Citadel

citadeldb-mcp

mcp-name: dev.citadeldb/mcp

Model Context Protocol (MCP) server for the Citadel encrypted memory engine. Gives any MCP client (Claude Desktop, an IDE, an agent) persistent, encrypted memory.

Memory lives in a local citadeldb-mem region: AES-256 encrypted at rest, per-atom sealed and HMAC-authenticated, recalled through a hybrid vector + keyword + recency + importance fusion over a PRISM approximate nearest-neighbor index, connected by a typed edge graph, and forgotten by destroying keys (cryptographic erasure).

Install

Run it with no install. For semantic recall, pull the recommended embedder and cross-encoder reranker once, then enable both:

uvx citadeldb-mcp pull e5-large
uvx citadeldb-mcp pull ms-marco-minilm

The pull commands do not open a vault. Before serving, set CITADEL_KEY to the vault passphrase (export CITADEL_KEY="your-passphrase" on macOS/Linux or $env:CITADEL_KEY = "your-passphrase" in PowerShell), then run:

uvx citadeldb-mcp --db memory.cdl --embedder e5-large --reranker ms-marco-minilm

e5-large + ms-marco-minilm is the recommended semantic-recall setup. See the memory benchmarks for measured configurations. Models are never downloaded automatically.

Built-in pulls use release-pinned Hugging Face revisions. Each complete snapshot is verified against compiled sizes and SHA-256 digests, then stored with a BLAKE3 manifest under <models-dir>/<name>/<revision>/. A flat cache created by an earlier CitadelDB release is not trusted; run pull again to create the pinned snapshot. --model-dir and --reranker-dir remain explicit bring-your-own-artifact paths and bypass the managed-cache manifest. Citadel treats those directories as user-trusted and does not attest their contents.

Or install the command with pip install citadeldb-mcp or cargo install citadeldb-mcp, then wire it into Claude Desktop (claude_desktop_config.json):

{
  "mcpServers": {
    "citadel": {
      "command": "citadeldb-mcp",
      "args": ["--db", "/absolute/path/to/memory.cdl", "--embedder", "e5-large", "--reranker", "ms-marco-minilm"],
      "env": { "CITADEL_KEY": "your-passphrase" }
    }
  }
}

The server supports stateless MCP 2026-07-28 discovery and per-request metadata, plus the initialize-based 2025-11-25 and 2025-06-18 revisions for existing clients.

Tools (over a bounded, cancellable JSON-RPC 2.0 stdio transport):

• mem_recall - hybrid retrieval (vector + keyword + recency + importance); filter by kind/payload, expand along the memory graph, override fusion weights, and optionally attach provenance (derived_from), per-hit integrity verdicts (attest), and resource_links to each hit
• mem_fetch - deterministic cursor-based listing of a kind (no embedding)
• mem_get - bounded exact-id batch retrieval in request order, with missing atoms marked explicitly
• mem_edges - cursor-based typed graph introspection
• mem_profile - what the memory knows about a query: recall plus its graph neighborhood
• mem_summarize - per-kind digest of a region
• mem_verify - re-authenticate atoms off disk: per-atom integrity verdict (authentic / tampered / key_erased / missing / plaintext_unattested)
• mem_remember - store one atom with optional provenance and retry-safe idempotency
• mem_remember_batch - atomically store an ordered batch; every entry carries a distinct idempotency key, and a changed reuse rejects the whole batch
• mem_update - replace a stored atom's payload in place (preserves id, edges, and embedding)
• mem_link / mem_unlink - add or remove one exact typed edge
• mem_evolve - recompute an atom's neighbor links and stored importance
• mem_evict - selective forgetting by policy (cryptographic erasure on encrypted regions)
• mem_forget - forget atoms by id and return a verifiable erasure receipt; optionally erase their region-local derived_from closure atomically (cryptographic erasure on encrypted regions; immutable atoms require the protected-erasure opt-in)

The citadeldb-mcp binary reads the passphrase from CITADEL_KEY and serves one region (encrypted by default); only protocol messages go to stdout, diagnostics to stderr. --region-mode plaintext disables per-atom encryption and cryptographic erasure for that region; the database remains encrypted at rest. Erasure does not revoke plaintext exports or keys retained in pre-erasure backups or snapshots.

Every server invocation must select an embedder. The CPU Candle embedder is compiled into the standalone server's default build, including the citadeldb-mcp Python package; it is not included in the default citadeldb library wheel. Models are fetched only on explicit pull.

Embedder pull names: e5-large (recommended), e5-large-v2, bge-small, bge-base, bge-large, minilm. Reranker: ms-marco-minilm. Or point --model-dir at a compatible local checkpoint for the selected catalog pipeline, and build with --features cuda-embed to run on an NVIDIA GPU.

This crate is part of the Citadel workspace.

License

Apache-2.0