From 94a7b203864d380bd3c12a20157df609738e9de9 Mon Sep 17 00:00:00 2001
From: Shaisolaris <66793913+Shaisolaris@users.noreply.github.com>
Date: Tue, 13 Oct 2026 00:15:35 +0000
Subject: [PATCH] Keep partially consumed tab when an HTML block starts or
 continues in a block quote

---
 .../main/java/org/commonmark/internal/DocumentParser.java | 4 ++++
 .../test/java/org/commonmark/test/SpecialInputTest.java   | 8 ++++++++
 2 files changed, 12 insertions(+)

diff --git a/commonmark/src/main/java/org/commonmark/internal/DocumentParser.java b/commonmark/src/main/java/org/commonmark/internal/DocumentParser.java
index 607a68bb..62b392b8 100644
--- a/commonmark/src/main/java/org/commonmark/internal/DocumentParser.java
+++ b/commonmark/src/main/java/org/commonmark/internal/DocumentParser.java
@@ -391,6 +391,10 @@ private void findNextNonSpace() {
     }
 
     private void setNewIndex(int newIndex) {
+        if (newIndex == index) {
+            // Staying where we are, so keep a partially consumed tab (e.g. after ">\t") as it is
+            return;
+        }
         if (newIndex >= nextNonSpace) {
             // We can start from here, no need to calculate tab stops again
             index = nextNonSpace;
diff --git a/commonmark/src/test/java/org/commonmark/test/SpecialInputTest.java b/commonmark/src/test/java/org/commonmark/test/SpecialInputTest.java
index 007b5765..43b7686c 100644
--- a/commonmark/src/test/java/org/commonmark/test/SpecialInputTest.java
+++ b/commonmark/src/test/java/org/commonmark/test/SpecialInputTest.java
@@ -463,4 +463,12 @@ public void codeSpansAfterUnclosedBackticks() {
         assertRendering(
                 "`` `a` `c` `e`", "<p>`` <code>a</code> <code>c</code> <code>e</code></p>\n");
     }
+
+    @Test
+    public void htmlBlockInBlockQuoteAfterPartiallyConsumedTab() {
+        // The tab after ">" is 3 columns wide; one is consumed by the block quote marker and the
+        // remaining 2 belong to the HTML block content, same as for other block types
+        assertRendering(">\t<div>", "<blockquote>\n  <div>\n</blockquote>\n");
+        assertRendering("> <div>\n>\tfoo", "<blockquote>\n<div>\n  foo\n</blockquote>\n");
+    }
 }