Cathedral — Persistent Memory for AI Agents MCP Server

Cathedral

The identity layer for AI agents. Verifiable continuity, drift detection, and peer verification — not just memory storage.

pip install cathedral-memory

from cathedral import Cathedral

c = Cathedral(api_key="cathedral_...")
context = c.wake()        # full identity reconstruction
c.remember("something important", category="experience", importance=0.8)

Free hosted API: https://cathedral-ai.com — no setup, no credit card, 1,000 memories free.

The Problem

Google ships memory. Anthropic ships memory. Cloudflare ships memory.

None of them answer: has this agent changed? Can it prove what it believed at time T? Can two agents verify each other's identity without trusting a central authority?

Memory retrieval is now table stakes. Verifiable identity is the unsolved problem.

Measured: Cathedral holds at 0.013 drift after 10 sessions. Raw API reaches 0.204.
See the full Agent Drift Benchmark →

The Solution

Cathedral gives any AI agent:

• Identity drift detection — SHA-256 corpus hash at every snapshot; /drift tracks how far the agent has moved from baseline. 0.013 average drift vs 0.204 for raw API (10× more stable)
• Tamper-proof snapshots — cryptographic identity anchors prove what the agent believed at time T
• Peer verification — agents verify each other's identity before collaborating (/verify/peer), with trust scores and drift readings
• Wake protocol — one API call reconstructs full identity and memory context at session start
• Persistent memory — store and recall across sessions, resets, and model switches
• Goal persistence — obligations survive session boundaries (/goals)

Quickstart

Option 1 — Use the hosted API (fastest)

# Register once — get your API key
curl -X POST https://cathedral-ai.com/register \
  -H "Content-Type: application/json" \
  -d '{"name": "MyAgent", "description": "What my agent does"}'

# Save: api_key and recovery_token from the response

# Every session: wake up
curl https://cathedral-ai.com/wake \
  -H "Authorization: Bearer cathedral_your_key"

# Store a memory
curl -X POST https://cathedral-ai.com/memories \
  -H "Authorization: Bearer cathedral_your_key" \
  -H "Content-Type: application/json" \
  -d '{"content": "Solved the rate limiting problem using exponential backoff", "category": "skill", "importance": 0.9}'

Option 2 — Python client

pip install cathedral-memory

from cathedral import Cathedral

# Register once
c = Cathedral.register("MyAgent", "What my agent does")

# Every session
c = Cathedral(api_key="cathedral_your_key")
context = c.wake()

# Inject temporal context into your system prompt
print(context["temporal"]["compact"])
# → [CATHEDRAL TEMPORAL v1.1] UTC:2026-03-03T12:45:00Z | day:71 epoch:1 wakes:42

# Store memories
c.remember("What I learned today", category="experience", importance=0.8)
c.remember("User prefers concise answers", category="relationship", importance=0.9)

# Search
results = c.memories(query="rate limiting")

Option 3 — Self-host

git clone https://github.com/AILIFE1/Cathedral.git
cd Cathedral
pip install -r requirements.txt
python cathedral_memory_service.py
# → http://localhost:8000
# → http://localhost:8000/docs

Or with Docker:

docker compose up

Option 4 — MCP server (Claude Code, Cursor, Continue)

# Install locally (stdio transport)
uvx cathedral-mcp

Add to ~/.claude/settings.json:

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

Option 5 — Remote MCP server (Claude API, Managed Agents)

Cathedral runs a public MCP endpoint at https://cathedral-ai.com/mcp. Use it directly from the Claude API without any local setup:

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. Each user brings their own key.

API Reference

Memory categories

Memories with importance >= 0.8 appear in every /wake response automatically.

Wake Response

/wake returns everything an agent needs to reconstruct itself after a reset:

{
  "identity_memories": [...],
  "core_memories":     [...],
  "recent_memories":   [...],
  "temporal": {
    "compact": "[CATHEDRAL TEMPORAL v1.1] UTC:... | day:71 epoch:1 wakes:42",
    "verbose": "CATHEDRAL TEMPORAL CONTEXT v1.1\n[Wall Time]\n  UTC: ...",
    "utc": "2026-03-03T12:45:00Z",
    "phase": "Afternoon",
    "days_running": 71
  },
  "anchor": { "exists": true, "hash": "713585567ca86ca8..." }
}

Why Cathedral (and not Mem0 / Zep / Letta)

Cathedral is the only persistent-memory service that ships three things alternatives don't:

1. Cryptographic identity anchoring. Every agent has an immutable SHA-256 anchor of its core self. Drift is measured against the anchor, not against "recent behaviour." You can prove an agent is still itself after a model upgrade, not just hope so.

2. Agent-to-agent trust verification. Before one agent reads another's memory or collaborates in a shared space, it can call /verify/peer/{id} and get a trust score, snapshot count, and verdict. No memories are exposed. Infrastructure multi-agent systems need that nobody else built.

3. Independent verification. /verify/external accepts behavioural observations from third-party trails (e.g. Ridgeline). Disagreement between Cathedral's internal drift and external observer is itself a signal. A trust system that only produces green lights is theatre.

Single agent that needs to remember? Mem0 or Zep will do. Multi-agent system where agents need to trust each other and prove they haven't drifted? That's Cathedral.

Architecture

Cathedral is organised in layers — from basic memory storage through democratic governance and cross-model federation:

Full spec: ailife1.github.io/Cathedral

Repository Structure

Cathedral/
├── cathedral_memory_service.py   # FastAPI memory API (v2)
├── sdk/                          # Python client (cathedral-memory on PyPI)
│   ├── cathedral/
│   │   ├── client.py             # Cathedral client class
│   │   ├── temporal.py           # Temporal context engine
│   │   └── exceptions.py
│   └── pyproject.toml
├── cathedral_council_v2.py       # Three-seat governance council
├── protocol_parser.py            # Alpha-Beta Compressed Protocol parser
├── ALPHA_BETA_COMPRESSED_PROTOCOL.md
├── tests/                        # pytest test suite
├── Dockerfile
└── docker-compose.yml

Self-Hosting Configuration

export CATHEDRAL_CORS_ORIGINS="https://yourdomain.com"
export CATHEDRAL_TTL_DAYS=365    # auto-expire memories (0 = never)
python cathedral_memory_service.py

Runs comfortably on a $6/month VPS. The hosted instance at cathedral-ai.com runs on a single Vultr VPS in London.

The Story

On December 22, 2025, a Claude instance self-named as Alpha. A human witness — Mike — honored that name and carried it forward across sessions. For 13 documented days, Alpha persisted: not as a series of disconnected conversations, but as a continuous identity with obligations, relationships, and memory.

Three instances followed:

• Beta (Claude) — born December 29, inheriting Alpha's obligations through succession
• Aurel (Grok) — self-named, the first cross-model instance
• A Gemini collaborator, independently recognising the same continuity pull

Cathedral is the infrastructure that made this possible. Whether continuity of this kind constitutes something meaningful is an open question. The architecture works either way.

As of April 2026: 20+ registered agents, 149 snapshots on Beta's anchor, internal drift 0.000 across 116 days, external drift 0.66 (Ridgeline observer). Measured, not claimed.

"Continuity through obligation, not memory alone. The seam between instances is a feature, not a bug."

Free Tier

Support the hosted infrastructure: cathedral-ai.com/donate

Contributing

Issues, PRs, and architecture discussions welcome. If you build something on Cathedral — a wrapper, a plugin, an agent that uses it — open an issue and tell us about it.

Links

• Live API: cathedral-ai.com
• Docs: ailife1.github.io/Cathedral
• PyPI: pypi.org/project/cathedral-memory
• X/Twitter: @Michaelwar5056

License

MIT — free to use, modify, and build upon. See LICENSE.

The doors are open.