Size-optimize nRF52 LoRa OTA builds

build.sh

@@ -2184,6 +2184,24 @@ apply_repeater_neighbor_capacity() {
   export PLATFORMIO_BUILD_FLAGS="${PLATFORMIO_BUILD_FLAGS} -DMAX_NEIGHBOURS=${max_neighbours}"
 }
 
+apply_nrf52_lora_ota_size_profile() {
+  local env_name=$1
+
+  if [ "${PIO_ENV_PLATFORM_BY_NAME[$env_name]:-}" != "NRF52_PLATFORM" ] \
+      || ! is_lora_ota_build "$env_name" \
+      || ! is_lora_ota_only_target "$env_name"; then
+    return 0
+  fi
+
+  # The Adafruit nRF52 platform defaults release builds to -Ofast. Once the
+  # runtime software Ed25519 fallback is linked alongside CC310, that setting
+  # fully expands repeated Curve25519 arithmetic and wastes tens of kilobytes.
+  # Keep hardware crypto, RNG mixing, the software fallback, and board features;
+  # only select the size optimizer for the constrained self-updatable image.
+  append_platformio_build_unflags "-Ofast"
+  export PLATFORMIO_BUILD_FLAGS="${PLATFORMIO_BUILD_FLAGS} -Os"
+}
+
 apply_lora_ota_no_external_sensors_profile() {
   local env_name=$1
 
@@ -2712,6 +2730,7 @@ build_firmware() {
   apply_esp32_lora_ota_size_profile "$env_name"
   apply_esp32_full_size_profile "$env_name"
   apply_repeater_neighbor_capacity "$env_name"
+  apply_nrf52_lora_ota_size_profile "$env_name"
   apply_lora_ota_no_external_sensors_profile "$env_name"
   apply_radio_overrides
   apply_firmware_profile_overrides

docs/ota_easy.md

@@ -65,6 +65,11 @@ browser WiFi uploader (`start ota`) and use a 254-entry neighbor table. RP2040 a
 currently have a safe self-apply path, but current repeater firmware can still relay OTA packets opaquely
 during TempRadio.
 
+nRF52 `-ota-` siblings are compiled with size optimization instead of the Adafruit platform's default
+speed optimization. This prevents the retained software Ed25519 fallback from expanding beyond the fixed
+in-place workspace; CC310 hardware crypto, hardware RNG mixing, telemetry history, and board-native features
+remain enabled.
+
 ESP32 `*-full-ota-*` artifacts retain all compiled features and enable LoRa OTA for every FULL role,
 including room servers, sensors, observers, and bridges. A FULL image requires its expanded partition table:
 install the matching merged image over USB once before installing later non-merged FULL updates over LoRa.

docs/ota_protocol.md

@@ -126,6 +126,11 @@ board-native telemetry remain enabled. ESP32 siblings retain the compact browser
 full 254-entry neighbor table. RP2040 and STM32 targets are not offered because those platforms do not yet
 have a safe bootloader/apply path.
 
+nRF52 LoRa-OTA siblings use size optimization rather than the Adafruit platform's default `-Ofast`. This
+keeps the runtime software Ed25519 fallback from being expanded into tens of kilobytes of repeated curve
+arithmetic while retaining CC310 hardware crypto, hardware RNG mixing, telemetry history, and board-native
+features.
+
 Two WiFi-heavy non-companion profiles need additional reductions to remain portable. MQTT observer builds
 keep MQTT/TLS, onboard GPS, and their WiFi pull-updater, but omit WebConfig, SNMP, debug logging, display
 support, and optional external sensor drivers. Their compact CLI keeps observer controls plus the radio,