Token refresh for AI agents: keeping long-running tasks authenticated

Token refresh is the process of exchanging a long-lived refresh token for a new access token once the current one expires, so an agent can keep acting on an app without asking you to sign in again. Access tokens are short-lived by design, typically about an hour, so any agent task that runs longer than that will hit an expired token unless something refreshes it in the background.

Why tokens expire in the middle of a task

OAuth providers issue two things at the end of a consent flow: a short-lived access token used on every API call, and a longer-lived refresh token used only to mint new access tokens. Typical access token lifetimes:

An agent that triages a mailbox for ninety minutes, or a scheduled job that runs unattended overnight, will cross at least one expiry boundary. The API call that crosses it returns 401 Unauthorized, and an agent without refresh logic simply fails, usually in a way that looks like a permissions bug rather than an expiry.

Reactive refresh versus proactive refresh

There are two ways to handle expiry, and the difference matters more than it looks.

Reactive refresh waits for a 401, exchanges the refresh token, and retries the original call. It is simple and it wastes no refreshes, but every expiry costs one failed round trip, and the retry has to be genuinely idempotent or you risk sending the same message twice.

Proactive refresh checks the expiry timestamp before each call and refreshes early if the token is close to the end of its life. Calls never fail for expiry, at the cost of tracking expiry per connection.

Production setups generally do both: refresh proactively, and still catch the 401 for the cases where a token was revoked or invalidated early.

The four ways refresh actually breaks

Expiry is the easy part. These are the failures that cost real debugging time.

1. Refresh token rotation. Some providers issue a new refresh token every time you refresh and immediately invalidate the old one. If you store the new one and the write fails, or two workers refresh concurrently and one overwrites the other, the connection is dead and the user has to reconnect. Concurrent refresh is the classic multi-worker bug here.
2. invalid_grant. The catch-all error when a refresh token no longer works: the user revoked access, changed their password, the token went unused past the provider's idle window, or an admin removed the app. It is not retryable. The only fix is a fresh consent flow.
3. Confusing 401 with 403. A 401 means the token is bad and refresh may help. A 403 means the token is fine but lacks the scope, or the account cannot reach that resource. Retrying a 403 with a refreshed token fails forever. See OAuth for AI agents on scopes.
4. Silent failure in unattended runs. When a scheduled agent hits a dead connection at 3am, nobody sees the error. Without a stored state flag and a way to surface it, the first sign of trouble is missing work.

Who should own the refresh loop

If you wire up an integration yourself, you own all of the above, once per provider, and each provider does it slightly differently. That is the real cost: not writing one refresh function, but maintaining a dozen of them against APIs that change without asking.

A hosted app connector centralises it. Tokens live server-side and encrypted, refresh happens outside the agent's process, and the agent's machine never stores app credentials at all. The agent just calls tools and they work.

That is ClawLink's model. Refresh is handled upstream of the agent, credentials are stored encrypted and cached briefly for performance, and when a connection genuinely cannot be recovered it is marked as needing re-authentication rather than failing silently. The failed tool call comes back with a clear reason and a reconnect path, so the agent can tell you what to do instead of retrying a dead token in a loop.

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