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.

---

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-mcp

CATHEDRAL_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  ← baseline

snapshot 2 (day 7): drift=0.023 ← minor snapshot 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