From 9f85b8379c231bf2cc2f48fede498d6910b32af9 Mon Sep 17 00:00:00 2001
From: Mutasem Aldmour <4711238+mutdmour@users.noreply.github.com>
Date: Fri, 9 Oct 2026 09:24:16 +0000
Subject: [PATCH] fix(editor): Remove trailing newline from AI Assistant code
 blocks (no-changelog) (#40731)

Co-authored-by: Claude Sonnet 5.5 <noreply@anthropic.com>
---
 .../messages/useMarkdown.test.ts              | 29 +++++++++++++++++++
 .../AskAssistantChat/messages/useMarkdown.ts  |  9 ++++++
 2 files changed, 38 insertions(+)
 create mode 100644 packages/frontend/@n8n/design-system/src/components/AskAssistantChat/messages/useMarkdown.test.ts

diff --git a/packages/frontend/@n8n/design-system/src/components/AskAssistantChat/messages/useMarkdown.test.ts b/packages/frontend/@n8n/design-system/src/components/AskAssistantChat/messages/useMarkdown.test.ts
new file mode 100644
index 00000000000..5279ee865a6
--- /dev/null
+++ b/packages/frontend/@n8n/design-system/src/components/AskAssistantChat/messages/useMarkdown.test.ts
@@ -0,0 +1,29 @@
+import { useMarkdown } from './useMarkdown';
+
+describe('useMarkdown', () => {
+	const { renderMarkdown } = useMarkdown();
+
+	it('should not add a trailing newline inside a fenced code block', () => {
+		const html = renderMarkdown('```\nhttps://example.com/webhook/abc\n```');
+
+		expect(html).toContain('<code>https://example.com/webhook/abc</code>');
+	});
+
+	it('should keep newlines between lines of a fenced code block', () => {
+		const html = renderMarkdown('```\nline 1\nline 2\n```');
+
+		expect(html).toContain('<code>line 1\nline 2</code>');
+	});
+
+	it('should keep the language class on a fenced code block', () => {
+		const html = renderMarkdown('```js\nconst a = 1;\n```');
+
+		expect(html).toContain('<code class="language-js">const a = 1;</code>');
+	});
+
+	it('should keep an intentional blank last line in a fenced code block', () => {
+		const html = renderMarkdown('```\nline 1\n\n```');
+
+		expect(html).toContain('<code>line 1\n</code>');
+	});
+});
diff --git a/packages/frontend/@n8n/design-system/src/components/AskAssistantChat/messages/useMarkdown.ts b/packages/frontend/@n8n/design-system/src/components/AskAssistantChat/messages/useMarkdown.ts
index c123f8aa733..4ac7b07c1e0 100644
--- a/packages/frontend/@n8n/design-system/src/components/AskAssistantChat/messages/useMarkdown.ts
+++ b/packages/frontend/@n8n/design-system/src/components/AskAssistantChat/messages/useMarkdown.ts
@@ -17,6 +17,15 @@ export function useMarkdown() {
 		},
 	});
 
+	// markdown-it ends fenced code with a newline. Triple-click copy would include it.
+	const renderFence = md.renderer.rules.fence;
+	md.renderer.rules.fence = (tokens, idx, options, env, self) => {
+		tokens[idx].content = tokens[idx].content.replace(/\n$/, '');
+		return renderFence
+			? renderFence(tokens, idx, options, env, self)
+			: self.renderToken(tokens, idx, options);
+	};
+
 	function renderMarkdown(content: string) {
 		try {
 			return md.render(content);