diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 189d50b..d9883e1 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -19,7 +19,7 @@ jobs:
 
     steps:
       - uses: actions/checkout@v3
-      - uses: NullVoxPopuli/action-setup-pnpm@v2
+      - uses: wyvox/action-setup-pnpm@v2
         with:
           node-version: 16
       - name: Lint
@@ -34,10 +34,9 @@ jobs:
 
     steps:
       - uses: actions/checkout@v3
-      - uses: NullVoxPopuli/action-setup-pnpm@v2
+      - uses: wyvox/action-setup-pnpm@v2
         with:
           node-version: 16
-          no-lockfile: true
       - name: Run Tests
         run: pnpm test
 
@@ -61,7 +60,7 @@ jobs:
 
     steps:
       - uses: actions/checkout@v3
-      - uses: NullVoxPopuli/action-setup-pnpm@v2
+      - uses: wyvox/action-setup-pnpm@v2
         with:
           node-version: 16
       - name: Run Tests
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index f05cccc..83680b4 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -16,7 +16,7 @@ jobs:
         uses: actions/checkout@v3
 
       - name: Setup pnpm and Node.js 16
-        uses: NullVoxPopuli/action-setup-pnpm@v2
+        uses: wyvox/action-setup-pnpm@v2
         with:
           node-version: 16
 
diff --git a/docs-app/app/components/sidebar.gts b/docs-app/app/components/sidebar.gts
index 129d658..e82434e 100644
--- a/docs-app/app/components/sidebar.gts
+++ b/docs-app/app/components/sidebar.gts
@@ -52,6 +52,7 @@ const Sidebar: TOC<{}> = <template>
         <SidebarItem @text='Glint types' />
         <SidebarItem @text='Configure (optional)' />
         <Separator />
+
         <SidebarTitle @text='Options' />
         <SidebarItem @text='Language' />
         <SidebarItem @text='Theme' />
@@ -62,6 +63,12 @@ const Sidebar: TOC<{}> = <template>
         <SidebarItem @text='Line highlighting' />
         <SidebarItem @text='Loading state' />
         <SidebarItem @text='Custom fonts' />
+        <Separator />
+
+        <SidebarTitle @text='Advanced' />
+        <SidebarItem @text='Custom grammar' />
+        <SidebarItem @text='Custom theme' />
+        <SidebarItem @text='Fastboot' />
       </ul>
 
       <p class="text-xs text-gray-500 mt-4">Built by
diff --git a/docs-app/app/controllers/application.ts b/docs-app/app/controllers/application.ts
index a5bcb88..95b76b3 100644
--- a/docs-app/app/controllers/application.ts
+++ b/docs-app/app/controllers/application.ts
@@ -158,6 +158,85 @@ function foo(x, y) {
   </Tab>
 </CodeGroup>`;
 
+  loadCustomGrammar = `import Route from '@ember/routing/route';
+import { service } from '@ember/service';
+
+export default class ApplicationRoute extends Route {
+  @service shiki;
+
+  async beforeModel() {
+    await this.loadCustomGrammar();
+  }
+
+  async loadCustomGrammar() {
+    // Shiki has to be initialized before the highlighter is available
+    await this.shiki.initialize.perform();
+    // Get custom grammar
+    const grammarTextmateDefinition = 'https://raw.githubusercontent.com/IgnaceMaes/glimmer-textmate-grammar/main/handlebars.tmLanguage.json';
+    const glimmerHandlebarsGrammar = await fetch(grammarTextmateDefinition);
+    const glimmerHandlebars = {
+      id: 'handlebars',
+      path: '',
+      scopeName: 'text.html.handlebars',
+      grammar: await glimmerHandlebarsGrammar.json(),
+      aliases: ['hbs'],
+    };
+    // Load embedded languages first
+    await this.shiki.loadLanguageAndEmbedded('js');
+    await this.shiki.loadLanguageAndEmbedded('css');
+    // Finally, register the custom language to the Shiki highlighter
+    await this.shiki.highlighter?.loadLanguage(glimmerHandlebars);
+  }
+}`;
+
+  loadCustomTheme = `import Route from '@ember/routing/route';
+import { service } from '@ember/service';
+
+export default class ApplicationRoute extends Route {
+  @service shiki;
+
+  async beforeModel() {
+    await this.loadCustomTheme();
+  }
+
+  async loadCustomTheme() {
+    // Shiki has to be initialized before the highlighter is available
+    await this.shiki.initialize.perform();
+    // Fetch custom theme
+    const nightOwlTheme = await fetch(
+      'https://raw.githubusercontent.com/sdras/night-owl-vscode-theme/main/themes/Night%20Owl-color-theme.json',
+    );
+    const nightOwlThemeJson = await nightOwlTheme.json();
+    // Make sure the name is set, as this is the value to be passed to the CodeBlock theme argument
+    nightOwlThemeJson.name = 'Night Owl';
+    await this.shiki.highlighter?.loadTheme(nightOwlThemeJson);
+  }
+}`;
+
+  fastbootConfig = `module.exports = function () {
+  return {
+    buildSandboxGlobals(defaultGlobals) {
+      return Object.assign({}, defaultGlobals, {
+        fetch: fetch,
+        AbortController,
+        ReadableStream:
+          typeof ReadableStream !== 'undefined'
+            ? ReadableStream
+            : require('node:stream/web').ReadableStream,
+        WritableStream:
+          typeof WritableStream !== 'undefined'
+            ? WritableStream
+            : require('node:stream/web').WritableStream,
+        TransformStream:
+          typeof TransformStream !== 'undefined'
+            ? TransformStream
+            : require('node:stream/web').TransformStream,
+        Headers: typeof Headers !== 'undefined' ? Headers : undefined,
+      });
+    },
+  };
+};`;
+
   changeTheme = (event: Event) => {
     this.theme = (event.target as HTMLSelectElement).value;
   };
diff --git a/docs-app/app/routes/application.ts b/docs-app/app/routes/application.ts
index 5e78491..d7d8348 100644
--- a/docs-app/app/routes/application.ts
+++ b/docs-app/app/routes/application.ts
@@ -6,6 +6,37 @@ export default class ApplicationRoute extends Route {
   @service declare shiki: ShikiService;
 
   async beforeModel() {
+    await this.loadCustomTheme();
+  }
+
+  async loadCustomGrammar() {
+    // Shiki has to be initialized before the highlighter is available
+    await this.shiki.initialize.perform();
+    // Get custom grammar
+    const glimmerHandlebarsGrammar = await fetch(
+      'https://raw.githubusercontent.com/IgnaceMaes/glimmer-textmate-grammar/main/handlebars.tmLanguage.json',
+    );
+    const glimmerHandlebars = {
+      id: 'handlebars',
+      path: '',
+      scopeName: 'text.html.handlebars',
+      grammar: await glimmerHandlebarsGrammar.json(),
+      aliases: ['hbs'],
+    };
+    // Load embedded languages first
+    await this.shiki.loadLanguageAndEmbedded('js');
+    await this.shiki.loadLanguageAndEmbedded('css');
+    // Finally, register the custom language to the Shiki highlighter
+    await this.shiki.highlighter?.loadLanguage(glimmerHandlebars);
+  }
+
+  async loadCustomTheme() {
     await this.shiki.initialize.perform();
+    const nightOwlTheme = await fetch(
+      'https://raw.githubusercontent.com/sdras/night-owl-vscode-theme/main/themes/Night%20Owl-color-theme.json',
+    );
+    const nightOwlThemeJson = await nightOwlTheme.json();
+    nightOwlThemeJson.name = 'Night Owl';
+    await this.shiki.highlighter?.loadTheme(nightOwlThemeJson);
   }
 }
diff --git a/docs-app/app/templates/application.hbs b/docs-app/app/templates/application.hbs
index e19fd06..ac655ab 100644
--- a/docs-app/app/templates/application.hbs
+++ b/docs-app/app/templates/application.hbs
@@ -340,6 +340,76 @@ function foo(x, y) {
       </div>
       <CodeBlock @code={{this.fontComicSans}} @language="hbs" />
 
+      <hr class="my-16 h-px border-0 bg-gray-700" />
+
+      <SectionTitle @text="Advanced" />
+      <SectionSubtitle @text="Custom grammar" />
+
+      <p>Shiki supports loading custom language grammar definitions in the
+        TextMate format. This can be useful if a new language hasn't landed in
+        the base package yet, or if you want to use a custom definition for an
+        existing language.</p>
+
+      <p>A great use case for this is Ember's template syntax. Ember uses
+        Glimmer to render component with templates defined in a
+        <InlineCode>.hbs</InlineCode>
+        file. Glimmer grammar, however, is more extensive than handlebars. If
+        you want to opt into Glimmer syntax parsing, you can load custom Glimmer
+        grammar for the
+        <InlineCode>handlebars</InlineCode>
+        language definition. Here's an example of how you could do it:</p>
+
+      <CodeBlock
+        @name="app/routes/application.js"
+        @code={{this.loadCustomGrammar}}
+        @language="js"
+      />
+      <p>Note: this is just an example way of how it's made possible, but not the recommended approach per se. In the future a more ergonomic, officially recommended way might be added.</p>
+
+      <SectionSubtitle @text="Custom theme" />
+      <p>Shiki ships with 29 themes available by default, but any VS Code theme
+        can be loaded dynamically. Simply register the theme config JSON and
+        pass the theme name to the
+        <InlineCode>CodeBlock</InlineCode>
+        component.</p>
+
+      <p>The following example shows a custom theme <InlineCode>Night Owl</InlineCode>:</p>
+
+      <CodeBlock
+        @name="app/routes/application.js"
+        @code={{this.loadCustomTheme}}
+        @language="js"
+        @theme="Night Owl"
+        style="--ember-shiki-background-color: #011627"
+      />
+      <p>Note: this is just an example way of how it's made possible, but not the recommended approach per se. In the future a more ergonomic, officially recommended way might be added.</p>
+
+      <SectionSubtitle @text="Fastboot" />
+      <p>The
+        <InlineCode>CodeBlock</InlineCode>
+        component automatically detects Fastboot if it's used in the app and
+        makes sure the rendering awaits until the highlighting is completed.</p>
+
+      <p>Shiki makes use of
+        <InlineCode>fetch</InlineCode>
+        which is not available in the runtime environment of Fastboot by
+        default. To make it available, set the globals in your fastboot config.
+        Note that fetch is only built into Node.js starting from v18. If you
+        want to support older versions you can install and import
+        <InlineCode>node-fetch</InlineCode>.</p>
+
+      <CodeBlock
+        @name="config/fastboot.js"
+        @code={{this.fastbootConfig}}
+        @language="js"
+      />
+      <p>Prember for pre-rendering the app to static html is also supported.
+        Make sure to use at least version
+        <InlineCode>^2.0.0</InlineCode>
+        so the
+        <InlineCode>fastboot.js</InlineCode>
+        config is correctly applied.</p>
+
       {{outlet}}
     </div>
   </article>