diff --git a/framework/py/flwr/supercore/state/alembic/versions/rev_2026_04_30_make_run_substatus_and_details_not_nullable.py b/framework/py/flwr/supercore/state/alembic/versions/rev_2026_04_30_make_run_substatus_and_details_not_nullable.py
new file mode 100644
index 000000000000..1b97848547e3
--- /dev/null
+++ b/framework/py/flwr/supercore/state/alembic/versions/rev_2026_04_30_make_run_substatus_and_details_not_nullable.py
@@ -0,0 +1,69 @@
+# Copyright 2026 Flower Labs GmbH. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+# ==============================================================================
+"""Make run sub_status and details not nullable.
+
+Revision ID: e566a1e755c5
+Revises: c7eb009ce75c
+Create Date: 2026-04-30 09:43:42.202183
+"""
+from collections.abc import Sequence
+
+import sqlalchemy as sa
+from alembic import op
+
+# pylint: disable=no-member
+
+# revision identifiers, used by Alembic.
+revision: str = "e566a1e755c5"
+down_revision: str | Sequence[str] | None = "c7eb009ce75c"
+branch_labels: str | Sequence[str] | None = None
+depends_on: str | Sequence[str] | None = None
+
+
+def upgrade() -> None:
+    """Upgrade schema."""
+    # Backfill existing NULLs before enforcing NOT NULL.
+    op.execute("UPDATE run SET sub_status = '' WHERE sub_status IS NULL")
+    op.execute("UPDATE run SET details = '' WHERE details IS NULL")
+    # ### commands auto generated by Alembic - please adjust! ###
+    with op.batch_alter_table("run", schema=None) as batch_op:
+        batch_op.alter_column(
+            "sub_status",
+            existing_type=sa.VARCHAR(),
+            server_default=sa.text("''"),
+            nullable=False,
+        )
+        batch_op.alter_column(
+            "details",
+            existing_type=sa.VARCHAR(),
+            server_default=sa.text("''"),
+            nullable=False,
+        )
+
+    # ### end Alembic commands ###
+
+
+def downgrade() -> None:
+    """Downgrade schema."""
+    # ### commands auto generated by Alembic - please adjust! ###
+    with op.batch_alter_table("run", schema=None) as batch_op:
+        batch_op.alter_column(
+            "details", existing_type=sa.VARCHAR(), server_default=None, nullable=True
+        )
+        batch_op.alter_column(
+            "sub_status", existing_type=sa.VARCHAR(), server_default=None, nullable=True
+        )
+
+    # ### end Alembic commands ###
diff --git a/framework/py/flwr/supercore/state/schema/README.md b/framework/py/flwr/supercore/state/schema/README.md
index c320f556ce7f..a8971e09d3b8 100644
--- a/framework/py/flwr/supercore/state/schema/README.md
+++ b/framework/py/flwr/supercore/state/schema/README.md
@@ -94,7 +94,7 @@ erDiagram
     BIGINT bytes_recv "nullable"
     BIGINT bytes_sent "nullable"
     FLOAT clientapp_runtime "nullable"
-    VARCHAR details "nullable"
+    VARCHAR details
     VARCHAR fab_hash "nullable"
     VARCHAR fab_id "nullable"
     VARCHAR fab_version "nullable"
@@ -109,7 +109,7 @@ erDiagram
     VARCHAR run_type
     VARCHAR running_at "nullable"
     VARCHAR starting_at "nullable"
-    VARCHAR sub_status "nullable"
+    VARCHAR sub_status
     VARCHAR usage_reported_at
   }
 
diff --git a/framework/py/flwr/supercore/state/schema/linkstate_tables.py b/framework/py/flwr/supercore/state/schema/linkstate_tables.py
index 7b8b10a87799..dc52c3dbb324 100644
--- a/framework/py/flwr/supercore/state/schema/linkstate_tables.py
+++ b/framework/py/flwr/supercore/state/schema/linkstate_tables.py
@@ -79,8 +79,8 @@ def create_linkstate_metadata() -> MetaData:
         Column("running_at", String),
         Column("finished_at", String),
         Column("usage_reported_at", String, nullable=False, server_default=text("''")),
-        Column("sub_status", String),
-        Column("details", String),
+        Column("sub_status", String, nullable=False, server_default=text("''")),
+        Column("details", String, nullable=False, server_default=text("''")),
         Column("federation", String),
         Column("primary_task_id", BigInteger, nullable=True),
         Column("federation_config", String),