diff --git a/alembic/versions/0127_drop_tasks_contact_id_fk.py b/alembic/versions/0127_drop_tasks_contact_id_fk.py
new file mode 100644
index 0000000..d6fd486
--- /dev/null
+++ b/alembic/versions/0127_drop_tasks_contact_id_fk.py
@@ -0,0 +1,36 @@
+"""Drop tasks_contact_id_fkey — contact_id is now derived from entity_id (ARCH-F-2).
+
+The tasks table has both a contact_id FK column (referencing contacts) and
+polymorphic entity_type/entity_id columns. The code now derives contact_id
+from entity_id when entity_type='contact', and stores NULL in the FK column.
+The FK constraint is redundant and prevents creating tasks with arbitrary
+entity references. This migration drops the FK constraint but keeps the column
+for backward compatibility.
+
+Revision ID: 0127
+Revises: 0126
+"""
+
+from alembic import op
+
+revision = "0127"
+down_revision = "0126"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    # Drop the FK constraint on tasks.contact_id
+    op.drop_constraint("tasks_contact_id_fkey", "tasks", type_="foreignkey")
+
+
+def downgrade() -> None:
+    # Re-create the FK constraint (best-effort — may fail if orphaned rows exist)
+    op.create_foreign_key(
+        "tasks_contact_id_fkey",
+        "tasks",
+        "contacts",
+        ["contact_id"],
+        ["id"],
+        ondelete="SET NULL",
+    )