Cairntir MCP Server

What is Cairntir?

Cairntir is a local-first, open-source memory system for Claude Code and other Model Context Protocol (MCP) clients. It stores every decision, fact, and lesson that a model writes down — verbatim, with no summarization — in a SQLite database, so that each new chat session inherits the full context from previous ones. It is designed for solo developers, small teams, tool builders, and researchers who want to eliminate the productivity tax of re‑explaining past work across chat sessions.

How to use Cairntir?

Install with pip install cairntir, then run cairntir setup — an interactive wizard that configures the MCP registration in one command. Fully quit and reopen Claude Code (or any MCP client). The server automatically registers a stable launcher and silently re‑registers if the client can’t find it. Six MCP tools are available over stdio: cairntir_session_start, cairntir_recall, cairntir_remember, cairntir_timeline, cairntir_audit, and cairntir_crucible. Two environment variables (CAIRNTIR_DISABLE_AUTOREGISTER and CAIRNTIR_DISABLE_UPDATE_CHECK) allow opt‑out for CI or air‑gapped use.

Key features of Cairntir

• Verbatim storage – no summarization, full context preserved forever.
• Four‑layer retrieval: identity, essential, on‑demand, and deep.
• Semantic search via sqlite-vec for fuzzy recall.
• Prediction‑bound drawers with belief‑as‑distribution ranking.
• Portable signed format (content‑addressed, HMAC‑signed) for sharing.
• Consolidation pass with forgetting curve and contradiction detection.
• One‑command installation wizard (cairntir setup).

Use cases of Cairntir

• Avoiding the Monday re‑explanation cycle for daily Claude Code users.
• Providing a per‑developer memory layer that can later become a shared, gossip‑able memory for small teams.
• Embedding persistent context into products that use an MCP client.
• Tracking which hypotheses held and which failed with prediction‑bound drawer schema (experiment journal).
• Supporting longer‑term projects such as post‑scarcity manufacturing research (horizon goal).