Nautilus Compass

What the Nautilus Compass MCP server does

The Nautilus Compass MCP server adds persistent memory and reliability checks to MCP-compatible agents. It can retain session information, retrieve relevant past content, inspect prompts for drift against known failure patterns, and support coordination between agents working with shared files.

The project is distributed as a Python package and includes the MCP server, command-line tools, an A2A adapter, and session-focused utilities. It supports local operation, where stored text and embeddings remain on the machine, as well as a hosted MCP gateway with per-user memory isolation.

How it works

For local memory, the system embeds raw text with BGE-m3. It does not require an extraction LLM during ingestion. Retrieval selects between two paths: questions tied to one session or a knowledge update use turn-window chunks, while other queries use session-level hybrid retrieval combining BM25 and dense search through reciprocal rank fusion.

Before an agent acts, drift detection compares the prompt with an anchor set containing positive and negative failure examples. The repository reports a held-out drift AUC of 0.83, p95 latency below 50 ms, and a 0.5% production fire rate. For multi-agent workflows, the system derives contracts from handoff files, follows whether those contracts are closed, and audits for fake closure or red drift.

Setup and configuration

Install the package with pip install nautilus-compass. The package exposes nautilus-compass, compass-mcp, and compass-a2a, along with tools for drift history, session search, and session writing.

For Claude Code or Claude Desktop, the repository provides an installer and a daemon startup script. The local daemon loads the BGE-m3 model and should be started once per boot. An additional installer can detect Claude Desktop, Cursor, Cline, Continue.dev, and Zed and update their MCP configuration.

A hosted option is available at https://compass.nautilus.social/mcp/ using streamable HTTP and a Bearer token. Registration and token creation occur through the hosted service. The gateway uses scoped tokens and isolates each user's memory space.

Tools and capabilities

The Nautilus Compass MCP server provides capabilities for:

• Recalling relevant long-term memory.
• Searching stored sessions.
• Writing session information and end-of-session summaries.
• Checking prompts for drift and reviewing drift history.
• Tracking cross-agent contracts and governance signals.
• Serving memory through local MCP or hosted streamable HTTP.
• Connecting agents through the included A2A adapter.

The Claude integration also installs prompt, post-tool, and stop hooks. These perform recall and drift checks, write information during a session, and save a final session report.

Limitations and notes

The first recall after the daemon has been idle can take up to 90 seconds while the model loads; the MCP client retries once with an extended timeout. Disabling COMPASS_USE_INOTIFY prevents discovery of new files, so recent writes may not appear in recalls. The daemon reports an anchor-file error when anchors.json is missing rather than treating the prompt as risk-free.

The hosted service requires registration and a token, while local use requires the package or repository installation and a running daemon for the documented hook-based setup. The README describes 17 MCP tools but does not enumerate their individual names in the supplied material.