diff --git a/migrations/1771200017000_modeling_provenance_cascade_on_delete/down.sql b/migrations/1771200017000_modeling_provenance_cascade_on_delete/down.sql
new file mode 100644
index 0000000..7cb2498
--- /dev/null
+++ b/migrations/1771200017000_modeling_provenance_cascade_on_delete/down.sql
@@ -0,0 +1,51 @@
+-- Restore ON DELETE RESTRICT on the modeling provenance and permission tables.
+-- This reinstates the deadlock described in up.sql: the `user` role can no
+-- longer delete a problem statement, a task or a thread by any order of
+-- operations. Clients written against the cascade will start reporting the
+-- delete as refused, which is the honest failure.
+
+BEGIN;
+
+ALTER TABLE public.problem_statement_provenance
+    DROP CONSTRAINT problem_statement_provenance_problem_statement_id_fkey;
+ALTER TABLE public.problem_statement_provenance
+    ADD CONSTRAINT problem_statement_provenance_problem_statement_id_fkey
+    FOREIGN KEY (problem_statement_id) REFERENCES public.problem_statement(id)
+    ON UPDATE RESTRICT ON DELETE RESTRICT;
+
+ALTER TABLE public.problem_statement_permission
+    DROP CONSTRAINT problem_statement_permission_problem_statement_id_fkey;
+ALTER TABLE public.problem_statement_permission
+    ADD CONSTRAINT problem_statement_permission_problem_statement_id_fkey
+    FOREIGN KEY (problem_statement_id) REFERENCES public.problem_statement(id)
+    ON UPDATE RESTRICT ON DELETE RESTRICT;
+
+ALTER TABLE public.task_provenance
+    DROP CONSTRAINT task_provenance_task_id_fkey;
+ALTER TABLE public.task_provenance
+    ADD CONSTRAINT task_provenance_task_id_fkey
+    FOREIGN KEY (task_id) REFERENCES public.task(id)
+    ON UPDATE RESTRICT ON DELETE RESTRICT;
+
+ALTER TABLE public.task_permission
+    DROP CONSTRAINT task_permission_task_id_fkey;
+ALTER TABLE public.task_permission
+    ADD CONSTRAINT task_permission_task_id_fkey
+    FOREIGN KEY (task_id) REFERENCES public.task(id)
+    ON UPDATE RESTRICT ON DELETE RESTRICT;
+
+ALTER TABLE public.thread_provenance
+    DROP CONSTRAINT thread_provenance_thread_id_fkey;
+ALTER TABLE public.thread_provenance
+    ADD CONSTRAINT thread_provenance_thread_id_fkey
+    FOREIGN KEY (thread_id) REFERENCES public.thread(id)
+    ON UPDATE RESTRICT ON DELETE RESTRICT;
+
+ALTER TABLE public.thread_permission
+    DROP CONSTRAINT thread_permission_thread_id_fkey;
+ALTER TABLE public.thread_permission
+    ADD CONSTRAINT thread_permission_thread_id_fkey
+    FOREIGN KEY (thread_id) REFERENCES public.thread(id)
+    ON UPDATE RESTRICT ON DELETE RESTRICT;
+
+COMMIT;
diff --git a/migrations/1771200017000_modeling_provenance_cascade_on_delete/up.sql b/migrations/1771200017000_modeling_provenance_cascade_on_delete/up.sql
new file mode 100644
index 0000000..596dc2e
--- /dev/null
+++ b/migrations/1771200017000_modeling_provenance_cascade_on_delete/up.sql
@@ -0,0 +1,65 @@
+-- Let a problem statement, task or thread carry its provenance and permission
+-- rows to the grave, instead of requiring the client to remove them first.
+--
+-- The `user` role may delete one of these rows only if the row still has a
+-- CREATE provenance event from that user:
+--
+--     filter: { events: { _and: [ {event: {_eq: CREATE}}, {userid: {_eq: X-Hasura-User-Id}} ] } }
+--
+-- With ON DELETE RESTRICT that permission was unsatisfiable. Deleting the
+-- provenance first (what every client does) removed the row's own delete
+-- permission, so the delete matched 0 rows and returned success. Deleting the
+-- row first was refused by this constraint. Neither order could work.
+--
+-- CASCADE breaks the tie: the client deletes only the row, while its CREATE
+-- event is still there to authorise the delete, and Postgres removes the
+-- dependants. Provenance and permission rows have no life of their own once
+-- their subject is gone, so cascading is also what they mean.
+--
+-- See https://github.com/mintproject/monorepo/issues/99
+
+BEGIN;
+
+ALTER TABLE public.problem_statement_provenance
+    DROP CONSTRAINT problem_statement_provenance_problem_statement_id_fkey;
+ALTER TABLE public.problem_statement_provenance
+    ADD CONSTRAINT problem_statement_provenance_problem_statement_id_fkey
+    FOREIGN KEY (problem_statement_id) REFERENCES public.problem_statement(id)
+    ON UPDATE RESTRICT ON DELETE CASCADE;
+
+ALTER TABLE public.problem_statement_permission
+    DROP CONSTRAINT problem_statement_permission_problem_statement_id_fkey;
+ALTER TABLE public.problem_statement_permission
+    ADD CONSTRAINT problem_statement_permission_problem_statement_id_fkey
+    FOREIGN KEY (problem_statement_id) REFERENCES public.problem_statement(id)
+    ON UPDATE RESTRICT ON DELETE CASCADE;
+
+ALTER TABLE public.task_provenance
+    DROP CONSTRAINT task_provenance_task_id_fkey;
+ALTER TABLE public.task_provenance
+    ADD CONSTRAINT task_provenance_task_id_fkey
+    FOREIGN KEY (task_id) REFERENCES public.task(id)
+    ON UPDATE RESTRICT ON DELETE CASCADE;
+
+ALTER TABLE public.task_permission
+    DROP CONSTRAINT task_permission_task_id_fkey;
+ALTER TABLE public.task_permission
+    ADD CONSTRAINT task_permission_task_id_fkey
+    FOREIGN KEY (task_id) REFERENCES public.task(id)
+    ON UPDATE RESTRICT ON DELETE CASCADE;
+
+ALTER TABLE public.thread_provenance
+    DROP CONSTRAINT thread_provenance_thread_id_fkey;
+ALTER TABLE public.thread_provenance
+    ADD CONSTRAINT thread_provenance_thread_id_fkey
+    FOREIGN KEY (thread_id) REFERENCES public.thread(id)
+    ON UPDATE RESTRICT ON DELETE CASCADE;
+
+ALTER TABLE public.thread_permission
+    DROP CONSTRAINT thread_permission_thread_id_fkey;
+ALTER TABLE public.thread_permission
+    ADD CONSTRAINT thread_permission_thread_id_fkey
+    FOREIGN KEY (thread_id) REFERENCES public.thread(id)
+    ON UPDATE RESTRICT ON DELETE CASCADE;
+
+COMMIT;