diff --git a/build.sh b/build.sh
index 5d6ae4439..a6ad41c63 100755
--- a/build.sh
+++ b/build.sh
@@ -203,10 +203,18 @@ build_firmware() {
   # the .ini declarations were removed rather than overridden.
   OTA_MANIFEST_BASE_URL="${OTA_MANIFEST_BASE_URL:-https://observer.gessaman.com/v}"
 
+  # Both named channel bases are baked into EVERY observer build so `ota branch`
+  # can re-point a device at either channel at runtime. OTA_MANIFEST_BASE above stays
+  # the build's NATIVE channel (= stable base for stable builds, dev base for dev
+  # builds), so `ota branch default` resolves correctly. These two must match the
+  # paths DutchMeshCore-OTA serves (feat/dev-stable-ota-channels): /mqtt/v + /mqtt/dev/v.
+  OTA_MANIFEST_BASE_STABLE_URL="${OTA_MANIFEST_BASE_STABLE_URL:-https://ota.dutchmeshcore.nl/mqtt/v}"
+  OTA_MANIFEST_BASE_DEV_URL="${OTA_MANIFEST_BASE_DEV_URL:-https://ota.dutchmeshcore.nl/mqtt/dev/v}"
+
   # add firmware version info to end of existing platformio build flags in environment vars.
   # OTA_VARIANT is the env name ($1) — it selects this build's slim per-variant manifest
   # (<OTA_MANIFEST_BASE>/<OTA_VARIANT>.json) that the observer pull-OTA fetches.
-  export PLATFORMIO_BUILD_FLAGS="${PLATFORMIO_BUILD_FLAGS} -DFIRMWARE_BUILD_DATE='\"${FIRMWARE_BUILD_DATE}\"' -DFIRMWARE_VERSION='\"${EMBEDDED_VERSION_STRING}\"' -DOTA_VARIANT='\"$1\"' -DOTA_MANIFEST_BASE='\"${OTA_MANIFEST_BASE_URL}\"'"
+  export PLATFORMIO_BUILD_FLAGS="${PLATFORMIO_BUILD_FLAGS} -DFIRMWARE_BUILD_DATE='\"${FIRMWARE_BUILD_DATE}\"' -DFIRMWARE_VERSION='\"${EMBEDDED_VERSION_STRING}\"' -DOTA_VARIANT='\"$1\"' -DOTA_MANIFEST_BASE='\"${OTA_MANIFEST_BASE_URL}\"' -DOTA_MANIFEST_BASE_STABLE='\"${OTA_MANIFEST_BASE_STABLE_URL}\"' -DOTA_MANIFEST_BASE_DEV='\"${OTA_MANIFEST_BASE_DEV_URL}\"'"
 
   # disable debug flags if requested
   disable_debug_flags