This Epic is to capture work by the Custom Models to enable top level Model Selection at the instance admin level on Self-Managed and Dedicated for customers accessing Gitlab Duo via the GitLab.com AIG/WFS. In this iteration, customers will be able to select from among Gitlab supported AI Vendor models at the instance administration level for each main feature. This will allow admins of Gitlab instance that are consuming Duo via the GitLab.com AIG/WFS admins to decide which models they want their end users to use at the top level -- the instance. This is follow-on work from https://gitlab.com/groups/gitlab-org/-/epics/18818+s, which enabled Model Selection at the namespace admin level for customer accessing GitLab Duo via the GitLab.com AIG on GitLab.com. If a model is NOT pinned by an instance-level admin, the choice to pin a model will then cascade down to the end user and the end user can choose from among all available models. If the instance admin HAS pinned a model then there is no action that the end user can take. Models available for each feature will include the default GitLab AI Vendor model for each feature/sub-feature, as well as Claude 3.5 Sonnet What's out of scope for this work * Only top level instance admins will be able to access the feature. Sub-groups will use the model selected by their top parent. This does NOT include cascading controls for group, sub-group, or project. * This iteration does NOT include model switching support for beta or experimental features. ## Definition of Done * Instance admins on Self-Managed and Dedicated that are consuming Gitlab Duo via the GL.com AIG/WFS can select a default model for their Duo features from among supported GitLab AI Vendor models for each Duo feature and sub-feature * If the administrator DOES NOT pin a specific model, Gitlab AI Vendor model defaults will be populated and used for all child levels * end users then have the option to select a model or use the default * If either the instance admin or namespace admin HAS selected a specific model for a feature, the feature will NOT fallback to another model * [All GA GitLab Duo features available on GitLab.com](https://docs.gitlab.com/user/gitlab_duo/#summary-of-gitlab-duo-features) will be available for model selection * Model selection options will include GitLab AI Vendor model defaults for each feature/sub-feature, as well as Claude 3.5 Sonnet * Model selection will be available to all Duo users, regardless of tier. This includes: * Duo Core * Duo Pro * Duo Enterprise * **This iteration will work to enable **[**end-user model selection**](https://gitlab.com/groups/gitlab-org/-/epics/18374)** in future iterations**