thatguygriff/infra#1 turned the runner cache server on, so actions/cache has an endpoint for the first time. v4 rather than v3 because v4.2+ can speak the cache service v2 API, which is what the runner serves. The instrumentation step now also prints ACTIONS_CACHE_URL, so a single run shows the endpoint arriving and the cache being read in one log rather than needing a separate probe. Refs #178. Co-Authored-By: Claude Opus 5 <[email protected]> Claude-Session: https://claude.ai/code/session_01Uw545F1vveNJKjzLxdi2ks