From 9b14869cb10daa09a65d0f4e321dc63cbd812363 Mon Sep 17 00:00:00 2001
From: Alexander Minges <alexander.minges@uni-due.de>
Date: Tue, 10 Feb 2026 15:56:21 +0100
Subject: [PATCH] feat(matrix): support inline markdown html for url and
 super/subscript

---
 nanobot/channels/matrix.py   | 16 +++++++++++++---
 tests/test_matrix_channel.py | 20 ++++++++++++++++++++
 2 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/nanobot/channels/matrix.py b/nanobot/channels/matrix.py
index fbe511b..61113ac 100644
--- a/nanobot/channels/matrix.py
+++ b/nanobot/channels/matrix.py
@@ -24,9 +24,16 @@ LOGGING_STACK_BASE_DEPTH = 2
 TYPING_NOTICE_TIMEOUT_MS = 30_000
 MATRIX_HTML_FORMAT = "org.matrix.custom.html"
 
+# Keep plugin output aligned with Matrix recommended HTML tags:
+# https://spec.matrix.org/latest/client-server-api/#mroommessage-msgtypes
+# - table/strikethrough/task_lists are already used in replies.
+# - url, superscript, and subscript map to common tags (<a>, <sup>, <sub>)
+#   that Matrix clients (e.g. Element/FluffyChat) can render consistently.
+# We intentionally avoid plugins that emit less-portable tags to keep output
+# predictable across clients.
 MATRIX_MARKDOWN = create_markdown(
     escape=True,
-    plugins=["table", "strikethrough", "task_lists"],
+    plugins=["table", "strikethrough", "task_lists", "url", "superscript", "subscript"],
 )
 
 
@@ -47,8 +54,11 @@ def _render_markdown_html(text: str) -> str | None:
 
     # Skip formatted_body for plain output (<p>...</p>) to keep payload minimal.
     stripped = formatted.strip()
-    if stripped.startswith("<p>") and stripped.endswith("</p>") and "<p>" not in stripped[3:-4]:
-        return None
+    if stripped.startswith("<p>") and stripped.endswith("</p>"):
+        paragraph_inner = stripped[3:-4]
+        # Keep plaintext-only paragraphs minimal, but preserve inline markup/links.
+        if "<" not in paragraph_inner and ">" not in paragraph_inner:
+            return None
 
     return formatted
 
diff --git a/tests/test_matrix_channel.py b/tests/test_matrix_channel.py
index cc834c3..2e3dad2 100644
--- a/tests/test_matrix_channel.py
+++ b/tests/test_matrix_channel.py
@@ -424,6 +424,26 @@ async def test_send_adds_formatted_body_for_markdown() -> None:
     assert "task-list-item-checkbox" in str(content["formatted_body"])
 
 
+@pytest.mark.asyncio
+async def test_send_adds_formatted_body_for_inline_url_superscript_subscript() -> None:
+    channel = MatrixChannel(_make_config(), MessageBus())
+    client = _FakeAsyncClient("", "", "", None)
+    channel.client = client
+
+    markdown_text = "Visit https://example.com and x^2^ plus H~2~O."
+    await channel.send(
+        OutboundMessage(channel="matrix", chat_id="!room:matrix.org", content=markdown_text)
+    )
+
+    content = client.room_send_calls[0]["content"]
+    assert content["msgtype"] == "m.text"
+    assert content["body"] == markdown_text
+    assert content["format"] == MATRIX_HTML_FORMAT
+    assert '<a href="https://example.com">' in str(content["formatted_body"])
+    assert "<sup>2</sup>" in str(content["formatted_body"])
+    assert "<sub>2</sub>" in str(content["formatted_body"])
+
+
 @pytest.mark.asyncio
 async def test_send_falls_back_to_plaintext_when_markdown_render_fails(monkeypatch) -> None:
     channel = MatrixChannel(_make_config(), MessageBus())