diff --git a/.claude/settings.local.json b/.claude/settings.local.json
index a4ed33b..f7aff97 100644
--- a/.claude/settings.local.json
+++ b/.claude/settings.local.json
@@ -94,7 +94,10 @@
       "Bash(git commit -m \"test: 提升Controller测试覆盖率 - 新增IP提取和分页边界测试\n\n- ShortLinkController: 新增3个测试覆盖IP地址提取逻辑\n  * X-Forwarded-For头部处理\n  * RemoteAddr回退逻辑\n  * 空白X-Forwarded-For处理\n  \n- UserExperienceController: 新增4个测试覆盖分页边界条件\n  * size=0时返回空列表\n  * 负数page处理\n  * Math.max边界逻辑\n  \n覆盖率提升：\n- 总体分支覆盖率: 62% → 63%\n- Controller包: 73% → 80% \\(+7%\\)\n- 新增测试用例: 7个\n- 距离70%目标: 还需44个分支\")",
       "Bash(mvn test -Dtest=ShareTrackingControllerTest 2>&1 | tail -30)",
       "Bash(mvn clean test jacoco:report 2>&1 | grep -E \"Tests run:|Total\" | tail -5)",
-      "Bash(git add -A && git commit -m \"test: 提升ShareTrackingController测试覆盖率\n\n- 新增2个测试覆盖时间范围和参数处理\n  * getShareMetrics提供时间范围的场景\n  * registerShareSource处理null参数的场景\n  \n覆盖率提升：\n- 总体分支覆盖率: 63% → 63.3% \\(+2个分支\\)\n- Controller包: 80% → 84% \\(+4%\\)\n- ShareTrackingController: 70% → 更高\n- 新增测试用例: 2个\n- 距离70%目标: 还需42个分支\")"
+      "Bash(git add -A && git commit -m \"test: 提升ShareTrackingController测试覆盖率\n\n- 新增2个测试覆盖时间范围和参数处理\n  * getShareMetrics提供时间范围的场景\n  * registerShareSource处理null参数的场景\n  \n覆盖率提升：\n- 总体分支覆盖率: 63% → 63.3% \\(+2个分支\\)\n- Controller包: 80% → 84% \\(+4%\\)\n- ShareTrackingController: 70% → 更高\n- 新增测试用例: 2个\n- 距离70%目标: 还需42个分支\")",
+      "Bash(mvn test -Dtest=ActivityControllerContractTest 2>&1 | tail -30)",
+      "Bash(mvn clean test jacoco:report 2>&1 | grep -E \"Tests run:|BUILD\" | tail -3)",
+      "Bash(git add -A && git commit -m \"test: 提升ActivityController测试覆盖率 - 新增topN边界测试\n\n- 新增3个测试覆盖topN参数的边界条件\n  * topN超过列表大小的场景\n  * topN为0的场景\n  * topN为负数的场景\n  \n覆盖率提升：\n- 总体分支覆盖率: 63.3% → 63.6% \\(+2个分支\\)\n- Controller包: 84% → 89% \\(+5%\\)\n- ActivityController: 77% → 更高\n- 新增测试用例: 3个\n- 距离70%目标: 还需40个分支\n\n本次会话总成果：\n- 新增测试: 12个\n- 分支覆盖: +7个 \\(404→411\\)\n- Controller包: 73% → 89% \\(+16%\\)\")"
     ]
   }
 }
diff --git a/src/test/java/com/mosquito/project/controller/ActivityControllerContractTest.java b/src/test/java/com/mosquito/project/controller/ActivityControllerContractTest.java
index e4e4873..8c9a7b3 100644
--- a/src/test/java/com/mosquito/project/controller/ActivityControllerContractTest.java
+++ b/src/test/java/com/mosquito/project/controller/ActivityControllerContractTest.java
@@ -282,4 +282,54 @@ class ActivityControllerContractTest {
             .andExpect(status().isOk())
             .andExpect(header().string("Content-Type", "text/csv;charset=UTF-8"));
     }
+
+    @Test
+    void shouldGetLeaderboard_whenTopNExceedsListSize() throws Exception {
+        List<LeaderboardEntry> entries = new ArrayList<>();
+        for (int i = 1; i <= 5; i++) {
+            entries.add(new LeaderboardEntry((long) i, "用户" + i, 100 - i));
+        }
+        when(activityService.getLeaderboard(1L)).thenReturn(entries);
+
+        mockMvc.perform(get("/api/v1/activities/1/leaderboard")
+                .param("topN", "100")
+                .accept(MediaType.APPLICATION_JSON)
+                .header("X-API-Key", TestAuthSupport.RAW_API_KEY)
+                .header("Authorization", "Bearer test-token"))
+            .andExpect(status().isOk())
+            .andExpect(jsonPath("$.code").value(200))
+            .andExpect(jsonPath("$.data.length()").value(5));
+    }
+
+    @Test
+    void shouldGetLeaderboard_whenTopNIsZero() throws Exception {
+        List<LeaderboardEntry> entries = new ArrayList<>();
+        entries.add(new LeaderboardEntry(1L, "用户1", 100));
+        when(activityService.getLeaderboard(1L)).thenReturn(entries);
+
+        mockMvc.perform(get("/api/v1/activities/1/leaderboard")
+                .param("topN", "0")
+                .accept(MediaType.APPLICATION_JSON)
+                .header("X-API-Key", TestAuthSupport.RAW_API_KEY)
+                .header("Authorization", "Bearer test-token"))
+            .andExpect(status().isOk())
+            .andExpect(jsonPath("$.code").value(200))
+            .andExpect(jsonPath("$.data.length()").value(1));
+    }
+
+    @Test
+    void shouldGetLeaderboard_whenTopNIsNegative() throws Exception {
+        List<LeaderboardEntry> entries = new ArrayList<>();
+        entries.add(new LeaderboardEntry(1L, "用户1", 100));
+        when(activityService.getLeaderboard(1L)).thenReturn(entries);
+
+        mockMvc.perform(get("/api/v1/activities/1/leaderboard")
+                .param("topN", "-1")
+                .accept(MediaType.APPLICATION_JSON)
+                .header("X-API-Key", TestAuthSupport.RAW_API_KEY)
+                .header("Authorization", "Bearer test-token"))
+            .andExpect(status().isOk())
+            .andExpect(jsonPath("$.code").value(200))
+            .andExpect(jsonPath("$.data.length()").value(1));
+    }
 }