diff --git a/changes/11661.fix.md b/changes/11661.fix.md
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+++ b/changes/11661.fix.md
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+Fix custom runtime variant not reading model-definition.yaml from the model vfolder during revision creation
diff --git a/src/ai/backend/manager/models/alembic/versions/0b10b2c6a972_seed_reads_vfolder_for_custom_variant.py b/src/ai/backend/manager/models/alembic/versions/0b10b2c6a972_seed_reads_vfolder_for_custom_variant.py
new file mode 100644
index 00000000000..9bf96f42509
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+++ b/src/ai/backend/manager/models/alembic/versions/0b10b2c6a972_seed_reads_vfolder_for_custom_variant.py
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+"""seed reads_vfolder_config_files for custom runtime variant
+
+The original seed migration (``9229f72fa447``) inserted runtime variants
+with only ``name`` / ``description``, so ``reads_vfolder_config_files``
+took its server default of ``false`` for every row. The install fixture
+sets the flag to ``true`` for the ``custom`` variant, but
+``populate_fixture`` uses ``ON CONFLICT DO NOTHING`` and therefore never
+overwrites the already-seeded row. Backfill the intended value here so
+``custom`` actually triggers the vfolder ``model-definition.yaml`` scan
+at revision-creation time.
+
+Revision ID: 0b10b2c6a972
+Revises: ba42cb865efe
+Create Date: 2026-05-18
+
+"""
+
+# Part of: 26.5.0
+
+import sqlalchemy as sa
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision = "0b10b2c6a972"
+down_revision = "ba42cb865efe"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.execute(
+        sa.text(
+            "UPDATE runtime_variants SET reads_vfolder_config_files = true WHERE name = 'custom'"
+        )
+    )
+
+
+def downgrade() -> None:
+    pass