fix(invitations): compare the join disclosure against new-membership creation

The membership consent guard compared the disclosed outcome against
`shouldJoinOrganization`, which stays true for an invitee who already belongs to
the target organization — the invitation's intent is still internal. The join
preview reports no-join for exactly that case, because nothing changes for them.
Every such acceptance therefore failed `disclosure-outdated`, and the retry
re-rendered the same preview, so the invitation became permanently unacceptable.

The guard now compares against whether acceptance creates a NEW membership
(`shouldJoinOrganization && !alreadyMemberOfTargetOrganization`), which is what
the disclosure actually promises and what the preview reports. The
already-a-member predicate is hoisted and shared with the join block below so
the guard and the billing path cannot disagree about it.

Regression test asserts a pre-existing member accepts with a no-join disclosure;
it fails with `disclosure-outdated` against the previous comparison.

Co-Authored-By: Claude <noreply@anthropic.com>

apps/sim/lib/invitations/core.test.ts

@@ -1391,6 +1391,81 @@ describe('acceptInvitation', () => {
     )
   })
 
+  it('lets a pre-existing member accept a no-join disclosure without looping', async () => {
+    /**
+     * The preview reports no-join for someone already in the target
+     * organization — nothing changes for them — while the invitation's intent
+     * stays internal, so `shouldJoinOrganization` remains true. Comparing the
+     * disclosure against that raw flag rejected every such acceptance as
+     * `disclosure-outdated`, and the retry re-rendered the same preview, so the
+     * invitation could never be accepted. The guard compares against whether a
+     * NEW membership is created instead.
+     */
+    mockGetWorkspaceWithOwner.mockResolvedValue({
+      id: 'workspace-1',
+      name: 'Workspace',
+      ownerId: 'owner-1',
+      organizationId: 'org-1',
+      workspaceMode: 'organization',
+      billedAccountUserId: 'owner-1',
+    })
+    mockGetUserOrganization.mockResolvedValue({
+      organizationId: 'org-1',
+      role: 'member',
+      memberId: 'member-1',
+    })
+    mockEnsureUserInOrganization.mockResolvedValueOnce({
+      success: true,
+      alreadyMember: true,
+      billingActions: { proUsageSnapshotted: false, proCancelledAtPeriodEnd: false },
+    })
+
+    queueWhereResponses([
+      [
+        {
+          id: 'inv-1',
+          kind: 'workspace',
+          email: 'invitee@example.com',
+          organizationId: 'org-1',
+          membershipIntent: 'internal',
+          inviterId: 'owner-1',
+          role: 'member',
+          status: 'pending',
+          token: 'tok-1',
+          expiresAt: new Date(Date.now() + 60_000),
+          createdAt: new Date(),
+          updatedAt: new Date(),
+        },
+      ],
+      [
+        {
+          id: 'grant-1',
+          workspaceId: 'workspace-1',
+          permission: 'write',
+          workspaceName: 'Workspace',
+        },
+      ],
+      [{ name: 'Acme' }],
+      [{ name: 'Owner', email: 'owner@example.com' }],
+      [],
+      [{ id: 'member-1' }],
+    ])
+
+    const result = await acceptInvitation({
+      userId: 'invitee-user',
+      userEmail: 'invitee@example.com',
+      invitationId: 'inv-1',
+      token: 'tok-1',
+      disclosedWorkspaceIds: [],
+      disclosedWillJoinOrganization: false,
+    })
+
+    expect(result.success ? 'ok' : result.kind).toBe('ok')
+    if (result.success) {
+      expect(result.membershipAlreadyExists).toBe(true)
+    }
+  })
+
   it('does not reconcile seats for an Enterprise organization (fixed seats)', async () => {
     mockGetWorkspaceWithOwner.mockResolvedValue({
       id: 'workspace-1',

apps/sim/lib/invitations/core.ts

@@ -726,18 +726,37 @@ async function acceptLockedInvitation(
     return { success: false, kind: 'external-requires-paid-plan' }
   }
 
+  /**
+   * Already in the organization the invitation lands in, so acceptance grants
+   * the workspaces without creating a membership or taking a seat. Shared with
+   * the join block below so the disclosure guard and the billing path cannot
+   * disagree about whether this acceptance creates a member.
+   */
+  const alreadyMemberOfTargetOrganization =
+    !!existingMembership &&
+    !!workspaceOrganizationId &&
+    existingMembership.organizationId === workspaceOrganizationId
+
   /**
    * Membership consent guard. The workspace-id token cannot distinguish "you
    * will join, and nothing of yours moves" from "you will not join at all" —
-   * both disclose an empty set — so the disclosed join outcome is compared
-   * directly. Catches an invitee who left their other organization between
-   * preview and accept (promised external, would now consume a seat) and the
-   * mirror case (promised membership, would now be external). Runs before any
-   * write, so a plain failure return needs no rollback.
+   * both disclose an empty set — so the disclosed outcome is compared directly.
+   *
+   * Compared against whether a NEW membership gets created, not against
+   * `shouldJoinOrganization`: the preview reports no-join for an invitee who
+   * already belongs to the target organization (nothing changes for them), and
+   * `shouldJoinOrganization` stays true there because the invitation's intent is
+   * still internal. Comparing the raw flag would reject every such acceptance
+   * as `disclosure-outdated`, and the retry would re-render the same preview —
+   * an unacceptable invitation. Catches the real drift in both directions: an
+   * invitee who left their other organization between preview and accept
+   * (promised external, would now consume a seat) and the mirror case. Runs
+   * before any write, so a plain failure return needs no rollback.
    */
+  const willCreateMembership = shouldJoinOrganization && !alreadyMemberOfTargetOrganization
   if (
     input.disclosedWillJoinOrganization !== undefined &&
-    input.disclosedWillJoinOrganization !== shouldJoinOrganization
+    input.disclosedWillJoinOrganization !== willCreateMembership
   ) {
     return { success: false, kind: 'disclosure-outdated' }
   }
@@ -758,10 +777,7 @@ async function acceptLockedInvitation(
   let targetOrganizationId = workspaceOrganizationId
 
   if (shouldJoinOrganization) {
-    const alreadyMemberOfTarget =
-      !!existingMembership &&
-      !!workspaceOrganizationId &&
-      existingMembership.organizationId === workspaceOrganizationId
+    const alreadyMemberOfTarget = alreadyMemberOfTargetOrganization
 
     let fixedSeats = false