# CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

## Commands

```bash
pnpm check              # Merge gate — must pass before every commit (knip + format + lint + typecheck + test)
pnpm knip               # Unused code detection (Knip)
pnpm test               # Run all tests (Vitest)
pnpm test:watch         # Tests in watch mode
pnpm typecheck          # tsc --build (project references)
pnpm lint               # Biome lint
pnpm format             # Biome format (writes)
pnpm --filter web dev   # Vite dev server (localhost:5173)
pnpm --filter web build # Production build
```

Run a single test file: `pnpm vitest run packages/domain/src/__tests__/advance-turn.test.ts`

## Architecture

Strict layered architecture with ports/adapters and enforced dependency direction:

```
apps/web (React 19 + Vite)  →  packages/application (use cases)  →  packages/domain (pure logic)
```

- **Domain** — Pure functions, no I/O, no framework imports. All state transitions are deterministic. Errors returned as values (`DomainError`), never thrown. Adapters may throw only for programmer errors.
- **Application** — Orchestrates domain calls via port interfaces (e.g., `EncounterStore`). No business logic here.
- **Web** — React adapter. Implements ports using hooks/state.

Layer boundaries are enforced by `scripts/check-layer-boundaries.mjs`, which runs as a Vitest test. Domain and application must never import from React, Vite, or upper layers.

## Conventions

- **Biome 2.0** for formatting and linting (no Prettier, no ESLint). Tab indentation, 80-char lines. Imports are auto-organized alphabetically.
- **TypeScript strict mode** with `verbatimModuleSyntax`. Use `.js` extensions in relative imports when required by the repo's ESM settings (e.g., `./types.js`).
- **Branded types** for identity values (e.g., `CombatantId`). Prefer immutability/`readonly` where practical.
- **Domain events** are plain data objects with a `type` discriminant — no classes.
- **Tests** live in `packages/*/src/__tests__/*.test.ts`. Test pure functions directly; map acceptance scenarios and invariants from specs to individual `it()` blocks.
- **Feature specs** live in `specs/<feature>/` with spec.md, plan.md, tasks.md. The project constitution is at `.specify/memory/constitution.md`.

## Constitution (key principles)

The constitution (`.specify/memory/constitution.md`) governs all feature work:

1. **Deterministic Domain Core** — Pure state transitions only; no I/O, randomness, or clocks in domain.
2. **Layered Architecture** — Domain → Application → Adapters. Never skip layers or reverse dependencies.
3. **Clarification-First** — Ask before making non-trivial assumptions.
4. **MVP Baseline** — Say "MVP baseline does not include X", never permanent bans.
5. **Every feature begins with a spec** — Spec → Plan → Tasks → Implementation.

## Active Technologies
- TypeScript 5.x (strict mode, verbatimModuleSyntax) + React 19, Vite (003-remove-combatant)
- In-memory React state (local-first, single-user MVP) (003-remove-combatant)
- TypeScript 5.x (project), Go binary via npm (Lefthook) + `lefthook` (npm devDependency) (006-pre-commit-gate)
- TypeScript 5.x (strict mode, verbatimModuleSyntax) + Knip v5 (new), Biome 2.0, Vitest, Vite 6, React 19 (007-add-knip)
- TypeScript 5.x (strict mode, verbatimModuleSyntax) + React 19, Vite 6, Biome 2.0, existing domain/application packages (008-persist-encounter)
- Browser localStorage (adapter layer only) (008-persist-encounter)
- TypeScript 5.x (strict mode, verbatimModuleSyntax) + React 19, Vite 6, Biome 2.0, Vites (009-combatant-hp)
- TypeScript 5.8 (strict mode, verbatimModuleSyntax) + React 19, Vite 6, Tailwind CSS v4, shadcn/ui, Lucide React (icons) (010-ui-baseline)
- N/A (no storage changes — localStorage persistence unchanged) (010-ui-baseline)
- TypeScript 5.8 (strict mode, verbatimModuleSyntax) + React 19, Vite 6, Tailwind CSS v4, shadcn/ui-style components, Lucide React (icons) (011-quick-hp-input)
- N/A (no storage changes -- existing localStorage persistence handles HP via `adjustHpUseCase`) (011-quick-hp-input)
- N/A (no storage changes -- existing localStorage persistence unchanged) (012-turn-navigation)
- N/A (no storage changes -- purely derived state, existing localStorage persistence unchanged) (013-hp-status-indicators)
- TypeScript 5.8 (strict mode, verbatimModuleSyntax) + jscpd (new dev dependency), Lefthook (existing), Biome 2.0 (existing), Knip (existing) (015-add-jscpd-gate)
- N/A (no storage changes) (015-add-jscpd-gate)
- Browser localStorage (existing adapter, transparent JSON serialization) (016-combatant-ac)
- TypeScript 5.8 (strict mode, verbatimModuleSyntax) + React 19, Vite 6, Tailwind CSS v4, Lucide React (icons) (017-combat-conditions)
- N/A (no storage changes — existing localStorage persistence unchanged) (019-combatant-row-declutter)
- TypeScript 5.8 (strict mode, verbatimModuleSyntax) + React 19, Tailwind CSS v4, Lucide React (icons) (020-fix-zero-hp-opacity)
- Browser localStorage (existing adapter, extended for creatureId) (021-bestiary-statblock)
- TypeScript 5.8 (strict mode, verbatimModuleSyntax) + React 19, Tailwind CSS v4 + React 19, Tailwind CSS v4, Vite 6 (022-fixed-layout-bars)
- N/A (no storage changes -- purely presentational) (022-fixed-layout-bars)
- Browser localStorage (existing adapter, updated to handle empty encounters) (023-clear-encounter)
- N/A (no storage changes — purely presentational fix) (024-fix-hp-popover-overflow)

## Recent Changes
- 003-remove-combatant: Added TypeScript 5.x (strict mode, verbatimModuleSyntax) + React 19, Vite