### Overview Update `AddOn` model to a `FixedItemsModel` with hard-coded add-on data. ### Prerequisites This issue depends on `AddOnPurchase` reads being migrated off `subscription_add_on_id` first (#601254), so the `FixedItemsModel` swap becomes a localized model-file change with no scope rewrites required here. See blocking issue (added under epic &19981). ### Scope (revised 2026-07-01) Convert `GitlabSubscriptions::AddOn` to a `FixedItemsModel`, **keeping the `GitlabSubscriptions::AddOn` constant name** (replace the AR model in place; do NOT rename to a new namespace). Renaming would rewrite ~47 references; the reference Plan impl (!237348) kept `Plan` and added `SystemDefined::Plan` alongside, so here the simpler move is an in-place replacement of the smaller `AddOn` model. **Prerequisite (deploy ordering):** #15787-B1 (drop the `subscription_add_on_id` FK, `NOT NULL`, and legacy unique indexes) must be finalized on `gitlab.com` *before* this issue. `subscription_add_on_id` is `NOT NULL` today, and `belongs_to_fixed_items` writes only `subscription_add_on_uid`, so without B1 first, new inserts leave `subscription_add_on_id` NULL and fail. * Include `ActiveRecord::FixedItemsModel::Model`; define `ITEMS` keyed by the existing `name` enum integers as `id` (code_suggestions:1 … secrets_manager:8), with `name` + `description` attributes. * Port constants/methods: `DUO_ADD_ONS`, `SEAT_ASSIGNABLE_DUO_ADD_ONS`, `descriptions`, `seat_assignable?`, and scopes `duo_add_ons`, `seat_assignable_duo_add_ons`. * Provide compatibility for the removed Rails-enum surface (callers depend on these): * `self.names` returning `{ name => id }` (or migrate `ee/app/models/ee/user_preference.rb:67`, `ee/lib/ee/api/helpers.rb:99`, `ee/lib/cloud_connector/tokens.rb:46`, factories/seeds to `names_for_uids` / `uids_for_names`). * enum predicates `code_suggestions?`, `duo_enterprise?`, etc. (used by `base_create_service.rb:65,69`, `self_managed/create_service.rb:25,26`). * enum value scopes `code_suggestions` / `duo_enterprise` / `duo_core` → callers move to `where(name:)` / `find_by(name:)`. * `find_or_create_by_name` → `find_by_name` (creation is meaningless for a fixed model). Update `provision_service.rb:112`, `self_managed/license_add_ons/base.rb:29`, `ee/api/helpers.rb:101`, dev setup; remove seed fixture `db/fixtures/development/28_add_ons.rb` (coordinate with gitlab#500226). * Repoint: `belongs_to :add_on` → `belongs_to_fixed_items :add_on, fixed_items_class: GitlabSubscriptions::AddOn, foreign_key: :subscription_add_on_uid`. Existing `add_on.*` callers keep working in-memory. * Move the write path + validations onto `subscription_add_on_uid`: remove `before_validation :set_subscription_add_on_uid` (the `belongs_to_fixed_items` setter writes the uid); switch `validates :subscription_add_on_id, uniqueness:` and `validates :add_on, presence:` to `subscription_add_on_uid` (DB already has the `(subscription_add_on_uid, namespace_id)` unique index). * Repoint the `AddOnPurchase.uid_for` helper at the new model. Drop `has_many :add_on_purchases` / `scope :active` from the model (grep shows no external users). ### Success Criteria (revised 2026-07-01) * `AddOn` is a `FixedItemsModel` under the same `GitlabSubscriptions::AddOn` constant; all 8 items present with stable enum-integer ids. * `add_on.*` instance reads resolve via the fixed-items association; no `AddOn.<enum scope>` / `find_or_create_by_name` / seed-based creation remains; predicates + `names` / `descriptions` compat verified for every value. * Writes/validations go through `subscription_add_on_uid`; `subscription_add_on_id` is written NULL on new rows (dropped later in #15787-B4). * Tests validate model functionality (ITEMS integrity, `seat_assignable?`, scope replacements, `find` / `where(name:)` finders). ### Related Work * Parent epic: &19981 * Reference Plan FixedItemsModel MR: gitlab-org/gitlab!237348 * Reference Plan epic: https://gitlab.com/groups/gitlab-org/-/work_items/20087 * Predecessor (already closed): #15785 (backfill finalization), gitlab-org/gitlab#588162 (backfill) * Already-closed tracking item to confirm did not partially ship this: gitlab-org/gitlab#580843 * POC branch (out of date — missing `gitlab_credits` and `secrets_manager`): https://gitlab.com/gitlab-org/gitlab/-/commits/15596-add-on-fixeditemsmodel ### Notes * The POC's `map_from_addon` / `map_to_addon` helpers are unnecessary once reads are already on `subscription_add_on_uid`. Do not port them. * Confirm gitlab-org/gitlab#580843 (closed 2026-05-26) did not already partially do this before opening the MR.