---
phase: 01-session-discovery
plan: 01
subsystem: process-detection
tags: [go, proc, linux, cli]

requires: []
provides:
  - "Go module scaffold (shell.nix, go.mod)"
  - "Shared types: Process, Session, SessionState"
  - "FindClaudeProcesses() scanning /proc for Claude PIDs"
  - "EncodePath() converting absolute paths to ~/.claude/projects/ folder names"
affects: [01-02, 02-session-state]

tech-stack:
  added: [go-1.25, go-stdlib-os]
  patterns: [injectable-procdir-for-testing, fake-proc-fixtures]

key-files:
  created: [shell.nix, go.mod, types.go, proc.go, proc_test.go]
  modified: []

key-decisions:
  - "filepath.Base matching for Claude binary detection (handles full paths)"
  - "procDir parameter injection for testability (no hardcoded /proc)"

patterns-established:
  - "Fake /proc fixtures: createFakeProc() builds temp dirs with cmdline files and cwd symlinks"
  - "Silent error skipping: permission denied and vanished processes are skipped, not fatal"

requirements-completed: [DISC-01, DISC-02]

duration: 2min
completed: 2026-03-23
---

# Phase 01 Plan 01: Scaffolding + Process Detection Summary

**Go module with FindClaudeProcesses() scanning /proc for active Claude Code PIDs and EncodePath() for session folder mapping**

## Performance

- **Duration:** 2 min
- **Started:** 2026-03-23T12:23:44Z
- **Completed:** 2026-03-23T12:25:44Z
- **Tasks:** 2
- **Files created:** 5

## Accomplishments
- Go project scaffolded with NixOS shell.nix, go.mod, and shared types (Process, Session, SessionState)
- FindClaudeProcesses() scans configurable /proc directory, filters by "claude" binary name, reads cwd via Readlink
- EncodePath() converts paths to ~/.claude/projects/ folder format (replace / and . with -)
- 5 tests covering normal detection, permission denied, empty proc, and path encoding edge cases

## Task Commits

Each task was committed atomically:

1. **Task 1: Scaffolding projet + types partages** - `12e1ba7` (feat)
2. **Task 2 RED: Failing tests for proc scanning** - `81ee7dc` (test)
3. **Task 2 GREEN: Implement FindClaudeProcesses and EncodePath** - `166e441` (feat)

## Files Created/Modified
- `shell.nix` - NixOS dev environment with go and gopls
- `go.mod` - Go module github.com/pieMusic/vmux
- `types.go` - Shared types: Process, Session, SessionState (Working/NeedsInput/Idle/Unknown)
- `proc.go` - FindClaudeProcesses() and EncodePath()
- `proc_test.go` - 5 unit tests with fake /proc fixtures

## Decisions Made
- Used `filepath.Base(parts[0])` for binary detection to handle full paths like `/nix/store/.../claude`
- Injected procDir as parameter for full testability without mocking os functions

## Deviations from Plan

None - plan executed exactly as written.

## Issues Encountered
- shell.nix was in Pierre's global gitignore; force-added with `git add -f` since it is project-specific

## User Setup Required

None - no external service configuration required.

## Next Phase Readiness
- Types and process detection ready for plan 01-02 (JSONL session matching, state heuristics, display)
- EncodePath enables PID-to-session folder mapping

---
*Phase: 01-session-discovery*
*Completed: 2026-03-23*