feat: add reminder system with cron scheduler and fix timezone formatting

- Add reminders to Prisma schema (Reminder model, TaskReminder relation)
- Add /api/reminders endpoint and cron send-reminders.ts script
- Add reminder fields to NewTaskModal and EditTaskModal components
- Fix reminder datetime serialization: use toISOString().slice(0,16) for
  UTC-safe YYYY-MM-DDTHH:mm format compatible with datetime-local inputs
- Update Dockerfile to install tsx for cron container
- Add AGENTS.md with project conventions
- Update docker-compose.yml with cron service and build context

src/app/api/reminders/route.ts

@@ -0,0 +1,62 @@
+import { NextRequest, NextResponse } from 'next/server';
+import prisma from '@/lib/db';
+
+export async function GET(request: NextRequest) {
+  const { searchParams } = new URL(request.url);
+  const sent = searchParams.get('sent');
+
+  try {
+    const where: Record<string, unknown> = {};
+    if (sent !== null) where.sent = sent === 'true';
+
+    const reminders = await prisma.reminder.findMany({
+      where,
+      orderBy: [{ dueDate: 'asc' }],
+    });
+
+    return NextResponse.json(
+      reminders.map((r) => ({
+        ...r,
+        dueDate: r.dueDate.toISOString(),
+      }))
+    );
+  } catch (error) {
+    console.error('Error fetching reminders:', error);
+    return NextResponse.json({ error: 'Failed to fetch reminders' }, { status: 500 });
+  }
+}
+
+export async function POST(request: NextRequest) {
+  let body;
+  try {
+    body = await request.json();
+  } catch {
+    return NextResponse.json({ error: 'Invalid JSON' }, { status: 400 });
+  }
+
+  const { message, dueDate } = body;
+
+  if (!message?.trim()) {
+    return NextResponse.json({ error: 'Message is required' }, { status: 400 });
+  }
+  if (!dueDate) {
+    return NextResponse.json({ error: 'dueDate is required' }, { status: 400 });
+  }
+
+  try {
+    const reminder = await prisma.reminder.create({
+      data: {
+        message: message.trim(),
+        dueDate: new Date(dueDate),
+      },
+    });
+
+    return NextResponse.json({
+      ...reminder,
+      dueDate: reminder.dueDate.toISOString(),
+    });
+  } catch (error) {
+    console.error('Error creating reminder:', error);
+    return NextResponse.json({ error: 'Failed to create reminder' }, { status: 500 });
+  }
+}

src/app/api/tasks/[id]/route.ts

@@ -2,6 +2,8 @@ import { NextRequest, NextResponse } from 'next/server';
 import prisma from '@/lib/db';
 import { addDays, addWeeks, addMonths, addYears } from 'date-fns';
 
+
+
 export async function GET(
   request: NextRequest,
   { params }: { params: Promise<{ id: string }> }
@@ -13,6 +15,7 @@ export async function GET(
       where: { id },
       include: {
         children: { orderBy: { sortOrder: 'asc' } },
+        reminders: { orderBy: { reminder: 'asc' } },
       },
     });
 
@@ -24,6 +27,10 @@ export async function GET(
       ...task,
       dueDate: task.dueDate ? task.dueDate.toISOString().split('T')[0] : null,
       nextOccurrence: task.nextOccurrence ? task.nextOccurrence.toISOString().split('T')[0] : null,
+      reminders: task.reminders.map((r) => ({
+        ...r,
+        reminder: r.reminder.toISOString().slice(0, 16),
+      })),
       subtasks: task.children.map((c) => ({
         ...c,
         dueDate: c.dueDate ? c.dueDate.toISOString().split('T')[0] : null,
@@ -49,7 +56,7 @@ export async function PUT(
     return NextResponse.json({ error: 'Invalid JSON' }, { status: 400 });
   }
 
-  const { title, description, projectId, priority, dueDate, status, recurrenceRule, recurrenceInterval, nextOccurrence } = body;
+  const { title, description, projectId, priority, dueDate, status, recurrenceRule, recurrenceInterval, nextOccurrence, reminders } = body;
 
   if (!title?.trim()) {
     return NextResponse.json({ error: 'Title is required' }, { status: 400 });
@@ -68,6 +75,21 @@ export async function PUT(
         recurrenceRule: recurrenceRule,
         recurrenceInterval: recurrenceInterval,
         nextOccurrence: nextOccurrence ? new Date(nextOccurrence) : undefined,
+        reminders: {
+          deleteMany: {},
+          create: (reminders || []).map((r: string) => {
+            // Parse local datetime string and construct Date to preserve local time
+            const [datePart, timePart] = r.split('T');
+            const [year, month, day] = datePart.split('-').map(Number);
+            const [hours, minutes] = timePart.split(':').map(Number);
+            return {
+              reminder: new Date(Date.UTC(year, month - 1, day, hours, minutes)),
+            };
+          }),
+        },
+      },
+      include: {
+        reminders: { orderBy: { reminder: 'asc' } },
       },
     });
 
@@ -75,6 +97,10 @@ export async function PUT(
       ...task,
       dueDate: task.dueDate ? task.dueDate.toISOString().split('T')[0] : null,
       nextOccurrence: task.nextOccurrence ? task.nextOccurrence.toISOString().split('T')[0] : null,
+      reminders: task.reminders.map((r) => ({
+        ...r,
+        reminder: r.reminder.toISOString().slice(0, 16),
+      })),
     });
   } catch (error) {
     console.error('Error updating task:', error);

src/app/api/tasks/route.ts

@@ -1,6 +1,8 @@
 import { NextRequest, NextResponse } from 'next/server';
 import prisma from '@/lib/db';
 
+
+
 export async function GET(request: NextRequest) {
   const { searchParams } = new URL(request.url);
 
@@ -29,13 +31,23 @@ export async function GET(request: NextRequest) {
       ? [{ priority: 'asc' }, { title: 'asc' }]
       : [{ dueDate: { sort: 'asc', nulls: 'last' } }, { title: 'asc' }];
 
-    const tasks = await prisma.task.findMany({ where, orderBy });
+    const tasks = await prisma.task.findMany({
+      where,
+      orderBy,
+      include: {
+        reminders: { orderBy: { reminder: 'asc' } },
+      },
+    });
 
     return NextResponse.json(
       tasks.map((t) => ({
         ...t,
         dueDate: t.dueDate ? t.dueDate.toISOString().split('T')[0] : null,
         nextOccurrence: t.nextOccurrence ? t.nextOccurrence.toISOString().split('T')[0] : null,
+        reminders: t.reminders.map((r) => ({
+          ...r,
+          reminder: r.reminder.toISOString().slice(0, 16),
+        })),
       }))
     );
   } catch (error) {
@@ -52,14 +64,17 @@ export async function POST(request: NextRequest) {
     return NextResponse.json({ error: 'Invalid JSON' }, { status: 400 });
   }
 
-  const { title, description, projectId, priority, dueDate, status, recurrenceRule, recurrenceInterval, parentTaskId } = body;
+  const {
+    title, description, projectId, priority, dueDate,
+    status, recurrenceRule, recurrenceInterval, parentTaskId,
+    reminders,
+  } = body;
 
   if (!title?.trim()) {
     return NextResponse.json({ error: 'Title is required' }, { status: 400 });
   }
 
   try {
-    // Get max sort_order for the project (or overall if no project)
     const maxSort = await prisma.task.aggregate({
       where: projectId ? { projectId } : undefined,
       _max: { sortOrder: true },
@@ -77,6 +92,20 @@ export async function POST(request: NextRequest) {
         recurrenceInterval: recurrenceInterval || 1,
         parentTaskId: parentTaskId || undefined,
         sortOrder: (maxSort._max.sortOrder ?? 0) + 1,
+        reminders: {
+          create: (reminders || []).map((r: string) => {
+            // Parse local datetime string and construct Date to preserve local time
+            const [datePart, timePart] = r.split('T');
+            const [year, month, day] = datePart.split('-').map(Number);
+            const [hours, minutes] = timePart.split(':').map(Number);
+            return {
+              reminder: new Date(Date.UTC(year, month - 1, day, hours, minutes)),
+            };
+          }),
+        },
+      },
+      include: {
+        reminders: { orderBy: { reminder: 'asc' } },
       },
     });
 
@@ -84,6 +113,10 @@ export async function POST(request: NextRequest) {
       ...task,
       dueDate: task.dueDate ? task.dueDate.toISOString().split('T')[0] : null,
       nextOccurrence: task.nextOccurrence ? task.nextOccurrence.toISOString().split('T')[0] : null,
+      reminders: task.reminders.map((r) => ({
+        ...r,
+        reminder: r.reminder.toISOString().slice(0, 16),
+      })),
     });
   } catch (error) {
     console.error('Error creating task:', error);

src/components/AppProvider.tsx

@@ -20,6 +20,13 @@ export interface Task {
   sortOrder: number;
   createdAt: string;
   updatedAt: string;
+  reminders?: Array<{
+    id: string;
+    taskId: string;
+    reminder: string;
+    sent: boolean;
+    createdAt: string;
+  }>;
 }
 
 export interface Project {

src/components/EditTaskModal.tsx

@@ -19,6 +19,7 @@ export default function EditTaskModal() {
   const [status, setStatus] = useState<'todo' | 'in_progress' | 'done'>('todo');
   const [recurrenceRule, setRecurrenceRule] = useState<'none' | 'daily' | 'weekly' | 'biweekly' | 'monthly' | 'yearly'>('none');
   const [recurrenceInterval, setRecurrenceInterval] = useState(1);
+  const [reminders, setReminders] = useState<string[]>([]);
   const [subtasks, setSubtasks] = useState<Task[]>([]);
   const [newSubtaskTitle, setNewSubtaskTitle] = useState('');
 
@@ -35,18 +36,35 @@ export default function EditTaskModal() {
     }
   }, [editingTask]);
 
-  // Fetch subtasks when modal opens
+  // Fetch subtasks and reminders when modal opens
   useEffect(() => {
     if (showEditTaskModal && editingTask) {
       fetch(`/api/tasks/${editingTask.id}`)
         .then(res => res.json())
         .then(data => {
           setSubtasks(data.subtasks || []);
+          if (data.reminders && data.reminders.length > 0) {
+            setReminders(data.reminders.map((r: any) => r.reminder));
+          }
         })
         .catch(console.error);
     }
   }, [showEditTaskModal, editingTask]);
 
+  const addReminder = () => {
+    setReminders([...reminders, '']);
+  };
+
+  const removeReminder = (index: number) => {
+    setReminders(reminders.filter((_, i) => i !== index));
+  };
+
+  const updateReminder = (index: number, value: string) => {
+    const updated = [...reminders];
+    updated[index] = value;
+    setReminders(updated);
+  };
+
   const handleSave = async () => {
     if (!editingTask || !title.trim()) return;
 
@@ -63,6 +81,7 @@ export default function EditTaskModal() {
           status,
           recurrenceRule,
           recurrenceInterval,
+          reminders: reminders.filter((r) => r !== ''),
         }),
       });
 
@@ -222,12 +241,50 @@ export default function EditTaskModal() {
               <option value="urgent">🔴 Urgent</option>
             </select>
 
-            <input
-              type="date"
-              value={dueDate}
-              onChange={(e) => setDueDate(e.target.value)}
-              className="bg-content border border-border rounded-lg px-3 py-2 text-sm focus:outline-none focus:border-accent"
-            />
+            <div>
+              <label className="block text-xs text-text-secondary mb-1">Due Date</label>
+              <input
+                type="date"
+                value={dueDate}
+                onChange={(e) => setDueDate(e.target.value)}
+                className="w-full bg-content border border-border rounded-lg px-3 py-2 text-sm focus:outline-none focus:border-accent"
+              />
+            </div>
+          </div>
+
+          {/* Reminders section */}
+          <div>
+            <div className="flex items-center justify-between mb-1">
+              <label className="text-xs text-text-secondary">🔔 Reminders</label>
+              <button
+                type="button"
+                onClick={addReminder}
+                className="text-xs text-accent hover:text-accent-hover transition-colors"
+              >
+                + Add Reminder
+              </button>
+            </div>
+            {reminders.length === 0 && (
+              <p className="text-xs text-text-secondary/60 italic">No reminders set</p>
+            )}
+            {reminders.map((reminder, index) => (
+              <div key={index} className="flex gap-2 mb-1.5">
+                <input
+                  type="datetime-local"
+                  value={reminder}
+                  onChange={(e) => updateReminder(index, e.target.value)}
+                  className="flex-1 bg-content border border-border rounded-lg px-3 py-2 text-sm focus:outline-none focus:border-accent"
+                />
+                <button
+                  type="button"
+                  onClick={() => removeReminder(index)}
+                  className="px-2 text-text-secondary hover:text-red-400 transition-colors text-sm"
+                  title="Remove reminder"
+                >
+                  ✕
+                </button>
+              </div>
+            ))}
           </div>
 
           {/* Recurrence */}

src/components/NewTaskModal.tsx

@@ -19,6 +19,7 @@ export default function NewTaskModal() {
   const [showRecurrence, setShowRecurrence] = useState(false);
   const [recurrenceRule, setRecurrenceRule] = useState<'none' | 'daily' | 'weekly' | 'biweekly' | 'monthly' | 'yearly'>('none');
   const [recurrenceInterval, setRecurrenceInterval] = useState(1);
+  const [reminders, setReminders] = useState<string[]>([]);
 
   const modalRef = useRef<HTMLDivElement>(null);
   const titleInputRef = useRef<HTMLInputElement>(null);
@@ -35,6 +36,20 @@ export default function NewTaskModal() {
     }
   }, [showNewTaskModal, selectedProject]);
 
+  const addReminder = () => {
+    setReminders([...reminders, '']);
+  };
+
+  const removeReminder = (index: number) => {
+    setReminders(reminders.filter((_, i) => i !== index));
+  };
+
+  const updateReminder = (index: number, value: string) => {
+    const updated = [...reminders];
+    updated[index] = value;
+    setReminders(updated);
+  };
+
   const handleCreate = async () => {
     if (!title.trim()) return;
 
@@ -51,6 +66,7 @@ export default function NewTaskModal() {
           status,
           recurrenceRule,
           recurrenceInterval,
+          reminders: reminders.filter((r) => r !== ''),
         }),
       });
 
@@ -59,6 +75,7 @@ export default function NewTaskModal() {
       setPriority('medium');
       setDueDate('');
       setStatus('todo');
+      setReminders([]);
       setShowRecurrence(false);
       setRecurrenceRule('none');
       setRecurrenceInterval(1);
@@ -87,11 +104,11 @@ export default function NewTaskModal() {
     >
       <div
         ref={modalRef}
-        className="bg-card rounded-xl w-full max-w-md mx-4 shadow-xl animate-slide-in"
+        className="bg-card rounded-xl w-full max-w-md mx-4 shadow-xl animate-slide-in max-h-[90vh] overflow-y-auto"
         onKeyDown={handleKeyDown}
       >
         {/* Header */}
-        <div className="flex items-center justify-between p-4 border-b border-border">
+        <div className="flex items-center justify-between p-4 border-b border-border sticky top-0 bg-card z-10">
           <h2 className="text-lg font-bold">New Task</h2>
           <button
             onClick={() => setShowNewTaskModal(false)}
@@ -147,12 +164,15 @@ export default function NewTaskModal() {
               <option value="urgent">🔴 Urgent</option>
             </select>
 
-            <input
-              type="date"
-              value={dueDate}
-              onChange={(e) => setDueDate(e.target.value)}
-              className="bg-content border border-border rounded-lg px-3 py-2 text-sm focus:outline-none focus:border-accent"
-            />
+            <div>
+              <label className="block text-xs text-text-secondary mb-1">Due Date</label>
+              <input
+                type="date"
+                value={dueDate}
+                onChange={(e) => setDueDate(e.target.value)}
+                className="w-full bg-content border border-border rounded-lg px-3 py-2 text-sm focus:outline-none focus:border-accent"
+              />
+            </div>
           </div>
 
           {/* Status */}
@@ -165,6 +185,41 @@ export default function NewTaskModal() {
             <option value="in_progress">In Progress</option>
           </select>
 
+          {/* Reminders section */}
+          <div>
+            <div className="flex items-center justify-between mb-1">
+              <label className="text-xs text-text-secondary">🔔 Reminders</label>
+              <button
+                type="button"
+                onClick={addReminder}
+                className="text-xs text-accent hover:text-accent-hover transition-colors"
+              >
+                + Add Reminder
+              </button>
+            </div>
+            {reminders.length === 0 && (
+              <p className="text-xs text-text-secondary/60 italic">No reminders set</p>
+            )}
+            {reminders.map((reminder, index) => (
+              <div key={index} className="flex gap-2 mb-1.5">
+                <input
+                  type="datetime-local"
+                  value={reminder}
+                  onChange={(e) => updateReminder(index, e.target.value)}
+                  className="flex-1 bg-content border border-border rounded-lg px-3 py-2 text-sm focus:outline-none focus:border-accent"
+                />
+                <button
+                  type="button"
+                  onClick={() => removeReminder(index)}
+                  className="px-2 text-text-secondary hover:text-red-400 transition-colors text-sm"
+                  title="Remove reminder"
+                >
+                  ✕
+                </button>
+              </div>
+            ))}
+          </div>
+
           {/* Recurrence toggle */}
           <div className="flex items-center justify-between">
             <button
@@ -213,7 +268,7 @@ export default function NewTaskModal() {
         </div>
 
         {/* Footer */}
-        <div className="flex items-center justify-end gap-2 p-4 border-t border-border">
+        <div className="flex items-center justify-end gap-2 p-4 border-t border-border sticky bottom-0 bg-card">
           <button
             onClick={() => setShowNewTaskModal(false)}
             className="px-4 py-2 text-sm text-text-secondary hover:text-text-primary transition-colors"