#3992 Collective invite shows "This invitation has expired or has already been used" after a successful join via Google sign-in

Description

An invitee who follows a collective invitation email and signs in with Google sees "This invitation has expired or has already been used", yet they have joined the collective. The error page appears on a successful join, so the invitee thinks it failed.

Steps to reproduce

1. As a collective owner on swamp-club.com, invite a colleague by their work email address (Member role).
2. Within the 48-hour window, the invitee opens the invitation email and follows the link.
3. On the sign-in page, the invitee signs in with Google using the invited address. This is the same address the invite was sent to.

Actual

• The accept-invite page says "This invitation has expired or has already been used".
• The invitee is nevertheless a member of the collective, and the owner sees them as a member.

Expected

The invitee lands on a confirmation such as "You've joined ", or is taken straight to the collective. The expired/used message should only appear when the invite really cannot be accepted and the invitee is not a member.

Likely cause

There seem to be two accept paths, and one runs ahead of the other:

1. The server-side auto-claim added for #1186 binds pending invitations for the address whenever a session is established. It runs during the Google sign-in, so it accepts the invitation first.
2. The returnUrl fix for #1204 then brings the invitee back to /o/<slug>/accept-invite. That page finds the invitation is no longer pending and shows the expired/used error.

Suggested fix

When the accept-invite page finds an invitation that isn't pending, check whether the signed-in user is already a member of that collective. If they are, show success or redirect to the collective. Only show the expired/used message to a user who is not a member.

Environment

• Surface: swamp.club web UI, collective invite by email, Google sign-in
• Date: 2026-10-26

Related: #1186, #1204, #1287, #1810