bug: Marked treats tabs and spaces differently in lists

src/Tokenizer.ts

@@ -267,7 +267,11 @@ export class _Tokenizer<ParserOutput = string, RendererOutput = string> {
         raw = cap[0];
         src = src.substring(raw.length);
 
-        let line = cap[2].split('\n', 1)[0].replace(this.rules.other.listReplaceTabs, (t: string) => ' '.repeat(3 * t.length));
+        // Normalize the first line by replacing tabs with 4 spaces so we can
+        // compute indent and slice the correct number of characters. This keeps
+        // behavior consistent with how subsequent lines are normalized.
+        const rawLineFirst = cap[2].split('\n', 1)[0];
+        let line = rawLineFirst.replace(this.rules.other.tabCharGlobal, '    ');
         let nextLine = src.split('\n', 1)[0];
         let blankLine = !line.trim();
 
@@ -278,7 +282,9 @@ export class _Tokenizer<ParserOutput = string, RendererOutput = string> {
         } else if (blankLine) {
           indent = cap[1].length + 1;
         } else {
-          indent = cap[2].search(this.rules.other.nonSpaceChar); // Find first non-space char
+          // Treat tabs as 4 spaces when finding first non-space char so a leading tab
+          // isn't considered a non-space and we compute indent correctly.
+          indent = line.search(this.rules.other.nonSpaceChar); // Find first non-space char
           indent = indent > 4 ? 1 : indent; // Treat indented code blocks (> 4 spaces) as having only 1 indent
           itemContents = line.slice(indent);
           indent += cap[1].length;

test/specs/new/list_with_tabs.md

@@ -0,0 +1,13 @@
+1.	Some Text
+2.	Some Text
+3.	Some Text
+
+Paragraph before list
+
+1.	Some Text
+2.	Some Text
+3.	Some Text
+
+-	Some Text
+-	Some Text
+-	Some Text

test/unit/marked.test.js

@@ -2,6 +2,15 @@ import { Marked, Renderer, lexer, parseInline, getDefaults, walkTokens, defaults
 import { timeout } from './utils.js';
 import assert from 'node:assert';
 import { describe, it, beforeEach, mock } from 'node:test';
+import fs from 'fs';
+import path from 'path';
+import { fileURLToPath } from 'node:url';
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = path.dirname(__filename);
+
+const mdPath = path.join(__dirname, '../specs/new/list_with_tabs.md');
+
 
 describe('marked unit', () => {
   let marked;
@@ -56,6 +65,15 @@ describe('marked unit', () => {
     });
   });
 
+  describe('lists with tabs', () => {
+  it('should correctly render markdown from the list_with_tabs fixture', () => {
+    const markdown = fs.readFileSync(mdPath, 'utf8');
+    const html = marked.parse(markdown);
+    assert.ok(html.includes('<ol>') && html.includes('<ul>'), 'Expected list HTML not found');
+  });
+});
+
+
   describe('parseInline', () => {
     it('should parse inline tokens', () => {
       const md = '**strong** _em_';