Six things that looked like they worked

None of these fails loudly and two of them correct themselves if you reload,
which is why five were found by reading rather than by anybody reporting them.

The reply that lost its author is the one worth knowing about: the frame that
replaces a bubble when a reply lands was looking the models up as nobody, and
"no user" answers "no models" rather than "all models" -- so every finished
reply swapped the model's avatar for the plain mark and put the instance's name
where the model's should be, until the next page load put it back.

Beside it: a concurrency quota enforced on two of the six paths that start a
reply, including neither of the two most used; a custom theme whose success and
warning colours moved the text and left the background behind; a phone shell
sized to one viewport inside a document sized to another, which is the reported
scroll past the bottom of Settings; a whole conversation's Markdown rendered on
every page load and read by nothing; a skip guard inert since it was written;
and an endpoint nothing has ever called.

The scroll fix folded five near-identical scroller rules into one, which is
also where the containment they were all missing now lives.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tests/test_ui_js.py

@@ -163,10 +163,15 @@ def test_the_tab_reset_finds_the_container_that_actually_scrolls():
     either alone leaves the bug.
     """
     admin = (ROOT / "web/static/css/admin.css").read_text(encoding="utf-8")
+    app = (ROOT / "web/static/css/app.css").read_text(encoding="utf-8")
 
-    # The scroller rule names where the tabs must be, not just the class.
-    assert ".main > .tabs > .tabs__body" in admin
+    # The scroller rule names where the tabs must be, not just the class. Which
+    # stylesheet it is written in is not the point and is not asserted -- the
+    # four declarations that make something a scroller now live once, in
+    # app.css, and this selector is listed there with the rest.
+    assert ".main > .tabs > .tabs__body" in admin + app
     assert "\n.tabs__body {" not in admin
+    assert "\n.tabs__body {" not in app
 
     assert "overflowY" in SOURCE
     assert "scrollHeight > " in SOURCE