Creates one new page in the project. Two kinds of page are creatable:

• CUSTOM: a bespoke merchant page addressed by a caller-chosen handle/path such as pages/gift-shop. Leading slashes are stripped, repeated slashes collapsed and trailing slashes removed. Starts with a blank root item unless basedOn is supplied.
• Resource-backed types (PRODUCT, COLLECTION, PAGE, BLOG, ARTICLE): a per-resource override (custom template) for one Shopify resource, where handle is the resource handle, kept verbatim. It clones the project's shared default template for that type when one exists, otherwise it starts with a blank root item. Pass shopifyResourceId to bind the Shopify resource for Studio's assignment UI.

Pass basedOn with a page id from the pages list to clone that page's layout instead. The source page must be assigned to the same project; a cross-project or unknown id returns 404 PAGE_NOT_FOUND.

This creates one page copy per call. To point many resources at a single shared template page without copying content, use POST /projects/{projectId}/template-assignments/{pageId}.

If a live assignment already exists for the same type, handle and locale (or market), the request returns 409 CONFLICT and creates nothing; read or edit the existing page instead. Any other type, or a missing or empty handle, returns 400 INVALID_PARAMS.

Legacy behaviour: a body containing pageIds or handles is treated as the bulk-delete fallback and returns a page_delete result. Prefer DELETE /projects/{projectId}/pages for deletion.

Required scope: content:write (the bulk-delete fallback also requires content:delete)