diff --git a/.github/workflows/apk-tts-engine.yaml b/.github/workflows/apk-tts-engine.yaml
index a08119bf..9fd62d3f 100644
--- a/.github/workflows/apk-tts-engine.yaml
+++ b/.github/workflows/apk-tts-engine.yaml
@@ -53,6 +53,23 @@ jobs:
         run: |
           python3 -m pip install --upgrade pip jinja2 iso639-lang
 
+      - name: Setup build tool version variable
+        shell: bash
+        run: |
+          echo "---"
+          ls -lh /usr/local/lib/android/
+          echo "---"
+
+          ls -lh /usr/local/lib/android/sdk
+          echo "---"
+
+          ls -lh /usr/local/lib/android/sdk/build-tools
+          echo "---"
+
+          BUILD_TOOL_VERSION=$(ls /usr/local/lib/android/sdk/build-tools/ | tail -n 1)
+          echo "BUILD_TOOL_VERSION=$BUILD_TOOL_VERSION" >> $GITHUB_ENV
+          echo "Last build tool version is: $BUILD_TOOL_VERSION"
+
       - name: Generate build script
         shell: bash
         run: |
@@ -82,10 +99,49 @@ jobs:
           ls -lh ./apks/
           du -h -d1 .
 
+      # https://github.com/marketplace/actions/sign-android-release
+      - uses: r0adkll/sign-android-release@v1
+        name: Sign app APK
+        with:
+          releaseDirectory: ./apks
+          signingKeyBase64: ${{ secrets.ANDROID_SIGNING_KEY }}
+          alias: ${{ secrets.ANDROID_SIGNING_KEY_ALIAS }}
+          keyStorePassword: ${{ secrets.ANDROID_SIGNING_KEY_STORE_PASSWORD }}
+        env:
+          BUILD_TOOLS_VERSION: ${{ env.BUILD_TOOL_VERSION }}
+
+      - name: Display APK for TTS engine after signing
+        shell: bash
+        run: |
+          ls -lh ./apks/
+          du -h -d1 .
+
+      - name: Rename APK for TTS engine after signing
+        shell: bash
+        run: |
+          cd apks
+          rm -fv signingKey.jks
+          rm -fv *.apk.idsig
+          rm -fv *-aligned.apk
+
+          all_apks=$(ls -1 *-signed.apk)
+          echo "----"
+          echo $all_apks
+          echo "----"
+          for apk in ${all_apks[@]}; do
+            n=$(echo $apk | sed -e s/-signed//)
+            mv -v $apk $n
+          done
+
+          cd ..
+
+          ls -lh ./apks/
+          du -h -d1 .
+
       - uses: actions/upload-artifact@v4
         if: false
         with:
-          name: tts-engine-apk
+          name: tts-engine-apk-${{ matrix.index }}
           path: ./apks/*.apk
 
       - name: Publish to huggingface
diff --git a/.github/workflows/apk-tts.yaml b/.github/workflows/apk-tts.yaml
index c195c376..f93e5d4a 100644
--- a/.github/workflows/apk-tts.yaml
+++ b/.github/workflows/apk-tts.yaml
@@ -53,6 +53,23 @@ jobs:
         run: |
           python3 -m pip install --upgrade pip jinja2 iso639-lang
 
+      - name: Setup build tool version variable
+        shell: bash
+        run: |
+          echo "---"
+          ls -lh /usr/local/lib/android/
+          echo "---"
+
+          ls -lh /usr/local/lib/android/sdk
+          echo "---"
+
+          ls -lh /usr/local/lib/android/sdk/build-tools
+          echo "---"
+
+          BUILD_TOOL_VERSION=$(ls /usr/local/lib/android/sdk/build-tools/ | tail -n 1)
+          echo "BUILD_TOOL_VERSION=$BUILD_TOOL_VERSION" >> $GITHUB_ENV
+          echo "Last build tool version is: $BUILD_TOOL_VERSION"
+
       - name: Generate build script
         shell: bash
         run: |
@@ -82,10 +99,49 @@ jobs:
           ls -lh ./apks/
           du -h -d1 .
 
+      # https://github.com/marketplace/actions/sign-android-release
+      - uses: r0adkll/sign-android-release@v1
+        name: Sign app APK
+        with:
+          releaseDirectory: ./apks
+          signingKeyBase64: ${{ secrets.ANDROID_SIGNING_KEY }}
+          alias: ${{ secrets.ANDROID_SIGNING_KEY_ALIAS }}
+          keyStorePassword: ${{ secrets.ANDROID_SIGNING_KEY_STORE_PASSWORD }}
+        env:
+          BUILD_TOOLS_VERSION: ${{ env.BUILD_TOOL_VERSION }}
+
+      - name: Display APK for TTS engine after signing
+        shell: bash
+        run: |
+          ls -lh ./apks/
+          du -h -d1 .
+
+      - name: Rename APK for TTS engine after signing
+        shell: bash
+        run: |
+          cd apks
+          rm -fv signingKey.jks
+          rm -fv *.apk.idsig
+          rm -fv *-aligned.apk
+
+          all_apks=$(ls -1 *-signed.apk)
+          echo "----"
+          echo $all_apks
+          echo "----"
+          for apk in ${all_apks[@]}; do
+            n=$(echo $apk | sed -e s/-signed//)
+            mv -v $apk $n
+          done
+
+          cd ..
+
+          ls -lh ./apks/
+          du -h -d1 .
+
       - uses: actions/upload-artifact@v4
         if: false
         with:
-          name: tts-apk
+          name: tts-apk-${{ matrix.index }}
           path: ./apks/*.apk
 
       - name: Publish to huggingface
diff --git a/scripts/apk/build-apk-tts-engine.sh.in b/scripts/apk/build-apk-tts-engine.sh.in
index 766846c1..5e46f8eb 100644
--- a/scripts/apk/build-apk-tts-engine.sh.in
+++ b/scripts/apk/build-apk-tts-engine.sh.in
@@ -84,10 +84,10 @@ for arch in arm64-v8a armeabi-v7a x86_64 x86; do
   pushd ./android/SherpaOnnxTtsEngine
   sed -i.bak s/2048/9012/g ./gradle.properties
   git diff ./gradle.properties
-  ./gradlew build
+  ./gradlew assembleRelease
   popd
 
-  mv android/SherpaOnnxTtsEngine/app/build/outputs/apk/debug/app-debug.apk ./apks/sherpa-onnx-${SHERPA_ONNX_VERSION}-$arch-$lang-tts-engine-$model_dir.apk
+  mv android/SherpaOnnxTtsEngine/app/build/outputs/apk/release/app-release-unsigned.apk ./apks/sherpa-onnx-${SHERPA_ONNX_VERSION}-$arch-$lang-tts-engine-$model_dir.apk
   ls -lh apks
   rm -v ./android/SherpaOnnxTtsEngine/app/src/main/jniLibs/$arch/*.so
 done
diff --git a/scripts/apk/build-apk-tts.sh.in b/scripts/apk/build-apk-tts.sh.in
index a5a0d5ea..a3dd6b48 100644
--- a/scripts/apk/build-apk-tts.sh.in
+++ b/scripts/apk/build-apk-tts.sh.in
@@ -82,10 +82,10 @@ for arch in arm64-v8a armeabi-v7a x86_64 x86; do
   pushd ./android/SherpaOnnxTts
   sed -i.bak s/2048/9012/g ./gradle.properties
   git diff ./gradle.properties
-  ./gradlew build
+  ./gradlew assembleRelease
   popd
 
-  mv android/SherpaOnnxTts/app/build/outputs/apk/debug/app-debug.apk ./apks/sherpa-onnx-${SHERPA_ONNX_VERSION}-$arch-$lang-tts-$model_dir.apk
+  mv android/SherpaOnnxTts/app/build/outputs/apk/release/app-release-unsigned.apk ./apks/sherpa-onnx-${SHERPA_ONNX_VERSION}-$arch-$lang-tts-$model_dir.apk
   ls -lh apks
   rm -v ./android/SherpaOnnxTts/app/src/main/jniLibs/$arch/*.so
 done