diff --git a/firmware/main/main.c b/firmware/main/main.c
index d0de904..7f2c4c1 100644
--- a/firmware/main/main.c
+++ b/firmware/main/main.c
@@ -1,35 +1,9 @@
 #include "display.h"
 #include "esp_lvgl_port.h"
-#include "esp_timer.h"
-#include "freertos/FreeRTOS.h"
-#include "freertos/task.h"
 #include "ui.h"
-#include "comm.h"
 #include "usb.h"
 #include "keepawake.h"
 
-/* Watchdog task: runs on Core1 at 5-second intervals.
- * Checks if comm_last_rx_ms() is older than 60s; if so, sets stale=true
- * and calls ui_update to grey-out all data fields.
- *
- * Cross-core safety: comm_last_rx_ms() returns volatile uint32_t
- * (atomic on ESP32-S3 Xtensa LX7), so no lock needed around that read. */
-static void watchdog_task(void *arg)
-{
-    while (1) {
-        uint32_t now_ms = (uint32_t)(esp_timer_get_time() / 1000);
-        uint32_t last   = comm_last_rx_ms();
-        /* Unsigned subtraction handles uint32_t wrap correctly */
-        if ((now_ms - last) > 60000U) {
-            ui_state_t st = { .stale = true };
-            lvgl_port_lock(0);
-            ui_update(&st);
-            lvgl_port_unlock();
-        }
-        vTaskDelay(pdMS_TO_TICKS(5000));
-    }
-}
-
 void app_main(void)
 {
     /* Display + LVGL */
@@ -47,7 +21,7 @@ void app_main(void)
     /* Start 30-second F15 keep-awake timer */
     keepawake_start();
 
-    /* Stale-data watchdog: grey-out UI if no snapshot received for >60s.
-     * Priority 3, default-core (Core1 on S3, opposite to TinyUSB on Core0). */
-    xTaskCreate(watchdog_task, "wd", 4096, NULL, 3, NULL);
+    /* No stale watchdog: the board holds the last received snapshot until a new
+     * one arrives (the UI only updates when comm gets a fresh line). On boot it
+     * shows the "--" placeholders until the first snapshot. */
 }
diff --git a/host/run.go b/host/run.go
index d5952ad..f08f98d 100644
--- a/host/run.go
+++ b/host/run.go
@@ -14,7 +14,8 @@ func Run(stdin io.Reader, stdout io.Writer, sink SnapshotSink, inner InnerCmd, n
 		raw = nil
 	}
 	// side effect:推板子(失败忽略,绝不影响 stdout)
-	if in, perr := ParseInput(raw); perr == nil {
+	// 只在有真实 rate_limits 时推:否则会把板子覆盖成全 0(板子保持上次真实值)。
+	if in, perr := ParseInput(raw); perr == nil && in.HasRateLimits() {
 		if line, lerr := BuildSnapshot(in, nowUnix).Line(); lerr == nil {
 			_ = sink.Send(line)
 		}
diff --git a/host/run_test.go b/host/run_test.go
index 47d00b1..37ce3de 100644
--- a/host/run_test.go
+++ b/host/run_test.go
@@ -65,3 +65,36 @@ func TestRun_BadJSONStillPassesThrough(t *testing.T) {
 		t.Errorf("stdout = %q, passthrough must still happen", out.String())
 	}
 }
+
+func TestRun_NoRateLimits_DoesNotPush(t *testing.T) {
+	// status-line payload without rate_limits (all-zero) must NOT overwrite the
+	// board with zeros — skip the push, board keeps its last real value.
+	sink := &fakeSink{}
+	var out bytes.Buffer
+	inner := func(stdin []byte) ([]byte, error) { return []byte("OK"), nil }
+	noRL := `{"model":{"display_name":"Opus 4.8"},"cost":{"total_cost_usd":0}}`
+	if err := Run(bytes.NewReader([]byte(noRL)), &out, sink, inner, 1000); err != nil {
+		t.Fatalf("run: %v", err)
+	}
+	if len(sink.lines) != 0 {
+		t.Fatalf("pushed %d lines, want 0 (no rate_limits)", len(sink.lines))
+	}
+	if out.String() != "OK" {
+		t.Errorf("stdout = %q, want passthrough", out.String())
+	}
+}
+
+func TestHasRateLimits(t *testing.T) {
+	none, _ := ParseInput([]byte(`{"cost":{"total_cost_usd":1}}`))
+	if none.HasRateLimits() {
+		t.Error("empty rate_limits should be false")
+	}
+	zeroReset, _ := ParseInput([]byte(`{"rate_limits":{"five_hour":{"used_percentage":0,"resets_at":0}}}`))
+	if zeroReset.HasRateLimits() {
+		t.Error("resets_at=0 should be false")
+	}
+	real, _ := ParseInput([]byte(`{"rate_limits":{"five_hour":{"used_percentage":0,"resets_at":5000}}}`))
+	if !real.HasRateLimits() {
+		t.Error("real window (0% but resets_at>0) should be true")
+	}
+}
diff --git a/host/snapshot.go b/host/snapshot.go
index 567c3ec..396923f 100644
--- a/host/snapshot.go
+++ b/host/snapshot.go
@@ -35,6 +35,15 @@ type Snapshot struct {
 	Providers []Provider `json:"providers"`
 }
 
+// HasRateLimits reports whether the input carries real rate-limit data.
+// Claude Code sometimes emits a status-line payload with no rate_limits (e.g.
+// before it has fetched them), which unmarshals to all-zero fields. A real
+// window always has a reset timestamp, so resets_at>0 distinguishes real data
+// (including a legitimate 0% at the start of a window) from "no data yet".
+func (in StatusLineInput) HasRateLimits() bool {
+	return in.RateLimits.FiveHour.ResetsAt > 0 || in.RateLimits.SevenDay.ResetsAt > 0
+}
+
 func ParseInput(b []byte) (StatusLineInput, error) {
 	var in StatusLineInput
 	err := json.Unmarshal(b, &in)