Full-Height Native Sidebar Integration (0-100% Viewport)

[Numek]

Summary

Allow the Firefox sidebar to extend across the entire height of the browser window (from the very top to the bottom edge of the screen). This requires modifying the structural hierarchy of the UI so that the sidebar is no longer strictly confined beneath the tab and address bar (#navigator-toolbox).

Description of the Current Issue

The current architecture of the Firefox interface stacks elements in a rigid vertical layout: the main toolbox (tabs, URL bar, bookmarks) occupies the full horizontal width at the top, forcing the sidebar (#sidebar-box) to sit entirely below it.

With the rise of modern web tools designed for sidebar integration — particularly AI chatbots (Gemini, ChatGPT) or persistent messaging feeds — this design choice creates a significant usability bottleneck:

• Severe Vertical Compression: The sidebar loses critical vertical pixels right from the start, squeezed under the main browser navigation header.

• The "Corridor Effect" (Constant Scrolling): Text-heavy AI responses are forced into a narrow, vertically restricted column. Users must constantly scroll up and down just to read a simple multi-paragraph answer.

• Lack of Flexibility: Current workarounds (like Split View) do not allow users to quickly show or hide the panel via a smooth toggle button without completely disrupting the layout of the open tabs.

Target Behavior (Inspiration from Competitors)

Browsers like Opera have solved this by making the sidebar a "master" component of the horizontal layout.

The goal is to provide an option in Firefox to switch to this structure:

1. 100% Height Viewport: The sidebar claims the entire left (or right) edge of the screen, from pixel 0 at the top to the very bottom.

2. UI Shifting: The tab bar, address bar, and main page content are pushed over to occupy the remaining width.

3. Instant Toggle: A dedicated shortcut or button cleanly slides the full-height panel in and out of view without any visual clutter breaking the top layout.

Benefits for Firefox

• Modernizing the UX: Aligns Firefox with current web trends, where vertical multitasking (AI assistance + active browsing) has become standard workflow.

• Enhanced Visual Comfort: Massive vertical screen real estate gains for reading data, feeds, or text-based conversations.

• Retaining Power Users: Solves a deep UI customization request that modern extensions cannot technically achieve due to current WebExtension API constraints.

[Jon]

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