fastcode

FastCode is a token-efficient framework for repository-level code understanding from HKUDS, providing 3-4x faster analysis with 44-55% cost reduction through hybrid retrieval (semantic + keyword + graph-based).

Location: /project/FastCode

When to Use

Use FastCode when you need to:

• Understand an unfamiliar codebase quickly
• Find where functionality is implemented
• Analyze cross-repository dependencies
• Debug issues in complex codebases
• Perform impact analysis for changes

Quick Setup

cd /project/FastCode
pip install -r requirements.txt

# Set environment variables
export OPENAI_API_KEY="your-key"
export MODEL="gpt-4-turbo"
export BASE_URL="https://api.openai.com/v1"

MCP Integration for Claude Code

Add to your Claude Code MCP settings:

{
  "mcpServers": {
    "fastcode": {
      "command": "python",
      "args": ["/project/FastCode/mcp_server.py"],
      "env": {
        "MODEL": "gpt-4-turbo",
        "BASE_URL": "https://api.openai.com/v1",
        "OPENAI_API_KEY": "your-key"
      }
    }
  }
}

Available MCP Tools

| Tool | Purpose | |------|---------| | code_qa(question, repos, multi_turn, session_id) | Query codebase with natural language | | list_sessions() | List conversation sessions | | get_session_history(session_id) | Get session history | | delete_session(session_id) | Delete a session | | list_indexed_repos() | List indexed repositories | | delete_repo_metadata(repo_name) | Clean up repo metadata |

Usage Patterns

Query a Repository

Use the code_qa tool:
- question: "How does authentication work?"
- repos: ["https://github.com/user/repo"] or ["/local/path"]
- multi_turn: true (for context persistence)
- session_id: "optional-session-id"

Multi-Repository Analysis

Query across multiple repos:
- question: "How do auth systems differ between services?"
- repos: ["auth-service", "user-service", "api-gateway"]
- multi_turn: true

Session-Based Conversations

Use consistent session_id for follow-up questions to maintain context:

1. First query: session_id="analysis-1"
2. Follow-up: session_id="analysis-1" (retains context)

Python API (Alternative)

from fastcode import FastCode

fc = FastCode(config_path="/project/FastCode/config/config.yaml")
fc.load_repository("https://github.com/user/repo", is_url=True)
fc.index_repository()
result = fc.query("How does X work?", multi_turn=True)

Common Scenarios

Understanding Auth Flow

code_qa:
  question: "Trace the authentication flow from login to token validation"
  repos: ["/project/target-repo"]

Impact Analysis

code_qa:
  question: "What would break if I change the User model schema?"
  repos: ["/project/target-repo"]

Finding Implementations

code_qa:
  question: "Where is the payment processing logic implemented?"
  repos: ["/project/target-repo"]

Supported Languages

Python, JavaScript, TypeScript, Java, Go, C/C++, Rust, C#

Troubleshooting

| Issue | Solution | |-------|----------| | Repository not indexing | Check supported extensions in config/config.yaml | | Empty results | Ensure repo is indexed first (auto-indexes on first query) | | API errors | Verify OPENAI_API_KEY, MODEL, BASE_URL are set | | Slow first query | Initial indexing takes time; subsequent queries are fast |

Configuration

Edit /project/FastCode/config/config.yaml for:

• Repository ignore patterns
• Embedding model settings
• Vector store (FAISS/ChromaDB)
• Retrieval parameters