Backend UI Design Codex

This skill guides creation of consistent, production-grade backend/backoffice interfaces using the established @open-mercato/ui component library. All implementations must leverage existing components to maintain visual and behavioral consistency across modules.

For complete component documentation, see references/ui-components.md. Pair this skill with packages/ui/AGENTS.md and packages/ui/src/backend/AGENTS.md for the current design-system and backend-host rules.

Design Principles

Backend UI prioritizes usability, consistency, and productivity over creative expression:

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

Required Component Library

ALWAYS import from @open-mercato/ui. Reference the component documentation at .ai/specs/SPEC-001-2026-01-21-ui-reusable-components.md.

Core Layout Pattern

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

// Every backend page follows this structure
<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 configuration patterns:

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

Forms

Use CrudForm for ALL forms. Never build forms from scratch.

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

Form field types available:

• text, textarea, number, email, password
• select, multiselect, combobox
• checkbox, switch
• date, datetime
• custom (for JsonBuilder, TagsInput, etc.)

Dialogs

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

// Dialog forms MUST use embedded={true}
<Dialog open={isOpen}
  <DialogContent className="sm:max-w-2xl [&_.grid]:!grid-cols-1">
    <DialogHeader>
      <DialogTitle>Edit Item</DialogTitle>
    </DialogHeader>
    <CrudForm
      fields={fields}
      groups={groups}
      initialValues={initialValues}
     
      embedded={true}
      submitLabel="Save"
    />
  </DialogContent>
</Dialog>

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'

// Success
flash('Record saved successfully', 'success')

// Error
flash('Failed to save record', 'error')

// Warning/Info
flash('This action cannot be undone', 'warning')
flash('Processing in background', 'info')

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 { 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 (use sparingly, prefer backend components)

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 { Alert, AlertTitle, AlertDescription } from '@open-mercato/ui/primitives/alert'
import { Separator } from '@open-mercato/ui/primitives/separator'
import { Switch } from '@open-mercato/ui/primitives/switch'
import { SimpleTooltip } from '@open-mercato/ui/primitives/tooltip'

Implementation Checklist

Before writing any backend UI code, verify:

• Using CrudForm for forms (not custom form implementations)
• Using DataTable for lists (not custom tables)
• Using flash() for notifications (not alert/toast)
• Dialog forms have embedded={true}
• Keyboard shortcuts: Cmd/Ctrl+Enter (submit), Escape (cancel)
• Loading states use LoadingMessage or DataLoader
• Error states use ErrorMessage or ErrorNotice
• Empty states use EmptyState
• Column truncation configured with meta.truncate and meta.maxWidth
• Boolean values use BooleanIcon
• Status/enum values use EnumBadge
• Row actions use RowActions component

Visual Guidelines

Spacing

• Use consistent padding: p-4 for cards, p-6 for page sections
• Use gap-4 or gap-6 for flex/grid layouts
• Maintain vertical rhythm with space-y-4 or space-y-6

Colors

• Use semantic colors from the theme (don't hardcode hex values)
• Destructive actions: variant="destructive" on buttons
• Status badges: Use useSeverityPreset() for consistent coloring

Typography

• Page titles: Handled by PageHeader
• Section titles: text-lg font-semibold
• Labels: Handled by form components
• Body text: Default sizing, avoid custom font sizes

Layout Patterns

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

Anti-Patterns to Avoid

1. Custom form implementations - Always use CrudForm
2. Manual table markup - Always use DataTable
3. Custom toast/notification - Always use flash()
4. Inline styles - Use Tailwind classes
5. Hardcoded colors - Use theme variables
6. Missing loading states - Every async operation needs feedback
7. Missing error handling - Every failure needs user-friendly messaging
8. Missing keyboard shortcuts - All dialogs need Cmd+Enter and Escape
9. Custom truncation logic - Use TruncatedCell with meta.maxWidth
10. Direct fetch() calls - Use apiCall/apiCallOrThrow from utils

API Integration Pattern

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

// For CRUD operations
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
}

// For custom endpoints
const result = await apiCall<ResponseType>('/api/custom-endpoint', {
  method: 'POST',
  body: JSON.stringify(data)
})

Custom Fields Integration

When building CRUD interfaces that support custom fields:

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'

When to Create New Components

Only create new components when:

1. No existing component serves the use case
2. The pattern will be reused across 3+ modules
3. Approved for addition to @open-mercato/ui

If creating something new, it should eventually be added to the shared library, not kept in a single module.