Markdown list items get extra blank lines in grid with Horizontal sibling

[fabge]

Checked closed issues — no duplicates found. Running latest Textual (7.5.0).

The bug

Markdown list items render with extra blank lines between them when a Horizontal container (with a child) is a sibling in a CSS grid that has both explicit grid-columns and grid-rows.

Expected: compact list — no blank lines between bullet items.
Actual: blank line between items.

Minimal reproduction

from textual.app import App, ComposeResult
from textual.containers import Horizontal
from textual.widgets import Markdown, Static

MD = "- one\n- two\n- three\n- four\n- five"

class BugDemo(App):
    CSS = \"\"\"
    Screen {
        layout: grid;
        grid-size: 2 2;
        grid-columns: 1fr 1fr;
        grid-rows: 1fr 1fr;
    }
    Horizontal { height: 1fr; }
    \"\"\"
    BINDINGS = [("q", "quit")]
    def compose(self) -> ComposeResult:
        yield Markdown(MD)
        yield Horizontal(Static("hi"))

BugDemo().run()

Output

  • one                                 hi
  • two

  • three
  • four

  • five

Trigger conditions (all required)

• CSS grid with both grid-columns and grid-rows set
• Markdown as a direct grid child
• Horizontal with a child widget as a sibling grid child

Any of these make the list render correctly

• Remove grid-columns or grid-rows
• Replace Horizontal with Vertical
• Use an empty Horizontal()

Textual Diagnostics

Versions

Name	Value
Textual	7.5.0
Rich	14.3.2

Python

Name	Value
Version	3.13.9
Implementation	CPython

Operating System

Name	Value
System	Darwin
Release	25.3.0

Terminal

Name	Value
Terminal Application	ghostty (1.2.3)
TERM	xterm-ghostty
COLORTERM	truecolor

[TomJGooding]

The problem is that setting Horizontal { height: 1fr; } will apply to all widgets that inherit from or use this container, including built-in Textual widgets.

Try using a CSS class or id to target your specific container instead.