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 engineering scope.

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

Need	Tools
Store	montycat_remember, montycat_remember_bulk, montycat_update, montycat_forget
Recall	montycat_semantic_search, montycat_recall, montycat_list_memories
Inspect schemas	montycat_list_enforced_schemas — check field names and data types before structured writes or filtered retrieval
Collaborate	montycat_await_memory_change — wait for another agent's write, no polling
Namespaces	montycat_list_keyspaces, montycat_create_keyspace, montycat_update_cache, montycat_remove_keyspace
Admin	semantic index, snapshot, and policy tools — see the plugin guide

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

Variable	Purpose
MONTYCAT_URI	Connection string: montycat://user:password@host:port/store
MONTYCAT_TLS	true for a remote TLS engine
MONTYCAT_TLS_VERIFY	Optional: true to verify with the platform trust store
MONTYCAT_TLS_CERTIFICATE_PATH	Optional PEM certificate path for exact certificate pinning
MONTYCAT_TLS_CERTIFICATE_FINGERPRINT	Optional SHA-256 certificate fingerprint as an alternative pin

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

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Existing MemoCat installs keep working: memocat-mcp, MEMOCAT_*, and memocat:// are still supported. New setups should use the Montycat names.

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