diff --git a/app/assets/javascripts/discourse/app/lib/highlight-syntax.js b/app/assets/javascripts/discourse/app/lib/highlight-syntax.js
index 55300c540a0..e0941e80110 100644
--- a/app/assets/javascripts/discourse/app/lib/highlight-syntax.js
+++ b/app/assets/javascripts/discourse/app/lib/highlight-syntax.js
@@ -58,7 +58,7 @@ export default async function highlightSyntax(elem, siteSettings, session) {
   });
 }
 
-async function ensureHighlightJs(langFile) {
+export async function ensureHighlightJs(langFile) {
   try {
     if (!hljsLoadPromise) {
       hljsLoadPromise = loadHighlightJs(langFile);
diff --git a/app/assets/javascripts/discourse/app/static/prosemirror/components/prosemirror-editor.gjs b/app/assets/javascripts/discourse/app/static/prosemirror/components/prosemirror-editor.gjs
index 91b5578f340..d17e3ee739e 100644
--- a/app/assets/javascripts/discourse/app/static/prosemirror/components/prosemirror-editor.gjs
+++ b/app/assets/javascripts/discourse/app/static/prosemirror/components/prosemirror-editor.gjs
@@ -73,7 +73,7 @@ export default class ProsemirrorEditor extends Component {
 
   get pluginParams() {
     return {
-      utils,
+      utils: { ...utils, convertFromMarkdown: this.convertFromMarkdown },
       schema: this.schema,
       pmState: ProsemirrorState,
       pmModel: ProsemirrorModel,
diff --git a/app/assets/javascripts/discourse/app/static/prosemirror/extensions/code-block.js b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/code-block.js
new file mode 100644
index 00000000000..d120271d7a8
--- /dev/null
+++ b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/code-block.js
@@ -0,0 +1,137 @@
+import { highlightPlugin } from "prosemirror-highlightjs";
+import { ensureHighlightJs } from "discourse/lib/highlight-syntax";
+
+// cached hljs instance with custom plugins/languages
+let hljs;
+
+class CodeBlockWithLangSelectorNodeView {
+  #selectAdded = false;
+
+  constructor(node, view, getPos) {
+    this.node = node;
+    this.view = view;
+    this.getPos = getPos;
+
+    const code = document.createElement("code");
+    const pre = document.createElement("pre");
+    pre.appendChild(code);
+
+    this.dom = pre;
+    this.contentDOM = code;
+
+    this.appendSelect();
+  }
+
+  changeListener(e) {
+    this.view.dispatch(
+      this.view.state.tr.setNodeMarkup(this.getPos(), null, {
+        params: e.target.value,
+      })
+    );
+
+    if (e.target.firstChild.textContent) {
+      e.target.firstChild.textContent = "";
+    }
+  }
+
+  appendSelect() {
+    if (!hljs || this.#selectAdded) {
+      return;
+    }
+
+    this.#selectAdded = true;
+
+    const select = document.createElement("select");
+    select.contentEditable = false;
+    select.addEventListener("change", (e) => this.changeListener(e));
+    select.classList.add("code-language-select");
+
+    const languages = hljs.listLanguages();
+
+    const empty = document.createElement("option");
+    empty.textContent = languages.includes(this.node.attrs.params)
+      ? ""
+      : this.node.attrs.params;
+    select.appendChild(empty);
+
+    languages.forEach((lang) => {
+      const option = document.createElement("option");
+      option.textContent = lang;
+      option.selected = lang === this.node.attrs.params;
+      select.appendChild(option);
+    });
+
+    this.dom.appendChild(select);
+  }
+
+  update(node) {
+    this.appendSelect();
+
+    return node.type === this.node.type;
+  }
+
+  destroy() {
+    this.dom.removeEventListener("change", (e) => this.changeListener(e));
+  }
+}
+
+/** @type {RichEditorExtension} */
+const extension = {
+  nodeViews: { code_block: CodeBlockWithLangSelectorNodeView },
+  plugins({ pmState: { Plugin }, getContext }) {
+    return [
+      async () =>
+        highlightPlugin(
+          (hljs = await ensureHighlightJs(
+            getContext().session.highlightJsPath
+          )),
+          ["code_block", "html_block"],
+
+          // NOTE: If the language has not been set with the code block, we default to plain
+          // text rather than autodetecting. This is to work around an infinite loop issue
+          // in prosemirror-highlightjs when autodetecting which hangs the browser sometimes
+          // for > 10 seconds, for example:
+          //
+          // https://github.com/b-kelly/prosemirror-highlightjs/issues/21
+          //
+          // We can remove this if we find some other workaround.
+          (node) => node.attrs.params || "text"
+        ),
+      new Plugin({
+        props: {
+          // Handles removal of the code_block when it's at the start of the document
+          handleKeyDown(view, event) {
+            if (
+              event.key === "Backspace" &&
+              view.state.selection.$from.parent.type ===
+                view.state.schema.nodes.code_block &&
+              view.state.selection.$from.start() === 1 &&
+              view.state.selection.$from.parentOffset === 0
+            ) {
+              const { tr } = view.state;
+
+              const codeBlock = view.state.selection.$from.parent;
+              const paragraph = view.state.schema.nodes.paragraph.create(
+                null,
+                codeBlock.content
+              );
+              tr.replaceWith(
+                view.state.selection.$from.before(),
+                view.state.selection.$from.after(),
+                paragraph
+              );
+              tr.setSelection(
+                new view.state.selection.constructor(tr.doc.resolve(1))
+              );
+
+              view.dispatch(tr);
+              return true;
+            }
+          },
+        },
+      }),
+    ];
+  },
+};
+
+export default extension;
diff --git a/app/assets/javascripts/discourse/app/static/prosemirror/extensions/markdown-paste.js b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/markdown-paste.js
new file mode 100644
index 00000000000..9469ff58823
--- /dev/null
+++ b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/markdown-paste.js
@@ -0,0 +1,20 @@
+/** @type {RichEditorExtension} */
+const extension = {
+  plugins({
+    pmState: { Plugin },
+    pmModel: { Fragment, Slice },
+    utils: { convertFromMarkdown },
+  }) {
+    return new Plugin({
+      props: {
+        clipboardTextParser(text) {
+          const { content } = convertFromMarkdown(text);
+
+          return Slice.maxOpen(Fragment.from(content));
+        },
+      },
+    });
+  },
+};
+
+export default extension;
diff --git a/app/assets/javascripts/discourse/app/static/prosemirror/extensions/register-default.js b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/register-default.js
index a7d689b891d..2abd4a799df 100644
--- a/app/assets/javascripts/discourse/app/static/prosemirror/extensions/register-default.js
+++ b/app/assets/javascripts/discourse/app/static/prosemirror/extensions/register-default.js
@@ -1,9 +1,11 @@
 import { registerRichEditorExtension } from "discourse/lib/composer/rich-editor-extensions";
+import codeBlock from "./code-block";
 import emoji from "./emoji";
 import hashtag from "./hashtag";
 import heading from "./heading";
 import image from "./image";
 import link from "./link";
+import markdownPaste from "./markdown-paste";
 import mention from "./mention";
 import quote from "./quote";
 import strikethrough from "./strikethrough";
@@ -21,12 +23,14 @@ const defaultExtensions = [
   image,
   link,
   heading,
+  codeBlock,
   quote,
   hashtag,
   mention,
   strikethrough,
   underline,
   table,
+  markdownPaste,
 ];
 
 defaultExtensions.forEach(registerRichEditorExtension);
diff --git a/app/assets/javascripts/discourse/tests/helpers/rich-editor-helper.gjs b/app/assets/javascripts/discourse/tests/helpers/rich-editor-helper.gjs
index 05ee0f6360b..c378cfa1769 100644
--- a/app/assets/javascripts/discourse/tests/helpers/rich-editor-helper.gjs
+++ b/app/assets/javascripts/discourse/tests/helpers/rich-editor-helper.gjs
@@ -25,10 +25,15 @@ export async function testMarkdown(
       />
     </template>
   );
+
+  // ensure toggling to rich editor and back works
+  await click(".composer-toggle-switch");
+  await click(".composer-toggle-switch");
   await click(".composer-toggle-switch");
 
   await waitFor(".ProseMirror");
   await settled();
+
   const editor = document.querySelector(".ProseMirror");
 
   // typeIn for contentEditable isn't reliable, and is slower
diff --git a/app/assets/javascripts/discourse/tests/integration/components/prosemirror-editor/code-block-test.gjs b/app/assets/javascripts/discourse/tests/integration/components/prosemirror-editor/code-block-test.gjs
new file mode 100644
index 00000000000..11743fab9b7
--- /dev/null
+++ b/app/assets/javascripts/discourse/tests/integration/components/prosemirror-editor/code-block-test.gjs
@@ -0,0 +1,58 @@
+import { module, test } from "qunit";
+import { setupRenderingTest } from "discourse/tests/helpers/component-test";
+import { testMarkdown } from "discourse/tests/helpers/rich-editor-helper";
+
+module(
+  "Integration | Component | prosemirror-editor - code-block extension",
+  function (hooks) {
+    setupRenderingTest(hooks);
+
+    hooks.beforeEach(function () {
+      this.siteSettings.rich_editor = true;
+    });
+
+    const select = (lang = "") =>
+      `<select contenteditable="false" class="code-language-select"><option>${lang}</option><option>javascript</option><option>ruby</option><option>sql</option></select>`;
+
+    Object.entries({
+      "basic code block": [
+        "```plaintext\nconsole.log('Hello, world!');\n```",
+        `<pre><code>console.log('Hello, world!');</code>${select(
+          "plaintext"
+        )}</pre>`,
+        "```plaintext\nconsole.log('Hello, world!');\n```",
+      ],
+      "basic code block without a lanuage": [
+        "```\nconsole.log('Hello, world!');\n```",
+        `<pre><code>console.log('Hello, world!');</code>${select()}</pre>`,
+        "```\nconsole.log('Hello, world!');\n```",
+      ],
+      "code block within list item": [
+        "- ```plaintext\n  console.log('Hello, world!');\n  ```",
+        `<ul><li><pre><code>console.log('Hello, world!');</code>${select(
+          "plaintext"
+        )}</pre></li></ul>`,
+        "* ```plaintext\n  console.log('Hello, world!');\n  ```",
+      ],
+      "code block with language": [
+        '```javascript\nconsole.log("Hello, world!");\n```',
+        `<pre><code><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">"Hello, world!"</span>);</code>${select()}</pre>`,
+        '```javascript\nconsole.log("Hello, world!");\n```',
+      ],
+      "code block with 4 spaces": [
+        "    print('Hello, world!')",
+        `<pre><code>print('Hello, world!')</code>${select()}</pre>`,
+        "```\nprint('Hello, world!')\n```",
+      ],
+      "code block with 4 spaces within list item": [
+        "-     print('Hello, world!')",
+        `<ul><li><pre><code>print('Hello, world!')</code>${select()}</pre></li></ul>`,
+        "* ```\n  print('Hello, world!')\n  ```",
+      ],
+    }).forEach(([name, [markdown, html, expectedMarkdown]]) => {
+      test(name, async function (assert) {
+        await testMarkdown(assert, markdown, html, expectedMarkdown);
+      });
+    });
+  }
+);
diff --git a/app/assets/javascripts/discourse/tests/integration/components/prosemirror-editor/prosemirror-editor-test.gjs b/app/assets/javascripts/discourse/tests/integration/components/prosemirror-editor/prosemirror-editor-test.gjs
index 10f32e83f44..131aa850447 100644
--- a/app/assets/javascripts/discourse/tests/integration/components/prosemirror-editor/prosemirror-editor-test.gjs
+++ b/app/assets/javascripts/discourse/tests/integration/components/prosemirror-editor/prosemirror-editor-test.gjs
@@ -12,13 +12,8 @@ import { testMarkdown } from "discourse/tests/helpers/rich-editor-helper";
 module("Integration | Component | prosemirror-editor", function (hooks) {
   setupRenderingTest(hooks);
 
-  hooks.beforeEach(function () {
-    clearRichEditorExtensions();
-  });
-
-  hooks.afterEach(function () {
-    resetRichEditorExtensions();
-  });
+  hooks.beforeEach(() => clearRichEditorExtensions());
+  hooks.afterEach(() => resetRichEditorExtensions());
 
   test("renders the editor", async function (assert) {
     await render(<template><ProsemirrorEditor /></template>);
diff --git a/app/assets/javascripts/discourse/tests/integration/components/prosemirror-editor/prosemirror-markdown-test.gjs b/app/assets/javascripts/discourse/tests/integration/components/prosemirror-editor/prosemirror-markdown-test.gjs
index eeb54849e21..d828493e176 100644
--- a/app/assets/javascripts/discourse/tests/integration/components/prosemirror-editor/prosemirror-markdown-test.gjs
+++ b/app/assets/javascripts/discourse/tests/integration/components/prosemirror-editor/prosemirror-markdown-test.gjs
@@ -1,4 +1,8 @@
 import { module, test } from "qunit";
+import {
+  clearRichEditorExtensions,
+  resetRichEditorExtensions,
+} from "discourse/lib/composer/rich-editor-extensions";
 import { setupRenderingTest } from "discourse/tests/helpers/component-test";
 import { testMarkdown } from "discourse/tests/helpers/rich-editor-helper";
 
@@ -7,6 +11,9 @@ module(
   function (hooks) {
     setupRenderingTest(hooks);
 
+    hooks.beforeEach(() => clearRichEditorExtensions());
+    hooks.afterEach(() => resetRichEditorExtensions());
+
     const testCases = {
       "paragraphs and hard breaks": [
         ["Hello", "<p>Hello</p>", "Hello"],
diff --git a/app/assets/stylesheets/common/base/code_highlighting.scss b/app/assets/stylesheets/common/base/code_highlighting.scss
index 0b8e75f8ab5..bf1a6cbe8fe 100644
--- a/app/assets/stylesheets/common/base/code_highlighting.scss
+++ b/app/assets/stylesheets/common/base/code_highlighting.scss
@@ -61,6 +61,12 @@ h6 code {
   color: var(--hljs-number);
 }
 
+.hljs-tag,
+.hljs-tag .hljs-title {
+  color: var(--hljs-tag);
+  font-weight: normal;
+}
+
 .hljs-string,
 .hljs-tag .hljs-string,
 .hljs-template-tag,
@@ -73,10 +79,6 @@ h6 code {
   color: var(--hljs-title);
 }
 
-.hljs-name {
-  color: var(--hljs-name);
-}
-
 .hljs-quote,
 .hljs-operator,
 .hljs-selector-pseudo,
@@ -94,10 +96,8 @@ h6 code {
   color: var(--hljs-title);
 }
 
-.hljs-tag,
-.hljs-tag .hljs-title {
-  color: var(--hljs-tag);
-  font-weight: normal;
+.hljs-name {
+  color: var(--hljs-name);
 }
 
 .hljs-punctuation {
diff --git a/app/assets/stylesheets/common/rich-editor/rich-editor.scss b/app/assets/stylesheets/common/rich-editor/rich-editor.scss
index 37caeae953a..06d18aa9257 100644
--- a/app/assets/stylesheets/common/rich-editor/rich-editor.scss
+++ b/app/assets/stylesheets/common/rich-editor/rich-editor.scss
@@ -134,10 +134,6 @@
     white-space: normal;
   }
 
-  .code-block {
-    position: relative;
-  }
-
   .code-language-select {
     position: absolute;
     right: 0.25rem;
@@ -149,8 +145,11 @@
     font-size: var(--font-down-1-rem);
   }
 
-  .html-block {
+  pre {
     position: relative;
+  }
+
+  .html-block {
     border: 1px dashed var(--primary-low-mid);
 
     &::after {
@@ -169,13 +168,14 @@
  Section below from prosemirror-view/style/prosemirror.css
  ********************************************************/
 
-/* stylelint-disable-next-line no-duplicate-selectors */
+// stylelint-disable-next-line no-duplicate-selectors
 .ProseMirror {
   position: relative;
   word-wrap: break-word;
   white-space: break-spaces;
 }
 
+// stylelint-disable-next-line no-duplicate-selectors
 .ProseMirror pre {
   white-space: pre-wrap;
 }
diff --git a/spec/system/composer/prosemirror_editor_spec.rb b/spec/system/composer/prosemirror_editor_spec.rb
index 64012db13c3..10af16c91bd 100644
--- a/spec/system/composer/prosemirror_editor_spec.rb
+++ b/spec/system/composer/prosemirror_editor_spec.rb
@@ -3,6 +3,7 @@
 describe "Composer - ProseMirror editor", type: :system do
   fab!(:user) { Fabricate(:user, refresh_auto_groups: true) }
   fab!(:tag)
+  let(:cdp) { PageObjects::CDP.new }
   let(:composer) { PageObjects::Components::Composer.new }
   let(:rich) { composer.rich_editor }
 
@@ -11,6 +12,12 @@ describe "Composer - ProseMirror editor", type: :system do
     SiteSetting.rich_editor = true
   end
 
+  def open_composer_and_toggle_rich_editor
+    page.visit "/new-topic"
+    expect(composer).to be_opened
+    composer.toggle_rich_editor
+  end
+
   it "hides the Composer container's preview button" do
     page.visit "/new-topic"
 
@@ -24,34 +31,21 @@ describe "Composer - ProseMirror editor", type: :system do
 
   context "with autocomplete" do
     it "triggers an autocomplete on mention" do
-      page.visit "/new-topic"
-
-      expect(composer).to be_opened
-
-      composer.toggle_rich_editor
-
+      open_composer_and_toggle_rich_editor
       composer.type_content("@#{user.username}")
 
       expect(composer).to have_mention_autocomplete
     end
 
     it "triggers an autocomplete on hashtag" do
-      page.visit "/new-topic"
-
-      expect(composer).to be_opened
-
-      find(".composer-toggle-switch").click
+      open_composer_and_toggle_rich_editor
       composer.type_content("##{tag.name}")
 
       expect(composer).to have_hashtag_autocomplete
     end
 
     it "triggers an autocomplete on emoji" do
-      page.visit "/new-topic"
-
-      expect(composer).to be_opened
-
-      composer.toggle_rich_editor
+      open_composer_and_toggle_rich_editor
       composer.type_content(":smile")
 
       expect(composer).to have_emoji_autocomplete
@@ -60,22 +54,14 @@ describe "Composer - ProseMirror editor", type: :system do
 
   context "with inputRules" do
     it "supports > to create a blockquote" do
-      page.visit "/new-topic"
-
-      expect(composer).to be_opened
-
-      composer.toggle_rich_editor
+      open_composer_and_toggle_rich_editor
       composer.type_content("> This is a blockquote")
 
       expect(rich).to have_css("blockquote", text: "This is a blockquote")
     end
 
     it "supports n. to create an ordered list" do
-      page.visit "/new-topic"
-
-      expect(composer).to be_opened
-
-      composer.toggle_rich_editor
+      open_composer_and_toggle_rich_editor
       composer.type_content("1. Item 1\n5. Item 2")
 
       expect(rich).to have_css("ol li", text: "Item 1")
@@ -83,11 +69,7 @@ describe "Composer - ProseMirror editor", type: :system do
     end
 
     it "supports *, - or + to create an unordered list" do
-      page.visit "/new-topic"
-
-      expect(composer).to be_opened
-
-      composer.toggle_rich_editor
+      open_composer_and_toggle_rich_editor
       composer.type_content("* Item 1\n")
       composer.type_content("- Item 2\n")
       composer.type_content("+ Item 3")
@@ -96,11 +78,7 @@ describe "Composer - ProseMirror editor", type: :system do
     end
 
     it "supports ``` or 4 spaces to create a code block" do
-      page.visit "/new-topic"
-
-      expect(composer).to be_opened
-
-      composer.toggle_rich_editor
+      open_composer_and_toggle_rich_editor
       composer.type_content("```\nThis is a code block")
       composer.send_keys(%i[shift enter])
       composer.type_content("    This is a code block")
@@ -109,11 +87,7 @@ describe "Composer - ProseMirror editor", type: :system do
     end
 
     it "supports 1-6 #s to create a heading" do
-      page.visit "/new-topic"
-
-      expect(composer).to be_opened
-
-      composer.toggle_rich_editor
+      open_composer_and_toggle_rich_editor
       composer.type_content("# Heading 1\n")
       composer.type_content("## Heading 2\n")
       composer.type_content("### Heading 3\n")
@@ -130,11 +104,7 @@ describe "Composer - ProseMirror editor", type: :system do
     end
 
     it "supports _ or * to create an italic text" do
-      page.visit "/new-topic"
-
-      expect(composer).to be_opened
-
-      composer.toggle_rich_editor
+      open_composer_and_toggle_rich_editor
       composer.type_content("_This is italic_\n")
       composer.type_content("*This is italic*")
 
@@ -142,11 +112,7 @@ describe "Composer - ProseMirror editor", type: :system do
     end
 
     it "supports __ or ** to create a bold text" do
-      page.visit "/new-topic"
-
-      expect(composer).to be_opened
-
-      composer.toggle_rich_editor
+      open_composer_and_toggle_rich_editor
       composer.type_content("__This is bold__\n")
       composer.type_content("**This is bold**")
 
@@ -154,11 +120,7 @@ describe "Composer - ProseMirror editor", type: :system do
     end
 
     it "supports ` to create a code text" do
-      page.visit "/new-topic"
-
-      expect(composer).to be_opened
-
-      composer.toggle_rich_editor
+      open_composer_and_toggle_rich_editor
       composer.type_content("`This is code`")
 
       expect(rich).to have_css("code", text: "This is code")
@@ -168,11 +130,7 @@ describe "Composer - ProseMirror editor", type: :system do
   context "with keymap" do
     PLATFORM_KEY_MODIFIER = SystemHelpers::PLATFORM_KEY_MODIFIER
     it "supports Ctrl + B to create a bold text" do
-      page.visit "/new-topic"
-
-      expect(composer).to be_opened
-
-      composer.toggle_rich_editor
+      open_composer_and_toggle_rich_editor
       composer.type_content([PLATFORM_KEY_MODIFIER, "b"])
       composer.type_content("This is bold")
 
@@ -180,11 +138,7 @@ describe "Composer - ProseMirror editor", type: :system do
     end
 
     it "supports Ctrl + I to create an italic text" do
-      page.visit "/new-topic"
-
-      expect(composer).to be_opened
-
-      composer.toggle_rich_editor
+      open_composer_and_toggle_rich_editor
       composer.type_content([PLATFORM_KEY_MODIFIER, "i"])
       composer.type_content("This is italic")
 
@@ -192,12 +146,7 @@ describe "Composer - ProseMirror editor", type: :system do
     end
 
     xit "supports Ctrl + K to create a link" do
-      page.visit "/new-topic"
-
-      expect(composer).to be_opened
-
-      composer.toggle_rich_editor
-      page.send_keys([PLATFORM_KEY_MODIFIER, "k"])
+      open_composer_and_toggle_rich_editor page.send_keys([PLATFORM_KEY_MODIFIER, "k"])
       page.send_keys("https://www.example.com\t")
       page.send_keys("This is a link")
       page.send_keys(:enter)
@@ -206,11 +155,7 @@ describe "Composer - ProseMirror editor", type: :system do
     end
 
     it "supports Ctrl + Shift + 7 to create an ordered list" do
-      page.visit "/new-topic"
-
-      expect(composer).to be_opened
-
-      composer.toggle_rich_editor
+      open_composer_and_toggle_rich_editor
       composer.type_content("Item 1")
       composer.send_keys([PLATFORM_KEY_MODIFIER, :shift, "7"])
 
@@ -218,11 +163,7 @@ describe "Composer - ProseMirror editor", type: :system do
     end
 
     it "supports Ctrl + Shift + 8 to create a bullet list" do
-      page.visit "/new-topic"
-
-      expect(composer).to be_opened
-
-      composer.toggle_rich_editor
+      open_composer_and_toggle_rich_editor
       composer.type_content("Item 1")
       composer.send_keys([PLATFORM_KEY_MODIFIER, :shift, "8"])
 
@@ -230,11 +171,7 @@ describe "Composer - ProseMirror editor", type: :system do
     end
 
     it "supports Ctrl + Shift + 9 to create a blockquote" do
-      page.visit "/new-topic"
-
-      expect(composer).to be_opened
-
-      composer.toggle_rich_editor
+      open_composer_and_toggle_rich_editor
       composer.type_content("This is a blockquote")
       composer.send_keys([PLATFORM_KEY_MODIFIER, :shift, "9"])
 
@@ -242,12 +179,7 @@ describe "Composer - ProseMirror editor", type: :system do
     end
 
     it "supports Ctrl + Shift + 1-6 for headings, 0 for reset" do
-      page.visit "/new-topic"
-
-      expect(composer).to be_opened
-
-      composer.toggle_rich_editor
-
+      open_composer_and_toggle_rich_editor
       (1..6).each do |i|
         composer.type_content("\nHeading #{i}")
         composer.send_keys([PLATFORM_KEY_MODIFIER, :shift, i.to_s])
@@ -260,11 +192,7 @@ describe "Composer - ProseMirror editor", type: :system do
     end
 
     it "supports Ctrl + Z and Ctrl + Shift + Z to undo and redo" do
-      page.visit "/new-topic"
-
-      expect(composer).to be_opened
-
-      composer.toggle_rich_editor
+      open_composer_and_toggle_rich_editor
       composer.type_content("This is a test")
       composer.send_keys([PLATFORM_KEY_MODIFIER, "z"])
 
@@ -276,15 +204,32 @@ describe "Composer - ProseMirror editor", type: :system do
     end
 
     it "supports Ctrl + Shift + _ to create a horizontal rule" do
-      page.visit "/new-topic"
-
-      expect(composer).to be_opened
-
-      composer.toggle_rich_editor
+      open_composer_and_toggle_rich_editor
       composer.type_content("This is a test")
       composer.send_keys([PLATFORM_KEY_MODIFIER, :shift, "_"])
 
       expect(rich).to have_css("hr")
     end
   end
+
+  describe "pasting content" do
+    it "does not freeze the editor when pasting markdown code blocks without a language" do
+      cdp.allow_clipboard
+      open_composer_and_toggle_rich_editor
+
+      # The example is a bit convoluted, but it's the simplest way to reproduce the issue.
+      cdp.write_clipboard <<~MARKDOWN
+      ```
+      puts SiteSetting.all_settings(filter_categories: ["uncategorized"]).map { |setting| setting[:setting] }.join("\n")
+      ```
+      MARKDOWN
+      composer.type_content("This is a test\n\n")
+      page.send_keys([PLATFORM_KEY_MODIFIER, "v"])
+      expect(page.driver.browser.logs.get(:browser)).not_to include(
+        "Maximum call stack size exceeded",
+      )
+      expect(rich).to have_css("pre code", wait: 1)
+      expect(rich).to have_css("select.code-language-select", wait: 1)
+    end
+  end
 end
diff --git a/spec/system/page_objects/cdp.rb b/spec/system/page_objects/cdp.rb
index a21af946073..512817369d4 100644
--- a/spec/system/page_objects/cdp.rb
+++ b/spec/system/page_objects/cdp.rb
@@ -30,6 +30,13 @@ module PageObjects
       page.evaluate_async_script("navigator.clipboard.readText().then(arguments[0])")
     end
 
+    def write_clipboard(text)
+      page.evaluate_async_script(
+        "navigator.clipboard.writeText(arguments[0]).then(arguments[1])",
+        text,
+      )
+    end
+
     def clipboard_has_text?(text, chomp: false, strict: true)
       try_until_success do
         clipboard_text = chomp ? read_clipboard.chomp : read_clipboard