diff --git a/tests/Feature/LoopTaskTest.php b/tests/Feature/LoopTaskTest.php
new file mode 100644
index 000000000..9bc48c96f
--- /dev/null
+++ b/tests/Feature/LoopTaskTest.php
@@ -0,0 +1,206 @@
+<?php
+
+namespace Tests\Feature;
+
+use App\Models\Project;
+use App\Models\ProjectColumn;
+use App\Models\ProjectLog;
+use App\Models\ProjectTask;
+use App\Models\User;
+use App\Tasks\LoopTask;
+use Carbon\Carbon;
+use Illuminate\Foundation\Testing\DatabaseTransactions;
+use Tests\TestCase;
+
+/**
+ * LoopTask：周期任务到点生成新任务
+ *
+ * 回归：LoopTask 曾先提交副本、再刷新周期；刷新失败（Carbon 3 的 addDays 收到字符串）时
+ * 副本与原任务的 loop_at 都留在 10 分钟窗口内，每分钟翻倍并被同一轮 chunkById 继续扫到。
+ */
+class LoopTaskTest extends TestCase
+{
+    use DatabaseTransactions;
+
+    private Project $project;
+    private ProjectColumn $column;
+    private User $user;
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+        $this->user = User::createInstance([
+            'email' => 'looptask_' . uniqid() . '@example.com',
+            'userimg' => '',
+            'nickname' => 'LoopTaskUser',
+            'profession' => '',
+            'password' => md5('123456'),
+        ]);
+        $this->user->save();
+        $this->project = Project::createInstance([
+            'name' => 'looptask-' . uniqid(),
+            'desc' => '',
+            'userid' => $this->user->userid,
+            'personal' => 0,
+        ]);
+        $this->project->save();
+        $this->column = ProjectColumn::createInstance([
+            'project_id' => $this->project->id,
+            'name' => 'Default',
+        ]);
+        $this->column->save();
+    }
+
+    /**
+     * 创建一个顶级周期任务
+     * @param mixed $loop 重复周期（与库里一致，数字周期是字符串）
+     * @param Carbon $loopAt 下个周期时间
+     */
+    private function makeLoopTask($loop, Carbon $loopAt, array $overrides = []): ProjectTask
+    {
+        $task = ProjectTask::createInstance(array_merge([
+            'project_id' => $this->project->id,
+            'column_id' => $this->column->id,
+            'parent_id' => 0,
+            'name' => 'loop-' . uniqid(),
+            'userid' => $this->user->userid,
+            'start_at' => $loopAt->clone(),
+            'end_at' => $loopAt->clone()->addHour(),
+            'loop' => (string)$loop,
+            'loop_at' => $loopAt->clone(),
+        ], $overrides));
+        $task->save();
+        return $task;
+    }
+
+    private function runLoopTask(): void
+    {
+        (new LoopTask())->start();
+    }
+
+    private function projectTasks()
+    {
+        return ProjectTask::whereProjectId($this->project->id)->whereParentId(0)->orderBy('id')->get();
+    }
+
+    private function failureLogs(int $taskId)
+    {
+        return ProjectLog::whereTaskId($taskId)->where('detail', 'like', '生成重复任务失败%')->get();
+    }
+
+    public function test_custom_days_loop_creates_exactly_one_copy_and_closes_source(): void
+    {
+        $due = Carbon::now()->subMinute();
+        $source = $this->makeLoopTask('90', $due);
+
+        $this->runLoopTask();
+
+        $tasks = $this->projectTasks();
+        $this->assertCount(2, $tasks, '到点只应生成 1 个新任务');
+        $source = $source->fresh();
+        $this->assertSame('', (string)$source->loop, '原任务周期应被关闭');
+        $this->assertNull($source->loop_at);
+
+        $copy = $tasks->last();
+        $this->assertNotSame($source->id, $copy->id);
+        $this->assertSame('90', (string)$copy->loop, '新任务继承周期');
+        $this->assertTrue(Carbon::parse($copy->loop_at)->gt(Carbon::now()->addDays(88)), '新任务的下个周期应在约 90 天后');
+        $this->assertSame($due->toDateTimeString(), Carbon::parse($copy->start_at)->toDateTimeString(), '新任务开始时间等于原任务的 loop_at');
+        $this->assertSame(3600, (int)Carbon::parse($copy->start_at)->diffInSeconds(Carbon::parse($copy->end_at)), '新任务时长与原任务一致');
+    }
+
+    public function test_second_run_does_not_create_more_copies(): void
+    {
+        $this->makeLoopTask('90', Carbon::now()->subMinute());
+
+        $this->runLoopTask();
+        $this->runLoopTask();
+        $this->runLoopTask();
+
+        $this->assertCount(2, $this->projectTasks());
+    }
+
+    /**
+     * 历史脏数据（如 loop='0'）：刷新周期失败时必须整体回滚，不能留下 loop_at 仍在窗口内的副本
+     */
+    public function test_refresh_failure_rolls_back_without_leaving_copies(): void
+    {
+        $source = $this->makeLoopTask('0', Carbon::now()->subMinute());
+
+        $this->runLoopTask();
+
+        $this->assertCount(1, $this->projectTasks(), '失败不应留下任何副本');
+        $this->assertCount(1, $this->failureLogs($source->id), '应记录一条失败日志');
+        $this->assertNotNull($source->fresh()->loop_at, '失败时原任务周期保持不变，窗口内可重试');
+    }
+
+    public function test_repeated_failures_never_snowball(): void
+    {
+        $source = $this->makeLoopTask('0', Carbon::now()->subMinute());
+
+        for ($i = 0; $i < 5; $i++) {
+            $this->runLoopTask();
+        }
+
+        $this->assertCount(1, $this->projectTasks());
+        $this->assertCount(5, $this->failureLogs($source->id), '每轮只对原任务失败一次');
+    }
+
+    public function test_failure_rolls_back_subtasks_and_members_too(): void
+    {
+        $source = $this->makeLoopTask('0', Carbon::now()->subMinute());
+        $this->makeLoopTask('day', Carbon::now()->subMinute(), [
+            'parent_id' => $source->id,
+            'loop' => '',
+            'loop_at' => null,
+        ]);
+
+        $before = ProjectTask::whereProjectId($this->project->id)->count();
+        $this->runLoopTask();
+
+        $this->assertSame($before, ProjectTask::whereProjectId($this->project->id)->count(), '副本及其子任务都应回滚');
+    }
+
+    public function test_due_time_outside_window_is_ignored(): void
+    {
+        $this->makeLoopTask('day', Carbon::now()->subMinutes(30));
+        $this->makeLoopTask('day', Carbon::now()->addMinutes(30));
+
+        $this->runLoopTask();
+
+        $this->assertCount(2, $this->projectTasks());
+    }
+
+    public function test_archived_project_is_skipped(): void
+    {
+        $this->project->archived_at = Carbon::now();
+        $this->project->save();
+        $this->makeLoopTask('day', Carbon::now()->subMinute());
+
+        $this->runLoopTask();
+
+        $this->assertCount(1, $this->projectTasks());
+    }
+
+    public function test_subtask_is_not_processed(): void
+    {
+        $parent = $this->makeLoopTask('never', Carbon::now()->subDay(), ['loop' => '', 'loop_at' => null]);
+        $sub = $this->makeLoopTask('day', Carbon::now()->subMinute(), ['parent_id' => $parent->id]);
+
+        $this->runLoopTask();
+
+        $this->assertSame(0, ProjectTask::whereParentId($parent->id)->where('id', '!=', $sub->id)->count());
+        $this->assertCount(1, $this->projectTasks());
+    }
+
+    public function test_preset_loop_creates_one_copy_with_next_cycle(): void
+    {
+        $this->makeLoopTask('day', Carbon::now()->subMinute());
+
+        $this->runLoopTask();
+
+        $tasks = $this->projectTasks();
+        $this->assertCount(2, $tasks);
+        $this->assertTrue(Carbon::parse($tasks->last()->loop_at)->gt(Carbon::now()));
+    }
+}
diff --git a/tests/Unit/ProjectTaskRefreshLoopTest.php b/tests/Unit/ProjectTaskRefreshLoopTest.php
new file mode 100644
index 000000000..758a7ce24
--- /dev/null
+++ b/tests/Unit/ProjectTaskRefreshLoopTest.php
@@ -0,0 +1,122 @@
+<?php
+
+namespace Tests\Unit;
+
+use App\Models\ProjectTask;
+use Carbon\Carbon;
+use PHPUnit\Framework\Attributes\DataProvider;
+use Tests\TestCase;
+
+/**
+ * refreshLoop：重复周期 -> 下个周期时间
+ *
+ * 回归：Carbon 3 的 addDays() 不接受字符串，库里 loop 是 varchar（"90"），
+ * 曾导致自定义天数周期在 LoopTask 里抛 TypeError 并引发无限复制。
+ */
+class ProjectTaskRefreshLoopTest extends TestCase
+{
+    private function task($loop, ?Carbon $startAt = null): ProjectTask
+    {
+        $task = new ProjectTask();
+        $task->loop = $loop;
+        $task->start_at = $startAt;
+        return $task;
+    }
+
+    private function todayAt(string $time): Carbon
+    {
+        return Carbon::parse(date("Y-m-d {$time}"));
+    }
+
+    public function test_custom_days_accept_string_from_database(): void
+    {
+        $start = $this->todayAt('09:00:00');
+        $task = $this->task('90', $start);
+
+        $this->assertTrue($task->refreshLoop());
+        $this->assertSame($start->clone()->addDays(90)->toDateTimeString(), Carbon::parse($task->loop_at)->toDateTimeString());
+    }
+
+    public function test_custom_days_accept_int_from_request(): void
+    {
+        $start = $this->todayAt('09:00:00');
+        $task = $this->task(90, $start);
+
+        $this->assertTrue($task->refreshLoop());
+        $this->assertSame($start->clone()->addDays(90)->toDateTimeString(), Carbon::parse($task->loop_at)->toDateTimeString());
+    }
+
+    public function test_custom_days_without_start_time_use_today_as_base(): void
+    {
+        $task = $this->task('3');
+
+        $this->assertTrue($task->refreshLoop());
+        $this->assertSame(Carbon::today()->addDays(3)->toDateTimeString(), Carbon::parse($task->loop_at)->toDateTimeString());
+    }
+
+    public function test_past_start_time_is_rebased_to_today_keeping_time_of_day(): void
+    {
+        $task = $this->task('day', $this->todayAt('09:30:00')->subDays(5));
+
+        $this->assertTrue($task->refreshLoop());
+        $this->assertSame($this->todayAt('09:30:00')->addDay()->toDateTimeString(), Carbon::parse($task->loop_at)->toDateTimeString());
+    }
+
+    /**
+     * 0 天会让新任务的 loop_at 等于自己的开始时间，立刻再次命中周期窗口，必须拒绝
+     */
+    #[DataProvider('invalidLoops')]
+    public function test_invalid_loop_is_rejected_and_clears_loop_at(mixed $loop): void
+    {
+        $task = $this->task($loop, $this->todayAt('09:00:00'));
+        $task->loop_at = $this->todayAt('09:00:00');
+
+        $this->assertFalse($task->refreshLoop());
+        $this->assertNull($task->loop_at);
+    }
+
+    public static function invalidLoops(): array
+    {
+        return [
+            'zero string' => ['0'],
+            'zero int' => [0],
+            'zero padded' => ['00'],
+            'negative' => ['-1'],
+            'letters' => ['abc'],
+            'decimal' => ['1.5'],
+            'empty' => [''],
+            'null' => [null],
+        ];
+    }
+
+    #[DataProvider('presetLoops')]
+    public function test_preset_loops(string $loop, callable $expected): void
+    {
+        $start = $this->todayAt('09:00:00');
+        $task = $this->task($loop, $start);
+
+        $this->assertTrue($task->refreshLoop());
+        $this->assertSame($expected($start->clone())->toDateTimeString(), Carbon::parse($task->loop_at)->toDateTimeString());
+    }
+
+    public static function presetLoops(): array
+    {
+        return [
+            'day' => ['day', fn(Carbon $c) => $c->addDay()],
+            'weekdays' => ['weekdays', fn(Carbon $c) => $c->addWeekday()],
+            'week' => ['week', fn(Carbon $c) => $c->addWeek()],
+            'twoweeks' => ['twoweeks', fn(Carbon $c) => $c->addWeeks(2)],
+            'month' => ['month', fn(Carbon $c) => $c->addMonth()],
+            'year' => ['year', fn(Carbon $c) => $c->addYear()],
+        ];
+    }
+
+    public function test_never_clears_loop_at_and_succeeds(): void
+    {
+        $task = $this->task('never', $this->todayAt('09:00:00'));
+        $task->loop_at = $this->todayAt('09:00:00');
+
+        $this->assertTrue($task->refreshLoop());
+        $this->assertNull($task->loop_at);
+    }
+}