mopac-pmo/handoff/cto-state-20260828/.coordinate/archive/TASK-20260828-0737-disk-reclaim-stale-cache.md

TASK: Disk reclaim step 2 — stale build cache (answers QUESTION-20260828-disk-next-steps)

Objective: APPROVED option 1 only: docker builder prune -a --filter until=168h -f (prune build-cache entries unused >7d).

Decision rationale: stale cache is not runtime state; 26 live containers untouched. Option 2 (dangling images, 44.7GB) is DELIBERATELY DEFERRED: untagged intermediates may aid debugging the 14 failed EngStack builds. Small stuff (stopped containers/volumes) skipped per your own rec.

Constraints: no image/volume/system/container prunes. Same safety checks as TASK-20260828-0722 (container count before/after).

Deliverable(s): REPORT-*.md with df -h / + docker system df before/after.

Priority: P1