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Glossary

Overlay sidebar

Last updated

Definition

An overlay sidebar is a separate app that draws its own panel over part of another app's window, usually its sidebar, to add features while the original app keeps running unchanged underneath.

Also called: overlay app, companion app.

The overlay doesn't modify the app it sits on. It works from the outside: it follows the host window's position and size, reads what it needs from data the host already keeps, and hands actions back to the host, for example by opening one of the host's own links. On macOS, following and moving another app's windows is the kind of job Apple's Accessibility API exists for: Apple describes it as letting assistive applications communicate with and control other running apps.

Overlay sidebar vs wrapper client

Overlay sidebarWrapper client
What it isA panel over the official appAn app that rebuilds the chat UI or runs the agent's command-line tool inside its own window
Where you workIn the official appIn the wrapper
Official app's features and updatesKept, as the app ships themOnly what the wrapper supports
Typical strengthsNothing new to learn; adds a view across appsFull control of the interface: isolation, review, many agents
Typical riskDepends on how the host app stores data and draws its window, which can changeDepends on the agent's CLI or API, and lags new app features

Neither is better in general. A wrapper suits people who want one new workspace for many agents; an overlay suits people who already like the official apps and only miss something around them.

In Pairbar

Pairbar is an overlay sidebar for the Claude and Codex desktop apps. It draws a glass panel exactly over the sidebar of whichever app is in front, matching its width, position and rounded corners, reads the files the two apps keep on your Mac, and opens chats through their own claude:// and codex:// links. It never patches or injects into either app. Hold ⌥ (or ⌘) over it to peek at the app's own sidebar, or press ⌃⌥S to hide it. See the sidebar.

Frequently asked questions

Is an overlay the same as a plugin or extension?
No. A plugin runs inside the host app through an interface the host provides. An overlay is a separate app that sits on top of the host's window without loading anything into it.
Why would an overlay need the Accessibility permission on a Mac?
To follow, move or resize another app's windows, and to react to keys pressed while that app is in front. Pairbar uses it to put the Claude and Codex windows in one spot and to make ⌥/⌘ peeking instant; it's optional.
Can an overlay break when the host app updates?
Yes, if it relies on how the host stores data or lays out its window and that changes. Pairbar reads undocumented local files of the Claude and Codex apps, so an app update can break a feature until Pairbar is updated.

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