diff --git a/frontend/src/__tests__/plans.test.ts b/frontend/src/__tests__/plans.test.ts
index 244efce70..d35465c18 100644
--- a/frontend/src/__tests__/plans.test.ts
+++ b/frontend/src/__tests__/plans.test.ts
@@ -1137,11 +1137,14 @@ describe('Plans Module', () => {
       await savePlan(event);
 
       expect(api.createPlan).toHaveBeenCalled();
+      // PR #861: no follow-up setPlanAccounts on the create path.
+      expect(api.setPlanAccounts).not.toHaveBeenCalled();
       expect(mockShowToast).toHaveBeenCalledWith(expect.objectContaining({ message: 'Plan created successfully' }));
     });
 
     test('updates existing plan when plan ID present', async () => {
       (api.updatePlan as jest.Mock).mockResolvedValue({});
+      (api.setPlanAccounts as jest.Mock).mockResolvedValue(undefined);
       (api.getPlans as jest.Mock).mockResolvedValue({ plans: [] });
       (api.getPlannedPurchases as jest.Mock).mockResolvedValue({ purchases: [] });
       (document.getElementById('plan-id') as HTMLInputElement).value = 'plan-123';
@@ -1150,6 +1153,8 @@ describe('Plans Module', () => {
       await savePlan(event);
 
       expect(api.updatePlan).toHaveBeenCalledWith('plan-123', expect.any(Object));
+      // PR #861: update path still calls setPlanAccounts (no atomic backend write on PUT).
+      expect(api.setPlanAccounts).toHaveBeenCalledWith('plan-123', expect.any(Array));
       expect(mockShowToast).toHaveBeenCalledWith(expect.objectContaining({ message: 'Plan updated successfully' }));
     });
 
@@ -1425,6 +1430,11 @@ describe('Plans Module', () => {
           '22222222-2222-2222-2222-222222222222',
         ],
       }));
+      // Regression guard for PR #861: the create path must NOT call
+      // setPlanAccounts -- the backend already persists plan_accounts
+      // atomically from target_accounts in the POST body (handler_plans.go
+      // createPlan). A follow-up PUT would be a redundant double-write.
+      expect(api.setPlanAccounts).not.toHaveBeenCalled();
     });
 
     // -------------------------------------------------------------------------
diff --git a/frontend/src/plans.ts b/frontend/src/plans.ts
index 7d8f3d18c..369f99078 100644
--- a/frontend/src/plans.ts
+++ b/frontend/src/plans.ts
@@ -1343,22 +1343,15 @@ export async function savePlan(e: Event): Promise<void> {
   plan.target_accounts = accountIds;
 
   try {
-    let savedPlanId = planId;
     if (planId) {
       await api.updatePlan(planId, plan as unknown as api.CreatePlanRequest);
+      // Update flow: push the selected account list via the dedicated endpoint.
+      await api.setPlanAccounts(planId, accountIds);
     } else {
-      const created = await api.createPlan(plan as unknown as api.CreatePlanRequest) as unknown as { id: string };
-      savedPlanId = created.id;
-    }
-
-    // On update, the create path's atomic plan_accounts insert doesn't fire
-    // (we only POST /plans on create). For updates we still need to push the
-    // selected account list via the dedicated endpoint. On create, we also
-    // re-push here so that subsequent reselection is reflected even if the
-    // backend later opens an "atomic-create-only" path that diverges from
-    // PUT semantics — same call already handles dedupe via DELETE+INSERT.
-    if (savedPlanId) {
-      await api.setPlanAccounts(savedPlanId, accountIds);
+      await api.createPlan(plan as unknown as api.CreatePlanRequest);
+      // Create flow: backend inserted plan_accounts atomically from
+      // target_accounts in the POST body (see internal/api/handler_plans.go
+      // createPlan). No follow-up account-write needed.
     }
 
     closePlanModal();