# Technical Spec

> Defines environment variables, architecture design, and build/test commands. Use when configuring environment or designing architecture. Use when this capability is needed.

- Skill: `tomevault-io/technical-spec-4` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add tomevault-io/technical-spec-4`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/technical-spec-4/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: tomevault-io (https://skillmd.com/u/tomevault-io)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tomevault-io/technical-spec-4

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# Technical Design Rules

## Basic Technology Stack Policy
TypeScript-based application implementation. Architecture patterns should be selected according to project requirements and scale.

## Environment Variable Management and Security

### Environment Variable Management
- Centrally manage environment variables and build mechanisms to ensure type safety
- Avoid direct references to `process.env`, obtain through configuration management layer
- Properly implement default value settings and mandatory checks

### Security
- Do not include `.env` files in Git
- Always manage API keys and secrets as environment variables
- Prohibit logging of sensitive information
- Do not include sensitive information in error messages

## Architecture Design

### Architecture Design Principles
Select appropriate architecture for each project and define clearly:

- **Separation of Responsibilities**: Clearly define responsibilities for each layer and module, and maintain boundaries

## Unified Data Flow Principles

#### Basic Principles
1. **Single Data Source**: Store the same information in only one place
2. **Structured Data Priority**: Use parsed objects rather than JSON strings
3. **Clear Responsibility Separation**: Clearly define responsibilities for each layer

#### Data Flow Best Practices
- **Validation at Input**: Validate data at input layer and pass internally in type-safe form
- **Centralized Transformation**: Consolidate data transformation logic in dedicated utilities
- **Structured Logging**: Output structured logs at each stage of data flow

## Build and Testing
Use the appropriate run command based on the `packageManager` field in package.json.

### Build Commands
- `build` - TypeScript build
- `type-check` - Type check (no emit)

### Testing Commands
- `test` - Run tests
- `test:coverage` - Run tests with coverage
- `test:coverage:fresh` - Run tests with coverage (fresh cache)
- `test:safe` - Safe test execution (with auto cleanup)
- `cleanup:processes` - Cleanup Vitest processes

### Quality Check Requirements

Quality checks are mandatory upon implementation completion:

**Phase 1-3: Code Quality Checks**
- Auto-detect and execute the following from package.json scripts:
  - lint + format check
  - Detect unused exports
  - Detect circular dependencies
  - TypeScript build

**Phase 4: Tests**
- `test` - Test execution

**Phase 5: Code Quality Re-verification**
- `check:code` - Re-verify code quality (clean up side effects from test fixes in Phase 4)

### Auxiliary Commands
- `check:all` - Overall integrated check (check:code + test) *for manual batch verification
- `open coverage/index.html` - Check coverage report
- `format` - Format fixes
- `lint:fix` - Lint fixes

### Troubleshooting
- **Port in use error**: Run the `cleanup:processes` script
- **Cache issues**: Run the `test:coverage:fresh` script
- **Dependency errors**: Clean reinstall dependencies

### Coverage Requirements
- **MANDATORY**: Unit test coverage MUST be 70% or higher
- **Metrics**: Statements, Branches, Functions, Lines

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<!-- tomevault:4.0:skill_md:2026-04-11 -->