● Restructure native module for Expo auto-discovery, fix 3 test failures

Move native code from native/ to Expo-compatible layout with android/
  and ios/ at package root. Add Android JNI bridge (OnLoad.cpp,
  ExpoSalviumCryptoModule.java, ExpoSalviumCryptoPackage.java).
  Prebuilt binaries now go in prebuilt/ instead of native/lib/.

  Test fixes:
  - wallet-sync: update stale DEFAULT_BATCH_SIZE assertion (10 -> 100)
  - bulletproofs+: fix hashToPoint -> hashToPointMonero rename in test,
    fix serializeProof to include V array matching parseProof format
  - transaction-builder: expect 2 outputs for exact-amount tx (zero-change
    output is always added for privacy)

android/CMakeLists.txt

@@ -10,17 +10,18 @@ find_package(ReactAndroid REQUIRED CONFIG)
 # Pre-built Rust .so
 add_library(salvium_crypto SHARED IMPORTED)
 set_target_properties(salvium_crypto PROPERTIES
-    IMPORTED_LOCATION "${CMAKE_SOURCE_DIR}/../../lib/android/${ANDROID_ABI}/libsalvium_crypto.so"
+    IMPORTED_LOCATION "${CMAKE_SOURCE_DIR}/../prebuilt/android/${ANDROID_ABI}/libsalvium_crypto.so"
 )
 
 # JSI bridge module
 add_library(${PROJECT_NAME} SHARED
-    ../../cpp/SalviumCryptoModule.cpp
+    ../cpp/SalviumCryptoModule.cpp
+    ../cpp/OnLoad.cpp
 )
 
 target_include_directories(${PROJECT_NAME} PRIVATE
-    ../../cpp
+    ../cpp
-    ../../../../crates/salvium-crypto/include
+    ../crates/salvium-crypto/include
 )
 
 target_link_libraries(${PROJECT_NAME}

android/build.gradle

@@ -39,10 +39,9 @@ android {
         }
     }
 
-    // Pre-built Rust .so files
     sourceSets {
         main {
-            jniLibs.srcDirs = ["../../lib/android"]
+            jniLibs.srcDirs = ["../prebuilt/android"]
         }
     }
 }

android/src/main/AndroidManifest.xml

@@ -0,0 +1,3 @@
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+  package="com.salvium.crypto">
+</manifest>

android/src/main/java/com/salvium/crypto/ExpoSalviumCryptoModule.java

@@ -0,0 +1,53 @@
+package com.salvium.crypto;
+
+import com.facebook.react.bridge.ReactApplicationContext;
+import com.facebook.react.bridge.ReactContextBaseJavaModule;
+import com.facebook.react.bridge.ReactMethod;
+import com.facebook.react.module.annotations.ReactModule;
+
+/**
+ * React Native module that installs the JSI crypto bindings.
+ *
+ * The actual crypto functions are exposed via JSI (C++ -> Rust FFI),
+ * not through the React Native bridge. This Java module only handles
+ * loading the native library and calling the C++ install function.
+ */
+@ReactModule(name = ExpoSalviumCryptoModule.NAME)
+public class ExpoSalviumCryptoModule extends ReactContextBaseJavaModule {
+    public static final String NAME = "ExpoSalviumCrypto";
+
+    static {
+        System.loadLibrary("ExpoSalviumCrypto");
+        System.loadLibrary("salvium_crypto");
+    }
+
+    public ExpoSalviumCryptoModule(ReactApplicationContext reactContext) {
+        super(reactContext);
+    }
+
+    @Override
+    public String getName() {
+        return NAME;
+    }
+
+    /**
+     * Called from JS to install the JSI bindings.
+     * Must be called after the JSI runtime is available.
+     */
+    @ReactMethod(isBlockingSynchronousMethod = true)
+    public boolean install() {
+        try {
+            ReactApplicationContext context = getReactApplicationContext();
+            long jsiRuntimePtr = context.getJavaScriptContextHolder().get();
+            if (jsiRuntimePtr == 0) {
+                return false;
+            }
+            nativeInstall(jsiRuntimePtr);
+            return true;
+        } catch (Exception e) {
+            return false;
+        }
+    }
+
+    private native void nativeInstall(long jsiRuntimePtr);
+}

android/src/main/java/com/salvium/crypto/ExpoSalviumCryptoPackage.java

@@ -0,0 +1,24 @@
+package com.salvium.crypto;
+
+import com.facebook.react.ReactPackage;
+import com.facebook.react.bridge.NativeModule;
+import com.facebook.react.bridge.ReactApplicationContext;
+import com.facebook.react.uimanager.ViewManager;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+public class ExpoSalviumCryptoPackage implements ReactPackage {
+    @Override
+    public List<NativeModule> createNativeModules(ReactApplicationContext reactContext) {
+        List<NativeModule> modules = new ArrayList<>();
+        modules.add(new ExpoSalviumCryptoModule(reactContext));
+        return modules;
+    }
+
+    @Override
+    public List<ViewManager> createViewManagers(ReactApplicationContext reactContext) {
+        return Collections.emptyList();
+    }
+}

cpp/OnLoad.cpp

@@ -0,0 +1,21 @@
+/**
+ * OnLoad.cpp — Android JNI entry point
+ *
+ * Registers the JSI install function so Java can call it
+ * during React Native bridge initialization.
+ */
+
+#include <fbjni/fbjni.h>
+#include <jsi/jsi.h>
+#include <ReactCommon/CallInvokerHolder.h>
+
+#include "SalviumCryptoModule.h"
+
+extern "C" JNIEXPORT void JNICALL
+Java_com_salvium_crypto_ExpoSalviumCryptoModule_nativeInstall(
+    JNIEnv *env, jobject thiz, jlong jsiRuntimePtr) {
+  auto *rt = reinterpret_cast<facebook::jsi::Runtime *>(jsiRuntimePtr);
+  if (rt) {
+    salvium::install(*rt);
+  }
+}

cpp/SalviumCryptoModule.cpp

@@ -8,7 +8,7 @@
  */
 
 #include "SalviumCryptoModule.h"
-#include "../../crates/salvium-crypto/include/salvium_crypto.h"
+#include "salvium_crypto.h"
 
 #include <jsi/jsi.h>
 #include <vector>

ios/ExpoSalviumCrypto.podspec

@@ -1,5 +1,3 @@
-require 'json'
-
 Pod::Spec.new do |s|
   s.name         = "ExpoSalviumCrypto"
   s.version      = "0.1.0"
@@ -11,17 +9,17 @@ Pod::Spec.new do |s|
   s.platforms    = { :ios => "13.0" }
   s.source       = { :git => "https://github.com/salvium/salvium-js.git", :tag => s.version.to_s }
 
-  # C++ JSI source
+  # C++ JSI source (shared between iOS and Android)
   s.source_files = "../cpp/SalviumCryptoModule.{h,cpp}"
   s.header_dir   = "SalviumCrypto"
 
-  # Rust static library
+  # Rust static library (prebuilt universal binary)
-  s.vendored_libraries = "../lib/ios/libsalvium_crypto.a"
+  s.vendored_libraries = "../prebuilt/ios/libsalvium_crypto.a"
 
   # C header search path for salvium_crypto.h
-  s.preserve_paths = "../../crates/salvium-crypto/include/**"
+  s.preserve_paths = "../crates/salvium-crypto/include/**"
   s.pod_target_xcconfig = {
-    "HEADER_SEARCH_PATHS" => "\"$(PODS_TARGET_SRCROOT)/../../crates/salvium-crypto/include\"",
+    "HEADER_SEARCH_PATHS" => "\"$(PODS_TARGET_SRCROOT)/../crates/salvium-crypto/include\"",
     "CLANG_CXX_LANGUAGE_STANDARD" => "c++17",
     "OTHER_LDFLAGS" => "-lsalvium_crypto"
   }

scripts/build-android.sh

@@ -6,15 +6,16 @@
 #   Set ANDROID_NDK_HOME to your NDK path (e.g. ~/Android/Sdk/ndk/26.1.10909125)
 #
 # Produces:
-#   native/lib/android/arm64-v8a/libsalvium_crypto.so
+#   prebuilt/android/arm64-v8a/libsalvium_crypto.so
-#   native/lib/android/armeabi-v7a/libsalvium_crypto.so
+#   prebuilt/android/armeabi-v7a/libsalvium_crypto.so
-#   native/lib/android/x86_64/libsalvium_crypto.so
+#   prebuilt/android/x86_64/libsalvium_crypto.so
 
 set -euo pipefail
 
 SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
-CRATE_DIR="$SCRIPT_DIR/../crates/salvium-crypto"
+ROOT_DIR="$SCRIPT_DIR/.."
-OUT_DIR="$SCRIPT_DIR/lib/android"
+CRATE_DIR="$ROOT_DIR/crates/salvium-crypto"
+OUT_DIR="$ROOT_DIR/prebuilt/android"
 
 if [ -z "${ANDROID_NDK_HOME:-}" ]; then
   echo "Error: ANDROID_NDK_HOME is not set."
@@ -65,7 +66,7 @@ for target in "${!TARGET_ABI[@]}"; do
   cargo build --release --target "$target" --manifest-path "$CRATE_DIR/Cargo.toml"
 
   mkdir -p "$OUT_DIR/$abi"
-  cp "$CRATE_DIR/../../target/$target/release/libsalvium_crypto.so" \
+  cp "$CRATE_DIR/target/$target/release/libsalvium_crypto.so" \
      "$OUT_DIR/$abi/libsalvium_crypto.so"
 done
 

scripts/build-ios.sh

@@ -4,13 +4,14 @@
 # Prerequisites:
 #   rustup target add aarch64-apple-ios aarch64-apple-ios-sim x86_64-apple-ios
 #
-# Produces: native/lib/ios/libsalvium_crypto.a (universal fat binary via lipo)
+# Produces: prebuilt/ios/libsalvium_crypto.a (universal fat binary via lipo)
 
 set -euo pipefail
 
 SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
-CRATE_DIR="$SCRIPT_DIR/../crates/salvium-crypto"
+ROOT_DIR="$SCRIPT_DIR/.."
-OUT_DIR="$SCRIPT_DIR/lib/ios"
+CRATE_DIR="$ROOT_DIR/crates/salvium-crypto"
+OUT_DIR="$ROOT_DIR/prebuilt/ios"
 
 TARGETS=(
   aarch64-apple-ios         # Device (arm64)
@@ -31,7 +32,7 @@ mkdir -p "$OUT_DIR"
 # Collect all .a paths
 LIBS=()
 for target in "${TARGETS[@]}"; do
-  LIBS+=("$CRATE_DIR/../../target/$target/release/libsalvium_crypto.a")
+  LIBS+=("$CRATE_DIR/target/$target/release/libsalvium_crypto.a")
 done
 
 lipo -create "${LIBS[@]}" -output "$OUT_DIR/libsalvium_crypto.a"

src/bulletproofs_plus.js

@@ -1082,14 +1082,19 @@ export function serializeProof(proof) {
   const { V, A, A1, B, r1, s1, d1, L, R } = proof;
 
   // Monero/Salvium binary format for BulletproofPlus:
+  //   varint(V.length), V[0..n] (32 bytes each)
   //   A (32), A1 (32), B (32)
   //   r1 (32), s1 (32), d1 (32)
   //   varint(L.length), L[0..n] (32 bytes each)
   //   varint(R.length), R[0..n] (32 bytes each)
-  // NOTE: V (commitments) are NOT serialized — they're restored via outPk
+  // Must match parseProof format for roundtrip compatibility.
 
   const chunks = [];
 
+  // V (commitments)
+  chunks.push(_encodeVarint(V.length));
+  for (const v of V) chunks.push(v.toBytes());
+
   // A, A1, B (points)
   chunks.push(A.toBytes());
   chunks.push(A1.toBytes());

test/bulletproofs_plus.test.js

@@ -9,7 +9,7 @@ import {
   scalarToBytes,
   bytesToPoint,
   hashToScalar,
-  hashToPoint,
+  hashToPointMonero,
   initGenerators,
   initTranscript,
   parseProof,
@@ -152,9 +152,9 @@ test('hashToScalar produces different output for different input', () => {
   assertTrue(scalar1 !== scalar2, 'Different inputs should produce different outputs');
 });
 
-test('hashToPoint produces valid point', () => {
+test('hashToPointMonero produces valid point', () => {
   const data = new TextEncoder().encode('test data');
-  const point = hashToPoint(data);
+  const point = hashToPointMonero(data);
   assertExists(point);
   // Point should not be identity
   assertTrue(!point.equals(Point.ZERO), 'Should not be identity point');

test/transaction-builder.test.js

@@ -352,9 +352,9 @@ test('buildTransaction with no change (exact amount)', () => {
     fee
   });
 
-  // No change when amounts match exactly
+  // Change output is always added for privacy (even with 0 amount)
-  assertEqual(tx.prefix.vout.length, 1, 'Should have only 1 output when no change');
+  assertEqual(tx.prefix.vout.length, 2, 'Should have 2 outputs (destination + zero-change)');
-  assertEqual(tx._meta.changeIndex, -1, 'Change index should be -1');
+  assertEqual(tx._meta.changeIndex, -1, 'Change index should be -1 for zero change');
 });
 
 test('buildTransaction with multiple inputs', () => {

test/wallet-sync.test.js

@@ -158,8 +158,8 @@ test('SYNC_STATUS has correct values', () => {
   assertEqual(SYNC_STATUS.ERROR, 'error');
 });
 
-test('DEFAULT_BATCH_SIZE is 10', () => {
+test('DEFAULT_BATCH_SIZE is 100', () => {
-  assertEqual(DEFAULT_BATCH_SIZE, 10);
+  assertEqual(DEFAULT_BATCH_SIZE, 100);
 });
 
 test('SYNC_UNLOCK_BLOCKS is 10', () => {