diff --git a/client/src/components/Admin/storage/AdminStoragePanel.tsx b/client/src/components/Admin/storage/AdminStoragePanel.tsx
index b567e1cc8..3223dedee 100644
--- a/client/src/components/Admin/storage/AdminStoragePanel.tsx
+++ b/client/src/components/Admin/storage/AdminStoragePanel.tsx
@@ -38,7 +38,7 @@ import {
   StatusPill,
 } from '../../Settings/settingsKit'
 import BackendForm from './BackendForm'
-import { CACHE_CATEGORIES, mirrorProbeTargets, primaryNameOf } from './storageModel'
+import { CACHE_CATEGORIES, primaryNameOf } from './storageModel'
 import { categoryNames, migrationPromptLine, useStoragePanel } from './useStoragePanel'
 
 /** The compact buttons of a backend row: white on a hairline, a size under the card's own. */
@@ -123,7 +123,7 @@ export default function AdminStoragePanel(): React.ReactElement {
     )
   }
   const {
-    state, draft, migrationCandidates, backendNames, rows, degenerate, effective, usageSums, startAdd, startEdit,
+    state, draft, migrationCandidates, backendNames, rows, degenerate, effective, usageSums, startAdd, startEdit, testRow,
     commitBackend, removeMessage, confirmRemoval, setCategory, save, moveAndSave, routeOnlySave,
   } = loaded
 
@@ -202,11 +202,6 @@ export default function AdminStoragePanel(): React.ReactElement {
           {rows.map((row) => {
             const resultKey = row.mirrorName ?? row.name
             const result = testResultFor(resultKey)
-            // row.mirrorName only exists when foldBackends adopted a draft mirror
-            // for this row, so the draft lookup below cannot miss.
-            const testCandidate = row.mirrorName
-              ? draft.backends.find((b) => b.name === row.mirrorName)!
-              : row.backend
             const rowUsage = usageSums?.[row.name]
             const backfill = row.mirrorName ? state.backfills.find((b) => b.backend === row.mirrorName) : undefined
             const TypeIcon = TYPE_ICON[row.type] ?? HardDrive
@@ -234,11 +229,7 @@ export default function AdminStoragePanel(): React.ReactElement {
                     <button type="button"
                       className={ROW_BUTTON}
                       style={fs(12, 'body')}
-                      onClick={() =>
-                        row.mirrorName
-                          ? admin.testMirror(resultKey, mirrorProbeTargets(draft, state, testCandidate))
-                          : admin.test(testCandidate)
-                      }
+                      onClick={() => void testRow(row)}
                     >
                       <PlugZap size={13} strokeWidth={2.2} />
                       {t('storage.actions.test')}
diff --git a/client/src/components/Admin/storage/useStoragePanel.test.ts b/client/src/components/Admin/storage/useStoragePanel.test.ts
index e1216908d..f75447f0c 100644
--- a/client/src/components/Admin/storage/useStoragePanel.test.ts
+++ b/client/src/components/Admin/storage/useStoragePanel.test.ts
@@ -1,4 +1,4 @@
-// FE-ADMIN-STOR-PANEL-001 to -012: the storage panel logic behind both admin shells.
+// FE-ADMIN-STOR-PANEL-001 to -017: the storage panel logic behind both admin shells.
 import { act, renderHook, waitFor } from '@testing-library/react';
 
 import { STORAGE_CATEGORIES, type StorageAdminState, type StorageBackend, type StorageConfig } from '@trek/shared';
@@ -218,6 +218,27 @@ describe('useStoragePanel', () => {
     expect(fake.admin.startMigration).toHaveBeenCalledTimes(1);
   });
 
+  it('FE-ADMIN-STOR-PANEL-017: testRow probes a plain row as it is and a mirrored row per draft target', () => {
+    const state = baseState();
+    const draft: StorageConfig = {
+      ...settingsDocumentOf(state),
+      backends: [
+        ...settingsDocumentOf(state).backends,
+        { name: 'off-box-mirror', type: 'mirror', options: { primary: 'off-box', replicas: ['uploads-local'] } },
+      ],
+    };
+    fake.admin = makeAdmin(state, draft);
+    const { result } = renderHook(() => useStoragePanel());
+    const rows = result.current.loaded!.rows;
+    void result.current.loaded!.testRow(rows.find((r) => r.name === 'uploads-local')!);
+    expect(fake.admin.test).toHaveBeenCalledWith(expect.objectContaining({ name: 'uploads-local' }));
+    void result.current.loaded!.testRow(rows.find((r) => r.name === 'off-box')!);
+    expect(fake.admin.testMirror).toHaveBeenCalledWith('off-box-mirror', [
+      expect.objectContaining({ name: 'off-box', type: 'local' }),
+      expect.objectContaining({ name: 'uploads-local', type: 'local' }),
+    ]);
+  });
+
   it('FE-ADMIN-STOR-PANEL-013: backfill and stats actions toast the server error', async () => {
     fake.admin = makeAdmin(baseState());
     vi.mocked(fake.admin.refreshStats).mockResolvedValueOnce('scan failed');
diff --git a/client/src/components/Admin/storage/useStoragePanel.ts b/client/src/components/Admin/storage/useStoragePanel.ts
index 460d0badd..6a5155889 100644
--- a/client/src/components/Admin/storage/useStoragePanel.ts
+++ b/client/src/components/Admin/storage/useStoragePanel.ts
@@ -17,6 +17,7 @@ import {
   computeMigrationCandidates,
   effectiveCategoryMap,
   foldBackends,
+  mirrorProbeTargets,
   removeBackend,
   removeBackendAndMirrors,
   renameBackendRefs,
@@ -225,6 +226,17 @@ export function useStoragePanel() {
       setEditing(null);
     };
 
+    // A mirrored row probes its primary and each replica one by one, with the draft
+    // options of each: the server would resolve a mirror stub against its SAVED
+    // backends by name, so unsaved edits (or a replica not saved yet) would be missed.
+    // row.mirrorName only exists when foldBackends adopted a draft mirror for this
+    // row, so the draft lookup cannot miss.
+    const testRow = (row: FoldedBackendRow) => {
+      if (!row.mirrorName) return admin.test(row.backend);
+      const mirror = draft.backends.find((b) => b.name === row.mirrorName)!;
+      return admin.testMirror(row.mirrorName, mirrorProbeTargets(draft, state, mirror));
+    };
+
     const removeMessage = (name: string, isDegenerate: boolean): string => {
       const row = rows.find((r) => r.name === name);
       const assigned = isDegenerate
@@ -333,6 +345,7 @@ export function useStoragePanel() {
       usageSums,
       startAdd,
       startEdit,
+      testRow,
       commitBackend,
       removeMessage,
       confirmRemoval,
diff --git a/client/src/mobile/screens/admin/MAdminStoragePanel.tsx b/client/src/mobile/screens/admin/MAdminStoragePanel.tsx
index d392997c9..6e0dfa252 100644
--- a/client/src/mobile/screens/admin/MAdminStoragePanel.tsx
+++ b/client/src/mobile/screens/admin/MAdminStoragePanel.tsx
@@ -190,7 +190,7 @@ export default function MAdminStoragePanel(): React.ReactElement {
     )
   }
   const {
-    state, draft, backendNames, rows, degenerate, effective, usageSums, startAdd, startEdit, commitBackend,
+    state, draft, backendNames, rows, degenerate, effective, usageSums, startAdd, startEdit, testRow, commitBackend,
     removeMessage, confirmRemoval, setCategory, save, moveAndSave, routeOnlySave,
   } = loaded
 
@@ -236,11 +236,6 @@ export default function MAdminStoragePanel(): React.ReactElement {
           {rows.map((row) => {
             const resultKey = row.mirrorName ?? row.name
             const result = admin.testResults[resultKey]
-            // row.mirrorName only exists when foldBackends adopted a draft mirror
-            // for this row, so the draft lookup below cannot miss.
-            const testCandidate = row.mirrorName
-              ? draft.backends.find((b) => b.name === row.mirrorName)!
-              : row.backend
             const rowUsage = usageSums?.[row.name]
             const backfill = row.mirrorName ? state.backfills.find((b) => b.backend === row.mirrorName) : undefined
             return (
@@ -285,7 +280,7 @@ export default function MAdminStoragePanel(): React.ReactElement {
                   <p className="mt-1 font-geist text-[0.625rem] text-m-muted">{t('storage.backends.envReadOnly')}</p>
                 )}
                 <div className="mt-2 flex gap-2">
-                  <MAdminButton variant="ghost" onClick={() => admin.test(testCandidate)}>
+                  <MAdminButton variant="ghost" onClick={() => void testRow(row)}>
                     {t('storage.actions.test')}
                   </MAdminButton>
                   {row.source !== 'env' && (
diff --git a/client/tests/unit/mobile/admin/MAdminStoragePanel.test.tsx b/client/tests/unit/mobile/admin/MAdminStoragePanel.test.tsx
index 3b5b8fa63..736d155cb 100644
--- a/client/tests/unit/mobile/admin/MAdminStoragePanel.test.tsx
+++ b/client/tests/unit/mobile/admin/MAdminStoragePanel.test.tsx
@@ -441,4 +441,26 @@ describe('MAdminStoragePanel', () => {
     await new Promise((r) => setTimeout(r, 100));
     expect(screen.queryByText(/Existing objects are not replicated yet/)).not.toBeInTheDocument();
   });
+
+  it('FE-MOB-MSTOR-018: Test on a mirrored primary probes the draft primary and each replica, never the mirror stub', async () => {
+    const posted: Array<{ name: string; type: string; options: Record<string, unknown> }> = [];
+    await renderPanel(mirroredState());
+    server.use(
+      http.post('/api/admin/storage/test', async ({ request }) => {
+        const body = (await request.json()) as { backend: { name: string; type: string; options: Record<string, unknown> } };
+        posted.push(body.backend);
+        return HttpResponse.json({ ok: true, targets: [{ name: body.backend.name, ok: true }] });
+      }),
+    );
+    // An unsaved endpoint change on the replica must be what the probe sees.
+    fireEvent.click(within(screen.getByTestId('m-storage-backend-off-box')).getByRole('button', { name: 'Edit' }));
+    fireEvent.change(screen.getByDisplayValue('http://127.0.0.1:9000'), { target: { value: 'http://edited.example:9000' } });
+    fireEvent.click(screen.getByRole('button', { name: 'Apply' }));
+    fireEvent.click(within(screen.getByTestId('m-storage-backend-backups-local')).getByRole('button', { name: 'Test' }));
+    await waitFor(() => expect(posted.length).toBeGreaterThan(0));
+    await new Promise((r) => setTimeout(r, 50));
+    expect(posted.map((b) => b.name).sort()).toEqual(['backups-local', 'off-box']);
+    expect(posted.every((b) => b.type !== 'mirror')).toBe(true);
+    expect(posted.find((b) => b.name === 'off-box')?.options.endpoint).toBe('http://edited.example:9000');
+  });
 });