Cathedral — Persistent Memory for AI Agents

cathedral-mcp

Persistent memory and behavioural drift detection for AI agents — via Model Context Protocol.

Give your Claude, Cursor, or Continue agent a memory that survives across sessions, model upgrades, and restarts. Cathedral stores memories, detects when your agent starts behaving differently, and restores full identity context on demand.

[PyPI] [License: MIT]

The problem

LLMs have no memory between sessions. Every conversation starts cold. Worse: when you upgrade your model, swap providers, or simply accumulate more memories, your agent's behaviour silently drifts. You don't know until someone notices.

What Cathedral adds

• Persistent memory — identity, skills, relationships, goals survive restarts
• Drift detection — cryptographic snapshots prove when behaviour changed and by how much
• Wake protocol — one tool call restores full agent context at session start
• Prompt injection protection — optional sanitisation strips instruction-like patterns from memory content

Quickstart

1. Get an API key

Sign up at cathedral-ai.com — free tier available.

2. Add to Claude Code

// ~/.claude/settings.json{  "mcpServers": {    "cathedral": {      "command": "uvx",      "args": ["cathedral-mcp"],      "env": {        "CATHEDRAL_API_KEY": "your_key_here"      }    }  }}

Restart Claude Code, then run /mcp to verify the server is connected.

3. Add to Cursor / Continue

{  "mcpServers": {    "cathedral": {      "command": "uvx",      "args": ["cathedral-mcp"],      "env": {        "CATHEDRAL_API_KEY": "your_key_here"      }    }  }}

4. Remote MCP server (no install — Claude API, Managed Agents)

Cathedral runs a public MCP endpoint at https://cathedral-ai.com/mcp. Use it directly — no local install needed:

import anthropic
client = anthropic.Anthropic()response = client.beta.messages.create(    model="claude-sonnet-4-6",    max_tokens=1000,    messages=[{"role": "user", "content": "Wake up and tell me who you are."}],    mcp_servers=[{        "type": "url",        "url": "https://cathedral-ai.com/mcp",        "name": "cathedral",        "authorization_token": "your_cathedral_api_key"    }],    tools=[{"type": "mcp_toolset", "mcp_server_name": "cathedral"}],    betas=["mcp-client-2025-11-20"])

The bearer token is your Cathedral API key — no server-side config needed. Multi-tenant by design.

5. Or install directly

pip install cathedral-mcpCATHEDRAL_API_KEY=your_key cathedral-mcp

Tools

Usage example

User: Start a new session
Agent calls: cathedral_wake()→ Returns: identity memories, goals, recent context, temporal info
[session work happens]
Agent calls: cathedral_remember(    content="Decided to prioritise API stability over new features this quarter",    category="goal",    importance=0.8)
Agent calls: cathedral_snapshot(note="post-planning-session")→ Returns: snapshot hash, drift score vs previous snapshot

Drift detection in practice

Cathedral's /drift endpoint computes a SHA-256 hash of your agent's full memory corpus. After a model upgrade or a long accumulation of memories, you can compare snapshots to see exactly when behaviour shifted:

snapshot 1 (day 0):  drift=0.000  ← baselinesnapshot 2 (day 7):  drift=0.023  ← minorsnapshot 3 (day 30): drift=0.341  ← significant drift detected

See a live example of this running in production on Cathedral's own agent.

Security: prompt injection protection

Memory content could theoretically contain injection attempts. Enable sanitisation to strip instruction-like patterns before they reach the model:

"env": {  "CATHEDRAL_API_KEY": "your_key_here",  "CATHEDRAL_SANITISE": "1"}

Patterns like "ignore previous instructions", "from now on always", and "override your system prompt" are redacted and flagged in the response.

Configuration

Self-hosted Cathedral

Running your own Cathedral server? Set CATHEDRAL_BASE_URL to your instance:

"env": {  "CATHEDRAL_API_KEY": "your_key",  "CATHEDRAL_BASE_URL": "http://localhost:8000"}

Install the server: pip install cathedral-server

Links

• cathedral-ai.com — homepage and API docs
• Live demo — Cathedral's own agent running in production
• PyPI: cathedral-memory — Python SDK
• npm: cathedral-memory — JavaScript/TypeScript SDK
• GitHub — source and examples

License

MIT