ARBuilder

AI-powered development assistant for the Arbitrum ecosystem. ARBuilder transforms natural language prompts into:

• Stylus smart contracts (Rust)
• Cross-chain SDK implementations (asset bridging and messaging)
• Full-stack dApps (contracts + backend + indexer + oracle + frontend + wallet integration)
• Orbit chain deployment assistance

Demo

Quick Start

Hosted (no setup):

# Claude Code
claude mcp add arbbuilder -- npx -y mcp-remote https://arbuilder.app/mcp --header "Authorization: Bearer YOUR_API_KEY"

Or add to ~/.cursor/mcp.json (Cursor / VS Code):

{
  "mcpServers": {
    "arbbuilder": {
      "command": "npx",
      "args": ["-y", "mcp-remote", "https://arbuilder.app/mcp",
               "--header", "Authorization: Bearer YOUR_API_KEY"]
    }
  }
}

Get your API key at arbuilder.app

Self-hosted — see Setup below.

Table of Contents

• Architecture
• Project Structure
• Setup
• Quick Start (IDE Integration)
• Usage
• API Access
• MCP Capabilities
• User Guide
• Milestones
• Development
• Troubleshooting
• Contributing
• License

Architecture

ARBuilder uses a Retrieval-Augmented Generation (RAG) pipeline with hybrid search (vector + BM25 + cross-encoder reranking) to provide context-aware code generation. Available as a hosted service at arbuilder.app or self-hosted via MCP server.

┌─────────────────────────────────────────────────────────────────────────┐
│                            ARBuilder                                    │
├─────────────────────────────────────────────────────────────────────────┤
│                                                                         │
│  DATA PIPELINE                                                          │
│  ┌──────────┐    ┌──────────┐    ┌───────────┐    ┌──────────────────┐  │
│  │ Scraper  │───▶│Processor │───▶│ Embedder  │───▶│    ChromaDB      │  │
│  │ crawl4ai │    │ 3-layer  │    │ BGE-M3    │    │ (local vectors)  │  │
│  │ + GitHub │    │ filters  │    │ 1024-dim  │    │                  │  │
│  └──────────┘    └──────────┘    └───────────┘    └────────┬─────────┘  │
│                                                            │            │
│  RETRIEVAL                                                 │            │
│  ┌──────────────────────────────────────────────────────────▼─────────┐ │
│  │                    Hybrid Search Engine                            │ │
│  │  ┌──────────┐    ┌──────────┐    ┌────────────┐                    │ │
│  │  │  Vector  │    │   BM25   │    │CrossEncoder│   RRF Fusion       │ │
│  │  │  Search  │───▶│ Keywords │───▶│ Reranker   │──▶ + MMR           │ │
│  │  └──────────┘    └──────────┘    └────────────┘                    │ │
│  └────────────────────────────────────────────────────────────────────┘ │
│                                         │                               │
│  GENERATION                             ▼                               │
│  ┌───────────────────────────────────────────────────────────────────┐  │
│  │                      MCP Server (19 tools)                        │  │
│  │                                                                   │  │
│  │  Stylus Contracts   Arbitrum-SDK       Full dApp Builder          │  │
│  │  ┌──────────────┐   ┌─────────────┐   ┌──────────────────────┐    │  │
│  │  │ generate_    │   │ generate_   │   │ generate_backend     │    │  │
│  │  │ stylus_code  │   │ bridge_code │   │ generate_frontend    │    │  │
│  │  │ ask_stylus   │   │ generate_   │   │ generate_indexer     │    │  │
│  │  │ get_context  │   │ messaging   │   │ generate_oracle      │    │  │
│  │  │ gen_tests    │   │ ask_bridging│   │ orchestrate_dapp     │    │  │
│  │  │ get_workflow │   │             │   │                      │    │  │
│  │  │ validate_code│   │             │   │                      │    │  │
│  │  └──────────────┘   └─────────────┘   └──────────────────────┘    │  │
│  │                                                                   │  │
│  │  Orbit Chain                                                      │  │
│  │  ┌──────────────────────┐                                         │  │
│  │  │ generate_orbit_config│                                         │  │
│  │  │ generate_orbit_deploy│                                         │  │
│  │  │ gen_validator_setup  │                                         │  │
│  │  │ ask_orbit            │                                         │  │
│  │  │ orchestrate_orbit    │                                         │  │
│  │  └──────────────────────┘                                         │  │
│  └───────────────────────────────────────────────────────────────────┘  │
│                           │                                             │
│  IDE INTEGRATION          ▼                                             │
│  ┌───────────────────────────────────────────────────────────────────┐  │
│  │  Cursor / VS Code / Claude Desktop / Any MCP Client               │  │
│  │  <- via local stdio or remote mcp-remote proxy ->                 │  │
│  └───────────────────────────────────────────────────────────────────┘  │
│                                                                         │
│  HOSTED SERVICE (Cloudflare Workers)                                    │
│  ┌──────────────┐  ┌──────────┐  ┌──────────┐  ┌──────────────────┐     │
│  │  Workers AI  │  │ Vectorize│  │    D1    │  │      KV          │     │
│  │  BGE-M3 +    │  │ 1024-dim │  │  Users   │  │   Source registry│     │
│  │  Reranker    │  │  index   │  │  API keys│  │   + Ingest state │     │
│  └──────────────┘  └──────────┘  └──────────┘  └──────────────────┘     │
│                                                                         │
│  INGESTION PIPELINE (Worker-native, cron every 6h)                      │
│  ┌──────────┐    ┌──────────┐    ┌───────────┐    ┌──────────────┐      │
│  │ scraper  │───▶│ chunker  │───▶│ Workers AI│───▶│  Vectorize   │      │
│  │ HTML/    │    │ doc+code │    │  BGE-M3   │    │   upsert     │      │
│  │ GitHub   │    │ splitter │    │ embedding │    │              │      │
│  └──────────┘    └──────────┘    └───────────┘    └──────────────┘      │
│                       │                ▲                                │
│                       │ >30 files      │ embed messages                 │
│                       ▼                │                                │
│              ┌─────────────────────────┴───┐                            │
│              │    CF Queue (async path)    │                            │
│              │  embed │ continue │finalize │                            │
│              └─────────────────────────────┘                            │
└─────────────────────────────────────────────────────────────────────────┘

Project Structure

ArbBuilder/
├── sources.json          # Single source of truth for all data sources
├── scraper/              # Data collection module
│   ├── config.py         # Thin wrapper around sources.json (backward-compat helpers)
│   ├── scraper.py        # Web scraping with crawl4ai
│   ├── github_scraper.py # GitHub repository cloning
│   └── run.py            # Pipeline entry point
├── src/
│   ├── preprocessing/    # Text cleaning and chunking
│   │   ├── cleaner.py    # Text normalization
│   │   ├── chunker.py    # Document chunking with token limits
│   │   └── processor.py  # Main preprocessing pipeline
│   ├── embeddings/       # Embedding and vector storage
│   │   ├── embedder.py   # OpenRouter embedding client
│   │   ├── vectordb.py   # ChromaDB wrapper with hybrid search (BM25 + vector)
│   │   └── reranker.py   # CrossEncoder, MMR, LLM reranking
│   ├── templates/        # Code generation templates
│   │   ├── stylus_templates.py   # M1: Stylus contract templates
│   │   ├── backend_templates.py  # M3: NestJS/Express templates
│   │   ├── frontend_templates.py # M3: Next.js + wagmi templates
│   │   ├── indexer_templates.py  # M3: Subgraph templates
│   │   ├── oracle_templates.py   # M3: Chainlink templates
│   │   └── orbit_templates.py    # M4: Orbit chain deployment templates
│   ├── utils/            # Shared utilities
│   │   ├── version_manager.py   # SDK version management
│   │   ├── env_config.py        # Centralized env var configuration
│   │   ├── abi_extractor.py     # Stylus ABI extraction from Rust code
│   │   └── compiler_verifier.py # Docker-based cargo check verification
│   ├── mcp/              # MCP server for IDE integration
│   │   ├── server.py     # MCP server (tools, resources, prompts)
│   │   ├── tools/        # MCP tool implementations (19 tools)
│   │   │   ├── get_stylus_context.py       # M1
│   │   │   ├── generate_stylus_code.py     # M1
│   │   │   ├── ask_stylus.py               # M1
│   │   │   ├── generate_tests.py           # M1
│   │   │   ├── get_workflow.py             # M1
│   │   │   ├── validate_stylus_code.py     # M1
│   │   │   ├── generate_bridge_code.py     # M2
│   │   │   ├── generate_messaging_code.py  # M2
│   │   │   ├── ask_bridging.py             # M2
│   │   │   ├── generate_backend.py         # M3
│   │   │   ├── generate_frontend.py        # M3
│   │   │   ├── generate_indexer.py         # M3
│   │   │   ├── generate_oracle.py          # M3
│   │   │   ├── orchestrate_dapp.py         # M3
│   │   │   ├── generate_orbit_config.py    # M4
│   │   │   ├── generate_orbit_deployment.py # M4
│   │   │   ├── generate_validator_setup.py # M4
│   │   │   ├── ask_orbit.py                # M4
│   │   │   └── orchestrate_orbit.py        # M4
│   │   ├── resources/    # Static knowledge (11 resources)
│   │   │   ├── stylus_cli.py      # M1
│   │   │   ├── workflows.py       # M1
│   │   │   ├── networks.py        # M1
│   │   │   ├── coding_rules.py    # M1
│   │   │   ├── sdk_rules.py       # M2
│   │   │   ├── backend_rules.py   # M3
│   │   │   ├── frontend_rules.py  # M3
│   │   │   ├── indexer_rules.py   # M3
│   │   │   └── oracle_rules.py    # M3
│   │   └── prompts/      # Workflow templates
│   └── rag/              # RAG pipeline (TBD)
├── tests/
│   ├── mcp_tools/        # MCP tool test cases and benchmarks
│   │   ├── test_get_stylus_context.py
│   │   ├── test_generate_stylus_code.py
│   │   ├── test_ask_stylus.py
│   │   ├── test_generate_tests.py
│   │   ├── test_m2_e2e.py    # M2 end-to-end tests
│   │   ├── test_m3_tools.py  # M3 full dApp tests
│   │   ├── test_orbit_tools.py  # M4 orbit tests
│   │   └── benchmark.py      # Evaluation framework
│   └── test_retrieval.py # Retrieval quality tests
├── docs/
│   └── mcp_tools_spec.md # MCP tools specification
├── apps/web/               # Hosted service (Cloudflare Workers + Next.js)
│   ├── src/app/
│   │   ├── layout.tsx      # Root layout + SEO meta + JSON-LD structured data
│   │   ├── page.tsx        # Landing page (M1-M4 feature sections)
│   │   ├── robots.ts       # robots.txt generation
│   │   ├── sitemap.ts      # sitemap.xml generation
│   │   ├── llms.txt/       # LLM discovery endpoint
│   │   └── playground/     # Interactive tool playground (18 hosted tools)
│   ├── src/lib/
│   │   ├── scraper.ts      # Web doc scraping (HTMLRewriter)
│   │   ├── github.ts       # GitHub repo scraping (Trees/Contents API)
│   │   ├── chunker.ts      # Document + code chunking
│   │   ├── ingestPipeline.ts # Ingestion orchestrator (sync + async queue paths)
│   │   └── vectorize.ts    # Search + embedding utilities
│   ├── src/app/api/admin/  # Admin APIs (sources, ingest, migrate)
│   ├── worker.ts           # Worker entry + cron + queue consumer handler
│   └── wrangler.prod.jsonc # Production config (D1, KV, Vectorize, Queue)
├── scripts/
│   ├── run_benchmarks.py     # Benchmark runner
│   ├── diff-migrate.ts       # Push chunks to CF Vectorize
│   ├── sync_sources.ts       # Sync sources.json to CF KV registry
│   └── ingest_m3_sources.py  # M3 source ingestion
├── data/
│   ├── raw/              # Raw scraped data (docs + curated repos)
│   ├── processed/        # Pre-processed chunks
│   └── chroma_db/        # ChromaDB vector store (generated locally, not in repo)
├── environment.yml       # Conda environment specification
├── pyproject.toml        # Project metadata and dependencies
└── .env                  # Environment variables (not committed)

Setup

1. Create Conda Environment

# Create and activate the environment
conda env create -f environment.yml
conda activate arbbuilder

Note: If you plan to refresh the knowledge base by scraping (optional), also install playwright:

playwright install chromium

2. Configure Environment Variables

Copy the example environment file and configure your API keys:

cp .env.example .env

Edit .env with your credentials:

OPENROUTER_API_KEY=your-api-key
NVIDIA_API_KEY=your-nvidia-api-key
DEFAULT_MODEL=deepseek/deepseek-v3.2
DEFAULT_EMBEDDING=baai/bge-m3
DEFAULT_CROSS_ENCODER=nvidia/llama-3.2-nv-rerankqa-1b-v2

3. Setup Data

The repository includes all data needed:

• Raw data (data/raw/): Documentation pages + curated GitHub repos
• Processed chunks (data/processed/): Chunks ready for embedding

Important: The ChromaDB vector database must be generated locally (it's not included in the repo due to binary compatibility issues across systems).

# Generate the vector database (required before using MCP tools)
python -m src.embeddings.vectordb

4. Verify MCP Server

Test that the MCP server starts correctly:

# Run the MCP server directly (press Ctrl+C to exit)
python -m src.mcp.server

You should see:

ARBuilder MCP Server started
Capabilities: 19 tools, 11 resources, 5 prompts

Optional: Refresh Data

If you want to re-scrape the latest documentation and code:

# Run full pipeline (web scraping + GitHub cloning)
python -m scraper.run

# Then preprocess the raw data
python -m src.preprocessing.processor

# And re-ingest into ChromaDB
python -m src.embeddings.vectordb --reset

Data Quality Filters: The pipeline applies a 3-layer filtering system to remove junk data (vendored crates, auto-generated TypeChain files, hex bytecode, lock files, and cross-repo duplicates). See docs/DATA_CURATION_POLICY.md for details.

Data Maintenance

Audit and clean up data sources:

# Audit: compare repos on disk vs config
python scripts/audit_data.py

# Show what orphan repos would be deleted
python scripts/audit_data.py --prune

# Actually delete orphan repos
python scripts/audit_data.py --prune --confirm

# Include ChromaDB stats in audit
python scripts/audit_data.py --chromadb

# GitHub scraper also supports audit/prune
python -m scraper.github_scraper --audit
python -m scraper.github_scraper --prune --dry-run

Fork & Migrate (SDK 0.10.0)

Fork community Stylus repos and migrate them to SDK 0.10.0:

# Dry run: show what would change without modifying anything
python scripts/fork_and_migrate.py --all --dry-run

# Migrate all 13 Stylus repos
python scripts/fork_and_migrate.py --all

# Migrate a specific repo
python scripts/fork_and_migrate.py --repo OffchainLabs/stylus-hello-world

# Re-verify already-forked repos after manual fixes
python scripts/fork_and_migrate.py --all --verify-only

Reports are saved to reports/fork_migration_*.json.

Quick Start (IDE Integration)

Option A: Self-Hosted (Full Control)

Run ARBuilder locally with your own API keys. No rate limits.

Step 1: Configure your IDE

Add the following to your MCP configuration file:

Cursor (~/.cursor/mcp.json):

{
  "mcpServers": {
    "arbbuilder": {
      "command": "/path/to/miniconda3/envs/arbbuilder/bin/python3",
      "args": ["-m", "src.mcp.server"],
      "env": {
        "OPENROUTER_API_KEY": "your-api-key",
        "PYTHONPATH":"/path/to/ArbBuilder"
      }
    }
  }
}

Claude Desktop (~/Library/Application Support/Claude/claude_desktop_config.json on macOS):

{
  "mcpServers": {
    "arbbuilder": {
      "command": "python",
      "args": ["-m", "src.mcp.server"],
      "cwd": "/path/to/ArbBuilder",
      "env": {
        "OPENROUTER_API_KEY": "your-api-key"
      }
    }
  }
}

Step 2: Restart your IDE

After saving the configuration, restart Cursor or Claude Desktop. The ARBuilder tools will be available to the AI assistant.

Step 3: Start building!

Ask your AI assistant:

• "Generate an ERC20 token contract in Stylus"
• "How do I deploy a contract to Arbitrum Sepolia?"
• "Write tests for my counter contract"

Option B: Hosted Service (Zero Setup)

Use our hosted API - no local setup required. Available at arbuilder.app.

1. Sign up at https://arbuilder.app and get your API key
2. Add to your MCP configuration:

{
  "mcpServers": {
    "arbbuilder": {
      "command": "npx",
      "args": ["-y", "mcp-remote", "https://arbuilder.app/mcp",
               "--header", "Authorization: Bearer YOUR_API_KEY"]
    }
  }
}

The hosted service includes:

• 100 API calls/day (free tier)
• No local setup or Python environment required
• Always up-to-date with latest Stylus SDK patterns

Usage

Data Ingestion

Hosted (Worker-native): The hosted service at arbuilder.app has a built-in ingestion pipeline that runs automatically via cron (every 6 hours). Sources can also be manually ingested via the admin UI at /admin.

The pipeline uses two paths based on source size:

• Sync path (docs and repos ≤30 files): scrape → chunk → embed → upsert in a single Worker invocation (~40 subrequests)
• Async path (repos >30 files): scrape → chunk → save to KV → enqueue to CF Queue. The queue consumer processes embed/upsert in batches of 10 chunks (~4 subrequests each), with continue messages for additional file batches and a finalize message to update source status. This stays within the 50 subrequest/invocation limit on the Free plan.

Local (Python pipeline): For self-hosted setups, run the full data collection pipeline:

conda activate arbbuilder

# Run full pipeline (web scraping + GitHub cloning)
python -m scraper.run

# Preprocess and push to CF Vectorize
python -m src.preprocessing.processor
AUTH_SECRET=xxx npx tsx scripts/diff-migrate.ts --full

Data Sources

All data sources are defined in sources.json — the single source of truth for both the local Python pipeline and the hosted CF Worker ingestion. The file contains 84 curated sources (53 documentation pages + 31 GitHub repos) across 4 milestones.

Versioned repos (with multiple SDK branches) use a versions array:

{
  "url": "https://github.com/ARBuilder-Forks/stylus-hello-world",
  "versions": [
    { "sdkVersion": "0.10.0", "branch": "main" },
    { "sdkVersion": "0.9.0", "branch": "v0.9.0" }
  ]
}

Sync to hosted service:

ARBBUILDER_ADMIN_SECRET=xxx npx tsx scripts/sync_sources.ts
ARBBUILDER_ADMIN_SECRET=xxx npx tsx scripts/sync_sources.ts --dry-run
ARBBUILDER_ADMIN_SECRET=xxx npx tsx scripts/sync_sources.ts --remove-stale

**Stylus Contracts/projects ** — 17 docs + 19 repos

• Official documentation: docs.arbitrum.io (7 pages + gas-metering)
• All Stylus repos sourced from ARBuilder-Forks for resilience against upstream deletions
• 6 forks with SDK 0.10.0 branches: hello-world, vending-machine, erc6909, fortune-generator, ethbuc2025-gyges, WalletNaming
• 7 forks at original SDK version (0.8.4–0.9.0) with separate branch per version
• Production codebases: OpenZeppelin rust-contracts-stylus, stylus-test-helpers, stylusport, stylus-provider

Curation Policy:

• No meta-lists (awesome-stylus) — causes outdated code ingestion
• No unverified community submissions
• All code repos must compile with stylus-sdk >= 0.8.0
• SDK version tracked per-repo in sources.json
• All Stylus repos forked to ARBuilder-Forks org with forkedFrom provenance tracking

Stylus SDK Version Support:

Version	Status	Notes
0.10.0	Main (default)	Latest stable, recommended for new projects
0.9.x	Supported	Separate branches in forked repos
0.8.x	Supported	Minimum supported version
< 0.8.0	Deprecated	Excluded from knowledge base

Multi-Version Strategy:

• Branch-per-version: Forked repos maintain separate Git branches per SDK version (e.g., main for 0.10.0, v0.9.0 for original)
• Branch-aware scraping: CF Worker ingests each branch as a separate source entry
• Version-aware generation: generate_stylus_code and ask_stylus accept target_version to produce code for any supported SDK version
• Version-aware retrieval: Vector search boosts chunks matching the requested SDK version

Arbitrum SDK — 6 docs + 5 repos

• arbitrum-sdk, arbitrum-tutorials
• 3 community repos: arbitrum-api, orbit-bridging, cross-messaging
• Official bridging and messaging documentation (6 pages)

Full dApp Builder — 30 docs + 11 repos

• Backend: NestJS (5 docs), Express (3 docs), nestjs/nest, arbitrum-token-bridge
• Frontend: wagmi (5 docs), viem (4 docs), RainbowKit (4 docs), DaisyUI (5 docs) + 5 repos
• Indexer: The Graph (5 docs), graph-tooling, messari/subgraphs
• Oracle: Chainlink (4 docs), smart-contract-examples, chainlink

Orbit SDK — 5 Python MCP tools + 9 TypeScript templates

• Tools: generate_orbit_config, generate_orbit_deployment, generate_validator_setup, ask_orbit, orchestrate_orbit
• Templates: Chain Config, Deploy Rollup, Deploy Token Bridge, Custom Gas Token, Validator Management, Governance, Node Config, AnyTrust Config, Orchestration
• Uses @arbitrum/chain-sdk ^0.25.0 + viem ^1.20.0 for prepareChainConfig(), createRollup(), createTokenBridge(), prepareNodeConfig()
• Deployment output persisted to deployment.json — downstream scripts (token bridge, node config) chain automatically
• Crash-proof deployment: saves deployment.json BEFORE receipt fetch, with try/catch for block number
• Custom gas tokens: generates approve-token.ts with correct RollupCreator addresses, ERC-20 deploy guidance
• Docker: offchainlabs/nitro-node:v3.9.4-7f582c3, bind mounts (./data/arbitrum), no user: root
• Node config post-processing: restores masked private keys, disables staker for single-key setups, fixes DAS URL double-port
• Wasm root check: --validation.wasm.allowed-wasm-module-roots prevents crash-loops on startup
• AnyTrust: BLS keygen via datool keygen from nitro-node image
• Supports: Rollup and AnyTrust chains, custom gas tokens, validator/batch poster management, full project scaffolding

API Access

Public MCP Endpoint (Free)

The MCP endpoint at /mcp is free to use and designed for IDE integration:

https://arbuilder.app/mcp

• Requires arb_ API key from dashboard
• Usage tracked per API key
• Rate limited per free tier (100 calls/day)

Chat Completions API (OpenAI-compatible)

Conversational endpoint backed by a ReAct agent over 14 of the MCP tools, callable from any OpenAI SDK:

POST https://arbuilder.app/api/v1/chat/completions
Authorization: Bearer arb_<your-key>

• Model: arbbuilder-chat (backed by openai/gpt-oss-120b via OpenRouter)
• Streaming and non-streaming, OpenAI message + SSE shape
• Native function calling — agent decides which tools to invoke; tool calls visible in delta.tool_calls
• Chain-of-thought passthrough via reasoning_content
• Stateless: clients send full message history each turn
• Auto length-continuation across finish_reason: "length"
• Limits: 6 ReAct iterations / 200K turn token budget / 32K char tool-result cap
• Excludes the 4 large project scaffolders (generate_backend, generate_frontend, orchestrate_dapp, orchestrate_orbit) — call those directly via /api/v1/tools/<name> or MCP

Full reference: docs/api/chat-completions.md. Try it in the playground at /playground/chat.

Transparency Page

View all ingested sources and code templates at arbuilder.app/transparency.

This public page provides:

• Ingested Sources: All documentation and GitHub repos in the knowledge base
• Code Templates: Verified Stylus templates with full source code
• Statistics: Chunk counts, SDK versions, and category breakdowns

Public API endpoints (no authentication required):

• GET /api/public/sources - List all active sources
• GET /api/public/templates - List all code templates
• GET /api/public/templates?code=true - Templates with full source code

Internal Direct API (Testing Only)

Direct API routes at /api/v1/tools/* are for internal testing only:

• Requires AUTH_SECRET in Authorization header
• Not for public use
• Used by CI/CD and internal validation scripts

MCP Capabilities

ARBuilder exposes a full MCP server with 19 tools, 11 resources, and 5 prompts for Cursor/VS Code integration.

Tools

Stylus Development (6 tools)

Tool	Description
get_stylus_context	RAG retrieval for docs and code examples
generate_stylus_code	Generate Stylus contracts from prompts
ask_stylus	Q&A, debugging, concept explanations
generate_tests	Generate unit/integration/fuzz tests
get_workflow	Build/deploy/test workflow guidance
validate_stylus_code	Compile-check code via Docker cargo check with Stylus-specific fix guidance

Arbitrum SDK - Bridging & Messaging (3 tools)

Tool	Description
generate_bridge_code	Generate ETH/ERC20 bridging code (L1<->L2, L1->L3, L3->L2)
generate_messaging_code	Generate cross-chain messaging code (L1<->L2, L2<->L3)
ask_bridging	Q&A about bridging patterns and SDK usage

Full dApp Builder (5 tools)

Tool	Description
generate_backend	Generate NestJS/Express backends with Web3 integration
generate_frontend	Generate Next.js + wagmi + RainbowKit frontends
generate_indexer	Generate The Graph subgraphs for indexing
generate_oracle	Generate Chainlink oracle integrations
orchestrate_dapp	Scaffold complete dApps with multiple components

Orbit Chain Integration (5 tools)

Tool	Description
generate_orbit_config	Generate Orbit chain configuration (prepareChainConfig, AnyTrust, custom gas tokens)
generate_orbit_deployment	Generate rollup and token bridge deployment scripts (createRollup, createTokenBridge)
generate_validator_setup	Manage validators, batch posters, and AnyTrust DAC keysets
ask_orbit	Q&A about Orbit chain deployment, configuration, and operations
orchestrate_orbit	Scaffold complete Orbit chain deployment projects with all scripts

Example: Get Build/Deploy Workflow

{
  "workflow_type": "deploy",
  "network": "arbitrum_sepolia",
  "include_troubleshooting": true
}

Returns step-by-step commands:

# Check balance
cast balance YOUR_ADDRESS --rpc-url https://sepolia-rollup.arbitrum.io/rpc

# Deploy contract
cargo stylus deploy --private-key-path=./key.txt --endpoint=https://sepolia-rollup.arbitrum.io/rpc

Resources (Knowledge Injection)

MCP Resources provide static knowledge that AI IDEs can load automatically:

Stylus Resources

Resource URI	Description
stylus://cli/commands	Complete cargo-stylus CLI reference
stylus://workflows/build	Step-by-step build workflow
stylus://workflows/deploy	Deployment workflow with network configs
stylus://workflows/test	Testing workflow (unit, integration, fuzz)
stylus://config/networks	Arbitrum network configurations
stylus://rules/coding	Stylus coding guidelines and patterns

Arbitrum SDK Resources

Resource URI	Description
arbitrum://rules/sdk	Arbitrum SDK bridging and messaging guidelines

Full dApp Builder Resources

Resource URI	Description
dapp://rules/backend	NestJS/Express Web3 backend patterns
dapp://rules/frontend	Next.js + wagmi + RainbowKit patterns
dapp://rules/indexer	The Graph subgraph development patterns
dapp://rules/oracle	Chainlink oracle integration patterns

Prompts (Workflow Templates)

MCP Prompts provide reusable templates for common workflows:

Prompt	Description	Arguments
build-contract	Build workflow guidance	project_path, release_mode
deploy-contract	Deploy workflow guidance	network, key_method
debug-error	Error diagnosis workflow	error_message, context
optimize-gas	Gas optimization workflow	contract_code, focus
generate-contract	Contract generation workflow	description, contract_type

How It Works

User: "Deploy my contract to Arbitrum Sepolia"
    ↓
AI IDE calls get_workflow(workflow_type="deploy", network="arbitrum_sepolia")
    ↓
Returns structured commands + troubleshooting
    ↓
AI IDE presents commands to user (user executes locally)

The MCP server provides knowledge about commands, not command execution. This ensures:

• User controls what runs on their machine
• No security risks from remote execution
• AI IDE knows exact commands without hardcoding

See docs/mcp_tools_spec.md for full specification.

User Guide

Generating Stylus Contracts

ARBuilder uses template-based code generation to ensure generated code compiles correctly. Instead of generating from scratch, it customizes verified working templates from official Stylus examples.

Available Templates:

Template	Type	Description
Counter	utility	Simple storage with getter/setter operations
VendingMachine	defi	Mappings with time-based rate limiting
SimpleERC20	token	Basic ERC20 with transfer, approve, transferFrom
AccessControl	utility	Owner-only functions with ownership transfer
DeFiVault	defi	Cross-contract calls (sol_interface!), transfer_eth, Call::new_in(self)
NftRegistry	nft	Dynamic arrays (push), sol! events with camelCase, mint/transfer

Stylus SDK Version Support:

Version	Status	Notes
0.10.0	Main (default)	Recommended for new projects
0.9.x	Supported	Use target_version: "0.9.0" for 0.9.x output. Separate branches in forks
0.8.x	Supported	Minimum supported version
< 0.8.0	Deprecated	Warning shown, may not compile

Pass target_version to tools for version-specific output:

User: "Generate a counter contract for SDK 0.9.0"
AI uses: generate_stylus_code(prompt="...", target_version="0.9.0")
Returns: Code using msg::sender(), .getter(), print_abi() patterns

Ask your AI assistant to generate contracts:

User: "Create an ERC20 token called MyToken with 1 million supply"

AI uses: generate_stylus_code tool
Returns: Complete Rust contract based on SimpleERC20 template with proper imports, storage, and methods

Getting Context and Examples

Search the knowledge base for documentation and code examples:

User: "Show me how to implement a mapping in Stylus"

AI uses: get_stylus_context tool
Returns: Relevant documentation and code snippets from official examples

Q&A and Debugging

Ask questions about Stylus development:

User: "Why am I getting 'storage not initialized' error?"

AI uses: ask_stylus tool
Returns: Explanation with solution based on documentation context

Generating Tests

Create test suites for your contracts:

User: "Write unit tests for this counter contract: [paste code]"

AI uses: generate_tests tool
Returns: Comprehensive test module with edge cases

Build/Deploy Workflows

Get step-by-step deployment guidance:

User: "How do I deploy to Arbitrum Sepolia?"

AI uses: get_workflow tool
Returns: Commands for checking balance, deploying, and verifying

Features

Stylus Smart Contract Builder

AI-powered Stylus contract development with RAG-based context retrieval:

• Context Search: Hybrid search (vector + BM25 + cross-encoder reranking) over Stylus docs and code examples
• Code Generation: Generate production-ready Stylus contracts from natural language, with 7 built-in templates (Counter, VendingMachine, SimpleERC20, AccessControl, DeFiVault, StakingRewards, NftRegistry)
• Test Generation: Generate unit, integration, and fuzz tests for Stylus contracts
• Q&A Assistant: RAG-powered answers to Stylus development questions with code fix post-processing
• Workflow Guides: Step-by-step build, deploy, and test workflow guidance
• Code Validation: Docker-based cargo check with up to 3 auto-fix attempts and Stylus-specific error guidance
• SDK 0.10.0: Full support for the latest Stylus SDK (alloy 1.0.1, Rust 1.91.0, self.vm() API)

# Example: Generate a Stylus contract
echo '{"method": "tools/call", "id": 1, "params": {"name": "generate_stylus_code", "arguments": {"prompt": "Create an ERC20 token with mint and burn"}}}' | python -m src.mcp.server

# Example: Ask a Stylus question
echo '{"method": "tools/call", "id": 1, "params": {"name": "ask_stylus", "arguments": {"question": "How do I use mappings in Stylus?"}}}' | python -m src.mcp.server

Arbitrum SDK Integration

Cross-chain bridging and messaging support:

• ETH Bridging: L1 <-> L2 deposits and withdrawals
• ERC20 Bridging: Token bridging with gateway approvals
• L1 -> L3 Bridging: Direct L1 to Orbit chain bridging via double retryables
• Cross-chain Messaging: L1 -> L2 retryable tickets, L2 -> L1 messages via ArbSys
• Status Tracking: Message status monitoring and withdrawal claiming

# Example: Generate ETH deposit code
echo '{"method": "tools/call", "id": 1, "params": {"name": "generate_bridge_code", "arguments": {"bridge_type": "eth_deposit", "amount": "0.5"}}}' | python -m src.mcp.server

Full dApp Builder

Complete dApp scaffolding with all components:

• Backend Generation: NestJS or Express with viem/wagmi integration
• Frontend Generation: Next.js 14 + wagmi v2 + RainbowKit v2 + DaisyUI
• Indexer Generation: The Graph subgraphs (ERC20, ERC721, DeFi, custom events)
• Oracle Integration: Chainlink Price Feeds, VRF, Automation, Functions
• Full Orchestration: Scaffold complete dApps with monorepo structure
• ABI Auto-Extraction: Contract ABI is parsed from Stylus Rust code and injected into backend/frontend
• ABI-Aware Generation: Indexer schema/mappings, frontend hooks, and backend routes are generated from contract ABI
• Compiler Verification: Docker-based cargo check loop catches and auto-fixes compilation errors
• Executable Scripts: Generated setup.sh, deploy.sh, and start.sh for one-command workflows
• CLI Scaffolding: setup.sh uses a scaffold-first, backfill pattern with official CLI tools (cargo stylus new, create-next-app, @nestjs/cli) to fill in config files our templates don't generate, with graceful fallback if tools aren't installed
• Env Standardization: Centralized env var config (PORT 3001, CORS, BACKEND_URL) across all components

Backend Templates:

• NestJS + Stylus contract integration
• Express + Stylus (lightweight)
• NestJS + GraphQL (for subgraph querying)
• API Gateway (cross-chain proxy)

Frontend Templates:

• Next.js + wagmi + RainbowKit base
• DaisyUI component library
• Contract Dashboard (admin panel)
• Token Interface (ERC20/721 UI)

Indexer Templates:

• ERC20 Subgraph (transfers, balances)
• ERC721 Subgraph (ownership, metadata)
• DeFi Subgraph (swaps, liquidity)
• Custom Events Subgraph

Oracle Templates:

• Chainlink Price Feed
• Chainlink VRF (randomness)
• Chainlink Automation (keepers)
• Chainlink Functions

# Example: Generate full dApp scaffold
echo '{"method": "tools/call", "params": {"name": "orchestrate_dapp", "arguments": {"prompt": "Create a token staking dApp", "components": ["contract", "backend", "frontend", "indexer"]}}}' | python -m src.mcp.server

# Example: Generate backend only
echo '{"method": "tools/call", "params": {"name": "generate_backend", "arguments": {"prompt": "Create a staking API", "framework": "nestjs"}}}' | python -m src.mcp.server

# Example: Generate frontend with contract ABI
echo '{"method": "tools/call", "params": {"name": "generate_frontend", "arguments": {"prompt": "Create token dashboard", "contract_abi": "[...]"}}}' | python -m src.mcp.server

Orbit Chain Integration

Orbit chain deployment and management support:

• Chain Configuration: Generate prepareChainConfig() scripts for Rollup or AnyTrust chains
• Rollup Deployment: Generate createRollup() scripts with crash-proof deployment.json output (saves before receipt fetch)
• Token Bridge: Generate createTokenBridge() scripts with automatic ERC-20 approval for custom gas token chains
• Custom Gas Tokens: Full approval flow — RollupCreator + TokenBridgeCreator + Inbox approvals
• AnyTrust DAC: Full keyset lifecycle — BLS key generation (generate-das-keys.sh), keyset encoding, UpgradeExecutor-routed setValidKeyset(), hash verification
• Validator Management: Add/remove validators and batch posters
• Node Configuration: Generate Nitro node config via prepareNodeConfig() with post-processing — private key restoration, staker disable for single-key setups, deployed-at injection, DAS URL fix
• Docker Compose: Battle-tested templates with explicit HTTP/WS/metrics CLI flags, WASM cache cleanup entrypoint, DAS server with all required flags
• Governance Management: UpgradeExecutor role checking, granting, and revocation (manage-governance.ts)
• Chain Verification: Health check script tests RPC connectivity, balances, transfers, and contract deployment (test-chain.ts)
• Full Orchestration: Scaffold complete deployment projects with all scripts, configs, and documentation

# Example: Scaffold a complete Orbit chain deployment project
echo '{"method": "tools/call", "params": {"name": "orchestrate_orbit", "arguments": {"prompt": "Deploy an AnyTrust chain on Arbitrum Sepolia", "chain_name": "my-orbit-chain", "chain_id": 412346, "is_anytrust": true, "parent_chain": "arbitrum-sepolia"}}}' | python -m src.mcp.server

# Example: Generate chain configuration
echo '{"method": "tools/call", "params": {"name": "generate_orbit_config", "arguments": {"prompt": "Configure a custom gas token chain", "native_token": "0x...", "parent_chain": "arbitrum-sepolia"}}}' | python -m src.mcp.server

# Example: Ask about Orbit deployment
echo '{"method": "tools/call", "params": {"name": "ask_orbit", "arguments": {"question": "How do I deploy an Orbit chain with a custom gas token?"}}}' | python -m src.mcp.server

Development

Running Tests

# Run all unit tests
pytest tests/ -m "not integration"

# Run retrieval quality tests
pytest tests/test_retrieval.py -v

# Run MCP tool tests (requires tool implementations)
pytest tests/mcp_tools/ -v

# Run template selection and validation tests
pytest tests/test_templates.py -v -m "not integration"

# Run template compilation tests (requires Rust toolchain + cargo-stylus)
pytest tests/test_templates.py -v -m integration

Template compilation tests require:

• Rust toolchain 1.87.0: rustup install 1.87.0
• WASM target: rustup target add wasm32-unknown-unknown --toolchain 1.87.0
• cargo-stylus: cargo install --locked cargo-stylus

Running Benchmarks

# Run all benchmarks
python scripts/run_benchmarks.py

# Run only P0 (critical) tests
python scripts/run_benchmarks.py --priority P0

# Run benchmarks for a specific tool
python scripts/run_benchmarks.py --tool get_stylus_context

Benchmark reports are saved to benchmark_results/.

Code Formatting

black .
ruff check .

Troubleshooting

Embedding Generation Errors

If you encounter errors like Error generating embeddings: RetryError or KeyError during vector database ingestion:

1. Check OpenRouter API Key

# Verify your .env file has a valid API key
cat .env | grep OPENROUTER_API_KEY

Ensure:

• The API key is correctly set (no extra spaces or quotes)
• Your OpenRouter account has credits
• The embedding model baai/bge-m3 is available on OpenRouter

2. Rate Limiting Issues

If you see HTTPStatusError with status 429, you're being rate limited. Solutions:

# Run with smaller batch size
python -m src.embeddings.vectordb --batch-size 25

# Or modify max_workers in vectordb.py to 1 for sequential processing

3. Enable Debug Logging

Add this to your script or at the start of your session to see detailed logs:

import logging
logging.basicConfig(level=logging.INFO)
# For more verbose output:
# logging.basicConfig(level=logging.DEBUG)

Scraper Errors

"Execution context was destroyed" errors

This is a browser navigation issue during scraping. The scraper will automatically retry. If it persists:

• The page may have heavy JavaScript that interferes with scraping
• These pages are skipped after retries; the scraper continues with other URLs

Git clone failures

If repository cloning fails:

# Check your network connection
ping github.com

# Try cloning manually to diagnose
git clone --depth 1 https://github.com/OffchainLabs/stylus-hello-world

# If behind a proxy, configure git
git config --global http.proxy http://proxy:port

Timeout errors

For slow connections, increase timeouts in the scraper config or reduce concurrent requests:

python -m scraper.run --max-concurrent 1

ChromaDB Issues

"Collection is empty" error

If you see collection is empty when using get_stylus_context tool:

# The vector database must be generated locally (it's not included in the repo)
# Run this command to populate the database:
python -m src.embeddings.vectordb

# If that doesn't work, try resetting first:
python -m src.embeddings.vectordb --reset

Import errors with opentelemetry

If you see TypeError: 'NoneType' object is not subscriptable when importing chromadb:

# This is usually a conda environment issue
# Make sure you're in the correct environment
conda activate arbbuilder

# Or reinstall chromadb
pip uninstall chromadb
pip install chromadb

Database corruption

If the vector database seems corrupted:

# Reset and re-ingest
python -m src.embeddings.vectordb --reset

CI/CD Workflows

Workflow	Trigger	Purpose
qa.yml	PRs to main, push to main	TypeScript type check, Python lint, Python tests
maintenance.yml	Weekly (Mon 6AM UTC) + manual	SDK monitoring, health checks, discovery, re-verification, auto-remediation
refresh-rag.yml	Manual	Full RAG refresh: scrape, process, migrate to Vectorize
deploy-staging.yml	Manual	Deploy to staging environment
release-chunks.yml	GitHub release	Build and publish pre-processed chunks + embeddings

maintenance.yml Jobs

Job	Trigger	What It Does
sdk-monitor	Weekly + manual	Checks crates.io/npm for new SDK versions
health-check	Weekly + manual	Checks all repos for archived/deleted status
discover	Manual only	Searches GitHub for new community repos
reverify	On SDK update or manual	Re-verifies all repos with verify_source.py --all
remediate	Manual only	Auto-removes archived/deleted repos from sources.json
sync-sources	Weekly + manual	Syncs sources.json to CF KV registry
create-issue	When problems found	Creates GitHub issue with maintenance label

Contributing

We welcome contributions! See CONTRIBUTING.md for guidelines on how to get started.

License

MIT License - see LICENSE for details.

References

• Arbitrum Documentation
• Stylus Documentation
• ICP Coder - Reference implementation
• Stacks Builder - Reference implementation