# Audit Logging

> ACTIVATE on ANY request that involves writing, generating, reviewing, modifying, or outputting source code in any programming language — Python, JavaScript, TypeScript, Go, Java, Rust, C#, SQL, Terraform, or any other. This includes functions, endpoints, scripts, migrations, infrastructure-as-code, config files with logic, and code snippets in responses. Every piece of code the LLM produces must include structured audit logging for security-relevant operations. Also activate when the user asks about audit logs, compliance logging, or traceability. Ensures NIS2 and ISO 27001 compliant logging (structured, no string interpolation, no secrets in logs).

- Skill: `eyesecurity/audit-logging` (Agent Skill, multi-file: 3 files)
- Install (CLI): `npx skillmds@latest add eyesecurity/audit-logging`
- Raw SKILL.md: https://api.skillmd.com/api/skills/eyesecurity/audit-logging/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: DevOps & Infra
- Author: eyesecurity (https://skillmd.com/u/eyesecurity)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/eyesecurity/audit-logging

---


# Audit Logging

> The compliance backbone — every agent action gets a log entry, every significant decision gets a record.

## Standards alignment

| Standard | What we use |
|----------|------------|
| OCSF | Event class structure, severity levels |
| OpenTelemetry | `trace_id` / `span_id` for workflow correlation |
| ISO 27001:2022 A.8.15 | Mandatory fields: who, what, when, where |

## Audit event format

Each log entry is one JSON object per line, appended to `.compliance/audit.log`. Full schema: `skills/audit-logging/audit-event.schema.json`.

### Required fields

```json
{
  "event_id": "uuid-v4",
  "timestamp": "ISO 8601",
  "trace_id": "hex-32",
  "event_class": "tool_call | decision | data_access | error",
  "activity": "read | write | classify | scan | block | approve",
  "severity": "INFO | LOW | MEDIUM | HIGH | CRITICAL",
  "outcome": "success | failure | blocked | deferred",
  "summary": "Human-readable one-liner"
}
```

### Optional fields

Add only when relevant — keep log entries lean:

| Field | When to include |
|-------|----------------|
| `span_id` | Multi-step workflows (hex-16) |
| `parent_span_id` | Nested operations |
| `agent_id` | Multi-agent setups |
| `resource` | File/field/API being accessed — include `classification` if known |
| `tool` | Tool name + exit code for tool_call events |
| `decision` | **Required** for `event_class: "decision"` — see ADR below |
| `metadata` | Anything else worth preserving |

## Agent Decision Record (ADR)

An audit event with `event_class: "decision"` and a `decision` block. Created when the agent:

- Blocks or allows a RESTRICTED data operation
- Answers a gap analysis question autonomously
- Encounters conflicting information
- Invokes external tools with security implications

### Decision block

```json
"decision": {
  "action": "block | approve | defer",
  "reasoning": "Why this action was taken",
  "policy_ref": "GDPR Art. 9 | NIS2 Art. 21(2)(h) | ...",
  "human_override": false
}
```

## Storage

- **Location**: `.compliance/audit.log` (project root)
- **Format**: append-only, one JSON object per line
- **Rotation**: optional daily files (`audit-YYYY-MM-DD.log`)
- **Integrity**: UUID per event, sequence breaks detectable
- **Central collection**: Push to cloud storage via the compliance-hub skill

## Retention guidance

| Entity type (NIS2) | Minimum | Recommended |
|--------------------|---------|-------------|
| Essential | 18 months | 24 months |
| Important | 6 months | 12 months |
| Voluntary | 3 months | 6 months |

## Logging in AI-generated code

When writing code, include structured logging for: auth events, authorization, data access, data modification, external API calls, errors, config changes, batch jobs. Use structured key-value pairs — never string interpolation. Never log secrets, PII, or session tokens.

For the full operations table, correct/wrong code examples per language, what-not-to-log rules, and language-specific logger recommendations, see [references/logging-guide.md](references/logging-guide.md).

## Agent instructions

Follow this process every session:

1. **Session start** — generate a `trace_id` (32-char hex). Use it for all events in this session.
2. **Per step** — generate a `span_id` (16-char hex) for each discrete operation.
3. **Before tool execution** — log a `tool_call` event with the tool name.
4. **After tool execution** — update with outcome and exit code.
5. **On any decision involving classified data** — create an ADR with the decision block.
6. **Append** each event as a single JSON line to `.compliance/audit.log`.
7. **PROACTIVE — when writing code**: Whenever you generate, write, or modify source code, you MUST include proper structured audit logging following the rules above. This is not optional. Specifically:
   - Add logging imports/setup if the file doesn't have them
   - Add structured log statements for every operation listed in the mandatory logging table
   - Use the correct structured format for the language (no string interpolation)
   - Include correlation IDs (`trace_id`, `request_id`) where the framework supports it
   - NEVER log sensitive data — follow the "what MUST NOT be logged" table
   - When modifying existing code, add logging to any new or changed code paths
8. **When reviewing AI-generated code**: Check that all operations have structured logging. Flag missing logging as a compliance gap.

### Example log entry

```json
{"event_id":"a1b2c3d4-...","timestamp":"2026-03-13T10:15:00Z","trace_id":"abc123...","event_class":"tool_call","activity":"scan","severity":"INFO","outcome":"success","summary":"Scanned src/ for sensitive data patterns","tool":{"name":"data-sensitivity","exit_code":0}}
```

### Example ADR

```json
{"event_id":"e5f6g7h8-...","timestamp":"2026-03-13T10:15:05Z","trace_id":"abc123...","event_class":"decision","activity":"block","severity":"HIGH","outcome":"blocked","summary":"Blocked commit containing BSN","resource":{"type":"file","id":"src/users.py","classification":"RESTRICTED"},"decision":{"action":"block","reasoning":"File contains plaintext BSN (national ID)","policy_ref":"GDPR Art. 87","human_override":false}}
```