Convert AI responses to Telegram HTML with blockquote wrapping

Markdown (headings, bold, italic, strikethrough, code blocks, links)
is converted to Telegram-compatible HTML tags before sending. Each
reply chunk is wrapped in <blockquote> for visual distinction.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/commands/builtins.py

@@ -1,5 +1,7 @@
 from __future__ import annotations
 
+import html
+import re
 from textwrap import wrap
 from typing import TYPE_CHECKING, Any
 
@@ -10,6 +12,40 @@ if TYPE_CHECKING:
     from app.commands.core import CommandContext
 
 
+_PH = "\x00{}\x00"
+_PH_RE = re.compile(r"\x00(\d+)\x00")
+
+
+def _md_to_tg(text: str) -> str:
+    """Convert markdown-ish text to Telegram HTML."""
+    saved: list[str] = []
+
+    def _save(s: str) -> str:
+        saved.append(s)
+        return _PH.format(len(saved) - 1)
+
+    def _fence(m: re.Match) -> str:
+        lang = (m.group(1) or "").strip()
+        code = html.escape(m.group(2) or "")
+        cls = f' class="language-{html.escape(lang)}"' if lang else ""
+        return _save(f"<pre><code{cls}>{code}</code></pre>")
+
+    text = re.sub(r"```(\w*)\n?(.*?)```", _fence, text, flags=re.DOTALL)
+    text = re.sub(r"`([^`\n]+)`", lambda m: _save(f"<code>{html.escape(m.group(1))}</code>"), text)
+
+    text = html.escape(text)
+
+    text = re.sub(r"^#{1,6}\s+(.+)$", r"<b>\1</b>", text, flags=re.MULTILINE)
+    text = re.sub(r"\*\*(.+?)\*\*", r"<b>\1</b>", text, flags=re.DOTALL)
+    text = re.sub(r"__(.+?)__", r"<b>\1</b>", text, flags=re.DOTALL)
+    text = re.sub(r"(?<!\*)\*(?!\*)(.+?)(?<!\*)\*(?!\*)", r"<i>\1</i>", text, flags=re.DOTALL)
+    text = re.sub(r"(?<!_)_(?!_)(.+?)(?<!_)_(?!_)", r"<i>\1</i>", text, flags=re.DOTALL)
+    text = re.sub(r"~~(.+?)~~", r"<s>\1</s>", text, flags=re.DOTALL)
+    text = re.sub(r"\[(.+?)\]\((.+?)\)", r'<a href="\2">\1</a>', text)
+
+    return _PH_RE.sub(lambda m: saved[int(m.group(1))], text)
+
+
 command_registry = CommandRegistry()
 DEFAULT_REGISTRY = command_registry
 
@@ -69,11 +105,13 @@ async def _reply_long(ctx: "CommandContext", text: str) -> None:
     if not chunks:
         await ctx.reply("")
         return
-    first = await ctx.reply(chunks[0])
+    html_chunks = [f"<blockquote>{_md_to_tg(c)}</blockquote>" for c in chunks]
-    for chunk in chunks[1:]:
+    first = await ctx.reply(html_chunks[0], parse_mode="html")
+    for chunk in html_chunks[1:]:
         await ctx.client.send_message(
             ctx.message.chat.id,
             chunk,
+            parse_mode="html",
             reply_to_message_id=getattr(first, "id", None),
         )