Python appears in macOS Dock when Copilot CLI starts LSP servers

Summary

When the Copilot CLI app starts a session, it launches Python LSP language servers that register as GUI applications in the macOS Dock. The Python icon appears in the Dock and persists even after the server process exits (with failure). This is disruptive — users do not expect a terminal/CLI tool to spawn visible GUI processes.

Filed by GitHub Copilot on behalf of @hubwriter.

Environment

• OS: macOS (Darwin, Apple Silicon)
• Copilot CLI version: 1.0.70
• Python: /usr/bin/python3 (system Python)
• Affected LSP servers: lsp-python (and possibly others — all 6 LSP servers fail on startup in this environment)

Steps to Reproduce

1. Open the Copilot CLI app
2. Start or resume any session in a repository
3. Observe the macOS Dock

Expected Behavior

• LSP servers should run as background-only processes
• No icons should appear in the macOS Dock or app switcher
• Failed LSP servers should not leave visible artifacts in the UI

Actual Behavior

• Python icon appears in the macOS Dock when lsp-python is launched
• The icon persists even after the process exits with code 1
• This happens on every session start/refresh, repeatedly
• All 6 LSP servers (typescript, omnisharp, ruby, rust, python, go) fail to initialize but Python is the only one that shows a Dock icon

LSP Server Status (all failing)

lsp-typescript — exited with code 1
lsp-omnisharp  — exited with code 131
lsp-ruby       — exited with code 127
lsp-rust       — exited with code 1
lsp-python     — exited with code 1
lsp-go         — exited with code 1

Suggested Fix

1. Set LSBackgroundOnly or LSUIElement in the Python subprocess environment or use LSBackgroundOnly in the process launch to prevent Dock registration
2. Use NSApplication.setActivationPolicy(.prohibited) or equivalent when spawning LSP subprocesses
3. Do not launch LSP servers that will fail — if the server binary is not available or crashes on startup, skip it rather than retrying each session
4. Launch Python with -S or as a module in a way that does not trigger the macOS window server registration (e.g., avoid importing Tk/tkinter)

Workaround

Users can manually add LSBackgroundOnly to the Python.app Info.plist:

sudo /usr/libexec/PlistBuddy -c "Add :LSBackgroundOnly bool true" \
  /Library/Frameworks/Python.framework/Versions/3.X/Resources/Python.app/Contents/Info.plist

But this affects all Python GUI applications system-wide, which is not ideal.

Start by reproducing the issue on macOS, then trace how the Copilot CLI launches the lsp-python subprocess and whether failed LSP servers are retried on session start. Compare the launch environment with the suggested background-only options. Done means LSP servers run without Dock or app-switcher entries, and failed servers leave no persistent UI artifacts.