@@ -0,0 +1,10 @@
+---
+'@object-ui/app-shell': patch
+---
+
+fix(app-shell): clearing a start node's Cron schedule in the flow designer no longer leaves a typed schedule block with no cadence
+
+Clause-②: no
+Metadata-protocol: none
+
+Clearing the Cron schedule box on a typed `config.schedule` such as `{ type: 'cron', expression, timezone }` used to store `{ type: 'cron', timezone }`. The engine binds nothing from that block, so a schedule flow silently never ran and a time-relative sweep did not fall back to its daily default the way the field's help says. The published `ScheduleSchema` refuses the same block. An untyped `{ expression, timezone }` had the same fault: clearing it left `{ timezone }`, which binds nothing either. The designer now removes `config.schedule` entirely whenever clearing the cron leaves no cadence, as it already did for an untyped `{ expression }`. Typing a cron over a typed block still keeps its `type` and `timezone`.
@@ -28,6 +28,10 @@ import * as React from 'react';
 import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
 import { render, screen, cleanup, fireEvent } from '@testing-library/react';
 import { resolveFlowTriggerKind } from '@objectstack/spec/automation';
+// The inspector's object picker and CEL authoring load `@objectstack/lint` with
+// function-body `import()`s. Warmed here so its first load is paid at
+// collection, not inside a case's bounded wait.
+import '@objectstack/lint';
 
 vi.mock('../previews/useFlowNodePalette', () => ({
   useActionConfigSchemas: () => ({}),
@@ -238,6 +242,30 @@ describe('a typed cron stores a descriptor the engine resolves to it (objectui#1
   });
 });
 
+describe('clearing the Cron schedule box drops a typed block it would leave with no cadence (objectstack#31383)', () => {
+  const typed: Array<[string, Record<string, unknown>]> = [
+    ['a typed cron', { type: 'cron', expression: '0 7 * * *' }],
+    ['a typed cron with a timezone', { type: 'cron', expression: '0 7 * * *', timezone: 'Asia/Shanghai' }],
+  ];
+  for (const [name, schedule] of typed) {
+    it(`clearing ${name} stores no schedule`, () => {
+      const { latest, patches } = mount(scheduleFlow({ schedule, objectName: 'todo_task' }));
+      fireEvent.change(controlOf('Cron schedule'), { target: { value: '' } });
+      expect(patches.length).toBeGreaterThan(0);
+      const config = startConfig(latest());
+      expect('schedule' in config).toBe(false);
+      expect(config.objectName).toBe('todo_task');
+      expect(controlOf('Cron schedule').value).toBe('');
+    });
+  }
+
+  it('CONTROL: clearing an untyped { expression } stores no schedule, as before', () => {
+    const { latest } = mount(scheduleFlow({ schedule: { expression: '0 6 * * *' }, objectName: 'todo_task' }));
+    fireEvent.change(controlOf('Cron schedule'), { target: { value: '' } });
+    expect('schedule' in startConfig(latest())).toBe(false);
+  });
+});
+
 describe('CONTROLS: the forms the field already read behave as before (objectui#12779)', () => {
   it('a typed cron with a timezone reads and writes with its type and timezone kept', () => {
     const { latest } = mount(scheduleFlow({ schedule: { type: 'cron', expression: '0 7 * * *', timezone: 'Asia/Shanghai' } }));
 
@@ -171,8 +171,54 @@ describe('a typed cron stores a descriptor that resolves to it (objectui#12779)'
     expect(scheduleWithExpression({ cron: '0 4 * * *' }, '')).toBeUndefined();
     expect(scheduleWithExpression({ expression: '0 4 * * *' }, undefined)).toBeUndefined();
     expect(scheduleWithExpression({ type: 'interval', intervalMs: 60000 }, undefined)).toBeUndefined();
-    expect(scheduleWithExpression({ type: 'cron', expression: '0 7 * * *', timezone: 'UTC' }, '')).toEqual({
+  });
+});
+
+describe('clearing never leaves a schedule block with no cadence (objectstack#31383)', () => {
+  // A typed block is judged by the published `ScheduleSchema`, which refuses a
+  // `type: 'cron'` with no `expression`; the engine binds nothing from it.
+  const typedCleared: Array<[string, Record<string, unknown>, unknown]> = [
+    ["a typed cron's expression", { type: 'cron', expression: '0 7 * * *' }, ''],
+    ["a typed cron's expression beside a timezone", { type: 'cron', expression: '0 7 * * *', timezone: 'UTC' }, ''],
+    ['a typed cron cleared to undefined', { type: 'cron', expression: '0 7 * * *', timezone: 'Asia/Shanghai' }, undefined],
+    ["a typed { cron }'s value", { type: 'cron', cron: '0 5 * * *', timezone: 'UTC' }, ''],
+    ['a typed cron that already carried no cadence', { type: 'cron', timezone: 'UTC' }, ''],
+    ['an interval type that carried only an expression', { type: 'interval', expression: '0 7 * * *' }, ''],
+    ['an unknown type beside an expression', { type: 'weekly', expression: '0 8 * * *', timezone: 'UTC' }, ''],
+  ];
+  for (const [name, schedule, value] of typedCleared) {
+    it(`clearing ${name} removes the whole schedule`, () => {
+      expect(normalizeScheduleCadence(scheduleWithExpression(schedule, value))).toBeNull();
+      expect(scheduleWithExpression(schedule, value)).toBeUndefined();
+    });
+  }
+
+  it('clearing an untyped { expression } beside a timezone removes the whole schedule', () => {
+    // `{ timezone }` alone binds nothing, and the flow parse reads nothing from it.
+    expect(normalizeScheduleCadence({ timezone: 'UTC' })).toBeNull();
+    expect(scheduleWithExpression({ expression: '0 4 * * *', timezone: 'UTC' }, '')).toBeUndefined();
+  });
+
+  it('CONTROL: clearing an untyped { expression } still removes the whole schedule', () => {
+    expect(scheduleWithExpression({ expression: '0 4 * * *' }, '')).toBeUndefined();
+  });
+
+  it('CONTROL: a cadence the cron stood in front of is kept when the cron is cleared', () => {
+    // The engine resolves `expression` ahead of `intervalMs`; with the cron gone the interval binds.
+    const stored = scheduleWithExpression({ expression: '0 4 * * *', intervalMs: 60000 }, '');
+    expect(stored).toEqual({ intervalMs: 60000 });
+    expect(normalizeScheduleCadence(stored)).toEqual({ type: 'interval', intervalMs: 60000 });
+  });
+
+  it('CONTROL: a cron typed over a typed block keeps its type and the other keys', () => {
+    expect(scheduleWithExpression({ type: 'cron', expression: '0 7 * * *', timezone: 'UTC' }, '0 9 * * *')).toEqual({
+      type: 'cron',
+      expression: '0 9 * * *',
+      timezone: 'UTC',
+    });
+    expect(scheduleWithExpression({ type: 'cron', timezone: 'UTC' }, '0 9 * * *')).toEqual({
       type: 'cron',
+      expression: '0 9 * * *',
       timezone: 'UTC',
     });
   });
 
@@ -526,7 +526,8 @@ const FLOW_NODE_CONFIG: Record<string, FlowConfigField[]> = {
     // it is (`readOnlyScheduleCadence`): the designer edits cron cadences only.
     // A commit rewrites the whole block through `scheduleWithExpression`, which
     // keeps a bare string a string and an object's `type` / `timezone`, so the
-    // stored cadence resolves to the cron the field shows.
+    // stored cadence resolves to the cron the field shows; clearing it never
+    // leaves a block with no cadence (objectstack#31383).
     //
     // objectui#12672 — gated on the flow's RESOLVED kind as well as on the
     // select: a `type: 'schedule'` flow, or a start node carrying
@@ -1705,7 +1706,12 @@ const NON_CRON_CADENCE_KEYS = ['intervalMs', 'every', 'at'] as const;
  *   only met on a descriptor the engine binds nothing from, since a live
  *   interval or once cadence offers no cron edit at all.
  * - Clearing removes `expression` and `cron`, or the whole schedule when it is
- *   a string, an interval or once cadence, or an object left empty.
+ *   a string, an interval or once cadence, or an object left with no cadence
+ *   (objectstack#31383). A `type` or `timezone` left behind is not a cadence:
+ *   the engine binds nothing from `{ type: 'cron', timezone }` or
+ *   `{ timezone }`, and the published `ScheduleSchema` refuses a typed block
+ *   with no `expression`. So a cleared `{ type: 'cron', expression, timezone }`
+ *   leaves no schedule, as an untyped `{ expression }` always did.
  */
 export function scheduleWithExpression(schedule: unknown, value: unknown): unknown {
   const expression = typeof value === 'string' ? value : '';
@@ -1717,12 +1723,12 @@ export function scheduleWithExpression(schedule: unknown, value: unknown): unkno
     const cadence = normalizeScheduleCadence(schedule);
     if (cadence && cadence.type !== 'cron') return undefined;
     delete next.expression;
-  } else {
-    if (typeof next.type === 'string' && next.type !== 'cron') delete next.type;
-    for (const key of NON_CRON_CADENCE_KEYS) delete next[key];
-    next.expression = expression;
+    return normalizeScheduleCadence(next) === null ? undefined : next;
   }
-  return Object.keys(next).length === 0 ? undefined : next;
+  if (typeof next.type === 'string' && next.type !== 'cron') delete next.type;
+  for (const key of NON_CRON_CADENCE_KEYS) delete next[key];
+  next.expression = expression;
+  return next;
 }
 
 /**