diff --git a/CHANGELOG.md b/CHANGELOG.md
index be74c157d0..254b20cc2f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -68,6 +68,15 @@ This section accumulates work toward the **2.3.0** milestone
 
 ### Fixed
 
+- **frontend:** Cron presets in the task form now require minute 0-59, hour
+  0-23 and day of month 1-31, so an out-of-range expression such as
+  `0 24 * * *` stays a custom schedule and keeps its original text. Previously,
+  it was parsed as a preset and could be clamped to a different time when
+  serialized for submission. Creating or duplicating a task with an invalid
+  expression, or updating its schedule configuration while the expression is
+  invalid, returns the Gateway's `422`; edits to other fields do not revalidate
+  an unchanged schedule. ([#8020])
+
 - **gateway:** Creating a thread with checkpoint-owned keys such as `step`,
   `parents` or `counters_since_delta_snapshot` in its metadata no longer
   leaves the thread broken. Those keys used to land on the thread's first
@@ -16415,6 +16424,7 @@ with **180 merged pull requests** since the first 2.0 milestone tag.
 [#7998]: https://github.com/bytedance/deer-flow/issues/7998
 [#8006]: https://github.com/bytedance/deer-flow/pull/8006
 [#8019]: https://github.com/bytedance/deer-flow/pull/8019
+[#8020]: https://github.com/bytedance/deer-flow/pull/8020
 [#8043]: https://github.com/bytedance/deer-flow/pull/8043
 [#8046]: https://github.com/bytedance/deer-flow/pull/8046
 [#8057]: https://github.com/bytedance/deer-flow/pull/8057
diff --git a/CHANGELOG_zh.md b/CHANGELOG_zh.md
index f5fd784a8e..0749d5a0c0 100644
--- a/CHANGELOG_zh.md
+++ b/CHANGELOG_zh.md
@@ -33,6 +33,12 @@
 
 ### 修复
 
+- **前端：** 任务表单的 Cron 预设现在要求分钟 0-59、小时 0-23、日期 1-31，
+  超出范围的表达式（例如 `0 24 * * *`）会保持为自定义并保留原始文本。此前它会被识别为预设，
+  在序列化以供提交时可能被限制到合法范围内的另一个时间。使用非法表达式创建或复制任务，
+  或在表达式仍非法时更新调度配置，会由 Gateway 返回 `422`；仅修改其他字段不会重新校验
+  未变化的调度配置。([#8020])
+
 - **网关：** 创建对话时在元数据中带上 `step`、`parents`、`counters_since_delta_snapshot`
   等由检查点自身维护的键，不再让该对话损坏。此前这些键会写入对话的首个检查点，错误的 `parents`
   会让该对话的历史记录永久返回 500，错误的 `step` 或增量计数器会让之后每一轮对话都失败；
@@ -12903,6 +12909,7 @@ DeerFlow 2.0 是围绕"超级智能体"框架的彻底重写，核心包含子
 [#7998]: https://github.com/bytedance/deer-flow/issues/7998
 [#8006]: https://github.com/bytedance/deer-flow/pull/8006
 [#8019]: https://github.com/bytedance/deer-flow/pull/8019
+[#8020]: https://github.com/bytedance/deer-flow/pull/8020
 [#8043]: https://github.com/bytedance/deer-flow/pull/8043
 [#8046]: https://github.com/bytedance/deer-flow/pull/8046
 [#8064]: https://github.com/bytedance/deer-flow/pull/8064
diff --git a/docs/guide/scheduled-tasks.md b/docs/guide/scheduled-tasks.md
index c5ca3b9e6c..e70c3cf951 100644
--- a/docs/guide/scheduled-tasks.md
+++ b/docs/guide/scheduled-tasks.md
@@ -48,6 +48,8 @@ Enable background polling with `config.yaml -> scheduler.enabled`. Manual trigge
 
 In the task form, switching an hourly, daily, weekly, or monthly schedule to **Custom cron** starts from its current timing, including selected weekdays or day of the month. Switching back to Custom cron after preset edits uses those edits rather than an older expression.
 
+Presets cover minute 0-59, hour 0-23 and day of month 1-31. An expression outside those ranges stays Custom and keeps its original text. Creating or duplicating a task with an invalid expression, or updating its schedule configuration while the expression is invalid, returns `422` from the Gateway. Editing only other fields, such as the title, leaves the schedule configuration out of the update request and does not revalidate the unchanged expression.
+
 ## Control proactive IM notifications
 
 Open **Settings → Notifications → IM notifications** to turn scheduled-task
diff --git a/frontend/src/core/scheduled-tasks/cron.ts b/frontend/src/core/scheduled-tasks/cron.ts
index 23de102898..b03bf30ed5 100644
--- a/frontend/src/core/scheduled-tasks/cron.ts
+++ b/frontend/src/core/scheduled-tasks/cron.ts
@@ -239,6 +239,12 @@ function isStar(field: string): boolean {
   return field === "*";
 }
 
+function cronNumber(field: string, min: number, max: number): number | null {
+  if (!/^\d+$/.test(field)) return null;
+  const value = Number(field);
+  return value >= min && value <= max ? value : null;
+}
+
 function isSimpleDowList(field: string): boolean {
   return field.split(",").every((tok) => /^[0-7]$/.test(tok));
 }
@@ -258,26 +264,23 @@ export function parseCron(cron: string): {
   const domF = fields[2]!;
   const monF = fields[3]!;
   const dowF = fields[4]!;
-  const numMinute = /^\d+$/.test(mF);
-  const numHour = /^\d+$/.test(hF);
-  const numDom = /^\d+$/.test(domF);
+  const minute = cronNumber(mF, 0, 59);
+  const hour = cronNumber(hF, 0, 23);
+  const dayOfMonth = cronNumber(domF, 1, 31);
   const stars = isStar(domF) && isStar(monF);
 
   // hourly: "M * * * *"
-  if (numMinute && isStar(hF) && stars && isStar(dowF)) {
-    return { preset: "hourly", parts: { minute: Number(mF) } };
+  if (minute !== null && isStar(hF) && stars && isStar(dowF)) {
+    return { preset: "hourly", parts: { minute } };
   }
   // daily: "M H * * *"
-  if (numMinute && numHour && stars && isStar(dowF)) {
-    return {
-      preset: "daily",
-      parts: { minute: Number(mF), hour: Number(hF) },
-    };
+  if (minute !== null && hour !== null && stars && isStar(dowF)) {
+    return { preset: "daily", parts: { minute, hour } };
   }
   // weekly: "M H * * DOW" (simple comma list of single digits only)
   if (
-    numMinute &&
-    numHour &&
+    minute !== null &&
+    hour !== null &&
     isStar(domF) &&
     isStar(monF) &&
     !isStar(dowF) &&
@@ -291,15 +294,21 @@ export function parseCron(cron: string): {
     if (ordered.length > 0) {
       return {
         preset: "weekly",
-        parts: { minute: Number(mF), hour: Number(hF), weekdays: ordered },
+        parts: { minute, hour, weekdays: ordered },
       };
     }
   }
   // monthly: "M H DOM * *"
-  if (numMinute && numHour && numDom && isStar(monF) && isStar(dowF)) {
+  if (
+    minute !== null &&
+    hour !== null &&
+    dayOfMonth !== null &&
+    isStar(monF) &&
+    isStar(dowF)
+  ) {
     return {
       preset: "monthly",
-      parts: { minute: Number(mF), hour: Number(hF), dayOfMonth: Number(domF) },
+      parts: { minute, hour, dayOfMonth },
     };
   }
   return { preset: "custom", parts: { raw: expr } };
@@ -395,13 +404,14 @@ function parseDisplayCron(cron: string): {
   }
   const fields = cron.split(/\s+/);
   const [m, h, dom, mon, dow] = fields;
+  if (fields.length !== 5 || !m || !h || !dow) {
+    return parsed;
+  }
+  const minute = cronNumber(m, 0, 59);
+  const hour = cronNumber(h, 0, 23);
   if (
-    fields.length !== 5 ||
-    !m ||
-    !h ||
-    !dow ||
-    !/^\d+$/.test(m) ||
-    !/^\d+$/.test(h) ||
+    minute === null ||
+    hour === null ||
     dom !== "*" ||
     mon !== "*" ||
     !/^[0-7](-[0-7])?(,[0-7](-[0-7])?)*$/.test(dow)
@@ -422,8 +432,8 @@ function parseDisplayCron(cron: string): {
   return {
     preset: "weekly",
     parts: {
-      minute: Number(m),
-      hour: Number(h),
+      minute,
+      hour,
       weekdays: orderedWeekdays([...days]),
     },
   };
diff --git a/frontend/tests/unit/core/scheduled-tasks/cron.test.ts b/frontend/tests/unit/core/scheduled-tasks/cron.test.ts
index 0dcc0ed703..e6ea1b5a6e 100644
--- a/frontend/tests/unit/core/scheduled-tasks/cron.test.ts
+++ b/frontend/tests/unit/core/scheduled-tasks/cron.test.ts
@@ -132,6 +132,21 @@ describe("parseCron", () => {
     expect(parseCron("garbage").preset).toBe("custom");
     expect(parseCron("garbage").parts.raw).toBe("garbage");
   });
+
+  test.each([
+    "60 * * * *",
+    "99 9 * * *",
+    "0 24 * * *",
+    "0 9 0 * *",
+    "0 9 32 * *",
+  ])("keeps the out-of-range cron %j as custom", (cron) => {
+    expect(parseCron(cron)).toEqual({ preset: "custom", parts: { raw: cron } });
+  });
+
+  test("accepts inclusive upper bounds for numeric fields", () => {
+    expect(parseCron("59 23 * * *").preset).toBe("daily");
+    expect(parseCron("0 9 31 * *").preset).toBe("monthly");
+  });
 });
 
 describe("describeSchedule", () => {
@@ -601,6 +616,13 @@ describe("describeTaskSchedule", () => {
     ).toBe("工作日 08:30 (Asia/Shanghai)");
   });
 
+  test("max valid weekdays still read as weekdays", () => {
+    expect(describeTaskSchedule(cronTask("59 23 * * 1-5"), "en-US")).toEqual({
+      text: "Weekdays at 23:59 (Asia/Shanghai)",
+      raw: "59 23 * * 1-5",
+    });
+  });
+
   test("daily reuses the preset wording", () => {
     expect(describeTaskSchedule(cronTask("0 9 * * *"), "en-US").text).toBe(
       "Every day at 09:00 (Asia/Shanghai)",
@@ -610,6 +632,16 @@ describe("describeTaskSchedule", () => {
     );
   });
 
+  test.each(["60 9 * * 1-5", "0 24 * * 1-5"])(
+    "does not describe the out-of-range cron %j as a preset",
+    (cron) => {
+      expect(describeTaskSchedule(cronTask(cron), "en-US")).toEqual({
+        text: "Custom schedule (Asia/Shanghai)",
+        raw: cron,
+      });
+    },
+  );
+
   test("a custom cron never shows the expression in text", () => {
     const { text, raw } = describeTaskSchedule(
       cronTask("*/15 9-17 * * 1-5"),