claude-hud/CLAUDE.md

CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

Project Overview

Claude HUD is a Claude Code plugin that displays a real-time terminal HUD (Heads-Up Display) in a split pane. It shows context usage, tool activity, agent status, todos, git status, and cost estimation.

Build Commands

# All commands run from tui/ directory
cd tui

bun install          # Install dependencies
bun run build        # Build TypeScript
bun run dev          # Watch mode for development
bun test             # Run all tests
bun test <pattern>   # Run specific test (e.g., bun test sparkline)

# Manual testing with a FIFO
mkfifo /tmp/test.fifo
bun run start -- --session test --fifo /tmp/test.fifo
# Then in another terminal, send test events to the FIFO

Architecture

Data Flow

Claude Code Hooks → capture-event.sh → FIFO → EventReader → React State → Ink Components

1. hooks/hooks.json - Registers shell scripts for Claude Code lifecycle events
2. scripts/capture-event.sh - Transforms hook JSON into HudEvent format, writes to session FIFO
3. scripts/session-start.sh - Creates FIFO, builds TUI if needed, spawns HUD in terminal split
4. tui/src/lib/event-reader.ts - Reads FIFO line-by-line, parses JSON, emits events with auto-reconnect
5. tui/src/index.tsx - Main App component, processes events and manages all state

Hook Events

Event	Script	Purpose
SessionStart	session-start.sh	Spawns HUD in split pane
PreToolUse	capture-event.sh	Shows tool as "running"
PostToolUse	capture-event.sh	Updates tool completion, tracks context/cost
UserPromptSubmit	capture-event.sh	Tracks user prompts, clears idle state
Stop	capture-event.sh	Sets idle state
PreCompact	capture-event.sh	Increments compaction count
SubagentStop	capture-event.sh	Marks agent complete
SessionEnd	cleanup.sh	Kills process, removes FIFO

Library Structure (tui/src/lib/)

• types.ts - All TypeScript interfaces (HudEvent, ToolEntry, TodoItem, ContextHealth, etc.)
• event-reader.ts - FIFO reader with connection status and exponential backoff reconnect
• context-tracker.ts - Estimates token usage, burn rate, compaction warnings
• cost-tracker.ts - Calculates API costs based on model pricing

Component Structure (tui/src/components/)

• ContextMeter - Token usage bar, sparkline history, burn rate
• ToolStream - Live tool calls with status, duration, path truncation
• AgentList - Running/completed subagents with elapsed time
• SessionStats - Tool counts, lines changed, session duration
• GitStatus - Branch, staged/modified/untracked counts
• TodoList - Current task list from TodoWrite events
• ModifiedFiles - Files changed via Edit/Write
• McpStatus - Connected MCP servers
• Sparkline - Unicode sparkline chart (▁▂▃▄▅▆▇█)

Session Files

Runtime files stored in ~/.claude/hud/:

• events/<session_id>.fifo - Named pipe for event streaming
• pids/<session_id>.pid - Process ID for cleanup
• logs/<session_id>.log - Fallback output when split pane unavailable

Dependencies

• Runtime: Node.js 18+ or Bun, jq (JSON parsing in hooks)
• TUI Framework: React 18 + Ink 5 (terminal UI via Yoga layout)
• Build: TypeScript 5, ES2022 target, NodeNext modules
• Testing: Vitest + @testing-library/react + ink-testing-library