diff --git a/hbd/client/main.py b/hbd/client/main.py
index d09c7e9..6885da1 100644
--- a/hbd/client/main.py
+++ b/hbd/client/main.py
@@ -356,7 +356,8 @@ async def _info_plugin_refresh_loop(conn: AsyncConnection, info_plugins: List):
             try:
                 data = await plugin.collect()
                 if data:
-                    await conn.sendto({"plugin": plugin.name, **data}, "PLG")
+                    await conn.sendto(
+                        {"plugin": plugin.name, **data, "_interval": plugin.interval}, "PLG")
                     logger.info(f"Resent {plugin.name} data")
             except Exception as e:
                 logger.error(f"Error re-collecting {plugin.name}: {e}", exc_info=True)
@@ -377,8 +378,8 @@ async def plugin_collector(conn: AsyncConnection, registry: PluginRegistry):
         try:
             data = await plugin.collect()
             if data:
-                # Create PLG message with plugin name
-                plugin_msg = {"plugin": plugin.name, **data}
+                # Create PLG message with plugin name and declared interval
+                plugin_msg = {"plugin": plugin.name, **data, "_interval": plugin.interval}
                 await conn.sendto(plugin_msg, "PLG")
                 logger.info(f"Sent {plugin.name} data")
         except Exception as e:
@@ -430,7 +431,7 @@ async def plugin_collector_interval(
                 data = await plugin.collect()
                 if data:
                     # Don't use encode_plugin_data - create dict directly
-                    plugin_msg = {"plugin": plugin.name, **data}
+                    plugin_msg = {"plugin": plugin.name, **data, "_interval": plugin.interval}
                     await conn.sendto(plugin_msg, "PLG")
                     logger.debug(f"Sent {plugin.name} data")
             except asyncio.CancelledError:
diff --git a/hbd/server/udp.py b/hbd/server/udp.py
index 5fb0037..0ff209b 100644
--- a/hbd/server/udp.py
+++ b/hbd/server/udp.py
@@ -16,6 +16,11 @@ from . import notify as notify_mod
 logger = logging.getLogger(__name__)
 eventlog = notify_mod.eventlog
 
+# Plugin data is declared stale after this many collection intervals without a
+# fresh sample. >= 2 so a single missed sample never purges live data (the user
+# directive: wait at least two full intervals after recovery before going stale).
+_STALE_INTERVAL_MULTIPLIER = 3
+
 # SO_TIMESTAMP: kernel attaches a struct timeval to each received datagram.
 # Supported on Linux, FreeBSD, and macOS.  The constant is not exposed by
 # Python's socket module on all platforms 
@@ -394,21 +399,36 @@ def handle_datagram(msg: dict, addr, transport, ctx: dict):
         plugin_name = msg.get("plugin")
         if plugin_name:
             # Extract plugin fields, dropping protocol metadata fields
+            # (_interval is the client-declared collection interval, not a metric).
             plugin_data = {k: v for k, v in msg.items()
-                           if k not in ("ID", "plugin", "id", "name")}
+                           if k not in ("ID", "plugin", "id", "name", "_interval")}
             # Store plugin data with timestamp
             host.add_plugin_data(plugin_name, plugin_data, timestamp=now)
-            # Reset stale timer using the observed send interval for this plugin.
-            # We need two samples to know the real interval; on the first sample
-            # we cancel any leftover timer but don't set a new one, to avoid
-            # false-stale firing for slow plugins (e.g. nagios_runner at 300 s).
+
+            # Set the stale timer. Prefer the interval the client declares: it is
+            # the true collection cadence and is correct from the very first
+            # post-recovery sample, so we never purge data too early after an
+            # outage. interval == 0 means a collect-once InfoPlugin that never
+            # goes stale. Legacy clients omit _interval, so fall back to inferring
+            # the cadence from the gap between the last two received samples.
             history = host.plugin_data.get(plugin_name, [])
-            if len(history) >= 2:
+            declared = msg.get("_interval")
+            if declared is not None:
+                if declared > 0:
+                    host.reset_plugin_timer(plugin_name, declared * _STALE_INTERVAL_MULTIPLIER,
+                                            _make_plugin_stale_callback(uname, ctx))
+                else:
+                    host.cancel_plugin_timer(plugin_name)
+            elif len(history) >= 2:
                 plugin_interval = max(history[-1][0] - history[-2][0], 1)
-                host.reset_plugin_timer(plugin_name, plugin_interval * 3,
+                host.reset_plugin_timer(plugin_name, plugin_interval * _STALE_INTERVAL_MULTIPLIER,
                                         _make_plugin_stale_callback(uname, ctx))
-                # Remove alert states for metrics present in the previous sample
-                # but absent now (e.g. a nagios check removed from configuration).
+            else:
+                host.cancel_plugin_timer(plugin_name)
+
+            # Remove alert states for metrics present in the previous sample but
+            # absent now (e.g. a nagios check removed from configuration).
+            if len(history) >= 2:
                 prev_keys = set(history[-2][1].keys())
                 curr_keys = set(plugin_data.keys())
                 for metric_name in prev_keys - curr_keys:
@@ -417,8 +437,6 @@ def handle_datagram(msg: dict, addr, transport, ctx: dict):
                         eventlog(uname, "INFO", f"stale check removed: {metric_path}")
                 if (prev_keys - curr_keys) and msg_to_websockets:
                     msg_to_websockets("host", host.stateinfo())
-            else:
-                host.cancel_plugin_timer(plugin_name)
 
             # If os_info reports an owner and none is configured server-side, apply it
             if plugin_name == "os_info":
diff --git a/scripts/c/hbc_mini.c b/scripts/c/hbc_mini.c
index 155f650..f5ded92 100644
--- a/scripts/c/hbc_mini.c
+++ b/scripts/c/hbc_mini.c
@@ -667,6 +667,7 @@ static void plugin_os_info(conn_t *c, const config_t *cfg) {
         if (osver[0]) kv_set(&d, "distro_version_id", osver);
     }
 #endif
+    kv_set_int(&d, "_interval", 0);   /* InfoPlugin: collect-once, never stale */
     conn_send(c, "PLG", &d);
     LOGI("sent os_info");
 }
@@ -781,6 +782,7 @@ static void plugin_cpu_monitor(conn_t *c, const config_t *cfg) {
     }
     read_cpu_extras(&d);
     kv_set_dbl(&d, "_timestamp", now_ts());
+    kv_set_int(&d, "_interval", cfg->cpu_interval);
     conn_send(c, "PLG", &d);
     LOGD("sent cpu_monitor");
 }
@@ -796,7 +798,7 @@ static void plugin_cpu_monitor(conn_t *c, const config_t *cfg) {
 static void mem_send(conn_t *c,
                      long long tot, long long used, long long av, long long fr,
                      long long act, long long ina, long long cac, long long buf,
-                     long long stot, long long sused) {
+                     long long stot, long long sused, int interval) {
     kvdict_t d; kv_clear(&d);
     kv_set(&d, "plugin", "memory_monitor");
     kv_set_ull(&d, "memory_total",     (unsigned long long)tot);
@@ -819,6 +821,7 @@ static void mem_send(conn_t *c,
         kv_set(&d, "swap_percent", pct);
     }
     kv_set_dbl(&d, "_timestamp", now_ts());
+    kv_set_int(&d, "_interval", interval);
     conn_send(c, "PLG", &d);
     LOGD("sent memory_monitor");
 }
@@ -863,7 +866,7 @@ static void plugin_memory_monitor(conn_t *c, const config_t *cfg) {
     /* values from /proc/meminfo are in kB */
     mem_send(c, tot*1024, used*1024, av*1024, fr*1024,
              act*1024, ina*1024, cac*1024, buf*1024,
-             stot*1024, (stot-sfr)*1024);
+             stot*1024, (stot-sfr)*1024, cfg->mem_interval);
 }
 
 #elif defined(__FreeBSD__) || defined(__DragonFly__)
@@ -889,7 +892,7 @@ static void plugin_memory_monitor(conn_t *c, const config_t *cfg) {
     long long cac  = (long long)v_cache    * ps;
     long long av   = fr + ina + cac; if (av > tot) av = tot;
     long long used = tot - av;
-    mem_send(c, tot, used, av, fr, act, ina, cac, 0, 0, 0);
+    mem_send(c, tot, used, av, fr, act, ina, cac, 0, 0, 0, cfg->mem_interval);
 }
 
 #elif defined(__NetBSD__)
@@ -910,7 +913,7 @@ static void plugin_memory_monitor(conn_t *c, const config_t *cfg) {
     long long used = tot - av;
     long long stot  = (long long)uvm.swpages   * ps;
     long long sinuse = (long long)uvm.swpginuse * ps;
-    mem_send(c, tot, used, av, fr, act, ina, 0, 0, stot, sinuse);
+    mem_send(c, tot, used, av, fr, act, ina, 0, 0, stot, sinuse, cfg->mem_interval);
 }
 
 #endif /* platform memory */
@@ -962,6 +965,7 @@ static void plugin_disk_monitor(conn_t *c, const config_t *cfg) {
     char *jval = malloc(MAX_VAL + 1);
     if (jval) { snprintf(jval, MAX_VAL, "@%s", json); kv_set(&d, "partitions", jval); free(jval); }
     kv_set_dbl(&d, "_timestamp", now_ts());
+    kv_set_int(&d, "_interval", cfg->disk_interval);
     conn_send(c, "PLG", &d);
     free(json);
     LOGD("sent disk_monitor");
@@ -1067,6 +1071,7 @@ static void plugin_network_monitor(conn_t *c, const config_t *cfg) {
     char *jval = malloc(MAX_VAL + 1);
     if (jval) { snprintf(jval, MAX_VAL, "@%s", json); kv_set(&d, "interfaces", jval); free(jval); }
     kv_set_dbl(&d, "_timestamp", now_ts());
+    kv_set_int(&d, "_interval", cfg->net_interval);
     conn_send(c, "PLG", &d);
     free(json);
     LOGD("sent network_monitor");
@@ -1125,6 +1130,7 @@ static void plugin_ping_monitor(conn_t *c, const config_t *cfg) {
         }
     }
     kv_set_dbl(&d, "_timestamp", now_ts());
+    kv_set_int(&d, "_interval", cfg->ping_interval);
     conn_send(c, "PLG", &d);
     LOGD("sent ping_monitor");
 }
@@ -1194,6 +1200,7 @@ static void plugin_nagios_runner(conn_t *c, const config_t *cfg) {
         parse_perfdata(output, &d, name);
     }
     kv_set_dbl(&d, "_timestamp", now_ts());
+    kv_set_int(&d, "_interval", cfg->nagios_interval);
     conn_send(c, "PLG", &d);
     LOGD("sent nagios_runner");
 }
diff --git a/scripts/hbc_mini.py b/scripts/hbc_mini.py
index 80e73ee..de27545 100755
--- a/scripts/hbc_mini.py
+++ b/scripts/hbc_mini.py
@@ -955,7 +955,7 @@ async def _run_info_plugins(conn: AsyncConnection, plugins: List[Plugin]):
         try:
             data = await plugin.collect()
             if data:
-                await conn.sendto({"plugin": plugin.name, **data}, "PLG")
+                await conn.sendto({"plugin": plugin.name, **data, "_interval": plugin.interval}, "PLG")
                 log.info("sent %s", plugin.name)
         except Exception as e:
             log.error("%s collect: %s", plugin.name, e)
@@ -968,7 +968,7 @@ async def _run_monitor_group(conn: AsyncConnection, plugins: List[Plugin], inter
             try:
                 data = await plugin.collect()
                 if data:
-                    await conn.sendto({"plugin": plugin.name, **data}, "PLG")
+                    await conn.sendto({"plugin": plugin.name, **data, "_interval": plugin.interval}, "PLG")
                     log.debug("sent %s", plugin.name)
             except asyncio.CancelledError:
                 raise