diff --git a/app/source.py b/app/source.py
index 0b699c8..0dea35c 100644
--- a/app/source.py
+++ b/app/source.py
@@ -1,52 +1,118 @@
 import re
 import typing
 
-from markdown import markdown
+from mistletoe import Document  # type: ignore
+from mistletoe.html_renderer import HTMLRenderer  # type: ignore
+from mistletoe.span_token import SpanToken  # type: ignore
+from pygments import highlight  # type: ignore
+from pygments.formatters import HtmlFormatter  # type: ignore
+from pygments.lexers import get_lexer_by_name as get_lexer  # type: ignore
+from pygments.lexers import guess_lexer  # type: ignore
 from sqlalchemy import select
 
 from app import webfinger
 from app.config import BASE_URL
+from app.config import CODE_HIGHLIGHTING_THEME
 from app.database import AsyncSession
 from app.utils import emoji
 
 if typing.TYPE_CHECKING:
     from app.actor import Actor
 
-
-def _set_a_attrs(attrs, new=False):
-    attrs[(None, "target")] = "_blank"
-    attrs[(None, "class")] = "external"
-    attrs[(None, "rel")] = "noopener"
-    attrs[(None, "title")] = attrs[(None, "href")]
-    return attrs
-
-
+_FORMATTER = HtmlFormatter(style=CODE_HIGHLIGHTING_THEME)
 _HASHTAG_REGEX = re.compile(r"(#[\d\w]+)")
 _MENTION_REGEX = re.compile(r"@[\d\w_.+-]+@[\d\w-]+\.[\d\w\-.]+")
 
 
-def hashtagify(content: str) -> tuple[str, list[dict[str, str]]]:
-    tags = []
-    hashtags = re.findall(_HASHTAG_REGEX, content)
-    hashtags = sorted(set(hashtags), reverse=True)  # unique tags, longest first
-    for hashtag in hashtags:
-        tag = hashtag[1:]
+class AutoLink(SpanToken):
+    parse_inner = False
+    precedence = 10
+    pattern = re.compile(
+        "(https?:\\/\\/(?:www\\.)?[-a-zA-Z0-9@:%._\\+~#=]{1,256}\\.[a-zA-Z0-9()]{1,6}\\b(?:[-a-zA-Z0-9()@:%_\\+.~#?&\\/=]*))"  # noqa: E501
+    )
+
+    def __init__(self, match_obj: re.Match) -> None:
+        self.target = match_obj.group()
+
+
+class Mention(SpanToken):
+    parse_inner = False
+    precedence = 10
+    pattern = re.compile(r"(@[\d\w_.+-]+@[\d\w-]+\.[\d\w\-.]+)")
+
+    def __init__(self, match_obj: re.Match) -> None:
+        self.target = match_obj.group()
+
+
+class Hashtag(SpanToken):
+    parse_inner = False
+    precedence = 10
+    pattern = re.compile(r"(#[\d\w]+)")
+
+    def __init__(self, match_obj: re.Match) -> None:
+        self.target = match_obj.group()
+
+
+class CustomRenderer(HTMLRenderer):
+    def __init__(
+        self,
+        mentioned_actors: dict[str, "Actor"] = {},
+        enable_mentionify: bool = True,
+        enable_hashtagify: bool = True,
+    ) -> None:
+        extra_tokens = []
+        if enable_mentionify:
+            extra_tokens.append(Mention)
+        if enable_hashtagify:
+            extra_tokens.append(Hashtag)
+        super().__init__(AutoLink, *extra_tokens)
+
+        self.tags: list[dict[str, str]] = []
+        self.mentioned_actors = mentioned_actors
+
+    def render_auto_link(self, token: AutoLink) -> str:
+        template = '<a href="{target}" rel="noopener">{inner}</a>'
+        target = self.escape_url(token.target)
+        return template.format(target=target, inner=target)
+
+    def render_mention(self, token: Mention) -> str:
+        mention = token.target
+        actor = self.mentioned_actors.get(mention)
+        if not actor:
+            return mention
+
+        self.tags.append(dict(type="Mention", href=actor.ap_id, name=mention))
+
+        link = f'<span class="h-card"><a href="{actor.url}" class="u-url mention">{actor.handle}</a></span>'  # noqa: E501
+        return link
+
+    def render_hashtag(self, token: Hashtag) -> str:
+        tag = token.target[1:]
         link = f'<a href="{BASE_URL}/t/{tag}" class="mention hashtag" rel="tag">#<span>{tag}</span></a>'  # noqa: E501
-        tags.append(dict(href=f"{BASE_URL}/t/{tag}", name=hashtag, type="Hashtag"))
-        content = content.replace(hashtag, link)
-    return content, tags
+        self.tags.append(
+            dict(href=f"{BASE_URL}/t/{tag}", name=token.target, type="Hashtag")
+        )
+        return link
+
+    def render_block_code(self, token: typing.Any) -> str:
+        code = token.children[0].content
+        lexer = get_lexer(token.language) if token.language else guess_lexer(code)
+        return highlight(code, lexer, _FORMATTER)
 
 
-async def _mentionify(
+async def _prefetch_mentioned_actors(
     db_session: AsyncSession,
     content: str,
-) -> tuple[str, list[dict[str, str]], list["Actor"]]:
+) -> dict[str, "Actor"]:
     from app import models
     from app.actor import fetch_actor
 
-    tags = []
-    mentioned_actors = []
+    actors = {}
+
     for mention in re.findall(_MENTION_REGEX, content):
+        if mention in actors:
+            continue
+
         _, username, domain = mention.split("@")
         actor = (
             await db_session.execute(
@@ -63,12 +129,22 @@ async def _mentionify(
                 continue
             actor = await fetch_actor(db_session, actor_url)
 
-        mentioned_actors.append(actor)
-        tags.append(dict(type="Mention", href=actor.ap_id, name=mention))
+        actors[mention] = actor
 
-        link = f'<span class="h-card"><a href="{actor.url}" class="u-url mention">{actor.handle}</a></span>'  # noqa: E501
-        content = content.replace(mention, link)
-    return content, tags, mentioned_actors
+    return actors
+
+
+def hashtagify(content: str) -> tuple[str, list[dict[str, str]]]:
+    # TODO: fix this, switch to mistletoe?
+    tags = []
+    hashtags = re.findall(_HASHTAG_REGEX, content)
+    hashtags = sorted(set(hashtags), reverse=True)  # unique tags, longest first
+    for hashtag in hashtags:
+        tag = hashtag[1:]
+        link = f'<a href="{BASE_URL}/t/{tag}" class="mention hashtag" rel="tag">#<span>{tag}</span></a>'  # noqa: E501
+        tags.append(dict(href=f"{BASE_URL}/t/{tag}", name=hashtag, type="Hashtag"))
+        content = content.replace(hashtag, link)
+    return content, tags
 
 
 async def markdownify(
@@ -82,17 +158,19 @@ async def markdownify(
 
     """
     tags = []
-    mentioned_actors: list["Actor"] = []
-    if enable_hashtagify:
-        content, hashtag_tags = hashtagify(content)
-        tags.extend(hashtag_tags)
+    mentioned_actors: dict[str, "Actor"] = {}
     if enable_mentionify:
-        content, mention_tags, mentioned_actors = await _mentionify(db_session, content)
-        tags.extend(mention_tags)
+        mentioned_actors = await _prefetch_mentioned_actors(db_session, content)
+
+    with CustomRenderer(
+        mentioned_actors=mentioned_actors,
+        enable_mentionify=enable_mentionify,
+        enable_hashtagify=enable_hashtagify,
+    ) as renderer:
+        rendered_content = renderer.render(Document(content))
+        tags.extend(renderer.tags)
 
     # Handle custom emoji
     tags.extend(emoji.tags(content))
 
-    content = markdown(content, extensions=["mdx_linkify", "fenced_code"])
-
-    return content, tags, mentioned_actors
+    return rendered_content, tags, list(mentioned_actors.values())
diff --git a/poetry.lock b/poetry.lock
index 769a7e0..fdf0378 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -648,6 +648,14 @@ BeautifulSoup4 = ">=4.6.0"
 html5lib = ">=1.0.1"
 requests = ">=2.18.4"
 
+[[package]]
+name = "mistletoe"
+version = "0.9.0"
+description = "A fast, extensible Markdown parser in pure Python."
+category = "main"
+optional = false
+python-versions = "~=3.5"
+
 [[package]]
 name = "mypy"
 version = "0.960"
@@ -1275,7 +1283,7 @@ dev = ["pytest (>=4.6.2)", "black (>=19.3b0)"]
 [metadata]
 lock-version = "1.1"
 python-versions = "^3.10"
-content-hash = "84b3a6dcfc055fb0712c6abbf1bf94d9526eda940c4ddb0bd275664e68a4c3e3"
+content-hash = "bc8585a0da6f4d4e54afafde1da287ed75ed6544981d11bba561a7678bc31b8f"
 
 [metadata.files]
 aiosqlite = [
@@ -1832,6 +1840,10 @@ mdx-linkify = [
 mf2py = [
     {file = "mf2py-1.1.2.tar.gz", hash = "sha256:84f1f8f2ff3f1deb1c30be497e7ccd805452996a662fd4a77f09e0105bede2c9"},
 ]
+mistletoe = [
+    {file = "mistletoe-0.9.0-py3-none-any.whl", hash = "sha256:11316e2fe0be422a8248293ad0efbee9ad0c6f3683b2f45bc6b989ea17a68c74"},
+    {file = "mistletoe-0.9.0.tar.gz", hash = "sha256:3cb96d78226d08f0d3bf09efcaf330d23902492006e18b2c06558e8b86bf7faf"},
+]
 mypy = [
     {file = "mypy-0.960-cp310-cp310-macosx_10_9_universal2.whl", hash = "sha256:3a3e525cd76c2c4f90f1449fd034ba21fcca68050ff7c8397bb7dd25dd8b8248"},
     {file = "mypy-0.960-cp310-cp310-macosx_10_9_x86_64.whl", hash = "sha256:7a76dc4f91e92db119b1be293892df8379b08fd31795bb44e0ff84256d34c251"},
diff --git a/pyproject.toml b/pyproject.toml
index 526d260..a9a050c 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -45,6 +45,7 @@ boussole = "^2.0.0"
 uvicorn = {extras = ["standard"], version = "^0.18.3"}
 Brotli = "^1.0.9"
 greenlet = "^1.1.3"
+mistletoe = "^0.9.0"
 
 [tool.poetry.dev-dependencies]
 black = "^22.3.0"
diff --git a/tests/test_outbox.py b/tests/test_outbox.py
index 5159e8f..09e1269 100644
--- a/tests/test_outbox.py
+++ b/tests/test_outbox.py
@@ -179,7 +179,7 @@ def test_send_create_activity__with_attachment(
     outbox_object = db.execute(select(models.OutboxObject)).scalar_one()
     assert outbox_object.ap_type == "Note"
     assert outbox_object.summary is None
-    assert outbox_object.content == "<p>hello</p>"
+    assert outbox_object.content == "<p>hello</p>\n"
     assert len(outbox_object.attachments) == 1
     attachment = outbox_object.attachments[0]
     assert attachment.type == "Document"
@@ -227,7 +227,7 @@ def test_send_create_activity__no_content_with_cw_and_attachments(
     outbox_object = db.execute(select(models.OutboxObject)).scalar_one()
     assert outbox_object.ap_type == "Note"
     assert outbox_object.summary is None
-    assert outbox_object.content == "<p>cw</p>"
+    assert outbox_object.content == "<p>cw</p>\n"
     assert len(outbox_object.attachments) == 1