Guardian Replay

Why this exists

CISOs and compliance teams face a recurring objection when evaluating AI governance tools:

"How do I know the governance layer was actually enforced — and not tampered with after the fact?"

Guardian Replay addresses this directly. Every POST /v1/authorize decision is stored with a replay envelope — a cryptographic snapshot of all inputs, policies, and the resulting verdict. Any decision can be reproduced exactly, byte-for-byte, at any future point in time.

How it works

When a decision is made, ABS stores a replay_envelope alongside the normal proof_hash:

Authorize request
  ↓
Policy evaluation
  ↓
Decision (ALLOWED / DENIED)
  ↓
[Replay envelope persisted] ← agent_id, tool_name, input_hash,
                               policy_version, timestamp, verdict,
                               risk_score, proof_hash

The envelope uses content-addressed storage: the proof_hash is a SHA256 of the full decision payload, so any modification to the stored data is immediately detectable.

Inspect a stored decision

GET /v1/decisions/{decision_id}/replay
Authorization: Bearer {your-api-key}

{
  "decision_id": "dec_01JN8K...",
  "verdict": "DENIED",
  "risk_score": 95,
  "proof_hash": "a3f8c2...",
  "timestamp": "2026-02-20T18:44:41Z",
  "replay_envelope": {
    "agent_id": "claudebot-prod",
    "tool_name": "exec_cmd",
    "input_hash": "b9e1d4...",
    "policy_tag": "FINANCIAL",
    "policy_version": "2.1.0",
    "risk_level": "HIGH"
  }
}

Re-run the decision (integrity check)

POST /v1/decisions/{decision_id}/replay
Authorization: Bearer {your-api-key}

ABS re-evaluates the stored envelope against the policy engine and compares the result:

{
  "decision_id": "dec_01JN8K...",
  "integrity": "VERIFIED",
  "original_verdict": "DENIED",
  "replayed_verdict": "DENIED",
  "proof_hash_match": true,
  "replayed_at": "2026-02-21T09:00:00Z"
}

If the policy was changed between the original decision and the replay, or the stored data was modified:

{
  "integrity": "INTEGRITY_VIOLATION",
  "original_verdict": "DENIED",
  "replayed_verdict": "ALLOWED",
  "proof_hash_match": false,
  "divergence_reason": "Policy version changed: 2.1.0 → 2.2.0"
}

Use cases

Compliance audit: An auditor requests proof that agent claudebot-prod was blocked from calling exec_cmd on Feb 20. You provide the decision ID — they can verify independently.

Post-incident forensics: An unauthorized action occurred. Replay all decisions in the incident window to find the first policy miss.

Policy regression testing: Before promoting a new policy version, replay the last 30 days of decisions to see what would have changed.

Availability

Replay envelopes are stored for all decisions made on ABS v10.1.5+. Decisions made before this version will return a 404 with the message "It may predate Guardian Replay (v10.1.5).".

Envelopes are subject to your configured audit log retention policy.