cmux Custom Sidebar

cmux renders custom sidebars from a small SwiftUI-style file at runtime: no Xcode, no build step, no signing. The file hot-reloads on save, binds to live cmux state (workspaces, tabs, git, PRs, clock), and runs real cmux commands on tap.

The person asking is describing a result ("a sidebar that shows my workspaces and lets me jump between them"), not an implementation. Make the engineering decisions for them; do not ask them about SwiftUI, files, or syntax.

This skill is the workflow summary. Read the complete authoring contract (every supported view, modifier, language feature, and data field) before writing a non-trivial sidebar:

cmux docs sidebars
curl -fsSL https://raw.githubusercontent.com/manaflow-ai/cmux/main/docs/custom-sidebars.md

Workflow

1. Enable the beta (once): Settings > Beta features > Custom sidebars (customSidebars.beta.enabled). If a written sidebar does not appear in the picker, check this first.
2. Write a named file at ~/.config/cmux/sidebars/<name>.swift. The name becomes the menu label; use short kebab-case. The file is a single SwiftUI-style view expression (no struct, no var body, no imports). A .json variant exists for static layouts; prefer .swift for anything dynamic.
3. Validate and select:

   cmux sidebar validate <name>   # parse/interpret check with real data shapes
   cmux sidebar select <name>
   

   The user can also right-click the sidebar toggle button to pick it.
4. Iterate. Saving hot-reloads in place (cmux sidebar reload forces it). Verify rows show real data and taps do the right thing before declaring it done.

Authoring rules