Frontend-Design AgentSkill

Overview

frontend-design is the sixth step in the SSDAM execution pipeline (after backend-design, optional). It transforms architectural and backend specifications into a complete frontend design specification covering pages, components, state management, API integration, and routing.

This skill produces a single output document (frontend-design.TSK-NNN.md) that drives the final implementation step (frontend-implementation).

Skill Chain Context

task-spec.TSK-NNN.yaml
  + architecture-design.TSK-NNN.md (required)
  + backend-design.TSK-NNN.md      (optional — provides API specs)
    ↓
[frontend-design]  ← YOU ARE HERE
    ↓
.ssdam/{id}/output/design/frontend-design.TSK-NNN.md
    ↓
[frontend-implementation]

Trigger and I/O

Aspect	Details
Trigger	/frontend-design <task-spec-path>
Input	task-spec.TSK-NNN.yaml + architecture-design.TSK-NNN.md (req.) + backend-design.TSK-NNN.md (opt.)
Output	.ssdam/{id}/output/design/frontend-design.TSK-NNN.md
Tech Stack	Svelte 5, TypeScript, TailwindCSS, Vite, SvelteKit (varies by task-spec.tech_stack)

Execution Procedure

Step 1: Load Inputs

1. Parse task-spec.TSK-NNN.yaml:

   • Extract purpose.scope_included (features/views requiring frontend)
   • Extract purpose.scope_excluded (out-of-scope frontend features)
   • Read execution_plan.tech_stack to determine frontend framework (default: Svelte 5)
   • Extract requirement_ids and output_contract (acceptance criteria)

2. Read architecture-design.TSK-NNN.md:

   • Extract domain_entities (data model overview)
   • Extract api_contract_overview (high-level API structure)
   • Extract module_boundaries (system partitioning)
   • Note any user roles and permission levels

3. If backend-design.TSK-NNN.md exists:

   • Read api_endpoints section (precise endpoints, methods, paths)
   • Read schemas section (TypeScript interfaces for request/response types)
   • Use these details for precise API integration plan (override api_contract_overview if conflicting)

Error handling:

• If architecture-design.TSK-NNN.md not found: Stop and instruct user to run /architecture-design first.
• If no frontend scope in scope_included: Warn that this task has no frontend work — skip frontend chain entirely.

Step 2: Identify Pages and Routes

For each item in scope_included that involves user interface:

1. Page identification: List each distinct page or view.

   • Page name: descriptive (e.g., "Library", "UploadManagement", "Marketplace")
   • Route: SvelteKit route pattern (e.g., /, /uploads, /marketplace/[id])
   • Purpose: one-sentence description of what the page does
   • Accessed by: which user role(s) can access this page (from architecture-design)
   • Layout: which layout wrapper component (e.g., "AppLayout", "AuthLayout", "BlankLayout")

2. Verify all UI-related scope_included items are represented by at least one page.

Step 3: Design Component Tree

For each page identified in Step 2:

1. Page component: Create a top-level page component.

   • File: src/routes/{route}/+page.svelte
   • Responsibility: page-level layout, data loading orchestration, page-specific state

2. Layout components: Identify shared UI (header, sidebar, footer, navigation).

   • Shared across pages → src/lib/components/layout/ (e.g., AppHeader.svelte, AppSidebar.svelte)
   • One layout per page category (e.g., "AppLayout" for authenticated pages, "AuthLayout" for login/signup)

3. Feature components: Components specific to a feature or page.

   • File: src/lib/components/features/{FeatureName}/
   • Examples: MediaGrid.svelte, FileUploadModal.svelte, FilterPanel.svelte
   • Responsibility: handle a discrete feature or interaction

4. Atomic components: Reusable, primitive components.

   • File: src/lib/components/atomic/ (e.g., Button.svelte, TextField.svelte, Modal.svelte)
   • Responsibility: single, focused UI pattern (no business logic)

For each component, define:

Attribute	Format	Example
Component name	PascalCase	MediaGrid, FileUploadModal
File path	Relative to project_root	src/lib/components/features/MediaGallery/Grid.svelte
Category	page | layout | feature | atomic	feature
Props	List with types	items: MediaFile[], selectedId: string | null
Events	Custom events dispatched	on:select={...} → { detail: { id: string } }
Stores used	List of stores read/written	mediaFilesStore, authStore

Step 4: Design State Management

For each piece of shared state (data needed across multiple components):

1. Store identification: One store per domain concept.

   • Examples: authStore, mediaFilesStore, purchasesStore, uiStateStore
   • Do NOT create one massive global store — partition by domain.

2. For each store, define:

Attribute	Format	Example
Store name	camelCase	mediaFilesStore
Store file	src/lib/stores/{storeName}.ts	src/lib/stores/mediaFiles.ts
State interface	TypeScript interface	interface MediaFilesState { items: MediaFile[]; loading: boolean }
Initial state	Concrete values	{ items: [], loading: false, error: null }
Actions/methods	Named operations	fetchFiles(), uploadFile(file), deleteFile(id)
Derived stores	Computed values	selectedCount$ = derived(...)

Step 5: Design API Integration

For each API call the frontend needs to make:

1. Endpoint mapping: Match each component action to a backend endpoint.

   • Method: GET, POST, PUT, DELETE, PATCH
   • Path: e.g., /api/media/files, /api/uploads/{id}
   • Source: from backend-design.api_endpoints if available, else from architecture-design.api_contract_overview

2. Trigger identification: Which user action initiates each call.

   • Example: "Click 'Upload' button" → POST /api/uploads
   • Example: "Page load on /library" → GET /api/media/files
   • Example: "Delete media" → DELETE /api/media/files/{id}

3. Component/store responsibility: Which component/store makes the call.

   • Prefer stores for shared data (mediaFilesStore.fetchFiles())
   • Prefer components for isolated actions

4. TypeScript types: For each endpoint, define request and response types.

   • Request interface (if body is required): CreateUploadRequest { filename: string; mimetype: string }
   • Response interface: MediaFile { id: string; filename: string; size: number; uploadedAt: Date }
   • Match field names exactly with backend schemas (from backend-design)

5. Loading and error handling:

   • Every API call must update a loading state before fetch, unset in finally block
   • Every API call must catch errors and update error state
   • Components displaying results show loading spinner, error message, or success state

6. Group into API client module:

   • File: src/lib/api/{domain}.ts (e.g., src/lib/api/mediaFiles.ts)
   • Export async functions (not methods on a class)
   • Examples:

     export async function fetchMediaFiles(): Promise<MediaFile[]> { ... }
     export async function uploadFile(file: File): Promise<MediaFile> { ... }
     

Step 6: UI/UX Decisions

For each significant interaction identified in Steps 2-5:

1. Interaction pattern: Name the interaction (e.g., "double-click to open detail", "drag-to-reorder", "search-to-filter")

2. Component responsible: Which component handles it.

3. Behavior: What happens in response.

   • Example: "Double-click media → open detail modal"
   • Example: "Type in search field → filter list in real-time"
   • Example: "Click upload → show file picker"

4. State changes: Which store(s) update, and how.

   • Example: mediaFilesStore.setSelectedId(id) → detail modal becomes visible

Step 7: Define File Structure

List all files and directories to be created in project_root/:

Directory/File	Description	Example
src/routes/	SvelteKit page routes	src/routes/+page.svelte, src/routes/library/+page.svelte
src/lib/components/	Reusable components	src/lib/components/MediaGrid.svelte
src/lib/components/layout/	Layout wrappers	src/lib/components/layout/AppLayout.svelte
src/lib/components/atomic/	Primitive components	src/lib/components/atomic/Button.svelte
src/lib/stores/	Svelte stores	src/lib/stores/mediaFiles.ts
src/lib/api/	API client functions	src/lib/api/mediaFiles.ts
src/lib/types/	TypeScript interfaces	src/lib/types/media.ts, src/lib/types/auth.ts
tests/	Component and store tests	tests/components/MediaGrid.test.ts

Step 8: Test Strategy and Write Output

1. Define testing approach:

   • Test runner: Vitest + Svelte Testing Library
   • Per-component testing: component renders, props work, events dispatch, stores integrate
   • Store testing: actions update state correctly, derived values compute
   • API client testing: functions call correct endpoints, handle errors, transform responses

2. Write output document .ssdam/{id}/output/design/frontend-design.TSK-NNN.md:

   • Follow structure in references/output.template.yaml
   • Include all pages, components, stores, API integrations, file structure, test strategy
   • Self-validation: verify all scope_included UI items are addressed

Post-Execution

On successful completion:

✓ frontend-design.TSK-NNN.md written.
  - N pages defined
  - N components defined
  - N stores defined
  - N API endpoints integrated

Next: run /frontend-implementation <task-spec-path>

Error Handling

Error	Action
architecture-design.TSK-NNN.md not found	Stop. Instruct user: "Run /architecture-design first."
No frontend scope in task-spec.scope_included	Warn: "This task has no frontend work — skipping frontend chain." Do not produce a document.
backend-design.TSK-NNN.md not found	Proceed using api_contract_overview from architecture-design as fallback. Document the fallback.
Incomplete pages/components	Return error: "Step 3: [list missing components needed for scope_included]"
Missing API integration for a page action	Return error: "Step 5: [page/action] has no API endpoint defined."

References

• input.template.yaml: Template for parsing task-spec, architecture-design, backend-design
• output.template.yaml: Schema for the output frontend-design.TSK-NNN.md document
• rules.md: Mandatory conventions (naming, store design, component structure, etc.)

Compatibility Notes

• Framework detection: Read task-spec.execution_plan.tech_stack.frontend to determine framework (Svelte 5, React, Vue, etc.). This skill is optimized for Svelte 5 but abstracts patterns for other frameworks.
• TypeScript: All interface definitions must match backend schemas exactly (same field names, compatible types).
• Styling: TailwindCSS is the default CSS framework. Adjust if task-spec specifies otherwise.