Common failure modes and fixes

Hallucinated facts
  → strict grounding instruction + abstain-on-low-coverage + show citations
Right answer not retrieved (low recall)
  → better chunking, hybrid retrieval, higher k, query rewriting
Irrelevant chunks crowding the prompt (low precision)
  → re-ranking, lower k, metadata filtering
Lost in the middle (model ignores mid-prompt context)
  → fewer, better chunks; reorder
Stale answers
  → re-index on source change (content hash)
Ambiguous query
  → query expansion / rewriting before retrieval