Montycat MCP - Shared Memory for AI Agents
A self-hosted MCP server that gives AI agents persistent, searchable memory. Claude, Codex, Cursor, and any Model Context Protocol client write to one memory and read each other's.
- Memory that survives the chat. Decisions, preferences, and project context carry into the next session.
- One memory, many agents. Every MCP client you use works from the same facts.
- Recall by meaning, keyword, or both. Vector search finds a memory when the wording differs, BM25 nails exact identifiers, and hybrid mode fuses the two. Exact-key and metadata lookup too.
- Yours. Server, engine, and embeddings run on your machine. No hosted memory service, no cloud embedding API.
Install
Claude Desktop — download
montycat-mcp.mcpb
and drag it into Claude Desktop. No Python needed. That link always serves the
current release; every release
also carries a version-named copy and a .sha256 to check it against.
Claude Code — install uv, then:
/plugin marketplace add MontyGovernance/montycat-mcp
/plugin install montycat-mcp@montygovernance
/mcp confirms the montycat server is connected.
Codex, Cursor, other MCP clients — point your client's stdio config at
uvx montycat-mcp (Python 3.10+). For Codex:
codex mcp add montycat -- uvx montycat-mcp
The engine
Memory lives in a Montycat Semantic engine. Montycat MCP starts a local one for you, so most people can stop reading here.
Point it at an engine you already run:
export MONTYCAT_URI="montycat://memory-agent:password@localhost:21210/memories"
export MONTYCAT_TLS=true # remote engines only
Or start one yourself with Docker:
docker run -d --name montycat -p 21210:21210 -p 21211:21211 \
-e MONTYCAT_SUPEROWNER=admin -e MONTYCAT_PASSWORD=change-me \
-v montycat_data:/var/lib/.montycat \
montygovernance/montycat:semantic
On Apple Silicon use the arm64-semantic tag instead — semantic is the amd64
image, and it crashes under emulation. Port 21211 carries live memory watches.
Use it
Talk to your agent normally; it picks the tool.
Remember that the team chose PostgreSQL for the billing service.
What did we decide about the billing database?
Save this to the shared
engineeringscope.
scope decides where a memory lives — alice for private, engineering for a
team, shared for common. It is a namespace, not a security boundary: for real
isolation, give each MCP server its own least-privilege Montycat credential.
Tools
For persistent namespaces, cache is a capacity in MB and compression is
chosen by montycat_create_keyspace. Compression cannot be changed after the
keyspace is created; migrate into a new keyspace to use a different setting.
Cache capacity can be changed later with montycat_update_cache.
Destructive tools are declared as such, so your client's confirmation prompts apply.
Configuration
All three verification settings are optional. With only MONTYCAT_TLS=true,
MCP retains the historical encrypted-but-unverified behavior; with TLS unset or
false, existing plaintext configurations are unchanged.
| MONTYCAT_DEFAULT_KEYSPACE | Memory namespace; memory by default |
| MONTYCAT_SCOPE | Default scope when a call omits one |
| MONTYCAT_AUTO_PROVISION | Create a permitted scope on first use; true by default |
| MONTYCAT_AUTOSTART | off to require an already-running engine |
Compose setup and the full variable list: compose.yaml and the plugin guide.
More
Changelog · Privacy · Issues · Docs · Docker Hub
Existing MemoCat installs keep working: memocat-mcp, MEMOCAT_*, and
memocat:// are still supported. New setups should use the Montycat names.
MIT