diff --git a/components/calendar/__tests__/task-modal-calendars.test.tsx b/components/calendar/__tests__/task-modal-calendars.test.tsx
new file mode 100644
index 000000000..1bd0abf30
--- /dev/null
+++ b/components/calendar/__tests__/task-modal-calendars.test.tsx
@@ -0,0 +1,36 @@
+import { render, screen, within } from '@testing-library/react';
+import { describe, it, expect, vi } from 'vitest';
+import { TaskModal } from '../task-modal';
+import type { Calendar, CalendarTask } from '@/lib/jmap/types';
+
+// The task editor's Calendar select offered the read-only Birthdays
+// calendar, which the event editor leaves out.
+
+const writable = { mayReadItems: true, mayWriteAll: true, mayWriteOwn: true, mayDelete: true };
+const readOnly = { mayReadItems: true, mayWriteAll: false, mayWriteOwn: false, mayDelete: false };
+const calendars = [
+  { id: 'work', name: 'Work', isShared: false, myRights: writable },
+  { id: 'personal', name: 'Personal', isShared: false, myRights: writable },
+  { id: 'birthdays', name: 'Birthdays', isShared: false, myRights: readOnly },
+  { id: 'feed', name: 'Holidays feed', isShared: false, myRights: writable },
+] as unknown as Calendar[];
+const isSubscriptionCalendar = (id: string) => id === 'feed';
+
+describe('task editor calendar select', () => {
+  it('lists only the calendars a task can go into', () => {
+    render(<TaskModal calendars={calendars} isSubscriptionCalendar={isSubscriptionCalendar} onSave={vi.fn()} onClose={vi.fn()} />);
+    const select = screen.getByLabelText('tasks.calendar');
+    const names = within(select).getAllByRole('option').map((o) => o.textContent);
+    expect(names).toEqual(['Work', 'Personal']);
+  });
+
+  it('keeps the calendar of a task that is already in a read-only one', () => {
+    const task = {
+      id: 't1', '@type': 'Task', title: 'Card for Ann', calendarIds: { birthdays: true },
+      progress: 'needs-action', priority: 0, due: null, showWithoutTime: true, alerts: null,
+    } as unknown as CalendarTask;
+    render(<TaskModal task={task} calendars={calendars} onSave={vi.fn()} onClose={vi.fn()} />);
+    const select = screen.getByLabelText('tasks.calendar') as HTMLSelectElement;
+    expect(select.value).toBe('birthdays');
+  });
+});
diff --git a/components/calendar/calendar-app.tsx b/components/calendar/calendar-app.tsx
index b9d63985b..b56e29ceb 100644
--- a/components/calendar/calendar-app.tsx
+++ b/components/calendar/calendar-app.tsx
@@ -2219,6 +2219,7 @@ export function CalendarApp({ linkSegments: routeSegments }: CalendarAppProps =
                 key={editTask?.id ?? 'new-task'}
                 task={editTask}
                 calendars={displayCalendars}
+                isSubscriptionCalendar={isSubscriptionCalendar}
                 onSave={handleSaveTask}
                 onDelete={handleDeleteTask}
                 onDirtyChange={setTaskEditorDirty}
@@ -2380,6 +2381,7 @@ export function CalendarApp({ linkSegments: routeSegments }: CalendarAppProps =
             key={editTask?.id ?? 'new-task'}
             task={editTask}
             calendars={displayCalendars}
+            isSubscriptionCalendar={isSubscriptionCalendar}
             onSave={handleSaveTask}
             onDelete={handleDeleteTask}
             onDirtyChange={setTaskEditorDirty}
diff --git a/components/calendar/task-modal.tsx b/components/calendar/task-modal.tsx
index 6d3069d4a..26507e54d 100644
--- a/components/calendar/task-modal.tsx
+++ b/components/calendar/task-modal.tsx
@@ -14,6 +14,7 @@ import { PluginSlot } from "@/components/plugins/plugin-slot";
 import { taskToView } from "@/lib/plugin-projection";
 import { ConfirmDialog } from "@/components/ui/confirm-dialog";
 import { useConfirmDialog } from "@/hooks/use-confirm-dialog";
+import { canCreateEventsIn } from "@/lib/calendar-editability";
 
 interface TaskModalProps {
   task?: CalendarTask | null;
@@ -25,6 +26,8 @@ interface TaskModalProps {
   /** Told whether the form holds changes that aren't saved, so the page can ask before it drops them. */
   onDirtyChange?: (dirty: boolean) => void;
   isMobile?: boolean;
+  /** Subscribed feeds are read-only: no tasks go there. */
+  isSubscriptionCalendar?: (calendarId: string) => boolean;
 }
 
 type PriorityLevel = "none" | "high" | "medium" | "low";
@@ -54,6 +57,7 @@ export function TaskModal({
   onClose,
   onDirtyChange,
   isMobile: _isMobile,
+  isSubscriptionCalendar,
 }: TaskModalProps) {
   const t = useTranslations("calendar");
   const tCommon = useTranslations("common");
@@ -63,7 +67,9 @@ export function TaskModal({
   // task-detail-section: the saved task, for an existing task only.
   const pluginTaskProps = useMemo(() => (task ? { task: taskToView(task) } : null), [task]);
 
-  const writableCalendars = calendars.filter(c => !c.isShared || c.myRights?.mayWriteAll || c.myRights?.mayWriteOwn);
+  // The calendars a task can go into: not read-only ones (Birthdays,
+  // feeds), the same rule as the event editor.
+  const writableCalendars = calendars.filter((c) => canCreateEventsIn(c, isSubscriptionCalendar));
   const defaultCalendarId = writableCalendars[0]?.id ?? calendars[0]?.id ?? "";
 
   const [title, setTitle] = useState(task?.title ?? "");
@@ -80,6 +86,8 @@ export function TaskModal({
     }
     return defaultCalendarId;
   });
+  // A task already in a read-only calendar keeps it listed.
+  const calendarOptions = calendars.filter((c) => c.id === calendarId || writableCalendars.includes(c));
   const [alertOption, setAlertOption] = useState<AlertOption>(() => {
     if (!task?.alerts) return "none";
     const first = Object.values(task.alerts)[0];
@@ -313,7 +321,7 @@ export function TaskModal({
         </div>
 
         {/* Calendar */}
-        {writableCalendars.length > 1 && (
+        {calendarOptions.length > 1 && (
           <div className="space-y-2">
             <label htmlFor={`${id}-calendar`} className="text-xs font-medium text-muted-foreground">
               {t("tasks.calendar")}
@@ -324,7 +332,7 @@ export function TaskModal({
               onChange={(e) => setCalendarId(e.target.value)}
               className="rounded-md border border-input bg-background px-3 py-1.5 text-sm w-full"
             >
-              {writableCalendars.map((cal) => (
+              {calendarOptions.map((cal) => (
                 <option key={cal.id} value={cal.id}>{cal.name}</option>
               ))}
             </select>