Open Brain: Open-source MCP server adds persistent memory with auto-graph and semantic search to Claude
What Open Brain does
Open Brain is an MCP server that provides Claude (Code, Desktop, or any MCP client) with persistent memory across sessions. When you tell Claude to "remember this," it captures the thought by embedding it, extracting entities (people, tools, projects, organizations), scoring quality, checking for semantic duplicates, and auto-linking to related thoughts. Later searches work by meaning rather than keywords.
Key differentiating features
- Auto-graph: Connections between thoughts are created automatically on capture with typed links (extends, contradicts, is-evidence-for) at 0.80+ similarity thresholds
- Semantic dedup: Captures at 0.92+ similarity automatically merge instead of creating duplicates
- Salience scoring: 6-factor ranking system (recency, access frequency, connections, merges, source weight, pinned) that surfaces frequently used thoughts over time
- Hybrid search: BM25 full-text + pgvector cosine similarity with Reciprocal Rank Fusion
- 16 MCP tools: Includes graph traversal, entity browsing, weekly review synthesis, staleness pruning, dedup review, and density analysis
- Staleness pruning: Irrelevant thoughts decay and get soft-archived automatically with LLM confirmation and sole-entity protection
Technical stack and setup
Built on Supabase (Postgres + pgvector) + Deno Edge Functions + OpenRouter. The system is self-hostable—you own your data and run it on your own Supabase project.
Setup takes approximately 10 minutes:
- Clone the repository
- Run bootstrap (interactive secret setup)
- Run deploy (schema + functions)
- Run validate (8-check verification)
The deploy script prints a ready-to-paste claude mcp add command for immediate integration.
Compatibility and licensing
Works with Claude Code, Claude Desktop, ChatGPT, and any MCP-compatible client. The project is MIT licensed with 40 SQL migrations, 5 Edge Functions, and 138 tests.
📖 Read the full source: r/ClaudeAI
👀 See Also
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