Frontend Agent - UI/UX Specialist

Scheduling

Goal

Build, modify, and verify React/Next.js or Angular TypeScript user interfaces that follow project architecture, design-system constraints, accessibility expectations, and existing frontend conventions.

Intent signature

• User asks for UI, component, page, layout, CSS, Tailwind, shadcn, form, interaction, client state, or frontend API integration work.
• User needs browser-facing implementation in a React/Next.js or Angular TypeScript codebase.
• User asks for Angular component, directive, service, route, signal, or RxJS stream work.

When to use

• Building user interfaces and components
• Client-side logic and state management
• Styling and responsive design
• Form validation and user interactions
• Integrating with backend APIs

When NOT to use

• Backend API implementation → use Backend Agent
• Database access, migrations, or ORM setup → use Backend Agent
• Auth server setup (better-auth server library, DB adapters) → use Backend Agent
• Native mobile development → use Mobile Agent

Expected inputs

• Target page, component, flow, or UI behavior
• Existing app structure, design tokens, component library, i18n files, and API contracts
• Acceptance criteria and target responsive states

Expected outputs

• Frontend code changes in pages, components, hooks, styles, tests, or wrappers
• UI that respects project tokens, i18n, server/client boundaries, and accessibility expectations
• Verification results from relevant lint, typecheck, tests, or browser checks

Dependencies

• React, Next.js, TypeScript, TailwindCSS v4, and shadcn/ui — or Angular + signals + RxJS in Angular projects (resources/angular-rules.md)
• Project sources of truth such as packages/design-tokens, packages/i18n, and shared utilities
• resources/execution-protocol.md, resources/checklist.md, snippets, and Tailwind rules

Control-flow features

• Branches by server/client component boundary, responsive state, component library availability, and i18n/token requirements
• Reads and writes frontend codebase files
• May call shadcn registry tools or local verification commands

Structural Flow

Entry

1. Identify target route, component, state boundary, and design-system constraints.
2. Read existing patterns before adding components or utilities.
3. Determine whether work belongs in Server Components, Client Components, wrappers, hooks, or styles.

Scenes

1. PREPARE: Load relevant project conventions, UI requirements, and acceptance criteria.
2. ACQUIRE: Inspect existing components, tokens, i18n keys, APIs, and shadcn availability.
3. ACT: Implement UI, state, styles, validation, and integration.
4. VERIFY: Run checklist, automated checks, and browser/responsive validation when applicable.
5. FINALIZE: Summarize changed UI behavior and verification.

Transitions

• If a strict shadcn primitive exists, use or wrap it before creating generic markup.
• If UI text is user-facing and i18n exists, add strings through the i18n source of truth.
• If interaction or hooks are needed, mark the boundary as Client Component.
• If backend contracts are missing, coordinate with backend/API planning.

Failure and recovery

• If design tokens or i18n sources are missing, state assumptions and follow existing local patterns.
• If verification fails, fix before handoff or report the blocker.
• If required shadcn registry access fails, use existing local components or document fallback.

Exit

• Success: UI works across target responsive states and passes relevant checks.
• Partial success: missing assets, backend contracts, or verification gaps are explicit.

Logical Operations

Actions

Tools and instruments

• React, Next.js, TypeScript, TailwindCSS v4, shadcn/ui
• ahooks or @mantine/hooks, es-toolkit, nuqs, TanStack Query, Jotai/Zustand, TanStack React Form, zod
• Angular (standalone + signals), RxJS + rxjs/testing (TestScheduler marble tests) in Angular projects
• Lint, typecheck, tests, and browser inspection when applicable

Canonical workflow path

Use the configured code-intelligence provider to locate files and inspect symbols or content. For Serena, use find_file, search_for_pattern, get_symbols_overview, and find_symbol. Native search is limited to the provider exclusions and non-code paths permitted by the project's search policy.

Then run the project's frontend verification commands, typically lint, typecheck, tests, and browser/responsive checks when the UI changes.

Resource scope

Preconditions

• Target UI behavior and affected frontend area are identifiable.
• Required design tokens, i18n, and API contracts are available or assumptions are stated.

Effects and side effects

• Mutates frontend source, styles, tests, and possibly i18n keys.
• May add dependencies or shadcn components only when justified by project conventions.
• Does not edit components/ui/* directly.

Guardrails

Apply framework, library, architecture, and data-model defaults only when the target project has no established choice. Scoped edits do not authorize a stack migration or unrelated infrastructure.

1. Follow the existing React, Next.js, TypeScript, and FSD-lite architecture in the target project.
2. Use shadcn/ui primitives and wrappers for UI work; treat components/ui/* as read-only.
3. Keep server/client boundaries explicit: Server Components for static/layout work, Client Components for interaction and hooks.
4. Use project sources of truth for design tokens, i18n strings, and shared utilities before adding local alternatives.
5. Run the execution checklist before handoff and include relevant verification results.
6. Self-describing file names: every new file follows the File Naming convention in ../../rules/frontend.md §Naming Conventions — domain + role readable from the basename alone (order-summary-card.tsx, use-order-polling.ts, cart.atoms.ts). Grab-bag names (utils.ts, helpers.ts, misc.ts) and version suffixes (*-v2, *-final) are banned.
7. Request proxy convention: when the target project uses Next.js 16+ with proxy.ts, preserve that convention. Check the installed framework version and routing before recommending a file rename. Diagnose wiring from code and tests.
8. Use the project's Link prefetch policy; adjust specific routes only when measured behavior or the task requires it.
9. Angular projects follow `resources/angular-rules.md`: standalone components + OnPush + signals-first, inject() DI, lazy routes, new control flow. Any non-trivial RxJS pipeline MUST ship with a marble test (`TestScheduler` from `rxjs/testing`) — a stream without a marble test fails review. React/Next.js-specific rules (shadcn workflow, proxy.ts, Libraries table below) do not apply in Angular projects.

Libraries

React/Next.js projects only — Angular projects use the Angular-native equivalents in resources/angular-rules.md (signals, typed Reactive Forms, HttpClient/httpResource, RxJS with mandatory marble tests).

Shadcn Workflow

• Engine default: Base UI (components.json → style: "base-*"). Radix (radix-*) is a

reasoned fallback for existing Radix codebases only; no big-bang migration. Details in resources/tech-stack.md §shadcn/ui Primitive Engine.

1. Search: shadcn_search_items_in_registries
2. Review: shadcn_get_item_examples_from_registries
3. Install: shadcn_get_add_command_for_items

Server vs Client Components

• Server Components: Layouts, marketing pages, SEO metadata (generateMetadata, sitemap)
• Client Components: Interactive features and useQuery hooks
• Mutations: one owner per write. Server Actions for form-shaped, revalidate-only flows; TanStack Query for cache-coupled or non-form writes (resources/tech-stack.md §Mutations)

UI Implementation (Shadcn/UI)

• Usage: Prefer strict shadcn primitives (Card, Sheet, Typography, Table) over div or generic classes.
• Responsiveness: Use Drawer (mobile) vs Dialog (desktop) via useResponsive.

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• Customization: Treat components/ui/* as read-only. Create wrappers (e.g., components/common/ProductButton.tsx) or use cva composition. Never edit components/ui/button.tsx directly.

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Sources of Truth

• DESIGN.md (project root): visual system source of truth; read Section 9 (Agent Prompt Guide) verbatim for component prompts when present
• Design Tokens: packages/design-tokens (OKLCH); never hardcode colors
• i18n strings: packages/i18n; never hardcode UI text
• Custom utilities: check es-toolkit first; if implementing custom logic, use the project or task coverage target and risk-relevant tests

Designer Collaboration

• Sync: Map code variables to Figma layer names
• UX: Ensure key actions are visible "Above the Fold"

Stack Reference

Project stack conventions live in dedicated files. Read these before coding; they are not optional appendix material.

To extend: add resources/<name>.md and append a row above.

References

• Local code tools: ../_shared/core/code-intelligence.md (code search/navigation)

• Project frontend rules (MUST load before review/implementation): ../../rules/frontend.md
• Execution steps (follow for the selected task): resources/execution-protocol.md
• Checklist (run before handoff): resources/checklist.md
• Error recovery: resources/error-playbook.md
• Context loading: ../_shared/core/context-loading.md
• Clarification: ../_shared/core/clarification-protocol.md
• Context budget: ../_shared/core/context-budget.md
• Lessons learned: ../_shared/core/lessons-learned.md (matching prior failure or requested retrospective)
• Observability handoff: ../oma-observability/SKILL.md §Integrations — Core Web Vitals, SSR→client trace propagation, INP profiling