend capability string. */
-const CAPABILITIES = [
-  {
-    id: 'create_workspace',
-    label: 'Create workspaces',
-    help: 'Lets this user create new workspaces — they get write access to any they create.',
-  },
-  {
-    id: 'manage_tags',
-    label: 'Manage tags',
-    help: 'Lets this user create, edit, delete, and assign tags in any workspace they can read.',
-  },
-] as const
+ *  Each id must match the backend capability string; its human label + help are resolved
+ *  from `users.grants.capabilityLabel.<id>` / `capabilityHelp.<id>` so they follow the language. */
+const CAPABILITY_IDS = ['create_workspace', 'manage_tags'] as const
+type CapabilityId = (typeof CAPABILITY_IDS)[number]
 
 /**
  * Permission editor for one user. Permissions SCOPE A USER DOWN: with none the user
@@ -54,17 +47,23 @@ export function PermissionsModal({
   user: User | null
   onClose: () => void
 }) {
+  const { t } = useTranslation()
   const userId = user?.id ?? ''
   const { data, isLoading, isError, error, refetch } = usePermissions(userId, open && Boolean(userId))
 
   return (
-    <Modal open={open} onClose={onClose} title={`Permissions — ${user?.email ?? ''}`} className="max-w-xl">
+    <Modal
+      open={open}
+      onClose={onClose}
+      title={t('users.grants.modalTitle', { email: user?.email ?? '' })}
+      className="max-w-xl"
+    >
       {user && (
         <div className="flex flex-col gap-5">
           <p className="rounded-control border border-border bg-canvas/50 px-3 py-2 text-xs text-ink-muted">
-            Permissions <span className="font-medium text-ink">scope this user down</span>. With none,
-            they see and write everything. A workspace limits them to it; add a collection (or document) to
-            narrow them to just that one.
+            {t('users.grants.intro.lead')}{' '}
+            <span className="font-medium text-ink">{t('users.grants.intro.emphasis')}</span>
+            {t('users.grants.intro.rest')}
           </p>
           <GrantForm userId={user.id} />
           {isLoading ? (
@@ -74,12 +73,16 @@ export function PermissionsModal({
               ))}
             </div>
           ) : isError ? (
-            <QueryError title="Could not load grants" message={error?.message} onRetry={() => void refetch()} />
+            <QueryError
+              title={t('users.grants.error')}
+              message={error ? apiErrorMessage(error, t) : undefined}
+              onRetry={() => void refetch()}
+            />
           ) : !data || data.length === 0 ? (
             <EmptyState
               icon={<ShieldCheck className="h-7 w-7" />}
-              title="No permissions yet"
-              description="Grant this user read or write on a workspace, collection, or document above."
+              title={t('users.grants.empty.title')}
+              description={t('users.grants.empty.description')}
             />
           ) : (
             <div className="divide-y divide-border rounded-card border border-border">
@@ -104,11 +107,12 @@ export function PermissionsModal({
 
 /** The add-a-grant form: resource type → resource picker → level → add. */
 function GrantForm({ userId }: { userId: string }) {
+  const { t } = useTranslation()
   const [resourceType, setResourceType] = useState<ResourceType>('collection')
   const [wsId, setWsId] = useState('')
   const [colId, setColId] = useState('')
   const [docId, setDocId] = useState('')
-  const [capabilityId, setCapabilityId] = useState<string>(CAPABILITIES[0].id)
+  const [capabilityId, setCapabilityId] = useState<CapabilityId>(CAPABILITY_IDS[0])
   const [level, setLevel] = useState<PermissionLevel>('read')
   const toast = useToast()
 
@@ -133,10 +137,10 @@ function GrantForm({ userId }: { userId: string }) {
       { resource_type: resourceType, resource_id: resourceId, level: grantLevel },
       {
         onSuccess: () => {
-          toast.success('Permission granted.')
+          toast.success(t('users.grants.toast.granted'))
           setDocId('')
         },
-        onError: (e) => toast.error(e.message),
+        onError: (e) => toast.error(apiErrorMessage(e, t)),
       },
     )
   }
@@ -144,7 +148,7 @@ function GrantForm({ userId }: { userId: string }) {
   return (
     <div className="flex flex-col gap-3 rounded-card border border-border p-3.5">
       <div className="grid grid-cols-2 gap-3">
-        <Field label="Resource type">
+        <Field label={t('users.grants.resourceType')}>
           <Select
             value={resourceType}
             onChange={(e) => {
@@ -153,41 +157,44 @@ function GrantForm({ userId }: { userId: string }) {
               setDocId('')
             }}
           >
-            <option value="workspace">Workspace</option>
-            <option value="collection">Collection</option>
-            <option value="document">Document</option>
-            <option value="capability">Capability</option>
+            <option value="workspace">{t('users.grants.type.workspace')}</option>
+            <option value="collection">{t('users.grants.type.collection')}</option>
+            <option value="document">{t('users.grants.type.document')}</option>
+            <option value="capability">{t('users.grants.type.capability')}</option>
           </Select>
         </Field>
         {resourceType !== 'capability' && (
-          <Field label="Level">
+          <Field label={t('users.grants.levelLabel')}>
             <Select value={level} onChange={(e) => setLevel(e.target.value as PermissionLevel)}>
-              <option value="read">Read — search, list, download</option>
-              <option value="write">Write — ingest, delete (and read)</option>
+              <option value="read">{t('users.grants.readOption')}</option>
+              <option value="write">{t('users.grants.writeOption')}</option>
             </Select>
           </Field>
         )}
       </div>
 
       {resourceType === 'capability' && (
-        <Field label="Capability">
-          <Select value={capabilityId} onChange={(e) => setCapabilityId(e.target.value)}>
-            {CAPABILITIES.map((cap) => (
-              <option key={cap.id} value={cap.id}>
-                {cap.label}
+        <Field label={t('users.grants.type.capability')}>
+          <Select
+            value={capabilityId}
+            onChange={(e) => setCapabilityId(e.target.value as CapabilityId)}
+          >
+            {CAPABILITY_IDS.map((id) => (
+              <option key={id} value={id}>
+                {t(`users.grants.capabilityLabel.${id}`)}
               </option>
             ))}
           </Select>
           <p className="mt-1.5 text-xs text-ink-muted">
-            {CAPABILITIES.find((cap) => cap.id === capabilityId)?.help}
+            {t(`users.grants.capabilityHelp.${capabilityId}`)}
           </p>
         </Field>
       )}
 
       {resourceType === 'workspace' && (
-        <Field label="Workspace">
+        <Field label={t('users.grants.type.workspace')}>
           <Select value={wsId} onChange={(e) => setWsId(e.target.value)}>
-            <option value="">Select a workspace…</option>
+            <option value="">{t('users.grants.selectWorkspace')}</option>
             {(workspaces.data ?? []).map((ws) => (
               <option key={ws.id} value={ws.id}>
                 {ws.name}
@@ -199,7 +206,7 @@ function GrantForm({ userId }: { userId: string }) {
 
       {resourceType === 'collection' && (
         <div className="grid grid-cols-2 gap-3">
-          <Field label="Workspace">
+          <Field label={t('users.grants.type.workspace')}>
             <Select
               value={wsId}
               onChange={(e) => {
@@ -207,7 +214,7 @@ function GrantForm({ userId }: { userId: string }) {
                 setColId('')
               }}
             >
-              <option value="">Select…</option>
+              <option value="">{t('users.grants.select')}</option>
               {(workspaces.data ?? []).map((ws) => (
                 <option key={ws.id} value={ws.id}>
                   {ws.name}
@@ -215,9 +222,11 @@ function GrantForm({ userId }: { userId: string }) {
               ))}
             </Select>
           </Field>
-          <Field label="Collection">
+          <Field label={t('users.grants.type.collection')}>
             <Select value={colId} onChange={(e) => setColId(e.target.value)} disabled={!wsId}>
-              <option value="">{wsId ? 'Select…' : 'Pick a workspace first'}</option>
+              <option value="">
+                {wsId ? t('users.grants.select') : t('users.grants.pickWorkspaceFirst')}
+              </option>
               {(collections.data ?? []).map((col) => (
                 <option key={col.id} value={col.id}>
                   {col.name}
@@ -229,7 +238,7 @@ function GrantForm({ userId }: { userId: string }) {
       )}
 
       {resourceType === 'document' && (
-        <Field label="Document ID" hint="The document's id (e.g. doc_…), from its collection.">
+        <Field label={t('users.grants.documentId')} hint={t('users.grants.documentIdHint')}>
           <Input value={docId} onChange={(e) => setDocId(e.target.value)} placeholder="doc_…" />
         </Field>
       )}
@@ -237,7 +246,7 @@ function GrantForm({ userId }: { userId: string }) {
       <div className="flex justify-end">
         <Button onClick={add} loading={grantMut.isPending} disabled={!resourceId}>
           <Plus className="h-5 w-5" />
-          Add permission
+          {t('users.grants.addPermission')}
         </Button>
       </div>
     </div>
@@ -260,13 +269,14 @@ function GrantRow({
   resourceName: string | null
   level: PermissionLevel
 }) {
+  const { t } = useTranslation()
   const revokeMut = useRevokePermission(userId)
   const [confirming, setConfirming] = useState(false)
   const toast = useToast()
   const revoke = () =>
     revokeMut.mutate(grantId, {
-      onSuccess: () => toast.success('Permission revoked.'),
-      onError: (e) => toast.error(e.message),
+      onSuccess: () => toast.success(t('users.grants.toast.revoked')),
+      onError: (e) => toast.error(apiErrorMessage(e, t)),
     })
 
   // Show the resource's name; the raw id becomes a click-to-copy chip. A deleted
@@ -276,8 +286,10 @@ function GrantRow({
   return (
     <div className="flex items-center justify-between gap-3 px-3.5 py-2.5">
       <div className="flex min-w-0 items-center gap-2">
-        <Badge>{level === 'write' ? 'Write' : 'Read'}</Badge>
-        <span className="shrink-0 text-xs capitalize text-ink-muted">{resourceType}</span>
+        <Badge>{level === 'write' ? t('users.grants.write') : t('users.grants.read')}</Badge>
+        <span className="shrink-0 text-xs text-ink-muted">
+          {t(`users.grants.type.${resourceType}`)}
+        </span>
         <span
           className={
             resourceName
@@ -286,7 +298,7 @@ function GrantRow({
           }
           title={resourceName ?? undefined}
         >
-          {resourceName ?? 'deleted'}
+          {resourceName ?? t('users.grants.deleted')}
         </span>
         <CopyButton
           text={resourceId}
@@ -294,24 +306,24 @@ function GrantRow({
           variant="ghost"
           iconClassName="h-3.5 w-3.5"
           className="shrink-0 font-mono"
-          title={`Copy id: ${resourceId}`}
-          aria-label={`Copy id ${resourceId}`}
+          title={t('users.grants.copyIdTitle', { id: resourceId })}
+          aria-label={t('users.grants.copyIdAria', { id: resourceId })}
         />
       </div>
       {confirming ? (
         <div className="flex shrink-0 items-center gap-1.5">
           <Button variant="danger" size="sm" onClick={revoke} loading={revokeMut.isPending}>
-            Revoke
+            {t('users.revoke')}
           </Button>
           <Button variant="ghost" size="sm" onClick={() => setConfirming(false)} disabled={revokeMut.isPending}>
-            Cancel
+            {t('common.cancel')}
           </Button>
         </div>
       ) : (
         <Button
           variant="ghost"
           size="sm"
-          aria-label="Revoke permission"
+          aria-label={t('users.grants.revokeAria')}
           onClick={() => setConfirming(true)}
           className="h-10 w-10 shrink-0 px-0 hover:text-err"
         >
diff --git a/ui/src/components/users/RevealOncePanel.tsx b/ui/src/components/users/RevealOncePanel.tsx
index 3e6975d..6dc7ddb 100644
--- a/ui/src/components/users/RevealOncePanel.tsx
+++ b/ui/src/components/users/RevealOncePanel.tsx
@@ -1,4 +1,5 @@
 import { ShieldAlert } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
 import { Button, CopyButton } from '../ui'
 
 /**
@@ -15,6 +16,7 @@ export function RevealOncePanel({
   message: string
   onDone: () => void
 }) {
+  const { t } = useTranslation()
   return (
     <div className="flex flex-col gap-3">
       <div className="flex items-start gap-2 rounded-control border border-warn/30 bg-warn/5 px-3 py-2.5">
@@ -25,10 +27,10 @@ export function RevealOncePanel({
         <code className="min-w-0 flex-1 truncate rounded-control border border-border bg-canvas px-3 py-2 font-mono text-[13px] text-ink">
           {secret}
         </code>
-        <CopyButton text={secret} label="Copy" size="md" iconClassName="h-5 w-5" className="shrink-0" />
+        <CopyButton text={secret} label={t('common.copy')} size="md" iconClassName="h-5 w-5" className="shrink-0" />
       </div>
       <div className="flex justify-end">
-        <Button onClick={onDone}>Done</Button>
+        <Button onClick={onDone}>{t('users.reveal.done')}</Button>
       </div>
     </div>
   )
diff --git a/ui/src/components/users/UserFormModal.tsx b/ui/src/components/users/UserFormModal.tsx
index 61ea3bd..b8bf542 100644
--- a/ui/src/components/users/UserFormModal.tsx
+++ b/ui/src/components/users/UserFormModal.tsx
@@ -1,4 +1,5 @@
 import { useEffect, useState } from 'react'
+import { useTranslation } from 'react-i18next'
 import type { User } from '../../api/types'
 import { Button, Field, Input, Modal } from '../ui'
 
@@ -55,6 +56,7 @@ export function UserFormModal({
   onSubmit: (values: UserFormValues) => void
   onClose: () => void
 }) {
+  const { t } = useTranslation()
   const [values, setValues] = useState<UserFormValues>(DEFAULTS)
 
   // Reseed every time the modal opens so stale edits never leak between rows.
@@ -81,38 +83,38 @@ export function UserFormModal({
     <Modal
       open={open}
       onClose={onClose}
-      title={editing ? 'Edit user' : 'New user'}
+      title={editing ? t('users.editTitle') : t('users.new')}
       footer={
         <>
           <Button variant="secondary" onClick={onClose} disabled={submitting}>
-            Cancel
+            {t('common.cancel')}
           </Button>
           <Button onClick={submit} loading={submitting} disabled={!valid}>
-            {editing ? 'Save changes' : 'Create'}
+            {editing ? t('common.saveChanges') : t('common.create')}
           </Button>
         </>
       }
     >
       <div className="flex flex-col gap-4">
         <Field
-          label="Username"
+          label={t('auth.field.username')}
           htmlFor="user-username"
-          hint="Used to sign in. Letters, digits, and . _ + @ - (3–64 chars)."
-          error={username && !usernameValid ? 'Enter a valid username (3–64 characters).' : undefined}
+          hint={t('users.form.usernameHint')}
+          error={username && !usernameValid ? t('users.form.usernameError') : undefined}
         >
           <Input
             id="user-username"
             autoFocus
             value={values.username}
             onChange={(e) => set('username', e.target.value)}
-            placeholder="e.g. jane"
+            placeholder={t('users.form.usernamePlaceholder')}
           />
         </Field>
         <Field
-          label="Email"
+          label={t('users.form.email')}
           htmlFor="user-email"
-          hint="Optional — leave blank if the user has no email."
-          error={email && !emailValid ? 'Enter a valid email address.' : undefined}
+          hint={t('users.form.emailHint')}
+          error={email && !emailValid ? t('users.form.emailError') : undefined}
         >
           <Input
             id="user-email"
@@ -122,21 +124,21 @@ export function UserFormModal({
             onKeyDown={(e) => {
               if (e.key === 'Enter') submit()
             }}
-            placeholder="e.g. jane@example.com"
+            placeholder={t('users.form.emailPlaceholder')}
           />
         </Field>
-        <Field label="Name" htmlFor="user-name" hint="Optional — a display name.">
+        <Field label={t('common.name')} htmlFor="user-name" hint={t('users.form.nameHint')}>
           <Input
             id="user-name"
             value={values.name}
             onChange={(e) => set('name', e.target.value)}
-            placeholder="Optional"
+            placeholder={t('common.optional')}
           />
         </Field>
         <Field
-          label="MCP rate limit (requests/min)"
+          label={t('users.form.rateLimit')}
           htmlFor="user-rate-limit"
-          hint="Caps this user's key on /api/mcp. 0 = use the global default."
+          hint={t('users.form.rateLimitHint')}
         >
           <Input
             id="user-rate-limit"
@@ -156,7 +158,7 @@ export function UserFormModal({
             onChange={(e) => set('is_active', e.target.checked)}
             className="h-4 w-4 rounded border-border accent-accent"
           />
-          Active — an inactive user can't sign in and their API key stops working
+          {t('users.form.activeLabel')}
         </label>
         <label className="flex items-center gap-2 text-sm text-ink">
           <input
@@ -165,7 +167,7 @@ export function UserFormModal({
             onChange={(e) => set('is_admin', e.target.checked)}
             className="h-4 w-4 rounded border-border accent-accent"
           />
-          Admin — full console access (manage users, settings, every workspace)
+          {t('users.form.adminLabel')}
         </label>
       </div>
     </Modal>
diff --git a/ui/src/components/users/UserKeyModal.tsx b/ui/src/components/users/UserKeyModal.tsx
index dddeb81..99193be 100644
--- a/ui/src/components/users/UserKeyModal.tsx
+++ b/ui/src/components/users/UserKeyModal.tsx
@@ -1,8 +1,10 @@
 import { useEffect, useState } from 'react'
 import { KeyRound, RefreshCw, Trash2 } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
 import { useMintUserKey, useRevokeUserKey } from '../../api/hooks'
 import type { MintedUserKey, User } from '../../api/types'
 import { Button, Modal, useToast } from '../ui'
+import { apiErrorMessage } from '../../i18n/apiError'
 import { formatDate, timeAgo } from '../../lib/format'
 import { RevealOncePanel } from './RevealOncePanel'
 
@@ -19,6 +21,7 @@ export function UserKeyModal({
   user: User | null
   onClose: () => void
 }) {
+  const { t } = useTranslation()
   const mintMut = useMintUserKey()
   const revokeMut = useRevokeUserKey()
   const [minted, setMinted] = useState<MintedUserKey | null>(null)
@@ -43,28 +46,33 @@ export function UserKeyModal({
   const mint = () =>
     mintMut.mutate(
       { id: user.id, body: {} },
-      { onSuccess: (key) => setMinted(key), onError: (e) => toast.error(e.message) },
+      { onSuccess: (key) => setMinted(key), onError: (e) => toast.error(apiErrorMessage(e, t)) },
     )
 
   const revoke = () =>
     revokeMut.mutate(user.id, {
       onSuccess: () => {
-        toast.success('Key revoked.')
+        toast.success(t('users.key.toast.revoked'))
         setConfirmingRevoke(false)
         setRevoked(true)
       },
-      onError: (e) => toast.error(e.message),
+      onError: (e) => toast.error(apiErrorMessage(e, t)),
     })
 
   return (
-    <Modal open={open} onClose={onClose} title={`API key — ${user.email ?? user.username}`} className="max-w-lg">
+    <Modal
+      open={open}
+      onClose={onClose}
+      title={t('users.key.title', { name: user.email ?? user.username })}
+      className="max-w-lg"
+    >
       {minted ? (
         // Close on Done rather than returning to the management view: the `user`
         // prop is a frozen snapshot, so its key metadata is stale post-rotation.
         // Reopening reads the freshly-invalidated list.
         <RevealOncePanel
           secret={minted.raw_key}
-          message="Copy this key now — it is shown in full only once and cannot be retrieved again."
+          message={t('users.key.revealMessage')}
           onDone={onClose}
         />
       ) : (
@@ -74,14 +82,16 @@ export function UserKeyModal({
               <div className="min-w-0">
                 <code className="font-mono text-[13px] text-ink">{existing.key_prefix}…</code>
                 <p className="mt-0.5 text-xs text-ink-faint">
-                  Created {formatDate(existing.created_at)} ·{' '}
-                  {existing.last_used_at ? `used ${timeAgo(existing.last_used_at)}` : 'never used'}
+                  {t('common.created', { date: formatDate(existing.created_at) })} ·{' '}
+                  {existing.last_used_at
+                    ? t('users.key.used', { ago: timeAgo(existing.last_used_at) })
+                    : t('users.key.neverUsed')}
                 </p>
               </div>
               {confirmingRevoke ? (
                 <div className="flex shrink-0 items-center gap-1.5">
                   <Button variant="danger" size="sm" onClick={revoke} loading={revokeMut.isPending}>
-                    Revoke
+                    {t('users.revoke')}
                   </Button>
                   <Button
                     variant="ghost"
@@ -89,14 +99,14 @@ export function UserKeyModal({
                     onClick={() => setConfirmingRevoke(false)}
                     disabled={revokeMut.isPending}
                   >
-                    Cancel
+                    {t('common.cancel')}
                   </Button>
                 </div>
               ) : (
                 <Button
                   variant="ghost"
                   size="sm"
-                  aria-label="Revoke key"
+                  aria-label={t('users.key.revokeAria')}
                   onClick={() => setConfirmingRevoke(true)}
                   className="h-10 w-10 shrink-0 px-0 hover:text-err"
                 >
@@ -105,26 +115,22 @@ export function UserKeyModal({
               )}
             </div>
           ) : (
-            <p className="text-[13px] text-ink-muted">This user has no API key yet.</p>
+            <p className="text-[13px] text-ink-muted">{t('users.key.none')}</p>
           )}
           <Button onClick={mint} loading={mintMut.isPending}>
             {existing ? (
               <>
                 <RefreshCw className="h-5 w-5" />
-                Rotate key
+                {t('users.key.rotate')}
               </>
             ) : (
               <>
                 <KeyRound className="h-5 w-5" />
-                Create key
+                {t('users.key.create')}
               </>
             )}
           </Button>
-          {existing && (
-            <p className="text-xs text-ink-faint">
-              Rotating replaces the current key — the old one stops working immediately.
-            </p>
-          )}
+          {existing && <p className="text-xs text-ink-faint">{t('users.key.rotateHint')}</p>}
         </div>
       )}
     </Modal>
diff --git a/ui/src/components/workspaces/WorkspaceFormModal.tsx b/ui/src/components/workspaces/WorkspaceFormModal.tsx
index eb35dd3..6d1c257 100644
--- a/ui/src/components/workspaces/WorkspaceFormModal.tsx
+++ b/ui/src/components/workspaces/WorkspaceFormModal.tsx
@@ -1,4 +1,5 @@
 import { useEffect, useState } from 'react'
+import { useTranslation } from 'react-i18next'
 import type { Workspace } from '../../api/types'
 import {
   Button,
@@ -54,6 +55,7 @@ export function WorkspaceFormModal({
   onSubmit: (values: WorkspaceFormValues) => void
   onClose: () => void
 }) {
+  const { t } = useTranslation()
   const [values, setValues] = useState<WorkspaceFormValues>(DEFAULTS)
 
   // Reseed every time the modal opens so stale edits never leak between rows.
@@ -75,20 +77,20 @@ export function WorkspaceFormModal({
     <Modal
       open={open}
       onClose={onClose}
-      title={editing ? 'Edit workspace' : 'New workspace'}
+      title={editing ? t('workspaces.editTitle') : t('workspaces.new')}
       footer={
         <>
           <Button variant="secondary" onClick={onClose} disabled={submitting}>
-            Cancel
+            {t('common.cancel')}
           </Button>
           <Button onClick={submit} loading={submitting} disabled={!name}>
-            {editing ? 'Save changes' : 'Create'}
+            {editing ? t('common.saveChanges') : t('common.create')}
           </Button>
         </>
       }
     >
       <div className="flex flex-col gap-4">
-        <Field label="Name" htmlFor="ws-name">
+        <Field label={t('common.name')} htmlFor="ws-name">
           <Input
             id="ws-name"
             autoFocus
@@ -97,21 +99,21 @@ export function WorkspaceFormModal({
             onKeyDown={(e) => {
               if (e.key === 'Enter') submit()
             }}
-            placeholder="e.g. Research"
+            placeholder={t('workspaces.namePlaceholder')}
           />
         </Field>
-        <Field label="Description" htmlFor="ws-desc" hint="Optional — what lives in this workspace.">
+        <Field label={t('common.description')} htmlFor="ws-desc" hint={t('workspaces.descHint')}>
           <Textarea
             id="ws-desc"
             value={values.description}
             onChange={(e) => set('description', e.target.value)}
-            placeholder="Optional"
+            placeholder={t('common.optional')}
           />
         </Field>
-        <Field label="Color">
+        <Field label={t('common.color')}>
           <ColorPicker value={values.color} onChange={(c) => set('color', c)} />
         </Field>
-        <Field label="Icon">
+        <Field label={t('common.icon')}>
           <IconPicker value={values.icon} onChange={(i) => set('icon', i)} />
         </Field>
       </div>
diff --git a/ui/src/i18n/apiError.ts b/ui/src/i18n/apiError.ts
new file mode 100644
index 0000000..8bf6fcf
--- /dev/null
+++ b/ui/src/i18n/apiError.ts
@@ -0,0 +1,34 @@
+import type { TFunction } from 'i18next'
+import { ApiError } from '../api/client'
+
+type ErrorKey =
+  | 'errors.network'
+  | 'errors.sessionExpired'
+  | 'errors.accountDeactivated'
+  | 'errors.adminRequired'
+  | 'errors.configNotLoaded'
+  | 'errors.passwordChangeRequired'
+
+// Curated map of known, *static* backend `detail` strings (and the sentinels the
+// API client throws) → localized keys. Interpolated / free-text details (anything
+// embedding `{exc}`) are deliberately left out — they fall through to the raw
+// message below rather than being string-matched.
+const DETAIL_KEYS: Record<string, ErrorKey> = {
+  'Your account has been deactivated.': 'errors.accountDeactivated',
+  'User is inactive': 'errors.accountDeactivated',
+  'Administrator access required': 'errors.adminRequired',
+  'Config not loaded yet': 'errors.configNotLoaded',
+  'Password change required': 'errors.passwordChangeRequired',
+}
+
+/**
+ * Map an error thrown by the API client to a user-facing, localized message.
+ * Status rules come first (prose-independent and robust), then the curated detail
+ * map; otherwise the raw message passes through so nothing user-visible is lost.
+ */
+export function apiErrorMessage(err: unknown, t: TFunction): string {
+  if (!(err instanceof ApiError)) return t('errors.network')
+  if (err.status === 401) return t('errors.sessionExpired')
+  const key = DETAIL_KEYS[err.message]
+  return key ? t(key) : err.message
+}
diff --git a/ui/src/i18n/detect.ts b/ui/src/i18n/detect.ts
new file mode 100644
index 0000000..4e2a01d
--- /dev/null
+++ b/ui/src/i18n/detect.ts
@@ -0,0 +1,57 @@
+/**
+ * Language detection + persistence for the console UI, decoupled from React and
+ * i18next so boot code can resolve a language synchronously (mirrors the storage
+ * try/catch shape of `api/tokenStore.ts`).
+ *
+ * Precedence: an explicit saved choice → the browser's languages → `en`.
+ */
+
+export const SUPPORTED = ['en', 'pt-BR'] as const
+export type Lang = (typeof SUPPORTED)[number]
+export const DEFAULT_LANG: Lang = 'en'
+
+const STORAGE_KEY = 'embedbase.lang'
+
+/** Map a raw BCP-47 tag (e.g. `pt`, `pt-BR`, `pt-PT`, `en-US`) to a supported
+ *  language, or `null` when it's neither Portuguese nor English. */
+export function normalize(raw: string | null | undefined): Lang | null {
+  if (!raw) return null
+  const tag = raw.toLowerCase()
+  if (tag.startsWith('pt')) return 'pt-BR'
+  if (tag.startsWith('en')) return 'en'
+  return null
+}
+
+/** The persisted explicit choice, or `null` (also `null` when storage is off). */
+export function readStoredLang(): Lang | null {
+  try {
+    return normalize(window.localStorage.getItem(STORAGE_KEY))
+  } catch {
+    // Private-mode / storage-disabled: fall back to detection.
+    return null
+  }
+}
+
+/** Persist the explicit choice; silently no-ops when storage is unavailable. */
+export function persistLang(lang: Lang): void {
+  try {
+    window.localStorage.setItem(STORAGE_KEY, lang)
+  } catch {
+    // Storage unavailable — the in-memory i18next language still applies.
+  }
+}
+
+/** Resolve the language to boot with: saved choice → browser scan → `en`. */
+export function detectInitialLang(): Lang {
+  const saved = readStoredLang()
+  if (saved) return saved
+  const candidates =
+    navigator.languages && navigator.languages.length > 0
+      ? navigator.languages
+      : [navigator.language]
+  for (const candidate of candidates) {
+    const match = normalize(candidate)
+    if (match) return match
+  }
+  return DEFAULT_LANG
+}
diff --git a/ui/src/i18n/i18next.d.ts b/ui/src/i18n/i18next.d.ts
new file mode 100644
index 0000000..a35a0b9
--- /dev/null
+++ b/ui/src/i18n/i18next.d.ts
@@ -0,0 +1,15 @@
+/**
+ * Type-safe translation keys: augment i18next's `CustomTypeOptions` with the `en`
+ * catalog as the source of truth, so every `t('…')` call is checked against the
+ * real key set at compile time. Catalog parity between locales is enforced
+ * separately in `parity.ts`.
+ */
+import 'i18next'
+import type en from './locales/en/translation.json'
+
+declare module 'i18next' {
+  interface CustomTypeOptions {
+    defaultNS: 'translation'
+    resources: { translation: typeof en }
+  }
+}
diff --git a/ui/src/i18n/index.ts b/ui/src/i18n/index.ts
new file mode 100644
index 0000000..c61c37b
--- /dev/null
+++ b/ui/src/i18n/index.ts
@@ -0,0 +1,45 @@
+/**
+ * i18next bootstrap — imported for its side effect from `main.tsx` before the app
+ * renders. Resources are bundled (no async backend), so `useTranslation()` works
+ * synchronously everywhere without a Suspense boundary or an `<I18nextProvider>`.
+ *
+ * The active language mirrors to the document's `lang` attribute and the shared
+ * date formatter (`lib/format`). Persistence is deliberately NOT done here — it's
+ * tied to the explicit `setLanguage` action, so a browser-detected default is
+ * never frozen into storage on first load (which would stop it tracking the
+ * browser on later visits).
+ */
+import i18n from 'i18next'
+import { initReactI18next } from 'react-i18next'
+import { setDateLocale } from '../lib/format'
+import { DEFAULT_LANG, SUPPORTED, detectInitialLang, persistLang, type Lang } from './detect'
+import en from './locales/en/translation.json'
+import ptBR from './locales/pt-BR/translation.json'
+
+/** Keep the document + date formatter aligned with the active language. */
+function applyLang(lang: string): void {
+  document.documentElement.lang = lang
+  setDateLocale(lang)
+}
+
+const initial = detectInitialLang()
+
+void i18n.use(initReactI18next).init({
+  resources: { en: { translation: en }, 'pt-BR': { translation: ptBR } },
+  lng: initial,
+  fallbackLng: DEFAULT_LANG,
+  supportedLngs: [...SUPPORTED],
+  interpolation: { escapeValue: false }, // React already escapes rendered values
+  react: { useSuspense: false },
+})
+
+applyLang(initial)
+i18n.on('languageChanged', applyLang)
+
+/** Switch + remember the console language — the only path that persists a choice. */
+export function setLanguage(lang: Lang): void {
+  persistLang(lang)
+  void i18n.changeLanguage(lang)
+}
+
+export default i18n
diff --git a/ui/src/i18n/locales/en/translation.json b/ui/src/i18n/locales/en/translation.json
new file mode 100644
index 0000000..88f1ee8
--- /dev/null
+++ b/ui/src/i18n/locales/en/translation.json
@@ -0,0 +1,782 @@
+{
+  "common": {
+    "saving": "Saving…",
+    "cancel": "Cancel",
+    "create": "Create",
+    "saveChanges": "Save changes",
+    "name": "Name",
+    "description": "Description",
+    "optional": "Optional",
+    "color": "Color",
+    "icon": "Icon",
+    "tags": "Tags",
+    "noDescription": "No description",
+    "created": "Created {{date}}",
+    "editAria": "Edit {{name}}",
+    "deleteAria": "Delete {{name}}",
+    "more": "More",
+    "clear": "Clear",
+    "retry": "Retry",
+    "retrying": "Retrying…",
+    "min": "min",
+    "max": "max",
+    "openAria": "Open {{name}}",
+    "downloadAria": "Download {{name}}",
+    "close": "Close",
+    "removeAria": "Remove {{name}}",
+    "confirm": "Confirm",
+    "copy": "Copy",
+    "copied": "Copied",
+    "dismiss": "Dismiss"
+  },
+  "nav": {
+    "dashboard": "Dashboard",
+    "workspaces": "Workspaces",
+    "graph": "Graph",
+    "search": "Search",
+    "indexing": "Indexing",
+    "ingestionQueue": "Ingestion Queue",
+    "users": "Users",
+    "settings": "Settings",
+    "admin": "Admin"
+  },
+  "topbar": {
+    "masterKey": "Master key",
+    "adminSuffix": " · admin",
+    "changePassword": "Change password",
+    "changePasswordTitle": "Change your password",
+    "signOut": "Sign out",
+    "signOutTitle": "Sign out and clear your session",
+    "language": "Change language"
+  },
+  "status": {
+    "uploading": "Uploading",
+    "pending": "Pending",
+    "processing": "Processing",
+    "done": "Done",
+    "failed": "Failed",
+    "deleting": "Deleting",
+    "rate_limited": "Rate limited"
+  },
+  "workspaces": {
+    "title": "Workspaces",
+    "subtitle": "Top-level containers for your collections.",
+    "new": "New workspace",
+    "editTitle": "Edit workspace",
+    "namePlaceholder": "e.g. Research",
+    "descHint": "Optional — what lives in this workspace.",
+    "empty": {
+      "title": "No workspaces yet",
+      "canCreate": "Create your first workspace to start organising collections.",
+      "readonly": "No workspaces are shared with you yet."
+    },
+    "error": "Could not load workspaces",
+    "toast": {
+      "created": "Workspace “{{name}}” created.",
+      "updated": "Workspace updated.",
+      "deleted": "Workspace “{{name}}” deleted."
+    },
+    "delete": {
+      "title": "Delete workspace",
+      "message": "Delete “{{name}}”? Its collections, API keys, and documents are permanently removed. This cannot be undone."
+    }
+  },
+  "collections": {
+    "title": "Collections",
+    "subtitle": "Searchable document sets within this workspace.",
+    "new": "New collection",
+    "editTitle": "Edit collection",
+    "namePlaceholder": "e.g. Q3 Reports",
+    "descHint": "Optional — what this collection holds.",
+    "empty": {
+      "title": "No collections yet",
+      "canCreate": "Create a collection to start ingesting and searching documents.",
+      "readonly": "No collections here yet."
+    },
+    "error": "Could not load collections",
+    "toast": {
+      "created": "Collection “{{name}}” created.",
+      "updated": "Collection updated.",
+      "deleted": "Collection “{{name}}” deleted."
+    },
+    "delete": {
+      "title": "Delete collection",
+      "message": "Delete “{{name}}”? Its documents and indexed vectors are permanently removed. This cannot be undone."
+    }
+  },
+  "documents": {
+    "title": "Documents",
+    "subtitle": {
+      "canWrite": "Upload files to ingest them into this collection.",
+      "readonly": "Browse and search documents in this collection."
+    },
+    "error": "Could not load documents",
+    "empty": {
+      "none": {
+        "title": "No documents yet",
+        "description": "Drop files into the area above to start ingesting them."
+      },
+      "filtered": {
+        "title": "No matching documents",
+        "description": "No documents match the current filters. Adjust or clear them to see more."
+      }
+    },
+    "retention": {
+      "label": "Temporary — automatically delete after",
+      "aria": "Retention in days",
+      "day_one": "day",
+      "day_other": "days"
+    },
+    "delete": {
+      "title": "Delete document",
+      "message": "Delete “{{name}}”? Its chunks and indexed vectors are removed. This cannot be undone."
+    },
+    "toast": {
+      "queued_one": "{{count}} file queued for ingestion.",
+      "queued_other": "{{count}} files queued for ingestion.",
+      "uploadError": "{{name}}: {{error}}",
+      "tooLarge": "{{name}} is larger than {{max}} MB and was skipped.",
+      "deleted": "Deleted “{{name}}”.",
+      "reprocessing": "Reprocessing “{{name}}”.",
+      "indexing": "Indexing “{{name}}”."
+    },
+    "progress": {
+      "ingesting": "Ingesting"
+    },
+    "row": {
+      "chunk_one": "{{count}} chunk",
+      "chunk_other": "{{count}} chunks",
+      "updated": "updated {{ago}}",
+      "original": "original: {{name}}",
+      "why": "Why?",
+      "hide": "Hide",
+      "downloadOriginalAria": "Download original source file ({{name}})"
+    },
+    "index": {
+      "indexed": "Indexed",
+      "indexedTitle": "Indexed for BM25 / keyword search",
+      "notIndexedTitle": "Not in the keyword index — click to index",
+      "index": "Index",
+      "indexing": "Indexing…"
+    },
+    "failure": {
+      "loading": "Loading error…",
+      "loadError": "Could not load the error detail.",
+      "none": "No error detail recorded."
+    },
+    "filters": {
+      "searchPlaceholder": "Search filenames…",
+      "statusAria": "Status",
+      "anyStatus": "Any status",
+      "typeAria": "File type",
+      "anyType": "Any type",
+      "indexedAria": "Indexed",
+      "indexedAny": "Indexed: any",
+      "indexed": "Indexed",
+      "notIndexed": "Not indexed",
+      "storageBackend": "Storage backend",
+      "embeddingModel": "Embedding model",
+      "size": "Size (bytes)",
+      "created": "Created"
+    },
+    "upload": {
+      "uploading": "Uploading…",
+      "drag": "Drag files here, or ",
+      "browse": "browse",
+      "hint": "PDF, text, Markdown · DOCX/PPTX with docling · up to {{max}} MB each"
+    }
+  },
+  "auth": {
+    "field": {
+      "username": "Username",
+      "password": "Password"
+    },
+    "login": {
+      "subtitle": "Sign in to your account.",
+      "submit": "Sign in",
+      "submitting": "Signing in…",
+      "useMaster": "Use master key instead",
+      "invalid": "Invalid username or password."
+    },
+    "unlock": {
+      "subtitle": "Enter your master key to unlock the console.",
+      "masterKey": "Master key",
+      "submit": "Unlock",
+      "submitting": "Verifying…",
+      "back": "Back to sign in",
+      "rejected": "That key was rejected. Check it and try again."
+    },
+    "api": {
+      "checking": "Checking API…",
+      "unreachable": "API unreachable",
+      "ready": "API ready · {{model}}",
+      "modelFallback": "model"
+    },
+    "password": {
+      "current": "Current password",
+      "new": "New password",
+      "confirm": "Confirm new password",
+      "hint": "At least {{min}} characters.",
+      "tooShort": "Use at least {{min}} characters.",
+      "mismatch": "Passwords do not match.",
+      "update": "Update password",
+      "setContinue": "Set password & continue",
+      "changeTitle": "Change password",
+      "updated": "Password updated.",
+      "failed": "Could not change the password.",
+      "setTitle": "Set a new password",
+      "signedInAs": "Signed in as {{name}}. ",
+      "chooseNew": "Choose a new password to finish signing in."
+    }
+  },
+  "errors": {
+    "network": "Could not reach the API. Is the stack running?",
+    "sessionExpired": "Session expired. Please sign in again.",
+    "accountDeactivated": "Your account has been deactivated.",
+    "adminRequired": "Administrator access required.",
+    "configNotLoaded": "Config not loaded yet.",
+    "passwordChangeRequired": "Password change required."
+  },
+  "search": {
+    "title": "Search",
+    "subtitle": "Hybrid BM25 + semantic search across your collections.",
+    "queryPlaceholder": "Search your collections…",
+    "submit": "Search",
+    "selectPrompt": "Select at least one collection to search.",
+    "topK": "Top-K",
+    "modeLabel": "Mode",
+    "mode": {
+      "hybrid": "Hybrid",
+      "semantic": "Semantic",
+      "bm25": "BM25",
+      "semantic_only": "Semantic only"
+    },
+    "modeHint": {
+      "hybrid": "BM25 + semantic",
+      "semantic": "Vector similarity",
+      "bm25": "Keyword ranking",
+      "semantic_only": "BM25 index unavailable — fell back to semantic"
+    },
+    "alpha": "Alpha",
+    "alphaHint": "0 = BM25 only, 1 = semantic only",
+    "hideFilters": "Hide filters",
+    "filters": "Filters",
+    "filename": "Filename",
+    "filenamePlaceholder": "e.g. report.pdf",
+    "commaSeparated": "Comma-separated",
+    "tagsPlaceholder": "e.g. finance, q3",
+    "failed": "Search failed",
+    "empty": {
+      "title": "Search your collections",
+      "description": "Pick one or more collections on the left, type a query, and run it."
+    },
+    "noMatches": {
+      "title": "No matches",
+      "description": "No chunks matched this query in the selected collections. Try broadening the query or relaxing filters."
+    },
+    "timing": "embed {{embed}}ms · search {{search}}ms · total {{total}}ms",
+    "underDelivered": {
+      "withTopK": "Fewer results than requested (top_k {{topK}}). A selective filter or a small candidate pool left some slots unfilled.",
+      "noTopK": "Fewer results than requested. A selective filter or a small candidate pool left some slots unfilled."
+    },
+    "breakdown": {
+      "title": "Per-collection breakdown",
+      "stats": "{{retrieved}} → {{returned}} · {{contributed}} in top-k"
+    },
+    "relevanceScore": "Relevance score",
+    "unknownFile": "Unknown file",
+    "pages": "· pp.{{range}}",
+    "page": "· p.{{page}}",
+    "tree": {
+      "noWorkspaces": "No workspaces yet.",
+      "collapse": "Collapse {{name}}",
+      "expand": "Expand {{name}}",
+      "all": "All",
+      "noCollections": "No collections"
+    }
+  },
+  "tags": {
+    "subtitle": "Correlate and filter collections and documents across this workspace.",
+    "new": "New tag",
+    "error": "Could not load tags",
+    "empty": {
+      "title": "No tags yet",
+      "description": "Create a tag to correlate and filter collections and documents."
+    },
+    "count": {
+      "col": "{{count}} col",
+      "doc": "{{count}} doc"
+    },
+    "workspaceBadge": "workspace",
+    "mergeAria": "Merge {{name}}",
+    "itemsError": "Could not load items",
+    "notAssigned": "Not assigned to anything yet.",
+    "none": "None",
+    "editTitle": "Edit tag",
+    "nameHint": "Lowercased and trimmed on save.",
+    "namePlaceholder": "e.g. finance",
+    "mergeTitle": "Merge tag",
+    "merge": "Merge",
+    "mergeInto": "Merge into",
+    "mergeIntro": {
+      "before": "Move every assignment of ",
+      "after": " onto another tag, then delete it."
+    },
+    "noMergeTargets": "No other tags to merge into.",
+    "selectTag": "Select a tag…",
+    "filterByTag": "Filter by tag:",
+    "delete": {
+      "title": "Delete tag",
+      "message": "Delete “{{name}}”? It is removed from every collection and document it tags. This cannot be undone."
+    },
+    "toast": {
+      "created": "Tag “{{name}}” created.",
+      "updated": "Tag updated.",
+      "merged": "Tags merged.",
+      "deleted": "Tag “{{name}}” deleted."
+    },
+    "picker": {
+      "add": "Tag",
+      "placeholder": "Filter or create…",
+      "create": "Create “{{name}}”",
+      "empty": "No tags yet."
+    }
+  },
+  "graph": {
+    "title": "Graph",
+    "subtitle": "Files (the larger nodes) linked through the tags they share. Hotter tag nodes are more-reused. Drag a node to pin and highlight it, click it to release; tune the repel force or reset to re-center.",
+    "workspaceAria": "Workspace",
+    "collectionAria": "Collection",
+    "allCollections": "All collections",
+    "error": "Could not load the graph",
+    "empty": {
+      "title": "Nothing to graph yet",
+      "description": "Tag some documents in this scope and they'll appear here, linked through their shared tags."
+    },
+    "resetView": "Reset view",
+    "reset": "Reset",
+    "heat": {
+      "title": "Tag heat",
+      "files_one": "{{count}} file",
+      "files_other": "{{count}} files"
+    },
+    "open": "Open",
+    "download": "Download",
+    "files": "Files",
+    "node": {
+      "usedBy_one": "Used by {{count}} file.",
+      "usedBy_other": "Used by {{count}} files.",
+      "tags_one": "{{count}} tag.",
+      "tags_other": "{{count}} tags."
+    },
+    "zoomIn": "Zoom in",
+    "zoomOut": "Zoom out",
+    "fitToView": "Fit to view",
+    "repel": {
+      "title": "Repel force — how strongly nodes push each other apart",
+      "aria": "Repel force"
+    }
+  },
+  "dashboard": {
+    "title": "Dashboard",
+    "subtitle": "System health and recent activity at a glance.",
+    "health": {
+      "unreachable": "Could not reach the health endpoint.",
+      "system": "System",
+      "vectorStore": "Vector store",
+      "version": "Version",
+      "uptime": "Uptime"
+    },
+    "viewAll": "View all",
+    "goToWorkspaces": "Go to Workspaces",
+    "recentActivity": "Recent activity",
+    "noActivity": {
+      "title": "No recent activity",
+      "description": "Document ingestion across your collections will show up here."
+    }
+  },
+  "indexing": {
+    "title": "Indexing",
+    "subtitle": "Keyword-index coverage per collection. A document is searchable once its chunks are stored — the keyword index is maintained automatically, so there is nothing to rebuild. Anything short of full coverage is an ingestion that has not finished; retry the failed ones here.",
+    "error": "Could not load index status",
+    "empty": {
+      "title": "Nothing to index yet",
+      "description": "Upload documents to a collection and they'll appear here."
+    },
+    "unindexed_one": "{{count}} unindexed",
+    "unindexed_other": "{{count}} unindexed",
+    "coverage": "{{indexed}}/{{total}} indexed",
+    "pendingSuffix": " · {{count}} ingesting",
+    "failedSuffix": " · {{count}} failed",
+    "failedDocs_one": "{{count}} failed document",
+    "failedDocs_other": "{{count}} failed documents",
+    "retryFailed": "Retry failed",
+    "retryDialog": {
+      "title": "Retry failed ingestions",
+      "message": "Re-ingest the {{docs}} in “{{name}}”? Each is re-queued and embedded again from its stored file — resuming where the last attempt stopped — so this spends embedding-provider quota. Documents still ingesting are left alone."
+    },
+    "toast": {
+      "requeued_one": "Re-queued {{count}} document.",
+      "requeued_other": "Re-queued {{count}} documents."
+    }
+  },
+  "queue": {
+    "retryFailed": "Retry failed",
+    "retryAllFailed": "Retry all failed",
+    "queueEmpty": "Queue empty",
+    "paused": "· paused on the embedding provider's quota — retrying in {{time}}",
+    "live": "Live",
+    "connecting": "Connecting…",
+    "error": "Could not load the queue",
+    "openInCollectionTitle": "Open in collection to edit or delete",
+    "open": "Open",
+    "unknownCollection": "Unknown collection",
+    "chunks": "Chunks",
+    "chunksLatest": "(latest)",
+    "chunkProgress": "{{current}} / {{total}} chunks",
+    "retryIn": "retry in {{time}}",
+    "retrying": "retrying…",
+    "parts": {
+      "ingesting": "{{count}} ingesting",
+      "queued": "{{count}} queued",
+      "waiting": "{{count}} waiting on rate limit"
+    },
+    "filters": {
+      "collectionPlaceholder": "Collection name"
+    },
+    "empty": {
+      "filtered": {
+        "title": "No matching jobs",
+        "description": "No ingestion jobs match the current filters. Adjust or clear them to see more."
+      },
+      "none": {
+        "title": "No ingestions yet",
+        "description": "Upload a document and its chunks will stream here in real time as they're embedded."
+      }
+    },
+    "retryDialog": {
+      "title": "Retry failed documents",
+      "message": "Re-run ingestion for every failed document in the queue? Each is re-queued from where it left off.",
+      "messageFiltered": "Re-run ingestion for every failed document matching the current filters? Each is re-queued from where it left off."
+    },
+    "toast": {
+      "reenqueued_one": "Re-enqueued {{count}} failed document.",
+      "reenqueued_other": "Re-enqueued {{count}} failed documents.",
+      "noneMatched": "No failed documents matched the current filters."
+    },
+    "phase": {
+      "parsing": "parsing",
+      "embedding": "embedding",
+      "storing": "storing",
+      "rate_limited": "rate limited",
+      "done": "done",
+      "failed": "failed"
+    }
+  },
+  "ui": {
+    "queryError": {
+      "title": "Could not load this"
+    },
+    "copyButton": {
+      "failed": "Copy failed — select it and copy manually."
+    },
+    "errorBoundary": {
+      "title": "Something went wrong"
+    },
+    "pager": {
+      "range": "Showing {{from}}–{{to}} of {{total}}",
+      "previous": "Previous",
+      "page": "Page {{page}} of {{pages}}",
+      "next": "Next"
+    }
+  },
+  "users": {
+    "title": "Users",
+    "subtitle": "Each user signs in with a username + password (admins get the full console; others are scoped by their grants) and may hold one API key for MCP/programmatic access.",
+    "new": "New user",
+    "editTitle": "Edit user",
+    "admin": "Admin",
+    "error": "Could not load users",
+    "revoke": "Revoke",
+    "empty": {
+      "title": "No users yet",
+      "description": "Create a user, share their one-time password, and grant access to workspaces or collections."
+    },
+    "status": {
+      "active": "Active",
+      "inactive": "Inactive"
+    },
+    "actions": {
+      "permissions": "Permissions",
+      "apiKey": "API key",
+      "edit": "Edit",
+      "delete": "Delete"
+    },
+    "row": {
+      "key": "key {{prefix}}…",
+      "noKey": "no API key",
+      "created": "created {{date}}",
+      "rpm": "{{rpm}} rpm",
+      "activateAria": "Activate user",
+      "deactivateAria": "Deactivate user",
+      "manageAria": "Manage {{username}}"
+    },
+    "toast": {
+      "updated": "User updated.",
+      "deleted": "User “{{username}}” deleted."
+    },
+    "reveal": {
+      "done": "Done",
+      "created": {
+        "title": "User “{{username}}” created",
+        "message": "Share this one-time password with the user — they will be asked to change it on first sign-in. It is shown only once."
+      },
+      "reset": {
+        "title": "Password reset for “{{username}}”",
+        "message": "Share this one-time password with the user — their old password no longer works and they will set a new one on next sign-in. Shown only once."
+      }
+    },
+    "delete": {
+      "title": "Delete user",
+      "message": "Delete “{{username}}”? Their API key and all permission grants are permanently removed. This cannot be undone."
+    },
+    "reset": {
+      "title": "Reset password",
+      "message": "Reset the password for “{{username}}”? Their current password stops working immediately and any active session is signed out."
+    },
+    "form": {
+      "usernameHint": "Used to sign in. Letters, digits, and . _ + @ - (3–64 chars).",
+      "usernameError": "Enter a valid username (3–64 characters).",
+      "usernamePlaceholder": "e.g. jane",
+      "email": "Email",
+      "emailHint": "Optional — leave blank if the user has no email.",
+      "emailError": "Enter a valid email address.",
+      "emailPlaceholder": "e.g. jane@example.com",
+      "nameHint": "Optional — a display name.",
+      "rateLimit": "MCP rate limit (requests/min)",
+      "rateLimitHint": "Caps this user's key on /api/mcp. 0 = use the global default.",
+      "activeLabel": "Active — an inactive user can't sign in and their API key stops working",
+      "adminLabel": "Admin — full console access (manage users, settings, every workspace)"
+    },
+    "key": {
+      "title": "API key — {{name}}",
+      "revealMessage": "Copy this key now — it is shown in full only once and cannot be retrieved again.",
+      "used": "used {{ago}}",
+      "neverUsed": "never used",
+      "revokeAria": "Revoke key",
+      "none": "This user has no API key yet.",
+      "rotate": "Rotate key",
+      "create": "Create key",
+      "rotateHint": "Rotating replaces the current key — the old one stops working immediately.",
+      "toast": {
+        "revoked": "Key revoked."
+      }
+    },
+    "grants": {
+      "modalTitle": "Permissions — {{email}}",
+      "intro": {
+        "lead": "Permissions",
+        "emphasis": "scope this user down",
+        "rest": ". With none, they see and write everything. A workspace limits them to it; add a collection (or document) to narrow them to just that one."
+      },
+      "error": "Could not load grants",
+      "empty": {
+        "title": "No permissions yet",
+        "description": "Grant this user read or write on a workspace, collection, or document above."
+      },
+      "resourceType": "Resource type",
+      "type": {
+        "workspace": "Workspace",
+        "collection": "Collection",
+        "document": "Document",
+        "capability": "Capability"
+      },
+      "levelLabel": "Level",
+      "readOption": "Read — search, list, download",
+      "writeOption": "Write — ingest, delete (and read)",
+      "read": "Read",
+      "write": "Write",
+      "capabilityLabel": {
+        "create_workspace": "Create workspaces",
+        "manage_tags": "Manage tags"
+      },
+      "capabilityHelp": {
+        "create_workspace": "Lets this user create new workspaces — they get write access to any they create.",
+        "manage_tags": "Lets this user create, edit, delete, and assign tags in any workspace they can read."
+      },
+      "selectWorkspace": "Select a workspace…",
+      "select": "Select…",
+      "pickWorkspaceFirst": "Pick a workspace first",
+      "documentId": "Document ID",
+      "documentIdHint": "The document's id (e.g. doc_…), from its collection.",
+      "addPermission": "Add permission",
+      "deleted": "deleted",
+      "copyIdTitle": "Copy id: {{id}}",
+      "copyIdAria": "Copy id {{id}}",
+      "revokeAria": "Revoke permission",
+      "toast": {
+        "granted": "Permission granted.",
+        "revoked": "Permission revoked."
+      }
+    }
+  },
+  "settings": {
+    "title": "Settings",
+    "subtitle": "Runtime configuration, console security, and MCP access.",
+    "tabs": {
+      "general": "General",
+      "mcp": "MCP server"
+    },
+    "config": {
+      "title": "Configuration",
+      "loadError": "Could not load configuration"
+    },
+    "runtime": {
+      "title": "Runtime",
+      "unreachable": "API unreachable",
+      "unreachableDetail": "Could not reach the health endpoint.",
+      "service": "Service",
+      "version": "Version",
+      "vectorStore": "Vector store",
+      "embeddingProvider": "Embedding provider",
+      "embeddingModel": "Embedding model",
+      "uptime": "Uptime"
+    },
+    "security": {
+      "title": "Security",
+      "session": "Session",
+      "sessionNote": "Your credential is held in this browser only. Sign out to clear it.",
+      "signOut": "Sign out"
+    },
+    "field": {
+      "provider": "Provider",
+      "model": "Model",
+      "baseUrl": "Base URL",
+      "apiKey": "API key",
+      "apiKeyHint": "Write-only; never shown after saving.",
+      "keySetPlaceholder": "key set — leave blank to keep",
+      "aiStudioKey": "AI Studio key",
+      "baseUrlRequiredOpenrouter": "required — e.g. https://openrouter.ai/api",
+      "baseUrlOllamaDefault": "blank uses the Ollama default",
+      "modelIdPlaceholder": "model id",
+      "ollamaModelsHint": "Installed Ollama models",
+      "ollamaUnreachable": "Could not reach Ollama",
+      "loadingModels": "Loading models…",
+      "noModelsInstalled": "No models installed"
+    },
+    "provider": {
+      "ollamaLocal": "Ollama (local)",
+      "sentenceTransformers": "Sentence-Transformers (in-process)",
+      "openaiCompat": "OpenAI-compatible",
+      "gemini": "Google Gemini",
+      "geminiAiStudio": "Google Gemini (AI Studio)"
+    },
+    "storage": {
+      "blurb": "Where uploaded files are stored. The active backend is chosen in <code>config.yaml</code> / <code>.env</code>. Retention is set <strong>per upload</strong> (1–30 days, or kept permanently) on the Documents page — there's no global retention setting.",
+      "title": "Object storage",
+      "activeBackend": "Active backend"
+    },
+    "parser": {
+      "title": "PDF parsing",
+      "backend": "Backend",
+      "optionPymupdf": "PyMuPDF — fast, one chunk per page",
+      "optionDocling": "docling — section-aware + tables/OCR",
+      "needsGpuSuffix": " (needs a GPU)",
+      "gpuOlderThanAmpere": "Your GPU ({{name}}, capability {{capability}}) is older than Ampere — ",
+      "noGpuDetected": "No GPU detected — ",
+      "doclingCpuWarn": "docling runs on CPU and is <strong>very slow</strong> (minutes per document, and large PDFs can hit the ingestion time limit). PyMuPDF is recommended on this hardware.",
+      "save": "Save PDF backend",
+      "detectingGpu": "Detecting GPU…",
+      "compatibleGpu": "Compatible GPU detected ({{name}}, capability {{capability}}).",
+      "gpuBelowAmpere": "GPU {{name}} (capability {{capability}}) is below Ampere.",
+      "noCompatibleGpu": "No compatible GPU detected.",
+      "recommendedLabel": "Recommended:"
+    },
+    "embedding": {
+      "blurb": "The embedding model turns documents into vectors. <strong>Changing the provider, model, or output dimensions changes the vector size</strong> — existing collections must be re-indexed or search will break. Changing only an API key is safe.",
+      "title": "Embedding model",
+      "modelHintGemini": "e.g. gemini-embedding-001",
+      "modelHint": "the exact model id on this server",
+      "outputDim": "Output dimensions",
+      "outputDimHint": "optional; blank = full 3072",
+      "maxRpm": "Max requests / min",
+      "maxRpmHint": "throttle embeds so bulk ingestion stays under the provider's quota (each text = one request); blank or 0 = unlimited",
+      "maxRpmPlaceholder": "0 (unlimited)",
+      "reindexRequired": "Re-index required after saving",
+      "save": "Save embedding config"
+    },
+    "reranker": {
+      "blurb": "The reranker reorders retrieved chunks by true query relevance before the final cut — the biggest precision win. It's <strong>optional and safe</strong>: if the model or a remote provider is unavailable, search falls back to its normal ranking.",
+      "title": "Reranker",
+      "enable": "Enable reranking",
+      "providerCrossEncoder": "Cross-encoder (local, no key)",
+      "providerRerankApi": "Hosted rerank API (Cohere / Jina / Voyage)",
+      "providerLlm": "LLM-as-reranker",
+      "llmProvider": "LLM provider",
+      "modelHintRerankApi": "e.g. rerank-v3.5 (Cohere), jina-reranker-v2 (Jina)",
+      "modelHintGemini": "e.g. gemini-2.5-flash",
+      "modelHintLlm": "the exact chat model id",
+      "modelHintCrossEncoder": "a HuggingFace cross-encoder id; the baked default is offline-safe",
+      "baseUrlHintRerankApi": "required — the full /rerank endpoint",
+      "topN": "Candidates scored (top_n)",
+      "topNHint": "max candidates the reranker scores per collection",
+      "save": "Save reranker config"
+    },
+    "search": {
+      "blurb": "Adjacency expansion pulls the chunks next to each result and merges them into one span, so a section that runs across pages comes back whole instead of cut at the top-K boundary. It's a plain lookup — no extra model calls — and <strong>safe</strong>: if it can't fetch, search returns the un-expanded results.",
+      "title": "Retrieval",
+      "expand": "Adjacency expansion (neighbours)",
+      "expandHint": "chunks pulled on each side of a hit; 0 = off, max {{max}}",
+      "save": "Save search config"
+    },
+    "mcp": {
+      "blurb": "The MCP endpoint (<code>/api/mcp</code>) throttles each API key to this many requests per minute; the next request in the same minute returns <code>429</code>. Each key gets its own budget, and the new limit <strong>applies to the next MCP request</strong>",
+      "title": "MCP server",
+      "rateLimit": "Rate limit (requests / min per key)",
+      "rateLimitHint": "per API key on /api/mcp; the next request in the same minute returns 429",
+      "save": "Save MCP config"
+    },
+    "toast": {
+      "pdfSaved": "PDF backend saved. Services are reloading.",
+      "embeddingSaved": "Embedding config saved. Services are reloading.",
+      "rerankerSaved": "Reranker config saved. Services are reloading.",
+      "searchSaved": "Search config saved. Services are reloading.",
+      "mcpSaved": "MCP config saved. Services are reloading."
+    }
+  },
+  "mcp": {
+    "tagsNote": "Tag tools need the manage_tags permission; assigning to a collection/document also needs write on it.",
+    "connection": {
+      "title": "Connection",
+      "address": "Server address",
+      "addressHintLocal": "This address only works on this machine; the server couldn't determine a LAN IP for other devices to use.",
+      "addressHint": "Auto-detected from the server. Used to build the endpoint and snippets below.",
+      "endpoint": "Endpoint",
+      "transport": "Transport",
+      "authHeader": "Auth header",
+      "authNote": "Send an <strong>API key</strong> on every request as <authcode></authcode> or <apikeycode></apikeycode> — the master key, or a <strong>per-user key</strong> for scoped access (each tool respects that user's read/write grants). Substitute your own in the snippets below; nothing is embedded here."
+    },
+    "clientSetup": {
+      "title": "Client setup",
+      "instructions": "Add this to your MCP client's server config (replace the placeholder key):",
+      "copyConfig": "Copy config"
+    },
+    "skill": {
+      "title": "Agent skill",
+      "download": "Download .zip",
+      "folderNote": "A small skill folder (<code>SKILL.md</code> + <code>references/</code>). Unzip it into your agent's skills directory (e.g. <code>.claude/skills/embedbase/</code>) — the agent loads <code>SKILL.md</code> up front and opens a reference file only when the task needs it, so a read-only session never pulls in the upload rules.",
+      "bundled": "Bundled:",
+      "unavailable": "The skill is unavailable — the tool catalogue could not be loaded."
+    },
+    "tools": {
+      "title": "Tools",
+      "count_one": "{{count}} tool · each respects your grants",
+      "count_other": "{{count}} tools · each respects your grants",
+      "loadError": "Could not load the tool catalogue"
+    },
+    "rest": {
+      "title": "REST API reference",
+      "blurb": "A standalone OpenAPI reference of just the integration endpoints — search and workspace/collection/document access — for the AI to read as the API standard."
+    }
+  }
+}
diff --git a/ui/src/i18n/locales/pt-BR/translation.json b/ui/src/i18n/locales/pt-BR/translation.json
new file mode 100644
index 0000000..86a11ae
--- /dev/null
+++ b/ui/src/i18n/locales/pt-BR/translation.json
@@ -0,0 +1,782 @@
+{
+  "common": {
+    "saving": "Salvando…",
+    "cancel": "Cancelar",
+    "create": "Criar",
+    "saveChanges": "Salvar alterações",
+    "name": "Nome",
+    "description": "Descrição",
+    "optional": "Opcional",
+    "color": "Cor",
+    "icon": "Ícone",
+    "tags": "Tags",
+    "noDescription": "Sem descrição",
+    "created": "Criado em {{date}}",
+    "editAria": "Editar {{name}}",
+    "deleteAria": "Excluir {{name}}",
+    "more": "Mais",
+    "clear": "Limpar",
+    "retry": "Tentar novamente",
+    "retrying": "Tentando…",
+    "min": "mín",
+    "max": "máx",
+    "openAria": "Abrir {{name}}",
+    "downloadAria": "Baixar {{name}}",
+    "close": "Fechar",
+    "removeAria": "Remover {{name}}",
+    "confirm": "Confirmar",
+    "copy": "Copiar",
+    "copied": "Copiado",
+    "dismiss": "Dispensar"
+  },
+  "nav": {
+    "dashboard": "Painel",
+    "workspaces": "Espaços de trabalho",
+    "graph": "Grafo",
+    "search": "Busca",
+    "indexing": "Indexação",
+    "ingestionQueue": "Fila de ingestão",
+    "users": "Usuários",
+    "settings": "Configurações",
+    "admin": "Admin"
+  },
+  "topbar": {
+    "masterKey": "Chave mestra",
+    "adminSuffix": " · admin",
+    "changePassword": "Alterar senha",
+    "changePasswordTitle": "Alterar sua senha",
+    "signOut": "Sair",
+    "signOutTitle": "Sair e encerrar sua sessão",
+    "language": "Alterar idioma"
+  },
+  "status": {
+    "uploading": "Enviando",
+    "pending": "Pendente",
+    "processing": "Processando",
+    "done": "Concluído",
+    "failed": "Falhou",
+    "deleting": "Excluindo",
+    "rate_limited": "Limite atingido"
+  },
+  "workspaces": {
+    "title": "Espaços de trabalho",
+    "subtitle": "Contêineres de nível superior para suas coleções.",
+    "new": "Novo espaço de trabalho",
+    "editTitle": "Editar espaço de trabalho",
+    "namePlaceholder": "ex.: Pesquisa",
+    "descHint": "Opcional — o que vive neste espaço de trabalho.",
+    "empty": {
+      "title": "Nenhum espaço de trabalho ainda",
+      "canCreate": "Crie seu primeiro espaço de trabalho para começar a organizar coleções.",
+      "readonly": "Nenhum espaço de trabalho foi compartilhado com você ainda."
+    },
+    "error": "Não foi possível carregar os espaços de trabalho",
+    "toast": {
+      "created": "Espaço de trabalho “{{name}}” criado.",
+      "updated": "Espaço de trabalho atualizado.",
+      "deleted": "Espaço de trabalho “{{name}}” excluído."
+    },
+    "delete": {
+      "title": "Excluir espaço de trabalho",
+      "message": "Excluir “{{name}}”? Suas coleções, chaves de API e documentos serão removidos permanentemente. Isso não pode ser desfeito."
+    }
+  },
+  "collections": {
+    "title": "Coleções",
+    "subtitle": "Conjuntos de documentos pesquisáveis neste espaço de trabalho.",
+    "new": "Nova coleção",
+    "editTitle": "Editar coleção",
+    "namePlaceholder": "ex.: Relatórios do 3º tri",
+    "descHint": "Opcional — o que esta coleção contém.",
+    "empty": {
+      "title": "Nenhuma coleção ainda",
+      "canCreate": "Crie uma coleção para começar a ingerir e pesquisar documentos.",
+      "readonly": "Nenhuma coleção aqui ainda."
+    },
+    "error": "Não foi possível carregar as coleções",
+    "toast": {
+      "created": "Coleção “{{name}}” criada.",
+      "updated": "Coleção atualizada.",
+      "deleted": "Coleção “{{name}}” excluída."
+    },
+    "delete": {
+      "title": "Excluir coleção",
+      "message": "Excluir “{{name}}”? Seus documentos e vetores indexados serão removidos permanentemente. Isso não pode ser desfeito."
+    }
+  },
+  "documents": {
+    "title": "Documentos",
+    "subtitle": {
+      "canWrite": "Envie arquivos para ingeri-los nesta coleção.",
+      "readonly": "Navegue e pesquise documentos nesta coleção."
+    },
+    "error": "Não foi possível carregar os documentos",
+    "empty": {
+      "none": {
+        "title": "Nenhum documento ainda",
+        "description": "Solte arquivos na área acima para começar a ingeri-los."
+      },
+      "filtered": {
+        "title": "Nenhum documento correspondente",
+        "description": "Nenhum documento corresponde aos filtros atuais. Ajuste ou limpe-os para ver mais."
+      }
+    },
+    "retention": {
+      "label": "Temporário — excluir automaticamente após",
+      "aria": "Retenção em dias",
+      "day_one": "dia",
+      "day_other": "dias"
+    },
+    "delete": {
+      "title": "Excluir documento",
+      "message": "Excluir “{{name}}”? Seus chunks e vetores indexados serão removidos. Isso não pode ser desfeito."
+    },
+    "toast": {
+      "queued_one": "{{count}} arquivo na fila para ingestão.",
+      "queued_other": "{{count}} arquivos na fila para ingestão.",
+      "uploadError": "{{name}}: {{error}}",
+      "tooLarge": "{{name}} é maior que {{max}} MB e foi ignorado.",
+      "deleted": "“{{name}}” excluído.",
+      "reprocessing": "Reprocessando “{{name}}”.",
+      "indexing": "Indexando “{{name}}”."
+    },
+    "progress": {
+      "ingesting": "Ingerindo"
+    },
+    "row": {
+      "chunk_one": "{{count}} chunk",
+      "chunk_other": "{{count}} chunks",
+      "updated": "atualizado {{ago}}",
+      "original": "original: {{name}}",
+      "why": "Por quê?",
+      "hide": "Ocultar",
+      "downloadOriginalAria": "Baixar arquivo de origem original ({{name}})"
+    },
+    "index": {
+      "indexed": "Indexado",
+      "indexedTitle": "Indexado para busca BM25 / por palavra-chave",
+      "notIndexedTitle": "Fora do índice de palavras-chave — clique para indexar",
+      "index": "Indexar",
+      "indexing": "Indexando…"
+    },
+    "failure": {
+      "loading": "Carregando erro…",
+      "loadError": "Não foi possível carregar o detalhe do erro.",
+      "none": "Nenhum detalhe de erro registrado."
+    },
+    "filters": {
+      "searchPlaceholder": "Buscar nomes de arquivo…",
+      "statusAria": "Status",
+      "anyStatus": "Qualquer status",
+      "typeAria": "Tipo de arquivo",
+      "anyType": "Qualquer tipo",
+      "indexedAria": "Indexado",
+      "indexedAny": "Indexado: qualquer",
+      "indexed": "Indexado",
+      "notIndexed": "Não indexado",
+      "storageBackend": "Backend de armazenamento",
+      "embeddingModel": "Modelo de embedding",
+      "size": "Tamanho (bytes)",
+      "created": "Criado"
+    },
+    "upload": {
+      "uploading": "Enviando…",
+      "drag": "Arraste arquivos aqui, ou ",
+      "browse": "procurar",
+      "hint": "PDF, texto, Markdown · DOCX/PPTX com docling · até {{max}} MB cada"
+    }
+  },
+  "auth": {
+    "field": {
+      "username": "Usuário",
+      "password": "Senha"
+    },
+    "login": {
+      "subtitle": "Entre na sua conta.",
+      "submit": "Entrar",
+      "submitting": "Entrando…",
+      "useMaster": "Usar chave mestra",
+      "invalid": "Usuário ou senha inválidos."
+    },
+    "unlock": {
+      "subtitle": "Digite sua chave mestra para desbloquear o console.",
+      "masterKey": "Chave mestra",
+      "submit": "Desbloquear",
+      "submitting": "Verificando…",
+      "back": "Voltar para o login",
+      "rejected": "Essa chave foi rejeitada. Verifique e tente novamente."
+    },
+    "api": {
+      "checking": "Verificando API…",
+      "unreachable": "API inacessível",
+      "ready": "API pronta · {{model}}",
+      "modelFallback": "modelo"
+    },
+    "password": {
+      "current": "Senha atual",
+      "new": "Nova senha",
+      "confirm": "Confirmar nova senha",
+      "hint": "Pelo menos {{min}} caracteres.",
+      "tooShort": "Use pelo menos {{min}} caracteres.",
+      "mismatch": "As senhas não coincidem.",
+      "update": "Atualizar senha",
+      "setContinue": "Definir senha e continuar",
+      "changeTitle": "Alterar senha",
+      "updated": "Senha atualizada.",
+      "failed": "Não foi possível alterar a senha.",
+      "setTitle": "Definir uma nova senha",
+      "signedInAs": "Conectado como {{name}}. ",
+      "chooseNew": "Escolha uma nova senha para concluir o login."
+    }
+  },
+  "errors": {
+    "network": "Não foi possível conectar à API. O sistema está em execução?",
+    "sessionExpired": "Sessão expirada. Entre novamente.",
+    "accountDeactivated": "Sua conta foi desativada.",
+    "adminRequired": "Acesso de administrador necessário.",
+    "configNotLoaded": "Configuração ainda não carregada.",
+    "passwordChangeRequired": "É necessário alterar a senha."
+  },
+  "search": {
+    "title": "Busca",
+    "subtitle": "Busca híbrida BM25 + semântica em todas as suas coleções.",
+    "queryPlaceholder": "Busque em suas coleções…",
+    "submit": "Buscar",
+    "selectPrompt": "Selecione ao menos uma coleção para buscar.",
+    "topK": "Top-K",
+    "modeLabel": "Modo",
+    "mode": {
+      "hybrid": "Híbrida",
+      "semantic": "Semântica",
+      "bm25": "BM25",
+      "semantic_only": "Somente semântica"
+    },
+    "modeHint": {
+      "hybrid": "BM25 + semântica",
+      "semantic": "Similaridade vetorial",
+      "bm25": "Ranking por palavra-chave",
+      "semantic_only": "Índice BM25 indisponível — recorreu à busca semântica"
+    },
+    "alpha": "Alfa",
+    "alphaHint": "0 = somente BM25, 1 = somente semântica",
+    "hideFilters": "Ocultar filtros",
+    "filters": "Filtros",
+    "filename": "Nome do arquivo",
+    "filenamePlaceholder": "ex.: relatorio.pdf",
+    "commaSeparated": "Separadas por vírgula",
+    "tagsPlaceholder": "ex.: financeiro, 3tri",
+    "failed": "A busca falhou",
+    "empty": {
+      "title": "Busque em suas coleções",
+      "description": "Escolha uma ou mais coleções à esquerda, digite uma consulta e execute."
+    },
+    "noMatches": {
+      "title": "Nenhum resultado",
+      "description": "Nenhum chunk correspondeu a esta consulta nas coleções selecionadas. Tente ampliar a consulta ou afrouxar os filtros."
+    },
+    "timing": "embedding {{embed}}ms · busca {{search}}ms · total {{total}}ms",
+    "underDelivered": {
+      "withTopK": "Menos resultados que o solicitado (top_k {{topK}}). Um filtro seletivo ou um conjunto pequeno de candidatos deixou algumas vagas sem preencher.",
+      "noTopK": "Menos resultados que o solicitado. Um filtro seletivo ou um conjunto pequeno de candidatos deixou algumas vagas sem preencher."
+    },
+    "breakdown": {
+      "title": "Detalhamento por coleção",
+      "stats": "{{retrieved}} → {{returned}} · {{contributed}} no top-k"
+    },
+    "relevanceScore": "Pontuação de relevância",
+    "unknownFile": "Arquivo desconhecido",
+    "pages": "· pp.{{range}}",
+    "page": "· p.{{page}}",
+    "tree": {
+      "noWorkspaces": "Nenhum espaço de trabalho ainda.",
+      "collapse": "Recolher {{name}}",
+      "expand": "Expandir {{name}}",
+      "all": "Todas",
+      "noCollections": "Nenhuma coleção"
+    }
+  },
+  "tags": {
+    "subtitle": "Correlacione e filtre coleções e documentos neste espaço de trabalho.",
+    "new": "Nova tag",
+    "error": "Não foi possível carregar as tags",
+    "empty": {
+      "title": "Nenhuma tag ainda",
+      "description": "Crie uma tag para correlacionar e filtrar coleções e documentos."
+    },
+    "count": {
+      "col": "{{count}} col",
+      "doc": "{{count}} doc"
+    },
+    "workspaceBadge": "espaço de trabalho",
+    "mergeAria": "Mesclar {{name}}",
+    "itemsError": "Não foi possível carregar os itens",
+    "notAssigned": "Ainda não atribuída a nada.",
+    "none": "Nenhum",
+    "editTitle": "Editar tag",
+    "nameHint": "Convertida para minúsculas e sem espaços nas pontas ao salvar.",
+    "namePlaceholder": "ex.: financeiro",
+    "mergeTitle": "Mesclar tag",
+    "merge": "Mesclar",
+    "mergeInto": "Mesclar em",
+    "mergeIntro": {
+      "before": "Mova todas as atribuições de ",
+      "after": " para outra tag e depois exclua-a."
+    },
+    "noMergeTargets": "Nenhuma outra tag para mesclar.",
+    "selectTag": "Selecione uma tag…",
+    "filterByTag": "Filtrar por tag:",
+    "delete": {
+      "title": "Excluir tag",
+      "message": "Excluir “{{name}}”? Ela será removida de todas as coleções e documentos que marca. Isso não pode ser desfeito."
+    },
+    "toast": {
+      "created": "Tag “{{name}}” criada.",
+      "updated": "Tag atualizada.",
+      "merged": "Tags mescladas.",
+      "deleted": "Tag “{{name}}” excluída."
+    },
+    "picker": {
+      "add": "Tag",
+      "placeholder": "Filtrar ou criar…",
+      "create": "Criar “{{name}}”",
+      "empty": "Nenhuma tag ainda."
+    }
+  },
+  "graph": {
+    "title": "Grafo",
+    "subtitle": "Arquivos (os nós maiores) ligados pelas tags que compartilham. Nós de tag mais quentes são mais reutilizados. Arraste um nó para fixá-lo e destacá-lo, clique para soltá-lo; ajuste a força de repulsão ou redefina para recentralizar.",
+    "workspaceAria": "Espaço de trabalho",
+    "collectionAria": "Coleção",
+    "allCollections": "Todas as coleções",
+    "error": "Não foi possível carregar o grafo",
+    "empty": {
+      "title": "Nada para exibir no grafo ainda",
+      "description": "Marque alguns documentos neste escopo e eles aparecerão aqui, ligados pelas tags que compartilham."
+    },
+    "resetView": "Redefinir visualização",
+    "reset": "Redefinir",
+    "heat": {
+      "title": "Calor das tags",
+      "files_one": "{{count}} arquivo",
+      "files_other": "{{count}} arquivos"
+    },
+    "open": "Abrir",
+    "download": "Baixar",
+    "files": "Arquivos",
+    "node": {
+      "usedBy_one": "Usada por {{count}} arquivo.",
+      "usedBy_other": "Usada por {{count}} arquivos.",
+      "tags_one": "{{count}} tag.",
+      "tags_other": "{{count}} tags."
+    },
+    "zoomIn": "Aproximar",
+    "zoomOut": "Afastar",
+    "fitToView": "Ajustar à tela",
+    "repel": {
+      "title": "Força de repulsão — o quanto os nós se afastam entre si",
+      "aria": "Força de repulsão"
+    }
+  },
+  "dashboard": {
+    "title": "Painel",
+    "subtitle": "Saúde do sistema e atividade recente num relance.",
+    "health": {
+      "unreachable": "Não foi possível acessar o endpoint de saúde.",
+      "system": "Sistema",
+      "vectorStore": "Armazenamento de vetores",
+      "version": "Versão",
+      "uptime": "Tempo de atividade"
+    },
+    "viewAll": "Ver todos",
+    "goToWorkspaces": "Ir para Espaços de trabalho",
+    "recentActivity": "Atividade recente",
+    "noActivity": {
+      "title": "Nenhuma atividade recente",
+      "description": "A ingestão de documentos em suas coleções aparecerá aqui."
+    }
+  },
+  "indexing": {
+    "title": "Indexação",
+    "subtitle": "Cobertura do índice de palavras-chave por coleção. Um documento fica pesquisável assim que seus chunks são armazenados — o índice de palavras-chave é mantido automaticamente, então não há nada a reconstruir. Qualquer cobertura incompleta é uma ingestão que não terminou; repita as que falharam aqui.",
+    "error": "Não foi possível carregar o status de indexação",
+    "empty": {
+      "title": "Nada para indexar ainda",
+      "description": "Envie documentos para uma coleção e eles aparecerão aqui."
+    },
+    "unindexed_one": "{{count}} não indexado",
+    "unindexed_other": "{{count}} não indexados",
+    "coverage": "{{indexed}}/{{total}} indexados",
+    "pendingSuffix": " · {{count}} em ingestão",
+    "failedSuffix": " · {{count}} com falha",
+    "failedDocs_one": "{{count}} documento com falha",
+    "failedDocs_other": "{{count}} documentos com falha",
+    "retryFailed": "Repetir falhas",
+    "retryDialog": {
+      "title": "Repetir ingestões com falha",
+      "message": "Reingerir {{docs}} em “{{name}}”? Cada um é reenfileirado e tem seus embeddings gerados novamente a partir do arquivo armazenado — retomando de onde a última tentativa parou — consumindo cota do provedor de embeddings. Documentos ainda em ingestão são mantidos."
+    },
+    "toast": {
+      "requeued_one": "{{count}} documento reenfileirado.",
+      "requeued_other": "{{count}} documentos reenfileirados."
+    }
+  },
+  "queue": {
+    "retryFailed": "Repetir falhas",
+    "retryAllFailed": "Repetir todas as falhas",
+    "queueEmpty": "Fila vazia",
+    "paused": "· pausado pela cota do provedor de embeddings — repetindo em {{time}}",
+    "live": "Ao vivo",
+    "connecting": "Conectando…",
+    "error": "Não foi possível carregar a fila",
+    "openInCollectionTitle": "Abrir na coleção para editar ou excluir",
+    "open": "Abrir",
+    "unknownCollection": "Coleção desconhecida",
+    "chunks": "Chunks",
+    "chunksLatest": "(mais recentes)",
+    "chunkProgress": "{{current}} / {{total}} chunks",
+    "retryIn": "repetir em {{time}}",
+    "retrying": "repetindo…",
+    "parts": {
+      "ingesting": "{{count}} em ingestão",
+      "queued": "{{count}} na fila",
+      "waiting": "{{count}} aguardando limite de taxa"
+    },
+    "filters": {
+      "collectionPlaceholder": "Nome da coleção"
+    },
+    "empty": {
+      "filtered": {
+        "title": "Nenhum trabalho correspondente",
+        "description": "Nenhum trabalho de ingestão corresponde aos filtros atuais. Ajuste ou limpe-os para ver mais."
+      },
+      "none": {
+        "title": "Nenhuma ingestão ainda",
+        "description": "Envie um documento e seus chunks aparecerão aqui em tempo real conforme seus embeddings são gerados."
+      }
+    },
+    "retryDialog": {
+      "title": "Repetir documentos com falha",
+      "message": "Reexecutar a ingestão de todos os documentos com falha na fila? Cada um é reenfileirado de onde parou.",
+      "messageFiltered": "Reexecutar a ingestão de todos os documentos com falha que correspondem aos filtros atuais? Cada um é reenfileirado de onde parou."
+    },
+    "toast": {
+      "reenqueued_one": "{{count}} documento com falha reenfileirado.",
+      "reenqueued_other": "{{count}} documentos com falha reenfileirados.",
+      "noneMatched": "Nenhum documento com falha corresponde aos filtros atuais."
+    },
+    "phase": {
+      "parsing": "análise",
+      "embedding": "embedding",
+      "storing": "armazenamento",
+      "rate_limited": "limite atingido",
+      "done": "concluído",
+      "failed": "falhou"
+    }
+  },
+  "ui": {
+    "queryError": {
+      "title": "Não foi possível carregar isto"
+    },
+    "copyButton": {
+      "failed": "Falha ao copiar — selecione e copie manualmente."
+    },
+    "errorBoundary": {
+      "title": "Algo deu errado"
+    },
+    "pager": {
+      "range": "Mostrando {{from}}–{{to}} de {{total}}",
+      "previous": "Anterior",
+      "page": "Página {{page}} de {{pages}}",
+      "next": "Próxima"
+    }
+  },
+  "users": {
+    "title": "Usuários",
+    "subtitle": "Cada usuário entra com nome de usuário + senha (administradores têm o console completo; os demais são restritos por suas permissões) e pode ter uma chave de API para acesso programático/via MCP.",
+    "new": "Novo usuário",
+    "editTitle": "Editar usuário",
+    "admin": "Admin",
+    "error": "Não foi possível carregar os usuários",
+    "revoke": "Revogar",
+    "empty": {
+      "title": "Nenhum usuário ainda",
+      "description": "Crie um usuário, compartilhe a senha de uso único e conceda acesso a espaços de trabalho ou coleções."
+    },
+    "status": {
+      "active": "Ativo",
+      "inactive": "Inativo"
+    },
+    "actions": {
+      "permissions": "Permissões",
+      "apiKey": "Chave de API",
+      "edit": "Editar",
+      "delete": "Excluir"
+    },
+    "row": {
+      "key": "chave {{prefix}}…",
+      "noKey": "sem chave de API",
+      "created": "criado em {{date}}",
+      "rpm": "{{rpm}} rpm",
+      "activateAria": "Ativar usuário",
+      "deactivateAria": "Desativar usuário",
+      "manageAria": "Gerenciar {{username}}"
+    },
+    "toast": {
+      "updated": "Usuário atualizado.",
+      "deleted": "Usuário “{{username}}” excluído."
+    },
+    "reveal": {
+      "done": "Concluir",
+      "created": {
+        "title": "Usuário “{{username}}” criado",
+        "message": "Compartilhe esta senha de uso único com o usuário — será solicitado que ele a altere no primeiro acesso. Ela é exibida apenas uma vez."
+      },
+      "reset": {
+        "title": "Senha redefinida para “{{username}}”",
+        "message": "Compartilhe esta senha de uso único com o usuário — a senha antiga não funciona mais e ele definirá uma nova no próximo acesso. Exibida apenas uma vez."
+      }
+    },
+    "delete": {
+      "title": "Excluir usuário",
+      "message": "Excluir “{{username}}”? A chave de API e todas as permissões concedidas serão removidas permanentemente. Isso não pode ser desfeito."
+    },
+    "reset": {
+      "title": "Redefinir senha",
+      "message": "Redefinir a senha de “{{username}}”? A senha atual para de funcionar imediatamente e qualquer sessão ativa é encerrada."
+    },
+    "form": {
+      "usernameHint": "Usado para entrar. Letras, dígitos e . _ + @ - (3–64 caracteres).",
+      "usernameError": "Digite um nome de usuário válido (3–64 caracteres).",
+      "usernamePlaceholder": "ex.: joana",
+      "email": "E-mail",
+      "emailHint": "Opcional — deixe em branco se o usuário não tiver e-mail.",
+      "emailError": "Digite um endereço de e-mail válido.",
+      "emailPlaceholder": "ex.: joana@exemplo.com",
+      "nameHint": "Opcional — um nome de exibição.",
+      "rateLimit": "Limite de requisições MCP (requisições/min)",
+      "rateLimitHint": "Limita a chave deste usuário em /api/mcp. 0 = usar o padrão global.",
+      "activeLabel": "Ativo — um usuário inativo não pode entrar e sua chave de API para de funcionar",
+      "adminLabel": "Admin — acesso total ao console (gerenciar usuários, configurações e todos os espaços de trabalho)"
+    },
+    "key": {
+      "title": "Chave de API — {{name}}",
+      "revealMessage": "Copie esta chave agora — ela é exibida por completo apenas uma vez e não pode ser recuperada novamente.",
+      "used": "usada {{ago}}",
+      "neverUsed": "nunca usada",
+      "revokeAria": "Revogar chave",
+      "none": "Este usuário ainda não tem chave de API.",
+      "rotate": "Rotacionar chave",
+      "create": "Criar chave",
+      "rotateHint": "Rotacionar substitui a chave atual — a antiga para de funcionar imediatamente.",
+      "toast": {
+        "revoked": "Chave revogada."
+      }
+    },
+    "grants": {
+      "modalTitle": "Permissões — {{email}}",
+      "intro": {
+        "lead": "As permissões",
+        "emphasis": "restringem este usuário",
+        "rest": ". Sem nenhuma, ele vê e grava tudo. Um espaço de trabalho o limita a ele; adicione uma coleção (ou documento) para restringi-lo a apenas essa."
+      },
+      "error": "Não foi possível carregar as permissões",
+      "empty": {
+        "title": "Nenhuma permissão ainda",
+        "description": "Conceda a este usuário leitura ou escrita em um espaço de trabalho, coleção ou documento acima."
+      },
+      "resourceType": "Tipo de recurso",
+      "type": {
+        "workspace": "Espaço de trabalho",
+        "collection": "Coleção",
+        "document": "Documento",
+        "capability": "Capacidade"
+      },
+      "levelLabel": "Nível",
+      "readOption": "Leitura — buscar, listar, baixar",
+      "writeOption": "Escrita — ingerir, excluir (e ler)",
+      "read": "Leitura",
+      "write": "Escrita",
+      "capabilityLabel": {
+        "create_workspace": "Criar espaços de trabalho",
+        "manage_tags": "Gerenciar tags"
+      },
+      "capabilityHelp": {
+        "create_workspace": "Permite que este usuário crie novos espaços de trabalho — ele obtém acesso de escrita a todos os que criar.",
+        "manage_tags": "Permite que este usuário crie, edite, exclua e atribua tags em qualquer espaço de trabalho que possa ler."
+      },
+      "selectWorkspace": "Selecione um espaço de trabalho…",
+      "select": "Selecione…",
+      "pickWorkspaceFirst": "Escolha um espaço de trabalho primeiro",
+      "documentId": "ID do documento",
+      "documentIdHint": "O id do documento (ex.: doc_…), da sua coleção.",
+      "addPermission": "Adicionar permissão",
+      "deleted": "excluído",
+      "copyIdTitle": "Copiar id: {{id}}",
+      "copyIdAria": "Copiar id {{id}}",
+      "revokeAria": "Revogar permissão",
+      "toast": {
+        "granted": "Permissão concedida.",
+        "revoked": "Permissão revogada."
+      }
+    }
+  },
+  "settings": {
+    "title": "Configurações",
+    "subtitle": "Configuração de runtime, segurança do console e acesso MCP.",
+    "tabs": {
+      "general": "Geral",
+      "mcp": "Servidor MCP"
+    },
+    "config": {
+      "title": "Configuração",
+      "loadError": "Não foi possível carregar a configuração"
+    },
+    "runtime": {
+      "title": "Runtime",
+      "unreachable": "API inacessível",
+      "unreachableDetail": "Não foi possível acessar o endpoint de health.",
+      "service": "Serviço",
+      "version": "Versão",
+      "vectorStore": "Vector store",
+      "embeddingProvider": "Provedor de embedding",
+      "embeddingModel": "Modelo de embedding",
+      "uptime": "Uptime"
+    },
+    "security": {
+      "title": "Segurança",
+      "session": "Sessão",
+      "sessionNote": "Sua credencial é mantida apenas neste navegador. Saia para limpá-la.",
+      "signOut": "Sair"
+    },
+    "field": {
+      "provider": "Provedor",
+      "model": "Modelo",
+      "baseUrl": "URL base",
+      "apiKey": "Chave de API",
+      "apiKeyHint": "Somente escrita; nunca exibida após salvar.",
+      "keySetPlaceholder": "chave definida — deixe em branco para manter",
+      "aiStudioKey": "Chave do AI Studio",
+      "baseUrlRequiredOpenrouter": "obrigatório — ex.: https://openrouter.ai/api",
+      "baseUrlOllamaDefault": "em branco usa o padrão do Ollama",
+      "modelIdPlaceholder": "id do modelo",
+      "ollamaModelsHint": "Modelos do Ollama instalados",
+      "ollamaUnreachable": "Não foi possível acessar o Ollama",
+      "loadingModels": "Carregando modelos…",
+      "noModelsInstalled": "Nenhum modelo instalado"
+    },
+    "provider": {
+      "ollamaLocal": "Ollama (local)",
+      "sentenceTransformers": "Sentence-Transformers (em processo)",
+      "openaiCompat": "Compatível com OpenAI",
+      "gemini": "Google Gemini",
+      "geminiAiStudio": "Google Gemini (AI Studio)"
+    },
+    "storage": {
+      "blurb": "Onde os arquivos enviados são armazenados. O backend ativo é escolhido em <code>config.yaml</code> / <code>.env</code>. A retenção é definida <strong>por upload</strong> (1–30 dias, ou mantido permanentemente) na página de Documentos — não há configuração global de retenção.",
+      "title": "Armazenamento de objetos",
+      "activeBackend": "Backend ativo"
+    },
+    "parser": {
+      "title": "Análise de PDF",
+      "backend": "Backend",
+      "optionPymupdf": "PyMuPDF — rápido, um chunk por página",
+      "optionDocling": "docling — reconhece seções + tabelas/OCR",
+      "needsGpuSuffix": " (precisa de GPU)",
+      "gpuOlderThanAmpere": "Sua GPU ({{name}}, capacidade {{capability}}) é anterior à Ampere — ",
+      "noGpuDetected": "Nenhuma GPU detectada — ",
+      "doclingCpuWarn": "o docling roda na CPU e é <strong>muito lento</strong> (minutos por documento, e PDFs grandes podem atingir o limite de tempo de ingestão). O PyMuPDF é recomendado neste hardware.",
+      "save": "Salvar backend de PDF",
+      "detectingGpu": "Detectando GPU…",
+      "compatibleGpu": "GPU compatível detectada ({{name}}, capacidade {{capability}}).",
+      "gpuBelowAmpere": "A GPU {{name}} (capacidade {{capability}}) é anterior à Ampere.",
+      "noCompatibleGpu": "Nenhuma GPU compatível detectada.",
+      "recommendedLabel": "Recomendado:"
+    },
+    "embedding": {
+      "blurb": "O modelo de embedding transforma documentos em vetores. <strong>Alterar o provedor, o modelo ou as dimensões de saída muda o tamanho do vetor</strong> — as coleções existentes precisam ser reindexadas ou a busca vai quebrar. Alterar apenas uma chave de API é seguro.",
+      "title": "Modelo de embedding",
+      "modelHintGemini": "ex.: gemini-embedding-001",
+      "modelHint": "o id exato do modelo neste servidor",
+      "outputDim": "Dimensões de saída",
+      "outputDimHint": "opcional; em branco = 3072 completo",
+      "maxRpm": "Máx. de requisições / min",
+      "maxRpmHint": "limite os embeds para que a ingestão em massa fique dentro da cota do provedor (cada texto = uma requisição); em branco ou 0 = ilimitado",
+      "maxRpmPlaceholder": "0 (ilimitado)",
+      "reindexRequired": "Reindexação necessária após salvar",
+      "save": "Salvar configuração de embedding"
+    },
+    "reranker": {
+      "blurb": "O reranker reordena os chunks recuperados pela relevância real da consulta antes do corte final — o maior ganho de precisão. Ele é <strong>opcional e seguro</strong>: se o modelo ou um provedor remoto estiver indisponível, a busca volta para a ordenação normal.",
+      "title": "Reranker",
+      "enable": "Ativar reranking",
+      "providerCrossEncoder": "Cross-encoder (local, sem chave)",
+      "providerRerankApi": "API de rerank hospedada (Cohere / Jina / Voyage)",
+      "providerLlm": "LLM como reranker",
+      "llmProvider": "Provedor de LLM",
+      "modelHintRerankApi": "ex.: rerank-v3.5 (Cohere), jina-reranker-v2 (Jina)",
+      "modelHintGemini": "ex.: gemini-2.5-flash",
+      "modelHintLlm": "o id exato do modelo de chat",
+      "modelHintCrossEncoder": "um id de cross-encoder do HuggingFace; o padrão embutido funciona offline",
+      "baseUrlHintRerankApi": "obrigatório — o endpoint /rerank completo",
+      "topN": "Candidatos avaliados (top_n)",
+      "topNHint": "máximo de candidatos que o reranker avalia por coleção",
+      "save": "Salvar configuração do reranker"
+    },
+    "search": {
+      "blurb": "A expansão de adjacência puxa os chunks vizinhos a cada resultado e os mescla em um único trecho, para que uma seção que se estende por várias páginas volte inteira em vez de cortada no limite do top-K. É uma busca simples — sem chamadas extras a modelos — e <strong>segura</strong>: se não conseguir buscar, a busca retorna os resultados não expandidos.",
+      "title": "Recuperação",
+      "expand": "Expansão de adjacência (vizinhos)",
+      "expandHint": "chunks puxados de cada lado de um acerto; 0 = desativado, máx {{max}}",
+      "save": "Salvar configuração de busca"
+    },
+    "mcp": {
+      "blurb": "O endpoint do MCP (<code>/api/mcp</code>) limita cada chave de API a esta quantidade de requisições por minuto; a próxima requisição no mesmo minuto retorna <code>429</code>. Cada chave tem seu próprio orçamento, e o novo limite <strong>vale a partir da próxima requisição MCP</strong>",
+      "title": "Servidor MCP",
+      "rateLimit": "Limite de taxa (requisições / min por chave)",
+      "rateLimitHint": "por chave de API em /api/mcp; a próxima requisição no mesmo minuto retorna 429",
+      "save": "Salvar configuração de MCP"
+    },
+    "toast": {
+      "pdfSaved": "Backend de PDF salvo. Os serviços estão recarregando.",
+      "embeddingSaved": "Configuração de embedding salva. Os serviços estão recarregando.",
+      "rerankerSaved": "Configuração do reranker salva. Os serviços estão recarregando.",
+      "searchSaved": "Configuração de busca salva. Os serviços estão recarregando.",
+      "mcpSaved": "Configuração de MCP salva. Os serviços estão recarregando."
+    }
+  },
+  "mcp": {
+    "tagsNote": "As ferramentas de tags precisam da permissão manage_tags; atribuir a uma coleção/documento também exige escrita nele.",
+    "connection": {
+      "title": "Conexão",
+      "address": "Endereço do servidor",
+      "addressHintLocal": "Este endereço só funciona nesta máquina; o servidor não conseguiu determinar um IP de rede local para outros dispositivos usarem.",
+      "addressHint": "Detectado automaticamente a partir do servidor. Usado para montar o endpoint e os trechos abaixo.",
+      "endpoint": "Endpoint",
+      "transport": "Transporte",
+      "authHeader": "Cabeçalho de autenticação",
+      "authNote": "Envie uma <strong>chave de API</strong> em cada requisição como <authcode></authcode> ou <apikeycode></apikeycode> — a chave mestra, ou uma <strong>chave por usuário</strong> para acesso restrito (cada ferramenta respeita as permissões de leitura/escrita desse usuário). Substitua pela sua nos trechos abaixo; nada fica embutido aqui."
+    },
+    "clientSetup": {
+      "title": "Configuração do cliente",
+      "instructions": "Adicione isto à configuração de servidores do seu cliente MCP (substitua a chave de exemplo):",
+      "copyConfig": "Copiar config"
+    },
+    "skill": {
+      "title": "Skill do agente",
+      "download": "Baixar .zip",
+      "folderNote": "Uma pequena pasta de skill (<code>SKILL.md</code> + <code>references/</code>). Descompacte-a no diretório de skills do seu agente (ex.: <code>.claude/skills/embedbase/</code>) — o agente carrega o <code>SKILL.md</code> logo de início e abre um arquivo de referência apenas quando a tarefa precisa, para que uma sessão somente leitura nunca puxe as regras de upload.",
+      "bundled": "Incluídos:",
+      "unavailable": "A skill está indisponível — não foi possível carregar o catálogo de ferramentas."
+    },
+    "tools": {
+      "title": "Ferramentas",
+      "count_one": "{{count}} ferramenta · cada uma respeita suas permissões",
+      "count_other": "{{count}} ferramentas · cada uma respeita suas permissões",
+      "loadError": "Não foi possível carregar o catálogo de ferramentas"
+    },
+    "rest": {
+      "title": "Referência da API REST",
+      "blurb": "Uma referência OpenAPI independente apenas dos endpoints de integração — busca e acesso a espaços de trabalho/coleções/documentos — para a IA ler como padrão da API."
+    }
+  }
+}
diff --git a/ui/src/i18n/parity.ts b/ui/src/i18n/parity.ts
new file mode 100644
index 0000000..743481a
--- /dev/null
+++ b/ui/src/i18n/parity.ts
@@ -0,0 +1,16 @@
+/**
+ * Compile-time completeness guard: the two catalogs must have identical key sets.
+ * A key present in one locale but missing from the other fails `tsc` (leaf values
+ * are widened to `string`, so differing translations are fine). This module is
+ * never imported at runtime — it exists purely so the typecheck covers it.
+ */
+import en from './locales/en/translation.json'
+import ptBR from './locales/pt-BR/translation.json'
+
+/** Same nested shape as `T`, but every leaf string widened to `string`. */
+type Stringify<T> = { [K in keyof T]: T[K] extends string ? string : Stringify<T[K]> }
+
+// Both assignments together enforce exact key parity: `_ptCoversEn` fails if
+// `pt-BR` is missing an `en` key; `_enCoversPt` fails for the reverse.
+export const _ptCoversEn: Stringify<typeof en> = ptBR
+export const _enCoversPt: Stringify<typeof ptBR> = en
diff --git a/ui/src/lib/format.ts b/ui/src/lib/format.ts
index 8a2903d..0722e94 100644
--- a/ui/src/lib/format.ts
+++ b/ui/src/lib/format.ts
@@ -12,35 +12,47 @@ export function formatUptime(seconds: number): string {
   return `${Math.floor(seconds)}s`
 }
 
-const UNITS: [limit: number, secs: number, label: string][] = [
-  [60, 1, 's'],
-  [3_600, 60, 'm'],
-  [86_400, 3_600, 'h'],
-  [2_592_000, 86_400, 'd'],
+// Thresholds → the Intl relative-time unit to render at that magnitude.
+const REL_UNITS: [limit: number, secs: number, unit: Intl.RelativeTimeFormatUnit][] = [
+  [60, 1, 'second'],
+  [3_600, 60, 'minute'],
+  [86_400, 3_600, 'hour'],
+  [2_592_000, 86_400, 'day'],
 ]
 
-/** Render an ISO timestamp as a coarse relative age (`3m ago`, `2h ago`). */
+/** Render an ISO timestamp as a coarse, localized relative age (`3 min ago` / `há 3 min`). */
 export function timeAgo(iso: string): string {
   const then = Date.parse(iso)
   if (Number.isNaN(then)) return '—'
   const diff = Math.max(0, (Date.now() - then) / 1_000)
-  for (const [limit, secs, label] of UNITS) {
-    if (diff < limit) return `${Math.floor(diff / secs)}${label} ago`
+  for (const [limit, secs, unit] of REL_UNITS) {
+    if (diff < limit) return relFmt.format(-Math.floor(diff / secs), unit)
   }
-  return `${Math.floor(diff / 2_592_000)}mo ago`
+  return relFmt.format(-Math.floor(diff / 2_592_000), 'month')
 }
 
-const DATE_FMT = new Intl.DateTimeFormat(undefined, {
+const DATE_FMT_OPTS: Intl.DateTimeFormatOptions = {
   year: 'numeric',
   month: 'short',
   day: 'numeric',
-})
+}
+// Both rebuilt on language change (see `i18n/index.ts`) so calendar dates and
+// relative ages track the active language; start on the runtime default until
+// i18n boots.
+let dateFmt = new Intl.DateTimeFormat(undefined, DATE_FMT_OPTS)
+let relFmt = new Intl.RelativeTimeFormat(undefined, { numeric: 'always', style: 'narrow' })
+
+/** Point the shared date + relative-time formatters at a new locale (e.g. `pt-BR`). */
+export function setDateLocale(locale: string): void {
+  dateFmt = new Intl.DateTimeFormat(locale, DATE_FMT_OPTS)
+  relFmt = new Intl.RelativeTimeFormat(locale, { numeric: 'always', style: 'narrow' })
+}
 
 /** Render an ISO timestamp as an absolute calendar date (`Jun 12, 2026`). */
 export function formatDate(iso: string): string {
   const ms = Date.parse(iso)
   if (Number.isNaN(ms)) return '—'
-  return DATE_FMT.format(ms)
+  return dateFmt.format(ms)
 }
 
 const BYTE_UNITS = ['B', 'KB', 'MB', 'GB']
diff --git a/ui/src/main.tsx b/ui/src/main.tsx
index d9e8cb0..4161dda 100644
--- a/ui/src/main.tsx
+++ b/ui/src/main.tsx
@@ -6,6 +6,7 @@ import '@fontsource-variable/public-sans'
 import '@fontsource-variable/jetbrains-mono'
 import App from './App'
 import './index.css'
+import './i18n'
 import { ErrorBoundary } from './components/layout/ErrorBoundary'
 import { ToastProvider } from './components/ui/Toast'
 import { AuthProvider } from './auth/AuthContext'
diff --git a/ui/src/pages/Collections.tsx b/ui/src/pages/Collections.tsx
index c5d24ed..f07a26d 100644
--- a/ui/src/pages/Collections.tsx
+++ b/ui/src/pages/Collections.tsx
@@ -1,6 +1,7 @@
 import { useMemo, useState, type MouseEvent } from 'react'
 import { Link, useNavigate, useParams } from 'react-router-dom'
 import { ChevronRight, FileText, Layers, Pencil, Plus, Tags as TagsIcon, Trash2 } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
 import {
   useAssignCollectionTag,
   useCollections,
@@ -30,6 +31,7 @@ import {
   CollectionFormModal,
   type CollectionFormValues,
 } from '../components/collections/CollectionFormModal'
+import { apiErrorMessage } from '../i18n/apiError'
 import { formatDate } from '../lib/format'
 import { useAuth } from '../auth/AuthContext'
 
@@ -52,6 +54,7 @@ function changedFields(col: Collection, values: CollectionFormValues): Collectio
 
 /** Collections within a workspace: list, create, edit, and delete. */
 export default function Collections() {
+  const { t } = useTranslation()
   const { wsId = '' } = useParams()
   const navigate = useNavigate()
   const workspace = useWorkspace(wsId)
@@ -85,10 +88,10 @@ export default function Collections() {
     if (dialog.kind === 'create') {
       createMut.mutate(values, {
         onSuccess: () => {
-          toast.success(`Collection “${values.name}” created.`)
+          toast.success(t('collections.toast.created', { name: values.name }))
           close()
         },
-        onError: (e) => toast.error(e.message),
+        onError: (e) => toast.error(apiErrorMessage(e, t)),
       })
     } else if (dialog.kind === 'edit') {
       const body = changedFields(dialog.col, values)
@@ -100,10 +103,10 @@ export default function Collections() {
         { colId: dialog.col.id, body },
         {
           onSuccess: () => {
-            toast.success('Collection updated.')
+            toast.success(t('collections.toast.updated'))
             close()
           },
-          onError: (e) => toast.error(e.message),
+          onError: (e) => toast.error(apiErrorMessage(e, t)),
         },
       )
     }
@@ -114,10 +117,10 @@ export default function Collections() {
     const { col } = dialog
     deleteMut.mutate(col.id, {
       onSuccess: () => {
-        toast.success(`Collection “${col.name}” deleted.`)
+        toast.success(t('collections.toast.deleted', { name: col.name }))
         close()
       },
-      onError: (e) => toast.error(e.message),
+      onError: (e) => toast.error(apiErrorMessage(e, t)),
     })
   }
 
@@ -125,7 +128,7 @@ export default function Collections() {
     <div className="animate-fade-in space-y-6">
       <nav className="flex items-center gap-1.5 text-xs text-ink-muted">
         <Link to="/workspaces" className="hover:text-ink">
-          Workspaces
+          {t('nav.workspaces')}
         </Link>
         <ChevronRight className="h-4 w-4 text-ink-faint" />
         <span className="text-ink">{workspace.data?.name ?? '…'}</span>
@@ -133,22 +136,20 @@ export default function Collections() {
 
       <header className="flex items-start justify-between gap-4">
         <div>
-          <h1 className="text-xl font-semibold tracking-tight text-ink">Collections</h1>
-          <p className="mt-1 text-[13px] text-ink-muted">
-            Searchable document sets within this workspace.
-          </p>
+          <h1 className="text-xl font-semibold tracking-tight text-ink">{t('collections.title')}</h1>
+          <p className="mt-1 text-[13px] text-ink-muted">{t('collections.subtitle')}</p>
         </div>
         <div className="flex gap-2">
           {canTag && (
             <Button variant="secondary" onClick={() => navigate(`/workspaces/${wsId}/tags`)}>
               <TagsIcon className="h-5 w-5" />
-              Tags
+              {t('common.tags')}
             </Button>
           )}
           {canWrite && (
             <Button onClick={() => setDialog({ kind: 'create' })}>
               <Plus className="h-5 w-5" />
-              New collection
+              {t('collections.new')}
             </Button>
           )}
         </div>
@@ -161,7 +162,7 @@ export default function Collections() {
         data={shown}
         isLoading={isLoading}
         isError={isError}
-        message={error?.message}
+        message={error ? apiErrorMessage(error, t) : undefined}
         canCreate={canWrite}
         onRetry={() => void refetch()}
         onCreate={() => setDialog({ kind: 'create' })}
@@ -179,10 +180,10 @@ export default function Collections() {
 
       <ConfirmDialog
         open={dialog.kind === 'delete'}
-        title="Delete collection"
+        title={t('collections.delete.title')}
         message={
           dialog.kind === 'delete'
-            ? `Delete “${dialog.col.name}”? Its documents and indexed vectors are permanently removed. This cannot be undone.`
+            ? t('collections.delete.message', { name: dialog.col.name })
             : ''
         }
         loading={deleteMut.isPending}
@@ -217,6 +218,7 @@ function CollectionList({
   onEdit: (col: Collection) => void
   onDelete: (col: Collection) => void
 }) {
+  const { t } = useTranslation()
   if (isLoading) {
     return (
       <div className="grid grid-cols-1 gap-3 sm:grid-cols-2 lg:grid-cols-3">
@@ -227,19 +229,15 @@ function CollectionList({
     )
   }
   if (isError) {
-    return <QueryError title="Could not load collections" message={message} onRetry={onRetry} />
+    return <QueryError title={t('collections.error')} message={message} onRetry={onRetry} />
   }
   if (!data || data.length === 0) {
     return (
       <EmptyState
         icon={<Layers className="h-7 w-7" />}
-        title="No collections yet"
-        description={
-          canCreate
-            ? 'Create a collection to start ingesting and searching documents.'
-            : 'No collections here yet.'
-        }
-        action={canCreate ? <Button onClick={onCreate}>New collection</Button> : undefined}
+        title={t('collections.empty.title')}
+        description={canCreate ? t('collections.empty.canCreate') : t('collections.empty.readonly')}
+        action={canCreate ? <Button onClick={onCreate}>{t('collections.new')}</Button> : undefined}
       />
     )
   }
@@ -270,6 +268,7 @@ function CollectionCard({
   onEdit: (col: Collection) => void
   onDelete: (col: Collection) => void
 }) {
+  const { t } = useTranslation()
   const navigate = useNavigate()
   const { isAdmin, canManageTags } = useAuth()
   // (Un)assigning a collection tag needs the manage_tags privilege AND write on the collection —
@@ -281,7 +280,7 @@ function CollectionCard({
   const unassignMut = useUnassignCollectionTag(wsId)
   const createMut = useCreateTag(wsId)
   const tagBusy = assignMut.isPending || unassignMut.isPending || createMut.isPending
-  const onErr = (e: Error) => toast.error(e.message)
+  const onErr = (e: Error) => toast.error(apiErrorMessage(e, t))
 
   const handleCreate = (name: string) =>
     createMut.mutate(
@@ -320,20 +319,20 @@ function CollectionCard({
             )}
           </div>
           <p className="mt-0.5 truncate text-xs text-ink-muted">
-            {col.description || 'No description'}
+            {col.description || t('common.noDescription')}
           </p>
         </div>
       </div>
       {((col.tags ?? []).length > 0 || canManageColTags) && (
         <div className="flex flex-wrap items-center gap-1.5" onClick={(e) => e.stopPropagation()}>
-          {(col.tags ?? []).map((t) => (
+          {(col.tags ?? []).map((tag) => (
             <TagChip
-              key={t.id}
-              name={t.name}
-              color={t.color}
+              key={tag.id}
+              name={tag.name}
+              color={tag.color}
               onRemove={
                 canManageColTags
-                  ? () => unassignMut.mutate({ colId: col.id, tagId: t.id }, { onError: onErr })
+                  ? () => unassignMut.mutate({ colId: col.id, tagId: tag.id }, { onError: onErr })
                   : undefined
               }
             />
@@ -353,13 +352,15 @@ function CollectionCard({
         </div>
       )}
       <div className="flex items-center justify-between">
-        <span className="text-xs text-ink-faint">Created {formatDate(col.created_at)}</span>
+        <span className="text-xs text-ink-faint">
+          {t('common.created', { date: formatDate(col.created_at) })}
+        </span>
         {col.can_write && (
           <div className="flex gap-1 opacity-0 transition-opacity group-hover:opacity-100 focus-within:opacity-100">
             <Button
               variant="ghost"
               size="sm"
-              aria-label={`Edit ${col.name}`}
+              aria-label={t('common.editAria', { name: col.name })}
               onClick={stop(() => onEdit(col))}
               className="h-10 w-10 px-0"
             >
@@ -368,7 +369,7 @@ function CollectionCard({
             <Button
               variant="ghost"
               size="sm"
-              aria-label={`Delete ${col.name}`}
+              aria-label={t('common.deleteAria', { name: col.name })}
               onClick={stop(() => onDelete(col))}
               className="h-10 w-10 px-0 hover:text-err"
             >
diff --git a/ui/src/pages/Dashboard.tsx b/ui/src/pages/Dashboard.tsx
index c278190..2860c71 100644
--- a/ui/src/pages/Dashboard.tsx
+++ b/ui/src/pages/Dashboard.tsx
@@ -1,5 +1,6 @@
 import { Link } from 'react-router-dom'
 import { FileClock, FileText, FolderKanban, Layers } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
 import { useHealth, useRecentDocuments, useWorkspaces } from '../api/hooks'
 import type { Workspace } from '../api/types'
 import {
@@ -12,17 +13,19 @@ import {
   Skeleton,
   StatusBadge,
 } from '../components/ui'
+import { apiErrorMessage } from '../i18n/apiError'
 import { cn } from '../lib/cn'
 import { formatUptime, timeAgo } from '../lib/format'
 
 /** Operator landing page: system health, workspace overview, recent activity. */
 export default function Dashboard() {
+  const { t } = useTranslation()
   return (
     <div className="animate-fade-in space-y-8">
       <header>
-        <h1 className="text-xl font-semibold tracking-tight text-ink">Dashboard</h1>
+        <h1 className="text-xl font-semibold tracking-tight text-ink">{t('dashboard.title')}</h1>
         <p className="mt-1 text-[13px] text-ink-muted">
-          System health and recent activity at a glance.
+          {t('dashboard.subtitle')}
         </p>
       </header>
       <HealthCard />
@@ -49,13 +52,14 @@ function StatItem({ label, value, online }: { label: string; value: string; onli
 
 /** `GET /healthz` summary card. */
 function HealthCard() {
+  const { t } = useTranslation()
   const { data, isLoading, isError, error, refetch } = useHealth()
   if (isLoading) return <Skeleton className="h-36 w-full rounded-card" />
   if (isError || !data) {
     return (
       <QueryError
-        title="API unreachable"
-        message={error?.message ?? 'Could not reach the health endpoint.'}
+        title={t('auth.api.unreachable')}
+        message={error ? apiErrorMessage(error, t) : t('dashboard.health.unreachable')}
         onRetry={() => void refetch()}
       />
     )
@@ -64,7 +68,7 @@ function HealthCard() {
   return (
     <Card className="p-5">
       <div className="mb-4 flex items-center justify-between">
-        <h2 className="text-sm font-semibold text-ink">System</h2>
+        <h2 className="text-sm font-semibold text-ink">{t('dashboard.health.system')}</h2>
         <span className="inline-flex items-center gap-1.5 text-xs">
           <span className={cn('h-1.5 w-1.5 rounded-full', healthy ? 'bg-ok' : 'bg-warn')} />
           <span className={healthy ? 'text-ok' : 'text-warn'}>{data.status}</span>
@@ -72,17 +76,17 @@ function HealthCard() {
       </div>
       <div className="grid grid-cols-2 gap-4 sm:grid-cols-4">
         <StatItem
-          label="Vector store"
+          label={t('dashboard.health.vectorStore')}
           value={data.vector_store}
           online={data.vector_store_connected}
         />
         <StatItem
-          label="Embedding model"
+          label={t('documents.filters.embeddingModel')}
           value={data.embedding_model}
           online={data.embedding_model_loaded}
         />
-        <StatItem label="Version" value={data.version} />
-        <StatItem label="Uptime" value={formatUptime(data.uptime_seconds)} />
+        <StatItem label={t('dashboard.health.version')} value={data.version} />
+        <StatItem label={t('dashboard.health.uptime')} value={formatUptime(data.uptime_seconds)} />
       </div>
       <p className="mt-4 text-xs text-ink-faint">
         {data.embedding_provider} · {data.service}
@@ -93,23 +97,24 @@ function HealthCard() {
 
 /** Workspace count plus a compact grid of clickable workspace cards. */
 function WorkspaceOverview() {
+  const { t } = useTranslation()
   const { data, isLoading, isError, error, refetch } = useWorkspaces()
   return (
     <section>
       <div className="mb-3 flex items-center justify-between">
         <h2 className="text-sm font-semibold text-ink">
-          Workspaces
+          {t('workspaces.title')}
           {data && <span className="ml-1 font-normal text-ink-faint">· {data.length}</span>}
         </h2>
         <Link to="/workspaces" className="text-xs font-medium text-accent hover:underline">
-          View all
+          {t('dashboard.viewAll')}
         </Link>
       </div>
       <WorkspaceGrid
         data={data}
         isLoading={isLoading}
         isError={isError}
-        message={error?.message}
+        message={error ? apiErrorMessage(error, t) : undefined}
         onRetry={() => void refetch()}
       />
     </section>
@@ -130,6 +135,7 @@ function WorkspaceGrid({
   message?: string
   onRetry: () => void
 }) {
+  const { t } = useTranslation()
   if (isLoading) {
     return (
       <div className="grid grid-cols-1 gap-3 sm:grid-cols-2 lg:grid-cols-3">
@@ -139,16 +145,16 @@ function WorkspaceGrid({
       </div>
     )
   }
-  if (isError) return <QueryError title="Could not load workspaces" message={message} onRetry={onRetry} />
+  if (isError) return <QueryError title={t('workspaces.error')} message={message} onRetry={onRetry} />
   if (!data || data.length === 0) {
     return (
       <EmptyState
         icon={<FolderKanban className="h-7 w-7" />}
-        title="No workspaces yet"
-        description="Create your first workspace to start organising collections."
+        title={t('workspaces.empty.title')}
+        description={t('workspaces.empty.canCreate')}
         action={
           <Link to="/workspaces">
-            <Button size="sm">Go to Workspaces</Button>
+            <Button size="sm">{t('dashboard.goToWorkspaces')}</Button>
           </Link>
         }
       />
@@ -165,6 +171,7 @@ function WorkspaceGrid({
 
 /** A single workspace card that links through to its collections. */
 function WorkspaceCard({ ws }: { ws: Workspace }) {
+  const { t } = useTranslation()
   return (
     <Link to={`/workspaces/${ws.id}`}>
       <Card interactive className="flex h-full items-start gap-3 p-4">
@@ -185,7 +192,7 @@ function WorkspaceCard({ ws }: { ws: Workspace }) {
             )}
           </div>
           <p className="mt-0.5 truncate text-xs text-ink-muted">
-            {ws.description || 'No description'}
+            {ws.description || t('common.noDescription')}
           </p>
         </div>
       </Card>
@@ -195,10 +202,11 @@ function WorkspaceCard({ ws }: { ws: Workspace }) {
 
 /** Most-recently-updated documents aggregated across every collection. */
 function RecentActivity() {
+  const { t } = useTranslation()
   const { documents, isLoading } = useRecentDocuments()
   return (
     <section>
-      <h2 className="mb-3 text-sm font-semibold text-ink">Recent activity</h2>
+      <h2 className="mb-3 text-sm font-semibold text-ink">{t('dashboard.recentActivity')}</h2>
       <RecentActivityBody documents={documents} isLoading={isLoading} />
     </section>
   )
@@ -211,6 +219,7 @@ function RecentActivityBody({
   documents: ReturnType<typeof useRecentDocuments>['documents']
   isLoading: boolean
 }) {
+  const { t } = useTranslation()
   if (isLoading && documents.length === 0) {
     return (
       <Card className="divide-y divide-border">
@@ -227,8 +236,8 @@ function RecentActivityBody({
     return (
       <EmptyState
         icon={<FileClock className="h-7 w-7" />}
-        title="No recent activity"
-        description="Document ingestion across your collections will show up here."
+        title={t('dashboard.noActivity.title')}
+        description={t('dashboard.noActivity.description')}
       />
     )
   }
diff --git a/ui/src/pages/Documents.tsx b/ui/src/pages/Documents.tsx
index 06e768b..a109231 100644
--- a/ui/src/pages/Documents.tsx
+++ b/ui/src/pages/Documents.tsx
@@ -1,6 +1,7 @@
 import { useEffect, useMemo, useState } from 'react'
 import { Link, useParams, useSearchParams } from 'react-router-dom'
 import { AlertCircle, ChevronRight, Database, DatabaseZap, Download, ExternalLink, FileDown, FileText, Trash2 } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
 import {
   useAssignDocumentTag,
   useCollection,
@@ -36,6 +37,7 @@ import {
 import { UploadZone } from '../components/documents/UploadZone'
 import { DocumentFilters, type DocumentFilterValues } from '../components/documents/DocumentFilters'
 import { Pager } from '../components/Pager'
+import { apiErrorMessage } from '../i18n/apiError'
 import { formatBytes, timeAgo } from '../lib/format'
 import { useAuth } from '../auth/AuthContext'
 
@@ -52,6 +54,7 @@ const PAGE_SIZE = 50
 
 /** Documents within a collection: upload, live ingestion status, and delete. */
 export default function Documents() {
+  const { t } = useTranslation()
   const { wsId = '', colId = '' } = useParams()
   const workspace = useWorkspace(wsId)
   const collection = useCollection(wsId, colId)
@@ -113,7 +116,7 @@ export default function Documents() {
   // page, so a selected tag stays deselectable even when it filters the list down to zero rows.
   const tagOptions = useMemo(() => {
     const present = collectTags(data?.items)
-    const names = new Set(present.map((t) => t.name))
+    const names = new Set(present.map((tag) => tag.name))
     const missing = tagFilter
       .filter((n) => !names.has(n))
       .map((n) => ({ id: n, name: n, color: null }))
@@ -129,11 +132,11 @@ export default function Documents() {
         await uploadMut.mutateAsync({ file: f, retentionDays })
         ok += 1
       } catch (e) {
-        toast.error(`${f.name}: ${(e as Error).message}`)
+        toast.error(t('documents.toast.uploadError', { name: f.name, error: apiErrorMessage(e, t) }))
       }
     }
     setUploading(false)
-    if (ok > 0) toast.success(`${ok} file${ok === 1 ? '' : 's'} queued for ingestion.`)
+    if (ok > 0) toast.success(t('documents.toast.queued', { count: ok }))
   }
 
   const handleFiles = (files: File[]) => {
@@ -141,7 +144,7 @@ export default function Documents() {
     const valid: File[] = []
     for (const f of files) {
       if (f.size > maxBytes) {
-        toast.error(`${f.name} is larger than ${MAX_FILE_SIZE_MB} MB and was skipped.`)
+        toast.error(t('documents.toast.tooLarge', { name: f.name, max: MAX_FILE_SIZE_MB }))
       } else {
         valid.push(f)
       }
@@ -155,10 +158,10 @@ export default function Documents() {
     const doc = deleteTarget
     deleteMut.mutate(doc.document_id, {
       onSuccess: () => {
-        toast.success(`Deleted “${doc.filename}”.`)
+        toast.success(t('documents.toast.deleted', { name: doc.filename }))
         setDeleteTarget(null)
       },
-      onError: (e) => toast.error(e.message),
+      onError: (e) => toast.error(apiErrorMessage(e, t)),
     })
   }
 
@@ -166,7 +169,7 @@ export default function Documents() {
     <div className="animate-fade-in space-y-6">
       <nav className="flex items-center gap-1.5 text-xs text-ink-muted">
         <Link to="/workspaces" className="hover:text-ink">
-          Workspaces
+          {t('nav.workspaces')}
         </Link>
         <ChevronRight className="h-4 w-4 text-ink-faint" />
         <Link to={`/workspaces/${wsId}`} className="hover:text-ink">
@@ -177,11 +180,9 @@ export default function Documents() {
       </nav>
 
       <header>
-        <h1 className="text-xl font-semibold tracking-tight text-ink">Documents</h1>
+        <h1 className="text-xl font-semibold tracking-tight text-ink">{t('documents.title')}</h1>
         <p className="mt-1 text-[13px] text-ink-muted">
-          {canWrite
-            ? 'Upload files to ingest them into this collection.'
-            : 'Browse and search documents in this collection.'}
+          {canWrite ? t('documents.subtitle.canWrite') : t('documents.subtitle.readonly')}
         </p>
       </header>
 
@@ -198,7 +199,7 @@ export default function Documents() {
               onChange={(e) => setRetentionDays(e.target.checked ? DEFAULT_RETENTION_DAYS : null)}
               className="h-4 w-4 accent-accent"
             />
-            Temporary — automatically delete after
+            {t('documents.retention.label')}
           </label>
           <input
             type="number"
@@ -207,10 +208,10 @@ export default function Documents() {
             value={retentionDays ?? DEFAULT_RETENTION_DAYS}
             disabled={retentionDays == null}
             onChange={(e) => setRetentionDays(clampRetention(Number(e.target.value)))}
-            aria-label="Retention in days"
+            aria-label={t('documents.retention.aria')}
             className="w-16 rounded-control border border-border bg-surface px-2 py-1 text-ink disabled:opacity-40"
           />
-          <span>day{retentionDays === 1 ? '' : 's'}</span>
+          <span>{t('documents.retention.day', { count: retentionDays ?? DEFAULT_RETENTION_DAYS })}</span>
         </div>
       )}
 
@@ -228,7 +229,7 @@ export default function Documents() {
         filtered={hasFilters}
         isLoading={isLoading}
         isError={isError}
-        message={error?.message}
+        message={error ? apiErrorMessage(error, t) : undefined}
         onRetry={() => void refetch()}
         onDelete={setDeleteTarget}
       />
@@ -244,10 +245,10 @@ export default function Documents() {
 
       <ConfirmDialog
         open={deleteTarget !== null}
-        title="Delete document"
+        title={t('documents.delete.title')}
         message={
           deleteTarget
-            ? `Delete “${deleteTarget.filename}”? Its chunks and indexed vectors are removed. This cannot be undone.`
+            ? t('documents.delete.message', { name: deleteTarget.filename })
             : ''
         }
         loading={deleteMut.isPending}
@@ -282,6 +283,7 @@ function DocumentList({
   onRetry: () => void
   onDelete: (doc: DocumentSummary) => void
 }) {
+  const { t } = useTranslation()
   const progressById = useIngestionProgress(wsId, colId)
   if (isLoading) {
     return (
@@ -296,20 +298,20 @@ function DocumentList({
     )
   }
   if (isError) {
-    return <QueryError title="Could not load documents" message={message} onRetry={onRetry} />
+    return <QueryError title={t('documents.error')} message={message} onRetry={onRetry} />
   }
   if (!data || data.length === 0) {
     return filtered ? (
       <EmptyState
         icon={<FileText className="h-7 w-7" />}
-        title="No matching documents"
-        description="No documents match the current filters. Adjust or clear them to see more."
+        title={t('documents.empty.filtered.title')}
+        description={t('documents.empty.filtered.description')}
       />
     ) : (
       <EmptyState
         icon={<FileText className="h-7 w-7" />}
-        title="No documents yet"
-        description="Drop files into the area above to start ingesting them."
+        title={t('documents.empty.none.title')}
+        description={t('documents.empty.none.description')}
       />
     )
   }
@@ -337,9 +339,10 @@ function DocumentList({
  *  parsing/embedding/storing. doc.status can't drive this — the list only refetches on
  *  the terminal event, so it's stale at "pending" for the whole run. */
 function IngestProgress({ progress }: { progress?: IngestionProgress }) {
+  const { t } = useTranslation()
   const pct = progress?.pct ?? null
   const determinate = pct != null
-  const label = progress ? 'Ingesting' : 'Uploading'
+  const label = progress ? t('documents.progress.ingesting') : t('status.uploading')
   return (
     <div className="flex w-40 shrink-0 flex-col gap-1">
       <div className="flex items-center justify-between text-xs text-ink-muted">
@@ -378,6 +381,7 @@ function DocumentRow({
   progress?: IngestionProgress
   onDelete: (doc: DocumentSummary) => void
 }) {
+  const { t } = useTranslation()
   const { isAdmin, canManageTags } = useAuth()
   // (Un)assigning a document tag needs the manage_tags privilege AND write on the resource —
   // mirror the backend (authorize_tag_management + authorize_document write) so we don't show a
@@ -393,7 +397,7 @@ function DocumentRow({
   const unassignMut = useUnassignDocumentTag(wsId, colId)
   const createMut = useCreateTag(wsId)
   const tagBusy = assignMut.isPending || unassignMut.isPending || createMut.isPending
-  const onErr = (e: Error) => toast.error(e.message)
+  const onErr = (e: Error) => toast.error(apiErrorMessage(e, t))
 
   const handleCreate = (name: string) =>
     createMut.mutate(
@@ -436,9 +440,10 @@ function DocumentRow({
             <p className="text-xs text-ink-faint">
               {doc.file_type.toUpperCase()} · {formatBytes(doc.file_size)}
               {doc.chunk_count != null &&
-                ` · ${doc.chunk_count} chunk${doc.chunk_count === 1 ? '' : 's'}`}{' '}
-              · updated {timeAgo(doc.updated_at)}
-              {doc.has_original && ` · original: ${doc.original_filename ?? doc.filename}`}
+                ` · ${t('documents.row.chunk', { count: doc.chunk_count })}`}{' '}
+              · {t('documents.row.updated', { ago: timeAgo(doc.updated_at) })}
+              {doc.has_original &&
+                ` · ${t('documents.row.original', { name: doc.original_filename ?? doc.filename })}`}
             </p>
           </div>
         </div>
@@ -449,7 +454,7 @@ function DocumentRow({
               onClick={() => setShowError((v) => !v)}
               className="text-xs font-medium text-err hover:underline"
             >
-              {showError ? 'Hide' : 'Why?'}
+              {showError ? t('documents.row.hide') : t('documents.row.why')}
             </button>
           )}
           {failed && canWrite && (
@@ -458,13 +463,13 @@ function DocumentRow({
               disabled={reprocessMut.isPending}
               onClick={() =>
                 reprocessMut.mutate(doc.document_id, {
-                  onSuccess: () => toast.success(`Reprocessing “${doc.filename}”.`),
+                  onSuccess: () => toast.success(t('documents.toast.reprocessing', { name: doc.filename })),
                   onError: onErr,
                 })
               }
               className="text-xs font-medium text-accent hover:underline disabled:opacity-60"
             >
-              {reprocessMut.isPending ? 'Retrying…' : 'Retry'}
+              {reprocessMut.isPending ? t('common.retrying') : t('common.retry')}
             </button>
           )}
           {doc.status === 'pending' || doc.status === 'processing' ? (
@@ -478,7 +483,7 @@ function DocumentRow({
             canWrite={canWrite}
             onIndex={() =>
               indexMut.mutate(doc.document_id, {
-                onSuccess: () => toast.success(`Indexing “${doc.filename}”.`),
+                onSuccess: () => toast.success(t('documents.toast.indexing', { name: doc.filename })),
                 onError: onErr,
               })
             }
@@ -486,7 +491,7 @@ function DocumentRow({
           <Button
             variant="ghost"
             size="sm"
-            aria-label={`Open ${doc.filename}`}
+            aria-label={t('common.openAria', { name: doc.filename })}
             onClick={() => void api.openDocument(doc.document_id).catch((e) => onErr(e as Error))}
             className="h-10 w-10 px-0"
           >
@@ -495,7 +500,7 @@ function DocumentRow({
           <Button
             variant="ghost"
             size="sm"
-            aria-label={`Download ${doc.filename}`}
+            aria-label={t('common.downloadAria', { name: doc.filename })}
             onClick={() =>
               void api.downloadDocument(doc.document_id, doc.filename).catch((e) => onErr(e as Error))
             }
@@ -507,7 +512,7 @@ function DocumentRow({
             <Button
               variant="ghost"
               size="sm"
-              aria-label={`Download original source file (${doc.original_filename ?? doc.filename})`}
+              aria-label={t('documents.row.downloadOriginalAria', { name: doc.original_filename ?? doc.filename })}
               onClick={() =>
                 void api
                   .downloadDocument(doc.document_id, doc.original_filename ?? doc.filename, {
@@ -524,7 +529,7 @@ function DocumentRow({
             <Button
               variant="ghost"
               size="sm"
-              aria-label={`Delete ${doc.filename}`}
+              aria-label={t('common.deleteAria', { name: doc.filename })}
               onClick={() => onDelete(doc)}
               className="h-10 w-10 px-0 hover:text-err"
             >
@@ -535,16 +540,16 @@ function DocumentRow({
       </div>
       {((doc.tags ?? []).length > 0 || canManageDocTags) && (
         <div className="mt-2 flex flex-wrap items-center gap-1.5">
-          {(doc.tags ?? []).map((t) => (
+          {(doc.tags ?? []).map((tag) => (
             <TagChip
-              key={t.id}
-              name={t.name}
-              color={t.color}
+              key={tag.id}
+              name={tag.name}
+              color={tag.color}
               onRemove={
                 canManageDocTags
                   ? () =>
                       unassignMut.mutate(
-                        { docId: doc.document_id, tagId: t.id },
+                        { docId: doc.document_id, tagId: tag.id },
                         { onError: onErr },
                       )
                   : undefined
@@ -589,15 +594,16 @@ function IndexBadge({
   canWrite: boolean
   onIndex: () => void
 }) {
+  const { t } = useTranslation()
   if (doc.status !== 'done') return null
   if (doc.indexed) {
     return (
       <span
-        title="Indexed for BM25 / keyword search"
+        title={t('documents.index.indexedTitle')}
         className="inline-flex items-center gap-1 rounded-full border border-ok/30 bg-ok/5 px-2 py-0.5 text-xs font-medium text-ok"
       >
         <Database className="h-3.5 w-3.5" />
-        Indexed
+        {t('documents.index.indexed')}
       </span>
     )
   }
@@ -608,23 +614,24 @@ function IndexBadge({
       type="button"
       onClick={onIndex}
       disabled={busy}
-      title="Not in the keyword index — click to index"
+      title={t('documents.index.notIndexedTitle')}
       className="inline-flex items-center gap-1 rounded-full border border-dashed border-warn/40 px-2 py-0.5 text-xs font-medium text-warn transition-colors hover:bg-warn/5 disabled:opacity-60"
     >
       <DatabaseZap className="h-3.5 w-3.5" />
-      {busy ? 'Indexing…' : 'Index'}
+      {busy ? t('documents.index.indexing') : t('documents.index.index')}
     </button>
   )
 }
 
 /** Lazily fetch and show a failed document's ingestion error. */
 function FailureReason({ wsId, colId, docId }: { wsId: string; colId: string; docId: string }) {
+  const { t } = useTranslation()
   const { data, isLoading, isError } = useDocumentStatus(wsId, colId, docId, true)
   const text = isLoading
-    ? 'Loading error…'
+    ? t('documents.failure.loading')
     : isError
-      ? 'Could not load the error detail.'
-      : (data?.error ?? 'No error detail recorded.')
+      ? t('documents.failure.loadError')
+      : (data?.error ?? t('documents.failure.none'))
   return (
     <div className="mt-2 flex items-start gap-2 rounded-control border border-err/30 bg-err/5 px-3 py-2">
       <AlertCircle className="mt-0.5 h-4 w-4 shrink-0 text-err" />
diff --git a/ui/src/pages/Graph.tsx b/ui/src/pages/Graph.tsx
index 979be6a..ba17fa0 100644
--- a/ui/src/pages/Graph.tsx
+++ b/ui/src/pages/Graph.tsx
@@ -1,13 +1,16 @@
 import { useEffect, useMemo, useState } from 'react'
 import { Download, ExternalLink, RotateCcw, Workflow, X } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
 import { useCollections, useGraph, useWorkspaces } from '../api/hooks'
 import { api } from '../api/client'
 import type { GraphNode, GraphResponse } from '../api/types'
 import { GraphCanvas } from '../components/graph/GraphCanvas'
 import { Badge, Button, Card, EmptyState, QueryError, Select, Skeleton, useToast } from '../components/ui'
+import { apiErrorMessage } from '../i18n/apiError'
 
 /** Tag-correlation graph: pick a scope, see files linked through their tags. */
 export default function Graph() {
+  const { t } = useTranslation()
   const workspaces = useWorkspaces()
   const [wsId, setWsId] = useState('')
   const [colId, setColId] = useState('') // '' = whole workspace
@@ -34,11 +37,9 @@ export default function Graph() {
     <div className="animate-fade-in space-y-4">
       <header className="flex flex-wrap items-start justify-between gap-4">
         <div>
-          <h1 className="text-xl font-semibold tracking-tight text-ink">Graph</h1>
+          <h1 className="text-xl font-semibold tracking-tight text-ink">{t('graph.title')}</h1>
           <p className="mt-1 text-[13px] text-ink-muted">
-            Files (the larger nodes) linked through the tags they share. Hotter tag nodes are
-            more-reused. Drag a node to pin and highlight it, click it to release; tune the repel
-            force or reset to re-center.
+            {t('graph.subtitle')}
           </p>
         </div>
         <div className="flex gap-2">
@@ -46,7 +47,7 @@ export default function Graph() {
             value={wsId}
             onChange={(e) => setWsId(e.target.value)}
             disabled={!workspaces.data || workspaces.data.length === 0}
-            aria-label="Workspace"
+            aria-label={t('graph.workspaceAria')}
             className="w-44"
           >
             {workspaces.data?.map((ws) => (
@@ -58,10 +59,10 @@ export default function Graph() {
           <Select
             value={colId}
             onChange={(e) => setColId(e.target.value)}
-            aria-label="Collection"
+            aria-label={t('graph.collectionAria')}
             className="w-44"
           >
-            <option value="">All collections</option>
+            <option value="">{t('graph.allCollections')}</option>
             {collections.data?.map((col) => (
               <option key={col.id} value={col.id}>
                 {col.name}
@@ -74,7 +75,7 @@ export default function Graph() {
       <GraphBody
         isLoading={graph.isLoading || workspaces.isLoading}
         isError={graph.isError}
-        message={graph.error?.message}
+        message={graph.error ? apiErrorMessage(graph.error, t) : undefined}
         onRetry={() => void graph.refetch()}
         data={graph.data}
         selected={selected}
@@ -111,14 +112,15 @@ function GraphBody({
   fitNonce: number
   onReset: () => void
 }) {
+  const { t } = useTranslation()
   if (isLoading) return <Skeleton className="h-[70vh] rounded-card" />
-  if (isError) return <QueryError title="Could not load the graph" message={message} onRetry={onRetry} />
+  if (isError) return <QueryError title={t('graph.error')} message={message} onRetry={onRetry} />
   if (!data || data.nodes.length === 0) {
     return (
       <EmptyState
         icon={<Workflow className="h-7 w-7" />}
-        title="Nothing to graph yet"
-        description="Tag some documents in this scope and they'll appear here, linked through their shared tags."
+        title={t('graph.empty.title')}
+        description={t('graph.empty.description')}
       />
     )
   }
@@ -131,10 +133,10 @@ function GraphBody({
         size="sm"
         onClick={onReset}
         className="absolute right-3 top-3"
-        aria-label="Reset view"
+        aria-label={t('graph.resetView')}
       >
         <RotateCcw className="h-4 w-4" />
-        Reset
+        {t('graph.reset')}
       </Button>
       {selected && <DetailPanel graph={data} nodeId={selected} onClose={() => onSelect(null)} />}
     </Card>
@@ -143,17 +145,18 @@ function GraphBody({
 
 /** Cold→hot gradient key for tag heat, anchored to the busiest tag. */
 function HeatLegend({ maxHeat }: { maxHeat: number }) {
+  const { t } = useTranslation()
   if (maxHeat <= 0) return null
   return (
     <div className="absolute bottom-3 left-3 rounded-control border border-border bg-surface/90 px-3 py-2 text-xs text-ink-muted backdrop-blur">
-      <div className="mb-1 font-medium text-ink">Tag heat</div>
+      <div className="mb-1 font-medium text-ink">{t('graph.heat.title')}</div>
       <div className="flex items-center gap-2">
         <span>1</span>
         <span
           className="h-2 w-24 rounded-full"
           style={{ background: 'linear-gradient(to right, rgb(37,99,235), rgb(220,38,38))' }}
         />
-        <span>{maxHeat} files</span>
+        <span>{t('graph.heat.files', { count: maxHeat })}</span>
       </div>
     </div>
   )
@@ -169,6 +172,7 @@ function DetailPanel({
   nodeId: string
   onClose: () => void
 }) {
+  const { t } = useTranslation()
   const toast = useToast()
   const node = useMemo(() => graph.nodes.find((n) => n.id === nodeId), [graph, nodeId])
   const neighbors = useMemo(() => neighborLabels(graph, nodeId), [graph, nodeId])
@@ -180,7 +184,7 @@ function DetailPanel({
           <span className="text-[11px] uppercase tracking-wide text-ink-faint">{node.kind}</span>
           <h3 className="truncate text-sm font-medium text-ink">{node.label}</h3>
         </div>
-        <button onClick={onClose} className="text-ink-faint hover:text-ink" aria-label="Close">
+        <button onClick={onClose} className="text-ink-faint hover:text-ink" aria-label={t('common.close')}>
           <X className="h-5 w-5" />
         </button>
       </div>
@@ -191,28 +195,28 @@ function DetailPanel({
             variant="secondary"
             size="sm"
             className="flex-1"
-            onClick={() => void api.openDocument(node.id).catch((e) => toast.error((e as Error).message))}
+            onClick={() => void api.openDocument(node.id).catch((e) => toast.error(apiErrorMessage(e, t)))}
           >
             <ExternalLink className="h-4 w-4" />
-            Open
+            {t('graph.open')}
           </Button>
           <Button
             variant="secondary"
             size="sm"
             className="flex-1"
             onClick={() =>
-              void api.downloadDocument(node.id, node.label).catch((e) => toast.error((e as Error).message))
+              void api.downloadDocument(node.id, node.label).catch((e) => toast.error(apiErrorMessage(e, t)))
             }
           >
             <Download className="h-4 w-4" />
-            Download
+            {t('graph.download')}
           </Button>
         </div>
       )}
       {neighbors.length > 0 && (
         <div className="mt-3">
           <div className="mb-1.5 text-[11px] uppercase tracking-wide text-ink-faint">
-            {node.kind === 'tag' ? 'Files' : 'Tags'}
+            {node.kind === 'tag' ? t('graph.files') : t('common.tags')}
           </div>
           <div className="flex flex-wrap gap-1.5">
             {neighbors.map((label) => (
@@ -227,11 +231,11 @@ function DetailPanel({
 
 /** The kind-specific stat line for a node. */
 function NodeFacts({ node }: { node: GraphNode }) {
+  const { t } = useTranslation()
   if (node.kind === 'tag') {
     return (
       <p className="mt-2 text-[13px] text-ink-muted">
-        Used by <span className="font-medium text-ink">{node.heat}</span> file
-        {node.heat === 1 ? '' : 's'}.
+        {t('graph.node.usedBy', { count: node.heat })}
       </p>
     )
   }
@@ -239,7 +243,7 @@ function NodeFacts({ node }: { node: GraphNode }) {
   return (
     <p className="mt-2 text-[13px] text-ink-muted">
       {type ? `${type.toUpperCase()} · ` : ''}
-      {node.degree} tag{node.degree === 1 ? '' : 's'}.
+      {t('graph.node.tags', { count: node.degree })}
     </p>
   )
 }
diff --git a/ui/src/pages/Indexing.tsx b/ui/src/pages/Indexing.tsx
index b6b935f..907cd9d 100644
--- a/ui/src/pages/Indexing.tsx
+++ b/ui/src/pages/Indexing.tsx
@@ -1,5 +1,6 @@
 import { useState } from 'react'
 import { AlertTriangle, DatabaseZap, RefreshCw } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
 import { useAuth } from '../auth/AuthContext'
 import { useIndexStatus, useRetryFailedJobs } from '../api/hooks'
 import type { CollectionIndexStatus } from '../api/types'
@@ -12,9 +13,11 @@ import {
   Skeleton,
   useToast,
 } from '../components/ui'
+import { apiErrorMessage } from '../i18n/apiError'
 
 /** Keyword-index coverage per workspace → collection, with a retry for failed ingestions. */
 export default function Indexing() {
+  const { t } = useTranslation()
   const { data, isLoading, isError, error, refetch } = useIndexStatus()
 
   if (isLoading) {
@@ -34,8 +37,8 @@ export default function Indexing() {
       <div className="animate-fade-in space-y-6">
         <Header />
         <QueryError
-          title="Could not load index status"
-          message={error?.message}
+          title={t('indexing.error')}
+          message={error ? apiErrorMessage(error, t) : undefined}
           onRetry={() => void refetch()}
         />
       </div>
@@ -48,8 +51,8 @@ export default function Indexing() {
       {workspaces.length === 0 ? (
         <EmptyState
           icon={<DatabaseZap className="h-7 w-7" />}
-          title="Nothing to index yet"
-          description="Upload documents to a collection and they'll appear here."
+          title={t('indexing.empty.title')}
+          description={t('indexing.empty.description')}
         />
       ) : (
         <div className="space-y-6">
@@ -72,14 +75,12 @@ export default function Indexing() {
 }
 
 function Header() {
+  const { t } = useTranslation()
   return (
     <header>
-      <h1 className="text-xl font-semibold tracking-tight text-ink">Indexing</h1>
+      <h1 className="text-xl font-semibold tracking-tight text-ink">{t('indexing.title')}</h1>
       <p className="mt-1 text-[13px] text-ink-muted">
-        Keyword-index coverage per collection. A document is searchable once its chunks are
-        stored — the keyword index is maintained automatically, so there is nothing to rebuild.
-        Anything short of full coverage is an ingestion that has not finished; retry the failed
-        ones here.
+        {t('indexing.subtitle')}
       </p>
     </header>
   )
@@ -94,6 +95,7 @@ function Header() {
  * documents — which re-embeds them, hence the confirmation. In-flight ones are left to finish.
  */
 function CollectionRow({ col }: { col: CollectionIndexStatus }) {
+  const { t } = useTranslation()
   // A non-admin sees coverage for their permitted collections but can't retry (re-ingest).
   const { isAdmin } = useAuth()
   const toast = useToast()
@@ -101,18 +103,18 @@ function CollectionRow({ col }: { col: CollectionIndexStatus }) {
   const [confirming, setConfirming] = useState(false)
   const pct = col.total > 0 ? Math.round((col.indexed / col.total) * 100) : 100
   const fullyIndexed = col.unindexed === 0
-  const failedDocs = `${col.failed} failed document${col.failed === 1 ? '' : 's'}`
+  const failedDocs = t('indexing.failedDocs', { count: col.failed })
 
   const retryFailed = () =>
     retryMut.mutate(
       { collection_id: col.collection_id },
       {
         onSuccess: ({ retried }) => {
-          toast.success(`Re-queued ${retried} document${retried === 1 ? '' : 's'}.`)
+          toast.success(t('indexing.toast.requeued', { count: retried }))
           setConfirming(false)
         },
         // Leave the dialog open on failure so it can be retried from there.
-        onError: (e) => toast.error(e.message),
+        onError: (e) => toast.error(apiErrorMessage(e, t)),
       },
     )
 
@@ -125,7 +127,7 @@ function CollectionRow({ col }: { col: CollectionIndexStatus }) {
             {!fullyIndexed && (
               <span className="inline-flex items-center gap-1 rounded-full border border-warn/40 bg-warn/5 px-2 py-0.5 text-xs font-medium text-warn">
                 <AlertTriangle className="h-3.5 w-3.5" />
-                {col.unindexed} unindexed
+                {t('indexing.unindexed', { count: col.unindexed })}
               </span>
             )}
           </div>
@@ -137,9 +139,9 @@ function CollectionRow({ col }: { col: CollectionIndexStatus }) {
               />
             </div>
             <span className="text-xs text-ink-faint">
-              {col.indexed}/{col.total} indexed
-              {col.pending > 0 && ` · ${col.pending} ingesting`}
-              {col.failed > 0 && ` · ${col.failed} failed`}
+              {t('indexing.coverage', { indexed: col.indexed, total: col.total })}
+              {col.pending > 0 && t('indexing.pendingSuffix', { count: col.pending })}
+              {col.failed > 0 && t('indexing.failedSuffix', { count: col.failed })}
             </span>
           </div>
         </div>
@@ -153,16 +155,19 @@ function CollectionRow({ col }: { col: CollectionIndexStatus }) {
             onClick={() => setConfirming(true)}
           >
             <RefreshCw className="h-4 w-4" />
-            Retry failed
+            {t('indexing.retryFailed')}
           </Button>
         )}
       </div>
 
       <ConfirmDialog
         open={confirming}
-        title="Retry failed ingestions"
-        message={`Re-ingest the ${failedDocs} in “${col.collection_name}”? Each is re-queued and embedded again from its stored file — resuming where the last attempt stopped — so this spends embedding-provider quota. Documents still ingesting are left alone.`}
-        confirmLabel="Retry failed"
+        title={t('indexing.retryDialog.title')}
+        message={t('indexing.retryDialog.message', {
+          docs: failedDocs,
+          name: col.collection_name,
+        })}
+        confirmLabel={t('indexing.retryFailed')}
         loading={retryMut.isPending}
         onConfirm={retryFailed}
         onClose={() => setConfirming(false)}
diff --git a/ui/src/pages/IngestionQueue.tsx b/ui/src/pages/IngestionQueue.tsx
index 583c785..4c39130 100644
--- a/ui/src/pages/IngestionQueue.tsx
+++ b/ui/src/pages/IngestionQueue.tsx
@@ -13,6 +13,7 @@ import {
   X,
   XCircle,
 } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
 import {
   Badge,
   Button,
@@ -25,6 +26,7 @@ import {
   useToast,
 } from '../components/ui'
 import type { BadgeStatus } from '../components/ui'
+import { apiErrorMessage } from '../i18n/apiError'
 import { Pager } from '../components/Pager'
 import {
   FILE_TYPES,
@@ -51,6 +53,7 @@ const PAGE_SIZE = 50
  * jobs start and settle, so page 1 stays current without polling.
  */
 export default function IngestionQueue() {
+  const { t } = useTranslation()
   // A non-admin views the queue scoped to their grants (the backend filters jobs, stats, and the
   // live stream); retrying re-ingests documents, so it stays an admin action.
   const { isAdmin } = useAuth()
@@ -76,12 +79,12 @@ export default function IngestionQueue() {
       onSuccess: ({ retried }) => {
         toast.success(
           retried > 0
-            ? `Re-enqueued ${retried} failed document${retried === 1 ? '' : 's'}.`
-            : 'No failed documents matched the current filters.',
+            ? t('queue.toast.reenqueued', { count: retried })
+            : t('queue.toast.noneMatched'),
         )
         setConfirmRetry(false)
       },
-      onError: (e) => toast.error(e.message),
+      onError: (e) => toast.error(apiErrorMessage(e, t)),
     })
   }
   const lastPage = Math.max(0, Math.ceil(total / PAGE_SIZE) - 1)
@@ -119,7 +122,7 @@ export default function IngestionQueue() {
         filtered={hasFilters}
         isLoading={isLoading}
         isError={isError}
-        message={error?.message}
+        message={error ? apiErrorMessage(error, t) : undefined}
         onRetry={() => void refetch()}
       />
       <Pager
@@ -133,13 +136,13 @@ export default function IngestionQueue() {
 
       <ConfirmDialog
         open={confirmRetry}
-        title="Retry failed documents"
+        title={t('queue.retryDialog.title')}
         message={
           hasFilters
-            ? 'Re-run ingestion for every failed document matching the current filters? Each is re-queued from where it left off.'
-            : 'Re-run ingestion for every failed document in the queue? Each is re-queued from where it left off.'
+            ? t('queue.retryDialog.messageFiltered')
+            : t('queue.retryDialog.message')
         }
-        confirmLabel="Retry failed"
+        confirmLabel={t('queue.retryFailed')}
         loading={retryMut.isPending}
         onConfirm={retryAllFailed}
         onClose={() => setConfirmRetry(false)}
@@ -172,27 +175,27 @@ function Header({
   retrying: boolean
   onRetryAll: () => void
 }) {
+  const { t } = useTranslation()
   const processing = counts.processing ?? 0
   const pending = counts.pending ?? 0
   const waiting = counts.rate_limited ?? 0
   const parts: string[] = []
-  if (processing > 0) parts.push(`${processing} ingesting`)
-  if (pending > 0) parts.push(`${pending} queued`)
-  if (waiting > 0) parts.push(`${waiting} waiting on rate limit`)
+  if (processing > 0) parts.push(t('queue.parts.ingesting', { count: processing }))
+  if (pending > 0) parts.push(t('queue.parts.queued', { count: pending }))
+  if (waiting > 0) parts.push(t('queue.parts.waiting', { count: waiting }))
   return (
     <div className="flex items-center justify-between gap-3">
       <div>
         <h1 className="flex items-center gap-2 text-xl font-semibold text-ink">
           <ListChecks className="h-6 w-6 text-accent" />
-          Ingestion Queue
+          {t('nav.ingestionQueue')}
         </h1>
         <p className="mt-1 text-[13px] text-ink-muted">
-          {parts.length ? parts.join(' · ') : 'Queue empty'}
+          {parts.length ? parts.join(' · ') : t('queue.queueEmpty')}
           {pausedSeconds > 0 && (
             <span className="text-warn">
               {' '}
-              · paused on the embedding provider's quota — retrying in{' '}
-              {formatBackoff(pausedSeconds)}
+              {t('queue.paused', { time: formatBackoff(pausedSeconds) })}
             </span>
           )}
         </p>
@@ -203,12 +206,12 @@ function Header({
         {canRetryAll && (
           <Button variant="secondary" size="sm" onClick={onRetryAll} disabled={retrying}>
             <RotateCcw className={cn('h-4 w-4', retrying && 'animate-spin')} />
-            {retrying ? 'Retrying…' : 'Retry all failed'}
+            {retrying ? t('common.retrying') : t('queue.retryAllFailed')}
           </Button>
         )}
         <span className="flex items-center gap-1.5 text-xs text-ink-faint">
           <span className={cn('h-2 w-2 rounded-full', connected ? 'bg-ok' : 'bg-ink-faint/50')} />
-          {connected ? 'Live' : 'Connecting…'}
+          {connected ? t('queue.live') : t('queue.connecting')}
         </span>
       </div>
     </div>
@@ -237,6 +240,7 @@ function JobFilters({
   value: JobFilterValues
   onChange: (next: JobFilterValues) => void
 }) {
+  const { t } = useTranslation()
   const [expanded, setExpanded] = useState(false)
   const set = <K extends keyof JobFilterValues>(key: K, v: JobFilterValues[K]) =>
     onChange({ ...value, [key]: v })
@@ -249,34 +253,34 @@ function JobFilters({
           <Search className="pointer-events-none absolute left-2.5 top-1/2 h-4 w-4 -translate-y-1/2 text-ink-faint" />
           <input
             className={`${inputCls} w-full pl-8`}
-            placeholder="Search filenames…"
+            placeholder={t('documents.filters.searchPlaceholder')}
             value={value.filename ?? ''}
             onChange={(e) => set('filename', text(e.target.value))}
           />
         </div>
         <select
           className={inputCls}
-          aria-label="Status"
+          aria-label={t('documents.filters.statusAria')}
           value={value.status ?? ''}
           onChange={(e) => set('status', text(e.target.value))}
         >
-          <option value="">Any status</option>
+          <option value="">{t('documents.filters.anyStatus')}</option>
           {STATUSES.map((s) => (
             <option key={s} value={s}>
-              {s}
+              {t(`status.${s}`)}
             </option>
           ))}
         </select>
         <select
           className={inputCls}
-          aria-label="File type"
+          aria-label={t('documents.filters.typeAria')}
           value={value.file_type ?? ''}
           onChange={(e) => set('file_type', text(e.target.value))}
         >
-          <option value="">Any type</option>
-          {FILE_TYPES.map((t) => (
-            <option key={t} value={t}>
-              {t}
+          <option value="">{t('documents.filters.anyType')}</option>
+          {FILE_TYPES.map((ft) => (
+            <option key={ft} value={ft}>
+              {ft}
             </option>
           ))}
         </select>
@@ -288,7 +292,7 @@ function JobFilters({
           }`}
         >
           <SlidersHorizontal className="h-4 w-4" />
-          More
+          {t('common.more')}
         </button>
         {active && (
           <button
@@ -297,7 +301,7 @@ function JobFilters({
             className="inline-flex h-9 items-center gap-1 rounded-control px-2 text-[13px] text-ink-muted hover:text-ink"
           >
             <X className="h-4 w-4" />
-            Clear
+            {t('common.clear')}
           </button>
         )}
       </div>
@@ -306,12 +310,12 @@ function JobFilters({
         <div className="flex flex-wrap items-center gap-x-3 gap-y-2 rounded-control border border-border/60 bg-canvas/50 p-2.5">
           <input
             className={inputCls}
-            placeholder="Collection name"
+            placeholder={t('queue.filters.collectionPlaceholder')}
             value={value.collection ?? ''}
             onChange={(e) => set('collection', text(e.target.value))}
           />
           <label className="flex items-center gap-1.5 text-xs text-ink-muted">
-            Created
+            {t('documents.filters.created')}
             <input
               type="date"
               className={`${inputCls} w-40`}
@@ -353,6 +357,7 @@ function QueueBody({
   message?: string
   onRetry: () => void
 }) {
+  const { t } = useTranslation()
   if (isLoading) {
     return (
       <div className="space-y-3">
@@ -366,20 +371,20 @@ function QueueBody({
     )
   }
   if (isError) {
-    return <QueryError title="Could not load the queue" message={message} onRetry={onRetry} />
+    return <QueryError title={t('queue.error')} message={message} onRetry={onRetry} />
   }
   if (jobs.length === 0) {
     return filtered ? (
       <EmptyState
         icon={<ListChecks className="h-7 w-7" />}
-        title="No matching jobs"
-        description="No ingestion jobs match the current filters. Adjust or clear them to see more."
+        title={t('queue.empty.filtered.title')}
+        description={t('queue.empty.filtered.description')}
       />
     ) : (
       <EmptyState
         icon={<ListChecks className="h-7 w-7" />}
-        title="No ingestions yet"
-        description="Upload a document and its chunks will stream here in real time as they're embedded."
+        title={t('queue.empty.none.title')}
+        description={t('queue.empty.none.description')}
       />
     )
   }
@@ -418,15 +423,16 @@ function OpenInCollection({
   collectionId: string
   filename: string
 }) {
+  const { t } = useTranslation()
   if (!workspaceId) return null
   return (
     <Link
       to={`/workspaces/${workspaceId}/collections/${collectionId}?filename=${encodeURIComponent(filename)}`}
-      title="Open in collection to edit or delete"
+      title={t('queue.openInCollectionTitle')}
       className="inline-flex shrink-0 items-center gap-1 text-xs font-medium text-ink-muted hover:text-ink"
     >
       <FolderOpen className="h-3.5 w-3.5" />
-      Open
+      {t('queue.open')}
     </Link>
   )
 }
@@ -434,6 +440,7 @@ function OpenInCollection({
 /** A static queue row for a job with no live stream (finished, failed, or not currently in the
  *  live buffer). The failure reason ships in the row payload, so no extra request is needed. */
 function JobRow({ job }: { job: JobSummary }) {
+  const { t } = useTranslation()
   const { isAdmin } = useAuth()
   const [showError, setShowError] = useState(false)
   const failed = job.status === 'failed'
@@ -447,9 +454,9 @@ function JobRow({ job }: { job: JobSummary }) {
           <div className="min-w-0">
             <p className="truncate text-[13px] font-medium text-ink">{job.filename}</p>
             <p className="truncate text-xs text-ink-faint">
-              {job.collection_name ?? 'Unknown collection'} · {job.file_type.toUpperCase()}
+              {job.collection_name ?? t('queue.unknownCollection')} · {job.file_type.toUpperCase()}
               {job.chunk_count != null &&
-                ` · ${job.chunk_count} chunk${job.chunk_count === 1 ? '' : 's'}`}{' '}
+                ` · ${t('documents.row.chunk', { count: job.chunk_count })}`}{' '}
               · {timeAgo(job.updated_at)}
             </p>
           </div>
@@ -466,7 +473,7 @@ function JobRow({ job }: { job: JobSummary }) {
               onClick={() => setShowError((v) => !v)}
               className="text-xs font-medium text-err hover:underline"
             >
-              {showError ? 'Hide' : 'Why?'}
+              {showError ? t('documents.row.hide') : t('documents.row.why')}
             </button>
           )}
           {failed && isAdmin && (
@@ -475,13 +482,13 @@ function JobRow({ job }: { job: JobSummary }) {
               disabled={reprocessMut.isPending}
               onClick={() =>
                 reprocessMut.mutate(job.document_id, {
-                  onSuccess: () => toast.success(`Reprocessing “${job.filename}”.`),
-                  onError: (e) => toast.error(e.message),
+                  onSuccess: () => toast.success(t('documents.toast.reprocessing', { name: job.filename })),
+                  onError: (e) => toast.error(apiErrorMessage(e, t)),
                 })
               }
               className="text-xs font-medium text-accent hover:underline disabled:opacity-60"
             >
-              {reprocessMut.isPending ? 'Retrying…' : 'Retry'}
+              {reprocessMut.isPending ? t('common.retrying') : t('common.retry')}
             </button>
           )}
           <StatusBadge status={job.status as BadgeStatus} />
@@ -508,6 +515,7 @@ const PHASE_STYLE: Record<string, string> = {
 }
 
 function QueueCard({ item }: { item: QueueItem }) {
+  const { t } = useTranslation()
   const determinate = item.pct != null
   const terminal = item.status === 'done' || item.status === 'failed'
   return (
@@ -542,11 +550,11 @@ function QueueCard({ item }: { item: QueueItem }) {
             {item.status === 'rate_limited' && item.retry_at ? (
               <RetryCountdown retryAt={item.retry_at} />
             ) : (
-              <span className="capitalize">{item.phase}</span>
+              <span className="capitalize">{t(`queue.phase.${item.phase}`)}</span>
             )}
             {item.total != null && (
               <span className="tabular-nums">
-                {item.current ?? 0} / {item.total} chunks
+                {t('queue.chunkProgress', { current: item.current ?? 0, total: item.total })}
               </span>
             )}
           </div>
@@ -566,7 +574,7 @@ function QueueCard({ item }: { item: QueueItem }) {
       {item.recentChunks.length > 0 && (
         <div className="rounded-control border border-border bg-canvas/50">
           <div className="border-b border-border px-3 py-1.5 text-[11px] font-medium uppercase tracking-wide text-ink-faint">
-            Chunks {terminal ? '' : '(latest)'}
+            {t('queue.chunks')} {terminal ? '' : t('queue.chunksLatest')}
           </div>
           <ul className="max-h-48 overflow-y-auto py-1">
             {[...item.recentChunks].reverse().map((c) => (
@@ -586,11 +594,12 @@ function QueueCard({ item }: { item: QueueItem }) {
 }
 
 function PhaseBadge({ item }: { item: QueueItem }) {
+  const { t } = useTranslation()
   if (item.status === 'rate_limited') {
     return (
       <Badge className="shrink-0 text-warn">
         <AlertTriangle className="h-3.5 w-3.5" />
-        Rate limited
+        {t('status.rate_limited')}
       </Badge>
     )
   }
@@ -606,13 +615,14 @@ function PhaseBadge({ item }: { item: QueueItem }) {
   return (
     <Badge className={cn('shrink-0 capitalize', cls)}>
       {icon}
-      {item.status === 'processing' ? item.phase : item.status}
+      {item.status === 'processing' ? t(`queue.phase.${item.phase}`) : t(`status.${item.status}`)}
     </Badge>
   )
 }
 
 /** Live "retry in M:SS" countdown to a paused item's scheduled resume time. */
 function RetryCountdown({ retryAt }: { retryAt: string }) {
+  const { t } = useTranslation()
   const [now, setNow] = useState(() => Date.now())
   useEffect(() => {
     const id = setInterval(() => setNow(Date.now()), 1000)
@@ -621,7 +631,9 @@ function RetryCountdown({ retryAt }: { retryAt: string }) {
   const remaining = Math.max(0, Math.round((new Date(retryAt).getTime() - now) / 1000))
   const label =
     remaining > 0
-      ? `retry in ${Math.floor(remaining / 60)}:${String(remaining % 60).padStart(2, '0')}`
-      : 'retrying…'
+      ? t('queue.retryIn', {
+          time: `${Math.floor(remaining / 60)}:${String(remaining % 60).padStart(2, '0')}`,
+        })
+      : t('queue.retrying')
   return <span className="tabular-nums text-warn">{label}</span>
 }
diff --git a/ui/src/pages/Search.tsx b/ui/src/pages/Search.tsx
index fa7f184..e364b4b 100644
--- a/ui/src/pages/Search.tsx
+++ b/ui/src/pages/Search.tsx
@@ -1,16 +1,13 @@
 import { useState } from 'react'
 import { Search as SearchIcon } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
 import { useSearch } from '../api/hooks'
 import type { SearchFilters, SearchModeRequest } from '../api/types'
 import { Button, Card, Field, Input } from '../components/ui'
 import { WorkspaceTree } from '../components/search/WorkspaceTree'
 import { SearchResults } from '../components/search/SearchResults'
 
-const MODES: { value: SearchModeRequest; label: string }[] = [
-  { value: 'hybrid', label: 'Hybrid' },
-  { value: 'semantic', label: 'Semantic' },
-  { value: 'bm25', label: 'BM25' },
-]
+const MODES: SearchModeRequest[] = ['hybrid', 'semantic', 'bm25']
 
 interface FilterForm {
   filename: string
@@ -24,7 +21,7 @@ function buildFilters(f: FilterForm): SearchFilters | undefined {
   const filename = f.filename.trim() || undefined
   const tags = f.tags
     .split(',')
-    .map((t) => t.trim())
+    .map((tag) => tag.trim())
     .filter(Boolean)
   if (!filename && tags.length === 0) return undefined
   return { filename, tags: tags.length > 0 ? tags : undefined }
@@ -32,6 +29,7 @@ function buildFilters(f: FilterForm): SearchFilters | undefined {
 
 /** Two-pane hybrid search: pick collections, query, read ranked chunks. */
 export default function Search() {
+  const { t } = useTranslation()
   const [selected, setSelected] = useState<Set<string>>(new Set())
   const [query, setQuery] = useState('')
   const [topK, setTopK] = useState(5)
@@ -69,9 +67,9 @@ export default function Search() {
   return (
     <div className="animate-fade-in space-y-6">
       <header>
-        <h1 className="text-xl font-semibold tracking-tight text-ink">Search</h1>
+        <h1 className="text-xl font-semibold tracking-tight text-ink">{t('search.title')}</h1>
         <p className="mt-1 text-[13px] text-ink-muted">
-          Hybrid BM25 + semantic search across your collections.
+          {t('search.subtitle')}
         </p>
       </header>
 
@@ -79,7 +77,8 @@ export default function Search() {
         <aside className="lg:w-72 lg:shrink-0">
           <Card className="p-3">
             <h2 className="mb-2 px-1 text-xs font-semibold uppercase tracking-wide text-ink-faint">
-              Collections {selected.size > 0 && <span className="text-accent">· {selected.size}</span>}
+              {t('collections.title')}{' '}
+              {selected.size > 0 && <span className="text-accent">· {selected.size}</span>}
             </h2>
             <WorkspaceTree selected={selected} onToggle={toggle} onToggleMany={toggleMany} />
           </Card>
@@ -93,15 +92,15 @@ export default function Search() {
               onKeyDown={(e) => {
                 if (e.key === 'Enter') run()
               }}
-              placeholder="Search your collections…"
+              placeholder={t('search.queryPlaceholder')}
             />
             <Button onClick={run} loading={searchMut.isPending} disabled={!canSearch}>
               <SearchIcon className="h-5 w-5" />
-              Search
+              {t('search.submit')}
             </Button>
           </div>
           {selected.size === 0 && (
-            <p className="text-xs text-ink-faint">Select at least one collection to search.</p>
+            <p className="text-xs text-ink-faint">{t('search.selectPrompt')}</p>
           )}
 
           <Controls
@@ -142,12 +141,13 @@ function Controls({
   filters: FilterForm
   setFilters: (f: FilterForm) => void
 }) {
+  const { t } = useTranslation()
   const [showFilters, setShowFilters] = useState(false)
   return (
     <Card className="flex flex-col gap-3 p-4">
       <div className="flex flex-wrap items-center gap-x-6 gap-y-3">
         <label className="flex items-center gap-2 text-[13px]">
-          <span className="text-ink-muted">Top-K</span>
+          <span className="text-ink-muted">{t('search.topK')}</span>
           <input
             type="range"
             min={1}
@@ -159,29 +159,29 @@ function Controls({
           <span className="w-6 font-mono text-xs text-ink">{topK}</span>
         </label>
         <div className="flex items-center gap-2 text-[13px]">
-          <span className="text-ink-muted">Mode</span>
+          <span className="text-ink-muted">{t('search.modeLabel')}</span>
           <div className="inline-flex overflow-hidden rounded-md border border-border" role="group">
             {MODES.map((m) => (
               <button
-                key={m.value}
+                key={m}
                 type="button"
-                onClick={() => setMode(m.value)}
-                aria-pressed={mode === m.value}
+                onClick={() => setMode(m)}
+                aria-pressed={mode === m}
                 className={
                   'px-3 py-1 text-xs font-medium transition-colors ' +
-                  (mode === m.value
+                  (mode === m
                     ? 'bg-accent text-white'
                     : 'bg-transparent text-ink-muted hover:bg-canvas')
                 }
               >
-                {m.label}
+                {t(`search.mode.${m}`)}
               </button>
             ))}
           </div>
         </div>
         {mode === 'hybrid' && (
-          <label className="flex items-center gap-2 text-[13px]" title="0 = BM25 only, 1 = semantic only">
-            <span className="text-ink-muted">Alpha</span>
+          <label className="flex items-center gap-2 text-[13px]" title={t('search.alphaHint')}>
+            <span className="text-ink-muted">{t('search.alpha')}</span>
             <input
               type="range"
               min={0}
@@ -199,25 +199,25 @@ function Controls({
           onClick={() => setShowFilters((s) => !s)}
           className="text-xs font-medium text-accent hover:underline"
         >
-          {showFilters ? 'Hide filters' : 'Filters'}
+          {showFilters ? t('search.hideFilters') : t('search.filters')}
         </button>
       </div>
       {showFilters && (
         <div className="grid grid-cols-1 gap-3 border-t border-border pt-3 sm:grid-cols-2">
-          <Field label="Filename" htmlFor="f-file">
+          <Field label={t('search.filename')} htmlFor="f-file">
             <Input
               id="f-file"
               value={filters.filename}
               onChange={(e) => setFilters({ ...filters, filename: e.target.value })}
-              placeholder="e.g. report.pdf"
+              placeholder={t('search.filenamePlaceholder')}
             />
           </Field>
-          <Field label="Tags" htmlFor="f-tags" hint="Comma-separated">
+          <Field label={t('common.tags')} htmlFor="f-tags" hint={t('search.commaSeparated')}>
             <Input
               id="f-tags"
               value={filters.tags}
               onChange={(e) => setFilters({ ...filters, tags: e.target.value })}
-              placeholder="e.g. finance, q3"
+              placeholder={t('search.tagsPlaceholder')}
             />
           </Field>
         </div>
diff --git a/ui/src/pages/Settings.tsx b/ui/src/pages/Settings.tsx
index a2a6b0e..2d4bbca 100644
--- a/ui/src/pages/Settings.tsx
+++ b/ui/src/pages/Settings.tsx
@@ -1,5 +1,6 @@
 import { useState } from 'react'
 import { Lock } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
 import { useHealth } from '../api/hooks'
 import { useAuth } from '../auth/AuthContext'
 import { Button, Card, QueryError, Skeleton } from '../components/ui'
@@ -9,38 +10,37 @@ import { cn } from '../lib/cn'
 import { formatUptime } from '../lib/format'
 
 const TABS = [
-  { id: 'general', label: 'General' },
-  { id: 'mcp', label: 'MCP server' },
+  { id: 'general', labelKey: 'settings.tabs.general' },
+  { id: 'mcp', labelKey: 'settings.tabs.mcp' },
 ] as const
 type TabId = (typeof TABS)[number]['id']
 
 /** Settings: a General tab (runtime, config, security) and an MCP server tab. */
 export default function Settings() {
+  const { t } = useTranslation()
   const [tab, setTab] = useState<TabId>('general')
   return (
     <div className="animate-fade-in space-y-6">
       <header>
-        <h1 className="text-xl font-semibold tracking-tight text-ink">Settings</h1>
-        <p className="mt-1 text-[13px] text-ink-muted">
-          Runtime configuration, console security, and MCP access.
-        </p>
+        <h1 className="text-xl font-semibold tracking-tight text-ink">{t('settings.title')}</h1>
+        <p className="mt-1 text-[13px] text-ink-muted">{t('settings.subtitle')}</p>
       </header>
 
       <div className="flex gap-1 border-b border-border" role="tablist">
-        {TABS.map((t) => (
+        {TABS.map((item) => (
           <button
-            key={t.id}
+            key={item.id}
             role="tab"
-            aria-selected={tab === t.id}
-            onClick={() => setTab(t.id)}
+            aria-selected={tab === item.id}
+            onClick={() => setTab(item.id)}
             className={cn(
               '-mb-px border-b-2 px-3 py-2 text-[13px] font-medium transition-colors',
-              tab === t.id
+              tab === item.id
                 ? 'border-accent text-ink'
                 : 'border-transparent text-ink-muted hover:text-ink',
             )}
           >
-            {t.label}
+            {t(item.labelKey)}
           </button>
         ))}
       </div>
@@ -52,20 +52,21 @@ export default function Settings() {
 
 /** The original settings content: runtime snapshot, config form, and security. */
 function GeneralTab() {
+  const { t } = useTranslation()
   return (
     <div className="space-y-8">
       <section className="space-y-3">
-        <h2 className="text-sm font-semibold text-ink">Runtime</h2>
+        <h2 className="text-sm font-semibold text-ink">{t('settings.runtime.title')}</h2>
         <RuntimeSummary />
       </section>
 
       <section className="space-y-3">
-        <h2 className="text-sm font-semibold text-ink">Configuration</h2>
+        <h2 className="text-sm font-semibold text-ink">{t('settings.config.title')}</h2>
         <ConfigPanel />
       </section>
 
       <section className="space-y-3">
-        <h2 className="text-sm font-semibold text-ink">Security</h2>
+        <h2 className="text-sm font-semibold text-ink">{t('settings.security.title')}</h2>
         <SecurityPanel />
       </section>
     </div>
@@ -74,25 +75,34 @@ function GeneralTab() {
 
 /** Read-only snapshot of the live config the API reports at `/healthz`. */
 function RuntimeSummary() {
+  const { t } = useTranslation()
   const { data, isLoading, isError, error, refetch } = useHealth()
   if (isLoading) return <Skeleton className="h-40 w-full rounded-card" />
   if (isError || !data) {
     return (
       <QueryError
-        title="API unreachable"
-        message={error?.message ?? 'Could not reach the health endpoint.'}
+        title={t('settings.runtime.unreachable')}
+        message={error?.message ?? t('settings.runtime.unreachableDetail')}
         onRetry={() => void refetch()}
       />
     )
   }
   return (
     <Card className="grid grid-cols-1 gap-x-8 gap-y-4 p-5 sm:grid-cols-2">
-      <Row label="Service" value={data.service} />
-      <Row label="Version" value={data.version} />
-      <Row label="Vector store" value={data.vector_store} online={data.vector_store_connected} />
-      <Row label="Embedding provider" value={data.embedding_provider} />
-      <Row label="Embedding model" value={data.embedding_model} online={data.embedding_model_loaded} />
-      <Row label="Uptime" value={formatUptime(data.uptime_seconds)} />
+      <Row label={t('settings.runtime.service')} value={data.service} />
+      <Row label={t('settings.runtime.version')} value={data.version} />
+      <Row
+        label={t('settings.runtime.vectorStore')}
+        value={data.vector_store}
+        online={data.vector_store_connected}
+      />
+      <Row label={t('settings.runtime.embeddingProvider')} value={data.embedding_provider} />
+      <Row
+        label={t('settings.runtime.embeddingModel')}
+        value={data.embedding_model}
+        online={data.embedding_model_loaded}
+      />
+      <Row label={t('settings.runtime.uptime')} value={formatUptime(data.uptime_seconds)} />
     </Card>
   )
 }
@@ -114,18 +124,17 @@ function Row({ label, value, online }: { label: string; value: string; online?:
 
 /** Session note plus a Sign-out action mirroring the Topbar. */
 function SecurityPanel() {
+  const { t } = useTranslation()
   const { logout } = useAuth()
   return (
     <Card className="flex items-center justify-between gap-4 p-5">
       <div>
-        <p className="text-[13px] text-ink">Session</p>
-        <p className="mt-0.5 text-xs text-ink-muted">
-          Your credential is held in this browser only. Sign out to clear it.
-        </p>
+        <p className="text-[13px] text-ink">{t('settings.security.session')}</p>
+        <p className="mt-0.5 text-xs text-ink-muted">{t('settings.security.sessionNote')}</p>
       </div>
       <Button variant="secondary" onClick={logout}>
         <Lock className="h-5 w-5" />
-        Sign out
+        {t('settings.security.signOut')}
       </Button>
     </Card>
   )
diff --git a/ui/src/pages/Tags.tsx b/ui/src/pages/Tags.tsx
index db36c9d..0b51c0b 100644
--- a/ui/src/pages/Tags.tsx
+++ b/ui/src/pages/Tags.tsx
@@ -1,6 +1,7 @@
 import { useEffect, useState } from 'react'
 import { Link, useParams } from 'react-router-dom'
 import { ChevronRight, GitMerge, Pencil, Plus, Tags as TagsIcon, Trash2 } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
 import {
   useCreateTag,
   useDeleteTag,
@@ -11,6 +12,7 @@ import {
   useWorkspace,
 } from '../api/hooks'
 import type { Tag, TagUpdate } from '../api/types'
+import { apiErrorMessage } from '../i18n/apiError'
 import {
   Badge,
   Button,
@@ -38,6 +40,7 @@ type Dialog =
 
 /** Workspace tags: list with counts, create / rename / recolor / merge / delete, correlation view. */
 export default function Tags() {
+  const { t } = useTranslation()
   const { wsId = '' } = useParams()
   const workspace = useWorkspace(wsId)
   const { data, isLoading, isError, error, refetch } = useTags(wsId)
@@ -54,10 +57,10 @@ export default function Tags() {
     if (dialog.kind === 'create') {
       createMut.mutate(values, {
         onSuccess: () => {
-          toast.success(`Tag “${values.name}” created.`)
+          toast.success(t('tags.toast.created', { name: values.name }))
           close()
         },
-        onError: (e) => toast.error(e.message),
+        onError: (e) => toast.error(apiErrorMessage(e, t)),
       })
     } else if (dialog.kind === 'edit') {
       const body = changedFields(dialog.tag, values)
@@ -66,10 +69,10 @@ export default function Tags() {
         { tagId: dialog.tag.id, body },
         {
           onSuccess: () => {
-            toast.success('Tag updated.')
+            toast.success(t('tags.toast.updated'))
             close()
           },
-          onError: (e) => toast.error(e.message),
+          onError: (e) => toast.error(apiErrorMessage(e, t)),
         },
       )
     }
@@ -81,10 +84,10 @@ export default function Tags() {
       { source_id: dialog.tag.id, target_id: targetId },
       {
         onSuccess: () => {
-          toast.success('Tags merged.')
+          toast.success(t('tags.toast.merged'))
           close()
         },
-        onError: (e) => toast.error(e.message),
+        onError: (e) => toast.error(apiErrorMessage(e, t)),
       },
     )
   }
@@ -94,10 +97,10 @@ export default function Tags() {
     const { tag } = dialog
     deleteMut.mutate(tag.id, {
       onSuccess: () => {
-        toast.success(`Tag “${tag.name}” deleted.`)
+        toast.success(t('tags.toast.deleted', { name: tag.name }))
         close()
       },
-      onError: (e) => toast.error(e.message),
+      onError: (e) => toast.error(apiErrorMessage(e, t)),
     })
   }
 
@@ -105,26 +108,26 @@ export default function Tags() {
     <div className="animate-fade-in space-y-6">
       <nav className="flex items-center gap-1.5 text-xs text-ink-muted">
         <Link to="/workspaces" className="hover:text-ink">
-          Workspaces
+          {t('nav.workspaces')}
         </Link>
         <ChevronRight className="h-4 w-4 text-ink-faint" />
         <Link to={`/workspaces/${wsId}`} className="hover:text-ink">
           {workspace.data?.name ?? '…'}
         </Link>
         <ChevronRight className="h-4 w-4 text-ink-faint" />
-        <span className="text-ink">Tags</span>
+        <span className="text-ink">{t('common.tags')}</span>
       </nav>
 
       <header className="flex items-start justify-between gap-4">
         <div>
-          <h1 className="text-xl font-semibold tracking-tight text-ink">Tags</h1>
+          <h1 className="text-xl font-semibold tracking-tight text-ink">{t('common.tags')}</h1>
           <p className="mt-1 text-[13px] text-ink-muted">
-            Correlate and filter collections and documents across this workspace.
+            {t('tags.subtitle')}
           </p>
         </div>
         <Button onClick={() => setDialog({ kind: 'create' })}>
           <Plus className="h-5 w-5" />
-          New tag
+          {t('tags.new')}
         </Button>
       </header>
 
@@ -133,7 +136,7 @@ export default function Tags() {
         data={data}
         isLoading={isLoading}
         isError={isError}
-        message={error?.message}
+        message={error ? apiErrorMessage(error, t) : undefined}
         onRetry={() => void refetch()}
         onCreate={() => setDialog({ kind: 'create' })}
         onEdit={(tag) => setDialog({ kind: 'edit', tag })}
@@ -160,10 +163,10 @@ export default function Tags() {
 
       <ConfirmDialog
         open={dialog.kind === 'delete'}
-        title="Delete tag"
+        title={t('tags.delete.title')}
         message={
           dialog.kind === 'delete'
-            ? `Delete “${dialog.tag.name}”? It is removed from every collection and document it tags. This cannot be undone.`
+            ? t('tags.delete.message', { name: dialog.tag.name })
             : ''
         }
         loading={deleteMut.isPending}
@@ -205,6 +208,7 @@ function TagList({
   onMerge: (tag: Tag) => void
   onDelete: (tag: Tag) => void
 }) {
+  const { t } = useTranslation()
   if (isLoading) {
     return (
       <div className="space-y-2">
@@ -215,15 +219,15 @@ function TagList({
     )
   }
   if (isError) {
-    return <QueryError title="Could not load tags" message={message} onRetry={onRetry} />
+    return <QueryError title={t('tags.error')} message={message} onRetry={onRetry} />
   }
   if (!data || data.length === 0) {
     return (
       <EmptyState
         icon={<TagsIcon className="h-7 w-7" />}
-        title="No tags yet"
-        description="Create a tag to correlate and filter collections and documents."
-        action={<Button onClick={onCreate}>New tag</Button>}
+        title={t('tags.empty.title')}
+        description={t('tags.empty.description')}
+        action={<Button onClick={onCreate}>{t('tags.new')}</Button>}
       />
     )
   }
@@ -257,6 +261,7 @@ function TagRow({
   onMerge: (tag: Tag) => void
   onDelete: (tag: Tag) => void
 }) {
+  const { t } = useTranslation()
   const [open, setOpen] = useState(false)
   return (
     <Card className="group p-3">
@@ -269,21 +274,21 @@ function TagRow({
         >
           <TagChip name={tag.name} color={tag.color} />
           <span className="flex gap-1.5 text-ink-muted">
-            <Badge>{tag.collection_count} col</Badge>
-            <Badge>{tag.document_count} doc</Badge>
-            {tag.workspace_count > 0 && <Badge>workspace</Badge>}
+            <Badge>{t('tags.count.col', { count: tag.collection_count })}</Badge>
+            <Badge>{t('tags.count.doc', { count: tag.document_count })}</Badge>
+            {tag.workspace_count > 0 && <Badge>{t('tags.workspaceBadge')}</Badge>}
           </span>
         </button>
         <div className="flex gap-1 opacity-0 transition-opacity group-hover:opacity-100 focus-within:opacity-100">
-          <Button variant="ghost" size="sm" aria-label={`Edit ${tag.name}`}
+          <Button variant="ghost" size="sm" aria-label={t('common.editAria', { name: tag.name })}
             onClick={() => onEdit(tag)} className="h-7 w-7 px-0">
             <Pencil className="h-4 w-4" />
           </Button>
-          <Button variant="ghost" size="sm" aria-label={`Merge ${tag.name}`}
+          <Button variant="ghost" size="sm" aria-label={t('tags.mergeAria', { name: tag.name })}
             onClick={() => onMerge(tag)} className="h-7 w-7 px-0">
             <GitMerge className="h-4 w-4" />
           </Button>
-          <Button variant="ghost" size="sm" aria-label={`Delete ${tag.name}`}
+          <Button variant="ghost" size="sm" aria-label={t('common.deleteAria', { name: tag.name })}
             onClick={() => onDelete(tag)} className="h-7 w-7 px-0 hover:text-err">
             <Trash2 className="h-4 w-4" />
           </Button>
@@ -296,35 +301,41 @@ function TagRow({
 
 /** Correlated collections + documents for one tag, loaded on first expand. */
 function ItemsPanel({ wsId, tag }: { wsId: string; tag: Tag }) {
+  const { t } = useTranslation()
   const { data, isLoading, isError, error, refetch } = useTagItems(wsId, tag.id, true)
   if (isLoading) return <Skeleton className="mt-3 h-16 rounded-control" />
   if (isError) {
     return (
       <div className="mt-3">
-        <QueryError title="Could not load items" message={error?.message} onRetry={() => void refetch()} />
+        <QueryError
+          title={t('tags.itemsError')}
+          message={error ? apiErrorMessage(error, t) : undefined}
+          onRetry={() => void refetch()}
+        />
       </div>
     )
   }
   const empty = !data || (data.collections.length === 0 && data.documents.length === 0)
   if (empty) {
-    return <p className="mt-3 text-xs text-ink-faint">Not assigned to anything yet.</p>
+    return <p className="mt-3 text-xs text-ink-faint">{t('tags.notAssigned')}</p>
   }
   return (
     <div className="mt-3 grid grid-cols-1 gap-3 border-t border-border pt-3 text-[13px] sm:grid-cols-2">
-      <ItemColumn label="Collections" items={data.collections.map((c) => c.name)} />
-      <ItemColumn label="Documents" items={data.documents.map((d) => d.filename)} />
+      <ItemColumn label={t('collections.title')} items={data.collections.map((c) => c.name)} />
+      <ItemColumn label={t('documents.title')} items={data.documents.map((d) => d.filename)} />
     </div>
   )
 }
 
 function ItemColumn({ label, items }: { label: string; items: string[] }) {
+  const { t } = useTranslation()
   return (
     <div>
       <p className="mb-1 text-xs font-medium text-ink-muted">
         {label} ({items.length})
       </p>
       {items.length === 0 ? (
-        <p className="text-xs text-ink-faint">None</p>
+        <p className="text-xs text-ink-faint">{t('tags.none')}</p>
       ) : (
         <ul className="space-y-0.5">
           {items.map((name, i) => (
@@ -352,6 +363,7 @@ function TagFormModal({
   onSubmit: (values: { name: string; color: string }) => void
   onClose: () => void
 }) {
+  const { t } = useTranslation()
   const [name, setName] = useState('')
   const [color, setColor] = useState<string>(SWATCHES[6])
 
@@ -372,20 +384,20 @@ function TagFormModal({
     <Modal
       open={open}
       onClose={onClose}
-      title={editing ? 'Edit tag' : 'New tag'}
+      title={editing ? t('tags.editTitle') : t('tags.new')}
       footer={
         <>
           <Button variant="secondary" onClick={onClose} disabled={submitting}>
-            Cancel
+            {t('common.cancel')}
           </Button>
           <Button onClick={submit} loading={submitting} disabled={!trimmed}>
-            {editing ? 'Save changes' : 'Create'}
+            {editing ? t('common.saveChanges') : t('common.create')}
           </Button>
         </>
       }
     >
       <div className="flex flex-col gap-4">
-        <Field label="Name" htmlFor="tag-name" hint="Lowercased and trimmed on save.">
+        <Field label={t('common.name')} htmlFor="tag-name" hint={t('tags.nameHint')}>
           <Input
             id="tag-name"
             autoFocus
@@ -394,10 +406,10 @@ function TagFormModal({
             onKeyDown={(e) => {
               if (e.key === 'Enter') submit()
             }}
-            placeholder="e.g. finance"
+            placeholder={t('tags.namePlaceholder')}
           />
         </Field>
-        <Field label="Color">
+        <Field label={t('common.color')}>
           <ColorPicker value={color} onChange={setColor} />
         </Field>
       </div>
@@ -421,8 +433,9 @@ function MergeModal({
   onMerge: (targetId: string) => void
   onClose: () => void
 }) {
+  const { t } = useTranslation()
   const [target, setTarget] = useState('')
-  const candidates = tags.filter((t) => t.id !== source?.id)
+  const candidates = tags.filter((tag) => tag.id !== source?.id)
 
   useEffect(() => {
     if (open) setTarget('')
@@ -432,32 +445,33 @@ function MergeModal({
     <Modal
       open={open}
       onClose={onClose}
-      title="Merge tag"
+      title={t('tags.mergeTitle')}
       footer={
         <>
           <Button variant="secondary" onClick={onClose} disabled={submitting}>
-            Cancel
+            {t('common.cancel')}
           </Button>
           <Button onClick={() => target && onMerge(target)} loading={submitting} disabled={!target}>
-            Merge
+            {t('tags.merge')}
           </Button>
         </>
       }
     >
       <div className="flex flex-col gap-4">
         <p className="text-[13px] text-ink-muted">
-          Move every assignment of <span className="font-medium text-ink">{source?.name}</span> onto
-          another tag, then delete it.
+          {t('tags.mergeIntro.before')}
+          <span className="font-medium text-ink">{source?.name}</span>
+          {t('tags.mergeIntro.after')}
         </p>
-        <Field label="Merge into" htmlFor="merge-target">
+        <Field label={t('tags.mergeInto')} htmlFor="merge-target">
           {candidates.length === 0 ? (
-            <p className="text-xs text-ink-faint">No other tags to merge into.</p>
+            <p className="text-xs text-ink-faint">{t('tags.noMergeTargets')}</p>
           ) : (
             <Select id="merge-target" value={target} onChange={(e) => setTarget(e.target.value)}>
-              <option value="">Select a tag…</option>
-              {candidates.map((t) => (
-                <option key={t.id} value={t.id}>
-                  {t.name}
+              <option value="">{t('tags.selectTag')}</option>
+              {candidates.map((tag) => (
+                <option key={tag.id} value={tag.id}>
+                  {tag.name}
                 </option>
               ))}
             </Select>
diff --git a/ui/src/pages/Users.tsx b/ui/src/pages/Users.tsx
index fca72b6..4bc5e4a 100644
--- a/ui/src/pages/Users.tsx
+++ b/ui/src/pages/Users.tsx
@@ -1,5 +1,6 @@
 import { useState } from 'react'
 import { KeyRound, Pencil, Plus, RotateCcw, ShieldCheck, Trash2, Users as UsersIcon } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
 import {
   useCreateUser,
   useDeleteUser,
@@ -24,6 +25,7 @@ import { UserFormModal, type UserFormValues } from '../components/users/UserForm
 import { UserKeyModal } from '../components/users/UserKeyModal'
 import { PermissionsModal } from '../components/users/PermissionsModal'
 import { RevealOncePanel } from '../components/users/RevealOncePanel'
+import { apiErrorMessage } from '../i18n/apiError'
 import { cn } from '../lib/cn'
 import { formatDate } from '../lib/format'
 
@@ -52,6 +54,7 @@ function changedFields(user: User, values: UserFormValues): UserUpdate {
 
 /** Users admin: sign-in accounts (username/password + role), API keys, and grants. */
 export default function Users() {
+  const { t } = useTranslation()
   const { data, isLoading, isError, error, refetch } = useUsers()
   const [dialog, setDialog] = useState<Dialog>({ kind: 'none' })
   const close = () => setDialog({ kind: 'none' })
@@ -67,12 +70,11 @@ export default function Users() {
         onSuccess: (user) =>
           setDialog({
             kind: 'reveal',
-            title: `User “${user.username}” created`,
-            message:
-              'Share this one-time password with the user — they will be asked to change it on first sign-in. It is shown only once.',
+            title: t('users.reveal.created.title', { username: user.username }),
+            message: t('users.reveal.created.message'),
             secret: user.temp_password,
           }),
-        onError: (e) => toast.error(e.message),
+        onError: (e) => toast.error(apiErrorMessage(e, t)),
       })
     } else if (dialog.kind === 'edit') {
       const body = changedFields(dialog.user, values)
@@ -84,10 +86,10 @@ export default function Users() {
         { id: dialog.user.id, body },
         {
           onSuccess: () => {
-            toast.success('User updated.')
+            toast.success(t('users.toast.updated'))
             close()
           },
-          onError: (e) => toast.error(e.message),
+          onError: (e) => toast.error(apiErrorMessage(e, t)),
         },
       )
     }
@@ -98,10 +100,10 @@ export default function Users() {
     const { user } = dialog
     deleteMut.mutate(user.id, {
       onSuccess: () => {
-        toast.success(`User “${user.username}” deleted.`)
+        toast.success(t('users.toast.deleted', { username: user.username }))
         close()
       },
-      onError: (e) => toast.error(e.message),
+      onError: (e) => toast.error(apiErrorMessage(e, t)),
     })
   }
 
@@ -112,34 +114,30 @@ export default function Users() {
       onSuccess: (res) =>
         setDialog({
           kind: 'reveal',
-          title: `Password reset for “${user.username}”`,
-          message:
-            'Share this one-time password with the user — their old password no longer works and they will set a new one on next sign-in. Shown only once.',
+          title: t('users.reveal.reset.title', { username: user.username }),
+          message: t('users.reveal.reset.message'),
           secret: res.temp_password,
         }),
-      onError: (e) => toast.error(e.message),
+      onError: (e) => toast.error(apiErrorMessage(e, t)),
     })
   }
 
   const toggleActive = (user: User) =>
     updateMut.mutate(
       { id: user.id, body: { is_active: !user.is_active } },
-      { onError: (e) => toast.error(e.message) },
+      { onError: (e) => toast.error(apiErrorMessage(e, t)) },
     )
 
   return (
     <div className="animate-fade-in space-y-6">
       <header className="flex items-start justify-between gap-4">
         <div>
-          <h1 className="text-xl font-semibold tracking-tight text-ink">Users</h1>
-          <p className="mt-1 text-[13px] text-ink-muted">
-            Each user signs in with a username + password (admins get the full console; others are
-            scoped by their grants) and may hold one API key for MCP/programmatic access.
-          </p>
+          <h1 className="text-xl font-semibold tracking-tight text-ink">{t('users.title')}</h1>
+          <p className="mt-1 text-[13px] text-ink-muted">{t('users.subtitle')}</p>
         </div>
         <Button onClick={() => setDialog({ kind: 'create' })} className="shrink-0">
           <Plus className="h-5 w-5 shrink-0" />
-          New user
+          {t('users.new')}
         </Button>
       </header>
 
@@ -147,7 +145,7 @@ export default function Users() {
         data={data}
         isLoading={isLoading}
         isError={isError}
-        message={error?.message}
+        message={error ? apiErrorMessage(error, t) : undefined}
         onRetry={() => void refetch()}
         onCreate={() => setDialog({ kind: 'create' })}
         onEdit={(user) => setDialog({ kind: 'edit', user })}
@@ -180,10 +178,10 @@ export default function Users() {
 
       <ConfirmDialog
         open={dialog.kind === 'delete'}
-        title="Delete user"
+        title={t('users.delete.title')}
         message={
           dialog.kind === 'delete'
-            ? `Delete “${dialog.user.username}”? Their API key and all permission grants are permanently removed. This cannot be undone.`
+            ? t('users.delete.message', { username: dialog.user.username })
             : ''
         }
         loading={deleteMut.isPending}
@@ -193,13 +191,13 @@ export default function Users() {
 
       <ConfirmDialog
         open={dialog.kind === 'reset'}
-        title="Reset password"
+        title={t('users.reset.title')}
         message={
           dialog.kind === 'reset'
-            ? `Reset the password for “${dialog.user.username}”? Their current password stops working immediately and any active session is signed out.`
+            ? t('users.reset.message', { username: dialog.user.username })
             : ''
         }
-        confirmLabel="Reset password"
+        confirmLabel={t('users.reset.title')}
         loading={resetMut.isPending}
         onConfirm={handleReset}
         onClose={close}
@@ -242,6 +240,7 @@ function UserList({
   onReset: (user: User) => void
   onToggleActive: (user: User) => void
 }) {
+  const { t } = useTranslation()
   if (isLoading) {
     return (
       <div className="flex flex-col gap-2">
@@ -252,15 +251,15 @@ function UserList({
     )
   }
   if (isError) {
-    return <QueryError title="Could not load users" message={message} onRetry={onRetry} />
+    return <QueryError title={t('users.error')} message={message} onRetry={onRetry} />
   }
   if (!data || data.length === 0) {
     return (
       <EmptyState
         icon={<UsersIcon className="h-7 w-7" />}
-        title="No users yet"
-        description="Create a user, share their one-time password, and grant access to workspaces or collections."
-        action={<Button onClick={onCreate}>New user</Button>}
+        title={t('users.empty.title')}
+        description={t('users.empty.description')}
+        action={<Button onClick={onCreate}>{t('users.new')}</Button>}
       />
     )
   }
@@ -300,48 +299,51 @@ function UserRow({
   onReset: (user: User) => void
   onToggleActive: (user: User) => void
 }) {
+  const { t } = useTranslation()
   return (
     <div className="flex items-center justify-between gap-3 px-4 py-3">
       <div className="min-w-0">
         <div className="flex items-center gap-2">
           <span className="truncate text-sm font-medium text-ink">{user.username}</span>
-          {user.is_admin && <Badge>Admin</Badge>}
+          {user.is_admin && <Badge>{t('users.admin')}</Badge>}
           {user.name && <span className="truncate text-xs text-ink-muted">{user.name}</span>}
         </div>
         <p className="mt-0.5 truncate text-xs text-ink-faint">
           {user.email ? `${user.email} · ` : ''}
-          {user.api_key ? `key ${user.api_key.key_prefix}…` : 'no API key'} · created{' '}
-          {formatDate(user.created_at)}
-          {user.rate_limit_rpm > 0 && ` · ${user.rate_limit_rpm} rpm`}
+          {user.api_key
+            ? t('users.row.key', { prefix: user.api_key.key_prefix })
+            : t('users.row.noKey')}{' '}
+          · {t('users.row.created', { date: formatDate(user.created_at) })}
+          {user.rate_limit_rpm > 0 && ` · ${t('users.row.rpm', { rpm: user.rate_limit_rpm })}`}
         </p>
       </div>
       <div className="flex shrink-0 items-center gap-1.5">
         <button
           type="button"
           onClick={() => onToggleActive(user)}
-          aria-label={user.is_active ? 'Deactivate user' : 'Activate user'}
+          aria-label={user.is_active ? t('users.row.deactivateAria') : t('users.row.activateAria')}
           className="inline-flex items-center gap-1.5 rounded-full border border-border bg-surface px-2 py-0.5 text-xs font-medium transition-colors hover:border-ink-faint"
         >
           <span className={cn('h-1.5 w-1.5 rounded-full', user.is_active ? 'bg-ok' : 'bg-ink-faint')} />
           <span className={user.is_active ? 'text-ok' : 'text-ink-muted'}>
-            {user.is_active ? 'Active' : 'Inactive'}
+            {user.is_active ? t('users.status.active') : t('users.status.inactive')}
           </span>
         </button>
-        <DropdownMenu triggerAriaLabel={`Manage ${user.username}`}>
+        <DropdownMenu triggerAriaLabel={t('users.row.manageAria', { username: user.username })}>
           <DropdownItem icon={<ShieldCheck className="h-4 w-4" />} onSelect={() => onPermissions(user)}>
-            Permissions
+            {t('users.actions.permissions')}
           </DropdownItem>
           <DropdownItem icon={<KeyRound className="h-4 w-4" />} onSelect={() => onKey(user)}>
-            API key
+            {t('users.actions.apiKey')}
           </DropdownItem>
           <DropdownItem icon={<RotateCcw className="h-4 w-4" />} onSelect={() => onReset(user)}>
-            Reset password
+            {t('users.reset.title')}
           </DropdownItem>
           <DropdownItem icon={<Pencil className="h-4 w-4" />} onSelect={() => onEdit(user)}>
-            Edit
+            {t('users.actions.edit')}
           </DropdownItem>
           <DropdownItem icon={<Trash2 className="h-4 w-4" />} danger onSelect={() => onDelete(user)}>
-            Delete
+            {t('users.actions.delete')}
           </DropdownItem>
         </DropdownMenu>
       </div>
diff --git a/ui/src/pages/Workspaces.tsx b/ui/src/pages/Workspaces.tsx
index fd5ff38..f8712d0 100644
--- a/ui/src/pages/Workspaces.tsx
+++ b/ui/src/pages/Workspaces.tsx
@@ -1,6 +1,7 @@
 import { useState, type MouseEvent } from 'react'
 import { useNavigate } from 'react-router-dom'
 import { FolderKanban, Layers, Pencil, Plus, Trash2 } from 'lucide-react'
+import { useTranslation } from 'react-i18next'
 import { useCreateWorkspace, useDeleteWorkspace, useUpdateWorkspace, useWorkspaces } from '../api/hooks'
 import type { Workspace, WorkspaceUpdate } from '../api/types'
 import {
@@ -19,6 +20,7 @@ import {
   type WorkspaceFormValues,
 } from '../components/workspaces/WorkspaceFormModal'
 import { useAuth } from '../auth/AuthContext'
+import { apiErrorMessage } from '../i18n/apiError'
 import { formatDate } from '../lib/format'
 
 /** Which dialog (if any) is currently open, plus the row it acts on. */
@@ -40,6 +42,7 @@ function changedFields(ws: Workspace, values: WorkspaceFormValues): WorkspaceUpd
 
 /** Workspaces index: list, create, edit, and delete the top-level containers. */
 export default function Workspaces() {
+  const { t } = useTranslation()
   const { canCreateWorkspaces } = useAuth()
   const { data, isLoading, isError, error, refetch } = useWorkspaces()
   const [dialog, setDialog] = useState<Dialog>({ kind: 'none' })
@@ -54,10 +57,10 @@ export default function Workspaces() {
     if (dialog.kind === 'create') {
       createMut.mutate(values, {
         onSuccess: () => {
-          toast.success(`Workspace “${values.name}” created.`)
+          toast.success(t('workspaces.toast.created', { name: values.name }))
           close()
         },
-        onError: (e) => toast.error(e.message),
+        onError: (e) => toast.error(apiErrorMessage(e, t)),
       })
     } else if (dialog.kind === 'edit') {
       const body = changedFields(dialog.ws, values)
@@ -69,10 +72,10 @@ export default function Workspaces() {
         { id: dialog.ws.id, body },
         {
           onSuccess: () => {
-            toast.success('Workspace updated.')
+            toast.success(t('workspaces.toast.updated'))
             close()
           },
-          onError: (e) => toast.error(e.message),
+          onError: (e) => toast.error(apiErrorMessage(e, t)),
         },
       )
     }
@@ -83,10 +86,10 @@ export default function Workspaces() {
     const { ws } = dialog
     deleteMut.mutate(ws.id, {
       onSuccess: () => {
-        toast.success(`Workspace “${ws.name}” deleted.`)
+        toast.success(t('workspaces.toast.deleted', { name: ws.name }))
         close()
       },
-      onError: (e) => toast.error(e.message),
+      onError: (e) => toast.error(apiErrorMessage(e, t)),
     })
   }
 
@@ -94,15 +97,13 @@ export default function Workspaces() {
     <div className="animate-fade-in space-y-6">
       <header className="flex items-start justify-between gap-4">
         <div>
-          <h1 className="text-xl font-semibold tracking-tight text-ink">Workspaces</h1>
-          <p className="mt-1 text-[13px] text-ink-muted">
-            Top-level containers for your collections.
-          </p>
+          <h1 className="text-xl font-semibold tracking-tight text-ink">{t('workspaces.title')}</h1>
+          <p className="mt-1 text-[13px] text-ink-muted">{t('workspaces.subtitle')}</p>
         </div>
         {canCreateWorkspaces && (
           <Button onClick={() => setDialog({ kind: 'create' })}>
             <Plus className="h-5 w-5" />
-            New workspace
+            {t('workspaces.new')}
           </Button>
         )}
       </header>
@@ -111,7 +112,7 @@ export default function Workspaces() {
         data={data}
         isLoading={isLoading}
         isError={isError}
-        message={error?.message}
+        message={error ? apiErrorMessage(error, t) : undefined}
         canCreate={canCreateWorkspaces}
         onRetry={() => void refetch()}
         onCreate={() => setDialog({ kind: 'create' })}
@@ -129,10 +130,10 @@ export default function Workspaces() {
 
       <ConfirmDialog
         open={dialog.kind === 'delete'}
-        title="Delete workspace"
+        title={t('workspaces.delete.title')}
         message={
           dialog.kind === 'delete'
-            ? `Delete “${dialog.ws.name}”? Its collections, API keys, and documents are permanently removed. This cannot be undone.`
+            ? t('workspaces.delete.message', { name: dialog.ws.name })
             : ''
         }
         loading={deleteMut.isPending}
@@ -165,6 +166,7 @@ function WorkspaceList({
   onEdit: (ws: Workspace) => void
   onDelete: (ws: Workspace) => void
 }) {
+  const { t } = useTranslation()
   if (isLoading) {
     return (
       <div className="grid grid-cols-1 gap-3 sm:grid-cols-2 lg:grid-cols-3">
@@ -175,19 +177,15 @@ function WorkspaceList({
     )
   }
   if (isError) {
-    return <QueryError title="Could not load workspaces" message={message} onRetry={onRetry} />
+    return <QueryError title={t('workspaces.error')} message={message} onRetry={onRetry} />
   }
   if (!data || data.length === 0) {
     return (
       <EmptyState
         icon={<FolderKanban className="h-7 w-7" />}
-        title="No workspaces yet"
-        description={
-          canCreate
-            ? 'Create your first workspace to start organising collections.'
-            : 'No workspaces are shared with you yet.'
-        }
-        action={canCreate ? <Button onClick={onCreate}>New workspace</Button> : undefined}
+        title={t('workspaces.empty.title')}
+        description={canCreate ? t('workspaces.empty.canCreate') : t('workspaces.empty.readonly')}
+        action={canCreate ? <Button onClick={onCreate}>{t('workspaces.new')}</Button> : undefined}
       />
     )
   }
@@ -210,6 +208,7 @@ function WorkspaceCard({
   onEdit: (ws: Workspace) => void
   onDelete: (ws: Workspace) => void
 }) {
+  const { t } = useTranslation()
   const navigate = useNavigate()
   const stop = (fn: () => void) => (e: MouseEvent) => {
     e.stopPropagation()
@@ -239,18 +238,20 @@ function WorkspaceCard({
             )}
           </div>
           <p className="mt-0.5 truncate text-xs text-ink-muted">
-            {ws.description || 'No description'}
+            {ws.description || t('common.noDescription')}
           </p>
         </div>
       </div>
       <div className="flex items-center justify-between">
-        <span className="text-xs text-ink-faint">Created {formatDate(ws.created_at)}</span>
+        <span className="text-xs text-ink-faint">
+          {t('common.created', { date: formatDate(ws.created_at) })}
+        </span>
         {ws.can_write && (
           <div className="flex gap-1 opacity-0 transition-opacity group-hover:opacity-100 focus-within:opacity-100">
             <Button
               variant="ghost"
               size="sm"
-              aria-label={`Edit ${ws.name}`}
+              aria-label={t('common.editAria', { name: ws.name })}
               onClick={stop(() => onEdit(ws))}
               className="h-10 w-10 px-0"
             >
@@ -259,7 +260,7 @@ function WorkspaceCard({
             <Button
               variant="ghost"
               size="sm"
-              aria-label={`Delete ${ws.name}`}
+              aria-label={t('common.deleteAria', { name: ws.name })}
               onClick={stop(() => onDelete(ws))}
               className="h-10 w-10 px-0 hover:text-err"
             >