Show HN: I replaced vector databases with Git for AI memory (PoC)

Summary

DiffMem: Git-Based Differential Memory for AI Agents DiffMem is a lightweight, git-based memory backend designed for AI agents and conversational systems. It uses Markdown files for human-readable storage, Git for tracking temporal evolution through differentials, and an in-memory BM25 index for fast, explainable retrieval. This project is a proof-of-concept (PoC) exploring how version control systems can serve as a foundation for efficient, scalable memory in AI applications. At its core, DiffMem treats memory as a versioned repository: the "current state" of knowledge is stored in editable files, while historical changes are preserved in Git's commit graph. This separation allows agents to query and search against a compact, up-to-date surface without the overhead of historical data, while enabling deep dives into evolution when needed. Why Git for AI Memory? Traditional memory systems for AI agents often rely on databases, vector stores, or graph structures. These work well for certain scales but can become bloated or inefficient when dealing with long-term, evolving personal knowledge. DiffMem takes a different path by leveraging Git's strengths: Current-State Focus : Memory files store only the "now" view of information (e.g., current relationships, facts, or timelines). This reduces the surface area for queries and searches, making operations faster and more token-efficient in LLM contexts. Historical states are not loaded by default—they live in Git's history, accessible on-demand. Differential Intelligence : Git diffs and logs provide a natural way to track how memories evolve. Agents can ask "How has this fact changed over time?" without scanning entire histories, pulling only relevant commits. This mirrors how human memory reconstructs events from cues, not full replays. Durability and Portability : Plaintext Markdown ensures memories are human-readable and tool-agnostic. Git's distributed nature means your data is backup-friendly and not locked into propr...