Add CompressionStream and DecompressionStream Web APIs

Implements the missing CompressionStream and DecompressionStream Web APIs to support libraries like @zip.js/zip.js@2.8.8 that require these APIs.

The implementation uses Node.js zlib streams as the backing implementation and wraps them in TransformStream-based APIs following the same pattern as TextEncoderStream.

Changes:
- Add src/js/builtins/CompressionStream.ts and DecompressionStream.ts with builtin implementations
- Add C++ bindings (JSCompressionStream.* and JSDecompressionStream.*)
- Register classes in ZigGlobalObject, DOMIsoSubspaces, DOMClientIsoSubspaces, and DOMConstructors
- Add private field symbols to BunBuiltinNames.h

Supports "deflate", "deflate-raw", and "gzip" compression formats as per the Compression Streams API spec.

Fixes #24161

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

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

src/bun.js/bindings/ZigGlobalObject.cpp

@@ -126,6 +126,8 @@
 #include "JSTextEncoder.h"
 #include "JSTextEncoderStream.h"
 #include "JSTextDecoderStream.h"
+#include "JSCompressionStream.h"
+#include "JSDecompressionStream.h"
 #include "JSTransformStream.h"
 #include "JSTransformStreamDefaultController.h"
 #include "JSURLSearchParams.h"
@@ -993,6 +995,8 @@ WEBCORE_GENERATED_CONSTRUCTOR_GETTER(SubtleCrypto);
 WEBCORE_GENERATED_CONSTRUCTOR_GETTER(TextEncoder);
 WEBCORE_GENERATED_CONSTRUCTOR_GETTER(TextEncoderStream);
 WEBCORE_GENERATED_CONSTRUCTOR_GETTER(TextDecoderStream);
+WEBCORE_GENERATED_CONSTRUCTOR_GETTER(CompressionStream);
+WEBCORE_GENERATED_CONSTRUCTOR_GETTER(DecompressionStream);
 WEBCORE_GENERATED_CONSTRUCTOR_GETTER(TransformStream)
 WEBCORE_GENERATED_CONSTRUCTOR_GETTER(TransformStreamDefaultController)
 WEBCORE_GENERATED_CONSTRUCTOR_GETTER(URLSearchParams);

src/bun.js/bindings/ZigGlobalObject.lut.txt

@@ -79,6 +79,8 @@
   TextDecoderStream               TextDecoderStreamConstructorCallback                 PropertyCallback
   TextEncoder                     TextEncoderConstructorCallback                       PropertyCallback
   TextEncoderStream               TextEncoderStreamConstructorCallback                 PropertyCallback
+  CompressionStream               CompressionStreamConstructorCallback                 PropertyCallback
+  DecompressionStream             DecompressionStreamConstructorCallback               PropertyCallback
   TransformStream                 TransformStreamConstructorCallback                   PropertyCallback
   TransformStreamDefaultController TransformStreamDefaultControllerConstructorCallback PropertyCallback
   URL                             DOMURLConstructorCallback                            DontEnum|PropertyCallback

src/bun.js/bindings/webcore/DOMClientIsoSubspaces.h

@@ -509,6 +509,8 @@ public:
     std::unique_ptr<GCClient::IsoSubspace> m_clientSubspaceForTextEncoder;
     std::unique_ptr<GCClient::IsoSubspace> m_clientSubspaceForTextEncoderStream;
     // std::unique_ptr<GCClient::IsoSubspace> m_clientSubspaceForTextEncoderStreamEncoder;
+    std::unique_ptr<GCClient::IsoSubspace> m_clientSubspaceForCompressionStream;
+    std::unique_ptr<GCClient::IsoSubspace> m_clientSubspaceForDecompressionStream;
     // std::unique_ptr<GCClient::IsoSubspace> m_clientSubspaceForTextEvent;
     // std::unique_ptr<GCClient::IsoSubspace> m_clientSubspaceForTransitionEvent;
     // std::unique_ptr<GCClient::IsoSubspace> m_clientSubspaceForTreeWalker;

src/bun.js/bindings/webcore/DOMConstructors.h

@@ -435,6 +435,8 @@ enum class DOMConstructorID : uint16_t {
     TextEncoder,
     TextEncoderStream,
     TextEncoderStreamEncoder,
+    CompressionStream,
+    DecompressionStream,
     TextEvent,
     TransitionEvent,
     TreeWalker,

src/bun.js/bindings/webcore/DOMIsoSubspaces.h

@@ -494,6 +494,8 @@ public:
     std::unique_ptr<IsoSubspace> m_subspaceForTextEncoder;
     std::unique_ptr<IsoSubspace> m_subspaceForTextEncoderStream;
     // std::unique_ptr<IsoSubspace> m_subspaceForTextEncoderStreamEncoder;
+    std::unique_ptr<IsoSubspace> m_subspaceForCompressionStream;
+    std::unique_ptr<IsoSubspace> m_subspaceForDecompressionStream;
     // std::unique_ptr<IsoSubspace> m_subspaceForTextEvent;
     // std::unique_ptr<IsoSubspace> m_subspaceForTransitionEvent;
     // std::unique_ptr<IsoSubspace> m_subspaceForTreeWalker;

src/bun.js/bindings/webcore/JSCompressionStream.cpp

@@ -0,0 +1,168 @@
+/*
+    This file is part of the WebKit open source project.
+    This file has been generated by generate-bindings.pl. DO NOT MODIFY!
+
+    This library is free software; you can redistribute it and/or
+    modify it under the terms of the GNU Library General Public
+    License as published by the Free Software Foundation; either
+    version 2 of the License, or (at your option) any later version.
+
+    This library is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+    Library General Public License for more details.
+
+    You should have received a copy of the GNU Library General Public License
+    along with this library; see the file COPYING.LIB.  If not, write to
+    the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+    Boston, MA 02110-1301, USA.
+*/
+
+#include "config.h"
+#include "JSCompressionStream.h"
+
+#include "ExtendedDOMClientIsoSubspaces.h"
+#include "ExtendedDOMIsoSubspaces.h"
+#include "JSDOMAttribute.h"
+#include "JSDOMBinding.h"
+#include "JSDOMBuiltinConstructor.h"
+#include "JSDOMExceptionHandling.h"
+#include "JSDOMGlobalObjectInlines.h"
+#include "JSDOMWrapperCache.h"
+// #include "CompressionStreamBuiltins.h"
+#include "WebCoreJSClientData.h"
+#include <JavaScriptCore/FunctionPrototype.h>
+#include <JavaScriptCore/JSCInlines.h>
+#include <JavaScriptCore/JSDestructibleObjectHeapCellType.h>
+#include <JavaScriptCore/SlotVisitorMacros.h>
+#include <JavaScriptCore/SubspaceInlines.h>
+#include <wtf/GetPtr.h>
+#include <wtf/PointerPreparations.h>
+
+namespace WebCore {
+using namespace JSC;
+
+// Attributes
+
+static JSC_DECLARE_CUSTOM_GETTER(jsCompressionStreamConstructor);
+
+class JSCompressionStreamPrototype final : public JSC::JSNonFinalObject {
+public:
+    using Base = JSC::JSNonFinalObject;
+    static JSCompressionStreamPrototype* create(JSC::VM& vm, JSDOMGlobalObject* globalObject, JSC::Structure* structure)
+    {
+        JSCompressionStreamPrototype* ptr = new (NotNull, JSC::allocateCell<JSCompressionStreamPrototype>(vm)) JSCompressionStreamPrototype(vm, globalObject, structure);
+        ptr->finishCreation(vm);
+        return ptr;
+    }
+
+    DECLARE_INFO;
+    template<typename CellType, JSC::SubspaceAccess>
+    static JSC::GCClient::IsoSubspace* subspaceFor(JSC::VM& vm)
+    {
+        STATIC_ASSERT_ISO_SUBSPACE_SHARABLE(JSCompressionStreamPrototype, Base);
+        return &vm.plainObjectSpace();
+    }
+    static JSC::Structure* createStructure(JSC::VM& vm, JSC::JSGlobalObject* globalObject, JSC::JSValue prototype)
+    {
+        return JSC::Structure::create(vm, globalObject, prototype, JSC::TypeInfo(JSC::ObjectType, StructureFlags), info());
+    }
+
+private:
+    JSCompressionStreamPrototype(JSC::VM& vm, JSC::JSGlobalObject*, JSC::Structure* structure)
+        : JSC::JSNonFinalObject(vm, structure)
+    {
+    }
+
+    void finishCreation(JSC::VM&);
+};
+STATIC_ASSERT_ISO_SUBSPACE_SHARABLE(JSCompressionStreamPrototype, JSCompressionStreamPrototype::Base);
+
+using JSCompressionStreamDOMConstructor = JSDOMBuiltinConstructor<JSCompressionStream>;
+
+template<> const ClassInfo JSCompressionStreamDOMConstructor::s_info = { "CompressionStream"_s, &Base::s_info, nullptr, nullptr, CREATE_METHOD_TABLE(JSCompressionStreamDOMConstructor) };
+
+template<> JSValue JSCompressionStreamDOMConstructor::prototypeForStructure(JSC::VM& vm, const JSDOMGlobalObject& globalObject)
+{
+    UNUSED_PARAM(vm);
+    return globalObject.functionPrototype();
+}
+
+template<> void JSCompressionStreamDOMConstructor::initializeProperties(VM& vm, JSDOMGlobalObject& globalObject)
+{
+    putDirect(vm, vm.propertyNames->length, jsNumber(0), JSC::PropertyAttribute::ReadOnly | JSC::PropertyAttribute::DontEnum);
+    JSString* nameString = jsNontrivialString(vm, "CompressionStream"_s);
+    m_originalName.set(vm, this, nameString);
+    putDirect(vm, vm.propertyNames->name, nameString, JSC::PropertyAttribute::ReadOnly | JSC::PropertyAttribute::DontEnum);
+    putDirect(vm, vm.propertyNames->prototype, JSCompressionStream::prototype(vm, globalObject), JSC::PropertyAttribute::ReadOnly | JSC::PropertyAttribute::DontEnum | JSC::PropertyAttribute::DontDelete);
+}
+
+template<> FunctionExecutable* JSCompressionStreamDOMConstructor::initializeExecutable(VM& vm)
+{
+    return compressionStreamInitializeCompressionStreamCodeGenerator(vm);
+}
+
+/* Hash table for prototype */
+
+static const HashTableValue JSCompressionStreamPrototypeTableValues[] = {
+    { "constructor"_s, static_cast<unsigned>(PropertyAttribute::DontEnum), NoIntrinsic, { HashTableValue::GetterSetterType, jsCompressionStreamConstructor, 0 } },
+    { "readable"_s, JSC::PropertyAttribute::ReadOnly | JSC::PropertyAttribute::Accessor | JSC::PropertyAttribute::Builtin, NoIntrinsic, { HashTableValue::BuiltinAccessorType, compressionStreamReadableCodeGenerator, 0 } },
+    { "writable"_s, JSC::PropertyAttribute::ReadOnly | JSC::PropertyAttribute::Accessor | JSC::PropertyAttribute::Builtin, NoIntrinsic, { HashTableValue::BuiltinAccessorType, compressionStreamWritableCodeGenerator, 0 } },
+};
+
+const ClassInfo JSCompressionStreamPrototype::s_info = { "CompressionStream"_s, &Base::s_info, nullptr, nullptr, CREATE_METHOD_TABLE(JSCompressionStreamPrototype) };
+
+void JSCompressionStreamPrototype::finishCreation(VM& vm)
+{
+    Base::finishCreation(vm);
+    reifyStaticProperties(vm, JSCompressionStream::info(), JSCompressionStreamPrototypeTableValues, *this);
+    JSC_TO_STRING_TAG_WITHOUT_TRANSITION();
+}
+
+const ClassInfo JSCompressionStream::s_info = { "CompressionStream"_s, &Base::s_info, nullptr, nullptr, CREATE_METHOD_TABLE(JSCompressionStream) };
+
+JSCompressionStream::JSCompressionStream(Structure* structure, JSDOMGlobalObject& globalObject)
+    : JSDOMObject(structure, globalObject)
+{
+}
+
+JSObject* JSCompressionStream::createPrototype(VM& vm, JSDOMGlobalObject& globalObject)
+{
+    auto* structure = JSCompressionStreamPrototype::createStructure(vm, &globalObject, globalObject.objectPrototype());
+    structure->setMayBePrototype(true);
+    return JSCompressionStreamPrototype::create(vm, &globalObject, structure);
+}
+
+JSObject* JSCompressionStream::prototype(VM& vm, JSDOMGlobalObject& globalObject)
+{
+    return getDOMPrototype<JSCompressionStream>(vm, globalObject);
+}
+
+JSValue JSCompressionStream::getConstructor(VM& vm, const JSGlobalObject* globalObject)
+{
+    return getDOMConstructor<JSCompressionStreamDOMConstructor, DOMConstructorID::CompressionStream>(vm, *jsCast<const JSDOMGlobalObject*>(globalObject));
+}
+
+void JSCompressionStream::destroy(JSC::JSCell* cell)
+{
+    JSCompressionStream* thisObject = static_cast<JSCompressionStream*>(cell);
+    thisObject->JSCompressionStream::~JSCompressionStream();
+}
+
+JSC_DEFINE_CUSTOM_GETTER(jsCompressionStreamConstructor, (JSGlobalObject * lexicalGlobalObject, EncodedJSValue thisValue, PropertyName))
+{
+    auto& vm = JSC::getVM(lexicalGlobalObject);
+    auto throwScope = DECLARE_THROW_SCOPE(vm);
+    auto* prototype = jsDynamicCast<JSCompressionStreamPrototype*>(JSValue::decode(thisValue));
+    if (!prototype) [[unlikely]]
+        return throwVMTypeError(lexicalGlobalObject, throwScope);
+    return JSValue::encode(JSCompressionStream::getConstructor(vm, prototype->globalObject()));
+}
+
+JSC::GCClient::IsoSubspace* JSCompressionStream::subspaceForImpl(JSC::VM& vm)
+{
+    return WebCore::subspaceForImpl<JSCompressionStream, UseCustomHeapCellType::No>(
+        vm, [](auto& spaces) { return spaces.m_clientSubspaceForCompressionStream.get(); }, [](auto& spaces, auto&& space) { spaces.m_clientSubspaceForCompressionStream = std::forward<decltype(space)>(space); }, [](auto& spaces) { return spaces.m_subspaceForCompressionStream.get(); }, [](auto& spaces, auto&& space) { spaces.m_subspaceForCompressionStream = std::forward<decltype(space)>(space); });
+}
+
+}

src/bun.js/bindings/webcore/JSCompressionStream.h

@@ -0,0 +1,64 @@
+/*
+    This file is part of the WebKit open source project.
+    This file has been generated by generate-bindings.pl. DO NOT MODIFY!
+
+    This library is free software; you can redistribute it and/or
+    modify it under the terms of the GNU Library General Public
+    License as published by the Free Software Foundation; either
+    version 2 of the License, or (at your option) any later version.
+
+    This library is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+    Library General Public License for more details.
+
+    You should have received a copy of the GNU Library General Public License
+    along with this library; see the file COPYING.LIB.  If not, write to
+    the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+    Boston, MA 02110-1301, USA.
+*/
+
+#pragma once
+
+#include "JSDOMWrapper.h"
+
+namespace WebCore {
+
+class JSCompressionStream : public JSDOMObject {
+public:
+    using Base = JSDOMObject;
+    static JSCompressionStream* create(JSC::Structure* structure, JSDOMGlobalObject* globalObject)
+    {
+        auto& vm = JSC::getVM(globalObject);
+        JSCompressionStream* ptr = new (NotNull, JSC::allocateCell<JSCompressionStream>(vm)) JSCompressionStream(structure, *globalObject);
+        ptr->finishCreation(vm);
+        return ptr;
+    }
+
+    static JSC::JSObject* createPrototype(JSC::VM&, JSDOMGlobalObject&);
+    static JSC::JSObject* prototype(JSC::VM&, JSDOMGlobalObject&);
+    static void destroy(JSC::JSCell*);
+
+    DECLARE_INFO;
+
+    static JSC::Structure* createStructure(JSC::VM& vm, JSC::JSGlobalObject* globalObject, JSC::JSValue prototype)
+    {
+        return JSC::Structure::create(vm, globalObject, prototype, JSC::TypeInfo(JSC::ObjectType, StructureFlags), info(), JSC::NonArray);
+    }
+
+    static JSC::JSValue getConstructor(JSC::VM&, const JSC::JSGlobalObject*);
+    template<typename, JSC::SubspaceAccess mode> static JSC::GCClient::IsoSubspace* subspaceFor(JSC::VM& vm)
+    {
+        if constexpr (mode == JSC::SubspaceAccess::Concurrently)
+            return nullptr;
+        return subspaceForImpl(vm);
+    }
+    static JSC::GCClient::IsoSubspace* subspaceForImpl(JSC::VM& vm);
+
+protected:
+    JSCompressionStream(JSC::Structure*, JSDOMGlobalObject&);
+
+    DECLARE_DEFAULT_FINISH_CREATION;
+};
+
+} // namespace WebCore

src/bun.js/bindings/webcore/JSDecompressionStream.cpp

@@ -0,0 +1,168 @@
+/*
+    This file is part of the WebKit open source project.
+    This file has been generated by generate-bindings.pl. DO NOT MODIFY!
+
+    This library is free software; you can redistribute it and/or
+    modify it under the terms of the GNU Library General Public
+    License as published by the Free Software Foundation; either
+    version 2 of the License, or (at your option) any later version.
+
+    This library is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+    Library General Public License for more details.
+
+    You should have received a copy of the GNU Library General Public License
+    along with this library; see the file COPYING.LIB.  If not, write to
+    the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+    Boston, MA 02110-1301, USA.
+*/
+
+#include "config.h"
+#include "JSDecompressionStream.h"
+
+#include "ExtendedDOMClientIsoSubspaces.h"
+#include "ExtendedDOMIsoSubspaces.h"
+#include "JSDOMAttribute.h"
+#include "JSDOMBinding.h"
+#include "JSDOMBuiltinConstructor.h"
+#include "JSDOMExceptionHandling.h"
+#include "JSDOMGlobalObjectInlines.h"
+#include "JSDOMWrapperCache.h"
+// #include "DecompressionStreamBuiltins.h"
+#include "WebCoreJSClientData.h"
+#include <JavaScriptCore/FunctionPrototype.h>
+#include <JavaScriptCore/JSCInlines.h>
+#include <JavaScriptCore/JSDestructibleObjectHeapCellType.h>
+#include <JavaScriptCore/SlotVisitorMacros.h>
+#include <JavaScriptCore/SubspaceInlines.h>
+#include <wtf/GetPtr.h>
+#include <wtf/PointerPreparations.h>
+
+namespace WebCore {
+using namespace JSC;
+
+// Attributes
+
+static JSC_DECLARE_CUSTOM_GETTER(jsDecompressionStreamConstructor);
+
+class JSDecompressionStreamPrototype final : public JSC::JSNonFinalObject {
+public:
+    using Base = JSC::JSNonFinalObject;
+    static JSDecompressionStreamPrototype* create(JSC::VM& vm, JSDOMGlobalObject* globalObject, JSC::Structure* structure)
+    {
+        JSDecompressionStreamPrototype* ptr = new (NotNull, JSC::allocateCell<JSDecompressionStreamPrototype>(vm)) JSDecompressionStreamPrototype(vm, globalObject, structure);
+        ptr->finishCreation(vm);
+        return ptr;
+    }
+
+    DECLARE_INFO;
+    template<typename CellType, JSC::SubspaceAccess>
+    static JSC::GCClient::IsoSubspace* subspaceFor(JSC::VM& vm)
+    {
+        STATIC_ASSERT_ISO_SUBSPACE_SHARABLE(JSDecompressionStreamPrototype, Base);
+        return &vm.plainObjectSpace();
+    }
+    static JSC::Structure* createStructure(JSC::VM& vm, JSC::JSGlobalObject* globalObject, JSC::JSValue prototype)
+    {
+        return JSC::Structure::create(vm, globalObject, prototype, JSC::TypeInfo(JSC::ObjectType, StructureFlags), info());
+    }
+
+private:
+    JSDecompressionStreamPrototype(JSC::VM& vm, JSC::JSGlobalObject*, JSC::Structure* structure)
+        : JSC::JSNonFinalObject(vm, structure)
+    {
+    }
+
+    void finishCreation(JSC::VM&);
+};
+STATIC_ASSERT_ISO_SUBSPACE_SHARABLE(JSDecompressionStreamPrototype, JSDecompressionStreamPrototype::Base);
+
+using JSDecompressionStreamDOMConstructor = JSDOMBuiltinConstructor<JSDecompressionStream>;
+
+template<> const ClassInfo JSDecompressionStreamDOMConstructor::s_info = { "DecompressionStream"_s, &Base::s_info, nullptr, nullptr, CREATE_METHOD_TABLE(JSDecompressionStreamDOMConstructor) };
+
+template<> JSValue JSDecompressionStreamDOMConstructor::prototypeForStructure(JSC::VM& vm, const JSDOMGlobalObject& globalObject)
+{
+    UNUSED_PARAM(vm);
+    return globalObject.functionPrototype();
+}
+
+template<> void JSDecompressionStreamDOMConstructor::initializeProperties(VM& vm, JSDOMGlobalObject& globalObject)
+{
+    putDirect(vm, vm.propertyNames->length, jsNumber(0), JSC::PropertyAttribute::ReadOnly | JSC::PropertyAttribute::DontEnum);
+    JSString* nameString = jsNontrivialString(vm, "DecompressionStream"_s);
+    m_originalName.set(vm, this, nameString);
+    putDirect(vm, vm.propertyNames->name, nameString, JSC::PropertyAttribute::ReadOnly | JSC::PropertyAttribute::DontEnum);
+    putDirect(vm, vm.propertyNames->prototype, JSDecompressionStream::prototype(vm, globalObject), JSC::PropertyAttribute::ReadOnly | JSC::PropertyAttribute::DontEnum | JSC::PropertyAttribute::DontDelete);
+}
+
+template<> FunctionExecutable* JSDecompressionStreamDOMConstructor::initializeExecutable(VM& vm)
+{
+    return decompressionStreamInitializeDecompressionStreamCodeGenerator(vm);
+}
+
+/* Hash table for prototype */
+
+static const HashTableValue JSDecompressionStreamPrototypeTableValues[] = {
+    { "constructor"_s, static_cast<unsigned>(PropertyAttribute::DontEnum), NoIntrinsic, { HashTableValue::GetterSetterType, jsDecompressionStreamConstructor, 0 } },
+    { "readable"_s, JSC::PropertyAttribute::ReadOnly | JSC::PropertyAttribute::Accessor | JSC::PropertyAttribute::Builtin, NoIntrinsic, { HashTableValue::BuiltinAccessorType, decompressionStreamReadableCodeGenerator, 0 } },
+    { "writable"_s, JSC::PropertyAttribute::ReadOnly | JSC::PropertyAttribute::Accessor | JSC::PropertyAttribute::Builtin, NoIntrinsic, { HashTableValue::BuiltinAccessorType, decompressionStreamWritableCodeGenerator, 0 } },
+};
+
+const ClassInfo JSDecompressionStreamPrototype::s_info = { "DecompressionStream"_s, &Base::s_info, nullptr, nullptr, CREATE_METHOD_TABLE(JSDecompressionStreamPrototype) };
+
+void JSDecompressionStreamPrototype::finishCreation(VM& vm)
+{
+    Base::finishCreation(vm);
+    reifyStaticProperties(vm, JSDecompressionStream::info(), JSDecompressionStreamPrototypeTableValues, *this);
+    JSC_TO_STRING_TAG_WITHOUT_TRANSITION();
+}
+
+const ClassInfo JSDecompressionStream::s_info = { "DecompressionStream"_s, &Base::s_info, nullptr, nullptr, CREATE_METHOD_TABLE(JSDecompressionStream) };
+
+JSDecompressionStream::JSDecompressionStream(Structure* structure, JSDOMGlobalObject& globalObject)
+    : JSDOMObject(structure, globalObject)
+{
+}
+
+JSObject* JSDecompressionStream::createPrototype(VM& vm, JSDOMGlobalObject& globalObject)
+{
+    auto* structure = JSDecompressionStreamPrototype::createStructure(vm, &globalObject, globalObject.objectPrototype());
+    structure->setMayBePrototype(true);
+    return JSDecompressionStreamPrototype::create(vm, &globalObject, structure);
+}
+
+JSObject* JSDecompressionStream::prototype(VM& vm, JSDOMGlobalObject& globalObject)
+{
+    return getDOMPrototype<JSDecompressionStream>(vm, globalObject);
+}
+
+JSValue JSDecompressionStream::getConstructor(VM& vm, const JSGlobalObject* globalObject)
+{
+    return getDOMConstructor<JSDecompressionStreamDOMConstructor, DOMConstructorID::DecompressionStream>(vm, *jsCast<const JSDOMGlobalObject*>(globalObject));
+}
+
+void JSDecompressionStream::destroy(JSC::JSCell* cell)
+{
+    JSDecompressionStream* thisObject = static_cast<JSDecompressionStream*>(cell);
+    thisObject->JSDecompressionStream::~JSDecompressionStream();
+}
+
+JSC_DEFINE_CUSTOM_GETTER(jsDecompressionStreamConstructor, (JSGlobalObject * lexicalGlobalObject, EncodedJSValue thisValue, PropertyName))
+{
+    auto& vm = JSC::getVM(lexicalGlobalObject);
+    auto throwScope = DECLARE_THROW_SCOPE(vm);
+    auto* prototype = jsDynamicCast<JSDecompressionStreamPrototype*>(JSValue::decode(thisValue));
+    if (!prototype) [[unlikely]]
+        return throwVMTypeError(lexicalGlobalObject, throwScope);
+    return JSValue::encode(JSDecompressionStream::getConstructor(vm, prototype->globalObject()));
+}
+
+JSC::GCClient::IsoSubspace* JSDecompressionStream::subspaceForImpl(JSC::VM& vm)
+{
+    return WebCore::subspaceForImpl<JSDecompressionStream, UseCustomHeapCellType::No>(
+        vm, [](auto& spaces) { return spaces.m_clientSubspaceForDecompressionStream.get(); }, [](auto& spaces, auto&& space) { spaces.m_clientSubspaceForDecompressionStream = std::forward<decltype(space)>(space); }, [](auto& spaces) { return spaces.m_subspaceForDecompressionStream.get(); }, [](auto& spaces, auto&& space) { spaces.m_subspaceForDecompressionStream = std::forward<decltype(space)>(space); });
+}
+
+}

src/bun.js/bindings/webcore/JSDecompressionStream.h

@@ -0,0 +1,64 @@
+/*
+    This file is part of the WebKit open source project.
+    This file has been generated by generate-bindings.pl. DO NOT MODIFY!
+
+    This library is free software; you can redistribute it and/or
+    modify it under the terms of the GNU Library General Public
+    License as published by the Free Software Foundation; either
+    version 2 of the License, or (at your option) any later version.
+
+    This library is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+    Library General Public License for more details.
+
+    You should have received a copy of the GNU Library General Public License
+    along with this library; see the file COPYING.LIB.  If not, write to
+    the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+    Boston, MA 02110-1301, USA.
+*/
+
+#pragma once
+
+#include "JSDOMWrapper.h"
+
+namespace WebCore {
+
+class JSDecompressionStream : public JSDOMObject {
+public:
+    using Base = JSDOMObject;
+    static JSDecompressionStream* create(JSC::Structure* structure, JSDOMGlobalObject* globalObject)
+    {
+        auto& vm = JSC::getVM(globalObject);
+        JSDecompressionStream* ptr = new (NotNull, JSC::allocateCell<JSDecompressionStream>(vm)) JSDecompressionStream(structure, *globalObject);
+        ptr->finishCreation(vm);
+        return ptr;
+    }
+
+    static JSC::JSObject* createPrototype(JSC::VM&, JSDOMGlobalObject&);
+    static JSC::JSObject* prototype(JSC::VM&, JSDOMGlobalObject&);
+    static void destroy(JSC::JSCell*);
+
+    DECLARE_INFO;
+
+    static JSC::Structure* createStructure(JSC::VM& vm, JSC::JSGlobalObject* globalObject, JSC::JSValue prototype)
+    {
+        return JSC::Structure::create(vm, globalObject, prototype, JSC::TypeInfo(JSC::ObjectType, StructureFlags), info(), JSC::NonArray);
+    }
+
+    static JSC::JSValue getConstructor(JSC::VM&, const JSC::JSGlobalObject*);
+    template<typename, JSC::SubspaceAccess mode> static JSC::GCClient::IsoSubspace* subspaceFor(JSC::VM& vm)
+    {
+        if constexpr (mode == JSC::SubspaceAccess::Concurrently)
+            return nullptr;
+        return subspaceForImpl(vm);
+    }
+    static JSC::GCClient::IsoSubspace* subspaceForImpl(JSC::VM& vm);
+
+protected:
+    JSDecompressionStream(JSC::Structure*, JSDOMGlobalObject&);
+
+    DECLARE_DEFAULT_FINISH_CREATION;
+};
+
+} // namespace WebCore

src/js/builtins/BunBuiltinNames.h

@@ -258,6 +258,10 @@ using namespace JSC;
     macro(textDecoderStreamTransform) \
     macro(textEncoderStreamEncoder) \
     macro(textEncoderStreamTransform) \
+    macro(compressionStreamTransform) \
+    macro(compressionStreamCompressor) \
+    macro(decompressionStreamTransform) \
+    macro(decompressionStreamDecompressor) \
     macro(toClass) \
     macro(toNamespacedPath) \
     macro(trace) \

src/js/builtins/CompressionStream.ts

@@ -0,0 +1,94 @@
+/*
+ * Copyright (C) 2025 Anthropic PBC. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1.  Redistributions of source code must retain the above copyright
+ *     notice, this list of conditions and the following disclaimer.
+ * 2.  Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in the
+ *     documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+export function initializeCompressionStream(format) {
+  // Validate format
+  if (format !== "deflate" && format !== "deflate-raw" && format !== "gzip") {
+    throw new TypeError(`The provided value '${format}' is not a valid enum value of type CompressionFormat.`);
+  }
+
+  const zlib = require("node:zlib");
+  let compressor;
+
+  // Create the appropriate compressor based on the format
+  if (format === "deflate") {
+    compressor = zlib.createDeflate();
+  } else if (format === "deflate-raw") {
+    compressor = zlib.createDeflateRaw();
+  } else if (format === "gzip") {
+    compressor = zlib.createGzip();
+  }
+
+  const startAlgorithm = () => {
+    return Promise.$resolve();
+  };
+
+  const transformAlgorithm = chunk => {
+    return new Promise((resolve, reject) => {
+      compressor.write(chunk, err => {
+        if (err) reject(err);
+        else resolve();
+      });
+    });
+  };
+
+  const flushAlgorithm = () => {
+    return new Promise((resolve, reject) => {
+      compressor.end(err => {
+        if (err) reject(err);
+        else resolve();
+      });
+    });
+  };
+
+  const transform = $createTransformStream(startAlgorithm, transformAlgorithm, flushAlgorithm);
+  $putByIdDirectPrivate(this, "compressionStreamTransform", transform);
+  $putByIdDirectPrivate(this, "compressionStreamCompressor", compressor);
+
+  // Set up event handlers to pipe compressed data through the transform stream
+  compressor.on("data", chunk => {
+    const transformStream = $getByIdDirectPrivate(this, "compressionStreamTransform");
+    const controller = $getByIdDirectPrivate(transformStream, "controller");
+    $transformStreamDefaultControllerEnqueue(controller, chunk);
+  });
+
+  return this;
+}
+
+$getter;
+export function readable() {
+  const transform = $getByIdDirectPrivate(this, "compressionStreamTransform");
+  if (!transform) throw $ERR_INVALID_THIS("CompressionStream");
+
+  return $getByIdDirectPrivate(transform, "readable");
+}
+
+$getter;
+export function writable() {
+  const transform = $getByIdDirectPrivate(this, "compressionStreamTransform");
+  if (!transform) throw $ERR_INVALID_THIS("CompressionStream");
+
+  return $getByIdDirectPrivate(transform, "writable");
+}

src/js/builtins/DecompressionStream.ts

@@ -0,0 +1,94 @@
+/*
+ * Copyright (C) 2025 Anthropic PBC. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1.  Redistributions of source code must retain the above copyright
+ *     notice, this list of conditions and the following disclaimer.
+ * 2.  Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in the
+ *     documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+export function initializeDecompressionStream(format) {
+  // Validate format
+  if (format !== "deflate" && format !== "deflate-raw" && format !== "gzip") {
+    throw new TypeError(`The provided value '${format}' is not a valid enum value of type CompressionFormat.`);
+  }
+
+  const zlib = require("node:zlib");
+  let decompressor;
+
+  // Create the appropriate decompressor based on the format
+  if (format === "deflate") {
+    decompressor = zlib.createInflate();
+  } else if (format === "deflate-raw") {
+    decompressor = zlib.createInflateRaw();
+  } else if (format === "gzip") {
+    decompressor = zlib.createGunzip();
+  }
+
+  const startAlgorithm = () => {
+    return Promise.$resolve();
+  };
+
+  const transformAlgorithm = chunk => {
+    return new Promise((resolve, reject) => {
+      decompressor.write(chunk, err => {
+        if (err) reject(err);
+        else resolve();
+      });
+    });
+  };
+
+  const flushAlgorithm = () => {
+    return new Promise((resolve, reject) => {
+      decompressor.end(err => {
+        if (err) reject(err);
+        else resolve();
+      });
+    });
+  };
+
+  const transform = $createTransformStream(startAlgorithm, transformAlgorithm, flushAlgorithm);
+  $putByIdDirectPrivate(this, "decompressionStreamTransform", transform);
+  $putByIdDirectPrivate(this, "decompressionStreamDecompressor", decompressor);
+
+  // Set up event handlers to pipe decompressed data through the transform stream
+  decompressor.on("data", chunk => {
+    const transformStream = $getByIdDirectPrivate(this, "decompressionStreamTransform");
+    const controller = $getByIdDirectPrivate(transformStream, "controller");
+    $transformStreamDefaultControllerEnqueue(controller, chunk);
+  });
+
+  return this;
+}
+
+$getter;
+export function readable() {
+  const transform = $getByIdDirectPrivate(this, "decompressionStreamTransform");
+  if (!transform) throw $ERR_INVALID_THIS("DecompressionStream");
+
+  return $getByIdDirectPrivate(transform, "readable");
+}
+
+$getter;
+export function writable() {
+  const transform = $getByIdDirectPrivate(this, "decompressionStreamTransform");
+  if (!transform) throw $ERR_INVALID_THIS("DecompressionStream");
+
+  return $getByIdDirectPrivate(transform, "writable");
+}