revert reka-ui update; fix DST cellMath;

.github/workflows/npm-test-unit.yml

@@ -0,0 +1,27 @@
+name: NPM Test Unit
+
+on: [push]
+permissions:
+  contents: read
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    env:
+      TZ: UTC
+
+    steps:
+      - name: "Checkout code"
+        uses: actions/checkout@v4
+
+      - name: "Use Node.js"
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20.x'
+
+      - name: "Install npm dependencies"
+        run: npm ci
+
+      - name: "Run vitest"
+        run: npm run test:unit

.npmrc

@@ -0,0 +1 @@
+min-release-age=7

app/Service/TimeEntryFilter.php

@@ -62,7 +62,7 @@ class TimeEntryFilter
         if ($start === null) {
             return $this;
         }
-        $this->builder->where('start', '>', $start);
+        $this->builder->where('start', '>=', $start);
 
         return $this;
     }

docker-compose.yml

@@ -107,7 +107,7 @@ services:
             - sail
             - reverse-proxy
     playwright:
-        image: mcr.microsoft.com/playwright:v1.58.1-jammy
+        image: mcr.microsoft.com/playwright:v1.59.1-jammy
         command: ['npx', 'playwright', 'test', '--ui-port=8080', '--ui-host=0.0.0.0']
         working_dir: /src
         extra_hosts:

e2e/members.spec.ts

@@ -907,7 +907,7 @@ test.describe('Employee Sidebar Navigation', () => {
 
         // Visible links
         await expect(employee.page.getByRole('link', { name: 'Dashboard' })).toBeVisible();
-        await expect(employee.page.getByRole('link', { name: 'Time' })).toBeVisible();
+        await expect(employee.page.getByRole('link', { name: 'Time', exact: true })).toBeVisible();
         await expect(employee.page.getByRole('link', { name: 'Calendar' })).toBeVisible();
         await expect(employee.page.getByRole('link', { name: 'Projects' })).toBeVisible();
         await expect(employee.page.getByRole('link', { name: 'Clients' })).toBeVisible();

e2e/projects.spec.ts

@@ -640,7 +640,7 @@ test('test that creating a project with estimated time in human-readable format
     await page.getByLabel('Project Name').fill(newProjectName);
 
     // Fill in estimated time using human-readable format
-    const estimatedTimeInput = page.getByPlaceholder('e.g. 2h 30m or 1.5');
+    const estimatedTimeInput = page.getByLabel('Time Estimated');
     await estimatedTimeInput.fill('2h 30m');
     await estimatedTimeInput.press('Tab');
 
@@ -668,7 +668,7 @@ test('test that creating a project with estimated time using decimal notation wo
     await page.getByLabel('Project Name').fill(newProjectName);
 
     // Fill in estimated time using decimal notation (1.5 hours = 1h 30m)
-    const estimatedTimeInput = page.getByPlaceholder('e.g. 2h 30m or 1.5');
+    const estimatedTimeInput = page.getByLabel('Time Estimated');
     await estimatedTimeInput.fill('1.5');
     await estimatedTimeInput.press('Tab');
 
@@ -696,7 +696,7 @@ test('test that creating a project with estimated time using comma decimal notat
     await page.getByLabel('Project Name').fill(newProjectName);
 
     // Fill in estimated time using comma decimal notation (2,5 hours = 2h 30m)
-    const estimatedTimeInput = page.getByPlaceholder('e.g. 2h 30m or 1.5');
+    const estimatedTimeInput = page.getByLabel('Time Estimated');
     await estimatedTimeInput.fill('2,5');
     await estimatedTimeInput.press('Tab');
 
@@ -727,7 +727,7 @@ test('test that updating estimated time on existing project works', async ({ pag
     await page.getByRole('menuitem').getByText('Edit').first().click();
 
     // Fill in estimated time
-    const estimatedTimeInput = page.getByPlaceholder('e.g. 2h 30m or 1.5');
+    const estimatedTimeInput = page.getByLabel('Time Estimated');
     await estimatedTimeInput.fill('4h 15m');
     await estimatedTimeInput.press('Tab');
 
@@ -748,7 +748,7 @@ test('test that estimated time input displays formatted value after blur', async
     await goToProjectsOverview(page);
     await page.getByRole('button', { name: 'Create Project' }).click();
 
-    const estimatedTimeInput = page.getByPlaceholder('e.g. 2h 30m or 1.5');
+    const estimatedTimeInput = page.getByLabel('Time Estimated');
 
     // Enter time in various formats and check the displayed value
     await estimatedTimeInput.fill('90');

e2e/timesheet-overlap.spec.ts

@@ -0,0 +1,437 @@
+/**
+ * E2E coverage for the timesheet overlap-prevention logic introduced
+ * in `useTimesheetCellMutations` (Phase 1+2+3 of the overlap fix).
+ *
+ * Each test:
+ *   1. Pre-creates entries via the API to set up a deterministic
+ *      day-of-work scenario,
+ *   2. Triggers ONE cell edit through the UI,
+ *   3. Reads the resulting entries back via the API and asserts on
+ *      the start/end placement.
+ *
+ * Pre-creating rows (rather than driving the "Add row" + project picker
+ * UI) keeps the tests focused on the placement logic and out of the
+ * project-dropdown's flake surface.
+ */
+
+import { PLAYWRIGHT_BASE_URL } from '../playwright/config';
+import { test } from '../playwright/fixtures';
+import { expect } from '@playwright/test';
+import type { Page, Request } from '@playwright/test';
+import {
+    createProjectViaApi,
+    createTimeEntryAtHourViaApi,
+    getTimeEntriesViaApi,
+} from './utils/api';
+
+// ──────────────────────────────────────────────────
+// Helpers
+// ──────────────────────────────────────────────────
+
+async function goToTimesheet(page: Page) {
+    await page.addInitScript(() => {
+        window.localStorage.setItem('showReleaseInfo-desktop', 'false');
+    });
+    await page.goto(PLAYWRIGHT_BASE_URL + '/timesheet');
+}
+
+function getMonday(d: Date): Date {
+    const date = new Date(d);
+    const day = date.getUTCDay();
+    const diff = date.getUTCDate() - day + (day === 0 ? -6 : 1);
+    date.setUTCDate(diff);
+    date.setUTCHours(0, 0, 0, 0);
+    return date;
+}
+
+function getCurrentWeekMonday(): Date {
+    return getMonday(new Date());
+}
+
+async function waitForTimesheetLoad(page: Page) {
+    await expect(page.getByTestId('timesheet_view')).toBeVisible();
+    await expect(page.getByTestId('timesheet_week_display')).toBeVisible();
+
+    const timezoneMismatchModal = page
+        .getByRole('dialog')
+        .filter({ hasText: 'Timezone mismatch detected' });
+    if (await timezoneMismatchModal.isVisible().catch(() => false)) {
+        await timezoneMismatchModal.getByRole('button', { name: 'Cancel' }).click();
+        await expect(timezoneMismatchModal).not.toBeVisible();
+    }
+}
+
+const HOUR = 3600;
+
+function utcHourOf(iso: string): number {
+    return new Date(iso).getUTCHours();
+}
+
+function utcMinuteOf(iso: string): number {
+    return new Date(iso).getUTCMinutes();
+}
+
+function sortByStart<T extends { start: string }>(entries: T[]): T[] {
+    return [...entries].sort((a, b) => a.start.localeCompare(b.start));
+}
+
+/**
+ * Returns the locator for the row whose project name matches the given
+ * substring. Robust against ordering changes.
+ */
+function rowByProject(page: Page, projectName: string) {
+    return page.locator('[data-testid="timesheet_row"]').filter({ hasText: projectName });
+}
+
+/**
+ * Returns the locator for the input in the (row, dayIndex) cell, where
+ * the row is identified by project name.
+ */
+function cellInputByProject(page: Page, projectName: string, dayIndex: number) {
+    return rowByProject(page, projectName)
+        .locator('[data-testid="timesheet_cell"]')
+        .nth(dayIndex)
+        .locator('input');
+}
+
+/** Asserts that no entries in the list overlap each other. */
+function expectNoOverlaps(entries: Array<{ start: string; end: string | null }>) {
+    const sorted = sortByStart(entries.filter((e) => e.end !== null));
+    for (let i = 1; i < sorted.length; i++) {
+        const prev = sorted[i - 1]!;
+        const curr = sorted[i]!;
+        expect(
+            curr.start >= prev.end!,
+            `entries overlap: ${prev.start}–${prev.end} vs ${curr.start}–${curr.end}`
+        ).toBe(true);
+    }
+}
+
+// ──────────────────────────────────────────────────
+// Phase 1: createCell — overlap avoidance when cell is empty
+// ──────────────────────────────────────────────────
+
+test('extendCell on a row that has no entries on the day yet places after another row (Scenario #4)', async ({
+    page,
+    ctx,
+}) => {
+    // Setup: project A has Monday 09:00–10:00, project B has Tuesday
+    // 09:00–10:00. The B row is therefore visible on the timesheet but
+    // has an EMPTY cell on Monday. Typing into B's Monday cell exercises
+    // the createCell path (cell empty → place a new entry).
+    const monday = getCurrentWeekMonday();
+    const tuesday = new Date(monday);
+    tuesday.setUTCDate(monday.getUTCDate() + 1);
+
+    const projectA = await createProjectViaApi(ctx, { name: 'OverlapAlpha' });
+    const projectB = await createProjectViaApi(ctx, { name: 'OverlapBravo' });
+
+    await createTimeEntryAtHourViaApi(ctx, {
+        date: monday,
+        startHour: 9,
+        durationSeconds: HOUR,
+        projectId: projectA.id,
+    });
+    await createTimeEntryAtHourViaApi(ctx, {
+        date: tuesday,
+        startHour: 9,
+        durationSeconds: HOUR,
+        projectId: projectB.id,
+    });
+
+    await Promise.all([goToTimesheet(page), waitForTimesheetLoad(page)]);
+    await expect(page.locator('[data-testid="timesheet_row"]')).toHaveCount(2);
+
+    // Type 1h into project B's Monday cell. The createCell path should
+    // place it AFTER project A's 09:00–10:00 (i.e. at 10:00 or later),
+    // not at 09:00.
+    const input = cellInputByProject(page, 'OverlapBravo', 0);
+    await input.click();
+    await input.fill('1');
+
+    await Promise.all([
+        page.waitForResponse(
+            (resp) =>
+                resp.url().includes('/time-entries') &&
+                resp.request().method() === 'POST' &&
+                resp.status() === 201
+        ),
+        input.press('Enter'),
+    ]);
+
+    const entries = await getTimeEntriesViaApi(ctx);
+    const bMondayEntry = entries.find(
+        (e) =>
+            e.project_id === projectB.id &&
+            new Date(e.start).getTime() >= monday.getTime() &&
+            new Date(e.start).getTime() < tuesday.getTime()
+    )!;
+    expect(bMondayEntry).toBeDefined();
+    // 09:00 is blocked → must be at 10:00 or later.
+    expect(utcHourOf(bMondayEntry.start)).toBeGreaterThanOrEqual(10);
+    expectNoOverlaps(entries);
+});
+
+test('createCell refuses to cross midnight when day is full (Scenario #3)', async ({
+    page,
+    ctx,
+}) => {
+    // Setup: fill Monday 01:00–23:00 (22 hours, leaving 1h before and
+    // 1h after — neither big enough for a 3h ask). Project B is on
+    // Tuesday so the B row exists with an empty Monday cell. Typing 3h
+    // into B's Monday cell should be refused.
+    //
+    // We start at 01:00 (not 00:00) because the API's time-entry
+    // filter excludes entries whose `start` equals the query's `start`
+    // bound exactly. Using 01:00 avoids that boundary condition.
+    const monday = getCurrentWeekMonday();
+    const tuesday = new Date(monday);
+    tuesday.setUTCDate(monday.getUTCDate() + 1);
+
+    const projectFull = await createProjectViaApi(ctx, { name: 'OverlapFull' });
+    const projectNew = await createProjectViaApi(ctx, { name: 'OverlapNoRoom' });
+
+    await createTimeEntryAtHourViaApi(ctx, {
+        date: monday,
+        startHour: 1,
+        durationSeconds: 22 * HOUR,
+        projectId: projectFull.id,
+    });
+    await createTimeEntryAtHourViaApi(ctx, {
+        date: tuesday,
+        startHour: 9,
+        durationSeconds: HOUR,
+        projectId: projectNew.id,
+    });
+
+    await Promise.all([goToTimesheet(page), waitForTimesheetLoad(page)]);
+    await expect(page.locator('[data-testid="timesheet_row"]')).toHaveCount(2);
+
+    const input = cellInputByProject(page, 'OverlapNoRoom', 0);
+    const seenMutationRequests: string[] = [];
+    const onRequest = (request: Request) => {
+        if (request.url().includes('/time-entries') && request.method() !== 'GET') {
+            seenMutationRequests.push(request.method());
+        }
+    };
+    page.on('request', onRequest);
+    await input.click();
+    await input.fill('3');
+    await input.press('Enter');
+
+    await expect(page.getByText("This day can't fit any more work")).toBeVisible();
+    page.off('request', onRequest);
+
+    const entries = await getTimeEntriesViaApi(ctx);
+    // The new project should still only have its Tuesday entry.
+    const newEntries = entries.filter((e) => e.project_id === projectNew.id);
+    expect(seenMutationRequests).toEqual([]);
+    expect(newEntries).toHaveLength(1);
+    expect(utcHourOf(newEntries[0]!.start)).toBe(9);
+    // The Tuesday entry's date is unchanged (still Tuesday).
+    expect(new Date(newEntries[0]!.start).getUTCDay()).toBe(2);
+});
+
+// ──────────────────────────────────────────────────
+// Phase 2: extendCell — collision detection + split
+// ──────────────────────────────────────────────────
+
+test('extendCell splits the extension when another row blocks the path (Scenario #5)', async ({
+    page,
+    ctx,
+}) => {
+    // Setup:
+    //   - project A on Monday 09:00–10:00 (1h)
+    //   - project B on Monday 10:30–11:30 (1h, blocker)
+    // Bumping A's Monday cell from 1h to 3h (+2h) should:
+    //   - extend A to 09:00–10:30 (filling the 30min gap)
+    //   - place a new A entry at 11:30–13:00 (the remaining 90min)
+    const monday = getCurrentWeekMonday();
+    const projectA = await createProjectViaApi(ctx, { name: 'OverlapExtend' });
+    const projectB = await createProjectViaApi(ctx, { name: 'OverlapBlocker' });
+
+    await createTimeEntryAtHourViaApi(ctx, {
+        date: monday,
+        startHour: 9,
+        durationSeconds: HOUR,
+        projectId: projectA.id,
+    });
+    await createTimeEntryAtHourViaApi(ctx, {
+        date: monday,
+        startHour: 10,
+        startMinute: 30,
+        durationSeconds: HOUR,
+        projectId: projectB.id,
+    });
+
+    await Promise.all([goToTimesheet(page), waitForTimesheetLoad(page)]);
+    await expect(page.locator('[data-testid="timesheet_row"]')).toHaveCount(2);
+
+    const input = cellInputByProject(page, 'OverlapExtend', 0);
+    await input.click();
+    await input.fill('3');
+    await Promise.all([
+        page.waitForResponse(
+            (resp) =>
+                resp.url().includes('/time-entries') &&
+                resp.request().method() === 'PUT' &&
+                resp.status() === 200
+        ),
+        page.waitForResponse(
+            (resp) =>
+                resp.url().includes('/time-entries') &&
+                resp.request().method() === 'POST' &&
+                resp.status() === 201
+        ),
+        input.press('Enter'),
+    ]);
+
+    const entries = await getTimeEntriesViaApi(ctx);
+    const aEntries = entries.filter((e) => e.project_id === projectA.id);
+    const bEntries = entries.filter((e) => e.project_id === projectB.id);
+
+    // The blocker is unchanged.
+    expect(bEntries).toHaveLength(1);
+    expect(utcHourOf(bEntries[0]!.start)).toBe(10);
+    expect(utcMinuteOf(bEntries[0]!.start)).toBe(30);
+
+    // Project A should now have 2 entries.
+    expect(aEntries).toHaveLength(2);
+    const sortedA = sortByStart(aEntries);
+    // Extended entry: 09:00 → 10:30
+    expect(utcHourOf(sortedA[0]!.start)).toBe(9);
+    expect(utcHourOf(sortedA[0]!.end!)).toBe(10);
+    expect(utcMinuteOf(sortedA[0]!.end!)).toBe(30);
+    // Split remainder: 11:30 → 13:00
+    expect(utcHourOf(sortedA[1]!.start)).toBe(11);
+    expect(utcMinuteOf(sortedA[1]!.start)).toBe(30);
+
+    // No overlaps anywhere on the day.
+    expectNoOverlaps(entries);
+});
+
+test('extendCell prefers latest-end (not latest-start) when nested entries exist (Scenario #6)', async ({
+    page,
+    ctx,
+}) => {
+    // Pre-existing nested overlap on the same project:
+    //   - outer: 09:00 → 12:00 (3h)
+    //   - inner: 10:00 → 11:00 (1h, contained inside outer)
+    // The cell total is 3h + 1h = 4h. Bumping to 5h (+1h) should grow
+    // the OUTER entry's end to 13:00, not the inner.
+    const monday = getCurrentWeekMonday();
+    const project = await createProjectViaApi(ctx, { name: 'OverlapNested' });
+
+    await createTimeEntryAtHourViaApi(ctx, {
+        date: monday,
+        startHour: 9,
+        durationSeconds: 3 * HOUR,
+        projectId: project.id,
+        description: 'outer',
+    });
+    await createTimeEntryAtHourViaApi(ctx, {
+        date: monday,
+        startHour: 10,
+        durationSeconds: HOUR,
+        projectId: project.id,
+        description: 'inner',
+    });
+
+    await Promise.all([goToTimesheet(page), waitForTimesheetLoad(page)]);
+    await expect(page.locator('[data-testid="timesheet_row"]')).toHaveCount(1);
+
+    const input = cellInputByProject(page, 'OverlapNested', 0);
+    await input.click();
+    await input.fill('5');
+
+    await Promise.all([
+        page.waitForResponse(
+            (resp) =>
+                resp.url().includes('/time-entries') &&
+                resp.request().method() === 'PUT' &&
+                resp.status() === 200
+        ),
+        input.press('Enter'),
+    ]);
+
+    const entries = await getTimeEntriesViaApi(ctx);
+    const outer = entries.find((e) => e.description === 'outer')!;
+    const inner = entries.find((e) => e.description === 'inner')!;
+
+    expect(utcHourOf(outer.start)).toBe(9);
+    expect(utcHourOf(outer.end!)).toBe(13); // extended from 12:00 → 13:00
+    expect(utcHourOf(inner.start)).toBe(10);
+    expect(utcHourOf(inner.end!)).toBe(11); // unchanged
+});
+
+// ──────────────────────────────────────────────────
+// Phase 1+2 spillover from previous day
+// ──────────────────────────────────────────────────
+
+test('createCell handles intra-week spillover from previous day (Scenario #2)', async ({
+    page,
+    ctx,
+}) => {
+    // Setup: an entry that starts on Monday 22:00 and ends Tuesday 03:00
+    // (5h, crosses midnight INTO Tuesday). This spillover starts inside
+    // the loaded week, so the timesheet query loads it.
+    //
+    // Then we try to place 1h on Tuesday for a different project. The
+    // expected behavior: the new entry must NOT overlap the spillover.
+    // Tuesday 09:00 is well clear of the [00:00, 03:00) spillover, so
+    // 09:00 is the correct placement.
+    const monday = getCurrentWeekMonday();
+    const tuesday = new Date(monday);
+    tuesday.setUTCDate(monday.getUTCDate() + 1);
+    const wednesday = new Date(monday);
+    wednesday.setUTCDate(monday.getUTCDate() + 2);
+
+    const projectSpill = await createProjectViaApi(ctx, { name: 'OverlapSpill' });
+    const projectNew = await createProjectViaApi(ctx, { name: 'OverlapToday' });
+
+    // Monday 22:00 → Tuesday 03:00 (5h spillover into Tuesday).
+    await createTimeEntryAtHourViaApi(ctx, {
+        date: monday,
+        startHour: 22,
+        durationSeconds: 5 * HOUR,
+        projectId: projectSpill.id,
+    });
+    // Stub Wednesday entry on the new project so its row is visible
+    // even before we type anything in Tuesday's cell.
+    await createTimeEntryAtHourViaApi(ctx, {
+        date: wednesday,
+        startHour: 9,
+        durationSeconds: HOUR,
+        projectId: projectNew.id,
+    });
+
+    await Promise.all([goToTimesheet(page), waitForTimesheetLoad(page)]);
+    await expect(page.locator('[data-testid="timesheet_row"]')).toHaveCount(2);
+
+    // Type 1h into the new project's Tuesday cell (day index 1).
+    const input = cellInputByProject(page, 'OverlapToday', 1);
+    await input.click();
+    await input.fill('1');
+
+    await Promise.all([
+        page.waitForResponse(
+            (resp) =>
+                resp.url().includes('/time-entries') &&
+                resp.request().method() === 'POST' &&
+                resp.status() === 201
+        ),
+        input.press('Enter'),
+    ]);
+
+    const entries = await getTimeEntriesViaApi(ctx);
+    const newTuesdayEntry = entries.find(
+        (e) =>
+            e.project_id === projectNew.id &&
+            new Date(e.start).getTime() >= tuesday.getTime() &&
+            new Date(e.start).getTime() < wednesday.getTime()
+    )!;
+    expect(newTuesdayEntry).toBeDefined();
+    // 09:00 is well past the spillover end (03:00) → should land at 09:00.
+    expect(utcHourOf(newTuesdayEntry.start)).toBe(9);
+    expectNoOverlaps(entries);
+});

e2e/timesheet.spec.ts

@@ -0,0 +1,641 @@
+import { PLAYWRIGHT_BASE_URL } from '../playwright/config';
+import { test } from '../playwright/fixtures';
+import { expect } from '@playwright/test';
+import type { Page } from '@playwright/test';
+import { createProjectViaApi, createTaskViaApi, createTimeEntryOnDateViaApi } from './utils/api';
+
+// ──────────────────────────────────────────────────
+// Helpers
+// ──────────────────────────────────────────────────
+
+async function goToTimesheet(page: Page) {
+    await page.addInitScript(() => {
+        window.localStorage.setItem('showReleaseInfo-desktop', 'false');
+    });
+    await page.goto(PLAYWRIGHT_BASE_URL + '/timesheet');
+}
+
+function getMonday(d: Date): Date {
+    const date = new Date(d);
+    const day = date.getUTCDay();
+    const diff = date.getUTCDate() - day + (day === 0 ? -6 : 1);
+    date.setUTCDate(diff);
+    date.setUTCHours(0, 0, 0, 0);
+    return date;
+}
+
+function getCurrentWeekMonday(): Date {
+    return getMonday(new Date());
+}
+
+function getLastWeekMonday(): Date {
+    const monday = getCurrentWeekMonday();
+    monday.setUTCDate(monday.getUTCDate() - 7);
+    return monday;
+}
+
+function getDayOfWeek(weekStart: Date, dayOffset: number): Date {
+    const date = new Date(weekStart);
+    date.setUTCDate(date.getUTCDate() + dayOffset);
+    return date;
+}
+
+async function waitForTimesheetLoad(page: Page) {
+    await page.waitForURL(/\/timesheet(?:$|\?)/);
+    await expect(page.getByTestId('timesheet_view')).toBeVisible();
+    await expect(page.getByTestId('timesheet_week_display')).toBeVisible();
+
+    const timezoneMismatchModal = page
+        .getByRole('dialog')
+        .filter({ hasText: 'Timezone mismatch detected' });
+    if (await timezoneMismatchModal.isVisible().catch(() => false)) {
+        await timezoneMismatchModal.getByRole('button', { name: 'Cancel' }).click();
+        await expect(timezoneMismatchModal).not.toBeVisible();
+    }
+}
+
+function addRowButton(page: Page) {
+    return page.getByRole('button', { name: /Add row/i }).first();
+}
+
+async function chooseRowIdentity(page: Page, optionName: string) {
+    await addRowButton(page).click();
+
+    const dialog = page.getByRole('dialog', { name: /Add row/i });
+    const dialogVisible = await dialog
+        .waitFor({ state: 'visible', timeout: 1000 })
+        .then(() => true)
+        .catch(() => false);
+
+    if (dialogVisible) {
+        await dialog.getByRole('option', { name: optionName }).click();
+        return;
+    }
+
+    if (optionName === 'No Project') return;
+
+    const row = page.locator('[data-testid="timesheet_row"]').first();
+    await row.getByText('No Project').click();
+    await page.getByText(optionName).click();
+}
+
+// ──────────────────────────────────────────────────
+// Navigation & Page Load
+// ──────────────────────────────────────────────────
+
+test('timesheet renders empty with add row + copy last week actions', async ({ page }) => {
+    await Promise.all([goToTimesheet(page), waitForTimesheetLoad(page)]);
+
+    await expect(page.locator('[data-testid="timesheet_row"]')).toHaveCount(0);
+    await expect(addRowButton(page)).toBeVisible();
+    await expect(page.getByRole('button', { name: /Copy last week/i })).toBeVisible();
+});
+
+// ──────────────────────────────────────────────────
+// Display Existing Time Entries
+// ──────────────────────────────────────────────────
+
+test('timesheet displays existing time entries grouped by project', async ({ page, ctx }) => {
+    const monday = getCurrentWeekMonday();
+    const tuesday = getDayOfWeek(monday, 1);
+    const wednesday = getDayOfWeek(monday, 2);
+
+    const projectA = await createProjectViaApi(ctx, { name: 'Project Alpha' });
+    const projectB = await createProjectViaApi(ctx, { name: 'Project Beta' });
+
+    await createTimeEntryOnDateViaApi(ctx, {
+        date: monday,
+        duration: '2h',
+        projectId: projectA.id,
+    });
+    await createTimeEntryOnDateViaApi(ctx, {
+        date: wednesday,
+        duration: '1h',
+        projectId: projectA.id,
+    });
+    await createTimeEntryOnDateViaApi(ctx, {
+        date: tuesday,
+        duration: '3h',
+        projectId: projectB.id,
+    });
+
+    await Promise.all([goToTimesheet(page), waitForTimesheetLoad(page)]);
+
+    const rows = page.locator('[data-testid="timesheet_row"]');
+    await expect(rows).toHaveCount(2);
+
+    // Check that the grand total is shown
+    await expect(page.getByTestId('timesheet_grand_total')).toBeVisible();
+});
+
+test('timesheet groups entries by project and task combination', async ({ page, ctx }) => {
+    const monday = getCurrentWeekMonday();
+
+    const project = await createProjectViaApi(ctx, { name: 'Task Project' });
+    const taskA = await createTaskViaApi(ctx, { name: 'Task A', project_id: project.id });
+    const taskB = await createTaskViaApi(ctx, { name: 'Task B', project_id: project.id });
+
+    await createTimeEntryOnDateViaApi(ctx, {
+        date: monday,
+        duration: '1h',
+        projectId: project.id,
+        taskId: taskA.id,
+    });
+    await createTimeEntryOnDateViaApi(ctx, {
+        date: monday,
+        duration: '2h',
+        projectId: project.id,
+        taskId: taskB.id,
+    });
+
+    await Promise.all([goToTimesheet(page), waitForTimesheetLoad(page)]);
+
+    const rows = page.locator('[data-testid="timesheet_row"]');
+    await expect(rows).toHaveCount(2);
+});
+
+// ──────────────────────────────────────────────────
+// Enter Duration in Cell
+// ──────────────────────────────────────────────────
+
+test('entering duration in empty cell creates a time entry', async ({ page, ctx }) => {
+    await createProjectViaApi(ctx, { name: 'Duration Test' });
+
+    await Promise.all([goToTimesheet(page), waitForTimesheetLoad(page)]);
+
+    await chooseRowIdentity(page, 'Duration Test');
+
+    const row = page.locator('[data-testid="timesheet_row"]').first();
+
+    // Click the first day cell and enter duration
+    const cells = row.locator('[data-testid="timesheet_cell"]');
+    const mondayCell = cells.first();
+    const mondayInput = mondayCell.locator('input');
+
+    await mondayInput.click();
+    await mondayInput.fill('2');
+
+    // Submit and wait for create response
+    const [response] = await Promise.all([
+        page.waitForResponse(
+            (resp) =>
+                resp.url().includes('/time-entries') &&
+                resp.request().method() === 'POST' &&
+                resp.status() === 201
+        ),
+        mondayInput.press('Enter'),
+    ]);
+
+    expect(response.status()).toBe(201);
+
+    // Verify the cell shows the duration
+    await expect(mondayInput).not.toHaveValue('');
+});
+
+// ──────────────────────────────────────────────────
+// Edit Duration (Increase)
+// ──────────────────────────────────────────────────
+
+test('increasing duration in cell extends the last time entry', async ({ page, ctx }) => {
+    const monday = getCurrentWeekMonday();
+    const project = await createProjectViaApi(ctx, { name: 'Increase Test' });
+
+    await createTimeEntryOnDateViaApi(ctx, {
+        date: monday,
+        duration: '1h',
+        projectId: project.id,
+    });
+
+    await Promise.all([goToTimesheet(page), waitForTimesheetLoad(page)]);
+
+    const row = page.locator('[data-testid="timesheet_row"]').first();
+    const cells = row.locator('[data-testid="timesheet_cell"]');
+    const mondayInput = cells.first().locator('input');
+
+    // Click and change to 3 hours
+    await mondayInput.click();
+    await mondayInput.fill('3');
+
+    const [response] = await Promise.all([
+        page.waitForResponse(
+            (resp) =>
+                resp.url().includes('/time-entries') &&
+                resp.request().method() === 'PUT' &&
+                resp.status() === 200
+        ),
+        mondayInput.press('Enter'),
+    ]);
+
+    expect(response.status()).toBe(200);
+});
+
+// ──────────────────────────────────────────────────
+// Edit Duration (Decrease)
+// ──────────────────────────────────────────────────
+
+test('decreasing duration in cell shortens the last time entry', async ({ page, ctx }) => {
+    const monday = getCurrentWeekMonday();
+    const project = await createProjectViaApi(ctx, { name: 'Decrease Test' });
+
+    await createTimeEntryOnDateViaApi(ctx, {
+        date: monday,
+        duration: '3h',
+        projectId: project.id,
+    });
+
+    await Promise.all([goToTimesheet(page), waitForTimesheetLoad(page)]);
+
+    const row = page.locator('[data-testid="timesheet_row"]').first();
+    const cells = row.locator('[data-testid="timesheet_cell"]');
+    const mondayInput = cells.first().locator('input');
+
+    await mondayInput.click();
+    await mondayInput.fill('1');
+
+    const [response] = await Promise.all([
+        page.waitForResponse(
+            (resp) =>
+                resp.url().includes('/time-entries') &&
+                resp.request().method() === 'PUT' &&
+                resp.status() === 200
+        ),
+        mondayInput.press('Enter'),
+    ]);
+
+    expect(response.status()).toBe(200);
+});
+
+// ──────────────────────────────────────────────────
+// Clear Cell
+// ──────────────────────────────────────────────────
+
+test('clearing a cell deletes all time entries for that project+day', async ({ page, ctx }) => {
+    const monday = getCurrentWeekMonday();
+    const project = await createProjectViaApi(ctx, { name: 'Clear Test' });
+
+    await createTimeEntryOnDateViaApi(ctx, {
+        date: monday,
+        duration: '2h',
+        projectId: project.id,
+    });
+
+    await Promise.all([goToTimesheet(page), waitForTimesheetLoad(page)]);
+
+    const row = page.locator('[data-testid="timesheet_row"]').first();
+    const cells = row.locator('[data-testid="timesheet_cell"]');
+    const mondayInput = cells.first().locator('input');
+
+    await mondayInput.click();
+    await mondayInput.fill('0');
+
+    const [response] = await Promise.all([
+        page.waitForResponse(
+            (resp) =>
+                resp.url().includes('/time-entries') &&
+                resp.request().method() === 'DELETE' &&
+                resp.status() === 200
+        ),
+        mondayInput.press('Enter'),
+    ]);
+
+    expect(response.status()).toBe(200);
+});
+
+test('Escape during cell edit reverts the displayed value without an API call', async ({
+    page,
+    ctx,
+}) => {
+    const monday = getCurrentWeekMonday();
+    const project = await createProjectViaApi(ctx, { name: 'Escape Cancel Test' });
+
+    await createTimeEntryOnDateViaApi(ctx, {
+        date: monday,
+        duration: '2h',
+        projectId: project.id,
+    });
+
+    await Promise.all([goToTimesheet(page), waitForTimesheetLoad(page)]);
+
+    const row = page.locator('[data-testid="timesheet_row"]').first();
+    const cells = row.locator('[data-testid="timesheet_cell"]');
+    const mondayInput = cells.first().locator('input');
+
+    // Capture the formatted display value before editing.
+    const originalValue = await mondayInput.inputValue();
+    expect(originalValue).toMatch(/2/);
+
+    let mutationFired = false;
+    page.on('request', (req) => {
+        if (req.url().includes('/time-entries') && req.method() !== 'GET') {
+            mutationFired = true;
+        }
+    });
+
+    await mondayInput.click();
+    await mondayInput.fill('5');
+    await mondayInput.press('Escape');
+
+    // The Escape handler reverts the displayed value synchronously, so
+    // once this assertion passes we know the handler ran. Any mutation
+    // request would have been queued by then.
+    await expect(mondayInput).toHaveValue(originalValue);
+    expect(mutationFired).toBe(false);
+});
+
+// ──────────────────────────────────────────────────
+// Week Navigation
+// ──────────────────────────────────────────────────
+
+test('navigating to previous week shows entries from that week', async ({ page, ctx }) => {
+    const lastMonday = getLastWeekMonday();
+    const project = await createProjectViaApi(ctx, { name: 'Last Week Project' });
+
+    await createTimeEntryOnDateViaApi(ctx, {
+        date: lastMonday,
+        duration: '2h',
+        projectId: project.id,
+    });
+
+    await Promise.all([goToTimesheet(page), waitForTimesheetLoad(page)]);
+
+    // Current week should have no entries
+    await expect(page.locator('[data-testid="timesheet_row"]')).toHaveCount(0);
+
+    // Go to previous week — the row-count assertion below auto-retries
+    // until the new week's data arrives.
+    await page.getByTestId('timesheet_prev_week').click();
+
+    // Should now see the entry
+    const rows = page.locator('[data-testid="timesheet_row"]');
+    await expect(rows).toHaveCount(1);
+});
+
+test('can navigate forward and return to current week', async ({ page }) => {
+    await Promise.all([goToTimesheet(page), waitForTimesheetLoad(page)]);
+
+    // Should show "This week"
+    await expect(page.getByTestId('timesheet_week_display')).toContainText('This week');
+
+    // Go to next week — the text assertions below auto-retry until the
+    // header label flips.
+    await page.getByTestId('timesheet_next_week').click();
+
+    // Should no longer show "This week"
+    await expect(page.getByTestId('timesheet_week_display')).not.toContainText('This week');
+
+    // Go back to this week
+    await page.getByTestId('timesheet_week_display').click();
+
+    await expect(page.getByTestId('timesheet_week_display')).toContainText('This week');
+});
+
+// ──────────────────────────────────────────────────
+// Copy Last Week
+// ──────────────────────────────────────────────────
+
+test('copy last week adds project rows from previous week without hours', async ({ page, ctx }) => {
+    const lastMonday = getLastWeekMonday();
+    const lastWednesday = getDayOfWeek(lastMonday, 2);
+
+    const projectA = await createProjectViaApi(ctx, { name: 'Copy Project A' });
+    const projectB = await createProjectViaApi(ctx, { name: 'Copy Project B' });
+
+    await createTimeEntryOnDateViaApi(ctx, {
+        date: lastMonday,
+        duration: '2h',
+        projectId: projectA.id,
+    });
+    await createTimeEntryOnDateViaApi(ctx, {
+        date: lastWednesday,
+        duration: '3h',
+        projectId: projectB.id,
+    });
+
+    await Promise.all([goToTimesheet(page), waitForTimesheetLoad(page)]);
+
+    // Current week should have no populated rows yet.
+    await expect(page.locator('[data-testid="timesheet_row"]')).toHaveCount(0);
+
+    // Open copy last week dropdown and click "Copy rows only"
+    await page.getByRole('button', { name: /Copy last week/i }).click();
+    await page.getByText('Copy rows only').click();
+
+    // Should now show 2 rows (one per project)
+    const rows = page.locator('[data-testid="timesheet_row"]');
+    await expect(rows).toHaveCount(2);
+
+    // All row totals should be 0
+    const rowTotals = page.locator('[data-testid="timesheet_row_total"]');
+    const count = await rowTotals.count();
+    for (let i = 0; i < count; i++) {
+        await expect(rowTotals.nth(i)).toContainText('-');
+    }
+});
+
+test('copy last week does not duplicate rows that already exist', async ({ page, ctx }) => {
+    const lastMonday = getLastWeekMonday();
+    const thisMonday = getCurrentWeekMonday();
+    const thisTuesday = getDayOfWeek(thisMonday, 1);
+
+    const project = await createProjectViaApi(ctx, { name: 'No Dup Project' });
+
+    // Create entry for last week
+    await createTimeEntryOnDateViaApi(ctx, {
+        date: lastMonday,
+        duration: '2h',
+        projectId: project.id,
+    });
+
+    // Create entry for current week
+    await createTimeEntryOnDateViaApi(ctx, {
+        date: thisTuesday,
+        duration: '1h',
+        projectId: project.id,
+    });
+
+    await Promise.all([goToTimesheet(page), waitForTimesheetLoad(page)]);
+
+    // Should have 1 row (from current week entry)
+    const rows = page.locator('[data-testid="timesheet_row"]');
+    await expect(rows).toHaveCount(1);
+
+    // Open copy last week dropdown and click "Copy rows only"
+    await page.getByRole('button', { name: /Copy last week/i }).click();
+    await page.getByText('Copy rows only').click();
+
+    // Should still have only 1 row (not duplicated)
+    await expect(rows).toHaveCount(1);
+});
+
+test('copy last week with time entries creates rows and entries', async ({ page, ctx }) => {
+    const lastMonday = getLastWeekMonday();
+
+    const project = await createProjectViaApi(ctx, { name: 'Copy Time Project' });
+
+    await createTimeEntryOnDateViaApi(ctx, {
+        date: lastMonday,
+        duration: '2h',
+        projectId: project.id,
+    });
+
+    await Promise.all([goToTimesheet(page), waitForTimesheetLoad(page)]);
+
+    // Current week should have no populated rows yet.
+    await expect(page.locator('[data-testid="timesheet_row"]')).toHaveCount(0);
+
+    // Open copy last week dropdown and click "Copy rows and time entries"
+    await page.getByRole('button', { name: /Copy last week/i }).click();
+
+    await Promise.all([
+        page.waitForResponse(
+            (resp) =>
+                resp.url().includes('/time-entries') &&
+                resp.request().method() === 'POST' &&
+                resp.status() === 201
+        ),
+        page.getByText('Copy rows and time entries').click(),
+    ]);
+
+    // Should now show 1 row with time entries
+    const rows = page.locator('[data-testid="timesheet_row"]');
+    await expect(rows).toHaveCount(1);
+
+    // Row total should not be 0 (entries were copied)
+    const rowTotal = page.locator('[data-testid="timesheet_row_total"]').first();
+    await expect(rowTotal).not.toContainText('0 h');
+});
+
+// ──────────────────────────────────────────────────
+// Row Removal
+// ──────────────────────────────────────────────────
+
+test('can remove an empty project row without confirmation', async ({ page, ctx }) => {
+    const project = await createProjectViaApi(ctx, { name: 'Empty Remove Project' });
+
+    await Promise.all([goToTimesheet(page), waitForTimesheetLoad(page)]);
+
+    await chooseRowIdentity(page, project.name);
+
+    const rows = page.locator('[data-testid="timesheet_row"]');
+    await expect(rows).toHaveCount(1);
+
+    // Hover the row to reveal the X button, then click it
+    await rows.first().hover();
+    await rows.first().getByRole('button', { name: 'Remove row' }).click();
+
+    // Row should be removed immediately (no dialog)
+    await expect(rows).toHaveCount(0);
+});
+
+test('removing a row with entries shows confirmation dialog and deletes entries', async ({
+    page,
+    ctx,
+}) => {
+    const monday = getCurrentWeekMonday();
+    const project = await createProjectViaApi(ctx, { name: 'Delete Row Project' });
+
+    await createTimeEntryOnDateViaApi(ctx, {
+        date: monday,
+        duration: '2h',
+        projectId: project.id,
+    });
+
+    await Promise.all([goToTimesheet(page), waitForTimesheetLoad(page)]);
+
+    const rows = page.locator('[data-testid="timesheet_row"]');
+    await expect(rows).toHaveCount(1);
+
+    // Hover and click X
+    await rows.first().hover();
+    await rows.first().getByRole('button', { name: 'Remove row' }).click();
+
+    // Confirmation dialog should appear
+    await expect(page.getByRole('alertdialog')).toBeVisible();
+    await expect(page.getByText('Remove timesheet row?')).toBeVisible();
+
+    // Click Delete
+    await Promise.all([
+        page.waitForResponse(
+            (resp) =>
+                resp.url().includes('/time-entries') &&
+                resp.request().method() === 'DELETE' &&
+                resp.status() === 200
+        ),
+        page
+            .getByRole('alertdialog')
+            .getByRole('button', { name: /Delete/i })
+            .click(),
+    ]);
+
+    // Row should be gone
+    await expect(rows).toHaveCount(0);
+});
+
+// ──────────────────────────────────────────────────
+// Multiple Entries Same Cell
+// ──────────────────────────────────────────────────
+
+test('cell correctly sums multiple entries for same project+day', async ({ page, ctx }) => {
+    const monday = getCurrentWeekMonday();
+    const project = await createProjectViaApi(ctx, { name: 'Sum Test' });
+
+    // Create 2 entries for the same project on Monday
+    await createTimeEntryOnDateViaApi(ctx, {
+        date: monday,
+        duration: '1h',
+        projectId: project.id,
+        description: 'Entry 1',
+    });
+    await createTimeEntryOnDateViaApi(ctx, {
+        date: monday,
+        duration: '2h',
+        projectId: project.id,
+        description: 'Entry 2',
+    });
+
+    await Promise.all([goToTimesheet(page), waitForTimesheetLoad(page)]);
+
+    // Should be 1 row (both entries grouped)
+    const rows = page.locator('[data-testid="timesheet_row"]');
+    await expect(rows).toHaveCount(1);
+
+    // The Monday cell should show 3h total
+    const cells = rows.first().locator('[data-testid="timesheet_cell"]');
+    const mondayInput = cells.first().locator('input');
+    // The value should contain "3" (for 3h in some format)
+    await expect(mondayInput).toHaveValue(/3/);
+});
+
+// ──────────────────────────────────────────────────
+// Duration Input Formats
+// ──────────────────────────────────────────────────
+
+test('cell accepts various duration input formats', async ({ page, ctx }) => {
+    await createProjectViaApi(ctx, { name: 'Format Test' });
+
+    await Promise.all([goToTimesheet(page), waitForTimesheetLoad(page)]);
+
+    await chooseRowIdentity(page, 'Format Test');
+
+    const row = page.locator('[data-testid="timesheet_row"]').first();
+
+    // Test entering "1.5" (should be 1h 30min)
+    const cells = row.locator('[data-testid="timesheet_cell"]');
+    const mondayInput = cells.first().locator('input');
+
+    await mondayInput.click();
+    await mondayInput.fill('1.5');
+
+    await Promise.all([
+        page.waitForResponse(
+            (resp) =>
+                resp.url().includes('/time-entries') &&
+                resp.request().method() === 'POST' &&
+                resp.status() === 201
+        ),
+        mondayInput.press('Enter'),
+    ]);
+
+    // 1.5 hours = 1h 30min
+    await expect(mondayInput).toHaveValue('1h 30min');
+});

e2e/utils/api.ts

@@ -170,10 +170,24 @@ function parseDurationToSeconds(duration: string): number {
     return totalSeconds;
 }
 
+/**
+ * Builds a start/end pair anchored to 09:00 UTC on today's UTC date.
+ *
+ * Intentionally pinned to UTC (rather than the runner's local time) so
+ * the produced timestamps are identical regardless of where the suite
+ * runs. Playwright test users default to UTC, so this matches what the
+ * app will see and keeps day-of-week / "this week" assertions stable
+ * for developers running the suite locally in non-UTC timezones.
+ */
 function createTimestamps(duration: string): { start: string; end: string } {
     const durationSeconds = parseDurationToSeconds(duration);
     const now = new Date();
-    const start = new Date(now.getFullYear(), now.getMonth(), now.getDate(), 9, 0, 0);
+    const start = createUtcTimestampFromDateParts(
+        now.getUTCFullYear(),
+        now.getUTCMonth(),
+        now.getUTCDate(),
+        9
+    );
     const end = new Date(start.getTime() + durationSeconds * 1000);
 
     return {
@@ -186,6 +200,32 @@ function formatTimestamp(date: Date): string {
     return date.toISOString().replace(/\.\d{3}Z$/, 'Z');
 }
 
+function createUtcTimestampFromDateParts(
+    year: number,
+    month: number,
+    date: number,
+    hours: number,
+    minutes: number = 0,
+    seconds: number = 0
+): Date {
+    return new Date(Date.UTC(year, month, date, hours, minutes, seconds));
+}
+
+function createTimestampsOnDate(date: Date, duration: string): { start: string; end: string } {
+    const durationSeconds = parseDurationToSeconds(duration);
+    const start = createUtcTimestampFromDateParts(
+        date.getUTCFullYear(),
+        date.getUTCMonth(),
+        date.getUTCDate(),
+        9
+    );
+    const end = new Date(start.getTime() + durationSeconds * 1000);
+    return {
+        start: formatTimestamp(start),
+        end: formatTimestamp(end),
+    };
+}
+
 function randomColor(): string {
     const colors = [
         '#ef5350',
@@ -375,6 +415,39 @@ export async function createTimeEntryViaApi(
     return body.data as { id: string; start: string; end: string; description: string };
 }
 
+export async function createTimeEntryOnDateViaApi(
+    ctx: TestContext,
+    data: {
+        date: Date;
+        duration: string;
+        description?: string;
+        projectId?: string | null;
+        taskId?: string | null;
+        tags?: string[];
+        billable?: boolean;
+    }
+) {
+    const { start, end } = createTimestampsOnDate(data.date, data.duration);
+    const response = await ctx.request.post(
+        `${PLAYWRIGHT_BASE_URL}/api/v1/organizations/${ctx.orgId}/time-entries`,
+        {
+            data: {
+                member_id: ctx.memberId,
+                start,
+                end,
+                description: data.description ?? '',
+                project_id: data.projectId ?? null,
+                task_id: data.taskId ?? null,
+                tags: data.tags ?? [],
+                billable: data.billable ?? false,
+            },
+        }
+    );
+    expect(response.status()).toBe(201);
+    const body = await response.json();
+    return body.data as { id: string; start: string; end: string; description: string };
+}
+
 export async function createProjectMemberViaApi(
     ctx: TestContext,
     projectId: string,
@@ -613,6 +686,72 @@ export async function getInvitationsViaApi(ctx: TestContext) {
 // Timestamp-based time entry helpers
 // ──────────────────────────────────────────────────
 
+/**
+ * Creates a time entry on `date` at a specific UTC hour with a duration
+ * in seconds. Playwright test users default to the UTC timezone, so this
+ * keeps time-placement scenarios stable across runner locales.
+ */
+export async function createTimeEntryAtHourViaApi(
+    ctx: TestContext,
+    data: {
+        date: Date;
+        startHour: number;
+        startMinute?: number;
+        durationSeconds: number;
+        projectId?: string | null;
+        taskId?: string | null;
+        description?: string;
+    }
+) {
+    const start = createUtcTimestampFromDateParts(
+        data.date.getUTCFullYear(),
+        data.date.getUTCMonth(),
+        data.date.getUTCDate(),
+        data.startHour,
+        data.startMinute ?? 0
+    );
+    const end = new Date(start.getTime() + data.durationSeconds * 1000);
+    return createTimeEntryWithTimestampsViaApi(ctx, {
+        start: formatTimestamp(start),
+        end: formatTimestamp(end),
+        projectId: data.projectId ?? null,
+        taskId: data.taskId ?? null,
+        description: data.description ?? '',
+    });
+}
+
+/**
+ * Reads time entries for the current member, optionally filtered to a
+ * date range. Returns the raw API objects (id, start, end, project_id,
+ * etc.) so tests can assert on the database state after a UI action.
+ */
+export async function getTimeEntriesViaApi(
+    ctx: TestContext,
+    filters: { start?: string; end?: string } = {}
+): Promise<
+    Array<{
+        id: string;
+        start: string;
+        end: string | null;
+        duration: number | null;
+        project_id: string | null;
+        task_id: string | null;
+        description: string;
+    }>
+> {
+    const params = new URLSearchParams();
+    params.set('member_id', ctx.memberId);
+    if (filters.start) params.set('start', filters.start);
+    if (filters.end) params.set('end', filters.end);
+
+    const response = await ctx.request.get(
+        `${PLAYWRIGHT_BASE_URL}/api/v1/organizations/${ctx.orgId}/time-entries?${params.toString()}`
+    );
+    expect(response.status()).toBe(200);
+    const body = await response.json();
+    return body.data;
+}
+
 export async function createTimeEntryWithTimestampsViaApi(
     ctx: TestContext,
     data: {

package.json

@@ -12,10 +12,17 @@
         "lint": "eslint resources/js",
         "lint:fix": "eslint --fix resources/js",
         "type-check": "vue-tsc --noEmit",
+        "test:unit": "vitest run",
+        "test:unit:watch": "vitest",
         "test:e2e": "rm -rf test-results/.auth && npx playwright test",
         "zod:generate": "npx openapi-zod-client http://localhost:80/docs/api.json --output resources/js/packages/api/src/openapi.json.client.ts --base-url /api",
         "format": "prettier --write './**/*.{js,jsx,cjs,mjs,ts,tsx,cts,mts,vue}'",
-        "format:check": "prettier --check './**/*.{js,jsx,cjs,mjs,ts,tsx,cts,mts,vue}'"
+        "format:check": "prettier --check './**/*.{js,jsx,cjs,mjs,ts,tsx,cts,mts,vue}'",
+        "build:ui": "npm run build --workspace=@solidtime/ui",
+        "build:api": "npm run build --workspace=@solidtime/api",
+        "build:packages": "npm run build:api && npm run build:ui",
+        "watch:ui": "npm run watch --workspace=@solidtime/ui",
+        "watch:api": "npm run watch --workspace=@solidtime/api"
     },
     "devDependencies": {
         "@eslint/eslintrc": "^3.2.0",
@@ -27,10 +34,12 @@
         "@types/chroma-js": "^3.1.0",
         "@types/node": "^22.10.10",
         "@vitejs/plugin-vue": "^6.0.3",
+        "@vue/test-utils": "^2.4.6",
         "@vue/tsconfig": "^0.8.0",
         "autoprefixer": "^10.4.20",
         "axios": "^1.6.4",
         "eslint-plugin-unused-imports": "^4.1.4",
+        "happy-dom": "^20.8.9",
         "laravel-vite-plugin": "^2.1.0",
         "openapi-zod-client": "^1.16.2",
         "postcss": "^8.4.47",
@@ -40,6 +49,7 @@
         "typescript": "^5.7.3",
         "vite": "^7.0.0",
         "vite-plugin-checker": "^0.12.0",
+        "vitest": "^4.1.4",
         "vue": "^3.5.0",
         "vue-tsc": "^3.0.0"
     },
@@ -68,7 +78,7 @@
         "parse-duration": "^2.0.1",
         "pinia": "^3.0.0",
         "radix-vue": "^1.9.6",
-        "reka-ui": "^2.8.2",
+        "reka-ui": "2.8.2",
         "tailwind-merge": "^2.6.0",
         "tailwindcss-animate": "^1.0.7",
         "vue-echarts": "^8.0.0",

resources/js/Components/Timesheet/RemoveRowDialog.vue

@@ -0,0 +1,46 @@
+<script setup lang="ts">
+import {
+    AlertDialog,
+    AlertDialogAction,
+    AlertDialogCancel,
+    AlertDialogContent,
+    AlertDialogDescription,
+    AlertDialogFooter,
+    AlertDialogHeader,
+    AlertDialogTitle,
+} from '@/Components/ui/alert-dialog';
+
+defineProps<{
+    open: boolean;
+    entryCount: number;
+    projectName: string;
+}>();
+
+defineEmits<{
+    (e: 'update:open', value: boolean): void;
+    (e: 'confirm'): void;
+}>();
+</script>
+
+<template>
+    <AlertDialog :open="open" @update:open="$emit('update:open', $event)">
+        <AlertDialogContent>
+            <AlertDialogHeader>
+                <AlertDialogTitle>Remove timesheet row?</AlertDialogTitle>
+                <AlertDialogDescription>
+                    This will delete {{ entryCount }} time
+                    {{ entryCount === 1 ? 'entry' : 'entries' }}
+                    for "{{ projectName }}". This action cannot be undone.
+                </AlertDialogDescription>
+            </AlertDialogHeader>
+            <AlertDialogFooter>
+                <AlertDialogCancel>Cancel</AlertDialogCancel>
+                <AlertDialogAction
+                    class="bg-destructive text-destructive-foreground hover:bg-destructive/90"
+                    @click="$emit('confirm')">
+                    Delete
+                </AlertDialogAction>
+            </AlertDialogFooter>
+        </AlertDialogContent>
+    </AlertDialog>
+</template>

resources/js/Components/Timesheet/TimesheetCell.test.ts

@@ -0,0 +1,65 @@
+import { describe, expect, it } from 'vitest';
+import { mount } from '@vue/test-utils';
+import { nextTick } from 'vue';
+import TimesheetCell from './TimesheetCell.vue';
+import { formatHumanReadableDuration } from '@/packages/ui/src/utils/time';
+import type { TimesheetCell as TimesheetCellType } from '@/utils/useTimesheetGrid';
+
+function buildCell(totalSeconds: number): TimesheetCellType {
+    return {
+        dayIndex: 0,
+        date: '2026-04-13',
+        entries: [],
+        totalSeconds,
+    };
+}
+
+function mountTimesheetCell(totalSeconds = 2 * 3600) {
+    return mount(TimesheetCell, {
+        props: {
+            cell: buildCell(totalSeconds),
+            dayIndex: 0,
+            date: '2026-04-13',
+            isToday: false,
+            hasRunningEntry: false,
+        },
+    });
+}
+
+describe('TimesheetCell', () => {
+    it('emits 0 when the cleared value is committed on blur', async () => {
+        const wrapper = mountTimesheetCell();
+        const input = wrapper.get('input');
+
+        await input.trigger('focus');
+        await input.setValue('');
+        await input.trigger('blur');
+
+        expect(wrapper.emitted('update')).toEqual([[0]]);
+    });
+
+    it('emits 0 when the cleared value is committed with Enter', async () => {
+        const wrapper = mountTimesheetCell();
+        const input = wrapper.get('input');
+
+        await input.trigger('focus');
+        await input.setValue('');
+        await input.trigger('keydown', { key: 'Enter' });
+
+        expect(wrapper.emitted('update')).toEqual([[0]]);
+    });
+
+    it('restores the previous value and emits nothing on Escape', async () => {
+        const wrapper = mountTimesheetCell();
+        const input = wrapper.get('input');
+        const previousValue = formatHumanReadableDuration(2 * 3600, 'hours-minutes', 'point');
+
+        await input.trigger('focus');
+        await input.setValue('');
+        await input.trigger('keydown', { key: 'Escape' });
+        await nextTick();
+
+        expect(wrapper.emitted('update')).toBeUndefined();
+        expect((input.element as HTMLInputElement).value).toBe(previousValue);
+    });
+});

resources/js/Components/Timesheet/TimesheetCell.vue

@@ -0,0 +1,63 @@
+<script setup lang="ts">
+import DurationSecondsInput from '@/packages/ui/src/Input/DurationSecondsInput.vue';
+import {
+    Tooltip,
+    TooltipContent,
+    TooltipProvider,
+    TooltipTrigger,
+} from '@/packages/ui/src/tooltip';
+import type { TimesheetCell } from '@/utils/useTimesheetGrid';
+
+defineProps<{
+    cell?: TimesheetCell;
+    dayIndex: number;
+    date: string;
+    isToday: boolean;
+    hasRunningEntry: boolean;
+}>();
+
+const emit = defineEmits<{
+    update: [newSeconds: number];
+}>();
+</script>
+
+<template>
+    <div
+        data-testid="timesheet_cell"
+        class="flex items-center justify-center border-t border-default-background-separator"
+        :class="{ 'bg-default-background': isToday }">
+        <TooltipProvider v-if="hasRunningEntry" :delay-duration="100">
+            <Tooltip>
+                <TooltipTrigger as-child>
+                    <span class="inline-block cursor-not-allowed">
+                        <DurationSecondsInput
+                            :model-value="cell?.totalSeconds ?? 0"
+                            disabled
+                            default-unit="hours"
+                            placeholder="-"
+                            size="sm"
+                            input-class="w-[80px] mx-auto text-center font-medium
+                                bg-transparent text-text-primary placeholder:text-text-quaternary
+                                rounded-lg border border-input-border shadow-none
+                                pointer-events-none
+                                disabled:opacity-50 disabled:cursor-not-allowed" />
+                    </span>
+                </TooltipTrigger>
+                <TooltipContent> Stop the running time entry to edit the timesheet </TooltipContent>
+            </Tooltip>
+        </TooltipProvider>
+        <DurationSecondsInput
+            v-else
+            :model-value="cell?.totalSeconds ?? 0"
+            default-unit="hours"
+            placeholder="-"
+            size="sm"
+            input-class="w-[80px] mx-auto text-center font-medium
+                bg-transparent text-text-primary placeholder:text-text-quaternary
+                rounded-lg border border-input-border shadow-none
+                hover:bg-card-background
+                focus-visible:bg-tertiary focus-visible:border-transparent
+                focus-visible:ring-2 focus-visible:ring-ring focus-visible:outline-none"
+            @commit="(seconds) => emit('update', seconds ?? 0)" />
+    </div>
+</template>

resources/js/Components/Timesheet/TimesheetFooterActions.vue

@@ -0,0 +1,48 @@
+<script setup lang="ts">
+import { Button } from '@/packages/ui/src/Buttons';
+import {
+    DropdownMenu,
+    DropdownMenuContent,
+    DropdownMenuItem,
+    DropdownMenuTrigger,
+} from '@/packages/ui/src/dropdown-menu';
+import LoadingSpinner from '@/packages/ui/src/LoadingSpinner.vue';
+import { ChevronDownIcon, ClockIcon, ListBulletIcon } from '@heroicons/vue/20/solid';
+
+defineProps<{
+    busy: boolean;
+}>();
+
+defineEmits<{
+    (e: 'copy-rows'): void;
+    (e: 'copy-with-time'): void;
+}>();
+</script>
+
+<template>
+    <div class="mt-2 flex items-center pl-4 pr-4">
+        <DropdownMenu>
+            <DropdownMenuTrigger as-child>
+                <Button variant="ghost" size="sm" :disabled="busy">
+                    <LoadingSpinner v-if="busy" class="h-3.5 w-3.5 m-0" />
+                    Copy last week
+                    <ChevronDownIcon v-if="!busy" class="h-3.5 w-3.5 ml-1 text-icon-default" />
+                </Button>
+            </DropdownMenuTrigger>
+            <DropdownMenuContent align="start" class="min-w-[220px]">
+                <DropdownMenuItem
+                    class="flex items-center space-x-3 cursor-pointer"
+                    @click="$emit('copy-rows')">
+                    <ListBulletIcon class="w-5 text-icon-default" />
+                    <span>Copy rows only</span>
+                </DropdownMenuItem>
+                <DropdownMenuItem
+                    class="flex items-center space-x-3 cursor-pointer"
+                    @click="$emit('copy-with-time')">
+                    <ClockIcon class="w-5 text-icon-default" />
+                    <span>Copy rows and time entries</span>
+                </DropdownMenuItem>
+            </DropdownMenuContent>
+        </DropdownMenu>
+    </div>
+</template>

resources/js/Components/Timesheet/TimesheetGrid.vue

@@ -0,0 +1,166 @@
+<script setup lang="ts">
+import { inject, type ComputedRef } from 'vue';
+import { Button } from '@/packages/ui/src/Buttons';
+import { PlusIcon } from '@heroicons/vue/20/solid';
+import TimesheetRow from '@/Components/Timesheet/TimesheetRow.vue';
+import TimeTrackerProjectTaskDropdown from '@/packages/ui/src/TimeTracker/TimeTrackerProjectTaskDropdown.vue';
+import { getDayJsInstance } from '@/packages/ui/src/utils/time';
+import type {
+    Client,
+    CreateClientBody,
+    CreateProjectBody,
+    Organization,
+    Project,
+    Tag,
+    Task,
+} from '@/packages/api/src';
+import type { TimesheetRow as TimesheetRowType, TimesheetRowKey } from '@/utils/useTimesheetGrid';
+
+const organization = inject<ComputedRef<Organization>>('organization');
+const dayjs = getDayJsInstance();
+
+defineProps<{
+    rows: TimesheetRowType[];
+    weekDays: string[];
+    todayDate: string;
+    dayTotals: number[];
+    weekTotalFormatted: string;
+    projects: Project[];
+    tasks: Task[];
+    clients: Client[];
+    tags: Tag[];
+    currency: string;
+    canCreateProject: boolean;
+    enableEstimatedTime: boolean;
+    createProject: (project: CreateProjectBody) => Promise<Project | undefined>;
+    createClient: (client: CreateClientBody) => Promise<Client | undefined>;
+    createTag: (name: string) => Promise<Tag | undefined>;
+    formatDuration: (seconds: number) => string;
+}>();
+
+const emit = defineEmits<{
+    (e: 'remove-row', key: TimesheetRowKey): void;
+    (e: 'cell-update', row: TimesheetRowType, dayIndex: number, seconds: number): void;
+    (
+        e: 'project-task-change',
+        row: TimesheetRowType,
+        projectId: string | null,
+        taskId: string | null
+    ): void;
+    (e: 'billable-change', row: TimesheetRowType, billable: boolean): void;
+    (e: 'tags-change', row: TimesheetRowType, tags: string[]): void;
+    (e: 'add-row', projectId: string | null, taskId: string | null): void;
+}>();
+</script>
+
+<template>
+    <div class="flow-root max-w-[100vw] overflow-x-auto">
+        <div class="inline-block min-w-full align-middle">
+            <div
+                class="grid min-w-full w-max border-y border-default-background-separator"
+                style="
+                    grid-template-columns:
+                        minmax(420px, 1fr) repeat(7, minmax(96px, 120px)) minmax(100px, auto)
+                        40px;
+                ">
+                <!-- Header row -->
+                <div
+                    class="bg-background dark:bg-secondary pl-7 pr-3 py-1 text-xs text-text-tertiary md:sticky md:left-0 md:z-10">
+                    Project
+                </div>
+                <div
+                    v-for="day in weekDays"
+                    :key="day"
+                    class="bg-background dark:bg-secondary px-2 py-1 text-center">
+                    <div class="text-xs font-medium text-text-secondary">
+                        {{ dayjs(day).format('ddd D') }}
+                    </div>
+                </div>
+                <div
+                    class="bg-background dark:bg-secondary pl-3 pr-3 py-1 text-right text-xs text-text-tertiary">
+                    Total
+                </div>
+                <div class="bg-background dark:bg-secondary"></div>
+
+                <!-- Data rows -->
+                <TimesheetRow
+                    v-for="row in rows"
+                    :key="row.key"
+                    :row="row"
+                    :week-days="weekDays"
+                    :today-date="todayDate"
+                    :projects="projects"
+                    :tasks="tasks"
+                    :clients="clients"
+                    :tags="tags"
+                    :currency="currency"
+                    :can-create-project="canCreateProject"
+                    :enable-estimated-time="enableEstimatedTime"
+                    :create-project="createProject"
+                    :create-client="createClient"
+                    :create-tag="createTag"
+                    :format-duration="formatDuration"
+                    @remove-row="$emit('remove-row', $event)"
+                    @cell-update="
+                        (dayIndex, seconds) => $emit('cell-update', row, dayIndex, seconds)
+                    "
+                    @project-task-change="(pId, tId) => $emit('project-task-change', row, pId, tId)"
+                    @billable-change="(billable) => $emit('billable-change', row, billable)"
+                    @tags-change="(t) => $emit('tags-change', row, t)" />
+
+                <!-- Add row -->
+                <div
+                    class="col-span-full flex items-center gap-2 border-t border-default-background-separator pl-4 pr-4 py-2">
+                    <TimeTrackerProjectTaskDropdown
+                        :project="null"
+                        :task="null"
+                        :projects="projects"
+                        :tasks="tasks"
+                        :clients="clients"
+                        :currency="currency"
+                        :can-create-project="canCreateProject"
+                        :enable-estimated-time="enableEstimatedTime"
+                        :create-project="createProject"
+                        :create-client="createClient"
+                        :organization-billable-rate="organization?.billable_rate ?? null"
+                        :no-project-value="null"
+                        align="start"
+                        @changed="(p, t) => emit('add-row', p, t)">
+                        <template #trigger>
+                            <Button variant="ghost" size="sm" class="text-text-secondary">
+                                <PlusIcon class="h-4 w-4 mr-1 text-icon-default" />
+                                Add row
+                            </Button>
+                        </template>
+                    </TimeTrackerProjectTaskDropdown>
+                </div>
+
+                <!-- Totals row -->
+                <div
+                    class="border-t border-default-background-separator bg-background dark:bg-secondary pl-7 pr-3 py-1 text-xs text-text-tertiary md:sticky md:left-0 md:z-10">
+                    Total
+                </div>
+                <div
+                    v-for="(total, dayIndex) in dayTotals"
+                    :key="dayIndex"
+                    data-testid="timesheet_day_total"
+                    :class="[
+                        'flex items-center justify-center border-t border-default-background-separator bg-background dark:bg-secondary px-2 py-1 text-xs font-medium',
+                        weekDays[dayIndex] === todayDate
+                            ? 'text-text-primary'
+                            : 'text-text-secondary',
+                    ]">
+                    <span class="w-[80px] text-center">
+                        {{ total > 0 ? formatDuration(total) : '-' }}
+                    </span>
+                </div>
+                <div
+                    class="flex items-center justify-end border-t border-default-background-separator bg-background dark:bg-secondary pl-3 pr-3 py-1 text-xs font-semibold text-text-primary">
+                    {{ weekTotalFormatted }}
+                </div>
+                <div
+                    class="border-t border-default-background-separator bg-background dark:bg-secondary"></div>
+            </div>
+        </div>
+    </div>
+</template>

resources/js/Components/Timesheet/TimesheetHeader.vue

@@ -0,0 +1,60 @@
+<script setup lang="ts">
+import { Button } from '@/packages/ui/src/Buttons';
+import { ChevronLeftIcon, ChevronRightIcon, CalendarIcon } from '@heroicons/vue/20/solid';
+
+defineProps<{
+    isCurrentWeek: boolean;
+    weekNumber: number;
+    weekRangeDisplay: string;
+    weekTotalFormatted: string;
+}>();
+
+defineEmits<{
+    (e: 'previous'): void;
+    (e: 'next'): void;
+    (e: 'current'): void;
+}>();
+</script>
+
+<template>
+    <div class="flex flex-wrap items-center justify-between gap-4 mb-4 px-2 sm:px-4 lg:px-6">
+        <!-- Left: Week navigation -->
+        <div class="flex items-center gap-2">
+            <Button
+                variant="outline"
+                size="icon"
+                class="h-8 w-8"
+                data-testid="timesheet_prev_week"
+                @click="$emit('previous')">
+                <ChevronLeftIcon class="h-4 w-4" />
+            </Button>
+            <button
+                data-testid="timesheet_week_display"
+                class="flex items-center gap-2 px-3 py-1.5 text-sm font-medium text-text-primary hover:bg-card-background rounded-md transition"
+                @click="$emit('current')">
+                <CalendarIcon class="h-4 w-4 text-icon-default" />
+                <span v-if="isCurrentWeek">This week</span>
+                <span v-else>{{ weekRangeDisplay }}</span>
+                <span class="text-text-tertiary">&middot; W{{ weekNumber }}</span>
+            </button>
+            <Button
+                variant="outline"
+                size="icon"
+                class="h-8 w-8"
+                data-testid="timesheet_next_week"
+                @click="$emit('next')">
+                <ChevronRightIcon class="h-4 w-4" />
+            </Button>
+        </div>
+
+        <!-- Right: Week total -->
+        <div class="flex items-center gap-2.5">
+            <span class="text-xs text-text-tertiary uppercase tracking-wider">Week Total</span>
+            <span
+                data-testid="timesheet_grand_total"
+                class="text-sm font-semibold text-text-primary">
+                {{ weekTotalFormatted }}
+            </span>
+        </div>
+    </div>
+</template>

resources/js/Components/Timesheet/TimesheetRow.vue

@@ -0,0 +1,134 @@
+<script setup lang="ts">
+import { computed, inject, type ComputedRef } from 'vue';
+import { XMarkIcon } from '@heroicons/vue/16/solid';
+import TimesheetCell from './TimesheetCell.vue';
+import TimeTrackerProjectTaskDropdown from '@/packages/ui/src/TimeTracker/TimeTrackerProjectTaskDropdown.vue';
+import TimeEntryRowTagDropdown from '@/packages/ui/src/TimeEntry/TimeEntryRowTagDropdown.vue';
+import BillableToggleButton from '@/packages/ui/src/Input/BillableToggleButton.vue';
+import type {
+    CreateClientBody,
+    CreateProjectBody,
+    Project,
+    Task,
+    Client,
+    Tag,
+    Organization,
+} from '@/packages/api/src';
+import type { TimesheetRow, TimesheetRowKey } from '@/utils/useTimesheetGrid';
+import { Button } from '@/packages/ui/src/Buttons';
+
+const organization = inject<ComputedRef<Organization>>('organization');
+
+const props = defineProps<{
+    row: TimesheetRow;
+    weekDays: string[];
+    todayDate: string;
+    projects: Project[];
+    tasks: Task[];
+    clients: Client[];
+    tags: Tag[];
+    currency: string;
+    canCreateProject: boolean;
+    enableEstimatedTime: boolean;
+    createProject: (project: CreateProjectBody) => Promise<Project | undefined>;
+    createClient: (client: CreateClientBody) => Promise<Client | undefined>;
+    createTag: (name: string) => Promise<Tag | undefined>;
+    formatDuration: (seconds: number) => string;
+}>();
+
+const emit = defineEmits<{
+    removeRow: [key: TimesheetRowKey];
+    cellUpdate: [dayIndex: number, newSeconds: number];
+    projectTaskChange: [projectId: string | null, taskId: string | null];
+    billableChange: [billable: boolean];
+    tagsChange: [tags: string[]];
+}>();
+
+const selectedProject = computed({
+    get: () => props.row.projectId,
+    set: (val) => emit('projectTaskChange', val, selectedTask.value),
+});
+
+const selectedTask = computed({
+    get: () => props.row.taskId,
+    set: (val) => emit('projectTaskChange', selectedProject.value, val),
+});
+
+const rowTotalFormatted = computed(() => props.formatDuration(props.row.totalSeconds));
+
+function hasRunningEntry(dayIndex: number): boolean {
+    const cell = props.row.cells.get(dayIndex);
+    if (!cell) return false;
+    return cell.entries.some((e) => e.end === null);
+}
+</script>
+
+<template>
+    <div data-testid="timesheet_row" class="contents group">
+        <!-- Project/Task column -->
+        <div
+            class="flex items-center gap-1 border-t border-default-background-separator bg-default-background pl-4 pr-3 py-2 md:sticky md:left-0 md:z-10">
+            <div class="flex-1 min-w-0">
+                <TimeTrackerProjectTaskDropdown
+                    v-model:project="selectedProject"
+                    v-model:task="selectedTask"
+                    :projects="projects"
+                    :tasks="tasks"
+                    :clients="clients"
+                    :currency="currency"
+                    :can-create-project="canCreateProject"
+                    :enable-estimated-time="enableEstimatedTime"
+                    :create-project="createProject"
+                    :create-client="createClient"
+                    :organization-billable-rate="organization?.billable_rate ?? null"
+                    :no-project-value="null"
+                    variant="ghost"
+                    size="sm"
+                    class="w-full" />
+            </div>
+            <div class="flex items-center gap-1 flex-shrink-0 ml-auto">
+                <TimeEntryRowTagDropdown
+                    :create-tag="createTag"
+                    :tags="tags"
+                    :model-value="row.tags"
+                    @changed="emit('tagsChange', $event)" />
+                <BillableToggleButton
+                    :model-value="row.billable"
+                    size="small"
+                    faded
+                    @changed="emit('billableChange', $event)" />
+            </div>
+        </div>
+
+        <!-- Day cells -->
+        <TimesheetCell
+            v-for="(day, dayIndex) in weekDays"
+            :key="day"
+            :cell="row.cells.get(dayIndex)"
+            :day-index="dayIndex"
+            :date="day"
+            :is-today="day === todayDate"
+            :has-running-entry="hasRunningEntry(dayIndex)"
+            @update="(seconds) => emit('cellUpdate', dayIndex, seconds)" />
+
+        <!-- Row total -->
+        <div
+            data-testid="timesheet_row_total"
+            class="flex items-center justify-end border-t border-default-background-separator pl-3 pr-3 py-3 text-sm font-medium text-text-primary">
+            {{ rowTotalFormatted }}
+        </div>
+
+        <!-- Remove action -->
+        <div
+            class="flex items-center justify-center border-t border-default-background-separator pr-4 py-3">
+            <Button
+                variant="ghost"
+                size="icon"
+                aria-label="Remove row"
+                class="h-6 w-6 flex-shrink-0 opacity-0 group-hover:opacity-100 transition-opacity"
+                @click="emit('removeRow', row.key)">
+                <XMarkIcon class="h-3.5 w-3.5 text-icon-default" />
+            </Button>
+        </div>
+    </div>
+</template>

resources/js/Components/ui/alert-dialog/AlertDialogAction.vue

@@ -1,8 +1,8 @@
 <script setup lang="ts">
 import { buttonVariants } from '@/packages/ui/src';
+import { cn } from '@/lib/utils';
 import { AlertDialogAction, type AlertDialogActionProps } from 'reka-ui';
 import { computed, type HTMLAttributes } from 'vue';
-import { twMerge } from 'tailwind-merge';
 const props = defineProps<AlertDialogActionProps & { class?: HTMLAttributes['class'] }>();
 
 const delegatedProps = computed(() => {
@@ -13,7 +13,7 @@ const delegatedProps = computed(() => {
 </script>
 
 <template>
-    <AlertDialogAction v-bind="delegatedProps" :class="twMerge(buttonVariants(), props.class)">
+    <AlertDialogAction v-bind="delegatedProps" :class="cn(buttonVariants(), props.class)">
         <slot />
     </AlertDialogAction>
 </template>

resources/js/Components/ui/alert-dialog/AlertDialogCancel.vue

@@ -1,8 +1,8 @@
 <script setup lang="ts">
 import { buttonVariants } from '@/packages/ui/src';
+import { cn } from '@/lib/utils';
 import { AlertDialogCancel, type AlertDialogCancelProps } from 'reka-ui';
 import { computed, type HTMLAttributes } from 'vue';
-import { twMerge } from 'tailwind-merge';
 
 const props = defineProps<AlertDialogCancelProps & { class?: HTMLAttributes['class'] }>();
 
@@ -16,7 +16,7 @@ const delegatedProps = computed(() => {
 <template>
     <AlertDialogCancel
         v-bind="delegatedProps"
-        :class="twMerge(buttonVariants({ variant: 'outline' }), 'mt-2 sm:mt-0', props.class)">
+        :class="cn(buttonVariants({ variant: 'outline' }), 'mt-2 sm:mt-0', props.class)">
         <slot />
     </AlertDialogCancel>
 </template>

resources/js/Layouts/AppLayout.vue

@@ -17,6 +17,7 @@ import {
     UserGroupIcon,
     XMarkIcon,
     DocumentTextIcon,
+    TableCellsIcon,
 } from '@heroicons/vue/20/solid';
 import { PanelLeft } from 'lucide-vue-next';
 import NavigationSidebarItem from '@/Components/NavigationSidebarItem.vue';
@@ -135,7 +136,7 @@ const page = usePage<{
                     ? 'max-lg:translate-x-0 max-lg:shadow-xl'
                     : 'max-lg:-translate-x-full',
             ]"
-            class="flex-shrink-0 h-screen fixed w-[280px] px-2.5 py-4 hidden lg:flex flex-col justify-between bg-background border-r border-default-background-separator max-lg:z-50 max-lg:transition-transform max-lg:duration-200 max-lg:ease-in-out lg:w-[230px] 2xl:w-[250px] 2xl:px-3 lg:border-r-0"
+            class="flex-shrink-0 h-screen fixed w-[280px] px-2.5 py-4 hidden lg:flex flex-col justify-between bg-background border-r border-default-background-separator max-lg:z-50 max-lg:transition-transform max-lg:duration-200 max-lg:ease-in-out lg:w-[230px] lg:border-r-0"
             :style="showSidebarMenu ? { display: 'flex' } : undefined">
             <div class="flex flex-col h-full">
                 <div
@@ -185,6 +186,11 @@ const page = usePage<{
                                 :icon="CalendarIcon"
                                 :current="route().current('calendar')"
                                 :href="route('calendar')"></NavigationSidebarItem>
+                            <NavigationSidebarItem
+                                title="Timesheet"
+                                :icon="TableCellsIcon"
+                                :current="route().current('timesheet')"
+                                :href="route('timesheet')"></NavigationSidebarItem>
                             <NavigationSidebarItem
                                 title="Reporting"
                                 :icon="ChartBarIcon"
@@ -308,7 +314,7 @@ const page = usePage<{
                 </div>
             </div>
         </div>
-        <div class="flex-1 lg:ml-[230px] 2xl:ml-[250px] min-w-0">
+        <div class="flex-1 lg:ml-[230px] min-w-0">
             <div
                 class="h-screen overflow-y-auto flex flex-col bg-default-background border-l border-default-background-separator">
                 <div

resources/js/Pages/Calendar.vue

@@ -3,6 +3,7 @@ import AppLayout from '@/Layouts/AppLayout.vue';
 import { useTimeEntriesCalendarQuery } from '@/utils/useTimeEntriesCalendarQuery';
 import { useTimeEntriesMutations } from '@/utils/useTimeEntriesMutations';
 import { computed, ref, onMounted } from 'vue';
+import type { Dayjs } from 'dayjs';
 import { useQueryClient } from '@tanstack/vue-query';
 import {
     type Client,
@@ -27,8 +28,8 @@ import { useOrganizationQuery } from '@/utils/useOrganizationQuery';
 import { getCurrentOrganizationId } from '@/utils/useUser';
 
 const { organization } = useOrganizationQuery(getCurrentOrganizationId()!);
-const calendarStart = ref<Date | undefined>(undefined);
-const calendarEnd = ref<Date | undefined>(undefined);
+const calendarStart = ref<Dayjs | undefined>(undefined);
+const calendarEnd = ref<Dayjs | undefined>(undefined);
 
 // Test-injectable activity periods (for E2E testing).
 // These hooks are no-ops in production — they only take effect when test code
@@ -99,7 +100,7 @@ const { tags } = useTagsQuery();
 
 const queryClient = useQueryClient();
 
-function onDatesChange({ start, end }: { start: Date; end: Date }) {
+function onDatesChange({ start, end }: { start: Dayjs; end: Dayjs }) {
     calendarStart.value = start;
     calendarEnd.value = end;
 }

resources/js/Pages/Timesheet.vue

@@ -0,0 +1,196 @@
+<script setup lang="ts">
+import { computed, watch } from 'vue';
+import { storeToRefs } from 'pinia';
+import AppLayout from '@/Layouts/AppLayout.vue';
+import LoadingSpinner from '@/packages/ui/src/LoadingSpinner.vue';
+import TimesheetHeader from '@/Components/Timesheet/TimesheetHeader.vue';
+import TimesheetGrid from '@/Components/Timesheet/TimesheetGrid.vue';
+import TimesheetFooterActions from '@/Components/Timesheet/TimesheetFooterActions.vue';
+import RemoveRowDialog from '@/Components/Timesheet/RemoveRowDialog.vue';
+import { useTimesheetQuery } from '@/utils/useTimesheetQuery';
+import { useTimesheetGrid } from '@/utils/useTimesheetGrid';
+import { useTimeEntriesMutations } from '@/utils/useTimeEntriesMutations';
+import { useProjectsQuery } from '@/utils/useProjectsQuery';
+import { useTasksQuery } from '@/utils/useTasksQuery';
+import { useClientsQuery } from '@/utils/useClientsQuery';
+import { useTagsQuery } from '@/utils/useTagsQuery';
+import { useOrganizationQuery } from '@/utils/useOrganizationQuery';
+import { useProjectsStore } from '@/utils/useProjects';
+import { useClientsStore } from '@/utils/useClients';
+import { useTagsStore } from '@/utils/useTags';
+import { getCurrentOrganizationId } from '@/utils/useUser';
+import { getOrganizationCurrencyString } from '@/utils/money';
+import { isAllowedToPerformPremiumAction } from '@/utils/billing';
+import { canCreateProjects } from '@/utils/permissions';
+import { formatHumanReadableDuration } from '@/packages/ui/src/utils/time';
+import { useTimesheetWeek } from '@/utils/timesheet/useTimesheetWeek';
+import { useTimesheetCellMutations } from '@/utils/timesheet/useTimesheetCellMutations';
+import { useTimesheetRowMutations } from '@/utils/timesheet/useTimesheetRowMutations';
+import { useTimesheetRowDeletion } from '@/utils/timesheet/useTimesheetRowDeletion';
+import { useCopyLastWeek } from '@/utils/timesheet/useCopyLastWeek';
+import { useCurrentTimeEntryStore } from '@/utils/useCurrentTimeEntry';
+import type { CreateClientBody, CreateProjectBody, Project, Client, Tag } from '@/packages/api/src';
+
+// ── Week state ────────────────────────────────────────────────────
+const {
+    weekStart,
+    weekEnd,
+    weekDays,
+    weekNumber,
+    isCurrentWeek,
+    todayDate,
+    goToPreviousWeek,
+    goToNextWeek,
+    goToCurrentWeek,
+} = useTimesheetWeek();
+
+// ── Data fetching ─────────────────────────────────────────────────
+const { data, isPending } = useTimesheetQuery(weekStart, weekEnd);
+const timeEntries = computed(() => data.value?.data ?? []);
+
+const { projects } = useProjectsQuery();
+const { tasks } = useTasksQuery();
+const { clients } = useClientsQuery();
+const { tags } = useTagsQuery();
+const { now: currentTimerNow } = storeToRefs(useCurrentTimeEntryStore());
+
+const mutations = useTimeEntriesMutations();
+
+// ── Grid computation ──────────────────────────────────────────────
+const { rows, dayTotals, grandTotal, addSlot, removeSlot, updateSlot, clearSlots } =
+    useTimesheetGrid(timeEntries, weekDays, projects, tasks, currentTimerNow);
+
+// Wipe slots on week navigation so the new week starts fresh — the
+// grid's watcher will reseed from the newly fetched entries.
+watch(weekStart, () => clearSlots());
+
+// ── Formatters ────────────────────────────────────────────────────
+// Pull number/interval format off the org via its query rather than
+// inject('organization'), which is undefined during the page's setup
+// (AppLayout provides it later in the lifecycle).
+const { organization } = useOrganizationQuery(getCurrentOrganizationId()!);
+const intervalFormat = computed(() => organization.value?.interval_format ?? 'hours-minutes');
+const numberFormat = computed(() => organization.value?.number_format ?? 'point');
+
+function formatDuration(seconds: number): string {
+    if (seconds === 0) return '-';
+    return formatHumanReadableDuration(seconds, intervalFormat.value, numberFormat.value);
+}
+
+const weekTotalFormatted = computed(() =>
+    formatHumanReadableDuration(grandTotal.value, intervalFormat.value, numberFormat.value)
+);
+
+const weekRangeDisplay = computed(() => {
+    const start = weekStart.value;
+    const end = start.add(6, 'day');
+    return start.month() === end.month()
+        ? `${start.format('MMM D')} - ${end.format('D')}`
+        : `${start.format('MMM D')} - ${end.format('MMM D')}`;
+});
+
+// ── Cell / row mutation handlers ──────────────────────────────────
+const { handleCellUpdate } = useTimesheetCellMutations(weekDays, timeEntries, rows, removeSlot);
+
+const { handleRowIdentityChange, handleAddRow } = useTimesheetRowMutations(
+    mutations,
+    projects,
+    rows,
+    addSlot,
+    updateSlot,
+    removeSlot
+);
+
+const {
+    showDeleteDialog,
+    deleteRowEntryCount,
+    deleteRowProjectName,
+    requestRemoveRow,
+    confirmDeleteRow,
+} = useTimesheetRowDeletion(projects, mutations, removeSlot);
+
+function handleRemoveRow(key: string) {
+    const row = rows.value.find((r) => r.key === key);
+    if (row) requestRemoveRow(row);
+}
+
+// ── Copy last week ────────────────────────────────────────────────
+const { isCopyingLastWeek, copyLastWeekRows, copyLastWeekWithTime } = useCopyLastWeek(
+    weekStart,
+    weekDays,
+    rows,
+    timeEntries,
+    addSlot
+);
+
+// ── Inline creation helpers (passed to TimesheetRow) ──────────────
+async function createProject(project: CreateProjectBody): Promise<Project | undefined> {
+    return await useProjectsStore().createProject(project);
+}
+
+async function createClient(body: CreateClientBody): Promise<Client | undefined> {
+    return await useClientsStore().createClient(body);
+}
+
+async function createTag(name: string): Promise<Tag | undefined> {
+    return await useTagsStore().createTag(name);
+}
+</script>
+
+<template>
+    <AppLayout title="Timesheet" data-testid="timesheet_view">
+        <div class="pt-5 lg:pt-8 pb-4 lg:pb-6">
+            <TimesheetHeader
+                :is-current-week="isCurrentWeek"
+                :week-number="weekNumber"
+                :week-range-display="weekRangeDisplay"
+                :week-total-formatted="weekTotalFormatted"
+                @previous="goToPreviousWeek"
+                @next="goToNextWeek"
+                @current="goToCurrentWeek" />
+
+            <TimesheetGrid
+                v-if="!isPending"
+                :rows="rows"
+                :week-days="weekDays"
+                :today-date="todayDate"
+                :day-totals="dayTotals"
+                :week-total-formatted="weekTotalFormatted"
+                :projects="projects"
+                :tasks="tasks"
+                :clients="clients"
+                :tags="tags"
+                :currency="getOrganizationCurrencyString()"
+                :can-create-project="canCreateProjects()"
+                :enable-estimated-time="isAllowedToPerformPremiumAction()"
+                :create-project="createProject"
+                :create-client="createClient"
+                :create-tag="createTag"
+                :format-duration="formatDuration"
+                @remove-row="handleRemoveRow"
+                @cell-update="handleCellUpdate"
+                @project-task-change="
+                    (row, projectId, taskId) => handleRowIdentityChange(row, { projectId, taskId })
+                "
+                @billable-change="(row, billable) => handleRowIdentityChange(row, { billable })"
+                @tags-change="(row, tags) => handleRowIdentityChange(row, { tags })"
+                @add-row="handleAddRow" />
+
+            <TimesheetFooterActions
+                v-if="!isPending"
+                :busy="isCopyingLastWeek"
+                @copy-rows="copyLastWeekRows"
+                @copy-with-time="copyLastWeekWithTime" />
+
+            <div v-else class="flex justify-center items-center py-12">
+                <LoadingSpinner />
+            </div>
+        </div>
+
+        <RemoveRowDialog
+            v-model:open="showDeleteDialog"
+            :entry-count="deleteRowEntryCount"
+            :project-name="deleteRowProjectName"
+            @confirm="confirmDeleteRow" />
+    </AppLayout>
+</template>

resources/js/packages/ui/src/FullCalendar/TimeEntryCalendar.vue

@@ -57,7 +57,7 @@ import type {
 import type { Dayjs } from 'dayjs';
 
 const emit = defineEmits<{
-    (e: 'dates-change', payload: { start: Date; end: Date }): void;
+    (e: 'dates-change', payload: { start: Dayjs; end: Dayjs }): void;
     (e: 'refresh'): void;
 }>();
 

resources/js/packages/ui/src/FullCalendar/useCalendarEvents.ts

@@ -265,9 +265,9 @@ export function useCalendarEvents(params: {
                     'seconds'
                 );
             } else {
-                durationSeconds = params.currentTime.value.diff(
-                    getDayJsInstance()(entry.start),
-                    'seconds'
+                durationSeconds = Math.max(
+                    0,
+                    params.currentTime.value.diff(getDayJsInstance()(entry.start), 'seconds')
                 );
             }
 

resources/js/packages/ui/src/FullCalendar/useCalendarNavigation.ts

@@ -1,27 +1,17 @@
 import { computed, ref } from 'vue';
 import type { Dayjs } from 'dayjs';
 import { getLocalizedDayJs } from '../utils/time';
-import { getWeekStart } from '../utils/settings';
+import { getWeekStartDayNumber } from '../utils/settings';
 
 export function useCalendarNavigation(callbacks: {
-    onDatesChange: (payload: { start: Date; end: Date }) => void;
+    onDatesChange: (payload: { start: Dayjs; end: Dayjs }) => void;
     scrollToCurrentTime: () => void;
 }) {
     const activeView = ref('timeGridWeek');
     const currentDate = ref(getLocalizedDayJs());
 
     function getFirstDay(): number {
-        const weekStart = getWeekStart();
-        const weekStartMap: Record<string, number> = {
-            sunday: 0,
-            monday: 1,
-            tuesday: 2,
-            wednesday: 3,
-            thursday: 4,
-            friday: 5,
-            saturday: 6,
-        };
-        return weekStartMap[weekStart] ?? 1;
+        return getWeekStartDayNumber();
     }
 
     const viewDays = computed<Dayjs[]>(() => {
@@ -67,8 +57,8 @@ export function useCalendarNavigation(callbacks: {
         const days = viewDays.value;
         if (days.length === 0) return;
 
-        const start = days[0]!.toDate();
-        const end = days[days.length - 1]!.add(1, 'day').toDate();
+        const start = days[0]!;
+        const end = days[days.length - 1]!.add(1, 'day');
         callbacks.onDatesChange({ start, end });
     }
 

resources/js/packages/ui/src/Input/DurationSecondsInput.vue

@@ -0,0 +1,145 @@
+<script setup lang="ts">
+import { computed, inject, ref, type ComputedRef } from 'vue';
+import { formatHumanReadableDuration, parseTimeInput } from '@/packages/ui/src/utils/time';
+import TextInput from '@/packages/ui/src/Input/TextInput.vue';
+import type { Organization } from '@/packages/api/src';
+
+const organization = inject<ComputedRef<Organization>>('organization');
+
+const organizationSettings = computed(() => ({
+    intervalFormat: organization?.value?.interval_format ?? 'hours-minutes',
+    numberFormat: organization?.value?.number_format ?? 'point',
+}));
+
+const props = withDefaults(
+    defineProps<{
+        modelValue?: number | null;
+        placeholder?: string;
+        disabled?: boolean;
+        inputClass?: string;
+        size?: 'sm' | 'base';
+        defaultUnit?: 'auto' | 'hours' | 'minutes';
+    }>(),
+    {
+        modelValue: null,
+        placeholder: '-',
+        disabled: false,
+        inputClass: '',
+        size: 'base',
+        defaultUnit: 'auto',
+    }
+);
+
+const emit = defineEmits<{
+    'update:modelValue': [value: number | null];
+    commit: [value: number | null];
+    submit: [];
+}>();
+
+const temporaryValue = ref('');
+const isEditing = ref(false);
+const hasPendingEdit = ref(false);
+const skipNextCommit = ref(false);
+
+function formatModelValue(value: number | null | undefined): string {
+    if (!value || value === 0) {
+        return '';
+    }
+
+    return formatHumanReadableDuration(
+        value,
+        organizationSettings.value.intervalFormat,
+        organizationSettings.value.numberFormat
+    );
+}
+
+const displayValue = computed({
+    get() {
+        if (isEditing.value) {
+            return temporaryValue.value;
+        }
+        return formatModelValue(props.modelValue);
+    },
+    set(newValue: string) {
+        temporaryValue.value = newValue;
+        hasPendingEdit.value = true;
+    },
+});
+
+function selectInput(event: Event) {
+    isEditing.value = true;
+    hasPendingEdit.value = false;
+    skipNextCommit.value = false;
+    temporaryValue.value = formatModelValue(props.modelValue);
+    const target = event.target as HTMLInputElement;
+    target.select();
+}
+
+function resetEditingState() {
+    temporaryValue.value = '';
+    isEditing.value = false;
+    hasPendingEdit.value = false;
+}
+
+function commitValue() {
+    if (skipNextCommit.value) {
+        skipNextCommit.value = false;
+        return;
+    }
+
+    const input = temporaryValue.value.trim();
+    const shouldCommit = hasPendingEdit.value;
+    resetEditingState();
+
+    if (!shouldCommit) {
+        return;
+    }
+
+    // Blank or literal "0" → null. Consumers decide what null means
+    // (clear estimate, delete cell, etc.) by reading their own emit.
+    if (input === '' || input === '0') {
+        emit('update:modelValue', null);
+        emit('commit', null);
+        return;
+    }
+
+    const defaultUnit =
+        props.defaultUnit === 'auto'
+            ? organizationSettings.value.intervalFormat === 'decimal'
+                ? 'hours'
+                : 'minutes'
+            : props.defaultUnit;
+    const seconds = parseTimeInput(input, organizationSettings.value.numberFormat, defaultUnit);
+
+    if (seconds !== null && seconds >= 0) {
+        emit('update:modelValue', seconds);
+        emit('commit', seconds);
+    }
+}
+
+function cancelEdit(event: Event) {
+    skipNextCommit.value = true;
+    resetEditingState();
+    (event.target as HTMLInputElement).blur();
+}
+
+function commitAndSubmit() {
+    commitValue();
+    emit('submit');
+}
+</script>
+
+<template>
+    <TextInput
+        v-model="displayValue"
+        data-testid="duration_seconds_input"
+        name="Duration"
+        :size="size"
+        :disabled="disabled"
+        :placeholder="isEditing ? '0' : placeholder"
+        :class="inputClass"
+        @focus="selectInput"
+        @blur="commitValue"
+        @keydown.enter.prevent="commitAndSubmit"
+        @keydown.escape="cancelEdit" />
+</template>

resources/js/packages/ui/src/Input/EstimatedTimeInput.vue

@@ -1,12 +1,6 @@
 <script setup lang="ts">
-import { onMounted, ref, watch, inject } from 'vue';
-import { formatHumanReadableDuration, parseTimeInput } from '@/packages/ui/src/utils/time';
+import DurationSecondsInput from '@/packages/ui/src/Input/DurationSecondsInput.vue';
 import { twMerge } from 'tailwind-merge';
-import { TextInput } from '@/packages/ui/src';
-import type { Organization } from '@/packages/api/src';
-import { type ComputedRef } from 'vue';
-
-const temporaryInput = ref<string>('');
 
 const model = defineModel<number | null>({
     default: null,
@@ -16,64 +10,16 @@ const emit = defineEmits<{
     submit: [];
 }>();
 
-const organization = inject<ComputedRef<Organization>>('organization');
-
-function updateDuration() {
-    const input = temporaryInput.value.trim();
-
-    if (input === '') {
-        model.value = null;
-        return;
-    }
-
-    const seconds = parseTimeInput(input, organization?.value?.number_format, 'hours');
-    if (seconds !== null && seconds > 0) {
-        model.value = seconds;
-    }
-
-    updateInputDisplay();
-}
-
 const props = defineProps<{
     class?: string;
 }>();
-
-watch(model, updateInputDisplay);
-onMounted(() => updateInputDisplay());
-
-function updateInputDisplay() {
-    if (model.value !== null && model.value > 0) {
-        temporaryInput.value = formatHumanReadableDuration(
-            model.value,
-            organization?.value?.interval_format,
-            organization?.value?.number_format
-        );
-    } else {
-        temporaryInput.value = '';
-    }
-}
-
-function selectInput(event: Event) {
-    const target = event.target as HTMLInputElement;
-    target.select();
-}
-
-function updateAndSubmit() {
-    updateDuration();
-    emit('submit');
-}
 </script>
 
 <template>
-    <TextInput
-        ref="inputField"
-        v-model="temporaryInput"
-        :class="twMerge('text-text-secondary', props.class)"
-        type="text"
+    <DurationSecondsInput
+        v-model="model"
+        :input-class="twMerge('placeholder:text-text-tertiary', props.class)"
         placeholder="e.g. 2h 30m or 1.5"
-        @focus="selectInput"
-        @blur="updateDuration"
-        @keydown.enter="updateAndSubmit" />
+        default-unit="hours"
+        @submit="emit('submit')" />
 </template>
-
-<style scoped></style>

resources/js/packages/ui/src/Input/TextInput.vue

@@ -1,11 +1,15 @@
 <script setup lang="ts">
-import { onMounted, ref } from 'vue';
+import { computed, onMounted, ref } from 'vue';
 import { twMerge } from 'tailwind-merge';
 
-const props = defineProps<{
-    name?: string;
-    class?: string;
-}>();
+const props = withDefaults(
+    defineProps<{
+        name?: string;
+        class?: string;
+        size?: 'sm' | 'base';
+    }>(),
+    { size: 'base' }
+);
 
 const input = ref<HTMLInputElement | null>(null);
 
@@ -17,6 +21,10 @@ onMounted(() => {
 
 defineExpose({ focus: () => input.value?.focus() });
 const model = defineModel();
+
+const sizeClasses = computed(() =>
+    props.size === 'sm' ? 'h-7 px-2 py-0.5 text-xs' : 'h-9 px-3 py-1 text-base sm:text-sm'
+);
 </script>
 
 <template>
@@ -25,7 +33,8 @@ const model = defineModel();
         v-model="model"
         :class="
             twMerge(
-                'h-9 px-3 py-1 text-base sm:text-sm border-input-border border bg-input-background text-text-primary focus-visible:ring-2 focus-visible:ring-ring focus-visible:border-transparent rounded-md shadow-sm',
+                'border-input-border border bg-input-background text-text-primary focus-visible:ring-2 focus-visible:ring-ring focus-visible:border-transparent rounded-md shadow-sm',
+                sizeClasses,
                 props.class
             )
         "

resources/js/packages/ui/src/TimeTracker/TimeTrackerProjectTaskDropdown.test.ts

@@ -0,0 +1,90 @@
+/* eslint-disable vue/one-component-per-file */
+import { mount } from '@vue/test-utils';
+import { describe, expect, it, vi } from 'vitest';
+import { defineComponent, h, nextTick, onMounted } from 'vue';
+import TimeTrackerProjectTaskDropdown from './TimeTrackerProjectTaskDropdown.vue';
+import type { Client, Project, Task } from '@/packages/api/src';
+
+const DropdownStub = defineComponent({
+    props: {
+        modelValue: {
+            type: Boolean,
+            default: false,
+        },
+    },
+    emits: ['update:modelValue'],
+    setup(_, { emit, slots }) {
+        onMounted(() => emit('update:modelValue', true));
+        return () => h('div', [slots.trigger?.(), slots.content?.()]);
+    },
+});
+
+const FocusTrapStub = defineComponent({
+    setup(_, { slots }) {
+        return () => h('div', slots.default?.());
+    },
+});
+
+function mountDropdown(props: Record<string, unknown> = {}) {
+    return mount(TimeTrackerProjectTaskDropdown, {
+        props: {
+            project: null,
+            task: null,
+            projects: [] as Project[],
+            tasks: [] as Task[],
+            clients: [] as Client[],
+            createProject: vi.fn(),
+            createClient: vi.fn(),
+            currency: 'EUR',
+            enableEstimatedTime: false,
+            organizationBillableRate: null,
+            canCreateProject: false,
+            ...props,
+        },
+        global: {
+            stubs: {
+                Dropdown: DropdownStub,
+                UseFocusTrap: FocusTrapStub,
+            },
+        },
+    });
+}
+
+async function openDropdown() {
+    const wrapper = mountDropdown();
+    await nextTick();
+    await nextTick();
+    return wrapper;
+}
+
+describe('TimeTrackerProjectTaskDropdown', () => {
+    it('keeps the existing empty-string no-project value by default', async () => {
+        const wrapper = await openDropdown();
+
+        await wrapper.find('[data-project-id=""]').trigger('click');
+
+        expect(wrapper.emitted('update:project')?.at(-1)).toEqual(['']);
+        expect(wrapper.emitted('changed')?.at(-1)).toEqual(['', null]);
+    });
+
+    it('can emit null for no-project consumers that use null as the domain value', async () => {
+        const wrapper = mountDropdown({ project: 'p-1', noProjectValue: null });
+        await nextTick();
+        await nextTick();
+
+        await wrapper.find('[data-project-id=""]').trigger('click');
+
+        expect(wrapper.emitted('update:project')?.at(-1)).toEqual([null]);
+        expect(wrapper.emitted('changed')?.at(-1)).toEqual([null, null]);
+    });
+
+    it('still exposes "No Project" when projects are empty and project creation is allowed', async () => {
+        const wrapper = mountDropdown({ canCreateProject: true });
+        await nextTick();
+        await nextTick();
+
+        await wrapper.find('[data-project-id=""]').trigger('click');
+
+        expect(wrapper.emitted('changed')?.at(-1)).toEqual(['', null]);
+    });
+});

resources/js/packages/ui/src/TimeTracker/TimeTrackerProjectTaskDropdown.vue

@@ -11,11 +11,13 @@ import type {
     Client,
 } from '@/packages/api/src';
 
-import { PlusIcon, PlusCircleIcon, MinusIcon, XMarkIcon } from '@heroicons/vue/16/solid';
+import { PlusCircleIcon, MinusIcon, XMarkIcon } from '@heroicons/vue/16/solid';
 import ProjectCreateModal from '@/packages/ui/src/Project/ProjectCreateModal.vue';
 import { twMerge } from 'tailwind-merge';
 import { Button } from '@/packages/ui/src/Buttons';
 
+const NO_PROJECT_ID = '';
+
 const task = defineModel<string | null>('task', {
     default: null,
 });
@@ -57,6 +59,7 @@ const props = withDefaults(
         currency: string;
         emptyPlaceholder?: string;
         allowReset?: boolean;
+        noProjectValue?: string | null;
         enableEstimatedTime: boolean;
         organizationBillableRate: number | null;
         canCreateProject: boolean;
@@ -68,6 +71,7 @@ const props = withDefaults(
     {
         emptyPlaceholder: 'No Project',
         allowReset: false,
+        noProjectValue: NO_PROJECT_ID,
         variant: 'ghost',
         align: 'center',
         size: 'sm',
@@ -164,10 +168,10 @@ function updateFilteredResults() {
             is_archived: false,
             projects: [
                 {
-                    id: '',
+                    id: NO_PROJECT_ID,
                     name: 'No Project',
                     color: 'var(--theme-color-icon-default)',
-                    value: '',
+                    value: NO_PROJECT_ID,
                     client_id: null,
                     billable_rate: null,
                     is_archived: false,
@@ -490,7 +494,7 @@ function selectTask(taskId: string) {
 }
 
 function selectProject(projectId: string) {
-    project.value = projectId;
+    project.value = projectId === NO_PROJECT_ID ? props.noProjectValue : projectId;
     task.value = null;
     open.value = false;
     searchValue.value = '';
@@ -507,41 +511,35 @@ const showCreateProject = ref(false);
 </script>
 
 <template>
-    <template v-if="projects.length === 0 && canCreateProject">
-        <Button
-            :variant="props.variant"
-            :size="props.size"
-            :class="twMerge('w-full justify-start', props.class)"
-            @click="showCreateProject = true">
-            <PlusIcon class="w-4" />
-            <span class="truncate">Add new project</span>
-        </Button>
-    </template>
-    <Dropdown v-else v-model="open" :close-on-content-click="false" :align="props.align">
+    <Dropdown v-model="open" :close-on-content-click="false" :align="props.align">
         <template #trigger>
-            <div class="flex items-center gap-1">
-                <Button
-                    :variant="props.variant"
-                    :size="props.size"
-                    :class="twMerge('w-full justify-start overflow-hidden', props.class)">
-                    <div
-                        class="w-3 h-3 rounded-full shrink-0"
-                        :style="{ backgroundColor: selectedProjectColor }"></div>
-                    <span class="truncate shrink-[1] pr-1">{{ selectedProjectName }}</span>
-                    <template v-if="currentTask">
-                        <ChevronRightIcon class="w-4 h-4 text-text-tertiary shrink-0" />
-                        <span class="truncate shrink-[100]">{{ currentTask.name }}</span>
-                    </template>
-                </Button>
-                <button
-                    v-if="allowReset && project !== null"
-                    type="button"
-                    data-testid="project_reset_button"
-                    class="p-1 rounded hover:bg-quaternary text-text-tertiary hover:text-text-primary"
-                    @click.stop="resetProject">
-                    <XMarkIcon class="w-4 h-4" />
-                </button>
-            </div>
+            <slot name="trigger">
+                <div class="flex items-center gap-1">
+                    <Button
+                        :variant="props.variant"
+                        :size="props.size"
+                        :class="twMerge('w-full justify-start overflow-hidden', props.class)">
+                        <div
+                            class="w-3 h-3 rounded-full shrink-0"
+                            :style="{ backgroundColor: selectedProjectColor }"></div>
+                        <span class="truncate shrink-[1] text-text-primary pr-1">{{
+                            selectedProjectName
+                        }}</span>
+                        <template v-if="currentTask">
+                            <ChevronRightIcon class="w-4 h-4 text-text-tertiary shrink-0" />
+                            <span class="truncate shrink-[100]">{{ currentTask.name }}</span>
+                        </template>
+                    </Button>
+                    <button
+                        v-if="allowReset && project !== null"
+                        type="button"
+                        data-testid="project_reset_button"
+                        class="p-1 rounded hover:bg-quaternary text-text-tertiary hover:text-text-primary"
+                        @click.stop="resetProject">
+                        <XMarkIcon class="w-4 h-4" />
+                    </button>
+                </div>
+            </slot>
         </template>
         <template #content>
             <UseFocusTrap v-if="open" :options="{ immediate: true, allowOutsideClick: true }">

resources/js/packages/ui/src/calendar/CalendarCell.vue

@@ -1,7 +1,7 @@
 <script lang="ts" setup>
 import { CalendarCell, type CalendarCellProps, useForwardProps } from 'reka-ui';
 import { computed, type HTMLAttributes } from 'vue';
-import { twMerge } from 'tailwind-merge';
+import { cn } from '../utils/cn';
 
 const props = defineProps<CalendarCellProps & { class?: HTMLAttributes['class'] }>();
 
@@ -17,7 +17,7 @@ const forwardedProps = useForwardProps(delegatedProps);
 <template>
     <CalendarCell
         :class="
-            twMerge(
+            cn(
                 'relative p-0 text-center text-sm focus-within:relative focus-within:z-20 [&:has([data-selected])]:rounded-md [&:has([data-selected])]:bg-accent [&:has([data-selected][data-outside-view])]:bg-accent/50',
                 props.class
             )

resources/js/packages/ui/src/utils/settings.ts

@@ -8,6 +8,20 @@ export function getWeekStart() {
     }
     return weekStart;
 }
+
+const weekStartMap: Record<string, number> = {
+    sunday: 0,
+    monday: 1,
+    tuesday: 2,
+    wednesday: 3,
+    thursday: 4,
+    friday: 5,
+    saturday: 6,
+};
+
+export function getWeekStartDayNumber(): number {
+    return weekStartMap[getWeekStart()] ?? 1;
+}
 export function getUserTimezone() {
     const timezone = window?.getTimezoneSetting() as string;
     if (!timezone) {

resources/js/packages/ui/src/utils/time.test.ts

@@ -0,0 +1,44 @@
+import { describe, expect, test } from 'vitest';
+import { formatHumanReadableDuration, formatReportingDuration } from './time';
+
+const seconds = 14 * 3600 + 45 * 60 + 6; // 14h 45m 06s
+
+describe('formatHumanReadableDuration', () => {
+    test('decimal', () => {
+        expect(formatHumanReadableDuration(seconds, 'decimal', 'comma-point')).toBe('14.75 h');
+    });
+
+    test('hours-minutes', () => {
+        expect(formatHumanReadableDuration(seconds, 'hours-minutes')).toBe('14h 45min');
+    });
+
+    test('hours-minutes-colon-separated', () => {
+        expect(formatHumanReadableDuration(seconds, 'hours-minutes-colon-separated')).toBe('14:45');
+    });
+
+    test('hours-minutes-seconds-colon-separated', () => {
+        expect(formatHumanReadableDuration(seconds, 'hours-minutes-seconds-colon-separated')).toBe(
+            '14:45:06'
+        );
+    });
+});
+
+describe('formatReportingDuration', () => {
+    test('decimal', () => {
+        expect(formatReportingDuration(seconds, 'decimal', 'comma-point')).toBe('14.75 h');
+    });
+
+    test('hours-minutes', () => {
+        expect(formatReportingDuration(seconds, 'hours-minutes')).toBe('14:45:06');
+    });
+
+    test('hours-minutes-colon-separated', () => {
+        expect(formatReportingDuration(seconds, 'hours-minutes-colon-separated')).toBe('14:45:06');
+    });
+
+    test('hours-minutes-seconds-colon-separated', () => {
+        expect(formatReportingDuration(seconds, 'hours-minutes-seconds-colon-separated')).toBe(
+            '14:45:06'
+        );
+    });
+});

resources/js/packages/ui/src/utils/time.ts

@@ -3,6 +3,8 @@ import duration from 'dayjs/plugin/duration';
 import relativeTime from 'dayjs/plugin/relativeTime';
 import isToday from 'dayjs/plugin/isToday';
 import isYesterday from 'dayjs/plugin/isYesterday';
+import isSameOrBefore from 'dayjs/plugin/isSameOrBefore';
+import isSameOrAfter from 'dayjs/plugin/isSameOrAfter';
 import utc from 'dayjs/plugin/utc';
 import timezone from 'dayjs/plugin/timezone';
 import weekOfYear from 'dayjs/plugin/weekOfYear';
@@ -68,6 +70,8 @@ function configureParseLocale(numberFormat?: string) {
 dayjs.extend(relativeTime);
 dayjs.extend(isToday);
 dayjs.extend(isYesterday);
+dayjs.extend(isSameOrBefore);
+dayjs.extend(isSameOrAfter);
 dayjs.extend(duration);
 dayjs.extend(utc);
 dayjs.extend(timezone);
@@ -188,6 +192,15 @@ export function getLocalizedDateFromTimestamp(timestamp: string) {
     return getLocalizedDayJs(timestamp).format('YYYY-MM-DD');
 }
 
+/**
+ * Converts a local Date to a UTC-formatted ISO string.
+ * Treats the Date as being in the user's timezone and converts to UTC.
+ * This is the inverse of getLocalizedDayJs (which goes UTC → local).
+ */
+export function localDateToUtc(date: dayjs.Dayjs): string {
+    return date.tz(getUserTimezone(), true).utc().format();
+}
+
 /*
  * Returns a formatted date.
  * @param date - date in the format of 'YYYY-MM-DD'

resources/js/packages/ui/tailwind.theme.js

@@ -104,7 +104,7 @@ export const solidtimeTheme = {
             border: 'var(--popover-border)',
         },
         destructive: {
-            DEFAULT: 'var(--destructive)',
+            DEFAULT: 'hsl(var(--destructive))',
             foreground: 'var(--destructive-foreground)',
         },
         border: 'var(--border)',

resources/js/test-setup.ts

@@ -0,0 +1,20 @@
+// Vitest setup file. Wires up the globals that the production code reads
+// off `window` (`getTimezoneSetting`, `getWeekStartSetting`, `getNumberFormat`,
+// `getIntervalFormat`) so that helpers under test don't crash when imported
+// outside the running app.
+
+import { vi } from 'vitest';
+
+declare global {
+    interface Window {
+        getTimezoneSetting: () => string;
+        getWeekStartSetting: () => string;
+        getNumberFormat: () => string;
+        getIntervalFormat: () => string;
+    }
+}
+
+window.getTimezoneSetting = vi.fn(() => 'UTC');
+window.getWeekStartSetting = vi.fn(() => 'monday');
+window.getNumberFormat = vi.fn(() => 'point');
+window.getIntervalFormat = vi.fn(() => 'hours-minutes');

resources/js/utils/notification.ts

@@ -57,6 +57,13 @@ export const useNotificationsStore = defineStore('notifications', () => {
                         'organization_has_no_subscription_but_multiple_members'
                     ) {
                         showActionBlockedModal.value = true;
+                    } else if (error?.response?.data?.key === 'overlapping_time_entry') {
+                        addNotification(
+                            'error',
+                            'Overlapping time entries are not allowed',
+                            error.response?.data?.message ??
+                                'This change would overlap with an existing time entry.'
+                        );
                     } else {
                         addNotification(
                             'error',

resources/js/utils/timesheet/cellMath.test.ts

@@ -0,0 +1,348 @@
+import { describe, it, expect } from 'vitest';
+import dayjs from 'dayjs';
+import utc from 'dayjs/plugin/utc';
+import timezone from 'dayjs/plugin/timezone';
+import { findFreeWindowOnDay, freeGapSecondsAfter, NoFreeWindowError } from './cellMath';
+import type { TimeEntry } from '@/packages/api/src';
+
+dayjs.extend(utc);
+dayjs.extend(timezone);
+
+// All times in the tests are in UTC for clarity. The "day" we search is
+// 2026-04-10 in UTC (so we use tz='UTC' to avoid local-machine surprises).
+const TZ = 'UTC';
+const DATE = '2026-04-10';
+
+/** Build a fake TimeEntry from UTC ISO timestamps. */
+function entry(start: string, end: string | null, id = `e-${start}-${end}`): TimeEntry {
+    const startMs = dayjs.utc(start).valueOf();
+    const endMs = end ? dayjs.utc(end).valueOf() : startMs;
+    return {
+        id,
+        start,
+        end,
+        duration: end ? Math.floor((endMs - startMs) / 1000) : null,
+        description: '',
+        member_id: 'm-1',
+        project_id: null,
+        task_id: null,
+        billable: false,
+        tags: [],
+        // The grid only reads the fields above; the rest are placeholders
+        // to satisfy the TimeEntry type without pulling in real fixtures.
+        user_id: 'u-1',
+        organization_id: 'o-1',
+    } as unknown as TimeEntry;
+}
+
+const HOUR = 3600;
+
+describe('findFreeWindowOnDay', () => {
+    // ── Empty / trivial cases ──────────────────────────────────────
+
+    it('returns the start of the day for a totally empty day', () => {
+        const result = findFreeWindowOnDay([], DATE, HOUR, TZ);
+        expect(result).toEqual({
+            start: '2026-04-10T00:00:00Z',
+            end: '2026-04-10T01:00:00Z',
+        });
+    });
+
+    it('returns null for zero or negative required seconds', () => {
+        expect(findFreeWindowOnDay([], DATE, 0, TZ)).toBeNull();
+        expect(findFreeWindowOnDay([], DATE, -1, TZ)).toBeNull();
+    });
+
+    it('refuses any duration > 24h on principle (single-day constraint)', () => {
+        const result = findFreeWindowOnDay([], DATE, 25 * HOUR, TZ);
+        expect(result).toBeNull();
+    });
+
+    // ── Single obstacle, basic gap finding ────────────────────────
+
+    it('finds the gap before a single obstacle if it fits', () => {
+        const obs = [entry('2026-04-10T10:00:00Z', '2026-04-10T11:00:00Z')];
+        const result = findFreeWindowOnDay(obs, DATE, HOUR, TZ);
+        expect(result?.start).toBe('2026-04-10T00:00:00Z');
+        expect(result?.end).toBe('2026-04-10T01:00:00Z');
+    });
+
+    it('finds the gap after a single obstacle when preferredStart skips earlier gaps', () => {
+        const obs = [entry('2026-04-10T10:00:00Z', '2026-04-10T11:00:00Z')];
+        const result = findFreeWindowOnDay(obs, DATE, HOUR, TZ, '2026-04-10T11:00:00Z');
+        expect(result?.start).toBe('2026-04-10T11:00:00Z');
+        expect(result?.end).toBe('2026-04-10T12:00:00Z');
+    });
+
+    // ── Multi-obstacle gap walking ────────────────────────────────
+
+    it('finds a gap between two obstacles', () => {
+        const obs = [
+            entry('2026-04-10T08:00:00Z', '2026-04-10T10:00:00Z'),
+            entry('2026-04-10T12:00:00Z', '2026-04-10T14:00:00Z'),
+        ];
+        // Search for 2h, expecting the [00:00, 08:00) gap (8h available)
+        const result = findFreeWindowOnDay(obs, DATE, 2 * HOUR, TZ);
+        expect(result?.start).toBe('2026-04-10T00:00:00Z');
+    });
+
+    it('walks past gaps that are too small', () => {
+        const obs = [
+            entry('2026-04-10T00:30:00Z', '2026-04-10T10:00:00Z'),
+            entry('2026-04-10T11:00:00Z', '2026-04-10T12:00:00Z'),
+        ];
+        // First gap is 30min, second gap is 1h, third is 12h.
+        // Asking for 90min → first two gaps are too small, third fits.
+        const result = findFreeWindowOnDay(obs, DATE, 90 * 60, TZ);
+        expect(result?.start).toBe('2026-04-10T12:00:00Z');
+    });
+
+    it('uses preferredStart even when it lands inside a gap', () => {
+        const obs = [
+            entry('2026-04-10T00:00:00Z', '2026-04-10T08:00:00Z'),
+            entry('2026-04-10T12:00:00Z', '2026-04-10T14:00:00Z'),
+        ];
+        // preferredStart 09:00 → gap is [09:00, 12:00) = 3h
+        const result = findFreeWindowOnDay(obs, DATE, 2 * HOUR, TZ, '2026-04-10T09:00:00Z');
+        expect(result?.start).toBe('2026-04-10T09:00:00Z');
+        expect(result?.end).toBe('2026-04-10T11:00:00Z');
+    });
+
+    it('skips ahead when preferredStart lands inside an obstacle', () => {
+        const obs = [entry('2026-04-10T08:00:00Z', '2026-04-10T12:00:00Z')];
+        // preferredStart 10:00 lands inside [08:00, 12:00). We must
+        // advance to the next free position (12:00).
+        const result = findFreeWindowOnDay(obs, DATE, HOUR, TZ, '2026-04-10T10:00:00Z');
+        expect(result?.start).toBe('2026-04-10T12:00:00Z');
+    });
+
+    // ── Spillover from previous day ───────────────────────────────
+
+    it('treats an entry that started yesterday but ends today as an obstacle', () => {
+        // Yesterday 23:00 → today 02:00 → blocks the first 2h of today.
+        const obs = [entry('2026-04-09T23:00:00Z', '2026-04-10T02:00:00Z')];
+        const result = findFreeWindowOnDay(obs, DATE, HOUR, TZ);
+        expect(result?.start).toBe('2026-04-10T02:00:00Z');
+    });
+
+    it('ignores an entry that ended exactly at the start of the day', () => {
+        // Yesterday 22:00 → today 00:00 (exclusive) → does NOT block today.
+        const obs = [entry('2026-04-09T22:00:00Z', '2026-04-10T00:00:00Z')];
+        const result = findFreeWindowOnDay(obs, DATE, HOUR, TZ);
+        expect(result?.start).toBe('2026-04-10T00:00:00Z');
+    });
+
+    // ── Running entries ────────────────────────────────────────────
+
+    it('treats a running entry as blocking up to "now"', () => {
+        const obs = [entry('2026-04-10T08:00:00Z', null)];
+        const now = '2026-04-10T10:30:00Z';
+        // The running entry blocks 08:00–10:30 → first free window is
+        // either before 08:00 (8h available, fits a 1h request).
+        const result = findFreeWindowOnDay(obs, DATE, HOUR, TZ, null, now);
+        expect(result?.start).toBe('2026-04-10T00:00:00Z');
+    });
+
+    it('places after a running entry when preferredStart pushes past it', () => {
+        const obs = [entry('2026-04-10T08:00:00Z', null)];
+        const now = '2026-04-10T10:30:00Z';
+        const result = findFreeWindowOnDay(obs, DATE, HOUR, TZ, '2026-04-10T09:00:00Z', now);
+        // preferredStart 09:00 lands inside the running entry's blocked
+        // range [08:00, 10:30) → must skip to 10:30.
+        expect(result?.start).toBe('2026-04-10T10:30:00Z');
+    });
+
+    // ── Midnight refusal ──────────────────────────────────────────
+
+    it('refuses to return a window that would cross midnight', () => {
+        const obs = [entry('2026-04-10T00:00:00Z', '2026-04-10T22:30:00Z')];
+        // Only 90min remain in the day. Asking for 2h → null.
+        const result = findFreeWindowOnDay(obs, DATE, 2 * HOUR, TZ);
+        expect(result).toBeNull();
+    });
+
+    it('accepts a window that ends exactly at midnight', () => {
+        const obs = [entry('2026-04-10T00:00:00Z', '2026-04-10T22:00:00Z')];
+        // Exactly 2h remain → 22:00–00:00.
+        const result = findFreeWindowOnDay(obs, DATE, 2 * HOUR, TZ);
+        expect(result?.start).toBe('2026-04-10T22:00:00Z');
+        expect(result?.end).toBe('2026-04-11T00:00:00Z');
+    });
+
+    // ── Pre-existing overlapping obstacles ────────────────────────
+
+    it('merges overlapping obstacles before computing gaps', () => {
+        const obs = [
+            entry('2026-04-10T09:00:00Z', '2026-04-10T11:00:00Z'),
+            entry('2026-04-10T10:00:00Z', '2026-04-10T13:00:00Z'),
+            entry('2026-04-10T15:00:00Z', '2026-04-10T16:00:00Z'),
+        ];
+        // Effective obstacles: [09:00, 13:00) and [15:00, 16:00)
+        // First gap is [00:00, 09:00) = 9h. Asking for 2h → 00:00.
+        const result = findFreeWindowOnDay(obs, DATE, 2 * HOUR, TZ);
+        expect(result?.start).toBe('2026-04-10T00:00:00Z');
+    });
+
+    // ── Day full ──────────────────────────────────────────────────
+
+    it('returns null when no gap is large enough', () => {
+        const obs = [
+            entry('2026-04-10T00:00:00Z', '2026-04-10T11:00:00Z'),
+            entry('2026-04-10T11:30:00Z', '2026-04-10T22:00:00Z'),
+            entry('2026-04-10T22:30:00Z', '2026-04-10T23:30:00Z'),
+        ];
+        // Gaps: 30min, 30min, 30min. Asking for 1h → null.
+        const result = findFreeWindowOnDay(obs, DATE, HOUR, TZ);
+        expect(result).toBeNull();
+    });
+
+    // ── Timezone awareness ────────────────────────────────────────
+
+    it('respects the user timezone for day boundaries', () => {
+        // In Pacific/Auckland (+13 in April 2026), 2026-04-10 starts at
+        // 2026-04-09T11:00:00Z (NZDT was UTC+13 until April 5 2026, then
+        // NZST UTC+12 — let's pick a date in NZST so the offset is +12).
+        // 2026-04-10 NZST = 2026-04-09T12:00:00Z to 2026-04-10T12:00:00Z
+        const tz = 'Pacific/Auckland';
+        const obs = [
+            // This entry is at 2026-04-10T08:00:00Z = 2026-04-10T20:00 NZ
+            // → falls in the NZ day for 2026-04-10. So it blocks from
+            // 20:00 to 21:00 NZ time.
+            entry('2026-04-10T08:00:00Z', '2026-04-10T09:00:00Z'),
+        ];
+        const result = findFreeWindowOnDay(obs, '2026-04-10', HOUR, tz);
+        // Day starts at 2026-04-09T12:00:00Z in NZST. First gap is the
+        // 20h before the obstacle starts.
+        expect(result?.start).toBe('2026-04-09T12:00:00Z');
+    });
+
+    it('does not place work past local midnight on spring-forward days', () => {
+        const tz = 'Europe/Vienna';
+        const obs = [entry('2026-03-28T23:00:00Z', '2026-03-29T22:00:00Z')];
+
+        const result = findFreeWindowOnDay(obs, '2026-03-29', HOUR, tz);
+
+        expect(result).toBeNull();
+    });
+
+    it('can use the final local hour on fall-back days', () => {
+        const tz = 'Europe/Vienna';
+
+        const result = findFreeWindowOnDay([], '2026-10-25', HOUR, tz, '2026-10-25T22:00:00Z');
+
+        expect(result).toEqual({
+            start: '2026-10-25T22:00:00Z',
+            end: '2026-10-25T23:00:00Z',
+        });
+    });
+});
+
+describe('freeGapSecondsAfter', () => {
+    it('returns the rest of the day for an empty day', () => {
+        const result = freeGapSecondsAfter([], DATE, TZ, '2026-04-10T09:00:00Z');
+        // 09:00 → 24:00 = 15 hours
+        expect(result).toBe(15 * HOUR);
+    });
+
+    it('returns 0 when cursor is at end-of-day', () => {
+        const result = freeGapSecondsAfter([], DATE, TZ, '2026-04-11T00:00:00Z');
+        expect(result).toBe(0);
+    });
+
+    it('returns 0 when cursor is after end-of-day', () => {
+        const result = freeGapSecondsAfter([], DATE, TZ, '2026-04-11T05:00:00Z');
+        expect(result).toBe(0);
+    });
+
+    it('returns 0 when cursor is before the day starts', () => {
+        const result = freeGapSecondsAfter([], DATE, TZ, '2026-04-09T23:00:00Z');
+        expect(result).toBe(0);
+    });
+
+    it('returns the gap to the next obstacle', () => {
+        const obs = [entry('2026-04-10T11:00:00Z', '2026-04-10T12:00:00Z')];
+        // cursor 09:00 → next obstacle 11:00 → 2h gap
+        const result = freeGapSecondsAfter(obs, DATE, TZ, '2026-04-10T09:00:00Z');
+        expect(result).toBe(2 * HOUR);
+    });
+
+    it('returns 0 when cursor sits inside an obstacle', () => {
+        const obs = [entry('2026-04-10T08:00:00Z', '2026-04-10T12:00:00Z')];
+        const result = freeGapSecondsAfter(obs, DATE, TZ, '2026-04-10T10:00:00Z');
+        expect(result).toBe(0);
+    });
+
+    it('returns the rest of the day when no obstacle is ahead', () => {
+        const obs = [entry('2026-04-10T08:00:00Z', '2026-04-10T09:00:00Z')];
+        const result = freeGapSecondsAfter(obs, DATE, TZ, '2026-04-10T09:00:00Z');
+        // 09:00 → 24:00 = 15h
+        expect(result).toBe(15 * HOUR);
+    });
+
+    it('skips obstacles strictly before the cursor', () => {
+        const obs = [
+            entry('2026-04-10T08:00:00Z', '2026-04-10T09:00:00Z'),
+            entry('2026-04-10T15:00:00Z', '2026-04-10T16:00:00Z'),
+        ];
+        // cursor 09:00 → first obstacle (08-09) is behind, next is 15:00 → 6h
+        const result = freeGapSecondsAfter(obs, DATE, TZ, '2026-04-10T09:00:00Z');
+        expect(result).toBe(6 * HOUR);
+    });
+
+    it('treats a running entry as blocking up to "now"', () => {
+        const obs = [entry('2026-04-10T08:00:00Z', null)];
+        const now = '2026-04-10T10:00:00Z';
+        // cursor 11:00 is after the running entry's effective end (10:00),
+        // so the gap is the rest of the day = 13h
+        const result = freeGapSecondsAfter(obs, DATE, TZ, '2026-04-10T11:00:00Z', now);
+        expect(result).toBe(13 * HOUR);
+    });
+
+    it('returns 0 when cursor is inside a running entry (cursor < now)', () => {
+        const obs = [entry('2026-04-10T08:00:00Z', null)];
+        const now = '2026-04-10T12:00:00Z';
+        // cursor 10:00 falls inside [08:00, 12:00) → blocked
+        const result = freeGapSecondsAfter(obs, DATE, TZ, '2026-04-10T10:00:00Z', now);
+        expect(result).toBe(0);
+    });
+
+    it('clips the gap to midnight, never beyond', () => {
+        const obs = [entry('2026-04-10T08:00:00Z', '2026-04-10T09:00:00Z')];
+        // cursor 23:00 → 1h until midnight
+        const result = freeGapSecondsAfter(obs, DATE, TZ, '2026-04-10T23:00:00Z');
+        expect(result).toBe(HOUR);
+    });
+
+    it('clips spring-forward days at the next local midnight', () => {
+        const result = freeGapSecondsAfter(
+            [],
+            '2026-03-29',
+            'Europe/Vienna',
+            '2026-03-29T22:00:00Z'
+        );
+
+        expect(result).toBe(0);
+    });
+
+    it('includes the final local hour on fall-back days', () => {
+        const result = freeGapSecondsAfter(
+            [],
+            '2026-10-25',
+            'Europe/Vienna',
+            '2026-10-25T22:00:00Z'
+        );
+
+        expect(result).toBe(HOUR);
+    });
+});
+
+describe('NoFreeWindowError', () => {
+    it('carries the date and required seconds', () => {
+        const err = new NoFreeWindowError('2026-04-10', 7200);
+        expect(err.code).toBe('no_free_window');
+        expect(err.date).toBe('2026-04-10');
+        expect(err.requiredSeconds).toBe(7200);
+        expect(err.message).toContain('2026-04-10');
+        expect(err instanceof Error).toBe(true);
+    });
+});

resources/js/utils/timesheet/cellMath.ts

@@ -0,0 +1,212 @@
+import { type Dayjs } from 'dayjs';
+import type { TimeEntry } from '@/packages/api/src';
+import { getDayJsInstance } from '@/packages/ui/src/utils/time';
+
+// `getDayJsInstance()` reads window-injected settings (week-start), which
+// aren't available at module load. Each function calls it lazily at use
+// time. The cost is a per-call locale update; cellMath doesn't use any
+// week-start-aware APIs so it's a no-op functionally.
+
+/**
+ * UTC ISO of 09:00 local on `date` — the preferred placement for new
+ * work when an empty day needs a default start time.
+ */
+export function workDayStartOn(date: string, tz: string): string {
+    const dayjs = getDayJsInstance();
+    return dayjs.tz(`${date} 09:00:00`, tz).utc().format();
+}
+
+export interface FreeWindow {
+    start: string;
+    end: string;
+}
+
+interface Interval {
+    start: Dayjs;
+    end: Dayjs;
+}
+
+function localDayBounds(date: string, tz: string): { dayStart: Dayjs; dayEnd: Dayjs } {
+    const dayjs = getDayJsInstance();
+    // `.add(1, 'day')` on a Dayjs instance advances by a fixed 24h, which is
+    // wrong on DST-transition days (the local day is 23h or 25h long). Derive
+    // the next calendar date in UTC (no DST) and take its local midnight, so
+    // `dayEnd` is always the real next local midnight.
+    const nextDate = dayjs.utc(date).add(1, 'day').format('YYYY-MM-DD');
+    return {
+        dayStart: dayjs.tz(`${date} 00:00:00`, tz).utc(),
+        dayEnd: dayjs.tz(`${nextDate} 00:00:00`, tz).utc(),
+    };
+}
+
+/**
+ * Collect entries that intersect the day `[dayStart, dayEnd)`, clipped
+ * to those bounds. Running entries use `nowDayjs` as their end.
+ */
+function collectDayObstacles(
+    entries: TimeEntry[],
+    dayStart: Dayjs,
+    dayEnd: Dayjs,
+    nowDayjs: Dayjs
+): Interval[] {
+    const dayjs = getDayJsInstance();
+    const obstacles: Interval[] = [];
+    for (const entry of entries) {
+        const entryStart = dayjs.utc(entry.start);
+        const entryEnd = entry.end ? dayjs.utc(entry.end) : nowDayjs;
+
+        if (entryEnd.isSameOrBefore(dayStart)) continue;
+        if (entryStart.isSameOrAfter(dayEnd)) continue;
+
+        const clippedStart = entryStart.isBefore(dayStart) ? dayStart : entryStart;
+        const clippedEnd = entryEnd.isAfter(dayEnd) ? dayEnd : entryEnd;
+
+        obstacles.push({ start: clippedStart, end: clippedEnd });
+    }
+    return obstacles;
+}
+
+/**
+ * First free window on the local calendar day that fits `requiredSeconds`
+ * without colliding with any existing entry. Returns `null` if nothing fits
+ * — never crosses midnight.
+ *
+ * Obstacles include same-day entries, spillovers from adjacent days, and
+ * running entries (treated as `end = now`). All are clipped to the day's
+ * `[00:00, 24:00)` boundaries.
+ *
+ * `preferredStart` (UTC ISO) is a hard floor — windows with `start` before
+ * it are rejected. Use it to place "after some cursor."
+ */
+export function findFreeWindowOnDay(
+    entries: TimeEntry[],
+    date: string,
+    requiredSeconds: number,
+    tz: string,
+    preferredStart?: string | null,
+    now?: string | Dayjs
+): FreeWindow | null {
+    if (requiredSeconds <= 0) return null;
+
+    const dayjs = getDayJsInstance();
+    const { dayStart, dayEnd } = localDayBounds(date, tz);
+
+    if (requiredSeconds > dayEnd.diff(dayStart, 'second')) return null;
+
+    const nowDayjs = now ? dayjs.utc(now) : dayjs.utc();
+
+    const obstacles = collectDayObstacles(entries, dayStart, dayEnd, nowDayjs);
+
+    // Sort + merge so we can walk a clean [gap, obstacle, gap, ...] sequence.
+    obstacles.sort((a, b) => a.start.diff(b.start));
+
+    // merge overlaps
+    const merged: Interval[] = [];
+    for (const obs of obstacles) {
+        const last = merged[merged.length - 1];
+        if (last && obs.start.isSameOrBefore(last.end)) {
+            if (obs.end.isAfter(last.end)) {
+                last.end = obs.end;
+            }
+        } else {
+            merged.push({ start: obs.start, end: obs.end });
+        }
+    }
+
+    let cursor: Dayjs = dayStart;
+    if (preferredStart) {
+        const pref = dayjs.utc(preferredStart);
+        if (pref.isAfter(cursor)) cursor = pref;
+    }
+    if (cursor.isSameOrAfter(dayEnd)) return null;
+
+    for (const obs of merged) {
+        if (obs.end.isSameOrBefore(cursor)) continue;
+
+        if (obs.start.isAfter(cursor)) {
+            const gapSeconds = obs.start.diff(cursor, 'second');
+            if (gapSeconds >= requiredSeconds) {
+                return {
+                    start: cursor.format(),
+                    end: cursor.add(requiredSeconds, 'second').format(),
+                };
+            }
+        }
+
+        if (obs.end.isAfter(cursor)) cursor = obs.end;
+        if (cursor.isSameOrAfter(dayEnd)) return null;
+    }
+
+    const trailingSeconds = dayEnd.diff(cursor, 'second');
+    if (trailingSeconds >= requiredSeconds) {
+        return {
+            start: cursor.format(),
+            end: cursor.add(requiredSeconds, 'second').format(),
+        };
+    }
+
+    return null;
+}
+
+/**
+ * Seconds of free space starting at `cursor` until the next obstacle
+ * (or end of day). Returns 0 if the cursor is inside an obstacle or past
+ * midnight. Used by the extend path: "how far can I push this end forward?"
+ */
+export function freeGapSecondsAfter(
+    entries: TimeEntry[],
+    date: string,
+    tz: string,
+    cursor: string,
+    now?: string | Dayjs
+): number {
+    const dayjs = getDayJsInstance();
+    const { dayStart, dayEnd } = localDayBounds(date, tz);
+    const cursorDjs = dayjs.utc(cursor);
+
+    if (cursorDjs.isSameOrAfter(dayEnd)) return 0;
+    if (cursorDjs.isBefore(dayStart)) return 0;
+
+    const nowDayjs = now ? dayjs.utc(now) : dayjs.utc();
+
+    // Drop obstacles ending at/before the cursor — they're behind us.
+    const obstacles = collectDayObstacles(entries, dayStart, dayEnd, nowDayjs).filter((obs) =>
+        obs.end.isAfter(cursorDjs)
+    );
+
+    obstacles.sort((a, b) => a.start.diff(b.start));
+
+    // Cursor inside an obstacle → no gap.
+    for (const obs of obstacles) {
+        if (obs.start.isSameOrBefore(cursorDjs) && obs.end.isAfter(cursorDjs)) {
+            return 0;
+        }
+    }
+
+    // Distance to first obstacle strictly after cursor, or to end of day.
+    for (const obs of obstacles) {
+        if (obs.start.isAfter(cursorDjs)) {
+            return Math.max(0, obs.start.diff(cursorDjs, 'second'));
+        }
+    }
+    return Math.max(0, dayEnd.diff(cursorDjs, 'second'));
+}
+
+/**
+ * Thrown when a required duration cannot fit on the target day without
+ * introducing an overlap. Callers reformat the message for end users.
+ */
+export class NoFreeWindowError extends Error {
+    public readonly code = 'no_free_window' as const;
+    public readonly date: string;
+    public readonly requiredSeconds: number;
+
+    constructor(date: string, requiredSeconds: number) {
+        super(
+            `Cannot fit ${requiredSeconds} seconds on ${date} without overlapping existing time entries.`
+        );
+        this.name = 'NoFreeWindowError';
+        this.date = date;
+        this.requiredSeconds = requiredSeconds;
+    }
+}

resources/js/utils/timesheet/useCopyLastWeek.ts

@@ -0,0 +1,242 @@
+import { ref, type Ref } from 'vue';
+import type { Dayjs } from 'dayjs';
+import axios from 'axios';
+import { useQueryClient } from '@tanstack/vue-query';
+import {
+    api,
+    type CreateTimeEntryBody,
+    type TimeEntry,
+    type TimeEntryResponse,
+} from '@/packages/api/src';
+import {
+    getDayJsInstance,
+    getLocalizedDateFromTimestamp,
+    localDateToUtc,
+} from '@/packages/ui/src/utils/time';
+import { getUserTimezone } from '@/packages/ui/src/utils/settings';
+import { fetchTimesheetEntries } from '@/utils/useTimesheetQuery';
+import { getCurrentMembershipId, getCurrentOrganizationId } from '@/utils/useUser';
+import { makeRowKey, type TimesheetRow } from '@/utils/useTimesheetGrid';
+import { useNotificationsStore } from '@/utils/notification';
+import { findFreeWindowOnDay, workDayStartOn } from './cellMath';
+
+/**
+ * Implements both variants of "Copy last week":
+ *
+ *   - `copyLastWeekRows()`       — only add rows for each distinct
+ *                                   (project, task) pair from last week
+ *                                   that doesn't already exist
+ *   - `copyLastWeekWithTime()`   — same, but also duplicates each
+ *                                   previous-week entry into the same
+ *                                   day-of-week in the current week,
+ *                                   stacking copies after any existing
+ *                                   work on that day
+ */
+export function useCopyLastWeek(
+    weekStart: Ref<Dayjs>,
+    weekDays: Ref<string[]>,
+    rows: Ref<TimesheetRow[]>,
+    timeEntries: Ref<TimeEntry[]>,
+    addSlot: (
+        projectId: string | null,
+        taskId: string | null,
+        billable: boolean,
+        tags: string[]
+    ) => string
+) {
+    const dayjs = getDayJsInstance();
+    const queryClient = useQueryClient();
+    const { addNotification } = useNotificationsStore();
+
+    const isCopyingLastWeek = ref(false);
+
+    async function fetchLastWeekEntries(): Promise<TimeEntryResponse | null> {
+        const prevStart = weekStart.value.subtract(7, 'day');
+        const prevEnd = weekStart.value;
+
+        const orgId = getCurrentOrganizationId();
+        const memberId = getCurrentMembershipId();
+        if (!orgId) return null;
+
+        return await fetchTimesheetEntries(
+            orgId,
+            memberId,
+            localDateToUtc(prevStart),
+            localDateToUtc(prevEnd)
+        );
+    }
+
+    /**
+     * For every entry in `prevEntries`, if the current week doesn't
+     * already have a row for that (project, task) combination, add one.
+     * Deduplicates so each combination is added at most once.
+     */
+    function addMissingRowsFromPreviousWeek(prevEntries: TimeEntry[]): void {
+        const existingIdentities = new Set(
+            rows.value.map((r) => makeRowKey(r.projectId, r.taskId, r.billable, r.tags))
+        );
+        const addedIdentities = new Set<string>();
+
+        for (const entry of prevEntries) {
+            const tags = entry.tags ?? [];
+            const identity = makeRowKey(entry.project_id, entry.task_id, entry.billable, tags);
+            if (!existingIdentities.has(identity) && !addedIdentities.has(identity)) {
+                addedIdentities.add(identity);
+                addSlot(entry.project_id, entry.task_id, entry.billable, tags);
+            }
+        }
+    }
+
+    async function copyLastWeekRows(): Promise<void> {
+        isCopyingLastWeek.value = true;
+        try {
+            const prev = await fetchLastWeekEntries();
+            if (!prev) return;
+            addMissingRowsFromPreviousWeek(prev.data);
+        } finally {
+            isCopyingLastWeek.value = false;
+        }
+    }
+
+    async function copyLastWeekWithTime(): Promise<void> {
+        isCopyingLastWeek.value = true;
+        try {
+            const prev = await fetchLastWeekEntries();
+            if (!prev) return;
+
+            const orgId = getCurrentOrganizationId();
+            const memberId = getCurrentMembershipId();
+            if (!orgId || !memberId) return;
+
+            const tz = getUserTimezone();
+
+            addMissingRowsFromPreviousWeek(prev.data);
+
+            const prevWeekStart = weekStart.value.subtract(7, 'day');
+
+            // Working copy of the current week's entries; placed copies
+            // are appended so subsequent placement queries see them as
+            // obstacles (timeEntries.value isn't refreshed until the
+            // queryClient.invalidate at the end of the loop).
+            const workingEntries: TimeEntry[] = [...timeEntries.value];
+
+            let attempted = 0;
+            let succeeded = 0;
+            let overlapFailures = 0;
+            let otherFailures = 0;
+
+            for (const entry of prev.data) {
+                if (!entry.end || !entry.duration) continue;
+
+                // Map previous-week date → same day-of-week in current week.
+                const entryDate = getLocalizedDateFromTimestamp(entry.start);
+                const dayOffset = dayjs(entryDate).diff(prevWeekStart, 'day');
+                const newDate = weekDays.value[dayOffset];
+                if (!newDate) continue;
+
+                // Try the source's wall-clock time on the target day first
+                // (preserves "Monday 14:00 meeting" → "Monday 14:00 meeting"
+                // when the slot is free); fall back to 09:00, then to
+                // anywhere on the day.
+                const sourceTimeOfDay = dayjs.utc(entry.start).tz(tz).format('HH:mm:ss');
+                const sourceStartOnTarget = dayjs
+                    .tz(`${newDate} ${sourceTimeOfDay}`, tz)
+                    .utc()
+                    .format();
+
+                const window =
+                    findFreeWindowOnDay(
+                        workingEntries,
+                        newDate,
+                        entry.duration,
+                        tz,
+                        sourceStartOnTarget
+                    ) ??
+                    findFreeWindowOnDay(
+                        workingEntries,
+                        newDate,
+                        entry.duration,
+                        tz,
+                        workDayStartOn(newDate, tz)
+                    ) ??
+                    findFreeWindowOnDay(workingEntries, newDate, entry.duration, tz);
+
+                if (!window) {
+                    attempted++;
+                    otherFailures++;
+                    continue;
+                }
+
+                const body: CreateTimeEntryBody = {
+                    member_id: memberId,
+                    project_id: entry.project_id,
+                    task_id: entry.task_id,
+                    start: window.start,
+                    end: window.end,
+                    billable: entry.billable,
+                    description: entry.description ?? null,
+                    tags: entry.tags ?? [],
+                };
+
+                attempted++;
+                try {
+                    await api.createTimeEntry(body, { params: { organization: orgId } });
+                    succeeded++;
+                    workingEntries.push({
+                        start: window.start,
+                        end: window.end,
+                    } as TimeEntry);
+                } catch (error) {
+                    if (
+                        axios.isAxiosError(error) &&
+                        error.response?.data?.key === 'overlapping_time_entry'
+                    ) {
+                        overlapFailures++;
+                    } else {
+                        otherFailures++;
+                    }
+                }
+            }
+
+            queryClient.invalidateQueries({ queryKey: ['timeEntries'] });
+
+            if (attempted === 0) return;
+
+            if (succeeded === attempted) {
+                addNotification(
+                    'success',
+                    `Copied ${succeeded} ${succeeded === 1 ? 'entry' : 'entries'} from last week`
+                );
+            } else if (succeeded > 0) {
+                const skipped = overlapFailures + otherFailures;
+                const detail =
+                    overlapFailures > 0 && otherFailures === 0
+                        ? `${overlapFailures} overlapping`
+                        : otherFailures > 0 && overlapFailures === 0
+                          ? `${otherFailures} failed`
+                          : `${skipped} skipped`;
+                addNotification(
+                    'error',
+                    `Copied ${succeeded} of ${attempted} entries from last week`,
+                    `${detail}.`
+                );
+            } else {
+                addNotification(
+                    'error',
+                    'Failed to copy entries from last week',
+                    overlapFailures > 0 && otherFailures === 0
+                        ? 'All entries would overlap with existing time entries.'
+                        : 'Please try again later.'
+                );
+            }
+        } finally {
+            isCopyingLastWeek.value = false;
+        }
+    }
+
+    return {
+        isCopyingLastWeek,
+        copyLastWeekRows,
+        copyLastWeekWithTime,
+    };
+}

resources/js/utils/timesheet/useTimesheetCellMutations.test.ts

@@ -0,0 +1,551 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
+import { ref } from 'vue';
+import { createPinia, setActivePinia } from 'pinia';
+import { useTimesheetCellMutations } from './useTimesheetCellMutations';
+import { api } from '@/packages/api/src';
+import type { TimesheetRow, TimesheetCell } from '@/utils/useTimesheetGrid';
+import type { TimeEntry } from '@/packages/api/src';
+
+const addNotification = vi.fn();
+
+vi.mock('@/utils/useUser', () => ({
+    getCurrentOrganizationId: vi.fn(() => 'org-1'),
+    getCurrentMembershipId: vi.fn(() => 'mem-1'),
+}));
+
+vi.mock('@tanstack/vue-query', () => ({
+    useQueryClient: () => ({
+        invalidateQueries: vi.fn(),
+    }),
+}));
+
+vi.mock('@/utils/notification', () => ({
+    useNotificationsStore: () => ({
+        addNotification,
+    }),
+}));
+
+vi.mock('@/packages/api/src', () => ({
+    api: {
+        createTimeEntry: vi.fn(async () => ({ data: { id: 'new-id' } })),
+        updateTimeEntry: vi.fn(async () => undefined),
+        deleteTimeEntry: vi.fn(async () => undefined),
+        deleteTimeEntries: vi.fn(async () => undefined),
+    },
+}));
+
+// All scenarios use UTC so the local "day" matches the UTC day exactly
+// (the test-setup mocks getTimezoneSetting to return 'UTC').
+
+const DATE = '2026-04-10';
+const HOUR = 3600;
+
+function entry(start: string, end: string | null, overrides: Partial<TimeEntry> = {}): TimeEntry {
+    const startMs = new Date(start).valueOf();
+    const endMs = end ? new Date(end).valueOf() : startMs;
+    return {
+        id: overrides.id ?? `e-${start}-${end ?? 'running'}`,
+        start,
+        end,
+        duration: end ? Math.floor((endMs - startMs) / 1000) : null,
+        description: '',
+        member_id: 'm-1',
+        project_id: 'p-1',
+        task_id: null,
+        billable: false,
+        tags: [],
+        ...overrides,
+    } as unknown as TimeEntry;
+}
+
+function buildCell(entries: TimeEntry[]): TimesheetCell {
+    return {
+        dayIndex: 0,
+        date: DATE,
+        entries,
+        totalSeconds: entries.reduce((sum, e) => sum + (e.duration ?? 0), 0),
+    };
+}
+
+function buildRow(
+    projectId: string | null,
+    entries: TimeEntry[],
+    key = `${projectId}:null`
+): TimesheetRow {
+    const cell = buildCell(entries);
+    return {
+        key,
+        projectId,
+        taskId: null,
+        billable: false,
+        tags: [],
+        cells: new Map([[0, cell]]),
+        totalSeconds: cell.totalSeconds,
+    };
+}
+
+function buildEmptyRow(projectId: string | null, key = `${projectId}:null`): TimesheetRow {
+    return {
+        key,
+        projectId,
+        taskId: null,
+        billable: false,
+        tags: [],
+        cells: new Map(),
+        totalSeconds: 0,
+    };
+}
+
+/** Shape of the body the cell-mutation logic passes to api.createTimeEntry. */
+interface CapturedEntry {
+    id?: string;
+    start: string;
+    end: string | null;
+    project_id?: string | null;
+    task_id?: string | null;
+    description?: string | null;
+}
+
+const apiMocks = vi.mocked(api);
+
+function firstArg(
+    mock: typeof apiMocks.createTimeEntry | typeof apiMocks.updateTimeEntry
+): CapturedEntry {
+    return mock.mock.calls[0]?.[0] as unknown as CapturedEntry;
+}
+
+function setup(
+    allEntries: TimeEntry[],
+    rowsValue: TimesheetRow[] = [],
+    removeSlot: (key: string) => void = () => undefined
+) {
+    const cellMutations = useTimesheetCellMutations(
+        ref([
+            DATE,
+            '2026-04-11',
+            '2026-04-12',
+            '2026-04-13',
+            '2026-04-14',
+            '2026-04-15',
+            '2026-04-16',
+        ]),
+        ref(allEntries),
+        ref(rowsValue),
+        removeSlot
+    );
+
+    return { cellMutations };
+}
+
+beforeEach(() => {
+    setActivePinia(createPinia());
+    apiMocks.createTimeEntry.mockClear();
+    apiMocks.updateTimeEntry.mockClear();
+    apiMocks.deleteTimeEntry.mockClear();
+    apiMocks.deleteTimeEntries.mockClear();
+    addNotification.mockClear();
+    // Lock the clock to mid-afternoon on the test day so running-entry
+    // tests have a deterministic "now". Past 12:00 to make spillover
+    // scenarios meaningful.
+    vi.useFakeTimers();
+    vi.setSystemTime(new Date('2026-04-10T14:00:00Z'));
+});
+
+afterEach(() => {
+    vi.useRealTimers();
+});
+
+describe('useTimesheetCellMutations.handleCellUpdate', () => {
+    // ── No-op ─────────────────────────────────────────────────────
+
+    it('does nothing when the diff is zero', async () => {
+        const { cellMutations } = setup([]);
+        const row = buildRow('p-1', [entry('2026-04-10T09:00:00Z', '2026-04-10T10:00:00Z')]);
+        await cellMutations.handleCellUpdate(row, 0, HOUR);
+
+        expect(apiMocks.createTimeEntry).not.toHaveBeenCalled();
+        expect(apiMocks.updateTimeEntry).not.toHaveBeenCalled();
+        expect(apiMocks.deleteTimeEntry).not.toHaveBeenCalled();
+        expect(apiMocks.deleteTimeEntries).not.toHaveBeenCalled();
+    });
+
+    // ── Delete cell ───────────────────────────────────────────────
+
+    it('clearing a cell deletes all entries in it', async () => {
+        const cellEntry = entry('2026-04-10T09:00:00Z', '2026-04-10T10:00:00Z');
+        const { cellMutations } = setup([cellEntry]);
+        const row = buildRow('p-1', [cellEntry]);
+
+        await cellMutations.handleCellUpdate(row, 0, 0);
+
+        expect(apiMocks.deleteTimeEntries).toHaveBeenCalledTimes(1);
+        const [, options] = apiMocks.deleteTimeEntries.mock.calls[0]!;
+        expect(options?.queries?.ids).toEqual([cellEntry.id]);
+        expect(options?.params?.organization).toBe('org-1');
+    });
+
+    // ── Create cell (Phase 1) ──────────────────────────────────────
+
+    describe('createCell', () => {
+        it('places a new entry at 09:00 on an empty day', async () => {
+            const { cellMutations } = setup([]);
+            const row = buildEmptyRow('p-1');
+
+            await cellMutations.handleCellUpdate(row, 0, HOUR);
+
+            expect(apiMocks.createTimeEntry).toHaveBeenCalledTimes(1);
+            const arg = firstArg(apiMocks.createTimeEntry);
+            expect(arg.start).toBe('2026-04-10T09:00:00Z');
+            expect(arg.end).toBe('2026-04-10T10:00:00Z');
+            expect(arg.project_id).toBe('p-1');
+        });
+
+        it('passes no-project rows to the API as null', async () => {
+            const { cellMutations } = setup([]);
+            const row = buildEmptyRow(null);
+
+            await cellMutations.handleCellUpdate(row, 0, HOUR);
+
+            expect(apiMocks.createTimeEntry).toHaveBeenCalledTimes(1);
+            expect(firstArg(apiMocks.createTimeEntry).project_id).toBeNull();
+        });
+
+        it('collapses an empty duplicate row after its first entry is created', async () => {
+            const removeSlot = vi.fn();
+            const existingRow = buildEmptyRow('p-1', 'existing-slot');
+            const duplicateRow = buildEmptyRow('p-1', 'duplicate-slot');
+            const { cellMutations } = setup([], [existingRow, duplicateRow], removeSlot);
+
+            await cellMutations.handleCellUpdate(duplicateRow, 0, HOUR);
+
+            expect(apiMocks.createTimeEntry).toHaveBeenCalledTimes(1);
+            expect(removeSlot).toHaveBeenCalledWith('duplicate-slot');
+            expect(addNotification).toHaveBeenCalledWith(
+                'success',
+                'Merged into matching row',
+                'Another row with the same project, task, billable status and tags already exists.'
+            );
+        });
+
+        it("falls back to the start of the day when 09:00 wouldn't fit", async () => {
+            // Block 09:00 → 23:30 with another row's entry. The only
+            // gap big enough for 1h is 00:00 → 09:00.
+            const blocker = entry('2026-04-10T09:00:00Z', '2026-04-10T23:30:00Z', {
+                id: 'blocker',
+            });
+            const { cellMutations } = setup([blocker]);
+            const row = buildEmptyRow('p-1');
+
+            await cellMutations.handleCellUpdate(row, 0, HOUR);
+
+            expect(apiMocks.createTimeEntry).toHaveBeenCalledTimes(1);
+            const arg = firstArg(apiMocks.createTimeEntry);
+            expect(arg.start).toBe('2026-04-10T00:00:00Z');
+            expect(arg.end).toBe('2026-04-10T01:00:00Z');
+        });
+
+        it('avoids overlapping with another row on the same day (Scenario #4)', async () => {
+            // Another row has an entry 09:00 → 10:00. The new entry must
+            // not overlap it.
+            const blocker = entry('2026-04-10T09:00:00Z', '2026-04-10T10:00:00Z', {
+                id: 'blocker',
+            });
+            const { cellMutations } = setup([blocker]);
+            const row = buildEmptyRow('p-1');
+
+            await cellMutations.handleCellUpdate(row, 0, HOUR);
+
+            const arg = firstArg(apiMocks.createTimeEntry);
+            // 09:00 is blocked → must place after, at 10:00
+            expect(arg.start).toBe('2026-04-10T10:00:00Z');
+            expect(arg.end).toBe('2026-04-10T11:00:00Z');
+        });
+
+        it('treats a running entry as a blocker (Scenario #1)', async () => {
+            const running = entry('2026-04-10T08:00:00Z', null, { id: 'running' });
+            const { cellMutations } = setup([running]);
+            const row = buildEmptyRow('p-1');
+
+            await cellMutations.handleCellUpdate(row, 0, HOUR);
+
+            const arg = firstArg(apiMocks.createTimeEntry);
+            // The running entry blocks [08:00, now=14:00). The 09:00
+            // work-hours default lands inside that block, so the
+            // search advances the cursor to 14:00 and places the new
+            // entry at 14:00 → 15:00. Critically, this does NOT
+            // overlap the running timer.
+            expect(arg.start).toBe('2026-04-10T14:00:00Z');
+            expect(arg.end).toBe('2026-04-10T15:00:00Z');
+        });
+
+        it('avoids spillover from the previous day (Scenario #2)', async () => {
+            // An entry from yesterday spills into today's first 4h.
+            const spillover = entry('2026-04-09T22:00:00Z', '2026-04-10T04:00:00Z', {
+                id: 'spillover',
+            });
+            const { cellMutations } = setup([spillover]);
+            const row = buildEmptyRow('p-1');
+
+            await cellMutations.handleCellUpdate(row, 0, HOUR);
+
+            const arg = firstArg(apiMocks.createTimeEntry);
+            // 09:00 is free (the spillover ends at 04:00).
+            expect(arg.start).toBe('2026-04-10T09:00:00Z');
+        });
+
+        it('refuses to cross midnight (Scenario #3)', async () => {
+            // Block all of the day except the last 2h. Asking for 3h
+            // → no single-day window fits → notification, no API call.
+            const blocker = entry('2026-04-10T00:00:00Z', '2026-04-10T22:00:00Z', {
+                id: 'blocker',
+            });
+            const { cellMutations } = setup([blocker]);
+            const row = buildEmptyRow('p-1');
+
+            await cellMutations.handleCellUpdate(row, 0, 3 * HOUR);
+
+            expect(apiMocks.createTimeEntry).not.toHaveBeenCalled();
+        });
+    });
+
+    // ── Extend cell (Phase 2) ──────────────────────────────────────
+
+    describe('extendCell', () => {
+        it("extends the cell's latest-ended entry forward when there is room", async () => {
+            const cellEntry = entry('2026-04-10T09:00:00Z', '2026-04-10T10:00:00Z', {
+                id: 'extend-me',
+            });
+            const { cellMutations } = setup([cellEntry]);
+            const row = buildRow('p-1', [cellEntry]);
+
+            // Cell is 1h, request 2h total → +1h
+            await cellMutations.handleCellUpdate(row, 0, 2 * HOUR);
+
+            expect(apiMocks.updateTimeEntry).toHaveBeenCalledTimes(1);
+            const updated = firstArg(apiMocks.updateTimeEntry);
+            expect(updated.id).toBe('extend-me');
+            expect(updated.end).toBe('2026-04-10T11:00:00Z');
+            expect(apiMocks.createTimeEntry).not.toHaveBeenCalled();
+        });
+
+        it('picks the latest-END entry when nested entries exist (Scenario #6)', async () => {
+            // Outer entry 09:00 → 12:00, inner entry 10:00 → 11:00.
+            // The latest START is "inner" but the latest END is "outer".
+            // Extending should grow the OUTER entry, not the inner.
+            const outer = entry('2026-04-10T09:00:00Z', '2026-04-10T12:00:00Z', { id: 'outer' });
+            const inner = entry('2026-04-10T10:00:00Z', '2026-04-10T11:00:00Z', { id: 'inner' });
+            const { cellMutations } = setup([outer, inner]);
+            const row = buildRow('p-1', [outer, inner]);
+
+            // Cell total = 3h + 1h = 4h. Bump to 5h → +1h.
+            await cellMutations.handleCellUpdate(row, 0, 5 * HOUR);
+
+            expect(apiMocks.updateTimeEntry).toHaveBeenCalledTimes(1);
+            const updated = firstArg(apiMocks.updateTimeEntry);
+            expect(updated.id).toBe('outer');
+            expect(updated.end).toBe('2026-04-10T13:00:00Z');
+        });
+
+        it('splits the extension when another row blocks the path (Scenario #5)', async () => {
+            // Cell entry: 09:00 → 10:00 (1h). Blocker on another row:
+            // 10:30 → 11:30. Bump cell to 3h (+2h):
+            //   - 30 minutes fit in the gap [10:00, 10:30) → extend to 10:30
+            //   - 90 minutes remain → place a NEW entry in the next free
+            //     window (11:30 → 13:00)
+            const cellEntry = entry('2026-04-10T09:00:00Z', '2026-04-10T10:00:00Z', {
+                id: 'cell-entry',
+            });
+            const blocker = entry('2026-04-10T10:30:00Z', '2026-04-10T11:30:00Z', {
+                id: 'blocker',
+                project_id: 'other-project',
+            });
+            const { cellMutations } = setup([cellEntry, blocker]);
+            const row = buildRow('p-1', [cellEntry]);
+
+            await cellMutations.handleCellUpdate(row, 0, 3 * HOUR);
+
+            expect(apiMocks.updateTimeEntry).toHaveBeenCalledTimes(1);
+            const updated = firstArg(apiMocks.updateTimeEntry);
+            expect(updated.id).toBe('cell-entry');
+            expect(updated.end).toBe('2026-04-10T10:30:00Z');
+
+            expect(apiMocks.createTimeEntry).toHaveBeenCalledTimes(1);
+            const created = firstArg(apiMocks.createTimeEntry);
+            // Remainder = 2h - 30min = 90min, placed in next free window
+            // (11:30 → 13:00)
+            expect(created.start).toBe('2026-04-10T11:30:00Z');
+            expect(created.end).toBe('2026-04-10T13:00:00Z');
+        });
+
+        it("places everything as a new entry when the cell's tail abuts another row immediately (Scenario #5 zero-gap)", async () => {
+            // Cell entry: 09:00 → 10:00. Another row starts EXACTLY at 10:00.
+            // Gap after cell entry = 0. The whole add becomes a new entry
+            // somewhere else.
+            const cellEntry = entry('2026-04-10T09:00:00Z', '2026-04-10T10:00:00Z', {
+                id: 'cell-entry',
+            });
+            const blocker = entry('2026-04-10T10:00:00Z', '2026-04-10T11:00:00Z', {
+                id: 'blocker',
+                project_id: 'other-project',
+            });
+            const { cellMutations } = setup([cellEntry, blocker]);
+            const row = buildRow('p-1', [cellEntry]);
+
+            // Bump cell from 1h to 2h → +1h
+            await cellMutations.handleCellUpdate(row, 0, 2 * HOUR);
+
+            // No update to cell entry (gap is zero)
+            expect(apiMocks.updateTimeEntry).not.toHaveBeenCalled();
+            // New entry placed in next free window: 11:00 → 12:00
+            expect(apiMocks.createTimeEntry).toHaveBeenCalledTimes(1);
+            const created = firstArg(apiMocks.createTimeEntry);
+            expect(created.start).toBe('2026-04-10T11:00:00Z');
+            expect(created.end).toBe('2026-04-10T12:00:00Z');
+        });
+
+        it('falls back to creating a new entry when the latest cell entry is running (Scenario #8)', async () => {
+            // Cell contains only a running timer.
+            const running = entry('2026-04-10T08:00:00Z', null, {
+                id: 'running',
+                duration: null,
+            });
+            // The grid would treat the cell total as 0 because duration is
+            // null, so we fake a non-zero totalSeconds via a manual cell.
+            const cell: TimesheetCell = {
+                dayIndex: 0,
+                date: DATE,
+                entries: [running],
+                // Pretend we computed 1h so that handleCellUpdate sees a
+                // diff > 0 and routes through extendCell rather than
+                // createCell.
+                totalSeconds: HOUR,
+            };
+            const row: TimesheetRow = {
+                key: 'p-1:null',
+                projectId: 'p-1',
+                taskId: null,
+                billable: false,
+                tags: [],
+                cells: new Map([[0, cell]]),
+                totalSeconds: HOUR,
+            };
+
+            const { cellMutations } = setup([running]);
+            // Bump from 1h to 2h → +1h. extendCell sees the running entry
+            // as the latest-end and falls through to createCell.
+            await cellMutations.handleCellUpdate(row, 0, 2 * HOUR);
+
+            expect(apiMocks.updateTimeEntry).not.toHaveBeenCalled();
+            expect(apiMocks.createTimeEntry).toHaveBeenCalledTimes(1);
+            // Running entry blocks [08:00, now=14:00). 09:00 lands inside
+            // → cursor advances to 14:00. Crucially the running entry is
+            // never modified.
+            const created = firstArg(apiMocks.createTimeEntry);
+            expect(created.start).toBe('2026-04-10T14:00:00Z');
+            expect(created.end).toBe('2026-04-10T15:00:00Z');
+        });
+
+        it('places the remainder strictly after the just-extended end (no stale-overlap)', async () => {
+            // Regression: timeEntries.value is stale right after the
+            // updateEntry call (still shows candidate.end at the old
+            // value). Without an explicit floor, findFreeWindowOnDay
+            // would propose a window inside the gap we just filled —
+            // overlapping the now-extended candidate.
+            //
+            // Cell entry: 09:00 → 10:00 (1h). Blocker on another row at
+            // 11:00 → 12:00. Gap is 1h. Bump cell to 2.5h (+1.5h):
+            //   - extend by 1h → newEnd = 11:00
+            //   - remainder = 30 min must land AFTER 11:00, not in the
+            //     stale-looking [10:00, 11:00] window.
+            const cellEntry = entry('2026-04-10T09:00:00Z', '2026-04-10T10:00:00Z', {
+                id: 'cell-entry',
+            });
+            const blocker = entry('2026-04-10T11:00:00Z', '2026-04-10T12:00:00Z', {
+                id: 'blocker',
+                project_id: 'other-project',
+            });
+            const { cellMutations } = setup([cellEntry, blocker]);
+            const row = buildRow('p-1', [cellEntry]);
+
+            await cellMutations.handleCellUpdate(row, 0, Math.round(2.5 * HOUR));
+
+            expect(apiMocks.updateTimeEntry).toHaveBeenCalledTimes(1);
+            const updated = firstArg(apiMocks.updateTimeEntry);
+            expect(updated.id).toBe('cell-entry');
+            expect(updated.end).toBe('2026-04-10T11:00:00Z');
+
+            expect(apiMocks.createTimeEntry).toHaveBeenCalledTimes(1);
+            const created = firstArg(apiMocks.createTimeEntry);
+            // Next free window after blocker, at 12:00.
+            expect(created.start).toBe('2026-04-10T12:00:00Z');
+            expect(created.end).toBe('2026-04-10T12:30:00Z');
+        });
+
+        it('refuses extension that would cross midnight before patching the server (Scenario #7)', async () => {
+            // Cell entry 22:00 → 23:00. Bump to 4h (+3h). Only 1h is
+            // available before midnight. Because the remaining 2h don't
+            // fit anywhere else on the day, the mutation now aborts
+            // before issuing the PATCH, leaving the entry untouched.
+            const cellEntry = entry('2026-04-10T22:00:00Z', '2026-04-10T23:00:00Z', {
+                id: 'cell-entry',
+            });
+            const fillEarly = entry('2026-04-10T00:00:00Z', '2026-04-10T22:00:00Z', {
+                id: 'fill',
+                project_id: 'other-project',
+            });
+            const { cellMutations } = setup([cellEntry, fillEarly]);
+            const row = buildRow('p-1', [cellEntry]);
+
+            // Bump from 1h to 4h → +3h
+            await cellMutations.handleCellUpdate(row, 0, 4 * HOUR);
+
+            // Nothing should be patched or created because the preflight
+            // fit-check rejects the whole edit.
+            expect(apiMocks.updateTimeEntry).not.toHaveBeenCalled();
+            expect(apiMocks.createTimeEntry).not.toHaveBeenCalled();
+        });
+    });
+
+    // ── Shrink (unchanged behavior, still correct) ─────────────────
+
+    describe('shrinkFromEnd', () => {
+        it('shortens the latest entry by the requested amount', async () => {
+            const cellEntry = entry('2026-04-10T09:00:00Z', '2026-04-10T12:00:00Z', {
+                id: 'shrink-me',
+            });
+            const { cellMutations } = setup([cellEntry]);
+            const row = buildRow('p-1', [cellEntry]);
+
+            // 3h → 2h: shrink by 1h
+            await cellMutations.handleCellUpdate(row, 0, 2 * HOUR);
+
+            expect(apiMocks.updateTimeEntry).toHaveBeenCalledTimes(1);
+            const updated = firstArg(apiMocks.updateTimeEntry);
+            expect(updated.end).toBe('2026-04-10T11:00:00Z');
+        });
+
+        it('deletes entries that are entirely consumed', async () => {
+            const a = entry('2026-04-10T09:00:00Z', '2026-04-10T10:00:00Z', {
+                id: 'a',
+            });
+            const b = entry('2026-04-10T11:00:00Z', '2026-04-10T12:00:00Z', {
+                id: 'b',
+            });
+            const { cellMutations } = setup([a, b]);
+            const row = buildRow('p-1', [a, b]);
+
+            // Cell = 2h, shrink to 0.5h: must delete b entirely (1h) and
+            // shorten a from 1h to 30min.
+            await cellMutations.handleCellUpdate(row, 0, 1800);
+
+            expect(apiMocks.deleteTimeEntry).toHaveBeenCalledTimes(1);
+            const [, deleteOptions] = apiMocks.deleteTimeEntry.mock.calls[0]!;
+            expect(deleteOptions?.params?.timeEntry).toBe('b');
+
+            expect(apiMocks.updateTimeEntry).toHaveBeenCalledTimes(1);
+            const updated = firstArg(apiMocks.updateTimeEntry);
+            expect(updated.id).toBe('a');
+            expect(updated.end).toBe('2026-04-10T09:30:00Z');
+        });
+    });
+});

resources/js/utils/timesheet/useTimesheetCellMutations.ts

@@ -0,0 +1,320 @@
+import type { Ref } from 'vue';
+import { useQueryClient } from '@tanstack/vue-query';
+import { api, type CreateTimeEntryBody, type TimeEntry } from '@/packages/api/src';
+import { formatHumanReadableDuration, getDayJsInstance } from '@/packages/ui/src/utils/time';
+import { getUserTimezone } from '@/packages/ui/src/utils/settings';
+import { getCurrentMembershipId, getCurrentOrganizationId } from '@/utils/useUser';
+import {
+    makeRowKey,
+    type TimesheetCell,
+    type TimesheetRow,
+    type TimesheetRowKey,
+} from '@/utils/useTimesheetGrid';
+import { useNotificationsStore } from '@/utils/notification';
+import {
+    findFreeWindowOnDay,
+    freeGapSecondsAfter,
+    NoFreeWindowError,
+    workDayStartOn,
+    type FreeWindow,
+} from './cellMath';
+
+/**
+ * Cell-level edit dispatcher. Picks one of four strategies based on
+ * the diff between current and requested totals:
+ *
+ *   - deleteCell    — new total is 0
+ *   - createCell    — empty cell, place in first free window
+ *   - extendCell    — diff > 0, push the latest-ending entry forward,
+ *                     splitting the remainder into a new entry if a
+ *                     collision blocks the path
+ *   - shrinkFromEnd — diff < 0, shorten / delete entries from most-
+ *                     recent backwards
+ *
+ * Running entries (end === null) are treated as immutable. Both create
+ * and extend can throw NoFreeWindowError when the day is too full.
+ *
+ * Calls the API directly (not via useTimeEntriesMutations) so a single
+ * cell edit fanning into multiple mutations produces exactly one toast
+ * and one cache invalidation.
+ */
+export function useTimesheetCellMutations(
+    weekDays: Ref<string[]>,
+    timeEntries: Ref<TimeEntry[]>,
+    rows: Ref<TimesheetRow[]>,
+    removeSlot: (key: TimesheetRowKey) => void
+) {
+    const dayjs = getDayJsInstance();
+    const queryClient = useQueryClient();
+    const notifications = useNotificationsStore();
+
+    async function handleCellUpdate(
+        row: TimesheetRow,
+        dayIndex: number,
+        newTotalSeconds: number
+    ): Promise<void> {
+        const cell = row.cells.get(dayIndex);
+        const existingSeconds = cell?.totalSeconds ?? 0;
+        if (newTotalSeconds === existingSeconds) return;
+
+        // Capture row state before the mutation: a row that was empty
+        // and shares identity with another slot collapses after the
+        // first entry lands, so the entry naturally identity-routes to
+        // the surviving slot.
+        const wasEmpty = row.totalSeconds === 0;
+
+        try {
+            await dispatchCellUpdate(row, dayIndex, newTotalSeconds);
+
+            if (wasEmpty && newTotalSeconds > 0 && hasDuplicateIdentitySlot(row)) {
+                removeSlot(row.key);
+                notifications.addNotification(
+                    'success',
+                    'Merged into matching row',
+                    'Another row with the same project, task, billable status and tags already exists.'
+                );
+            }
+        } catch (err) {
+            if (err instanceof NoFreeWindowError) {
+                const friendlyDuration = formatHumanReadableDuration(
+                    err.requiredSeconds,
+                    'hours-minutes',
+                    'point'
+                );
+                notifications.addNotification(
+                    'error',
+                    "This day can't fit any more work",
+                    `Couldn't fit ${friendlyDuration} on ${err.date} without overlapping existing entries.`
+                );
+                return;
+            }
+            notifications.addNotification(
+                'error',
+                'Failed to update timesheet',
+                'Please try again later.'
+            );
+            throw err;
+        } finally {
+            queryClient.invalidateQueries({ queryKey: ['timeEntries'] });
+        }
+    }
+
+    function hasDuplicateIdentitySlot(row: TimesheetRow): boolean {
+        const target = makeRowKey(row.projectId, row.taskId, row.billable, row.tags);
+        return rows.value.some(
+            (r) =>
+                r.key !== row.key &&
+                makeRowKey(r.projectId, r.taskId, r.billable, r.tags) === target
+        );
+    }
+
+    async function dispatchCellUpdate(
+        row: TimesheetRow,
+        dayIndex: number,
+        newTotalSeconds: number
+    ): Promise<void> {
+        const cell = row.cells.get(dayIndex);
+        const existingSeconds = cell?.totalSeconds ?? 0;
+        const diff = newTotalSeconds - existingSeconds;
+
+        if (newTotalSeconds === 0 && cell) {
+            await deleteCell(cell);
+            return;
+        }
+
+        if (!cell || existingSeconds === 0) {
+            await createCell(row, dayIndex, newTotalSeconds);
+            return;
+        }
+
+        if (diff > 0) {
+            await extendCell(row, dayIndex, cell, diff);
+            return;
+        }
+
+        await shrinkFromEnd(cell, -diff);
+    }
+
+    async function deleteCell(cell: TimesheetCell): Promise<void> {
+        const orgId = requireOrgId();
+        await api.deleteTimeEntries(undefined, {
+            queries: { ids: cell.entries.map((e) => e.id) },
+            params: { organization: orgId },
+        });
+    }
+
+    /**
+     * Place a new entry on the cell's day. Without `afterCursor`, prefers
+     * 09:00 local with a fall-back to start-of-day. With `afterCursor`,
+     * places strictly at-or-after that timestamp (used by extendCell to
+     * skip past a just-written extension that timeEntries.value doesn't
+     * yet reflect). Throws NoFreeWindowError if nothing fits.
+     */
+    async function createCell(
+        row: TimesheetRow,
+        dayIndex: number,
+        totalSeconds: number,
+        afterCursor?: string
+    ): Promise<void> {
+        const date = weekDays.value[dayIndex]!;
+        const tz = getUserTimezone();
+
+        let window: FreeWindow | null;
+        if (afterCursor) {
+            window = findFreeWindowOnDay(timeEntries.value, date, totalSeconds, tz, afterCursor);
+        } else {
+            window =
+                findFreeWindowOnDay(
+                    timeEntries.value,
+                    date,
+                    totalSeconds,
+                    tz,
+                    workDayStartOn(date, tz)
+                ) ?? findFreeWindowOnDay(timeEntries.value, date, totalSeconds, tz);
+        }
+
+        if (!window) throw new NoFreeWindowError(date, totalSeconds);
+
+        const orgId = requireOrgId();
+        const memberId = getCurrentMembershipId();
+        if (!memberId) throw new Error('No member context');
+
+        const body: CreateTimeEntryBody = {
+            member_id: memberId,
+            project_id: row.projectId,
+            task_id: row.taskId,
+            start: window.start,
+            end: window.end,
+            billable: row.billable,
+            description: null,
+            tags: row.tags,
+        };
+        await api.createTimeEntry(body, { params: { organization: orgId } });
+    }
+
+    /**
+     * Push the latest-ending entry's end forward by `addSeconds`, and if
+     * a collision blocks the path before that's exhausted, place the
+     * remainder as a fresh entry in the next free window on the day.
+     */
+    async function extendCell(
+        row: TimesheetRow,
+        dayIndex: number,
+        cell: TimesheetCell,
+        addSeconds: number
+    ): Promise<void> {
+        const date = weekDays.value[dayIndex]!;
+        const tz = getUserTimezone();
+
+        // Latest END (not latest start) — extending a nested inner entry
+        // would leave the outer one as the true tail.
+        const candidate = pickLatestEndedEntry(cell);
+
+        // Running timer (or no ended entry): can't extend, place it all
+        // as a new entry instead.
+        if (!candidate || !candidate.end) {
+            await createCell(row, dayIndex, addSeconds);
+            return;
+        }
+
+        const gap = freeGapSecondsAfter(timeEntries.value, date, tz, candidate.end);
+        const extendBy = Math.min(addSeconds, gap);
+        const remainder = addSeconds - extendBy;
+        const projectedNewEnd = dayjs.utc(candidate.end).add(extendBy, 'second').format();
+
+        // Pre-flight: if there's a remainder, make sure it'll fit in a
+        // window after `projectedNewEnd` BEFORE we issue the extend PATCH.
+        // Otherwise a successful extend followed by a no-fit createCell
+        // would leave the entry persistently lengthened on the server
+        // while the user sees a "can't fit" error.
+        if (remainder > 0) {
+            const fit = findFreeWindowOnDay(
+                timeEntries.value,
+                date,
+                remainder,
+                tz,
+                projectedNewEnd
+            );
+            if (!fit) throw new NoFreeWindowError(date, addSeconds);
+        }
+
+        if (extendBy > 0) {
+            await updateEntry({ ...candidate, end: projectedNewEnd });
+        }
+        if (remainder <= 0) return;
+
+        // timeEntries.value is stale here (still shows candidate's old
+        // end). Force the placement search past projectedNewEnd so it
+        // can't propose a window that overlaps the just-extended candidate.
+        await createCell(row, dayIndex, remainder, projectedNewEnd);
+    }
+
+    async function shrinkFromEnd(cell: TimesheetCell, removeSeconds: number): Promise<void> {
+        let toRemove = removeSeconds;
+
+        // Shrink doesn't introduce overlaps, so latest-START is fine here.
+        const sortedEntries = [...cell.entries].sort((a, b) => b.start.localeCompare(a.start));
+
+        for (const entry of sortedEntries) {
+            if (toRemove <= 0) break;
+            if (!entry.end) continue; // running entries are immutable
+
+            const entryDuration = entry.duration ?? 0;
+
+            if (entryDuration <= toRemove) {
+                await deleteEntry(entry.id);
+                toRemove -= entryDuration;
+            } else {
+                const newEnd = dayjs
+                    .utc(entry.start)
+                    .add(entryDuration - toRemove, 'second')
+                    .format();
+                await updateEntry({ ...entry, end: newEnd });
+                toRemove = 0;
+            }
+        }
+    }
+
+    // ── api helpers ───────────────────────────────────────────────
+
+    function requireOrgId(): string {
+        const id = getCurrentOrganizationId();
+        if (!id) throw new Error('No organization context');
+        return id;
+    }
+
+    async function updateEntry(entry: TimeEntry) {
+        const orgId = requireOrgId();
+        await api.updateTimeEntry(entry, {
+            params: { organization: orgId, timeEntry: entry.id },
+        });
+    }
+
+    async function deleteEntry(id: string) {
+        const orgId = requireOrgId();
+        await api.deleteTimeEntry(undefined, {
+            params: { organization: orgId, timeEntry: id },
+        });
+    }
+
+    function pickLatestEndedEntry(cell: TimesheetCell): TimeEntry | null {
+        let best: TimeEntry | null = null;
+        for (const entry of cell.entries) {
+            if (!best) {
+                best = entry;
+                continue;
+            }
+            // Running entries are treated as "infinite" — they win.
+            if (!entry.end) {
+                best = entry;
+                continue;
+            }
+            if (best.end && entry.end > best.end) {
+                best = entry;
+            }
+        }
+        return best;
+    }
+
+    return { handleCellUpdate };
+}

resources/js/utils/timesheet/useTimesheetRowDeletion.ts

@@ -0,0 +1,70 @@
+import { computed, ref, type Ref } from 'vue';
+import type { Project, TimeEntry } from '@/packages/api/src';
+import type { TimesheetRow, TimesheetRowKey } from '@/utils/useTimesheetGrid';
+import type { useTimeEntriesMutations } from '@/utils/useTimeEntriesMutations';
+
+type Mutations = ReturnType<typeof useTimeEntriesMutations>;
+
+/**
+ * Holds the state and handlers for the "remove row" confirmation flow.
+ *
+ * Empty rows (no entries) are removed immediately without confirmation;
+ * rows with entries open a confirmation dialog, and on confirm we bulk
+ * delete every entry in the row before dropping the row from the grid.
+ */
+export function useTimesheetRowDeletion(
+    projects: Ref<Project[]>,
+    mutations: Pick<Mutations, 'deleteTimeEntries'>,
+    removeSlot: (key: TimesheetRowKey) => void
+) {
+    const showDeleteDialog = ref(false);
+    const rowToDelete = ref<TimesheetRow | null>(null);
+
+    const deleteRowEntryCount = computed(() => {
+        if (!rowToDelete.value) return 0;
+        let count = 0;
+        for (const cell of rowToDelete.value.cells.values()) {
+            count += cell.entries.length;
+        }
+        return count;
+    });
+
+    const deleteRowProjectName = computed(() => {
+        if (!rowToDelete.value?.projectId) return 'No Project';
+        return projects.value.find((p) => p.id === rowToDelete.value?.projectId)?.name ?? 'Unknown';
+    });
+
+    function requestRemoveRow(row: TimesheetRow): void {
+        if (row.totalSeconds === 0) {
+            removeSlot(row.key);
+            return;
+        }
+        rowToDelete.value = row;
+        showDeleteDialog.value = true;
+    }
+
+    async function confirmDeleteRow(): Promise<void> {
+        if (!rowToDelete.value) return;
+
+        const allEntries: TimeEntry[] = [];
+        for (const cell of rowToDelete.value.cells.values()) {
+            allEntries.push(...cell.entries);
+        }
+
+        if (allEntries.length > 0) {
+            await mutations.deleteTimeEntries(allEntries);
+        }
+        removeSlot(rowToDelete.value.key);
+        showDeleteDialog.value = false;
+        rowToDelete.value = null;
+    }
+
+    return {
+        showDeleteDialog,
+        rowToDelete,
+        deleteRowEntryCount,
+        deleteRowProjectName,
+        requestRemoveRow,
+        confirmDeleteRow,
+    };
+}

resources/js/utils/timesheet/useTimesheetRowMutations.test.ts

@@ -0,0 +1,272 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+import { ref } from 'vue';
+import type { Project, TimeEntry } from '@/packages/api/src';
+import type { TimesheetCell, TimesheetRow } from '@/utils/useTimesheetGrid';
+import { useTimesheetRowMutations } from './useTimesheetRowMutations';
+
+const addNotification = vi.fn();
+
+vi.mock('@/utils/notification', () => ({
+    useNotificationsStore: () => ({
+        addNotification,
+    }),
+}));
+
+function project(id: string, isBillable: boolean): Project {
+    return {
+        id,
+        name: id,
+        is_billable: isBillable,
+    } as unknown as Project;
+}
+
+function entry(id: string): TimeEntry {
+    return {
+        id,
+        start: '2026-04-10T09:00:00Z',
+        end: '2026-04-10T10:00:00Z',
+        duration: 3600,
+        description: '',
+        member_id: 'm-1',
+        project_id: 'p-1',
+        task_id: null,
+        billable: false,
+        tags: [],
+    } as unknown as TimeEntry;
+}
+
+function buildCell(entries: TimeEntry[]): TimesheetCell {
+    return {
+        dayIndex: 0,
+        date: '2026-04-10',
+        entries,
+        totalSeconds: entries.reduce((sum, item) => sum + (item.duration ?? 0), 0),
+    };
+}
+
+function buildRow(key: string, projectId: string | null, entries: TimeEntry[]): TimesheetRow {
+    const cells = entries.length > 0 ? new Map([[0, buildCell(entries)]]) : new Map();
+    const totalSeconds = entries.reduce((sum, item) => sum + (item.duration ?? 0), 0);
+
+    return {
+        key,
+        projectId,
+        taskId: null,
+        billable: false,
+        tags: [],
+        cells,
+        totalSeconds,
+    };
+}
+
+describe('useTimesheetRowMutations', () => {
+    beforeEach(() => {
+        addNotification.mockClear();
+    });
+
+    it('collapses a populated row into an existing matching row after identity change', async () => {
+        const existingRow = buildRow('row-a', 'p-1', [entry('e-a')]);
+        const editedRow = buildRow('row-b', 'p-2', [entry('e-b')]);
+        const rows = ref([existingRow, editedRow]);
+        const updateTimeEntries = vi.fn().mockResolvedValue(undefined);
+        const addSlot = vi.fn();
+        const updateSlot = vi.fn();
+        const removeSlot = vi.fn();
+
+        const { handleRowIdentityChange } = useTimesheetRowMutations(
+            { updateTimeEntries },
+            ref<Project[]>([]),
+            rows,
+            addSlot,
+            updateSlot,
+            removeSlot
+        );
+
+        await handleRowIdentityChange(editedRow, { projectId: 'p-1' });
+
+        expect(updateTimeEntries).toHaveBeenCalledWith({
+            ids: ['e-b'],
+            changes: { project_id: 'p-1' },
+        });
+        expect(removeSlot).toHaveBeenCalledWith('row-b');
+        expect(updateSlot).not.toHaveBeenCalled();
+        expect(addNotification).toHaveBeenCalledWith(
+            'success',
+            'Merged into matching row',
+            'Another row with the same project, task, billable status and tags already exists.'
+        );
+    });
+
+    it('translates identity fields to snake_case API field names', async () => {
+        const row = buildRow('row-a', 'p-1', [entry('e-a')]);
+        const rows = ref([row]);
+        const updateTimeEntries = vi.fn().mockResolvedValue(undefined);
+
+        const { handleRowIdentityChange } = useTimesheetRowMutations(
+            { updateTimeEntries },
+            ref<Project[]>([]),
+            rows,
+            vi.fn(),
+            vi.fn(),
+            vi.fn()
+        );
+
+        await handleRowIdentityChange(row, {
+            projectId: 'p-2',
+            taskId: 't-1',
+            billable: true,
+            tags: ['tag-1'],
+        });
+
+        expect(updateTimeEntries).toHaveBeenCalledWith({
+            ids: ['e-a'],
+            changes: {
+                project_id: 'p-2',
+                task_id: 't-1',
+                billable: true,
+                tags: ['tag-1'],
+            },
+        });
+    });
+
+    it('only includes touched fields in the API changeset', async () => {
+        const row = buildRow('row-a', 'p-1', [entry('e-a')]);
+        const rows = ref([row]);
+        const updateTimeEntries = vi.fn().mockResolvedValue(undefined);
+
+        const { handleRowIdentityChange } = useTimesheetRowMutations(
+            { updateTimeEntries },
+            ref<Project[]>([]),
+            rows,
+            vi.fn(),
+            vi.fn(),
+            vi.fn()
+        );
+
+        await handleRowIdentityChange(row, { tags: ['tag-1'] });
+
+        expect(updateTimeEntries).toHaveBeenCalledWith({
+            ids: ['e-a'],
+            changes: { tags: ['tag-1'] },
+        });
+    });
+
+    it('keeps an empty duplicate row until it receives time', async () => {
+        const existingRow = buildRow('row-a', 'p-1', [entry('e-a')]);
+        const emptyRow = buildRow('row-b', 'p-2', []);
+        const rows = ref([existingRow, emptyRow]);
+        const updateTimeEntries = vi.fn().mockResolvedValue(undefined);
+        const addSlot = vi.fn();
+        const updateSlot = vi.fn();
+        const removeSlot = vi.fn();
+
+        const { handleRowIdentityChange } = useTimesheetRowMutations(
+            { updateTimeEntries },
+            ref<Project[]>([]),
+            rows,
+            addSlot,
+            updateSlot,
+            removeSlot
+        );
+
+        await handleRowIdentityChange(emptyRow, { projectId: 'p-1' });
+
+        expect(updateTimeEntries).not.toHaveBeenCalled();
+        expect(updateSlot).toHaveBeenCalledWith('row-b', {
+            projectId: 'p-1',
+            taskId: null,
+            billable: false,
+            tags: [],
+        });
+        expect(removeSlot).not.toHaveBeenCalled();
+    });
+
+    it('sends null project updates when an existing row changes to no project', async () => {
+        const row = buildRow('row-a', 'p-1', [entry('e-a')]);
+        const rows = ref([row]);
+        const updateTimeEntries = vi.fn().mockResolvedValue(undefined);
+        const updateSlot = vi.fn();
+
+        const { handleRowIdentityChange } = useTimesheetRowMutations(
+            { updateTimeEntries },
+            ref<Project[]>([]),
+            rows,
+            vi.fn(),
+            updateSlot,
+            vi.fn()
+        );
+
+        await handleRowIdentityChange(row, { projectId: null });
+
+        expect(updateTimeEntries).toHaveBeenCalledWith({
+            ids: ['e-a'],
+            changes: { project_id: null },
+        });
+        expect(updateSlot).toHaveBeenCalledWith('row-a', {
+            projectId: null,
+            taskId: null,
+            billable: false,
+            tags: [],
+        });
+    });
+
+    it('defaults billable from the selected project when an empty row picks its first project', async () => {
+        const emptyRow = buildRow('row-a', null, []);
+        const rows = ref([emptyRow]);
+        const updateTimeEntries = vi.fn().mockResolvedValue(undefined);
+        const updateSlot = vi.fn();
+
+        const { handleRowIdentityChange } = useTimesheetRowMutations(
+            { updateTimeEntries },
+            ref([project('p-billable', true)]),
+            rows,
+            vi.fn(),
+            updateSlot,
+            vi.fn()
+        );
+
+        await handleRowIdentityChange(emptyRow, { projectId: 'p-billable' });
+
+        expect(updateTimeEntries).not.toHaveBeenCalled();
+        expect(updateSlot).toHaveBeenCalledWith('row-a', {
+            projectId: 'p-billable',
+            taskId: null,
+            billable: true,
+            tags: [],
+        });
+    });
+
+    it('handleAddRow defaults billable from the selected project metadata', () => {
+        const addSlot = vi.fn();
+
+        const { handleAddRow } = useTimesheetRowMutations(
+            { updateTimeEntries: vi.fn() },
+            ref([project('p-billable', true)]),
+            ref<TimesheetRow[]>([]),
+            addSlot,
+            vi.fn(),
+            vi.fn()
+        );
+
+        handleAddRow('p-billable', 't-1');
+
+        expect(addSlot).toHaveBeenCalledWith('p-billable', 't-1', true, []);
+    });
+
+    it('can add a no-project row', () => {
+        const addSlot = vi.fn();
+
+        const { handleAddRow } = useTimesheetRowMutations(
+            { updateTimeEntries: vi.fn() },
+            ref([project('p-billable', true)]),
+            ref<TimesheetRow[]>([]),
+            addSlot,
+            vi.fn(),
+            vi.fn()
+        );
+
+        handleAddRow(null, null);
+
+        expect(addSlot).toHaveBeenCalledWith(null, null, false, []);
+    });
+});

resources/js/utils/timesheet/useTimesheetRowMutations.ts

@@ -0,0 +1,150 @@
+import type { Ref } from 'vue';
+import type { Project, UpdateMultipleTimeEntriesChangeset } from '@/packages/api/src';
+import {
+    makeRowKey,
+    type TimesheetRow,
+    type TimesheetRowIdentity,
+    type TimesheetRowKey,
+} from '@/utils/useTimesheetGrid';
+import type { useTimeEntriesMutations } from '@/utils/useTimeEntriesMutations';
+import { useNotificationsStore } from '@/utils/notification';
+
+function identityPartialToApiChanges(
+    partial: Partial<TimesheetRowIdentity>
+): UpdateMultipleTimeEntriesChangeset {
+    const changes: UpdateMultipleTimeEntriesChangeset = {};
+    if ('projectId' in partial) changes.project_id = partial.projectId;
+    if ('taskId' in partial) changes.task_id = partial.taskId;
+    if ('billable' in partial) changes.billable = partial.billable;
+    if ('tags' in partial) changes.tags = partial.tags;
+    return changes;
+}
+
+type Mutations = ReturnType<typeof useTimeEntriesMutations>;
+
+/**
+ * Row-level mutations that don't involve confirmation.
+ *
+ * Rows are keyed by slot id (not identity), so any partial change to
+ * a row's identity is handled the same way: push the change to the
+ * server for any entries in the row, then migrate the slot's identity
+ * in place so the row stays at its existing position.
+ */
+export function useTimesheetRowMutations(
+    mutations: Pick<Mutations, 'updateTimeEntries'>,
+    projects: Ref<Project[]>,
+    rows: Ref<TimesheetRow[]>,
+    addSlot: (
+        projectId: string | null,
+        taskId: string | null,
+        billable: boolean,
+        tags: string[]
+    ) => TimesheetRowKey,
+    updateSlot: (key: TimesheetRowKey, identity: TimesheetRowIdentity) => void,
+    removeSlot: (key: TimesheetRowKey) => void
+) {
+    const notifications = useNotificationsStore();
+
+    function collectEntryIds(row: TimesheetRow): string[] {
+        const ids: string[] = [];
+        for (const cell of row.cells.values()) {
+            for (const entry of cell.entries) ids.push(entry.id);
+        }
+        return ids;
+    }
+
+    function hasDuplicateIdentityRow(
+        rowKey: TimesheetRowKey,
+        identity: TimesheetRowIdentity
+    ): boolean {
+        const target = makeRowKey(
+            identity.projectId,
+            identity.taskId,
+            identity.billable,
+            identity.tags
+        );
+
+        return rows.value.some(
+            (candidate) =>
+                candidate.key !== rowKey &&
+                makeRowKey(
+                    candidate.projectId,
+                    candidate.taskId,
+                    candidate.billable,
+                    candidate.tags
+                ) === target
+        );
+    }
+
+    async function handleRowIdentityChange(
+        row: TimesheetRow,
+        partial: Partial<TimesheetRowIdentity>
+    ): Promise<void> {
+        const entryIds = collectEntryIds(row);
+        const currentIdentity = makeRowKey(row.projectId, row.taskId, row.billable, row.tags);
+        let merged: TimesheetRowIdentity = {
+            projectId: row.projectId,
+            taskId: row.taskId,
+            billable: row.billable,
+            tags: row.tags,
+            ...partial,
+        };
+
+        // Auto-default billable on the first project pick for an empty
+        // row (project provides the default; user can override after).
+        if (
+            entryIds.length === 0 &&
+            partial.projectId !== undefined &&
+            partial.projectId !== row.projectId &&
+            partial.projectId &&
+            partial.billable === undefined
+        ) {
+            const projectBillable = projects.value.find(
+                (p) => p.id === partial.projectId
+            )?.is_billable;
+            if (projectBillable !== undefined) {
+                merged = { ...merged, billable: projectBillable };
+            }
+        }
+
+        const mergedIdentity = makeRowKey(
+            merged.projectId,
+            merged.taskId,
+            merged.billable,
+            merged.tags
+        );
+        const shouldMergeIntoExistingRow =
+            entryIds.length > 0 &&
+            currentIdentity !== mergedIdentity &&
+            hasDuplicateIdentityRow(row.key, merged);
+
+        if (entryIds.length > 0) {
+            await mutations.updateTimeEntries({
+                ids: entryIds,
+                changes: identityPartialToApiChanges(partial),
+            });
+        }
+
+        if (shouldMergeIntoExistingRow) {
+            removeSlot(row.key);
+            notifications.addNotification(
+                'success',
+                'Merged into matching row',
+                'Another row with the same project, task, billable status and tags already exists.'
+            );
+            return;
+        }
+
+        updateSlot(row.key, merged);
+    }
+
+    function handleAddRow(projectId: string | null = null, taskId: string | null = null): void {
+        const project = projectId ? projects.value.find((p) => p.id === projectId) : null;
+        addSlot(projectId, taskId, project?.is_billable ?? false, []);
+    }
+
+    return {
+        handleRowIdentityChange,
+        handleAddRow,
+    };
+}

resources/js/utils/timesheet/useTimesheetWeek.ts

@@ -0,0 +1,82 @@
+import { computed, ref, watch } from 'vue';
+import type { Dayjs } from 'dayjs';
+import { useQueryClient } from '@tanstack/vue-query';
+import { getDayJsInstance } from '@/packages/ui/src/utils/time';
+import { getUserTimezone } from '@/packages/ui/src/utils/settings';
+import { prefetchTimesheetWeek } from '@/utils/useTimesheetQuery';
+import { getInitialWeekRange } from '@/utils/useTimeEntriesCalendarQuery';
+
+/**
+ * Owns week-navigation state for the timesheet page.
+ *
+ * Exposes the current week start/end, the list of day strings, derived
+ * display helpers (week number, today's date, whether this is the
+ * current week), and navigation functions.
+ *
+ * Also prefetches the adjacent weeks whenever `weekStart` changes so
+ * that clicking prev/next feels instant.
+ */
+export function useTimesheetWeek() {
+    const dayjs = getDayJsInstance();
+    const queryClient = useQueryClient();
+
+    const weekStart = ref<Dayjs>(getInitialWeekRange().start);
+    const weekEnd = computed(() => weekStart.value.add(7, 'day'));
+
+    const weekDays = computed(() => {
+        const days: string[] = [];
+        for (let i = 0; i < 7; i++) {
+            days.push(weekStart.value.add(i, 'day').format('YYYY-MM-DD'));
+        }
+        return days;
+    });
+
+    const weekNumber = computed(() => weekStart.value.week());
+
+    const isCurrentWeek = computed(() =>
+        weekStart.value.isSame(getInitialWeekRange().start, 'day')
+    );
+
+    const todayDate = computed(() => {
+        const tz = getUserTimezone();
+        return dayjs().tz(tz).format('YYYY-MM-DD');
+    });
+
+    // Prefetch adjacent weeks so prev/next feels instant.
+    watch(
+        weekStart,
+        () => {
+            const prevStart = weekStart.value.subtract(7, 'day');
+            const prevEnd = weekStart.value;
+            const nextStart = weekStart.value.add(7, 'day');
+            const nextEnd = weekStart.value.add(14, 'day');
+            prefetchTimesheetWeek(queryClient, prevStart, prevEnd);
+            prefetchTimesheetWeek(queryClient, nextStart, nextEnd);
+        },
+        { immediate: true }
+    );
+
+    function goToPreviousWeek() {
+        weekStart.value = weekStart.value.subtract(7, 'day');
+    }
+
+    function goToNextWeek() {
+        weekStart.value = weekStart.value.add(7, 'day');
+    }
+
+    function goToCurrentWeek() {
+        weekStart.value = getInitialWeekRange().start;
+    }
+
+    return {
+        weekStart,
+        weekEnd,
+        weekDays,
+        weekNumber,
+        isCurrentWeek,
+        todayDate,
+        goToPreviousWeek,
+        goToNextWeek,
+        goToCurrentWeek,
+    };
+}

resources/js/utils/useTimeEntriesCalendarQuery.ts

@@ -2,43 +2,28 @@ import { useQuery } from '@tanstack/vue-query';
 import { api, type TimeEntryResponse, type TimeEntry } from '@/packages/api/src';
 import { getCurrentMembershipId, getCurrentOrganizationId } from '@/utils/useUser';
 import { computed, type Ref } from 'vue';
-import { getDayJsInstance } from '@/packages/ui/src/utils/time';
-import { getUserTimezone, getWeekStart } from '@/packages/ui/src/utils/settings';
-
-const weekStartMap: Record<string, number> = {
-    sunday: 0,
-    monday: 1,
-    tuesday: 2,
-    wednesday: 3,
-    thursday: 4,
-    friday: 5,
-    saturday: 6,
-};
+import type { Dayjs } from 'dayjs';
+import { getDayJsInstance, localDateToUtc } from '@/packages/ui/src/utils/time';
+import { getWeekStartDayNumber } from '@/packages/ui/src/utils/settings';
 
 /**
  * Calculate expanded date range to include previous and next periods with timezone transformations.
  * This allows smooth navigation between calendar views without loading delays.
  */
 export function getExpandedCalendarDateRange(
-    calendarStart: Date,
-    calendarEnd: Date
+    calendarStart: Dayjs,
+    calendarEnd: Dayjs
 ): { start: string; end: string } {
-    const dayjs = getDayJsInstance();
-    const duration = dayjs(calendarEnd).diff(dayjs(calendarStart), 'milliseconds');
+    const duration = calendarEnd.diff(calendarStart, 'milliseconds');
 
     // Calculate previous period
-    const previousStart = dayjs(calendarStart).subtract(duration, 'milliseconds');
+    const previousStart = calendarStart.subtract(duration, 'milliseconds');
     // Calculate next period
-    const nextEnd = dayjs(calendarEnd).add(duration, 'milliseconds');
-
-    // Apply timezone transformations
-    const timezone = getUserTimezone();
-    const formattedStart = previousStart.utc().tz(timezone, true).utc().format();
-    const formattedEnd = nextEnd.utc().tz(timezone, true).utc().format();
+    const nextEnd = calendarEnd.add(duration, 'milliseconds');
 
     return {
-        start: formattedStart,
-        end: formattedEnd,
+        start: localDateToUtc(previousStart),
+        end: localDateToUtc(nextEnd),
     };
 }
 
@@ -46,21 +31,17 @@ export function getExpandedCalendarDateRange(
  * Get the initial week view date range based on user's week start preference.
  * Matches FullCalendar's timeGridWeek initial view.
  */
-export function getInitialWeekRange(): { start: Date; end: Date } {
+export function getInitialWeekRange(): { start: Dayjs; end: Dayjs } {
     const dayjs = getDayJsInstance();
-    const weekStart = getWeekStart();
-    const firstDay = weekStartMap[weekStart] ?? 1;
+    const firstDay = getWeekStartDayNumber();
 
     const now = dayjs();
     const currentDayOfWeek = now.day();
     const daysFromWeekStart = (currentDayOfWeek - firstDay + 7) % 7;
-    const calendarStart = now.subtract(daysFromWeekStart, 'day').startOf('day');
-    const calendarEnd = calendarStart.add(7, 'day');
+    const start = now.subtract(daysFromWeekStart, 'day').startOf('day');
+    const end = start.add(7, 'day');
 
-    return {
-        start: calendarStart.toDate(),
-        end: calendarEnd.toDate(),
-    };
+    return { start, end };
 }
 
 /**
@@ -115,8 +96,8 @@ export async function fetchAllCalendarEntries(
 }
 
 export function useTimeEntriesCalendarQuery(
-    calendarStart: Ref<Date | undefined>,
-    calendarEnd: Ref<Date | undefined>
+    calendarStart: Ref<Dayjs | undefined>,
+    calendarEnd: Ref<Dayjs | undefined>
 ) {
     const enableCalendarQuery = computed(() => {
         return !!getCurrentOrganizationId() && !!calendarStart.value && !!calendarEnd.value;

resources/js/utils/useTimesheetGrid.test.ts

@@ -0,0 +1,277 @@
+import { describe, expect, it } from 'vitest';
+import { nextTick, ref } from 'vue';
+import dayjs from 'dayjs';
+import utc from 'dayjs/plugin/utc';
+import type { Dayjs } from 'dayjs';
+import type { Project, Task, TimeEntry } from '@/packages/api/src';
+import { useTimesheetGrid } from './useTimesheetGrid';
+
+dayjs.extend(utc);
+
+const WEEK_DAYS = [
+    '2026-04-06',
+    '2026-04-07',
+    '2026-04-08',
+    '2026-04-09',
+    '2026-04-10',
+    '2026-04-11',
+    '2026-04-12',
+];
+
+function entry(start: string, end: string | null, overrides: Partial<TimeEntry> = {}): TimeEntry {
+    const startMs = new Date(start).valueOf();
+    const endMs = end ? new Date(end).valueOf() : startMs;
+
+    return {
+        id: overrides.id ?? `e-${start}-${end ?? 'running'}`,
+        start,
+        end,
+        duration: end ? Math.floor((endMs - startMs) / 1000) : null,
+        description: '',
+        member_id: 'm-1',
+        project_id: 'p-1',
+        task_id: null,
+        billable: false,
+        tags: [],
+        ...overrides,
+    } as unknown as TimeEntry;
+}
+
+function project(id: string, name: string, isBillable = false): Project {
+    return {
+        id,
+        name,
+        is_billable: isBillable,
+    } as unknown as Project;
+}
+
+function task(id: string, name: string, projectId: string): Task {
+    return {
+        id,
+        name,
+        project_id: projectId,
+    } as unknown as Task;
+}
+
+describe('useTimesheetGrid', () => {
+    it('seeds unseen identities and re-sorts seeded rows when project metadata changes', async () => {
+        const timeEntries = ref([
+            entry('2026-04-10T09:00:00Z', '2026-04-10T10:00:00Z', {
+                id: 'seed-b',
+                project_id: 'p-b',
+                task_id: null,
+            }),
+            entry('2026-04-10T10:00:00Z', '2026-04-10T11:00:00Z', {
+                id: 'seed-a-z',
+                project_id: 'p-a',
+                task_id: 't-z',
+            }),
+            entry('2026-04-10T11:00:00Z', '2026-04-10T12:00:00Z', {
+                id: 'seed-a-a',
+                project_id: 'p-a',
+                task_id: 't-a',
+            }),
+        ]);
+        const projects = ref([project('p-a', 'Bravo'), project('p-b', 'Alpha')]);
+        const tasks = ref([task('t-z', 'Zulu Task', 'p-a'), task('t-a', 'Alpha Task', 'p-a')]);
+
+        const { rows } = useTimesheetGrid(
+            timeEntries,
+            ref(WEEK_DAYS),
+            projects,
+            tasks,
+            ref<Dayjs | null>(null)
+        );
+
+        expect(rows.value.map((row) => `${row.projectId}:${row.taskId}`)).toEqual([
+            'p-b:null',
+            'p-a:t-a',
+            'p-a:t-z',
+        ]);
+
+        projects.value = [project('p-a', 'Aardvark'), project('p-b', 'Zulu')];
+        await nextTick();
+
+        expect(rows.value.map((row) => `${row.projectId}:${row.taskId}`)).toEqual([
+            'p-a:t-a',
+            'p-a:t-z',
+            'p-b:null',
+        ]);
+    });
+
+    it('keeps user-added slots below seeded rows in insertion order', async () => {
+        const timeEntries = ref([
+            entry('2026-04-10T09:00:00Z', '2026-04-10T10:00:00Z', {
+                id: 'seed-b',
+                project_id: 'p-seed-b',
+            }),
+            entry('2026-04-10T10:00:00Z', '2026-04-10T11:00:00Z', {
+                id: 'seed-a',
+                project_id: 'p-seed-a',
+            }),
+        ]);
+        const projects = ref([
+            project('p-seed-a', 'Bravo Seed'),
+            project('p-seed-b', 'Alpha Seed'),
+            project('p-user-1', 'Alpha User'),
+            project('p-user-2', 'Zulu User'),
+        ]);
+
+        const { rows, addSlot } = useTimesheetGrid(
+            timeEntries,
+            ref(WEEK_DAYS),
+            projects,
+            ref<Task[]>([]),
+            ref<Dayjs | null>(null)
+        );
+
+        addSlot('p-user-2', null, false, []);
+        addSlot('p-user-1', null, false, []);
+        await nextTick();
+
+        expect(rows.value.map((row) => row.projectId)).toEqual([
+            'p-seed-b',
+            'p-seed-a',
+            'p-user-2',
+            'p-user-1',
+        ]);
+
+        projects.value = [
+            project('p-seed-a', 'Zulu Seed'),
+            project('p-seed-b', 'Alpha Seed'),
+            project('p-user-1', 'Aardvark User'),
+            project('p-user-2', 'Bravo User'),
+        ];
+        await nextTick();
+
+        expect(rows.value.map((row) => row.projectId)).toEqual([
+            'p-seed-b',
+            'p-seed-a',
+            'p-user-2',
+            'p-user-1',
+        ]);
+    });
+
+    it('assigns entries to the first duplicate-identity slot and leaves later duplicates empty', async () => {
+        const timeEntries = ref<TimeEntry[]>([]);
+
+        const { rows, addSlot } = useTimesheetGrid(
+            timeEntries,
+            ref(WEEK_DAYS),
+            ref([project('p-1', 'Project One')]),
+            ref<Task[]>([]),
+            ref<Dayjs | null>(null)
+        );
+
+        const firstKey = addSlot('p-1', null, false, []);
+        const secondKey = addSlot('p-1', null, false, []);
+        await nextTick();
+
+        timeEntries.value = [
+            entry('2026-04-10T09:00:00Z', '2026-04-10T10:00:00Z', { project_id: 'p-1' }),
+        ];
+        await nextTick();
+
+        expect(rows.value).toHaveLength(2);
+        expect(rows.value[0]?.key).toBe(firstKey);
+        expect(rows.value[0]?.totalSeconds).toBe(3600);
+        expect(rows.value[1]?.key).toBe(secondKey);
+        expect(rows.value[1]?.totalSeconds).toBe(0);
+        expect(rows.value[1]?.cells.size).toBe(0);
+    });
+
+    it('keeps no-project user slots aligned with refetched no-project entries', async () => {
+        const timeEntries = ref<TimeEntry[]>([]);
+
+        const { rows, addSlot } = useTimesheetGrid(
+            timeEntries,
+            ref(WEEK_DAYS),
+            ref<Project[]>([]),
+            ref<Task[]>([]),
+            ref<Dayjs | null>(null)
+        );
+
+        const rowKey = addSlot(null, null, false, []);
+        await nextTick();
+
+        expect(rows.value).toHaveLength(1);
+        expect(rows.value[0]).toMatchObject({ key: rowKey, projectId: null });
+
+        timeEntries.value = [
+            entry('2026-04-10T09:00:00Z', '2026-04-10T10:00:00Z', {
+                id: 'no-project',
+                project_id: null,
+            }),
+        ];
+        await nextTick();
+
+        expect(rows.value).toHaveLength(1);
+        expect(rows.value[0]).toMatchObject({
+            key: rowKey,
+            projectId: null,
+            totalSeconds: 3600,
+        });
+    });
+
+    it('updates a slot identity in place and clearSlots removes all rows', async () => {
+        const { rows, slots, addSlot, updateSlot, clearSlots } = useTimesheetGrid(
+            ref<TimeEntry[]>([]),
+            ref(WEEK_DAYS),
+            ref([project('p-next', 'Next Project')]),
+            ref([task('t-1', 'Task One', 'p-next')]),
+            ref<Dayjs | null>(null)
+        );
+
+        const key = addSlot(null, null, false, []);
+        await nextTick();
+
+        updateSlot(key, {
+            projectId: 'p-next',
+            taskId: 't-1',
+            billable: true,
+            tags: ['b-tag', 'a-tag'],
+        });
+        await nextTick();
+
+        expect(rows.value).toHaveLength(1);
+        expect(rows.value[0]).toMatchObject({
+            key,
+            projectId: 'p-next',
+            taskId: 't-1',
+            billable: true,
+            tags: ['a-tag', 'b-tag'],
+        });
+
+        clearSlots();
+        await nextTick();
+
+        expect(rows.value).toHaveLength(0);
+        expect(slots.value).toHaveLength(0);
+    });
+
+    it('includes running entries in row and week totals using the live timer clock', () => {
+        const currentTime = ref(dayjs.utc('2026-04-10T10:00:00Z'));
+        const runningEntry = entry('2026-04-10T09:00:00Z', null, { id: 'running' });
+
+        const { rows, dayTotals, grandTotal } = useTimesheetGrid(
+            ref([runningEntry]),
+            ref(WEEK_DAYS),
+            ref<Project[]>([]),
+            ref<Task[]>([]),
+            currentTime
+        );
+
+        expect(rows.value).toHaveLength(1);
+        expect(rows.value[0]?.cells.get(4)?.totalSeconds).toBe(3600);
+        expect(rows.value[0]?.totalSeconds).toBe(3600);
+        expect(dayTotals.value[4]).toBe(3600);
+        expect(grandTotal.value).toBe(3600);
+
+        currentTime.value = dayjs.utc('2026-04-10T11:30:00Z');
+
+        expect(rows.value[0]?.cells.get(4)?.totalSeconds).toBe(9000);
+        expect(rows.value[0]?.totalSeconds).toBe(9000);
+        expect(dayTotals.value[4]).toBe(9000);
+        expect(grandTotal.value).toBe(9000);
+    });
+});

resources/js/utils/useTimesheetGrid.ts

@@ -0,0 +1,284 @@
+import type { TimeEntry, Project, Task } from '@/packages/api/src';
+import { getDayJsInstance, getLocalizedDateFromTimestamp } from '@/packages/ui/src/utils/time';
+import type { Dayjs } from 'dayjs';
+import { computed, ref, watch, type Ref } from 'vue';
+
+export type TimesheetRowKey = string;
+
+export interface TimesheetCell {
+    dayIndex: number;
+    date: string;
+    entries: TimeEntry[];
+    totalSeconds: number;
+}
+
+export interface TimesheetRow {
+    key: TimesheetRowKey;
+    projectId: string | null;
+    taskId: string | null;
+    billable: boolean;
+    tags: string[];
+    cells: Map<number, TimesheetCell>;
+    totalSeconds: number;
+}
+
+export interface TimesheetRowIdentity {
+    projectId: string | null;
+    taskId: string | null;
+    billable: boolean;
+    tags: string[];
+}
+
+interface Slot extends TimesheetRowIdentity {
+    id: string;
+    // 'seeded' slots are derived from the entries query and re-sort
+    // alphabetically whenever project/task lists change. 'user' slots
+    // were created via Add Row / project-change interactions and keep
+    // their insertion order (always below the seeded block).
+    origin: 'seeded' | 'user';
+}
+
+function sortTags(tags: string[] | null | undefined): string[] {
+    return [...(tags ?? [])].sort();
+}
+
+export function makeRowKey(
+    projectId: string | null,
+    taskId: string | null,
+    billable: boolean,
+    tags: string[]
+): TimesheetRowKey {
+    return JSON.stringify([projectId, taskId, billable, sortTags(tags)]);
+}
+
+function slotIdentityKey(slot: Slot): TimesheetRowKey {
+    return makeRowKey(slot.projectId, slot.taskId, slot.billable, slot.tags);
+}
+
+let slotCounter = 0;
+
+function newSlotId(): string {
+    return `s${++slotCounter}`;
+}
+
+/**
+ * Slot-first row model.
+ *
+ * The timesheet renders one row per slot, in insertion order. Slots
+ * carry a stable id — the row's Vue key never changes across mutations,
+ * so rows don't jump positions as entries load or get edited.
+ *
+ * Entries hydrate slots: `rows` is computed by grouping entries by
+ * identity (projectId, taskId, billable, tags) and attaching the
+ * matching group to the first slot with that identity. Duplicate
+ * slots with the same identity render empty (the first one claims
+ * the entries) — callers are expected to collapse duplicates after a
+ * cell-create rather than letting them linger.
+ *
+ * Seeding: a watcher scans `timeEntries` and appends a slot for every
+ * identity that doesn't already have one. Initial loads come in as a
+ * batch and are sorted by project name so the first render is stable;
+ * slots added later (via `addSlot` or post-mutation refetches) append
+ * at the end.
+ *
+ * Mutations:
+ *   - `addSlot`           push a blank or pre-populated slot at the end
+ *   - `removeSlot`        drop a slot by id (the row's `key`)
+ *   - `updateSlot`        migrate a slot's identity in place — used by
+ *                         project/billable/tags changes so the row
+ *                         stays put while the server roundtrips
+ *   - `clearSlots`        wipe everything (used on week navigation)
+ */
+export function useTimesheetGrid(
+    timeEntries: Ref<TimeEntry[]>,
+    weekDays: Ref<string[]>,
+    projects: Ref<Project[]>,
+    tasks: Ref<Task[]>,
+    currentTime: Ref<Dayjs | null>
+) {
+    const dayjs = getDayJsInstance();
+    const slots = ref<Slot[]>([]);
+
+    // Seed / re-sort the seeded portion of slots whenever entries,
+    // projects or tasks change. Seeded slots sort alphabetically by
+    // project name → task name → billable → tags so reloads are
+    // deterministic. User-added slots keep their insertion order and
+    // stay after the seeded block.
+    watch(
+        [() => timeEntries.value, () => projects.value, () => tasks.value],
+        ([entries, projectList, taskList]) => {
+            const present = new Set(slots.value.map(slotIdentityKey));
+            for (const entry of entries) {
+                const key = makeRowKey(
+                    entry.project_id,
+                    entry.task_id,
+                    entry.billable,
+                    sortTags(entry.tags)
+                );
+                if (present.has(key)) continue;
+                present.add(key);
+                slots.value.push({
+                    id: newSlotId(),
+                    origin: 'seeded',
+                    projectId: entry.project_id,
+                    taskId: entry.task_id,
+                    billable: entry.billable,
+                    tags: sortTags(entry.tags),
+                });
+            }
+
+            const projectNameMap = new Map<string, string>();
+            for (const p of projectList) projectNameMap.set(p.id, p.name);
+            const taskNameMap = new Map<string, string>();
+            for (const t of taskList) taskNameMap.set(t.id, t.name);
+
+            const sortKey = (s: Slot): string => {
+                const projectName = s.projectId ? (projectNameMap.get(s.projectId) ?? '') : '';
+                const taskName = s.taskId ? (taskNameMap.get(s.taskId) ?? '') : '';
+                return `${projectName}\x00${taskName}\x00${s.billable ? '1' : '0'}\x00${s.tags.join(',')}`;
+            };
+
+            const seeded = slots.value.filter((s) => s.origin === 'seeded');
+            const userAdded = slots.value.filter((s) => s.origin === 'user');
+            seeded.sort((a, b) => sortKey(a).localeCompare(sortKey(b)));
+            slots.value = [...seeded, ...userAdded];
+        },
+        { immediate: true }
+    );
+
+    const rows = computed<TimesheetRow[]>(() => {
+        const dayIndexMap = new Map<string, number>();
+        weekDays.value.forEach((date, index) => dayIndexMap.set(date, index));
+
+        // Group entries by identity. The first slot (in render order) with
+        // a given identity claims that group; later duplicate-identity
+        // slots render empty.
+        const entriesByIdentity = new Map<TimesheetRowKey, TimeEntry[]>();
+        for (const entry of timeEntries.value) {
+            const identityKey = makeRowKey(
+                entry.project_id,
+                entry.task_id,
+                entry.billable,
+                sortTags(entry.tags)
+            );
+            if (!entriesByIdentity.has(identityKey)) entriesByIdentity.set(identityKey, []);
+            entriesByIdentity.get(identityKey)!.push(entry);
+        }
+
+        const claimed = new Set<TimesheetRowKey>();
+
+        function buildCellsFromEntries(entries: TimeEntry[]) {
+            const cells = new Map<number, TimesheetCell>();
+            let totalSeconds = 0;
+
+            function getEntryDurationSeconds(entry: TimeEntry): number {
+                if (entry.end !== null) {
+                    return entry.duration ?? 0;
+                }
+
+                const liveNow = currentTime.value ?? dayjs.utc();
+                return Math.max(0, liveNow.diff(dayjs.utc(entry.start), 'second'));
+            }
+
+            for (const entry of entries) {
+                const entryDate = getLocalizedDateFromTimestamp(entry.start);
+                const dayIndex = dayIndexMap.get(entryDate);
+                if (dayIndex === undefined) continue;
+                const existing = cells.get(dayIndex);
+                const duration = getEntryDurationSeconds(entry);
+                if (existing) {
+                    existing.entries.push(entry);
+                    existing.totalSeconds += duration;
+                } else {
+                    cells.set(dayIndex, {
+                        dayIndex,
+                        date: weekDays.value[dayIndex]!,
+                        entries: [entry],
+                        totalSeconds: duration,
+                    });
+                }
+                totalSeconds += duration;
+            }
+            return { cells, totalSeconds };
+        }
+
+        return slots.value.map((slot) => {
+            const identityKey = slotIdentityKey(slot);
+            let collected: TimeEntry[] = [];
+
+            if (!claimed.has(identityKey)) {
+                const byIdentity = entriesByIdentity.get(identityKey);
+                if (byIdentity) {
+                    claimed.add(identityKey);
+                    collected = byIdentity;
+                }
+            }
+
+            const { cells, totalSeconds } = buildCellsFromEntries(collected);
+
+            return {
+                key: slot.id,
+                projectId: slot.projectId,
+                taskId: slot.taskId,
+                billable: slot.billable,
+                tags: slot.tags,
+                cells,
+                totalSeconds,
+            };
+        });
+    });
+
+    const dayTotals = computed<number[]>(() =>
+        weekDays.value.map((_, dayIndex) =>
+            rows.value.reduce((sum, row) => sum + (row.cells.get(dayIndex)?.totalSeconds ?? 0), 0)
+        )
+    );
+
+    const grandTotal = computed(() => dayTotals.value.reduce((a, b) => a + b, 0));
+
+    function addSlot(
+        projectId: string | null,
+        taskId: string | null,
+        billable: boolean,
+        tags: string[]
+    ): TimesheetRowKey {
+        const id = newSlotId();
+        slots.value.push({
+            id,
+            origin: 'user',
+            projectId,
+            taskId,
+            billable,
+            tags: sortTags(tags),
+        });
+        return id;
+    }
+
+    function removeSlot(key: TimesheetRowKey) {
+        slots.value = slots.value.filter((s) => s.id !== key);
+    }
+
+    function updateSlot(key: TimesheetRowKey, identity: TimesheetRowIdentity) {
+        const slot = slots.value.find((s) => s.id === key);
+        if (!slot) return;
+        slot.projectId = identity.projectId;
+        slot.taskId = identity.taskId;
+        slot.billable = identity.billable;
+        slot.tags = sortTags(identity.tags);
+    }
+
+    function clearSlots() {
+        slots.value = [];
+    }
+
+    return {
+        rows,
+        dayTotals,
+        grandTotal,
+        slots,
+        addSlot,
+        removeSlot,
+        updateSlot,
+        clearSlots,
+    };
+}

resources/js/utils/useTimesheetQuery.ts

@@ -0,0 +1,102 @@
+import { useQuery, type QueryClient } from '@tanstack/vue-query';
+import { api, type TimeEntry, type TimeEntryResponse } from '@/packages/api/src';
+import { getCurrentMembershipId, getCurrentOrganizationId } from '@/utils/useUser';
+import { computed, type Ref } from 'vue';
+import type { Dayjs } from 'dayjs';
+import { localDateToUtc } from '@/packages/ui/src/utils/time';
+
+function createTimesheetQueryKey(
+    start: string | null,
+    end: string | null,
+    organizationId: string | null
+) {
+    return ['timeEntries', 'timesheet', { start, end, organization: organizationId }] as const;
+}
+
+async function fetchTimesheetEntries(
+    organizationId: string,
+    memberId: string | undefined,
+    start: string,
+    end: string
+): Promise<TimeEntryResponse> {
+    const allEntries: TimeEntry[] = [];
+
+    while (true) {
+        const response = await api.getTimeEntries({
+            params: { organization: organizationId },
+            queries: {
+                start,
+                end,
+                member_id: memberId,
+                offset: allEntries.length || undefined,
+            },
+        });
+
+        if (response.data.length === 0) {
+            return { data: allEntries, meta: response.meta };
+        }
+
+        allEntries.push(...response.data);
+
+        if (allEntries.length >= response.meta.total) {
+            return { data: allEntries, meta: response.meta };
+        }
+    }
+}
+
+export function useTimesheetQuery(
+    weekStart: Ref<Dayjs | undefined>,
+    weekEnd: Ref<Dayjs | undefined>
+) {
+    const enabled = computed(() => {
+        return !!getCurrentOrganizationId() && !!weekStart.value && !!weekEnd.value;
+    });
+
+    const dateRange = computed(() => {
+        if (!weekStart.value || !weekEnd.value) return { start: null, end: null };
+        return {
+            start: localDateToUtc(weekStart.value),
+            end: localDateToUtc(weekEnd.value),
+        };
+    });
+
+    return useQuery<TimeEntryResponse>({
+        queryKey: computed(() =>
+            createTimesheetQueryKey(
+                dateRange.value.start,
+                dateRange.value.end,
+                getCurrentOrganizationId()
+            )
+        ),
+        enabled,
+        queryFn: async () => {
+            return fetchTimesheetEntries(
+                getCurrentOrganizationId() || '',
+                getCurrentMembershipId(),
+                dateRange.value.start!,
+                dateRange.value.end!
+            );
+        },
+        staleTime: 1000 * 30,
+        placeholderData: (previousData) => previousData,
+    });
+}
+
+export function prefetchTimesheetWeek(queryClient: QueryClient, weekStart: Dayjs, weekEnd: Dayjs) {
+    const start = localDateToUtc(weekStart);
+    const end = localDateToUtc(weekEnd);
+    const organizationId = getCurrentOrganizationId();
+    const memberId = getCurrentMembershipId();
+
+    if (!organizationId) return;
+
+    const queryKey = createTimesheetQueryKey(start, end, organizationId);
+
+    queryClient.prefetchQuery({
+        queryKey,
+        queryFn: () => fetchTimesheetEntries(organizationId, memberId, start, end),
+        staleTime: 1000 * 30,
+    });
+}
+
+export { fetchTimesheetEntries };

tests/Unit/Service/TimeEntryFilterTest.php

@@ -10,12 +10,57 @@ use App\Models\Tag;
 use App\Models\Task;
 use App\Models\TimeEntry;
 use App\Service\TimeEntryFilter;
+use Illuminate\Support\Carbon;
 use PHPUnit\Framework\Attributes\CoversClass;
 use Tests\TestCaseWithDatabase;
 
 #[CoversClass(TimeEntryFilter::class)]
 class TimeEntryFilterTest extends TestCaseWithDatabase
 {
+    public function test_add_start_is_inclusive_of_boundary(): void
+    {
+        // Arrange
+        $boundary = Carbon::parse('2024-01-01 12:00:00', 'UTC');
+        $entryAtBoundary = TimeEntry::factory()->start($boundary)->create();
+        $entryAfterBoundary = TimeEntry::factory()->start($boundary->copy()->addSecond())->create();
+        $entryBeforeBoundary = TimeEntry::factory()->start($boundary->copy()->subSecond())->create();
+
+        $builder = TimeEntry::query();
+        $filter = new TimeEntryFilter($builder);
+
+        // Act
+        $filter->addStart($boundary);
+
+        // Assert
+        $timeEntries = $builder->get();
+        $this->assertCount(2, $timeEntries);
+        $this->assertTrue($timeEntries->contains($entryAtBoundary));
+        $this->assertTrue($timeEntries->contains($entryAfterBoundary));
+        $this->assertFalse($timeEntries->contains($entryBeforeBoundary));
+    }
+
+    public function test_add_end_is_exclusive_of_boundary(): void
+    {
+        // Arrange
+        $boundary = Carbon::parse('2024-01-01 12:00:00', 'UTC');
+        $entryAtBoundary = TimeEntry::factory()->start($boundary)->create();
+        $entryAfterBoundary = TimeEntry::factory()->start($boundary->copy()->addSecond())->create();
+        $entryBeforeBoundary = TimeEntry::factory()->start($boundary->copy()->subSecond())->create();
+
+        $builder = TimeEntry::query();
+        $filter = new TimeEntryFilter($builder);
+
+        // Act
+        $filter->addEnd($boundary);
+
+        // Assert
+        $timeEntries = $builder->get();
+        $this->assertCount(1, $timeEntries);
+        $this->assertTrue($timeEntries->contains($entryBeforeBoundary));
+        $this->assertFalse($timeEntries->contains($entryAtBoundary));
+        $this->assertFalse($timeEntries->contains($entryAfterBoundary));
+    }
+
     public function test_add_tag_ids_filter_is_or(): void
     {
         // Arrange

vitest.config.ts

@@ -0,0 +1,19 @@
+import { defineConfig } from 'vitest/config';
+import vue from '@vitejs/plugin-vue';
+import { fileURLToPath } from 'node:url';
+
+export default defineConfig({
+    plugins: [vue()],
+    resolve: {
+        alias: {
+            '@': fileURLToPath(new URL('./resources/js', import.meta.url)),
+        },
+    },
+    test: {
+        environment: 'happy-dom',
+        globals: false,
+        setupFiles: ['./resources/js/test-setup.ts'],
+        include: ['resources/js/**/*.{test,spec}.{ts,tsx}'],
+        exclude: ['**/node_modules/**', '**/e2e/**', '**/dist/**'],
+    },
+});