# Implementation Plan: Frontend Style Unification

**Branch**: `[001-unify-frontend-style]` | **Date**: 2026-02-23 | **Spec**: [spec.md](./spec.md)  
**Input**: Feature specification from `/specs/001-unify-frontend-style/spec.md`

## Summary

Unify the frontend visual system and interaction patterns across primary product routes so users experience a coherent, predictable interface.  
The implementation approach is to standardize shared UI primitives and page-shell patterns first, then align navigation and state feedback patterns, while preserving existing behavior and i18n/accessibility constraints. UX consistency in `ux_reference.md` is treated as a hard requirement and mapped to concrete component contracts and verification steps.

## Technical Context

**Language/Version**: Node.js 18+ runtime, SvelteKit (existing frontend stack)  
**Primary Dependencies**: SvelteKit, Tailwind CSS, existing frontend UI primitives under `frontend/src/lib/components/ui`  
**Storage**: N/A (UI styling and component behavior only)  
**Testing**: Vitest + existing frontend component/store tests  
**Target Platform**: Web browser (desktop-first internal product UI)  
**Project Type**: Web application (frontend + backend repository, frontend-focused scope)  
**Performance Goals**: Preserve existing perceived responsiveness; avoid layout shifts in loading/error/success/empty states  
**Constraints**:  
- Must follow Tailwind-first styling and avoid introducing native `fetch` usage (Constitution)  
- Must keep user-facing text compatible with existing i18n strategy  
- Must not regress core task flows while refactoring UI  
- Must preserve accessibility-visible focus and readable contrast behavior  
**Scale/Scope**: Core primary routes and shared layout/components used by dashboards, tasks, reports, settings

## Constitution Check

*GATE: Must pass before Phase 0 research. Re-check after Phase 1 design.*

- ✅ **Semantic Protocol Compliance**: Planned artifacts include contracts with `[DEF]`/`@TIER`/`@PRE`/`@POST`/`@UX_STATE` for affected modules in `contracts/modules.md`.
- ✅ **Unified Frontend Experience**: Scope is frontend style unification with Tailwind-first constraints; i18n consistency explicitly included.
- ✅ **Independent Testability**: Spec includes independent tests per user story; quickstart includes isolated verification flows.
- ✅ **Architecture Integrity**: No plugin or backend execution model changes required; frontend-only structural alignment.
- ⚠️ **Known Repository Risk (External to this feature)**: Multiple `specs/001-*` directories exist in repo and trigger script warnings. Feature plan continues with explicit active feature directory `specs/001-unify-frontend-style`.

## Project Structure

### Documentation (this feature)

```text
specs/001-unify-frontend-style/
├── plan.md
├── research.md
├── data-model.md
├── quickstart.md
├── contracts/
│   └── modules.md
└── tasks.md
```

### Source Code (repository root)

```text
backend/
└── src/
    ├── api/
    ├── models/
    └── services/

frontend/
├── src/
│   ├── lib/
│   │   ├── components/
│   │   │   ├── layout/
│   │   │   ├── reports/
│   │   │   └── ui/
│   │   ├── stores/
│   │   └── i18n/
│   ├── components/
│   └── routes/
└── tests/
```

**Structure Decision**: Use existing web-application layout and implement changes primarily in `frontend/src/lib/components`, `frontend/src/routes`, and related frontend tests.

## Phase 0: Research Focus

1. Standardize style baseline strategy for existing Tailwind-based Svelte components.
2. Define migration strategy for legacy/non-conformant components without behavior regression.
3. Define UX-consistent state patterns (loading/empty/error/success) reusable across pages.
4. Define i18n and accessibility safeguards during style unification.
5. Define validation approach (visual conformance + behavior safety checks).

## Phase 1: Design & Contracts Outputs

- Produce `data-model.md` with style/token/pattern/conformance entities.
- Produce `contracts/modules.md` with semantic contracts and UX states for critical modules.
- Produce `quickstart.md` with executable validation steps for independent scenario checks.
- Re-run Constitution check after design to confirm no UX compromise.

## Complexity Tracking

No constitution violations requiring explicit exceptions.

## Test Data Reference

| Component | TIER | Fixture Name | Location |
|-----------|------|--------------|----------|
| FrontendStyleReview | CRITICAL | style_review_sample | spec.md#test-data-fixtures |
| StateFeedbackPattern | CRITICAL | state_feedback_sample | spec.md#test-data-fixtures |

**Note**: Tester Agent MUST use these fixtures when writing unit/integration tests for CRITICAL modules.