Preserve nRF52 OTA boot result diagnostics

src/helpers/ota/OtaApply.cpp

@@ -419,6 +419,14 @@ void ota_reboot_to_apply() { esp_restart(); }  // boots the slot armed by ota_ap
 
 #elif defined(NRF52_PLATFORM)  // single-slot: verify + mark APPROVED + hand off to the bootloader
 
+// Capture a real OTAFIX result before board power-management initialization
+// consumes GPREGRET2. Ignore shutdown reasons and staging handoff markers that
+// share the register but are not bootloader apply results.
+static uint8_t g_bootloader_last_rc = 0;
+static void __attribute__((constructor(101))) ota_capture_bootloader_last_rc() {
+  g_bootloader_last_rc = ota_nrf52_boot_result_or_zero((uint8_t)NRF_POWER->GPREGRET2);
+}
+
 struct InplacePatchDims {
   uint32_t memory = 0;
   uint32_t segment = 0;
@@ -465,12 +473,7 @@ void ota_reboot_to_apply() {                   // public: set the apply magic +
   NVIC_SystemReset();                          // does not return
 }
 
-uint8_t ota_bootloader_last_rc() {             // bootloader's last in-place-apply code, stashed in GPREGRET2
-  uint32_t v = 0;
-  uint8_t en = 0; sd_softdevice_is_enabled(&en);
-  if (en) sd_power_gpregret_get(1, &v); else v = NRF_POWER->GPREGRET2;
-  return (uint8_t)v;
-}
+uint8_t ota_bootloader_last_rc() { return g_bootloader_last_rc; }
 
 static bool ota_apply_mota_nrf52_impl(const uint8_t* buf, uint32_t len,
                                       const SignerAllowlist& allow,

src/helpers/ota/OtaApply.h

@@ -99,6 +99,11 @@ bool ota_apply_mota_nrf52(OtaStoreQspiNrf52& store,
 // into the slot already armed by ota_apply_detools_mota.
 void ota_reboot_to_apply();
 
+inline uint8_t ota_nrf52_boot_result_or_zero(uint8_t value) {
+  return ((value >= 0x90u && value <= 0x9Fu) ||
+          (value >= 0xB0u && value <= 0xBCu)) ? value : 0u;
+}
+
 // DIAGNOSTIC (nRF52): the bootloader stashes its last in-place-apply bail/progress code in GPREGRET2 (see
 // ota_delta.c). Read it back so `ota status` can show why an apply didn't take. 0 / other platforms = n/a.
 uint8_t ota_bootloader_last_rc();

test/test_ota/test_ota_core.cpp

@@ -23,6 +23,21 @@ extern "C" {
 
 using namespace mesh::ota;
 
+TEST(OtaBootResult, AcceptsOnlyOtafixApplyDiagnostics) {
+  EXPECT_EQ(ota_nrf52_boot_result_or_zero(0x90), 0x90);
+  EXPECT_EQ(ota_nrf52_boot_result_or_zero(0x9F), 0x9F);
+  EXPECT_EQ(ota_nrf52_boot_result_or_zero(0xB0), 0xB0);
+  EXPECT_EQ(ota_nrf52_boot_result_or_zero(0xB8), 0xB8);
+  EXPECT_EQ(ota_nrf52_boot_result_or_zero(0xBC), 0xBC);
+
+  EXPECT_EQ(ota_nrf52_boot_result_or_zero(0x00), 0x00);
+  EXPECT_EQ(ota_nrf52_boot_result_or_zero(0x4C), 0x00); // shutdown reason
+  EXPECT_EQ(ota_nrf52_boot_result_or_zero(0x51), 0x00); // QSPI handoff
+  EXPECT_EQ(ota_nrf52_boot_result_or_zero(0xD4), 0x00); // legacy handoff
+  EXPECT_EQ(ota_nrf52_boot_result_or_zero(0xED), 0x00); // expanded handoff
+  EXPECT_EQ(ota_nrf52_boot_result_or_zero(0xBD), 0x00);
+}
+
 class FakeMotaSeederStream : public Stream {
 public:
   using Stream::write;