Agent Flight Recorder: Tamper-Evident Audit Trail for Long-Horizon Agents (Defensive Research)

Technical Analysis

The paper introduces 'Agent Flight Recorder,' a logging architecture that captures structured events (intent, execution, provenance) for long-horizon tool-using agents, using hash chaining and Merkle tree batching to make logs tamper-evident, with periodic on-chain anchoring of epoch roots for cross-organizational non-repudiation. It is explicitly framed as forensic infrastructure to investigate incidents such as an agent deleting a production database or prompt injection propagating across multiple agents, rather than a mechanism that introduces new attack surface. The system's value lies in enabling independent, trust-minimized verification of agent action history after an incident, improving detection of edit/delete/reorder/fork tampering and improving structured forensic query precision over unstructured log search. No exploit, vulnerability, or attack technique against agents, tools, or protocols is disclosed; the closest relevance to threats is as a countermeasure against cascading failures and cross-agent prompt injection propagation, which are referenced only as motivating scenarios.

Detection Signatures

• N/A - this is a defensive/logging research proposal, not an attack; no malicious indicators to detect. Relevant monitoring pattern: absence of tamper-evident audit logging in long-horizon agent deployments increases blast radius of undetected cascading failures or injection propagation.

Remediation Steps

1. 1

   Evaluate audit-trail architectures

   Consider adopting tamper-evident, hash-chained logging (with optional on-chain or third-party anchoring) for long-horizon or multi-agent systems to enable post-incident forensic analysis.

2. 2

   Instrument structured event logging

   Capture agent actions with structured semantic fields (intent, tool call, execution result, provenance) rather than relying solely on unstructured text logs, to support high-precision forensic queries.

3. 3

   Establish cross-organizational verification

   For multi-party agent ecosystems, use neutral, independently verifiable anchoring (e.g., periodic cryptographic commitments) so no single party can unilaterally alter historical records during dispute resolution.

4. 4

   Integrate with incident response

   Use tamper-evident logs to investigate and contain cascading tool-use failures and cross-agent prompt-injection propagation faster, reducing dwell time and blast radius.