diff --git a/claw/core/gateway.c b/claw/core/gateway.c
index ba450ff..4457e19 100644
--- a/claw/core/gateway.c
+++ b/claw/core/gateway.c
@@ -38,6 +38,10 @@ int gateway_register_service(const char *name, uint8_t type_mask,
     return CLAW_OK;
 }
 
+/* --- Statistics --- */
+
+static struct gateway_stats s_stats;
+
 /* --- Message dispatch --- */
 
 static void dispatch_msg(struct gateway_msg *msg)
@@ -45,12 +49,18 @@ static void dispatch_msg(struct gateway_msg *msg)
     uint8_t bit = (uint8_t)(1 << msg->type);
     int delivered = 0;
 
+    s_stats.total++;
+    if (msg->type < GW_MSG_TYPE_MAX) {
+        s_stats.per_type[msg->type]++;
+    }
+
     for (int i = 0; i < s_service_count; i++) {
         if (s_services[i].type_mask & bit) {
             if (claw_mq_send(s_services[i].inbox, msg, sizeof(*msg),
                              CLAW_NO_WAIT) == CLAW_OK) {
                 delivered++;
             } else {
+                s_stats.dropped++;
                 CLAW_LOGW(TAG, "drop msg type=%d -> %s (queue full)",
                           msg->type, s_services[i].name);
             }
@@ -58,6 +68,7 @@ static void dispatch_msg(struct gateway_msg *msg)
     }
 
     if (delivered == 0) {
+        s_stats.no_consumer++;
         CLAW_LOGD(TAG, "msg type=%d len=%d (no consumer)", msg->type,
                   msg->len);
     }
@@ -85,6 +96,7 @@ static void gateway_thread_entry(void *param)
 int gateway_init(void)
 {
     memset(s_services, 0, sizeof(s_services));
+    memset(&s_stats, 0, sizeof(s_stats));
     s_service_count = 0;
 
     gw_mq = claw_mq_create("gw_mq", sizeof(struct gateway_msg),
@@ -114,3 +126,10 @@ int gateway_send(struct gateway_msg *msg)
 {
     return claw_mq_send(gw_mq, msg, sizeof(*msg), CLAW_NO_WAIT);
 }
+
+void gateway_get_stats(struct gateway_stats *out)
+{
+    if (out) {
+        memcpy(out, &s_stats, sizeof(s_stats));
+    }
+}
diff --git a/claw/core/heartbeat.c b/claw/core/heartbeat.c
index e60c63f..9fcb690 100644
--- a/claw/core/heartbeat.c
+++ b/claw/core/heartbeat.c
@@ -20,6 +20,12 @@
 #include <string.h>
 #include <stdio.h>
 
+#ifdef CLAW_PLATFORM_ESP_IDF
+#include "esp_heap_caps.h"
+#elif defined(CLAW_PLATFORM_RTTHREAD)
+#include <rtthread.h>
+#endif
+
 #define TAG "heartbeat"
 
 /* LLM connectivity state: -1 = unknown, 0 = offline, 1 = online */
@@ -129,10 +135,53 @@ static void heartbeat_ai_thread(void *arg)
     claw_mutex_unlock(s_lock);
 }
 
+/*
+ * Device health check — collect anomalies and post events.
+ * Runs before the LLM ping so anomalies are included in the
+ * next heartbeat AI summary.
+ */
+static void check_device_health(void)
+{
+    uint32_t free_kb = 0;
+    uint32_t total_kb = 0;
+
+#ifdef CLAW_PLATFORM_ESP_IDF
+    size_t free_sz = heap_caps_get_free_size(MALLOC_CAP_DEFAULT);
+    size_t total_sz = heap_caps_get_total_size(MALLOC_CAP_DEFAULT);
+    free_kb = (uint32_t)(free_sz / 1024);
+    total_kb = (uint32_t)(total_sz / 1024);
+#elif defined(CLAW_PLATFORM_RTTHREAD)
+    rt_size_t total_rt = 0, used_rt = 0, max_rt = 0;
+    rt_memory_info(&total_rt, &used_rt, &max_rt);
+    free_kb = (uint32_t)((total_rt - used_rt) / 1024);
+    total_kb = (uint32_t)(total_rt / 1024);
+#endif
+
+    if (total_kb == 0) {
+        return;
+    }
+
+    uint32_t used_pct = 100 - (free_kb * 100 / total_kb);
+
+    /* Alert when heap usage exceeds 80% */
+    if (used_pct > 80) {
+        char msg[80];
+        snprintf(msg, sizeof(msg),
+                 "heap %lu%% used (%luKB free / %luKB total)",
+                 (unsigned long)used_pct,
+                 (unsigned long)free_kb,
+                 (unsigned long)total_kb);
+        heartbeat_post("memory", msg);
+    }
+}
+
 /* LLM connectivity probe — runs in its own thread */
 static void ping_thread(void *arg)
 {
     (void)arg;
+
+    check_device_health();
+
     int ok = (ai_ping() == CLAW_OK) ? 1 : 0;
     int prev = s_llm_state;
     s_llm_state = ok;
diff --git a/claw/shell/shell_commands.c b/claw/shell/shell_commands.c
index 295a2d4..564e2b7 100644
--- a/claw/shell/shell_commands.c
+++ b/claw/shell/shell_commands.c
@@ -92,6 +92,17 @@ void shell_nvs_config_load(void)
 
 /* ---- Common command handlers ---- */
 
+static const char *log_level_name(int level)
+{
+    switch (level) {
+    case CLAW_LOG_ERROR: return "error";
+    case CLAW_LOG_WARN:  return "warn";
+    case CLAW_LOG_INFO:  return "info";
+    case CLAW_LOG_DEBUG: return "debug";
+    default:             return "unknown";
+    }
+}
+
 static void cmd_log(int argc, char **argv)
 {
     if (argc < 2) {
@@ -100,8 +111,31 @@ static void cmd_log(int argc, char **argv)
         claw_log_set_enabled(1);
     } else if (strcmp(argv[1], "off") == 0) {
         claw_log_set_enabled(0);
+    } else if (strcmp(argv[1], "level") == 0) {
+        if (argc < 3) {
+            printf("Log level: %s\n",
+                   log_level_name(claw_log_get_level()));
+            return;
+        }
+        int lv = -1;
+        if (strcmp(argv[2], "error") == 0) {
+            lv = CLAW_LOG_ERROR;
+        } else if (strcmp(argv[2], "warn") == 0) {
+            lv = CLAW_LOG_WARN;
+        } else if (strcmp(argv[2], "info") == 0) {
+            lv = CLAW_LOG_INFO;
+        } else if (strcmp(argv[2], "debug") == 0) {
+            lv = CLAW_LOG_DEBUG;
+        }
+        if (lv < 0) {
+            printf("Usage: /log level <error|warn|info|debug>\n");
+            return;
+        }
+        claw_log_set_level(lv);
+        printf("Log level: %s\n", log_level_name(lv));
+        return;
     } else {
-        printf("Usage: /log [on|off]\n");
+        printf("Usage: /log [on|off|level <error|warn|info|debug>]\n");
         return;
     }
     printf("Log output: %s\n",
@@ -305,7 +339,7 @@ static void cmd_nodes(int argc, char **argv)
 /* ---- Common command table ---- */
 
 const shell_cmd_t shell_common_commands[] = {
-    SHELL_CMD("/log",           cmd_log,           "Toggle log [on|off]"),
+    SHELL_CMD("/log",           cmd_log,           "Log [on|off|level <lvl>]"),
     SHELL_CMD("/history",       cmd_history,       "Show conversation count"),
     SHELL_CMD("/clear",         cmd_clear,         "Clear conversation memory"),
     SHELL_CMD("/ai_set",        cmd_ai_set,        "Set AI config (NVS)"),
diff --git a/claw/tools/tool_system.c b/claw/tools/tool_system.c
index b492d88..42d2008 100644
--- a/claw/tools/tool_system.c
+++ b/claw/tools/tool_system.c
@@ -177,14 +177,22 @@ static int tool_memory_info(const cJSON *params, cJSON *result)
     size_t total = heap_caps_get_total_size(MALLOC_CAP_DEFAULT);
     size_t free_sz = heap_caps_get_free_size(MALLOC_CAP_DEFAULT);
     size_t min_free = heap_caps_get_minimum_free_size(MALLOC_CAP_DEFAULT);
+    size_t largest = heap_caps_get_largest_free_block(MALLOC_CAP_DEFAULT);
 
     cJSON_AddStringToObject(result, "status", "ok");
     cJSON_AddNumberToObject(result, "heap_total_bytes", total);
     cJSON_AddNumberToObject(result, "heap_free_bytes", free_sz);
     cJSON_AddNumberToObject(result, "heap_min_free_bytes", min_free);
+    cJSON_AddNumberToObject(result, "heap_largest_block", largest);
     cJSON_AddNumberToObject(result, "heap_used_percent",
                             (double)(total - free_sz) / total * 100.0);
 
+    /* fragmentation: 100% = all fragments, 0% = single block */
+    if (free_sz > 0) {
+        double frag = (1.0 - (double)largest / free_sz) * 100.0;
+        cJSON_AddNumberToObject(result, "fragmentation_percent", frag);
+    }
+
     return CLAW_OK;
 }
 
@@ -231,8 +239,8 @@ void claw_tools_register_system(void)
         0, CLAW_TOOL_LOCAL_ONLY);
 
     claw_tool_register("memory_info",
-        "Get heap memory status: total, free, minimum-ever-free bytes, "
-        "and usage percentage.",
+        "Get heap memory status: total, free, minimum-ever-free, "
+        "largest contiguous block, usage and fragmentation percent.",
         schema_empty, tool_memory_info,
         0, CLAW_TOOL_LOCAL_ONLY);
 
diff --git a/docs/en/architecture.md b/docs/en/architecture.md
index 6ff4f6a..2f6586f 100644
--- a/docs/en/architecture.md
+++ b/docs/en/architecture.md
@@ -65,7 +65,8 @@ Message routing hub with service registry and type-based dispatch. Services
 register with a type_mask bitmap and their own message queue; the gateway
 delivers incoming messages to all matching consumers. Message types: DATA,
 CMD, EVENT, SWARM, AI_REQ. Queue: 16 messages x 256 bytes. Dedicated thread
-at priority 15.
+at priority 15. Built-in dispatch statistics track total/per-type/dropped/
+no-consumer message counts via `gateway_get_stats()`.
 
 ### Scheduler (`claw/core/scheduler.c`)
 
@@ -78,9 +79,12 @@ executed in turn, preventing task starvation.
 
 ### Heartbeat (`claw/core/heartbeat.c`)
 
-Optional periodic AI check-in every 5 minutes. Sends a heartbeat prompt
-to the AI engine so the assistant can perform background monitoring.
-Depends on the scheduler service for timing.
+Optional periodic AI check-in every 5 minutes. Three-layer tick logic:
+(1) events pending -- AI summary via `ai_chat_raw()`;
+(2) no events -- device health check (heap > 80% triggers auto-alert)
+    followed by lightweight LLM connectivity ping (`ai_ping()`,
+    max_tokens=1); (3) state change (online/offline) -- notification
+delivered to IM or console. Depends on the scheduler service for timing.
 
 ### AI Engine (`claw/services/ai/`)
 
diff --git a/docs/en/usage.md b/docs/en/usage.md
index f58ef92..f4de92d 100644
--- a/docs/en/usage.md
+++ b/docs/en/usage.md
@@ -28,6 +28,7 @@ Commands start with `/`.
 | `/skill <name> [args]` | Execute skill |
 | `/nodes` | Show swarm nodes |
 | `/log [on\|off]` | Toggle log output |
+| `/log level <lvl>` | Set log level (error/warn/info/debug) |
 | `/history` | Show message count |
 | `/clear` | Clear conversation |
 | `/help` | List commands |
@@ -73,7 +74,7 @@ is always enabled).
 | Tool | Parameters | Description |
 |------|------------|-------------|
 | `system_info` | — | Show system information |
-| `memory_info` | — | Show heap usage |
+| `memory_info` | — | Show heap usage, largest block, fragmentation |
 | `clear_history` | — | Clear conversation history |
 | `system_restart` | — | Reboot the device |
 | `save_memory` | `key`, `value` | Save to long-term memory |
diff --git a/docs/zh/architecture.md b/docs/zh/architecture.md
index f16a307..c82dcf8 100644
--- a/docs/zh/architecture.md
+++ b/docs/zh/architecture.md
@@ -65,6 +65,7 @@ claw/*.c  --->  #include "osal/claw_os.h"
 和自有消息队列注册；网关将传入消息投递到所有匹配的消费者。
 消息类型：DATA、CMD、EVENT、SWARM、AI_REQ。
 队列容量：16 条消息 x 256 字节。专用线程优先级为 15。
+内置消息统计：通过 `gateway_get_stats()` 查询总计/按类型/丢弃/无消费者计数。
 
 ### 调度器（`claw/core/scheduler.c`）
 
@@ -75,8 +76,12 @@ claw/*.c  --->  #include "osal/claw_os.h"
 
 ### 心跳（`claw/core/heartbeat.c`）
 
-可选的周期性 AI 签到功能，每 5 分钟执行一次。向 AI 引擎发送心跳提示，
-使助手能够执行后台监控。依赖调度器服务进行计时。
+可选的周期性 AI 签到功能，每 5 分钟执行一次。三层 tick 逻辑：
+（1）有待处理事件——通过 `ai_chat_raw()` 进行 AI 总结；
+（2）无事件——设备健康检查（堆使用 > 80% 触发自动告警），
+随后进行轻量级 LLM 连通性探测（`ai_ping()`，max_tokens=1）；
+（3）状态变化（在线/离线）——通知投递到 IM 或控制台。
+依赖调度器服务进行计时。
 
 ### AI 引擎（`claw/services/ai/`）
 
diff --git a/docs/zh/usage.md b/docs/zh/usage.md
index bbbbd31..b095219 100644
--- a/docs/zh/usage.md
+++ b/docs/zh/usage.md
@@ -28,6 +28,7 @@
 | `/skill <name> [args]` | 执行技能 |
 | `/nodes` | 显示集群节点 |
 | `/log [on\|off]` | 切换日志输出 |
+| `/log level <lvl>` | 设置日志级别（error/warn/info/debug） |
 | `/history` | 显示消息数量 |
 | `/clear` | 清空对话 |
 | `/help` | 列出命令 |
@@ -72,7 +73,7 @@ Kconfig 选项控制（Audio 除外，始终启用）。
 | 工具 | 参数 | 说明 |
 |------|------|------|
 | `system_info` | — | 显示系统信息 |
-| `memory_info` | — | 显示堆内存使用情况 |
+| `memory_info` | — | 显示堆内存使用、最大连续块、碎片率 |
 | `clear_history` | — | 清空对话历史 |
 | `system_restart` | — | 重启设备 |
 | `save_memory` | `key`, `value` | 保存到长期记忆 |
diff --git a/include/claw/core/gateway.h b/include/claw/core/gateway.h
index c6341b6..ff0eb0a 100644
--- a/include/claw/core/gateway.h
+++ b/include/claw/core/gateway.h
@@ -49,8 +49,17 @@ struct gw_service_entry {
     claw_mq_t inbox;            /* service's own message queue */
 };
 
+/* Message statistics */
+struct gateway_stats {
+    uint32_t total;                         /* total dispatched */
+    uint32_t per_type[GW_MSG_TYPE_MAX];     /* per message type */
+    uint32_t dropped;                       /* queue-full drops */
+    uint32_t no_consumer;                   /* msgs with no match */
+};
+
 int gateway_init(void);
 int gateway_send(struct gateway_msg *msg);
+void gateway_get_stats(struct gateway_stats *out);
 
 /**
  * Register a service to receive messages matching type_mask.
diff --git a/include/osal/claw_os.h b/include/osal/claw_os.h
index b9e4c39..5da5d0d 100644
--- a/include/osal/claw_os.h
+++ b/include/osal/claw_os.h
@@ -104,6 +104,8 @@ void claw_log(int level, const char *tag, const char *fmt, ...);
 void claw_log_raw(const char *fmt, ...);
 void claw_log_set_enabled(int enabled);
 int  claw_log_get_enabled(void);
+void claw_log_set_level(int level);
+int  claw_log_get_level(void);
 
 /* Convenience macros */
 #define CLAW_LOGE(tag, fmt, ...) claw_log(CLAW_LOG_ERROR, tag, fmt, ##__VA_ARGS__)
diff --git a/osal/freertos/claw_os_freertos.c b/osal/freertos/claw_os_freertos.c
index da4ee7e..65f1596 100644
--- a/osal/freertos/claw_os_freertos.c
+++ b/osal/freertos/claw_os_freertos.c
@@ -267,6 +267,7 @@ void claw_free(void *ptr)
 /* ---------- Log ---------- */
 
 static int s_log_enabled = 1;
+static int s_log_level = CLAW_LOG_DEBUG;  /* show all by default */
 
 void claw_log_set_enabled(int enabled)
 {
@@ -285,11 +286,33 @@ int claw_log_get_enabled(void)
     return s_log_enabled;
 }
 
+void claw_log_set_level(int level)
+{
+    if (level < CLAW_LOG_ERROR) {
+        level = CLAW_LOG_ERROR;
+    }
+    if (level > CLAW_LOG_DEBUG) {
+        level = CLAW_LOG_DEBUG;
+    }
+    s_log_level = level;
+#ifdef CLAW_PLATFORM_ESP_IDF
+    static const esp_log_level_t map[] = {
+        ESP_LOG_ERROR, ESP_LOG_WARN, ESP_LOG_INFO, ESP_LOG_DEBUG
+    };
+    esp_log_level_set("*", map[level]);
+#endif
+}
+
+int claw_log_get_level(void)
+{
+    return s_log_level;
+}
+
 #ifdef CLAW_PLATFORM_ESP_IDF
 
 void claw_log(int level, const char *tag, const char *fmt, ...)
 {
-    if (!s_log_enabled) {
+    if (!s_log_enabled || level > s_log_level) {
         return;
     }
 
@@ -346,7 +369,7 @@ void claw_log(int level, const char *tag, const char *fmt, ...)
 {
     va_list ap;
 
-    if (!s_log_enabled) {
+    if (!s_log_enabled || level > s_log_level) {
         return;
     }
     if (level < 0) {
diff --git a/osal/rtthread/claw_os_rtthread.c b/osal/rtthread/claw_os_rtthread.c
index b5acf57..e404e30 100644
--- a/osal/rtthread/claw_os_rtthread.c
+++ b/osal/rtthread/claw_os_rtthread.c
@@ -203,6 +203,7 @@ void claw_free(void *ptr)
 /* ---------- Log ---------- */
 
 static int s_log_enabled = 1;
+static int s_log_level = CLAW_LOG_DEBUG;  /* show all by default */
 static const char *level_str[] = { "E", "W", "I", "D" };
 
 void claw_log_set_enabled(int enabled)
@@ -215,11 +216,27 @@ int claw_log_get_enabled(void)
     return s_log_enabled;
 }
 
+void claw_log_set_level(int level)
+{
+    if (level < CLAW_LOG_ERROR) {
+        level = CLAW_LOG_ERROR;
+    }
+    if (level > CLAW_LOG_DEBUG) {
+        level = CLAW_LOG_DEBUG;
+    }
+    s_log_level = level;
+}
+
+int claw_log_get_level(void)
+{
+    return s_log_level;
+}
+
 void claw_log(int level, const char *tag, const char *fmt, ...)
 {
     va_list ap;
 
-    if (!s_log_enabled) {
+    if (!s_log_enabled || level > s_log_level) {
         return;
     }
     if (level < 0) {