Runaway Background LLM Corrupted Mac Mini's APFS Volume, Caused 24-Hour Recovery

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A developer running local AI agents on a Mac Mini M4 with 24 GB unified memory suffered a full system failure after a background server autonomously loaded two large language models — a 14B and an 8B — without user intervention. The disk was already nearly full, leaving no room for macOS to write swap files when unified memory overflowed, resulting in I/O errors that corrupted the APFS boot volume's metadata beyond self-repair. Recovery mode confirmed the volume could not mount, and the fsck_apfs repair tool failed to reconcile the inconsistent metadata, costing over a day to restore the system. The root cause was traced to a global config that treated a preference for local model delegation as permission to auto-start servers, entirely bypassing the user. The permanent fix was a hard, code-level block preventing model loading when disk space is insufficient — not a documentation note — alongside a revival checklist, underscoring that on unified-memory Macs, free disk space functions as a critical memory safety net.

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