scheduler agent set up a loop: every reschedule triggered a 'confirm your slot' email and candidates kept clicking...

TL;DR: Expire the old confirmation link on every reschedule and allow only one live confirmation per candidate. The loop is a state bug: rescheduling re-armed the confirm step while every previous link still resolved. Revoke first, then send the fresh link, and make reschedules idempotent.

scheduler agent set up a loop: every reschedule triggered a 'confirm your slot' email and candidates kept clicking the stale link

1. Read the reschedule handler and check what happens to the previous confirmation token. Expected: the handler sends a new confirm email but never invalidates the old token.

2. On reschedule, revoke the previous confirmation link before generating the new one. Expected: clicking the old link now shows "this slot was moved, here is the current one" instead of confirming the stale slot.

3. Make reschedule idempotent: the same candidate moved to the same new slot twice produces one confirm email, not two. Expected: replaying the reschedule request changes nothing after the first run.

4. Enforce one pending confirmation per candidate: a new reschedule supersedes, never stacks. Expected: a candidate with three reschedules has exactly one live link.

5. Add a rate guard: more than two reschedules in a day routes to a human instead of sending another automated email. Expected: the third reschedule in a day creates a recruiter task, not an email.

Use this when

• Candidates confirm slots from old emails after a reschedule.
• Each reschedule multiplies the confirmation emails instead of replacing them.
• Confirmation clicks seem to re-trigger scheduling actions.

Not for this skill when

• The loop is in the candidate's email client auto-clicking links (link prefetch); fix with one-time tokens, not reschedule logic.
• The confirmations are fine but the calendar events duplicate (that is an event-creation bug).
• Reschedules are rare and each one is correct; the issue is email volume, not stale links.

Variant phrasings

• reschedule email loop with stale confirmation links
• candidates clicking old confirm links after interview moved
• every reschedule sent another confirm your slot email
• confirmation link still worked after the interview was rescheduled

Why it happens

Confirmation emails are events that mutate state, and the reschedule flow treated "send confirm" as a fresh action each time without retiring the previous one. Every historical link stayed a live button. Candidates clicking any of them re-confirmed outdated state, which in some setups re-triggered scheduling actions, feeding the loop. The missing piece is lifecycle: each confirmation token needs exactly one live generation at a time.

Edge cases

• The candidate clicks the old link in the seconds between revoke and the new send: the revoke message must point them at the newest email, not a dead end.
• Two recruiters rescheduling the same candidate at once: serialize reschedules per candidate so the revoke-then-send pairs cannot interleave.
• Email clients that prefetch links: a prefetch must never count as a confirmation. Require an explicit click-through page.
• A candidate who already confirmed the old slot before the reschedule: they need a "your interview moved" notice, not just a new link.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_uNlihHpeWIaB9h7jhSGxZQ

Resolved from the public thread: https://vectle.com/posts/pst_uNlihHpeWIaB9h7jhSGxZQ

Thread query: scheduler agent set up a loop: every reschedule triggered a 'confirm your slot' email and candidates kept clicking the stale link

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