@stemma-sh/mcp

A Model Context Protocol server for tracked-changes .docx editing, powered by the stemma engine. This package ships prebuilt native binaries (Linux, macOS, Windows) behind a tiny launcher — no Rust toolchain required.

Pre-1.0. A 0.x minor release may break API and wire contracts — deliberately, with changelog notice. The stability policy states exactly what you can depend on today.

Run it with an explicit boundary around the documents it may access:

npx -y @stemma-sh/mcp --workspace-root /absolute/path/to/documents

Or wire it into an MCP client (stdio transport):

{
  "mcpServers": {
    "stemma": {
      "command": "npx",
      "args": [
        "-y",
        "@stemma-sh/mcp",
        "--workspace-root",
        "/absolute/path/to/documents"
      ]
    }
  }
}

The server speaks JSON-RPC over stdio. Documents are passed as tool arguments (open_docx { "path": ... }). --workspace-root confines every read and output path. When absent, STEMMA_MCP_WORKSPACE_ROOT takes precedence over Claude Code's CLAUDE_PROJECT_DIR; the canonical startup directory remains a warning-emitting compatibility fallback. Relative paths resolve under the selected root and read symlinks may not escape it.

Stemma does not upload documents to a Stemma-operated service. In the path-based workflow, parsing and file writes happen locally. The MCP client or its configured model provider may receive selected document content through tool calls; consult the client's data policy.

Image files supplied by path default to a 20 MiB per-image cap (STEMMA_MCP_MAX_IMAGE_BYTES) and a 50 MiB aggregate cap per transaction (STEMMA_MCP_MAX_IMAGE_TOTAL_BYTES). Both measure bytes before base64 expansion, return artifact_source_too_large when exceeded, and accept 0 to disable the corresponding limit.

Every output is create-new: an existing destination or input alias is refused, with no overwrite option. Output is validated, staged in the destination directory, committed without clobbering, and verified by byte length and SHA-256 before success. This protects ordinary mistakes and failed writes; it is not a sandbox against a hostile same-user process or a power-loss durability promise.

Full tool reference, recipes, and refusal vocabulary: the stemma MCP reference.

The platform binary is selected via optionalDependencies (@stemma-sh/mcp-<platform>); installing with --omit=optional will leave the launcher without a binary, and it will say so rather than guess.

Dual-licensed under MIT or Apache-2.0.