Do you work on a sandbox or directly on my live store?

Sandbox or local Stencil preview first, every time. We reproduce the bug on a stencil-cli preview or a sandbox store and fix it there before anything touches your live storefront. Because theme changes ship via stencil bundle + Git, the live push is a reviewable, revertible theme version, not a blind edit in the file browser. API and webhook changes are tested against a sandbox store too.