A2RG MCP Bridge

A2RG MCP Bridge connects MCP clients to an open Obsidian vault through a local desktop plugin. It exposes eight vault tools through Streamable HTTP MCP and keeps an optional Bun stdio process for filesystem fallback.

Current release: 1.0.12.

Components

• Obsidian plugin mcp-vault-connector: reads and writes the active vault through Obsidian APIs and exposes a loopback HTTP or HTTPS server.

• MCP executable dist/a2rg-obsidian-mcp: optional stdio fallback for filesystem access when Obsidian or the plugin bridge is unavailable.

• Public npm package @a2rg/obsidian-mcp: Node stdio executable for plugin-first access and automatic filesystem fallback.

• Shared tool registry: the plugin and stdio executable expose the same eight tools and argument schemas.

Related MCP server: obsidian-cli-mcp

Architecture

MCP client
  -> Streamable HTTP /mcp
  -> authenticated local plugin bridge
  -> App.vault / App.metadataCache / App.workspace

Local HTTPS is the default. Plain HTTP is blocked unless explicitly enabled for trusted loopback testing.

Quick start

1. Install dependencies and build:

   npm install
   npm run build

2. Copy manifest.json and main.js into:

   <vault>/.obsidian/plugins/mcp-vault-connector/

3. Enable A2RG MCP Bridge in Obsidian Community Plugins.

4. In plugin settings:

   • Enable the bridge.

   • Keep port 27125 unless a conflict requires another port.

   • Keep local HTTPS enabled and trust the generated certificate.

   • Copy the 64-character bearer token.

5. Configure the MCP client:

   {
     "mcpServers": {
       "obsidian": {
         "type": "http",
         "url": "https://127.0.0.1:27125/mcp",
         "headers": {
           "Authorization": "Bearer <64-character-plugin-token>"
         }
       }
     }
   }

Direct HTTPS uses https://127.0.0.1:27125/mcp. Trust the plugin certificate before connecting. The certificate and private key persist across Obsidian reloads and restarts. Use Regenerate local TLS certificate in plugin settings only when you intentionally replace that identity.

Direct HTTPS MCP does not require OBSIDIAN_VAULT_PATH, OBSIDIAN_CONFIG_DIR, OBSIDIAN_API_KEY, OBSIDIAN_API_URL, a command, or an executable path. The provider needs only the MCP URL and the bearer token.

Network and privacy disclosure

The plugin starts a server only on 127.0.0.1 (localhost). It does not expose the vault to the public internet, send vault content to a remote service, collect telemetry, or include dynamic advertising.

The plugin enumerates vault file paths only to implement list_files and search_vault. It returns relative paths and matching snippets after bearer authentication, skips hidden directories and symlinks, and rejects absolute or traversal paths.

Every /mcp and REST request requires a generated bearer token. HTTP requires an explicit testing-only opt-in; HTTPS is recommended. The optional npm stdio package can access only the discovered local vault when the bridge is unavailable, and does not provide a public network endpoint.

Verify

curl --fail --silent \
  --cacert /absolute/path/to/localhost.pem \
  -H "Authorization: Bearer <64-character-plugin-token>" \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  --data '{"jsonrpc":"2.0","id":1,"method":"tools/list","params":{}}' \
  https://127.0.0.1:27125/mcp

The server exposes:

• get_file

• write_file

• append_file

• delete_file

• search_vault

• get_linked_notes

• list_files

• get_active_file

Requirements

• Obsidian Desktop 1.14.4 or later.

• Node.js 22 or later for source builds.

• npm.

• A local Markdown vault.

• An MCP client with Streamable HTTP support.

Optional stdio fallback

The stdio executable remains available when Obsidian or the plugin bridge is unavailable. It can discover the vault and plugin settings automatically. Environment variables remain available for overrides.

Run the public npm package without a global install:

npx -y @a2rg/obsidian-mcp

Or install it with npm/pnpm:

npm install -g @a2rg/obsidian-mcp
# or
pnpm add -g @a2rg/obsidian-mcp

With pnpm without a global install:

pnpm dlx @a2rg/obsidian-mcp --discover
pnpm dlx @a2rg/obsidian-mcp

Discovery can be checked without starting MCP:

npx -y @a2rg/obsidian-mcp --discover

The package:

1. Tries plugin HTTP/HTTPS REST first.

2. Uses the Obsidian vault filesystem if the bridge is unavailable.

3. Avoids filesystem fallback after definite 4xx/5xx responses.

4. Avoids filesystem writes after ambiguous REST write, append, or delete operations.

See npm and pnpm Package for MCP client configuration, auto-discovery, CLI flags, cache behavior, and publication.

Documentation

• Architecture

• Quick Start

• Plugin Guide

• MCP Tools

• Troubleshooting

• Security and Public Deployment

• npm and pnpm Package

• Contributing

• Changelog

Development

npm test
npm run dev:mcp
npm run dev:plugin
npm run build:npm
npm run build

Run synthetic search benchmarks:

npm run benchmark:search -- 1000
npm run benchmark:search -- 10000
npm run benchmark:search -- 100000

Search benchmark

The reproducible synthetic benchmark uses 10 relevance sets, known expected documents, and the same BM25 implementation used by the plugin and npm package.

Measured metrics:

• MRR@10: 1.0

• Recall@10: 1.0

• Recall@100: 1.0

• Gzip snapshot: 4.668 MB

• Test suite: 29 tests passing

The benchmark proves indexed-search behavior and incremental updates, not semantic similarity from embeddings. It is useful for comparing future search implementations against a reproducible baseline.

Field-aware BM25 weights title/H1, headings, tags, and frontmatter above unstructured content while preserving exact and filename matches.

npm test runs the Bun test suite. npm run build type-checks both targets, bundles main.js, and compiles dist/a2rg-obsidian-mcp.

Release

Plugin releases use .github/workflows/release.yml.

1. Update manifest.json, package.json, package-lock.json, and versions.json to the same version.

2. Run npm test and npm run build.

3. Commit and push the source changes.

4. Create and push a tag that exactly matches manifest.json.version; do not prefix it with v.

5. Publish the GitHub draft release with main.js and manifest.json.

6. Submit or refresh the Obsidian community review.

7. Run or trigger .github/workflows/npm-publish.yml to publish the npm CLI.

Security boundary

• The plugin binds only to 127.0.0.1.

• Every /mcp and REST request requires the bearer token.

• Relative vault paths are validated.

• Absolute paths and . / .. path segments are rejected.

• Request bodies are capped at 5 MB.

• HTTP is limited to local testing.

• HTTPS uses a generated self-signed certificate that clients must trust.

• The stdio fallback does not replace authentication for a public service.

Read Security and Public Deployment before changing this local-only deployment model.