diff --git a/zephcore/adapters/radio/LoRaRadioBase.cpp b/zephcore/adapters/radio/LoRaRadioBase.cpp
index b59e730..40bf76e 100644
--- a/zephcore/adapters/radio/LoRaRadioBase.cpp
+++ b/zephcore/adapters/radio/LoRaRadioBase.cpp
@@ -504,6 +504,11 @@ bool LoRaRadioBase::startSendRaw(const uint8_t *bytes, int len)
 		return false;
 	}
 
+	/* Defensive gate: callers should defer TX while radio is BUSY. */
+	if (!isRadioReady()) {
+		return false;
+	}
+
 	/* Last-moment hardware check before killing active RX.
 	 * Closes the race between the Dispatcher's isReceiving() guard
 	 * and hwCancelReceive() — if a preamble arrived in that gap,
@@ -561,6 +566,13 @@ float LoRaRadioBase::getLastSNR() const
 	return _last_snr;
 }
 
+bool LoRaRadioBase::isRadioReady()
+{
+	/* BUSY high means the radio cannot accept SPI commands now
+	 * (e.g. duty-cycle sleep phase on SX126x/LR11xx). */
+	return !hwIsChipBusy();
+}
+
 /* ── Airtime + scoring ────────────────────────────────────────────────── */
 
 uint32_t LoRaRadioBase::getEstAirtimeFor(int len_bytes)
@@ -617,12 +629,9 @@ void LoRaRadioBase::triggerNoiseFloorCalibrate(int threshold)
 		return;
 	}
 
-	/* When duty cycle is active the chip alternates between short RX
-	 * windows and sleep.  GetRssiInst during the sleep phase hangs the
-	 * SPI bus (BUSY stuck high for the full 3 s timeout).  Check the
-	 * BUSY pin directly (GPIO read, no SPI) — if the chip is sleeping,
-	 * skip this cycle and try again next housekeeping tick. */
-	if (_rx_duty_cycle_enabled && hwIsChipBusy()) {
+	/* Skip when the radio cannot accept commands right now
+	 * (e.g. duty-cycle sleep BUSY window). */
+	if (!isRadioReady()) {
 		return;
 	}
 
diff --git a/zephcore/adapters/radio/LoRaRadioBase.h b/zephcore/adapters/radio/LoRaRadioBase.h
index 398ed9b..bb37285 100644
--- a/zephcore/adapters/radio/LoRaRadioBase.h
+++ b/zephcore/adapters/radio/LoRaRadioBase.h
@@ -53,6 +53,7 @@ public:
 	bool isInRecvMode() const override;
 	float getLastRSSI() const override;
 	float getLastSNR() const override;
+	bool isRadioReady() override;
 
 	/* Packet statistics */
 	uint32_t getPacketsRecv() const override { return (uint32_t)atomic_get(&_packets_recv); }
diff --git a/zephcore/include/mesh/Radio.h b/zephcore/include/mesh/Radio.h
index f9a1203..6bba447 100644
--- a/zephcore/include/mesh/Radio.h
+++ b/zephcore/include/mesh/Radio.h
@@ -1,42 +1,43 @@
-/*
- * SPDX-License-Identifier: Apache-2.0
- * ZephCore Radio interface - matches Dispatcher.h
- */
-
-#pragma once
-
-#include <stdint.h>
-
-namespace mesh {
-
-class Radio {
-public:
-	virtual void begin() {}
-
-	virtual int recvRaw(uint8_t *bytes, int sz) = 0;
-	virtual uint32_t getEstAirtimeFor(int len_bytes) = 0;
-	virtual float packetScore(float snr, int packet_len) = 0;
-	virtual bool startSendRaw(const uint8_t *bytes, int len) = 0;
-	virtual bool isSendComplete() = 0;
-	virtual void onSendFinished() = 0;
-
-	virtual int getNoiseFloor() const { return 0; }
-	virtual void triggerNoiseFloorCalibrate(int threshold) { (void)threshold; }
-	virtual void resetAGC() {}
-
-	virtual bool isInRecvMode() const = 0;
-	virtual bool isReceiving() { return false; }
-	virtual float getLastRSSI() const { return 0; }
-	virtual float getLastSNR() const { return 0; }
-
-	/* Adaptive Power Control */
-	virtual void setTxPowerReduction(int8_t reduction_db) { (void)reduction_db; }
-	virtual int8_t getTxPowerReduction() const { return 0; }
-
-	/* Packet statistics */
-	virtual uint32_t getPacketsRecv() const { return 0; }
-	virtual uint32_t getPacketsSent() const { return 0; }
-	virtual uint32_t getPacketsRecvErrors() const { return 0; }
-};
-
-} /* namespace mesh */
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * ZephCore Radio interface - matches Dispatcher.h
+ */
+
+#pragma once
+
+#include <stdint.h>
+
+namespace mesh {
+
+class Radio {
+public:
+	virtual void begin() {}
+
+	virtual int recvRaw(uint8_t *bytes, int sz) = 0;
+	virtual uint32_t getEstAirtimeFor(int len_bytes) = 0;
+	virtual float packetScore(float snr, int packet_len) = 0;
+	virtual bool startSendRaw(const uint8_t *bytes, int len) = 0;
+	virtual bool isSendComplete() = 0;
+	virtual void onSendFinished() = 0;
+
+	virtual int getNoiseFloor() const { return 0; }
+	virtual void triggerNoiseFloorCalibrate(int threshold) { (void)threshold; }
+	virtual void resetAGC() {}
+
+	virtual bool isInRecvMode() const = 0;
+	virtual bool isReceiving() { return false; }
+	virtual bool isRadioReady() { return true; }
+	virtual float getLastRSSI() const { return 0; }
+	virtual float getLastSNR() const { return 0; }
+
+	/* Adaptive Power Control */
+	virtual void setTxPowerReduction(int8_t reduction_db) { (void)reduction_db; }
+	virtual int8_t getTxPowerReduction() const { return 0; }
+
+	/* Packet statistics */
+	virtual uint32_t getPacketsRecv() const { return 0; }
+	virtual uint32_t getPacketsSent() const { return 0; }
+	virtual uint32_t getPacketsRecvErrors() const { return 0; }
+};
+
+} /* namespace mesh */
diff --git a/zephcore/src/Dispatcher.cpp b/zephcore/src/Dispatcher.cpp
index 83c48a0..b0c28a5 100644
--- a/zephcore/src/Dispatcher.cpp
+++ b/zephcore/src/Dispatcher.cpp
@@ -376,8 +376,9 @@ void Dispatcher::checkSend()
 		}
 	}
 
-	if (_radio->isReceiving()) {
-		/* Channel busy — enforce retry timer so we don't hammer the check */
+	if (_radio->isReceiving() || !_radio->isRadioReady()) {
+		/* Channel busy or radio not command-ready — enforce retry timer
+		 * so we don't hammer checks during RX activity or BUSY windows. */
 		if (!millisHasNowPassed(next_tx_time)) {
 			if (_tx_queued_cb) {
 				uint32_t remaining = next_tx_time - now;
@@ -443,10 +444,9 @@ void Dispatcher::checkSend()
 			}
 #endif
 
-			/* Final LBT check — close the gap between initial
-			 * isReceiving() and actual TX start (serialisation +
-			 * logging can take 1-5 ms). */
-			if (_radio->isReceiving()) {
+			/* Final gate — close the gap between initial checks and
+			 * actual TX start (serialisation + logging can take 1-5 ms). */
+			if (_radio->isReceiving() || !_radio->isRadioReady()) {
 				uint32_t retry = getCADFailRetryDelay();
 				_mgr->queueOutbound(outbound, 0, futureMillis((int)retry));
 				outbound = nullptr;