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backend/app/db/migrations/versions/d3a9f6b2c8e1_session_backend_owner.py

@@ -0,0 +1,31 @@
+"""persist backend node ownership for active sessions
+
+Revision ID: d3a9f6b2c8e1
+Revises: c2d7e9f4a1b6
+Create Date: 2026-09-24
+"""
+
+import sqlalchemy as sa
+from alembic import op
+
+revision = "d3a9f6b2c8e1"
+down_revision = "c2d7e9f4a1b6"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        "sessions",
+        sa.Column("backend_node_id", sa.String(length=128), nullable=True),
+    )
+    op.create_index(
+        "ix_sessions_backend_node_active",
+        "sessions",
+        ["backend_node_id", "ended_at"],
+    )
+
+
+def downgrade() -> None:
+    op.drop_index("ix_sessions_backend_node_active", table_name="sessions")
+    op.drop_column("sessions", "backend_node_id")