---
phase: 01.1-hexagonal-architecture
plan: 01
subsystem: events
tags: [vitest, events, eventbus, eventemitter, hexagonal]

# Dependency graph
requires: []
provides:
  - EventBus port interface
  - EventEmitterBus adapter implementation
  - Domain event types (Process, Server, Log events)
  - Test infrastructure with Vitest
affects: [01.1-02, 01.1-03, 01.1-04, 01.1-05, 01.1-06]

# Tech tracking
tech-stack:
  added: [vitest]
  patterns: [ports-and-adapters, event-bus, domain-events]

key-files:
  created:
    - src/events/types.ts
    - src/events/bus.ts
    - src/events/index.ts
    - src/events/bus.test.ts
    - vitest.config.ts
  modified:
    - package.json

key-decisions:
  - "EventBus is the PORT, EventEmitterBus is the ADAPTER"
  - "Node.js EventEmitter wrapped behind interface for future swapability"
  - "Domain events use discriminated union pattern with type property"

patterns-established:
  - "Port/Adapter pattern for event infrastructure"
  - "Typed domain events with payload generics"
  - "Test globals enabled (describe, it, expect without imports)"

# Metrics
duration: 3min
completed: 2026-01-30
---

# Phase 1.1 Plan 01: Event Bus Foundation Summary

**Vitest test framework configured with typed EventBus port/adapter pattern and domain events for process, server, and log lifecycle**

## Performance

- **Duration:** 3 min
- **Started:** 2026-01-30T13:50:00Z
- **Completed:** 2026-01-30T13:55:00Z
- **Tasks:** 3
- **Files modified:** 6

## Accomplishments

- Vitest test framework installed and configured with globals, TypeScript support
- EventBus interface (PORT) defined with emit, on, off, once methods
- EventEmitterBus class (ADAPTER) implemented using Node.js EventEmitter
- Domain events defined: ProcessSpawned, ProcessStopped, ProcessCrashed, ServerStarted, ServerStopped, LogEntry
- Full test coverage for event bus patterns (10 tests passing)

## Task Commits

Each task was committed atomically:

1. **Task 1: Install and configure Vitest** - `03d5527` (chore)
2. **Task 2: Create EventBus port and adapter** - `83e6adb` (feat)
3. **Task 3: Define domain events and write tests** - `437e76e` (feat)

## Files Created/Modified

- `vitest.config.ts` - Vitest configuration with globals, TypeScript, coverage
- `package.json` - Added test scripts and vitest dependency
- `src/events/types.ts` - EventBus port interface and domain event types
- `src/events/bus.ts` - EventEmitterBus adapter implementation
- `src/events/index.ts` - Public API exports and createEventBus factory
- `src/events/bus.test.ts` - Comprehensive test suite (10 tests)

## Decisions Made

1. **EventBus as PORT, EventEmitterBus as ADAPTER** - Enables swapping to RabbitMQ/Kafka/WebSocket later without changing consumers
2. **Node.js EventEmitter internally** - Simplest path to external event systems, well-tested foundation
3. **Discriminated union for domain events** - DomainEventMap type enables type-safe event handling

## Deviations from Plan

None - plan executed exactly as written.

## Issues Encountered

None

## User Setup Required

None - no external service configuration required.

## Next Phase Readiness

- Event bus foundation complete and tested
- Ready for 01.1-02: tRPC Foundation
- All subsequent plans can depend on the events module

---
*Phase: 01.1-hexagonal-architecture*
*Completed: 2026-01-30*
