diff --git a/.github/workflows/native-themes-sync.yml b/.github/workflows/native-themes-sync.yml
new file mode 100644
index 0000000000..05d57b44fd
--- /dev/null
+++ b/.github/workflows/native-themes-sync.yml
@@ -0,0 +1,80 @@
+name: Native Themes Sync
+
+# After every push to master that touches the native-theme CSS sources,
+# the CSS compiler, or the build script, regenerate the shipped
+# `.res` files and commit them straight back to master (no PR). Every
+# downstream pipeline (port builds, BuildDaemon, archetypes, website)
+# just consumes the committed `.res` instead of rebuilding it, so this
+# workflow is the single producer.
+#
+# Pushes made with GITHUB_TOKEN do not retrigger workflow runs, so the
+# commit-back step cannot loop.
+
+on:
+  workflow_dispatch:
+  push:
+    branches:
+      - master
+    paths:
+      - 'native-themes/**'
+      - 'maven/css-compiler/**'
+      - 'scripts/build-native-themes.sh'
+      - '.github/workflows/native-themes-sync.yml'
+
+permissions:
+  contents: write
+
+concurrency:
+  group: native-themes-sync
+  cancel-in-progress: false
+
+jobs:
+  rebuild-and-commit:
+    runs-on: ubuntu-latest
+    container: ghcr.io/codenameone/codenameone/pr-ci-container:latest
+    defaults:
+      run:
+        shell: bash
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+          token: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Use JDK 8
+        run: |
+          echo "JAVA_HOME=${JAVA_HOME_8}" >> $GITHUB_ENV
+          echo "${JAVA_HOME_8}/bin" >> $GITHUB_PATH
+
+      - name: Cache Maven dependencies
+        uses: actions/cache@v4
+        with:
+          path: ~/.m2
+          key: ${{ runner.os }}-m2-${{ hashFiles('**/pom.xml') }}
+          restore-keys: |
+            ${{ runner.os }}-m2
+
+      - name: Build css-compiler
+        run: |
+          cd maven
+          mvn -B -pl css-compiler -am install -DskipTests -Dmaven.javadoc.skip=true -Plocal-dev-javase
+
+      - name: Rebuild native themes
+        run: ./scripts/build-native-themes.sh
+
+      - name: Commit and push regenerated .res files
+        run: |
+          set -euo pipefail
+          git config user.name "github-actions[bot]"
+          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
+          # Themes/ holds the single source of truth. Each downstream consumer
+          # (nativeios.jar, the Android port jar, the simulator fat-jar, the
+          # BuildDaemon's sibling cn1 checkout) copies from Themes/ at its own
+          # build time, so this workflow only commits these two files.
+          git add Themes/iOSModernTheme.res Themes/AndroidMaterialTheme.res
+          if git diff --staged --quiet; then
+            echo "No .res changes; nothing to commit."
+            exit 0
+          fi
+          git commit -m "ci: auto-regenerate native theme .res files"
+          git push
diff --git a/Ports/Android/build.xml b/Ports/Android/build.xml
index 7fbc590bae..6be4303383 100644
--- a/Ports/Android/build.xml
+++ b/Ports/Android/build.xml
@@ -74,12 +74,10 @@
     <target name="-pre-compile">
         <copy file="../../Themes/androidTheme.res" todir="src" />
         <copy file="../../Themes/android_holo_light.res" todir="src" />
-        <!-- Android Material 3 theme generated by
-             scripts/build-native-themes.sh from
-             native-themes/android-material/theme.css.
-             failonerror=false so the port still builds if the generator
-             hasn't run yet; runtime falls back to holo light. -->
-        <copy file="../../Themes/AndroidMaterialTheme.res" todir="src" failonerror="false" />
+        <!-- Android Material 3 theme committed under Themes/ and kept in sync
+             by .github/workflows/native-themes-sync.yml from
+             native-themes/android-material/theme.css. -->
+        <copy file="../../Themes/AndroidMaterialTheme.res" todir="src" />
     </target>
 
     <target name="-pre-jar">
diff --git a/Ports/JavaScriptPort/src/main/webapp/assets/.gitignore b/Ports/JavaScriptPort/src/main/webapp/assets/.gitignore
index caa62305a9..48c6b4dfae 100644
--- a/Ports/JavaScriptPort/src/main/webapp/assets/.gitignore
+++ b/Ports/JavaScriptPort/src/main/webapp/assets/.gitignore
@@ -1,5 +1,5 @@
-# Generated by scripts/build-native-themes.sh. Mirrors of Themes/ so the
-# JS port runtime picks up the modern native themes. The CSS sources in
-# native-themes/ are authoritative.
+# Mirrors of Themes/*.res written by scripts/build-native-themes.sh so a local
+# JS port run can fetch them as webapp assets. The canonical .res lives in
+# Themes/ and is committed; this mirror is a build artifact.
 iOSModernTheme.res
 AndroidMaterialTheme.res
diff --git a/Ports/iOSPort/build.xml b/Ports/iOSPort/build.xml
index c7aafebde3..605f37fd29 100644
--- a/Ports/iOSPort/build.xml
+++ b/Ports/iOSPort/build.xml
@@ -74,11 +74,10 @@
     <target name="-pre-compile">
         <copy file="../../Themes/iPhoneTheme.res" todir="nativeSources" />
         <copy file="../../Themes/iOS7Theme.res" todir="nativeSources" />
-        <!-- iOS Modern (liquid-glass) theme generated by
-             scripts/build-native-themes.sh from native-themes/ios-modern/theme.css.
-             failonerror=false so the port still builds if the generator
-             hasn't run yet; runtime falls back to iOS 7. -->
-        <copy file="../../Themes/iOSModernTheme.res" todir="nativeSources" failonerror="false" />
+        <!-- iOS Modern (liquid-glass) theme committed under Themes/ and kept
+             in sync by .github/workflows/native-themes-sync.yml from
+             native-themes/ios-modern/theme.css. -->
+        <copy file="../../Themes/iOSModernTheme.res" todir="nativeSources" />
     </target>
     <target name="-post-jar">
         <delete file="${dist.jar}.old" />
diff --git a/Themes/.gitignore b/Themes/.gitignore
deleted file mode 100644
index 36ce6ac0c2..0000000000
--- a/Themes/.gitignore
+++ /dev/null
@@ -1,4 +0,0 @@
-# Generated by scripts/build-native-themes.sh from native-themes/*/theme.css.
-# These are build artifacts; the CSS sources in native-themes/ are authoritative.
-iOSModernTheme.res
-AndroidMaterialTheme.res
diff --git a/Themes/AndroidMaterialTheme.res b/Themes/AndroidMaterialTheme.res
new file mode 100644
index 0000000000..24e035cc17
Binary files /dev/null and b/Themes/AndroidMaterialTheme.res differ
diff --git a/Themes/iOSModernTheme.res b/Themes/iOSModernTheme.res
new file mode 100644
index 0000000000..a5ad76267f
Binary files /dev/null and b/Themes/iOSModernTheme.res differ
diff --git a/maven/android/pom.xml b/maven/android/pom.xml
index 43b617ddee..a85d8f2b50 100644
--- a/maven/android/pom.xml
+++ b/maven/android/pom.xml
@@ -86,9 +86,22 @@
                                 <configuration>
                                     <target>
                                         <mkdir dir="${project.build.outputDirectory}/com/codename1/android"/>
+                                        <!-- android_port_sources.jar is the
+                                             bundle AndroidGradleBuilder unzips
+                                             into the user app's APK assets/.
+                                             AndroidMaterialTheme.res must be in
+                                             here for the runtime to find it;
+                                             pull it directly from the canonical
+                                             Themes/ copy rather than staging
+                                             into Ports/Android/src/. The .res
+                                             is kept in sync by
+                                             .github/workflows/native-themes-sync.yml. -->
                                         <zip destfile="${project.build.outputDirectory}/com/codename1/android/android_port_sources.jar">
                                             <fileset dir="${real.src.dir}" />
                                             <fileset dir="${codename1.src.dir}"/>
+                                            <fileset dir="${project.basedir}/../../Themes">
+                                                <include name="AndroidMaterialTheme.res"/>
+                                            </fileset>
                                         </zip>
                                     </target>
                                 </configuration>
@@ -280,6 +293,18 @@
                         <resource>
                             <directory>${src.dir}</directory>
                         </resource>
+                        <!-- Themes/AndroidMaterialTheme.res is the single
+                             source of truth; pull it into the Android port
+                             jar here instead of pre-staging a copy under
+                             Ports/Android/src/. The .res is committed and
+                             kept in sync by
+                             .github/workflows/native-themes-sync.yml. -->
+                        <resource>
+                            <directory>${project.basedir}/../../Themes</directory>
+                            <includes>
+                                <include>AndroidMaterialTheme.res</include>
+                            </includes>
+                        </resource>
                     </resources>
 
 
diff --git a/maven/core-unittests/src/test/java/com/codename1/ui/plaf/BorderAndPlafTest.java b/maven/core-unittests/src/test/java/com/codename1/ui/plaf/BorderAndPlafTest.java
index d8f69104d4..57f6c60e71 100644
--- a/maven/core-unittests/src/test/java/com/codename1/ui/plaf/BorderAndPlafTest.java
+++ b/maven/core-unittests/src/test/java/com/codename1/ui/plaf/BorderAndPlafTest.java
@@ -15,6 +15,7 @@
 import com.codename1.ui.plaf.StyleParser.PaddingInfo;
 import com.codename1.ui.plaf.StyleParser.ScalarValue;
 import com.codename1.ui.plaf.StyleParser.StyleInfo;
+import java.lang.reflect.Field;
 import java.util.List;
 import org.junit.jupiter.api.BeforeEach;
 
@@ -215,7 +216,7 @@ void testStyleParserImageAndBorderParsing() {
     }
 
     @FormTest
-    void testRoundBorderShadowSpreadAndPaintingCaches() {
+    void testRoundBorderShadowSpreadAndPaintingCaches() throws Exception {
         RoundBorder border = RoundBorder.create().shadowSpread(3).shadowBlur(4f).shadowOpacity(128).uiid(false);
         com.codename1.ui.Label label = new com.codename1.ui.Label();
         label.setWidth(20);
@@ -223,19 +224,17 @@ void testRoundBorderShadowSpreadAndPaintingCaches() {
         label.setX(0);
         label.setY(0);
         border.paintBorderBackground(graphics, label);
-        RoundBorder.CacheValue cacheValue = null;
-        Object baseCache = label.getClientProperty("cn1$$-rbcache");
-        if (baseCache instanceof RoundBorder.CacheValue) {
-            cacheValue = (RoundBorder.CacheValue) baseCache;
-        }
-        for (int i = 0; cacheValue == null && i < 50; i++) {
-            Object cached = label.getClientProperty("cn1$$-rbcache" + (i + 1));
-            if (cached instanceof RoundBorder.CacheValue) {
-                cacheValue = (RoundBorder.CacheValue) cached;
-                break;
-            }
-        }
-        assertNotNull(cacheValue);
+        // RoundBorder stores its cache under "cn1$$-rbcache" + instanceVal where
+        // instanceVal is a per-instance id off a static counter. Read the actual
+        // instanceVal off this border so the lookup doesn't depend on how many
+        // RoundBorder instances earlier tests in the same JVM happened to mint.
+        Field instanceValField = RoundBorder.class.getDeclaredField("instanceVal");
+        instanceValField.setAccessible(true);
+        int instanceVal = instanceValField.getInt(border);
+        Object cached = label.getClientProperty("cn1$$-rbcache" + instanceVal);
+        assertNotNull(cached, "RoundBorder.paintBorderBackground should populate the cache under cn1$$-rbcache" + instanceVal);
+        assertTrue(cached instanceof RoundBorder.CacheValue);
+        RoundBorder.CacheValue cacheValue = (RoundBorder.CacheValue) cached;
         assertEquals(label.getWidth(), cacheValue.img.getWidth());
         assertTrue(border.getMinimumHeight() > 0);
         assertTrue(border.getMinimumWidth() > 0);
diff --git a/maven/ios/pom.xml b/maven/ios/pom.xml
index 3efbc557b5..a8a6f68858 100644
--- a/maven/ios/pom.xml
+++ b/maven/ios/pom.xml
@@ -109,8 +109,21 @@
                             <target>
                                 <mkdir dir="${project.build.outputDirectory}/codenameone/iosport-bundle"/>
 
+                                <!-- Themes/iOSModernTheme.res is the single
+                                     source of truth; pull it into nativeios.jar
+                                     here instead of pre-staging a copy under
+                                     ${codename1.nativeios.dir}. The exclude on
+                                     the nativeSources fileset guarantees a
+                                     stale local copy can't shadow the canonical
+                                     one. The .res is committed and kept in sync
+                                     by .github/workflows/native-themes-sync.yml. -->
                                 <zip destfile="${project.build.directory}/codenameone/iosport-bundle/nativeios.jar">
-                                    <fileset dir="${codename1.nativeios.dir}" />
+                                    <fileset dir="${codename1.nativeios.dir}">
+                                        <exclude name="iOSModernTheme.res"/>
+                                    </fileset>
+                                    <fileset dir="${project.basedir}/../../Themes">
+                                        <include name="iOSModernTheme.res"/>
+                                    </fileset>
                                 </zip>
                                 <copy file="${project.build.directory}/${project.build.finalName}-jar-with-dependencies.jar" tofile="${project.build.directory}/codenameone/iosport-bundle/iOSPort.jar" overwrite="true"/>
                                 <zip destfile="${project.build.directory}/${project.build.finalName}-bundle.jar">
diff --git a/maven/javase/pom.xml b/maven/javase/pom.xml
index bf65ded8c7..2585df0123 100644
--- a/maven/javase/pom.xml
+++ b/maven/javase/pom.xml
@@ -146,11 +146,10 @@
                                      simulator fat jar so JavaSEPort.loadSkinFile can
                                      load the right .res based on the current skin's
                                      platformName (or the Simulator "Native Theme"
-                                     menu override). failonerror=false lets the
-                                     simulator still build if
-                                     scripts/build-native-themes.sh hasn't produced
-                                     the modern .res files yet. -->
-                                <copy todir="${project.build.outputDirectory}" failonerror="false">
+                                     menu override). All .res files are committed
+                                     under Themes/; the modern pair is regenerated
+                                     by .github/workflows/native-themes-sync.yml. -->
+                                <copy todir="${project.build.outputDirectory}">
                                     <fileset dir="${project.basedir}/../../Themes">
                                         <include name="iOSModernTheme.res"/>
                                         <include name="AndroidMaterialTheme.res"/>
diff --git a/scripts/build-android-port.sh b/scripts/build-android-port.sh
index 54e959964b..d184a78cf5 100755
--- a/scripts/build-android-port.sh
+++ b/scripts/build-android-port.sh
@@ -131,13 +131,11 @@ if [ ! -f "$BUILD_CLIENT" ]; then
   fi
 fi
 
-# Compile native CSS themes (AndroidMaterialTheme.res) and stage them in the
-# Android port's src/ so the Maven build packages them into the port jar. The
-# runtime falls back to android_holo_light.res if AndroidMaterialTheme.res is
-# missing, which loses the Material 3 palette + all $DarkUIID entries.
-./scripts/build-native-themes.sh
-mkdir -p Ports/Android/src
-cp Themes/AndroidMaterialTheme.res Ports/Android/src/AndroidMaterialTheme.res
+# maven/android/pom.xml pulls Themes/AndroidMaterialTheme.res directly into
+# the Android port jar (resource entry on Themes/), so no pre-staging copy
+# under Ports/Android/src/ is needed. The .res is committed under Themes/ and
+# kept in sync by .github/workflows/native-themes-sync.yml. For local iteration
+# on native-themes/android-material/theme.css, run scripts/build-native-themes.sh.
 
 # Rebuild the `designer` module first so changes under maven/css-compiler/
 # are picked up by the maven plugin's CSS compile step. The designer module's
diff --git a/scripts/build-ios-port.sh b/scripts/build-ios-port.sh
index f17e058e32..f9346263da 100755
--- a/scripts/build-ios-port.sh
+++ b/scripts/build-ios-port.sh
@@ -37,14 +37,11 @@ if [ ! -f "$BUILD_CLIENT" ]; then
   fi
 fi
 
-# Compile native CSS themes (iOSModernTheme.res) and copy into the iOS port's
-# native sources so the Maven iOS build packages them into nativeios.jar. The
-# iOS runtime falls back to iOS7Theme.res when iOSModernTheme.res is missing,
-# which loses all $DarkUIID entries (dark mode appears broken) and the liquid-
-# glass styling — so make sure this runs before the port is built.
-./scripts/build-native-themes.sh
-mkdir -p Ports/iOSPort/nativeSources
-cp Themes/iOSModernTheme.res Ports/iOSPort/nativeSources/iOSModernTheme.res
+# maven/ios/pom.xml pulls Themes/iOSModernTheme.res directly into nativeios.jar,
+# so no pre-staging copy under Ports/iOSPort/nativeSources/ is needed. The .res
+# is committed under Themes/ and kept in sync by
+# .github/workflows/native-themes-sync.yml. For local iteration on
+# native-themes/ios-modern/theme.css, run scripts/build-native-themes.sh.
 
 # Rebuild the `designer` module first so changes under maven/css-compiler/
 # are picked up by the maven plugin's CSS compile step. The designer module's
diff --git a/scripts/build-native-themes.sh b/scripts/build-native-themes.sh
index 6befddb66a..2010eb6534 100755
--- a/scripts/build-native-themes.sh
+++ b/scripts/build-native-themes.sh
@@ -28,7 +28,9 @@ CSS_COMPILER_MODULE="$REPO_ROOT/maven/css-compiler"
 CSS_SRC_ROOT="$REPO_ROOT/native-themes"
 OUT_DIR="$REPO_ROOT/Themes"
 # JavaScriptPort's runtime serves themes out of its webapp assets folder;
-# mirror the generated .res files there too so the JS port picks them up.
+# mirror the generated .res files there too so a local JS port run picks them
+# up. The mirror is gitignored - Themes/ is the single source of truth, and
+# the port poms (maven/ios, maven/android) consume it directly at build time.
 JS_ASSETS_DIR="$REPO_ROOT/Ports/JavaScriptPort/src/main/webapp/assets"
 
 # Resolve the compiler jar. Prefer a freshly-built target/ jar (so CSS compiler
diff --git a/scripts/cn1playground/common/pom.xml b/scripts/cn1playground/common/pom.xml
index 04b672d8b3..06b87e131e 100644
--- a/scripts/cn1playground/common/pom.xml
+++ b/scripts/cn1playground/common/pom.xml
@@ -417,12 +417,11 @@
             </plugin>
 
             <!--
-              Bundle the generated iOS Modern + Android Material native theme .res
-              files into the playground's classpath so the deployed JS bundle can
+              Bundle the iOS Modern + Android Material native theme .res files
+              into the playground's classpath so the deployed JS bundle can
               `Resources.openLayered("/iOSModernTheme")` from inside the live
-              preview. The files are gitignored build artifacts produced by
-              scripts/build-native-themes.sh; failonerror=false keeps standalone
-              builds working when they haven't been generated yet.
+              preview. The .res files are committed under Themes/ and kept in
+              sync by .github/workflows/native-themes-sync.yml.
             -->
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
@@ -436,8 +435,8 @@
                         </goals>
                         <configuration>
                             <target>
-                                <copy todir="${project.build.outputDirectory}" failonerror="false" verbose="true">
-                                    <fileset dir="${project.basedir}/../../../Themes" erroronmissingdir="false">
+                                <copy todir="${project.build.outputDirectory}" verbose="true">
+                                    <fileset dir="${project.basedir}/../../../Themes">
                                         <include name="iOSModernTheme.res"/>
                                         <include name="AndroidMaterialTheme.res"/>
                                     </fileset>
diff --git a/scripts/initializr/common/pom.xml b/scripts/initializr/common/pom.xml
index 829b8b4834..4fde35c158 100644
--- a/scripts/initializr/common/pom.xml
+++ b/scripts/initializr/common/pom.xml
@@ -390,12 +390,11 @@
             </plugin>
 
             <!--
-              Bundle the generated iOS Modern native theme .res file into the
-              initializr's classpath so the deployed JS bundle can
+              Bundle the iOS Modern native theme .res file into the initializr's
+              classpath so the deployed JS bundle can
               `Resources.openLayered("/iOSModernTheme")` for the live preview.
-              The file is a gitignored build artifact produced by
-              scripts/build-native-themes.sh; failonerror=false keeps standalone
-              builds working when it hasn't been generated yet.
+              The .res files are committed under Themes/ and kept in sync by
+              .github/workflows/native-themes-sync.yml.
             -->
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
@@ -409,8 +408,8 @@
                         </goals>
                         <configuration>
                             <target>
-                                <copy todir="${project.build.outputDirectory}" failonerror="false" verbose="true">
-                                    <fileset dir="${project.basedir}/../../../Themes" erroronmissingdir="false">
+                                <copy todir="${project.build.outputDirectory}" verbose="true">
+                                    <fileset dir="${project.basedir}/../../../Themes">
                                         <include name="iOSModernTheme.res"/>
                                         <include name="AndroidMaterialTheme.res"/>
                                     </fileset>
diff --git a/scripts/website/build.sh b/scripts/website/build.sh
index a921d3e9aa..7d9d19880a 100755
--- a/scripts/website/build.sh
+++ b/scripts/website/build.sh
@@ -36,15 +36,6 @@ if [ "${WEBSITE_INCLUDE_INITIALIZR}" = "auto" ]; then
   fi
 fi
 
-ensure_native_themes() {
-  if [ -f "${REPO_ROOT}/Themes/iOSModernTheme.res" ] \
-      && [ -f "${REPO_ROOT}/Themes/AndroidMaterialTheme.res" ]; then
-    return
-  fi
-  echo "Generating native theme .res files via build-native-themes.sh..." >&2
-  bash "${REPO_ROOT}/scripts/build-native-themes.sh"
-}
-
 bootstrap_local_cn1_snapshots() {
   if [ "${WEBSITE_BOOTSTRAP_CN1_SNAPSHOTS}" != "true" ]; then
     return
@@ -571,12 +562,6 @@ build_initializr_for_site() {
     return
   fi
 
-  # The initializr's live preview overlays the iOS Modern theme, which is
-  # bundled from the gitignored Themes/iOSModernTheme.res. Generate it now
-  # so the antrun copy in scripts/initializr/common/pom.xml has something
-  # to pick up.
-  ensure_native_themes
-
   echo "Building Initializr JavaScript bundle for website..." >&2
   (
     cd "${REPO_ROOT}/scripts/initializr"
@@ -638,12 +623,6 @@ build_playground_for_site() {
 
   bootstrap_local_cn1_snapshots
 
-  # The playground's live preview switches between iOS Modern and Android
-  # Material via Resources.openLayered. Both .res files are gitignored
-  # build artifacts; generate them now so the antrun copy in
-  # scripts/cn1playground/common/pom.xml has something to pick up.
-  ensure_native_themes
-
   echo "Building Playground JavaScript bundle for website..." >&2
   (
     cd "${REPO_ROOT}/scripts/cn1playground"