diff --git a/.github/workflows/run-java-test.yaml b/.github/workflows/run-java-test.yaml
index 647384f056..240ec4217d 100644
--- a/.github/workflows/run-java-test.yaml
+++ b/.github/workflows/run-java-test.yaml
@@ -252,6 +252,14 @@ jobs:
           # Delete model files to save space
           rm -rf sherpa-onnx-punct-*
 
+      - name:  Run java test (Offline add diacritics)
+        shell: bash
+        run: |
+          cd ./java-api-examples
+          ./run-offline-add-diacritics.sh
+          # Delete model files to save space
+          rm -rf catt_eo_model_onnx
+
       - name:  Run java test (speaker diarization)
         shell: bash
         run: |
diff --git a/java-api-examples/OfflineAddDiacritics.java b/java-api-examples/OfflineAddDiacritics.java
new file mode 100644
index 0000000000..f1da5031ea
--- /dev/null
+++ b/java-api-examples/OfflineAddDiacritics.java
@@ -0,0 +1,38 @@
+// Copyright 2026 Matias Lin
+
+// This file shows how to use a CATT diacritization model to add diacritics to Arabic text.
+import com.k2fsa.sherpa.onnx.*;
+
+public class OfflineAddDiacritics {
+  public static void main(String[] args) {
+    // please download the model from
+    // https://github.com/abjadai/catt/releases/download/v2/eo_model_onnx.zip
+    String cattEncoder = "./catt_eo_model_onnx/encoder.onnx";
+    String cattDecoder = "./catt_eo_model_onnx/decoder.onnx";
+    OfflineDiacritizationModelConfig modelConfig =
+        OfflineDiacritizationModelConfig.builder()
+            .setCattEncoder(cattEncoder)
+            .setCattDecoder(cattDecoder)
+            .setNumThreads(1)
+            .setDebug(true)
+            .build();
+    OfflineDiacritizationConfig config =
+        OfflineDiacritizationConfig.builder().setModel(modelConfig).build();
+
+    OfflineDiacritization diacrt = new OfflineDiacritization(config);
+
+    String[] sentences =
+        new String[] {
+          "وقالت مجلة نيوزويك الأمريكية التحديث الجديد ل إنستجرام يمكن أن يساهم في إيقاف وكشف الحسابات المزورة بسهولة شديدة",
+          "اللغة العربية من أقدم اللغات السامية",
+        };
+
+    System.out.println("---");
+    for (String text : sentences) {
+      String out = diacrt.addDiacritics(text);
+      System.out.printf("Input: %s\n", text);
+      System.out.printf("Output: %s\n", out);
+      System.out.println("---");
+    }
+  }
+}
diff --git a/java-api-examples/run-offline-add-diacritics.sh b/java-api-examples/run-offline-add-diacritics.sh
new file mode 100755
index 0000000000..ef9099be79
--- /dev/null
+++ b/java-api-examples/run-offline-add-diacritics.sh
@@ -0,0 +1,37 @@
+#!/usr/bin/env bash
+
+set -ex
+
+if [[ ! -f ../build/lib/libsherpa-onnx-jni.dylib  && ! -f ../build/lib/libsherpa-onnx-jni.so ]]; then
+  mkdir -p ../build
+  pushd ../build
+  cmake \
+    -DSHERPA_ONNX_ENABLE_PYTHON=OFF \
+    -DSHERPA_ONNX_ENABLE_TESTS=OFF \
+    -DSHERPA_ONNX_ENABLE_CHECK=OFF \
+    -DBUILD_SHARED_LIBS=ON \
+    -DSHERPA_ONNX_ENABLE_PORTAUDIO=OFF \
+    -DSHERPA_ONNX_ENABLE_JNI=ON \
+    ..
+
+  make -j4
+  ls -lh lib
+  popd
+fi
+
+if [ ! -f ../sherpa-onnx/java-api/build/sherpa-onnx.jar ]; then
+  pushd ../sherpa-onnx/java-api
+  make
+  popd
+fi
+
+if [[ ! -f "./catt_eo_model_onnx/encoder.onnx" || ! -f "./catt_eo_model_onnx/decoder.onnx"  ]]; then
+  curl -SL -O https://github.com/abjadai/catt/releases/download/v2/eo_model_onnx.zip
+  unzip eo_model_onnx.zip -d catt_eo_model_onnx
+  rm eo_model_onnx.zip
+fi
+
+java \
+  -Djava.library.path=$PWD/../build/lib \
+  -cp ../sherpa-onnx/java-api/build/sherpa-onnx.jar \
+  ./OfflineAddDiacritics.java
diff --git a/sherpa-onnx/java-api/Makefile b/sherpa-onnx/java-api/Makefile
index fcb61fcda0..56c3688336 100644
--- a/sherpa-onnx/java-api/Makefile
+++ b/sherpa-onnx/java-api/Makefile
@@ -117,6 +117,10 @@ java_files += OfflineSpeechDenoiser.java
 java_files += OnlineSpeechDenoiserConfig.java
 java_files += OnlineSpeechDenoiser.java
 
+java_files += OfflineDiacritizationModelConfig.java
+java_files += OfflineDiacritizationConfig.java
+java_files += OfflineDiacritization.java
+
 class_files := $(java_files:%.java=%.class)
 
 java_files := $(addprefix src/main/java/$(package_dir)/,$(java_files))
diff --git a/sherpa-onnx/java-api/src/main/java/com/k2fsa/sherpa/onnx/OfflineDiacritization.java b/sherpa-onnx/java-api/src/main/java/com/k2fsa/sherpa/onnx/OfflineDiacritization.java
new file mode 100644
index 0000000000..1e2b08f24a
--- /dev/null
+++ b/sherpa-onnx/java-api/src/main/java/com/k2fsa/sherpa/onnx/OfflineDiacritization.java
@@ -0,0 +1,39 @@
+// Copyright 2026 Matias Lin
+
+package com.k2fsa.sherpa.onnx;
+
+public class OfflineDiacritization {
+    private long ptr = 0;
+
+    public OfflineDiacritization(OfflineDiacritizationConfig config) {
+        LibraryLoader.maybeLoad();
+        ptr = newFromFile(config);
+        if (ptr == 0) {
+            throw new IllegalArgumentException("Invalid OfflineDiacritizationConfig: failed to create native OfflineDiacritization");
+        }
+    }
+
+    public String addDiacritics(String text) {
+        return addDiacritics(ptr, text);
+    }
+
+    @Override
+    protected void finalize() throws Throwable {
+        release();
+    }
+
+    // You'd better call it manually if it is not used anymore
+    public void release() {
+        if (this.ptr == 0) {
+            return;
+        }
+        delete(this.ptr);
+        this.ptr = 0;
+    }
+
+    private native void delete(long ptr);
+
+    private native long newFromFile(OfflineDiacritizationConfig config);
+
+    private native String addDiacritics(long ptr, String text);
+}
diff --git a/sherpa-onnx/java-api/src/main/java/com/k2fsa/sherpa/onnx/OfflineDiacritizationConfig.java b/sherpa-onnx/java-api/src/main/java/com/k2fsa/sherpa/onnx/OfflineDiacritizationConfig.java
new file mode 100644
index 0000000000..39334b2bd9
--- /dev/null
+++ b/sherpa-onnx/java-api/src/main/java/com/k2fsa/sherpa/onnx/OfflineDiacritizationConfig.java
@@ -0,0 +1,32 @@
+// Copyright 2026 Matias Lin
+
+package com.k2fsa.sherpa.onnx;
+
+public class OfflineDiacritizationConfig {
+    private final OfflineDiacritizationModelConfig model;
+
+    private OfflineDiacritizationConfig(Builder builder) {
+        this.model = builder.model;
+    }
+
+    public static Builder builder() {
+        return new Builder();
+    }
+
+    public OfflineDiacritizationModelConfig getModel() {
+        return model;
+    }
+
+    public static class Builder {
+        private OfflineDiacritizationModelConfig model = OfflineDiacritizationModelConfig.builder().build();
+
+        public OfflineDiacritizationConfig build() {
+            return new OfflineDiacritizationConfig(this);
+        }
+
+        public Builder setModel(OfflineDiacritizationModelConfig model) {
+            this.model = model;
+            return this;
+        }
+    }
+}
diff --git a/sherpa-onnx/java-api/src/main/java/com/k2fsa/sherpa/onnx/OfflineDiacritizationModelConfig.java b/sherpa-onnx/java-api/src/main/java/com/k2fsa/sherpa/onnx/OfflineDiacritizationModelConfig.java
new file mode 100644
index 0000000000..a41aaf1611
--- /dev/null
+++ b/sherpa-onnx/java-api/src/main/java/com/k2fsa/sherpa/onnx/OfflineDiacritizationModelConfig.java
@@ -0,0 +1,68 @@
+// Copyright 2026 Matias Lin
+
+package com.k2fsa.sherpa.onnx;
+
+public class OfflineDiacritizationModelConfig {
+    private final String cattEncoder;
+    private final String cattDecoder;
+    private final int numThreads;
+    private final boolean debug;
+    private final String provider;
+
+    private OfflineDiacritizationModelConfig(Builder builder) {
+        this.cattEncoder = builder.cattEncoder;
+        this.cattDecoder = builder.cattDecoder;
+        this.numThreads = builder.numThreads;
+        this.debug = builder.debug;
+        this.provider = builder.provider;
+    }
+
+    public static Builder builder() {
+        return new Builder();
+    }
+
+    public String getCattEncoder() {
+        return cattEncoder;
+    }
+
+    public String getCattDecoder() {
+        return cattDecoder;
+    }
+
+    public static class Builder {
+        private String cattEncoder = "";
+        private String cattDecoder = "";
+        private int numThreads = 1;
+        private boolean debug = true;
+        private String provider = "cpu";
+
+        public OfflineDiacritizationModelConfig build() {
+            return new OfflineDiacritizationModelConfig(this);
+        }
+
+        public Builder setCattEncoder(String cattEncoder) {
+            this.cattEncoder = cattEncoder;
+            return this;
+        }
+
+        public Builder setCattDecoder(String cattDecoder) {
+            this.cattDecoder = cattDecoder;
+            return this;
+        }
+
+        public Builder setNumThreads(int numThreads) {
+            this.numThreads = numThreads;
+            return this;
+        }
+
+        public Builder setDebug(boolean debug) {
+            this.debug = debug;
+            return this;
+        }
+
+        public Builder setProvider(String provider) {
+            this.provider = provider;
+            return this;
+        }
+    }
+}
diff --git a/sherpa-onnx/jni/CMakeLists.txt b/sherpa-onnx/jni/CMakeLists.txt
index 3996afb43a..d0ce4e3f2e 100644
--- a/sherpa-onnx/jni/CMakeLists.txt
+++ b/sherpa-onnx/jni/CMakeLists.txt
@@ -15,6 +15,7 @@ set(sources
   common.cc
   jni.cc
   keyword-spotter.cc
+  offline-diacritization.cc
   offline-punctuation.cc
   offline-recognizer.cc
   offline-speech-denoiser.cc
diff --git a/sherpa-onnx/jni/offline-diacritization.cc b/sherpa-onnx/jni/offline-diacritization.cc
new file mode 100644
index 0000000000..16cbcaecae
--- /dev/null
+++ b/sherpa-onnx/jni/offline-diacritization.cc
@@ -0,0 +1,124 @@
+// sherpa-onnx/jni/offline-diacritization.cc
+//
+// Copyright (c)  2026  Matias Lin
+
+#include "sherpa-onnx/csrc/offline-diacritization.h"
+
+#include <string>
+
+#include "sherpa-onnx/csrc/macros.h"
+#include "sherpa-onnx/jni/common.h"
+
+namespace sherpa_onnx {
+
+static OfflineDiacritizationConfig GetOfflineDiacritizationConfig(
+    JNIEnv *env, jobject config, bool *ok) {
+  OfflineDiacritizationConfig ans;
+
+  jclass cls = env->GetObjectClass(config);
+  jfieldID fid;
+
+  fid = env->GetFieldID(
+      cls, "model", "Lcom/k2fsa/sherpa/onnx/OfflineDiacritizationModelConfig;");
+  jobject model_config = env->GetObjectField(config, fid);
+  jclass model_config_cls = env->GetObjectClass(model_config);
+
+  SHERPA_ONNX_JNI_READ_STRING(ans.model.catt_encoder, cattEncoder,
+                              model_config_cls, model_config);
+
+  SHERPA_ONNX_JNI_READ_STRING(ans.model.catt_decoder, cattDecoder,
+                              model_config_cls, model_config);
+
+  SHERPA_ONNX_JNI_READ_INT(ans.model.num_threads, numThreads, model_config_cls,
+                           model_config);
+
+  SHERPA_ONNX_JNI_READ_BOOL(ans.model.debug, debug, model_config_cls,
+                            model_config);
+
+  SHERPA_ONNX_JNI_READ_STRING(ans.model.provider, provider, model_config_cls,
+                              model_config);
+
+  *ok = true;
+  return ans;
+}
+
+}  // namespace sherpa_onnx
+
+SHERPA_ONNX_EXTERN_C
+JNIEXPORT jlong JNICALL
+Java_com_k2fsa_sherpa_onnx_OfflineDiacritization_newFromAsset(
+    JNIEnv *env, jobject /*obj*/, jobject asset_manager, jobject _config) {
+#if __ANDROID_API__ >= 9
+  AAssetManager *mgr = AAssetManager_fromJava(env, asset_manager);
+  if (!mgr) {
+    SHERPA_ONNX_LOGE("Failed to get asset manager: %p", mgr);
+    return 0;
+  }
+#endif
+  bool ok = false;
+  auto config = sherpa_onnx::GetOfflineDiacritizationConfig(env, _config, &ok);
+
+  if (!ok) {
+    SHERPA_ONNX_LOGE("Please read the error message carefully");
+    return 0;
+  }
+
+  SHERPA_ONNX_LOGE("config:\n%s", config.ToString().c_str());
+
+  auto model = new sherpa_onnx::OfflineDiacritization(
+#if __ANDROID_API__ >= 9
+      mgr,
+#endif
+      config);
+
+  return (jlong)model;
+}
+
+SHERPA_ONNX_EXTERN_C
+JNIEXPORT jlong JNICALL
+Java_com_k2fsa_sherpa_onnx_OfflineDiacritization_newFromFile(JNIEnv *env,
+                                                             jobject /*obj*/,
+                                                             jobject _config) {
+  bool ok = false;
+  auto config = sherpa_onnx::GetOfflineDiacritizationConfig(env, _config, &ok);
+
+  if (!ok) {
+    SHERPA_ONNX_LOGE("Please read the error message carefully");
+    return 0;
+  }
+
+  SHERPA_ONNX_LOGE("config:\n%s", config.ToString().c_str());
+
+  if (!config.Validate()) {
+    SHERPA_ONNX_LOGE("Errors found in config!");
+    return 0;
+  }
+
+  auto model = new sherpa_onnx::OfflineDiacritization(config);
+
+  return (jlong)model;
+}
+
+SHERPA_ONNX_EXTERN_C
+JNIEXPORT void JNICALL Java_com_k2fsa_sherpa_onnx_OfflineDiacritization_delete(
+    JNIEnv * /*env*/, jobject /*obj*/, jlong ptr) {
+  delete reinterpret_cast<sherpa_onnx::OfflineDiacritization *>(ptr);
+}
+
+SHERPA_ONNX_EXTERN_C
+JNIEXPORT jstring JNICALL
+Java_com_k2fsa_sherpa_onnx_OfflineDiacritization_addDiacritics(JNIEnv *env,
+                                                               jobject /*obj*/,
+                                                               jlong ptr,
+                                                               jstring text) {
+  auto diacrt =
+      reinterpret_cast<const sherpa_onnx::OfflineDiacritization *>(ptr);
+
+  const char *ptext = env->GetStringUTFChars(text, nullptr);
+
+  std::string result = diacrt->AddDiacritics(ptext);
+
+  env->ReleaseStringUTFChars(text, ptext);
+
+  return SafeNewStringUTF(env, result);
+}
diff --git a/sherpa-onnx/jni/sherpa-onnx-symbols.exp b/sherpa-onnx/jni/sherpa-onnx-symbols.exp
index bb3ef6c313..7353a2b603 100644
--- a/sherpa-onnx/jni/sherpa-onnx-symbols.exp
+++ b/sherpa-onnx/jni/sherpa-onnx-symbols.exp
@@ -13,6 +13,10 @@ _Java_com_k2fsa_sherpa_onnx_KeywordSpotter_isReady
 _Java_com_k2fsa_sherpa_onnx_KeywordSpotter_newFromAsset
 _Java_com_k2fsa_sherpa_onnx_KeywordSpotter_newFromFile
 _Java_com_k2fsa_sherpa_onnx_KeywordSpotter_reset
+_Java_com_k2fsa_sherpa_onnx_OfflineDiacritization_addDiacritics
+_Java_com_k2fsa_sherpa_onnx_OfflineDiacritization_delete
+_Java_com_k2fsa_sherpa_onnx_OfflineDiacritization_newFromAsset
+_Java_com_k2fsa_sherpa_onnx_OfflineDiacritization_newFromFile
 _Java_com_k2fsa_sherpa_onnx_OfflinePunctuation_addPunctuation
 _Java_com_k2fsa_sherpa_onnx_OfflinePunctuation_delete
 _Java_com_k2fsa_sherpa_onnx_OfflinePunctuation_newFromAsset