feat: collapsible sidebar

[basmilius]

What Changed

• Added a sidebar.toggle keybinding command bound to mod+b by default, gated on when: "!terminalFocus" so it stays out of the way inside the terminal drawer.
• Added a matching Toggle sidebar action to the command palette that surfaces the active shortcut hint.
• Lifted SidebarProvider to the root layout so both the palette and the global chat shortcut handler can call useSidebar().toggleSidebar().
• Exposed sidebar open/collapsed state via data-state on the sidebar wrapper so chrome can react with group-data-* classes instead of reading the context everywhere.
• Electron drag-region headers (ChatView, NoActiveThreadState, settings) reserve pl-[90px] when the sidebar is collapsed so the macOS traffic lights don't overlap the active title. Windows/Linux fall through to the existing wco: overrides. The padding transitions at the same duration-200 ease-linear as the sidebar width, so it slides in sync.
• Ran the sidebar toggle on the capture phase because Lexical's core onKeyDown claims mod+b for the bold command and calls preventDefault, which would trip the event.defaultPrevented guard in the shared handler.
• Updated apps/web/src/keybindings.test.ts, apps/server/src/keybindings.test.ts defaults, and KEYBINDINGS.md.

Why

Closes #2282. The thread sidebar was always visible, which made it hard to fully focus on the active chat. A toggle is the smallest useful change that enables focus mode while keeping thread switching (mod+1..9, mod+shift+[/]) available even when the sidebar is collapsed — those listeners live on window in Sidebar.tsx and the sidebar DOM stays mounted under collapsible="offcanvas", so nothing extra was needed to satisfy that requirement from the issue.

Reusing the existing SidebarProvider / useSidebar() / cookie persistence already shipped in ui/sidebar.tsx kept the diff small and means sidebar state still survives reloads.

UI Changes

Video attached showing open → collapsed → open with mod+b, thread switching while collapsed, and the animated header padding on macOS so the traffic lights aren't covered.

Schermopname.2026-04-23.om.12.20.58.mov

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for any UI changes
• I included a video for animation/interaction changes

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Note

Medium Risk
Introduces a new global shortcut (mod+b) and capture-phase keydown handler to toggle the sidebar, which can affect keyboard event precedence and editor behavior. Also changes layout/provider wiring and Electron header padding based on sidebar state, with moderate UI regression risk.

Overview
Adds a new sidebar.toggle command (default mod+b when !terminalFocus) and surfaces it as a Toggle sidebar action in the command palette.

Moves SidebarProvider to the authenticated root so both the command palette and chat route global shortcuts can call useSidebar().toggleSidebar(), and exposes sidebar state via data-state on the sidebar wrapper for styling.

Updates Electron drag-region headers (chat, empty state, settings) to adjust left padding with a transition when the sidebar is collapsed, and adds tests/docs for the new default binding (including a capture-phase handler so the toggle wins over in-editor mod+b).

^{Reviewed by Cursor Bugbot for commit 8f620b9. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Add collapsible sidebar with mod+b keyboard shortcut

• Adds a sidebar.toggle command bound to mod+b (when not in terminal focus) as a default keybinding in shared/src/keybindings.ts and registered in the keybindings contract.
• Moves SidebarProvider from AppSidebarLayout up to the root route so CommandPalette and the global shortcut handler can both access sidebar context.
• Adds a capture-phase keydown handler in _chat.tsx that intercepts mod+b before Lexical's bold handler can claim it.
• Exposes data-state on the sidebar wrapper div, allowing ChatView and NoActiveThreadState headers to animate left-padding on collapse via CSS group selectors.
• Adds a 'Toggle sidebar' action to the command palette with the sidebar.toggle shortcut.

^{Macroscope summarized 8f620b9.}

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[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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[macroscopeapp]

Approvability

Verdict: Needs human review

This PR introduces a new user-facing feature allowing users to collapse/expand the sidebar via mod+b shortcut. While well-implemented with tests, new UI capabilities warrant human review to ensure the behavior meets product expectations.

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[basmilius]

@juliusmarminge Do I need to authenticate with Vercel or is it something that needs approval?

[Almighty-Shogun]

For someone who doesn't use T3 on fullscreen, this is very usefull!

[vercel]

@basmilius is attempting to deploy a commit to the Ping Labs Team on Vercel.

A member of the Team first needs to authorize it.