Collapsible Stderr Warnings

The theme automatically detects and collapses stderr output in Jupyter notebook cells, improving the reading experience when code produces verbose warnings.

How It Works

When a notebook cell produces stderr output (typically warnings), the theme:

1. Detects the stderr output in the cell

2. Wraps it in a collapsible interface

3. Displays a compact “⚠ Code warnings” button

4. Allows readers to expand/collapse the warnings

Example

Before (stderr visible by default)

model = create_js_with_sep_model()
...

W1123 10:15:26.780179   23830 cuda_executor.cc:1802] GPU interconnect information not available...
W1123 10:15:26.783637   23767 cuda_executor.cc:1802] GPU interconnect information not available...

After (with collapsible feature)

model = create_js_with_sep_model()
...

[⚠ Code warnings ▶]  (click to expand)

Benefits

• Cleaner presentation — verbose warnings don’t disrupt reading flow

• Information preserved — warnings remain accessible when needed

• Automatic — no manual tagging or configuration required

• User control — readers can view warnings when troubleshooting

Technical Details

• Runs on page load via DOMContentLoaded event

• Works with any number of stderr outputs per cell

• Compatible with dark mode

• Includes ARIA attributes for screen readers

CSS Customization

Target these classes to customize the appearance:

• .stderr-collapsible-wrapper — the outer container

• .stderr-toggle-button — the clickable button

• .stderr-content — the expandable content area

• .stderr-icon — the warning icon

• .stderr-label — the “Warnings” text

• .stderr-chevron — the expand/collapse indicator