diff --git a/changes/12907.fix.md b/changes/12907.fix.md
new file mode 100644
index 00000000000..8b42cc7d582
--- /dev/null
+++ b/changes/12907.fix.md
@@ -0,0 +1 @@
+Reconcile indexes that differed between fresh installs and migrated databases, adding the two that back a foreign key and dropping the unused vfolder creator index
diff --git a/src/ai/backend/manager/models/alembic/versions/a3b4c5d6e7f8_add_preset_category_description_rank.py b/src/ai/backend/manager/models/alembic/versions/a3b4c5d6e7f8_add_preset_category_description_rank.py
index 883f876c24e..84af88c8a18 100644
--- a/src/ai/backend/manager/models/alembic/versions/a3b4c5d6e7f8_add_preset_category_description_rank.py
+++ b/src/ai/backend/manager/models/alembic/versions/a3b4c5d6e7f8_add_preset_category_description_rank.py
@@ -65,7 +65,9 @@ def upgrade() -> None:
 
 
 def downgrade() -> None:
-    op.drop_index("ix_prometheus_query_presets_category_id", table_name="prometheus_query_presets")
+    # drop_column below takes the column's index and foreign key with it;
+    # dropping either by name first only breaks on installs that never had
+    # that name.
     op.drop_column("prometheus_query_presets", "category_id")
     op.drop_column("prometheus_query_presets", "rank")
     op.drop_column("prometheus_query_presets", "description")
diff --git a/src/ai/backend/manager/models/alembic/versions/ad7acfe8aa1c_add_role_invitations_table.py b/src/ai/backend/manager/models/alembic/versions/ad7acfe8aa1c_add_role_invitations_table.py
index 6526cc1ae53..bf3fe15e078 100644
--- a/src/ai/backend/manager/models/alembic/versions/ad7acfe8aa1c_add_role_invitations_table.py
+++ b/src/ai/backend/manager/models/alembic/versions/ad7acfe8aa1c_add_role_invitations_table.py
@@ -248,6 +248,6 @@ def upgrade() -> None:
 
 
 def downgrade() -> None:
-    op.drop_index("uq_role_invitations_active", table_name="role_invitations")
-    op.drop_index("ix_role_invitations_invitee_user_id", table_name="role_invitations")
+    # drop_table takes the table's indexes with it; dropping them by name first
+    # only breaks on installs that never had them.
     op.drop_table("role_invitations")
diff --git a/src/ai/backend/manager/models/alembic/versions/b2f7c1a94e30_reconcile_index_drift_across_install_paths.py b/src/ai/backend/manager/models/alembic/versions/b2f7c1a94e30_reconcile_index_drift_across_install_paths.py
new file mode 100644
index 00000000000..6f5b261d945
--- /dev/null
+++ b/src/ai/backend/manager/models/alembic/versions/b2f7c1a94e30_reconcile_index_drift_across_install_paths.py
@@ -0,0 +1,53 @@
+"""reconcile index drift across install paths
+
+A fresh install builds tables from the model metadata (`mgr schema oneshot`) and
+stamps head without running a migration; an existing install replays the
+migration files. Three indexes were created by migrations but never declared on
+the models, so they existed only on migrated databases. This migration makes
+every database agree with the models, in whichever direction each index earns.
+
+Created here, because each backs a foreign key whose parent-side delete has to
+find the referencing rows -- the index costs a write and saves a scan:
+  - ix_role_invitations_invitee_user_id (users delete cascades)
+  - ix_prometheus_query_presets_category_id (category delete sets null)
+
+Dropped here, because nothing reads it: vfolders.creator_id carries no foreign
+key and is never filtered, joined, or ordered by -- it is only written and
+selected. Its creation has been removed from b4e7f1a2c3d5, so this drop is what
+clears it from databases that already ran that revision.
+
+The existence checks keep every statement a no-op where the database already
+agrees.
+
+Revision ID: b2f7c1a94e30
+Revises: 3f9a1c7b2e04
+Create Date: 2026-07-16
+
+"""
+
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision = "b2f7c1a94e30"
+down_revision = "3f9a1c7b2e04"
+# Part of: NEXT_RELEASE_VERSION
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.execute(
+        "CREATE INDEX IF NOT EXISTS ix_role_invitations_invitee_user_id"
+        " ON role_invitations (invitee_user_id)"
+    )
+    op.execute(
+        "CREATE INDEX IF NOT EXISTS ix_prometheus_query_presets_category_id"
+        " ON prometheus_query_presets (category_id)"
+    )
+    op.execute("DROP INDEX IF EXISTS ix_vfolders_creator_id")
+
+
+def downgrade() -> None:
+    # Intentionally a no-op. This migration exists to make the two install paths
+    # agree with the models; undoing it would only put the drift back.
+    pass
diff --git a/src/ai/backend/manager/models/alembic/versions/b4e7f1a2c3d5_add_creator_id_to_vfolders.py b/src/ai/backend/manager/models/alembic/versions/b4e7f1a2c3d5_add_creator_id_to_vfolders.py
index bbc8f29f3f1..ce5072e36dd 100644
--- a/src/ai/backend/manager/models/alembic/versions/b4e7f1a2c3d5_add_creator_id_to_vfolders.py
+++ b/src/ai/backend/manager/models/alembic/versions/b4e7f1a2c3d5_add_creator_id_to_vfolders.py
@@ -23,12 +23,6 @@ def upgrade() -> None:
         "vfolders",
         sa.Column("creator_id", GUID, nullable=True),
     )
-    op.create_index(
-        op.f("ix_vfolders_creator_id"),
-        "vfolders",
-        ["creator_id"],
-        unique=False,
-    )
     # Backfill creator_id from users table by matching creator (email) → users.email
     op.execute(
         sa.text(
@@ -38,5 +32,6 @@ def upgrade() -> None:
 
 
 def downgrade() -> None:
-    op.drop_index(op.f("ix_vfolders_creator_id"), table_name="vfolders")
+    # drop_column takes the column's index with it; dropping it by name first
+    # only breaks on installs that never had it.
     op.drop_column("vfolders", "creator_id")
diff --git a/src/ai/backend/manager/models/prometheus_query_preset/row.py b/src/ai/backend/manager/models/prometheus_query_preset/row.py
index 983eda94283..4b525fc62fe 100644
--- a/src/ai/backend/manager/models/prometheus_query_preset/row.py
+++ b/src/ai/backend/manager/models/prometheus_query_preset/row.py
@@ -46,6 +46,7 @@ class PrometheusQueryPresetRow(LifecycleTimestampsMixin, Base):  # type: ignore[
         GUID,
         sa.ForeignKey("prometheus_query_preset_categories.id", ondelete="SET NULL"),
         nullable=True,
+        index=True,
     )
     options: Mapped[PresetOptions] = mapped_column(
         "options",
diff --git a/src/ai/backend/manager/models/role_invitation/row.py b/src/ai/backend/manager/models/role_invitation/row.py
index 2f3f0f295d8..13ffdacc29b 100644
--- a/src/ai/backend/manager/models/role_invitation/row.py
+++ b/src/ai/backend/manager/models/role_invitation/row.py
@@ -39,6 +39,10 @@ class RoleInvitationRow(Base):  # type: ignore[misc]
         GUID,
         sa.ForeignKey("users.uuid", onupdate="CASCADE", ondelete="CASCADE"),
         nullable=False,
+        # The ON DELETE CASCADE above has to find every row for a user, including
+        # accepted ones, so uq_role_invitations_active cannot serve it -- that
+        # index is partial (state != 'accepted').
+        index=True,
     )
     role_id: Mapped[uuid.UUID] = mapped_column(
         "role_id",