diff --git a/apps/server/tests/unit/services/concurrency-manager.test.ts b/apps/server/tests/unit/services/concurrency-manager.test.ts
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+++ b/apps/server/tests/unit/services/concurrency-manager.test.ts
@@ -0,0 +1,612 @@
+import { describe, it, expect, beforeEach, vi } from 'vitest';
+import { ConcurrencyManager, type RunningFeature } from '@/services/concurrency-manager.js';
+
+// Mock git-utils to control getCurrentBranch behavior
+vi.mock('@automaker/git-utils', () => ({
+  getCurrentBranch: vi.fn(),
+}));
+
+import { getCurrentBranch } from '@automaker/git-utils';
+const mockGetCurrentBranch = vi.mocked(getCurrentBranch);
+
+describe('ConcurrencyManager', () => {
+  let manager: ConcurrencyManager;
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+    manager = new ConcurrencyManager();
+    // Default: primary branch is 'main'
+    mockGetCurrentBranch.mockResolvedValue('main');
+  });
+
+  describe('acquire', () => {
+    it('should create new entry with leaseCount: 1 on first acquire', () => {
+      const result = manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+      });
+
+      expect(result.featureId).toBe('feature-1');
+      expect(result.projectPath).toBe('/test/project');
+      expect(result.isAutoMode).toBe(true);
+      expect(result.leaseCount).toBe(1);
+      expect(result.worktreePath).toBeNull();
+      expect(result.branchName).toBeNull();
+      expect(result.startTime).toBeDefined();
+      expect(result.abortController).toBeInstanceOf(AbortController);
+    });
+
+    it('should increment leaseCount when allowReuse is true for existing feature', () => {
+      // First acquire
+      manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+      });
+
+      // Second acquire with allowReuse
+      const result = manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+        allowReuse: true,
+      });
+
+      expect(result.leaseCount).toBe(2);
+    });
+
+    it('should throw "already running" when allowReuse is false for existing feature', () => {
+      // First acquire
+      manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+      });
+
+      // Second acquire without allowReuse
+      expect(() =>
+        manager.acquire({
+          featureId: 'feature-1',
+          projectPath: '/test/project',
+          isAutoMode: true,
+        })
+      ).toThrow('already running');
+    });
+
+    it('should throw "already running" when allowReuse is explicitly false', () => {
+      manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+      });
+
+      expect(() =>
+        manager.acquire({
+          featureId: 'feature-1',
+          projectPath: '/test/project',
+          isAutoMode: true,
+          allowReuse: false,
+        })
+      ).toThrow('already running');
+    });
+
+    it('should use provided abortController', () => {
+      const customAbortController = new AbortController();
+
+      const result = manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+        abortController: customAbortController,
+      });
+
+      expect(result.abortController).toBe(customAbortController);
+    });
+
+    it('should return the existing entry when allowReuse is true', () => {
+      const first = manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+      });
+
+      const second = manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+        allowReuse: true,
+      });
+
+      // Should be the same object reference
+      expect(second).toBe(first);
+    });
+
+    it('should allow multiple nested acquire calls with allowReuse', () => {
+      manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+      });
+
+      manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+        allowReuse: true,
+      });
+
+      const result = manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+        allowReuse: true,
+      });
+
+      expect(result.leaseCount).toBe(3);
+    });
+  });
+
+  describe('release', () => {
+    it('should decrement leaseCount on release', () => {
+      manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+      });
+
+      manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+        allowReuse: true,
+      });
+
+      manager.release('feature-1');
+
+      const entry = manager.getRunningFeature('feature-1');
+      expect(entry?.leaseCount).toBe(1);
+    });
+
+    it('should delete entry when leaseCount reaches 0', () => {
+      manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+      });
+
+      manager.release('feature-1');
+
+      expect(manager.isRunning('feature-1')).toBe(false);
+      expect(manager.getRunningFeature('feature-1')).toBeUndefined();
+    });
+
+    it('should delete entry immediately when force is true regardless of leaseCount', () => {
+      manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+      });
+
+      manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+        allowReuse: true,
+      });
+
+      manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+        allowReuse: true,
+      });
+
+      // leaseCount is 3, but force should still delete
+      manager.release('feature-1', { force: true });
+
+      expect(manager.isRunning('feature-1')).toBe(false);
+    });
+
+    it('should do nothing when releasing non-existent feature', () => {
+      // Should not throw
+      manager.release('non-existent-feature');
+      manager.release('non-existent-feature', { force: true });
+    });
+
+    it('should only delete entry after all leases are released', () => {
+      manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+      });
+
+      manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+        allowReuse: true,
+      });
+
+      manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+        allowReuse: true,
+      });
+
+      // leaseCount is 3
+      manager.release('feature-1');
+      expect(manager.isRunning('feature-1')).toBe(true);
+
+      manager.release('feature-1');
+      expect(manager.isRunning('feature-1')).toBe(true);
+
+      manager.release('feature-1');
+      expect(manager.isRunning('feature-1')).toBe(false);
+    });
+  });
+
+  describe('isRunning', () => {
+    it('should return false when feature is not running', () => {
+      expect(manager.isRunning('feature-1')).toBe(false);
+    });
+
+    it('should return true when feature is running', () => {
+      manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+      });
+
+      expect(manager.isRunning('feature-1')).toBe(true);
+    });
+
+    it('should return false after feature is released', () => {
+      manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+      });
+
+      manager.release('feature-1');
+
+      expect(manager.isRunning('feature-1')).toBe(false);
+    });
+  });
+
+  describe('getRunningFeature', () => {
+    it('should return undefined for non-existent feature', () => {
+      expect(manager.getRunningFeature('feature-1')).toBeUndefined();
+    });
+
+    it('should return the RunningFeature entry', () => {
+      manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+      });
+
+      const entry = manager.getRunningFeature('feature-1');
+      expect(entry).toBeDefined();
+      expect(entry?.featureId).toBe('feature-1');
+      expect(entry?.projectPath).toBe('/test/project');
+    });
+  });
+
+  describe('getRunningCount (project-level)', () => {
+    it('should return 0 when no features are running', () => {
+      expect(manager.getRunningCount('/test/project')).toBe(0);
+    });
+
+    it('should count features for specific project', () => {
+      manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+      });
+
+      manager.acquire({
+        featureId: 'feature-2',
+        projectPath: '/test/project',
+        isAutoMode: false,
+      });
+
+      expect(manager.getRunningCount('/test/project')).toBe(2);
+    });
+
+    it('should only count features for the specified project', () => {
+      manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/project-a',
+        isAutoMode: true,
+      });
+
+      manager.acquire({
+        featureId: 'feature-2',
+        projectPath: '/project-b',
+        isAutoMode: true,
+      });
+
+      manager.acquire({
+        featureId: 'feature-3',
+        projectPath: '/project-a',
+        isAutoMode: false,
+      });
+
+      expect(manager.getRunningCount('/project-a')).toBe(2);
+      expect(manager.getRunningCount('/project-b')).toBe(1);
+      expect(manager.getRunningCount('/project-c')).toBe(0);
+    });
+  });
+
+  describe('getRunningCountForWorktree', () => {
+    it('should return 0 when no features are running', async () => {
+      const count = await manager.getRunningCountForWorktree('/test/project', null);
+      expect(count).toBe(0);
+    });
+
+    it('should count features with null branchName as main worktree', async () => {
+      const entry = manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+      });
+      // entry.branchName is null by default
+
+      const count = await manager.getRunningCountForWorktree('/test/project', null);
+      expect(count).toBe(1);
+    });
+
+    it('should count features matching primary branch as main worktree', async () => {
+      mockGetCurrentBranch.mockResolvedValue('main');
+
+      const entry = manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+      });
+      manager.updateRunningFeature('feature-1', { branchName: 'main' });
+
+      const count = await manager.getRunningCountForWorktree('/test/project', null);
+      expect(count).toBe(1);
+    });
+
+    it('should count features with exact branch match for feature worktrees', async () => {
+      const entry = manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+      });
+      manager.updateRunningFeature('feature-1', { branchName: 'feature-branch' });
+
+      manager.acquire({
+        featureId: 'feature-2',
+        projectPath: '/test/project',
+        isAutoMode: true,
+      });
+      // feature-2 has null branchName
+
+      const featureBranchCount = await manager.getRunningCountForWorktree(
+        '/test/project',
+        'feature-branch'
+      );
+      expect(featureBranchCount).toBe(1);
+
+      const mainWorktreeCount = await manager.getRunningCountForWorktree('/test/project', null);
+      expect(mainWorktreeCount).toBe(1);
+    });
+
+    it('should respect branch normalization (main is treated as null)', async () => {
+      mockGetCurrentBranch.mockResolvedValue('main');
+
+      // Feature with branchName 'main' should count as main worktree
+      manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+      });
+      manager.updateRunningFeature('feature-1', { branchName: 'main' });
+
+      // Feature with branchName null should also count as main worktree
+      manager.acquire({
+        featureId: 'feature-2',
+        projectPath: '/test/project',
+        isAutoMode: true,
+      });
+
+      const mainCount = await manager.getRunningCountForWorktree('/test/project', null);
+      expect(mainCount).toBe(2);
+    });
+
+    it('should filter by both projectPath and branchName', async () => {
+      manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/project-a',
+        isAutoMode: true,
+      });
+      manager.updateRunningFeature('feature-1', { branchName: 'feature-x' });
+
+      manager.acquire({
+        featureId: 'feature-2',
+        projectPath: '/project-b',
+        isAutoMode: true,
+      });
+      manager.updateRunningFeature('feature-2', { branchName: 'feature-x' });
+
+      const countA = await manager.getRunningCountForWorktree('/project-a', 'feature-x');
+      const countB = await manager.getRunningCountForWorktree('/project-b', 'feature-x');
+
+      expect(countA).toBe(1);
+      expect(countB).toBe(1);
+    });
+  });
+
+  describe('getAllRunning', () => {
+    it('should return empty array when no features are running', () => {
+      expect(manager.getAllRunning()).toEqual([]);
+    });
+
+    it('should return array with all running features', () => {
+      manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/project-a',
+        isAutoMode: true,
+      });
+
+      manager.acquire({
+        featureId: 'feature-2',
+        projectPath: '/project-b',
+        isAutoMode: false,
+      });
+
+      const running = manager.getAllRunning();
+      expect(running).toHaveLength(2);
+      expect(running.map((r) => r.featureId)).toContain('feature-1');
+      expect(running.map((r) => r.featureId)).toContain('feature-2');
+    });
+
+    it('should include feature metadata', () => {
+      manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/project-a',
+        isAutoMode: true,
+      });
+      manager.updateRunningFeature('feature-1', { model: 'claude-sonnet-4', provider: 'claude' });
+
+      const running = manager.getAllRunning();
+      expect(running[0].model).toBe('claude-sonnet-4');
+      expect(running[0].provider).toBe('claude');
+    });
+  });
+
+  describe('updateRunningFeature', () => {
+    it('should update worktreePath and branchName', () => {
+      manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+      });
+
+      manager.updateRunningFeature('feature-1', {
+        worktreePath: '/worktrees/feature-1',
+        branchName: 'feature-1-branch',
+      });
+
+      const entry = manager.getRunningFeature('feature-1');
+      expect(entry?.worktreePath).toBe('/worktrees/feature-1');
+      expect(entry?.branchName).toBe('feature-1-branch');
+    });
+
+    it('should update model and provider', () => {
+      manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+      });
+
+      manager.updateRunningFeature('feature-1', {
+        model: 'claude-opus-4-5-20251101',
+        provider: 'claude',
+      });
+
+      const entry = manager.getRunningFeature('feature-1');
+      expect(entry?.model).toBe('claude-opus-4-5-20251101');
+      expect(entry?.provider).toBe('claude');
+    });
+
+    it('should do nothing for non-existent feature', () => {
+      // Should not throw
+      manager.updateRunningFeature('non-existent', { model: 'test' });
+    });
+
+    it('should preserve other properties when updating partial fields', () => {
+      manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+      });
+
+      const original = manager.getRunningFeature('feature-1');
+      const originalStartTime = original?.startTime;
+
+      manager.updateRunningFeature('feature-1', { model: 'claude-sonnet-4' });
+
+      const updated = manager.getRunningFeature('feature-1');
+      expect(updated?.startTime).toBe(originalStartTime);
+      expect(updated?.projectPath).toBe('/test/project');
+      expect(updated?.isAutoMode).toBe(true);
+      expect(updated?.model).toBe('claude-sonnet-4');
+    });
+  });
+
+  describe('edge cases', () => {
+    it('should handle multiple features for same project', () => {
+      manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+      });
+
+      manager.acquire({
+        featureId: 'feature-2',
+        projectPath: '/test/project',
+        isAutoMode: true,
+      });
+
+      manager.acquire({
+        featureId: 'feature-3',
+        projectPath: '/test/project',
+        isAutoMode: false,
+      });
+
+      expect(manager.getRunningCount('/test/project')).toBe(3);
+      expect(manager.isRunning('feature-1')).toBe(true);
+      expect(manager.isRunning('feature-2')).toBe(true);
+      expect(manager.isRunning('feature-3')).toBe(true);
+    });
+
+    it('should handle features across different worktrees', async () => {
+      // Main worktree feature
+      manager.acquire({
+        featureId: 'feature-1',
+        projectPath: '/test/project',
+        isAutoMode: true,
+      });
+
+      // Worktree A feature
+      manager.acquire({
+        featureId: 'feature-2',
+        projectPath: '/test/project',
+        isAutoMode: true,
+      });
+      manager.updateRunningFeature('feature-2', {
+        worktreePath: '/worktrees/a',
+        branchName: 'branch-a',
+      });
+
+      // Worktree B feature
+      manager.acquire({
+        featureId: 'feature-3',
+        projectPath: '/test/project',
+        isAutoMode: true,
+      });
+      manager.updateRunningFeature('feature-3', {
+        worktreePath: '/worktrees/b',
+        branchName: 'branch-b',
+      });
+
+      expect(await manager.getRunningCountForWorktree('/test/project', null)).toBe(1);
+      expect(await manager.getRunningCountForWorktree('/test/project', 'branch-a')).toBe(1);
+      expect(await manager.getRunningCountForWorktree('/test/project', 'branch-b')).toBe(1);
+      expect(manager.getRunningCount('/test/project')).toBe(3);
+    });
+
+    it('should return 0 counts and empty arrays for empty state', () => {
+      expect(manager.getRunningCount('/any/project')).toBe(0);
+      expect(manager.getAllRunning()).toEqual([]);
+      expect(manager.isRunning('any-feature')).toBe(false);
+      expect(manager.getRunningFeature('any-feature')).toBeUndefined();
+    });
+  });
+});