diff --git a/packages/@lwc/engine-core/src/framework/api.ts b/packages/@lwc/engine-core/src/framework/api.ts
index 5f453bec45..bc83e15a6a 100644
--- a/packages/@lwc/engine-core/src/framework/api.ts
+++ b/packages/@lwc/engine-core/src/framework/api.ts
@@ -50,6 +50,8 @@ import {
     VText,
     VStaticPart,
     VStaticPartData,
+    isVBaseElement,
+    isVStatic,
 } from './vnodes';
 import { getComponentRegisteredName } from './component';
 
@@ -92,6 +94,7 @@ function st(fragment: Element, key: Key, parts?: VStaticPart[]): VStatic {
         fragment,
         owner,
         parts,
+        slotAssignment: undefined,
     };
 
     return vnode;
@@ -160,7 +163,7 @@ function h(sel: string, data: VElementData, children: VNodes = EmptyArray): VEle
         });
     }
 
-    const { key } = data;
+    const { key, slotAssignment } = data;
 
     const vnode: VElement = {
         type: VNodeType.Element,
@@ -170,6 +173,7 @@ function h(sel: string, data: VElementData, children: VNodes = EmptyArray): VEle
         elm: undefined,
         key,
         owner: vmBeingRendered,
+        slotAssignment,
     };
 
     return vnode;
@@ -207,6 +211,10 @@ function s(
         assert.isTrue(isObject(data), `s() 2nd argument data must be an object.`);
         assert.isTrue(isArray(children), `h() 3rd argument children must be an array.`);
     }
+
+    const vmBeingRendered = getVMBeingRendered()!;
+    const { renderMode, apiVersion } = vmBeingRendered;
+
     if (
         !isUndefined(slotset) &&
         !isUndefined(slotset.slotAssignments) &&
@@ -236,7 +244,6 @@ function s(
                 }
                 // If the passed slot content is factory, evaluate it and add the produced vnodes
                 if (assignedNodeIsScopedSlot) {
-                    const vmBeingRenderedInception = getVMBeingRendered();
                     // Evaluate in the scope of the slot content's owner
                     // if a slotset is provided, there will always be an owner. The only case where owner is
                     // undefined is for root components, but root components cannot accept slotted content
@@ -249,19 +256,34 @@ function s(
                             ArrayPush.call(newChildren, vnode.factory(data.slotData, data.key));
                         });
                     } finally {
-                        setVMBeingRendered(vmBeingRenderedInception);
+                        setVMBeingRendered(vmBeingRendered);
                     }
                 } else {
+                    // This block is for standard slots (non-scoped slots)
+                    let clonedVNode;
+                    if (
+                        renderMode === RenderMode.Light &&
+                        isAPIFeatureEnabled(APIFeature.USE_LIGHT_DOM_SLOT_FORWARDING, apiVersion) &&
+                        (isVBaseElement(vnode) || isVStatic(vnode)) &&
+                        // We only need to copy the vnodes when the slot assignment changes, copying every time causes issues with
+                        // disconnected/connected callback firing.
+                        vnode.slotAssignment !== data.slotAssignment
+                    ) {
+                        // When the light DOM slot assignment (slot attribute) changes we can't use the same reference
+                        // to the vnode because the current way the diffing algo works, it will replace the original reference
+                        // to the host element with a new one. This means the new element will be mounted and immediately unmounted.
+                        // Creating a copy of the vnode to preserve a reference to the previous host element.
+                        clonedVNode = { ...vnode, slotAssignment: data.slotAssignment };
+                    }
                     // If the slot content is standard type, the content is static, no additional
                     // processing needed on the vnode
-                    ArrayPush.call(newChildren, vnode);
+                    ArrayPush.call(newChildren, clonedVNode ?? vnode);
                 }
             }
         }
         children = newChildren;
     }
-    const vmBeingRendered = getVMBeingRendered()!;
-    const { renderMode, shadowMode, apiVersion } = vmBeingRendered;
+    const { shadowMode } = vmBeingRendered;
 
     if (renderMode === RenderMode.Light) {
         // light DOM slots - backwards-compatible behavior uses flattening, new behavior uses fragments
@@ -324,7 +346,7 @@ function c(
             });
         }
     }
-    const { key } = data;
+    const { key, slotAssignment } = data;
     let elm, aChildren, vm;
     const vnode: VCustomElement = {
         type: VNodeType.CustomElement,
@@ -333,6 +355,7 @@ function c(
         children,
         elm,
         key,
+        slotAssignment,
 
         ctor: Ctor,
         owner: vmBeingRendered,
diff --git a/packages/@lwc/engine-core/src/framework/modules/attrs.ts b/packages/@lwc/engine-core/src/framework/modules/attrs.ts
index 3aa20cbc17..16d6f88f3f 100644
--- a/packages/@lwc/engine-core/src/framework/modules/attrs.ts
+++ b/packages/@lwc/engine-core/src/framework/modules/attrs.ts
@@ -15,7 +15,7 @@ import {
 import { RendererAPI } from '../renderer';
 
 import { EmptyObject } from '../utils';
-import { VBaseElement } from '../vnodes';
+import { VBaseElement, VStatic } from '../vnodes';
 
 const ColonCharCode = 58;
 
@@ -63,3 +63,24 @@ export function patchAttributes(
         }
     }
 }
+
+export function patchSlotAssignment(
+    oldVnode: VBaseElement | VStatic | null,
+    vnode: VBaseElement | VStatic,
+    renderer: RendererAPI
+) {
+    const { slotAssignment } = vnode;
+
+    if (oldVnode?.slotAssignment === slotAssignment) {
+        return;
+    }
+
+    const { elm } = vnode;
+    const { setAttribute, removeAttribute } = renderer;
+
+    if (isUndefined(slotAssignment) || isNull(slotAssignment)) {
+        removeAttribute(elm, 'slot');
+    } else {
+        setAttribute(elm, 'slot', slotAssignment);
+    }
+}
diff --git a/packages/@lwc/engine-core/src/framework/rendering.ts b/packages/@lwc/engine-core/src/framework/rendering.ts
index 586f2a784f..d487f9c04b 100644
--- a/packages/@lwc/engine-core/src/framework/rendering.ts
+++ b/packages/@lwc/engine-core/src/framework/rendering.ts
@@ -47,6 +47,7 @@ import {
     isVCustomElement,
     isVFragment,
     isVScopedSlotFragment,
+    isVStatic,
     Key,
     VBaseElement,
     VComment,
@@ -60,7 +61,7 @@ import {
     VText,
 } from './vnodes';
 
-import { patchAttributes } from './modules/attrs';
+import { patchAttributes, patchSlotAssignment } from './modules/attrs';
 import { patchProps } from './modules/props';
 import { patchClassAttribute } from './modules/computed-class-attr';
 import { patchStyleAttribute } from './modules/computed-style-attr';
@@ -266,6 +267,8 @@ function mountElement(
 function patchStatic(n1: VStatic, n2: VStatic, renderer: RendererAPI) {
     const elm = (n2.elm = n1.elm!);
 
+    // slotAssignments can only apply to the top level element, never to a static part.
+    patchSlotAssignment(n1, n2, renderer);
     // The `refs` object is blown away in every re-render, so we always need to re-apply them
     applyStaticParts(elm, n2, renderer, false);
 }
@@ -299,6 +302,8 @@ function mountStatic(
         }
     }
 
+    // slotAssignments can only apply to the top level element, never to a static part.
+    patchSlotAssignment(null, vnode, renderer);
     insertNode(elm, parent, anchor, renderer);
     applyStaticParts(elm, vnode, renderer, true);
 }
@@ -601,6 +606,7 @@ function patchElementPropsAndAttrsAndRefs(
 
     patchAttributes(oldVnode, vnode, renderer);
     patchProps(oldVnode, vnode, renderer);
+    patchSlotAssignment(oldVnode, vnode, renderer);
 
     // The `refs` object is blown away in every re-render, so we always need to re-apply them
     applyRefs(vnode, vnode.owner);
@@ -799,8 +805,8 @@ function allocateInSlot(vm: VM, children: VNodes, owner: VM) {
         }
 
         let slotName: unknown = '';
-        if (isVBaseElement(vnode)) {
-            slotName = vnode.data.attrs?.slot ?? '';
+        if (isVBaseElement(vnode) || isVStatic(vnode)) {
+            slotName = vnode.slotAssignment ?? '';
         } else if (isVScopedSlotFragment(vnode)) {
             slotName = vnode.slotName;
         }
diff --git a/packages/@lwc/engine-core/src/framework/vnodes.ts b/packages/@lwc/engine-core/src/framework/vnodes.ts
index c663a9c67b..ea040890c9 100644
--- a/packages/@lwc/engine-core/src/framework/vnodes.ts
+++ b/packages/@lwc/engine-core/src/framework/vnodes.ts
@@ -63,6 +63,8 @@ export interface VStatic extends BaseVNode {
     readonly fragment: Element;
     readonly parts: VStaticPart[] | undefined;
     elm: Element | undefined;
+    // Corresponds to the slot attribute of the element and indicates which `slot` element it should be assigned to
+    slotAssignment: string | undefined;
 }
 
 export interface VFragment extends BaseVNode, BaseVParent {
@@ -99,6 +101,8 @@ export interface VBaseElement extends BaseVNode, BaseVParent {
     data: VElementData;
     elm: Element | undefined;
     key: Key;
+    // Corresponds to the slot attribute of the element and indicates which `slot` element it should be assigned to
+    slotAssignment: string | undefined;
 }
 
 export interface VElement extends VBaseElement {
@@ -134,6 +138,8 @@ export interface VElementData extends VNodeData {
     readonly external?: boolean;
     readonly ref?: string;
     readonly slotData?: any;
+    // Corresponds to the slot attribute of the element and indicates which `slot` element it should be assigned to
+    readonly slotAssignment?: string;
 }
 
 export function isVBaseElement(vnode: VNode): vnode is VElement | VCustomElement {
@@ -156,3 +162,7 @@ export function isVFragment(vnode: VNode): vnode is VFragment {
 export function isVScopedSlotFragment(vnode: VNode): vnode is VScopedSlotFragment {
     return vnode.type === VNodeType.ScopedSlotFragment;
 }
+
+export function isVStatic(vnode: VNode): vnode is VStatic {
+    return vnode.type === VNodeType.Static;
+}
diff --git a/packages/@lwc/integration-karma/helpers/test-utils.js b/packages/@lwc/integration-karma/helpers/test-utils.js
index cdc4636372..3bea9d7ba0 100644
--- a/packages/@lwc/integration-karma/helpers/test-utils.js
+++ b/packages/@lwc/integration-karma/helpers/test-utils.js
@@ -22,9 +22,9 @@ window.TestUtils = (function (lwc, jasmine, beforeAll) {
     // TODO [#869]: Replace this custom spy with standard spyOn jasmine spy when logWarning doesn't use console.group
     // anymore. On IE11 console.group has a different behavior when the F12 inspector is attached to the page.
     function spyConsole() {
-        var originalConsole = window.console;
+        const originalConsole = window.console;
 
-        var calls = {
+        const calls = {
             log: [],
             warn: [],
             error: [],
@@ -67,15 +67,15 @@ window.TestUtils = (function (lwc, jasmine, beforeAll) {
         return function consoleDevMatcher() {
             return {
                 negativeCompare: function negativeCompare(actual) {
-                    var spy = spyConsole();
+                    const spy = spyConsole();
                     try {
                         actual();
                     } finally {
                         spy.reset();
                     }
 
-                    var callsArgs = spy.calls[methodName];
-                    var formattedCalls = callsArgs
+                    const callsArgs = spy.calls[methodName];
+                    const formattedCalls = callsArgs
                         .map(function (arg) {
                             return '"' + formatConsoleCall(arg) + '"';
                         })
@@ -118,7 +118,7 @@ window.TestUtils = (function (lwc, jasmine, beforeAll) {
                         );
                     }
 
-                    var spy = spyConsole();
+                    const spy = spyConsole();
 
                     try {
                         actual();
@@ -126,8 +126,8 @@ window.TestUtils = (function (lwc, jasmine, beforeAll) {
                         spy.reset();
                     }
 
-                    var callsArgs = spy.calls[methodName];
-                    var formattedCalls = callsArgs
+                    const callsArgs = spy.calls[methodName];
+                    const formattedCalls = callsArgs
                         .map(function (callArgs) {
                             return '"' + formatConsoleCall(callArgs) + '"';
                         })
@@ -168,10 +168,10 @@ window.TestUtils = (function (lwc, jasmine, beforeAll) {
                                         ' time(s).'
                                 );
                             }
-                            for (var i = 0; i < callsArgs.length; i++) {
-                                var callsArg = callsArgs[i];
-                                var expectedMessage = expectedMessages[i];
-                                var actualMessage = formatConsoleCall(callsArg);
+                            for (let i = 0; i < callsArgs.length; i++) {
+                                const callsArg = callsArgs[i];
+                                const expectedMessage = expectedMessages[i];
+                                const actualMessage = formatConsoleCall(callsArg);
                                 if (!matchMessage(actualMessage, expectedMessage)) {
                                     return fail(
                                         'Expected console.' +
@@ -243,7 +243,7 @@ window.TestUtils = (function (lwc, jasmine, beforeAll) {
                         );
                     }
 
-                    var thrown = errorListener(actual);
+                    const thrown = errorListener(actual);
 
                     if (!expectInProd && process.env.NODE_ENV === 'production') {
                         if (thrown !== undefined) {
@@ -294,7 +294,7 @@ window.TestUtils = (function (lwc, jasmine, beforeAll) {
 
     // Listen for errors using window.addEventListener('error')
     function windowErrorListener(callback) {
-        var error;
+        let error;
         function onError(event) {
             event.preventDefault(); // don't log the error
             error = event.error;
@@ -302,7 +302,7 @@ window.TestUtils = (function (lwc, jasmine, beforeAll) {
 
         // Prevent jasmine from handling the global error. There doesn't seem to be another
         // way to disable this behavior: https://github.com/jasmine/jasmine/pull/1860
-        var originalOnError = window.onerror;
+        const originalOnError = window.onerror;
         window.onerror = null;
         window.addEventListener('error', onError);
 
@@ -329,7 +329,7 @@ window.TestUtils = (function (lwc, jasmine, beforeAll) {
             : directErrorListener(callback);
     }
 
-    var customMatchers = {
+    const customMatchers = {
         toLogErrorDev: consoleDevMatcherFactory('error'),
         toLogError: consoleDevMatcherFactory('error', true),
         toLogWarningDev: consoleDevMatcherFactory('warn'),
@@ -365,7 +365,7 @@ window.TestUtils = (function (lwc, jasmine, beforeAll) {
     }
 
     function extractDataIds(root) {
-        var nodes = {};
+        const nodes = {};
 
         function processElement(elm) {
             if (elm.hasAttribute('data-id')) {
@@ -383,14 +383,14 @@ window.TestUtils = (function (lwc, jasmine, beforeAll) {
 
         // Work around Internet Explorer wanting a function instead of an object. IE also *requires* this argument where
         // other browsers don't.
-        var safeFilter = acceptNode;
+        const safeFilter = acceptNode;
         safeFilter.acceptNode = acceptNode;
 
-        var walker = document.createTreeWalker(root, NodeFilter.SHOW_ELEMENT, safeFilter, false);
+        const walker = document.createTreeWalker(root, NodeFilter.SHOW_ELEMENT, safeFilter, false);
 
         processElement(root);
 
-        var elm;
+        let elm;
         while ((elm = walker.nextNode())) {
             processElement(elm);
         }
@@ -399,26 +399,26 @@ window.TestUtils = (function (lwc, jasmine, beforeAll) {
     }
 
     function extractShadowDataIds(shadowRoot) {
-        var nodes = {};
+        const nodes = {};
 
         // Add the shadow root here even if they don't have [data-id] attributes. This reference is
         // subsequently used to add event listeners.
-        var dataId = shadowRoot.host.getAttribute('data-id');
+        const dataId = shadowRoot.host.getAttribute('data-id');
         if (dataId) {
             nodes[dataId + '.shadowRoot'] = shadowRoot;
         }
 
         // We can't use a TreeWalker directly on the ShadowRoot since with synthetic shadow the ShadowRoot is not an
         // actual DOM nodes. So we need to iterate over the children manually and run the tree walker on each child.
-        for (var i = 0; i < shadowRoot.childNodes.length; i++) {
-            var child = shadowRoot.childNodes[i];
+        for (let i = 0; i < shadowRoot.childNodes.length; i++) {
+            const child = shadowRoot.childNodes[i];
             Object.assign(nodes, extractDataIds(child));
         }
 
         return nodes;
     }
 
-    var register = {};
+    let register = {};
     function load(id) {
         return Promise.resolve(register[id]);
     }
@@ -447,7 +447,7 @@ window.TestUtils = (function (lwc, jasmine, beforeAll) {
     }
 
     // Providing overridable hooks for tests
-    var sanitizeHtmlContentHook = function () {
+    let sanitizeHtmlContentHook = function () {
         throw new Error('sanitizeHtmlContent hook must be implemented.');
     };
 
@@ -470,7 +470,7 @@ window.TestUtils = (function (lwc, jasmine, beforeAll) {
     }
 
     // This mapping should be kept up-to-date with the mapping in @lwc/shared -> aria.ts
-    var ariaPropertiesMapping = {
+    const ariaPropertiesMapping = {
         ariaAutoComplete: 'aria-autocomplete',
         ariaChecked: 'aria-checked',
         ariaCurrent: 'aria-current',
@@ -526,7 +526,7 @@ window.TestUtils = (function (lwc, jasmine, beforeAll) {
     };
 
     // See the README for @lwc/aria-reflection
-    var nonStandardAriaProperties = [
+    const nonStandardAriaProperties = [
         'ariaActiveDescendant',
         'ariaControls',
         'ariaDescribedBy',
@@ -539,7 +539,7 @@ window.TestUtils = (function (lwc, jasmine, beforeAll) {
 
     // These properties are not included in the global polyfill, but were added to LightningElement/BridgeElement
     // prototypes in https://github.com/salesforce/lwc/pull/3702
-    var nonPolyfilledAriaProperties = [
+    const nonPolyfilledAriaProperties = [
         'ariaColIndexText',
         'ariaBrailleLabel',
         'ariaBrailleRoleDescription',
@@ -547,10 +547,10 @@ window.TestUtils = (function (lwc, jasmine, beforeAll) {
         'ariaRowIndexText',
     ];
 
-    var ariaProperties = Object.keys(ariaPropertiesMapping);
+    const ariaProperties = Object.keys(ariaPropertiesMapping);
 
     // Can't use Object.values because we need to support IE11
-    var ariaAttributes = [];
+    const ariaAttributes = [];
     for (let i = 0; i < ariaProperties.length; i++) {
         ariaAttributes.push(ariaPropertiesMapping[ariaProperties[i]]);
     }
@@ -558,7 +558,7 @@ window.TestUtils = (function (lwc, jasmine, beforeAll) {
     // Keep traversing up the prototype chain until a property descriptor is found
     function getPropertyDescriptor(object, prop) {
         do {
-            var descriptor = Object.getOwnPropertyDescriptor(object, prop);
+            const descriptor = Object.getOwnPropertyDescriptor(object, prop);
             if (descriptor) {
                 return descriptor;
             }
@@ -566,6 +566,10 @@ window.TestUtils = (function (lwc, jasmine, beforeAll) {
         } while (object);
     }
 
+    // These values are based on the API versions in @lwc/shared/api-version
+    const lightDomSlotForwardingEnabled = process.env.API_VERSION > 60;
+    const vFragBookEndEnabled = process.env.API_VERSION > 59;
+
     return {
         clearRegister: clearRegister,
         extractDataIds: extractDataIds,
@@ -588,5 +592,7 @@ window.TestUtils = (function (lwc, jasmine, beforeAll) {
         attachReportingControlDispatcher: attachReportingControlDispatcher,
         detachReportingControlDispatcher: detachReportingControlDispatcher,
         nativeCustomElementLifecycleEnabled: nativeCustomElementLifecycleEnabled,
+        lightDomSlotForwardingEnabled: lightDomSlotForwardingEnabled,
+        vFragBookEndEnabled: vFragBookEndEnabled,
     };
 })(LWC, jasmine, beforeAll);
diff --git a/packages/@lwc/integration-karma/test/act/act-components/test-multiple-slots.js b/packages/@lwc/integration-karma/test/act/act-components/test-multiple-slots.js
index d2056cc029..2b022e5de1 100644
--- a/packages/@lwc/integration-karma/test/act/act-components/test-multiple-slots.js
+++ b/packages/@lwc/integration-karma/test/act/act-components/test-multiple-slots.js
@@ -27,9 +27,7 @@ export default function (define) {
                                 'ui-something',
                                 _uiSomething__default['default'],
                                 {
-                                    attrs: {
-                                        slot: 'first',
-                                    },
+                                    slotAssignment: 'first',
                                     props: {
                                         text: 'Hello',
                                     },
@@ -41,9 +39,7 @@ export default function (define) {
                                 'ui-another',
                                 _uiAnother__default['default'],
                                 {
-                                    attrs: {
-                                        slot: 'second',
-                                    },
+                                    slotAssignment: 'second',
                                     props: {
                                         value: 'Foo',
                                     },
diff --git a/packages/@lwc/integration-karma/test/act/act-components/test-slot-adjacent-to-named-slot.js b/packages/@lwc/integration-karma/test/act/act-components/test-slot-adjacent-to-named-slot.js
index 5ff313343d..a10b99998f 100644
--- a/packages/@lwc/integration-karma/test/act/act-components/test-slot-adjacent-to-named-slot.js
+++ b/packages/@lwc/integration-karma/test/act/act-components/test-slot-adjacent-to-named-slot.js
@@ -27,9 +27,7 @@ export default function (define) {
                                 'ui-another',
                                 _uiAnother__default['default'],
                                 {
-                                    attrs: {
-                                        slot: 'adjacent',
-                                    },
+                                    slotAssignment: 'adjacent',
                                     props: {
                                         value: 'Foo',
                                     },
diff --git a/packages/@lwc/integration-karma/test/act/act-components/test-slot-in-grandchild.js b/packages/@lwc/integration-karma/test/act/act-components/test-slot-in-grandchild.js
index 310b62c3ca..04e4c4fd8a 100644
--- a/packages/@lwc/integration-karma/test/act/act-components/test-slot-in-grandchild.js
+++ b/packages/@lwc/integration-karma/test/act/act-components/test-slot-in-grandchild.js
@@ -27,9 +27,7 @@ export default function (define) {
                                 'ui-something',
                                 _uiSomething__default['default'],
                                 {
-                                    attrs: {
-                                        slot: 'first',
-                                    },
+                                    slotAssignment: 'first',
                                     props: {
                                         text: 'Hello',
                                     },
@@ -40,9 +38,7 @@ export default function (define) {
                                         'ui-another',
                                         _uiAnother__default['default'],
                                         {
-                                            attrs: {
-                                                slot: 'second',
-                                            },
+                                            slotAssignment: 'second',
                                             props: {
                                                 value: 'Foo',
                                             },
diff --git a/packages/@lwc/integration-karma/test/api/CustomElementConstructor-getter/index.spec.js b/packages/@lwc/integration-karma/test/api/CustomElementConstructor-getter/index.spec.js
index a589e99f46..5ccc20934b 100644
--- a/packages/@lwc/integration-karma/test/api/CustomElementConstructor-getter/index.spec.js
+++ b/packages/@lwc/integration-karma/test/api/CustomElementConstructor-getter/index.spec.js
@@ -1,4 +1,5 @@
 import { LightningElement } from 'lwc';
+import { vFragBookEndEnabled } from 'test-utils';
 
 import ReflectElement from 'x/reflect';
 import LifecycleParent from 'x/lifecycleParent';
@@ -10,7 +11,7 @@ import ReflectCamel from 'x/reflectCamel';
 import WithChildElmsHasSlot from 'x/withChildElmsHasSlot';
 import WithChildElmsHasSlotLight from 'x/withChildElmsHasSlotLight';
 
-const vFragBookend = process.env.API_VERSION > 59 ? '<!---->' : '';
+const vFragBookend = vFragBookEndEnabled ? '<!---->' : '';
 
 it('should throw when trying to claim abstract LightningElement as custom element', () => {
     expect(() => LightningElement.CustomElementConstructor).toThrowError(
diff --git a/packages/@lwc/integration-karma/test/light-dom/scoped-slot/if-block/index.spec.js b/packages/@lwc/integration-karma/test/light-dom/scoped-slot/if-block/index.spec.js
index 3976a57dd8..ed3d52def6 100644
--- a/packages/@lwc/integration-karma/test/light-dom/scoped-slot/if-block/index.spec.js
+++ b/packages/@lwc/integration-karma/test/light-dom/scoped-slot/if-block/index.spec.js
@@ -1,8 +1,9 @@
 import { createElement } from 'lwc';
+import { vFragBookEndEnabled } from 'test-utils';
 
 import MixedSlotParent from 'x/mixedSlotParent';
 
-const vFragBookend = process.env.API_VERSION > 59 ? '<!---->' : '';
+const vFragBookend = vFragBookEndEnabled ? '<!---->' : '';
 
 describe('if-block', () => {
     it('should work when parent and child have matching slot types', () => {
diff --git a/packages/@lwc/integration-karma/test/light-dom/scoped-slot/index.spec.js b/packages/@lwc/integration-karma/test/light-dom/scoped-slot/index.spec.js
index 1751554f0a..447ff25540 100644
--- a/packages/@lwc/integration-karma/test/light-dom/scoped-slot/index.spec.js
+++ b/packages/@lwc/integration-karma/test/light-dom/scoped-slot/index.spec.js
@@ -1,4 +1,5 @@
 import { createElement } from 'lwc';
+import { lightDomSlotForwardingEnabled, vFragBookEndEnabled } from 'test-utils';
 
 import BasicParent from 'x/basicParent';
 import ParentOfChildWithForEach from 'x/parentOfChildWithForEach';
@@ -6,7 +7,7 @@ import ParentWNoSlotContent from 'x/parentWNoSlotContent';
 import ParentOfChildWithNamedSlots from 'x/parentOfChildWithNamedSlots';
 import NestedSlots from 'x/nestedSlots';
 
-const vFragBookend = process.env.API_VERSION > 59 ? '<!---->' : '';
+const vFragBookend = vFragBookEndEnabled ? '<!---->' : '';
 
 describe('scoped slots', () => {
     it('scoped slots work with default slots', () => {
@@ -61,7 +62,9 @@ describe('scoped slots', () => {
         // For standard slot content, "slot" attribute goes directly on the element unlike scoped
         //  slots where the attribute goes on the template tag
         expect(child.querySelector('.slotname3').innerHTML).toBe(
-            `${vFragBookend}<p slot="slotname3">MLB</p>${vFragBookend}`
+            lightDomSlotForwardingEnabled
+                ? `${vFragBookend}<p>MLB</p>${vFragBookend}`
+                : `${vFragBookend}<p slot="slotname3">MLB</p>${vFragBookend}`
         );
     });
 
diff --git a/packages/@lwc/integration-karma/test/light-dom/scoped-slot/runtime-checks/index.spec.js b/packages/@lwc/integration-karma/test/light-dom/scoped-slot/runtime-checks/index.spec.js
index fc1a8afb33..7a38b8016e 100644
--- a/packages/@lwc/integration-karma/test/light-dom/scoped-slot/runtime-checks/index.spec.js
+++ b/packages/@lwc/integration-karma/test/light-dom/scoped-slot/runtime-checks/index.spec.js
@@ -1,9 +1,10 @@
 import { createElement } from 'lwc';
+import { vFragBookEndEnabled } from 'test-utils';
 
 import ParentWithScopedSlotContent from 'x/parentWithScopedSlotContent';
 import ParentWithStandardSlotContent from 'x/parentWithStandardSlotContent';
 
-const vFragBookend = process.env.API_VERSION > 59 ? '<!---->' : '';
+const vFragBookend = vFragBookEndEnabled ? '<!---->' : '';
 
 describe('runtime validation of slot content and slot', () => {
     it('Ignores content when parent uses scoped slot and child has standard slot', () => {
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/scoped-slots/index.spec.js b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/scoped-slots/index.spec.js
new file mode 100644
index 0000000000..f195526561
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/scoped-slots/index.spec.js
@@ -0,0 +1,31 @@
+import { createElement } from 'lwc';
+
+import LightContainer from './x/lightContainer/lightContainer';
+
+describe('scoped slots, slot forwarding', () => {
+    let lightContainer;
+    beforeAll(() => {
+        lightContainer = createElement('x-light-container', { is: LightContainer });
+        document.body.appendChild(lightContainer);
+    });
+
+    afterAll(() => {
+        document.body.removeChild(lightContainer);
+    });
+
+    // TODO [#3889]: This test should be updated once a fix is ready.
+    it('does not reassign slot content', () => {
+        const leaf = lightContainer.querySelector('x-leaf');
+        expect(leaf.shadowRoot.children.length).toEqual(2);
+
+        const defaultSlot = leaf.shadowRoot.querySelector('slot');
+        const defaultSlotContent = defaultSlot.assignedNodes();
+        expect(defaultSlotContent.length).toEqual(1);
+        expect(defaultSlotContent[0].innerText).toEqual('Hello world!');
+
+        const fooSlot = leaf.shadowRoot.querySelector('[name="foo"]');
+        const fooSlotContent = fooSlot.assignedNodes();
+        // Note the slot reassignment does not work on scoped slots
+        expect(fooSlotContent.length).toEqual(0);
+    });
+});
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/scoped-slots/x/leaf/leaf.html b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/scoped-slots/x/leaf/leaf.html
new file mode 100644
index 0000000000..68f2c67ef3
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/scoped-slots/x/leaf/leaf.html
@@ -0,0 +1,4 @@
+<template>
+    <slot></slot>
+    <slot name="foo"></slot>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/scoped-slots/x/leaf/leaf.js b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/scoped-slots/x/leaf/leaf.js
new file mode 100644
index 0000000000..ca8dce94e0
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/scoped-slots/x/leaf/leaf.js
@@ -0,0 +1,3 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {}
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/scoped-slots/x/lightContainer/lightContainer.html b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/scoped-slots/x/lightContainer/lightContainer.html
new file mode 100644
index 0000000000..4511f208bb
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/scoped-slots/x/lightContainer/lightContainer.html
@@ -0,0 +1,3 @@
+<template lwc:render-mode="light">
+    <x-scoped-slot-parent></x-scoped-slot-parent>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/scoped-slots/x/lightContainer/lightContainer.js b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/scoped-slots/x/lightContainer/lightContainer.js
new file mode 100644
index 0000000000..0679d2bc10
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/scoped-slots/x/lightContainer/lightContainer.js
@@ -0,0 +1,5 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {
+    static renderMode = 'light';
+}
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/scoped-slots/x/scopedSlotChild/scopedSlotChild.html b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/scoped-slots/x/scopedSlotChild/scopedSlotChild.html
new file mode 100644
index 0000000000..4a385ec61a
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/scoped-slots/x/scopedSlotChild/scopedSlotChild.html
@@ -0,0 +1,6 @@
+<template lwc:render-mode="light">
+    <x-leaf>
+        <!-- Note the slot mapping does not work for scoped slots -->
+        <slot lwc:slot-bind={title} slot="foo"></slot>
+    </x-leaf>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/scoped-slots/x/scopedSlotChild/scopedSlotChild.js b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/scoped-slots/x/scopedSlotChild/scopedSlotChild.js
new file mode 100644
index 0000000000..ba52afd521
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/scoped-slots/x/scopedSlotChild/scopedSlotChild.js
@@ -0,0 +1,7 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {
+    static renderMode = 'light';
+
+    title = 'Hello world!';
+}
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/scoped-slots/x/scopedSlotParent/scopedSlotParent.html b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/scoped-slots/x/scopedSlotParent/scopedSlotParent.html
new file mode 100644
index 0000000000..ab8f526ad6
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/scoped-slots/x/scopedSlotParent/scopedSlotParent.html
@@ -0,0 +1,7 @@
+<template lwc:render-mode="light">
+    <x-scoped-slot-child>
+        <template lwc:slot-data="title">
+            <h2>{title}</h2>
+        </template>
+    </x-scoped-slot-child>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/scoped-slots/x/scopedSlotParent/scopedSlotParent.js b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/scoped-slots/x/scopedSlotParent/scopedSlotParent.js
new file mode 100644
index 0000000000..0679d2bc10
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/scoped-slots/x/scopedSlotParent/scopedSlotParent.js
@@ -0,0 +1,5 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {
+    static renderMode = 'light';
+}
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/index.spec.js b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/index.spec.js
new file mode 100644
index 0000000000..81dd3b706c
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/index.spec.js
@@ -0,0 +1,271 @@
+import { createElement } from 'lwc';
+import { extractDataIds, lightDomSlotForwardingEnabled, vFragBookEndEnabled } from 'test-utils';
+
+import LightContainer from './x/lightContainer/lightContainer';
+
+const commentNode = document.createComment(' comments being forwarded ');
+
+const slotAssignmentWithForwarding = {
+    expectedUpperSlot: {
+        tagName: 'x-shadow-dom-element',
+        content: 'Lower slot forwarded content',
+        slotAttr: null,
+    },
+    expectedLowerSlot: {
+        tagName: 'x-light-dom-element',
+        content: 'Upper slot forwarded content',
+        slotAttr: null,
+    },
+    expectedDefaultSlot: {
+        innerText: 'Static vnode default slot forwarded',
+        textContent: 'Text being forwarded',
+    },
+};
+
+const slotAssignmentWithoutForwarding = {
+    expectedUpperSlot: {
+        tagName: 'x-light-dom-element',
+        content: 'Upper slot forwarded content',
+        slotAttr: 'upper',
+    },
+    expectedLowerSlot: {
+        tagName: 'x-shadow-dom-element',
+        content: 'Lower slot forwarded content',
+        slotAttr: 'lower',
+    },
+    expectedDefaultSlot: {
+        innerText: 'Static vnode default slot forwarded',
+        textContent: 'Text being forwarded',
+    },
+};
+
+const expectedSlotAssignment = lightDomSlotForwardingEnabled
+    ? slotAssignmentWithForwarding
+    : slotAssignmentWithoutForwarding;
+
+describe('slot forwarding', () => {
+    let nodes;
+    let lightContainer;
+    beforeAll(() => {
+        lightContainer = createElement('x-light-container', { is: LightContainer });
+        document.body.appendChild(lightContainer);
+        nodes = extractDataIds(lightContainer);
+    });
+
+    afterAll(() => {
+        document.body.removeChild(lightContainer);
+    });
+
+    it('should correctly forward slot assignments - light > light slot', () => {
+        const lightLightLeaf = nodes['light-light-leaf'];
+        // Note these include the vFragmentBookend elements
+        expect(lightLightLeaf.children.length).toBe(5);
+
+        const { expectedUpperSlot, expectedLowerSlot, expectedDefaultSlot } =
+            expectedSlotAssignment;
+
+        const slotContent = Array.from(lightLightLeaf.children);
+        const upperSlotContent = slotContent.slice(0, 2);
+        // Lower content is now mapped to upper slot
+        expect(upperSlotContent[0].getAttribute('slot')).toBe(expectedUpperSlot.slotAttr);
+        expect(upperSlotContent[0].tagName.toLowerCase()).toBe(expectedUpperSlot.tagName);
+        expect(upperSlotContent[1].getAttribute('slot')).toBe(expectedUpperSlot.slotAttr);
+        expect(upperSlotContent[1].innerText).toEqual(expectedUpperSlot.content);
+
+        // Upper content is now mapped to lower slot
+        const lowerSlotContent = slotContent.slice(2, 4);
+        expect(lowerSlotContent[0].getAttribute('slot')).toBe(expectedLowerSlot.slotAttr);
+        expect(lowerSlotContent[0].tagName.toLowerCase()).toEqual(expectedLowerSlot.tagName);
+        expect(lowerSlotContent[1].getAttribute('slot')).toBe(expectedLowerSlot.slotAttr);
+        expect(lowerSlotContent[1].innerText).toEqual(expectedLowerSlot.content);
+
+        // Default slot content is mapped to `defaultSlotReassigned` slot
+        const remappedDefaultSlotContent = slotContent.slice(4, 5);
+        expect(remappedDefaultSlotContent[0].innerText).toEqual(expectedDefaultSlot.innerText);
+
+        // These are to cover API versions 60, 59 and below
+        const defaultSlotTextIndex = lightDomSlotForwardingEnabled
+            ? 12
+            : vFragBookEndEnabled
+            ? 11
+            : 4;
+        const defaultSlotCommentIndex = lightDomSlotForwardingEnabled
+            ? 13
+            : vFragBookEndEnabled
+            ? 12
+            : 5;
+
+        expect(lightLightLeaf.childNodes[defaultSlotTextIndex].textContent).toEqual(
+            expectedDefaultSlot.textContent
+        );
+        expect(lightLightLeaf.childNodes[defaultSlotCommentIndex]).toEqual(commentNode);
+    });
+
+    it('should correctly forward slot assignments - light > shadow slot', () => {
+        const lightShadowLeaf = nodes['light-shadow-leaf'];
+        expect(lightShadowLeaf.shadowRoot.children.length).toBe(4);
+
+        const { expectedUpperSlot, expectedLowerSlot, expectedDefaultSlot } =
+            expectedSlotAssignment;
+
+        const slots = extractDataIds(lightShadowLeaf);
+        const upperSlotContent = slots['upper-slot'].assignedNodes();
+        expect(upperSlotContent[0].getAttribute('slot')).toBe('upper');
+        expect(upperSlotContent[0].tagName.toLowerCase()).toBe(expectedUpperSlot.tagName);
+        expect(upperSlotContent[1].getAttribute('slot')).toBe('upper');
+        expect(upperSlotContent[1].innerText).toEqual(expectedUpperSlot.content);
+
+        const lowerSlotContent = slots['lower-slot'].assignedNodes();
+        expect(lowerSlotContent[0].getAttribute('slot')).toBe('lower');
+        expect(lowerSlotContent[0].tagName.toLowerCase()).toEqual(expectedLowerSlot.tagName);
+        expect(lowerSlotContent[1].getAttribute('slot')).toBe('lower');
+        expect(lowerSlotContent[1].innerText).toEqual(expectedLowerSlot.content);
+
+        const defaultSlotContent = slots['default-slot'].assignedNodes();
+        expect(defaultSlotContent[0].textContent).toEqual(expectedDefaultSlot.textContent);
+        if (!process.env.NATIVE_SHADOW) {
+            // Native shadow doesn't slot comments
+            expect(defaultSlotContent[1]).toEqual(commentNode);
+        }
+
+        if (lightDomSlotForwardingEnabled) {
+            // With slot forwarding
+            const reassginedDefaultSlot = slots['default-slot-reassigned'].assignedNodes();
+            // Verify static vnode `slot` attribute is reassigned
+            expect(reassginedDefaultSlot[0].getAttribute('slot')).toBe('defaultSlotReassigned');
+            expect(reassginedDefaultSlot[0].innerText).toEqual(expectedDefaultSlot.innerText);
+        } else {
+            // Without slot forwarding
+            expect(defaultSlotContent[process.env.NATIVE_SHADOW ? 1 : 2].innerText).toEqual(
+                expectedDefaultSlot.innerText
+            );
+        }
+    });
+
+    it('should correctly forward slot assignments - shadow > light slot', () => {
+        const shadowLightLeaf = nodes['shadow-light-leaf'];
+        expect(shadowLightLeaf.children.length).toBe(3);
+
+        const { expectedUpperSlot, expectedLowerSlot, expectedDefaultSlot } =
+            slotAssignmentWithForwarding;
+
+        const slots = extractDataIds(shadowLightLeaf);
+        const upperSlot = slots['upper-slot'];
+        // In this test, the shadow slot is passed directly to the light DOM slot which will cause the
+        // slot attribute to be remapped to the slot attribute on the light DOM slot.
+        // Verify the slot attribute was correctly updated.
+        // Api versions < 61 slot forwarding is not enabled, so the slot attribute is untouched
+        expect(upperSlot.hasAttribute('slot')).toBe(!lightDomSlotForwardingEnabled);
+
+        const upperSlotContent = upperSlot.assignedNodes();
+        // Note that because the shadow slot is passed, the slot element is what's updated.
+        // Verify that the children have not been modified.
+        expect(upperSlotContent[0].getAttribute('slot')).toBe('lower');
+        expect(upperSlotContent[0].tagName.toLowerCase()).toBe(expectedUpperSlot.tagName);
+        expect(upperSlotContent[1].getAttribute('slot')).toBe('lower');
+        expect(upperSlotContent[1].innerText).toEqual(expectedUpperSlot.content);
+
+        const lowerSlot = slots['lower-slot'];
+        expect(lowerSlot.hasAttribute('slot')).toBe(!lightDomSlotForwardingEnabled);
+
+        const lowerSlotContent = lowerSlot.assignedNodes();
+        expect(lowerSlotContent[0].getAttribute('slot')).toBe('upper');
+        expect(lowerSlotContent[0].tagName.toLowerCase()).toEqual(expectedLowerSlot.tagName);
+        expect(lowerSlotContent[1].getAttribute('slot')).toBe('upper');
+        expect(lowerSlotContent[1].innerText).toEqual(expectedLowerSlot.content);
+
+        const defaultSlot = slots['default-slot'];
+        expect(defaultSlot.hasAttribute('slot')).toBe(!lightDomSlotForwardingEnabled);
+
+        // Note since the content forwarded to the default shadow slot are wrapped in an actual slot element,
+        // all content inside of it is forwarded together.
+        // This is in contrast to the above test where the static element is re-parented to reassginedDefaultSlot
+        const defaultSlotContent = defaultSlot.assignedNodes();
+        expect(defaultSlotContent[0].textContent).toEqual(expectedDefaultSlot.textContent);
+        if (!process.env.NATIVE_SHADOW) {
+            // Native shadow doesn't slot comments
+            expect(defaultSlotContent[1]).toEqual(commentNode);
+        }
+        expect(defaultSlotContent[process.env.NATIVE_SHADOW ? 1 : 2].innerText).toEqual(
+            expectedDefaultSlot.innerText
+        );
+    });
+
+    it('should correctly forward slot assignments - shadow > shadow slot', () => {
+        const shadowShadowLeaf = nodes['shadow-shadow-leaf'];
+        expect(shadowShadowLeaf.children.length).toBe(3);
+
+        const slots = extractDataIds(shadowShadowLeaf);
+        const upperLeafSlot = slots['upper-slot'];
+        // Verify the slot element is not replaced with children at the leaf
+        expect(upperLeafSlot.tagName.toLowerCase()).toEqual('slot');
+        expect(upperLeafSlot.getAttribute('name')).toEqual('upper');
+
+        const upperForwardedSlot = upperLeafSlot.assignedNodes();
+        expect(upperForwardedSlot.length).toEqual(1);
+        // Verify slot was not modified, ie:
+        // <slot slot="lower" name="upper"></slot>
+        expect(upperForwardedSlot[0].tagName.toLowerCase()).toEqual('slot');
+        expect(upperForwardedSlot[0].getAttribute('slot')).toEqual('upper');
+        expect(upperForwardedSlot[0].getAttribute('name')).toEqual('lower');
+
+        const upperSlotContent = upperForwardedSlot[0].assignedNodes();
+        expect(upperSlotContent.length).toEqual(2);
+        expect(upperSlotContent[0].getAttribute('slot')).toBe('lower');
+        expect(upperSlotContent[0].tagName.toLowerCase()).toBe('x-shadow-dom-element');
+        expect(upperSlotContent[1].getAttribute('slot')).toBe('lower');
+        expect(upperSlotContent[1].innerText).toEqual('Lower slot forwarded content');
+
+        const lowerLeafSlot = slots['lower-slot'];
+        // Verify the slot element is not replaced with children at the leaf
+        expect(lowerLeafSlot.tagName.toLowerCase()).toEqual('slot');
+        expect(lowerLeafSlot.getAttribute('name')).toEqual('lower');
+
+        const lowerForwardedSlot = lowerLeafSlot.assignedNodes();
+        expect(lowerForwardedSlot.length).toEqual(1);
+        // Verify slot was not modified, ie:
+        // <slot slot="upper" name="lower"></slot>
+        expect(lowerForwardedSlot[0].tagName.toLowerCase()).toEqual('slot');
+        expect(lowerForwardedSlot[0].getAttribute('slot')).toEqual('lower');
+        expect(lowerForwardedSlot[0].getAttribute('name')).toEqual('upper');
+
+        const lowerSlotContent = lowerForwardedSlot[0].assignedNodes();
+        expect(lowerSlotContent.length).toEqual(2);
+        expect(lowerSlotContent[0].getAttribute('slot')).toBe('upper');
+        expect(lowerSlotContent[0].tagName.toLowerCase()).toEqual('x-light-dom-element');
+        expect(lowerSlotContent[1].getAttribute('slot')).toBe('upper');
+        expect(lowerSlotContent[1].innerText).toEqual('Upper slot forwarded content');
+
+        const defaultLeafSlot = slots['default-slot'];
+        expect(defaultLeafSlot.hasAttribute('slot')).toBe(false);
+
+        const defaultForwardedSlot = defaultLeafSlot.assignedNodes();
+        // No slots were reassigned to the default leaf slot because they are remapped at the forwarded slot
+        expect(defaultForwardedSlot.length).toEqual(0);
+
+        const defaultRemappedLeafSlot = slots['default-slot-reassigned'];
+        expect(defaultRemappedLeafSlot.tagName.toLowerCase()).toEqual('slot');
+        expect(defaultRemappedLeafSlot.getAttribute('name')).toEqual('defaultSlotReassigned');
+
+        const defaultRemappedForwardedSlot = defaultRemappedLeafSlot.assignedNodes();
+        expect(defaultRemappedForwardedSlot.length).toEqual(1);
+
+        // Verify slot was not modified, ie:
+        // <slot slot="defaultSlotReassigned">Default slot not yet forwarded</slot>
+        expect(defaultRemappedForwardedSlot[0].tagName.toLowerCase()).toEqual('slot');
+        expect(defaultRemappedForwardedSlot[0].getAttribute('slot')).toEqual(
+            'defaultSlotReassigned'
+        );
+
+        const defaultRemappedSlotContent = defaultRemappedForwardedSlot[0].assignedNodes();
+        expect(defaultRemappedSlotContent.length).toEqual(process.env.NATIVE_SHADOW ? 2 : 3);
+        expect(defaultRemappedSlotContent[0].textContent).toEqual('Text being forwarded');
+        if (!process.env.NATIVE_SHADOW) {
+            // Native shadow doesn't slot comments
+            expect(defaultRemappedSlotContent[1]).toEqual(commentNode);
+        }
+        expect(defaultRemappedSlotContent[process.env.NATIVE_SHADOW ? 1 : 2].innerText).toEqual(
+            'Static vnode default slot forwarded'
+        );
+    });
+});
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/lightContainer/lightContainer.html b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/lightContainer/lightContainer.html
new file mode 100644
index 0000000000..a87a857acc
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/lightContainer/lightContainer.html
@@ -0,0 +1,41 @@
+<template lwc:render-mode="light" lwc:preserve-comments>
+    <x-light-light-slot data-id="light-light-slot">
+        <x-light-dom-element slot="upper"></x-light-dom-element>
+        <x-shadow-dom-element slot="lower"></x-shadow-dom-element>
+        <p slot="upper">Upper slot forwarded content</p>
+        <p slot="lower">Lower slot forwarded content</p>
+        Text being forwarded
+        <!-- comments being forwarded -->
+        <p>Static vnode default slot forwarded</p>
+    </x-light-light-slot>
+    
+    <x-light-shadow-slot data-id="light-shadow-slot">
+        <x-light-dom-element slot="upper"></x-light-dom-element>
+        <x-shadow-dom-element slot="lower"></x-shadow-dom-element>
+        <p slot="upper">Upper slot forwarded content</p>
+        <p slot="lower">Lower slot forwarded content</p>
+        Text being forwarded
+        <!-- comments being forwarded -->
+        <p>Static vnode default slot forwarded</p>
+    </x-light-shadow-slot>
+
+    <x-shadow-light-slot data-id="shadow-light-slot">
+        <x-light-dom-element slot="upper"></x-light-dom-element>
+        <x-shadow-dom-element slot="lower"></x-shadow-dom-element>
+        <p slot="upper">Upper slot forwarded content</p>
+        <p slot="lower">Lower slot forwarded content</p>
+        Text being forwarded
+        <!-- comments being forwarded -->
+        <p>Static vnode default slot forwarded</p>
+    </x-shadow-light-slot>
+
+    <x-shadow-shadow-slot>
+        <x-light-dom-element slot="upper"></x-light-dom-element>
+        <x-shadow-dom-element slot="lower"></x-shadow-dom-element>
+        <p slot="upper">Upper slot forwarded content</p>
+        <p slot="lower">Lower slot forwarded content</p>
+        Text being forwarded
+        <!-- comments being forwarded -->
+        <p>Static vnode default slot forwarded</p>
+    </x-shadow-shadow-slot>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/lightContainer/lightContainer.js b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/lightContainer/lightContainer.js
new file mode 100644
index 0000000000..0679d2bc10
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/lightContainer/lightContainer.js
@@ -0,0 +1,5 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {
+    static renderMode = 'light';
+}
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/lightDomElement/lightDomElement.html b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/lightDomElement/lightDomElement.html
new file mode 100644
index 0000000000..49246e22f2
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/lightDomElement/lightDomElement.html
@@ -0,0 +1,3 @@
+<template lwc:render-mode="light">
+    <h2>Light DOM custom element content</h2>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/lightDomElement/lightDomElement.js b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/lightDomElement/lightDomElement.js
new file mode 100644
index 0000000000..0679d2bc10
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/lightDomElement/lightDomElement.js
@@ -0,0 +1,5 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {
+    static renderMode = 'light';
+}
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/lightLeaf/lightLeaf.html b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/lightLeaf/lightLeaf.html
new file mode 100644
index 0000000000..de49d4feda
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/lightLeaf/lightLeaf.html
@@ -0,0 +1,6 @@
+<template lwc:render-mode="light">
+    <slot name="upper"></slot>
+    <slot name="lower"></slot>
+    <slot name="defaultSlotReassigned"></slot>
+    <slot></slot>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/lightLeaf/lightLeaf.js b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/lightLeaf/lightLeaf.js
new file mode 100644
index 0000000000..4f98e8c1bc
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/lightLeaf/lightLeaf.js
@@ -0,0 +1,5 @@
+import { LightningElement } from 'lwc';
+
+export default class LightContainer extends LightningElement {
+    static renderMode = 'light';
+}
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/lightLightSlot/lightLightSlot.html b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/lightLightSlot/lightLightSlot.html
new file mode 100644
index 0000000000..7e54c84012
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/lightLightSlot/lightLightSlot.html
@@ -0,0 +1,10 @@
+<template lwc:render-mode="light">
+    <x-light-leaf data-id="light-light-leaf">
+        <!-- Note upper and lower have mapping swapped here -->
+        <slot slot="lower" name="upper"></slot>
+        <slot slot="upper" name="lower"></slot>
+        <!-- Note default slot is mapped to a new slot name -->
+        <!-- Only applies to non text or comments -->
+        <slot slot="defaultSlotReassigned">Default slot not yet forwarded</slot>
+    </x-light-leaf>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/lightLightSlot/lightLightSlot.js b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/lightLightSlot/lightLightSlot.js
new file mode 100644
index 0000000000..0679d2bc10
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/lightLightSlot/lightLightSlot.js
@@ -0,0 +1,5 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {
+    static renderMode = 'light';
+}
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/lightShadowSlot/lightShadowSlot.html b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/lightShadowSlot/lightShadowSlot.html
new file mode 100644
index 0000000000..2ef5abd89a
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/lightShadowSlot/lightShadowSlot.html
@@ -0,0 +1,9 @@
+<template lwc:render-mode="light">
+    <x-shadow-leaf data-id="light-shadow-leaf">
+        <!-- Note upper and lower have mapping swapped here -->
+        <slot slot="lower" name="upper"></slot>
+        <slot slot="upper" name="lower"></slot>
+        <!-- Note default slot is mapped to a new slot name -->
+        <slot slot="defaultSlotReassigned">Default slot not yet forwarded</slot>
+    </x-shadow-leaf>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/lightShadowSlot/lightShadowSlot.js b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/lightShadowSlot/lightShadowSlot.js
new file mode 100644
index 0000000000..0679d2bc10
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/lightShadowSlot/lightShadowSlot.js
@@ -0,0 +1,5 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {
+    static renderMode = 'light';
+}
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/shadowDomElement/shadowDomElement.html b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/shadowDomElement/shadowDomElement.html
new file mode 100644
index 0000000000..15804f5198
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/shadowDomElement/shadowDomElement.html
@@ -0,0 +1,3 @@
+<template>
+    <h2>Shadow DOM custom element content</h2>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/shadowDomElement/shadowDomElement.js b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/shadowDomElement/shadowDomElement.js
new file mode 100644
index 0000000000..ca8dce94e0
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/shadowDomElement/shadowDomElement.js
@@ -0,0 +1,3 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {}
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/shadowLeaf/shadowLeaf.html b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/shadowLeaf/shadowLeaf.html
new file mode 100644
index 0000000000..ce609204be
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/shadowLeaf/shadowLeaf.html
@@ -0,0 +1,6 @@
+<template>
+    <slot name="upper" data-id="upper-slot"></slot>
+    <slot name="lower" data-id="lower-slot"></slot>
+    <slot name="defaultSlotReassigned" data-id="default-slot-reassigned"></slot>
+    <slot data-id="default-slot"></slot>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/shadowLeaf/shadowLeaf.js b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/shadowLeaf/shadowLeaf.js
new file mode 100644
index 0000000000..ca8dce94e0
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/shadowLeaf/shadowLeaf.js
@@ -0,0 +1,3 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {}
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/shadowLightSlot/shadowLightSlot.html b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/shadowLightSlot/shadowLightSlot.html
new file mode 100644
index 0000000000..77f3a43370
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/shadowLightSlot/shadowLightSlot.html
@@ -0,0 +1,9 @@
+<template>
+    <x-light-leaf data-id="shadow-light-leaf">
+        <!-- Note upper and lower have mapping swapped here -->
+        <slot slot="lower" name="upper" data-id="lower-slot"></slot>
+        <slot slot="upper" name="lower" data-id="upper-slot"></slot>
+        <!-- Note default slot is mapped to a new slot name -->
+        <slot slot="defaultSlotReassigned" data-id="default-slot">Default slot not yet forwarded</slot>
+    </x-light-leaf>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/shadowLightSlot/shadowLightSlot.js b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/shadowLightSlot/shadowLightSlot.js
new file mode 100644
index 0000000000..ca8dce94e0
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/shadowLightSlot/shadowLightSlot.js
@@ -0,0 +1,3 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {}
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/shadowShadowSlot/shadowShadowSlot.html b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/shadowShadowSlot/shadowShadowSlot.html
new file mode 100644
index 0000000000..c4815fd97d
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/shadowShadowSlot/shadowShadowSlot.html
@@ -0,0 +1,10 @@
+<template>
+    <x-shadow-leaf data-id="shadow-shadow-leaf">
+        <!-- Note upper and lower have mapping swapped here -->
+        <slot slot="lower" name="upper"></slot>
+        <slot slot="upper" name="lower"></slot>
+        <!-- Note default slot is mapped to a new slot name -->
+        <!-- Only applies to non text or comments -->
+        <slot slot="defaultSlotReassigned">Default slot not yet forwarded</slot>
+    </x-shadow-leaf>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/shadowShadowSlot/shadowShadowSlot.js b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/shadowShadowSlot/shadowShadowSlot.js
new file mode 100644
index 0000000000..ca8dce94e0
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/forwarding/x/shadowShadowSlot/shadowShadowSlot.js
@@ -0,0 +1,3 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {}
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/index.spec.js b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/index.spec.js
new file mode 100644
index 0000000000..a1735fa91b
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/index.spec.js
@@ -0,0 +1,269 @@
+import { createElement } from 'lwc';
+import { extractDataIds, lightDomSlotForwardingEnabled } from 'test-utils';
+
+import LightContainer from './x/lightContainer/lightContainer';
+
+describe('light DOM slot forwarding reactivity', () => {
+    let nodes;
+    let lightContainer;
+
+    beforeAll(() => {
+        lightContainer = createElement('x-light-container', { is: LightContainer });
+        document.body.appendChild(lightContainer);
+        nodes = extractDataIds(lightContainer);
+    });
+
+    afterAll(() => {
+        document.body.removeChild(lightContainer);
+    });
+
+    const verifySlotContent = (leaf, expected) => {
+        const children = Array.from(leaf.shadowRoot?.children ?? leaf.children);
+        let expectedIndex = 0;
+        children.forEach((child) => {
+            const actualSlotContent =
+                child.tagName.toLowerCase() === 'slot' ? child.assignedNodes() : [child];
+
+            actualSlotContent.forEach((slotContent) => {
+                expect(child.getAttribute('slot')).toEqual(expected[expectedIndex].slotAssignment);
+                expect(slotContent.innerText).toEqual(expected[expectedIndex++].slotContent);
+            });
+        });
+    };
+
+    const expectedDefaultSlotContent = (shadowMode) => [
+        {
+            slotAssignment: 'upper',
+            slotContent: 'Upper slot content',
+        },
+        {
+            slotAssignment: 'lower',
+            slotContent: 'Lower slot content',
+        },
+        {
+            slotAssignment:
+                shadowMode.includes('shadow') || lightDomSlotForwardingEnabled ? '' : null,
+            slotContent: 'Default slot content',
+        },
+    ];
+
+    const expectedSlotContentAfterParentMutation = (shadowMode) => [
+        {
+            slotAssignment: 'upper',
+            slotContent: 'Lower slot content',
+        },
+        {
+            slotAssignment: 'lower',
+            slotContent: 'Upper slot content',
+        },
+        {
+            slotAssignment:
+                shadowMode.includes('shadow') || lightDomSlotForwardingEnabled ? '' : null,
+            slotContent: 'Default slot content',
+        },
+    ];
+
+    const expectedSlotContentAfterForwardedSlotMutation = [
+        {
+            slotAssignment: 'upper',
+            slotContent: 'Upper slot content',
+        },
+        {
+            slotAssignment: 'lower',
+            slotContent: 'Default slot content',
+        },
+        {
+            slotAssignment: '',
+            slotContent: 'Lower slot content',
+        },
+    ];
+
+    const expectedSlotContentAfterLeafMutation = (shadowMode) => [
+        {
+            slotAssignment: 'lower',
+            slotContent:
+                shadowMode.includes('shadow') && !lightDomSlotForwardingEnabled
+                    ? 'Lower slot content'
+                    : 'Upper slot content',
+        },
+        {
+            slotAssignment: '',
+            slotContent:
+                shadowMode.includes('shadow') && !lightDomSlotForwardingEnabled
+                    ? 'Upper slot content'
+                    : 'Default slot content',
+        },
+        {
+            slotAssignment: 'upper',
+            slotContent:
+                shadowMode.includes('shadow') && !lightDomSlotForwardingEnabled
+                    ? 'Default slot content'
+                    : 'Lower slot content',
+        },
+    ];
+
+    const expectedSlotContentAfterConditionalMutation = [
+        {
+            slotAssignment: 'lower',
+            slotContent: 'Upper slot content',
+        },
+        {
+            slotAssignment: '',
+            slotContent: 'Default slot content',
+        },
+        {
+            slotAssignment: 'upper',
+            slotContent: 'Lower slot content',
+        },
+        {
+            slotAssignment: 'upper',
+            slotContent: 'Conditional slot content',
+        },
+    ];
+
+    const testCases = [
+        {
+            testName: 'lightLight',
+            expectedDefaultSlotContent: expectedDefaultSlotContent('light'),
+            expectedSlotContentAfterParentMutation: expectedSlotContentAfterParentMutation('light'),
+            expectedSlotContentAfterForwardedSlotMutation: lightDomSlotForwardingEnabled
+                ? expectedSlotContentAfterForwardedSlotMutation
+                : expectedSlotContentAfterParentMutation('light'),
+            expectedSlotContentAfterLeafMutation: lightDomSlotForwardingEnabled
+                ? expectedSlotContentAfterLeafMutation('light')
+                : expectedSlotContentAfterParentMutation('light'),
+            expectedSlotContentAfterConditionalMutation: lightDomSlotForwardingEnabled
+                ? expectedSlotContentAfterConditionalMutation
+                : [
+                      {
+                          slotAssignment: 'upper',
+                          slotContent: 'Lower slot content',
+                      },
+                      {
+                          slotAssignment: 'upper',
+                          slotContent: 'Conditional slot content',
+                      },
+                      {
+                          slotAssignment: 'lower',
+                          slotContent: 'Upper slot content',
+                      },
+                      {
+                          slotAssignment: null,
+                          slotContent: 'Default slot content',
+                      },
+                  ],
+        },
+        {
+            testName: 'lightShadow',
+            expectedDefaultSlotContent: expectedDefaultSlotContent('shadow'),
+            expectedSlotContentAfterParentMutation:
+                expectedSlotContentAfterParentMutation('shadow'),
+            expectedSlotContentAfterForwardedSlotMutation: lightDomSlotForwardingEnabled
+                ? expectedSlotContentAfterForwardedSlotMutation
+                : expectedSlotContentAfterParentMutation('shadow'),
+            expectedSlotContentAfterLeafMutation: expectedSlotContentAfterLeafMutation('shadow'),
+            expectedSlotContentAfterConditionalMutation: lightDomSlotForwardingEnabled
+                ? expectedSlotContentAfterConditionalMutation
+                : [
+                      {
+                          slotAssignment: 'lower',
+                          slotContent: 'Lower slot content',
+                      },
+                      {
+                          slotAssignment: 'lower',
+                          slotContent: 'Conditional slot content',
+                      },
+                      {
+                          slotAssignment: '',
+                          slotContent: 'Upper slot content',
+                      },
+                      {
+                          slotAssignment: 'upper',
+                          slotContent: 'Default slot content',
+                      },
+                  ],
+        },
+    ];
+
+    if (process.env.NATIVE_SHADOW) {
+        // TODO [#3885]: Using expressions on forwarded synthetic shadow DOM slots throws an error, only test in native for now
+        testCases.push({
+            testName: 'shadowLight',
+            expectedDefaultSlotContent: expectedDefaultSlotContent('shadow'),
+            expectedSlotContentAfterParentMutation:
+                expectedSlotContentAfterParentMutation('shadow'),
+            expectedSlotContentAfterForwardedSlotMutation,
+            expectedSlotContentAfterLeafMutation: lightDomSlotForwardingEnabled
+                ? expectedSlotContentAfterLeafMutation('shadow')
+                : expectedSlotContentAfterForwardedSlotMutation,
+            expectedSlotContentAfterConditionalMutation: lightDomSlotForwardingEnabled
+                ? expectedSlotContentAfterConditionalMutation
+                : [
+                      {
+                          slotAssignment: 'upper',
+                          slotContent: 'Upper slot content',
+                      },
+                      {
+                          slotAssignment: 'lower',
+                          slotContent: 'Default slot content',
+                      },
+                      {
+                          slotAssignment: '',
+                          slotContent: 'Lower slot content',
+                      },
+                      {
+                          slotAssignment: '',
+                          slotContent: 'Conditional slot content',
+                      },
+                  ],
+        });
+    }
+
+    testCases.forEach(
+        ({
+            testName,
+            expectedDefaultSlotContent,
+            expectedSlotContentAfterParentMutation,
+            expectedSlotContentAfterForwardedSlotMutation,
+            expectedSlotContentAfterLeafMutation,
+            expectedSlotContentAfterConditionalMutation,
+        }) => {
+            it(`should update correctly for ${testName} slots`, async () => {
+                const parent = nodes[testName];
+                const leaf = parent.leaf;
+                expect((leaf.shadowRoot?.children ?? leaf.children).length).toBe(3);
+
+                verifySlotContent(leaf, expectedDefaultSlotContent);
+
+                lightContainer[`${testName}Upper`] = 'lower';
+                lightContainer[`${testName}Lower`] = 'upper';
+
+                await Promise.resolve();
+
+                verifySlotContent(leaf, expectedSlotContentAfterParentMutation);
+
+                parent.upperSlot = '';
+                parent.lowerSlot = 'upper';
+                parent.defaultSlot = 'lower';
+
+                await Promise.resolve();
+
+                verifySlotContent(leaf, expectedSlotContentAfterForwardedSlotMutation);
+
+                leaf.upperSlot = 'lower';
+                leaf.lowerSlot = '';
+                leaf.defaultSlot = 'upper';
+
+                await Promise.resolve();
+
+                verifySlotContent(leaf, expectedSlotContentAfterLeafMutation);
+
+                lightContainer[`${testName}ConditionalSlot`] = true;
+
+                await Promise.resolve();
+
+                verifySlotContent(leaf, expectedSlotContentAfterConditionalMutation);
+            });
+        }
+    );
+});
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/lightContainer/lightContainer.html b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/lightContainer/lightContainer.html
new file mode 100644
index 0000000000..8cb20994c3
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/lightContainer/lightContainer.html
@@ -0,0 +1,25 @@
+<template lwc:render-mode="light">
+    <x-light-light-slot data-id="lightLight">
+        <p slot={lightLightUpper}>Upper slot content</p>
+        <p slot={lightLightLower}>Lower slot content</p>
+        <p>Default slot content</p>
+        <!-- if:true triggers static diffing algo -->
+        <p slot="upper" if:true={lightLightConditionalSlot}>Conditional slot content</p>
+    </x-light-light-slot>
+
+    <x-light-shadow-slot data-id="lightShadow">
+        <p slot={lightShadowUpper}>Upper slot content</p>
+        <p slot={lightShadowLower}>Lower slot content</p>
+        <p>Default slot content</p>
+        <!-- if:true triggers static diffing algo -->
+        <p slot="upper" if:true={lightShadowConditionalSlot}>Conditional slot content</p>
+    </x-light-shadow-slot>
+
+    <x-shadow-light-slot data-id="shadowLight">
+        <p slot={shadowLightUpper}>Upper slot content</p>
+        <p slot={shadowLightLower}>Lower slot content</p>
+        <p>Default slot content</p>
+        <!-- if:true triggers static diffing algo -->
+        <p slot="upper" if:true={shadowLightConditionalSlot}>Conditional slot content</p>
+    </x-shadow-light-slot>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/lightContainer/lightContainer.js b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/lightContainer/lightContainer.js
new file mode 100644
index 0000000000..56de5c3645
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/lightContainer/lightContainer.js
@@ -0,0 +1,24 @@
+import { LightningElement, api } from 'lwc';
+
+export default class extends LightningElement {
+    static renderMode = 'light';
+
+    @api
+    lightLightUpper = 'upper';
+    @api
+    lightLightLower = 'lower';
+    @api
+    lightShadowUpper = 'upper';
+    @api
+    lightShadowLower = 'lower';
+    @api
+    shadowLightUpper = 'upper';
+    @api
+    shadowLightLower = 'lower';
+    @api
+    lightLightConditionalSlot = false;
+    @api
+    lightShadowConditionalSlot = false;
+    @api
+    shadowLightConditionalSlot = false;
+}
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/lightLeaf/lightLeaf.html b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/lightLeaf/lightLeaf.html
new file mode 100644
index 0000000000..6d057b78cb
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/lightLeaf/lightLeaf.html
@@ -0,0 +1,5 @@
+<template lwc:render-mode="light">
+    <slot slot={upperSlot} name="upper"></slot>
+    <slot slot={lowerSlot} name="lower"></slot>
+    <slot slot={defaultSlot}></slot>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/lightLeaf/lightLeaf.js b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/lightLeaf/lightLeaf.js
new file mode 100644
index 0000000000..734b6bc1cc
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/lightLeaf/lightLeaf.js
@@ -0,0 +1,14 @@
+import { LightningElement, api } from 'lwc';
+
+export default class extends LightningElement {
+    static renderMode = 'light';
+
+    @api
+    upperSlot = 'upper';
+
+    @api
+    lowerSlot = 'lower';
+
+    @api
+    defaultSlot = '';
+}
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/lightLightSlot/lightLightSlot.html b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/lightLightSlot/lightLightSlot.html
new file mode 100644
index 0000000000..2b7d823a6a
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/lightLightSlot/lightLightSlot.html
@@ -0,0 +1,7 @@
+<template lwc:render-mode="light">
+    <x-light-leaf>
+        <slot slot={upperSlot} name="upper"></slot>
+        <slot slot={lowerSlot} name="lower"></slot>
+        <slot slot={defaultSlot}></slot>
+    </x-light-leaf>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/lightLightSlot/lightLightSlot.js b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/lightLightSlot/lightLightSlot.js
new file mode 100644
index 0000000000..c4fd897542
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/lightLightSlot/lightLightSlot.js
@@ -0,0 +1,19 @@
+import { LightningElement, api } from 'lwc';
+
+export default class extends LightningElement {
+    static renderMode = 'light';
+
+    @api
+    upperSlot = 'upper';
+
+    @api
+    lowerSlot = 'lower';
+
+    @api
+    defaultSlot = '';
+
+    @api
+    get leaf() {
+        return this.querySelector('x-light-leaf');
+    }
+}
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/lightShadowSlot/lightShadowSlot.html b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/lightShadowSlot/lightShadowSlot.html
new file mode 100644
index 0000000000..390b647b7f
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/lightShadowSlot/lightShadowSlot.html
@@ -0,0 +1,7 @@
+<template lwc:render-mode="light">
+    <x-shadow-leaf>
+        <slot slot={upperSlot} name="upper"></slot>
+        <slot slot={lowerSlot} name="lower"></slot>
+        <slot slot={defaultSlot}></slot>
+    </x-shadow-leaf>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/lightShadowSlot/lightShadowSlot.js b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/lightShadowSlot/lightShadowSlot.js
new file mode 100644
index 0000000000..444666838d
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/lightShadowSlot/lightShadowSlot.js
@@ -0,0 +1,19 @@
+import { LightningElement, api } from 'lwc';
+
+export default class extends LightningElement {
+    static renderMode = 'light';
+
+    @api
+    upperSlot = 'upper';
+
+    @api
+    lowerSlot = 'lower';
+
+    @api
+    defaultSlot = '';
+
+    @api
+    get leaf() {
+        return this.querySelector('x-shadow-leaf');
+    }
+}
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/shadowLeaf/shadowLeaf.html b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/shadowLeaf/shadowLeaf.html
new file mode 100644
index 0000000000..219614dce5
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/shadowLeaf/shadowLeaf.html
@@ -0,0 +1,5 @@
+<template>
+    <slot slot={upperSlot} name="upper"></slot>
+    <slot slot={lowerSlot} name="lower"></slot>
+    <slot slot={defaultSlot}></slot>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/shadowLeaf/shadowLeaf.js b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/shadowLeaf/shadowLeaf.js
new file mode 100644
index 0000000000..5a76401672
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/shadowLeaf/shadowLeaf.js
@@ -0,0 +1,12 @@
+import { LightningElement, api } from 'lwc';
+
+export default class extends LightningElement {
+    @api
+    upperSlot = 'upper';
+
+    @api
+    lowerSlot = 'lower';
+
+    @api
+    defaultSlot = '';
+}
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/shadowLightSlot/shadowLightSlot.html b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/shadowLightSlot/shadowLightSlot.html
new file mode 100644
index 0000000000..0d7a512339
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/shadowLightSlot/shadowLightSlot.html
@@ -0,0 +1,7 @@
+<template>
+    <x-light-leaf>
+        <slot slot={upperSlot} name="upper"></slot>
+        <slot slot={lowerSlot} name="lower"></slot>
+        <slot slot={defaultSlot}></slot>
+    </x-light-leaf>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/shadowLightSlot/shadowLightSlot.js b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/shadowLightSlot/shadowLightSlot.js
new file mode 100644
index 0000000000..724c307373
--- /dev/null
+++ b/packages/@lwc/integration-karma/test/light-dom/slot-fowarding/slots/reactivity/x/shadowLightSlot/shadowLightSlot.js
@@ -0,0 +1,17 @@
+import { LightningElement, api } from 'lwc';
+
+export default class extends LightningElement {
+    @api
+    upperSlot = 'upper';
+
+    @api
+    lowerSlot = 'lower';
+
+    @api
+    defaultSlot = '';
+
+    @api
+    get leaf() {
+        return this.template.querySelector('x-light-leaf');
+    }
+}
diff --git a/packages/@lwc/integration-karma/test/light-dom/slotting/index.spec.js b/packages/@lwc/integration-karma/test/light-dom/slotting/index.spec.js
index 99e4665444..0406c4c5ac 100644
--- a/packages/@lwc/integration-karma/test/light-dom/slotting/index.spec.js
+++ b/packages/@lwc/integration-karma/test/light-dom/slotting/index.spec.js
@@ -1,6 +1,8 @@
 import { createElement } from 'lwc';
 import { extractDataIds } from 'test-utils';
 
+import { vFragBookEndEnabled, lightDomSlotForwardingEnabled } from 'test-utils';
+
 import BasicSlot from 'x/basicSlot';
 import DynamicChildren from 'x/dynamicChildren';
 import LightConsumer from 'x/lightConsumer';
@@ -9,7 +11,7 @@ import ConditionalSlot from 'x/conditionalSlot';
 import ConditionalSlotted from 'x/conditionalSlotted';
 import ForwardedSlotConsumer from 'x/forwardedSlotConsumer';
 
-const vFragBookend = process.env.API_VERSION > 59 ? '<!---->' : '';
+const vFragBookend = vFragBookEndEnabled ? '<!---->' : '';
 
 function createTestElement(tag, component) {
     const elm = createElement(tag, { is: component });
@@ -105,7 +107,9 @@ describe('Slotting', () => {
         const nodes = createTestElement('x-forwarded-slot-consumer', ForwardedSlotConsumer);
         const elm = nodes['x-forwarded-slot-consumer'];
         expect(elm.innerHTML).toEqual(
-            `<x-forwarded-slot><x-light-container>${vFragBookend}<p slot="upper">Upper slot content forwarded</p>${vFragBookend}${vFragBookend}<p>Default slot forwarded</p>${vFragBookend}${vFragBookend}<p slot="lower">Lower slot content forwarded</p>${vFragBookend}</x-light-container></x-forwarded-slot>`
+            lightDomSlotForwardingEnabled
+                ? `<x-forwarded-slot><x-light-container>${vFragBookend}<p>Upper slot content forwarded</p>${vFragBookend}${vFragBookend}<p>Default slot forwarded</p>${vFragBookend}${vFragBookend}<p>Lower slot content forwarded</p>${vFragBookend}</x-light-container></x-forwarded-slot>`
+                : `<x-forwarded-slot><x-light-container>${vFragBookend}<p slot="upper">Upper slot content forwarded</p>${vFragBookend}${vFragBookend}<p>Default slot forwarded</p>${vFragBookend}${vFragBookend}<p slot="lower">Lower slot content forwarded</p>${vFragBookend}</x-light-container></x-forwarded-slot>`
         );
     });
     it('should render default content in forwarded slots', async () => {
diff --git a/packages/@lwc/shared/src/api-version.ts b/packages/@lwc/shared/src/api-version.ts
index 58c257a144..833ed2fbae 100644
--- a/packages/@lwc/shared/src/api-version.ts
+++ b/packages/@lwc/shared/src/api-version.ts
@@ -80,6 +80,11 @@ export const enum APIFeature {
      * instead of comment nodes.
      */
     USE_COMMENTS_FOR_FRAGMENT_BOOKENDS,
+    /**
+     * If enabled, allows slot forwarding for light DOM slots. This will cause the slot attribute of the slotted
+     * content to be updated to match the slot attribute of the light DOM slot it slotted into.
+     */
+    USE_LIGHT_DOM_SLOT_FORWARDING,
     /**
      * If enabled, we use the native custom element lifecycle events: connectedCallback, disconnectedCallback
      * rather than synthetic events.
@@ -100,6 +105,7 @@ export function isAPIFeatureEnabled(
         case APIFeature.SKIP_UNNECESSARY_REGISTER_DECORATORS:
         case APIFeature.USE_COMMENTS_FOR_FRAGMENT_BOOKENDS:
             return apiVersion >= APIVersion.V60_248_SPRING_24;
+        case APIFeature.USE_LIGHT_DOM_SLOT_FORWARDING:
         case APIFeature.ENABLE_NATIVE_CUSTOM_ELEMENT_LIFECYCLE:
             return apiVersion >= APIVersion.V61_250_SUMMER_24;
     }
diff --git a/packages/@lwc/template-compiler/src/__tests__/fixtures/directive-lwc-if-else/slots/named-slots/simple/expected.js b/packages/@lwc/template-compiler/src/__tests__/fixtures/directive-lwc-if-else/slots/named-slots/simple/expected.js
index 805ecf841d..c8b2952df9 100644
--- a/packages/@lwc/template-compiler/src/__tests__/fixtures/directive-lwc-if-else/slots/named-slots/simple/expected.js
+++ b/packages/@lwc/template-compiler/src/__tests__/fixtures/directive-lwc-if-else/slots/named-slots/simple/expected.js
@@ -4,9 +4,7 @@ const stc0 = {
   key: 0,
 };
 const stc1 = {
-  attrs: {
-    slot: "slotname1",
-  },
+  slotAssignment: "slotname1",
   key: 2,
 };
 function tmpl($api, $cmp, $slotset, $ctx) {
diff --git a/packages/@lwc/template-compiler/src/__tests__/fixtures/directive-render-mode/template/expected.js b/packages/@lwc/template-compiler/src/__tests__/fixtures/directive-render-mode/template/expected.js
index 6d45ef492a..9bd15e0836 100644
--- a/packages/@lwc/template-compiler/src/__tests__/fixtures/directive-render-mode/template/expected.js
+++ b/packages/@lwc/template-compiler/src/__tests__/fixtures/directive-render-mode/template/expected.js
@@ -10,9 +10,9 @@ const stc1 = {
   key: 3,
 };
 const stc2 = {
+  slotAssignment: "forward",
   attrs: {
     name: "forwarded",
-    slot: "forward",
   },
   key: 4,
 };
diff --git a/packages/@lwc/template-compiler/src/__tests__/fixtures/dynamic-components/valid/attributes/expected.js b/packages/@lwc/template-compiler/src/__tests__/fixtures/dynamic-components/valid/attributes/expected.js
index 89b3f8d583..37ecf7fad3 100644
--- a/packages/@lwc/template-compiler/src/__tests__/fixtures/dynamic-components/valid/attributes/expected.js
+++ b/packages/@lwc/template-compiler/src/__tests__/fixtures/dynamic-components/valid/attributes/expected.js
@@ -2,16 +2,13 @@ import { registerTemplate } from "lwc";
 const stc0 = {
   "slds-style": true,
 };
-const stc1 = {
-  slot: "slotName",
-};
 function tmpl($api, $cmp, $slotset, $ctx) {
   const { b: api_bind, dc: api_dynamic_component } = $api;
   const { _m0 } = $ctx;
   return [
     api_dynamic_component($cmp.ctor, {
       classMap: stc0,
-      attrs: stc1,
+      slotAssignment: "slotName",
       key: 0,
       on: {
         click: _m0 || ($ctx._m0 = api_bind($cmp.handleClick)),
diff --git a/packages/@lwc/template-compiler/src/__tests__/fixtures/scoped-slots/parent-mixed-slot-content/expected.js b/packages/@lwc/template-compiler/src/__tests__/fixtures/scoped-slots/parent-mixed-slot-content/expected.js
index 6c0bbfe860..049e3cd3b6 100644
--- a/packages/@lwc/template-compiler/src/__tests__/fixtures/scoped-slots/parent-mixed-slot-content/expected.js
+++ b/packages/@lwc/template-compiler/src/__tests__/fixtures/scoped-slots/parent-mixed-slot-content/expected.js
@@ -8,9 +8,7 @@ const stc1 = {
   key: 1,
 };
 const stc2 = {
-  attrs: {
-    slot: "slotname2",
-  },
+  slotAssignment: "slotname2",
   key: 2,
 };
 function tmpl($api, $cmp, $slotset, $ctx) {
diff --git a/packages/@lwc/template-compiler/src/__tests__/fixtures/scoped-slots/slot-content-with-directives/valid/dynamic-components/parent/expected.js b/packages/@lwc/template-compiler/src/__tests__/fixtures/scoped-slots/slot-content-with-directives/valid/dynamic-components/parent/expected.js
index 0342eeb461..db2d4ba154 100644
--- a/packages/@lwc/template-compiler/src/__tests__/fixtures/scoped-slots/slot-content-with-directives/valid/dynamic-components/parent/expected.js
+++ b/packages/@lwc/template-compiler/src/__tests__/fixtures/scoped-slots/slot-content-with-directives/valid/dynamic-components/parent/expected.js
@@ -4,21 +4,15 @@ const stc0 = {
   key: 0,
 };
 const stc1 = {
-  attrs: {
-    slot: "header",
-  },
+  slotAssignment: "header",
   key: 1,
 };
 const stc2 = {
-  attrs: {
-    slot: "body",
-  },
+  slotAssignment: "body",
   key: 2,
 };
 const stc3 = {
-  attrs: {
-    slot: "footer",
-  },
+  slotAssignment: "footer",
   key: 3,
 };
 function tmpl($api, $cmp, $slotset, $ctx) {
diff --git a/packages/@lwc/template-compiler/src/__tests__/fixtures/slots/dynamic-components/usage/expected.js b/packages/@lwc/template-compiler/src/__tests__/fixtures/slots/dynamic-components/usage/expected.js
index 139076ca7b..6e4b610910 100644
--- a/packages/@lwc/template-compiler/src/__tests__/fixtures/slots/dynamic-components/usage/expected.js
+++ b/packages/@lwc/template-compiler/src/__tests__/fixtures/slots/dynamic-components/usage/expected.js
@@ -3,15 +3,11 @@ const stc0 = {
   key: 0,
 };
 const stc1 = {
-  attrs: {
-    slot: "header",
-  },
+  slotAssignment: "header",
   key: 1,
 };
 const stc2 = {
-  attrs: {
-    slot: "",
-  },
+  slotAssignment: "",
   key: 2,
 };
 function tmpl($api, $cmp, $slotset, $ctx) {
diff --git a/packages/@lwc/template-compiler/src/__tests__/fixtures/slots/dynamic-name/expected.js b/packages/@lwc/template-compiler/src/__tests__/fixtures/slots/dynamic-name/expected.js
index 1082e59275..4eda155e48 100644
--- a/packages/@lwc/template-compiler/src/__tests__/fixtures/slots/dynamic-name/expected.js
+++ b/packages/@lwc/template-compiler/src/__tests__/fixtures/slots/dynamic-name/expected.js
@@ -8,9 +8,7 @@ function tmpl($api, $cmp, $slotset, $ctx) {
   return [
     api_custom_element("ns-cmp", _nsCmp, stc0, [
       api_element("p", {
-        attrs: {
-          slot: $cmp.mySlot,
-        },
+        slotAssignment: $cmp.mySlot,
         key: 1,
       }),
     ]),
diff --git a/packages/@lwc/template-compiler/src/__tests__/fixtures/slots/usage-if/expected.js b/packages/@lwc/template-compiler/src/__tests__/fixtures/slots/usage-if/expected.js
index 7780905e00..bac675a407 100644
--- a/packages/@lwc/template-compiler/src/__tests__/fixtures/slots/usage-if/expected.js
+++ b/packages/@lwc/template-compiler/src/__tests__/fixtures/slots/usage-if/expected.js
@@ -7,15 +7,11 @@ const stc1 = {
   key: 1,
 };
 const stc2 = {
-  attrs: {
-    slot: "",
-  },
+  slotAssignment: "",
   key: 2,
 };
 const stc3 = {
-  attrs: {
-    slot: "",
-  },
+  slotAssignment: "",
   key: 3,
 };
 function tmpl($api, $cmp, $slotset, $ctx) {
diff --git a/packages/@lwc/template-compiler/src/__tests__/fixtures/slots/usage/actual.html b/packages/@lwc/template-compiler/src/__tests__/fixtures/slots/usage/actual.html
index 6f3d2eff26..5132cfbcaf 100644
--- a/packages/@lwc/template-compiler/src/__tests__/fixtures/slots/usage/actual.html
+++ b/packages/@lwc/template-compiler/src/__tests__/fixtures/slots/usage/actual.html
@@ -1,8 +1,16 @@
 <template>
     <section>
         <ns-cmp>
+            <p>Default Slot No Slot Attribute</p>
+            <p slot="">Slot Empty String Attribute</p>
+            <p slot=true>Slot Boolean Attribute</p>
+            <p slot={slot.name}>Dynamic Slot Content</p>
+            <p slot={slotVariable}>Variable As Slot Assignment</p>
             <p slot="header">Header Slot Content</p>
             <p slot>Default Content</p>
+            <p slot=undefined>Undefined Slot Content</p>
+            <p slot=null>Null Slot Content</p>
+            <p slot>Empty slot value</p>
         </ns-cmp>
     </section>
 </template>
diff --git a/packages/@lwc/template-compiler/src/__tests__/fixtures/slots/usage/ast.json b/packages/@lwc/template-compiler/src/__tests__/fixtures/slots/usage/ast.json
index 46a94615e7..af0bb45928 100644
--- a/packages/@lwc/template-compiler/src/__tests__/fixtures/slots/usage/ast.json
+++ b/packages/@lwc/template-compiler/src/__tests__/fixtures/slots/usage/ast.json
@@ -4,10 +4,10 @@
         "location": {
             "startLine": 1,
             "startColumn": 1,
-            "endLine": 8,
+            "endLine": 16,
             "endColumn": 12,
             "start": 0,
-            "end": 179,
+            "end": 605,
             "startTag": {
                 "startLine": 1,
                 "startColumn": 1,
@@ -17,12 +17,12 @@
                 "end": 10
             },
             "endTag": {
-                "startLine": 8,
+                "startLine": 16,
                 "startColumn": 1,
-                "endLine": 8,
+                "endLine": 16,
                 "endColumn": 12,
-                "start": 168,
-                "end": 179
+                "start": 594,
+                "end": 605
             }
         },
         "directives": [],
@@ -34,10 +34,10 @@
                 "location": {
                     "startLine": 2,
                     "startColumn": 5,
-                    "endLine": 7,
+                    "endLine": 15,
                     "endColumn": 15,
                     "start": 15,
-                    "end": 167,
+                    "end": 593,
                     "startTag": {
                         "startLine": 2,
                         "startColumn": 5,
@@ -47,12 +47,12 @@
                         "end": 24
                     },
                     "endTag": {
-                        "startLine": 7,
+                        "startLine": 15,
                         "startColumn": 5,
-                        "endLine": 7,
+                        "endLine": 15,
                         "endColumn": 15,
-                        "start": 157,
-                        "end": 167
+                        "start": 583,
+                        "end": 593
                     }
                 },
                 "attributes": [],
@@ -67,10 +67,10 @@
                         "location": {
                             "startLine": 3,
                             "startColumn": 9,
-                            "endLine": 6,
+                            "endLine": 14,
                             "endColumn": 18,
                             "start": 33,
-                            "end": 152,
+                            "end": 578,
                             "startTag": {
                                 "startLine": 3,
                                 "startColumn": 9,
@@ -80,12 +80,12 @@
                                 "end": 41
                             },
                             "endTag": {
-                                "startLine": 6,
+                                "startLine": 14,
                                 "startColumn": 9,
-                                "endLine": 6,
+                                "endLine": 14,
                                 "endColumn": 18,
-                                "start": 143,
-                                "end": 152
+                                "start": 569,
+                                "end": 578
                             }
                         },
                         "attributes": [],
@@ -101,24 +101,380 @@
                                     "startLine": 4,
                                     "startColumn": 13,
                                     "endLine": 4,
-                                    "endColumn": 53,
+                                    "endColumn": 50,
                                     "start": 54,
-                                    "end": 94,
+                                    "end": 91,
                                     "startTag": {
                                         "startLine": 4,
                                         "startColumn": 13,
                                         "endLine": 4,
-                                        "endColumn": 30,
+                                        "endColumn": 16,
                                         "start": 54,
-                                        "end": 71
+                                        "end": 57
                                     },
                                     "endTag": {
                                         "startLine": 4,
-                                        "startColumn": 49,
+                                        "startColumn": 46,
                                         "endLine": 4,
+                                        "endColumn": 50,
+                                        "start": 87,
+                                        "end": 91
+                                    }
+                                },
+                                "attributes": [],
+                                "properties": [],
+                                "directives": [],
+                                "listeners": [],
+                                "children": [
+                                    {
+                                        "type": "Text",
+                                        "raw": "Default Slot No Slot Attribute",
+                                        "value": {
+                                            "type": "Literal",
+                                            "value": "Default Slot No Slot Attribute"
+                                        },
+                                        "location": {
+                                            "startLine": 4,
+                                            "startColumn": 16,
+                                            "endLine": 4,
+                                            "endColumn": 46,
+                                            "start": 57,
+                                            "end": 87
+                                        }
+                                    }
+                                ]
+                            },
+                            {
+                                "type": "Element",
+                                "name": "p",
+                                "namespace": "http://www.w3.org/1999/xhtml",
+                                "location": {
+                                    "startLine": 5,
+                                    "startColumn": 13,
+                                    "endLine": 5,
+                                    "endColumn": 55,
+                                    "start": 104,
+                                    "end": 146,
+                                    "startTag": {
+                                        "startLine": 5,
+                                        "startColumn": 13,
+                                        "endLine": 5,
+                                        "endColumn": 24,
+                                        "start": 104,
+                                        "end": 115
+                                    },
+                                    "endTag": {
+                                        "startLine": 5,
+                                        "startColumn": 51,
+                                        "endLine": 5,
+                                        "endColumn": 55,
+                                        "start": 142,
+                                        "end": 146
+                                    }
+                                },
+                                "attributes": [
+                                    {
+                                        "type": "Attribute",
+                                        "name": "slot",
+                                        "value": {
+                                            "type": "Literal",
+                                            "value": ""
+                                        },
+                                        "location": {
+                                            "startLine": 5,
+                                            "startColumn": 16,
+                                            "endLine": 5,
+                                            "endColumn": 23,
+                                            "start": 107,
+                                            "end": 114
+                                        }
+                                    }
+                                ],
+                                "properties": [],
+                                "directives": [],
+                                "listeners": [],
+                                "children": [
+                                    {
+                                        "type": "Text",
+                                        "raw": "Slot Empty String Attribute",
+                                        "value": {
+                                            "type": "Literal",
+                                            "value": "Slot Empty String Attribute"
+                                        },
+                                        "location": {
+                                            "startLine": 5,
+                                            "startColumn": 24,
+                                            "endLine": 5,
+                                            "endColumn": 51,
+                                            "start": 115,
+                                            "end": 142
+                                        }
+                                    }
+                                ]
+                            },
+                            {
+                                "type": "Element",
+                                "name": "p",
+                                "namespace": "http://www.w3.org/1999/xhtml",
+                                "location": {
+                                    "startLine": 6,
+                                    "startColumn": 13,
+                                    "endLine": 6,
+                                    "endColumn": 52,
+                                    "start": 159,
+                                    "end": 198,
+                                    "startTag": {
+                                        "startLine": 6,
+                                        "startColumn": 13,
+                                        "endLine": 6,
+                                        "endColumn": 26,
+                                        "start": 159,
+                                        "end": 172
+                                    },
+                                    "endTag": {
+                                        "startLine": 6,
+                                        "startColumn": 48,
+                                        "endLine": 6,
+                                        "endColumn": 52,
+                                        "start": 194,
+                                        "end": 198
+                                    }
+                                },
+                                "attributes": [
+                                    {
+                                        "type": "Attribute",
+                                        "name": "slot",
+                                        "value": {
+                                            "type": "Literal",
+                                            "value": "true"
+                                        },
+                                        "location": {
+                                            "startLine": 6,
+                                            "startColumn": 16,
+                                            "endLine": 6,
+                                            "endColumn": 25,
+                                            "start": 162,
+                                            "end": 171
+                                        }
+                                    }
+                                ],
+                                "properties": [],
+                                "directives": [],
+                                "listeners": [],
+                                "children": [
+                                    {
+                                        "type": "Text",
+                                        "raw": "Slot Boolean Attribute",
+                                        "value": {
+                                            "type": "Literal",
+                                            "value": "Slot Boolean Attribute"
+                                        },
+                                        "location": {
+                                            "startLine": 6,
+                                            "startColumn": 26,
+                                            "endLine": 6,
+                                            "endColumn": 48,
+                                            "start": 172,
+                                            "end": 194
+                                        }
+                                    }
+                                ]
+                            },
+                            {
+                                "type": "Element",
+                                "name": "p",
+                                "namespace": "http://www.w3.org/1999/xhtml",
+                                "location": {
+                                    "startLine": 7,
+                                    "startColumn": 13,
+                                    "endLine": 7,
+                                    "endColumn": 57,
+                                    "start": 211,
+                                    "end": 255,
+                                    "startTag": {
+                                        "startLine": 7,
+                                        "startColumn": 13,
+                                        "endLine": 7,
+                                        "endColumn": 33,
+                                        "start": 211,
+                                        "end": 231
+                                    },
+                                    "endTag": {
+                                        "startLine": 7,
+                                        "startColumn": 53,
+                                        "endLine": 7,
+                                        "endColumn": 57,
+                                        "start": 251,
+                                        "end": 255
+                                    }
+                                },
+                                "attributes": [
+                                    {
+                                        "type": "Attribute",
+                                        "name": "slot",
+                                        "value": {
+                                            "type": "MemberExpression",
+                                            "start": 1,
+                                            "end": 10,
+                                            "object": {
+                                                "type": "Identifier",
+                                                "start": 1,
+                                                "end": 5,
+                                                "name": "slot"
+                                            },
+                                            "property": {
+                                                "type": "Identifier",
+                                                "start": 6,
+                                                "end": 10,
+                                                "name": "name"
+                                            },
+                                            "computed": false,
+                                            "optional": false,
+                                            "location": {
+                                                "startLine": 7,
+                                                "startColumn": 16,
+                                                "endLine": 7,
+                                                "endColumn": 32,
+                                                "start": 214,
+                                                "end": 230
+                                            }
+                                        },
+                                        "location": {
+                                            "startLine": 7,
+                                            "startColumn": 16,
+                                            "endLine": 7,
+                                            "endColumn": 32,
+                                            "start": 214,
+                                            "end": 230
+                                        }
+                                    }
+                                ],
+                                "properties": [],
+                                "directives": [],
+                                "listeners": [],
+                                "children": [
+                                    {
+                                        "type": "Text",
+                                        "raw": "Dynamic Slot Content",
+                                        "value": {
+                                            "type": "Literal",
+                                            "value": "Dynamic Slot Content"
+                                        },
+                                        "location": {
+                                            "startLine": 7,
+                                            "startColumn": 33,
+                                            "endLine": 7,
+                                            "endColumn": 53,
+                                            "start": 231,
+                                            "end": 251
+                                        }
+                                    }
+                                ]
+                            },
+                            {
+                                "type": "Element",
+                                "name": "p",
+                                "namespace": "http://www.w3.org/1999/xhtml",
+                                "location": {
+                                    "startLine": 8,
+                                    "startColumn": 13,
+                                    "endLine": 8,
+                                    "endColumn": 67,
+                                    "start": 268,
+                                    "end": 322,
+                                    "startTag": {
+                                        "startLine": 8,
+                                        "startColumn": 13,
+                                        "endLine": 8,
+                                        "endColumn": 36,
+                                        "start": 268,
+                                        "end": 291
+                                    },
+                                    "endTag": {
+                                        "startLine": 8,
+                                        "startColumn": 63,
+                                        "endLine": 8,
+                                        "endColumn": 67,
+                                        "start": 318,
+                                        "end": 322
+                                    }
+                                },
+                                "attributes": [
+                                    {
+                                        "type": "Attribute",
+                                        "name": "slot",
+                                        "value": {
+                                            "type": "Identifier",
+                                            "start": 1,
+                                            "end": 13,
+                                            "name": "slotVariable",
+                                            "location": {
+                                                "startLine": 8,
+                                                "startColumn": 16,
+                                                "endLine": 8,
+                                                "endColumn": 35,
+                                                "start": 271,
+                                                "end": 290
+                                            }
+                                        },
+                                        "location": {
+                                            "startLine": 8,
+                                            "startColumn": 16,
+                                            "endLine": 8,
+                                            "endColumn": 35,
+                                            "start": 271,
+                                            "end": 290
+                                        }
+                                    }
+                                ],
+                                "properties": [],
+                                "directives": [],
+                                "listeners": [],
+                                "children": [
+                                    {
+                                        "type": "Text",
+                                        "raw": "Variable As Slot Assignment",
+                                        "value": {
+                                            "type": "Literal",
+                                            "value": "Variable As Slot Assignment"
+                                        },
+                                        "location": {
+                                            "startLine": 8,
+                                            "startColumn": 36,
+                                            "endLine": 8,
+                                            "endColumn": 63,
+                                            "start": 291,
+                                            "end": 318
+                                        }
+                                    }
+                                ]
+                            },
+                            {
+                                "type": "Element",
+                                "name": "p",
+                                "namespace": "http://www.w3.org/1999/xhtml",
+                                "location": {
+                                    "startLine": 9,
+                                    "startColumn": 13,
+                                    "endLine": 9,
+                                    "endColumn": 53,
+                                    "start": 335,
+                                    "end": 375,
+                                    "startTag": {
+                                        "startLine": 9,
+                                        "startColumn": 13,
+                                        "endLine": 9,
+                                        "endColumn": 30,
+                                        "start": 335,
+                                        "end": 352
+                                    },
+                                    "endTag": {
+                                        "startLine": 9,
+                                        "startColumn": 49,
+                                        "endLine": 9,
                                         "endColumn": 53,
-                                        "start": 90,
-                                        "end": 94
+                                        "start": 371,
+                                        "end": 375
                                     }
                                 },
                                 "attributes": [
@@ -130,12 +486,12 @@
                                             "value": "header"
                                         },
                                         "location": {
-                                            "startLine": 4,
+                                            "startLine": 9,
                                             "startColumn": 16,
-                                            "endLine": 4,
+                                            "endLine": 9,
                                             "endColumn": 29,
-                                            "start": 57,
-                                            "end": 70
+                                            "start": 338,
+                                            "end": 351
                                         }
                                     }
                                 ],
@@ -151,12 +507,12 @@
                                             "value": "Header Slot Content"
                                         },
                                         "location": {
-                                            "startLine": 4,
+                                            "startLine": 9,
                                             "startColumn": 30,
-                                            "endLine": 4,
+                                            "endLine": 9,
                                             "endColumn": 49,
-                                            "start": 71,
-                                            "end": 90
+                                            "start": 352,
+                                            "end": 371
                                         }
                                     }
                                 ]
@@ -166,27 +522,27 @@
                                 "name": "p",
                                 "namespace": "http://www.w3.org/1999/xhtml",
                                 "location": {
-                                    "startLine": 5,
+                                    "startLine": 10,
                                     "startColumn": 13,
-                                    "endLine": 5,
+                                    "endLine": 10,
                                     "endColumn": 40,
-                                    "start": 107,
-                                    "end": 134,
+                                    "start": 388,
+                                    "end": 415,
                                     "startTag": {
-                                        "startLine": 5,
+                                        "startLine": 10,
                                         "startColumn": 13,
-                                        "endLine": 5,
+                                        "endLine": 10,
                                         "endColumn": 21,
-                                        "start": 107,
-                                        "end": 115
+                                        "start": 388,
+                                        "end": 396
                                     },
                                     "endTag": {
-                                        "startLine": 5,
+                                        "startLine": 10,
                                         "startColumn": 36,
-                                        "endLine": 5,
+                                        "endLine": 10,
                                         "endColumn": 40,
-                                        "start": 130,
-                                        "end": 134
+                                        "start": 411,
+                                        "end": 415
                                     }
                                 },
                                 "attributes": [
@@ -198,12 +554,12 @@
                                             "value": true
                                         },
                                         "location": {
-                                            "startLine": 5,
+                                            "startLine": 10,
                                             "startColumn": 16,
-                                            "endLine": 5,
+                                            "endLine": 10,
                                             "endColumn": 20,
-                                            "start": 110,
-                                            "end": 114
+                                            "start": 391,
+                                            "end": 395
                                         }
                                     }
                                 ],
@@ -219,12 +575,216 @@
                                             "value": "Default Content"
                                         },
                                         "location": {
-                                            "startLine": 5,
+                                            "startLine": 10,
                                             "startColumn": 21,
-                                            "endLine": 5,
+                                            "endLine": 10,
                                             "endColumn": 36,
-                                            "start": 115,
-                                            "end": 130
+                                            "start": 396,
+                                            "end": 411
+                                        }
+                                    }
+                                ]
+                            },
+                            {
+                                "type": "Element",
+                                "name": "p",
+                                "namespace": "http://www.w3.org/1999/xhtml",
+                                "location": {
+                                    "startLine": 11,
+                                    "startColumn": 13,
+                                    "endLine": 11,
+                                    "endColumn": 57,
+                                    "start": 428,
+                                    "end": 472,
+                                    "startTag": {
+                                        "startLine": 11,
+                                        "startColumn": 13,
+                                        "endLine": 11,
+                                        "endColumn": 31,
+                                        "start": 428,
+                                        "end": 446
+                                    },
+                                    "endTag": {
+                                        "startLine": 11,
+                                        "startColumn": 53,
+                                        "endLine": 11,
+                                        "endColumn": 57,
+                                        "start": 468,
+                                        "end": 472
+                                    }
+                                },
+                                "attributes": [
+                                    {
+                                        "type": "Attribute",
+                                        "name": "slot",
+                                        "value": {
+                                            "type": "Literal",
+                                            "value": "undefined"
+                                        },
+                                        "location": {
+                                            "startLine": 11,
+                                            "startColumn": 16,
+                                            "endLine": 11,
+                                            "endColumn": 30,
+                                            "start": 431,
+                                            "end": 445
+                                        }
+                                    }
+                                ],
+                                "properties": [],
+                                "directives": [],
+                                "listeners": [],
+                                "children": [
+                                    {
+                                        "type": "Text",
+                                        "raw": "Undefined Slot Content",
+                                        "value": {
+                                            "type": "Literal",
+                                            "value": "Undefined Slot Content"
+                                        },
+                                        "location": {
+                                            "startLine": 11,
+                                            "startColumn": 31,
+                                            "endLine": 11,
+                                            "endColumn": 53,
+                                            "start": 446,
+                                            "end": 468
+                                        }
+                                    }
+                                ]
+                            },
+                            {
+                                "type": "Element",
+                                "name": "p",
+                                "namespace": "http://www.w3.org/1999/xhtml",
+                                "location": {
+                                    "startLine": 12,
+                                    "startColumn": 13,
+                                    "endLine": 12,
+                                    "endColumn": 47,
+                                    "start": 485,
+                                    "end": 519,
+                                    "startTag": {
+                                        "startLine": 12,
+                                        "startColumn": 13,
+                                        "endLine": 12,
+                                        "endColumn": 26,
+                                        "start": 485,
+                                        "end": 498
+                                    },
+                                    "endTag": {
+                                        "startLine": 12,
+                                        "startColumn": 43,
+                                        "endLine": 12,
+                                        "endColumn": 47,
+                                        "start": 515,
+                                        "end": 519
+                                    }
+                                },
+                                "attributes": [
+                                    {
+                                        "type": "Attribute",
+                                        "name": "slot",
+                                        "value": {
+                                            "type": "Literal",
+                                            "value": "null"
+                                        },
+                                        "location": {
+                                            "startLine": 12,
+                                            "startColumn": 16,
+                                            "endLine": 12,
+                                            "endColumn": 25,
+                                            "start": 488,
+                                            "end": 497
+                                        }
+                                    }
+                                ],
+                                "properties": [],
+                                "directives": [],
+                                "listeners": [],
+                                "children": [
+                                    {
+                                        "type": "Text",
+                                        "raw": "Null Slot Content",
+                                        "value": {
+                                            "type": "Literal",
+                                            "value": "Null Slot Content"
+                                        },
+                                        "location": {
+                                            "startLine": 12,
+                                            "startColumn": 26,
+                                            "endLine": 12,
+                                            "endColumn": 43,
+                                            "start": 498,
+                                            "end": 515
+                                        }
+                                    }
+                                ]
+                            },
+                            {
+                                "type": "Element",
+                                "name": "p",
+                                "namespace": "http://www.w3.org/1999/xhtml",
+                                "location": {
+                                    "startLine": 13,
+                                    "startColumn": 13,
+                                    "endLine": 13,
+                                    "endColumn": 41,
+                                    "start": 532,
+                                    "end": 560,
+                                    "startTag": {
+                                        "startLine": 13,
+                                        "startColumn": 13,
+                                        "endLine": 13,
+                                        "endColumn": 21,
+                                        "start": 532,
+                                        "end": 540
+                                    },
+                                    "endTag": {
+                                        "startLine": 13,
+                                        "startColumn": 37,
+                                        "endLine": 13,
+                                        "endColumn": 41,
+                                        "start": 556,
+                                        "end": 560
+                                    }
+                                },
+                                "attributes": [
+                                    {
+                                        "type": "Attribute",
+                                        "name": "slot",
+                                        "value": {
+                                            "type": "Literal",
+                                            "value": true
+                                        },
+                                        "location": {
+                                            "startLine": 13,
+                                            "startColumn": 16,
+                                            "endLine": 13,
+                                            "endColumn": 20,
+                                            "start": 535,
+                                            "end": 539
+                                        }
+                                    }
+                                ],
+                                "properties": [],
+                                "directives": [],
+                                "listeners": [],
+                                "children": [
+                                    {
+                                        "type": "Text",
+                                        "raw": "Empty slot value",
+                                        "value": {
+                                            "type": "Literal",
+                                            "value": "Empty slot value"
+                                        },
+                                        "location": {
+                                            "startLine": 13,
+                                            "startColumn": 21,
+                                            "endLine": 13,
+                                            "endColumn": 37,
+                                            "start": 540,
+                                            "end": 556
                                         }
                                     }
                                 ]
diff --git a/packages/@lwc/template-compiler/src/__tests__/fixtures/slots/usage/expected.js b/packages/@lwc/template-compiler/src/__tests__/fixtures/slots/usage/expected.js
index a990a56eca..999e159ae0 100644
--- a/packages/@lwc/template-compiler/src/__tests__/fixtures/slots/usage/expected.js
+++ b/packages/@lwc/template-compiler/src/__tests__/fixtures/slots/usage/expected.js
@@ -1,5 +1,6 @@
 import _nsCmp from "ns/cmp";
-import { registerTemplate } from "lwc";
+import { parseFragment, registerTemplate } from "lwc";
+const $fragment1 = parseFragment`<p${3}>Default Slot No Slot Attribute</p>`;
 const stc0 = {
   key: 0,
 };
@@ -7,24 +8,67 @@ const stc1 = {
   key: 1,
 };
 const stc2 = {
-  attrs: {
-    slot: "header",
-  },
-  key: 2,
+  slotAssignment: "",
+  key: 4,
 };
 const stc3 = {
-  attrs: {
-    slot: "",
-  },
-  key: 3,
+  slotAssignment: "true",
+  key: 5,
+};
+const stc4 = {
+  slotAssignment: "header",
+  key: 8,
+};
+const stc5 = {
+  slotAssignment: "",
+  key: 9,
+};
+const stc6 = {
+  slotAssignment: "undefined",
+  key: 10,
+};
+const stc7 = {
+  slotAssignment: "null",
+  key: 11,
+};
+const stc8 = {
+  slotAssignment: "",
+  key: 12,
 };
 function tmpl($api, $cmp, $slotset, $ctx) {
-  const { t: api_text, h: api_element, c: api_custom_element } = $api;
+  const {
+    st: api_static_fragment,
+    t: api_text,
+    h: api_element,
+    c: api_custom_element,
+  } = $api;
   return [
     api_element("section", stc0, [
       api_custom_element("ns-cmp", _nsCmp, stc1, [
-        api_element("p", stc2, [api_text("Header Slot Content")]),
-        api_element("p", stc3, [api_text("Default Content")]),
+        api_static_fragment($fragment1(), 3),
+        api_element("p", stc2, [api_text("Slot Empty String Attribute")]),
+        api_element("p", stc3, [api_text("Slot Boolean Attribute")]),
+        api_element(
+          "p",
+          {
+            slotAssignment: $cmp.slot.name,
+            key: 6,
+          },
+          [api_text("Dynamic Slot Content")]
+        ),
+        api_element(
+          "p",
+          {
+            slotAssignment: $cmp.slotVariable,
+            key: 7,
+          },
+          [api_text("Variable As Slot Assignment")]
+        ),
+        api_element("p", stc4, [api_text("Header Slot Content")]),
+        api_element("p", stc5, [api_text("Default Content")]),
+        api_element("p", stc6, [api_text("Undefined Slot Content")]),
+        api_element("p", stc7, [api_text("Null Slot Content")]),
+        api_element("p", stc8, [api_text("Empty slot value")]),
       ]),
     ]),
   ];
diff --git a/packages/@lwc/template-compiler/src/codegen/index.ts b/packages/@lwc/template-compiler/src/codegen/index.ts
index b6a10d2194..90273fa7f1 100644
--- a/packages/@lwc/template-compiler/src/codegen/index.ts
+++ b/packages/@lwc/template-compiler/src/codegen/index.ts
@@ -547,6 +547,14 @@ function transform(codeGen: CodeGen): t.Expression {
                         const styleAST = styleMapToStyleDeclsAST(styleMap);
                         data.push(t.property(t.identifier('styleDecls'), styleAST));
                     }
+                } else if (name === 'slot') {
+                    let slotValue;
+                    if (isExpression(value)) {
+                        slotValue = codeGen.bindExpression(value);
+                    } else {
+                        slotValue = isStringLiteral(value) ? t.literal(value.value) : t.literal('');
+                    }
+                    data.push(t.property(t.identifier('slotAssignment'), slotValue));
                 } else {
                     rest[name] = computeAttrValue(attr, element, !addSanitizationHook);
                 }