diff --git a/apps/frontend/src/renderer/stores/github/__tests__/label-sync-store.test.ts b/apps/frontend/src/renderer/stores/github/__tests__/label-sync-store.test.ts
new file mode 100644
index 00000000..89df158d
--- /dev/null
+++ b/apps/frontend/src/renderer/stores/github/__tests__/label-sync-store.test.ts
@@ -0,0 +1,69 @@
+import { describe, it, expect, beforeEach } from 'vitest';
+import { useLabelSyncStore } from '../label-sync-store';
+
+describe('useLabelSyncStore', () => {
+  beforeEach(() => {
+    useLabelSyncStore.getState().reset();
+  });
+
+  it('has correct initial state', () => {
+    const state = useLabelSyncStore.getState();
+    expect(state.config.enabled).toBe(false);
+    expect(state.config.lastSyncedAt).toBeNull();
+    expect(state.isLoaded).toBe(false);
+    expect(state.isSyncing).toBe(false);
+    expect(state.error).toBeNull();
+    expect(state.lastResult).toBeNull();
+  });
+
+  it('setConfig updates config and marks loaded', () => {
+    useLabelSyncStore.getState().setConfig({
+      enabled: true,
+      lastSyncedAt: '2026-01-01T00:00:00Z',
+    });
+
+    const state = useLabelSyncStore.getState();
+    expect(state.config.enabled).toBe(true);
+    expect(state.config.lastSyncedAt).toBe('2026-01-01T00:00:00Z');
+    expect(state.isLoaded).toBe(true);
+    expect(state.error).toBeNull();
+  });
+
+  it('setSyncing updates syncing state', () => {
+    useLabelSyncStore.getState().setSyncing(true);
+    expect(useLabelSyncStore.getState().isSyncing).toBe(true);
+
+    useLabelSyncStore.getState().setSyncing(false);
+    expect(useLabelSyncStore.getState().isSyncing).toBe(false);
+  });
+
+  it('setError updates error and clears syncing', () => {
+    useLabelSyncStore.getState().setSyncing(true);
+    useLabelSyncStore.getState().setError('Rate limited');
+
+    const state = useLabelSyncStore.getState();
+    expect(state.error).toBe('Rate limited');
+    expect(state.isSyncing).toBe(false);
+  });
+
+  it('setLastResult stores sync result', () => {
+    const result = { created: 7, updated: 0, removed: 0, errors: [] };
+    useLabelSyncStore.getState().setLastResult(result);
+
+    expect(useLabelSyncStore.getState().lastResult).toEqual(result);
+  });
+
+  it('reset returns to initial state', () => {
+    useLabelSyncStore.getState().setConfig({ enabled: true, lastSyncedAt: 'now' });
+    useLabelSyncStore.getState().setSyncing(true);
+    useLabelSyncStore.getState().setError('fail');
+
+    useLabelSyncStore.getState().reset();
+
+    const state = useLabelSyncStore.getState();
+    expect(state.config.enabled).toBe(false);
+    expect(state.isLoaded).toBe(false);
+    expect(state.isSyncing).toBe(false);
+    expect(state.error).toBeNull();
+  });
+});
diff --git a/apps/frontend/src/renderer/stores/github/__tests__/phase4-store.test.ts b/apps/frontend/src/renderer/stores/github/__tests__/phase4-store.test.ts
new file mode 100644
index 00000000..74992991
--- /dev/null
+++ b/apps/frontend/src/renderer/stores/github/__tests__/phase4-store.test.ts
@@ -0,0 +1,119 @@
+import { describe, it, expect, beforeEach } from 'vitest';
+import { usePhase4Store } from '../phase4-store';
+
+describe('usePhase4Store', () => {
+  beforeEach(() => {
+    const state = usePhase4Store.getState();
+    state.clearDependencies();
+    state.setMetrics({
+      stateCounts: { new: 0, triage: 0, ready: 0, in_progress: 0, review: 0, done: 0, blocked: 0 },
+      avgTimeInState: { new: 0, triage: 0, ready: 0, in_progress: 0, review: 0, done: 0, blocked: 0 },
+      weeklyThroughput: [],
+      completenessDistribution: { low: 0, medium: 0, high: 0, excellent: 0 },
+      avgBacklogAge: 0,
+      totalTransitions: 0,
+      computedAt: '',
+    });
+    state.setMetricsError(null);
+    state.setTriageModeEnabled(false);
+  });
+
+  describe('dependencies', () => {
+    it('returns empty dependencies for unknown issue', () => {
+      const deps = usePhase4Store.getState().getDependencies(999);
+      expect(deps.tracks).toEqual([]);
+      expect(deps.trackedBy).toEqual([]);
+    });
+
+    it('setDependencies stores per-issue data', () => {
+      const deps = {
+        tracks: [{ issueNumber: 10, title: 'Sub', state: 'open' as const }],
+        trackedBy: [],
+      };
+      usePhase4Store.getState().setDependencies(42, deps);
+
+      expect(usePhase4Store.getState().getDependencies(42)).toEqual(deps);
+    });
+
+    it('setDependencyLoading tracks loading state', () => {
+      usePhase4Store.getState().setDependencyLoading(42, true);
+      expect(usePhase4Store.getState().isDependencyLoading(42)).toBe(true);
+
+      usePhase4Store.getState().setDependencyLoading(42, false);
+      expect(usePhase4Store.getState().isDependencyLoading(42)).toBe(false);
+    });
+
+    it('setDependencyError stores error and clears loading', () => {
+      usePhase4Store.getState().setDependencyLoading(42, true);
+      usePhase4Store.getState().setDependencyError(42, 'API unavailable');
+
+      const state = usePhase4Store.getState();
+      expect(state.dependencyErrors[42]).toBe('API unavailable');
+      expect(state.isDependencyLoading(42)).toBe(false);
+    });
+
+    it('clearDependencies removes all cached data', () => {
+      usePhase4Store.getState().setDependencies(1, { tracks: [], trackedBy: [] });
+      usePhase4Store.getState().setDependencies(2, { tracks: [], trackedBy: [] });
+
+      usePhase4Store.getState().clearDependencies();
+
+      expect(Object.keys(usePhase4Store.getState().dependencies)).toHaveLength(0);
+    });
+  });
+
+  describe('metrics', () => {
+    it('has default empty metrics', () => {
+      const state = usePhase4Store.getState();
+      expect(state.metrics.totalTransitions).toBe(0);
+      expect(state.metricsTimeWindow).toBe('30d');
+    });
+
+    it('setMetrics updates metrics and clears loading/error', () => {
+      usePhase4Store.getState().setMetricsLoading(true);
+      usePhase4Store.getState().setMetrics({
+        stateCounts: { new: 5, triage: 3, ready: 0, in_progress: 0, review: 0, done: 0, blocked: 0 },
+        avgTimeInState: { new: 0, triage: 0, ready: 0, in_progress: 0, review: 0, done: 0, blocked: 0 },
+        weeklyThroughput: [{ week: '2026-02-10', count: 8 }],
+        completenessDistribution: { low: 1, medium: 2, high: 3, excellent: 2 },
+        avgBacklogAge: 86400000,
+        totalTransitions: 15,
+        computedAt: '2026-02-12T00:00:00Z',
+      });
+
+      const state = usePhase4Store.getState();
+      expect(state.metrics.totalTransitions).toBe(15);
+      expect(state.metrics.stateCounts.new).toBe(5);
+      expect(state.metricsLoading).toBe(false);
+      expect(state.metricsError).toBeNull();
+    });
+
+    it('setMetricsTimeWindow updates window', () => {
+      usePhase4Store.getState().setMetricsTimeWindow('7d');
+      expect(usePhase4Store.getState().metricsTimeWindow).toBe('7d');
+    });
+
+    it('setMetricsError stores error and clears loading', () => {
+      usePhase4Store.getState().setMetricsLoading(true);
+      usePhase4Store.getState().setMetricsError('Computation failed');
+
+      const state = usePhase4Store.getState();
+      expect(state.metricsError).toBe('Computation failed');
+      expect(state.metricsLoading).toBe(false);
+    });
+  });
+
+  describe('triage mode', () => {
+    it('defaults to disabled', () => {
+      expect(usePhase4Store.getState().triageModeEnabled).toBe(false);
+    });
+
+    it('setTriageModeEnabled toggles triage mode', () => {
+      usePhase4Store.getState().setTriageModeEnabled(true);
+      expect(usePhase4Store.getState().triageModeEnabled).toBe(true);
+
+      usePhase4Store.getState().setTriageModeEnabled(false);
+      expect(usePhase4Store.getState().triageModeEnabled).toBe(false);
+    });
+  });
+});
diff --git a/apps/frontend/src/renderer/stores/github/label-sync-store.ts b/apps/frontend/src/renderer/stores/github/label-sync-store.ts
new file mode 100644
index 00000000..1be4bf7e
--- /dev/null
+++ b/apps/frontend/src/renderer/stores/github/label-sync-store.ts
@@ -0,0 +1,43 @@
+import { create } from 'zustand';
+import type { LabelSyncConfig, LabelSyncResult } from '../../../shared/types/label-sync';
+import { createDefaultLabelSyncConfig } from '../../../shared/types/label-sync';
+
+interface LabelSyncState {
+  // Data
+  config: LabelSyncConfig;
+  isLoaded: boolean;
+
+  // UI State
+  isSyncing: boolean;
+  error: string | null;
+  lastResult: LabelSyncResult | null;
+
+  // Actions
+  setConfig: (config: LabelSyncConfig) => void;
+  setSyncing: (syncing: boolean) => void;
+  setError: (error: string | null) => void;
+  setLastResult: (result: LabelSyncResult | null) => void;
+  reset: () => void;
+}
+
+export const useLabelSyncStore = create<LabelSyncState>((set) => ({
+  // Initial state
+  config: createDefaultLabelSyncConfig(),
+  isLoaded: false,
+  isSyncing: false,
+  error: null,
+  lastResult: null,
+
+  // Actions
+  setConfig: (config) => set({ config, isLoaded: true, error: null }),
+  setSyncing: (isSyncing) => set({ isSyncing }),
+  setError: (error) => set({ error, isSyncing: false }),
+  setLastResult: (lastResult) => set({ lastResult }),
+  reset: () => set({
+    config: createDefaultLabelSyncConfig(),
+    isLoaded: false,
+    isSyncing: false,
+    error: null,
+    lastResult: null,
+  }),
+}));
diff --git a/apps/frontend/src/renderer/stores/github/phase4-store.ts b/apps/frontend/src/renderer/stores/github/phase4-store.ts
new file mode 100644
index 00000000..ac9f5642
--- /dev/null
+++ b/apps/frontend/src/renderer/stores/github/phase4-store.ts
@@ -0,0 +1,85 @@
+import { create } from 'zustand';
+import type { IssueDependencies } from '../../../shared/types/dependencies';
+import type { TriageMetrics, MetricsTimeWindow } from '../../../shared/types/metrics';
+import { createEmptyDependencies } from '../../../shared/types/dependencies';
+import { createEmptyMetrics } from '../../../shared/types/metrics';
+
+interface Phase4State {
+  // Dependencies (per-issue cache)
+  dependencies: Record<number, IssueDependencies>;
+  dependencyLoading: Record<number, boolean>;
+  dependencyErrors: Record<number, string>;
+
+  // Metrics
+  metrics: TriageMetrics;
+  metricsTimeWindow: MetricsTimeWindow;
+  metricsLoading: boolean;
+  metricsError: string | null;
+
+  // Triage mode
+  triageModeEnabled: boolean;
+
+  // Dependency actions
+  setDependencies: (issueNumber: number, deps: IssueDependencies) => void;
+  setDependencyLoading: (issueNumber: number, loading: boolean) => void;
+  setDependencyError: (issueNumber: number, error: string) => void;
+  clearDependencies: () => void;
+
+  // Metrics actions
+  setMetrics: (metrics: TriageMetrics) => void;
+  setMetricsTimeWindow: (window: MetricsTimeWindow) => void;
+  setMetricsLoading: (loading: boolean) => void;
+  setMetricsError: (error: string | null) => void;
+
+  // Triage mode actions
+  setTriageModeEnabled: (enabled: boolean) => void;
+
+  // Selectors
+  getDependencies: (issueNumber: number) => IssueDependencies;
+  isDependencyLoading: (issueNumber: number) => boolean;
+}
+
+export const usePhase4Store = create<Phase4State>((set, get) => ({
+  // Initial state
+  dependencies: {},
+  dependencyLoading: {},
+  dependencyErrors: {},
+  metrics: createEmptyMetrics(),
+  metricsTimeWindow: '30d',
+  metricsLoading: false,
+  metricsError: null,
+  triageModeEnabled: false,
+
+  // Dependency actions
+  setDependencies: (issueNumber, deps) =>
+    set((state) => ({
+      dependencies: { ...state.dependencies, [issueNumber]: deps },
+      dependencyErrors: { ...state.dependencyErrors, [issueNumber]: undefined as unknown as string },
+    })),
+
+  setDependencyLoading: (issueNumber, loading) =>
+    set((state) => ({
+      dependencyLoading: { ...state.dependencyLoading, [issueNumber]: loading },
+    })),
+
+  setDependencyError: (issueNumber, error) =>
+    set((state) => ({
+      dependencyErrors: { ...state.dependencyErrors, [issueNumber]: error },
+      dependencyLoading: { ...state.dependencyLoading, [issueNumber]: false },
+    })),
+
+  clearDependencies: () => set({ dependencies: {}, dependencyLoading: {}, dependencyErrors: {} }),
+
+  // Metrics actions
+  setMetrics: (metrics) => set({ metrics, metricsLoading: false, metricsError: null }),
+  setMetricsTimeWindow: (metricsTimeWindow) => set({ metricsTimeWindow }),
+  setMetricsLoading: (metricsLoading) => set({ metricsLoading }),
+  setMetricsError: (metricsError) => set({ metricsError, metricsLoading: false }),
+
+  // Triage mode actions
+  setTriageModeEnabled: (triageModeEnabled) => set({ triageModeEnabled }),
+
+  // Selectors
+  getDependencies: (issueNumber) => get().dependencies[issueNumber] ?? createEmptyDependencies(),
+  isDependencyLoading: (issueNumber) => get().dependencyLoading[issueNumber] ?? false,
+}));