From 84bf9b5a3a5b1e2261121b2a36e1df058dc4b486 Mon Sep 17 00:00:00 2001
From: mck09 <mck097@gmail.com>
Date: Tue, 1 Sep 2026 20:30:21 +0200
Subject: [PATCH 1/2] fix: strip a tab that follows spaces in an indented code
 block

codeRemoveIndent tried its space alternative first, so a line indented
with spaces then a tab lost only the spaces and kept the tab as content.
Trying the tab alternative first matches CommonMark example 2, where a
tab advances to the next four column stop and the whole run is indent.
---
 src/rules.ts             |  2 +-
 test/unit/marked.test.js | 28 ++++++++++++++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/src/rules.ts b/src/rules.ts
index aeb880c597..92fe66498a 100644
--- a/src/rules.ts
+++ b/src/rules.ts
@@ -41,7 +41,7 @@ try {
 })();
 
 export const other = {
-  codeRemoveIndent: /^(?: {1,4}| {0,3}\t)/gm,
+  codeRemoveIndent: /^(?: {0,3}\t| {1,4})/gm,
   outputLinkReplace: /\\([\[\]])/g,
   indentCodeCompensation: /^(\s+)(?:```)/,
   beginningSpace: /^\s+/,
diff --git a/test/unit/marked.test.js b/test/unit/marked.test.js
index 5d1449b4aa..dabbe9f594 100644
--- a/test/unit/marked.test.js
+++ b/test/unit/marked.test.js
@@ -22,6 +22,34 @@ describe('marked unit', () => {
     });
   });
 
+  // The spec suite compares through htmlIsEqual, which leaves ignoreWhitespaces at its default
+  // of true, so it cannot see indentation inside pre. These assert exact output.
+  describe('tab expansion in block structure', () => {
+    it('should treat spaces then a tab as reaching the next four column stop', () => {
+      assert.strictEqual(marked.parse('  \tfoo\n'), '<pre><code>foo\n</code></pre>\n');
+    });
+
+    it('should keep tabs in the content of an indented code block', () => {
+      assert.strictEqual(marked.parse('  \tfoo\tbaz\t\tbim\n'), '<pre><code>foo\tbaz\t\tbim\n</code></pre>\n');
+    });
+
+    it('should strip three spaces and a tab', () => {
+      assert.strictEqual(marked.parse('   \tfoo\n'), '<pre><code>foo\n</code></pre>\n');
+    });
+
+    it('should still strip a lone leading tab', () => {
+      assert.strictEqual(marked.parse('\tfoo\n'), '<pre><code>foo\n</code></pre>\n');
+    });
+
+    it('should still strip exactly four spaces', () => {
+      assert.strictEqual(marked.parse('    foo\n'), '<pre><code>foo\n</code></pre>\n');
+    });
+
+    it('should keep a fifth space as content', () => {
+      assert.strictEqual(marked.parse('     foo\n'), '<pre><code> foo\n</code></pre>\n');
+    });
+  });
+
   describe('changeDefaults', () => {
     it('should change global defaults', async() => {
       const { defaults, setOptions } = await import('../../lib/marked.esm.js');

From e6490be223100a2a5a3a944d65d4c9089da0f2a3 Mon Sep 17 00:00:00 2001
From: mck09 <mck097@gmail.com>
Date: Tue, 1 Sep 2026 20:41:38 +0200
Subject: [PATCH 2/2] test: move the tab tests to test/specs/new

Uses renderExact so the fixture compares exactly, which htmlIsEqual
does not, and keeps the assertions out of marked.test.js.
---
 test/specs/new/tabs_indented_code.html | 14 +++++++++++++
 test/specs/new/tabs_indented_code.md   | 20 ++++++++++++++++++
 test/unit/marked.test.js               | 28 --------------------------
 3 files changed, 34 insertions(+), 28 deletions(-)
 create mode 100644 test/specs/new/tabs_indented_code.html
 create mode 100644 test/specs/new/tabs_indented_code.md

diff --git a/test/specs/new/tabs_indented_code.html b/test/specs/new/tabs_indented_code.html
new file mode 100644
index 0000000000..d036d907c6
--- /dev/null
+++ b/test/specs/new/tabs_indented_code.html
@@ -0,0 +1,14 @@
+<pre><code>foo	baz		bim
+</code></pre>
+<p>sep</p>
+<pre><code>three spaces and a tab
+</code></pre>
+<p>sep</p>
+<pre><code>lone tab
+</code></pre>
+<p>sep</p>
+<pre><code>four spaces
+</code></pre>
+<p>sep</p>
+<pre><code> five spaces
+</code></pre>
diff --git a/test/specs/new/tabs_indented_code.md b/test/specs/new/tabs_indented_code.md
new file mode 100644
index 0000000000..86081e613d
--- /dev/null
+++ b/test/specs/new/tabs_indented_code.md
@@ -0,0 +1,20 @@
+---
+renderExact: true
+---
+  	foo	baz		bim
+
+sep
+
+   	three spaces and a tab
+
+sep
+
+	lone tab
+
+sep
+
+    four spaces
+
+sep
+
+     five spaces
diff --git a/test/unit/marked.test.js b/test/unit/marked.test.js
index dabbe9f594..5d1449b4aa 100644
--- a/test/unit/marked.test.js
+++ b/test/unit/marked.test.js
@@ -22,34 +22,6 @@ describe('marked unit', () => {
     });
   });
 
-  // The spec suite compares through htmlIsEqual, which leaves ignoreWhitespaces at its default
-  // of true, so it cannot see indentation inside pre. These assert exact output.
-  describe('tab expansion in block structure', () => {
-    it('should treat spaces then a tab as reaching the next four column stop', () => {
-      assert.strictEqual(marked.parse('  \tfoo\n'), '<pre><code>foo\n</code></pre>\n');
-    });
-
-    it('should keep tabs in the content of an indented code block', () => {
-      assert.strictEqual(marked.parse('  \tfoo\tbaz\t\tbim\n'), '<pre><code>foo\tbaz\t\tbim\n</code></pre>\n');
-    });
-
-    it('should strip three spaces and a tab', () => {
-      assert.strictEqual(marked.parse('   \tfoo\n'), '<pre><code>foo\n</code></pre>\n');
-    });
-
-    it('should still strip a lone leading tab', () => {
-      assert.strictEqual(marked.parse('\tfoo\n'), '<pre><code>foo\n</code></pre>\n');
-    });
-
-    it('should still strip exactly four spaces', () => {
-      assert.strictEqual(marked.parse('    foo\n'), '<pre><code>foo\n</code></pre>\n');
-    });
-
-    it('should keep a fifth space as content', () => {
-      assert.strictEqual(marked.parse('     foo\n'), '<pre><code> foo\n</code></pre>\n');
-    });
-  });
-
   describe('changeDefaults', () => {
     it('should change global defaults', async() => {
       const { defaults, setOptions } = await import('../../lib/marked.esm.js');