---
phase: 01-core-infrastructure
plan: 05
subsystem: infra
tags: [http, server, graceful-shutdown, pid-file, coordination]

# Dependency graph
requires:
  - phase: 01-02
    provides: CLI entry point with Commander
  - phase: 01-03
    provides: ProcessManager and ProcessRegistry for process lifecycle
  - phase: 01-04
    provides: LogManager for logging infrastructure
provides:
  - CoordinationServer class with HTTP health endpoint
  - GracefulShutdown handler for SIGTERM/SIGINT/SIGHUP
  - PID file management to prevent duplicate servers
  - Server mode via cw --server flag
affects: [02-agent-lifecycle, 04-orchestration, monitoring]

# Tech tracking
tech-stack:
  added: []
  patterns:
    - "Native node:http server (no Express for minimal footprint)"
    - "PID file locking pattern for singleton server"
    - "Signal handler orchestration with timeout"

key-files:
  created:
    - src/server/types.ts
    - src/server/index.ts
    - src/server/shutdown.ts
  modified:
    - src/cli/index.ts
    - src/bin/cw.ts

key-decisions:
  - "Used node:http instead of Express for minimal dependencies"
  - "10-second shutdown timeout before force exit"
  - "Double SIGINT forces immediate exit for stuck situations"
  - "PID file at ~/.cw/server.pid with stale detection"

patterns-established:
  - "Server module structure: types.ts, index.ts (main class), shutdown.ts"
  - "Health endpoint pattern: GET /health returns {status, uptime, processCount}"
  - "Signal handling: install() method registers handlers after server starts"

# Metrics
duration: 7min
completed: 2026-01-30
---

# Phase 1 Plan 05: Server Mode Summary

**HTTP coordination server with health endpoint, PID file management, and graceful shutdown via SIGTERM/SIGINT/SIGHUP**

## Performance

- **Duration:** 7 min
- **Started:** 2026-01-30T12:19:21Z
- **Completed:** 2026-01-30T12:27:05Z
- **Tasks:** 2
- **Files created:** 3
- **Files modified:** 2

## Accomplishments

- CoordinationServer class using native node:http (no Express dependency)
- GET /health endpoint returning status, uptime, and processCount
- GET /status endpoint returning server state and process list
- PID file management with stale PID detection
- GracefulShutdown class handling SIGTERM, SIGINT, SIGHUP
- 10-second timeout before force exit
- Double SIGINT for immediate force exit
- CLI --server flag and --port option integration

## Task Commits

Each task was committed atomically:

1. **Task 1: Create HTTP server with health endpoint and PID file** - `bec46aa` (feat)
2. **Task 2: Implement graceful shutdown** - `59b2337` (feat)

**Plan metadata:** (this commit)

## Files Created/Modified

- `src/server/types.ts` - ServerConfig, ServerState, HealthResponse, StatusResponse types
- `src/server/index.ts` - CoordinationServer class with HTTP routes and PID file management
- `src/server/shutdown.ts` - GracefulShutdown class with signal handlers
- `src/cli/index.ts` - Added --server flag handling and startServer function
- `src/bin/cw.ts` - Updated to use async runCli()

## Decisions Made

| Decision | Rationale |
|----------|-----------|
| node:http over Express | Minimal dependencies, server only needs 2 routes |
| 10-second shutdown timeout | Industry standard, enough time for graceful cleanup |
| PID file at ~/.cw/server.pid | Follows Unix conventions, easy to check/remove manually |
| Stale PID detection | Handles crashes gracefully by checking if PID is alive |

## Deviations from Plan

None - plan executed exactly as written.

## Issues Encountered

None.

## User Setup Required

None - no external service configuration required.

## Next Phase Readiness

- Server infrastructure complete, satisfies INFRA-04 (graceful shutdown)
- Health endpoint enables monitoring and readiness checks
- Foundation ready for agent coordination in Phase 4
- Server mode is the entry point for the coordination layer

---
*Phase: 01-core-infrastructure*
*Completed: 2026-01-30*
