Ask @workspace where something is actually handled before you change it

Why this works

@workspace is the Copilot Chat participant scoped specifically to search and reason across the current workspace rather than only the open file or the current selection — it is the mechanism that makes a genuinely cross-file question answerable at all inside Copilot Chat's normal editor-context window. A bare where is X handled without structure tends to return the file the model finds most semantically central rather than an exhaustive list, because nothing tells it exhaustiveness is the goal over a single good-enough answer; asking for every file plus the specific export forces coverage instead of a representative example. Separating source of truth from downstream consumer matters because the real risk in a cross-cutting change is rarely the file you are editing — it is the file depending on the old shape that nobody remembers to update, which is the exact question a change-impact review exists to answer. The instruction to say not found rather than infer a plausible file directly targets @workspace's failure mode under thin retrieval: producing a confident-sounding file reference that matches the pattern of what should exist in a codebase like this one, rather than what this codebase actually has.