diff --git a/src/plugins/built-in/writing-studio/goal-tracker.js b/src/plugins/built-in/writing-studio/goal-tracker.js
new file mode 100644
index 0000000..ec04d98
--- /dev/null
+++ b/src/plugins/built-in/writing-studio/goal-tracker.js
@@ -0,0 +1,87 @@
+const HISTORY_KEY = 'plugins.writing-studio.history';
+
+class GoalTracker {
+  /**
+   * @param {object} store - { get(key), set(key, value) } settings backend
+   */
+  constructor(store) {
+    this.store = store;
+  }
+
+  _getHistory() {
+    const raw = this.store.get(HISTORY_KEY);
+    return raw ? JSON.parse(raw) : {};
+  }
+
+  _setHistory(history) {
+    this.store.set(HISTORY_KEY, JSON.stringify(history));
+  }
+
+  _setHistoryDay(dateStr, data) {
+    const history = this._getHistory();
+    history[dateStr] = data;
+    this._setHistory(history);
+  }
+
+  addWords(count) {
+    const today = new Date().toISOString().split('T')[0];
+    const history = this._getHistory();
+    if (!history[today]) {
+      history[today] = { words: 0, sessions: 0 };
+    }
+    history[today].words += count;
+    history[today].sessions += 1;
+    this._setHistory(history);
+  }
+
+  getDailyProgress(goal) {
+    const today = new Date().toISOString().split('T')[0];
+    const history = this._getHistory();
+    const written = history[today]?.words || 0;
+    return { written, goal, pct: goal > 0 ? Math.min(100, Math.round((written / goal) * 100)) : 0 };
+  }
+
+  getStreak(goal) {
+    const history = this._getHistory();
+    let streak = 0;
+    const d = new Date();
+    for (let i = 0; i < 365; i++) {
+      const key = d.toISOString().split('T')[0];
+      const day = history[key];
+      if (day && day.words >= goal) {
+        streak++;
+        d.setDate(d.getDate() - 1);
+      } else {
+        break;
+      }
+    }
+    return streak;
+  }
+
+  getLast30Days() {
+    const history = this._getHistory();
+    const days = [];
+    const d = new Date();
+    for (let i = 0; i < 30; i++) {
+      const key = d.toISOString().split('T')[0];
+      const day = history[key];
+      days.push({ date: key, words: day?.words || 0 });
+      d.setDate(d.getDate() - 1);
+    }
+    return days.reverse();
+  }
+
+  getWeeklyTotal() {
+    const history = this._getHistory();
+    let total = 0;
+    const d = new Date();
+    for (let i = 0; i < 7; i++) {
+      const key = d.toISOString().split('T')[0];
+      if (history[key]) total += history[key].words || 0;
+      d.setDate(d.getDate() - 1);
+    }
+    return total;
+  }
+}
+
+module.exports = { GoalTracker };
diff --git a/tests/goal-tracker.test.js b/tests/goal-tracker.test.js
new file mode 100644
index 0000000..9bca693
--- /dev/null
+++ b/tests/goal-tracker.test.js
@@ -0,0 +1,82 @@
+const { GoalTracker } = require('../src/plugins/built-in/writing-studio/goal-tracker');
+
+describe('GoalTracker', () => {
+  let tracker;
+  let store;
+
+  beforeEach(() => {
+    store = {};
+    tracker = new GoalTracker({
+      get: (key) => store[key],
+      set: (key, value) => { store[key] = value; }
+    });
+  });
+
+  test('addWords records words for today', () => {
+    tracker.addWords(500);
+    const today = new Date().toISOString().split('T')[0];
+    expect(store['plugins.writing-studio.history']).toBeDefined();
+    const history = JSON.parse(store['plugins.writing-studio.history']);
+    expect(history[today].words).toBe(500);
+  });
+
+  test('addWords accumulates across multiple calls', () => {
+    tracker.addWords(300);
+    tracker.addWords(200);
+    const today = new Date().toISOString().split('T')[0];
+    const history = JSON.parse(store['plugins.writing-studio.history']);
+    expect(history[today].words).toBe(500);
+  });
+
+  test('getDailyProgress returns 0 when no history', () => {
+    expect(tracker.getDailyProgress(1000)).toEqual({ written: 0, goal: 1000, pct: 0 });
+  });
+
+  test('getDailyProgress returns percentage', () => {
+    tracker.addWords(500);
+    const progress = tracker.getDailyProgress(1000);
+    expect(progress.written).toBe(500);
+    expect(progress.pct).toBe(50);
+  });
+
+  test('getStreak counts consecutive days meeting goal', () => {
+    const today = new Date();
+    for (let i = 0; i < 3; i++) {
+      const d = new Date(today);
+      d.setDate(d.getDate() - i);
+      const key = d.toISOString().split('T')[0];
+      tracker._setHistoryDay(key, { words: 1200 });
+    }
+    const streak = tracker.getStreak(1000);
+    expect(streak).toBe(3);
+  });
+
+  test('getStreak breaks on missed day', () => {
+    const today = new Date();
+    tracker._setHistoryDay(today.toISOString().split('T')[0], { words: 1200 });
+    const yesterday = new Date(today);
+    yesterday.setDate(yesterday.getDate() - 1);
+    tracker._setHistoryDay(yesterday.toISOString().split('T')[0], { words: 500 });
+    const dayBefore = new Date(today);
+    dayBefore.setDate(dayBefore.getDate() - 2);
+    tracker._setHistoryDay(dayBefore.toISOString().split('T')[0], { words: 1200 });
+    expect(tracker.getStreak(1000)).toBe(1);
+  });
+
+  test('getLast30Days returns array of 30 entries', () => {
+    tracker.addWords(100);
+    const days = tracker.getLast30Days();
+    expect(days.length).toBe(30);
+    expect(days[29].words).toBe(100);
+  });
+
+  test('getWeeklyTotal sums last 7 days', () => {
+    const today = new Date();
+    for (let i = 0; i < 7; i++) {
+      const d = new Date(today);
+      d.setDate(d.getDate() - i);
+      tracker._setHistoryDay(d.toISOString().split('T')[0], { words: 200 });
+    }
+    expect(tracker.getWeeklyTotal()).toBe(1400);
+  });
+});