Open Extensions (Cmd+Shift+X), search "Phel Lang", click Install. Or:
code --install-extension Phel-Lang.phel-lang
Requires VS Code 1.75+.
Configuration
The extension expects the Phel CLI at vendor/bin/phel (Composer default). For other layouts, set phel.executablePath once in .vscode/settings.json:
{ "phel.executablePath": "bin/phel" }
Per-subsystem overrides (phel.diagnostics.command, phel.format.command, phel.test.command, phel.repl.command) take precedence when set. Full settings reference: docs/settings.md.