This feature covers **global** sub-types, managed by instance administrators and available to every project. Project-owned sub-types, the project permission, in-project visibility isolation, and promotion to global are a separate, larger feature (to be creatd)

**As an** OpenProject  administrator
**I want to** create and manage global sub-types under an existing work package type
**so that** I can offer instance-wide variations of a type that present as the parent but can behave differently.

## Acceptance criteria

* I can create a global sub-type under any root type. _(F0-C1, F0-C4)_

* A sub-type cannot itself have Begin of the insertionsub-types. The applicationEnd of the insertion Begin of the deletion sub-types; the systemEnd of the deletion enforces a single level. _(F0-C1)_

* A sub-type cannot be its own parent, and standard types cannot be sub-typed or re-parented. _(F0-C1)_

* A new sub-type starts with every aspect (workflow, form configuration, settings) linked to its parent, so it behaves exactly like the parent until I change it. _(F0-C1, F0-C2)_

* A sub-type appears in administration nested under its parent and labelled with its composite name ("Bug: Hardware"). _(F0-C3, F0-C4)_

* A sub-type Begin of the insertioninheritsEnd of the insertion Begin of the deletion hasEnd of the deletion its Begin of the insertioncore settings from the parent and cannot edit them: color, `is_milestone`, `is_in_roadmap`, and `is_default` are shown read-only and always follow the parent. _(F0-C3)_

* A sub-type carries only itsEnd of the insertion own Begin of the insertionvariant label, used in administration, hover, and the composite name; the displayed typeEnd of the insertion Begin of the deletion administrativeEnd of the deletion name Begin of the deletion but no own color; its displayEnd of the deletion always Begin of the insertionresolves toEnd of the insertion Begin of the deletion usesEnd of the deletion the Begin of the insertionparent.End of the insertion Begin of the deletion parent's color.End of the deletion _(F0-C3)_

* The system prevents creating a cyclic dependency between reuse sources. _(F0-C2)_

* The entire capability is hidden and inert unless the `work_package_subtypes` feature flag is enabled. _(F0-C0)_


## Permissions and visibility considerations

* **To whom is this feature visible?** Instance administrators (the existing global type administration).

* **When is it not visible?** Feature Flag turned Begin of the insertionoff,End of the insertion Begin of the deletion off;End of the deletion all non-admin users.


## Translation considerations

<figure class="table op-uc-figure_align-center op-uc-figure"><table class="op-uc-table"><thead class="op-uc-table--head"><tr class="op-uc-table--row"><th class="op-uc-table--cell op-uc-table--cell_head"><p class="op-uc-p">English</p></th><th class="op-uc-table--cell op-uc-table--cell_head"><p class="op-uc-p">German (verify)</p></th><th class="op-uc-table--cell op-uc-table--cell_head"><p class="op-uc-p">French (verify)</p></th><th class="op-uc-table--cell op-uc-table--cell_head"><p class="op-uc-p">Spanish (verify)</p></th></tr></thead><tbody><tr class="op-uc-table--row"><td class="op-uc-table--cell"><p class="op-uc-p">Sub-type</p></td><td class="op-uc-table--cell"><p class="op-uc-p">Untertyp</p></td><td class="op-uc-table--cell"><p class="op-uc-p">Sous-type</p></td><td class="op-uc-table--cell"><p class="op-uc-p">Subtipo</p></td></tr><tr class="op-uc-table--row"><td class="op-uc-table--cell"><p class="op-uc-p">Parent type</p></td><td class="op-uc-table--cell"><p class="op-uc-p">Übergeordneter Typ</p></td><td class="op-uc-table--cell"><p class="op-uc-p">Type parent</p></td><td class="op-uc-table--cell"><p class="op-uc-p">Tipo principal</p></td></tr><tr class="op-uc-table--row"><td class="op-uc-table--cell"><p class="op-uc-p">Source type</p></td><td class="op-uc-table--cell"><p class="op-uc-p">Quelltyp</p></td><td class="op-uc-table--cell"><p class="op-uc-p">Type source</p></td><td class="op-uc-table--cell"><p class="op-uc-p">Tipo de origen</p></td></tr></tbody></table></figure>

* Document the hierarchical name (`"TYPE: SUBTYPE"`) used in admin, possibly on hover, and API.


## Out of scope

* Project-owned sub-types, the `:manage_subtypes` project permission, in-project visibility isolation, and promotion to global (Feature 8).

* Per-aspect reuse behavior beyond the default parent links (Features 1, 2, 3).

* Project activation and the one-per-family rule (Feature 5).

* Display routing across the product (Feature 4).