Argon

Argon is open source branching and merge for MongoDB, built for AI agents. It gives each agent its own branch of the data, checked out as a real MongoDB database, so the agent can test changes, look back at earlier states and propose edits that a person reviews as a diff before merging anything into the main data. It is aimed at developers building agents and evaluations that write to MongoDB. Branches are lightweight metadata built on a deterministic write ahead log, while checkout materializes a real database whose time and storage depend on the dataset. Time travel queries read retained history by log position or timestamp, and pins protect referenced history. Agent workflows include managed sandboxes with a time to live, branch scoped undo per actor, dataset pins and a LangGraph checkpointer. The engine is reached through four surfaces: a CLI, an MCP server with 13 tools for Claude Code or Cursor, a REST API with a Python SDK, and a wire proxy for stable connection strings. Agents keep their usual MongoDB driver. Argon is free, MIT licensed and self hosted, installed from npm, Homebrew or the Python SDK, and it connects to a user's own MongoDB replica set. No paid plan or pricing is published, and a live demo runs without a login on sample data. The vendor documents operating limits plainly: undo requires complete change images and retained history, unsupported drop or rename operations mark history incomplete, and separate agents need separate branches for attribution.