If you suspect index corruption in Vald, set agent.ngt.broken_index_history_limit to 1 or more before restarting the pod. By default the agent discards a broken index and keeps running, which deletes the evidence you need to find the cause, like a crash during a save-index operation or partial storage corruption.

Context: Official backup guide: documents the gotcha that a corrupted Vald index is discarded by default. The agent fails to load the broken index file, deletes it, and keeps running. Teams that need to investigate corruption later must set agent.ngt.broken_index_history_limit to at least 1, which preserves generations of broken indexes under the index path for later inspection.

## Matched source
Source: Published skill
Original query: "Vald discards corrupted indexes by default, enable backup to investigate"
Key terms: backup, corrupted, default, discards, enable, indexes, investigate, vald