You need to add a "terminiating condition" in order to terminate the recursion.
For example:
```
SELECT ?1 IN (
WITH found(id) AS NOT MATERIALIZED
(
SELECT self_hash_id
FROM causal
WHERE self_hash_id == ?2
UNION ALL
SELECT parent_id
FROM causal_parent
JOIN found
ON found.id == causal_id
)
SELECT id
FROM found
WHERE id == ?1
LIMIT 1
)
;
```
which will cause the list population to cease once the value is found. If the value is not found then the recursion will complete when the recursion is exhausted.
** NB ** NOT MATERIALIZED is the default, however, the short-circuit termination only applies if `found(id)` is not materialized.