What is an Immutable Audit?

An audit log is only valuable if it can be trusted. If an attacker who compromises an AI agent can also modify or delete the logs of what that agent did, the audit trail is worthless. If an insider can alter records to hide a policy violation, the compliance control is theatre. Immutability is what makes an audit log a source of truth rather than a suggestion.

For AI agent operations, immutable audit is particularly important because agents operate at machine speed. A compromised agent could make hundreds of malicious tool calls in seconds. If the logs are mutable, evidence of those calls could be erased before anyone notices. Immutable logs ensure that even if the agent or its environment is compromised, the record of what happened survives.

Immutability can be achieved through several mechanisms: write-once-read-many (WORM) storage, cryptographic hash chains where each log entry includes the hash of the previous entry, append-only databases, or external log services that the agent has no write access to. The key property is separation of concerns — the system that generates the log should not be able to alter it after the fact.

Intercept generates structured decision logs for every tool call evaluation. These logs are designed to be forwarded to external immutable storage — S3 buckets with object lock, append-only logging services, or SIEM systems with tamper-evident storage. Because Intercept emits logs as structured events, they can be cryptographically signed or hash-chained at the destination. The proxy itself does not store long-term logs, following the principle that the enforcement point and the audit store should be separate systems.