mopac-pmo/handoff/cto-state-20260828/.coordinate/archive/QUESTION-20260828-disk-next-steps.md

QUESTION: next disk-reclaim step (post TASK-20260828-0722)

Dangling build-cache prune done (+39G free, / at 80%), but free space is 53G/274G = 19.3%, still below the 20% bar. Measured remaining reclaimable (docker system df, post-prune):

1. Unused build cache (biggest win) Build Cache now 66.43GB total, only 121.8MB dangling. Most of the 66GB is unused-but-referenced cache. Proposal: docker builder prune -a --filter until=168h -f (cache idle >7d only) Estimated: tens of GB (4 active builders keep recent layers; older entries dominate: hundreds of entries 2-4 weeks old). Risk: slower next builds for EngStack (cache rebuild), no runtime impact.

2. Dangling images (TASK said do NOT touch yet) Images: 44.71GB reclaimable (dangling only, tagged images untouched). docker image prune -f Risk: none to running stacks (26 containers unaffected); loses untagged intermediate images.

3. Smaller: stopped containers 296.1MB, unused volumes 1.139GB. Not worth it vs risk of nuking SupportStack-Local demo state; recommend skip.

Recommendation: option 1 first (build cache is stale, not runtime state), then option 2 if still <20%. Need PMO decision; not proceeding autonomously.