fix: LaTeX processing within blockquotes

Author: allozaur

tools/server/webui/src/lib/utils/latex-protection.test.ts

@@ -318,4 +318,38 @@ $$\n\\pi_n(\\mathbb{S}^3) = \\begin{cases}
 		// mhchem-escape would insert a backslash here.
 		expect(output).toBe('mchem pu:\n$\\pu{-572 kJ mol^{-1}}$');
 	});
+
+	test('LaTeX in blockquotes with display math', () => {
+		const input =
+			'> **Definition (limit):**  \n>  \\[\n>  \\lim_{x\\to a} f(x) = L\n>  \\]\n>  means that as \\(x\\) gets close to \\(a\\).';
+		const output = preprocessLaTeX(input);
+
+		// Blockquote markers should be preserved, LaTeX should be converted
+		expect(output).toContain('> **Definition (limit):**');
+		expect(output).toContain('$$');
+		expect(output).toContain('$x$');
+		expect(output).not.toContain('\\[');
+		expect(output).not.toContain('\\]');
+		expect(output).not.toContain('\\(');
+		expect(output).not.toContain('\\)');
+	});
+
+	test('LaTeX in blockquotes with inline math', () => {
+		const input =
+			"> The derivative \\(f'(x)\\) at point \\(x=a\\) measures slope.\n> Formula: \\(f'(a)=\\lim_{h\\to 0}\\frac{f(a+h)-f(a)}{h}\\)";
+		const output = preprocessLaTeX(input);
+
+		// Blockquote markers should be preserved, inline LaTeX converted to $...$
+		expect(output).toContain("> The derivative $f'(x)$ at point $x=a$ measures slope.");
+		expect(output).toContain("> Formula: $f'(a)=\\lim_{h\\to 0}\\frac{f(a+h)-f(a)}{h}$");
+	});
+
+	test('Mixed content with blockquotes and regular text', () => {
+		const input =
+			'Regular text with \\(x^2\\).\n\n> Quote with \\(y^2\\).\n\nMore text with \\(z^2\\).';
+		const output = preprocessLaTeX(input);
+
+		// All LaTeX should be converted, blockquote markers preserved
+		expect(output).toBe('Regular text with $x^2$.\n\n> Quote with $y^2$.\n\nMore text with $z^2$.');
+	});
 });

tools/server/webui/src/lib/utils/latex-protection.ts

@@ -148,6 +148,20 @@ export function preprocessLaTeX(content: string): string {
 	// See also:
 	// https://github.com/danny-avila/LibreChat/blob/main/client/src/utils/latex.ts
 
+	// Step 0: Temporarily remove blockquote markers (>) to process LaTeX correctly
+	// Store the structure so we can restore it later
+	const blockquoteMarkers: Map<number, string> = new Map();
+	const lines = content.split('\n');
+	const processedLines = lines.map((line, index) => {
+		const match = line.match(/^(>\s*)/);
+		if (match) {
+			blockquoteMarkers.set(index, match[1]);
+			return line.slice(match[1].length);
+		}
+		return line;
+	});
+	content = processedLines.join('\n');
+
 	// Step 1: Protect code blocks
 	const codeBlocks: string[] = [];
 
@@ -239,5 +253,15 @@ export function preprocessLaTeX(content: string): string {
 			}
 		);
 
+	// Step 7: Restore blockquote markers
+	if (blockquoteMarkers.size > 0) {
+		const finalLines = content.split('\n');
+		const restoredLines = finalLines.map((line, index) => {
+			const marker = blockquoteMarkers.get(index);
+			return marker ? marker + line : line;
+		});
+		content = restoredLines.join('\n');
+	}
+
 	return content;
 }