fix: prevent negative task durations and day end times

AGENTS.md

@@ -1,6 +1,6 @@
 # AGENTS.md - AI Assistant Codebase Guide
 
-**Last Updated:** 2026-09-18
+**Last Updated:** 2026-10-19
 **Version:** 2.8.0
 
 Timetraked is a React 18 + TypeScript time tracking PWA for freelancers and consultants, with dual storage (localStorage guest mode and optional Supabase cloud sync).
@@ -22,16 +22,16 @@ Timetraked is a React 18 + TypeScript time tracking PWA for freelancers and cons
 - When fixing a bug, add a regression test as part of the same change.
 - Verify version alignment between related dev tools (e.g., vitest + @vitest/coverage) when test errors appear.
 
-### Test File Inventory (~390 JS/TS tests across 37 files, plus 17 Rust unit tests across `src-tauri/src/backup.rs`/`menu.rs`/`quit_flush.rs` run via `cargo test`)
+### Test File Inventory (~410 JS/TS tests across 37 files, plus 17 Rust unit tests across `src-tauri/src/backup.rs`/`menu.rs`/`quit_flush.rs` run via `cargo test`)
 
 | File | Coverage |
 |---|---|
-| `src/utils/calculationUtils.test.ts` | `getDayStats`, hours/revenue/billable per-day and per-period |
+| `src/utils/calculationUtils.test.ts` | `getDayStats`, hours/revenue/billable per-day and per-period, plus legacy negative durations being ignored |
 | `src/utils/checklistUtils.test.ts` | `parseTaskChecklist`, `toggleDescriptionChecklistItem` |
 | `src/utils/exportUtils.test.ts` | `exportToCSV`, `exportToJSON`, `generateInvoiceData`, `parseCSVImport` |
 | `src/utils/reportUtils.test.ts` | Report generation utilities |
-| `src/utils/timeUtil.test.ts` | Time formatting utilities |
-| `src/contexts/TimeTracking.test.tsx` | Full context: day/task/archive management, todos, planned tasks, project CRUD, category CRUD, `discardDay`, `adjustTaskTime`, `addBackdatedDay`, client archive/restore |
+| `src/utils/timeUtil.test.ts` | Time formatting utilities, `elapsedMs` zero floor, `isEndBeforeStart` |
+| `src/contexts/TimeTracking.test.tsx` | Full context: day/task/archive management, todos, planned tasks, project CRUD, category CRUD, `discardDay`, `adjustTaskTime` (incl. end-before-start clamp), `endDay` never producing negative durations, `addBackdatedDay`, client archive/restore |
 | `src/contexts/TimeTrackingContext.forceSync.test.tsx` | `forceSyncToDatabase` behavior |
 | `src/services/dataService.test.ts` | `LocalStorageService` save/load round-trips |
 | `src/services/supabaseService.test.ts` | Upsert-only bulk saves and single-row deletes (`saveProjects`, `deleteProject`, `saveCategories`, `deleteCategory`, `saveTodos`), plus `getCurrentDay`/`saveCurrentDay`, `getArchivedDays` task pagination past the 1000-row PostgREST cap, `checkNewSchema` schema detection, and `migrateFromLocalStorage` (no-op/no-existing-data/client-name-reconcile/error-swallow paths) |
@@ -50,8 +50,8 @@ Timetraked is a React 18 + TypeScript time tracking PWA for freelancers and cons
 | `src/components/NewTaskForm.test.tsx` | Form render, submit, validation, cancel, FAB toggle |
 | `src/components/TaskItem.test.tsx` | Badge render, delete confirm, edit dialog |
 | `src/components/PlannedTaskPicker.test.tsx` | Dashboard empty-day picker: ordering, filtering, start vs resume, list cap |
-| `src/components/ArchiveEditDialog.test.tsx` | Archive edit dialog render and task editing flow |
-| `src/components/ArchivedTaskRow.test.tsx` | Inline expandable archived task row editing |
+| `src/components/ArchiveEditDialog.test.tsx` | Archive edit dialog render, task editing flow, and end-before-start validation (day form and Add Task) |
+| `src/components/ArchivedTaskRow.test.tsx` | Inline expandable archived task row editing, including end-before-start validation |
 | `src/components/dateParsing.test.ts` | Date parsing utilities |
 | `src/components/BackgroundTimerNotifier.test.tsx` | Document title/OS notification updates while a timer runs in the background |
 | `src/components/CommandPalette.test.tsx` | `Cmd/Ctrl+K` command palette actions and navigation |
@@ -172,7 +172,7 @@ export const MyComponent = () => {
 | `src/hooks/useLongPress.ts`                   | 500 ms hold detector for context menu trigger on touch                             |
 | `src/components/ui/responsive-select.tsx`     | `ResponsiveSelect` — branches on `useIsMobile()` to render a native `<select>` on mobile (OS picker) vs the Radix `Select` on desktop; flat `options` array API shared by `NewTaskForm`, `ProjectSheet`, `BackdatedEntryDialog`, `PlannedTaskDialog`, `ArchivedTaskRow` |
 | `src/components/PlannedTaskPicker.tsx`        | Empty started-day card on the Dashboard: lists in-progress/to-do planned tasks with Start (`pullPlannedTaskToDay`) / Resume (`addPlannedTaskToDay`) buttons. Task Board cards and the Tasks page header can also start the day (`startDayAndPullPlannedTask`, "now" rounded to 15 min, no dialog) |
-| `src/components/ArchivedTaskRow.tsx`          | Inline expandable row for editing a single task within `ArchiveEditDialog` (replaces the old `TaskEditInArchiveDialog` modal) |
+| `src/components/ArchivedTaskRow.tsx`          | Inline expandable row for editing a single task within `ArchiveEditDialog` (replaces the old `TaskEditInArchiveDialog` modal); disables Save and shows an inline alert when the end time is before the start |
 | `src/services/localStorageService/recovery.ts` | Lists/previews/restores localStorage schema-mismatch backup keys and desktop (Tauri) disk-backup snapshots; the read side of the write-only backup safety nets |
 | `src/hooks/useDataRecovery.ts`                | Unifies browser (`recovery.ts`) and desktop (`useElectronBackup`'s `listDiskBackups`/`readDiskBackup`, Tauri-backed) backup sources behind one list/preview/restore API |
 | `src/components/DataRecoveryDialog.tsx`       | Settings → "Data Recovery" (guest mode only): lists backups, previews entity-count diffs against current state, restores and reloads |
@@ -186,6 +186,15 @@ export const MyComponent = () => {
 
 ---
 
+## Time Tracking Invariants
+
+- **Tracked time is never negative.** Compute durations with `elapsedMs(start, end)` from `@/utils/timeUtil` (zero-floored), never a bare `end.getTime() - start.getTime()`. Rounding one end of a span to 15 minutes can push it before the other.
+- `endDay` clamps its rounded end time to the latest of the day start, the running task's start, and the latest recorded task end.
+- `adjustTaskTime` collapses an end-before-start edit to a zero-length task; calculation and format helpers ignore or zero any negative value already in storage.
+- Archive editors (`ArchivedTaskRow`, the `ArchiveEditDialog` day form and Add Task form) reject an end before the start via `isEndBeforeStart` and `END_BEFORE_START_MESSAGE`. Equal times are allowed, since rounding can collapse a short task to zero length.
+
+---
+
 ## Client Management
 
 Clients are a managed entity (added in the client-management feature) that backs the project form's client dropdown.

CHANGELOG.md

@@ -57,6 +57,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- Archive editors now reject an end time before the start time instead of silently saving a zero-length task. `ArchivedTaskRow` and the Add Task form in `ArchiveEditDialog` show an inline `role="alert"` message, set `aria-invalid`/`aria-describedby` on the end-time input, and disable Save/Add Task until corrected; the day summary form rejects it through its zod schema, and Save Changes reopens a collapsed summary editor so the error is visible. Equal start and end times remain allowed because 15-minute rounding can collapse a short task to zero length. New shared `isEndBeforeStart` and `END_BEFORE_START_MESSAGE` in `timeUtil`; `TimePicker` accepts `aria-invalid`
+  — `src/utils/timeUtil.ts`, `src/components/ArchivedTaskRow.tsx`, `src/components/ArchiveEditDialog.tsx`, `src/components/ui/scroll-time-picker.tsx`, `src/components/ArchivedTaskRow.test.tsx`, `src/components/ArchiveEditDialog.test.tsx`, `src/utils/timeUtil.test.ts`
+- Task durations and a day's end time can no longer go negative. `endDay` rounds the end time to 15 minutes while a running task's start is unrounded, so ending a day shortly after starting a task (e.g. task started 9:20, day ended 9:21 → rounded to 9:15) produced a negative task duration and an end time before the task began. `endDay` now never ends earlier than the day start, the running task's start, or the latest recorded task end. Every duration subtraction (task end, `beginTask`, `adjustTaskTime`, planned-task completion, archive task edit/add) goes through a new zero-floored `elapsedMs` helper, and `adjustTaskTime` collapses an end-before-start edit to a zero-length task. Stored negative values from earlier versions are ignored by the day/period/hours/revenue calculations and display as zero in `formatDuration`/`formatDurationLong`
+  — `src/utils/timeUtil.ts`, `src/utils/calculationUtils.ts`, `src/utils/reportUtils.ts`, `src/contexts/TimeTrackingContext.tsx`, `src/components/ArchivedTaskRow.tsx`, `src/components/ArchiveEditDialog.tsx`, `src/contexts/TimeTracking.test.tsx`, `src/utils/timeUtil.test.ts`, `src/utils/calculationUtils.test.ts`
 - Editing a current-day task's start time no longer leaves the day starting after its own first task: `adjustTaskTime` now pulls `dayStartTime` earlier when a task is moved before it (moving a task later leaves the day start alone). It also now persists the change through `saveCurrentDay` like the other task mutations, instead of only flagging unsaved changes and waiting for the next sync
   — `src/contexts/TimeTrackingContext.tsx`, `src/contexts/TimeTracking.test.tsx`
 - Archived-day editing (`ArchiveEditDialog`, `ArchivedTaskRow`) had several accessibility gaps and unmemoized re-render/re-parse patterns. The "Restore" button no longer grabs focus via `autoFocus` when the dialog opens, letting Radix's default dialog focus behavior take over instead of landing keyboard focus on a state-changing action before the user has read anything. The day-summary and per-task edit toggles now announce their expanded/collapsed state via `aria-expanded`/`aria-controls`. The tasks table's header cells gained `scope="col"` and the table itself an accessible name tied to the day being edited. Per-task delete now requires a same-row Confirm/Cancel step instead of removing the row on a single click, matching the destructive-action pattern used elsewhere (the task isn't persisted until "Save Changes," so this doesn't need the full undo-toast machinery). On the performance side, the day/task dirty-check (`tasksChanged`) and the `handleTaskSave`/`handleTaskDelete`/toggle-expand callbacks are now memoized (`useMemo`/`useCallback`), and `ArchivedTaskRow`/`MarkdownDisplay` are wrapped in `React.memo`, so expanding one task row no longer re-renders every sibling row or re-parses unrelated markdown

README-EXT.md

@@ -52,7 +52,7 @@ For the main overview, see [README.md](README.md).
 
 **Ongoing:**
 
-- View archived days on the **Archive** page.
+- View archived days on the **Archive** page. When editing an archived day, task, or new task, an end time before the start time is flagged inline and Save/Add Task stays disabled until it is corrected.
 - Manage projects and rates via **Archive → Projects**.
 - Customize categories on the **Categories** page.
 - Export data via **Archive → Export**.
@@ -70,7 +70,7 @@ For the main overview, see [README.md](README.md).
    - **Description** (optional) — detailed notes with markdown support
    - **Project** (optional) — assign to a client/project
    - **Category** (optional) — categorize the work type
-3. Task duration calculates automatically.
+3. Task duration calculates automatically. Durations are never negative: ending a day snaps its end time to the nearest 15 minutes but never earlier than the running task's start, and editing a task so it ends before it starts collapses it to zero length.
 4. Create new tasks as you switch between work items.
 
 **Evening:**
@@ -473,7 +473,7 @@ src/
 │   ├── checklistUtils.ts         # GFM checklist extraction
 │   ├── exportUtils.ts            # CSV import/export
 │   ├── reportUtils.ts            # Report grouping and formatting
-│   └── timeUtil.ts               # Time formatting
+│   └── timeUtil.ts               # Time formatting, 15-minute rounding, zero-floored `elapsedMs`, end-before-start check
 ├── App.css
 ├── App.tsx
 ├── index.css

README.md

@@ -16,7 +16,7 @@ A Progressive Web App (PWA) for time tracking built with React, TypeScript, and
 ## Features
 
 - **Daily Time Tracking** — start/stop your workday with clear daily boundaries
-- **Task Management** — create, edit, and delete tasks with real-time duration tracking
+- **Task Management** — create, edit, and delete tasks with real-time duration tracking; tracked time is never negative, and an end time earlier than its start is rejected in the archive editors
 - **Projects & Clients** — organize work by project with per-project hourly rates; projects and clients can be archived and restored
 - **Client Management** — maintain a managed client list with address and contact details; add, edit, and archive clients (blocked while they still have active projects); pick clients from a dropdown when creating projects
 - **Revenue Tracking** — automatic earnings calculation based on hourly rates
@@ -60,7 +60,7 @@ pnpm preview             # Preview production build
 
 # Code Quality
 pnpm lint                # ESLint
-pnpm test                # Vitest unit tests (395 tests across 38 files)
+pnpm test                # Vitest unit tests (410 tests across 37 files)
 
 # PWA Screenshots
 pnpm screenshots:install   # Install Playwright (first time)

agents/pitfalls.md

@@ -72,6 +72,19 @@ Any utility that needs archived days must consume the context or accept
 `DayRecord[]` as a parameter. Use `dayRecordsToArchivedDays()` from
 `src/utils/reportUtils.ts` to convert to the `ArchivedDay[]` shape.
 
+### 7. Subtracting Timestamps Directly
+
+```typescript
+// ❌ WRONG — goes negative when rounding moves one end past the other
+const duration = endTime.getTime() - startTime.getTime();
+
+// ✅ CORRECT — zero-floored
+import { elapsedMs } from "@/utils/timeUtil";
+const duration = elapsedMs(startTime, endTime);
+```
+
+Time forms that take a start and an end should also reject an end before the start with `isEndBeforeStart`.
+
 ---
 
 ## Architecture Gotchas

src/components/ArchiveEditDialog.test.tsx

@@ -1,5 +1,5 @@
 import { describe, it, expect, vi, beforeEach } from "vitest";
-import { render, screen, within } from "@testing-library/react";
+import { render, screen, within, fireEvent } from "@testing-library/react";
 import userEvent from "@testing-library/user-event";
 import { ArchiveEditDialog } from "@/components/ArchiveEditDialog";
 import { TooltipProvider } from "@/components/ui/tooltip";
@@ -185,4 +185,70 @@ describe("ArchiveEditDialog", () => {
     expect(lastTask.endTime.getHours()).toBe(17);
     expect(lastTask.endTime.getMinutes()).toBe(45);
   });
+
+  it("rejects a day end time before the start time and keeps the editor open with the error", async () => {
+    const user = userEvent.setup();
+    renderDialog({ day: buildDay(), isOpen: true, onClose: vi.fn() });
+
+    await user.click(screen.getByRole("button", { name: "Edit day summary" }));
+    fireEvent.change(screen.getByLabelText("Day end time"), {
+      target: { value: "08:00" },
+    });
+    await user.click(screen.getByRole("button", { name: /save changes/i }));
+
+    expect(
+      await screen.findByText("End time must be after start time.")
+    ).toBeInTheDocument();
+    expect(updateArchivedDay).not.toHaveBeenCalled();
+  });
+
+  it("opens the day-summary editor to show the error when a collapsed day is invalid", async () => {
+    const user = userEvent.setup();
+    const day = buildDay();
+    // Legacy bad data: the day ends before it starts.
+    day.endTime = new Date(2026, 5, 15, 8, 0, 0);
+    renderDialog({ day, isOpen: true, onClose: vi.fn() });
+
+    // Stage an unrelated task edit so Save Changes is enabled.
+    const taskTwoRow = screen.getByText("Task Two").closest("tr")!;
+    await user.click(within(taskTwoRow).getByRole("button", { name: "Edit task" }));
+    const titleInput = screen.getByLabelText(/Task Title/);
+    await user.clear(titleInput);
+    await user.type(titleInput, "Task Two Updated");
+    await user.click(screen.getByRole("button", { name: "Save" }));
+
+    expect(screen.queryByLabelText("Day end time")).not.toBeInTheDocument();
+    await user.click(screen.getByRole("button", { name: /save changes/i }));
+
+    expect(await screen.findByLabelText("Day end time")).toBeInTheDocument();
+    expect(
+      screen.getByText("End time must be after start time.")
+    ).toBeInTheDocument();
+    expect(updateArchivedDay).not.toHaveBeenCalled();
+  });
+
+  it("disables Add Task and shows an error when the new task ends before it starts", async () => {
+    const user = userEvent.setup();
+    renderDialog({ day: buildDay(), isOpen: true, onClose: vi.fn() });
+
+    await user.click(screen.getByRole("button", { name: "Add Task" }));
+    await user.type(screen.getByLabelText(/Task Title/), "Late task");
+    fireEvent.change(screen.getByLabelText("Task start time"), {
+      target: { value: "14:00" },
+    });
+    fireEvent.change(screen.getByLabelText("Task end time"), {
+      target: { value: "13:00" },
+    });
+
+    expect(screen.getByRole("alert")).toHaveTextContent(
+      "End time must be after start time."
+    );
+    expect(screen.getByRole("button", { name: "Add Task" })).toBeDisabled();
+
+    fireEvent.change(screen.getByLabelText("Task end time"), {
+      target: { value: "15:00" },
+    });
+    expect(screen.queryByRole("alert")).not.toBeInTheDocument();
+    expect(screen.getByRole("button", { name: "Add Task" })).toBeEnabled();
+  });
 });