diff --git a/CLAUDE.md b/CLAUDE.md
new file mode 100644
index 0000000..9b9ca75
--- /dev/null
+++ b/CLAUDE.md
@@ -0,0 +1,70 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Commands
+
+```bash
+npm test                  # Run tests once (Vitest + JSDOM)
+npm run test:watch        # Run tests in watch mode
+npm run test:coverage     # Generate v8 coverage report
+npm run check:syntax      # Validate JS syntax via Acorn (extracts <script> from index.html)
+npm run build:min         # Minify HTML/CSS/JS into build/sp-dashboard/
+npm run screenshot        # Regenerate assets/ screenshots via Puppeteer
+make build                # Full plugin build → sp-dashboard.zip
+make release-check        # Verify prerequisites before releasing (clean state, tag, gh CLI)
+make release              # Tag, push, create GitHub release (requires clean git state + gh CLI)
+make clean                # Remove generated files
+```
+
+To run a single test: `npx vitest run --reporter=verbose tests/index.test.js -t "test name pattern"`
+
+## Architecture
+
+This is a **Super Productivity plugin** — a sandboxed iframe widget. All UI logic must live in `sp-dashboard/index.html` as a self-contained file (embedded CSS + JS, no external runtime dependencies).
+
+### Two-file plugin model
+
+- **`sp-dashboard/plugin.js`** — runs in the host app context. Registers an ACTION Redux hook with `PluginAPI.addEventListener`, then fires a `postMessage` to the iframe on every state change. This is the only bridge between the host app and the UI.
+- **`sp-dashboard/index.html`** — runs in an isolated iframe. Receives `SP_STATE_CHANGED` messages and pulls fresh data via `PluginAPI.getTasks()` / `getArchivedTasks()` / `getAllProjects()`. All rendering, state, and logic lives here.
+
+Available PluginAPI methods (beyond data fetching): `showSnack({ msg, ico })` for toast notifications, `getStorage()` / `setStorage(data)` for persistence (declared in manifest but currently unused).
+
+### Data flow inside index.html
+
+```
+postMessage → loadData() → PluginAPI calls → cachedTasks / cachedProjects
+  → processData(tasks, projects, dateRange) → metrics object
+    → updateDashboardUI()   (stat cards)
+    → updateBarChart()      (weekly time, CSS flex bars)
+    → updatePieChart()      (project breakdown, CSS conic-gradient)
+    → renderTable()         (detailed entries, sortable)
+```
+
+`processData()` is the core aggregation function. It deduplicates active + archived tasks (Map by ID, active takes precedence), filters by date range, and computes: time spent, completion counts, overdue/late flags, per-day breakdowns, and per-project summaries.
+
+### Mock data fallback
+
+If `PluginAPI` is unavailable (standalone file:// development), a 500ms timeout injects mock data so the full UI renders without the host app.
+
+### Charts
+
+No charting library. Bar chart uses CSS flexbox with `height` set as a percentage of max value; it automatically buckets data when the date range exceeds 30 days. Pie/donut chart uses a single `<div>` with `conic-gradient` computed from cumulative percentages.
+
+### Theming
+
+All colors are CSS custom properties (`--bg`, `--text-color`, `--c-primary`, etc.). Dark mode is toggled by `.dark-theme` on `<body>` — mirroring the host app's class injection.
+
+### Build pipeline
+
+`make build` runs: template substitution on `manifest.json.template` (injects VERSION/DESCRIPTION) → `scripts/minify.sh` (html-minifier-terser) → zip packaging. Version is the single source of truth in `package.json`.
+
+## Testing
+
+Tests live in `tests/index.test.js` and use Vitest with a JSDOM environment. The test harness sets `document.documentElement.innerHTML = html`, then executes the `<script>` block via `new Function()` — this means **any function you want to test must be explicitly assigned to `window`** inside the script (e.g. `window.processData = processData`). Mock `PluginAPI` is injected via `global.PluginAPI` before each test.
+
+## Key constraints
+
+- Keep `index.html` self-contained — no `import` statements, no external CDN links, no `require()`.
+- All user-visible strings in the UI must be sanitized before insertion into the DOM (use `textContent`, not `innerHTML`, for any data-derived content).
+- Plugin permissions are declared in `manifest.json.template`; `persistDataSynced` / `loadSyncedData` are declared but currently unused.
diff --git a/sp-dashboard/index.html b/sp-dashboard/index.html
index 0751107..c9b167b 100644
--- a/sp-dashboard/index.html
+++ b/sp-dashboard/index.html
@@ -265,6 +265,7 @@ <h1 class="title">Dashboard</h1>
           <label for="date-preset">Period</label>
           <select id="date-preset">
             <option value="today" selected>Today</option>
+            <option value="this-week">This Week</option>
             <option value="week">Past Week</option>
             <option value="month">Past Month</option>
             <option value="year">Past Year</option>
@@ -417,6 +418,8 @@ <h3 class="card-title">Project Breakdown</h3>
       return `${hours}h ${minutes}m`;
     };
 
+    const toLocalDate = d => `${d.getFullYear()}-${String(d.getMonth()+1).padStart(2,'0')}-${String(d.getDate()).padStart(2,'0')}`;
+
     const formatDateShort = (dateStr) => {
       const d = new Date(dateStr + "T00:00:00"); 
       return d.toLocaleDateString('en-US', { month: 'short', day: 'numeric', year: 'numeric' });
@@ -424,10 +427,10 @@ <h3 class="card-title">Project Breakdown</h3>
 
     const getDatesInRange = (startDate, endDate) => {
       const dates = [];
-      let currentDate = new Date(startDate);
-      const end = new Date(endDate);
+      let currentDate = new Date(startDate.split('T')[0] + "T00:00:00");
+      const end = new Date(endDate.split('T')[0] + "T00:00:00");
       while (currentDate <= end) {
-        dates.push(new Date(currentDate).toISOString().split('T')[0]);
+        dates.push(toLocalDate(currentDate));
         currentDate.setDate(currentDate.getDate() + 1);
       }
       return dates;
@@ -512,8 +515,8 @@ <h3 class="card-title">Project Breakdown</h3>
     const todayObjInit = new Date();
     const lastWeekObjInit = new Date();
     lastWeekObjInit.setDate(todayObjInit.getDate() - 6);
-    document.getElementById('date-from').value = todayObjInit.toISOString().split('T')[0];
-    document.getElementById('date-to').value = todayObjInit.toISOString().split('T')[0];
+    document.getElementById('date-from').value = toLocalDate(todayObjInit);
+    document.getElementById('date-to').value = toLocalDate(todayObjInit);
 
     const presetSelect = document.getElementById('date-preset');
     const customContainer = document.getElementById('custom-date-container');
@@ -736,13 +739,18 @@ <h3 class="card-title">Project Breakdown</h3>
     const getDueBounds = (task) => {
       let dueStart = null;
       if (task.dueDay) {
-        // parse original YYYY-MM-DD string – Date.parse yields UTC midnight
-        const parsed = Date.parse(task.dueDay);
+        // parse as local midnight so due-window aligns with the user's calendar day
+        const parsed = new Date(task.dueDay.split('T')[0] + "T00:00:00").getTime();
         if (!isNaN(parsed)) {
-          dueStart = parsed; // no timezone shift
+          dueStart = parsed;
         }
       }
-      const dueEnd = dueStart !== null ? dueStart + 86400000 - 1 : null;
+      let dueEnd = null;
+      if (dueStart !== null) {
+        const d = new Date(dueStart);
+        d.setDate(d.getDate() + 1);
+        dueEnd = d.getTime() - 1;
+      }
       return { dueStart, dueEnd };
     };
 
@@ -756,16 +764,23 @@ <h3 class="card-title">Project Breakdown</h3>
         dateToStr = document.getElementById('date-to').value;
       } else {
         const endObj = new Date();
-        const startObj = new Date();
-        if (preset === 'week') {
+        const startObj = new Date(endObj);
+        if (preset === 'this-week') {
+          const day = endObj.getDay(); // 0=Sun, 1=Mon, …, 6=Sat
+          const diff = day === 0 ? 6 : day - 1; // days back to most recent Monday
+          startObj.setDate(endObj.getDate() - diff);
+        } else if (preset === 'week') {
           startObj.setDate(endObj.getDate() - 6);
         } else if (preset === 'month') {
           startObj.setMonth(endObj.getMonth() - 1);
+          if (startObj.getDate() !== endObj.getDate()) {
+            startObj.setDate(0); // rewind to last day of previous month
+          }
         } else if (preset === 'year') {
           startObj.setFullYear(endObj.getFullYear() - 1);
         }
-        dateFromStr = startObj.toISOString().split('T')[0];
-        dateToStr = endObj.toISOString().split('T')[0];
+        dateFromStr = toLocalDate(startObj);
+        dateToStr = toLocalDate(endObj);
       }
       const dateRange = getDatesInRange(dateFromStr, dateToStr);
       console.log("[sp-dashboard] computed date range", dateFromStr, dateToStr, dateRange);
@@ -845,7 +860,9 @@ <h3 class="card-title">Project Breakdown</h3>
 
         dateRange.forEach((dateStr, index) => {
           const dayStart = new Date(dateStr + "T00:00:00").getTime();
-          const dayEnd = dayStart + 86400000 - 1;
+          const dayEndObj = new Date(dayStart);
+          dayEndObj.setDate(dayEndObj.getDate() + 1);
+          const dayEnd = dayEndObj.getTime() - 1;
 
           // Time Spent Logging
           const spentOnDate = task.timeSpentOnDay && task.timeSpentOnDay[dateStr];
@@ -884,7 +901,7 @@ <h3 class="card-title">Project Breakdown</h3>
         
         // if completed in window with no time, add entry (but skip if we'll show an overdue/late badge)
         if (taskTimeInRange === 0 && task.isDone && task.doneOn) {
-          const doneDate = new Date(task.doneOn).toISOString().split('T')[0];
+          const doneDate = toLocalDate(new Date(task.doneOn));
           if (dateRange.includes(doneDate) && !(isOverdue || isLate)) {
             metrics.tableEntries.push({
               date: doneDate,
@@ -901,7 +918,7 @@ <h3 class="card-title">Project Breakdown</h3>
         // add a row for overdue or late tasks that had no time entries
         if (taskTimeInRange === 0 && (isOverdue || isLate)) {
           const badge = isLate ? 'Late' : 'Overdue';
-          const dateStr = dueStart ? new Date(dueStart).toISOString().split('T')[0] : '';
+          const dateStr = dueStart ? toLocalDate(new Date(dueStart)) : '';
           metrics.tableEntries.push({
             date: dateStr,
             projectName: pName,
@@ -921,7 +938,7 @@ <h3 class="card-title">Project Breakdown</h3>
         }
 
         // count tasks that had activity OR were completed OR are due (in range)
-        const taskCompletedInRange = task.isDone && task.doneOn && dateRange.includes(new Date(task.doneOn).toISOString().split('T')[0]);
+        const taskCompletedInRange = task.isDone && task.doneOn && dateRange.includes(toLocalDate(new Date(task.doneOn)));
         const taskDueInRange = task.dueDay && dateRange.includes(task.dueDay);
         if (taskTimeInRange > 0 || taskCompletedInRange || taskDueInRange) {
           metrics.totalTasks++;
@@ -981,6 +998,7 @@ <h3 class="card-title">Project Breakdown</h3>
     window.formatTime = formatTime;
     window.formatDateShort = formatDateShort;
     window.getDatesInRange = getDatesInRange;
+    window.getDueBounds = getDueBounds;
     window.switchTab = switchTab;
     window.processData = processData;
     window.updateBarChart = updateBarChart;
diff --git a/tests/index.test.js b/tests/index.test.js
index 20edc57..4b20ea0 100644
--- a/tests/index.test.js
+++ b/tests/index.test.js
@@ -6,6 +6,8 @@ import { resolve } from 'path';
 // file moved into the sp-dashboard subdirectory
 const html = readFileSync(resolve(__dirname, '../sp-dashboard/index.html'), 'utf8');
 
+const toLocalDate = (d) => `${d.getFullYear()}-${String(d.getMonth()+1).padStart(2,'0')}-${String(d.getDate()).padStart(2,'0')}`;
+
 describe('Date Range Reporter UI', () => {
   let scriptContent;
 
@@ -41,6 +43,43 @@ describe('Date Range Reporter UI', () => {
       const range = window.getDatesInRange('2026-02-20', '2026-02-22');
       expect(range).toEqual(['2026-02-20', '2026-02-21', '2026-02-22']);
     });
+
+    it('getDatesInRange should tolerate full ISO timestamps as inputs', () => {
+      const range = window.getDatesInRange('2026-02-20T10:00:00Z', '2026-02-22T10:00:00Z');
+      expect(range).toEqual(['2026-02-20', '2026-02-21', '2026-02-22']);
+    });
+
+    it('getDueBounds dueEnd should be end-of-day (DST-safe calculation)', () => {
+      const { dueStart, dueEnd } = window.getDueBounds({ dueDay: '2026-03-28' });
+      expect(dueStart).not.toBeNull();
+      expect(dueEnd).toBeGreaterThan(dueStart);
+      expect(dueEnd - dueStart).toBeGreaterThanOrEqual(82800000); // at least 23h
+      expect(dueEnd - dueStart).toBeLessThanOrEqual(90000000);    // at most 25h
+    });
+
+    it('getDueBounds should handle a full ISO timestamp in dueDay', () => {
+      const { dueStart, dueEnd } = window.getDueBounds({ dueDay: '2026-02-20T10:00:00Z' });
+      expect(dueStart).not.toBeNull();
+      expect(dueEnd).not.toBeNull();
+      // dueStart should parse to 2026-02-20 local midnight
+      expect(toLocalDate(new Date(dueStart))).toBe('2026-02-20');
+    });
+
+    it('month preset should not roll over when today is the 31st', () => {
+      // March 31, 2026 at noon — without the fix, setMonth(Feb) on Mar 31 rolls to Mar 3
+      vi.useFakeTimers({ now: new Date('2026-03-31T12:00:00').getTime() });
+      const consoleSpy = vi.spyOn(console, 'log');
+      const presetSelect = document.getElementById('date-preset');
+      presetSelect.value = 'month';
+      presetSelect.dispatchEvent(new Event('change'));
+      window.processData([], []);
+      vi.useRealTimers();
+      const rangeLog = consoleSpy.mock.calls.find(args => String(args[0]).includes('computed date range'));
+      expect(rangeLog).toBeDefined();
+      expect(rangeLog[1]).toBe('2026-02-28'); // should be Feb 28, not Mar 3
+      expect(rangeLog[2]).toBe('2026-03-31');
+      consoleSpy.mockRestore();
+    });
   });
 
   describe('Dashboard State Updates', () => {
@@ -52,14 +91,14 @@ describe('Date Range Reporter UI', () => {
           title: 'Task 1',
           isDone: true,
           doneOn: new Date().getTime(),
-          timeSpentOnDay: { [new Date().toISOString().split('T')[0]]: 7200000 } // 2h
+          timeSpentOnDay: { [toLocalDate(new Date())]: 7200000 } // 2h
         },
         {
           id: 't2',
           parentId: null,
           title: 'Task 2',
           isDone: false,
-          timeSpentOnDay: { [new Date().toISOString().split('T')[0]]: 3600000 } // 1h
+          timeSpentOnDay: { [toLocalDate(new Date())]: 3600000 } // 1h
         }
       ];
       const mockProjects = [{ id: 'p1', title: 'Test Project' }];
@@ -79,7 +118,7 @@ describe('Date Range Reporter UI', () => {
 
     it('should honor dueDay provided initially', () => {
       const now = Date.now();
-      const dueStr = new Date(now - 86400000).toISOString().split('T')[0];
+      const dueStr = toLocalDate(new Date(now - 86400000));
       const task = {
         id: 't-initial',
         parentId: null,
@@ -112,7 +151,7 @@ describe('Date Range Reporter UI', () => {
       expect(document.getElementById('stat-overdue').innerText).toBe('0');
 
       // add dueDay yesterday and trigger again
-      task.dueDay = new Date(now - 86400000).toISOString().split('T')[0];
+      task.dueDay = toLocalDate(new Date(now - 86400000));
       window.processData(tasks, []);
       expect(document.getElementById('stat-overdue').innerText).toBe('1');
     });
@@ -134,7 +173,7 @@ describe('Date Range Reporter UI', () => {
       expect(document.getElementById('stat-late').innerText).toBe('0');
 
       // now add dueDay equal to today
-      task.dueDay = new Date(now).toISOString().split('T')[0];
+      task.dueDay = toLocalDate(new Date(now));
       window.processData(tasks, []);
       expect(document.getElementById('stat-overdue').innerText).toBe('0');
       expect(document.getElementById('stat-late').innerText).toBe('0');
@@ -149,7 +188,7 @@ describe('Date Range Reporter UI', () => {
         title: 'Done Late',
         isDone: true,
         doneOn: now,
-        dueDay: due.toISOString().split('T')[0],
+        dueDay: toLocalDate(due),
         timeSpentOnDay: {}
       };
       window.processData([task], []);
@@ -178,7 +217,7 @@ describe('Date Range Reporter UI', () => {
 
     it('should not mark a task due today as late if completed same day', () => {
       const now = Date.now();
-      const todayStr = new Date(now).toISOString().split('T')[0];
+      const todayStr = toLocalDate(new Date(now));
       const task = {
         id: 't-due-today',
         parentId: null,
@@ -206,7 +245,7 @@ describe('Date Range Reporter UI', () => {
         title: 'subtask done',
         isDone: true,
         doneOn: now,
-        dueDay: new Date(now).toISOString().split('T')[0],
+        dueDay: toLocalDate(new Date(now)),
         timeSpentOnDay: {}
       };
       window.processData([sub], []);
@@ -215,7 +254,7 @@ describe('Date Range Reporter UI', () => {
     });
 
     it('should count tasks due today in totalTasks denominator even with no time logged', () => {
-      const todayStr = new Date().toISOString().split('T')[0];
+      const todayStr = toLocalDate(new Date());
       const taskDueToday = {
         id: 't-due-no-time',
         parentId: null,
@@ -239,7 +278,7 @@ describe('Date Range Reporter UI', () => {
         title: 'Done Task',
         isDone: true,
         doneOn: now,
-        dueDay: new Date(now).toISOString().split('T')[0],
+        dueDay: toLocalDate(new Date(now)),
         timeSpentOnDay: {}
       };
       // Simulate what happens when pullDataFromSP combines activeTasks and archivedTasks
@@ -313,10 +352,38 @@ describe('Date Range Reporter UI', () => {
       expect(barContainer.querySelectorAll('.bar-col').length).toBe(1);
     });
 
+    it('this-week preset should include Monday through today and exclude last Sunday', () => {
+      const presetSelect = document.getElementById('date-preset');
+      presetSelect.value = 'this-week';
+      presetSelect.dispatchEvent(new Event('change'));
+
+      // Build a task logged on last Sunday (always before this week's Monday)
+      const now = new Date();
+      const dayOfWeek = now.getDay();
+      const daysToMonday = dayOfWeek === 0 ? 6 : dayOfWeek - 1;
+      const lastSunday = new Date(now);
+      lastSunday.setDate(now.getDate() - daysToMonday - 1);
+      const lastSundayStr = toLocalDate(lastSunday);
+      const todayStr = toLocalDate(now);
+
+      const taskThisWeek = { id: 'tw1', parentId: null, title: 'This Week Task', isDone: true, doneOn: now.getTime(), timeSpentOnDay: { [todayStr]: 3600000 } };
+      const taskLastWeek = { id: 'tw2', parentId: null, title: 'Last Week Task', isDone: true, doneOn: lastSunday.getTime(), timeSpentOnDay: { [lastSundayStr]: 3600000 } };
+
+      window.processData([taskThisWeek, taskLastWeek], []);
+
+      // Only this week's task time should be counted
+      expect(document.getElementById('stat-time').innerText).toBe('1h 0m');
+
+      // Bar chart should have at most 7 bars (Mon–today)
+      const barContainer = document.getElementById('bar-chart-container');
+      expect(barContainer.querySelectorAll('.bar-col').length).toBeLessThanOrEqual(7);
+      expect(barContainer.querySelectorAll('.bar-col').length).toBeGreaterThanOrEqual(1);
+    });
+
     it('bar and pie charts should render for overdue and late types and details show badges', () => {
       // prepare metrics with one overdue task and one late task
       const now = Date.now();
-      const yesterdayStr = new Date(now - 86400000).toISOString().split('T')[0];
+      const yesterdayStr = toLocalDate(new Date(now - 86400000));
       const overdueTask = { id:'t1', parentId:null, title:'Foo', isDone:false, dueDay:'2026-02-20', timeSpentOnDay:{'2026-02-20':0} };
       const lateTask = { id:'t2', parentId:null, title:'Bar', isDone:true, doneOn: now, dueDay: yesterdayStr, timeSpentOnDay:{} };
       window.processData([overdueTask, lateTask], []);
