feat: relation field and picker

web/src/components/BuilderInspector.vue

@@ -29,6 +29,7 @@ const props = defineProps<{
 	field: BuilderField
 	errors: FieldErrors
 	compact: boolean
+	ownerName?: string
 }>()
 
 const uid = () => props.field.uid
@@ -40,12 +41,15 @@ const uid = () => props.field.uid
 		:errors="errors"
 		:disabled="saving"
 		:compact="compact"
+		:owner-name="ownerName"
 		:focus-token="focusToken"
 		@label="actions.setLabel(uid(), $event)"
 		@key="actions.setFieldKey(uid(), $event)"
 		@unlock="actions.unlockFieldKey(uid())"
 		@reset="actions.resetFieldKey(uid())"
 		@type="actions.setFieldType(uid(), $event)"
+		@relation-type="actions.patchField(uid(), { relationType: $event }, 'relation')"
+		@relation-kind="actions.patchField(uid(), { relationKind: $event })"
 		@required="actions.patchField(uid(), { required: $event })"
 		@unique="actions.patchField(uid(), { unique: $event })"
 		@limit="(which, value) => actions.setLimit(uid(), which, value)"

web/src/components/DeleteTypeDialog.vue

@@ -11,6 +11,7 @@ const props = defineProps<{
 	name: string
 	keyValue: string
 	total: number
+	referrer: string
 	pending: boolean
 	offline: boolean
 }>()
@@ -43,6 +44,20 @@ const notice = computed(() => {
 			),
 		}
 	}
+	if (props.stage === 'referenced') {
+		return {
+			title: t("You can't delete {0} yet", [props.name]),
+			description: props.referrer
+				? t('{0} has a field that points to {1}. Remove that field first.', [
+						props.referrer,
+						props.name,
+					])
+				: t(
+						'Another content type has a field that points to {0}. Remove that field first.',
+						[props.name],
+					),
+		}
+	}
 	if (props.stage === 'failed') {
 		return {
 			title: t("Couldn't delete the content type"),

web/src/components/EntryCardList.vue

@@ -11,7 +11,9 @@ import {
 	thumbnailColumn,
 } from '@/lib/entryCells'
 import { t } from '@/i18n'
+import { fieldTypeSpec } from '@/lib/fieldTypes'
 import { mediaOf } from '@/lib/mediaField'
+import { summariesOf } from '@/lib/relationField'
 import { entryPath } from '@/lib/routePaths'
 import { computed } from 'vue'
 
@@ -26,11 +28,21 @@ const props = defineProps<{
 
 const shown = computed(() => cardFields(props.fields))
 const lead = computed(() => thumbnailColumn(props.columns))
+const relationColumns = computed(() =>
+	props.columns.filter(
+		(field) => field !== shown.value.first && fieldTypeSpec(field.type).cell === 'relation',
+	),
+)
 
 function textOf(field: BuiltinField | undefined, entry: ContentEntry) {
 	return field
 		? plainCellText(
-				describeCell(field, entry.data[field.key], mediaOf(entry, field.key) ?? undefined),
+				describeCell(
+					field,
+					entry.data[field.key],
+					mediaOf(entry, field.key) ?? undefined,
+					summariesOf(entry, field.key),
+				),
 			)
 		: ''
 }
@@ -80,6 +92,20 @@ function nameOf(entry: ContentEntry) {
 					<span class="truncate text-md/5.25 font-medium text-highlighted">{{
 						titleOf(entry)
 					}}</span>
+					<span
+						v-for="field in relationColumns"
+						:key="field.key"
+						data-testid="entry-card-relation"
+						class="flex flex-wrap items-center gap-1.5"
+					>
+						<span class="text-xs text-muted">{{ field.label }}</span>
+						<FieldCell
+							:field="field"
+							:value="entry.data[field.key]"
+							:relations="summariesOf(entry, field.key)"
+							compact
+						/>
+					</span>
 					<span class="flex items-center gap-2 text-xs text-muted">
 						<template v-if="shown.second && !secondIsChoice">
 							<span class="shrink-0">{{ textOf(shown.second, entry) }}</span>

web/src/components/EntryEditor.vue

@@ -111,6 +111,8 @@ function backToList() {
 				:fields="page.fields.value"
 				:values="page.form.values.value"
 				:images="page.form.images.value"
+				:relations="page.form.relations.value"
+				:type-name="page.typeName.value"
 				:issues="page.form.issues.value"
 				:first-issue="page.form.firstIssue.value"
 				:focus-token="page.focusToken.value"

web/src/components/EntryField.vue

@@ -4,10 +4,12 @@ import BuilderBadge from '@/components/BuilderBadge.vue'
 import DirectoryField from '@/components/DirectoryField.vue'
 import EntryControl from '@/components/EntryControl.vue'
 import MediaFieldControl from '@/components/MediaFieldControl.vue'
+import RelationField from '@/components/RelationField.vue'
 import type { BuiltinField } from '@/lib/contentTypes'
 import type { FieldIssue } from '@/lib/entryForm'
 import { fieldTypeSpec } from '@/lib/fieldTypes'
 import { isMediaId, type MediaSummary } from '@/lib/mediaField'
+import { holdsManyRelations, type RelationSummary } from '@/lib/relationField'
 
 const props = defineProps<{
 	field: BuiltinField
@@ -16,14 +18,24 @@ const props = defineProps<{
 	isDefault: boolean
 	disabled: boolean
 	image?: MediaSummary | null
+	relations?: RelationSummary[]
+	typeName: string
 }>()
 
-const emit = defineEmits<{ update: [key: string, value: unknown, image?: MediaSummary | null] }>()
+const emit = defineEmits<{
+	update: [
+		key: string,
+		value: unknown,
+		image?: MediaSummary | null,
+		relations?: RelationSummary[],
+	]
+}>()
 
 const editor = computed(() => fieldTypeSpec(props.field.type).editor)
 const counter = computed(() => editor.value.counter(props.field, props.value))
 const help = computed(() => editor.value.help(props.field))
 const isMedia = computed(() => editor.value.control === 'media')
+const isRelation = computed(() => editor.value.control === 'relation')
 const mediaId = computed(() => (isMediaId(props.value) ? props.value : null))
 </script>
 
@@ -40,6 +52,20 @@ const mediaId = computed(() => (isMediaId(props.value) ? props.value : null))
 			:error="issue?.message"
 			@change="(id, picked) => emit('update', field.key, id, picked)"
 		/>
+		<RelationField
+			v-else-if="isRelation"
+			:label="field.label"
+			:name="field.key"
+			:required="field.required"
+			:many="holdsManyRelations(field)"
+			:target="field.relation?.content_type ?? ''"
+			:type-name="typeName"
+			:value="value"
+			:summaries="relations"
+			:disabled="disabled"
+			:error="issue?.message"
+			@change="(next, summaries) => emit('update', field.key, next, undefined, summaries)"
+		/>
 		<DirectoryField
 			v-else
 			:label="field.label"

web/src/components/EntryForm.vue

@@ -6,6 +6,7 @@ import EntryField from '@/components/EntryField.vue'
 import type { BuiltinField } from '@/lib/contentTypes'
 import type { EntryIssues, EntryValues } from '@/lib/entryForm'
 import type { MediaMap, MediaSummary } from '@/lib/mediaField'
+import type { RelationSummaries, RelationSummary } from '@/lib/relationField'
 import { groupFields } from '@/lib/entryLayout'
 
 const FOCUSABLE =
@@ -15,6 +16,8 @@ const props = defineProps<{
 	fields: BuiltinField[]
 	values: EntryValues
 	images: MediaMap
+	relations: RelationSummaries
+	typeName: string
 	issues: EntryIssues
 	firstIssue: string | null
 	focusToken: number
@@ -28,7 +31,12 @@ const props = defineProps<{
 }>()
 
 const emit = defineEmits<{
-	update: [key: string, value: unknown, image?: MediaSummary | null]
+	update: [
+		key: string,
+		value: unknown,
+		image?: MediaSummary | null,
+		relations?: RelationSummary[],
+	]
 	submit: []
 }>()
 
@@ -73,10 +81,14 @@ watch(() => props.focusToken, focusFirstIssue)
 				:field="field"
 				:value="values[field.key]"
 				:image="images[field.key] ?? null"
+				:relations="relations[field.key] ?? []"
+				:type-name="typeName"
 				:issue="issues[field.key]"
 				:is-default="isDefault(field)"
 				:disabled="locked"
-				@update="(key, value, image) => emit('update', key, value, image)"
+				@update="
+					(key, value, image, summaries) => emit('update', key, value, image, summaries)
+				"
 			/>
 		</div>
 

web/src/components/EntryNotices.vue

@@ -20,12 +20,17 @@ const props = defineProps<{
 
 defineEmits<{ retry: []; reload: [] }>()
 
+const NAMED_CONTROLS = ['media', 'relation']
+
 const uniqueField = computed(() =>
-	props.fields.find((field) => props.issues[field.key]?.rule === 'unique'),
+	props.fields.find(
+		(field) =>
+			props.issues[field.key]?.rule === 'unique' && fieldTypeSpec(field.type).supportsUnique,
+	),
 )
 const changedLine = computed(() => {
 	const changed = props.fields.find((field) => field.key === props.schemaField)
-	return changed && fieldTypeSpec(changed.type).editor.control === 'media'
+	return changed && NAMED_CONTROLS.includes(fieldTypeSpec(changed.type).editor.control)
 		? mediaChangedLine(changed.label)
 		: schemaChangedLine(props.schemaField)
 })

web/src/components/EntryTable.vue

@@ -9,11 +9,13 @@ import { EMPTY_TEXT, formatEntryDate } from '@/lib/entryCells'
 import { ENTRY_SORT_FIELDS, sortParts } from '@/lib/entryListQuery'
 import { fieldTypeSpec } from '@/lib/fieldTypes'
 import { mediaOf } from '@/lib/mediaField'
+import { summariesOf } from '@/lib/relationField'
 import { entryPath } from '@/lib/routePaths'
 
 const ID_WIDTH = 'w-16.5'
 const NARROW_WIDTH = 'w-23'
 const FIELD_WIDTH = 'w-33'
+const WIDE_WIDTH = 'w-50'
 const CREATED_WIDTH = 'w-30.5'
 const UPDATED_WIDTH = 'w-40.5'
 const UPDATED_BY_WIDTH = 'w-37'
@@ -37,7 +39,11 @@ function widthOf(field: BuiltinField, index: number) {
 	if (index === 0) {
 		return ''
 	}
-	return fieldTypeSpec(field.type).narrowColumn ? NARROW_WIDTH : FIELD_WIDTH
+	const spec = fieldTypeSpec(field.type)
+	if (spec.wideColumn) {
+		return WIDE_WIDTH
+	}
+	return spec.narrowColumn ? NARROW_WIDTH : FIELD_WIDTH
 }
 
 function column(id: string, header: string, width: string, edge = 'px-1.5') {
@@ -152,6 +158,7 @@ watchPostEffect(() => {
 						:field="field"
 						:value="row.original.data[field.key]"
 						:image="mediaOf(row.original, field.key)"
+						:relations="summariesOf(row.original, field.key)"
 						class="min-w-0"
 					/>
 				</RouterLink>
@@ -160,6 +167,7 @@ watchPostEffect(() => {
 					:field="field"
 					:value="row.original.data[field.key]"
 					:image="mediaOf(row.original, field.key)"
+					:relations="summariesOf(row.original, field.key)"
 				/>
 			</template>
 

web/src/components/FieldCell.vue

@@ -2,18 +2,23 @@
 import { t } from '@/i18n'
 
 import { computed } from 'vue'
+import RelationChip from '@/components/RelationChip.vue'
 import type { BuiltinField } from '@/lib/contentTypes'
 import { EMPTY_TEXT, describeCell, isEmptyCell } from '@/lib/entryCells'
 import { isMissingImage, type MediaSummary } from '@/lib/mediaField'
+import type { RelationSummary } from '@/lib/relationField'
 
 const props = defineProps<{
 	field: BuiltinField
 	value: unknown
 	image?: MediaSummary | null
+	relations?: RelationSummary[]
 	compact?: boolean
 }>()
 
-const cell = computed(() => describeCell(props.field, props.value, props.image ?? undefined))
+const cell = computed(() =>
+	describeCell(props.field, props.value, props.image ?? undefined, props.relations),
+)
 const shownImage = computed(() => {
 	const image = cell.value.image
 	return image && !isMissingImage(image) ? image : null
@@ -61,6 +66,21 @@ const TIP_UI = {
 			<UIcon name="i-lucide-unlink" :class="compact ? 'size-3' : 'size-3.5'" />
 		</span>
 	</UTooltip>
+	<span
+		v-else-if="cell.kind === 'relation'"
+		data-testid="relation-cell"
+		:title="cell.text"
+		class="flex min-w-0 items-center gap-1"
+		:class="compact ? 'flex-wrap' : 'overflow-hidden'"
+	>
+		<RelationChip
+			v-for="chip in cell.chips"
+			:key="chip.id"
+			:label="chip.label"
+			:missing="chip.missing"
+		/>
+		<span v-if="cell.more" class="text-xs text-muted">+{{ cell.more }}</span>
+	</span>
 	<span v-else-if="cell.kind === 'boolean'" class="flex items-center gap-1.5">
 		<UIcon
 			:name="cell.yes ? 'i-lucide-check' : 'i-lucide-minus'"

web/src/components/FieldInspector.vue

@@ -6,6 +6,7 @@ import AppSwitch from '@/components/AppSwitch.vue'
 import ChoiceList from '@/components/ChoiceList.vue'
 import DirectoryField from '@/components/DirectoryField.vue'
 import FieldTypePicker from '@/components/FieldTypePicker.vue'
+import RelationPicker from '@/components/RelationPicker.vue'
 import SlugField from '@/components/SlugField.vue'
 import { fieldTypeSpec } from '@/lib/fieldTypes'
 import {
@@ -18,6 +19,7 @@ import {
 	type BuilderField,
 	type FieldType,
 } from '@/lib/schemaBuilderModel'
+import type { RelationKind } from '@/lib/relationField'
 import type { FieldErrors } from '@/lib/schemaBuilderValidation'
 
 const NO_DEFAULT = 'none'
@@ -29,6 +31,7 @@ const props = defineProps<{
 	disabled: boolean
 	compact: boolean
 	focusToken: number
+	ownerName?: string
 }>()
 
 const emit = defineEmits<{
@@ -37,6 +40,8 @@ const emit = defineEmits<{
 	unlock: []
 	reset: []
 	type: [type: FieldType]
+	relationType: [key: string]
+	relationKind: [kind: RelationKind]
 	required: [value: boolean]
 	unique: [value: boolean]
 	limit: [which: 'min' | 'max', value: string]
@@ -58,6 +63,7 @@ const showUnique = computed(() => canUnique.value || spec.value.showsUnsupported
 const showRuleGrid = computed(
 	() => hasLimits.value || spec.value.supportsDefault || spec.value.showsUnsupportedOptions,
 )
+const holdsRelation = computed(() => spec.value.holdsRelation)
 const hint = computed(() => spec.value.builderHint?.() ?? '')
 const keyMode = computed(() => keyDisplayMode(props.field.keyMode, props.field.key))
 const gridClass = computed(() => (props.compact ? 'grid-cols-1' : 'md:grid-cols-2'))
@@ -193,6 +199,20 @@ watch(
 			@update:model-value="emit('type', $event)"
 		/>
 
+		<RelationPicker
+			v-if="holdsRelation"
+			:label="field.label"
+			:owner-name="ownerName ?? ''"
+			:type-key="field.relationType"
+			:kind="field.relationKind"
+			:locked="field.saved"
+			:disabled="disabled"
+			:compact="compact"
+			:error="errors.relation"
+			@type="emit('relationType', $event)"
+			@kind="emit('relationKind', $event)"
+		/>
+
 		<div class="flex min-w-0 flex-col border-t border-default">
 			<AppSwitch
 				:model-value="field.required"

web/src/components/RelationChip.vue

@@ -0,0 +1,29 @@
+<script setup lang="ts">
+withDefaults(defineProps<{ label: string; missing?: boolean; tall?: boolean }>(), {
+	missing: false,
+	tall: false,
+})
+</script>
+
+<template>
+	<UBadge
+		color="neutral"
+		variant="soft"
+		:label="label"
+		data-testid="relation-chip"
+		:data-missing="missing ? 'true' : undefined"
+		class="max-w-full ring-0"
+		:class="
+			missing
+				? 'border border-dashed border-accented bg-transparent text-toned'
+				: 'bg-(--rc-sand) text-(--rc-on-sand)'
+		"
+		:ui="{
+			base: [
+				tall ? 'h-5.5 px-2' : 'h-5 px-1.5',
+				'rounded-none py-0 text-xs font-medium whitespace-nowrap',
+			],
+			label: 'truncate',
+		}"
+	/>
+</template>

web/src/components/RelationField.vue

@@ -0,0 +1,461 @@
+<script setup lang="ts">
+import { t } from '@/i18n'
+
+import { computed, nextTick, onMounted, ref, useId, watch } from 'vue'
+import DirectoryField from '@/components/DirectoryField.vue'
+import { useRelationSearch } from '@/composables/useRelationSearch'
+import { relationLabel } from '@/lib/entryCells'
+import {
+	RELATION_MAX,
+	isMissingRelation,
+	relationIdsOf,
+	type RelationSummary,
+} from '@/lib/relationField'
+import { relationRowOf } from '@/lib/relationRows'
+import { useContentTypesStore } from '@/stores/contentTypes'
+
+interface ChipItem {
+	label: string
+	value: number
+	missing: boolean
+	summary: RelationSummary
+}
+
+interface RowItem {
+	label: string
+	description: string
+	value: number
+	summary: RelationSummary
+}
+
+interface HighlightPayload {
+	ref?: HTMLElement
+}
+
+const SKELETON_ROWS = 3
+const LISTBOX = '[role="listbox"]'
+const OWNER_ATTRIBUTE = 'data-relation-owner'
+const VOWEL = /^[aeiou]/
+
+const props = withDefaults(
+	defineProps<{
+		label: string
+		name?: string
+		required?: boolean
+		many?: boolean
+		target: string
+		typeName: string
+		value: unknown
+		summaries?: RelationSummary[]
+		disabled?: boolean
+		error?: string
+	}>(),
+	{
+		name: undefined,
+		required: false,
+		many: false,
+		summaries: () => [],
+		disabled: false,
+		error: '',
+	},
+)
+
+const emit = defineEmits<{
+	change: [value: number | number[] | null, summaries: RelationSummary[]]
+}>()
+
+const id = useId()
+const labelId = `${id}-label`
+const helpId = `${id}-help`
+const errorId = `${id}-error`
+
+const store = useContentTypesStore()
+const search = useRelationSearch(() => props.target)
+const open = ref(false)
+const searchTerm = ref('')
+const announcement = ref('')
+const activeId = ref<string | undefined>(undefined)
+const listboxId = ref<string | undefined>(undefined)
+
+const ids = computed(() => relationIdsOf(props.value))
+const chips = computed<ChipItem[]>(() =>
+	ids.value.map((chipId) => {
+		const summary = props.summaries.find((candidate) => candidate.id === chipId) ?? {
+			id: chipId,
+			missing: true as const,
+		}
+		return {
+			label: relationLabel(summary),
+			value: chipId,
+			missing: isMissingRelation(summary),
+			summary,
+		}
+	}),
+)
+const targetType = computed(() => store.items.find((type) => type.key === props.target))
+const targetName = computed(() => targetType.value?.name ?? props.target)
+const atCap = computed(() => props.many && ids.value.length >= RELATION_MAX)
+const rows = computed<RowItem[]>(() =>
+	search.entries.value
+		.map((entry) => relationRowOf(entry, props.target, targetType.value?.fields ?? []))
+		.filter((row) => !ids.value.includes(row.id))
+		.map((row) => ({
+			label: row.title,
+			description: row.detail,
+			value: row.id,
+			summary: row.summary,
+		})),
+)
+const menuItems = computed(() => (atCap.value || search.showSkeleton.value ? [] : rows.value))
+const hasMissing = computed(() => chips.value.some((chip) => chip.missing))
+const ownerWord = computed(() => props.typeName.replace(/s$/i, '').toLowerCase())
+const help = computed(() => {
+	if (hasMissing.value) {
+		return props.required
+			? t('{0} is required. Choose another to save.', [props.label])
+			: t('You can still save. The entry keeps the link until you change it.')
+	}
+	if (!props.many) {
+		return ''
+	}
+	const plural = props.label.toLowerCase()
+	return VOWEL.test(ownerWord.value)
+		? t('An {0} can have many {1}.', [ownerWord.value, plural])
+		: t('A {0} can have many {1}.', [ownerWord.value, plural])
+})
+const describedBy = computed(() => (props.error ? `${errorId} ${helpId}` : helpId))
+const emptyKind = computed(() => {
+	if (atCap.value) {
+		return 'cap'
+	}
+	if (search.showSkeleton.value) {
+		return 'loading'
+	}
+	const status = search.status.value
+	if (status === 'limited' || status === 'failed') {
+		return status
+	}
+	if (status !== 'ready') {
+		return 'none'
+	}
+	if (search.total.value > 0) {
+		return 'chosen'
+	}
+	return search.query.value === '' ? 'empty' : 'noMatch'
+})
+const baseUi = computed(() =>
+	props.error
+		? 'border-error shadow-[inset_0_0_0_1px_var(--ui-error)] has-focus-visible:border-error'
+		: 'border-accented has-focus-visible:border-primary has-focus-visible:shadow-[inset_0_0_0_1px_var(--ui-primary)]',
+)
+const menuUi = computed(() => ({
+	base: `min-h-8 gap-1.5 rounded-none border bg-default px-2 py-1 text-sm ring-0 outline-0 has-focus-visible:ring-0 has-focus-visible:outline-0 max-md:min-h-11 max-md:text-lg ${baseUi.value} ${props.many ? '' : 'pe-8'}`,
+	tagsItem:
+		'h-6 gap-1.5 rounded-none bg-(--rc-sand) py-0 ps-2 pe-1 text-sm font-medium text-(--rc-on-sand) ring-0 has-data-[missing=true]:border has-data-[missing=true]:border-dashed has-data-[missing=true]:border-accented has-data-[missing=true]:bg-transparent has-data-[missing=true]:font-normal has-data-[missing=true]:text-toned max-md:h-8',
+	tagsItemText: 'truncate',
+	tagsItemDelete:
+		'relative rounded-none text-inherit hover:bg-transparent hover:text-inherit max-md:before:absolute max-md:before:-inset-1.5',
+	tagsInput: 'min-w-20 flex-1 placeholder:text-muted',
+	trailing: 'pe-2.5',
+	trailingIcon: 'size-3.5 text-muted',
+	content: 'rounded-none border border-default p-1 shadow-(--shadow-popover) ring-0',
+	empty: 'p-2 text-left text-sm text-muted',
+	group: 'p-0',
+	item: 'min-h-10 flex-col justify-center gap-0 rounded-none px-2 py-1 before:inset-0 before:rounded-none data-highlighted:not-data-disabled:before:bg-elevated max-md:min-h-12',
+	itemLabel: 'font-medium text-highlighted',
+	itemDescription: 'text-xs/5 text-muted',
+}))
+
+function removeName(element: HTMLElement, binding: { value: string }) {
+	const button = element.closest('button')
+	button?.removeAttribute('aria-labelledby')
+	button?.setAttribute('aria-label', binding.value)
+}
+
+const vRemoveName = { mounted: removeName, updated: removeName }
+
+function removeLabel(item: ChipItem) {
+	return t('Remove {0} from {1}', [item.label, props.label])
+}
+
+function announce(message: string) {
+	announcement.value = ''
+	nextTick(() => {
+		announcement.value = message
+	})
+}
+
+function summaryOf(chipId: number, picked: RowItem[]) {
+	return (
+		chips.value.find((chip) => chip.value === chipId)?.summary ??
+		picked.find((row) => row.value === chipId)?.summary
+	)
+}
+
+function changeSingle(picked: RowItem[]) {
+	const row = picked[picked.length - 1]
+	if (!row) {
+		emit('change', null, [])
+		announce(t('{0} cleared.', [props.label]))
+		return
+	}
+	emit('change', row.value, [row.summary])
+	announce(t('{0} set to {1}.', [props.label, row.label]))
+	open.value = false
+}
+
+function changeMany(next: Array<ChipItem | RowItem>, picked: RowItem[]) {
+	const nextIds = next.map((item) => item.value)
+	emit(
+		'change',
+		nextIds,
+		nextIds.flatMap((nextId) => summaryOf(nextId, picked) ?? []),
+	)
+	const removed = chips.value.find((chip) => !nextIds.includes(chip.value))
+	if (removed) {
+		announce(t('{0} removed from {1}.', [removed.label, props.label]))
+	} else if (picked[0]) {
+		announce(t('{0} added to {1}.', [picked[0].label, props.label]))
+	}
+}
+
+function onUpdate(next: Array<ChipItem | RowItem>) {
+	if (props.disabled) {
+		return
+	}
+	const picked = next.filter(
+		(item): item is RowItem => !ids.value.includes(item.value) && 'description' in item,
+	)
+	if (props.many) {
+		changeMany(next, picked)
+	} else {
+		changeSingle(picked)
+	}
+}
+
+function onBackspace(event: KeyboardEvent) {
+	const input = event.target as HTMLInputElement
+	const lastChip = chips.value.length - 1
+	if (
+		event.key !== 'Backspace' ||
+		input.getAttribute('role') !== 'combobox' ||
+		input.value !== '' ||
+		lastChip < 0 ||
+		props.disabled
+	) {
+		return
+	}
+	event.preventDefault()
+	event.stopPropagation()
+	onUpdate(chips.value.slice(0, lastChip))
+}
+
+function onHighlight(payload: HighlightPayload | undefined) {
+	activeId.value = payload?.ref?.id || undefined
+}
+
+function clearSearch() {
+	searchTerm.value = ''
+}
+
+async function trackListbox() {
+	await nextTick()
+	const owned = `[${OWNER_ATTRIBUTE}="${id}"]`
+	listboxId.value =
+		document.querySelector<HTMLElement>(`${owned}${LISTBOX}, ${owned} ${LISTBOX}`)?.id ||
+		undefined
+}
+
+function announceResults() {
+	const total = search.total.value
+	announce(total > 0 ? t('{0} results', [total]) : t('No results'))
+}
+
+watch(searchTerm, (term) => {
+	if (open.value) {
+		search.search(term)
+	}
+})
+
+watch(open, (isOpen) => {
+	if (isOpen) {
+		search.search(searchTerm.value)
+		trackListbox()
+	} else {
+		activeId.value = undefined
+		listboxId.value = undefined
+	}
+})
+
+watch(
+	() => search.status.value,
+	(status) => {
+		if (open.value && status === 'ready') {
+			announceResults()
+		}
+	},
+)
+
+onMounted(() => store.load())
+</script>
+
+<template>
+	<div class="min-w-0">
+		<DirectoryField
+			:label="label"
+			:required="required"
+			:name="name"
+			:label-id="labelId"
+			:error="error"
+			:error-id="errorId"
+		>
+			<div
+				role="group"
+				:aria-labelledby="labelId"
+				data-testid="relation-control"
+				@keydown.capture="onBackspace"
+			>
+				<UInputMenu
+					:model-value="chips"
+					v-model:open="open"
+					v-model:search-term="searchTerm"
+					multiple
+					ignore-filter
+					open-on-focus
+					open-on-click
+					by="value"
+					:items="menuItems"
+					:placeholder="t('Search to add')"
+					:disabled="disabled"
+					:color="error ? 'error' : undefined"
+					:trailing="!many"
+					trailing-icon="i-lucide-search"
+					:aria-controls="listboxId"
+					:aria-required="required ? 'true' : undefined"
+					:aria-activedescendant="activeId"
+					:aria-describedby="describedBy"
+					class="w-full"
+					:content="{ sideOffset: 6, [OWNER_ATTRIBUTE]: id }"
+					:ui="menuUi"
+					@update:model-value="onUpdate"
+					@highlight="onHighlight"
+				>
+					<template #tags-item-text="{ item }">
+						<span :data-missing="item.missing ? 'true' : undefined">{{
+							item.label
+						}}</span>
+					</template>
+					<template #tags-item-delete="{ item }">
+						<UIcon
+							v-remove-name="removeLabel(item)"
+							name="i-lucide-x"
+							class="size-3.5"
+						/>
+					</template>
+					<template #item="{ item }">
+						<span class="font-medium text-highlighted">{{ item.label }}</span>
+						<span v-if="item.description" class="text-xs/5 text-muted">{{
+							item.description
+						}}</span>
+					</template>
+					<template #empty>
+						<div data-testid="relation-empty" class="flex flex-col items-start gap-2">
+							<template v-if="emptyKind === 'loading'">
+								<span class="sr-only" role="status" aria-live="polite">{{
+									t('Searching…')
+								}}</span>
+								<USkeleton
+									v-for="row in SKELETON_ROWS"
+									:key="row"
+									data-testid="relation-skeleton"
+									class="h-10 w-full rounded-none bg-accented max-md:h-12"
+								/>
+							</template>
+							<template v-else-if="emptyKind === 'failed'">
+								<span class="font-medium text-error">{{
+									t("Couldn't load {0}", [targetName])
+								}}</span>
+								<span>{{ t('Check your connection and try again.') }}</span>
+								<UButton
+									color="neutral"
+									variant="outline"
+									icon="i-lucide-rotate-cw"
+									class="h-8 border border-accented bg-default px-2.5 text-xs text-highlighted ring-0 max-md:h-11"
+									@click="search.reload()"
+								>
+									{{ t('Try again') }}
+								</UButton>
+							</template>
+							<template v-else-if="emptyKind === 'limited'">
+								<span class="font-medium text-warning">{{
+									t('Too many requests')
+								}}</span>
+								<span>{{
+									search.limit.active.value
+										? t('Try again in {0}', [search.limit.formatted.value])
+										: t('Wait a moment before trying again.')
+								}}</span>
+								<UButton
+									v-if="!search.limit.active.value"
+									color="neutral"
+									variant="outline"
+									icon="i-lucide-rotate-cw"
+									class="h-8 border border-accented bg-default px-2.5 text-xs text-highlighted ring-0 max-md:h-11"
+									@click="search.reload()"
+								>
+									{{ t('Try again') }}
+								</UButton>
+							</template>
+							<span v-else-if="emptyKind === 'cap'">{{
+								t('You can add up to {0}.', [RELATION_MAX])
+							}}</span>
+							<span v-else-if="emptyKind === 'empty'">{{
+								t('No {0} yet. Add one in Content, then come back.', [targetName])
+							}}</span>
+							<template v-else-if="emptyKind === 'noMatch'">
+								<span>{{
+									t('No {0} match "{1}"', [targetName, search.query.value])
+								}}</span>
+								<UButton
+									color="neutral"
+									variant="ghost"
+									class="h-8 px-2 text-xs text-highlighted max-md:h-11"
+									@click="clearSearch"
+								>
+									{{ t('Clear search') }}
+								</UButton>
+							</template>
+							<span v-else-if="emptyKind === 'chosen'">{{
+								t('No other {0} to add.', [targetName])
+							}}</span>
+						</div>
+					</template>
+					<template #content-bottom>
+						<UButton
+							v-if="search.hasMore.value && !atCap"
+							color="neutral"
+							variant="ghost"
+							:loading="search.loadingMore.value"
+							class="h-8 w-full justify-center text-xs text-highlighted max-md:h-11"
+							@click="search.more()"
+						>
+							{{ t('Load more') }}
+						</UButton>
+					</template>
+				</UInputMenu>
+			</div>
+			<p
+				v-if="help"
+				:id="helpId"
+				data-testid="relation-help"
+				class="mt-1.5 text-xs/4.5 text-pretty text-muted"
+				:class="error ? 'sr-only' : ''"
+			>
+				{{ help }}
+			</p>
+			<span class="sr-only" role="status" aria-live="polite" data-testid="relation-live">{{
+				announcement
+			}}</span>
+		</DirectoryField>
+	</div>
+</template>

web/src/components/RelationPicker.vue

@@ -0,0 +1,257 @@
+<script setup lang="ts">
+import { t } from '@/i18n'
+
+import { computed, onMounted } from 'vue'
+import DirectoryField from '@/components/DirectoryField.vue'
+import RelationChip from '@/components/RelationChip.vue'
+import { RELATION_KINDS, isRelationKind, type RelationKind } from '@/lib/relationField'
+import {
+	inverseNoun,
+	inverseSide,
+	kindFromInverseSide,
+	kindFromOwnerSide,
+	kindSentence,
+	ownerNoun,
+	ownerSide,
+	relationNames,
+	relationSample,
+	type RelationSide,
+} from '@/lib/relationSentences'
+import { useContentTypesStore } from '@/stores/contentTypes'
+
+const DIAGRAMS: Record<RelationKind, readonly [number, number]> = {
+	one_to_one: [1, 1],
+	one_to_many: [3, 1],
+	many_to_many: [2, 2],
+}
+
+const props = defineProps<{
+	label: string
+	ownerName: string
+	typeKey: string
+	kind: RelationKind
+	locked: boolean
+	disabled: boolean
+	compact: boolean
+	error?: string
+}>()
+
+const emit = defineEmits<{ type: [key: string]; kind: [kind: RelationKind] }>()
+
+const store = useContentTypesStore()
+
+const typeItems = computed(() =>
+	store.items.map((type) => ({ label: type.name, value: type.key, hint: type.key })),
+)
+const related = computed(() => store.items.find((type) => type.key === props.typeKey))
+const names = computed(() => relationNames(props.ownerName, related.value?.name ?? '', props.label))
+const frozen = computed(() => props.locked || props.disabled)
+const kindItems = computed(() =>
+	RELATION_KINDS.map((kind) => ({
+		value: kind,
+		label: kindTitle(kind),
+		sentence: kindSentence(kind, names.value),
+	})),
+)
+const sideItems = computed(() => [
+	{ label: t('one'), value: 'one' },
+	{ label: t('many'), value: 'many' },
+])
+const sample = computed(() => relationSample(props.kind))
+
+function kindTitle(kind: RelationKind) {
+	if (kind === 'one_to_one') {
+		return t('One to one')
+	}
+	return kind === 'one_to_many' ? t('One to many') : t('Many to many')
+}
+
+function squares(count: number) {
+	return Array.from({ length: count }, (_, index) => index)
+}
+
+function onKind(value: unknown) {
+	if (isRelationKind(value)) {
+		emit('kind', value)
+	}
+}
+
+function onOwnerSide(value: unknown) {
+	emit('kind', kindFromOwnerSide(value as RelationSide, props.kind))
+}
+
+function onInverseSide(value: unknown) {
+	emit('kind', kindFromInverseSide(value as RelationSide, props.kind))
+}
+
+const SIDE_UI = {
+	base: 'mx-1 h-7 w-auto gap-1.5 rounded-none border border-accented bg-default py-0 ps-2 pe-7 text-sm font-medium text-highlighted ring-0',
+	trailing: 'pe-2',
+	trailingIcon: 'size-3 text-muted',
+	value: 'truncate',
+}
+const CARD_UI = {
+	root: 'w-full',
+	legend: 'mb-1.5 w-full font-medium text-highlighted',
+	item: 'group min-h-0 rounded-none border-accented p-2.5 text-highlighted has-data-[state=checked]:border-primary has-data-[state=checked]:bg-(--rc-sand) has-data-[state=checked]:text-(--rc-on-sand)',
+	wrapper: 'ms-0 w-full',
+	label: 'w-full text-base font-medium text-inherit',
+}
+
+onMounted(() => store.load())
+</script>
+
+<template>
+	<div class="flex min-w-0 flex-col gap-3.5" data-testid="relation-picker">
+		<p
+			v-if="locked"
+			data-testid="relation-locked-note"
+			class="flex items-center gap-1.5 text-xs/4.5 text-muted"
+		>
+			<UIcon name="i-lucide-lock" class="size-3 shrink-0" />
+			{{ t("The related type and the connection can't change after saving.") }}
+		</p>
+
+		<DirectoryField
+			:label="t('Related content type')"
+			name="relation-type"
+			:error="error"
+			:help="t('Choose the content type this field points to.')"
+		>
+			<USelect
+				:model-value="typeKey === '' ? undefined : typeKey"
+				:items="typeItems"
+				:placeholder="t('Choose a content type')"
+				:disabled="frozen"
+				:color="error ? 'error' : undefined"
+				class="w-full"
+				:ui="{
+					base: 'h-11 text-lg disabled:bg-elevated disabled:opacity-100 md:h-8 md:text-sm',
+					content: 'rounded-none shadow-(--shadow-popover)',
+				}"
+				@update:model-value="emit('type', String($event))"
+			>
+				<template #item-label="{ item }">
+					<span class="flex min-w-0 items-baseline gap-2">
+						<span class="truncate">{{ item.label }}</span>
+						<span class="font-mono text-xs text-muted">{{ item.hint }}</span>
+					</span>
+				</template>
+			</USelect>
+		</DirectoryField>
+
+		<URadioGroup
+			:model-value="kind"
+			:items="kindItems"
+			:disabled="frozen"
+			:legend="t('How are they connected?')"
+			variant="card"
+			indicator="hidden"
+			orientation="horizontal"
+			:ui="{
+				...CARD_UI,
+				fieldset: compact ? 'grid grid-cols-1 gap-2' : 'grid grid-cols-3 gap-2',
+			}"
+			@update:model-value="onKind"
+		>
+			<template #label="{ item }">
+				<span
+					class="flex flex-col gap-1.5 text-left"
+					:class="frozen && !(item.value === kind) ? 'opacity-60' : ''"
+				>
+					<span class="flex items-center gap-1.5" aria-hidden="true">
+						<span class="flex gap-0.75">
+							<span
+								v-for="square in squares(DIAGRAMS[item.value as RelationKind][0])"
+								:key="square"
+								class="size-2.5 bg-current"
+							/>
+						</span>
+						<span class="h-px w-5 bg-current" />
+						<span class="flex gap-0.75">
+							<span
+								v-for="square in squares(DIAGRAMS[item.value as RelationKind][1])"
+								:key="square"
+								class="size-2.5 bg-current"
+							/>
+						</span>
+					</span>
+					<span class="font-medium">{{ item.label }}</span>
+					<span
+						class="text-xs/4 font-normal text-pretty text-muted group-has-data-[state=checked]:text-(--rc-on-sand)"
+						>{{ item.sentence }}</span
+					>
+				</span>
+			</template>
+		</URadioGroup>
+
+		<div data-testid="relation-preview" class="flex flex-col gap-2 bg-elevated p-3">
+			<span class="flex flex-wrap items-center" data-testid="relation-owner-sentence">
+				{{ t('Each {0} has', [names.ownerSingular]) }}
+				<USelect
+					:model-value="ownerSide(kind)"
+					:items="sideItems"
+					:disabled="frozen"
+					:aria-label="t('Each {0} has', [names.ownerSingular])"
+					:ui="SIDE_UI"
+					@update:model-value="onOwnerSide"
+				/>
+				{{ ownerNoun(kind, names) }}
+			</span>
+			<span class="flex flex-wrap items-center" data-testid="relation-inverse-sentence">
+				{{ t('Each {0} has', [names.relatedSingular]) }}
+				<USelect
+					:model-value="inverseSide(kind)"
+					:items="sideItems"
+					:disabled="frozen"
+					:aria-label="t('Each {0} has', [names.relatedSingular])"
+					:ui="SIDE_UI"
+					@update:model-value="onInverseSide"
+				/>
+				{{ inverseNoun(kind, names) }}
+				<span class="text-muted">{{
+					` · ${t('shown on {0} as the field "{1}"', [names.relatedSingular, names.ownerPlural])}`
+				}}</span>
+			</span>
+		</div>
+
+		<div class="flex gap-3" :class="compact ? 'flex-col' : 'flex-row'">
+			<div
+				data-testid="relation-example-owner"
+				class="flex min-w-0 flex-1 flex-col gap-2 border border-default bg-default p-3"
+			>
+				<span class="font-semibold text-highlighted">{{ names.ownerSingular }}</span>
+				<span class="text-xs text-muted">{{ ownerNoun(kind, names) }}</span>
+				<div class="flex flex-wrap items-center gap-1.5">
+					<RelationChip
+						v-for="chip in sample.ownerChips"
+						:key="chip"
+						:label="chip"
+						tall
+					/>
+					<span v-if="sample.ownerMore" class="self-center text-xs text-muted"
+						>+{{ sample.ownerMore }}</span
+					>
+				</div>
+			</div>
+			<div
+				data-testid="relation-example-related"
+				class="flex min-w-0 flex-1 flex-col gap-2 border border-default bg-default p-3"
+			>
+				<span class="font-semibold text-highlighted">{{ names.relatedSingular }}</span>
+				<span class="text-xs text-muted">{{ inverseNoun(kind, names) }}</span>
+				<div class="flex flex-wrap items-center gap-1.5">
+					<RelationChip
+						v-for="chip in sample.relatedChips"
+						:key="chip"
+						:label="chip"
+						tall
+					/>
+					<span v-if="sample.relatedMore" class="self-center text-xs text-muted"
+						>+{{ sample.relatedMore }}</span
+					>
+				</div>
+			</div>
+		</div>
+	</div>
+</template>

web/src/components/SchemaBuilderPage.vue

@@ -262,6 +262,7 @@ async function restoreRowFocus() {
 							:field="builder.selected.value"
 							:errors="selectedErrors"
 							:compact="false"
+							:owner-name="form.name"
 						/>
 					</template>
 					<template v-else>
@@ -320,6 +321,7 @@ async function restoreRowFocus() {
 					:focus-token="builder.labelFocusToken.value"
 					:field="builder.selected.value"
 					:errors="selectedErrors"
+					:owner-name="form.name"
 					compact
 				/>
 			</FieldSheet>

web/src/components/SchemaDeleteControls.vue

@@ -35,6 +35,7 @@ watch(
 		:name="remove.type.value.name"
 		:key-value="remove.type.value.key"
 		:total="remove.total.value"
+		:referrer="remove.referrer.value"
 		:pending="remove.pending.value"
 		:offline="remove.offline.value"
 		@confirm="remove.confirm"

web/src/components/SchemaReviewDialog.vue

@@ -7,7 +7,7 @@ import SchemaChangeList from '@/components/SchemaChangeList.vue'
 import { entriesLine } from '@/lib/schemaEntries'
 import {
 	hasRefusedChange,
-	isMediaOnlyClean,
+	isNoDefaultOnlyClean,
 	summaryLine,
 	type FieldChange,
 } from '@/lib/schemaBuilderDiff'
@@ -25,7 +25,7 @@ defineEmits<{ apply: []; close: [] }>()
 const summary = computed(() => summaryLine(props.changes))
 const entries = computed(() => entriesLine(props.name, props.total))
 const refused = computed(() => hasRefusedChange(props.changes))
-const mediaOnlyClean = computed(() => isMediaOnlyClean(props.changes))
+const noDefaultOnlyClean = computed(() => isNoDefaultOnlyClean(props.changes))
 </script>
 
 <template>
@@ -53,7 +53,7 @@ const mediaOnlyClean = computed(() => isMediaOnlyClean(props.changes))
 		<p v-if="refused" class="text-xs/4.5 text-muted">
 			{{ t('Back to editing keeps your other changes.') }}
 		</p>
-		<p v-else-if="!mediaOnlyClean && !applying" class="text-xs/4.5 text-muted">
+		<p v-else-if="!noDefaultOnlyClean && !applying" class="text-xs/4.5 text-muted">
 			{{
 				t(
 					"Flagged changes can be refused if existing entries don't fit. If that happens, nothing is changed.",

web/src/composables/__tests__/useRelationSearch.spec.ts

@@ -0,0 +1,232 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+import { defineComponent, h } from 'vue'
+import { flushPromises, mount, type VueWrapper } from '@vue/test-utils'
+import { ApiError } from '@/composables/useApi'
+import { RELATION_SEARCH_DEBOUNCE_MS, useRelationSearch } from '@/composables/useRelationSearch'
+import type { ContentEntry } from '@/lib/contentTypes'
+import { RELATION_PAGE_SIZE } from '@/lib/relationField'
+
+const searchEntries = vi.fn()
+
+vi.mock('@/composables/useEntries', () => ({
+	useEntries: () => ({ searchEntries }),
+}))
+
+interface Deferred {
+	resolve: (value: unknown) => void
+	reject: (error: unknown) => void
+}
+
+let wrappers: VueWrapper[] = []
+
+function setup() {
+	let api!: ReturnType<typeof useRelationSearch>
+	const wrapper = mount(
+		defineComponent({
+			setup() {
+				api = useRelationSearch(() => 'venues')
+				return () => h('div')
+			},
+		}),
+	)
+	wrappers.push(wrapper)
+	return api
+}
+
+function entry(id: number): ContentEntry {
+	return { id, data: {} } as unknown as ContentEntry
+}
+
+function answer(ids: number[], total: number, page = 1) {
+	return { items: ids.map(entry), total, page, size: RELATION_PAGE_SIZE }
+}
+
+function deferred() {
+	const pending: Deferred[] = []
+	searchEntries.mockImplementation(
+		() =>
+			new Promise((resolve, reject) => {
+				pending.push({ resolve, reject })
+			}),
+	)
+	return pending
+}
+
+async function debounce() {
+	await vi.advanceTimersByTimeAsync(RELATION_SEARCH_DEBOUNCE_MS)
+	await flushPromises()
+}
+
+beforeEach(() => {
+	vi.useFakeTimers()
+	searchEntries.mockReset()
+})
+
+afterEach(() => {
+	wrappers.forEach((wrapper) => wrapper.unmount())
+	wrappers = []
+	vi.useRealTimers()
+})
+
+describe('useRelationSearch query', () => {
+	it('tracks the latest trimmed query across consecutive searches', async () => {
+		searchEntries.mockResolvedValue(answer([], 0))
+		const search = setup()
+
+		search.search('  alpha ')
+		await debounce()
+		expect(search.query.value).toBe('alpha')
+
+		search.search('beta')
+		await debounce()
+		expect(search.query.value).toBe('beta')
+		expect(searchEntries).toHaveBeenLastCalledWith('venues', {
+			q: 'beta',
+			page: 1,
+			size: RELATION_PAGE_SIZE,
+		})
+
+		search.search('')
+		await debounce()
+		expect(search.query.value).toBe('')
+	})
+})
+
+describe('useRelationSearch debounce', () => {
+	it('issues one request for rapid searches', async () => {
+		searchEntries.mockResolvedValue(answer([1], 1))
+		const search = setup()
+
+		search.search('a')
+		await vi.advanceTimersByTimeAsync(RELATION_SEARCH_DEBOUNCE_MS - 1)
+		search.search('ab')
+		await vi.advanceTimersByTimeAsync(RELATION_SEARCH_DEBOUNCE_MS - 1)
+		expect(searchEntries).not.toHaveBeenCalled()
+		await debounce()
+
+		expect(searchEntries).toHaveBeenCalledTimes(1)
+		expect(searchEntries.mock.calls[0]![1].q).toBe('ab')
+		expect(search.status.value).toBe('ready')
+	})
+})
+
+describe('useRelationSearch stale responses', () => {
+	it('discards a page-1 answer superseded by a newer load', async () => {
+		const pending = deferred()
+		const search = setup()
+
+		search.search('old')
+		await debounce()
+		search.search('new')
+		await debounce()
+		expect(pending).toHaveLength(2)
+
+		pending[1]!.resolve(answer([2], 1))
+		await flushPromises()
+		pending[0]!.resolve(answer([1], 1))
+		await flushPromises()
+
+		expect(search.entries.value.map((item) => item.id)).toEqual([2])
+	})
+
+	it('discards an in-flight answer when a new search starts during the debounce', async () => {
+		const pending = deferred()
+		const search = setup()
+
+		search.search('old')
+		await debounce()
+		search.search('new')
+		pending[0]!.resolve(answer([1], 1))
+		await flushPromises()
+
+		expect(search.entries.value).toEqual([])
+		expect(search.status.value).toBe('loading')
+	})
+
+	it('discards an answer after stop', async () => {
+		const pending = deferred()
+		const search = setup()
+
+		search.search('x')
+		await debounce()
+		search.stop()
+		pending[0]!.resolve(answer([1], 1))
+		await flushPromises()
+
+		expect(search.entries.value).toEqual([])
+	})
+})
+
+describe('useRelationSearch load more', () => {
+	it('appends the next page and ends when everything is loaded', async () => {
+		searchEntries
+			.mockResolvedValueOnce(answer([1, 2], 3))
+			.mockResolvedValueOnce(answer([3], 3, 2))
+		const search = setup()
+
+		await search.reload()
+		expect(search.hasMore.value).toBe(true)
+		await search.more()
+
+		expect(searchEntries).toHaveBeenLastCalledWith('venues', {
+			q: '',
+			page: 2,
+			size: RELATION_PAGE_SIZE,
+		})
+		expect(search.entries.value.map((item) => item.id)).toEqual([1, 2, 3])
+		expect(search.hasMore.value).toBe(false)
+		expect(search.more()).toBeUndefined()
+	})
+
+	it('starts the limiter on a 429 and keeps the loaded rows', async () => {
+		searchEntries
+			.mockResolvedValueOnce(answer([1], 5))
+			.mockRejectedValueOnce(new ApiError(429, 7))
+		const search = setup()
+
+		await search.reload()
+		await search.more()
+
+		expect(search.status.value).toBe('limited')
+		expect(search.limit.remaining.value).toBe(7)
+		expect(search.entries.value.map((item) => item.id)).toEqual([1])
+		expect(search.loadingMore.value).toBe(false)
+	})
+
+	it('surfaces other errors as failed and keeps the loaded rows', async () => {
+		searchEntries.mockResolvedValueOnce(answer([1], 5)).mockRejectedValueOnce(new ApiError(500))
+		const search = setup()
+
+		await search.reload()
+		await search.more()
+
+		expect(search.status.value).toBe('failed')
+		expect(search.entries.value.map((item) => item.id)).toEqual([1])
+	})
+
+	it('goes idle on a 401 during load more', async () => {
+		searchEntries.mockResolvedValueOnce(answer([1], 5)).mockRejectedValueOnce(new ApiError(401))
+		const search = setup()
+
+		await search.reload()
+		await search.more()
+
+		expect(search.status.value).toBe('idle')
+	})
+
+	it('does not request page+1 of a stale set after a failed page-1', async () => {
+		searchEntries
+			.mockResolvedValueOnce(answer([1], 5))
+			.mockRejectedValueOnce(new ApiError(500))
+			.mockResolvedValueOnce(answer([9], 9))
+		const search = setup()
+
+		await search.reload()
+		await search.reload()
+		expect(search.status.value).toBe('failed')
+		await search.reload()
+		await search.more()
+
+		expect(searchEntries.mock.calls.map((call) => call[1].page)).toEqual([1, 1, 1, 2])
+	})
+})

web/src/composables/useEntries.ts

@@ -3,6 +3,12 @@ import type { ContentEntry, EntryPage, EntryPageQuery } from '@/lib/contentTypes
 import { entryEndpoint } from '@/lib/contentEndpoints'
 import { jsonInit } from '@/lib/directoryRequest'
 
+export interface EntrySearchQuery {
+	q: string
+	page: number
+	size: number
+}
+
 export function useEntries() {
 	const { request } = useApi()
 	const options = { onForbidden: 'passthrough' } as const
@@ -21,6 +27,21 @@ export function useEntries() {
 		return page
 	}
 
+	async function searchEntries(key: string, query: EntrySearchQuery): Promise<EntryPage> {
+		const params = new URLSearchParams()
+		if (query.q !== '') {
+			params.set('q', query.q)
+		}
+		params.set('page', String(query.page))
+		params.set('size', String(query.size))
+		const url = `${entryEndpoint(key)}?${params.toString()}`
+		const page = await request<EntryPage>(url, options)
+		if (!Array.isArray(page?.items) || typeof page.total !== 'number') {
+			throw new Error(`Unexpected response from ${url}`)
+		}
+		return page
+	}
+
 	async function requestEntry(url: string, init: RequestInit): Promise<ContentEntry> {
 		const entry = await request<ContentEntry>(url, { ...init, ...options })
 		if (
@@ -49,5 +70,5 @@ export function useEntries() {
 		await request<void>(entryEndpoint(key, id), { method: 'DELETE', ...options })
 	}
 
-	return { listEntries, getEntry, createEntry, saveEntry, deleteEntry }
+	return { listEntries, searchEntries, getEntry, createEntry, saveEntry, deleteEntry }
 }

web/src/composables/useEntryDraft.ts

@@ -6,6 +6,7 @@ import { useEntryForm } from '@/composables/useEntryForm'
 import { useEntryLoad } from '@/composables/useEntryLoad'
 import type { ContentEntry } from '@/lib/contentTypes'
 import type { MediaSummary } from '@/lib/mediaField'
+import type { RelationSummary } from '@/lib/relationField'
 import { resolveEditorPhase, type EntryTarget } from '@/lib/entryEditorState'
 import { buildData, issueFor, validateEntry } from '@/lib/entryForm'
 import { classifyRefusal, isGoneError, parseEntryRefusal } from '@/lib/entryServerError'
@@ -92,7 +93,12 @@ export function useEntryDraft(typeKey: string, target: EntryTarget) {
 			return null
 		}
 		failure.value = 'none'
-		const issues = validateEntry(fields.value, form.values.value, form.images.value)
+		const issues = validateEntry(
+			fields.value,
+			form.values.value,
+			form.images.value,
+			form.relations.value,
+		)
 		if (Object.keys(issues).length > 0) {
 			form.reject(issues)
 			focusToken.value++
@@ -114,8 +120,13 @@ export function useEntryDraft(typeKey: string, target: EntryTarget) {
 		}
 	}
 
-	function change(key: string, value: unknown, image?: MediaSummary | null) {
-		form.setValue(key, value, image)
+	function change(
+		key: string,
+		value: unknown,
+		image?: MediaSummary | null,
+		summaries?: RelationSummary[],
+	) {
+		form.setValue(key, value, image, summaries)
 	}
 
 	function reload() {

web/src/composables/useEntryForm.ts

@@ -1,10 +1,12 @@
 import { computed, ref } from 'vue'
 import type { BuiltinField, ContentEntry } from '@/lib/contentTypes'
 import type { MediaMap, MediaSummary } from '@/lib/mediaField'
+import type { RelationSummaries, RelationSummary } from '@/lib/relationField'
 import {
 	carriesDefault,
 	firstIssueKey,
 	initialImages,
+	initialRelations,
 	initialValues,
 	valuesDiffer,
 	type EntryIssues,
@@ -16,6 +18,7 @@ export function useEntryForm(fields: () => BuiltinField[], creating: () => boole
 	const values = ref<EntryValues>({})
 	const saved = ref<EntryValues>({})
 	const images = ref<MediaMap>({})
+	const relations = ref<RelationSummaries>({})
 	const issues = ref<EntryIssues>({})
 	const rejected = ref(false)
 
@@ -28,6 +31,7 @@ export function useEntryForm(fields: () => BuiltinField[], creating: () => boole
 		values.value = { ...next }
 		saved.value = { ...next }
 		images.value = initialImages(fields(), entry)
+		relations.value = initialRelations(fields(), entry)
 		issues.value = {}
 		rejected.value = false
 	}
@@ -45,9 +49,21 @@ export function useEntryForm(fields: () => BuiltinField[], creating: () => boole
 		images.value = next
 	}
 
-	function setValue(key: string, value: unknown, image?: MediaSummary | null) {
+	function setRelations(key: string, summaries: RelationSummary[] | undefined) {
+		if (summaries !== undefined) {
+			relations.value = { ...relations.value, [key]: summaries }
+		}
+	}
+
+	function setValue(
+		key: string,
+		value: unknown,
+		image?: MediaSummary | null,
+		summaries?: RelationSummary[],
+	) {
 		values.value = { ...values.value, [key]: value }
 		setImage(key, image)
+		setRelations(key, summaries)
 		rejected.value = false
 		if (issues.value[key]) {
 			const rest = { ...issues.value }
@@ -72,6 +88,7 @@ export function useEntryForm(fields: () => BuiltinField[], creating: () => boole
 	return {
 		values,
 		images,
+		relations,
 		issues,
 		rejected,
 		dirty,

web/src/composables/useRelationSearch.ts

@@ -0,0 +1,131 @@
+import { computed, onBeforeUnmount, ref } from 'vue'
+import { ApiError } from '@/composables/useApi'
+import { useDelayedSkeleton } from '@/composables/useDelayedSkeleton'
+import { useEntries } from '@/composables/useEntries'
+import { useRetryAfter } from '@/composables/useRetryAfter'
+import type { ContentEntry } from '@/lib/contentTypes'
+import { RELATION_PAGE_SIZE } from '@/lib/relationField'
+
+export const RELATION_SEARCH_DEBOUNCE_MS = 200
+
+const UNAUTHORIZED = 401
+const RATE_LIMITED = 429
+const RATE_LIMIT_FALLBACK_SECONDS = 30
+
+export type RelationSearchStatus = 'idle' | 'loading' | 'ready' | 'failed' | 'limited'
+
+export function useRelationSearch(target: () => string) {
+	const { searchEntries } = useEntries()
+	const skeleton = useDelayedSkeleton()
+	const limit = useRetryAfter()
+	const entries = ref<ContentEntry[]>([])
+	const total = ref(0)
+	const page = ref(0)
+	const status = ref<RelationSearchStatus>('idle')
+	const loadingMore = ref(false)
+	const query = ref('')
+	let token = 0
+	let timer: ReturnType<typeof setTimeout> | null = null
+
+	const hasMore = computed(() => status.value === 'ready' && entries.value.length < total.value)
+	const searching = computed(() => status.value === 'loading' && !loadingMore.value)
+	const showSkeleton = computed(() => searching.value && skeleton.visible.value)
+
+	function clearTimer() {
+		if (timer !== null) {
+			clearTimeout(timer)
+			timer = null
+		}
+	}
+
+	function fail(error: unknown) {
+		if (error instanceof ApiError && error.status === UNAUTHORIZED) {
+			status.value = 'idle'
+		} else if (error instanceof ApiError && error.status === RATE_LIMITED) {
+			limit.start(error.retryAfter ?? RATE_LIMIT_FALLBACK_SECONDS)
+			status.value = 'limited'
+		} else {
+			status.value = 'failed'
+		}
+	}
+
+	async function load(pageNumber: number) {
+		const current = ++token
+		loadingMore.value = pageNumber > 1
+		status.value = 'loading'
+		skeleton.start()
+		try {
+			const answer = await searchEntries(target(), {
+				q: query.value,
+				page: pageNumber,
+				size: RELATION_PAGE_SIZE,
+			})
+			if (current !== token) {
+				return
+			}
+			entries.value = pageNumber === 1 ? answer.items : [...entries.value, ...answer.items]
+			total.value = answer.total
+			page.value = pageNumber
+			status.value = 'ready'
+		} catch (error) {
+			if (current === token) {
+				if (pageNumber === 1) {
+					page.value = 0
+				}
+				fail(error)
+			}
+		} finally {
+			if (current === token) {
+				skeleton.stop()
+				loadingMore.value = false
+			}
+		}
+	}
+
+	function search(text: string) {
+		clearTimer()
+		query.value = text.trim()
+		token++
+		skeleton.stop()
+		loadingMore.value = false
+		timer = setTimeout(() => {
+			timer = null
+			load(1)
+		}, RELATION_SEARCH_DEBOUNCE_MS)
+	}
+
+	function reload() {
+		clearTimer()
+		return load(1)
+	}
+
+	function more() {
+		if (hasMore.value) {
+			return load(page.value + 1)
+		}
+	}
+
+	function stop() {
+		clearTimer()
+		token++
+		skeleton.stop()
+		loadingMore.value = false
+	}
+
+	onBeforeUnmount(stop)
+
+	return {
+		entries,
+		total,
+		status,
+		query,
+		hasMore,
+		loadingMore,
+		showSkeleton,
+		limit,
+		search,
+		reload,
+		more,
+		stop,
+	}
+}

web/src/composables/useSchemaDelete.ts

@@ -12,6 +12,7 @@ import { SCHEMA_PATH } from '@/lib/routePaths'
 import { useContentTypesStore } from '@/stores/contentTypes'
 
 const HAS_ENTRIES_BODY = 'content_type_has_entries'
+const REFERENCED_BODY = 'content_type_referenced'
 const TOAST_ID = 'content-type-deleted'
 
 export function useSchemaDelete(source: () => EditSource) {
@@ -27,6 +28,12 @@ export function useSchemaDelete(source: () => EditSource) {
 	const offline = computed(() => !online.value)
 	const type = computed(() => source().type)
 	const total = computed(() => source().total)
+	const referrer = computed(
+		() =>
+			store.items.find((candidate) =>
+				candidate.fields.some((field) => field.relation?.content_type === type.value.key),
+			)?.name ?? '',
+	)
 
 	function open() {
 		if (pending.value) {
@@ -60,6 +67,8 @@ export function useSchemaDelete(source: () => EditSource) {
 			forbidden.value = true
 		} else if (status === 409 && body === HAS_ENTRIES_BODY) {
 			stage.value = 'conflict'
+		} else if (status === 409 && body === REFERENCED_BODY) {
+			stage.value = 'referenced'
 		} else {
 			stage.value = 'failed'
 		}
@@ -95,6 +104,7 @@ export function useSchemaDelete(source: () => EditSource) {
 		offline,
 		type,
 		total,
+		referrer,
 		open,
 		close,
 		viewEntries,

web/src/i18n/mediaFieldMessages.spec.ts

@@ -16,7 +16,7 @@ const SOURCES = [
 	'lib/schemaBuilderDiff.ts',
 ]
 
-const SAME_IN_FRENCH = new Set<string>(['Date'])
+const SAME_IN_FRENCH = new Set<string>(['Date', 'Relation'])
 
 const LITERAL = /\bt\(\s*(?:'((?:\\.|[^'\\])*)'|"((?:\\.|[^"\\])*)")/g
 

web/src/i18n/messages.ts

@@ -2663,6 +2663,61 @@ export const messages = {
 	"A media field can't have a default, so the {0} existing entries would have no image. Make {1} optional to add it.":
 		'Un champ média ne peut pas avoir de valeur par défaut, donc les {0} entrées existantes n’auraient pas d’image. Rendez {1} facultatif pour l’ajouter.',
 	'{0} entries are unaffected.': '{0} entrées ne sont pas concernées.',
+	'Entry no longer exists': 'Cette entrée n’existe plus',
+	'Choose a {0}.': 'Choisissez une valeur pour {0}.',
+	'{0} must point to an existing entry.': '{0} doit pointer vers une entrée existante.',
+	'That {0} is already used by another entry.':
+		'Cette valeur de {0} est déjà utilisée par une autre entrée.',
+	Relation: 'Relation',
+	"Links to another type's entries": 'Renvoie vers les entrées d’un autre type',
+	"A relation can't have a default, so the existing entry would have no {0}. Make {0} optional to add it.":
+		'Une relation ne peut pas avoir de valeur par défaut, donc l’entrée existante n’aurait pas de valeur pour {0}. Rendez {0} facultatif pour l’ajouter.',
+	"A relation can't have a default, so the {0} existing entries would have no {1}. Make {1} optional to add it.":
+		'Une relation ne peut pas avoir de valeur par défaut, donc les {0} entrées existantes n’auraient pas de valeur pour {1}. Rendez {1} facultatif pour l’ajouter.',
+	Entries: 'Entrées',
+	'Each {0} has one {1}, and each {1} has one {0}.':
+		'Chaque {0} a un seul {1}, et chaque {1} a un seul {0}.',
+	'Each {0} has one {1}. A {1} has many {2}.':
+		'Chaque {0} a un seul {1}. Un {1} a plusieurs {2}.',
+	'Each {0} has many {1}, and each {2} has many {3}.':
+		'Chaque {0} a plusieurs {1}, et chaque {2} a plusieurs {3}.',
+	'Choose a related content type.': 'Choisissez un type de contenu lié.',
+	'{0} has a field that points to {1}. Remove that field first.':
+		'{0} a un champ qui pointe vers {1}. Supprimez d’abord ce champ.',
+	'Another content type has a field that points to {0}. Remove that field first.':
+		'Un autre type de contenu a un champ qui pointe vers {0}. Supprimez d’abord ce champ.',
+	'{0} is required. Choose another to save.':
+		'{0} est obligatoire. Choisissez une autre valeur pour enregistrer.',
+	'An {0} can have many {1}.': 'Un {0} peut avoir plusieurs {1}.',
+	'A {0} can have many {1}.': 'Un {0} peut avoir plusieurs {1}.',
+	'Remove {0} from {1}': 'Retirer {0} de {1}',
+	'{0} set to {1}.': '{0} défini sur {1}.',
+	'{0} removed from {1}.': '{0} retiré de {1}.',
+	'{0} added to {1}.': '{0} ajouté à {1}.',
+	'{0} results': '{0} résultats',
+	'No results': 'Aucun résultat',
+	'Search to add': 'Rechercher pour ajouter',
+	'Searching…': 'Recherche en cours…',
+	"Couldn't load {0}": 'Impossible de charger {0}',
+	'You can add up to {0}.': 'Vous pouvez en ajouter jusqu’à {0}.',
+	'No {0} yet. Add one in Content, then come back.':
+		'Aucun élément dans {0} pour l’instant. Ajoutez-en depuis Contenu, puis revenez.',
+	'No {0} match "{1}"': 'Aucun résultat dans {0} pour « {1} »',
+	'No other {0} to add.': 'Aucun autre élément de {0} à ajouter.',
+	one: 'un',
+	many: 'plusieurs',
+	'One to one': 'Un à un',
+	'One to many': 'Un à plusieurs',
+	'Many to many': 'Plusieurs à plusieurs',
+	"The related type and the connection can't change after saving.":
+		'Le type lié et la connexion ne peuvent plus changer après l’enregistrement.',
+	'Related content type': 'Type de contenu lié',
+	'Choose the content type this field points to.':
+		'Choisissez le type de contenu vers lequel ce champ pointe.',
+	'Choose a content type': 'Choisissez un type de contenu',
+	'How are they connected?': 'Comment sont-ils liés ?',
+	'Each {0} has': 'Chaque {0} a',
+	'shown on {0} as the field "{1}"': 'affiché sur {0} comme le champ « {1} »',
 } as const
 
 export type MessageKey = keyof typeof messages

web/src/i18n/relationFieldMessages.spec.ts

@@ -0,0 +1,53 @@
+import { readFileSync } from 'node:fs'
+import { join } from 'node:path'
+import { describe, expect, it } from 'vitest'
+import { messages } from './messages'
+
+const SOURCES = [
+	'components/RelationField.vue',
+	'components/RelationPicker.vue',
+	'components/DeleteTypeDialog.vue',
+	'lib/relationSentences.ts',
+	'lib/fieldTypes.ts',
+	'lib/entryCells.ts',
+	'lib/entryMessages.ts',
+	'lib/schemaBuilderValidation.ts',
+]
+
+const SAME_IN_FRENCH = new Set<string>(['Relation'])
+
+const LITERAL = /\bt\(\s*(?:'((?:\\.|[^'\\])*)'|"((?:\\.|[^"\\])*)")/g
+
+function keysIn(source: string) {
+	return [...source.matchAll(LITERAL)].map((match) =>
+		(match[1] ?? match[2] ?? '').replace(/\\u0022/g, '"').replace(/\\(['"\\])/g, '$1'),
+	)
+}
+
+describe('Relation field messages', () => {
+	const keys = SOURCES.flatMap((file) =>
+		keysIn(readFileSync(join(import.meta.dirname, '..', file), 'utf8')).map((key) => ({
+			file,
+			key,
+		})),
+	)
+
+	it('finds the strings of the feature', () => {
+		expect(keys.length).toBeGreaterThan(40)
+	})
+
+	it.each(keys.map(({ file, key }) => [file, key]))(
+		'%s: "%s" has its own French entry',
+		(_file, key) => {
+			const french = (messages as Record<string, string>)[key as string]
+
+			expect(french).toMatch(/\S/)
+			if (
+				!SAME_IN_FRENCH.has(key as string) &&
+				!(key as string).match(/^(Date|Text|Number)$/)
+			) {
+				expect(french).not.toBe(key)
+			}
+		},
+	)
+})

web/src/lib/__tests__/fieldTypes.spec.ts

@@ -10,6 +10,7 @@ const CONTROLS: Record<FieldType, string> = {
 	date: 'date',
 	select: 'select',
 	media: 'media',
+	relation: 'relation',
 }
 
 function editor(type: FieldType) {

web/src/lib/__tests__/mediaField.spec.ts

@@ -50,9 +50,10 @@ function mediaField(rest: object = {}) {
 const media = ENTRY_EDITORS.media
 
 describe('media in the registry', () => {
-	it('is the seventh type, after select', () => {
-		expect(FIELD_TYPES).toHaveLength(7)
+	it('is the seventh type, after select and before relation', () => {
+		expect(FIELD_TYPES).toHaveLength(8)
 		expect(FIELD_TYPES[6]).toBe('media')
+		expect(FIELD_TYPES[7]).toBe('relation')
 		expect(FIELD_TYPES[5]).toBe('select')
 	})
 
@@ -82,7 +83,7 @@ describe('media in the registry', () => {
 		)
 	})
 
-	it.each(FIELD_TYPES.filter((type) => type !== 'media'))(
+	it.each(FIELD_TYPES.filter((type) => type !== 'media' && type !== 'relation'))(
 		'%s keeps its builder options and has no hint',
 		(type) => {
 			const spec = fieldTypeSpec(type)
@@ -374,6 +375,7 @@ describe('media in the schema builder', () => {
 			min: null,
 			max: null,
 			options: [],
+			relation: null,
 		})
 		expect(payloadField({ ...field, required: true }).required).toBe(true)
 	})

web/src/lib/__tests__/relationField.spec.ts

@@ -0,0 +1,483 @@
+import { describe, expect, it } from 'vitest'
+import type { ContentEntry } from '@/lib/contentTypes'
+import { describeCell, plainCellText, relationLabel } from '@/lib/entryCells'
+import { ENTRY_EDITORS } from '@/lib/entryEditors'
+import {
+	buildData,
+	entryTitle,
+	initialRelations,
+	initialValues,
+	validateEntry,
+	valuesDiffer,
+} from '@/lib/entryForm'
+import { ruleMessage } from '@/lib/entryMessages'
+import { groupFields } from '@/lib/entryLayout'
+import { classifyRefusal, parseEntryRefusal } from '@/lib/entryServerError'
+import { FIELD_TYPES, fieldTypeSpec } from '@/lib/fieldTypes'
+import { isRelationId, relationIdsOf, summariesOf, type RelationSummary } from '@/lib/relationField'
+import { relationRowOf } from '@/lib/relationRows'
+import { ApiError } from '@/lib/apiError'
+import { diffFields } from '@/lib/schemaBuilderDiff'
+import { baselinePayload, fieldFromApi, formFromType } from '@/lib/schemaBuilderLoad'
+import { createField } from '@/lib/schemaBuilderModel'
+import { buildPayload, payloadField } from '@/lib/schemaBuilderPayload'
+import { sampleEntry } from '@/lib/schemaBuilderSample'
+import { validateField } from '@/lib/schemaBuilderValidation'
+import { apiField } from './schemaFixtures'
+
+const relation = ENTRY_EDITORS.relation
+
+function field(kind: 'one_to_one' | 'one_to_many' | 'many_to_many', rest: object = {}) {
+	return apiField('Venue', 'venue', 'relation', {
+		options: [],
+		relation: { content_type: 'venues', kind },
+		...rest,
+	})
+}
+
+const single = field('one_to_many')
+const many = field('many_to_many')
+
+function target(id: number, name: string | null): RelationSummary {
+	return {
+		id,
+		content_type: 'venues',
+		first_field: { key: 'name', type: 'text', value: name },
+	}
+}
+
+describe('relation in the registry', () => {
+	it('is the eighth type, after media', () => {
+		expect(FIELD_TYPES).toHaveLength(8)
+		expect(FIELD_TYPES[7]).toBe('relation')
+		expect(FIELD_TYPES[6]).toBe('media')
+	})
+
+	it('describes itself', () => {
+		const spec = fieldTypeSpec('relation')
+
+		expect(spec.label()).toBe('Relation')
+		expect(spec.description()).toBe("Links to another type's entries")
+		expect(spec.icon).toBe('i-lucide-link')
+		expect(spec.editor.control).toBe('relation')
+		expect(spec.cell).toBe('relation')
+		expect(spec.pairs).toBe(false)
+		expect(spec.supportsUnique).toBe(false)
+		expect(spec.supportsLimits).toBe(false)
+		expect(spec.supportsDefault).toBe(false)
+		expect(spec.supportsChoices).toBe(false)
+		expect(spec.showsUnsupportedOptions).toBe(false)
+		expect(spec.builderHint).toBeNull()
+		expect(spec.holdsRelation).toBe(true)
+	})
+
+	it('is never the fallback type, while an unknown type still is', () => {
+		expect(fieldTypeSpec('relation')).not.toBe(fieldTypeSpec('text'))
+		expect(fieldTypeSpec('mystery')).toBe(fieldTypeSpec('text'))
+		expect(fieldFromApi(single, 1).type).toBe('relation')
+	})
+
+	it('has no counter and no help of its own', () => {
+		expect(relation.counter(single, 3)).toBeNull()
+		expect(relation.help(single)).toBe('')
+	})
+
+	it('never pairs with a neighbour', () => {
+		const fields = [
+			apiField('Online', 'online', 'boolean'),
+			single,
+			apiField('Cap', 'cap', 'number'),
+		]
+
+		expect(groupFields(fields).map((row) => row.length)).toEqual([1, 1, 1])
+	})
+})
+
+describe('empty and initial values', () => {
+	it.each([
+		['one_to_one', null],
+		['one_to_many', null],
+		['many_to_many', []],
+	] as const)('starts empty for %s on create', (kind, empty) => {
+		expect(relation.initial(field(kind), 3, true)).toEqual(empty)
+	})
+
+	it('has no default, so no Default tag ever shows', () => {
+		expect(relation.initial(field('one_to_many', { default: 3 }), undefined, true)).toBeNull()
+	})
+
+	it('takes the stored id or ids on edit', () => {
+		expect(relation.initial(single, 3, false)).toBe(3)
+		expect(relation.initial(single, null, false)).toBeNull()
+		expect(relation.initial(many, [11, 12], false)).toEqual([11, 12])
+		expect(relation.initial(many, undefined, false)).toEqual([])
+	})
+
+	it('copies the stored array', () => {
+		const stored = [11]
+
+		expect(relation.initial(many, stored, false)).not.toBe(stored)
+	})
+})
+
+describe('client validation of a relation value', () => {
+	it.each([
+		['single', true, null, 'required'],
+		['single', false, null, null],
+		['single', true, 3, null],
+		['single', false, 0, 'type'],
+		['single', false, '3', 'type'],
+		['single', false, [3], 'type'],
+		['many', true, [], 'required'],
+		['many', false, [], null],
+		['many', false, [11, 12], null],
+		['many', false, [11, 11], 'type'],
+		['many', false, 11, 'type'],
+		['many', false, Array.from({ length: 51 }, (_, index) => index + 1), 'type'],
+		['many', false, Array.from({ length: 50 }, (_, index) => index + 1), null],
+	])('%s required=%s value %j gives %s', (kind, required, value, rule) => {
+		const subject = kind === 'single' ? single : many
+
+		expect(relation.validate({ ...subject, required }, value)).toBe(rule)
+	})
+
+	it('treats a required relation whose targets are all missing as empty', () => {
+		const gone: RelationSummary = { id: 3, missing: true }
+
+		expect(
+			relation.validate({ ...single, required: true }, 3, { image: null, relations: [gone] }),
+		).toBe('required')
+		expect(
+			relation.validate({ ...single, required: false }, 3, {
+				image: null,
+				relations: [gone],
+			}),
+		).toBeNull()
+		expect(
+			relation.validate({ ...many, required: true }, [3, 4], {
+				image: null,
+				relations: [gone, { id: 4, missing: true }],
+			}),
+		).toBe('required')
+		expect(
+			relation.validate({ ...many, required: true }, [3, 4], {
+				image: null,
+				relations: [gone, target(4, 'Hall')],
+			}),
+		).toBeNull()
+	})
+
+	it('never produces min, max or options', () => {
+		const rules = [null, 0, '3', [3], [], [1, 1], 5].flatMap((value) =>
+			[single, many].map((subject) =>
+				relation.validate({ ...subject, required: true }, value),
+			),
+		)
+
+		expect(rules.filter((rule) => ['min', 'max', 'options'].includes(rule ?? ''))).toEqual([])
+	})
+})
+
+describe('messages of a relation field', () => {
+	it.each([
+		['required', 'Choose a Venue.'],
+		['type', 'Venue must point to an existing entry.'],
+		['unique', 'That Venue is already used by another entry.'],
+	] as const)('the rule %s reads "%s"', (rule, message) => {
+		expect(ruleMessage(rule, single)).toBe(message)
+	})
+})
+
+describe('the payload', () => {
+	it('sends the id, null, or an array of ids', () => {
+		expect(relation.payload(single, 3)).toBe(3)
+		expect(relation.payload(single, null)).toBeNull()
+		expect(relation.payload(single, undefined)).toBeNull()
+		expect(relation.payload(many, [11, 12])).toEqual([11, 12])
+		expect(relation.payload(many, undefined)).toEqual([])
+	})
+
+	it('puts null and [] in a create body, never absent', () => {
+		const fields = [single, { ...many, key: 'speakers' }]
+
+		const body = buildData(fields, initialValues(fields, null))
+
+		expect(body).toEqual({ venue: null, speakers: [] })
+		expect(Object.keys(body)).toEqual(['venue', 'speakers'])
+	})
+})
+
+describe('the ids helpers', () => {
+	it('accepts uint32 ids of at least 1', () => {
+		expect(isRelationId(1)).toBe(true)
+		expect(isRelationId(4294967295)).toBe(true)
+		expect(isRelationId(0)).toBe(false)
+		expect(isRelationId(4294967296)).toBe(false)
+		expect(isRelationId(1.5)).toBe(false)
+		expect(isRelationId('3')).toBe(false)
+	})
+
+	it('reads one id or many', () => {
+		expect(relationIdsOf(3)).toEqual([3])
+		expect(relationIdsOf([3, 'x', 4])).toEqual([3, 4])
+		expect(relationIdsOf(null)).toEqual([])
+	})
+})
+
+describe('summaries of an entry', () => {
+	const entry = {
+		id: 42,
+		data: { venue: 3, speakers: [11, 12] },
+		relations: {
+			venue: target(3, 'Rue Verte hall'),
+			speakers: [target(11, 'Ines Duarte'), target(12, 'Jonas Pereira')],
+		},
+	} as unknown as ContentEntry
+
+	it('wraps a single summary in an array', () => {
+		expect(summariesOf(entry, 'venue').map((summary) => summary.id)).toEqual([3])
+		expect(summariesOf(entry, 'speakers').map((summary) => summary.id)).toEqual([11, 12])
+		expect(summariesOf(entry, 'other')).toEqual([])
+		expect(summariesOf(null, 'venue')).toEqual([])
+	})
+
+	it('keeps only the summaries of the stored ids', () => {
+		const stale = { ...entry, data: { venue: 4, speakers: [12] } } as ContentEntry
+
+		const kept = initialRelations([single, { ...many, key: 'speakers' }], stale)
+
+		expect(kept).toEqual({ speakers: [entry.relations!.speakers![1]] })
+	})
+})
+
+describe('dirty tracking', () => {
+	it('compares ids by value and by order', () => {
+		expect(valuesDiffer([single], { venue: 3 }, { venue: 3 })).toBe(false)
+		expect(valuesDiffer([many], { venue: [11, 12] }, { venue: [11, 12] })).toBe(false)
+		expect(valuesDiffer([many], { venue: [12, 11] }, { venue: [11, 12] })).toBe(true)
+		expect(valuesDiffer([many], { venue: [11] }, { venue: [11, 12] })).toBe(true)
+	})
+})
+
+describe('labels and cells', () => {
+	it('uses the first field of the target, formatted like the list', () => {
+		expect(relationLabel(target(3, 'Rue Verte hall'))).toBe('Rue Verte hall')
+		expect(
+			relationLabel({
+				id: 5,
+				content_type: 'x',
+				first_field: { key: 'on', type: 'boolean', value: true },
+			}),
+		).toBe('Yes')
+		expect(
+			relationLabel({
+				id: 6,
+				content_type: 'x',
+				first_field: { key: 'on', type: 'number', value: 1500 },
+			}),
+		).toBe('1,500')
+	})
+
+	it('falls back to Entry N for a null first field', () => {
+		expect(relationLabel(target(7, null))).toBe('Entry 7')
+		expect(
+			relationLabel({
+				id: 8,
+				content_type: 'x',
+				first_field: { key: 'm', type: 'media', value: 9 },
+			}),
+		).toBe('Entry 8')
+	})
+
+	it('labels a missing target', () => {
+		expect(relationLabel({ id: 3, missing: true })).toBe('Entry no longer exists')
+	})
+
+	it('describes one chip, two chips and a +N, or an empty cell', () => {
+		const summaries = [11, 12, 13, 14].map((id) => target(id, `Speaker ${id}`))
+
+		const cell = describeCell(many, [11, 12, 13, 14], undefined, summaries)
+
+		expect(cell.kind).toBe('relation')
+		expect(cell.chips!.map((chip) => chip.label)).toEqual(['Speaker 11', 'Speaker 12'])
+		expect(cell.more).toBe(2)
+		expect(plainCellText(cell)).toBe('Speaker 11, Speaker 12, Speaker 13, Speaker 14')
+		expect(describeCell(many, []).kind).toBe('empty')
+		expect(describeCell(single, null).kind).toBe('empty')
+		expect(plainCellText(describeCell(many, []))).toBe('–')
+	})
+
+	it('never shows the numeric id when no summary came with the item', () => {
+		const cell = describeCell(single, 3)
+
+		expect(cell.chips).toEqual([{ id: 3, label: 'Entry no longer exists', missing: true }])
+		expect(cell.text).not.toContain('3')
+	})
+
+	it('titles an entry whose first field is a relation "Entry N"', () => {
+		const entry = {
+			id: 42,
+			data: { venue: 3 },
+			relations: { venue: target(3, 'Hall') },
+		} as unknown as ContentEntry
+
+		expect(entryTitle([single], entry)).toBe('Entry 42')
+	})
+})
+
+describe('rows of the picker', () => {
+	const fields = [
+		apiField('Name', 'name', 'text'),
+		apiField('City', 'city', 'text'),
+		apiField('Seats', 'seats', 'number'),
+		apiField('Notes', 'notes', 'text'),
+	]
+	const entry = (data: Record<string, unknown>) => ({ id: 3, data }) as unknown as ContentEntry
+
+	it('puts the first field in the title and up to two next fields in the second line', () => {
+		const row = relationRowOf(
+			entry({ name: 'Rue Verte hall', city: 'Lyon', seats: 120, notes: 'x' }),
+			'venues',
+			fields,
+		)
+
+		expect(row.title).toBe('Rue Verte hall')
+		expect(row.detail).toBe('Lyon · 120')
+		expect(row.summary.first_field).toEqual({
+			key: 'name',
+			type: 'text',
+			value: 'Rue Verte hall',
+		})
+	})
+
+	it('skips empty fields and falls back to Entry N', () => {
+		const row = relationRowOf(entry({ name: '', city: '', seats: 5 }), 'venues', fields)
+
+		expect(row.title).toBe('Entry 3')
+		expect(row.detail).toBe('5')
+	})
+
+	it('copes with a type that is not known yet', () => {
+		const row = relationRowOf(entry({ name: 'x' }), 'venues', [])
+
+		expect(row.title).toBe('Entry 3')
+		expect(row.detail).toBe('')
+	})
+})
+
+describe('server refusals', () => {
+	it.each([
+		[422, 'invalid_entry: venue: required', 'required'],
+		[422, 'invalid_entry: venue: type', 'type'],
+		[409, 'invalid_entry: venue: unique', 'unique'],
+	])('maps %i %s to a rule of the field', (status, body, rule) => {
+		const outcome = classifyRefusal(
+			[single],
+			parseEntryRefusal(new ApiError(status, undefined, body)),
+		)
+
+		expect(outcome).toMatchObject({ kind: 'field', rule })
+	})
+
+	it('maps unknown_field to a schema change', () => {
+		const outcome = classifyRefusal(
+			[single],
+			parseEntryRefusal(new ApiError(422, undefined, 'invalid_entry: venue: unknown_field')),
+		)
+
+		expect(outcome).toEqual({ kind: 'schema', key: 'venue' })
+	})
+})
+
+describe('the entry validation', () => {
+	it('reports the first rule of each relation field', () => {
+		const fields = [
+			{ ...single, required: true },
+			{ ...many, key: 'speakers', required: true },
+		]
+
+		const issues = validateEntry(fields, { venue: null, speakers: [] })
+
+		expect(issues.venue!.rule).toBe('required')
+		expect(issues.speakers!.rule).toBe('required')
+		expect(issues.venue!.message).toBe('Choose a Venue.')
+	})
+})
+
+describe('relation in the builder model', () => {
+	const events = {
+		id: 1,
+		key: 'events',
+		name: 'Events',
+		icon: null,
+		created_at: '',
+		updated_at: '',
+	}
+
+	it('loads the target and the kind', () => {
+		const loaded = fieldFromApi(field('many_to_many'), 1)
+
+		expect(loaded.relationType).toBe('venues')
+		expect(loaded.relationKind).toBe('many_to_many')
+		expect(loaded.saved).toBe(true)
+	})
+
+	it('sends the relation only for a relation field', () => {
+		const sent = payloadField(
+			createField(1, {
+				label: 'Venue',
+				key: 'venue',
+				type: 'relation',
+				relationType: 'venues',
+			}),
+		)
+
+		expect(sent).toEqual({
+			key: 'venue',
+			label: 'Venue',
+			type: 'relation',
+			required: false,
+			unique: false,
+			default: null,
+			min: null,
+			max: null,
+			options: [],
+			relation: { content_type: 'venues', kind: 'one_to_many' },
+		})
+		expect(
+			payloadField(createField(2, { label: 'T', key: 't', relationType: 'venues' })).relation,
+		).toBeNull()
+	})
+
+	it('round trips a loaded field with no change', () => {
+		const type = { ...events, fields: [single, { ...many, key: 'speakers' }] }
+		let uid = 0
+		const form = formFromType(type, () => ++uid)
+
+		expect(buildPayload(form).fields).toEqual(baselinePayload(type))
+		expect(diffFields(baselinePayload(type), form.fields, 3)).toEqual([])
+	})
+
+	it('needs a related type', () => {
+		const created = createField(1, { label: 'Venue', key: 'venue', type: 'relation' })
+
+		expect(validateField(created, []).relation).toBe('Choose a related content type.')
+		expect(validateField({ ...created, relationType: 'venues' }, []).relation).toBeUndefined()
+		expect(validateField(createField(2, { label: 'T', key: 't' }), []).relation).toBeUndefined()
+	})
+
+	it('samples null for a single kind and [] for many_to_many', () => {
+		const singleField = createField(1, { label: 'Venue', key: 'venue', type: 'relation' })
+		const manyField = createField(2, {
+			label: 'Speakers',
+			key: 'speakers',
+			type: 'relation',
+			relationKind: 'many_to_many',
+		})
+
+		const data = sampleEntry('events', [singleField, manyField]).data
+
+		expect(data.venue).toBeNull()
+		expect(data.speakers).toEqual([])
+	})
+})

web/src/lib/__tests__/relationRows.spec.ts

@@ -0,0 +1,62 @@
+import { describe, expect, it } from 'vitest'
+import type { BuiltinField, ContentEntry } from '@/lib/contentTypes'
+import { ROW_DETAIL_FIELDS, relationRowOf } from '@/lib/relationRows'
+
+function field(key: string, type: string): BuiltinField {
+	return { key, type, label: key } as unknown as BuiltinField
+}
+
+function entry(id: number, data: Record<string, unknown>): ContentEntry {
+	return { id, data } as unknown as ContentEntry
+}
+
+describe('relationRowOf', () => {
+	it('builds the summary from the first field', () => {
+		const row = relationRowOf(entry(7, { name: 'Hall' }), 'venues', [field('name', 'text')])
+
+		expect(row.id).toBe(7)
+		expect(row.title).toBe('Hall')
+		expect(row.summary).toEqual({
+			id: 7,
+			content_type: 'venues',
+			first_field: { key: 'name', type: 'text', value: 'Hall' },
+		})
+	})
+
+	it('falls back to an empty text summary when the type has no fields', () => {
+		const row = relationRowOf(entry(3, {}), 'venues', [])
+
+		expect(row.summary.first_field).toEqual({ key: '', type: 'text', value: null })
+		expect(row.detail).toBe('')
+	})
+
+	it('uses null when the first field is absent from the data', () => {
+		const row = relationRowOf(entry(3, {}), 'venues', [field('name', 'text')])
+
+		expect(row.summary.first_field).toEqual({ key: 'name', type: 'text', value: null })
+	})
+
+	it('joins at most the first detail fields and skips empty ones', () => {
+		const fields = [
+			field('name', 'text'),
+			field('city', 'text'),
+			field('country', 'text'),
+			field('zip', 'text'),
+		]
+		const row = relationRowOf(
+			entry(1, { name: 'Hall', city: 'Paris', country: 'France', zip: '75000' }),
+			'venues',
+			fields,
+		)
+
+		expect(ROW_DETAIL_FIELDS).toBe(2)
+		expect(row.detail).toBe('Paris · France')
+
+		const sparse = relationRowOf(
+			entry(1, { name: 'Hall', city: '', country: 'France', zip: '75000' }),
+			'venues',
+			fields,
+		)
+		expect(sparse.detail).toBe('France')
+	})
+})

web/src/lib/__tests__/relationSentences.spec.ts

@@ -0,0 +1,89 @@
+import { describe, expect, it } from 'vitest'
+import {
+	inverseNoun,
+	inverseSide,
+	kindFromInverseSide,
+	kindFromOwnerSide,
+	kindSentence,
+	ownerNoun,
+	ownerSide,
+	relationNames,
+	relationSample,
+	singularOf,
+} from '@/lib/relationSentences'
+import { RELATION_KINDS } from '@/lib/relationField'
+
+const names = relationNames('Events', 'Venues', 'Venue')
+
+describe('the names of both sides', () => {
+	it('draws the singular from the type name and the related singular from the field label', () => {
+		expect(names).toEqual({
+			ownerSingular: 'Event',
+			ownerPlural: 'Events',
+			relatedSingular: 'Venue',
+			relatedPlural: 'Venues',
+		})
+	})
+
+	it('removes only one final s and keeps one-letter names', () => {
+		expect(singularOf('Press mentions')).toBe('Press mention')
+		expect(singularOf('Glass')).toBe('Glas')
+		expect(singularOf('S')).toBe('S')
+	})
+
+	it('falls back when the related type is not chosen yet', () => {
+		expect(relationNames('Events', '', 'Place').relatedPlural).toBe('Places')
+		expect(relationNames('Events', 'Places', '').relatedSingular).toBe('Place')
+		expect(relationNames('', '', '').ownerSingular).toBe('Entry')
+	})
+})
+
+describe('the sentences of the cards', () => {
+	it.each([
+		['one_to_one', 'Each Event has one Venue, and each Venue has one Event.'],
+		['one_to_many', 'Each Event has one Venue. A Venue has many Events.'],
+		['many_to_many', 'Each Event has many Venues, and each Venue has many Events.'],
+	] as const)('reads %s as the design says', (kind, sentence) => {
+		expect(kindSentence(kind, names)).toBe(sentence)
+	})
+})
+
+describe('the preview', () => {
+	it.each([
+		['one_to_one', 'one', 'Venue', 'one', 'Event'],
+		['one_to_many', 'one', 'Venue', 'many', 'Events'],
+		['many_to_many', 'many', 'Venues', 'many', 'Events'],
+	] as const)('follows %s', (kind, owner, ownerWord, inverse, inverseWord) => {
+		expect(ownerSide(kind)).toBe(owner)
+		expect(ownerNoun(kind, names)).toBe(ownerWord)
+		expect(inverseSide(kind)).toBe(inverse)
+		expect(inverseNoun(kind, names)).toBe(inverseWord)
+	})
+
+	it('maps the selects of the sentences back to a kind', () => {
+		expect(kindFromOwnerSide('many', 'one_to_one')).toBe('many_to_many')
+		expect(kindFromOwnerSide('one', 'many_to_many')).toBe('one_to_many')
+		expect(kindFromOwnerSide('one', 'one_to_one')).toBe('one_to_one')
+		expect(kindFromInverseSide('one', 'many_to_many')).toBe('one_to_one')
+		expect(kindFromInverseSide('many', 'one_to_one')).toBe('one_to_many')
+		expect(kindFromInverseSide('many', 'many_to_many')).toBe('many_to_many')
+	})
+
+	it('keeps every kind stable through its own sides', () => {
+		for (const kind of RELATION_KINDS) {
+			expect(kindFromOwnerSide(ownerSide(kind), kind)).toBe(kind)
+			expect(kindFromInverseSide(inverseSide(kind), kind)).toBe(kind)
+		}
+	})
+
+	it('draws the example chips of the board', () => {
+		expect(relationSample('one_to_many')).toEqual({
+			ownerChips: ['Rue Verte hall'],
+			ownerMore: 0,
+			relatedChips: ['Open day', 'Lime plaster workshop'],
+			relatedMore: 1,
+		})
+		expect(relationSample('one_to_one').relatedChips).toEqual(['Open day'])
+		expect(relationSample('many_to_many').ownerChips).toHaveLength(2)
+	})
+})

web/src/lib/__tests__/schemaBuilderPayload.spec.ts

@@ -79,6 +79,7 @@ describe('create payload', () => {
 					min: null,
 					max: 80,
 					options: [],
+					relation: null,
 				},
 				{
 					key: 'starts_on',
@@ -90,6 +91,7 @@ describe('create payload', () => {
 					min: '2026-01-01',
 					max: '2027-12-31',
 					options: [],
+					relation: null,
 				},
 				{
 					key: 'online',
@@ -101,6 +103,7 @@ describe('create payload', () => {
 					min: null,
 					max: null,
 					options: [],
+					relation: null,
 				},
 				{
 					key: 'capacity',
@@ -112,6 +115,7 @@ describe('create payload', () => {
 					min: 1,
 					max: 5000,
 					options: [],
+					relation: null,
 				},
 				{
 					key: 'category',
@@ -123,6 +127,7 @@ describe('create payload', () => {
 					min: null,
 					max: null,
 					options: ['Talk', 'Workshop', 'Meetup'],
+					relation: null,
 				},
 				{
 					key: 'description',
@@ -134,12 +139,13 @@ describe('create payload', () => {
 					min: null,
 					max: 5000,
 					options: [],
+					relation: null,
 				},
 			],
 		})
 	})
 
-	it('has no icon key and exactly the nine field keys', () => {
+	it('has no icon key and exactly the ten field keys', () => {
 		const body = buildPayload(EVENTS)
 
 		expect(Object.keys(body).sort()).toEqual(['fields', 'key', 'name'])
@@ -151,6 +157,7 @@ describe('create payload', () => {
 				'max',
 				'min',
 				'options',
+				'relation',
 				'required',
 				'type',
 				'unique',

web/src/lib/__tests__/schemaFixtures.ts

@@ -9,6 +9,7 @@ export function apiField(label: string, key: string, type: string, rest: object
 		min: null,
 		max: null,
 		options: null,
+		relation: null,
 		...rest,
 	}
 }

web/src/lib/contentTypes.ts

@@ -1,4 +1,5 @@
 import type { MediaMap } from '@/lib/mediaField'
+import type { RelationDefinition, RelationMap } from '@/lib/relationField'
 
 export interface BuiltinField {
 	key: string
@@ -10,6 +11,7 @@ export interface BuiltinField {
 	min: number | string | null
 	max: number | string | null
 	options: unknown[] | null
+	relation?: RelationDefinition | null
 }
 
 export interface ContentType {
@@ -27,6 +29,7 @@ export interface ContentEntry {
 	content_type: string
 	data: Record<string, unknown>
 	media?: MediaMap
+	relations?: RelationMap
 	created_by: number
 	updated_by: number
 	created_at: string

web/src/lib/entryCells.ts

@@ -3,19 +3,30 @@ import type { BuiltinField } from '@/lib/contentTypes'
 import { fieldTypeSpec, type FieldCellKind } from '@/lib/fieldTypes'
 import { formatDayValue } from '@/lib/entryValue'
 import { isMissingImage, type MediaSummary } from '@/lib/mediaField'
+import { isMissingRelation, relationIdsOf, type RelationSummary } from '@/lib/relationField'
 import { formatAbsoluteDateFromIso } from '@/lib/relativeDate'
 
 export { formatDayValue }
 
 export type CellKind = 'empty' | FieldCellKind
 
+export interface RelationChip {
+	id: number
+	label: string
+	missing: boolean
+}
+
 export interface CellView {
 	kind: CellKind
 	text: string
 	yes?: boolean
 	image?: MediaSummary
+	chips?: RelationChip[]
+	more?: number
 }
 
+export const RELATION_CHIPS_SHOWN = 2
+
 export const EMPTY_TEXT = '–'
 
 const EMPTY: CellView = { kind: 'empty', text: '' }
@@ -48,7 +59,57 @@ function thumbnailCell(value: unknown, image: MediaSummary | undefined): CellVie
 	}
 }
 
-export function describeCell(field: BuiltinField, value: unknown, image?: MediaSummary): CellView {
+function summaryField(first: { key: string; type: string }): BuiltinField {
+	return {
+		key: first.key,
+		label: '',
+		type: first.type,
+		required: false,
+		unique: false,
+		default: null,
+		min: null,
+		max: null,
+		options: null,
+	}
+}
+
+export function relationLabel(summary: RelationSummary) {
+	if (isMissingRelation(summary)) {
+		return t('Entry no longer exists')
+	}
+	const first = summary.first_field
+	const cell = describeCell(summaryField(first), first.value)
+	return cell.kind === 'empty' || cell.kind === 'thumbnail' || cell.kind === 'relation'
+		? t('Entry {0}', [summary.id])
+		: plainCellText(cell)
+}
+
+function relationCell(value: unknown, summaries: RelationSummary[]): CellView {
+	const ids = relationIdsOf(value)
+	if (ids.length === 0) {
+		return EMPTY
+	}
+	const chips = ids.map((id): RelationChip => {
+		const summary = summaries.find((candidate) => candidate.id === id) ?? {
+			id,
+			missing: true as const,
+		}
+		return { id, label: relationLabel(summary), missing: isMissingRelation(summary) }
+	})
+	return {
+		kind: 'relation',
+		text: chips.map((chip) => chip.label).join(', '),
+		chips: chips.slice(0, RELATION_CHIPS_SHOWN),
+		more: Math.max(0, chips.length - RELATION_CHIPS_SHOWN),
+	}
+}
+
+export function describeCell(
+	field: BuiltinField,
+	value: unknown,
+	image?: MediaSummary,
+	relations: RelationSummary[] = [],
+): CellView {
 	if (value === undefined || value === null || value === '') {
 		return EMPTY
 	}
@@ -56,6 +117,8 @@ export function describeCell(field: BuiltinField, value: unknown, image?: MediaS
 	switch (kind) {
 		case 'thumbnail':
 			return thumbnailCell(value, image)
+		case 'relation':
+			return relationCell(value, relations)
 		case 'boolean':
 			return { kind, text: '', yes: value === true }
 		case 'number':

web/src/lib/entryEditors.ts

@@ -4,8 +4,22 @@ import { rangeHelp, uniqueHelp, type EntryRule } from '@/lib/entryMessages'
 import { asBoolean, asNumber, asText, charCount, isBlank, isIsoDay } from '@/lib/entryValue'
 import type { FieldType } from '@/lib/fieldTypes'
 import { isMediaId, isMissingImage, type MediaSummary } from '@/lib/mediaField'
+import {
+	relationInitial,
+	relationPayload,
+	relationViolation,
+	type RelationSummary,
+} from '@/lib/relationField'
 
-export type FieldControl = 'input' | 'markdown' | 'number' | 'switch' | 'date' | 'select' | 'media'
+export type FieldControl =
+	| 'input'
+	| 'markdown'
+	| 'number'
+	| 'switch'
+	| 'date'
+	| 'select'
+	| 'media'
+	| 'relation'
 
 export interface FieldCounter {
 	text: string
@@ -14,6 +28,7 @@ export interface FieldCounter {
 
 export interface EntryContext {
 	image: MediaSummary | null
+	relations: RelationSummary[]
 }
 
 export interface EntryEditorSpec {
@@ -197,4 +212,12 @@ export const ENTRY_EDITORS: Record<FieldType, EntryEditorSpec> = {
 		help: () => t('One image from your library.'),
 		counter: noCounter,
 	},
+	relation: {
+		control: 'relation',
+		initial: relationInitial,
+		validate: relationViolation,
+		payload: relationPayload,
+		help: noHelp,
+		counter: noCounter,
+	},
 }

web/src/lib/entryForm.ts

@@ -2,9 +2,10 @@ import { t } from '@/i18n'
 import type { BuiltinField, ContentEntry } from '@/lib/contentTypes'
 import { describeCell, plainCellText } from '@/lib/entryCells'
 import { ruleMessage, type EntryRule } from '@/lib/entryMessages'
-import { isBlank } from '@/lib/entryValue'
+import { isBlank, sameValue } from '@/lib/entryValue'
 import { fieldTypeSpec } from '@/lib/fieldTypes'
 import { mediaOf, type MediaMap } from '@/lib/mediaField'
+import { relationSummariesFor, type RelationSummaries } from '@/lib/relationField'
 
 export type EntryValues = Record<string, unknown>
 
@@ -39,6 +40,17 @@ export function initialImages(fields: BuiltinField[], stored: ContentEntry | nul
 	return images
 }
 
+export function isRelationField(field: BuiltinField) {
+	return fieldTypeSpec(field.type).editor.control === 'relation'
+}
+
+export function initialRelations(
+	fields: BuiltinField[],
+	stored: ContentEntry | null,
+): RelationSummaries {
+	return relationSummariesFor(fields, stored, isRelationField)
+}
+
 export function buildData(fields: BuiltinField[], values: EntryValues) {
 	return Object.fromEntries(
 		fields.map((field) => [
@@ -56,11 +68,13 @@ export function validateEntry(
 	fields: BuiltinField[],
 	values: EntryValues,
 	images: MediaMap = {},
+	relations: RelationSummaries = {},
 ): EntryIssues {
 	const issues: EntryIssues = {}
 	for (const field of fields) {
 		const rule = fieldTypeSpec(field.type).editor.validate(field, values[field.key], {
 			image: images[field.key] ?? null,
+			relations: relations[field.key] ?? [],
 		})
 		if (rule) {
 			issues[field.key] = issueFor(field, rule)
@@ -74,7 +88,7 @@ export function firstIssueKey(fields: BuiltinField[], issues: EntryIssues) {
 }
 
 export function valuesDiffer(fields: BuiltinField[], current: EntryValues, saved: EntryValues) {
-	return fields.some((field) => !Object.is(current[field.key], saved[field.key]))
+	return fields.some((field) => !sameValue(current[field.key], saved[field.key]))
 }
 
 export function carriesDefault(field: BuiltinField, value: unknown) {
@@ -91,7 +105,7 @@ export function entryTitle(fields: BuiltinField[], entry: ContentEntry | null) {
 		return entry ? t('Entry {0}', [entry.id]) : t('New entry')
 	}
 	const cell = describeCell(first, entry.data[first.key])
-	return cell.kind === 'empty' || cell.kind === 'thumbnail'
+	return cell.kind === 'empty' || cell.kind === 'thumbnail' || cell.kind === 'relation'
 		? t('Entry {0}', [entry.id])
 		: plainCellText(cell)
 }

web/src/lib/entryMessages.ts

@@ -26,6 +26,8 @@ function requiredMessage(field: BuiltinField) {
 			return t('Choose yes or no for {0}.', [field.label])
 		case 'media':
 			return t('Pick an image for {0}.', [field.label])
+		case 'relation':
+			return t('Choose a {0}.', [field.label])
 		default:
 			return t('Fill in {0}.', [field.label])
 	}
@@ -43,6 +45,8 @@ function typeMessage(field: BuiltinField) {
 			return t('{0} must be one of the choices.', [field.label])
 		case 'media':
 			return t('{0} must be an image from the library.', [field.label])
+		case 'relation':
+			return t('{0} must point to an existing entry.', [field.label])
 		default:
 			return t('{0} must be text.', [field.label])
 	}
@@ -76,6 +80,8 @@ function uniqueMessage(field: BuiltinField) {
 			return t('Another entry already uses this choice for {0}.', [field.label])
 		case 'date':
 			return t('Another entry already uses this date for {0}.', [field.label])
+		case 'relation':
+			return t('That {0} is already used by another entry.', [field.label])
 		default:
 			return t('Another entry already uses this {0}. Enter a different one.', [field.label])
 	}

web/src/lib/entryValue.ts

@@ -57,3 +57,13 @@ export function freeSentinel(taken: string[], base = '__none__') {
 	}
 	return sentinel
 }
+
+export function sameValue(left: unknown, right: unknown) {
+	if (Array.isArray(left) && Array.isArray(right)) {
+		return (
+			left.length === right.length &&
+			left.every((item, index) => Object.is(item, right[index]))
+		)
+	}
+	return Object.is(left, right)
+}

web/src/lib/fieldTypes.ts

@@ -1,4 +1,4 @@
-import { t } from '@/i18n'
+import { formatNumber, t } from '@/i18n'
 import { ENTRY_EDITORS, type EntryEditorSpec } from '@/lib/entryEditors'
 
 export const FIELD_TYPES = [
@@ -9,6 +9,7 @@ export const FIELD_TYPES = [
 	'date',
 	'select',
 	'media',
+	'relation',
 ] as const
 
 export type FieldType = (typeof FIELD_TYPES)[number]
@@ -21,6 +22,7 @@ export type FieldCellKind =
 	| 'date'
 	| 'choice'
 	| 'thumbnail'
+	| 'relation'
 
 export interface FieldTypeSpec {
 	icon: string
@@ -28,6 +30,7 @@ export interface FieldTypeSpec {
 	description: () => string
 	cell: FieldCellKind
 	narrowColumn: boolean
+	wideColumn: boolean
 	alignEnd: boolean
 	supportsUnique: boolean
 	supportsLimits: boolean
@@ -35,6 +38,8 @@ export interface FieldTypeSpec {
 	supportsChoices: boolean
 	showsUnsupportedOptions: boolean
 	builderHint: (() => string) | null
+	noDefaultCause: ((label: string, total: number) => string) | null
+	holdsRelation: boolean
 	pairs: boolean
 	editor: EntryEditorSpec
 }
@@ -48,6 +53,7 @@ export const FIELD_TYPE_SPECS: Record<FieldType, FieldTypeSpec> = {
 		description: () => t('Short text, like a title or a name'),
 		cell: 'text',
 		narrowColumn: false,
+		wideColumn: false,
 		alignEnd: false,
 		supportsUnique: true,
 		supportsLimits: true,
@@ -55,6 +61,8 @@ export const FIELD_TYPE_SPECS: Record<FieldType, FieldTypeSpec> = {
 		supportsChoices: false,
 		showsUnsupportedOptions: true,
 		builderHint: null,
+		noDefaultCause: null,
+		holdsRelation: false,
 		pairs: false,
 		editor: ENTRY_EDITORS.text,
 	},
@@ -64,6 +72,7 @@ export const FIELD_TYPE_SPECS: Record<FieldType, FieldTypeSpec> = {
 		description: () => t('Long text with formatting, written in Markdown'),
 		cell: 'richtext',
 		narrowColumn: false,
+		wideColumn: false,
 		alignEnd: false,
 		supportsUnique: false,
 		supportsLimits: true,
@@ -71,6 +80,8 @@ export const FIELD_TYPE_SPECS: Record<FieldType, FieldTypeSpec> = {
 		supportsChoices: false,
 		showsUnsupportedOptions: true,
 		builderHint: null,
+		noDefaultCause: null,
+		holdsRelation: false,
 		pairs: false,
 		editor: ENTRY_EDITORS.richtext,
 	},
@@ -80,6 +91,7 @@ export const FIELD_TYPE_SPECS: Record<FieldType, FieldTypeSpec> = {
 		description: () => t('Whole or decimal numbers'),
 		cell: 'number',
 		narrowColumn: true,
+		wideColumn: false,
 		alignEnd: true,
 		supportsUnique: true,
 		supportsLimits: true,
@@ -87,6 +99,8 @@ export const FIELD_TYPE_SPECS: Record<FieldType, FieldTypeSpec> = {
 		supportsChoices: false,
 		showsUnsupportedOptions: true,
 		builderHint: null,
+		noDefaultCause: null,
+		holdsRelation: false,
 		pairs: true,
 		editor: ENTRY_EDITORS.number,
 	},
@@ -96,6 +110,7 @@ export const FIELD_TYPE_SPECS: Record<FieldType, FieldTypeSpec> = {
 		description: () => t('An on or off switch'),
 		cell: 'boolean',
 		narrowColumn: true,
+		wideColumn: false,
 		alignEnd: false,
 		supportsUnique: false,
 		supportsLimits: false,
@@ -103,6 +118,8 @@ export const FIELD_TYPE_SPECS: Record<FieldType, FieldTypeSpec> = {
 		supportsChoices: false,
 		showsUnsupportedOptions: true,
 		builderHint: null,
+		noDefaultCause: null,
+		holdsRelation: false,
 		pairs: true,
 		editor: ENTRY_EDITORS.boolean,
 	},
@@ -112,6 +129,7 @@ export const FIELD_TYPE_SPECS: Record<FieldType, FieldTypeSpec> = {
 		description: () => t('A calendar day, without a time'),
 		cell: 'date',
 		narrowColumn: false,
+		wideColumn: false,
 		alignEnd: false,
 		supportsUnique: true,
 		supportsLimits: true,
@@ -119,6 +137,8 @@ export const FIELD_TYPE_SPECS: Record<FieldType, FieldTypeSpec> = {
 		supportsChoices: false,
 		showsUnsupportedOptions: true,
 		builderHint: null,
+		noDefaultCause: null,
+		holdsRelation: false,
 		pairs: true,
 		editor: ENTRY_EDITORS.date,
 	},
@@ -128,6 +148,7 @@ export const FIELD_TYPE_SPECS: Record<FieldType, FieldTypeSpec> = {
 		description: () => t('One option from a list you define'),
 		cell: 'choice',
 		narrowColumn: false,
+		wideColumn: false,
 		alignEnd: false,
 		supportsUnique: true,
 		supportsLimits: false,
@@ -135,6 +156,8 @@ export const FIELD_TYPE_SPECS: Record<FieldType, FieldTypeSpec> = {
 		supportsChoices: true,
 		showsUnsupportedOptions: true,
 		builderHint: null,
+		noDefaultCause: null,
+		holdsRelation: false,
 		pairs: false,
 		editor: ENTRY_EDITORS.select,
 	},
@@ -144,6 +167,7 @@ export const FIELD_TYPE_SPECS: Record<FieldType, FieldTypeSpec> = {
 		description: () => t('One image from your media library'),
 		cell: 'thumbnail',
 		narrowColumn: true,
+		wideColumn: false,
 		alignEnd: false,
 		supportsUnique: false,
 		supportsLimits: false,
@@ -154,9 +178,48 @@ export const FIELD_TYPE_SPECS: Record<FieldType, FieldTypeSpec> = {
 			t(
 				'Holds one image from the media library. Entries link to the image instead of keeping a copy, so they always show its current version.',
 			),
+		noDefaultCause: (label, total) =>
+			total === 1
+				? t(
+						"A media field can't have a default, so the existing entry would have no image. Make {0} optional to add it.",
+						[label],
+					)
+				: t(
+						"A media field can't have a default, so the {0} existing entries would have no image. Make {1} optional to add it.",
+						[formatNumber(total), label],
+					),
+		holdsRelation: false,
 		pairs: false,
 		editor: ENTRY_EDITORS.media,
 	},
+	relation: {
+		icon: 'i-lucide-link',
+		label: () => t('Relation'),
+		description: () => t("Links to another type's entries"),
+		cell: 'relation',
+		narrowColumn: false,
+		wideColumn: true,
+		alignEnd: false,
+		supportsUnique: false,
+		supportsLimits: false,
+		supportsDefault: false,
+		supportsChoices: false,
+		showsUnsupportedOptions: false,
+		builderHint: null,
+		noDefaultCause: (label, total) =>
+			total === 1
+				? t(
+						"A relation can't have a default, so the existing entry would have no {0}. Make {0} optional to add it.",
+						[label],
+					)
+				: t(
+						"A relation can't have a default, so the {0} existing entries would have no {1}. Make {1} optional to add it.",
+						[formatNumber(total), label],
+					),
+		holdsRelation: true,
+		pairs: false,
+		editor: ENTRY_EDITORS.relation,
+	},
 }
 
 export function isFieldType(type: string): type is FieldType {

web/src/lib/mediaUsage.ts

@@ -51,7 +51,9 @@ export function usageEntryTitle(item: MediaUsageItem) {
 		},
 		first.value,
 	)
-	return cell.kind === 'empty' || cell.kind === 'thumbnail' ? fallback : plainCellText(cell)
+	return cell.kind === 'empty' || cell.kind === 'thumbnail' || cell.kind === 'relation'
+		? fallback
+		: plainCellText(cell)
 }
 
 function toEntry(item: MediaUsageItem): UsageEntry {

web/src/lib/relationField.ts

@@ -0,0 +1,170 @@
+import type { BuiltinField, ContentEntry } from '@/lib/contentTypes'
+import type { EntryRule } from '@/lib/entryMessages'
+
+export const RELATION_KINDS = ['one_to_one', 'one_to_many', 'many_to_many'] as const
+
+export type RelationKind = (typeof RELATION_KINDS)[number]
+
+export const DEFAULT_RELATION_KIND: RelationKind = 'one_to_many'
+export const RELATION_MAX = 50
+export const RELATION_PAGE_SIZE = 10
+
+const RELATION_ID_MAX = 4294967295
+
+export interface RelationDefinition {
+	content_type: string
+	kind: RelationKind
+}
+
+export interface RelationFirstField {
+	key: string
+	type: string
+	value: unknown
+}
+
+export interface RelationTarget {
+	id: number
+	content_type: string
+	first_field: RelationFirstField
+}
+
+export interface MissingRelation {
+	id: number
+	missing: true
+}
+
+export type RelationSummary = RelationTarget | MissingRelation
+
+export type RelationMap = Record<string, RelationSummary | RelationSummary[]>
+
+export type RelationSummaries = Record<string, RelationSummary[]>
+
+export interface RelationContext {
+	relations: RelationSummary[]
+}
+
+export function isMissingRelation(summary: RelationSummary): summary is MissingRelation {
+	return 'missing' in summary
+}
+
+export function isRelationKind(value: unknown): value is RelationKind {
+	return (RELATION_KINDS as readonly unknown[]).includes(value)
+}
+
+export function isRelationId(value: unknown): value is number {
+	return (
+		typeof value === 'number' &&
+		Number.isInteger(value) &&
+		value >= 1 &&
+		value <= RELATION_ID_MAX
+	)
+}
+
+export function holdsManyRelations(field: Pick<BuiltinField, 'relation'>) {
+	return field.relation?.kind === 'many_to_many'
+}
+
+export function emptyRelationValue(field: Pick<BuiltinField, 'relation'>) {
+	return holdsManyRelations(field) ? [] : null
+}
+
+export function relationIdsOf(value: unknown): number[] {
+	if (Array.isArray(value)) {
+		return value.filter(isRelationId)
+	}
+	return isRelationId(value) ? [value] : []
+}
+
+export function relationInitial(field: BuiltinField, stored: unknown, creating: boolean) {
+	if (creating) {
+		return emptyRelationValue(field)
+	}
+	if (holdsManyRelations(field)) {
+		return Array.isArray(stored) && stored.every(isRelationId) ? [...stored] : []
+	}
+	return isRelationId(stored) ? stored : null
+}
+
+function hasDuplicates(ids: number[]) {
+	return new Set(ids).size !== ids.length
+}
+
+function onlyMissing(ids: number[], summaries: RelationSummary[]) {
+	const gone = new Set(summaries.filter(isMissingRelation).map((summary) => summary.id))
+	return ids.length > 0 && ids.every((id) => gone.has(id))
+}
+
+function manyViolation(field: BuiltinField, value: unknown, context?: RelationContext) {
+	if (value === null || value === undefined) {
+		return field.required ? 'required' : null
+	}
+	if (!Array.isArray(value)) {
+		return 'type'
+	}
+	if (value.length === 0) {
+		return field.required ? 'required' : null
+	}
+	if (value.length > RELATION_MAX || !value.every(isRelationId) || hasDuplicates(value)) {
+		return 'type'
+	}
+	return field.required && onlyMissing(value, context?.relations ?? []) ? 'required' : null
+}
+
+function singleViolation(field: BuiltinField, value: unknown, context?: RelationContext) {
+	if (value === null || value === undefined) {
+		return field.required ? 'required' : null
+	}
+	if (!isRelationId(value)) {
+		return 'type'
+	}
+	return field.required && onlyMissing([value], context?.relations ?? []) ? 'required' : null
+}
+
+export function relationViolation(
+	field: BuiltinField,
+	value: unknown,
+	context?: RelationContext,
+): EntryRule | null {
+	return holdsManyRelations(field)
+		? manyViolation(field, value, context)
+		: singleViolation(field, value, context)
+}
+
+export function relationPayload(field: BuiltinField, value: unknown) {
+	if (holdsManyRelations(field)) {
+		return Array.isArray(value) ? [...value] : []
+	}
+	return value === undefined ? null : value
+}
+
+export function summariesOf(
+	entry: Pick<ContentEntry, 'relations'> | null | undefined,
+	key: string,
+): RelationSummary[] {
+	const found = entry?.relations?.[key]
+	if (found === undefined) {
+		return []
+	}
+	return Array.isArray(found) ? found : [found]
+}
+
+export function relationSummariesFor(
+	fields: BuiltinField[],
+	entry: ContentEntry | null,
+	isRelation: (field: BuiltinField) => boolean,
+): RelationSummaries {
+	const result: RelationSummaries = {}
+	for (const field of fields) {
+		if (!isRelation(field)) {
+			continue
+		}
+		const stored = relationIdsOf(entry?.data[field.key])
+		const summaries = summariesOf(entry, field.key).filter((summary) =>
+			stored.includes(summary.id),
+		)
+		if (summaries.length > 0) {
+			result[field.key] = summaries
+		}
+	}
+	return result
+}

web/src/lib/relationRows.ts

@@ -0,0 +1,47 @@
+import type { BuiltinField, ContentEntry } from '@/lib/contentTypes'
+import { describeCell, isEmptyCell, plainCellText, relationLabel } from '@/lib/entryCells'
+import type { RelationTarget } from '@/lib/relationField'
+
+export const ROW_DETAIL_FIELDS = 2
+const DETAIL_SEPARATOR = ' · '
+const UNKNOWN_FIELD_TYPE = 'text'
+
+const NO_TEXT_KINDS = ['thumbnail', 'relation']
+
+export interface RelationRow {
+	id: number
+	title: string
+	detail: string
+	summary: RelationTarget
+}
+
+function summaryOf(entry: ContentEntry, targetKey: string, fields: BuiltinField[]): RelationTarget {
+	const first = fields[0]
+	return {
+		id: entry.id,
+		content_type: targetKey,
+		first_field: {
+			key: first?.key ?? '',
+			type: first?.type ?? UNKNOWN_FIELD_TYPE,
+			value: first ? (entry.data[first.key] ?? null) : null,
+		},
+	}
+}
+
+function detailOf(entry: ContentEntry, fields: BuiltinField[]) {
+	return fields
+		.slice(1, 1 + ROW_DETAIL_FIELDS)
+		.map((field) => describeCell(field, entry.data[field.key]))
+		.filter((cell) => !isEmptyCell(cell) && !NO_TEXT_KINDS.includes(cell.kind))
+		.map(plainCellText)
+		.join(DETAIL_SEPARATOR)
+}
+
+export function relationRowOf(
+	entry: ContentEntry,
+	targetKey: string,
+	fields: BuiltinField[],
+): RelationRow {
+	const summary = summaryOf(entry, targetKey, fields)
+	return { id: entry.id, title: relationLabel(summary), detail: detailOf(entry, fields), summary }
+}

web/src/lib/relationSentences.ts

@@ -0,0 +1,108 @@
+import { t } from '@/i18n'
+import type { RelationKind } from '@/lib/relationField'
+
+export type RelationSide = 'one' | 'many'
+
+export interface RelationNames {
+	ownerSingular: string
+	ownerPlural: string
+	relatedSingular: string
+	relatedPlural: string
+}
+
+export interface RelationSample {
+	ownerChips: string[]
+	ownerMore: number
+	relatedChips: string[]
+	relatedMore: number
+}
+
+const FINAL_PLURAL = /s$/i
+
+const SAMPLE_VENUES = ['Rue Verte hall', 'Rue Verte yard']
+const SAMPLE_EVENTS = ['Open day', 'Lime plaster workshop']
+const SAMPLE_EVENTS_MORE = 1
+
+export function singularOf(name: string) {
+	return name.length > 1 ? name.replace(FINAL_PLURAL, '') : name
+}
+
+export function relationNames(
+	ownerName: string,
+	relatedName: string,
+	fieldLabel: string,
+): RelationNames {
+	const ownerPlural = ownerName.trim() || t('Entries')
+	const ownerSingular = ownerName.trim() ? singularOf(ownerPlural) : t('Entry')
+	const relatedSingular = fieldLabel.trim() || singularOf(relatedName.trim()) || t('Entry')
+	return {
+		ownerSingular,
+		ownerPlural,
+		relatedSingular,
+		relatedPlural: relatedName.trim() || `${relatedSingular}s`,
+	}
+}
+
+export function ownerSide(kind: RelationKind): RelationSide {
+	return kind === 'many_to_many' ? 'many' : 'one'
+}
+
+export function inverseSide(kind: RelationKind): RelationSide {
+	return kind === 'one_to_one' ? 'one' : 'many'
+}
+
+export function kindFromOwnerSide(side: RelationSide, kind: RelationKind): RelationKind {
+	if (side === 'many') {
+		return 'many_to_many'
+	}
+	return inverseSide(kind) === 'one' ? 'one_to_one' : 'one_to_many'
+}
+
+export function kindFromInverseSide(side: RelationSide, kind: RelationKind): RelationKind {
+	if (side === 'one') {
+		return 'one_to_one'
+	}
+	return ownerSide(kind) === 'many' ? 'many_to_many' : 'one_to_many'
+}
+
+export function kindSentence(kind: RelationKind, names: RelationNames) {
+	const { ownerSingular, ownerPlural, relatedSingular, relatedPlural } = names
+	switch (kind) {
+		case 'one_to_one':
+			return t('Each {0} has one {1}, and each {1} has one {0}.', [
+				ownerSingular,
+				relatedSingular,
+			])
+		case 'one_to_many':
+			return t('Each {0} has one {1}. A {1} has many {2}.', [
+				ownerSingular,
+				relatedSingular,
+				ownerPlural,
+			])
+		default:
+			return t('Each {0} has many {1}, and each {2} has many {3}.', [
+				ownerSingular,
+				relatedPlural,
+				relatedSingular,
+				ownerPlural,
+			])
+	}
+}
+
+export function ownerNoun(kind: RelationKind, names: RelationNames) {
+	return ownerSide(kind) === 'many' ? names.relatedPlural : names.relatedSingular
+}
+
+export function inverseNoun(kind: RelationKind, names: RelationNames) {
+	return inverseSide(kind) === 'many' ? names.ownerPlural : names.ownerSingular
+}
+
+export function relationSample(kind: RelationKind): RelationSample {
+	const many = inverseSide(kind) === 'many'
+	return {
+		ownerChips: ownerSide(kind) === 'many' ? SAMPLE_VENUES : SAMPLE_VENUES.slice(0, 1),
+		ownerMore: 0,
+		relatedChips: many ? SAMPLE_EVENTS : SAMPLE_EVENTS.slice(0, 1),
+		relatedMore: many ? SAMPLE_EVENTS_MORE : 0,
+	}
+}

web/src/lib/schemaBuilderDiff.ts

@@ -19,7 +19,7 @@ export interface FieldChange {
 	label: string
 	notes: ChangeNote[]
 	flag: ChangeFlag | null
-	mediaAdd?: boolean
+	noDefaultAdd?: boolean
 }
 
 type Bound = number | string | null
@@ -151,20 +151,15 @@ function changeNotes(before: PayloadField, after: PayloadField) {
 	return notes
 }
 
-function mediaAddNote(field: PayloadField, total: number) {
-	const summary = `${fieldTypeSpec(field.type).label()}, ${field.required ? t('required') : t('optional')}.`
+function noDefaultAddNote(field: PayloadField, total: number) {
+	const spec = fieldTypeSpec(field.type)
+	const summary = `${spec.label()}, ${field.required ? t('required') : t('optional')}.`
 	if (field.required) {
-		const cause =
-			total === 1
-				? t(
-						"A media field can't have a default, so the existing entry would have no image. Make {0} optional to add it.",
-						[field.label],
-					)
-				: t(
-						"A media field can't have a default, so the {0} existing entries would have no image. Make {1} optional to add it.",
-						[formatNumber(total), field.label],
-					)
-		return note(`${summary} ${cause}`, '', true)
+		return note(
+			`${summary} ${spec.noDefaultCause?.(field.label, total) ?? ''}`.trim(),
+			'',
+			true,
+		)
 	}
 	if (total <= 0) {
 		return note(summary)
@@ -178,7 +173,7 @@ function mediaAddNote(field: PayloadField, total: number) {
 
 function addNote(field: PayloadField, total: number) {
 	if (!fieldTypeSpec(field.type).supportsDefault) {
-		return mediaAddNote(field, total)
+		return noDefaultAddNote(field, total)
 	}
 	const parts = [
 		fieldTypeSpec(field.type).label(),
@@ -233,7 +228,7 @@ export function diffFields(
 				label: after.label,
 				notes,
 				flag: addFlag(after, notes, total),
-				...(fieldTypeSpec(after.type).supportsDefault ? {} : { mediaAdd: true }),
+				...(fieldTypeSpec(after.type).supportsDefault ? {} : { noDefaultAdd: true }),
 			})
 		} else if (fieldSignature(previous) !== fieldSignature(after)) {
 			const notes = changeNotes(previous, after)
@@ -287,8 +282,10 @@ export function flaggedChanges(changes: readonly FieldChange[]) {
 	return changes.filter((change) => change.flag === 'mayNotFit')
 }
 
-export function isMediaOnlyClean(changes: readonly FieldChange[]) {
-	return changes.length > 0 && changes.every((change) => change.mediaAdd && change.flag === null)
+export function isNoDefaultOnlyClean(changes: readonly FieldChange[]) {
+	return (
+		changes.length > 0 && changes.every((change) => change.noDefaultAdd && change.flag === null)
+	)
 }
 
 export function hasRefusedChange(changes: readonly FieldChange[]) {

web/src/lib/schemaBuilderLoad.ts

@@ -7,6 +7,7 @@ import {
 	type FieldType,
 } from '@/lib/schemaBuilderModel'
 import { payloadField, type PayloadField } from '@/lib/schemaBuilderPayload'
+import { DEFAULT_RELATION_KIND } from '@/lib/relationField'
 
 const DATE_LENGTH = 10
 
@@ -42,6 +43,8 @@ export function fieldFromApi(source: BuiltinField, uid: number): BuilderField {
 		min: bound(source.min),
 		max: bound(source.max),
 		options: type === 'select' ? asOptions(source.options) : [],
+		relationType: source.relation?.content_type ?? '',
+		relationKind: source.relation?.kind ?? DEFAULT_RELATION_KIND,
 		saved: true,
 	})
 }

web/src/lib/schemaBuilderModel.ts

@@ -1,4 +1,5 @@
 import { FIELD_TYPE_SPECS, FIELD_TYPES, type FieldType } from '@/lib/fieldTypes'
+import { DEFAULT_RELATION_KIND, type RelationKind } from '@/lib/relationField'
 
 export { FIELD_TYPES, type FieldType }
 export type KeyMode = 'auto' | 'manual'
@@ -39,6 +40,8 @@ export interface BuilderField {
 	min: string
 	max: string
 	options: string[]
+	relationType: string
+	relationKind: RelationKind
 	saved: boolean
 }
 
@@ -71,6 +74,8 @@ export function createField(uid: number, overrides: Partial<BuilderField> = {}):
 		min: '',
 		max: '',
 		options: [],
+		relationType: '',
+		relationKind: DEFAULT_RELATION_KIND,
 		saved: false,
 		...overrides,
 	}
@@ -111,6 +116,10 @@ export function supportsChoices(type: FieldType) {
 	return FIELD_TYPE_SPECS[type].supportsChoices
 }
 
+export function holdsRelation(type: FieldType) {
+	return FIELD_TYPE_SPECS[type].holdsRelation
+}
+
 export function supportsLimits(type: FieldType) {
 	return FIELD_TYPE_SPECS[type].supportsLimits
 }

web/src/lib/schemaBuilderPayload.ts

@@ -1,5 +1,6 @@
 import {
 	effectiveDefault,
+	holdsRelation,
 	isUnique,
 	supportsChoices,
 	supportsLimits,
@@ -7,6 +8,7 @@ import {
 	type BuilderField,
 	type BuilderForm,
 } from '@/lib/schemaBuilderModel'
+import type { RelationDefinition } from '@/lib/relationField'
 
 export interface PayloadField {
 	key: string
@@ -18,6 +20,7 @@ export interface PayloadField {
 	min: number | string | null
 	max: number | string | null
 	options: string[]
+	relation: RelationDefinition | null
 }
 
 export interface ContentTypePayload {
@@ -50,6 +53,12 @@ export interface UpdatePayload {
 	fields: PayloadField[]
 }
 
+function relationFor(field: BuilderField): RelationDefinition | null {
+	return holdsRelation(field.type)
+		? { content_type: field.relationType, kind: field.relationKind }
+		: null
+}
+
 export function payloadField(field: BuilderField): PayloadField {
 	return {
 		key: field.key,
@@ -61,6 +70,7 @@ export function payloadField(field: BuilderField): PayloadField {
 		min: limit(field, field.min),
 		max: limit(field, field.max),
 		options: supportsChoices(field.type) ? trimmedOptions(field) : [],
+		relation: relationFor(field),
 	}
 }
 

web/src/lib/schemaBuilderSample.ts

@@ -30,7 +30,7 @@ export function previewRoutes(key: string) {
 	]
 }
 
-export function sampleValue(field: BuilderField): string | number | boolean | null {
+export function sampleValue(field: BuilderField): string | number | boolean | null | never[] {
 	const given = effectiveDefault(field)
 	switch (field.type) {
 		case 'richtext':
@@ -49,6 +49,8 @@ export function sampleValue(field: BuilderField): string | number | boolean | nu
 			return given === '' ? SAMPLE_DATE : given
 		case 'media':
 			return null
+		case 'relation':
+			return field.relationKind === 'many_to_many' ? [] : null
 		case 'select': {
 			const choices = trimmedOptions(field).filter((option) => option !== '')
 			return given !== '' ? given : (choices[0] ?? null)
@@ -59,7 +61,7 @@ export function sampleValue(field: BuilderField): string | number | boolean | nu
 }
 
 export function sampleEntry(key: string, fields: readonly BuilderField[]) {
-	const data: Record<string, string | number | boolean | null> = {}
+	const data: Record<string, string | number | boolean | null | never[]> = {}
 	for (const field of fields) {
 		if (isValidFieldKey(field.key)) {
 			data[field.key] = sampleValue(field)

web/src/lib/schemaBuilderTouch.ts

@@ -1,7 +1,7 @@
 import type { FieldErrors } from '@/lib/schemaBuilderValidation'
 
 export type TypeTouch = 'name' | 'key' | 'fields'
-export type FieldTouch = 'label' | 'key' | 'min' | 'max' | 'default' | 'choices'
+export type FieldTouch = 'label' | 'key' | 'min' | 'max' | 'default' | 'choices' | 'relation'
 
 export function typeTouchKey(name: TypeTouch) {
 	return `type:${name}`
@@ -19,4 +19,5 @@ export const FIELD_ERROR_TOUCH: readonly (readonly [keyof FieldErrors, FieldTouc
 	['default', 'default'],
 	['options', 'choices'],
 	['choices', 'choices'],
+	['relation', 'relation'],
 ]

web/src/lib/schemaBuilderValidation.ts

@@ -2,6 +2,7 @@ import { t } from '@/i18n'
 import {
 	BUILDER_LIMITS,
 	RESERVED_TYPE_KEYS,
+	holdsRelation,
 	trimmedOptions,
 	type BuilderField,
 	type BuilderForm,
@@ -25,6 +26,7 @@ export interface FieldErrors {
 	default?: string
 	options?: string
 	choices?: Record<number, string>
+	relation?: string
 }
 
 export interface FormErrors {
@@ -190,6 +192,9 @@ export function validateField(field: BuilderField, earlierKeys: readonly string[
 	if (key) {
 		errors.key = key
 	}
+	if (holdsRelation(field.type) && field.relationType === '') {
+		errors.relation = t('Choose a related content type.')
+	}
 	if (field.type === 'text' || field.type === 'richtext') {
 		textLimits(field, errors)
 	} else if (field.type === 'number') {

web/src/lib/schemaDeleteStage.ts

@@ -1,5 +1,5 @@
-export type DeleteStage = 'closed' | 'blocked' | 'confirm' | 'failed' | 'conflict'
+export type DeleteStage = 'closed' | 'blocked' | 'confirm' | 'failed' | 'conflict' | 'referenced'
 
 export function isConfirmStage(stage: DeleteStage) {
-	return stage === 'confirm' || stage === 'failed'
+	return stage === 'confirm' || stage === 'failed' || stage === 'referenced'
 }

web/src/views/__tests__/ContentListRelation.spec.ts

@@ -0,0 +1,243 @@
+import { afterEach, beforeAll, describe, expect, it, vi } from 'vitest'
+import router from '@/router'
+import { MOBILE_WIDTH } from '@/components/__tests__/viewport'
+import type { RelationSummary } from '@/lib/relationField'
+import {
+	calls,
+	eventEntries,
+	installSelectPolyfills,
+	listPage,
+	mountList,
+	text,
+	unmountAll,
+} from './contentTestKit'
+import { drawsIcon } from './mediaFieldKit'
+import { eventsFields } from './schemaTestKit'
+import { apiField } from '@/lib/__tests__/schemaFixtures'
+import { relationField, summaryFor } from './relationKit'
+
+vi.mock('@/composables/useApi', async (importOriginal) => {
+	const actual = await importOriginal<typeof import('@/composables/useApi')>()
+	return { ...actual, useApi: vi.fn() }
+})
+
+beforeAll(installSelectPolyfills)
+
+afterEach(async () => {
+	void router
+	await unmountAll()
+})
+
+const KEY = 'renewcms-content-columns-events'
+const COLUMNS = ['title', 'starts_on', 'venue', 'speakers']
+
+const MISSING: RelationSummary = { id: 9, missing: true }
+
+type Relations = Record<string, RelationSummary | RelationSummary[]>
+
+const RELATIONS: Record<number, [number | null, number[], Relations]> = {
+	42: [3, [11, 12, 13, 14], {}],
+	41: [null, [12], {}],
+	40: [4, [], {}],
+}
+
+const eventType = () => ({
+	id: 1,
+	key: 'events',
+	name: 'Events',
+	icon: 'files',
+	created_at: '2026-09-01T09:30:00Z',
+	updated_at: '2026-10-15T09:30:00Z',
+	fields: [
+		eventsFields[0]!,
+		eventsFields[1]!,
+		relationField('Venue', 'venue', 'venues', 'one_to_many'),
+		relationField('Speakers', 'speakers', 'speakers', 'many_to_many'),
+	],
+})
+
+function itemOf(id: number, overrides: { relations?: Relations; venue?: number | null } = {}) {
+	const [venue, speakers] = RELATIONS[id]!
+	const base = eventEntries.find((entry) => entry.id === id)!
+	const shownVenue = overrides.venue === undefined ? venue : overrides.venue
+	return {
+		...base,
+		data: { ...base.data, venue: shownVenue, speakers },
+		relations: overrides.relations ?? {
+			...(shownVenue === null ? {} : { venue: summaryFor('venues', shownVenue) }),
+			...(speakers.length === 0
+				? {}
+				: { speakers: speakers.map((speaker) => summaryFor('speakers', speaker)) }),
+		},
+	}
+}
+
+function mountRelations(
+	width?: number,
+	items = [itemOf(42), itemOf(41), itemOf(40)],
+	type = eventType,
+	columns: string[] = COLUMNS,
+) {
+	return mountList('/content/events', {
+		width,
+		before: () => localStorage.setItem(KEY, JSON.stringify(columns)),
+		type,
+		content: () => [type()],
+		list: (_key, query) => listPage(items, items.length, query),
+	})
+}
+
+const headers = () => [...document.body.querySelectorAll('thead th')]
+const rowsOf = () => [...document.body.querySelectorAll('tbody tr')]
+const cellOf = (row: number, column: number) => rowsOf()[row]!.querySelectorAll('td')[column]!
+const chipsIn = (element: Element) => [...element.querySelectorAll('[data-testid="relation-chip"]')]
+
+describe('The relation cell', () => {
+	it('shows one chip for a single relation', async () => {
+		await mountRelations()
+
+		const chips = chipsIn(cellOf(0, 3))
+		expect(chips.map(text)).toEqual(['Rue Verte hall'])
+		expect(chips[0]!.className).toContain('h-5')
+		expect(chips[0]!.className).toContain('px-1.5')
+		expect(chips[0]!.className).toContain('bg-(--rc-sand)')
+	})
+
+	it('shows two chips and a muted +2 for four speakers', async () => {
+		await mountRelations()
+
+		expect(chipsIn(cellOf(0, 4)).map(text)).toEqual(['Ines Duarte', 'Jonas Pereira'])
+		expect(text(cellOf(0, 4))).toBe('Ines Duarte Jonas Pereira +2')
+		const more = [...cellOf(0, 4).querySelectorAll('span')].find((span) => text(span) === '+2')!
+		expect(more.className).toContain('text-muted')
+	})
+
+	it('shows the muted dash for no venue and for an empty speakers list', async () => {
+		await mountRelations()
+
+		expect(text(cellOf(1, 3))).toBe('–')
+		expect(cellOf(1, 3).querySelector('span')!.className).toContain('text-muted')
+		expect(text(cellOf(2, 4))).toBe('–')
+		expect(text(cellOf(1, 4))).toBe('Jonas Pereira')
+		expect(text(cellOf(2, 3))).toBe('Rue Verte yard')
+	})
+
+	it('shows a dashed chip for a missing venue', async () => {
+		await mountRelations(undefined, [
+			itemOf(42, { venue: 9, relations: { venue: MISSING } }),
+			itemOf(41),
+			itemOf(40),
+		])
+
+		const chip = chipsIn(cellOf(0, 3))[0]!
+		expect(text(chip)).toBe('Entry no longer exists')
+		expect(chip.getAttribute('data-missing')).toBe('true')
+		expect(chip.className).toContain('border-dashed')
+	})
+
+	it('reads each item own relations with no extra request', async () => {
+		await mountRelations()
+
+		expect(calls.filter((url) => url.includes('/venues') || url.includes('/speakers'))).toEqual(
+			[],
+		)
+	})
+})
+
+describe('The grid of the board', () => {
+	it('lists the relation headers with the wide column and no sort', async () => {
+		await mountRelations()
+
+		expect(headers().map(text).slice(0, 5)).toEqual([
+			'ID',
+			'Title',
+			'Starts on',
+			'Venue',
+			'Speakers',
+		])
+		for (const index of [3, 4]) {
+			expect(headers()[index]!.className).toContain('w-50')
+			expect(headers()[index]!.querySelector('svg')).toBeNull()
+			expect(headers()[index]!.hasAttribute('aria-sort')).toBe(false)
+		}
+	})
+
+	it('keeps rows 48 px high', async () => {
+		await mountRelations()
+
+		expect(cellOf(0, 0).className).toContain('h-12')
+	})
+})
+
+describe('The mobile card', () => {
+	it('lists the title, then a labelled line for Venue and Speakers', async () => {
+		await mountRelations(MOBILE_WIDTH)
+
+		const cards = [...document.body.querySelectorAll('[data-testid="entry-card"]')]
+		const lines = [...cards[0]!.querySelectorAll('[data-testid="entry-card-relation"]')]
+		expect(lines.map(text)).toEqual([
+			'Venue Rue Verte hall',
+			'Speakers Ines Duarte Jonas Pereira +2',
+		])
+		expect(text(cards[1]!.querySelectorAll('[data-testid="entry-card-relation"]')[0])).toBe(
+			'Venue –',
+		)
+		expect(text(cards[2]!.querySelectorAll('[data-testid="entry-card-relation"]')[1])).toBe(
+			'Speakers –',
+		)
+	})
+})
+
+describe('The columns menu', () => {
+	it('lists Venue and Speakers with the link icon and their keys', async () => {
+		await mountRelations()
+
+		const toggle = [...document.body.querySelectorAll('button')].find(
+			(button) =>
+				text(button) === 'Columns' || button.getAttribute('aria-label') === 'Columns',
+		)!
+		toggle.click()
+		await vi.waitFor(() =>
+			expect(document.body.querySelectorAll('[data-testid="column-row"]').length).toBe(4),
+		)
+
+		const rows = [...document.body.querySelectorAll('[data-testid="column-row"]')]
+		expect(rows.map(text).slice(2)).toEqual(['Venue venue', 'Speakers speakers'])
+		expect(drawsIcon(rows[2]!, 'link')).toBe(true)
+		expect(drawsIcon(rows[3]!, 'link')).toBe(true)
+	})
+})
+
+describe('A relation as the first column', () => {
+	it('keeps the link to the editor around the chips', async () => {
+		const type = () => {
+			const [, , venue, speakers] = eventType().fields
+			return { ...eventType(), fields: [venue!, speakers!, eventsFields[0]!] }
+		}
+		await mountRelations(undefined, undefined, type, ['venue', 'speakers', 'title'])
+
+		const link = rowsOf()[0]!.querySelector<HTMLAnchorElement>('[data-testid="entry-link"]')!
+		expect(chipsIn(link).map(text)).toEqual(['Rue Verte hall'])
+		expect(link.getAttribute('href')).toBe('/content/events/42')
+	})
+
+	it('reads the labels joined by a comma as plain text on the card', async () => {
+		const type = () => {
+			const [, , venue, speakers] = eventType().fields
+			return { ...eventType(), fields: [speakers!, venue!, eventsFields[0]!] }
+		}
+		await mountRelations(MOBILE_WIDTH, undefined, type, ['speakers', 'venue', 'title'])
+
+		const titles = [
+			...document.body.querySelectorAll('[data-testid="entry-card"] .truncate'),
+		].map(text)
+		expect(titles[0]).toBe('Ines Duarte, Jonas Pereira, Ana Costa, Luc Moreau')
+		expect(titles.join('|')).not.toMatch(/\b1[1-4]\b/)
+	})
+})
+
+describe('Fixtures', () => {
+	it('keeps unrelated field helpers', () => {
+		expect(apiField('X', 'x', 'text').relation).toBeNull()
+	})
+})

web/src/views/__tests__/EntryEditorRelation.spec.ts

@@ -0,0 +1,563 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+import { flushPromises } from '@vue/test-utils'
+import {
+	button,
+	calls,
+	chip,
+	entryWrites,
+	fieldWrapper,
+	installSelectPolyfills,
+	save,
+	setField,
+	text,
+	typeInto,
+	unmountAll,
+} from './entryEditorKit'
+import {
+	allTypes,
+	chipLabels,
+	entryWithRelations,
+	liveText,
+	mountRelation,
+	openList,
+	optionLabels,
+	pickOption,
+	press,
+	relationError,
+	relationInput,
+	removeButtons,
+	settleSearch,
+	summaryFor,
+	typeSearch,
+} from './relationKit'
+
+vi.mock('@/composables/useApi', async (importOriginal) => {
+	const actual = await importOriginal<typeof import('@/composables/useApi')>()
+	return { ...actual, useApi: vi.fn() }
+})
+
+beforeEach(() => {
+	installSelectPolyfills()
+	vi.useFakeTimers({ toFake: ['setTimeout', 'clearTimeout', 'setInterval', 'clearInterval'] })
+})
+
+afterEach(unmountAll)
+
+const searches = () => calls.filter((url) => url.includes('/entry?') && !url.endsWith('size=5'))
+const sentData = (index = 0) => entryWrites[index]!.body.data as Record<string, unknown>
+const fieldKeys = () =>
+	[...document.body.querySelectorAll<HTMLElement>('[data-entry-field]')].map(
+		(element) => element.dataset.entryField,
+	)
+
+describe('Where the controls sit', () => {
+	it('follows the schema order, full width, each with its label', async () => {
+		await mountRelation('/content/events/42', { venue: 3, speakers: [11, 12] })
+
+		expect(fieldKeys().slice(-2)).toEqual(['venue', 'speakers'])
+		for (const key of ['venue', 'speakers']) {
+			const row = fieldWrapper(key).parentElement!
+			expect(row.children).toHaveLength(1)
+			expect(row.className).not.toContain('md:grid-cols-2')
+		}
+		expect(text(fieldWrapper('venue').querySelector('label'))).toBe('Venue')
+		expect(text(fieldWrapper('speakers').querySelector('label'))).toBe('Speakers')
+	})
+
+	it('never pairs with a boolean, number or date field before it', async () => {
+		await mountRelation('/content/events/new')
+
+		const rows = [...document.body.querySelectorAll('#entry-form > div')]
+		const venueRow = rows.find((row) => row.querySelector('[data-entry-field="venue"]'))!
+		expect(venueRow.children).toHaveLength(1)
+		expect(
+			venueRow.previousElementSibling!.querySelector('[data-entry-field="description"]'),
+		).not.toBeNull()
+	})
+})
+
+describe('Single relation, empty, focused search', () => {
+	it('sends only the trimmed, debounced search and lists rows with a second line', async () => {
+		await mountRelation('/content/events/42')
+
+		await typeSearch('venue', ' ru ')
+		await vi.advanceTimersByTimeAsync(100)
+		await typeSearch('venue', 'rue ')
+		await settleSearch(vi)
+
+		expect(searches()).toEqual(['/v1/content-type/venues/entry?q=rue&page=1&size=10'])
+		expect(optionLabels()).toEqual([
+			'Rue Verte hall Lyon · 120 seats',
+			'Rue Verte yard Lyon · outdoor',
+			'Rue du Port studio Nantes · 24 seats',
+		])
+		expect(relationInput('venue').getAttribute('placeholder')).toBe('Search to add')
+		expect(
+			document.body.querySelector('[role="option"]')!.hasAttribute('data-highlighted'),
+		).toBe(true)
+		expect(liveText('venue')).toBe('3 results')
+	})
+
+	it('lists the first page without q when the input is empty', async () => {
+		await mountRelation('/content/events/42')
+
+		await openList('venue', vi)
+
+		expect(searches()).toEqual(['/v1/content-type/venues/entry?page=1&size=10'])
+		expect(optionLabels()).toHaveLength(4)
+	})
+
+	it('never lets a stale answer overwrite a newer one', async () => {
+		const gates = new Map<string, (value: unknown) => void>()
+		await mountRelation('/content/events/42', {
+			search: (_key, query) =>
+				new Promise((resolve) => gates.set(query.get('q') ?? '', resolve)),
+		})
+		const body = (name: string) => ({
+			items: [{ id: 3, data: { name, city: '', details: '' }, relations: {} }],
+			total: 1,
+			page: 1,
+			size: 10,
+		})
+
+		await typeSearch('venue', 'old')
+		await settleSearch(vi)
+		await typeSearch('venue', 'new')
+		await settleSearch(vi)
+		gates.get('new')!(body('Fresh'))
+		await flushPromises()
+		gates.get('old')!(body('Stale'))
+		await flushPromises()
+
+		expect(optionLabels()).toEqual(['Fresh'])
+	})
+})
+
+describe('Picking a single target', () => {
+	it('shows one chip, sets the value, dirties the page and announces it', async () => {
+		await mountRelation('/content/events/42')
+		await openList('venue', vi, 'rue')
+
+		await pickOption('Rue Verte hall')
+
+		expect(chipLabels('venue')).toEqual(['Rue Verte hall'])
+		expect(liveText('venue')).toBe('Venue set to Rue Verte hall.')
+		expect(chip()!.textContent).toBe('Unsaved changes')
+		expect(relationInput('venue').getAttribute('aria-expanded')).toBe('false')
+		expect(document.activeElement).toBe(relationInput('venue'))
+		expect(calls.filter((url) => url.includes('/venues/entry/'))).toEqual([])
+		await save()
+		expect(sentData().venue).toBe(3)
+	})
+
+	it('removes the chip with its x and says the field was cleared', async () => {
+		await mountRelation('/content/events/42', { venue: 3 })
+
+		expect(chipLabels('venue')).toEqual(['Rue Verte hall'])
+		removeButtons('venue')[0]!.click()
+		await flushPromises()
+
+		expect(chipLabels('venue')).toEqual([])
+		expect(liveText('venue')).toBe('Venue cleared.')
+		await save()
+		expect(sentData().venue).toBeNull()
+	})
+
+	it('replaces the chip when another row is picked', async () => {
+		await mountRelation('/content/events/42', { venue: 3 })
+		await openList('venue', vi, 'rue')
+		expect(optionLabels()).not.toContain('Rue Verte hall Lyon · 120 seats')
+
+		await pickOption('Rue Verte yard')
+
+		expect(chipLabels('venue')).toEqual(['Rue Verte yard'])
+		await save()
+		expect(sentData().venue).toBe(4)
+	})
+})
+
+describe('Many relation', () => {
+	it('shows the chips, the placeholder and the help line', async () => {
+		await mountRelation('/content/events/42', { speakers: [11, 12] })
+
+		expect(chipLabels('speakers')).toEqual(['Ines Duarte', 'Jonas Pereira'])
+		expect(relationInput('speakers').getAttribute('placeholder')).toBe('Search to add')
+		expect(text(fieldWrapper('speakers').querySelector('[data-testid="relation-help"]'))).toBe(
+			'An event can have many speakers.',
+		)
+	})
+
+	it('adds at the end, hides picked rows and announces', async () => {
+		await mountRelation('/content/events/42', { speakers: [11, 12] })
+
+		await openList('speakers', vi, 'ana')
+		expect(optionLabels()).toEqual(['Ana Costa'])
+		await pickOption('Ana Costa')
+
+		expect(chipLabels('speakers')).toEqual(['Ines Duarte', 'Jonas Pereira', 'Ana Costa'])
+		expect(liveText('speakers')).toBe('Ana Costa added to Speakers.')
+		await save()
+		expect(sentData().speakers).toEqual([11, 12, 13])
+	})
+
+	it('removes a chip with its x or Backspace in the empty input', async () => {
+		await mountRelation('/content/events/42', { speakers: [11, 12] })
+
+		removeButtons('speakers')[0]!.click()
+		await flushPromises()
+		expect(chipLabels('speakers')).toEqual(['Jonas Pereira'])
+		expect(liveText('speakers')).toBe('Ines Duarte removed from Speakers.')
+
+		relationInput('speakers').focus()
+		await press('speakers', 'Backspace')
+		expect(chipLabels('speakers')).toEqual([])
+		expect(liveText('speakers')).toBe('Jonas Pereira removed from Speakers.')
+	})
+
+	it('names each x "Remove <name> from <field>"', async () => {
+		await mountRelation('/content/events/42', { speakers: [11, 12] })
+
+		expect(
+			removeButtons('speakers').map((remove) => remove.getAttribute('aria-label')),
+		).toEqual(['Remove Ines Duarte from Speakers', 'Remove Jonas Pereira from Speakers'])
+		expect(removeButtons('speakers')[0]!.hasAttribute('aria-labelledby')).toBe(false)
+	})
+
+	it('cannot add a 51st target', async () => {
+		const ids = Array.from({ length: 50 }, (_, index) => 100 + index)
+		const relations = {
+			speakers: ids.map((id) => ({
+				id,
+				content_type: 'speakers',
+				first_field: { key: 'name', type: 'text', value: `Speaker ${id}` },
+			})),
+		}
+		await mountRelation('/content/events/42', { speakers: ids, relations })
+
+		await openList('speakers', vi)
+
+		expect(optionLabels()).toEqual([])
+		expect(text(document.body.querySelector('[data-testid="relation-empty"]'))).toBe(
+			'You can add up to 50.',
+		)
+	})
+})
+
+describe('What the control shows and sends', () => {
+	it('sends null and [] for a create left empty, never absent', async () => {
+		const wrapper = await mountRelation('/content/events/new')
+		await typeInto('title', 'Open day')
+		await setField(wrapper, 'starts_on', '2026-11-21')
+
+		await save()
+
+		expect(entryWrites).toHaveLength(1)
+		expect(entryWrites[0]!.method).toBe('POST')
+		expect(entryWrites[0]!.url).toBe('/v1/content-type/events/entry')
+		expect(sentData()).toMatchObject({ venue: null, speakers: [] })
+		expect('venue' in sentData()).toBe(true)
+	})
+
+	it('sends a JSON number once a venue is picked on create', async () => {
+		const wrapper = await mountRelation('/content/events/new')
+		await typeInto('title', 'Open day')
+		await setField(wrapper, 'starts_on', '2026-11-21')
+		await openList('venue', vi, 'rue')
+		await pickOption('Rue Verte hall')
+
+		await save()
+
+		expect(sentData().venue).toBe(3)
+	})
+
+	it.each([
+		['loaded 3 and saved untouched', 3, [], 'Rue Verte hall', 3],
+		['loaded null and saved untouched', null, [], undefined, null],
+	])('%s', async (_name, venue, speakers, shown, sent) => {
+		await mountRelation('/content/events/42', { venue, speakers })
+		await typeInto('title', 'Lime plaster workshop, two days')
+
+		await save()
+
+		expect(chipLabels('venue')[0]).toBe(shown)
+		expect(sentData().venue).toBe(sent)
+	})
+
+	it('saves a missing venue untouched with the same id', async () => {
+		await mountRelation('/content/events/42', {
+			venue: 3,
+			relations: { venue: { id: 3, missing: true } },
+		})
+		await typeInto('title', 'Lime plaster workshop, two days')
+
+		await save()
+
+		expect(sentData().venue).toBe(3)
+	})
+
+	it('adds Jonas Pereira to [11] and removes both from [11, 12]', async () => {
+		await mountRelation('/content/events/42', { speakers: [11] })
+		await openList('speakers', vi, 'jonas')
+		await pickOption('Jonas Pereira')
+		expect(chipLabels('speakers')).toHaveLength(2)
+		await save()
+		expect(sentData().speakers).toEqual([11, 12])
+	})
+
+	it('removes both speakers and sends an empty array', async () => {
+		await mountRelation('/content/events/42', { speakers: [11, 12] })
+		removeButtons('speakers')[0]!.click()
+		await flushPromises()
+		removeButtons('speakers')[0]!.click()
+		await flushPromises()
+
+		await save()
+
+		expect(sentData().speakers).toEqual([])
+	})
+
+	it('rebuilds the control from the answered relations after a save', async () => {
+		await mountRelation('/content/events/42', { venue: 3 })
+		await openList('venue', vi, 'rue')
+		await pickOption('Rue Verte yard')
+
+		await save()
+
+		expect(chipLabels('venue')).toEqual(['Rue Verte yard'])
+		expect(chip()!.textContent).toContain('Saved')
+	})
+})
+
+describe('Dirty tracking', () => {
+	it('is saved again after picking 4 then 3', async () => {
+		await mountRelation('/content/events/42', { venue: 3 })
+		await openList('venue', vi, 'rue')
+		await pickOption('Rue Verte yard')
+		expect(chip()!.textContent).toBe('Unsaved changes')
+		await openList('venue', vi, 'rue')
+		await pickOption('Rue Verte hall')
+
+		expect(chip()!.textContent).toBe('Saved')
+		expect(button('Save')?.hasAttribute('disabled')).toBe(true)
+	})
+
+	it('counts the same ids in another order as changed', async () => {
+		const wrapper = await mountRelation('/content/events/42', { speakers: [11, 12] })
+
+		await setField(wrapper, 'speakers', [12, 11])
+		expect(chip()!.textContent).toBe('Unsaved changes')
+
+		await setField(wrapper, 'speakers', [11, 12])
+		expect(chip()!.textContent).toBe('Saved')
+	})
+})
+
+describe('Required and empty', () => {
+	it('sends nothing, shows the error, the chip and focuses the control', async () => {
+		await mountRelation('/content/events/42', { venueField: { required: true } })
+		await typeInto('title', 'Lime plaster workshop, two days')
+
+		await save()
+
+		expect(entryWrites).toHaveLength(0)
+		expect(relationError('venue')).toBe('Choose a Venue.')
+		expect(chip()!.textContent).toBe('Not saved')
+		expect(document.activeElement).toBe(relationInput('venue'))
+		expect(relationInput('venue').getAttribute('aria-invalid')).toBe('true')
+		expect(relationInput('venue').getAttribute('aria-required')).toBe('true')
+
+		await openList('venue', vi, 'rue')
+		await pickOption('Rue Verte hall')
+		expect(relationError('venue')).toBe('')
+		expect(chip()!.textContent).toBe('Unsaved changes')
+	})
+
+	it('focuses only the first field in schema order that has an error', async () => {
+		await mountRelation('/content/events/42', {
+			venueField: { required: true },
+			speakersField: { required: true },
+		})
+		await typeInto('title', 'Lime plaster workshop, two days')
+
+		await save()
+
+		expect(document.activeElement).toBe(relationInput('venue'))
+		expect(relationError('speakers')).toBe('Choose a Speakers.')
+	})
+})
+
+describe('Server answers for a relation field', () => {
+	it.each([
+		[422, 'invalid_entry: venue: required', 'Choose a Venue.'],
+		[422, 'invalid_entry: venue: type', 'Venue must point to an existing entry.'],
+		[409, 'invalid_entry: venue: unique', 'That Venue is already used by another entry.'],
+	])('%i %s shows its copy under the control', async (status, body, message) => {
+		const { ApiError } = await import('@/composables/useApi')
+		await mountRelation('/content/events/42', {
+			venue: 3,
+			writeEntry: () => {
+				throw new ApiError(status, undefined, body)
+			},
+		})
+		await typeInto('title', 'Lime plaster workshop, two days')
+
+		await save()
+
+		expect(relationError('venue')).toBe(message)
+		expect(chip()!.textContent).toBe('Not saved')
+		expect(document.activeElement).toBe(relationInput('venue'))
+		expect(document.body.querySelector('[role="alert"]')?.textContent).not.toContain(
+			'Not saved',
+		)
+	})
+
+	it('shows the read-only reload alert for unknown_field, as for media', async () => {
+		const { ApiError } = await import('@/composables/useApi')
+		await mountRelation('/content/events/42', {
+			venue: 3,
+			writeEntry: () => {
+				throw new ApiError(422, undefined, 'invalid_entry: venue: unknown_field')
+			},
+		})
+		await typeInto('title', 'Lime plaster workshop, two days')
+
+		await save()
+
+		expect(text(document.body)).toContain('The fields of Events changed')
+		expect(text(document.body)).toContain(
+			'The Venue field was changed after you opened this form.',
+		)
+		expect(button('Reload form')).toBeDefined()
+	})
+})
+
+describe('Saving', () => {
+	it('dims the form and makes the control inoperable while the PUT is pending', async () => {
+		let release!: (value: unknown) => void
+		await mountRelation('/content/events/42', {
+			venue: 3,
+			speakers: [11],
+			writeEntry: () => new Promise((resolve) => (release = resolve)),
+		})
+		await typeInto('title', 'Lime plaster workshop, two days')
+
+		await save()
+
+		expect(document.body.querySelector('#entry-form')!.className).toContain('opacity-70')
+		expect(relationInput('venue').disabled).toBe(true)
+		expect(button('Saving…')).toBeDefined()
+		release(entryWithRelations(3, [11]))
+		await flushPromises()
+	})
+})
+
+describe('Accessibility of the control', () => {
+	it('points aria-controls at its own listbox, not a foreign one earlier in the page', async () => {
+		await mountRelation('/content/events/42', { speakers: [11] })
+		const foreign = document.createElement('div')
+		foreign.setAttribute('role', 'listbox')
+		foreign.id = 'foreign-listbox'
+		document.body.prepend(foreign)
+		await openList('speakers', vi, 'a')
+
+		const own = document.body.querySelector(
+			'[data-relation-owner] [role="listbox"], [data-relation-owner][role="listbox"]',
+		)!
+		expect(own.id).not.toBe('')
+		expect(relationInput('speakers').getAttribute('aria-controls')).toBe(own.id)
+		foreign.remove()
+	})
+
+	it('is a labelled combobox on a listbox of options', async () => {
+		await mountRelation('/content/events/42', { speakers: [11] })
+		await openList('speakers', vi, 'a')
+
+		const input = relationInput('speakers')
+		const listbox = document.body.querySelector('[role="listbox"]')!
+		expect(input.getAttribute('aria-expanded')).toBe('true')
+		expect(input.getAttribute('aria-controls')).toBe(listbox.id)
+		expect(input.getAttribute('aria-activedescendant')).toBe(
+			document.body.querySelector('[role="option"]')!.id,
+		)
+		expect(fieldWrapper('speakers').querySelector('label')!.getAttribute('for')).toBe(input.id)
+		const group = fieldWrapper('speakers').querySelector('[role="group"]')!
+		expect(text(document.getElementById(group.getAttribute('aria-labelledby')!))).toBe(
+			'Speakers',
+		)
+		expect(input.getAttribute('aria-describedby')).toContain('-help')
+	})
+
+	it('has one polite live region', async () => {
+		await mountRelation('/content/events/42', { venue: 3 })
+
+		const live = fieldWrapper('venue').querySelector('[data-testid="relation-live"]')!
+		expect(live.getAttribute('role')).toBe('status')
+		expect(live.getAttribute('aria-live')).toBe('polite')
+	})
+})
+
+describe('Keyboard', () => {
+	it('moves with the arrows, picks with Enter and closes with Escape keeping the text', async () => {
+		await mountRelation('/content/events/42')
+		await openList('venue', vi, 'rue')
+
+		await press('venue', 'ArrowDown')
+		const highlighted = () =>
+			text(document.body.querySelector('[role="option"][data-highlighted]'))
+		expect(highlighted()).toContain('Rue Verte yard')
+		await press('venue', 'ArrowUp')
+		expect(highlighted()).toContain('Rue Verte hall')
+		await press('venue', 'ArrowDown')
+		await press('venue', 'Enter')
+		expect(chipLabels('venue')).toEqual(['Rue Verte yard'])
+
+		await openList('venue', vi, 'port')
+		await press('venue', 'Escape')
+		expect(relationInput('venue').getAttribute('aria-expanded')).toBe('false')
+		expect(relationInput('venue').value).toBe('port')
+	})
+})
+
+describe('Chips and the keyboard', () => {
+	it('reaches the chips with ArrowLeft from the empty input', async () => {
+		await mountRelation('/content/events/42', { speakers: [11, 12] })
+
+		relationInput('speakers').focus()
+		await press('speakers', 'ArrowLeft')
+
+		const items = [...fieldWrapper('speakers').querySelectorAll('[data-slot="tagsItem"]')]
+		expect(items.map((item) => item.getAttribute('data-state'))).toEqual(['inactive', 'active'])
+	})
+
+	it('keeps Backspace for the text when the input is not empty', async () => {
+		await mountRelation('/content/events/42', { speakers: [11, 12] })
+		await typeSearch('speakers', 'ab')
+
+		await press('speakers', 'Backspace')
+
+		expect(chipLabels('speakers')).toEqual(['Ines Duarte', 'Jonas Pereira'])
+	})
+})
+
+describe('Fixtures', () => {
+	it('keeps the sample data of the board', () => {
+		expect(allTypes()).toHaveLength(3)
+		expect(summaryFor('venues', 3).id).toBe(3)
+	})
+})
+
+describe('A relation as the first field', () => {
+	it('titles the page and the breadcrumb "Entry 42"', async () => {
+		const types = allTypes()
+		const [events] = types
+		const relationFirst = { ...events!, fields: [events!.fields[7]!, events!.fields[0]!] }
+		await mountRelation('/content/events/42', {
+			venue: 3,
+			type: () => relationFirst,
+			content: () => [relationFirst, ...types.slice(1)],
+		})
+
+		expect(text(document.body.querySelector('h1'))).toBe('Entry 42')
+		expect(text(document.body)).toContain('Events · Entry 42')
+	})
+})

web/src/views/__tests__/EntryEditorRelationStates.spec.ts

@@ -0,0 +1,230 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+import { flushPromises } from '@vue/test-utils'
+import { ApiError, NetworkError } from '@/composables/useApi'
+import {
+	button,
+	calls,
+	entryWrites,
+	fieldWrapper,
+	installSelectPolyfills,
+	save,
+	text,
+	typeInto,
+	unmountAll,
+} from './entryEditorKit'
+import {
+	chipLabels,
+	emptyText,
+	liveText,
+	mountRelation,
+	openList,
+	optionLabels,
+	pickOption,
+	relationError,
+	relationInput,
+	searchBody,
+	settleSearch,
+	typeSearch,
+} from './relationKit'
+
+vi.mock('@/composables/useApi', async (importOriginal) => {
+	const actual = await importOriginal<typeof import('@/composables/useApi')>()
+	return { ...actual, useApi: vi.fn() }
+})
+
+beforeEach(() => {
+	installSelectPolyfills()
+	vi.useFakeTimers({ toFake: ['setTimeout', 'clearTimeout', 'setInterval', 'clearInterval'] })
+})
+
+afterEach(unmountAll)
+
+const SKELETON_DELAY_MS = 150
+const searches = () => calls.filter((url) => url.includes('/venues/entry?'))
+const empty = { items: [], total: 0, page: 1, size: 10 }
+const skeletons = () => document.body.querySelectorAll('[data-testid="relation-skeleton"]')
+
+function failing(error: unknown) {
+	return () => {
+		throw error
+	}
+}
+
+describe('Picker loading', () => {
+	it('shows three skeleton rows after 150 ms and announces Searching…', async () => {
+		await mountRelation('/content/events/42', { search: () => new Promise(() => undefined) })
+
+		await typeSearch('venue', 'zzz')
+		await settleSearch(vi)
+		expect(skeletons()).toHaveLength(0)
+		await vi.advanceTimersByTimeAsync(SKELETON_DELAY_MS)
+		await flushPromises()
+
+		expect(skeletons()).toHaveLength(3)
+		expect(
+			text(document.body.querySelector('[data-testid="relation-empty"] [role="status"]')),
+		).toBe('Searching…')
+		expect(optionLabels()).toEqual([])
+	})
+})
+
+describe('No match', () => {
+	it('names the query and clears the search', async () => {
+		await mountRelation('/content/events/42', {
+			search: (key, query) => searchBody(key, query),
+		})
+
+		await openList('venue', vi, 'zzz')
+
+		expect(emptyText()).toBe('No Venues match "zzz" Clear search')
+		expect(liveText('venue')).toBe('No results')
+		button('Clear search')!.click()
+		await flushPromises()
+		await settleSearch(vi)
+		expect(relationInput('venue').value).toBe('')
+		expect(searches().at(-1)).toBe('/v1/content-type/venues/entry?page=1&size=10')
+	})
+
+	it('says the type has no entries at all', async () => {
+		await mountRelation('/content/events/42', { search: () => empty })
+
+		await openList('venue', vi)
+
+		expect(emptyText()).toBe('No Venues yet. Add one in Content, then come back.')
+	})
+})
+
+describe('Search failures', () => {
+	it.each([
+		['500', new ApiError(500)],
+		['a network error', new NetworkError()],
+		['404', new ApiError(404)],
+	])(
+		'shows the load error on %s and sends only the search again on Try again',
+		async (_name, error) => {
+			let fail = true
+			await mountRelation('/content/events/42', {
+				search: (key, query) => {
+					if (fail) {
+						throw error
+					}
+					return searchBody(key, query)
+				},
+			})
+
+			await openList('venue', vi, 'rue')
+
+			expect(emptyText()).toBe(
+				"Couldn't load Venues Check your connection and try again. Try again",
+			)
+			fail = false
+			const before = calls.length
+			button('Try again')!.click()
+			await flushPromises()
+
+			expect(calls.slice(before)).toEqual([
+				'/v1/content-type/venues/entry?q=rue&page=1&size=10',
+			])
+			expect(optionLabels()).toHaveLength(3)
+		},
+	)
+
+	it('shows the rate limit countdown on 429', async () => {
+		await mountRelation('/content/events/42', { search: failing(new ApiError(429, 3)) })
+
+		await openList('venue', vi, 'rue')
+
+		expect(emptyText()).toBe('Too many requests Try again in 0:03')
+		await vi.advanceTimersByTimeAsync(3000)
+		await flushPromises()
+		expect(emptyText()).toContain('Wait a moment before trying again.')
+		expect(button('Try again')).toBeDefined()
+	})
+
+	it('adds no local copy on 401', async () => {
+		await mountRelation('/content/events/42', { search: failing(new ApiError(401)) })
+
+		await openList('venue', vi, 'rue')
+
+		expect(emptyText()).toBe('')
+	})
+})
+
+describe('Load more', () => {
+	it('appends the next page', async () => {
+		const names = Array.from({ length: 12 }, (_, index) => `Hall ${index + 1}`)
+		await mountRelation('/content/events/42', {
+			search: (_key, query) => {
+				const page = Number(query.get('page'))
+				const slice = names.slice((page - 1) * 10, page * 10)
+				return {
+					items: slice.map((name, index) => ({
+						id: 100 + (page - 1) * 10 + index,
+						data: { name, city: '', details: '' },
+						relations: {},
+					})),
+					total: 12,
+					page,
+					size: 10,
+				}
+			},
+		})
+		await openList('venue', vi)
+		expect(optionLabels()).toHaveLength(10)
+
+		button('Load more')!.click()
+		await flushPromises()
+
+		expect(searches().at(-1)).toBe('/v1/content-type/venues/entry?page=2&size=10')
+		expect(optionLabels()).toHaveLength(12)
+		expect(button('Load more')).toBeUndefined()
+	})
+})
+
+describe('A missing target', () => {
+	it('shows a dashed chip and lets an optional field save with the same id', async () => {
+		await mountRelation('/content/events/42', {
+			venue: 3,
+			relations: { venue: { id: 3, missing: true } },
+		})
+
+		expect(chipLabels('venue')).toEqual(['Entry no longer exists'])
+		expect(fieldWrapper('venue').querySelector('[data-missing="true"]')).not.toBeNull()
+		expect(text(fieldWrapper('venue').querySelector('[data-testid="relation-help"]'))).toBe(
+			'You can still save. The entry keeps the link until you change it.',
+		)
+		await typeInto('title', 'Lime plaster workshop, two days')
+		await save()
+		expect(entryWrites[0]!.body.data).toMatchObject({ venue: 3 })
+	})
+
+	it('refuses to save a required field with only a missing target', async () => {
+		await mountRelation('/content/events/42', {
+			venue: 3,
+			venueField: { required: true },
+			relations: { venue: { id: 3, missing: true } },
+		})
+
+		expect(text(fieldWrapper('venue').querySelector('[data-testid="relation-help"]'))).toBe(
+			'Venue is required. Choose another to save.',
+		)
+		await typeInto('title', 'Lime plaster workshop, two days')
+		await save()
+
+		expect(entryWrites).toHaveLength(0)
+		expect(relationError('venue')).toBe('Choose a Venue.')
+		expect(document.activeElement).toBe(relationInput('venue'))
+	})
+
+	it('replaces the missing chip when another target is picked', async () => {
+		await mountRelation('/content/events/42', {
+			venue: 3,
+			relations: { venue: { id: 3, missing: true } },
+		})
+		await openList('venue', vi, 'rue')
+
+		await pickOption('Rue Verte yard')
+
+		expect(chipLabels('venue')).toEqual(['Rue Verte yard'])
+	})
+})

web/src/views/__tests__/SchemaBuilderEditLoad.spec.ts

@@ -388,7 +388,7 @@ describe('Saved fields are locked', () => {
 		expect(text(inspector())).toContain("Used in the API, so it can't change.")
 		expect(inspector()!.querySelector('button[aria-label="Edit key"]')).toBeNull()
 		expect(text(inspector())).toContain("Can't change after saving")
-		expect(all('[role="radio"]')).toHaveLength(7)
+		expect(all('[role="radio"]')).toHaveLength(8)
 		expect(tile('Date').getAttribute('data-state')).toBe('checked')
 		const others = all<HTMLButtonElement>('[role="radio"]').filter(
 			(radio) => radio !== tile('Date'),

web/src/views/__tests__/SchemaBuilderEditSave.spec.ts

@@ -76,6 +76,7 @@ const FIELD_KEYS = [
 	'min',
 	'max',
 	'options',
+	'relation',
 ]
 
 async function editRecipes() {

web/src/views/__tests__/SchemaBuilderMedia.spec.ts

@@ -57,6 +57,7 @@ const TILES = [
 	['Date', 'calendar', 'A calendar day, without a time'],
 	['Choice', 'list', 'One option from a list you define'],
 	['Media', 'image', 'One image from your media library'],
+	['Relation', 'link', "Links to another type's entries"],
 ]
 
 const HINT =
@@ -70,14 +71,14 @@ async function addMediaField() {
 	await pickTile('Media')
 }
 
-describe('Seven type tiles', () => {
-	it('lists the seven tiles in order, each with its name and description', async () => {
+describe('Eight type tiles', () => {
+	it('lists the eight tiles in order, each with its name and description', async () => {
 		await mountAt('/schema/events')
 		await click(button('Add field'))
 
 		const labels = all('[role="radio"]').map((radio) => radio.closest('label')!)
 
-		expect(labels).toHaveLength(7)
+		expect(labels).toHaveLength(8)
 		labels.forEach((label, index) => {
 			const [name, , description] = TILES[index]!
 			expect(text(label)).toBe(`${name} ${description}`)
@@ -112,7 +113,7 @@ describe('Seven type tiles', () => {
 })
 
 describe('Adding a media field', () => {
-	it('shows the New badge, an editable Auto key with its help and all seven tiles enabled', async () => {
+	it('shows the New badge, an editable Auto key with its help and all eight tiles enabled', async () => {
 		await mountAt('/schema/events')
 
 		await addMediaField()
@@ -123,7 +124,7 @@ describe('Adding a media field', () => {
 		expect(text(inspector())).toContain(
 			'The name used in the API. Starts with a letter. Lowercase letters, digits and underscores.',
 		)
-		expect(all('[role="radio"]')).toHaveLength(7)
+		expect(all('[role="radio"]')).toHaveLength(8)
 		expect(all<HTMLButtonElement>('[role="radio"]').every((radio) => !radio.disabled)).toBe(
 			true,
 		)
@@ -198,17 +199,17 @@ describe('The inspector of a saved media field', () => {
 		expect(inspector()!.querySelector('[data-testid="slug-lock"]')).not.toBeNull()
 	})
 
-	it('selects Media, dims the six other tiles and makes them unselectable', async () => {
+	it('selects Media, dims the seven other tiles and makes them unselectable', async () => {
 		await mountAt('/schema/events', savedThumbnail())
 
 		await selectRow('Thumbnail')
 
-		expect(all('[role="radio"]')).toHaveLength(7)
+		expect(all('[role="radio"]')).toHaveLength(8)
 		expect(tile('Media').getAttribute('data-state')).toBe('checked')
 		const others = all<HTMLButtonElement>('[role="radio"]').filter(
 			(radio) => radio !== tile('Media'),
 		)
-		expect(others).toHaveLength(6)
+		expect(others).toHaveLength(7)
 		expect(others.every((radio) => radio.disabled || radio.hasAttribute('data-disabled'))).toBe(
 			true,
 		)
@@ -330,6 +331,7 @@ describe('Saving a media field', () => {
 			min: null,
 			max: null,
 			options: [],
+			relation: null,
 		})
 	})
 
@@ -354,6 +356,7 @@ describe('Saving a media field', () => {
 			min: null,
 			max: null,
 			options: [],
+			relation: null,
 		})
 	})
 

web/src/views/__tests__/SchemaBuilderRelation.spec.ts

@@ -0,0 +1,537 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+import { flushPromises } from '@vue/test-utils'
+import { addCollection } from '@iconify/vue'
+import lucide from 'virtual:lucide-subset'
+import { MOBILE_WIDTH } from '@/components/__tests__/viewport'
+import {
+	button,
+	deletes,
+	entryPage,
+	failWithBody,
+	mountAt,
+	posts,
+	puts,
+	text,
+	unmountAll,
+} from './schemaTestKit'
+import {
+	addField,
+	all,
+	badgesOf,
+	byLabel,
+	chip,
+	click,
+	dialog,
+	el,
+	fieldKeyInput,
+	inspector,
+	inspectorTitle,
+	labelInput,
+	nameInput,
+	pickTile,
+	rowOf,
+	saveButton,
+	selectRow,
+	tile,
+	toggle,
+	typeInto,
+} from './builderKit'
+import { drawsIcon } from './mediaFieldKit'
+import { allTypes, eventsWithRelations, speakersType, venuesType } from './relationKit'
+import { customTypes } from './schemaTestKit'
+
+vi.mock('@/composables/useApi', async (importOriginal) => {
+	const actual = await importOriginal<typeof import('@/composables/useApi')>()
+	return { ...actual, useApi: vi.fn() }
+})
+
+addCollection(lucide)
+
+beforeEach(() => {
+	Element.prototype.scrollIntoView = () => undefined
+	Element.prototype.hasPointerCapture = vi.fn(() => false)
+	Element.prototype.releasePointerCapture = vi.fn()
+})
+
+afterEach(async () => {
+	vi.restoreAllMocks()
+	await unmountAll()
+})
+
+const SENTENCES = {
+	one_to_one: 'Each Event has one Venue, and each Venue has one Event.',
+	one_to_many: 'Each Event has one Venue. A Venue has many Events.',
+	many_to_many: 'Each Event has many Venues, and each Venue has many Events.',
+}
+
+const types = () => [customTypes[0]!, venuesType, speakersType, customTypes[1]!]
+
+function mountBuilder(path = '/schema/events', options: object = {}) {
+	return mountAt(path, { content: types, ...options })
+}
+
+const picker = () => el('[data-testid="relation-picker"]')!
+const cards = () => all('[data-testid="relation-picker"] [role="radio"]')
+const selectTrigger = () => picker().querySelector<HTMLElement>('button[role="combobox"]')!
+const ownerSentence = () => text(el('[data-testid="relation-owner-sentence"]'))
+const inverseSentence = () => text(el('[data-testid="relation-inverse-sentence"]'))
+
+function openTrigger(trigger: Element) {
+	trigger.dispatchEvent(
+		Object.assign(new MouseEvent('pointerdown', { bubbles: true, button: 0 }), {
+			pointerType: 'mouse',
+		}),
+	)
+}
+
+async function chooseOption(trigger: Element, label: string) {
+	openTrigger(trigger)
+	await flushPromises()
+	const option = all('[role="option"]').find((candidate) => text(candidate).startsWith(label))!
+	option.dispatchEvent(new MouseEvent('pointerup', { bubbles: true }))
+	option.click()
+	await flushPromises()
+}
+
+async function addRelation(label = 'Venue') {
+	await addField(label)
+	await pickTile('Relation')
+}
+
+async function relateTo(name: string) {
+	await chooseOption(selectTrigger(), name)
+}
+
+describe('The type gallery', () => {
+	it('gains Relation as the last tile with the link icon, selectable like the others', async () => {
+		await mountBuilder()
+		await click(button('Add field'))
+
+		const labels = all('[role="radio"]').map((radio) => radio.closest('label')!)
+
+		expect(labels).toHaveLength(8)
+		const last = labels[7]!
+		expect(text(last)).toBe("Relation Links to another type's entries")
+		expect(drawsIcon(last, 'link')).toBe(true)
+		expect(tile('Relation').disabled).toBe(false)
+	})
+
+	it('dims the other tiles on a saved relation', async () => {
+		await mountBuilder('/schema/events', {
+			type: () => eventsWithRelations(),
+			content: () => allTypes(),
+		})
+		await selectRow('Venue')
+
+		expect(tile('Relation').getAttribute('data-state')).toBe('checked')
+		const others = all<HTMLButtonElement>('[role="radio"]').filter((radio) =>
+			radio.closest('label')!.innerHTML.includes('opacity-40'),
+		)
+		expect(others).toHaveLength(7)
+		expect(text(inspector())).toContain("Can't change after saving")
+	})
+})
+
+describe('Adding a relation field', () => {
+	it('shows New, an editable Auto key, the unsaved chip and the relation controls in order', async () => {
+		await mountBuilder()
+
+		await addRelation()
+
+		expect(badgesOf('Venue')).toContain('New')
+		expect(fieldKeyInput()!.value).toBe('venue')
+		expect(inspector()!.querySelector('button[aria-label="Edit key"]')).not.toBeNull()
+		expect(chip()).toBe('1 problem to fix')
+		expect(inspectorTitle()).toBe('Field: Venue')
+		const copy = text(inspector())
+		expect(copy.indexOf('Type')).toBeLessThan(copy.indexOf('Related content type'))
+		expect(copy.indexOf('Related content type')).toBeLessThan(
+			copy.indexOf('How are they connected?'),
+		)
+		expect(copy).toContain('Choose the content type this field points to.')
+	})
+
+	it('cannot send a relation without a related type', async () => {
+		await mountBuilder('/schema/events', {
+			entries: () => entryPage(0),
+		})
+		await addRelation()
+
+		await click(saveButton())
+
+		expect(puts).toHaveLength(0)
+		expect(text(inspector())).toContain('Choose a related content type.')
+	})
+})
+
+describe('The related content type select', () => {
+	it('lists every custom type by name with its key, Events included', async () => {
+		await mountBuilder()
+		await addRelation()
+
+		openTrigger(selectTrigger())
+		await flushPromises()
+
+		expect(all('[role="option"]').map(text)).toEqual([
+			'Events events',
+			'Venues venues',
+			'Speakers speakers',
+			'Recipes recipes',
+		])
+	})
+
+	it('sets the sentences of the preview from the chosen type', async () => {
+		await mountBuilder()
+		await addRelation()
+
+		await relateTo('Venues')
+
+		expect(ownerSentence()).toBe('Each Event has one Venue')
+		expect(inverseSentence()).toContain('Each Venue has many Events')
+	})
+})
+
+describe('The three shape cards', () => {
+	it('shows the titles and sentences, with One to many selected by default', async () => {
+		await mountBuilder()
+		await addRelation()
+		await relateTo('Venues')
+
+		expect(cards().map((card) => text(card.closest('label')))).toEqual([
+			`One to one ${SENTENCES.one_to_one}`,
+			`One to many ${SENTENCES.one_to_many}`,
+			`Many to many ${SENTENCES.many_to_many}`,
+		])
+		expect(cards().map((card) => card.getAttribute('data-state'))).toEqual([
+			'unchecked',
+			'checked',
+			'unchecked',
+		])
+		expect(cards()[1]!.closest('label')!.className).toContain(
+			'has-data-[state=checked]:bg-(--rc-sand)',
+		)
+	})
+
+	it('is a radio group, one card at a time', async () => {
+		await mountBuilder()
+		await addRelation()
+		await relateTo('Venues')
+
+		await click(cards()[2])
+
+		expect(cards().map((card) => card.getAttribute('data-state'))).toEqual([
+			'unchecked',
+			'unchecked',
+			'checked',
+		])
+	})
+
+	it('stacks on one column on mobile', async () => {
+		await mountBuilder('/schema/events', { width: MOBILE_WIDTH })
+		await addRelation()
+
+		const fieldset = cards()[0]!.closest('[class*="grid-cols"]')!
+		expect(fieldset.className).toContain('grid-cols-1')
+	})
+})
+
+describe('The preview of both sides', () => {
+	it.each([
+		['One to one', 'Each Event has one Venue', 'Each Venue has one Event'],
+		['One to many', 'Each Event has one Venue', 'Each Venue has many Events'],
+		['Many to many', 'Each Event has many Venues', 'Each Venue has many Events'],
+	])('follows the card %s', async (card, owner, inverse) => {
+		await mountBuilder()
+		await addRelation()
+		await relateTo('Venues')
+
+		await click(cards().find((radio) => text(radio.closest('label')).startsWith(card)))
+
+		expect(ownerSentence()).toBe(owner)
+		expect(inverseSentence()).toContain(inverse)
+	})
+
+	it('shows the muted note and the board example cards for One to many', async () => {
+		await mountBuilder()
+		await addRelation()
+		await relateTo('Venues')
+
+		expect(inverseSentence()).toContain('· shown on Venue as the field "Events"')
+		expect(el('[data-testid="relation-preview"]')!.className).toContain('bg-elevated')
+		expect(text(el('[data-testid="relation-example-owner"]'))).toBe(
+			'Event Venue Rue Verte hall',
+		)
+		expect(text(el('[data-testid="relation-example-related"]'))).toBe(
+			'Venue Events Open day Lime plaster workshop +1',
+		)
+	})
+
+	it('changes the kind through the selects of the sentences', async () => {
+		await mountBuilder()
+		await addRelation()
+		await relateTo('Venues')
+
+		const triggers = all('[data-testid="relation-preview"] button[role="combobox"]')
+		await chooseOption(triggers[0]!, 'many')
+
+		expect(cards().map((card) => card.getAttribute('data-state'))).toEqual([
+			'unchecked',
+			'unchecked',
+			'checked',
+		])
+		await chooseOption(triggers[1]!, 'one')
+		expect(cards().map((card) => card.getAttribute('data-state'))).toEqual([
+			'checked',
+			'unchecked',
+			'unchecked',
+		])
+	})
+
+	it('sends nothing about the inverse side', async () => {
+		await mountBuilder('/schema/events', { entries: () => entryPage(0) })
+		await addRelation()
+		await relateTo('Venues')
+
+		await click(saveButton())
+
+		const fields = (puts[0]!.body as { fields: { relation: unknown }[] }).fields
+		expect(fields[7]!.relation).toEqual({ content_type: 'venues', kind: 'one_to_many' })
+		expect(JSON.stringify(puts[0]!.body)).not.toContain('inverse')
+	})
+})
+
+describe('Plural and names', () => {
+	it('draws singular and plural forms from the type names and the field label', async () => {
+		await mountBuilder()
+		await addRelation('Place')
+		await relateTo('Venues')
+		await click(cards()[2])
+
+		expect(ownerSentence()).toBe('Each Event has many Venues')
+		expect(inverseSentence()).toContain('Each Place has many Events')
+	})
+})
+
+describe('The PUT and POST body', () => {
+	it('sends the relation as content_type and kind and every other field with relation null', async () => {
+		await mountBuilder('/schema/events', { entries: () => entryPage(0) })
+		await addRelation()
+		await relateTo('Venues')
+
+		await click(saveButton())
+
+		expect(puts).toHaveLength(1)
+		const fields = (puts[0]!.body as { fields: Record<string, unknown>[] }).fields
+		expect(fields[7]).toEqual({
+			key: 'venue',
+			label: 'Venue',
+			type: 'relation',
+			required: false,
+			unique: false,
+			default: null,
+			min: null,
+			max: null,
+			options: [],
+			relation: { content_type: 'venues', kind: 'one_to_many' },
+		})
+		expect(fields.slice(0, 7).every((field) => field.relation === null)).toBe(true)
+	})
+
+	it('sends the chosen kind in the POST body of a new type', async () => {
+		await mountBuilder('/schema/new')
+		await typeInto(nameInput(), 'Gallery')
+		await selectRow('Title')
+		await addRelation('Speakers')
+		await relateTo('Speakers')
+		await click(cards()[2])
+
+		await click(saveButton())
+
+		const fields = (posts[0]!.body as { fields: Record<string, unknown>[] }).fields
+		expect(fields[1]!.relation).toEqual({ content_type: 'speakers', kind: 'many_to_many' })
+	})
+
+	it('makes a no-change round trip of a loaded relation', async () => {
+		await mountBuilder('/schema/events', {
+			type: () => eventsWithRelations(),
+			content: () => allTypes(),
+			entries: () => entryPage(0),
+		})
+		await typeInto(nameInput(), 'Events and talks')
+
+		await click(saveButton())
+
+		const fields = (puts[0]!.body as { fields: Record<string, unknown>[] }).fields
+		expect(fields[7]).toMatchObject({
+			key: 'venue',
+			relation: { content_type: 'venues', kind: 'one_to_many' },
+		})
+		expect(fields[8]).toMatchObject({
+			key: 'speakers',
+			relation: { content_type: 'speakers', kind: 'many_to_many' },
+		})
+	})
+})
+
+describe('The inspector of a saved relation', () => {
+	async function openSaved() {
+		await mountBuilder('/schema/events', {
+			type: () => eventsWithRelations(),
+			content: () => allTypes(),
+		})
+		await selectRow('Venue')
+	}
+
+	it('locks the key, the tiles, the related type and the cards but not Label or Required', async () => {
+		await openSaved()
+
+		expect(fieldKeyInput()!.readOnly).toBe(true)
+		expect(labelInput()!.disabled).toBe(false)
+		expect(selectTrigger().hasAttribute('disabled')).toBe(true)
+		expect(
+			cards().every(
+				(card) => card.hasAttribute('disabled') || card.hasAttribute('data-disabled'),
+			),
+		).toBe(true)
+		expect(cards()[1]!.getAttribute('data-state')).toBe('checked')
+		expect(text(el('[data-testid="relation-locked-note"]'))).toBe(
+			"The related type and the connection can't change after saving.",
+		)
+		expect(text(selectTrigger())).toContain('Venues')
+		await toggle('Required')
+		expect(chip()).toBe('Unsaved changes')
+	})
+})
+
+describe('Review before saving', () => {
+	async function reviewRelation(required: boolean, total = 12) {
+		await mountBuilder('/schema/events', { entries: () => entryPage(total) })
+		await addRelation()
+		await relateTo('Venues')
+		if (required) {
+			await toggle('Required')
+		}
+		await click(saveButton())
+	}
+
+	it('refuses a required relation on a type with entries without sending the PUT', async () => {
+		await reviewRelation(true)
+
+		expect(puts).toHaveLength(0)
+		expect(text(dialog())).toContain('Review changes to Events')
+		expect(text(el('[data-testid="change-title"]'))).toBe('Add Venue')
+		expect(text(el('[data-testid="change-flag"]'))).toBe("Can't be applied")
+		expect(text(el('[data-testid="change-text"]'))).toBe(
+			"Relation, required. A relation can't have a default, so the 12 existing entries would have no Venue. Make Venue optional to add it.",
+		)
+		expect((button('Back to editing') as HTMLButtonElement).disabled).toBe(false)
+		button('Apply changes')!.click()
+		await flushPromises()
+		expect(puts).toHaveLength(0)
+	})
+
+	it('shows the clean row for an optional relation and applies it', async () => {
+		await reviewRelation(false)
+
+		expect(text(el('[data-testid="change-text"]'))).toBe(
+			'Relation, optional. 12 entries are unaffected.',
+		)
+		expect(el('[data-testid="change-flag"]')).toBeNull()
+		await click(button('Apply changes'))
+		expect(puts).toHaveLength(1)
+	})
+
+	it('sends a required relation at once when the type has no entries', async () => {
+		await reviewRelation(true, 0)
+
+		expect(dialog()).toBeNull()
+		expect(puts).toHaveLength(1)
+	})
+
+	it('flags making a saved optional relation required', async () => {
+		await mountBuilder('/schema/events', {
+			type: () => eventsWithRelations(),
+			content: () => allTypes(),
+			entries: () => entryPage(12),
+		})
+		await selectRow('Venue')
+		await toggle('Required')
+
+		await click(saveButton())
+
+		expect(text(el('[data-testid="change-flag"]'))).toBe('Entries may not fit')
+		expect((button('Apply changes') as HTMLButtonElement).hasAttribute('aria-disabled')).toBe(
+			false,
+		)
+	})
+})
+
+describe('The server answers on the builder', () => {
+	it('runs the existing refusal flow on 409 schema_incompatible', async () => {
+		await mountBuilder('/schema/events', {
+			entries: () => entryPage(0),
+			update: failWithBodyUpdate(409, 'schema_incompatible'),
+		})
+		await addRelation()
+		await relateTo('Venues')
+
+		await click(saveButton())
+
+		expect(text(dialog())).toContain('Nothing was changed')
+	})
+
+	it('shows the invalid-field failure on 422 and keeps the edits', async () => {
+		await mountBuilder('/schema/events', {
+			entries: () => entryPage(0),
+			update: failWithBodyUpdate(422, 'invalid_field'),
+		})
+		await addRelation()
+		await relateTo('Venues')
+
+		await click(saveButton())
+
+		expect(text(el('[role="alert"]'))).toContain('Check the fields marked in the list.')
+		expect(rowOf('Venue')).toBeDefined()
+		expect(selectTrigger()).not.toBeNull()
+	})
+})
+
+function failWithBodyUpdate(status: number, body: string) {
+	const respond = failWithBody(status, body)
+	return () => respond()
+}
+
+describe('Deleting a type that another type points at', () => {
+	it('shows the referenced refusal and keeps the type', async () => {
+		await mountAt('/schema/venues', {
+			content: () => allTypes(),
+			type: (key: string) => allTypes().find((type) => type.key === key),
+			entries: () => entryPage(0),
+			remove: failWithBody(409, 'content_type_referenced'),
+		})
+
+		await click(byLabel('More actions'))
+		await click(all('[role="menuitem"]').find((item) => text(item) === 'Delete content type'))
+		await click(
+			all('button', dialog()).find((candidate) =>
+				text(candidate).startsWith('Delete content type'),
+			),
+		)
+
+		expect(deletes).toEqual(['/v1/content-type/venues'])
+		expect(text(dialog())).toContain("You can't delete Venues yet")
+		expect(text(dialog())).toContain(
+			'Events has a field that points to Venues. Remove that field first.',
+		)
+		expect(dialog()).not.toBeNull()
+	})
+})
+
+describe('The builder is for owners and admins', () => {
+	it('keeps the forbidden state and renders no relation control', async () => {
+		await mountAt('/schema/events', { role: 'user', content: types })
+
+		expect(text(el('#dashboard-content'))).toContain("You don't have access to Schema")
+		expect(el('[data-testid="relation-picker"]')).toBeNull()
+	})
+})

web/src/views/__tests__/SchemaBuilderSave.spec.ts

@@ -70,6 +70,7 @@ const EVENTS_BODY = {
 			min: null,
 			max: 80,
 			options: [],
+			relation: null,
 		},
 		{
 			key: 'starts_on',
@@ -81,6 +82,7 @@ const EVENTS_BODY = {
 			min: '2026-01-01',
 			max: '2027-12-31',
 			options: [],
+			relation: null,
 		},
 		{
 			key: 'category',
@@ -92,6 +94,7 @@ const EVENTS_BODY = {
 			min: null,
 			max: null,
 			options: ['Talk', 'Workshop', 'Meetup'],
+			relation: null,
 		},
 	],
 }

web/src/views/__tests__/SchemaBuilderView.spec.ts

@@ -160,7 +160,7 @@ describe('New type, desktop (design state 1)', () => {
 		expect(copy).toContain(
 			'The name used in the API. Starts with a letter. Lowercase letters, digits and underscores.',
 		)
-		expect(all('[role="radio"]')).toHaveLength(7)
+		expect(all('[role="radio"]')).toHaveLength(8)
 		expect(el('[role="radio"][aria-checked="true"]')!.closest('label')!.textContent).toContain(
 			'Text',
 		)

web/src/views/__tests__/relationKit.ts

@@ -0,0 +1,254 @@
+import { flushPromises } from '@vue/test-utils'
+import type { RelationKind, RelationSummary } from '@/lib/relationField'
+import {
+	answerWrite,
+	entry42,
+	fieldWrapper,
+	lookupNames,
+	mountEditor,
+	text,
+} from './entryEditorKit'
+import { apiField, customTypes, eventsFields, type SchemaMount } from './schemaTestKit'
+
+export const SEARCH_DEBOUNCE_MS = 200
+export const SEARCH_SIZE = 10
+
+interface Row {
+	id: number
+	data: Record<string, unknown>
+}
+
+export const VENUES: Row[] = [
+	{ id: 3, data: { name: 'Rue Verte hall', city: 'Lyon', details: '120 seats' } },
+	{ id: 4, data: { name: 'Rue Verte yard', city: 'Lyon', details: 'outdoor' } },
+	{ id: 5, data: { name: 'Rue du Port studio', city: 'Nantes', details: '24 seats' } },
+	{ id: 6, data: { name: 'Quai Nord', city: 'Nantes', details: '' } },
+]
+
+export const SPEAKERS: Row[] = [
+	{ id: 11, data: { name: 'Ines Duarte' } },
+	{ id: 12, data: { name: 'Jonas Pereira' } },
+	{ id: 13, data: { name: 'Ana Costa' } },
+	{ id: 14, data: { name: 'Luc Moreau' } },
+]
+
+const ROWS: Record<string, Row[]> = { venues: VENUES, speakers: SPEAKERS }
+const FIRST_FIELD: Record<string, string> = { venues: 'name', speakers: 'name' }
+
+export const venuesType = {
+	...customTypes[1]!,
+	id: 4,
+	key: 'venues',
+	name: 'Venues',
+	fields: [
+		apiField('Name', 'name', 'text', { required: true, options: [] }),
+		apiField('City', 'city', 'text', { options: [] }),
+		apiField('Details', 'details', 'text', { options: [] }),
+	],
+}
+
+export const speakersType = {
+	...customTypes[1]!,
+	id: 5,
+	key: 'speakers',
+	name: 'Speakers',
+	fields: [apiField('Name', 'name', 'text', { required: true, options: [] })],
+}
+
+export function relationField(
+	label: string,
+	key: string,
+	target: string,
+	kind: RelationKind,
+	rest: object = {},
+) {
+	return apiField(label, key, 'relation', {
+		options: [],
+		relation: { content_type: target, kind },
+		...rest,
+	})
+}
+
+export function eventsWithRelations(
+	venue: object = {},
+	speakers: object = {},
+	venueKind: RelationKind = 'one_to_many',
+) {
+	return {
+		...customTypes[0]!,
+		fields: [
+			...eventsFields,
+			relationField('Venue', 'venue', 'venues', venueKind, venue),
+			relationField('Speakers', 'speakers', 'speakers', 'many_to_many', speakers),
+		],
+	}
+}
+
+export function allTypes(venue: object = {}, speakers: object = {}) {
+	return [eventsWithRelations(venue, speakers), venuesType, speakersType]
+}
+
+export function summaryFor(typeKey: string, id: number): RelationSummary {
+	const row = ROWS[typeKey]!.find((candidate) => candidate.id === id)!
+	const key = FIRST_FIELD[typeKey]!
+	return {
+		id,
+		content_type: typeKey,
+		first_field: { key, type: 'text', value: row.data[key] },
+	}
+}
+
+export const MISSING_VENUE: RelationSummary = { id: 3, missing: true }
+
+export function entryWithRelations(
+	venue: number | null,
+	speakers: number[],
+	relations?: Record<string, RelationSummary | RelationSummary[]>,
+) {
+	const shown = relations ?? {
+		...(venue === null ? {} : { venue: summaryFor('venues', venue) }),
+		...(speakers.length === 0
+			? {}
+			: { speakers: speakers.map((id) => summaryFor('speakers', id)) }),
+	}
+	return {
+		...entry42,
+		data: { ...entry42.data, venue, speakers },
+		relations: shown,
+	}
+}
+
+export function searchBody(typeKey: string, query: URLSearchParams) {
+	const needle = (query.get('q') ?? '').toLowerCase()
+	const page = Number(query.get('page') ?? '1')
+	const size = Number(query.get('size') ?? String(SEARCH_SIZE))
+	const matches = ROWS[typeKey]!.filter((row) =>
+		String(row.data[FIRST_FIELD[typeKey]!]).toLowerCase().includes(needle),
+	)
+	const items = matches.slice((page - 1) * size, page * size).map((row) => ({
+		...entry42,
+		id: row.id,
+		content_type: typeKey,
+		data: row.data,
+		relations: {},
+	}))
+	return { items, total: matches.length, page, size }
+}
+
+export function answerRelationWrite(write: {
+	method: string
+	url: string
+	body: Record<string, unknown>
+}) {
+	const answered = answerWrite(write as never) as { data: Record<string, unknown> }
+	const data = answered.data
+	const venue = data.venue
+	const speakers = (data.speakers as number[] | undefined) ?? []
+	return {
+		...answered,
+		relations: {
+			...(typeof venue === 'number' ? { venue: summaryFor('venues', venue) } : {}),
+			...(speakers.length > 0
+				? { speakers: speakers.map((id) => summaryFor('speakers', id)) }
+				: {}),
+		},
+	}
+}
+
+export interface RelationMount extends SchemaMount {
+	venue?: number | null
+	speakers?: number[]
+	venueField?: object
+	speakersField?: object
+	relations?: Record<string, RelationSummary | RelationSummary[]>
+	search?: (typeKey: string, query: URLSearchParams) => unknown
+}
+
+export function mountRelation(path: string, options: RelationMount = {}) {
+	const {
+		venue = null,
+		speakers = [],
+		venueField,
+		speakersField,
+		relations,
+		search,
+		...rest
+	} = options
+	const types = allTypes(venueField, speakersField)
+	return mountEditor(path, {
+		type: (key) => types.find((type) => type.key === key),
+		content: () => types,
+		entry: () => entryWithRelations(venue, speakers, relations),
+		writeEntry: answerRelationWrite,
+		lookup: lookupNames,
+		list: (key, query) => (search ?? searchBody)(key, query),
+		...rest,
+	})
+}
+
+export function relationInput(key: string) {
+	return fieldWrapper(key).querySelector<HTMLInputElement>('input[role="combobox"]')!
+}
+
+export function chipLabels(key: string) {
+	return [...fieldWrapper(key).querySelectorAll('[data-slot="tagsItemText"]')].map((item) =>
+		text(item),
+	)
+}
+
+export function optionLabels() {
+	return [...document.body.querySelectorAll<HTMLElement>('[role="option"]')].map((option) =>
+		text(option),
+	)
+}
+
+export async function typeSearch(key: string, value: string) {
+	const input = relationInput(key)
+	input.focus()
+	input.value = value
+	input.dispatchEvent(new Event('input', { bubbles: true }))
+	await flushPromises()
+}
+
+export async function settleSearch(vi: {
+	advanceTimersByTimeAsync: (ms: number) => Promise<unknown>
+}) {
+	await vi.advanceTimersByTimeAsync(SEARCH_DEBOUNCE_MS + 10)
+	await flushPromises()
+}
+
+export function liveText(key: string) {
+	return text(fieldWrapper(key).querySelector('[data-testid="relation-live"]'))
+}
+
+export async function pickOption(label: string) {
+	const option = [...document.body.querySelectorAll<HTMLElement>('[role="option"]')].find(
+		(candidate) => text(candidate).startsWith(label),
+	)!
+	option.click()
+	await flushPromises()
+}
+
+export async function openList(key: string, vi: Parameters<typeof settleSearch>[0], value = '') {
+	await typeSearch(key, value)
+	await settleSearch(vi)
+}
+
+export function removeButtons(key: string) {
+	return [
+		...fieldWrapper(key).querySelectorAll<HTMLButtonElement>('[data-slot="tagsItemDelete"]'),
+	]
+}
+
+export async function press(key: string, name: string) {
+	relationInput(key).dispatchEvent(new KeyboardEvent('keydown', { key: name, bubbles: true }))
+	await flushPromises()
+}
+
+export function relationError(key: string) {
+	return text(fieldWrapper(key).querySelector('[role="alert"]'))
+}
+
+export function emptyText() {
+	return text(document.body.querySelector('[data-testid="relation-empty"]'))
+}