diff --git a/.cursor/rules/frontend-components.mdc b/.cursor/rules/frontend-components.mdc
index f338867..a523428 100644
--- a/.cursor/rules/frontend-components.mdc
+++ b/.cursor/rules/frontend-components.mdc
@@ -60,5 +60,6 @@ Reference: `app/.../treatment/page.tsx` + `components/ui/treatment/TreatmentWork
 | Filter or inline `<select>` | `FORM_SELECT_CLASS` from `components/shared/formSelectStyles.ts` |
 | Tiny select (sort dir, etc.) | `FORM_SELECT_COMPACT_CLASS` |
 | Desktop data table | `Table` (`ui/shared/Table.tsx`) — logical alignment only |
+| API action button | `Button` — return the Promise from `onClick` (`() => doThing()` not `() => void doThing()`); auto-disables until settle. List/icon mutations: `useAsyncAction` / `useAsyncActionById` |
 
 Styles for `.form-select` chevrons live in `styles/globals.css`. Do not duplicate chevron icons on raw selects.
diff --git a/frontend/src/app/[locale]/(public)/accept-invite/page.tsx b/frontend/src/app/[locale]/(public)/accept-invite/page.tsx
index 443a137..6ad568e 100644
--- a/frontend/src/app/[locale]/(public)/accept-invite/page.tsx
+++ b/frontend/src/app/[locale]/(public)/accept-invite/page.tsx
@@ -148,7 +148,7 @@ function AcceptInviteContent() {
                   onChange={(e) => setConfirmPassword(e.target.value)}
                   passwordToggleLabels={passwordToggleLabels}
                 />
-                <Button type="button" fullWidth isLoading={submitting} onClick={() => void onAccept()}>
+                <Button type="button" fullWidth isLoading={submitting} onClick={() => onAccept()}>
                   {t('activateAccount')}
                 </Button>
               </div>
diff --git a/frontend/src/app/[locale]/(public)/accept-organization-invite/page.tsx b/frontend/src/app/[locale]/(public)/accept-organization-invite/page.tsx
index 6362110..213af59 100644
--- a/frontend/src/app/[locale]/(public)/accept-organization-invite/page.tsx
+++ b/frontend/src/app/[locale]/(public)/accept-organization-invite/page.tsx
@@ -244,7 +244,7 @@ function AcceptOrganizationInviteContent() {
                       icon={<Lock className="h-5 w-5 icon-flat" />}
                       passwordToggleLabels={passwordToggleLabels}
                     />
-                    <Button type="button" variant="primary" onClick={() => void handleNext()} fullWidth>
+                    <Button type="button" variant="primary" onClick={() => handleNext()} fullWidth>
                       {tCommon('continue')}
                     </Button>
                   </>
diff --git a/frontend/src/app/[locale]/(public)/forgot-password/page.tsx b/frontend/src/app/[locale]/(public)/forgot-password/page.tsx
index 29eca1d..1f2aa19 100644
--- a/frontend/src/app/[locale]/(public)/forgot-password/page.tsx
+++ b/frontend/src/app/[locale]/(public)/forgot-password/page.tsx
@@ -182,7 +182,7 @@ export default function ForgotPasswordPage() {
               variant="primary"
               isLoading={isSending}
               fullWidth
-              onClick={() => void onSendCode()}
+              onClick={() => onSendCode()}
             >
               {t('sendCode')}
             </Button>
diff --git a/frontend/src/components/ui/appointments/AppointmentBookingModal.tsx b/frontend/src/components/ui/appointments/AppointmentBookingModal.tsx
index b36111d..b576174 100644
--- a/frontend/src/components/ui/appointments/AppointmentBookingModal.tsx
+++ b/frontend/src/components/ui/appointments/AppointmentBookingModal.tsx
@@ -319,7 +319,7 @@ export function AppointmentBookingModal({
             <Button
               type="button"
               variant="danger"
-              onClick={() => void onDelete()}
+              onClick={() => onDelete()}
               disabled={loading || deleting}
               isLoading={deleting}
               fullWidth
@@ -342,7 +342,7 @@ export function AppointmentBookingModal({
             <Button
               type="button"
               variant="primary"
-              onClick={() => void handleSubmit()}
+              onClick={() => handleSubmit()}
               isLoading={loading}
               disabled={deleting}
               fullWidth
diff --git a/frontend/src/components/ui/appointments/AppointmentsPage.tsx b/frontend/src/components/ui/appointments/AppointmentsPage.tsx
index 17b72ce..dffcbd9 100644
--- a/frontend/src/components/ui/appointments/AppointmentsPage.tsx
+++ b/frontend/src/components/ui/appointments/AppointmentsPage.tsx
@@ -285,7 +285,7 @@ export function AppointmentsPage() {
           !!activeEditingAppointment &&
           !activeEditingAppointment.hasTreatment
         }
-        onDelete={() => void handleDeleteEditingAppointment()}
+        onDelete={() => handleDeleteEditingAppointment()}
         deleting={deletingAppointment}
       />
     </div>
diff --git a/frontend/src/components/ui/dashboard/DashboardAccountMenu.tsx b/frontend/src/components/ui/dashboard/DashboardAccountMenu.tsx
index 9c35c77..e5c71d0 100644
--- a/frontend/src/components/ui/dashboard/DashboardAccountMenu.tsx
+++ b/frontend/src/components/ui/dashboard/DashboardAccountMenu.tsx
@@ -13,8 +13,10 @@ import {
   ChevronDown,
 } from 'lucide-react';
 import { useAuth } from '@/lib/hooks/useAuth';
+import { useAsyncAction } from '@/lib/hooks/useAsyncAction';
 import { authApi } from '@/lib/api/auth';
 import type { SubscriptionAlertData } from '@/types/subscription';
+import { Button } from '@/components/ui/shared/Button';
 
 function warningTooltip(
   data: SubscriptionAlertData | null,
@@ -32,6 +34,7 @@ export function DashboardAccountMenu() {
   const t = useTranslations('auth');
   const tAccount = useTranslations('accountMenu');
   const { user, currentOrganization, logout } = useAuth();
+  const { pending: logoutPending, run: runLogout } = useAsyncAction();
   const [open, setOpen] = useState(false);
   const menuRef = useRef<HTMLDivElement>(null);
   const [alert, setAlert] = useState<SubscriptionAlertData | null>(null);
@@ -70,9 +73,11 @@ export function DashboardAccountMenu() {
   const tooltip = useMemo(() => warningTooltip(alert, tAccount), [alert, tAccount]);
 
   const handleLogout = useCallback(() => {
-    setOpen(false);
-    void logout();
-  }, [logout]);
+    return runLogout(async () => {
+      await logout();
+      setOpen(false);
+    });
+  }, [logout, runLogout]);
 
   return (
     <div className="relative z-[120]" ref={menuRef}>
@@ -146,15 +151,17 @@ export function DashboardAccountMenu() {
           </div>
 
           <div className="border-t border-border/60 pt-1">
-            <button
+            <Button
               type="button"
+              variant="ghost"
               role="menuitem"
-              className="flex w-full items-center gap-3 px-3 py-2.5 text-sm text-text-secondary hover:bg-background-card/70 hover:text-text-primary"
-              onClick={handleLogout}
+              className="flex w-full items-center justify-start gap-3 rounded-none px-3 py-2.5 text-sm text-text-secondary hover:bg-background-card/70 hover:text-text-primary"
+              isLoading={logoutPending}
+              onClick={() => handleLogout()}
             >
               <LogOut className="h-4 w-4 icon-flat shrink-0" />
               {t('signOut')}
-            </button>
+            </Button>
           </div>
         </div>
       )}
diff --git a/frontend/src/components/ui/lab/LabCaseAttachmentsDialog.tsx b/frontend/src/components/ui/lab/LabCaseAttachmentsDialog.tsx
index fb5251d..018d8a2 100644
--- a/frontend/src/components/ui/lab/LabCaseAttachmentsDialog.tsx
+++ b/frontend/src/components/ui/lab/LabCaseAttachmentsDialog.tsx
@@ -185,7 +185,7 @@ export function LabCaseAttachmentsDialog({
                 variant="outline"
                 size="sm"
                 disabled={downloadingAll}
-                onClick={() => void handleDownloadAll()}
+                onClick={() => handleDownloadAll()}
               >
                 <Download className="h-4 w-4 me-1.5" />
                 {t('downloadAllAttachments')}
diff --git a/frontend/src/components/ui/lab/LabCaseCommentsPanel.tsx b/frontend/src/components/ui/lab/LabCaseCommentsPanel.tsx
index a76fbf2..8a50f62 100644
--- a/frontend/src/components/ui/lab/LabCaseCommentsPanel.tsx
+++ b/frontend/src/components/ui/lab/LabCaseCommentsPanel.tsx
@@ -4,6 +4,7 @@ import { useCallback, useEffect, useState, type KeyboardEvent } from 'react';
 import { useTranslations } from 'next-intl';
 import { Eye, EyeOff, Send } from 'lucide-react';
 import { getUserFacingError } from '@/components/shared/formatApiError';
+import { useAsyncActionById } from '@/lib/hooks/useAsyncAction';
 import type { LabCaseComment } from '@/types/cases';
 
 interface LabCaseCommentsPanelProps {
@@ -42,6 +43,7 @@ export function LabCaseCommentsPanel({
   const [posting, setPosting] = useState(false);
   const [body, setBody] = useState('');
   const [visibleToClinic, setVisibleToClinic] = useState(false);
+  const toggleBusy = useAsyncActionById();
 
   const refresh = useCallback(async () => {
     setLoading(true);
@@ -84,12 +86,14 @@ export function LabCaseCommentsPanel({
 
   async function handleToggle(comment: LabCaseComment) {
     if (!onToggleVisibility || !canToggleVisibility) return;
-    try {
-      const updated = await onToggleVisibility(comment.id, !comment.visibleToClinic);
-      setComments((prev) => prev.map((c) => (c.id === updated.id ? updated : c)));
-    } catch (error: unknown) {
-      onError?.(getUserFacingError(error, tErrors, t('errorToggle')));
-    }
+    await toggleBusy.run(comment.id, async () => {
+      try {
+        const updated = await onToggleVisibility(comment.id, !comment.visibleToClinic);
+        setComments((prev) => prev.map((c) => (c.id === updated.id ? updated : c)));
+      } catch (error: unknown) {
+        onError?.(getUserFacingError(error, tErrors, t('errorToggle')));
+      }
+    });
   }
 
   return (
@@ -127,10 +131,14 @@ export function LabCaseCommentsPanel({
                 {canToggleVisibility && comment.canToggleVisibility && onToggleVisibility ? (
                   <button
                     type="button"
-                    onClick={() => void handleToggle(comment)}
-                    className="shrink-0 p-1 rounded hover:bg-border text-text-muted"
+                    onClick={() => handleToggle(comment)}
+                    disabled={toggleBusy.pendingId !== null}
+                    className={`shrink-0 p-1 rounded hover:bg-border text-text-muted disabled:opacity-40 disabled:cursor-not-allowed ${
+                      toggleBusy.pendingId === comment.id ? 'animate-pulse' : ''
+                    }`}
                     title={comment.visibleToClinic ? t('makeHidden') : t('makeVisible')}
                     aria-label={comment.visibleToClinic ? t('makeHidden') : t('makeVisible')}
+                    aria-busy={toggleBusy.pendingId === comment.id || undefined}
                   >
                     {comment.visibleToClinic ? (
                       <Eye className="h-4 w-4" />
@@ -184,7 +192,7 @@ export function LabCaseCommentsPanel({
             ) : null}
             <button
               type="button"
-              onClick={() => void handlePost()}
+              onClick={() => handlePost()}
               disabled={posting || !body.trim()}
               className="shrink-0 p-2 rounded-md bg-primary text-white transition-colors hover:opacity-90 disabled:opacity-40 disabled:cursor-not-allowed"
               title={t('send')}
diff --git a/frontend/src/components/ui/lab/LabCaseShareQrDialog.tsx b/frontend/src/components/ui/lab/LabCaseShareQrDialog.tsx
index 7db4e82..b10ff77 100644
--- a/frontend/src/components/ui/lab/LabCaseShareQrDialog.tsx
+++ b/frontend/src/components/ui/lab/LabCaseShareQrDialog.tsx
@@ -68,7 +68,7 @@ export function LabCaseShareQrDialog({ open, onClose, shareUrl }: LabCaseShareQr
             variant="outline"
             disabled={copying}
             className="w-full sm:w-auto"
-            onClick={() => void handleCopy()}
+            onClick={() => handleCopy()}
           >
             <Copy className="h-4 w-4 me-1.5" />
             {t('copyShareLink')}
diff --git a/frontend/src/components/ui/lab/TaskRow.tsx b/frontend/src/components/ui/lab/TaskRow.tsx
index 0f830d3..5caf1cc 100644
--- a/frontend/src/components/ui/lab/TaskRow.tsx
+++ b/frontend/src/components/ui/lab/TaskRow.tsx
@@ -38,7 +38,7 @@ interface TaskRowProps {
   onStatusUpdate: (taskId: string, status: LabTaskStatus) => void;
   onToggleComments: (taskId: string) => void;
   onCommentError: (message: string) => void;
-  onShowInCase?: (task: LabTaskListItem) => void;
+  onShowInCase?: (task: LabTaskListItem) => void | Promise<void>;
 }
 
 function formatPatientName(patient: { firstName: string; lastName: string }) {
diff --git a/frontend/src/components/ui/lab/TasksPage.tsx b/frontend/src/components/ui/lab/TasksPage.tsx
index a746d98..f06aa6d 100644
--- a/frontend/src/components/ui/lab/TasksPage.tsx
+++ b/frontend/src/components/ui/lab/TasksPage.tsx
@@ -368,7 +368,7 @@ export function TasksPage() {
         setExpandedCommentsTaskId((prev) => (prev === id ? null : id))
       }
       onCommentError={showError}
-      onShowInCase={flatMode ? (row) => void handleShowInCase(row) : undefined}
+      onShowInCase={flatMode ? (row) => handleShowInCase(row) : undefined}
     />
   );
 
diff --git a/frontend/src/components/ui/organizations/OrganizationConnectionsMobileList.tsx b/frontend/src/components/ui/organizations/OrganizationConnectionsMobileList.tsx
index d0530fc..1b49570 100644
--- a/frontend/src/components/ui/organizations/OrganizationConnectionsMobileList.tsx
+++ b/frontend/src/components/ui/organizations/OrganizationConnectionsMobileList.tsx
@@ -135,7 +135,7 @@ export function OrganizationConnectionsMobileList({
                       <button
                         type="button"
                         className="p-2 rounded-md text-text-secondary hover:bg-background-card/80 hover:text-text-primary disabled:opacity-50"
-                        disabled={pendingConnectionRowId !== null && pendingConnectionRowId !== row.id}
+                        disabled={pendingConnectionRowId !== null}
                         onClick={() => onRespond(row.id, 'ACCEPT')}
                         aria-label={labels.acceptRequest}
                         title={labels.acceptRequest}
@@ -145,7 +145,7 @@ export function OrganizationConnectionsMobileList({
                       <button
                         type="button"
                         className="p-2 rounded-md text-text-secondary hover:bg-red-500/15 hover:text-red-600 disabled:opacity-50"
-                        disabled={pendingConnectionRowId !== null && pendingConnectionRowId !== row.id}
+                        disabled={pendingConnectionRowId !== null}
                         onClick={() => onRespond(row.id, 'REJECT')}
                         aria-label={labels.declineRequest}
                         title={labels.declineRequest}
@@ -158,7 +158,7 @@ export function OrganizationConnectionsMobileList({
                     <button
                       type="button"
                       className="p-2 rounded-md text-text-secondary hover:bg-red-500/15 hover:text-red-600 disabled:opacity-50"
-                      disabled={deleteConnectionRowId !== null && deleteConnectionRowId !== row.id}
+                      disabled={deleteConnectionRowId !== null}
                       onClick={() => onDeleteConnection(row.id)}
                       aria-label={labels.removeConnection}
                       title={labels.removeConnection}
@@ -195,7 +195,7 @@ export function OrganizationConnectionsMobileList({
                 <button
                   type="button"
                   className="p-2 rounded-md text-text-secondary hover:bg-background-card/80 hover:text-text-primary disabled:opacity-50"
-                  disabled={pendingConnectionRowId !== null && pendingConnectionRowId !== result.id}
+                  disabled={pendingConnectionRowId !== null}
                   onClick={() => onSendConnectionRequest(result.id)}
                   aria-label={labels.sendRequest}
                   title={labels.sendRequest}
diff --git a/frontend/src/components/ui/organizations/OrganizationsPage.tsx b/frontend/src/components/ui/organizations/OrganizationsPage.tsx
index 7a3d3fc..db86c0d 100644
--- a/frontend/src/components/ui/organizations/OrganizationsPage.tsx
+++ b/frontend/src/components/ui/organizations/OrganizationsPage.tsx
@@ -4,6 +4,7 @@ import { useCallback, useEffect, useState } from 'react';
 import { useSearchParams } from 'next/navigation';
 import { useLocale, useTranslations } from 'next-intl';
 import { useToast } from '@/lib/hooks/useToast';
+import { useAsyncActionById } from '@/lib/hooks/useAsyncAction';
 import { Check, Trash2, UserPlus, X } from 'lucide-react';
 import { useAuth } from '@/lib/hooks/useAuth';
 import { notifyPendingConnectionsChanged } from '@/lib/hooks/usePendingConnectionsCount';
@@ -81,8 +82,8 @@ export function OrganizationsPage() {
   const [mode, setMode] = useState<TableMode>('existing');
   const [searching, setSearching] = useState(false);
   const [searchResults, setSearchResults] = useState<CounterpartSearchResultDto[]>([]);
-  const [pendingConnectionRowId, setPendingConnectionRowId] = useState<string | null>(null);
-  const [deleteConnectionRowId, setDeleteConnectionRowId] = useState<string | null>(null);
+  const connectionBusy = useAsyncActionById();
+  const deleteBusy = useAsyncActionById();
 
   const [items, setItems] = useState<CounterpartItemDto[]>([]);
   const [manualOrganizationName, setManualOrganizationName] = useState('');
@@ -171,20 +172,19 @@ export function OrganizationsPage() {
   }, [query, formatApiMessage, showError, setToastError]);
 
   async function submitConnectionRequest(targetOrganizationId: string) {
-    setPendingConnectionRowId(targetOrganizationId);
-    toast.setError('');
-    try {
-      await organizationApi.createConnectionRequest(targetOrganizationId);
-      toast.showSuccess(t('successConnectionSent', { counterpart }));
-      setSearchResults([]);
-      setQuery('');
-      setMode('existing');
-      await loadList();
-    } catch (e) {
-      toast.showError(formatApiMessage(e));
-    } finally {
-      setPendingConnectionRowId(null);
-    }
+    await connectionBusy.run(targetOrganizationId, async () => {
+      toast.setError('');
+      try {
+        await organizationApi.createConnectionRequest(targetOrganizationId);
+        toast.showSuccess(t('successConnectionSent', { counterpart }));
+        setSearchResults([]);
+        setQuery('');
+        setMode('existing');
+        await loadList();
+      } catch (e) {
+        toast.showError(formatApiMessage(e));
+      }
+    });
   }
 
   async function sendInvite() {
@@ -272,34 +272,32 @@ export function OrganizationsPage() {
   }
 
   async function respondToPendingConnection(connectionId: string, action: 'ACCEPT' | 'REJECT') {
-    setPendingConnectionRowId(connectionId);
-    toast.setError('');
-    try {
-      await organizationApi.respondToConnectionRequest(connectionId, action);
-      toast.showSuccess(
-        action === 'ACCEPT' ? t('successAccepted') : t('successDeclined'),
-      );
-      notifyPendingConnectionsChanged();
-      await loadList();
-    } catch (e) {
-      toast.showError(formatApiMessage(e));
-    } finally {
-      setPendingConnectionRowId(null);
-    }
+    await connectionBusy.run(connectionId, async () => {
+      toast.setError('');
+      try {
+        await organizationApi.respondToConnectionRequest(connectionId, action);
+        toast.showSuccess(
+          action === 'ACCEPT' ? t('successAccepted') : t('successDeclined'),
+        );
+        notifyPendingConnectionsChanged();
+        await loadList();
+      } catch (e) {
+        toast.showError(formatApiMessage(e));
+      }
+    });
   }
 
   async function deleteConnection(connectionId: string) {
-    setDeleteConnectionRowId(connectionId);
-    toast.setError('');
-    try {
-      await organizationApi.deleteConnection(connectionId);
-      toast.showSuccess(t('successRemoved'));
-      await loadList();
-    } catch (e) {
-      toast.showError(formatApiMessage(e));
-    } finally {
-      setDeleteConnectionRowId(null);
-    }
+    await deleteBusy.run(connectionId, async () => {
+      toast.setError('');
+      try {
+        await organizationApi.deleteConnection(connectionId);
+        toast.showSuccess(t('successRemoved'));
+        await loadList();
+      } catch (e) {
+        toast.showError(formatApiMessage(e));
+      }
+    });
   }
 
   function clearSearchView() {
@@ -320,7 +318,7 @@ export function OrganizationsPage() {
           <h1 className="text-xl sm:text-2xl font-semibold text-text-primary">{tabLabel}</h1>
           <p className="text-sm text-text-secondary mt-1">{t('subtitle')}</p>
         </div>
-        <Button type="button" size="sm" className="w-full sm:w-auto shrink-0" onClick={() => void openInvitationHistory()}>
+        <Button type="button" size="sm" className="w-full sm:w-auto shrink-0" onClick={() => openInvitationHistory()}>
           {t('invitationHistory')}
         </Button>
       </div>
@@ -349,8 +347,8 @@ export function OrganizationsPage() {
         searchResults={searchResults}
         currentOrganizationId={currentOrganization.id}
         counterpart={counterpart}
-        pendingConnectionRowId={pendingConnectionRowId}
-        deleteConnectionRowId={deleteConnectionRowId}
+        pendingConnectionRowId={connectionBusy.pendingId}
+        deleteConnectionRowId={deleteBusy.pendingId}
         copiedId={copiedId}
         copyingInvitationId={copyingInvitationId}
         showInviteForm={showInviteForm}
@@ -360,14 +358,14 @@ export function OrganizationsPage() {
         formatConnectionStatusLabel={formatConnectionStatusLabel}
         formatTableDate={formatTableDate}
         getInvitationTarget={(row) => invitationTargetFromConnectionRow(row, currentOrganization.id)}
-        onCopyInvitation={(row) => void handleCopyInvitationFromRow(row)}
-        onRespond={(rowId, action) => void respondToPendingConnection(rowId, action)}
-        onDeleteConnection={(rowId) => void deleteConnection(rowId)}
-        onSendConnectionRequest={(orgId) => void submitConnectionRequest(orgId)}
+        onCopyInvitation={(row) => handleCopyInvitationFromRow(row)}
+        onRespond={(rowId, action) => respondToPendingConnection(rowId, action)}
+        onDeleteConnection={(rowId) => deleteConnection(rowId)}
+        onSendConnectionRequest={(orgId) => submitConnectionRequest(orgId)}
         onToggleInviteForm={() => setShowInviteForm((v) => !v)}
         onManualOrganizationNameChange={setManualOrganizationName}
         onManualOwnerEmailChange={setManualOwnerEmail}
-        onSendInvite={() => void sendInvite()}
+        onSendInvite={() => sendInvite()}
         labels={{
           loading: tCommon('loadingEllipsis'),
           emptyConnections: t('emptyConnections'),
@@ -462,8 +460,8 @@ export function OrganizationsPage() {
                               <button
                                 type="button"
                                 className="p-2 rounded-md text-text-secondary hover:bg-background-card/80 hover:text-text-primary disabled:text-text-muted disabled:opacity-50"
-                                disabled={pendingConnectionRowId !== null && pendingConnectionRowId !== row.id}
-                                onClick={() => void respondToPendingConnection(row.id, 'ACCEPT')}
+                                disabled={connectionBusy.pendingId !== null}
+                                onClick={() => respondToPendingConnection(row.id, 'ACCEPT')}
                                 aria-label={t('acceptRequest')}
                                 title={t('acceptRequest')}
                               >
@@ -472,8 +470,8 @@ export function OrganizationsPage() {
                               <button
                                 type="button"
                                 className="p-2 rounded-md text-text-secondary hover:bg-red-500/15 hover:text-red-600 disabled:text-text-muted disabled:opacity-50"
-                                disabled={pendingConnectionRowId !== null && pendingConnectionRowId !== row.id}
-                                onClick={() => void respondToPendingConnection(row.id, 'REJECT')}
+                                disabled={connectionBusy.pendingId !== null}
+                                onClick={() => respondToPendingConnection(row.id, 'REJECT')}
                                 aria-label={t('declineRequest')}
                                 title={t('declineRequest')}
                               >
@@ -486,8 +484,8 @@ export function OrganizationsPage() {
                               <button
                                 type="button"
                                 className="p-2 rounded-md text-text-secondary hover:bg-red-500/15 hover:text-red-600 disabled:text-text-muted disabled:opacity-50"
-                                disabled={deleteConnectionRowId !== null && deleteConnectionRowId !== row.id}
-                                onClick={() => void deleteConnection(row.id)}
+                                disabled={deleteBusy.pendingId !== null}
+                                onClick={() => deleteConnection(row.id)}
                                 aria-label={t('removeConnection')}
                                 title={t('removeConnection')}
                               >
@@ -514,10 +512,8 @@ export function OrganizationsPage() {
                     <button
                       type="button"
                       className="p-2 rounded-md text-text-secondary hover:bg-background-card/80 hover:text-text-primary disabled:text-text-muted disabled:opacity-50"
-                      disabled={
-                        pendingConnectionRowId !== null && pendingConnectionRowId !== r.id
-                      }
-                      onClick={() => void submitConnectionRequest(r.id)}
+                      disabled={connectionBusy.pendingId !== null}
+                      onClick={() => submitConnectionRequest(r.id)}
                       aria-label={t('sendRequest')}
                       title={t('sendRequest')}
                     >
@@ -556,7 +552,7 @@ export function OrganizationsPage() {
                             type="button"
                             isLoading={inviteLoading}
                             disabled={!manualOrganizationName.trim() || !manualOwnerEmail.trim()}
-                            onClick={() => void sendInvite()}
+                            onClick={() => sendInvite()}
                             className="w-full"
                           >
                             {t('sendInvitation')}
diff --git a/frontend/src/components/ui/patient/PatientsPage.tsx b/frontend/src/components/ui/patient/PatientsPage.tsx
index bf37645..3f1d0b7 100644
--- a/frontend/src/components/ui/patient/PatientsPage.tsx
+++ b/frontend/src/components/ui/patient/PatientsPage.tsx
@@ -142,7 +142,7 @@ export function PatientsPage() {
           isOpen={isCreateOpen}
           formData={patientForm}
           onChange={(patch) => setPatientForm((prev) => ({ ...prev, ...patch }))}
-          onSubmit={() => void handleCreatePatient()}
+          onSubmit={() => handleCreatePatient()}
           onClose={() => {
             setIsCreateOpen(false);
             setPatientForm(EMPTY_PATIENT_FORM);
diff --git a/frontend/src/components/ui/settings/AccountSettingsPage.tsx b/frontend/src/components/ui/settings/AccountSettingsPage.tsx
index 244392e..252c173 100644
--- a/frontend/src/components/ui/settings/AccountSettingsPage.tsx
+++ b/frontend/src/components/ui/settings/AccountSettingsPage.tsx
@@ -435,7 +435,7 @@ export function AccountSettingsPage() {
                 type="button"
                 variant="primary"
                 isLoading={participationLoading}
-                onClick={() => void confirmRevokeParticipation()}
+                onClick={() => confirmRevokeParticipation()}
               >
                 {t('participateConfirmRevokeConfirm')}
               </Button>
diff --git a/frontend/src/components/ui/settings/OwnerWorkingHoursDialog.tsx b/frontend/src/components/ui/settings/OwnerWorkingHoursDialog.tsx
index 6105d1b..fc964f2 100644
--- a/frontend/src/components/ui/settings/OwnerWorkingHoursDialog.tsx
+++ b/frontend/src/components/ui/settings/OwnerWorkingHoursDialog.tsx
@@ -140,7 +140,7 @@ export function OwnerWorkingHoursDialog({
             type="button"
             variant="outline"
             isLoading={loading}
-            onClick={() => void handleSkip()}
+            onClick={() => handleSkip()}
           >
             {tStaff('skipForNow')}
           </Button>
@@ -148,7 +148,7 @@ export function OwnerWorkingHoursDialog({
             type="button"
             isLoading={loading}
             disabled={Boolean(validationError)}
-            onClick={() => void handleSave()}
+            onClick={() => handleSave()}
           >
             {t('participateSaveHours')}
           </Button>
diff --git a/frontend/src/components/ui/shared/Button.tsx b/frontend/src/components/ui/shared/Button.tsx
index 71e1384..ee2853f 100644
--- a/frontend/src/components/ui/shared/Button.tsx
+++ b/frontend/src/components/ui/shared/Button.tsx
@@ -1,14 +1,25 @@
-import React from 'react';
+import React, { useRef, useState } from 'react';
 
 type ButtonVariant = 'primary' | 'secondary' | 'outline' | 'danger' | 'ghost';
 type ButtonSize = 'sm' | 'md' | 'lg';
 
-interface ButtonProps extends React.ButtonHTMLAttributes<HTMLButtonElement> {
+type ButtonClickHandler = (
+  event: React.MouseEvent<HTMLButtonElement>,
+) => void | Promise<void>;
+
+interface ButtonProps extends Omit<React.ButtonHTMLAttributes<HTMLButtonElement>, 'onClick'> {
   variant?: ButtonVariant;
   size?: ButtonSize;
+  /** External loading (e.g. form-level busy). ORed with auto-pending from async onClick. */
   isLoading?: boolean;
   fullWidth?: boolean;
   children: React.ReactNode;
+  /**
+   * If the handler returns a Promise, the button stays loading/disabled until it
+   * settles — prevents double-clicks without a separate busy flag per call site.
+   * Prefer `onClick={() => doThing()}` over `onClick={() => void doThing()}`.
+   */
+  onClick?: ButtonClickHandler;
 }
 
 export const Button: React.FC<ButtonProps> = ({
@@ -19,15 +30,20 @@ export const Button: React.FC<ButtonProps> = ({
   children,
   className = '',
   disabled,
+  onClick,
   ...props
 }) => {
+  const [autoPending, setAutoPending] = useState(false);
+  const autoPendingRef = useRef(false);
+
+  const pending = isLoading || autoPending;
+
   const baseClasses =
     'inline-flex items-center justify-center rounded-[var(--radius-md)] font-medium transition-all duration-200 ' +
     'focus:outline-none focus:ring-2 focus:ring-primary/40 disabled:cursor-not-allowed';
 
   const variantClasses: Record<ButtonVariant, string> = {
-    primary:
-      'bg-primary text-white hover:opacity-90 disabled:opacity-60',
+    primary: 'bg-primary text-white hover:opacity-90 disabled:opacity-60',
 
     secondary:
       'bg-surface-elevated text-text-primary border border-border hover:border-border-strong disabled:opacity-50',
@@ -48,14 +64,34 @@ export const Button: React.FC<ButtonProps> = ({
   };
 
   const widthClass = fullWidth ? 'w-full' : '';
-  const loadingClass = isLoading ? 'opacity-70 animate-pulse pointer-events-none' : '';
+  const loadingClass = pending ? 'opacity-70 animate-pulse pointer-events-none' : '';
+
+  const handleClick = (event: React.MouseEvent<HTMLButtonElement>) => {
+    if (disabled || pending || autoPendingRef.current) {
+      event.preventDefault();
+      return;
+    }
+    if (!onClick) return;
+
+    const result = onClick(event);
+    if (result != null && typeof (result as Promise<void>).then === 'function') {
+      autoPendingRef.current = true;
+      setAutoPending(true);
+      void Promise.resolve(result).finally(() => {
+        autoPendingRef.current = false;
+        setAutoPending(false);
+      });
+    }
+  };
 
   return (
     <button
-      className={`${baseClasses} ${variantClasses[variant]} ${sizeClasses[size]} ${widthClass} ${loadingClass} ${className}`}
-      disabled={disabled || isLoading}
-      aria-busy={isLoading || undefined}
+      type="button"
       {...props}
+      className={`${baseClasses} ${variantClasses[variant]} ${sizeClasses[size]} ${widthClass} ${loadingClass} ${className}`}
+      disabled={disabled || pending}
+      aria-busy={pending || undefined}
+      onClick={handleClick}
     >
       {children}
     </button>
diff --git a/frontend/src/components/ui/shared/LanguageToggle.tsx b/frontend/src/components/ui/shared/LanguageToggle.tsx
index 0ed6c48..b7e839f 100644
--- a/frontend/src/components/ui/shared/LanguageToggle.tsx
+++ b/frontend/src/components/ui/shared/LanguageToggle.tsx
@@ -79,7 +79,7 @@ export function LanguageToggle() {
                 <button
                   type="button"
                   className="flex w-full items-center justify-between gap-3 px-3 py-2 text-sm text-text-primary hover:bg-background-card/70"
-                  onClick={() => void switchLocale(option)}
+                  onClick={() => switchLocale(option)}
                 >
                   <span>{t(option)}</span>
                   {selected && <Check className="h-4 w-4 text-primary shrink-0" />}
diff --git a/frontend/src/components/ui/staff/StaffPage.tsx b/frontend/src/components/ui/staff/StaffPage.tsx
index e007f00..fe4c64b 100644
--- a/frontend/src/components/ui/staff/StaffPage.tsx
+++ b/frontend/src/components/ui/staff/StaffPage.tsx
@@ -597,39 +597,37 @@ export function StaffPage() {
                 variant="outline"
                 size="sm"
                 isLoading={copyingInviteMembershipId === lastInviteInfo.membershipId}
-                onClick={() => {
+                onClick={async () => {
                   const member = members.find((item) => item.id === lastInviteInfo.membershipId);
                   if (member) {
-                    void copyStaffInviteLink(member);
+                    await copyStaffInviteLink(member);
                     return;
                   }
-                  void (async () => {
-                    setCopyingInviteMembershipId(lastInviteInfo.membershipId);
-                    toast.setError('');
-                    try {
-                      const res = await staffApi.getInvitationLink(lastInviteInfo.membershipId);
-                      if (currentOrganization?.id) {
-                        const nextLinks = {
-                          ...pendingInviteLinks,
-                          [lastInviteInfo.membershipId]: {
-                            membershipId: lastInviteInfo.membershipId,
-                            email: lastInviteInfo.email,
-                            invitationUrl: res.data.invitationUrl,
-                          },
-                        };
-                        setPendingInviteLinks(nextLinks);
-                        writeStoredInviteLinks(currentOrganization.id, nextLinks);
-                      }
-                      setLastInviteInfo({ ...lastInviteInfo, invitationUrl: res.data.invitationUrl });
-                      await navigator.clipboard.writeText(res.data.invitationUrl);
-                      setCopiedInviteMembershipId(lastInviteInfo.membershipId);
-                      setTimeout(() => setCopiedInviteMembershipId(null), 1500);
-                    } catch (e) {
-                      toast.showError(getUserFacingError(e, tErrors, t('errorCopyInvite')));
-                    } finally {
-                      setCopyingInviteMembershipId(null);
+                  setCopyingInviteMembershipId(lastInviteInfo.membershipId);
+                  toast.setError('');
+                  try {
+                    const res = await staffApi.getInvitationLink(lastInviteInfo.membershipId);
+                    if (currentOrganization?.id) {
+                      const nextLinks = {
+                        ...pendingInviteLinks,
+                        [lastInviteInfo.membershipId]: {
+                          membershipId: lastInviteInfo.membershipId,
+                          email: lastInviteInfo.email,
+                          invitationUrl: res.data.invitationUrl,
+                        },
+                      };
+                      setPendingInviteLinks(nextLinks);
+                      writeStoredInviteLinks(currentOrganization.id, nextLinks);
                     }
-                  })();
+                    setLastInviteInfo({ ...lastInviteInfo, invitationUrl: res.data.invitationUrl });
+                    await navigator.clipboard.writeText(res.data.invitationUrl);
+                    setCopiedInviteMembershipId(lastInviteInfo.membershipId);
+                    setTimeout(() => setCopiedInviteMembershipId(null), 1500);
+                  } catch (e) {
+                    toast.showError(getUserFacingError(e, tErrors, t('errorCopyInvite')));
+                  } finally {
+                    setCopyingInviteMembershipId(null);
+                  }
                 }}
               >
                 {copiedInviteMembershipId === lastInviteInfo.membershipId
@@ -661,7 +659,7 @@ export function StaffPage() {
             canShareInviteLink={canShareStaffInviteLink}
             canEnable={canEnableStaff}
             canDisable={canDisableStaff}
-            onCopyInviteLink={(member) => void copyStaffInviteLink(member)}
+            onCopyInviteLink={(member) => copyStaffInviteLink(member)}
             onEnable={setEnableTarget}
             onDisable={setDisableTarget}
             onEdit={openEdit}
@@ -747,7 +745,7 @@ export function StaffPage() {
                             type="button"
                             className="p-2 rounded-md text-text-secondary hover:bg-background-card/80 hover:text-text-primary disabled:opacity-50"
                             disabled={copyingInviteMembershipId === m.id}
-                            onClick={() => void copyStaffInviteLink(m)}
+                            onClick={() => copyStaffInviteLink(m)}
                             aria-label={t('copyInviteLink')}
                             title={t('copyInviteLinkTitle')}
                           >
@@ -930,7 +928,7 @@ export function StaffPage() {
                     type="button"
                     isLoading={inviteLoading}
                     disabled={!inviteEmail.trim() || !inviteName.trim()}
-                    onClick={() => void submitInvite(false)}
+                    onClick={() => submitInvite(false)}
                   >
                     {t('sendInvite')}
                   </Button>
@@ -941,7 +939,7 @@ export function StaffPage() {
                     type="button"
                     variant="outline"
                     isLoading={inviteLoading}
-                    onClick={() => void submitInvite(false)}
+                    onClick={() => submitInvite(false)}
                   >
                     {t('skipForNow')}
                   </Button>
@@ -949,7 +947,7 @@ export function StaffPage() {
                     type="button"
                     isLoading={inviteLoading}
                     disabled={Boolean(inviteHoursValidationError)}
-                    onClick={() => void submitInvite(true)}
+                    onClick={() => submitInvite(true)}
                   >
                     {t('sendInvite')}
                   </Button>
@@ -1004,7 +1002,7 @@ export function StaffPage() {
                 variant="primary"
                 isLoading={enablingMembershipId === enableTarget.id}
                 disabled={Boolean(enablingMembershipId) || !hasAvailableSeat}
-                onClick={() => void confirmEnableMember()}
+                onClick={() => confirmEnableMember()}
               >
                 {t('enableMemberButton')}
               </Button>
@@ -1054,7 +1052,7 @@ export function StaffPage() {
                 variant="danger"
                 isLoading={disablingMembershipId === disableTarget.id}
                 disabled={Boolean(disablingMembershipId)}
-                onClick={() => void confirmDisableMember()}
+                onClick={() => confirmDisableMember()}
               >
                 {t('disableMemberButton')}
               </Button>
@@ -1136,7 +1134,7 @@ export function StaffPage() {
                     {tCommon('next')}
                   </Button>
                 ) : (
-                  <Button type="button" isLoading={editLoading} onClick={() => void submitEdit()}>
+                  <Button type="button" isLoading={editLoading} onClick={() => submitEdit()}>
                     {tCommon('save')}
                   </Button>
                 )
@@ -1145,7 +1143,7 @@ export function StaffPage() {
                   type="button"
                   isLoading={editLoading}
                   disabled={Boolean(editHoursValidationError)}
-                  onClick={() => void submitEdit()}
+                  onClick={() => submitEdit()}
                 >
                   {tCommon('save')}
                 </Button>
diff --git a/frontend/src/components/ui/treatment/LabCasesDispatchPanel.tsx b/frontend/src/components/ui/treatment/LabCasesDispatchPanel.tsx
index 3af6d7b..d0df2c1 100644
--- a/frontend/src/components/ui/treatment/LabCasesDispatchPanel.tsx
+++ b/frontend/src/components/ui/treatment/LabCasesDispatchPanel.tsx
@@ -45,8 +45,8 @@ interface LabCasesDispatchPanelProps {
   canInviteLab?: boolean;
   onInviteLab?: () => void;
   sendBusyId: string | null;
-  onAddLabCase: () => void;
-  onSendLabCase: (labCase: LabCaseDraft, comment?: string) => void;
+  onAddLabCase: () => void | Promise<void>;
+  onSendLabCase: (labCase: LabCaseDraft, comment?: string) => void | Promise<void>;
   onCommentError?: (message: string) => void;
 }
 
diff --git a/frontend/src/components/ui/treatment/TreatmentWorkspace.tsx b/frontend/src/components/ui/treatment/TreatmentWorkspace.tsx
index a672cc9..b8b4565 100644
--- a/frontend/src/components/ui/treatment/TreatmentWorkspace.tsx
+++ b/frontend/src/components/ui/treatment/TreatmentWorkspace.tsx
@@ -2054,8 +2054,8 @@ export function TreatmentWorkspace({
                     });
                   }}
                   sendBusyId={sendBusyId}
-                  onAddLabCase={() => void handleAddLabCase()}
-                  onSendLabCase={(lc, comment) => void handleSendLabCase(lc, comment)}
+                  onAddLabCase={() => handleAddLabCase()}
+                  onSendLabCase={(lc, comment) => handleSendLabCase(lc, comment)}
                   onCommentError={showError}
                   canInviteLab={canAccessOrganizations}
                   onInviteLab={() => router.push('/organizations?action=invite-lab')}
diff --git a/frontend/src/lib/hooks/useAsyncAction.ts b/frontend/src/lib/hooks/useAsyncAction.ts
new file mode 100644
index 0000000..2daf89a
--- /dev/null
+++ b/frontend/src/lib/hooks/useAsyncAction.ts
@@ -0,0 +1,50 @@
+'use client';
+
+import { useCallback, useRef, useState } from 'react';
+
+/**
+ * Runs an async action at most once at a time (sync re-entry guard via ref).
+ * Use for API mutations from buttons/controls that are not the shared Button,
+ * or when several controls share one pending flag.
+ */
+export function useAsyncAction() {
+  const [pending, setPending] = useState(false);
+  const pendingRef = useRef(false);
+
+  const run = useCallback(async <T,>(fn: () => Promise<T>): Promise<T | undefined> => {
+    if (pendingRef.current) return undefined;
+    pendingRef.current = true;
+    setPending(true);
+    try {
+      return await fn();
+    } finally {
+      pendingRef.current = false;
+      setPending(false);
+    }
+  }, []);
+
+  return { pending, run };
+}
+
+/**
+ * Same as useAsyncAction, but tracks which row/id is in flight so list UIs
+ * can disable sibling actions while one mutation runs.
+ */
+export function useAsyncActionById() {
+  const [pendingId, setPendingId] = useState<string | null>(null);
+  const pendingIdRef = useRef<string | null>(null);
+
+  const run = useCallback(async <T,>(id: string, fn: () => Promise<T>): Promise<T | undefined> => {
+    if (pendingIdRef.current) return undefined;
+    pendingIdRef.current = id;
+    setPendingId(id);
+    try {
+      return await fn();
+    } finally {
+      pendingIdRef.current = null;
+      setPendingId(null);
+    }
+  }, []);
+
+  return { pendingId, run };
+}