Backend UI Design

Backend UI Design

Guide for creating consistent, production-grade backend interfaces using the @open-mercato/ui component library. All implementations must use existing components for visual and behavioral consistency.

For complete component API reference, see references/ui-components.md. Pair this skill with .ai/guides/ui.md when present and with the standalone AGENTS.md rules for DataTable hosts, design-system primitives, and backend page conventions.

Design Principles

1. Consistency First: Every page should feel like part of the same application.
2. Component Reuse: Never create custom implementations when a shared component exists.
3. Data Density: Admin users need information-rich interfaces. Optimize for scanning.
4. Keyboard Navigation: Cmd/Ctrl+Enter for primary actions, Escape to cancel.
5. Clear Hierarchy: Page → Section → Content. Use PageHeader, PageBody, consistent spacing.
6. Design System Discipline: Use semantic status tokens plus shared primitives like StatusBadge, Alert, FormField, SectionHeader, CollapsibleSection, and EmptyState. No hardcoded status colors or arbitrary text sizes.

Required Component Library

ALWAYS import from @open-mercato/ui.

Core Layout

import { Page, PageHeader, PageBody } from '@open-mercato/ui/backend/Page'

<Page>
  <PageHeader>{/* Title, actions, breadcrumbs */}</PageHeader>
  <PageBody>{/* Main content */}</PageBody>
</Page>

Data Display (Lists)

Use DataTable for ALL tabular data. Never implement custom tables.

import { DataTable } from '@open-mercato/ui/backend/DataTable'
import type { FilterDef } from '@open-mercato/ui/backend/FilterBar'
import { RowActions } from '@open-mercato/ui/backend/RowActions'
import { TruncatedCell } from '@open-mercato/ui/backend/TruncatedCell'
import { BooleanIcon, EnumBadge } from '@open-mercato/ui/backend/ValueIcons'

Column patterns:

• Text: TruncatedCell with meta.maxWidth
• Boolean: BooleanIcon
• Status/enum: EnumBadge with severity presets
• Actions: RowActions for context menus

Preferred DataTable Host Pattern

For standard CRUD lists, prefer the built-in host pattern instead of manually fetching and shaping rows:

<DataTable
  entityId="tickets.ticket"
  apiPath="tickets/tickets"
  extensionTableId="tickets.ticket"
  columns={columns}
  createHref="/backend/tickets/tickets/new"
  emptyState={{
    title: t('tickets.list.empty.title'),
    description: t('tickets.list.empty.description'),
  }}
/>

Keep extensionTableId stable so DataTable injections remain backward-compatible.

DataTable Pagination

DataTable MUST be configured with pagination props to display all data correctly. Without these, the table only shows the first page with no way to navigate:

<DataTable
  columns={columns}
  data={items}
  page={page}
  pageSize={pageSize}
  totalCount={totalCount}
 
/>

When using a custom API (not makeCrudRoute), ensure the list response always returns:

• items — array of records for the current page
• totalCount — total records matching the query (not just the current page)
• page — current page number (1-based)
• pageSize — records per page

The default pageSize is 25. Keep at or below 100. If you see fewer records than expected, verify your API returns totalCount and the DataTable has pagination props wired.

Forms

Use CrudForm for ALL forms. Never build from scratch.

import { CrudForm, type CrudField, type CrudFormGroup } from '@open-mercato/ui/backend/CrudForm'

Field types: text, textarea, number, email, password, select, multiselect, combobox, checkbox, switch, date, datetime, custom.

Form Headers & Footers

import { FormHeader, FormFooter, FormActionButtons, ActionsDropdown } from '@open-mercato/ui/backend/forms'

• FormHeader mode="edit" — compact header for CrudForm pages
• FormHeader mode="detail" — large header for view/detail pages with entity type label, title, status badge, and Actions dropdown
• FormFooter — footer wrapping FormActionButtons
• ActionsDropdown — groups additional context actions (Convert, Send, Print). Delete is never inside the dropdown.

Dialogs

import { Dialog, DialogContent, DialogHeader, DialogTitle } from '@open-mercato/ui/primitives/dialog'

// Dialog forms MUST use embedded={true}
<CrudForm fields={fields} embedded={true} submitLabel="Save" />

Detail Pages

import { DetailFieldsSection, LoadingMessage, ErrorMessage, TabEmptyState } from '@open-mercato/ui/backend/detail'
import { NotesSection } from '@open-mercato/ui/backend/detail/NotesSection'
import { TagsSection } from '@open-mercato/ui/backend/detail/TagsSection'
import { CustomDataSection } from '@open-mercato/ui/backend/detail/CustomDataSection'

Notifications

import { flash } from '@open-mercato/ui/backend/FlashMessages'

flash('Record saved successfully', 'success')
flash('Failed to save record', 'error')
flash('This action cannot be undone', 'warning')

NEVER use alert(), console.log(), or custom toast implementations.

Loading & Error States

import { Spinner } from '@open-mercato/ui/primitives/spinner'
import { DataLoader } from '@open-mercato/ui/primitives/DataLoader'
import { Notice } from '@open-mercato/ui/primitives/Notice'
import { ErrorNotice } from '@open-mercato/ui/primitives/ErrorNotice'
import { EmptyState } from '@open-mercato/ui/backend/EmptyState'
import { LoadingMessage, ErrorMessage } from '@open-mercato/ui/backend/detail'

Primitives

import { Button } from '@open-mercato/ui/primitives/button'
import { Input } from '@open-mercato/ui/primitives/input'
import { Label } from '@open-mercato/ui/primitives/label'
import { Badge } from '@open-mercato/ui/primitives/badge'
import { Switch } from '@open-mercato/ui/primitives/switch'
import { SimpleTooltip } from '@open-mercato/ui/primitives/tooltip'

API Integration

import { apiCall, apiCallOrThrow } from '@open-mercato/ui/backend/utils/apiCall'
import { createCrud, updateCrud, deleteCrud } from '@open-mercato/ui/backend/utils/crud'
import { createCrudFormError } from '@open-mercato/ui/backend/utils/serverErrors'

const handleCreate = async (values: FormValues) => {
  const result = await createCrud<ResponseType>('module/resource', values)
  if (result.ok) {
    flash('Created successfully', 'success')
    router.push(`/backend/module/${result.result.id}`)
  }
  return result
}

Custom Fields Integration

import { useCustomFieldDefinitions } from '@open-mercato/ui/backend/utils/customFieldDefs'
import { buildCustomFieldFormFields } from '@open-mercato/ui/backend/utils/customFieldForms'
import { buildCustomFieldColumns } from '@open-mercato/ui/backend/utils/customFieldColumns'
import { collectCustomFieldValues } from '@open-mercato/ui/backend/utils/customFieldValues'

Implementation Checklist

• Forms use CrudForm (not custom)
• Tables use DataTable (not custom)
• Notifications use flash() (not alert/toast)
• Dialog forms have embedded={true}
• Keyboard: Cmd/Ctrl+Enter (submit), Escape (cancel)
• Loading states use LoadingMessage or DataLoader
• Error states use ErrorMessage, ErrorNotice, or Notice variant="error"
• Empty states use EmptyState
• Status displays use StatusBadge or EnumBadge, not hardcoded colors
• Standalone inputs use FormField; detail sections use SectionHeader / CollapsibleSection when applicable
• Column truncation uses meta.truncate and meta.maxWidth
• Boolean values use BooleanIcon
• Status/enum values use EnumBadge
• Row actions use RowActions with stable id values
• API calls use apiCall/apiCallOrThrow (not raw fetch)

Anti-Patterns

1. Custom form implementations — use CrudForm
2. Manual table markup — use DataTable
3. Custom toast/notification — use flash()
4. Inline styles — use Tailwind classes
5. Hardcoded colors or status classes — use theme variables and semantic status tokens
6. Missing loading states — every async operation needs feedback
7. Missing error handling — every failure needs messaging
8. Missing keyboard shortcuts — all dialogs need Cmd+Enter and Escape
9. Custom truncation — use TruncatedCell with meta.maxWidth
10. Direct fetch() — use apiCall/apiCallOrThrow

Visual Guidelines

Spacing

• p-4 for cards, p-6 for page sections
• gap-4 or gap-6 for flex/grid layouts
• space-y-4 or space-y-6 for vertical rhythm

Colors

• Use semantic colors from theme (no hardcoded hex)
• Destructive: variant="destructive" on buttons
• Status badges: useSeverityPreset()

Layout Patterns

• List pages: FilterBar + DataTable + Pagination
• Detail pages: Header + Tabs/Sections + Related data
• Create/Edit: Full-page CrudForm or Dialog with embedded CrudForm
• Settings: Grouped sections with inline editing

Page Navigation Metadata

Every backend page needs correct page.meta.ts for sidebar placement. See .ai/skills/module-scaffold/references/navigation-patterns.md for:

• Complete field reference (pageGroup, pageOrder, pageContext, navHidden)
• Settings page pattern (pageContext: 'settings' as const + navHidden: true)
• Common anti-patterns (missing group, mismatched keys, broken icons)