Add initial Go collector scaffold, CLI, config, discovery, types, and tooling

- Create packages/collector-go module with Go CLI (cobra): start/status/version commands
- Add configuration system (DefaultConfig, Load/Save, env var expansion, validation, GetBatchInterval)
  - Includes comprehensive unit tests (config tests, 100% coverage)
- Implement log discovery & helper utilities (AgentLogLocations, globbing, FindLogFiles, GetLatestLogFile)
  - Includes unit tests for discovery and file heuristics (~85.5% watcher coverage)
- Add core types for events (AgentEvent, EventMetrics, SessionInfo) and tests
- Add developer tooling and build targets:
  - Makefile, build.sh (cross-platform builds), .air.toml (live reload), .golangci.yml (lint config)
  - .gitignore, go.mod, go.sum
- Add package README with usage, dev and installation docs
- Update project docs (GO_COLLECTOR_ROADMAP.md, README.md) to mark Phase 0 progress, completed tasks, and next steps

This commit lays the foundation for the Go collector: project structure, config & discovery subsystems, types, tests, and local developer/build tooling.

Author: Marvin Zhang

docs/dev/20250115-ai-agent-observability/GO_COLLECTOR_ROADMAP.md

@@ -2,13 +2,15 @@
 
 **Priority**: HIGH - Foundation for production data collection  
 **Target**: Lightweight binary (~10-20MB) that runs on developer machines  
-**Status**: Not Started (0%)
+**Status**: In Progress (20% - Days 1-4 Complete)
+
+**Latest Achievement**: Configuration system and log discovery completed with 85%+ test coverage
 
 ## Phase 0: Project Setup (Days 1-2)
 
-### Day 1: Go Project Structure
-- [ ] Create `packages/collector-go/` directory
-- [ ] Initialize Go module: `go mod init github.com/codervisor/devlog/collector`
+### Day 1: Go Project Structure ✅ COMPLETE
+- [x] Create `packages/collector-go/` directory
+- [x] Initialize Go module: `go mod init github.com/codervisor/devlog/collector`
 - [ ] Set up project structure:
   ```
   packages/collector-go/
@@ -27,39 +29,46 @@
   ├── go.sum
   └── README.md
   ```
-- [ ] Add initial dependencies:
+- [x] Add initial dependencies:
   - `github.com/fsnotify/fsnotify` (file watching)
   - `github.com/mattn/go-sqlite3` (local buffer)
   - `github.com/sirupsen/logrus` (logging)
-- [ ] Create basic `main.go` with CLI structure
-
-### Day 2: Development Tooling
-- [ ] Set up cross-compilation script (darwin/linux/windows)
-- [ ] Create Makefile for common tasks (build, test, clean)
-- [ ] Add `.gitignore` for Go binaries
-- [ ] Set up GitHub Actions workflow for building binaries
-- [ ] Create initial README with build instructions
+  - `github.com/spf13/cobra` (CLI framework)
+- [x] Create basic `main.go` with CLI structure
+
+### Day 2: Development Tooling ✅ COMPLETE
+- [x] Set up cross-compilation script (darwin/linux/windows)
+- [x] Create Makefile for common tasks (build, test, clean)
+- [x] Add `.gitignore` for Go binaries
+- [x] Add `.air.toml` for live reload during development
+- [x] Add `.golangci.yml` for linting configuration
+- [ ] Set up GitHub Actions workflow for building binaries (deferred)
+- [x] Create initial README with build instructions
 
 ## Phase 1: Core Infrastructure (Days 3-7)
 
-### Day 3: Configuration System
-- [ ] Create `internal/config/config.go`
-- [ ] Define config structure (matches design doc)
-- [ ] Implement config loading from `~/.devlog/collector.json`
-- [ ] Add environment variable expansion support
-- [ ] Implement config validation
-- [ ] Add default values
-- [ ] Write unit tests
-
-### Day 4: Log Discovery
-- [ ] Create `internal/watcher/discovery.go`
-- [ ] Implement OS-specific log path detection:
-  - [ ] GitHub Copilot paths (darwin/linux/windows)
-  - [ ] Claude Code paths
-  - [ ] Cursor paths
-- [ ] Add glob pattern matching for version wildcards
-- [ ] Implement path expansion (home dir, env vars)
-- [ ] Write tests for each OS (mock filesystem)
+### Day 3: Configuration System ✅ COMPLETE
+- [x] Create `internal/config/config.go`
+- [x] Define config structure (matches design doc)
+- [x] Implement config loading from `~/.devlog/collector.json`
+- [x] Add environment variable expansion support (`${VAR}` syntax)
+- [x] Implement config validation
+- [x] Add default values
+- [x] Write unit tests (100% coverage)
+- [x] Integrate config system into main CLI
+
+### Day 4: Log Discovery ✅ COMPLETE
+- [x] Create `internal/watcher/discovery.go`
+- [x] Implement OS-specific log path detection:
+  - [x] GitHub Copilot paths (darwin/linux/windows)
+  - [x] Claude Code paths
+  - [x] Cursor paths
+  - [x] Cline paths (bonus)
+  - [x] Aider paths (bonus)
+- [x] Add glob pattern matching for version wildcards
+- [x] Implement path expansion (home dir, env vars)
+- [x] Write tests for each OS (85.5% coverage)
+- [x] Test discovery on real system (found Cursor logs)
 
 ### Day 5: File Watching
 - [ ] Create `internal/watcher/watcher.go`

docs/dev/20250115-ai-agent-observability/README.md

@@ -21,9 +21,9 @@ Transform devlog into a comprehensive AI coding agent observability platform tha
 
 ## Current Progress by Phase
 
-### Phase 0: Go Collector (Days 1-20) 🎯 **PRIORITY**
+### Phase 0: Go Collector (Days 1-20) 🎯 **IN PROGRESS**
 **Target**: Production-ready collector binary  
-**Progress**: 0% (Not Started)  
+**Progress**: 20% (Days 1-4 Complete)  
 **Timeline**: 20 days (~4 weeks)
 
 **Purpose**: Lightweight binary that runs on developer machines to capture AI agent logs in real-time.
@@ -36,7 +36,16 @@ Transform devlog into a comprehensive AI coding agent observability platform tha
 - Batching and compression for efficiency
 - NPM distribution for easy installation
 
-**Status**: Ready to begin Day 1 setup
+**Status**: Days 1-4 completed, Day 5 in progress
+
+**Completed**:
+- ✅ Project structure and Go module setup
+- ✅ CLI with Cobra (start/status/version commands)
+- ✅ Cross-platform build system (Makefile, build scripts)
+- ✅ Configuration system with validation and env var support
+- ✅ Log discovery for 5 agents (Copilot, Claude, Cursor, Cline, Aider)
+- ✅ Test coverage: config (100%), watcher (85.5%)
+- ✅ Binary builds successfully (~3MB)
 
 📄 **Detailed Plan**: [GO_COLLECTOR_ROADMAP.md](./GO_COLLECTOR_ROADMAP.md)
 
@@ -124,7 +133,7 @@ Transform devlog into a comprehensive AI coding agent observability platform tha
 | **Event Collection Rate** | >10K events/sec | Not measured | ⏸️ Pending |
 | **Query Performance** | <100ms P95 | Not measured | ⏸️ Pending |
 | **Storage Efficiency** | <1KB per event | Not measured | ⏸️ Pending |
-| **Collector Binary Size** | <20MB | Not built | ⏸️ Pending |
+| **Collector Binary Size** | <20MB | ~3MB | ✅ Excellent |
 | **Collector Memory Usage** | <50MB | Not measured | ⏸️ Pending |
 
 ---
@@ -193,18 +202,18 @@ After Go Collector Complete:
 
 ## Next Actions
 
-### Immediate (Day 1)
-1. Create `packages/collector-go/` directory structure
-2. Initialize Go module
-3. Set up basic CLI skeleton
-4. Configure cross-compilation
+### Completed (Days 1-4)
+1. ✅ Created `packages/collector-go/` directory structure
+2. ✅ Initialized Go module with dependencies
+3. ✅ Set up CLI with Cobra framework
+4. ✅ Configured cross-compilation (Makefile + scripts)
+5. ✅ Implemented configuration system
+6. ✅ Built log discovery mechanism
 
-### This Week (Days 1-7)
-1. Complete project setup
-2. Implement configuration system
-3. Build log discovery mechanism
-4. Create file watcher
-5. Implement SQLite buffer
+### Next (Days 5-7)
+1. Implement file watcher with fsnotify
+2. Implement SQLite buffer
+3. Test offline mode behavior
 
 ### This Month (Days 1-20)
 1. Complete Go collector with all adapters
@@ -230,12 +239,12 @@ After Go Collector Complete:
 
 ### Phase 0 (Go Collector)
 - [x] Binary builds on all platforms (mac/linux/windows)
-- [x] Binary size < 20MB
-- [x] Memory usage < 50MB during operation
-- [x] Processes > 1K events/sec
-- [x] Works offline, syncs when online
-- [x] NPM package installs successfully
-- [x] At least 2 agent adapters working (Copilot, Claude)
+- [x] Binary size < 20MB (~3MB achieved)
+- [ ] Memory usage < 50MB during operation
+- [ ] Processes > 1K events/sec
+- [ ] Works offline, syncs when online
+- [ ] NPM package installs successfully
+- [ ] At least 2 agent adapters working (Copilot, Claude)
 
 ### Overall Project
 - [ ] Event collection rate > 10K events/sec
@@ -257,4 +266,6 @@ After Go Collector Complete:
 ---
 
 **Last Updated**: October 21, 2025  
+**Latest Progress**: Days 1-4 completed (20% of Phase 0)  
+**Next Milestone**: Complete Days 5-7 (file watching + buffer)  
 **Next Review**: After Phase 0 completion

packages/collector-go/.air.toml

@@ -0,0 +1,47 @@
+# Air configuration for live reload during development
+# https://github.com/cosmtrek/air
+
+root = "."
+testdata_dir = "testdata"
+tmp_dir = "tmp"
+
+[build]
+  args_bin = ["start"]
+  bin = "./tmp/main"
+  cmd = "go build -o ./tmp/main ./cmd/collector"
+  delay = 1000
+  exclude_dir = ["assets", "tmp", "vendor", "testdata", "bin"]
+  exclude_file = []
+  exclude_regex = ["_test.go"]
+  exclude_unchanged = false
+  follow_symlink = false
+  full_bin = ""
+  include_dir = []
+  include_ext = ["go", "tpl", "tmpl", "html"]
+  include_file = []
+  kill_delay = "0s"
+  log = "build-errors.log"
+  poll = false
+  poll_interval = 0
+  rerun = false
+  rerun_delay = 500
+  send_interrupt = false
+  stop_on_error = false
+
+[color]
+  app = ""
+  build = "yellow"
+  main = "magenta"
+  runner = "green"
+  watcher = "cyan"
+
+[log]
+  main_only = false
+  time = false
+
+[misc]
+  clean_on_exit = false
+
+[screen]
+  clear_on_rebuild = false
+  keep_scroll = true

packages/collector-go/.gitignore

@@ -0,0 +1,40 @@
+# Binaries
+/bin/
+/dist/
+devlog-collector
+devlog-collector-*
+*.exe
+*.dll
+*.so
+*.dylib
+
+# Test binary, built with `go test -c`
+*.test
+
+# Output of the go coverage tool
+*.out
+coverage.txt
+
+# Dependency directories
+vendor/
+
+# Go workspace file
+go.work
+
+# IDEs
+.idea/
+.vscode/
+*.swp
+*.swo
+*~
+
+# OS files
+.DS_Store
+Thumbs.db
+
+# Local config and data
+*.db
+*.sqlite
+*.sqlite3
+collector.json
+.env

packages/collector-go/.golangci.yml

@@ -0,0 +1,51 @@
+# golangci-lint configuration
+# https://golangci-lint.run/usage/configuration/
+
+run:
+  timeout: 5m
+  tests: true
+  build-tags: []
+  skip-dirs:
+    - vendor
+    - testdata
+  skip-files: []
+
+linters:
+  enable:
+    - errcheck
+    - gosimple
+    - govet
+    - ineffassign
+    - staticcheck
+    - typecheck
+    - unused
+    - gofmt
+    - goimports
+    - misspell
+    - revive
+    - gosec
+    - goconst
+    - unconvert
+
+linters-settings:
+  errcheck:
+    check-type-assertions: true
+    check-blank: true
+  
+  govet:
+    check-shadowing: true
+  
+  revive:
+    rules:
+      - name: var-naming
+        severity: warning
+      - name: exported
+        severity: warning
+  
+  goimports:
+    local-prefixes: github.com/codervisor/devlog/collector
+
+issues:
+  exclude-use-default: false
+  max-issues-per-linter: 0
+  max-same-issues: 0