Problem

When multiple dialogs were stacked (nested dialogs), the second and subsequent dialogs could not scroll properly when their content exceeded the viewport height. Users could scroll the first dialog normally, but any additional dialogs opened on top would have their scrolling functionality broken.

Root Cause

The CSS rule .modal-multiple .modal-dialog used position: fixed with inset: 0, which made nested dialogs fill the entire viewport and overrode Bootstrap's normal modal scrolling behavior. This prevented the standard Bootstrap modal scrolling mechanism from functioning correctly.

Solution

Enhanced the CSS for multiple dialogs to maintain proper modal behavior while preserving the stacking functionality:

.modal-multiple .modal-dialog {
    position: fixed;
    inset: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: var(--bs-modal-margin, 0.5rem);

    // Ensure scrolling works for multiple dialogs
    .modal-content {
        max-height: calc(100vh - var(--bs-modal-margin, 0.5rem) * 2);
        overflow: hidden;
        display: flex;
        flex-direction: column;
    }

    .modal-body {
        overflow-y: auto;
        flex: 1 1 auto;
    }
}

The fix:

1. Maintains proper centering using flexbox layout
2. Preserves modal spacing with Bootstrap's modal margins
3. Controls content height to fit within viewport constraints
4. Enables scrolling in the modal body while keeping headers/footers fixed

Testing

• All existing unit tests pass (27/27 dialog/modal tests)
• Created comprehensive test page demonstrating the fix
• Verified nested dialogs now scroll properly at any depth
• No breaking changes to existing modal functionality

Before/After

Before: Nested dialogs filled entire viewport, no scrolling possible
After: Nested dialogs properly centered and scrollable, maintaining Bootstrap modal behavior

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