Python: fix prompt template engine blocking HTML tags in content

python/semantic_kernel/contents/chat_history.py

@@ -353,6 +353,23 @@ def from_rendered_prompt(cls: type[_T], rendered_prompt: str) -> _T:
             elif item.tag == CHAT_HISTORY_TAG:
                 for message in item:
                     messages.append(ChatMessageContent.from_element(message))
+            else:
+                # Unknown XML tags (e.g. HTML tags like <p>, <div>) are not SK
+                # template tags.  Serialize them back to text and append to the
+                # previous message so that the original content is preserved.
+                saved_tail = item.tail
+                item.tail = None
+                raw = unescape(tostring(item, encoding="unicode", short_empty_elements=False))
+                item.tail = saved_tail
+                if messages:
+                    messages[-1].content = (messages[-1].content or "") + raw
+                else:
+                    messages.append(ChatMessageContent(role=AuthorRole.USER, content=raw))
+                # For unknown tags the tail is part of the surrounding text,
+                # so keep it in the same message instead of starting a new one.
+                if item.tail:
+                    messages[-1].content = (messages[-1].content or "") + unescape(item.tail)
+                continue
             if item.tail and item.tail.strip():
                 messages.append(ChatMessageContent(role=AuthorRole.USER, content=unescape(item.tail.strip())))
         if len(messages) == 1 and messages[0].role == AuthorRole.SYSTEM:

python/tests/unit/contents/test_chat_history.py

@@ -612,6 +612,48 @@ def test_to_from_file(chat_history: ChatHistory, tmp_path):
     assert chat_history_2.messages[4] == chat_history.messages[4]
 
 
+def test_from_rendered_prompt_preserves_html_p_tag():
+    """HTML <p> tags in prompts should be preserved as text, not treated as template tags.
+
+    Regression test for https://github.com/microsoft/semantic-kernel/issues/13632
+    """
+    rendered = (
+        'Translate following message from English language into the Spanish language - "<p>What is your name?</p>"'
+    )
+    chat_history = ChatHistory.from_rendered_prompt(rendered)
+    assert len(chat_history.messages) == 1
+    assert chat_history.messages[0].role == AuthorRole.USER
+    assert "<p>What is your name?</p>" in chat_history.messages[0].content
+
+
+def test_from_rendered_prompt_preserves_multiple_html_tags():
+    """Multiple HTML tags in prompts should be preserved as text."""
+    rendered = "<p>First paragraph</p><div>A div</div>"
+    chat_history = ChatHistory.from_rendered_prompt(rendered)
+    assert len(chat_history.messages) == 1
+    assert "<p>First paragraph</p>" in chat_history.messages[0].content
+    assert "<div>A div</div>" in chat_history.messages[0].content
+
+
+def test_from_rendered_prompt_preserves_html_with_text_around():
+    """HTML tags surrounded by plain text should preserve all content."""
+    rendered = "Hello <b>world</b> today"
+    chat_history = ChatHistory.from_rendered_prompt(rendered)
+    assert len(chat_history.messages) == 1
+    assert "Hello" in chat_history.messages[0].content
+    assert "<b>world</b>" in chat_history.messages[0].content
+    assert "today" in chat_history.messages[0].content
+
+
+def test_from_rendered_prompt_sk_tags_still_work_with_html():
+    """SK template tags should still be parsed correctly even when HTML tags are present."""
+    rendered = '<message role="user">Tell me about <b>bold</b> text</message>'
+    chat_history = ChatHistory.from_rendered_prompt(rendered)
+    # The <b> tag inside a <message> is handled by ChatMessageContent.from_element
+    assert len(chat_history.messages) == 1
+    assert chat_history.messages[0].role == AuthorRole.USER
+
+
 def test_chat_history_serialize(chat_history: ChatHistory):
     class CustomResultClass:
         def __init__(self, result):