Refact – Open-Source AI Agent, Code Generator & Chat for JavaScript, Python, TypeScript, Java, PHP, Go, and more.Extension40/100 via “codebase-wide semantic understanding with rag-indexed retrieval”
Refact.ai is the #1 free open-source AI Agent on the SWE-bench verified leaderboard. It autonomously handles software engineering tasks end to end. It understands large and complex codebases, adapts to your workflow, and connects with the tools developers actually use (including MCP). It tracks your
Unique: Implements full-codebase RAG indexing with semantic search, enabling the AI to retrieve project-specific patterns without requiring users to manually specify context via @-commands. Unlike Copilot's context window approach, Refact pre-indexes the entire codebase and fetches relevant snippets on-demand.
vs others: More scalable than context-window-based approaches for large codebases because it retrieves only relevant snippets rather than sending entire files, reducing latency and enabling reasoning over projects larger than the LLM's context window.