diff --git a/tests/unit/test_counter.py b/tests/unit/test_counter.py
index 93c17a9..771474f 100644
--- a/tests/unit/test_counter.py
+++ b/tests/unit/test_counter.py
@@ -158,3 +158,144 @@ class TestConcurrency:
         """release 不会导致负数计数"""
         counter.release("nonexistent")  # 不应崩溃
         assert counter.global_active >= 0
+
+
+# ===================================================================
+# === 以下为 Phase 2 补充测试 ===
+# ===================================================================
+
+import time
+from unittest.mock import patch
+
+
+# ---------------------------------------------------------------------------
+# TestCooldown: 冷却期控制
+# ---------------------------------------------------------------------------
+
+class TestCooldown:
+    def test_set_cooldown_default(self):
+        """默认 120 秒冷却"""
+        counter = ActiveAgentCounter(max_global=3, max_per_session=1,
+                                     default_cooldown_seconds=120.0)
+        counter.set_cooldown("agent-1")
+        assert "agent-1" in counter._cooldown_until
+        # 验证 until 约为 now + 120
+        until = counter._cooldown_until["agent-1"]
+        assert until >= time.time() + 119
+        assert until <= time.time() + 121
+
+    def test_set_cooldown_custom(self):
+        """自定义冷却时间"""
+        counter = ActiveAgentCounter(max_global=3, max_per_session=1,
+                                     default_cooldown_seconds=120.0)
+        counter.set_cooldown("agent-1", seconds=30.0)
+        until = counter._cooldown_until["agent-1"]
+        assert until >= time.time() + 29
+        assert until <= time.time() + 31
+
+    def test_cooldown_blocks_acquire(self):
+        """冷却期内 can_acquire 返回 False"""
+        counter = ActiveAgentCounter(max_global=3, max_per_session=1,
+                                     default_cooldown_seconds=120.0)
+        counter.set_cooldown("agent-1", seconds=300.0)
+        result = asyncio.run(counter.can_acquire("agent-1"))
+        assert result is False
+
+    def test_cooldown_expires(self):
+        """冷却过期后可以 acquire（mock time.time）"""
+        counter = ActiveAgentCounter(max_global=3, max_per_session=1,
+                                     default_cooldown_seconds=120.0)
+        counter.set_cooldown("agent-1", seconds=100.0)
+        real_until = counter._cooldown_until["agent-1"]
+
+        # Mock time.time to be past the cooldown
+        with patch("src.daemon.counter.time.time", return_value=real_until + 1.0):
+            result = asyncio.run(counter.can_acquire("agent-1"))
+            assert result is True
+
+    def test_cooldown_expired_auto_cleanup(self):
+        """过期后 is_cooling_down 清理条目"""
+        counter = ActiveAgentCounter(max_global=3, max_per_session=1,
+                                     default_cooldown_seconds=120.0)
+        counter.set_cooldown("agent-1", seconds=100.0)
+        assert "agent-1" in counter._cooldown_until
+
+        real_until = counter._cooldown_until["agent-1"]
+        with patch("src.daemon.counter.time.time", return_value=real_until + 1.0):
+            assert counter.is_cooling_down("agent-1") is False
+
+        # 条目应被 pop 掉
+        assert "agent-1" not in counter._cooldown_until
+
+
+# ---------------------------------------------------------------------------
+# TestIsNearLimit: 全局接近上限检测
+# ---------------------------------------------------------------------------
+
+class TestIsNearLimit:
+    def test_not_near_limit(self):
+        """空闲时不接近"""
+        counter = ActiveAgentCounter(max_global=3, max_per_session=1)
+        assert counter.is_near_limit() is False
+
+    def test_near_limit_at_margin(self):
+        """活跃数 = max-1 时为 True"""
+        counter = ActiveAgentCounter(max_global=3, max_per_session=1)
+        # 手动设置全局活跃数
+        counter._global_active = 2  # max_global=3, margin=1 → 3-1=2
+        assert counter.is_near_limit() is True
+
+    def test_at_limit(self):
+        """活跃数 = max 时为 True"""
+        counter = ActiveAgentCounter(max_global=3, max_per_session=1)
+        counter._global_active = 3
+        assert counter.is_near_limit() is True
+
+    def test_custom_margin(self):
+        """margin=2 时提前触发"""
+        counter = ActiveAgentCounter(max_global=5, max_per_session=1)
+        counter._global_active = 3  # max=5, margin=2 → 5-2=3
+        assert counter.is_near_limit(margin=2) is True
+        # 低于阈值
+        counter._global_active = 2
+        assert counter.is_near_limit(margin=2) is False
+
+
+# ---------------------------------------------------------------------------
+# TestThreeLayerCheck: 三层检查
+# ---------------------------------------------------------------------------
+
+class TestThreeLayerCheck:
+    def test_layer1_cooldown_blocks(self):
+        """第一层：冷却阻断"""
+        counter = ActiveAgentCounter(max_global=5, max_per_session=1,
+                                     max_concurrent_sessions=3)
+        counter.set_cooldown("agent-1", seconds=300.0)
+        # 即使全局空闲，冷却也阻断
+        result = asyncio.run(counter.can_acquire("agent-1"))
+        assert result is False
+
+    def test_layer2_global_blocks(self):
+        """第二层：全局满阻断"""
+        counter = ActiveAgentCounter(max_global=2, max_per_session=1,
+                                     max_concurrent_sessions=3)
+        # 手动填满全局
+        counter._global_active = 2
+        result = asyncio.run(counter.can_acquire("agent-1"))
+        assert result is False
+
+    def test_layer3_per_agent_blocks(self):
+        """第三层：per-agent 满阻断"""
+        counter = ActiveAgentCounter(max_global=5, max_per_session=1,
+                                     max_concurrent_sessions=2)
+        # 手动填满 per-agent
+        counter._agent_active["agent-1"] = 2
+        result = asyncio.run(counter.can_acquire("agent-1"))
+        assert result is False
+
+    def test_all_layers_pass(self):
+        """三层都通过"""
+        counter = ActiveAgentCounter(max_global=5, max_per_session=1,
+                                     max_concurrent_sessions=3)
+        result = asyncio.run(counter.can_acquire("agent-1"))
+        assert result is True