Fresh prod install ran Grav rc.10 (stale .env.prod GRAV_VERSION), so GPM would not serve the api plugin (needs >=2.0.4); admin2 (auth via /api/v1) then 404'd login silently. Documents the dead ends (deploying api config, gpm index -f, same-channel assumption) and the fix (self-upgrade core + reinstall + bump .env.prod). Adds reciprocal 'same 2026-07-04 cutover' cross-links across the three sibling deploy gotchas. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Np4cMQLF77i664CAQXySzU