Log Immutability

Explanation

Log immutability checks that the decision traces a bank's AI systems produce cannot be altered or deleted after the fact — they are written once and preserved exactly as recorded. This matters because audit and dispute defence rely on records that demonstrably have not been tampered with; an editable log proves nothing, since a wrong or contested decision could appear to have been logged differently. It is measured by the Log Immutability Score (the calcMethod is given simply as Log Immutability Score, so report the proportion of decision traces held in genuinely immutable storage rather than inventing a formula). Implement it by routing all decision traces from Document Extraction, RAG, and Summarization and Chat into a WORM (write-once-read-many) or equivalent immutable store, enforcing append-only writes, applying cryptographic hashing or sealing so any alteration is detectable, and retaining the traces for the required period; the evidence is the storage configuration plus integrity checks. The threshold requires that 100% of decision traces sit in a WORM or immutable store; any trace found in mutable storage is a breach that must trigger immediate remediation of the logging path, because it undermines the trustworthiness of the entire audit trail.