fix: redact sensitive config secrets from admin API response

app/admin/_tabs/auth.tsx

@@ -5,8 +5,12 @@ import { Save, Loader2, RotateCcw, Sparkles } from 'lucide-react';
 import { apiFetch } from '@/lib/browser-navigation';
 
 interface ConfigEntry {
-  value: unknown;
+  // Sensitive keys (sessionSecret, oauthClientSecret) come back with
+  // `value` omitted and `hasValue` set instead — the server never echoes
+  // the raw secret to the client.
+  value?: unknown;
   source: 'admin' | 'env' | 'default';
+  hasValue?: boolean;
 }
 
 export function AuthTab() {
@@ -267,7 +271,7 @@ export function AuthTab() {
         <Toggle label="OAuth Enabled" configKey="oauthEnabled" value={currentValue('oauthEnabled') as boolean} source={config.oauthEnabled?.source} onChange={handleChange} onRevert={handleRevert} />
         <Toggle label="OAuth Only" description="Hide password login form when enabled" configKey="oauthOnly" value={currentValue('oauthOnly') as boolean} source={config.oauthOnly?.source} onChange={handleChange} onRevert={handleRevert} />
         <Text label="OAuth Client ID" configKey="oauthClientId" value={currentValue('oauthClientId') as string} source={config.oauthClientId?.source} onChange={handleChange} onRevert={handleRevert} />
-        <Text label="OAuth Client Secret" configKey="oauthClientSecret" value={currentValue('oauthClientSecret') as string} source={config.oauthClientSecret?.source} onChange={handleChange} onRevert={handleRevert} type="password" />
+        <Text label="OAuth Client Secret" configKey="oauthClientSecret" value={currentValue('oauthClientSecret') as string} source={config.oauthClientSecret?.source} onChange={handleChange} onRevert={handleRevert} type="password" placeholder={config.oauthClientSecret?.hasValue ? '••••••••  (saved — type to replace)' : undefined} />
         <Text label="OAuth Issuer URL" configKey="oauthIssuerUrl" value={currentValue('oauthIssuerUrl') as string} source={config.oauthIssuerUrl?.source} onChange={handleChange} onRevert={handleRevert} placeholder="https://auth.example.com" />
       </Section>
 

app/admin/_tabs/branding.tsx

@@ -5,8 +5,9 @@ import { Save, Loader2, RotateCcw, ImageIcon, Upload, Trash2 } from 'lucide-reac
 import { apiFetch } from '@/lib/browser-navigation';
 
 interface ConfigEntry {
-  value: unknown;
+  value?: unknown;
   source: 'admin' | 'env' | 'default';
+  hasValue?: boolean;
 }
 
 const IMAGE_FIELDS = [

app/admin/_tabs/dashboard.tsx

@@ -26,7 +26,7 @@ export function DashboardTab() {
   const [status, setStatus] = useState<AdminStatus | null>(null);
   const [recentActivity, setRecentActivity] = useState<AuditEntry[]>([]);
   const [config, setConfig] = useState<ConfigData | null>(null);
-  const [, setConfigSources] = useState<Record<string, { value: unknown; source: string }> | null>(null);
+  const [, setConfigSources] = useState<Record<string, { value?: unknown; source: string; hasValue?: boolean }> | null>(null);
   const [warnings, setWarnings] = useState<string[]>([]);
   const [pluginCount, setPluginCount] = useState(0);
   const [themeCount, setThemeCount] = useState(0);
@@ -96,7 +96,9 @@ export function DashboardTab() {
       const sources = await adminConfigRes.json();
       setConfigSources(sources);
       const sessionSecret = sources?.sessionSecret;
-      if (!sessionSecret?.value || sessionSecret.value === 'your-secret-key-here') {
+      // Server redacts the raw value for sensitive keys; rely on hasValue,
+      // which is false when unset or matching a known placeholder default.
+      if (!sessionSecret?.hasValue) {
         w.push('SESSION_SECRET is not set or using a default value. Sessions are insecure.');
       }
       const adminPassword = sources?.adminPassword;

app/admin/_tabs/settings.tsx

@@ -7,8 +7,9 @@ import { JmapServersSection } from './_jmap-servers-section';
 import type { JmapServerEntry } from '@/lib/admin/jmap-servers';
 
 interface ConfigEntry {
-  value: unknown;
+  value?: unknown;
   source: 'admin' | 'env' | 'default';
+  hasValue?: boolean;
 }
 
 export function SettingsTab() {

app/api/admin/config/route.ts

@@ -2,12 +2,23 @@ import { NextRequest, NextResponse } from 'next/server';
 import { configManager } from '@/lib/admin/config-manager';
 import { requireAdminAuth, getClientIP } from '@/lib/admin/session';
 import { auditLog } from '@/lib/admin/audit';
-import { CONFIG_ENV_MAP } from '@/lib/admin/types';
+import { CONFIG_ENV_MAP, SENSITIVE_CONFIG_KEYS } from '@/lib/admin/types';
 import { parseJmapServers } from '@/lib/admin/jmap-servers';
 import { logger } from '@/lib/logger';
 
+// Strings that count as "no real secret configured" — used so the dashboard
+// can warn about a placeholder session secret without us ever returning the
+// raw value to the client.
+const SENSITIVE_PLACEHOLDERS = new Set(['your-secret-key-here']);
+
 /**
  * GET /api/admin/config - Get full config with sources (admin-protected)
+ *
+ * Sensitive keys (sessionSecret, oauthClientSecret) are returned with
+ * `value` omitted and a `hasValue` boolean instead. An admin session is
+ * enough to read every other config knob; the secrets themselves stay on
+ * the server so that an XSS or session-theft can't lift them in one
+ * request and forge admin/user session cookies offline.
  */
 export async function GET() {
   try {
@@ -17,7 +28,19 @@ export async function GET() {
     await configManager.ensureLoaded();
     const config = configManager.getAllWithSources();
 
-    return NextResponse.json(config, {
+    const safe: Record<string, { value?: unknown; source: 'admin' | 'env' | 'default'; hasValue?: boolean }> = {};
+    for (const [key, entry] of Object.entries(config)) {
+      if (SENSITIVE_CONFIG_KEYS.has(key)) {
+        const v = entry.value;
+        const hasValue =
+          typeof v === 'string' && v.length > 0 && !SENSITIVE_PLACEHOLDERS.has(v);
+        safe[key] = { source: entry.source, hasValue };
+      } else {
+        safe[key] = entry;
+      }
+    }
+
+    return NextResponse.json(safe, {
       headers: { 'Cache-Control': 'no-store' },
     });
   } catch (error) {