[autofix.ci] apply automated fixes

Navigator properties (userAgent, platform, hardwareConcurrency) were
incorrectly writable, allowing code to modify these standard read-only
properties. This fixes the behavior to match Node.js where these
properties have getters but no setters.

Changes:
- Replace putDirect with putDirectCustomAccessor for navigator properties
- Create dedicated getter functions for each property
- Preserve existing platform detection logic and TODO comments
- Add comprehensive tests for the new behavior

Behavior change:
- Before: navigator.userAgent = "x" would change the value
- After: navigator.userAgent = "x" silently ignored (Node.js compatible)

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/bun.js/bindings/ZigGlobalObject.cpp

@@ -257,6 +257,58 @@ extern "C" unsigned getJSCBytecodeCacheVersion()
     return getWebKitBytecodeCacheVersion();
 }
 
+// Navigator property getters - defined early to be available in lambdas
+JSC_DEFINE_CUSTOM_GETTER(navigatorUserAgentGetter,
+    (JSC::JSGlobalObject * globalObject, JSC::EncodedJSValue thisValue,
+        JSC::PropertyName))
+{
+    UNUSED_PARAM(thisValue);
+    auto& vm = JSC::getVM(globalObject);
+    auto str = WTF::String::fromUTF8(Bun__userAgent);
+    return JSC::JSValue::encode(JSC::jsString(vm, str));
+}
+
+JSC_DEFINE_CUSTOM_GETTER(navigatorPlatformGetter,
+    (JSC::JSGlobalObject * globalObject, JSC::EncodedJSValue thisValue,
+        JSC::PropertyName))
+{
+    UNUSED_PARAM(thisValue);
+    auto& vm = JSC::getVM(globalObject);
+// https://developer.mozilla.org/en-US/docs/Web/API/Navigator/platform
+// https://github.com/oven-sh/bun/issues/4588
+#if OS(DARWIN)
+    return JSC::JSValue::encode(JSC::jsString(vm, String("MacIntel"_s)));
+#elif OS(WINDOWS)
+    return JSC::JSValue::encode(JSC::jsString(vm, String("Win32"_s)));
+#elif OS(LINUX)
+    return JSC::JSValue::encode(JSC::jsString(vm, String("Linux x86_64"_s)));
+#else
+    return JSC::JSValue::encode(JSC::jsString(vm, String("Unknown"_s)));
+#endif
+}
+
+JSC_DEFINE_CUSTOM_GETTER(navigatorHardwareConcurrencyGetter,
+    (JSC::JSGlobalObject * globalObject, JSC::EncodedJSValue thisValue,
+        JSC::PropertyName))
+{
+    UNUSED_PARAM(thisValue);
+    auto& vm = JSC::getVM(globalObject);
+    UNUSED_PARAM(vm);
+    int cpuCount = 0;
+#ifdef __APPLE__
+    size_t count_len = sizeof(cpuCount);
+    sysctlbyname("hw.logicalcpu", &cpuCount, &count_len, NULL, 0);
+#elif OS(WINDOWS)
+    SYSTEM_INFO sysinfo;
+    GetSystemInfo(&sysinfo);
+    cpuCount = sysinfo.dwNumberOfProcessors;
+#else
+    // TODO: windows
+    cpuCount = sysconf(_SC_NPROCESSORS_ONLN);
+#endif
+    return JSC::JSValue::encode(JSC::jsNumber(cpuCount));
+}
+
 extern "C" void JSCInitialize(const char* envp[], size_t envc, void (*onCrash)(const char* ptr, size_t length), bool evalMode)
 {
     static bool has_loaded_jsc = false;
@@ -3090,39 +3142,27 @@ void GlobalObject::finishCreation(VM& vm)
 
     m_navigatorObject.initLater(
         [](const Initializer<JSObject>& init) {
-            int cpuCount = 0;
-#ifdef __APPLE__
-            size_t count_len = sizeof(cpuCount);
-            sysctlbyname("hw.logicalcpu", &cpuCount, &count_len, NULL, 0);
-#elif OS(WINDOWS)
-            SYSTEM_INFO sysinfo;
-            GetSystemInfo(&sysinfo);
-            cpuCount = sysinfo.dwNumberOfProcessors;
-#else
-            // TODO: windows
-            cpuCount = sysconf(_SC_NPROCESSORS_ONLN);
-#endif
-
-            auto str = WTF::String::fromUTF8(Bun__userAgent);
-            JSC::Identifier userAgentIdentifier = JSC::Identifier::fromString(init.vm, "userAgent"_s);
-            JSC::Identifier hardwareConcurrencyIdentifier = JSC::Identifier::fromString(init.vm, "hardwareConcurrency"_s);
-
             JSC::JSObject* obj = JSC::constructEmptyObject(init.owner, init.owner->objectPrototype(), 4);
-            obj->putDirect(init.vm, userAgentIdentifier, JSC::jsString(init.vm, str));
             obj->putDirect(init.vm, init.vm.propertyNames->toStringTagSymbol,
                 jsNontrivialString(init.vm, "Navigator"_s), PropertyAttribute::DontEnum | PropertyAttribute::ReadOnly);
 
-// https://developer.mozilla.org/en-US/docs/Web/API/Navigator/platform
-// https://github.com/oven-sh/bun/issues/4588
-#if OS(DARWIN)
-            obj->putDirect(init.vm, JSC::Identifier::fromString(init.vm, "platform"_s), JSC::jsString(init.vm, String("MacIntel"_s)));
-#elif OS(WINDOWS)
-            obj->putDirect(init.vm, JSC::Identifier::fromString(init.vm, "platform"_s), JSC::jsString(init.vm, String("Win32"_s)));
-#elif OS(LINUX)
-            obj->putDirect(init.vm, JSC::Identifier::fromString(init.vm, "platform"_s), JSC::jsString(init.vm, String("Linux x86_64"_s)));
-#endif
+            // Define getter-only properties like Node.js
+            JSC::Identifier userAgentIdentifier = JSC::Identifier::fromString(init.vm, "userAgent"_s);
+            JSC::Identifier platformIdentifier = JSC::Identifier::fromString(init.vm, "platform"_s);
+            JSC::Identifier hardwareConcurrencyIdentifier = JSC::Identifier::fromString(init.vm, "hardwareConcurrency"_s);
+
+            obj->putDirectCustomAccessor(init.vm, userAgentIdentifier,
+                JSC::CustomGetterSetter::create(init.vm, navigatorUserAgentGetter, nullptr),
+                PropertyAttribute::CustomAccessor | PropertyAttribute::DontDelete);
+
+            obj->putDirectCustomAccessor(init.vm, platformIdentifier,
+                JSC::CustomGetterSetter::create(init.vm, navigatorPlatformGetter, nullptr),
+                PropertyAttribute::CustomAccessor | PropertyAttribute::DontDelete);
+
+            obj->putDirectCustomAccessor(init.vm, hardwareConcurrencyIdentifier,
+                JSC::CustomGetterSetter::create(init.vm, navigatorHardwareConcurrencyGetter, nullptr),
+                PropertyAttribute::CustomAccessor | PropertyAttribute::DontDelete);
 
-            obj->putDirect(init.vm, hardwareConcurrencyIdentifier, JSC::jsNumber(cpuCount));
             init.set(obj);
         });
 

test/js/web/navigator-readonly.test.ts

@@ -0,0 +1,50 @@
+import { expect, test } from "bun:test";
+
+test("navigator properties should be getter-only like Node.js", () => {
+  const originalUserAgent = navigator.userAgent;
+  const originalPlatform = navigator.platform;
+  const originalHardwareConcurrency = navigator.hardwareConcurrency;
+
+  // Attempting to modify getter-only properties should silently fail (like Node.js)
+  navigator.userAgent = "modified";
+  navigator.platform = "modified";
+  navigator.hardwareConcurrency = 999;
+
+  // Values should remain unchanged
+  expect(navigator.userAgent).toBe(originalUserAgent);
+  expect(navigator.platform).toBe(originalPlatform);
+  expect(navigator.hardwareConcurrency).toBe(originalHardwareConcurrency);
+});
+
+test("navigator properties should have getter-only descriptors like Node.js", () => {
+  const userAgentDescriptor = Object.getOwnPropertyDescriptor(navigator, "userAgent");
+  const platformDescriptor = Object.getOwnPropertyDescriptor(navigator, "platform");
+  const hardwareConcurrencyDescriptor = Object.getOwnPropertyDescriptor(navigator, "hardwareConcurrency");
+
+  // Properties should have getters but no setters
+  expect(userAgentDescriptor?.get).toBeTypeOf("function");
+  expect(userAgentDescriptor?.set).toBeUndefined();
+  expect(userAgentDescriptor?.configurable).toBe(false);
+
+  expect(platformDescriptor?.get).toBeTypeOf("function");
+  expect(platformDescriptor?.set).toBeUndefined();
+  expect(platformDescriptor?.configurable).toBe(false);
+
+  expect(hardwareConcurrencyDescriptor?.get).toBeTypeOf("function");
+  expect(hardwareConcurrencyDescriptor?.set).toBeUndefined();
+  expect(hardwareConcurrencyDescriptor?.configurable).toBe(false);
+});
+
+test("Object.defineProperty should not be able to modify navigator properties", () => {
+  const originalUserAgent = navigator.userAgent;
+
+  expect(() => {
+    Object.defineProperty(navigator, "userAgent", {
+      value: "modified",
+      writable: true,
+      configurable: true,
+    });
+  }).toThrow();
+
+  expect(navigator.userAgent).toBe(originalUserAgent);
+});