# Implementation Plan: Set Initiative

**Branch**: `005-set-initiative` | **Date**: 2026-03-04 | **Spec**: [spec.md](./spec.md)
**Input**: Feature specification from `/specs/005-set-initiative/spec.md`

## Summary

Add an optional integer initiative property to combatants and a `setInitiative` domain function that sets/changes/clears the value and automatically reorders combatants descending by initiative (unset last, stable sort for ties). The active combatant's turn is preserved through reorders by tracking identity rather than position.

## Technical Context

**Language/Version**: TypeScript 5.x (strict mode, verbatimModuleSyntax)
**Primary Dependencies**: React 19, Vite
**Storage**: In-memory React state (local-first, single-user MVP)
**Testing**: Vitest
**Target Platform**: Web browser (localhost:5173 dev)
**Project Type**: Web application (monorepo: domain → application → web adapter)
**Performance Goals**: N/A (local in-memory, trivial data sizes)
**Constraints**: Pure domain functions, no I/O in domain layer
**Scale/Scope**: Single-user, single encounter

## Constitution Check

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

| Principle | Status | Notes |
|-----------|--------|-------|
| I. Deterministic Domain Core | PASS | `setInitiative` is a pure function: same encounter + id + value → same result. No I/O, randomness, or clocks. |
| II. Layered Architecture | PASS | Domain function in `packages/domain`, use case in `packages/application`, UI in `apps/web`. Dependency direction preserved. |
| III. Agent Boundary | N/A | No agent layer involvement in this feature. |
| IV. Clarification-First | PASS | Spec has no NEEDS CLARIFICATION markers. All design decisions are spec-driven. |
| V. Escalation Gates | PASS | Feature scope matches spec exactly. No out-of-scope additions. |
| VI. MVP Baseline Language | PASS | Spec uses "MVP baseline does not include" for secondary tiebreakers. |
| VII. No Gameplay Rules | PASS | Constitution contains no gameplay mechanics; initiative logic is in the spec. |

All gates pass. No violations to justify.

**Post-Design Re-check**: All gates still pass. The `setInitiative` domain function is pure, layering is preserved, and no out-of-scope additions were introduced during design.

## Project Structure

### Documentation (this feature)

```text
specs/005-set-initiative/
├── spec.md
├── plan.md              # This file
├── research.md          # Phase 0 output
├── data-model.md        # Phase 1 output
├── quickstart.md        # Phase 1 output
├── contracts/           # Phase 1 output
│   └── domain-api.md
├── checklists/
│   └── requirements.md
└── tasks.md             # Phase 2 output (via /speckit.tasks)
```

### Source Code (repository root)

```text
packages/domain/src/
├── types.ts                    # Modified: add initiative to Combatant
├── events.ts                   # Modified: add InitiativeSet event
├── set-initiative.ts           # New: setInitiative domain function
├── index.ts                    # Modified: export setInitiative
└── __tests__/
    └── set-initiative.test.ts  # New: tests for setInitiative

packages/application/src/
├── set-initiative-use-case.ts  # New: setInitiativeUseCase
└── index.ts                    # Modified: export use case

apps/web/src/
├── hooks/
│   └── use-encounter.ts        # Modified: add setInitiative callback
└── App.tsx                     # Modified: add initiative input field
```

**Structure Decision**: Follows existing monorepo layered structure. Each new domain operation gets its own file per established convention.

## Complexity Tracking

No constitution violations. Table not needed.