---
phase: 01-core-infrastructure
plan: 04
subsystem: infra
tags: [logging, filesystem, node:fs, streams]

# Dependency graph
requires:
  - phase: 01-01
    provides: TypeScript project structure
provides:
  - LogManager for directory management
  - ProcessLogWriter for per-process stdout/stderr capture
  - createLogger convenience function
affects: [agent-spawning, process-management, debugging]

# Tech tracking
tech-stack:
  added: []
  patterns:
    - "Per-process log directory structure: ~/.cw/logs/{processId}/"
    - "Timestamped log entries: [YYYY-MM-DD HH:mm:ss.SSS]"
    - "WriteStream backpressure handling via drain events"

key-files:
  created:
    - src/logging/types.ts
    - src/logging/manager.ts
    - src/logging/writer.ts
    - src/logging/index.ts
  modified: []

key-decisions:
  - "Log directory structure: ~/.cw/logs/{processId}/stdout.log and stderr.log"
  - "Timestamp format: [YYYY-MM-DD HH:mm:ss.SSS] prefix per line"
  - "Append mode for log files (flags: 'a') to support resumption"

patterns-established:
  - "Module structure: types.ts, implementation.ts, index.ts"
  - "Async/await for file operations with node:fs/promises"
  - "WriteStream backpressure handling pattern"

# Metrics
duration: 5 min
completed: 2026-01-30
---

# Phase 1 Plan 4: File-Based Logging Summary

**Per-process logging infrastructure with timestamped stdout/stderr capture to ~/.cw/logs/{processId}/**

## Performance

- **Duration:** 5 min
- **Started:** 2026-01-30T12:12:19Z
- **Completed:** 2026-01-30T12:17:03Z
- **Tasks:** 2
- **Files created:** 4

## Accomplishments

- LogManager class for directory creation and path management
- ProcessLogWriter class for per-process stdout/stderr file capture
- Timestamp prefixing for each line of output
- Backpressure handling for write streams
- cleanOldLogs for log retention management
- createLogger convenience function for common use case

## Task Commits

Each task was committed atomically:

1. **Task 1: Create log directory management** - `e64e243` (feat)
2. **Task 2: Create per-process log writer** - `fc410e2` (feat)

## Files Created/Modified

- `src/logging/types.ts` - LogLevel, LogEntry, LogConfig, LogStream types
- `src/logging/manager.ts` - LogManager class for directory/path management
- `src/logging/writer.ts` - ProcessLogWriter class for file output capture
- `src/logging/index.ts` - Module exports and createLogger helper

## Decisions Made

1. **Directory structure:** `~/.cw/logs/{processId}/stdout.log` and `stderr.log` - keeps process logs isolated and easy to clean up
2. **Timestamp format:** `[YYYY-MM-DD HH:mm:ss.SSS]` - readable and sortable, includes milliseconds for debugging
3. **Append mode:** Files opened with `flags: 'a'` to support process restarts without losing prior logs

## Deviations from Plan

None - plan executed exactly as written.

## Issues Encountered

None.

## User Setup Required

None - no external service configuration required.

## Next Phase Readiness

- Logging infrastructure ready for integration with process spawning (01-03)
- ProcessLogWriter.getStdoutStream()/getStderrStream() ready for direct piping from child processes
- LogManager can be shared across multiple ProcessLogWriter instances

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