Issue Summary

In RBAC transition mode, copying access from a custom-access source spaces into a target with existing roles can remove the copied custom permissions for overlapping principals. The operation reports success despite the incomplete result.

Steps to Reproduce

Preconditions: Space roles are enabled in transition mode (ROLES_TRANSITION). A principal has custom access on the source and a role on the target. The caller can administer both spaces.

1. Create a private source space.
2. Change the creator's permissions to custom access, for example by removing Export space while keeping space administration. Confirm the source creator has no stored role assignment.
3. Give a control group only View and Add pages on the source. Use a group that has no role assignment on the target.
4. Create a target space using default access. Confirm the creator has an Admin role on the target.
5. Use Copy access in the target's space-access settings to copy from the source.
6. Compare the creator's and control group's permissions on the source and target.

Expected Results

The target receives the source's supported Custom access configuration. A principal's previous target role must not cause newly copied source permissions to disappear.

Actual Results

The copy reports success, but the creator's copied Custom permissions are absent from the target. The control group's Custom permissions survive because it had no previous target role assignment.

The copy reports success, but the creator's copied Custom permissions are absent from the target. The control group's Custom permissions survive because it had no previous target role assignment.

Workaround

Currently there is no known workaround for this behavior. A workaround will be added here when available