ADR-205: A column every content type carries excludes no type 

Context 

ADR-196 offers a content type unless, among other things, its form holds an excluding column: a FlexForm, inline records, a record reference, a user field and every TCA type the tool does not know. One excluding column excludes the type.

On the Netresearch demo that rule offered no type at all. The TCA was loaded, tt_content.CType declared 65 items, and every candidate carried two excluding columns that are not its own:

• background_image_options, a FlexForm bootstrap_package adds to core's frames palette, which every content type uses;
• tx_contexts_settings, a user field EXT:contexts appends to the showitem of every type (64 of 65).

create_content_element_draft refused every call with Allowed here: none, and update_content_element, which checks the same list, refused every element. Measured on 2026-09-24 in a CLI process of the demo's web container with the tool's own availableTypes().

Decision 

The form of core's header type is the shared form, and its columns do not decide. An excluding column of that form is left at its default, like an unfilled column; fields never accepted an excluding column and still does not. The fillable columns of that form — date, header_layout — stay settable through fields as before. Every other excluding column still excludes the type, as before.

header is the smallest content form, and core copies it onto a plugin registered without a form of its own. An extension that adds a column to every content type reaches header as well, whichever way it adds it — through one of the palettes core gives every type, or through every showitem. What only some types carry is theirs: bootstrap_package's accordion, carousel or tab keep their inline items and pi_flexform and stay excluded.

Consequences 

• On the demo, header, text, textmedia, bullets, table and the other prose types are offered again; a type with a FlexForm or inline column of its own is still refused.
• An extension that puts a payload column into the header form would have it treated as shared. No such extension is known; the column would be left at its default, and the element would be created without it, as for an unfilled column.
• An installation without a header type has no shared form, and the rule of ADR-196 applies unchanged.

Alternatives considered 

The columns every candidate type carries. Measured on the demo, the intersection over all 29 candidate types does not contain background_image_options: one type of the site package lacks it. A single type that differs would take the relief away again.

Excluding only required columns. An inline column with no minimum is optional, and an accordion without items is still not a text. The rule would offer types whose content the draft cannot carry.