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The Agent Sentinel SDK writes append-only JSON Lines to a local ledger by default.

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Location

Default path (relative to your current working directory): 
.agent-sentinel/ledger.jsonl
Override the base directory with: 
export AGENT_SENTINEL_HOME="/var/log/my-agent"

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Format (JSONL)

Each line is a complete JSON object representing one action: 
{
  "id": "uuid",
  "timestamp": "ISO-8601",
  "action": "action_name",
  "cost_usd": 0.01,
  "duration_ms": 123.4,
  "outcome": "success",
  "tags": ["tag1", "tag2"],
  "payload": {
    "inputs": {"args": [], "kwargs": {}},
    "outputs": {}
  }
}

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Fail-open behavior

Ledger writes are fail-open: if the SDK cannot write (permissions, disk full, etc.), it logs an internal error and your agent continues.

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PII / secrets

Inputs and outputs may contain sensitive data. You should treat the ledger like application logs:
  • Store it securely
  • Rotate and redact if needed
  • Avoid logging raw secrets in tool inputs

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Rotation

Ledger files grow over time. A simple rotation pattern: 
mv .agent-sentinel/ledger.jsonl .agent-sentinel/ledger-$(date +%Y%m%d).jsonl
gzip .agent-sentinel/ledger-*.jsonl