No single retention period fits every AI agent log. Keep each log class for the longest period that a law, contract or investigation need requires, and no longer. Write the period down, apply it automatically, and delete on schedule, because logs also hold sensitive data.
What the guidance says
OWASP's logging cheat sheet states the principle plainly: log data must not be destroyed before the required retention period ends, and must not be kept beyond it. It adds that legal, regulatory and contractual obligations can set those periods. So the honest answer to "how long" starts with "what are you obliged to keep, and why?"
I will not give you a number of days, because the right one depends on your sector, your customers' contracts and your own incident history. Check with your compliance and legal contacts.
Split the logs into classes
Agent systems produce several kinds of record, and they do not need the same lifespan.
| Log class | Typical purpose | Retention driver |
|---|---|---|
| Approval and access decisions | Show who allowed what | Audit and contract evidence |
| Tool call records (name, caller, outcome) | Reconstruct actions | Investigation and audit |
| Full prompts and model outputs | Debugging, quality | Privacy risk, keep short |
| Debug and trace data | Engineering | Shortest of all |
Approval records and tool call metadata are small and valuable, so they tend to justify longer storage. Full prompts and outputs are bulky and often contain personal or confidential data, so they tend to justify shorter storage.
Steps to set a period
- List who might ask for the records: auditors, customers, regulators, your own incident team.
- For each log class, note any obligation that names a period. Ask legal, do not guess.
- Where nothing is mandated, pick a period based on how long you realistically investigate. A slow discovery needs longer history than a fast one.
- Write the period into a retention table and link it to the agent registry.
- Automate deletion and test it. A policy no job enforces is only a wish.
- Add a legal hold path so that an open investigation pauses deletion for the relevant records.
Retention is also a risk decision
OWASP warns that logs can contain personal data and technical secrets, and that attackers target them. Every extra month you keep a full prompt log is another month it can leak. This is why metadata and content should be stored and aged separately.
Do not forget copies. Backups, exports and the temporary debug files that an engineer enabled last quarter all count. OWASP says disposal applies to backups, copies and extractions too.
When retention and deletion requests collide
If a log holds personal data, a deletion request or privacy rule may conflict with a long retention period. Resolve this in advance with your privacy team by keeping personal content out of the long term records in the first place. Keeping identifiers and action metadata rather than full text makes the conflict much smaller.
Safeguard offers compliance and evidence automation for teams that need records organized for audits, and a free scan is available at https://gold.safeguard.sh/scan.
Quick check
Is longer retention always safer?
No. Longer retention helps investigations but increases privacy and leak risk. Keep what you need and delete the rest.
Do backups of logs follow the same period?
Yes. Copies, exports and backups should be disposed of on the same schedule.
Sources
Last reviewed: 19 October 2026.
