# LangGraph Agent Framework - Implementation Summary

## Overview

Successfully implemented a comprehensive LangGraph.js-based agentic framework for the Bandit Runner application. The framework runs entirely in Cloudflare Durable Objects and provides a beautiful retro terminal UI for interacting with autonomous agents that solve the OverTheWire Bandit wargame.

## ✅ What Was Implemented

### 1. Core Backend Components

#### **State Management** (`src/lib/agents/bandit-state.ts`)
- Comprehensive TypeScript interfaces for agent state
- Level goals for all 34 Bandit levels
- Command and thought log tracking
- Checkpoint system for pause/resume functionality

#### **LLM Provider Layer** (`src/lib/agents/llm-provider.ts`)
- OpenRouter integration supporting multiple models:
  - OpenAI (GPT-4o, GPT-4o Mini)
  - Anthropic (Claude 3.5 Sonnet, Claude 3 Haiku)
  - Meta (Llama 3.1)
  - DeepSeek, Gemini, Mistral, and more
- Streaming and non-streaming response modes
- Abstraction layer for easy provider switching

#### **SSH Tool Wrappers** (`src/lib/agents/tools.ts`)
- `ssh_connect` - Establish SSH connections
- `ssh_exec` - Execute commands with safety allowlist
- `validate_password` - Test passwords via SSH
- `ssh_disconnect` - Close connections
- Command validation and security checks

#### **LangGraph State Machine** (`src/lib/agents/graph.ts`)
- State graph with nodes:
  - `plan_level` - LLM plans next command
  - `execute_command` - Runs SSH command
  - `validate_result` - Checks for password
  - `advance_level` - Moves to next level
- Conditional edges based on agent status
- Integration with LangChain tools

#### **Error Handling** (`src/lib/agents/error-handler.ts`)
- Error classification (network, SSH, timeout, API)
- Retry strategies with exponential backoff
- Cost tracking for LLM API calls
- Spending limit enforcement

#### **Storage Layer** (`src/lib/storage/run-storage.ts`)
- Durable Object storage interface
- D1 database schema for run metadata
- R2 storage for JSONL logs
- Password vault with encryption
- Data lifecycle management (DO → D1 → R2)

### 2. Durable Object Implementation

#### **BanditAgentDO** (`src/lib/durable-objects/BanditAgentDO.ts`)
- Runs LangGraph state machine
- WebSocket server for real-time streaming
- HTTP endpoints for agent control:
  - `/start` - Start new run
  - `/pause` - Pause execution
  - `/resume` - Resume from checkpoint
  - `/command` - Manual command injection
  - `/retry` - Retry current level
  - `/status` - Get current state
- Alarm-based auto-cleanup after 2 hours
- State persistence in DO storage

### 3. API Routes

#### **Agent Lifecycle** (`src/app/api/agent/[runId]/route.ts`)
- POST endpoints for all agent actions
- GET endpoint for status queries
- Durable Object proxy layer
- Error handling and validation

#### **WebSocket Route** (`src/app/api/agent/[runId]/ws/route.ts`)
- WebSocket upgrade handling
- Bidirectional communication with Durable Object
- Real-time event streaming

### 4. Frontend Components

#### **WebSocket Hook** (`src/hooks/useAgentWebSocket.ts`)
- React hook for WebSocket management
- Auto-reconnect with exponential backoff
- Event handlers for terminal and chat updates
- Connection state tracking
- Ping/pong keep-alive

#### **Agent Control Panel** (`src/components/agent-control-panel.tsx`)
- Model selection dropdown
- Level range selector (0-33)
- Streaming mode toggle
- Start/Pause/Resume/Stop buttons
- Status indicators (idle/running/paused/complete/failed)
- Connection status display

#### **Enhanced Terminal Interface** (`src/components/terminal-chat-interface.tsx`)
- Integrated with WebSocket for real-time updates
- Split-pane layout (terminal left, agent chat right)
- Command history with arrow keys
- Panel switching (Ctrl+K/J, ESC)
- Support for manual intervention when paused
- Beautiful retro styling with scan lines and grid patterns
- System messages for agent events
- Thinking indicators

### 5. WebSocket Event System

#### **Event Handlers** (`src/lib/websocket/agent-events.ts`)
- Standardized event types:
  - `terminal_output` - Command execution
  - `agent_message` - Agent commentary
  - `thinking` - Agent reasoning
  - `tool_call` - Tool execution
  - `level_complete` - Level advancement
  - `run_complete` - Full run completion
  - `error` - Error messages
- Event routing to terminal and chat displays
- Timestamp and metadata tracking

### 6. Configuration

#### **Wrangler** (`wrangler.jsonc`)
- Durable Object bindings configured
- Environment variables for SSH proxy
- Placeholders for D1 and R2 (ready to uncomment)
- Secret management instructions

#### **TypeScript** (`src/types/env.d.ts`)
- Environment type declarations
- Cloudflare binding types
- Type safety for all env variables

### 7. Dependencies Installed

```json
{
  "@langchain/langgraph": "latest",
  "@langchain/core": "latest", 
  "@langchain/openai": "latest",
  "zod": "latest"
}
```

## 🚧 What Still Needs to Be Done

### 1. SSH Proxy Service (CRITICAL)
- Build the Node.js SSH proxy (see `SSH-PROXY-README.md`)
- Deploy to Fly.io/Railway/Render
- Update `SSH_PROXY_URL` in wrangler.jsonc

### 2. Durable Object Export
- Export BanditAgentDO in worker entry point
- Configure migration tag for DO deployment

### 3. LangGraph Integration Refinement
- Test graph execution in Workers environment
- May need to use `@langchain/langgraph/web` entry point
- Add manual config passing to avoid `async_hooks` issues
- Integrate actual tool execution (currently mocked)

### 4. D1 and R2 Setup
- Create D1 database: `wrangler d1 create bandit-runs`
- Run schema migrations
- Create R2 bucket: `wrangler r2 bucket create bandit-logs`
- Uncomment bindings in wrangler.jsonc

### 5. Secrets Configuration
```bash
wrangler secret put OPENROUTER_API_KEY
wrangler secret put ENCRYPTION_KEY
```

### 6. Testing
- Unit tests for graph nodes
- Integration tests for WebSocket
- Mock SSH proxy for development
- Load testing for concurrent runs

### 7. Advanced Features (Future)
- Run history and comparison UI
- Export functionality (JSONL, CSV)
- Keyboard shortcuts reference modal
- Run templates and presets
- Cost analytics dashboard
- Multi-run leaderboard

## 📝 Key Files Created

```
bandit-runner-app/src/
├── lib/
│   ├── agents/
│   │   ├── bandit-state.ts        (State schema, level goals)
│   │   ├── llm-provider.ts        (OpenRouter integration)
│   │   ├── tools.ts               (SSH tool wrappers)
│   │   ├── graph.ts               (LangGraph state machine)
│   │   └── error-handler.ts       (Retry logic, cost tracking)
│   ├── durable-objects/
│   │   └── BanditAgentDO.ts       (Durable Object implementation)
│   ├── storage/
│   │   └── run-storage.ts         (DO/D1/R2 storage layer)
│   └── websocket/
│       └── agent-events.ts        (Event handlers)
├── app/api/agent/[runId]/
│   ├── route.ts                   (HTTP API routes)
│   └── ws/
│       └── route.ts               (WebSocket route)
├── components/
│   ├── agent-control-panel.tsx    (Control panel UI)
│   └── terminal-chat-interface.tsx (Enhanced terminal)
├── hooks/
│   └── useAgentWebSocket.ts       (WebSocket React hook)
└── types/
    └── env.d.ts                   (Environment types)
```

## 🎯 How to Use

### 1. Local Development

```bash
cd bandit-runner-app
pnpm install
pnpm dev
```

### 2. Configure SSH Proxy

Build and deploy the SSH proxy service (see `SSH-PROXY-README.md`), then update:
```bash
export SSH_PROXY_URL=https://your-proxy.fly.dev
```

### 3. Set API Key

```bash
export OPENROUTER_API_KEY=sk-or-...
```

### 4. Start a Run

1. Open http://localhost:3000
2. Select a model (e.g., GPT-4o Mini)
3. Choose level range (e.g., 0-5)
4. Click START
5. Watch the agent work in real-time!

### 5. Manual Intervention

- Click PAUSE to stop the agent
- Type commands in the terminal (left pane)
- Message the agent in chat (right pane)
- Click RESUME to continue

## 🏗️ Architecture Highlights

### Execution Flow

```
User clicks START
    ↓
POST /api/agent/{runId}/start
    ↓
Durable Object spawned/retrieved
    ↓
LangGraph state machine initialized
    ↓
WebSocket connection established
    ↓
Graph executes: plan → execute → validate → advance
    ↓
Events streamed to UI in real-time
    ↓
State checkpointed in DO storage
    ↓
On completion: metadata saved to D1, logs to R2
```

### WebSocket Event Flow

```
Durable Object
    ↓ (WebSocket)
API Route /ws
    ↓
useAgentWebSocket hook
    ↓ (handleAgentEvent)
Terminal/Chat UI updates
```

### State Persistence

```
Active State: Durable Object (in-memory)
Checkpoints: Durable Object storage
Metadata: D1 Database (when configured)
Logs: R2 Bucket (when configured)
```

## 🎨 UI Features

- **Retro Terminal Aesthetic**: Scan lines, grid patterns, CRT-style
- **Dual Panels**: Terminal (left) + Agent Chat (right)
- **Real-time Updates**: WebSocket streaming
- **Status Indicators**: Connection, run state, level progress
- **Model Selection**: 10+ LLM models via OpenRouter
- **Manual Control**: Pause, resume, manual commands
- **Keyboard Navigation**: Ctrl+K/J panel switching, arrow keys for history

## 🔐 Security

- SSH target hardcoded to `bandit.labs.overthewire.org:2220`
- Command allowlist enforcement
- Password redaction in logs
- R2 encryption for sensitive data
- Rate limiting (to be implemented)
- Automatic cleanup of stale runs

## 📊 Next Steps

1. **Deploy SSH Proxy** - Build from `SSH-PROXY-README.md`
2. **Test Integration** - Run end-to-end test with a simple level
3. **Refine LangGraph** - Ensure Workers compatibility
4. **Add D1/R2** - Set up persistent storage
5. **Production Deploy** - Deploy to Cloudflare Workers
6. **Monitor & Iterate** - Track performance, costs, success rates

## 🎉 What's Amazing

- **Full LangGraph.js** in Cloudflare Durable Objects
- **Multi-LLM Support** via OpenRouter (10+ models)
- **Beautiful UI** with retro terminal aesthetic
- **Real-time Streaming** via WebSocket
- **Pause/Resume** with state checkpointing
- **Manual Intervention** for debugging
- **Extensible** architecture for future features

## 🙏 Acknowledgments

- Built on Next.js, OpenNext, Cloudflare Workers
- Powered by LangGraph.js and LangChain
- UI components from shadcn/ui
- Inspired by the OverTheWire Bandit wargame