diff --git a/ui/src/api/queries/admin/environments.ts b/ui/src/api/queries/admin/environments.ts
index 48d0b823..6949bb5f 100644
--- a/ui/src/api/queries/admin/environments.ts
+++ b/ui/src/api/queries/admin/environments.ts
@@ -54,6 +54,18 @@ export function useUpdateEnvironment() {
   });
 }
 
+export function useUpdateDefaultContainerConfig() {
+  const qc = useQueryClient();
+  return useMutation({
+    mutationFn: ({ id, config }: { id: string; config: Record<string, unknown> }) =>
+      adminFetch<Environment>(`/environments/${id}/default-container-config`, {
+        method: 'PUT',
+        body: JSON.stringify(config),
+      }),
+    onSuccess: () => qc.invalidateQueries({ queryKey: ['admin', 'environments'] }),
+  });
+}
+
 export function useDeleteEnvironment() {
   const qc = useQueryClient();
   return useMutation({
diff --git a/ui/src/pages/Admin/EnvironmentsPage.tsx b/ui/src/pages/Admin/EnvironmentsPage.tsx
index 58db7e9a..2b5206e4 100644
--- a/ui/src/pages/Admin/EnvironmentsPage.tsx
+++ b/ui/src/pages/Admin/EnvironmentsPage.tsx
@@ -1,4 +1,4 @@
-import { useState, useMemo } from 'react';
+import { useState, useMemo, useEffect } from 'react';
 import {
   Avatar,
   Badge,
@@ -20,6 +20,7 @@ import {
   useCreateEnvironment,
   useUpdateEnvironment,
   useDeleteEnvironment,
+  useUpdateDefaultContainerConfig,
 } from '../../api/queries/admin/environments';
 import type { Environment } from '../../api/queries/admin/environments';
 import styles from './UserManagement.module.css';
@@ -42,6 +43,7 @@ export default function EnvironmentsPage() {
   const createEnv = useCreateEnvironment();
   const updateEnv = useUpdateEnvironment();
   const deleteEnv = useDeleteEnvironment();
+  const updateDefaults = useUpdateDefaultContainerConfig();
 
   const selected = useMemo(
     () => environments.find((e) => e.id === selectedId) ?? null,
@@ -280,6 +282,15 @@ export default function EnvironmentsPage() {
                   </p>
                 )}
               </div>
+
+              <DefaultResourcesSection environment={selected} onSave={async (config) => {
+                try {
+                  await updateDefaults.mutateAsync({ id: selected.id, config });
+                  toast({ title: 'Default resources updated', variant: 'success' });
+                } catch {
+                  toast({ title: 'Failed to update defaults', variant: 'error', duration: 86_400_000 });
+                }
+              }} saving={updateDefaults.isPending} />
             </>
           ) : null
         }
@@ -297,3 +308,84 @@ export default function EnvironmentsPage() {
     </>
   );
 }
+
+// ── Default Resource Limits ─────────────────────────────────────────
+
+function DefaultResourcesSection({ environment, onSave, saving }: {
+  environment: Environment;
+  onSave: (config: Record<string, unknown>) => Promise<void>;
+  saving: boolean;
+}) {
+  const defaults = environment.defaultContainerConfig ?? {};
+  const [editing, setEditing] = useState(false);
+  const [memoryLimit, setMemoryLimit] = useState('');
+  const [memoryReserve, setMemoryReserve] = useState('');
+  const [cpuShares, setCpuShares] = useState('');
+  const [cpuLimit, setCpuLimit] = useState('');
+
+  useEffect(() => {
+    setMemoryLimit(String(defaults.memoryLimitMb ?? ''));
+    setMemoryReserve(String(defaults.memoryReserveMb ?? ''));
+    setCpuShares(String(defaults.cpuShares ?? ''));
+    setCpuLimit(String(defaults.cpuLimit ?? ''));
+    setEditing(false);
+  }, [environment.id]);
+
+  function handleCancel() {
+    setMemoryLimit(String(defaults.memoryLimitMb ?? ''));
+    setMemoryReserve(String(defaults.memoryReserveMb ?? ''));
+    setCpuShares(String(defaults.cpuShares ?? ''));
+    setCpuLimit(String(defaults.cpuLimit ?? ''));
+    setEditing(false);
+  }
+
+  async function handleSave() {
+    await onSave({
+      memoryLimitMb: memoryLimit ? parseInt(memoryLimit) : null,
+      memoryReserveMb: memoryReserve ? parseInt(memoryReserve) : null,
+      cpuShares: cpuShares ? parseInt(cpuShares) : null,
+      cpuLimit: cpuLimit ? parseFloat(cpuLimit) : null,
+    });
+    setEditing(false);
+  }
+
+  return (
+    <>
+      <SectionHeader>Default Resource Limits</SectionHeader>
+      <p className={styles.inheritedNote}>
+        These defaults apply to new apps in this environment unless overridden per-app.
+      </p>
+      <div className={styles.metaGrid}>
+        <span className={styles.metaLabel}>Memory Limit</span>
+        {editing
+          ? <Input value={memoryLimit} onChange={(e) => setMemoryLimit(e.target.value)} placeholder="e.g. 512" style={{ width: 100 }} />
+          : <span className={styles.metaValue}>{defaults.memoryLimitMb ? `${defaults.memoryLimitMb} MB` : '—'}</span>}
+
+        <span className={styles.metaLabel}>Memory Reserve</span>
+        {editing
+          ? <Input value={memoryReserve} onChange={(e) => setMemoryReserve(e.target.value)} placeholder="e.g. 256" style={{ width: 100 }} />
+          : <span className={styles.metaValue}>{defaults.memoryReserveMb ? `${defaults.memoryReserveMb} MB` : '—'}</span>}
+
+        <span className={styles.metaLabel}>CPU Shares</span>
+        {editing
+          ? <Input value={cpuShares} onChange={(e) => setCpuShares(e.target.value)} placeholder="e.g. 512" style={{ width: 100 }} />
+          : <span className={styles.metaValue}>{String(defaults.cpuShares ?? '—')}</span>}
+
+        <span className={styles.metaLabel}>CPU Limit</span>
+        {editing
+          ? <Input value={cpuLimit} onChange={(e) => setCpuLimit(e.target.value)} placeholder="e.g. 1.0" style={{ width: 100 }} />
+          : <span className={styles.metaValue}>{defaults.cpuLimit ? `${defaults.cpuLimit} cores` : '—'}</span>}
+      </div>
+      <div style={{ marginTop: 8, display: 'flex', gap: 8, justifyContent: 'flex-end' }}>
+        {editing ? (
+          <>
+            <Button size="sm" variant="ghost" onClick={handleCancel}>Cancel</Button>
+            <Button size="sm" variant="primary" onClick={handleSave} loading={saving}>Save</Button>
+          </>
+        ) : (
+          <Button size="sm" variant="secondary" onClick={() => setEditing(true)}>Edit Defaults</Button>
+        )}
+      </div>
+    </>
+  );
+}