diff --git a/test-app/app/src/main/assets/app/tests/testPrimitiveCallbackReturns.js b/test-app/app/src/main/assets/app/tests/testPrimitiveCallbackReturns.js
index d206de91f..5fec0b5d4 100644
--- a/test-app/app/src/main/assets/app/tests/testPrimitiveCallbackReturns.js
+++ b/test-app/app/src/main/assets/app/tests/testPrimitiveCallbackReturns.js
@@ -49,41 +49,43 @@ describe("Primitive return values of JS callbacks", function () {
         "{}": function () { return {}; }
     };
 
-    // Captured from the boxed conversion; columns are z b c s i j f d.
+    // Columns are z b c s i j f d. A value converts only when the return type
+    // can hold it (whole numbers in range for integer types, float range for
+    // float, a one-character string for char); otherwise the binding throws.
     var expected = {
-        "0": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:0 ok:0 ex:ClassCastException ex:ClassCastException",
-        "1": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:1 ok:1 ex:ClassCastException ex:ClassCastException",
-        "-1": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:-1 ok:-1 ex:ClassCastException ex:ClassCastException",
-        "-0": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:0 ok:0 ex:ClassCastException ex:ClassCastException",
-        "2^31": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:2147483648 ex:ClassCastException ex:ClassCastException",
-        "-2^31-1": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:-2147483649 ex:ClassCastException ex:ClassCastException",
-        "2^40": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:1099511627776 ex:ClassCastException ex:ClassCastException",
-        "2^60": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:1152921504606846976 ex:ClassCastException ex:ClassCastException",
+        "0": "ex:ClassCastException ok:0 ex:ClassCastException ok:0 ok:0 ok:0 ok:0 ok:0",
+        "1": "ex:ClassCastException ok:1 ex:ClassCastException ok:1 ok:1 ok:1 ok:1 ok:1",
+        "-1": "ex:ClassCastException ok:-1 ex:ClassCastException ok:-1 ok:-1 ok:-1 ok:-1 ok:-1",
+        "-0": "ex:ClassCastException ok:0 ex:ClassCastException ok:0 ok:0 ok:0 ok:0 ok:0",
+        "2^31": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:2147483648 ok:2.14748365E+9 ok:2147483648",
+        "-2^31-1": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:-2147483649 ok:-2.14748365E+9 ok:-2147483649",
+        "2^40": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:1099511627776 ok:1.09951163E+12 ok:1099511627776",
+        "2^60": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:1152921504606846976 ok:1.1529215E+18 ok:1.152921504606847E+18",
         "1.5": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:1.5 ok:1.5",
-        "-1.5": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:-1.5",
-        "1e-40": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:1.0E-40",
-        "3.5e38": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:3.5E38",
-        "NaN": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:NaN",
-        "Infinity": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:Infinity",
-        "-Infinity": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:-Infinity",
-        "-2.5": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:-2.5",
+        "-1.5": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:-1.5 ok:-1.5",
+        "1e-40": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:9.9999999999999993E-41",
+        "3.5e38": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:3.5E+38",
+        "NaN": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:NaN ok:NaN",
+        "Infinity": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:Infinity ok:Infinity",
+        "-Infinity": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:-Infinity ok:-Infinity",
+        "-2.5": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:-2.5 ok:-2.5",
         "true": "ok:true ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException",
         "false": "ok:false ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException",
-        "'1'": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException",
-        "'a'": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException",
-        "null": "ok:false ok:0 ok:0 ok:0 ok:0 ok:0 ok:0.0 ok:0.0",
-        "undefined": "ok:false ok:0 ok:0 ok:0 ok:0 ok:0 ok:0.0 ok:0.0",
-        "Number(5)": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:5 ok:5 ex:ClassCastException ex:ClassCastException",
+        "'1'": "ex:ClassCastException ex:ClassCastException ok:49 ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException",
+        "'a'": "ex:ClassCastException ex:ClassCastException ok:97 ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException",
+        "null": "ok:false ok:0 ok:0 ok:0 ok:0 ok:0 ok:0 ok:0",
+        "undefined": "ok:false ok:0 ok:0 ok:0 ok:0 ok:0 ok:0 ok:0",
+        "Number(5)": "ex:ClassCastException ok:5 ex:ClassCastException ok:5 ok:5 ok:5 ok:5 ok:5",
         "Number(2.5)": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:2.5 ok:2.5",
         "Boolean(true)": "ok:true ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException",
-        "Boolean(false)": "ok:true ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException",
+        "Boolean(false)": "ok:false ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException",
         "long(5)": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:5 ex:ClassCastException ex:ClassCastException",
         "byte(2)": "ex:ClassCastException ok:2 ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException",
         "short(3)": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:3 ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException",
         "char('a')": "ex:ClassCastException ex:ClassCastException ok:97 ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException",
         "float(1.5)": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:1.5 ex:ClassCastException",
-        "double(2)": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:2.0",
-        "{}": "ok:false ok:0 ok:0 ok:0 ok:0 ok:0 ok:0.0 ok:0.0"
+        "double(2)": "ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ex:ClassCastException ok:2",
+        "{}": "ok:false ok:0 ok:0 ok:0 ok:0 ok:0 ok:0 ok:0"
     };
 
     var kinds = ["z", "b", "c", "s", "i", "j", "f", "d"];
diff --git a/test-app/app/src/main/java/com/tns/tests/PrimitiveReturnTest.java b/test-app/app/src/main/java/com/tns/tests/PrimitiveReturnTest.java
index 284084e14..96aac8ce7 100644
--- a/test-app/app/src/main/java/com/tns/tests/PrimitiveReturnTest.java
+++ b/test-app/app/src/main/java/com/tns/tests/PrimitiveReturnTest.java
@@ -1,5 +1,8 @@
 package com.tns.tests;
 
+import java.math.BigDecimal;
+import java.math.MathContext;
+
 /**
  * Calls each primitive-returning method of a JS implementation and reports either the
  * returned value or the class of what was thrown, so a spec can pin how JS return values
@@ -24,6 +27,15 @@ public interface Returns {
         double d();
     }
 
+    // Float.toString/Double.toString changed their shortest-digits algorithm
+    // across Android versions; BigDecimal rounding prints the same everywhere.
+    private static String format(double value, int digits) {
+        if (Double.isNaN(value) || Double.isInfinite(value)) {
+            return Double.toString(value);
+        }
+        return new BigDecimal(value).round(new MathContext(digits)).stripTrailingZeros().toString();
+    }
+
     public static String call(Returns r, String kind) {
         try {
             switch (kind) {
@@ -40,9 +52,9 @@ public static String call(Returns r, String kind) {
                 case "j":
                     return "ok:" + r.j();
                 case "f":
-                    return "ok:" + r.f();
+                    return "ok:" + format(r.f(), 9);
                 case "d":
-                    return "ok:" + r.d();
+                    return "ok:" + format(r.d(), 17);
                 default:
                     throw new IllegalArgumentException(kind);
             }
diff --git a/test-app/runtime/src/main/cpp/Runtime.cpp b/test-app/runtime/src/main/cpp/Runtime.cpp
index 7dca92805..dd45ea3d4 100644
--- a/test-app/runtime/src/main/cpp/Runtime.cpp
+++ b/test-app/runtime/src/main/cpp/Runtime.cpp
@@ -56,6 +56,7 @@
 
 #include <cfloat>
 #include <climits>
+#include <cstdint>
 #include <cmath>
 #include <cstring>
 
@@ -503,10 +504,12 @@ jobject Runtime::RunScript(JNIEnv* _env, jobject obj, jstring scriptFile) {
 }
 
 /*
- * The primitive-returning cases of JsArgToArrayConverter::ConvertArg that box
- * into exactly the declared wrapper type, which is all the generated binding's
- * cast accepts. Everything else keeps the boxed conversion, including the
- * values it turns into a ClassCastException or a defaulted null.
+ * A JS callback result for a primitive Java return type, converted only when
+ * the declared type can hold it: whole numbers in range for the integer types,
+ * a value within float range (or 0, NaN, +-Infinity) for float, any number for
+ * double, a one-character string for char. Anything else keeps the boxed
+ * conversion, whose result the generated binding rejects with a
+ * ClassCastException.
  */
 static bool TryGetPrimitiveReturnBits(Isolate* isolate,
                                       const Local<Value>& value, Type type,
@@ -516,49 +519,76 @@ static bool TryGetPrimitiveReturnBits(Isolate* isolate,
   }
 
   if (type == Type::Boolean) {
-    if (!value->IsBoolean() && !value->IsBooleanObject()) {
-      return false;
+    if (value->IsBoolean()) {
+      bits = value->IsTrue() ? 1 : 0;
+      return true;
+    }
+    if (value->IsBooleanObject()) {
+      bits = value.As<BooleanObject>()->ValueOf() ? 1 : 0;
+      return true;
     }
-    // ToBoolean, as the boxed path does: a Boolean object is always true.
-    bits = value->BooleanValue(isolate) ? 1 : 0;
-    return true;
-  }
-
-  // Number objects are left to the boxed path: reading one calls valueOf,
-  // which must not run twice if this path then declines.
-  if (!value->IsNumber()) {
     return false;
   }
 
-  if (type == Type::Int && value->IsInt32()) {
-    bits = value.As<Int32>()->Value();
+  if (type == Type::Char) {
+    Local<String> str;
+    if (value->IsString()) {
+      str = value.As<String>();
+    } else if (value->IsStringObject()) {
+      str = value.As<StringObject>()->ValueOf();
+    } else {
+      return false;
+    }
+    if (str->Length() != 1) {
+      return false;
+    }
+    uint16_t unit;
+    str->WriteV2(isolate, 0, 1, &unit);
+    bits = unit;
     return true;
   }
 
-  double d = value.As<Number>()->Value();
-  // Beyond int64 the boxed path's double -> int64 cast is undefined.
-  constexpr double kTwoPow63 = 9223372036854775808.0;
-  if (std::isfinite(d) && std::fabs(d) >= kTwoPow63) {
+  double d;
+  if (value->IsNumber()) {
+    d = value.As<Number>()->Value();
+  } else if (value->IsNumberObject()) {
+    d = value.As<NumberObject>()->ValueOf();
+  } else {
     return false;
   }
-  bool isWholeNumber =
-      std::isfinite(d) && d == static_cast<double>(static_cast<int64_t>(d));
 
+  bool isWhole = std::isfinite(d) && std::trunc(d) == d;
   switch (type) {
+    case Type::Byte:
+      if (isWhole && d >= INT8_MIN && d <= INT8_MAX) {
+        bits = static_cast<jbyte>(d);
+        return true;
+      }
+      return false;
+    case Type::Short:
+      if (isWhole && d >= INT16_MIN && d <= INT16_MAX) {
+        bits = static_cast<jshort>(d);
+        return true;
+      }
+      return false;
     case Type::Int:
-      if (isWholeNumber && INT_MIN <= d && d <= INT_MAX) {
+      if (isWhole && d >= INT32_MIN && d <= INT32_MAX) {
         bits = static_cast<jint>(d);
         return true;
       }
       return false;
     case Type::Long:
-      if (isWholeNumber) {
+      // 2^63 itself is not representable; the boxed path's handling of it is
+      // undefined, so it is left there.
+      if (isWhole && std::fabs(d) < 9223372036854775808.0) {
         bits = static_cast<jlong>(d);
         return true;
       }
       return false;
-    case Type::Float:
-      if (!isWholeNumber && FLT_MIN <= d && d <= FLT_MAX) {
+    case Type::Float: {
+      double magnitude = std::fabs(d);
+      if (!std::isfinite(d) || d == 0 ||
+          (magnitude >= FLT_MIN && magnitude <= FLT_MAX)) {
         float f = static_cast<jfloat>(d);
         int32_t raw;
         memcpy(&raw, &f, sizeof(raw));
@@ -566,12 +596,10 @@ static bool TryGetPrimitiveReturnBits(Isolate* isolate,
         return true;
       }
       return false;
+    }
     case Type::Double:
-      if (!isWholeNumber) {
-        memcpy(&bits, &d, sizeof(bits));
-        return true;
-      }
-      return false;
+      memcpy(&bits, &d, sizeof(bits));
+      return true;
     default:
       return false;
   }
diff --git a/test-app/runtime/src/main/java/com/tns/Runtime.java b/test-app/runtime/src/main/java/com/tns/Runtime.java
index 5e1d5e302..3aa1709e4 100644
--- a/test-app/runtime/src/main/java/com/tns/Runtime.java
+++ b/test-app/runtime/src/main/java/com/tns/Runtime.java
@@ -1537,14 +1537,13 @@ private static Object discardCall(String methodName, Class<?> retType, String re
     }
 
     /*
-     * For return types the native side can hand back as raw bits instead of a
-     * boxed object: it writes {bits, 1} here and returns null, or leaves the
-     * array untouched and returns the boxed value as before.
+     * For primitive return types the native side hands the converted value back
+     * as raw bits: it writes {bits, 1} here and returns null, or leaves the
+     * array untouched and returns a boxed value from the generic conversion.
      */
     private static long[] newPrimitiveResult(int returnType) {
-        boolean raw = returnType == TypeIDs.Boolean || returnType == TypeIDs.Int || returnType == TypeIDs.Long
-                || returnType == TypeIDs.Float || returnType == TypeIDs.Double;
-        return raw ? new long[2] : null;
+        boolean primitive = returnType >= TypeIDs.Boolean && returnType <= TypeIDs.Double;
+        return primitive ? new long[2] : null;
     }
 
     private static Object takePrimitiveResult(Object nativeResult, int returnType, long[] primitiveResult) {
@@ -1555,6 +1554,12 @@ private static Object takePrimitiveResult(Object nativeResult, int returnType, l
         long bits = primitiveResult[0];
         if (returnType == TypeIDs.Boolean) {
             return bits != 0;
+        } else if (returnType == TypeIDs.Char) {
+            return (char) bits;
+        } else if (returnType == TypeIDs.Byte) {
+            return (byte) bits;
+        } else if (returnType == TypeIDs.Short) {
+            return (short) bits;
         } else if (returnType == TypeIDs.Int) {
             return (int) bits;
         } else if (returnType == TypeIDs.Long) {