ANSI colors css missing

[mvanderlee]

Related: jupyter-widgets/ipywidgets#3957

Environment data

• VS Code version: 1.98.2
• Jupyter Extension version (available under the Extensions sidebar): 2025.2.0
• Python Extension version (available under the Extensions sidebar): 2025.2.0
• OS (Windows | Mac | Linux distro) and version: Windows 11
• Python and/or Anaconda version: 3.11.3
• Type of virtual environment used (N/A | venv | virtualenv | conda | ...): virtualenv
• Jupyter server running: Local

Expected behaviour

I expect ANSI colors to be shown

Actual behaviour

ANSI colors are not rendered

Steps to reproduce:

import ipywidgets as widgets

print("\033[91mHello World\033[0m")
output = widgets.Output()
output.append_stdout("\033[91mHello World\033[0m")
output

The element has the correct CSS class, but the class stylesheet is missing.
https://github.com/jupyterlab/jupyterlab/blob/main/packages/rendermime/style/base.css#L126

[mvanderlee]

Workaround: Import the missing stylesheet manually.

from IPython.display import HTML
from urllib.request import urlopen
html = urlopen("https://raw.githubusercontent.com/jupyterlab/jupyterlab/refs/heads/main/packages/rendermime/style/base.css")
HTML(f"<style>{html.read().decode('utf-8')}</style>")