Based on the information in the provided knowledge sources, the limitation described in https://github.com/ory/keto/issues/1330#issuecomment-1686584096—that traversals for cross-namespace relationships require the use of

subject_set

in the relation tuples, and that using only

subject_id

does not work for traversals—appears to still be applicable. Specifically, a user comment confirms that for checks involving traversal (e.g., using

.traverse(...)

in OPL), the parent relationships in the tuples must use

subject_set

rather than just

subject_id

. This is necessary for the traversal logic to function correctly, especially in cross-namespace scenarios. The comment also notes that this worked for them on self-hosted Keto, and there is no indication in the knowledge sources that this limitation has been lifted or changed in more recent versions or in Ory Network: > The key insight for me was that parent relationships for checks that use traversal require subject_set in the tuples themselves in addition to the traverse definition in the OPL schema. There is no documentation in the provided sources indicating that traversals utilizing only

subject_id

for cross-namespace relationships are currently supported. Therefore, you should continue to use

subject_set

for such cases until official documentation states otherwise or the limitation is explicitly addressed in a release or update[OPL traverse.(...) not working](https://github.com/ory/keto/issues/1330). If you need to model cross-namespace relationships for traversals, ensure your relation tuples use the

subject_set

structure.

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