diff --git a/package.json b/package.json
index 1e656b2..0e8d234 100644
--- a/package.json
+++ b/package.json
@@ -44,7 +44,7 @@
     "test": "vitest run"
   },
   "dependencies": {
-    "ember-estree": "^0.4.2"
+    "ember-estree": "^0.4.3"
   },
   "devDependencies": {
     "@types/node": "^25.5.0",
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 4e0b948..7c321ed 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -9,8 +9,8 @@ importers:
   .:
     dependencies:
       ember-estree:
-        specifier: ^0.4.2
-        version: 0.4.2
+        specifier: ^0.4.3
+        version: 0.4.3
     devDependencies:
       '@types/node':
         specifier: ^25.5.0
@@ -1196,8 +1196,8 @@ packages:
   eastasianwidth@0.2.0:
     resolution: {integrity: sha512-I88TYZWc9XiYHRQ4/3c5rjjfgkjhLyW2luGIheGERbNQ6OY7yTybanSpDXZa8y7VUP9YmDcYa+eyq4ca7iLqWA==}
 
-  ember-estree@0.4.2:
-    resolution: {integrity: sha512-Runf+IVY+hUhlk0QwwljhPYj0/kjza5CCRp/Hlfdk9MawKSxXQqR0WX4f2rChXAGbDIzK7JVopVaet5oIZr8tg==}
+  ember-estree@0.4.3:
+    resolution: {integrity: sha512-742Wp/Dx2g9IZFOd9+JaRTpyflptxhtdMaG7MA2nl8lZOM9zTzlD+FfT3Vx/o+CZX976ZGDBbKg/gr5WErfqxA==}
 
   emoji-regex@8.0.0:
     resolution: {integrity: sha512-MSjYzcWNOA0ewAHpz0MxpYFvwg6yjy1NG3xteoqz644VCo/RPgnr1/GGt+ic3iJTzQ8Eu3TdM14SawnVUmGE6A==}
@@ -2895,7 +2895,7 @@ snapshots:
 
   eastasianwidth@0.2.0: {}
 
-  ember-estree@0.4.2:
+  ember-estree@0.4.3:
     dependencies:
       '@glimmer/env': 0.1.7
       '@glimmer/syntax': 0.95.0
diff --git a/tests/glimmer-comments.test.ts b/tests/glimmer-comments.test.ts
new file mode 100644
index 0000000..d94b24e
--- /dev/null
+++ b/tests/glimmer-comments.test.ts
@@ -0,0 +1,369 @@
+import { describe, expect, it } from "vitest";
+import { z } from "zmod";
+import { emberParser } from "../src/index.ts";
+
+const j = z.withParser(emberParser);
+
+// ── HTML comments <!-- --> ─────────────────────────────────────────────
+
+describe("Glimmer — HTML comments (<!-- -->)", () => {
+  it("finds an HTML comment in a template", () => {
+    const source = `<template><!-- TODO: remove this --><div>content</div></template>`;
+    const root = j(source, { filePath: "test.gjs" });
+
+    const comments = root.find("GlimmerCommentStatement");
+    expect(comments.length).toBe(1);
+    expect(comments.get()?.node.value).toBe(" TODO: remove this ");
+  });
+
+  it("replaces the content of an HTML comment", () => {
+    const source = `<template><!-- old comment --></template>`;
+    const root = j(source, { filePath: "test.gjs" });
+
+    root.find("GlimmerCommentStatement").replaceWith("<!-- new comment -->");
+    const output = root.toSource();
+
+    expect(output).toContain("<!-- new comment -->");
+    expect(output).not.toContain("<!-- old comment -->");
+  });
+
+  it("replaces an HTML comment while preserving surrounding elements", () => {
+    const source = `<template>
+  <header>Header</header>
+  <!-- old section comment -->
+  <main>Content</main>
+</template>`;
+    const root = j(source, { filePath: "test.gjs" });
+
+    root.find("GlimmerCommentStatement").replaceWith("<!-- updated section comment -->");
+    const output = root.toSource();
+
+    expect(output).toContain("<!-- updated section comment -->");
+    expect(output).not.toContain("<!-- old section comment -->");
+    expect(output).toContain("<header>Header</header>");
+    expect(output).toContain("<main>Content</main>");
+  });
+
+  it("replaces one HTML comment among multiple", () => {
+    const source = `<template>
+  <!-- first comment -->
+  <div>content</div>
+  <!-- second comment -->
+</template>`;
+    const root = j(source, { filePath: "test.gjs" });
+
+    root
+      .find("GlimmerCommentStatement")
+      .filter((path) => path.node.value.includes("first"))
+      .replaceWith("<!-- replaced first comment -->");
+    const output = root.toSource();
+
+    expect(output).toContain("<!-- replaced first comment -->");
+    expect(output).toContain("<!-- second comment -->");
+    expect(output).not.toContain("<!-- first comment -->");
+  });
+
+  it("removes an HTML comment by replacing with empty string", () => {
+    const source = `<template><!-- temporary --><span>text</span></template>`;
+    const root = j(source, { filePath: "test.gjs" });
+
+    root.find("GlimmerCommentStatement").replaceWith("");
+    const output = root.toSource();
+
+    expect(output).not.toContain("<!--");
+    expect(output).toContain("<span>text</span>");
+  });
+
+  it("finds HTML comment value by matching on node properties", () => {
+    const source = `<template>
+  <!-- keep this -->
+  <!-- remove this -->
+  <div>content</div>
+</template>`;
+    const root = j(source, { filePath: "test.gjs" });
+
+    const found = root.find("GlimmerCommentStatement", { value: " remove this " });
+    expect(found.length).toBe(1);
+  });
+
+  it("does not find HTML comments when only mustache comments exist", () => {
+    const source = `<template>{{! a mustache comment }}<div>content</div></template>`;
+    const root = j(source, { filePath: "test.gjs" });
+
+    expect(root.find("GlimmerCommentStatement").length).toBe(0);
+  });
+});
+
+// ── Short mustache comments {{! }} ────────────────────────────────────
+
+describe("Glimmer — short mustache comments ({{! }})", () => {
+  it("finds a short mustache comment in a template", () => {
+    const source = `<template>{{! TODO: fix this }}<div>content</div></template>`;
+    const root = j(source, { filePath: "test.gjs" });
+
+    const comments = root.find("GlimmerMustacheCommentStatement");
+    expect(comments.length).toBe(1);
+    expect(comments.get()?.node.value).toBe(" TODO: fix this ");
+  });
+
+  it("replaces the content of a short mustache comment", () => {
+    const source = `<template>{{! old comment }}<div>content</div></template>`;
+    const root = j(source, { filePath: "test.gjs" });
+
+    root.find("GlimmerMustacheCommentStatement").replaceWith("{{! new comment }}");
+    const output = root.toSource();
+
+    expect(output).toContain("{{! new comment }}");
+    expect(output).not.toContain("{{! old comment }}");
+  });
+
+  it("replaces a short mustache comment while preserving surrounding elements", () => {
+    const source = `<template>
+  <header>Header</header>
+  {{! old section label }}
+  <main>Content</main>
+</template>`;
+    const root = j(source, { filePath: "test.gjs" });
+
+    root.find("GlimmerMustacheCommentStatement").replaceWith("{{! updated section label }}");
+    const output = root.toSource();
+
+    expect(output).toContain("{{! updated section label }}");
+    expect(output).not.toContain("{{! old section label }}");
+    expect(output).toContain("<header>Header</header>");
+    expect(output).toContain("<main>Content</main>");
+  });
+
+  it("replaces a short mustache comment with a long-form one", () => {
+    const source = `<template>{{! short form }}</template>`;
+    const root = j(source, { filePath: "test.gjs" });
+
+    root.find("GlimmerMustacheCommentStatement").replaceWith("{{!-- now long form --}}");
+    const output = root.toSource();
+
+    expect(output).toContain("{{!-- now long form --}}");
+    expect(output).not.toContain("{{! short form }}");
+  });
+
+  it("removes a short mustache comment by replacing with empty string", () => {
+    const source = `<template>{{! placeholder }}<span>text</span></template>`;
+    const root = j(source, { filePath: "test.gjs" });
+
+    root.find("GlimmerMustacheCommentStatement").replaceWith("");
+    const output = root.toSource();
+
+    expect(output).not.toContain("{{!");
+    expect(output).toContain("<span>text</span>");
+  });
+});
+
+// ── Long mustache comments {{!-- --}} ─────────────────────────────────
+
+describe("Glimmer — long mustache comments ({{!-- --}})", () => {
+  it("finds a long-form mustache comment in a template", () => {
+    const source = `<template>{{!-- multi-word comment --}}<div>content</div></template>`;
+    const root = j(source, { filePath: "test.gjs" });
+
+    const comments = root.find("GlimmerMustacheCommentStatement");
+    expect(comments.length).toBe(1);
+    expect(comments.get()?.node.value).toBe(" multi-word comment ");
+  });
+
+  it("replaces the content of a long-form mustache comment", () => {
+    const source = `<template>{{!-- old content --}}</template>`;
+    const root = j(source, { filePath: "test.gjs" });
+
+    root.find("GlimmerMustacheCommentStatement").replaceWith("{{!-- new content --}}");
+    const output = root.toSource();
+
+    expect(output).toContain("{{!-- new content --}}");
+    expect(output).not.toContain("{{!-- old content --}}");
+  });
+
+  it("replaces a long-form mustache comment while preserving surrounding elements", () => {
+    const source = `<template>
+  <header>Header</header>
+  {{!-- section: main content area --}}
+  <main>Content</main>
+</template>`;
+    const root = j(source, { filePath: "test.gjs" });
+
+    root
+      .find("GlimmerMustacheCommentStatement")
+      .replaceWith("{{!-- section: updated main content area --}}");
+    const output = root.toSource();
+
+    expect(output).toContain("{{!-- section: updated main content area --}}");
+    expect(output).not.toContain("{{!-- section: main content area --}}");
+    expect(output).toContain("<header>Header</header>");
+    expect(output).toContain("<main>Content</main>");
+  });
+
+  it("replaces a long-form comment with a short-form one", () => {
+    const source = `<template>{{!-- was long --}}</template>`;
+    const root = j(source, { filePath: "test.gjs" });
+
+    root.find("GlimmerMustacheCommentStatement").replaceWith("{{! now short }}");
+    const output = root.toSource();
+
+    expect(output).toContain("{{! now short }}");
+    expect(output).not.toContain("{{!-- was long --}}");
+  });
+
+  it("finds long-form comment by source slice when distinguishing from short form", () => {
+    const source = `<template>{{! short form }}{{!-- long form --}}</template>`;
+    const root = j(source, { filePath: "test.gjs" });
+
+    const longFormComments = root
+      .find("GlimmerMustacheCommentStatement")
+      .filter((path) => source.slice(path.node.start, path.node.end).startsWith("{{!--"));
+
+    expect(longFormComments.length).toBe(1);
+    expect(longFormComments.get()?.node.value).toBe(" long form ");
+
+    longFormComments.replaceWith("{{!-- updated long form --}}");
+    const output = root.toSource();
+
+    expect(output).toContain("{{! short form }}");
+    expect(output).toContain("{{!-- updated long form --}}");
+    expect(output).not.toContain("{{!-- long form --}}");
+  });
+});
+
+// ── Mixed comment types ────────────────────────────────────────────────
+
+describe("Glimmer — mixed comment types", () => {
+  it("finds HTML and mustache comments separately", () => {
+    const source = `<template>
+  <!-- html comment -->
+  {{! short mustache }}
+  {{!-- long mustache --}}
+  <div>content</div>
+</template>`;
+    const root = j(source, { filePath: "test.gjs" });
+
+    const htmlComments = root.find("GlimmerCommentStatement");
+    const mustacheComments = root.find("GlimmerMustacheCommentStatement");
+
+    expect(htmlComments.length).toBe(1);
+    expect(mustacheComments.length).toBe(2);
+  });
+
+  it("replaces only HTML comments leaving mustache comments intact", () => {
+    const source = `<template>
+  <!-- html comment -->
+  {{! mustache comment }}
+  <div>content</div>
+</template>`;
+    const root = j(source, { filePath: "test.gjs" });
+
+    root.find("GlimmerCommentStatement").replaceWith("<!-- updated html comment -->");
+    const output = root.toSource();
+
+    expect(output).toContain("<!-- updated html comment -->");
+    expect(output).toContain("{{! mustache comment }}");
+    expect(output).not.toContain("<!-- html comment -->");
+  });
+
+  it("replaces only mustache comments leaving HTML comments intact", () => {
+    const source = `<template>
+  <!-- html comment -->
+  {{! mustache comment }}
+  <div>content</div>
+</template>`;
+    const root = j(source, { filePath: "test.gjs" });
+
+    root.find("GlimmerMustacheCommentStatement").replaceWith("{{! updated mustache comment }}");
+    const output = root.toSource();
+
+    expect(output).toContain("{{! updated mustache comment }}");
+    expect(output).toContain("<!-- html comment -->");
+    expect(output).not.toContain("{{! mustache comment }}");
+  });
+
+  it("replaces all comment types in one pass", () => {
+    const source = `<template>
+  <!-- html comment -->
+  {{! short mustache }}
+  {{!-- long mustache --}}
+  <div>content</div>
+</template>`;
+    const root = j(source, { filePath: "test.gjs" });
+
+    root.find("GlimmerCommentStatement").replaceWith("<!-- updated html -->");
+    root.find("GlimmerMustacheCommentStatement").replaceWith("{{! updated mustache }}");
+    const output = root.toSource();
+
+    expect(output).toContain("<!-- updated html -->");
+    expect(output).not.toContain("<!-- html comment -->");
+    expect(output).not.toContain("{{! short mustache }}");
+    expect(output).not.toContain("{{!-- long mustache --}}");
+    expect(output).toContain("<div>content</div>");
+  });
+
+  it("targets short {{! }} and long {{!-- --}} mustache comments individually", () => {
+    const root = j(`<template>{{! short }}{{!-- long --}}</template>`, { filePath: "test.gjs" });
+
+    root
+      .find("GlimmerMustacheCommentStatement")
+      .filter((path) => !path.node.longForm)
+      .replaceWith("{{! updated short }}");
+
+    root
+      .find("GlimmerMustacheCommentStatement")
+      .filter((path) => path.node.longForm)
+      .replaceWith("{{!-- updated long --}}");
+
+    const output = root.toSource();
+    expect(output).toContain("{{! updated short }}");
+    expect(output).toContain("{{!-- updated long --}}");
+    expect(output).not.toContain("{{! short }}");
+    expect(output).not.toContain("{{!-- long --}}");
+  });
+
+  it("handles comments inside a class-based component in .gjs", () => {
+    const source = `import Component from '@glimmer/component';
+
+export default class MyPage extends Component {
+  <template>
+    <!-- page header -->
+    {{! page body }}
+    <main>Content</main>
+  </template>
+}
+`;
+    const root = j(source, { filePath: "page.gjs" });
+
+    root.find("GlimmerCommentStatement").replaceWith("<!-- updated page header -->");
+    root.find("GlimmerMustacheCommentStatement").replaceWith("{{! updated page body }}");
+    const output = root.toSource();
+
+    expect(output).toContain("<!-- updated page header -->");
+    expect(output).toContain("{{! updated page body }}");
+    expect(output).not.toContain("<!-- page header -->");
+    expect(output).not.toContain("{{! page body }}");
+    expect(output).toContain("import Component");
+    expect(output).toContain("export default class MyPage");
+    expect(output).toContain("<main>Content</main>");
+  });
+
+  it("handles comments nested inside a block expression", () => {
+    const source = `<template>
+  {{#if this.show}}
+    <!-- conditional html comment -->
+    {{! conditional mustache comment }}
+    <div>shown</div>
+  {{/if}}
+</template>`;
+    const root = j(source, { filePath: "test.gjs" });
+
+    root.find("GlimmerCommentStatement").replaceWith("<!-- updated html -->");
+    root.find("GlimmerMustacheCommentStatement").replaceWith("{{! updated mustache }}");
+    const output = root.toSource();
+
+    expect(output).toContain("<!-- updated html -->");
+    expect(output).toContain("{{! updated mustache }}");
+    expect(output).toContain("{{#if this.show}}");
+    expect(output).toContain("<div>shown</div>");
+  });
+});