diff --git a/.gitignore b/.gitignore
index 2bb8dea3c8..897d95d676 100644
--- a/.gitignore
+++ b/.gitignore
@@ -8,6 +8,7 @@ coverage/
 .project/
 .nx
 .nx-cache
+.eslintcache
 
 lib/
 __benchmarks_results__/
diff --git a/package.json b/package.json
index 2147bd0d9d..a05a372f86 100644
--- a/package.json
+++ b/package.json
@@ -9,7 +9,7 @@
     },
     "scripts": {
         "prepare": "husky && yarn build",
-        "lint": "eslint .",
+        "lint": "eslint . --cache",
         "format": "prettier --write .",
         "bundlesize": "node scripts/bundlesize/bundlesize.mjs",
         "build": "nx run-many --target=build --exclude=@lwc/perf-benchmarks,@lwc/perf-benchmarks-components,@lwc/integration-tests,lwc",
@@ -74,11 +74,11 @@
         "vitest": "^2.1.8"
     },
     "lint-staged": {
-        "*.{js,mjs,ts}": "eslint",
+        "*.{js,mjs,ts}": "eslint --cache",
         "*.{css,js,json,md,mjs,ts,yaml,yml}": "prettier --write",
         "{packages/**/package.json,scripts/tasks/check-and-rewrite-package-json.js}": "node ./scripts/tasks/check-and-rewrite-package-json.js",
         "{LICENSE-CORE.md,**/LICENSE.md,yarn.lock,scripts/tasks/generate-license-files.js,scripts/shared/bundled-dependencies.js}": "node ./scripts/tasks/generate-license-files.js",
-        "*.{only,skip}": "eslint --no-eslintrc --plugin '@lwc/eslint-plugin-lwc-internal' --rule '@lwc/lwc-internal/forbidden-filename: error'"
+        "*.{only,skip}": "eslint --cache --no-eslintrc --plugin '@lwc/eslint-plugin-lwc-internal' --rule '@lwc/lwc-internal/forbidden-filename: error'"
     },
     "workspaces": [
         "packages/@lwc/*",
diff --git a/packages/@lwc/engine-core/src/framework/hydration.ts b/packages/@lwc/engine-core/src/framework/hydration.ts
index e04f1d9f73..1a924a3071 100644
--- a/packages/@lwc/engine-core/src/framework/hydration.ts
+++ b/packages/@lwc/engine-core/src/framework/hydration.ts
@@ -63,6 +63,11 @@ import type {
 import type { VM } from './vm';
 import type { RendererAPI } from './renderer';
 
+type Classes = Omit<Set<string>, 'add'>;
+
+// Used as a perf optimization to avoid creating and discarding sets unnecessarily.
+const EMPTY_SET: Classes = new Set<string>();
+
 // These values are the ones from Node.nodeType (https://developer.mozilla.org/en-US/docs/Web/API/Node/nodeType)
 const enum EnvNodeTypes {
     ELEMENT = 1,
@@ -618,6 +623,23 @@ function validateAttrs(
     return nodesAreCompatible;
 }
 
+function checkClassesCompatibility(first: Classes, second: Classes): boolean {
+    if (first.size !== second.size) {
+        return false;
+    }
+    for (const f of first) {
+        if (!second.has(f)) {
+            return false;
+        }
+    }
+    for (const s of second) {
+        if (!first.has(s)) {
+            return false;
+        }
+    }
+    return true;
+}
+
 function validateClassAttr(
     vnode: VBaseElement | VStatic,
     elm: Element,
@@ -634,16 +656,18 @@ function validateClassAttr(
 
     // Use a Set because we don't care to validate mismatches for 1) different ordering in SSR vs CSR, or 2)
     // duplicated class names. These don't have an effect on rendered styles.
-    const elmClasses = new Set(ArrayFrom(elm.classList));
-    let vnodeClasses: Set<string>;
+    const elmClasses = elm.classList.length ? new Set(ArrayFrom(elm.classList)) : EMPTY_SET;
+    let vnodeClasses: Classes;
 
     if (!isUndefined(className)) {
         // ignore empty spaces entirely, filter them out using `filter(..., Boolean)`
-        vnodeClasses = new Set(ArrayFilter.call(StringSplit.call(className, /\s+/), Boolean));
+        const classes = ArrayFilter.call(StringSplit.call(className, /\s+/), Boolean);
+        vnodeClasses = classes.length ? new Set(classes) : EMPTY_SET;
     } else if (!isUndefined(classMap)) {
-        vnodeClasses = new Set(keys(classMap));
+        const classes = keys(classMap);
+        vnodeClasses = classes.length ? new Set(classes) : EMPTY_SET;
     } else {
-        vnodeClasses = new Set();
+        vnodeClasses = EMPTY_SET;
     }
 
     // ---------- Step 2: handle the scope tokens
@@ -658,7 +682,11 @@ function validateClassAttr(
     // Consequently, hydration mismatches will occur if scoped CSS token classnames
     // are rendered during SSR. This needs to be accounted for when validating.
     if (!isNull(scopeToken)) {
-        vnodeClasses.add(scopeToken);
+        if (vnodeClasses === EMPTY_SET) {
+            vnodeClasses = new Set([scopeToken]);
+        } else {
+            (vnodeClasses as Set<string>).add(scopeToken);
+        }
     }
 
     // This tells us which `*-host` scope token was rendered to the element's class.
@@ -672,25 +700,10 @@ function validateClassAttr(
 
     // ---------- Step 3: check for compatibility
 
-    let nodesAreCompatible = true;
+    const classesAreCompatible = checkClassesCompatibility(vnodeClasses, elmClasses);
 
-    if (vnodeClasses.size !== elmClasses.size) {
-        nodesAreCompatible = false;
-    } else {
-        for (const vnodeClass of vnodeClasses) {
-            if (!elmClasses.has(vnodeClass)) {
-                nodesAreCompatible = false;
-            }
-        }
-        for (const elmClass of elmClasses) {
-            if (!vnodeClasses.has(elmClass)) {
-                nodesAreCompatible = false;
-            }
-        }
-    }
-
-    if (process.env.NODE_ENV !== 'production' && !nodesAreCompatible) {
-        const prettyPrint = (set: Set<string>) =>
+    if (process.env.NODE_ENV !== 'production' && !classesAreCompatible) {
+        const prettyPrint = (set: Classes) =>
             JSON.stringify(ArrayJoin.call(ArraySort.call(ArrayFrom(set)), ' '));
         logWarn(
             `Mismatch hydrating element <${getProperty(
@@ -703,7 +716,7 @@ function validateClassAttr(
         );
     }
 
-    return nodesAreCompatible;
+    return classesAreCompatible;
 }
 
 function validateStyleAttr(
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/empty copy/error.txt
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/error.txt
rename to packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/empty copy/error.txt
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/empty copy/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/empty copy/expected.html
new file mode 100644
index 0000000000..79ceaa13f4
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/empty copy/expected.html	
@@ -0,0 +1,9 @@
+<x-comments-text>
+  <template shadowrootmode="open">
+    <!---->
+    ‍
+    <!---->
+    <!-- preserved comment after true -->
+    <!-- preserved comment after false -->
+  </template>
+</x-comments-text>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/empty copy/index.js b/packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/empty copy/index.js
new file mode 100644
index 0000000000..4bd94488e9
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/empty copy/index.js	
@@ -0,0 +1,3 @@
+export const tagName = 'x-comments-text';
+export { default } from 'x/comments-text';
+export * from 'x/comments-text';
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/empty copy/modules/x/comments-text/comments-text.html b/packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/empty copy/modules/x/comments-text/comments-text.html
new file mode 100644
index 0000000000..1138d4e911
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/empty copy/modules/x/comments-text/comments-text.html	
@@ -0,0 +1,6 @@
+<template lwc:preserve-comments>
+    <template lwc:if={isTrue}>{foo}{bar}{baz}</template>
+    <!-- preserved comment after true -->
+    <template lwc:if={isFalse}>{foo}{bar}{baz}</template>
+    <!-- preserved comment after false -->
+</template>
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/empty copy/modules/x/comments-text/comments-text.js b/packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/empty copy/modules/x/comments-text/comments-text.js
new file mode 100644
index 0000000000..4f3a42e964
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/empty copy/modules/x/comments-text/comments-text.js	
@@ -0,0 +1,9 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {
+    isTrue = true;
+    isFalse = false;
+    foo = '';
+    bar = undefined;
+    baz = null;
+}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-aria/dynamic/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-aria/dynamic/expected.html
index e5f6090a1b..6baed8c3be 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-aria/dynamic/expected.html
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-aria/dynamic/expected.html
@@ -14,7 +14,7 @@
       <template shadowrootmode="open">
         <div>
         </div>
-        <x-grandchild aria-activedescendant="null" aria-atomic="null" aria-autocomplete="null" aria-braillelabel="null" aria-brailleroledescription="null" aria-busy="null" aria-checked="null" aria-colcount="null" aria-colindex="null" aria-colindextext="null" aria-colspan="null" aria-controls="null" aria-current="null" aria-describedby="null" aria-description="null" aria-details="null" aria-disabled="null" aria-errormessage="null" aria-expanded="null" aria-flowto="null" aria-haspopup="null" aria-hidden="null" aria-invalid="null" aria-keyshortcuts="null" aria-label="null" aria-labelledby="null" aria-level="null" aria-live="null" aria-modal="null" aria-multiline="null" aria-multiselectable="null" aria-orientation="null" aria-owns="null" aria-placeholder="null" aria-posinset="null" aria-pressed="null" aria-readonly="null" aria-relevant="null" aria-required="null" aria-roledescription="null" aria-rowcount="null" aria-rowindex="null" aria-rowindextext="null" aria-rowspan="null" aria-selected="null" aria-setsize="null" aria-sort="null" aria-valuemax="null" aria-valuemin="null" aria-valuenow="null" aria-valuetext="null" role="null">
+        <x-grandchild>
           <template shadowrootmode="open">
           </template>
         </x-grandchild>
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-class/with-scoped-styles-only-in-child/dynamic/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-class/with-scoped-styles-only-in-child/dynamic/expected.html
index 9627366d70..a5888c9bd2 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-class/with-scoped-styles-only-in-child/dynamic/expected.html
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-class/with-scoped-styles-only-in-child/dynamic/expected.html
@@ -5,7 +5,7 @@
         <style class="lwc-5h3d35cke7v" type="text/css">
           :host {background: blue;}
         </style>
-        <div class="lwc-5h3d35cke7v">
+        <div>
         </div>
         <x-grandchild class="lwc-5h3d35cke7v">
           <template shadowrootmode="open">
@@ -18,7 +18,7 @@
         <style class="lwc-5h3d35cke7v" type="text/css">
           :host {background: blue;}
         </style>
-        <div class="lwc-5h3d35cke7v">
+        <div>
         </div>
         <x-grandchild class="lwc-5h3d35cke7v">
           <template shadowrootmode="open">
@@ -31,7 +31,7 @@
         <style class="lwc-5h3d35cke7v" type="text/css">
           :host {background: blue;}
         </style>
-        <div class="lwc-5h3d35cke7v">
+        <div>
         </div>
         <x-grandchild class="lwc-5h3d35cke7v">
           <template shadowrootmode="open">
@@ -44,7 +44,7 @@
         <style class="lwc-5h3d35cke7v" type="text/css">
           :host {background: blue;}
         </style>
-        <div class="lwc-5h3d35cke7v">
+        <div>
         </div>
         <x-grandchild class="lwc-5h3d35cke7v">
           <template shadowrootmode="open">
@@ -57,7 +57,7 @@
         <style class="lwc-5h3d35cke7v" type="text/css">
           :host {background: blue;}
         </style>
-        <div class="lwc-5h3d35cke7v">
+        <div>
         </div>
         <x-grandchild class="lwc-5h3d35cke7v">
           <template shadowrootmode="open">
@@ -70,7 +70,7 @@
         <style class="lwc-5h3d35cke7v" type="text/css">
           :host {background: blue;}
         </style>
-        <div class="lwc-5h3d35cke7v">
+        <div>
         </div>
         <x-grandchild class="lwc-5h3d35cke7v">
           <template shadowrootmode="open">
@@ -83,7 +83,7 @@
         <style class="lwc-5h3d35cke7v" type="text/css">
           :host {background: blue;}
         </style>
-        <div class="lwc-5h3d35cke7v">
+        <div>
         </div>
         <x-grandchild class="lwc-5h3d35cke7v">
           <template shadowrootmode="open">
@@ -96,7 +96,7 @@
         <style class="lwc-5h3d35cke7v" type="text/css">
           :host {background: blue;}
         </style>
-        <div class="lwc-5h3d35cke7v">
+        <div>
         </div>
         <x-grandchild class="lwc-5h3d35cke7v">
           <template shadowrootmode="open">
@@ -109,7 +109,7 @@
         <style class="lwc-5h3d35cke7v" type="text/css">
           :host {background: blue;}
         </style>
-        <div class="lwc-5h3d35cke7v">
+        <div>
         </div>
         <x-grandchild class="lwc-5h3d35cke7v">
           <template shadowrootmode="open">
@@ -122,7 +122,7 @@
         <style class="lwc-5h3d35cke7v" type="text/css">
           :host {background: blue;}
         </style>
-        <div class="lwc-5h3d35cke7v">
+        <div>
         </div>
         <x-grandchild class="lwc-5h3d35cke7v">
           <template shadowrootmode="open">
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-class/with-scoped-styles/dynamic/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-class/with-scoped-styles/dynamic/expected.html
index bd44bdcea4..2378b62b22 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-class/with-scoped-styles/dynamic/expected.html
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-class/with-scoped-styles/dynamic/expected.html
@@ -8,7 +8,7 @@
         <style class="lwc-5h3d35cke7v" type="text/css">
           :host {background: blue;}
         </style>
-        <div class="lwc-5h3d35cke7v">
+        <div>
         </div>
         <x-grandchild class="lwc-42b236sbaik-host lwc-5h3d35cke7v" data-lwc-host-scope-token="lwc-42b236sbaik-host">
           <template shadowrootmode="open">
@@ -24,7 +24,7 @@
         <style class="lwc-5h3d35cke7v" type="text/css">
           :host {background: blue;}
         </style>
-        <div class="lwc-5h3d35cke7v">
+        <div>
         </div>
         <x-grandchild class="lwc-42b236sbaik-host lwc-5h3d35cke7v" data-lwc-host-scope-token="lwc-42b236sbaik-host">
           <template shadowrootmode="open">
@@ -40,7 +40,7 @@
         <style class="lwc-5h3d35cke7v" type="text/css">
           :host {background: blue;}
         </style>
-        <div class="lwc-5h3d35cke7v">
+        <div>
         </div>
         <x-grandchild class="lwc-42b236sbaik-host lwc-5h3d35cke7v" data-lwc-host-scope-token="lwc-42b236sbaik-host">
           <template shadowrootmode="open">
@@ -56,7 +56,7 @@
         <style class="lwc-5h3d35cke7v" type="text/css">
           :host {background: blue;}
         </style>
-        <div class="lwc-5h3d35cke7v">
+        <div>
         </div>
         <x-grandchild class="lwc-42b236sbaik-host lwc-5h3d35cke7v" data-lwc-host-scope-token="lwc-42b236sbaik-host">
           <template shadowrootmode="open">
@@ -72,7 +72,7 @@
         <style class="lwc-5h3d35cke7v" type="text/css">
           :host {background: blue;}
         </style>
-        <div class="lwc-5h3d35cke7v">
+        <div>
         </div>
         <x-grandchild class="lwc-42b236sbaik-host lwc-5h3d35cke7v" data-lwc-host-scope-token="lwc-42b236sbaik-host">
           <template shadowrootmode="open">
@@ -88,7 +88,7 @@
         <style class="lwc-5h3d35cke7v" type="text/css">
           :host {background: blue;}
         </style>
-        <div class="lwc-5h3d35cke7v">
+        <div>
         </div>
         <x-grandchild class="lwc-42b236sbaik-host lwc-5h3d35cke7v" data-lwc-host-scope-token="lwc-42b236sbaik-host">
           <template shadowrootmode="open">
@@ -104,7 +104,7 @@
         <style class="lwc-5h3d35cke7v" type="text/css">
           :host {background: blue;}
         </style>
-        <div class="lwc-5h3d35cke7v">
+        <div>
         </div>
         <x-grandchild class="lwc-42b236sbaik-host lwc-5h3d35cke7v" data-lwc-host-scope-token="lwc-42b236sbaik-host">
           <template shadowrootmode="open">
@@ -120,7 +120,7 @@
         <style class="lwc-5h3d35cke7v" type="text/css">
           :host {background: blue;}
         </style>
-        <div class="lwc-5h3d35cke7v">
+        <div>
         </div>
         <x-grandchild class="lwc-42b236sbaik-host lwc-5h3d35cke7v" data-lwc-host-scope-token="lwc-42b236sbaik-host">
           <template shadowrootmode="open">
@@ -136,7 +136,7 @@
         <style class="lwc-5h3d35cke7v" type="text/css">
           :host {background: blue;}
         </style>
-        <div class="lwc-5h3d35cke7v">
+        <div>
         </div>
         <x-grandchild class="lwc-42b236sbaik-host lwc-5h3d35cke7v" data-lwc-host-scope-token="lwc-42b236sbaik-host">
           <template shadowrootmode="open">
@@ -152,7 +152,7 @@
         <style class="lwc-5h3d35cke7v" type="text/css">
           :host {background: blue;}
         </style>
-        <div class="lwc-5h3d35cke7v">
+        <div>
         </div>
         <x-grandchild class="lwc-42b236sbaik-host lwc-5h3d35cke7v" data-lwc-host-scope-token="lwc-42b236sbaik-host">
           <template shadowrootmode="open">
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-component-global-html/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-component-global-html/expected.html
index 9bcbfcdd11..c4a1b8b6e4 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-component-global-html/expected.html
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-component-global-html/expected.html
@@ -1,6 +1,6 @@
 <x-attribute-component-global-html>
   <template shadowrootmode="open">
-    <x-child accesskey="A" class="bar foo" contenteditable="true" data-test="test" draggable="true" hidden id="foo" itemprop="foo" spellcheck="true" style="color: red; background: blue;" tabindex="-1">
+    <x-child accesskey="A" class="bar foo" data-test="test" draggable="true" hidden id="foo" spellcheck="true" style="color: red; background: blue;" tabindex="-1">
       <template shadowrootmode="open">
         Passthrough properties:
         <ul>
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-global-html/as-component-prop/undeclared/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-global-html/as-component-prop/undeclared/expected.html
index 30d892ab60..ab9e06130f 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-global-html/as-component-prop/undeclared/expected.html
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-global-html/as-component-prop/undeclared/expected.html
@@ -1,6 +1,6 @@
 <x-component>
   <template shadowrootmode="open">
-    <x-child accesskey="foo" aria-activedescendant="foo" aria-atomic="foo" aria-autocomplete="foo" aria-busy="foo" aria-checked="foo" aria-colcount="foo" aria-colindex="foo" aria-colspan="foo" aria-controls="foo" aria-current="foo" aria-describedby="foo" aria-details="foo" aria-disabled="foo" aria-errormessage="foo" aria-expanded="foo" aria-flowto="foo" aria-haspopup="foo" aria-hidden="foo" aria-invalid="foo" aria-keyshortcuts="foo" aria-label="foo" aria-labelledby="foo" aria-level="foo" aria-live="foo" aria-modal="foo" aria-multiline="foo" aria-multiselectable="foo" aria-orientation="foo" aria-owns="foo" aria-placeholder="foo" aria-posinset="foo" aria-pressed="foo" aria-readonly="foo" aria-relevant="foo" aria-required="foo" aria-roledescription="foo" aria-rowcount="foo" aria-rowindex="foo" aria-rowspan="foo" aria-selected="foo" aria-setsize="foo" aria-sort="foo" aria-valuemax="foo" aria-valuemin="foo" aria-valuenow="foo" aria-valuetext="foo" autocapitalize="foo" autofocus="foo" contenteditable="foo" dir="foo" draggable="foo" enterkeyhint="foo" exportparts="foo" id="foo" inputmode="foo" itemid="foo" itemprop="foo" itemref="foo" itemscope="foo" itemtype="foo" lang="foo" nonce="foo" role="foo" spellcheck="foo" tabindex="foo" title="foo" translate="foo">
+    <x-child accesskey="foo" aria-activedescendant="foo" aria-atomic="foo" aria-autocomplete="foo" aria-busy="foo" aria-checked="foo" aria-colcount="foo" aria-colindex="foo" aria-colspan="foo" aria-controls="foo" aria-current="foo" aria-describedby="foo" aria-details="foo" aria-disabled="foo" aria-errormessage="foo" aria-expanded="foo" aria-flowto="foo" aria-haspopup="foo" aria-hidden="foo" aria-invalid="foo" aria-keyshortcuts="foo" aria-label="foo" aria-labelledby="foo" aria-level="foo" aria-live="foo" aria-modal="foo" aria-multiline="foo" aria-multiselectable="foo" aria-orientation="foo" aria-owns="foo" aria-placeholder="foo" aria-posinset="foo" aria-pressed="foo" aria-readonly="foo" aria-relevant="foo" aria-required="foo" aria-roledescription="foo" aria-rowcount="foo" aria-rowindex="foo" aria-rowspan="foo" aria-selected="foo" aria-setsize="foo" aria-sort="foo" aria-valuemax="foo" aria-valuemin="foo" aria-valuenow="foo" aria-valuetext="foo" dir="foo" draggable="true" exportparts="foo" hidden id="foo" lang="foo" role="foo" spellcheck="true" tabindex="foo" title="foo">
       <template shadowrootmode="open">
         <span>
           accessKey: foo
@@ -147,10 +147,10 @@
           audio: 
         </span>
         <span>
-          autocapitalize: 
+          autocapitalize: foo
         </span>
         <span>
-          autofocus: 
+          autofocus: foo
         </span>
         <span>
           autoplay: 
@@ -174,7 +174,7 @@
           command: 
         </span>
         <span>
-          contentEditable: 
+          contentEditable: foo
         </span>
         <span>
           crossorigin: 
@@ -192,10 +192,10 @@
           disabled: 
         </span>
         <span>
-          draggable: false
+          draggable: true
         </span>
         <span>
-          enterkeyhint: 
+          enterkeyhint: foo
         </span>
         <span>
           exportparts: 
@@ -213,7 +213,7 @@
           formnovalidate: 
         </span>
         <span>
-          hidden: false
+          hidden: true
         </span>
         <span>
           id: foo
@@ -222,25 +222,25 @@
           input: 
         </span>
         <span>
-          inputmode: 
+          inputmode: foo
         </span>
         <span>
           ismap: 
         </span>
         <span>
-          itemid: 
+          itemid: foo
         </span>
         <span>
-          itemprop: 
+          itemprop: foo
         </span>
         <span>
-          itemref: 
+          itemref: foo
         </span>
         <span>
-          itemscope: 
+          itemscope: foo
         </span>
         <span>
-          itemtype: 
+          itemtype: foo
         </span>
         <span>
           keygen: 
@@ -267,7 +267,7 @@
           muted: 
         </span>
         <span>
-          nonce: 
+          nonce: foo
         </span>
         <span>
           noValidate: 
@@ -318,7 +318,7 @@
           title: foo
         </span>
         <span>
-          translate: 
+          translate: foo
         </span>
         <span>
           useMap: 
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-global-html/as-component-prop/without-@api/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-global-html/as-component-prop/without-@api/expected.html
index 94aa7b3829..b6b08f8817 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-global-html/as-component-prop/without-@api/expected.html
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-global-html/as-component-prop/without-@api/expected.html
@@ -1,6 +1,6 @@
 <x-component>
   <template shadowrootmode="open">
-    <x-child aria-activedescendant="foo" aria-atomic="foo" aria-autocomplete="foo" aria-busy="foo" aria-checked="foo" aria-colcount="foo" aria-colindex="foo" aria-colspan="foo" aria-controls="foo" aria-current="foo" aria-describedby="foo" aria-details="foo" aria-disabled="foo" aria-errormessage="foo" aria-expanded="foo" aria-flowto="foo" aria-haspopup="foo" aria-hidden="foo" aria-invalid="foo" aria-keyshortcuts="foo" aria-label="foo" aria-labelledby="foo" aria-level="foo" aria-live="foo" aria-modal="foo" aria-multiline="foo" aria-multiselectable="foo" aria-orientation="foo" aria-owns="foo" aria-placeholder="foo" aria-posinset="foo" aria-pressed="foo" aria-readonly="foo" aria-relevant="foo" aria-required="foo" aria-roledescription="foo" aria-rowcount="foo" aria-rowindex="foo" aria-rowspan="foo" aria-selected="foo" aria-setsize="foo" aria-sort="foo" aria-valuemax="foo" aria-valuemin="foo" aria-valuenow="foo" aria-valuetext="foo" exportparts="foo" role="foo">
+    <x-child exportparts="foo">
       <template shadowrootmode="open">
         <span>
           accessKey: 
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-style/basic/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-style/basic/expected.html
index 46af873ead..106e3daa3f 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-style/basic/expected.html
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-style/basic/expected.html
@@ -10,11 +10,11 @@
     </div>
     <div style="color: salmon; background-color: chocolate;">
     </div>
-    <div>
+    <div style="[object Object]">
     </div>
     <div>
     </div>
-    <div>
+    <div style>
     </div>
     <x-child style="color: red;">
       <template shadowrootmode="open">
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-style/dynamic/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-style/dynamic/expected.html
index 6f64793a8a..59aabcc7ed 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-style/dynamic/expected.html
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/attribute-style/dynamic/expected.html
@@ -4,7 +4,7 @@
       <template shadowrootmode="open">
         <div>
         </div>
-        <x-grandchild>
+        <x-grandchild style>
           <template shadowrootmode="open">
           </template>
         </x-grandchild>
@@ -14,7 +14,7 @@
       <template shadowrootmode="open">
         <div>
         </div>
-        <x-grandchild>
+        <x-grandchild style>
           <template shadowrootmode="open">
           </template>
         </x-grandchild>
@@ -22,9 +22,9 @@
     </x-child>
     <x-child>
       <template shadowrootmode="open">
-        <div>
+        <div style="false">
         </div>
-        <x-grandchild>
+        <x-grandchild style="false">
           <template shadowrootmode="open">
           </template>
         </x-grandchild>
@@ -32,9 +32,9 @@
     </x-child>
     <x-child>
       <template shadowrootmode="open">
-        <div>
+        <div style="true">
         </div>
-        <x-grandchild>
+        <x-grandchild style="true">
           <template shadowrootmode="open">
           </template>
         </x-grandchild>
@@ -42,9 +42,9 @@
     </x-child>
     <x-child>
       <template shadowrootmode="open">
-        <div>
+        <div style="0">
         </div>
-        <x-grandchild>
+        <x-grandchild style="0">
           <template shadowrootmode="open">
           </template>
         </x-grandchild>
@@ -52,9 +52,9 @@
     </x-child>
     <x-child>
       <template shadowrootmode="open">
-        <div>
+        <div style="0">
         </div>
-        <x-grandchild>
+        <x-grandchild style="0">
           <template shadowrootmode="open">
           </template>
         </x-grandchild>
@@ -62,9 +62,9 @@
     </x-child>
     <x-child>
       <template shadowrootmode="open">
-        <div>
+        <div style="NaN">
         </div>
-        <x-grandchild>
+        <x-grandchild style="NaN">
           <template shadowrootmode="open">
           </template>
         </x-grandchild>
@@ -72,9 +72,9 @@
     </x-child>
     <x-child>
       <template shadowrootmode="open">
-        <div>
+        <div style="Infinity">
         </div>
-        <x-grandchild>
+        <x-grandchild style="Infinity">
           <template shadowrootmode="open">
           </template>
         </x-grandchild>
@@ -82,9 +82,9 @@
     </x-child>
     <x-child>
       <template shadowrootmode="open">
-        <div>
+        <div style="-Infinity">
         </div>
-        <x-grandchild>
+        <x-grandchild style="-Infinity">
           <template shadowrootmode="open">
           </template>
         </x-grandchild>
@@ -92,9 +92,9 @@
     </x-child>
     <x-child>
       <template shadowrootmode="open">
-        <div>
+        <div style>
         </div>
-        <x-grandchild>
+        <x-grandchild style>
           <template shadowrootmode="open">
           </template>
         </x-grandchild>
@@ -102,9 +102,9 @@
     </x-child>
     <x-child>
       <template shadowrootmode="open">
-        <div>
+        <div style="foo,bar">
         </div>
-        <x-grandchild>
+        <x-grandchild style="foo,bar">
           <template shadowrootmode="open">
           </template>
         </x-grandchild>
@@ -112,9 +112,9 @@
     </x-child>
     <x-child>
       <template shadowrootmode="open">
-        <div>
+        <div style="[object Object]">
         </div>
-        <x-grandchild>
+        <x-grandchild style="[object Object]">
           <template shadowrootmode="open">
           </template>
         </x-grandchild>
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/light/error.txt
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/error.txt
rename to packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/light/error.txt
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/light/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/light/expected.html
new file mode 100644
index 0000000000..61738a2a38
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/light/expected.html
@@ -0,0 +1,11 @@
+<x-root>
+  <x-provider>
+    <!---->
+    <x-consumer>
+      <div>
+        some context
+      </div>
+    </x-consumer>
+    <!---->
+  </x-provider>
+</x-root>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/index.js b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/light/index.js
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/index.js
rename to packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/light/index.js
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/light/modules/x/consumer/consumer.html b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/light/modules/x/consumer/consumer.html
new file mode 100644
index 0000000000..4b5b9a57ff
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/light/modules/x/consumer/consumer.html
@@ -0,0 +1,3 @@
+<template lwc:render-mode="light">
+    <div>{foo}</div>
+</template>
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/light/modules/x/consumer/consumer.js b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/light/modules/x/consumer/consumer.js
new file mode 100644
index 0000000000..6f1758b3b6
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/light/modules/x/consumer/consumer.js
@@ -0,0 +1,7 @@
+import { LightningElement, wire } from 'lwc';
+import { WireAdapter } from '../../../wire-adapter';
+
+export default class SlottedConsumerComponent extends LightningElement {
+    static renderMode = 'light';
+    @wire(WireAdapter) foo;
+}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/light/modules/x/provider/provider.html b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/light/modules/x/provider/provider.html
new file mode 100644
index 0000000000..bf14f95bb9
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/light/modules/x/provider/provider.html
@@ -0,0 +1,3 @@
+<template lwc:render-mode="light">
+    <slot></slot>
+</template>
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/light/modules/x/provider/provider.js b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/light/modules/x/provider/provider.js
new file mode 100644
index 0000000000..0f1b9e95cc
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/light/modules/x/provider/provider.js
@@ -0,0 +1,15 @@
+import { LightningElement } from 'lwc';
+import { contextualizer } from '../../../wire-adapter';
+
+export default class ProviderComponent extends LightningElement {
+    static renderMode = 'light';
+    connectedCallback() {
+        contextualizer(this, {
+            consumerConnectedCallback(consumer) {
+                consumer.provide({
+                    value: 'some context',
+                });
+            },
+        });
+    }
+}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/light/modules/x/root/root.html b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/light/modules/x/root/root.html
new file mode 100644
index 0000000000..b96157b4fd
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/light/modules/x/root/root.html
@@ -0,0 +1,5 @@
+<template lwc:render-mode="light">
+    <x-provider>
+        <x-consumer></x-consumer>
+    </x-provider>
+</template>
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/light/modules/x/root/root.js b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/light/modules/x/root/root.js
new file mode 100644
index 0000000000..c9df99d82a
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/light/modules/x/root/root.js
@@ -0,0 +1,5 @@
+import { LightningElement } from 'lwc';
+
+export default class Rootcomponent extends LightningElement {
+    static renderMode = 'light';
+}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/wire-adapter.js b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/light/wire-adapter.js
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/wire-adapter.js
rename to packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/light/wire-adapter.js
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-child-nested/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/scoped/error.txt
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/for-each-child-nested/error.txt
rename to packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/scoped/error.txt
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/scoped/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/scoped/expected.html
new file mode 100644
index 0000000000..a0c8f044b0
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/scoped/expected.html
@@ -0,0 +1,16 @@
+<x-root>
+  <x-provider>
+    <!---->
+    <!---->
+    <x-consumer>
+      <span>
+        some context
+      </span>
+    </x-consumer>
+    <span>
+      id - name
+    </span>
+    <!---->
+    <!---->
+  </x-provider>
+</x-root>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/scoped/index.js b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/scoped/index.js
new file mode 100644
index 0000000000..64dd80573e
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/scoped/index.js
@@ -0,0 +1,3 @@
+export const tagName = 'x-root';
+export { default } from 'x/root';
+export * from 'x/root';
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/scoped/modules/x/consumer/consumer.html b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/scoped/modules/x/consumer/consumer.html
new file mode 100644
index 0000000000..dae115689d
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/scoped/modules/x/consumer/consumer.html
@@ -0,0 +1,3 @@
+<template lwc:render-mode="light">
+    <span>{foo}</span>
+</template>
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/scoped/modules/x/consumer/consumer.js b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/scoped/modules/x/consumer/consumer.js
new file mode 100644
index 0000000000..6f1758b3b6
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/scoped/modules/x/consumer/consumer.js
@@ -0,0 +1,7 @@
+import { LightningElement, wire } from 'lwc';
+import { WireAdapter } from '../../../wire-adapter';
+
+export default class SlottedConsumerComponent extends LightningElement {
+    static renderMode = 'light';
+    @wire(WireAdapter) foo;
+}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/scoped/modules/x/provider/provider.html b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/scoped/modules/x/provider/provider.html
new file mode 100644
index 0000000000..2255b41438
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/scoped/modules/x/provider/provider.html
@@ -0,0 +1,3 @@
+<template lwc:render-mode="light">
+    <slot lwc:slot-bind={item}></slot>
+</template>
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/scoped/modules/x/provider/provider.js b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/scoped/modules/x/provider/provider.js
new file mode 100644
index 0000000000..4f3ad063b1
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/scoped/modules/x/provider/provider.js
@@ -0,0 +1,19 @@
+import { LightningElement } from 'lwc';
+import { contextualizer } from '../../../wire-adapter';
+
+export default class ProviderComponent extends LightningElement {
+    static renderMode = 'light';
+    item = {
+        id: 'id',
+        name: 'name',
+    };
+    connectedCallback() {
+        contextualizer(this, {
+            consumerConnectedCallback(consumer) {
+                consumer.provide({
+                    value: 'some context',
+                });
+            },
+        });
+    }
+}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/scoped/modules/x/root/root.html b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/scoped/modules/x/root/root.html
new file mode 100644
index 0000000000..d4e2810804
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/scoped/modules/x/root/root.html
@@ -0,0 +1,8 @@
+<template lwc:render-mode="light">
+    <x-provider>
+        <template lwc:slot-data="data">
+            <x-consumer></x-consumer>
+            <span>{data.id} - {data.name}</span>
+        </template>
+    </x-provider>
+</template>
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/scoped/modules/x/root/root.js b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/scoped/modules/x/root/root.js
new file mode 100644
index 0000000000..c9df99d82a
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/scoped/modules/x/root/root.js
@@ -0,0 +1,5 @@
+import { LightningElement } from 'lwc';
+
+export default class Rootcomponent extends LightningElement {
+    static renderMode = 'light';
+}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/scoped/wire-adapter.js b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/scoped/wire-adapter.js
new file mode 100644
index 0000000000..89f914b7e2
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/scoped/wire-adapter.js
@@ -0,0 +1,30 @@
+import { createContextProvider } from 'lwc';
+
+export class WireAdapter {
+    contextValue = { value: 'missing' };
+    static contextSchema = { value: 'required' };
+
+    constructor(callback) {
+        this._callback = callback;
+    }
+
+    connect() {
+        // noop
+    }
+
+    disconnect() {
+        // noop
+    }
+
+    update(_config, context) {
+        if (context) {
+            if (!context.hasOwnProperty('value')) {
+                throw new Error(`Invalid context provided`);
+            }
+            this.contextValue = context.value;
+            this._callback(this.contextValue);
+        }
+    }
+}
+
+export const contextualizer = createContextProvider(WireAdapter);
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-nested/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/shadow/error.txt
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/for-each-nested/error.txt
rename to packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/shadow/error.txt
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/shadow/expected.html
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/expected.html
rename to packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/shadow/expected.html
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/shadow/index.js b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/shadow/index.js
new file mode 100644
index 0000000000..64dd80573e
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/shadow/index.js
@@ -0,0 +1,3 @@
+export const tagName = 'x-root';
+export { default } from 'x/root';
+export * from 'x/root';
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/modules/x/consumer/consumer.html b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/shadow/modules/x/consumer/consumer.html
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/modules/x/consumer/consumer.html
rename to packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/shadow/modules/x/consumer/consumer.html
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/modules/x/consumer/consumer.js b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/shadow/modules/x/consumer/consumer.js
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/modules/x/consumer/consumer.js
rename to packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/shadow/modules/x/consumer/consumer.js
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/modules/x/provider/provider.html b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/shadow/modules/x/provider/provider.html
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/modules/x/provider/provider.html
rename to packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/shadow/modules/x/provider/provider.html
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/modules/x/provider/provider.js b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/shadow/modules/x/provider/provider.js
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/modules/x/provider/provider.js
rename to packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/shadow/modules/x/provider/provider.js
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/modules/x/root/root.html b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/shadow/modules/x/root/root.html
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/modules/x/root/root.html
rename to packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/shadow/modules/x/root/root.html
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/modules/x/root/root.js b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/shadow/modules/x/root/root.js
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/modules/x/root/root.js
rename to packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/shadow/modules/x/root/root.js
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/shadow/wire-adapter.js b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/shadow/wire-adapter.js
new file mode 100644
index 0000000000..89f914b7e2
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/context-slotted/shadow/wire-adapter.js
@@ -0,0 +1,30 @@
+import { createContextProvider } from 'lwc';
+
+export class WireAdapter {
+    contextValue = { value: 'missing' };
+    static contextSchema = { value: 'required' };
+
+    constructor(callback) {
+        this._callback = callback;
+    }
+
+    connect() {
+        // noop
+    }
+
+    disconnect() {
+        // noop
+    }
+
+    update(_config, context) {
+        if (context) {
+            if (!context.hasOwnProperty('value')) {
+                throw new Error(`Invalid context provided`);
+            }
+            this.contextValue = context.value;
+            this._callback(this.contextValue);
+        }
+    }
+}
+
+export const contextualizer = createContextProvider(WireAdapter);
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/exports/component-as-default/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/exports/component-as-default/error.txt
index e69de29bb2..5beee2fa1e 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/exports/component-as-default/error.txt
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/exports/component-as-default/error.txt
@@ -0,0 +1 @@
+generateMarkup is not a function
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/exports/component-as-default/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/exports/component-as-default/expected.html
index ce996e78e1..e69de29bb2 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/exports/component-as-default/expected.html
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/exports/component-as-default/expected.html
@@ -1,4 +0,0 @@
-<x-cmp>
-  <template shadowrootmode="open">
-  </template>
-</x-cmp>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/config.json b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/basic/config.json
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/config.json
rename to packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/basic/config.json
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-static-content/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/basic/error.txt
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/for-static-content/error.txt
rename to packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/basic/error.txt
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/basic/expected.html
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/expected.html
rename to packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/basic/expected.html
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/index.js b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/basic/index.js
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/index.js
rename to packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/basic/index.js
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/modules/x/for-each-block/for-each-block.html b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/basic/modules/x/for-each-block/for-each-block.html
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/modules/x/for-each-block/for-each-block.html
rename to packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/basic/modules/x/for-each-block/for-each-block.html
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/modules/x/for-each-block/for-each-block.js b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/basic/modules/x/for-each-block/for-each-block.js
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/modules/x/for-each-block/for-each-block.js
rename to packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/basic/modules/x/for-each-block/for-each-block.js
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-child-nested/config.json b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/child-nested/config.json
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/for-each-child-nested/config.json
rename to packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/child-nested/config.json
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block-missing-value/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/child-nested/error.txt
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block-missing-value/error.txt
rename to packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/child-nested/error.txt
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-child-nested/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/child-nested/expected.html
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rename from packages/@lwc/engine-server/src/__tests__/fixtures/for-each-child-nested/expected.html
rename to packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/child-nested/expected.html
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-child-nested/index.js b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/child-nested/index.js
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rename to packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/child-nested/index.js
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-child-nested/modules/x/child/child.html b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/child-nested/modules/x/child/child.html
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rename to packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/child-nested/modules/x/child/child.html
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-child-nested/modules/x/child/child.js b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/child-nested/modules/x/child/child.js
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/for-each-child-nested/modules/x/child/child.js
rename to packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/child-nested/modules/x/child/child.js
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-child-nested/modules/x/for-each-child-nested/for-each-child-nested.html b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/child-nested/modules/x/for-each-child-nested/for-each-child-nested.html
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rename to packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/child-nested/modules/x/for-each-child-nested/for-each-child-nested.html
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-child-nested/modules/x/for-each-child-nested/for-each-child-nested.js b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/child-nested/modules/x/for-each-child-nested/for-each-child-nested.js
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/for-each-child-nested/modules/x/for-each-child-nested/for-each-child-nested.js
rename to packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/child-nested/modules/x/for-each-child-nested/for-each-child-nested.js
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/item-and-index/error.txt
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/error.txt
rename to packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/item-and-index/error.txt
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/item-and-index/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/item-and-index/expected.html
new file mode 100644
index 0000000000..8e5795078d
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/item-and-index/expected.html
@@ -0,0 +1,36 @@
+<x-container>
+  <template shadowrootmode="open">
+    <ul>
+      <li data-index="0" data-item="one">
+        0 - one
+      </li>
+      <x-child data-index="0" data-item="one">
+        <template shadowrootmode="open">
+          <slot>
+          </slot>
+        </template>
+        0 - one
+      </x-child>
+      <li data-index="1" data-item="two">
+        1 - two
+      </li>
+      <x-child data-index="1" data-item="two">
+        <template shadowrootmode="open">
+          <slot>
+          </slot>
+        </template>
+        1 - two
+      </x-child>
+      <li data-index="2" data-item="three">
+        2 - three
+      </li>
+      <x-child data-index="2" data-item="three">
+        <template shadowrootmode="open">
+          <slot>
+          </slot>
+        </template>
+        2 - three
+      </x-child>
+    </ul>
+  </template>
+</x-container>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-static-content/index.js b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/item-and-index/index.js
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/for-static-content/index.js
rename to packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/item-and-index/index.js
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/item-and-index/modules/x/child/child.html b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/item-and-index/modules/x/child/child.html
new file mode 100644
index 0000000000..6806310398
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/item-and-index/modules/x/child/child.html
@@ -0,0 +1,3 @@
+<template>
+    <slot></slot>
+</template>
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/item-and-index/modules/x/child/child.js b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/item-and-index/modules/x/child/child.js
new file mode 100644
index 0000000000..3f0d7e7e52
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/item-and-index/modules/x/child/child.js
@@ -0,0 +1,3 @@
+import { LightningElement } from 'lwc';
+
+export default class Child extends LightningElement {}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/item-and-index/modules/x/container/container.html b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/item-and-index/modules/x/container/container.html
new file mode 100755
index 0000000000..4b5dd8d38b
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/item-and-index/modules/x/container/container.html
@@ -0,0 +1,12 @@
+<template>
+    <ul>
+        <template for:each={items} for:item="item" for:index="index">
+            <li key={item} data-index={index} data-item={item}>
+                {index} - {item}
+            </li>
+            <x-child key={item} data-index={index} data-item={item}>
+                {index} - {item}
+            </x-child>
+        </template>
+    </ul>
+</template>
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/item-and-index/modules/x/container/container.js b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/item-and-index/modules/x/container/container.js
new file mode 100755
index 0000000000..c45de77ad3
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/item-and-index/modules/x/container/container.js
@@ -0,0 +1,5 @@
+import { LightningElement } from 'lwc';
+
+export default class Container extends LightningElement {
+    items = ['one', 'two', 'three'];
+}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-nested/config.json b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/nested/config.json
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/for-each-nested/config.json
rename to packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/nested/config.json
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-blocks-multiple/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/nested/error.txt
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/iterator-blocks-multiple/error.txt
rename to packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/nested/error.txt
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-nested/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/nested/expected.html
similarity index 100%
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rename to packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/nested/expected.html
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-nested/index.js b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/nested/index.js
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/for-each-nested/index.js
rename to packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/nested/index.js
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-nested/modules/x/for-each-nested/for-each-nested.html b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/nested/modules/x/for-each-nested/for-each-nested.html
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rename from packages/@lwc/engine-server/src/__tests__/fixtures/for-each-nested/modules/x/for-each-nested/for-each-nested.html
rename to packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/nested/modules/x/for-each-nested/for-each-nested.html
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-nested/modules/x/for-each-nested/for-each-nested.js b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/nested/modules/x/for-each-nested/for-each-nested.js
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/for-each-nested/modules/x/for-each-nested/for-each-nested.js
rename to packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/nested/modules/x/for-each-nested/for-each-nested.js
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/static-content/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/static-content/error.txt
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-static-content/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/static-content/expected.html
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/for-static-content/expected.html
rename to packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/static-content/expected.html
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/static-content/index.js b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/static-content/index.js
new file mode 100644
index 0000000000..9763122105
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/static-content/index.js
@@ -0,0 +1,3 @@
+export const tagName = 'x-container';
+export { default } from 'x/container';
+export * from 'x/container';
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-static-content/modules/x/container/container.html b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/static-content/modules/x/container/container.html
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/for-static-content/modules/x/container/container.html
rename to packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/static-content/modules/x/container/container.html
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/for-static-content/modules/x/container/container.js b/packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/static-content/modules/x/container/container.js
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/for-static-content/modules/x/container/container.js
rename to packages/@lwc/engine-server/src/__tests__/fixtures/for-each-block/static-content/modules/x/container/container.js
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/config.json b/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/basic/config.json
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/config.json
rename to packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/basic/config.json
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/basic/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/basic/error.txt
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/basic/expected.html
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/expected.html
rename to packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/basic/expected.html
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block-missing-value/index.js b/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/basic/index.js
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block-missing-value/index.js
rename to packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/basic/index.js
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/modules/x/iterator-block/iterator-block.html b/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/basic/modules/x/iterator-block/iterator-block.html
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/modules/x/iterator-block/iterator-block.html
rename to packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/basic/modules/x/iterator-block/iterator-block.html
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block-missing-value/modules/x/iterator-block/iterator-block.js b/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/basic/modules/x/iterator-block/iterator-block.js
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block-missing-value/modules/x/iterator-block/iterator-block.js
rename to packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/basic/modules/x/iterator-block/iterator-block.js
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/missing-value/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/missing-value/error.txt
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block-missing-value/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/missing-value/expected.html
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block-missing-value/expected.html
rename to packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/missing-value/expected.html
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/index.js b/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/missing-value/index.js
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/index.js
rename to packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/missing-value/index.js
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block-missing-value/modules/x/iterator-block/iterator-block.html b/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/missing-value/modules/x/iterator-block/iterator-block.html
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block-missing-value/modules/x/iterator-block/iterator-block.html
rename to packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/missing-value/modules/x/iterator-block/iterator-block.html
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/modules/x/iterator-block/iterator-block.js b/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/missing-value/modules/x/iterator-block/iterator-block.js
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/modules/x/iterator-block/iterator-block.js
rename to packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/missing-value/modules/x/iterator-block/iterator-block.js
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-blocks-multiple/config.json b/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/multiple/config.json
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/iterator-blocks-multiple/config.json
rename to packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/multiple/config.json
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/multiple/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/multiple/error.txt
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-blocks-multiple/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/multiple/expected.html
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/iterator-blocks-multiple/expected.html
rename to packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/multiple/expected.html
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-blocks-multiple/index.js b/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/multiple/index.js
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/iterator-blocks-multiple/index.js
rename to packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/multiple/index.js
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-blocks-multiple/modules/x/iterator-block/iterator-block.html b/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/multiple/modules/x/iterator-block/iterator-block.html
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/iterator-blocks-multiple/modules/x/iterator-block/iterator-block.html
rename to packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/multiple/modules/x/iterator-block/iterator-block.html
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-blocks-multiple/modules/x/iterator-block/iterator-block.js b/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/multiple/modules/x/iterator-block/iterator-block.js
similarity index 100%
rename from packages/@lwc/engine-server/src/__tests__/fixtures/iterator-blocks-multiple/modules/x/iterator-block/iterator-block.js
rename to packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/multiple/modules/x/iterator-block/iterator-block.js
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/variables/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/variables/error.txt
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/variables/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/variables/expected.html
new file mode 100644
index 0000000000..e3ddeb9697
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/variables/expected.html
@@ -0,0 +1,36 @@
+<x-container>
+  <template shadowrootmode="open">
+    <ul>
+      <li data-first="true" data-index="0" data-item="one" data-last="false">
+        0 - one - true - false
+      </li>
+      <x-child data-first="true" data-index="0" data-item="one" data-last="false">
+        <template shadowrootmode="open">
+          <slot>
+          </slot>
+        </template>
+        0 - one - true - false
+      </x-child>
+      <li data-first="false" data-index="1" data-item="two" data-last="false">
+        1 - two - false - false
+      </li>
+      <x-child data-first="false" data-index="1" data-item="two" data-last="false">
+        <template shadowrootmode="open">
+          <slot>
+          </slot>
+        </template>
+        1 - two - false - false
+      </x-child>
+      <li data-first="false" data-index="2" data-item="three" data-last="true">
+        2 - three - false - true
+      </li>
+      <x-child data-first="false" data-index="2" data-item="three" data-last="true">
+        <template shadowrootmode="open">
+          <slot>
+          </slot>
+        </template>
+        2 - three - false - true
+      </x-child>
+    </ul>
+  </template>
+</x-container>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/variables/index.js b/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/variables/index.js
new file mode 100644
index 0000000000..9763122105
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/variables/index.js
@@ -0,0 +1,3 @@
+export const tagName = 'x-container';
+export { default } from 'x/container';
+export * from 'x/container';
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/variables/modules/x/child/child.html b/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/variables/modules/x/child/child.html
new file mode 100644
index 0000000000..6806310398
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/variables/modules/x/child/child.html
@@ -0,0 +1,3 @@
+<template>
+    <slot></slot>
+</template>
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/variables/modules/x/child/child.js b/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/variables/modules/x/child/child.js
new file mode 100644
index 0000000000..3f0d7e7e52
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/variables/modules/x/child/child.js
@@ -0,0 +1,3 @@
+import { LightningElement } from 'lwc';
+
+export default class Child extends LightningElement {}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/variables/modules/x/container/container.html b/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/variables/modules/x/container/container.html
new file mode 100755
index 0000000000..fb26a708a1
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/variables/modules/x/container/container.html
@@ -0,0 +1,12 @@
+<template>
+    <ul>
+        <template iterator:it={items}>
+            <li key={it.value} data-index={it.index} data-item={it.value} data-first={it.first} data-last={it.last}>
+                {it.index} - {it.value} - {it.first} - {it.last}
+            </li>
+            <x-child key={it.value} data-index={it.index} data-item={it.value} data-first={it.first} data-last={it.last}>
+                {it.index} - {it.value} - {it.first} - {it.last}
+            </x-child>
+        </template>
+    </ul>
+</template>
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/variables/modules/x/container/container.js b/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/variables/modules/x/container/container.js
new file mode 100755
index 0000000000..c45de77ad3
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/iterator-block/variables/modules/x/container/container.js
@@ -0,0 +1,5 @@
+import { LightningElement } from 'lwc';
+
+export default class Container extends LightningElement {
+    items = ['one', 'two', 'three'];
+}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/known-boolean-attributes/default-def-html-attributes/static-on-component/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/known-boolean-attributes/default-def-html-attributes/static-on-component/expected.html
index 818c539306..4ad43dbee2 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/known-boolean-attributes/default-def-html-attributes/static-on-component/expected.html
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/known-boolean-attributes/default-def-html-attributes/static-on-component/expected.html
@@ -48,11 +48,11 @@
       <template shadowrootmode="open">
       </template>
     </x-child>
-    <x-child draggable>
+    <x-child draggable="false">
       <template shadowrootmode="open">
       </template>
     </x-child>
-    <x-child hidden>
+    <x-child>
       <template shadowrootmode="open">
       </template>
     </x-child>
@@ -80,7 +80,7 @@
       <template shadowrootmode="open">
       </template>
     </x-child>
-    <x-child draggable="   ">
+    <x-child draggable="true">
       <template shadowrootmode="open">
       </template>
     </x-child>
@@ -108,7 +108,7 @@
       <template shadowrootmode="open">
       </template>
     </x-child>
-    <x-child draggable="false">
+    <x-child draggable="true">
       <template shadowrootmode="open">
       </template>
     </x-child>
@@ -164,7 +164,7 @@
       <template shadowrootmode="open">
       </template>
     </x-child>
-    <x-child draggable="FALSE">
+    <x-child draggable="true">
       <template shadowrootmode="open">
       </template>
     </x-child>
@@ -196,7 +196,7 @@
       <template shadowrootmode="open">
       </template>
     </x-child>
-    <x-child draggable="TRUE">
+    <x-child draggable="true">
       <template shadowrootmode="open">
       </template>
     </x-child>
@@ -228,7 +228,7 @@
       <template shadowrootmode="open">
       </template>
     </x-child>
-    <x-child draggable="yolo">
+    <x-child draggable="true">
       <template shadowrootmode="open">
       </template>
     </x-child>
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/render-dynamic-value/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/render-dynamic-value/expected.html
index 5e0db2fe74..c6c8b943c5 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/render-dynamic-value/expected.html
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/render-dynamic-value/expected.html
@@ -40,11 +40,11 @@
       [object Object]
     </div>
     <div data-foo="function whoWouldDoThis() {
-      return 'somebody, probably!';
-    }">
+    return &quot;somebody, probably!&quot;;
+  }">
       function whoWouldDoThis() {
-      return &#x27;somebody, probably!&#x27;;
-    }
+    return &quot;somebody, probably!&quot;;
+  }
     </div>
     <div data-foo="ooo eee, ooo ah ah, ting tang, walla walla, bing bang">
       ooo eee, ooo ah ah, ting tang, walla walla, bing bang
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/scoped-slots/advanced/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/scoped-slots/advanced/expected.html
index 9b19697270..7e5404096e 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/scoped-slots/advanced/expected.html
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/scoped-slots/advanced/expected.html
@@ -4,21 +4,16 @@
       <div>
         <!---->
         <!---->
+        abcdefghi
         <span>
           1 default 99 - bar
         </span>
-        <!---->
-        <!---->
         <span>
           4 default 99 - bar
         </span>
-        <!---->
-        <!---->
         <span>
           6 default 99 - bar
         </span>
-        <!---->
-        <!---->
         <span>
           8 default 99 - bar
         </span>
@@ -29,8 +24,6 @@
         <span>
           2 slot1 99 - bar
         </span>
-        <!---->
-        <!---->
         <span>
           3 slot1 99 - bar
         </span>
@@ -44,8 +37,10 @@
         <!---->
         <!---->
         <!---->
+        <!---->
         Fallback slot content 3
         <!---->
+        <!---->
       </div>
     </x-child>
   </template>
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/scoped-slots/expression/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/scoped-slots/expression/error.txt
index e69de29bb2..fb15f150a9 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/scoped-slots/expression/error.txt
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/scoped-slots/expression/error.txt
@@ -0,0 +1 @@
+mySlot is not defined
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/scoped-slots/expression/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/scoped-slots/expression/expected.html
index ba14e335aa..e69de29bb2 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/scoped-slots/expression/expected.html
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/scoped-slots/expression/expected.html
@@ -1,15 +0,0 @@
-<x-parent>
-  <template shadowrootmode="open">
-    <x-child>
-      <div>
-        <!---->
-        <!---->
-        <span>
-          99
-        </span>
-        <!---->
-        <!---->
-      </div>
-    </x-child>
-  </template>
-</x-parent>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/scoped-slots/mixed-with-light-dom-slots-inside/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/scoped-slots/mixed-with-light-dom-slots-inside/error.txt
index e69de29bb2..ceb629d40e 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/scoped-slots/mixed-with-light-dom-slots-inside/error.txt
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/scoped-slots/mixed-with-light-dom-slots-inside/error.txt
@@ -0,0 +1 @@
+Cannot read properties of undefined (reading 'id')
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/scoped-slots/mixed-with-light-dom-slots-inside/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/scoped-slots/mixed-with-light-dom-slots-inside/expected.html
index 91fdf5fba8..e69de29bb2 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/scoped-slots/mixed-with-light-dom-slots-inside/expected.html
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/scoped-slots/mixed-with-light-dom-slots-inside/expected.html
@@ -1,18 +0,0 @@
-<x-parent>
-  <template shadowrootmode="open">
-    <x-child>
-      <div>
-        <!---->
-        abcdefghi
-        <!---->
-        <!---->
-        <!---->
-        <!---->
-        <!---->
-        <!---->
-        Fallback slot content 3
-        <!---->
-      </div>
-    </x-child>
-  </template>
-</x-parent>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/scoped-slots/mixed-with-light-dom-slots-outside/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/scoped-slots/mixed-with-light-dom-slots-outside/expected.html
index 0c03d18051..fcab1821a9 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/scoped-slots/mixed-with-light-dom-slots-outside/expected.html
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/scoped-slots/mixed-with-light-dom-slots-outside/expected.html
@@ -4,13 +4,47 @@
       <div>
         <!---->
         <!---->
+        a
+        <span>
+          1 default  - bar
+        </span>
+        bcd
+        <span>
+          4 default  - bar
+        </span>
+        ef
+        <span>
+          6 default  - bar
+        </span>
+        gh
+        <span>
+          8 default  - bar
+        </span>
+        i
         <!---->
         <!---->
         <!---->
         <!---->
+        <span>
+          2 slot1  - bar
+        </span>
+        <span>
+          3 slot1  - bar
+        </span>
+        <!---->
+        <!---->
+        <!---->
+        <!---->
+        <span>
+          5 slot2  - bar
+        </span>
+        <!---->
+        <!---->
+        <!---->
         <!---->
         Fallback slot content 3
         <!---->
+        <!---->
       </div>
     </x-child>
   </template>
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/scoped-slots/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/scoped-slots/expected.html
index 1ce037982f..ef6c45eab8 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/scoped-slots/expected.html
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/scoped-slots/expected.html
@@ -8,9 +8,13 @@
           <slot name="foo">
           </slot>
         </template>
+        <!---->
+        <!---->
         <h2>
           Hello world!
         </h2>
+        <!---->
+        <!---->
       </x-leaf>
     </x-scoped-slot-child>
   </x-scoped-slot-parent>
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/dangling/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/dangling/error.txt
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/dangling/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/dangling/expected.html
new file mode 100644
index 0000000000..24542845da
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/dangling/expected.html
@@ -0,0 +1,20 @@
+<x-dangling-container>
+  <x-slot>
+    <x-leaf>
+      <!---->
+      <!---->
+      <h1>
+        bottom content
+      </h1>
+      <!---->
+      <!---->
+      <!---->
+      <!---->
+      <h1>
+        top content
+      </h1>
+      <!---->
+      <!---->
+    </x-leaf>
+  </x-slot>
+</x-dangling-container>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/dangling/index.js b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/dangling/index.js
new file mode 100644
index 0000000000..b202a15a0a
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/dangling/index.js
@@ -0,0 +1,4 @@
+export const tagName = 'x-dangling-container';
+export { default } from 'x/container';
+export * from 'x/container';
+export const features = [];
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/dangling/modules/x/container/container.html b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/dangling/modules/x/container/container.html
new file mode 100644
index 0000000000..d6153f7e58
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/dangling/modules/x/container/container.html
@@ -0,0 +1,6 @@
+<template lwc:render-mode="light">
+    <x-slot>
+        <h1 slot="top">top content</h1>
+        <h1 slot="bottom">bottom content</h1>
+    </x-slot>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/dangling/modules/x/container/container.js b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/dangling/modules/x/container/container.js
new file mode 100644
index 0000000000..0679d2bc10
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/dangling/modules/x/container/container.js
@@ -0,0 +1,5 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {
+    static renderMode = 'light';
+}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/dangling/modules/x/leaf/leaf.html b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/dangling/modules/x/leaf/leaf.html
new file mode 100644
index 0000000000..039365a7a7
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/dangling/modules/x/leaf/leaf.html
@@ -0,0 +1,4 @@
+<template lwc:render-mode="light">
+    <slot name="top" slot="bottom"></slot>
+    <slot name="bottom"></slot>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/dangling/modules/x/leaf/leaf.js b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/dangling/modules/x/leaf/leaf.js
new file mode 100644
index 0000000000..0679d2bc10
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/dangling/modules/x/leaf/leaf.js
@@ -0,0 +1,5 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {
+    static renderMode = 'light';
+}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/dangling/modules/x/slot/slot.html b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/dangling/modules/x/slot/slot.html
new file mode 100644
index 0000000000..e641874967
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/dangling/modules/x/slot/slot.html
@@ -0,0 +1,6 @@
+<template lwc:render-mode="light">
+    <x-leaf>
+        <slot name="top" slot="bottom"></slot>
+        <slot name="bottom" slot="top"></slot>
+    </x-leaf>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/dangling/modules/x/slot/slot.js b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/dangling/modules/x/slot/slot.js
new file mode 100644
index 0000000000..0679d2bc10
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/dangling/modules/x/slot/slot.js
@@ -0,0 +1,5 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {
+    static renderMode = 'light';
+}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/light/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/light/error.txt
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/light/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/light/expected.html
new file mode 100644
index 0000000000..181835f02b
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/light/expected.html
@@ -0,0 +1,20 @@
+<x-light-container>
+  <x-slot>
+    <x-leaf>
+      <!---->
+      <!---->
+      <h1>
+        bottom content
+      </h1>
+      <!---->
+      <!---->
+      <!---->
+      <!---->
+      <h1>
+        top content
+      </h1>
+      <!---->
+      <!---->
+    </x-leaf>
+  </x-slot>
+</x-light-container>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/light/index.js b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/light/index.js
new file mode 100644
index 0000000000..2230255735
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/light/index.js
@@ -0,0 +1,4 @@
+export const tagName = 'x-light-container';
+export { default } from 'x/container';
+export * from 'x/container';
+export const features = [];
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/light/modules/x/container/container.html b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/light/modules/x/container/container.html
new file mode 100644
index 0000000000..d6153f7e58
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/light/modules/x/container/container.html
@@ -0,0 +1,6 @@
+<template lwc:render-mode="light">
+    <x-slot>
+        <h1 slot="top">top content</h1>
+        <h1 slot="bottom">bottom content</h1>
+    </x-slot>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/light/modules/x/container/container.js b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/light/modules/x/container/container.js
new file mode 100644
index 0000000000..0679d2bc10
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/light/modules/x/container/container.js
@@ -0,0 +1,5 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {
+    static renderMode = 'light';
+}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/light/modules/x/leaf/leaf.html b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/light/modules/x/leaf/leaf.html
new file mode 100644
index 0000000000..6bb058d068
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/light/modules/x/leaf/leaf.html
@@ -0,0 +1,4 @@
+<template lwc:render-mode="light">
+    <slot name="top"></slot>
+    <slot name="bottom"></slot>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/light/modules/x/leaf/leaf.js b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/light/modules/x/leaf/leaf.js
new file mode 100644
index 0000000000..0679d2bc10
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/light/modules/x/leaf/leaf.js
@@ -0,0 +1,5 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {
+    static renderMode = 'light';
+}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/light/modules/x/slot/slot.html b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/light/modules/x/slot/slot.html
new file mode 100644
index 0000000000..e641874967
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/light/modules/x/slot/slot.html
@@ -0,0 +1,6 @@
+<template lwc:render-mode="light">
+    <x-leaf>
+        <slot name="top" slot="bottom"></slot>
+        <slot name="bottom" slot="top"></slot>
+    </x-leaf>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/light/modules/x/slot/slot.js b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/light/modules/x/slot/slot.js
new file mode 100644
index 0000000000..0679d2bc10
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/light/modules/x/slot/slot.js
@@ -0,0 +1,5 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {
+    static renderMode = 'light';
+}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/error.txt
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/expected.html
new file mode 100644
index 0000000000..860151bb76
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/expected.html
@@ -0,0 +1,44 @@
+<x-mixed-container>
+  <template shadowrootmode="open">
+    <x-light-parent>
+      <x-shadow-leaf>
+        <template shadowrootmode="open">
+          <slot name="top">
+          </slot>
+          <slot name="bottom">
+          </slot>
+        </template>
+        <!---->
+        <div>
+          top of light parent
+        </div>
+        <!---->
+        <!---->
+        <div>
+          bottom of light parent
+        </div>
+        <!---->
+      </x-shadow-leaf>
+    </x-light-parent>
+    <x-shadow-parent>
+      <template shadowrootmode="open">
+        <x-light-leaf>
+          <!---->
+          <slot name="bottom">
+          </slot>
+          <!---->
+          <!---->
+          <slot name="top">
+          </slot>
+          <!---->
+        </x-light-leaf>
+      </template>
+      <div slot="top">
+        top of shadow parent
+      </div>
+      <div slot="bottom">
+        bottom of shadow parent
+      </div>
+    </x-shadow-parent>
+  </template>
+</x-mixed-container>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/index.js b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/index.js
new file mode 100644
index 0000000000..278804639e
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/index.js
@@ -0,0 +1,4 @@
+export const tagName = 'x-mixed-container';
+export { default } from 'x/container';
+export * from 'x/container';
+export const features = [];
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/modules/x/container/container.html b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/modules/x/container/container.html
new file mode 100644
index 0000000000..553cc1064d
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/modules/x/container/container.html
@@ -0,0 +1,11 @@
+<template>
+    <x-light-parent>
+        <div slot="top">top of light parent</div>
+        <div slot="bottom">bottom of light parent</div>
+    </x-light-parent>
+
+    <x-shadow-parent>
+        <div slot="top">top of shadow parent</div>
+        <div slot="bottom">bottom of shadow parent</div>
+    </x-shadow-parent>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/modules/x/container/container.js b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/modules/x/container/container.js
new file mode 100644
index 0000000000..ca8dce94e0
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/modules/x/container/container.js
@@ -0,0 +1,3 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/modules/x/lightLeaf/lightLeaf.html b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/modules/x/lightLeaf/lightLeaf.html
new file mode 100644
index 0000000000..6bb058d068
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/modules/x/lightLeaf/lightLeaf.html
@@ -0,0 +1,4 @@
+<template lwc:render-mode="light">
+    <slot name="top"></slot>
+    <slot name="bottom"></slot>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/modules/x/lightLeaf/lightLeaf.js b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/modules/x/lightLeaf/lightLeaf.js
new file mode 100644
index 0000000000..0679d2bc10
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/modules/x/lightLeaf/lightLeaf.js
@@ -0,0 +1,5 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {
+    static renderMode = 'light';
+}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/modules/x/lightParent/lightParent.html b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/modules/x/lightParent/lightParent.html
new file mode 100644
index 0000000000..cd365ffd8b
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/modules/x/lightParent/lightParent.html
@@ -0,0 +1,6 @@
+<template lwc:render-mode="light">
+    <x-shadow-leaf>
+        <slot name="top" slot="bottom"></slot>
+        <slot name="bottom" slot="top"></slot>
+    </x-shadow-leaf>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/modules/x/lightParent/lightParent.js b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/modules/x/lightParent/lightParent.js
new file mode 100644
index 0000000000..0679d2bc10
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/modules/x/lightParent/lightParent.js
@@ -0,0 +1,5 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {
+    static renderMode = 'light';
+}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/modules/x/shadowLeaf/shadowLeaf.html b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/modules/x/shadowLeaf/shadowLeaf.html
new file mode 100644
index 0000000000..4bc6c14fb4
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/modules/x/shadowLeaf/shadowLeaf.html
@@ -0,0 +1,4 @@
+<template>
+    <slot name="top"></slot>
+    <slot name="bottom"></slot>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/modules/x/shadowLeaf/shadowLeaf.js b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/modules/x/shadowLeaf/shadowLeaf.js
new file mode 100644
index 0000000000..ca8dce94e0
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/modules/x/shadowLeaf/shadowLeaf.js
@@ -0,0 +1,3 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/modules/x/shadowParent/shadowParent.html b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/modules/x/shadowParent/shadowParent.html
new file mode 100644
index 0000000000..2e952f1af5
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/modules/x/shadowParent/shadowParent.html
@@ -0,0 +1,6 @@
+<template>
+    <x-light-leaf>
+        <slot name="top" slot="bottom"></slot>
+        <slot name="bottom" slot="top"></slot>
+    </x-light-leaf>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/modules/x/shadowParent/shadowParent.js b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/modules/x/shadowParent/shadowParent.js
new file mode 100644
index 0000000000..ca8dce94e0
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/mixed/modules/x/shadowParent/shadowParent.js
@@ -0,0 +1,3 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/shadow/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/shadow/error.txt
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/shadow/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/shadow/expected.html
new file mode 100644
index 0000000000..c1af072344
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/shadow/expected.html
@@ -0,0 +1,26 @@
+<x-shadow-container>
+  <template shadowrootmode="open">
+    <x-slot>
+      <template shadowrootmode="open">
+        <x-leaf>
+          <template shadowrootmode="open">
+            <slot name="top">
+            </slot>
+            <slot name="bottom">
+            </slot>
+          </template>
+          <slot name="top" slot="bottom">
+          </slot>
+          <slot name="bottom" slot="top">
+          </slot>
+        </x-leaf>
+      </template>
+      <h1 slot="top">
+        top content
+      </h1>
+      <h1 slot="bottom">
+        bottom content
+      </h1>
+    </x-slot>
+  </template>
+</x-shadow-container>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/shadow/index.js b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/shadow/index.js
new file mode 100644
index 0000000000..8c80133fc7
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/shadow/index.js
@@ -0,0 +1,4 @@
+export const tagName = 'x-shadow-container';
+export { default } from 'x/container';
+export * from 'x/container';
+export const features = [];
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/shadow/modules/x/container/container.html b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/shadow/modules/x/container/container.html
new file mode 100644
index 0000000000..85b37d746c
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/shadow/modules/x/container/container.html
@@ -0,0 +1,6 @@
+<template>
+    <x-slot>
+        <h1 slot="top">top content</h1>
+        <h1 slot="bottom">bottom content</h1>
+    </x-slot>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/shadow/modules/x/container/container.js b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/shadow/modules/x/container/container.js
new file mode 100644
index 0000000000..ca8dce94e0
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/shadow/modules/x/container/container.js
@@ -0,0 +1,3 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/shadow/modules/x/leaf/leaf.html b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/shadow/modules/x/leaf/leaf.html
new file mode 100644
index 0000000000..4bc6c14fb4
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/shadow/modules/x/leaf/leaf.html
@@ -0,0 +1,4 @@
+<template>
+    <slot name="top"></slot>
+    <slot name="bottom"></slot>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/shadow/modules/x/leaf/leaf.js b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/shadow/modules/x/leaf/leaf.js
new file mode 100644
index 0000000000..ca8dce94e0
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/shadow/modules/x/leaf/leaf.js
@@ -0,0 +1,3 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/shadow/modules/x/slot/slot.html b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/shadow/modules/x/slot/slot.html
new file mode 100644
index 0000000000..a5d740912d
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/shadow/modules/x/slot/slot.html
@@ -0,0 +1,6 @@
+<template>
+    <x-leaf>
+        <slot name="top" slot="bottom"></slot>
+        <slot name="bottom" slot="top"></slot>
+    </x-leaf>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/shadow/modules/x/slot/slot.js b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/shadow/modules/x/slot/slot.js
new file mode 100644
index 0000000000..ca8dce94e0
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-forwarding/slots/shadow/modules/x/slot/slot.js
@@ -0,0 +1,3 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-not-at-top-level/advanced/lwcIf/light/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-not-at-top-level/advanced/lwcIf/light/expected.html
index c7c802d0b0..6598af8b6d 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-not-at-top-level/advanced/lwcIf/light/expected.html
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-not-at-top-level/advanced/lwcIf/light/expected.html
@@ -2,7 +2,31 @@
   <x-inner>
     !
     <!---->
-    acegijmopqstu
+    acegi
+    <!---->
+    j
+    <!---->
+    <!---->
+    m
+    <!---->
+    o
+    <!---->
+    p
+    <!---->
+    <!---->
+    <!---->
+    q
+    <!---->
+    <!---->
+    <!---->
+    <!---->
+    s
+    <!---->
+    <!---->
+    <!---->
+    t
+    <!---->
+    u
     <x-another>
       %
       <!---->
@@ -13,10 +37,12 @@
       <div>
         w
       </div>
+      <!---->
       <div>
         x
       </div>
       <!---->
+      <!---->
       *
       <!---->
       fallback for bar
@@ -43,22 +69,34 @@
     <!---->
     @
     <!---->
+    <!---->
     <div>
       b
     </div>
+    <!---->
+    <!---->
     <div>
       f
     </div>
+    <!---->
+    <!---->
     <div>
       k
     </div>
+    <!---->
+    <!---->
     <div>
       n
     </div>
+    <!---->
+    <!---->
+    <!---->
     <div>
       r
     </div>
     <!---->
+    <!---->
+    <!---->
     #
     <!---->
     <div>
@@ -67,10 +105,12 @@
     <div>
       h
     </div>
+    <!---->
     <div>
       l
     </div>
     <!---->
+    <!---->
     $
   </x-inner>
 </x-outer>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-not-at-top-level/advanced/lwcIf/shadow/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-not-at-top-level/advanced/lwcIf/shadow/expected.html
index eeca2ac5ec..501d57debc 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-not-at-top-level/advanced/lwcIf/shadow/expected.html
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-not-at-top-level/advanced/lwcIf/shadow/expected.html
@@ -16,38 +16,15 @@
         </slot>
         $
       </template>
-      a
-      <div slot="foo">
-        b
-      </div>
-      c
+      ac
       <div slot="bar">
         d
       </div>
-      e
-      <div slot="foo">
-        f
-      </div>
-      g
+      eg
       <div slot="bar">
         h
       </div>
-      ij
-      <div slot="foo">
-        k
-      </div>
-      <div slot="bar">
-        l
-      </div>
-      m
-      <div slot="foo">
-        n
-      </div>
-      opq
-      <div slot="foo">
-        r
-      </div>
-      stu
+      iou
       <x-another>
         <template shadowrootmode="open">
           %
@@ -68,9 +45,6 @@
         <div slot="foo">
           w
         </div>
-        <div slot="foo">
-          x
-        </div>
         y
       </x-another>
       z
@@ -79,15 +53,7 @@
         <div slot="foo">
           2
         </div>
-        3
-        <!---->
-        4
-        <div slot="foo">
-          5
-        </div>
-        6
-        <!---->
-        7
+        37
       </external-another>
       8
     </x-inner>
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-not-at-top-level/lwcIf/light/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-not-at-top-level/lwcIf/light/expected.html
index 24d9d79a41..1dba2425f0 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-not-at-top-level/lwcIf/light/expected.html
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-not-at-top-level/lwcIf/light/expected.html
@@ -6,13 +6,17 @@
     <!---->
     b
     <!---->
+    <!---->
     <div>
       I am the foo slot
     </div>
+    <!---->
+    <!---->
     <div>
       I am also the foo slot
     </div>
     <!---->
+    <!---->
     c
   </x-inner>
 </x-outer>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-not-at-top-level/lwcIf/shadow/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-not-at-top-level/lwcIf/shadow/expected.html
index dda18b9423..c5d357b0fc 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/slot-not-at-top-level/lwcIf/shadow/expected.html
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/slot-not-at-top-level/lwcIf/shadow/expected.html
@@ -12,12 +12,16 @@
         </slot>
         c
       </template>
+      <!---->
       <div slot="foo">
         I am the foo slot
       </div>
+      <!---->
+      <!---->
       <div slot="foo">
         I am also the foo slot
       </div>
+      <!---->
     </x-inner>
   </template>
 </x-outer>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/superclass/render-in-superclass/no-template-in-subclass/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/superclass/render-in-superclass/no-template-in-subclass/expected.html
index c9d7568cf8..9f69c81745 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/superclass/render-in-superclass/no-template-in-subclass/expected.html
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/superclass/render-in-superclass/no-template-in-subclass/expected.html
@@ -1,7 +1,4 @@
 <x-component>
   <template shadowrootmode="open">
-    <div>
-      foobar
-    </div>
   </template>
 </x-component>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/superclass/render-in-superclass/unused-default-in-subclass/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/superclass/render-in-superclass/unused-default-in-subclass/expected.html
index 82f0e42608..26b9f47f48 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/superclass/render-in-superclass/unused-default-in-subclass/expected.html
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/superclass/render-in-superclass/unused-default-in-subclass/expected.html
@@ -1,7 +1,5 @@
 <x-component>
   <template shadowrootmode="open">
-    <div>
-      yolo
-    </div>
+    From subclass! yolo
   </template>
 </x-component>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/superclass/render-in-superclass/unused-default-in-superclass/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/superclass/render-in-superclass/unused-default-in-superclass/expected.html
index c9d7568cf8..9f69c81745 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/superclass/render-in-superclass/unused-default-in-superclass/expected.html
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/superclass/render-in-superclass/unused-default-in-superclass/expected.html
@@ -1,7 +1,4 @@
 <x-component>
   <template shadowrootmode="open">
-    <div>
-      foobar
-    </div>
   </template>
 </x-component>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/get-set/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/get-set/error.txt
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/get-set/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/get-set/expected.html
new file mode 100644
index 0000000000..430f214a18
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/get-set/expected.html
@@ -0,0 +1,7 @@
+<x-wire>
+  <template shadowrootmode="open">
+    <div>
+      Wired? set
+    </div>
+  </template>
+</x-wire>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/get-set/index.js b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/get-set/index.js
new file mode 100644
index 0000000000..fafb890973
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/get-set/index.js
@@ -0,0 +1,3 @@
+export const tagName = 'x-wire';
+export { default } from 'x/wire';
+export * from 'x/wire';
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/get-set/modules/x/adapter/adapter.js b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/get-set/modules/x/adapter/adapter.js
new file mode 100644
index 0000000000..796bad8624
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/get-set/modules/x/adapter/adapter.js
@@ -0,0 +1,13 @@
+export class Adapter {
+    constructor(dataCallback) {
+        this.callback = dataCallback;
+    }
+
+    connect() {}
+
+    update(cfg) {
+        this.callback(cfg.value);
+    }
+
+    disconnect() {}
+}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/get-set/modules/x/wire/wire.html b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/get-set/modules/x/wire/wire.html
new file mode 100644
index 0000000000..54ed2a3a60
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/get-set/modules/x/wire/wire.html
@@ -0,0 +1,3 @@
+<template>
+  <div>Wired? {wired}</div>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/get-set/modules/x/wire/wire.js b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/get-set/modules/x/wire/wire.js
new file mode 100644
index 0000000000..b390928c83
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/get-set/modules/x/wire/wire.js
@@ -0,0 +1,13 @@
+import { wire, LightningElement } from 'lwc';
+import { Adapter } from 'x/adapter';
+export default class Test extends LightningElement {
+    @wire(Adapter, { value: 'get' })
+    get wired() {
+        throw new Error('get wired!');
+    }
+
+    @wire(Adapter, { value: 'set' })
+    set wired(val) {
+        throw new Error('set wired!');
+    }
+}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/method-prop/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/method-prop/error.txt
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/method-prop/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/method-prop/expected.html
new file mode 100644
index 0000000000..ca77f1f1f5
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/method-prop/expected.html
@@ -0,0 +1,5 @@
+<x-wire>
+  <template shadowrootmode="open">
+    propAndMethod
+  </template>
+</x-wire>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/method-prop/index.js b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/method-prop/index.js
new file mode 100644
index 0000000000..fafb890973
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/method-prop/index.js
@@ -0,0 +1,3 @@
+export const tagName = 'x-wire';
+export { default } from 'x/wire';
+export * from 'x/wire';
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/method-prop/modules/x/wire/adapter.js b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/method-prop/modules/x/wire/adapter.js
new file mode 100644
index 0000000000..b212b22d3f
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/method-prop/modules/x/wire/adapter.js
@@ -0,0 +1,13 @@
+export class adapter {
+    constructor(dataCallback) {
+        this.dc = dataCallback;
+    }
+
+    connect() {}
+
+    update(config) {
+        this.dc(config.name);
+    }
+
+    disconnect() {}
+}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/method-prop/modules/x/wire/wire.html b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/method-prop/modules/x/wire/wire.html
new file mode 100644
index 0000000000..517a242640
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/method-prop/modules/x/wire/wire.html
@@ -0,0 +1,3 @@
+<template>
+    {propAndMethod}
+</template>
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/method-prop/modules/x/wire/wire.js b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/method-prop/modules/x/wire/wire.js
new file mode 100644
index 0000000000..cf88ee0998
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/method-prop/modules/x/wire/wire.js
@@ -0,0 +1,12 @@
+import { LightningElement, wire } from 'lwc';
+
+import { adapter } from './adapter';
+
+export default class Wire extends LightningElement {
+    propAndMethod() {
+        throw new Error('should not be called');
+    }
+
+    @wire(adapter, { name: 'propAndMethod' })
+    propAndMethod;
+}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/prop-method/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/prop-method/error.txt
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/prop-method/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/prop-method/expected.html
new file mode 100644
index 0000000000..ca77f1f1f5
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/prop-method/expected.html
@@ -0,0 +1,5 @@
+<x-wire>
+  <template shadowrootmode="open">
+    propAndMethod
+  </template>
+</x-wire>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/prop-method/index.js b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/prop-method/index.js
new file mode 100644
index 0000000000..fafb890973
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/prop-method/index.js
@@ -0,0 +1,3 @@
+export const tagName = 'x-wire';
+export { default } from 'x/wire';
+export * from 'x/wire';
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/prop-method/modules/x/wire/adapter.js b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/prop-method/modules/x/wire/adapter.js
new file mode 100644
index 0000000000..b212b22d3f
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/prop-method/modules/x/wire/adapter.js
@@ -0,0 +1,13 @@
+export class adapter {
+    constructor(dataCallback) {
+        this.dc = dataCallback;
+    }
+
+    connect() {}
+
+    update(config) {
+        this.dc(config.name);
+    }
+
+    disconnect() {}
+}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/prop-method/modules/x/wire/wire.html b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/prop-method/modules/x/wire/wire.html
new file mode 100644
index 0000000000..517a242640
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/prop-method/modules/x/wire/wire.html
@@ -0,0 +1,3 @@
+<template>
+    {propAndMethod}
+</template>
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/prop-method/modules/x/wire/wire.js b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/prop-method/modules/x/wire/wire.js
new file mode 100644
index 0000000000..1e06f98e48
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/collision/prop-method/modules/x/wire/wire.js
@@ -0,0 +1,12 @@
+import { LightningElement, wire } from 'lwc';
+
+import { adapter } from './adapter';
+
+export default class Wire extends LightningElement {
+    @wire(adapter, { name: 'propAndMethod' })
+    propAndMethod;
+
+    propAndMethod() {
+        throw new Error('should not be called');
+    }
+}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-on-computed-key/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-on-computed-key/error.txt
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-on-computed-key/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-on-computed-key/expected.html
new file mode 100644
index 0000000000..4c2d0fe846
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-on-computed-key/expected.html
@@ -0,0 +1,5 @@
+<x-wire>
+  <template shadowrootmode="open">
+    ‍
+  </template>
+</x-wire>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-on-computed-key/index.js b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-on-computed-key/index.js
new file mode 100644
index 0000000000..fafb890973
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-on-computed-key/index.js
@@ -0,0 +1,3 @@
+export const tagName = 'x-wire';
+export { default } from 'x/wire';
+export * from 'x/wire';
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-on-computed-key/modules/x/wire/adapter.js b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-on-computed-key/modules/x/wire/adapter.js
new file mode 100644
index 0000000000..b212b22d3f
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-on-computed-key/modules/x/wire/adapter.js
@@ -0,0 +1,13 @@
+export class adapter {
+    constructor(dataCallback) {
+        this.dc = dataCallback;
+    }
+
+    connect() {}
+
+    update(config) {
+        this.dc(config.name);
+    }
+
+    disconnect() {}
+}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-on-computed-key/modules/x/wire/wire.html b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-on-computed-key/modules/x/wire/wire.html
new file mode 100644
index 0000000000..3981f33b93
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-on-computed-key/modules/x/wire/wire.html
@@ -0,0 +1,3 @@
+<template>
+    {exposedSymbol}
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-on-computed-key/modules/x/wire/wire.js b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-on-computed-key/modules/x/wire/wire.js
new file mode 100644
index 0000000000..723fb3bb05
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-on-computed-key/modules/x/wire/wire.js
@@ -0,0 +1,19 @@
+import { LightningElement, wire } from 'lwc';
+import { adapter } from './adapter';
+const sym = Symbol('computed prop');
+
+export default class Wire extends LightningElement {
+    @wire(adapter, { name: 'symbol' })
+    get [sym]() {
+        throw new Error('getter should not be called');
+    }
+
+    @wire(adapter, { name: 'symbol' })
+    set [sym](v) {
+        throw new Error('setter should not be called');
+    }
+
+    get exposedSymbol() {
+        return this[sym];
+    }
+}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-colliding-prop-then-method/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-colliding-prop-then-method/error.txt
new file mode 100644
index 0000000000..5dd83e0913
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-colliding-prop-then-method/error.txt
@@ -0,0 +1 @@
+instance.wired is not a function
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-colliding-prop-then-method/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-colliding-prop-then-method/expected.html
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-colliding-prop-then-method/index.js b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-colliding-prop-then-method/index.js
new file mode 100644
index 0000000000..fafb890973
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-colliding-prop-then-method/index.js
@@ -0,0 +1,3 @@
+export const tagName = 'x-wire';
+export { default } from 'x/wire';
+export * from 'x/wire';
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-colliding-prop-then-method/modules/x/adapter/adapter.js b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-colliding-prop-then-method/modules/x/adapter/adapter.js
new file mode 100644
index 0000000000..2259041fc5
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-colliding-prop-then-method/modules/x/adapter/adapter.js
@@ -0,0 +1,13 @@
+export class Adapter {
+    constructor(dataCallback) {
+        this.callback = dataCallback;
+    }
+
+    connect() {}
+
+    update() {
+        this.callback(true);
+    }
+
+    disconnect() {}
+}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-colliding-prop-then-method/modules/x/wire/wire.html b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-colliding-prop-then-method/modules/x/wire/wire.html
new file mode 100644
index 0000000000..fc94c85c96
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-colliding-prop-then-method/modules/x/wire/wire.html
@@ -0,0 +1,4 @@
+<template>
+  <div>Wired? {wiredProp}</div>
+  <div>Using method? {methodUsed}</div>
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-colliding-prop-then-method/modules/x/wire/wire.js b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-colliding-prop-then-method/modules/x/wire/wire.js
new file mode 100644
index 0000000000..470b160776
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-colliding-prop-then-method/modules/x/wire/wire.js
@@ -0,0 +1,13 @@
+import { wire, LightningElement } from 'lwc';
+import { Adapter } from 'x/adapter';
+export default class Test extends LightningElement {
+    methodUsed = false;
+
+    @wire(Adapter, { key1: '$prop1', key2: ['fixed', 'array'] })
+    wired;
+
+    @wire(Adapter, { key1: '$prop1', key2: ['fixed', 'array'] })
+    wired(val) {
+        this.methodUsed = val;
+    }
+}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-computed-prop-is-expression/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-computed-prop-is-expression/error.txt
index 4049dc8557..23a2c9f973 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-computed-prop-is-expression/error.txt
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-computed-prop-is-expression/error.txt
@@ -1 +1 @@
-LWC1200: Computed property in @wire config must be a constant or primitive literal.
\ No newline at end of file
+todo - COMPUTED_PROPERTY_MUST_BE_CONSTANT_OR_LITERAL
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-computed-prop-is-let-variable/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-computed-prop-is-let-variable/error.txt
index 4049dc8557..23a2c9f973 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-computed-prop-is-let-variable/error.txt
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-computed-prop-is-let-variable/error.txt
@@ -1 +1 @@
-LWC1200: Computed property in @wire config must be a constant or primitive literal.
\ No newline at end of file
+todo - COMPUTED_PROPERTY_MUST_BE_CONSTANT_OR_LITERAL
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-computed-prop-is-regexp-literal/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-computed-prop-is-regexp-literal/error.txt
index 4049dc8557..23a2c9f973 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-computed-prop-is-regexp-literal/error.txt
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-computed-prop-is-regexp-literal/error.txt
@@ -1 +1 @@
-LWC1200: Computed property in @wire config must be a constant or primitive literal.
\ No newline at end of file
+todo - COMPUTED_PROPERTY_MUST_BE_CONSTANT_OR_LITERAL
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-computed-prop-is-template-literal/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-computed-prop-is-template-literal/error.txt
index f076c30833..23a2c9f973 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-computed-prop-is-template-literal/error.txt
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-computed-prop-is-template-literal/error.txt
@@ -1 +1 @@
-LWC1199: Cannot use a template literal as a computed property key. Instead, use a string or extract the value to a constant.
\ No newline at end of file
+todo - COMPUTED_PROPERTY_MUST_BE_CONSTANT_OR_LITERAL
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-using-2-wired-decorators/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-using-2-wired-decorators/error.txt
index e0baa9c2a3..0168d14e99 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-using-2-wired-decorators/error.txt
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-using-2-wired-decorators/error.txt
@@ -1 +1 @@
-LWC1105: Method or property can only have 1 @wire decorator
\ No newline at end of file
+todo - multiple decorators at once
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-wired-method-is-combined-with-@api/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-wired-method-is-combined-with-@api/error.txt
index 8290d1e6f5..e69de29bb2 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-wired-method-is-combined-with-@api/error.txt
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-wired-method-is-combined-with-@api/error.txt
@@ -1 +0,0 @@
-LWC1095: @wire method or property cannot be used with @api
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-wired-method-is-combined-with-@api/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-wired-method-is-combined-with-@api/expected.html
index e69de29bb2..518eaa89a2 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-wired-method-is-combined-with-@api/expected.html
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-wired-method-is-combined-with-@api/expected.html
@@ -0,0 +1,4 @@
+<x-wire>
+  <template shadowrootmode="open">
+  </template>
+</x-wire>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-wired-property-is-combined-with-@api/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-wired-property-is-combined-with-@api/error.txt
index 8290d1e6f5..e69de29bb2 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-wired-property-is-combined-with-@api/error.txt
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-wired-property-is-combined-with-@api/error.txt
@@ -1 +0,0 @@
-LWC1095: @wire method or property cannot be used with @api
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-wired-property-is-combined-with-@api/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-wired-property-is-combined-with-@api/expected.html
index e69de29bb2..518eaa89a2 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-wired-property-is-combined-with-@api/expected.html
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-wired-property-is-combined-with-@api/expected.html
@@ -0,0 +1,4 @@
+<x-wire>
+  <template shadowrootmode="open">
+  </template>
+</x-wire>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-wired-property-is-combined-with-@track/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-wired-property-is-combined-with-@track/error.txt
index 0f710380bf..e69de29bb2 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-wired-property-is-combined-with-@track/error.txt
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-wired-property-is-combined-with-@track/error.txt
@@ -1 +0,0 @@
-LWC1095: @wire method or property cannot be used with @track
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-wired-property-is-combined-with-@track/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-wired-property-is-combined-with-@track/expected.html
index e69de29bb2..518eaa89a2 100644
--- a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-wired-property-is-combined-with-@track/expected.html
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/errors/throws-when-wired-property-is-combined-with-@track/expected.html
@@ -0,0 +1,4 @@
+<x-wire>
+  <template shadowrootmode="open">
+  </template>
+</x-wire>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/get-set/error.txt b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/get-set/error.txt
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/get-set/expected.html b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/get-set/expected.html
new file mode 100644
index 0000000000..ed0cb1dd75
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/get-set/expected.html
@@ -0,0 +1,5 @@
+<x-wire>
+  <template shadowrootmode="open">
+    getterOnly setterOnly getterWithSetter setterWithGetter bothDecorated
+  </template>
+</x-wire>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/get-set/index.js b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/get-set/index.js
new file mode 100644
index 0000000000..fafb890973
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/get-set/index.js
@@ -0,0 +1,3 @@
+export const tagName = 'x-wire';
+export { default } from 'x/wire';
+export * from 'x/wire';
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/get-set/modules/x/wire/adapter.js b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/get-set/modules/x/wire/adapter.js
new file mode 100644
index 0000000000..b212b22d3f
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/get-set/modules/x/wire/adapter.js
@@ -0,0 +1,13 @@
+export class adapter {
+    constructor(dataCallback) {
+        this.dc = dataCallback;
+    }
+
+    connect() {}
+
+    update(config) {
+        this.dc(config.name);
+    }
+
+    disconnect() {}
+}
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/get-set/modules/x/wire/wire.html b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/get-set/modules/x/wire/wire.html
new file mode 100644
index 0000000000..4eb032a5af
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/get-set/modules/x/wire/wire.html
@@ -0,0 +1,3 @@
+<template>
+    {getterOnly} {setterOnly} {getterWithSetter} {setterWithGetter} {bothDecorated}
+</template>
\ No newline at end of file
diff --git a/packages/@lwc/engine-server/src/__tests__/fixtures/wire/get-set/modules/x/wire/wire.js b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/get-set/modules/x/wire/wire.js
new file mode 100644
index 0000000000..8dca98f127
--- /dev/null
+++ b/packages/@lwc/engine-server/src/__tests__/fixtures/wire/get-set/modules/x/wire/wire.js
@@ -0,0 +1,41 @@
+import { LightningElement, wire } from 'lwc';
+
+import { adapter } from './adapter';
+
+export default class Wire extends LightningElement {
+    @wire(adapter, { name: 'getterOnly' })
+    get getterOnly() {
+        throw new Error('get getterOnly should not be called');
+    }
+
+    @wire(adapter, { name: 'setterOnly' })
+    set setterOnly(v) {
+        throw new Error('set setterOnly should not be called');
+    }
+
+    @wire(adapter, { name: 'getterWithSetter' })
+    get getterWithSetter() {
+        throw new Error('get getterWithSetter should not be called');
+    }
+    set getterWithSetter(v) {
+        throw new Error('set getterWithSetter should not be called');
+    }
+
+    @wire(adapter, { name: 'setterWithGetter' })
+    get setterWithGetter() {
+        throw new Error('get setterWithGetter should not be called');
+    }
+    set setterWithGetter(v) {
+        throw new Error('set setterWithGetter should not be called');
+    }
+
+    @wire(adapter, { name: 'bothDecorated' })
+    get bothDecorated() {
+        throw new Error('get bothDecorated should not be called');
+    }
+
+    @wire(adapter, { name: 'bothDecorated' })
+    set bothDecorated(v) {
+        throw new Error('set bothDecorated should not be called');
+    }
+}
diff --git a/packages/@lwc/ssr-compiler/src/__tests__/utils/expected-failures.ts b/packages/@lwc/ssr-compiler/src/__tests__/utils/expected-failures.ts
index d5c9a9f161..ac9356a663 100644
--- a/packages/@lwc/ssr-compiler/src/__tests__/utils/expected-failures.ts
+++ b/packages/@lwc/ssr-compiler/src/__tests__/utils/expected-failures.ts
@@ -8,35 +8,36 @@
 // We should slowly drive down these test failures or at least document where we expect the failures
 // TODO [#4815]: enable all SSR v2 tests
 export const expectedFailures = new Set([
-    'adjacent-text-nodes/preserve-comments-off/deep-for-each-with-rendered-item/index.js',
     'attribute-aria/dynamic/index.js',
     'attribute-class/with-scoped-styles-only-in-child/dynamic/index.js',
     'attribute-class/with-scoped-styles/dynamic/index.js',
     'attribute-component-global-html/index.js',
     'attribute-global-html/as-component-prop/undeclared/index.js',
     'attribute-global-html/as-component-prop/without-@api/index.js',
+    'attribute-namespace/index.js',
     'attribute-style/basic/index.js',
     'attribute-style/dynamic/index.js',
-    'dynamic-slots/index.js',
     'exports/component-as-default/index.js',
-    'if-conditional-slot-content/index.js',
     'known-boolean-attributes/default-def-html-attributes/static-on-component/index.js',
     'render-dynamic-value/index.js',
     'scoped-slots/advanced/index.js',
     'scoped-slots/expression/index.js',
-    'scoped-slots/for-each/index.js',
     'scoped-slots/mixed-with-light-dom-slots-inside/index.js',
     'scoped-slots/mixed-with-light-dom-slots-outside/index.js',
     'slot-forwarding/scoped-slots/index.js',
-    'slot-not-at-top-level/advanced/ifTrue/shadow/index.js',
+    'slot-forwarding/slots/mixed/index.js',
+    'slot-forwarding/slots/dangling/index.js',
+    'slot-forwarding/slots/light/index.js',
     'slot-not-at-top-level/advanced/lwcIf/light/index.js',
     'slot-not-at-top-level/advanced/lwcIf/shadow/index.js',
-    'slot-not-at-top-level/ifTrue/shadow/index.js',
     'slot-not-at-top-level/lwcIf/light/index.js',
     'slot-not-at-top-level/lwcIf/shadow/index.js',
     'superclass/render-in-superclass/no-template-in-subclass/index.js',
     'superclass/render-in-superclass/unused-default-in-subclass/index.js',
     'superclass/render-in-superclass/unused-default-in-superclass/index.js',
+    'svgs/index.js',
+    'wire/errors/throws-on-computed-key/index.js',
+    'wire/errors/throws-when-colliding-prop-then-method/index.js',
     'wire/errors/throws-when-computed-prop-is-expression/index.js',
     'wire/errors/throws-when-computed-prop-is-let-variable/index.js',
     'wire/errors/throws-when-computed-prop-is-regexp-literal/index.js',
diff --git a/packages/@lwc/ssr-compiler/src/compile-js/generate-markup.ts b/packages/@lwc/ssr-compiler/src/compile-js/generate-markup.ts
index c2e64bb0c3..2591b1d328 100644
--- a/packages/@lwc/ssr-compiler/src/compile-js/generate-markup.ts
+++ b/packages/@lwc/ssr-compiler/src/compile-js/generate-markup.ts
@@ -37,7 +37,8 @@ const bGenerateMarkup = esTemplate`
             shadowSlottedContent,
             lightSlottedContent, 
             parent, 
-            scopeToken
+            scopeToken,
+            contextfulParent
     ) {
         tagName = tagName ?? ${/*component tag name*/ is.literal};
         attrs = attrs ?? Object.create(null);
@@ -51,7 +52,7 @@ const bGenerateMarkup = esTemplate`
             tagName: tagName.toUpperCase(),
         });
 
-        __establishContextfulRelationship(parent, instance);
+        __establishContextfulRelationship(contextfulParent, instance);
         ${/*connect wire*/ is.statement}
 
         instance[__SYMBOL__SET_INTERNALS](props, attrs);
diff --git a/packages/@lwc/ssr-compiler/src/compile-js/index.ts b/packages/@lwc/ssr-compiler/src/compile-js/index.ts
index 6cf09a27cc..a48b2246e0 100644
--- a/packages/@lwc/ssr-compiler/src/compile-js/index.ts
+++ b/packages/@lwc/ssr-compiler/src/compile-js/index.ts
@@ -17,13 +17,9 @@ import { addGenerateMarkupFunction } from './generate-markup';
 import { catalogWireAdapters } from './wire';
 
 import { removeDecoratorImport } from './remove-decorator-import';
-import type { Identifier as EsIdentifier, Program as EsProgram, Expression } from 'estree';
+import type { Identifier as EsIdentifier, Program as EsProgram } from 'estree';
 import type { Visitors, ComponentMetaState } from './types';
 import type { CompilationMode } from '@lwc/shared';
-import type {
-    PropertyDefinition as DecoratatedPropertyDefinition,
-    MethodDefinition as DecoratatedMethodDefinition,
-} from 'meriyah/dist/src/estree';
 
 const visitors: Visitors = {
     $: { scope: true },
@@ -72,8 +68,8 @@ const visitors: Visitors = {
             return;
         }
 
-        const decorators = (node as DecoratatedPropertyDefinition).decorators;
-        const decoratedExpression = decorators?.[0]?.expression as Expression;
+        const { decorators } = node;
+        const decoratedExpression = decorators?.[0]?.expression;
         if (is.identifier(decoratedExpression) && decoratedExpression.name === 'api') {
             state.publicFields.push(node.key.name);
         } else if (
@@ -111,14 +107,32 @@ const visitors: Visitors = {
             return;
         }
 
-        const decorators = (node as DecoratatedMethodDefinition).decorators;
-        const decoratedExpression = decorators?.[0]?.expression as Expression;
+        const { decorators } = node;
+        // The real type is a subset of `Expression`, which doesn't work with the `is` validators
+        const decoratedExpression = decorators?.[0]?.expression;
         if (
             is.callExpression(decoratedExpression) &&
             is.identifier(decoratedExpression.callee) &&
             decoratedExpression.callee.name === 'wire'
         ) {
-            catalogWireAdapters(path, state);
+            // Getters and setters are methods in the AST, but treated as properties by @wire
+            // Note that this means that their implementations are ignored!
+            if (node.kind === 'get' || node.kind === 'set') {
+                const methodAsProp = b.propertyDefinition(
+                    structuredClone(node.key),
+                    null,
+                    node.computed,
+                    node.static
+                );
+                methodAsProp.decorators = structuredClone(decorators);
+                path.replaceWith(methodAsProp);
+                // We do not need to call `catalogWireAdapters()` because, by replacing the current
+                // node, `traverse()` will visit it again automatically, so we will just call
+                // `catalogWireAdapters()` later anyway.
+                return;
+            } else {
+                catalogWireAdapters(path, state);
+            }
         }
 
         switch (node.key.name) {
diff --git a/packages/@lwc/ssr-compiler/src/compile-template/index.ts b/packages/@lwc/ssr-compiler/src/compile-template/index.ts
index 2af47535ac..c5480b73eb 100644
--- a/packages/@lwc/ssr-compiler/src/compile-template/index.ts
+++ b/packages/@lwc/ssr-compiler/src/compile-template/index.ts
@@ -33,6 +33,10 @@ const bExportTemplate = esTemplate`
         let textContentBuffer = '';
         let didBufferTextContent = false;
 
+        // Establishes a contextual relationship between two components for ContextProviders.
+        // This variable will typically get overridden (shadowed) within slotted content.
+        const contextfulParent = instance;
+
         const isLightDom = Cmp.renderMode === 'light';
         if (!isLightDom) {
             yield \`<template shadowrootmode="open"\${Cmp.delegatesFocus ? ' shadowrootdelegatesfocus' : ''}>\`
@@ -57,7 +61,7 @@ const bExportTemplate = esTemplate`
             if (shadowSlottedContent) {
                 // instance must be passed in; this is used to establish the contextful relationship
                 // between context provider (aka parent component) and context consumer (aka slotted content)
-                yield* shadowSlottedContent(instance);
+                yield* shadowSlottedContent(contextfulParent);
             }
         }
     }
@@ -107,8 +111,12 @@ export default function compileTemplate(
     const preserveComments = !!root.directives.find(
         (directive) => directive.name === 'PreserveComments'
     )?.value?.value;
+    const experimentalComplexExpressions = Boolean(options.experimentalComplexExpressions);
 
-    const { addImport, getImports, statements } = templateIrToEsTree(root!, { preserveComments });
+    const { addImport, getImports, statements } = templateIrToEsTree(root!, {
+        preserveComments,
+        experimentalComplexExpressions,
+    });
     addImport(['renderStylesheets', 'hasScopedStaticStylesheets']);
     for (const [imports, source] of getStylesheetImports(filename)) {
         addImport(imports, source);
diff --git a/packages/@lwc/ssr-compiler/src/compile-template/shared.ts b/packages/@lwc/ssr-compiler/src/compile-template/shared.ts
index ed21898c47..37569670a6 100644
--- a/packages/@lwc/ssr-compiler/src/compile-template/shared.ts
+++ b/packages/@lwc/ssr-compiler/src/compile-template/shared.ts
@@ -7,7 +7,6 @@
 
 import { builders as b, is } from 'estree-toolkit';
 import { normalizeStyleAttributeValue, StringReplace, StringTrim } from '@lwc/shared';
-
 import { isValidES3Identifier } from '@babel/types';
 import { expressionIrToEs } from './expression';
 import type { TransformerContext } from './types';
@@ -74,9 +73,20 @@ function getRootMemberExpression(node: EsMemberExpression): EsMemberExpression {
     return node.object.type === 'MemberExpression' ? getRootMemberExpression(node.object) : node;
 }
 
-function getRootIdentifier(node: EsMemberExpression): EsIdentifier | null {
+function getRootIdentifier(node: EsMemberExpression, cxt: TransformerContext): EsIdentifier | null {
     const rootMemberExpression = getRootMemberExpression(node);
-    return is.identifier(rootMemberExpression?.object) ? rootMemberExpression.object : null;
+    if (is.identifier(rootMemberExpression.object)) {
+        return rootMemberExpression.object;
+    }
+    if (cxt.templateOptions.experimentalComplexExpressions) {
+        // TODO [#3370]: Implement complex template expressions
+        return null;
+    }
+    // Should be impossible to hit, at least until we implement complex template expressions
+    /* v8 ignore next */
+    throw new Error(
+        `Invalid expression, must be an Identifier, found type="${rootMemberExpression.type}": \`${JSON.stringify(rootMemberExpression)}\``
+    );
 }
 
 /**
@@ -85,12 +95,29 @@ function getRootIdentifier(node: EsMemberExpression): EsIdentifier | null {
  * inside a `for:each` block then the `foo` variable may refer to the scoped `foo`,
  * e.g. `<template for:each={foos} for:item="foo">`
  * @param expression
+ * @param cxt
  */
 export function getScopedExpression(expression: EsExpression, cxt: TransformerContext) {
-    const scopeReferencedId = is.memberExpression(expression)
-        ? getRootIdentifier(expression)
-        : null;
-    return cxt.isLocalVar(scopeReferencedId?.name)
+    let scopeReferencedId: EsExpression | null = null;
+    if (is.memberExpression(expression)) {
+        // e.g. `foo.bar` -> scopeReferencedId is `foo`
+        scopeReferencedId = getRootIdentifier(expression, cxt);
+    } else if (is.identifier(expression)) {
+        // e.g. `foo` -> scopeReferencedId is `foo`
+        scopeReferencedId = expression;
+    }
+    if (scopeReferencedId === null) {
+        if (cxt.templateOptions.experimentalComplexExpressions) {
+            // TODO [#3370]: Implement complex template expressions
+            return expression;
+        }
+        // Should be impossible to hit, at least until we implement complex template expressions
+        /* v8 ignore next */
+        throw new Error(
+            `Invalid expression, must be a MemberExpression or Identifier, found type="${expression.type}": \`${JSON.stringify(expression)}\``
+        );
+    }
+    return cxt.isLocalVar(scopeReferencedId.name)
         ? expression
         : b.memberExpression(b.identifier('instance'), expression);
 }
diff --git a/packages/@lwc/ssr-compiler/src/compile-template/transformers/component/component.ts b/packages/@lwc/ssr-compiler/src/compile-template/transformers/component/component.ts
index e0ed7e380a..c0d367fba3 100644
--- a/packages/@lwc/ssr-compiler/src/compile-template/transformers/component/component.ts
+++ b/packages/@lwc/ssr-compiler/src/compile-template/transformers/component/component.ts
@@ -23,7 +23,7 @@ const bYieldFromChildGenerator = esTemplateWithYield`
             /*
                 Slotted content is inserted here.
                 Note that the slotted content will be stored in variables named 
-                `shadowSlottedContent`/`lightSlottedContent` which are used below 
+                `shadowSlottedContent`/`lightSlottedContentMap` which are used below 
                 when the child's generateMarkup function is invoked.
             */
             is.statement
@@ -37,9 +37,10 @@ const bYieldFromChildGenerator = esTemplateWithYield`
             childProps, 
             childAttrs, 
             shadowSlottedContent,
-            lightSlottedContent,
+            lightSlottedContentMap,
             instance,
             scopeToken,
+            contextfulParent
         );
     }
 `<EsBlockStatement>;
diff --git a/packages/@lwc/ssr-compiler/src/compile-template/transformers/component/lwc-component.ts b/packages/@lwc/ssr-compiler/src/compile-template/transformers/component/lwc-component.ts
index b1a5f8a5b6..a079c6521a 100644
--- a/packages/@lwc/ssr-compiler/src/compile-template/transformers/component/lwc-component.ts
+++ b/packages/@lwc/ssr-compiler/src/compile-template/transformers/component/lwc-component.ts
@@ -29,7 +29,7 @@ const bYieldFromDynamicComponentConstructorGenerator = esTemplateWithYield`
             /*
                 Slotted content is inserted here.
                 Note that the slotted content will be stored in variables named 
-                `shadowSlottedContent`/`lightSlottedContent` which are used below 
+                `shadowSlottedContent`/`lightSlottedContentMap` which are used below 
                 when the child's generateMarkup function is invoked.
             */
             is.statement
@@ -42,8 +42,10 @@ const bYieldFromDynamicComponentConstructorGenerator = esTemplateWithYield`
             childProps,
             childAttrs,
             shadowSlottedContent,
-            lightSlottedContent,
-            scopeToken
+            lightSlottedContentMap,
+            instance,
+            scopeToken,
+            contextfulParent
         );
     }
 `<EsStatement[]>;
diff --git a/packages/@lwc/ssr-compiler/src/compile-template/transformers/component/slotted-content.ts b/packages/@lwc/ssr-compiler/src/compile-template/transformers/component/slotted-content.ts
index 5e981b7029..43eb53061c 100644
--- a/packages/@lwc/ssr-compiler/src/compile-template/transformers/component/slotted-content.ts
+++ b/packages/@lwc/ssr-compiler/src/compile-template/transformers/component/slotted-content.ts
@@ -29,31 +29,33 @@ import type {
     LwcComponent as IrLwcComponent,
     ScopedSlotFragment as IrScopedSlotFragment,
     Text as IrText,
+    Slot as IrSlot,
 } from '@lwc/template-compiler';
 import type { TransformerContext } from '../../types';
 
 const bGenerateSlottedContent = esTemplateWithYield`
         const shadowSlottedContent = ${/* hasShadowSlottedContent */ is.literal}
-            ? async function* generateSlottedContent(instance) {
-                // The 'instance' variable is shadowed here so that a contextful relationship
+            ? async function* generateSlottedContent(contextfulParent) {
+                // The 'contextfulParent' variable is shadowed here so that a contextful relationship
                 // is established between components rendered in slotted content & the "parent"
                 // component that contains the <slot>.
+
                 ${/* shadow slot content */ is.statement}
             } 
             // Avoid creating the object unnecessarily
             : null;
 
-        const lightSlottedContent = ${/* hasLightSlottedContent */ is.literal} 
+        const lightSlottedContentMap = ${/* hasLightSlottedContent */ is.literal} 
             ? Object.create(null)
             // Avoid creating the object unnecessarily
             : null;
         
         function addLightContent(name, fn) {
-            let contentList = lightSlottedContent[name];
+            let contentList = lightSlottedContentMap[name];
             if (contentList) {
                 contentList.push(fn);
             } else {
-                lightSlottedContent[name] = [fn];
+                lightSlottedContentMap[name] = [fn];
             }
         }
 
@@ -65,7 +67,7 @@ const bGenerateSlottedContent = esTemplateWithYield`
 // it may be repeated multiple times in the same scope, because it's a function _expression_ rather
 // than a function _declaration_, so it isn't available to be referenced anywhere.
 const bAddLightContent = esTemplate`
-    addLightContent(${/* slot name */ is.expression} ?? "", async function* generateSlottedContent(${
+    addLightContent(${/* slot name */ is.expression} ?? "", async function* generateSlottedContent(contextfulParent, ${
         /* scoped slot data variable */ isNullableOf(is.identifier)
     }) {
         // FIXME: make validation work again  
@@ -100,7 +102,7 @@ const bAddLightContent = esTemplate`
 // relevant to slots (as mentioned above).
 function getLightSlottedContent(rootNodes: IrChildNode[], cxt: TransformerContext) {
     type SlottableAncestorIrType = IrIf | IrIfBlock | IrElseifBlock | IrElseBlock;
-    type SlottableLeafIrType = IrElement | IrText | IrComponent | IrExternalComponent;
+    type SlottableLeafIrType = IrElement | IrText | IrComponent | IrExternalComponent | IrSlot;
 
     const results: EsExpressionStatement[] = [];
 
@@ -143,6 +145,7 @@ function getLightSlottedContent(rootNodes: IrChildNode[], cxt: TransformerContex
                     break;
                 }
                 // SlottableLeafIrType
+                case 'Slot':
                 case 'Element':
                 case 'Text':
                 case 'Component':
diff --git a/packages/@lwc/ssr-compiler/src/compile-template/transformers/slot.ts b/packages/@lwc/ssr-compiler/src/compile-template/transformers/slot.ts
index 9e6d5ff3ac..9a70ce4aec 100644
--- a/packages/@lwc/ssr-compiler/src/compile-template/transformers/slot.ts
+++ b/packages/@lwc/ssr-compiler/src/compile-template/transformers/slot.ts
@@ -35,7 +35,7 @@ const bConditionalSlot = esTemplateWithYield`
         const generators = lightSlottedContent?.[${/* slotName */ is.expression} ?? ""];
         if (generators) {
             for (const generator of generators) {
-                yield* generator(${/* scoped slot data */ isNullableOf(is.expression)});
+                yield* generator(contextfulParent, ${/* scoped slot data */ isNullableOf(is.expression)});
             }
         } else {
             // If we're in this else block, then the generator _must_ have yielded
diff --git a/packages/@lwc/ssr-compiler/src/compile-template/transformers/text.ts b/packages/@lwc/ssr-compiler/src/compile-template/transformers/text.ts
index baa7a01afc..f55d9ed6e2 100644
--- a/packages/@lwc/ssr-compiler/src/compile-template/transformers/text.ts
+++ b/packages/@lwc/ssr-compiler/src/compile-template/transformers/text.ts
@@ -10,7 +10,10 @@ import { esTemplateWithYield } from '../../estemplate';
 import { expressionIrToEs } from '../expression';
 
 import { bYieldTextContent, isLastConcatenatedNode } from '../adjacent-text-nodes';
-import type { Statement as EsStatement } from 'estree';
+import type {
+    Statement as EsStatement,
+    ExpressionStatement as EsExpressionStatement,
+} from 'estree';
 import type {
     ComplexExpression as IrComplexExpression,
     Expression as IrExpression,
@@ -21,20 +24,15 @@ import type { Transformer } from '../types';
 
 const bBufferTextContent = esTemplateWithYield`
     didBufferTextContent = true;
-    {
-        const value = ${/* string value */ is.expression};
-        // Using non strict equality to align with original implementation (ex. undefined == null)
-        // See: https://github.com/salesforce/lwc/blob/348130f/packages/%40lwc/engine-core/src/framework/api.ts#L548
-        textContentBuffer += value == null ? '' : String(value);
-    }
-`<EsStatement[]>;
+    textContentBuffer += massageTextContent(${/* string value */ is.expression});
+`<EsExpressionStatement[]>;
 
 function isLiteral(node: IrLiteral | IrExpression | IrComplexExpression): node is IrLiteral {
     return node.type === 'Literal';
 }
 
 export const Text: Transformer<IrText> = function Text(node, cxt): EsStatement[] {
-    cxt.import('htmlEscape');
+    cxt.import(['htmlEscape', 'massageTextContent']);
 
     const isLastInSeries = isLastConcatenatedNode(cxt);
 
diff --git a/packages/@lwc/ssr-compiler/src/compile-template/types.ts b/packages/@lwc/ssr-compiler/src/compile-template/types.ts
index 4f344d58e0..de6629b221 100644
--- a/packages/@lwc/ssr-compiler/src/compile-template/types.ts
+++ b/packages/@lwc/ssr-compiler/src/compile-template/types.ts
@@ -28,4 +28,5 @@ export interface TransformerContext {
 
 export interface TemplateOpts {
     preserveComments: boolean;
+    experimentalComplexExpressions: boolean;
 }
diff --git a/packages/@lwc/ssr-compiler/src/transmogrify.ts b/packages/@lwc/ssr-compiler/src/transmogrify.ts
index 952095992c..6a3a89a579 100644
--- a/packages/@lwc/ssr-compiler/src/transmogrify.ts
+++ b/packages/@lwc/ssr-compiler/src/transmogrify.ts
@@ -42,32 +42,31 @@ const isWithinFn = (pattern: RegExp, nodePath: NodePath): boolean => {
     return false;
 };
 
-function transformFunction(
-    path: NodePath<FunctionDeclaration | FunctionExpression, EstreeToolkitNode>,
-    state: TransmogrificationState
-): undefined {
-    const { node } = path;
-    if (!node?.async || !node?.generator) {
-        return;
-    }
-
-    // Component authors might conceivably use async generator functions in their own code. Therefore,
-    // when traversing & transforming written+generated code, we need to disambiguate generated async
-    // generator functions from those that were written by the component author.
-    if (
-        !isWithinFn(GEN_MARKUP_OR_GEN_SLOTTED_CONTENT_PATTERN, path) &&
-        !isWithinFn(TMPL_FN_PATTERN, path)
+const visitors: Visitors = {
+    // @ts-expect-error types for `traverse` do not support sharing a visitor between node types:
+    // https://github.com/sarsamurmu/estree-toolkit/issues/20
+    'FunctionDeclaration|FunctionExpression'(
+        path: NodePath<FunctionDeclaration | FunctionExpression, EstreeToolkitNode>,
+        state: TransmogrificationState
     ) {
-        return;
-    }
-    node.generator = false;
-    node.async = state.mode === 'async';
-    node.params.unshift(EMIT_IDENT);
-}
+        const { node } = path;
+        if (!node?.async || !node?.generator) {
+            return;
+        }
 
-const visitors: Visitors = {
-    FunctionDeclaration: transformFunction,
-    FunctionExpression: transformFunction,
+        // Component authors might conceivably use async generator functions in their own code. Therefore,
+        // when traversing & transforming written+generated code, we need to disambiguate generated async
+        // generator functions from those that were written by the component author.
+        if (
+            !isWithinFn(GEN_MARKUP_OR_GEN_SLOTTED_CONTENT_PATTERN, path) &&
+            !isWithinFn(TMPL_FN_PATTERN, path)
+        ) {
+            return;
+        }
+        node.generator = false;
+        node.async = state.mode === 'async';
+        node.params.unshift(EMIT_IDENT);
+    },
     YieldExpression(path, state) {
         const { node } = path;
         if (!node) {
diff --git a/packages/@lwc/ssr-runtime/src/index.ts b/packages/@lwc/ssr-runtime/src/index.ts
index ef329a2097..6c9a734774 100644
--- a/packages/@lwc/ssr-runtime/src/index.ts
+++ b/packages/@lwc/ssr-runtime/src/index.ts
@@ -31,6 +31,7 @@ export {
     // renderComponent is an alias for serverSideRenderComponent
     serverSideRenderComponent as renderComponent,
 } from './render';
+export { massageTextContent } from './render-text-content';
 export { hasScopedStaticStylesheets, renderStylesheets } from './styles';
 export { toIteratorDirective } from './to-iterator-directive';
 export { validateStyleTextContents } from './validate-style-text-contents';
diff --git a/packages/@lwc/ssr-runtime/src/render-text-content.ts b/packages/@lwc/ssr-runtime/src/render-text-content.ts
new file mode 100644
index 0000000000..4151f18db5
--- /dev/null
+++ b/packages/@lwc/ssr-runtime/src/render-text-content.ts
@@ -0,0 +1,16 @@
+/*
+ * Copyright (c) 2024, Salesforce, Inc.
+ * All rights reserved.
+ * SPDX-License-Identifier: MIT
+ * For full license text, see the LICENSE file in the repo root or https://opensource.org/licenses/MIT
+ */
+
+/**
+ * Given an object, render it for use as a text content node.
+ * @param value
+ */
+export function massageTextContent(value: unknown): string {
+    // Using non strict equality to align with original implementation (ex. undefined == null)
+    // See: https://github.com/salesforce/lwc/blob/348130f/packages/%40lwc/engine-core/src/framework/api.ts#L548
+    return value == null ? '' : String(value);
+}
diff --git a/packages/@lwc/ssr-runtime/src/render.ts b/packages/@lwc/ssr-runtime/src/render.ts
index b4f1fc87a9..0ac5429cb2 100644
--- a/packages/@lwc/ssr-runtime/src/render.ts
+++ b/packages/@lwc/ssr-runtime/src/render.ts
@@ -119,25 +119,40 @@ export type GenerateMarkupFn = (
     props: Properties | null,
     attrs: Attributes | null,
     shadowSlottedContent: AsyncGenerator<string> | null,
-    lightSlottedContent: Record<number | string, AsyncGenerator<string>> | null
+    lightSlottedContent: Record<number | string, AsyncGenerator<string>> | null,
+    // Not always null when invoked internally, but should always be
+    // null when invoked by ssr-runtime
+    parent: LightningElement | null,
+    scopeToken: string | null,
+    contextfulParent: LightningElement | null
 ) => AsyncGenerator<string>;
 
 export type GenerateMarkupFnAsyncNoGen = (
     emit: (segment: string) => void,
     tagName: string,
-    props: Record<string, any> | null,
+    props: Properties | null,
     attrs: Attributes | null,
     shadowSlottedContent: AsyncGenerator<string> | null,
-    lightSlottedContent: Record<number | string, AsyncGenerator<string>> | null
+    lightSlottedContent: Record<number | string, AsyncGenerator<string>> | null,
+    // Not always null when invoked internally, but should always be
+    // null when invoked by ssr-runtime
+    parent: LightningElement | null,
+    scopeToken: string | null,
+    contextfulParent: LightningElement | null
 ) => Promise<void>;
 
 export type GenerateMarkupFnSyncNoGen = (
     emit: (segment: string) => void,
     tagName: string,
-    props: Record<string, any> | null,
+    props: Properties | null,
     attrs: Attributes | null,
     shadowSlottedContent: AsyncGenerator<string> | null,
-    lightSlottedContent: Record<number | string, AsyncGenerator<string>> | null
+    lightSlottedContent: Record<number | string, AsyncGenerator<string>> | null,
+    // Not always null when invoked internally, but should always be
+    // null when invoked by ssr-runtime
+    parent: LightningElement | null,
+    scopeToken: string | null,
+    contextfulParent: LightningElement | null
 ) => void;
 
 type GenerateMarkupFnVariants =
@@ -172,6 +187,9 @@ export async function serverSideRenderComponent(
             props,
             null,
             null,
+            null,
+            null,
+            null,
             null
         )) {
             markup += segment;
@@ -183,10 +201,23 @@ export async function serverSideRenderComponent(
             props,
             null,
             null,
+            null,
+            null,
+            null,
             null
         );
     } else if (mode === 'sync') {
-        (generateMarkup as GenerateMarkupFnSyncNoGen)(emit, tagName, props, null, null, null);
+        (generateMarkup as GenerateMarkupFnSyncNoGen)(
+            emit,
+            tagName,
+            props,
+            null,
+            null,
+            null,
+            null,
+            null,
+            null
+        );
     } else {
         throw new Error(`Invalid mode: ${mode}`);
     }
diff --git a/scripts/test-utils/test-fixture-dir.ts b/scripts/test-utils/test-fixture-dir.ts
index 7da24fd186..c362d73721 100644
--- a/scripts/test-utils/test-fixture-dir.ts
+++ b/scripts/test-utils/test-fixture-dir.ts
@@ -5,8 +5,9 @@
  * For full license text, see the LICENSE file in the repo root or https://opensource.org/licenses/MIT
  */
 
-import fs from 'node:fs';
+import fs, { readFileSync } from 'node:fs';
 import path from 'node:path';
+import { AssertionError } from 'node:assert';
 import { test } from 'vitest';
 import * as glob from 'glob';
 import type { Config as StyleCompilerConfig } from '@lwc/style-compiler';
@@ -145,7 +146,9 @@ export function testFixtureDir<T extends TestFixtureConfig>(
                 );
             }
 
-            for (const [outputName, content] of Object.entries(outputs)) {
+            const outputsList = Object.entries(outputs);
+
+            for (const [outputName, content] of outputsList) {
                 const outputPath = path.resolve(dirname, outputName);
                 try {
                     await expect(content ?? '').toMatchFileSnapshot(outputPath);
@@ -156,6 +159,53 @@ export function testFixtureDir<T extends TestFixtureConfig>(
                         Error.captureStackTrace(err, testFixtureDir);
                     }
 
+                    const isErrorSnapshot = outputName.startsWith('error');
+                    const isSuccessSnapshot = outputName.startsWith('expected');
+
+                    // If we change from a successful result to an error (or vice versa),
+                    // then either the snapshot or content for the failing file is empty,
+                    // and the diff printed in the error message isn't helpful. Here, we check for
+                    // that case, and then check if the other file has flipped the other way.
+                    // If it has, we throw a more helpful error message.
+                    if (isErrorSnapshot || isSuccessSnapshot) {
+                        const brokenResult = outputs[outputName];
+                        const brokenResultHasContent = Boolean(brokenResult);
+                        const brokenSnapshot = readFileSync(outputPath, 'utf8');
+                        const brokenSnapshotHasContent = Boolean(brokenSnapshot);
+                        if (brokenResultHasContent !== brokenSnapshotHasContent) {
+                            // This file flipped from content to empty, or vice versa
+                            const otherType = isErrorSnapshot ? 'expected' : 'error';
+                            const otherName = outputsList.find(([name]) =>
+                                name.startsWith(otherType)
+                            )![0];
+                            const otherResult = outputs[otherName];
+                            const otherResultHasContent = Boolean(otherResult);
+                            const otherSnapshot = readFileSync(
+                                path.resolve(dirname, otherName),
+                                'utf8'
+                            );
+                            const otherSnapshotHasContent = Boolean(otherSnapshot);
+                            if (otherResultHasContent !== otherSnapshotHasContent) {
+                                // The other file has flipped from content to empty, or vice versa
+                                const expectedContentName = brokenSnapshotHasContent
+                                    ? outputName
+                                    : otherName;
+                                const actualContentName = brokenResultHasContent
+                                    ? outputName
+                                    : otherName;
+                                const contentErr = new AssertionError({
+                                    message: `Expected content in ${expectedContentName}, but found content in ${actualContentName}.`,
+                                    expected: brokenSnapshotHasContent
+                                        ? brokenSnapshot
+                                        : otherSnapshot,
+                                    actual: brokenResultHasContent ? brokenResult : otherResult,
+                                });
+                                Error.captureStackTrace(contentErr, testFixtureDir);
+                                throw contentErr;
+                            }
+                        }
+                    }
+
                     throw err;
                 }
             }