diff --git a/core/build-android.sh b/core/build-android.sh
index 2d2885d..966ac9e 100755
--- a/core/build-android.sh
+++ b/core/build-android.sh
@@ -11,6 +11,12 @@ cd "$(dirname "$0")"
 APP="../android/app/src/main"
 ABIS=(arm64-v8a x86_64)
 
+# Optional Cargo features, e.g. TETHER_FEATURES=iroh-transport for the iroh core.
+# Plain string (not an array) for macOS bash 3.2 + `set -u`.
+FEATURES="${TETHER_FEATURES:-}"
+FEAT_ARGS=""
+[ -n "$FEATURES" ] && FEAT_ARGS="--features $FEATURES" && echo "▸ features: $FEATURES"
+
 if ! command -v cargo-ndk >/dev/null; then
   echo "missing cargo-ndk → cargo install cargo-ndk; also install the Android NDK and set ANDROID_NDK_HOME" >&2
   exit 1
@@ -18,10 +24,12 @@ fi
 
 echo "▸ building .so for ${ABIS[*]}…"
 rustup target add aarch64-linux-android x86_64-linux-android >/dev/null 2>&1 || true
-cargo ndk -t arm64-v8a -t x86_64 -o "$APP/jniLibs" build --release
+# shellcheck disable=SC2086  # intentional word-split of FEAT_ARGS
+cargo ndk -t arm64-v8a -t x86_64 -o "$APP/jniLibs" build --release $FEAT_ARGS
 
 echo "▸ generating Kotlin bindings…"
-cargo build --release --lib
+# shellcheck disable=SC2086
+cargo build --release --lib $FEAT_ARGS
 cargo run --release --bin uniffi-bindgen -- \
   generate --library target/release/libtethercore.dylib \
   --language kotlin --out-dir "$APP/java"