diff --git a/Source/JavaScriptCore/runtime/CachedTypes.cpp b/Source/JavaScriptCore/runtime/CachedTypes.cpp
index 8b9f5a668154..51215d6f81a9 100644
--- a/Source/JavaScriptCore/runtime/CachedTypes.cpp
+++ b/Source/JavaScriptCore/runtime/CachedTypes.cpp
@@ -2688,6 +2688,56 @@ RefPtr<CachedBytecode> encodeFunctionCodeBlock(VM& vm, const UnlinkedFunctionCod
     return encoder.release(error);
 }
 
+#if USE(BUN_JSC_ADDITIONS)
+// Top-level entry for a builtin UnlinkedFunctionExecutable.
+// Simpler than GenericCacheEntry: no SourceCodeKey (source is fixed at build time),
+// no bootSessionUUID (Bun fork already neutralizes it). Only version check.
+class BuiltinFunctionCacheEntry {
+public:
+    BuiltinFunctionCacheEntry()
+        : m_cacheVersion(computeJSCBytecodeCacheVersion())
+    {
+    }
+
+    void encode(Encoder& encoder, const UnlinkedFunctionExecutable& executable)
+    {
+        m_executable.encode(encoder, executable);
+    }
+
+    UnlinkedFunctionExecutable* decode(Decoder& decoder) const
+    {
+        if (m_cacheVersion != computeJSCBytecodeCacheVersion())
+            return nullptr;
+        return m_executable.decode(decoder);
+    }
+
+private:
+    uint32_t m_cacheVersion;
+    CachedFunctionExecutable m_executable;
+};
+static_assert(alignof(BuiltinFunctionCacheEntry) <= alignof(std::max_align_t));
+
+RefPtr<CachedBytecode> encodeBuiltinFunctionExecutable(VM& vm, UnlinkedFunctionExecutable* executable)
+{
+    BytecodeCacheError error;
+    FileSystem::FileHandle invalidFileHandle;
+    Encoder encoder(vm, invalidFileHandle);
+    encoder.malloc<BuiltinFunctionCacheEntry>()->encode(encoder, *executable);
+    return encoder.release(error);
+}
+
+UnlinkedFunctionExecutable* decodeBuiltinFunctionExecutable(VM& vm, Ref<CachedBytecode> cachedBytecode)
+{
+    auto span = cachedBytecode->span();
+    if (span.empty())
+        return nullptr;
+    const auto* entry = std::bit_cast<const BuiltinFunctionCacheEntry*>(span.data());
+    Ref decoder = Decoder::create(vm, WTF::move(cachedBytecode));
+    DeferGC deferGC(vm);
+    return entry->decode(decoder.get());
+}
+#endif
+
 std::optional<SourceCodeKey> decodeSourceCodeKey(VM& vm, Ref<CachedBytecode> cachedBytecode)
 {
     const auto* cachedEntry = std::bit_cast<const GenericCacheEntry*>(cachedBytecode->span().data());
diff --git a/Source/JavaScriptCore/runtime/CachedTypes.h b/Source/JavaScriptCore/runtime/CachedTypes.h
index 4fe52e63238f..ad70041558cd 100644
--- a/Source/JavaScriptCore/runtime/CachedTypes.h
+++ b/Source/JavaScriptCore/runtime/CachedTypes.h
@@ -130,4 +130,12 @@ JS_EXPORT_PRIVATE void decodeFunctionCodeBlock(Decoder&, int32_t cachedFunctionC
 
 bool isCachedBytecodeStillValid(VM&, Ref<CachedBytecode>, const SourceCodeKey&, SourceCodeType);
 
+#if USE(BUN_JSC_ADDITIONS)
+// Encode/decode a top-level UnlinkedFunctionExecutable (including nested code blocks)
+// for Bun's builtin module bytecode cache. Unlike encodeCodeBlock, this skips
+// SourceCodeKey validation since builtin sources are fixed at build time.
+JS_EXPORT_PRIVATE RefPtr<CachedBytecode> encodeBuiltinFunctionExecutable(VM&, UnlinkedFunctionExecutable*);
+JS_EXPORT_PRIVATE UnlinkedFunctionExecutable* decodeBuiltinFunctionExecutable(VM&, Ref<CachedBytecode>);
+#endif
+
 } // namespace JSC
diff --git a/Source/JavaScriptCore/runtime/CodeCache.cpp b/Source/JavaScriptCore/runtime/CodeCache.cpp
index d539c7a50833..d53bc09bc500 100644
--- a/Source/JavaScriptCore/runtime/CodeCache.cpp
+++ b/Source/JavaScriptCore/runtime/CodeCache.cpp
@@ -30,6 +30,10 @@
 #include "IndirectEvalExecutable.h"
 #include <wtf/TZoneMallocInlines.h>
 
+#if USE(BUN_JSC_ADDITIONS)
+#include "BuiltinExecutables.h"
+#endif
+
 namespace JSC {
 
 WTF_MAKE_TZONE_ALLOCATED_IMPL(CodeCache);
@@ -168,6 +172,31 @@ UnlinkedModuleProgramCodeBlock* recursivelyGenerateUnlinkedCodeBlockForModulePro
     return recursivelyGenerateUnlinkedCodeBlock<UnlinkedModuleProgramCodeBlock>(vm, source, lexicallyScopedFeatures, scriptMode, codeGenerationMode, error, evalContextType);
 }
 
+#if USE(BUN_JSC_ADDITIONS)
+UnlinkedFunctionExecutable* recursivelyGenerateUnlinkedCodeBlockForBuiltinFunction(VM& vm, const SourceCode& source, const Identifier& name, ParserError& error, ImplementationVisibility implementationVisibility, ConstructorKind constructorKind, ConstructAbility constructAbility, InlineAttribute inlineAttribute)
+{
+    UnlinkedFunctionExecutable* executable = BuiltinExecutables::createExecutable(
+        vm, source, name, implementationVisibility,
+        constructorKind, constructAbility, inlineAttribute,
+        NeedsClassFieldInitializer::No, PrivateBrandRequirement::None);
+    if (!executable)
+        return nullptr;
+
+    SourceCode innerSource = executable->linkedSourceCode(source);
+    UnlinkedFunctionCodeBlock* codeBlock = executable->unlinkedCodeBlockFor(
+        vm, innerSource, CodeSpecializationKind::CodeForCall, { }, error,
+        executable->parseMode());
+    if (error.isValid() || !codeBlock)
+        return nullptr;
+
+    generateUnlinkedCodeBlockForFunctions(vm, codeBlock, innerSource, { }, error);
+    if (error.isValid())
+        return nullptr;
+
+    return executable;
+}
+#endif
+
 template<class UnlinkedCodeBlockType, class ExecutableType>
 UnlinkedCodeBlockType* CodeCache::getUnlinkedGlobalCodeBlock(VM& vm, ExecutableType* executable, const SourceCode& source, JSParserScriptMode scriptMode, OptionSet<CodeGenerationMode> codeGenerationMode, ParserError& error, EvalContextType evalContextType)
 {
diff --git a/Source/JavaScriptCore/runtime/CodeCache.h b/Source/JavaScriptCore/runtime/CodeCache.h
index 2aa836bdb247..d147b0e68b55 100644
--- a/Source/JavaScriptCore/runtime/CodeCache.h
+++ b/Source/JavaScriptCore/runtime/CodeCache.h
@@ -266,6 +266,13 @@ UnlinkedEvalCodeBlock* generateUnlinkedCodeBlockForDirectEval(VM&, DirectEvalExe
 UnlinkedProgramCodeBlock* recursivelyGenerateUnlinkedCodeBlockForProgram(VM&, const SourceCode&, LexicallyScopedFeatures, JSParserScriptMode, OptionSet<CodeGenerationMode>, ParserError&, EvalContextType);
 UnlinkedModuleProgramCodeBlock* recursivelyGenerateUnlinkedCodeBlockForModuleProgram(VM&, const SourceCode&, LexicallyScopedFeatures, JSParserScriptMode, OptionSet<CodeGenerationMode>, ParserError&, EvalContextType);
 
+#if USE(BUN_JSC_ADDITIONS)
+// Parse a builtin function source (with @-prefixed private identifiers) and
+// recursively generate bytecode for all nested functions. Used by Bun to
+// pre-generate bytecode for internal modules at build time.
+JS_EXPORT_PRIVATE UnlinkedFunctionExecutable* recursivelyGenerateUnlinkedCodeBlockForBuiltinFunction(VM&, const SourceCode&, const Identifier& name, ParserError&, ImplementationVisibility = ImplementationVisibility::Public, ConstructorKind = ConstructorKind::None, ConstructAbility = ConstructAbility::CannotConstruct, InlineAttribute = InlineAttribute::None);
+#endif
+
 void writeCodeBlock(const SourceCodeKey&, const SourceCodeValue&);
 RefPtr<CachedBytecode> serializeBytecode(VM&, UnlinkedCodeBlock*, const SourceCode&, SourceCodeType, LexicallyScopedFeatures, JSParserScriptMode, FileSystem::FileHandle&, BytecodeCacheError&, OptionSet<CodeGenerationMode>);
 SourceCodeKey sourceCodeKeyForSerializedProgram(VM&, const SourceCode&);