diff --git a/context_chat_backend/repair/repair5004_date20260716145303.py b/context_chat_backend/repair/repair5004_date20260716145303.py
new file mode 100644
index 00000000..8d74e4f5
--- /dev/null
+++ b/context_chat_backend/repair/repair5004_date20260716145303.py
@@ -0,0 +1,40 @@
+#
+# SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+# SPDX-License-Identifier: AGPL-3.0-or-later
+#
+import os
+
+import sqlalchemy as sa
+
+'''
+Drop the "id" column from the access_list table since its auto-increment sequence
+(32-bit integer) gets exhausted after many ownership modifications, causing:
+  psycopg.errors.SequenceGeneratorLimitExceeded: nextval: reached maximum value of
+  sequence "access_list_id_seq" (2147483647)
+Also, "id" isn't used anywhere except as a primary key.
+
+The composite (uid, source_id) key is promoted to primary key instead.
+'''
+
+
+def run(_previous_version: int):
+	db_url = os.environ.get('CCB_DB_URL')
+	if not db_url:
+		print('CCB_DB_URL not set, skipping "id" column drop from "access_list" table', flush=True)
+		return
+
+	engine = sa.create_engine(db_url)
+	with engine.connect() as conn:
+		# Drop the unique index that we'll convert to primary key
+		conn.execute(sa.text(
+			'DROP INDEX IF EXISTS uid_chunk_id_idx'
+		))
+		# Drop the id column (also removes the old PK constraint and sequence)
+		conn.execute(sa.text(
+			'ALTER TABLE access_list DROP COLUMN IF EXISTS id'
+		))
+		# Add the primary key constraint using the existing unique columns
+		conn.execute(sa.text(
+			'ALTER TABLE access_list ADD CONSTRAINT access_list_pkey PRIMARY KEY (uid, source_id)'
+		))
+		conn.commit()
diff --git a/context_chat_backend/vectordb/pgvector.py b/context_chat_backend/vectordb/pgvector.py
index e562f94a..382baff0 100644
--- a/context_chat_backend/vectordb/pgvector.py
+++ b/context_chat_backend/vectordb/pgvector.py
@@ -79,8 +79,6 @@ class AccessListStore(Base):
 
 	__tablename__ = ACCESS_LIST_TABLE_NAME
 
-	id: orm.Mapped[int] = orm.mapped_column(primary_key=True, autoincrement=True)
-
 	uid: orm.Mapped[str] = orm.mapped_column(nullable=False)
 	source_id: orm.Mapped[str] = orm.mapped_column(
 		sa.ForeignKey(
@@ -91,16 +89,15 @@ class AccessListStore(Base):
 	)
 
 	__table_args__ = (
-		sa.Index(
-			'uid_chunk_id_idx',
+		sa.PrimaryKeyConstraint(
 			'uid',
 			'source_id',
-			unique=True,
+			name='access_list_pkey',
 		),
 		sa.Index(
 			'idx_access_list_source_id',
 			'source_id',
-		)
+		),
 	)
 
 	@classmethod
@@ -348,7 +345,7 @@ def decl_update_access(self, user_ids: list[str], source_id: str, session_: orm.
 						}
 						for user_id in batched_uids
 					])
-					.on_conflict_do_nothing(index_elements=['uid', 'source_id'])
+					.on_conflict_do_nothing(constraint='access_list_pkey')
 				)
 				session.execute(stmt)
 
@@ -402,7 +399,7 @@ def update_access(
 								}
 								for user_id in batched_uids
 							])
-							.on_conflict_do_nothing(index_elements=['uid', 'source_id'])
+							.on_conflict_do_nothing(constraint='access_list_pkey')
 						)
 						session.execute(stmt)
 					session.commit()