The cache key hashed filename + size + mtime. PVC remounts on different
nodes change file timestamps without changing data, producing a different
key every pod boot. Result: fxcache MISS on every H100 run, forcing
10+ min DBN feature extraction from 148GB raw MBP-10 data.
Fix: hash filename + size only. Deterministic across remounts.
Note: existing cache must be rebuilt once (key format changed).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>