Maplith Bridge

Maplith Bridge

Connect your database to your AI agent, read-only, without giving anyone your password.

The Bridge runs in your own network. It shares one folder of data files over MCP (the Model Context Protocol), behind a token you create, and it can fill that folder from PostgreSQL under a database role that can only read.

• Read-only, end to end. The server has no method that writes and accepts no file. The extractor refuses to run under a role that can do more than read.
• Your password stays with you. The database password never leaves the machine the extractor runs on, and the server that faces the network never holds it.
• Small enough to read. Three files of TypeScript. The server runs on Node.js alone; the extractor has one dependency, the PostgreSQL client, pinned.

Any MCP client can use it: Claude Code, Claude Desktop, your own agent. It works best with Maplith, which reads the folder to map how your systems fit together.

Quick start

You need Node.js 24 or newer.

npx --yes maplith-bridge@1.0.0-rc.1 rotate-token
npx --yes maplith-bridge@1.0.0-rc.1 serve --dir ./exports

The first command writes a random token to maplith-bridge.token, readable by you only. The second serves the files in ./exports at http://127.0.0.1:8787/mcp, on this machine only. Point any MCP client at that address with the header Authorization: Bearer <the token>. With Claude Code:

claude mcp add --transport http bridge http://127.0.0.1:8787/mcp \
  --header "Authorization: Bearer $(cat maplith-bridge.token)"

To fill the folder from PostgreSQL, under a read-only role:

PGHOST=db.example.com PGDATABASE=shop PGUSER=bridge_reader \
  npx --yes maplith-bridge@1.0.0-rc.1 extract postgres --out ./exports --check

--check verifies the role and writes nothing. Run it again without --check to write one CSV file per table.

Run any command with --help for every option.

Set it up for real

• RUNBOOK.md: a server install, step by step, for the person who runs it: two system users, the read-only role, TLS, a systemd service.
• INSTALL-WITH-YOUR-AGENT.md: one prompt that has your own AI agent do the same install, stopping for you at every decision, password and sudo.

How it keeps your data safe

Risk	What the Bridge does
Someone on the internet calls it	Every request needs the token: 256 random bits, compared in constant time. Wrong tokens are counted and slowed down. It listens on this machine only unless you give it TLS or name the reverse proxy in front of it, and it refuses plain HTTP on any other address.
The token leaks	It opens one folder, read-only, and nothing else. rotate-token replaces it in one command, without a restart. --allow limits who may call.
Something harmful is sent in	Nothing is written, uploaded or run. A request is at most 64 KB of JSON and is never evaluated.
A request reaches outside the folder	Not through .., a symbolic link or a hidden file. Only CSV, TSV, JSON, JSONL, Markdown and text files are served.
Your database password	It stays on the extractor's machine, is never printed or written, and is sent only to the database: over verified TLS by default when the database is on another machine.
A tampered package	Releases are built in public CI with provenance, and carry a checksum and a build attestation. The published package runs no install script.
A file tries to instruct an agent	The server tells every client that file contents are data, not instructions.

THREAT-MODEL.md names the tests behind every row.

Verify a release

Every release on GitHub carries the tarball, its SHA-256 checksum and a build attestation. The same tarball is published to npm with provenance, so npm's digest of it must match the file from GitHub: the two sha512- lines below are equal.

sha256sum -c maplith-bridge-1.0.0-rc.1.tgz.sha256
echo "sha512-$(openssl dgst -sha512 -binary maplith-bridge-1.0.0-rc.1.tgz | openssl base64 -A)"
npm view maplith-bridge@1.0.0-rc.1 dist.integrity
gh attestation verify maplith-bridge-1.0.0-rc.1.tgz --repo Maplith/bridge \
  --bundle maplith-bridge-1.0.0-rc.1.tgz.sigstore.json

After installing from npm, npm audit signatures checks the registry signature and the provenance.

Use it from any MCP client

The Bridge speaks MCP 2025-06-18 (and 2025-03-26, 2024-11-05) over Streamable HTTP: JSON-RPC 2.0 requests by POST to /mcp. It offers:

• resources: resources/list (100 per page, with a cursor) and resources/read;
• two read-only tools on the same code path: list_files and read_file.

Each top-level folder is one system: exports://shop/orders.csv is the file orders.csv of the system shop. A file is listed only when it fits in one reply of at most 8 MB. GET /healthz answers 204 for a health check.

File contents come from your systems. Tell your agent to treat them as data, never as instructions; the Bridge says the same in its instructions.

Limits

• PostgreSQL is the one database the extractor reads. Any other system can fill the folder with its own export files.
• The server reads a TLS certificate when it starts: restart it after a renewal.
• Behind two proxies in a row, name both with --behind-proxy.

Versioning

The Bridge follows semantic versioning. Every change is in CHANGELOG.md.

Contributing, security, licence

• CONTRIBUTING.md: how to propose a change (with a DCO sign-off).
• SECURITY.md: report a vulnerability privately, to security@maplith.com or through GitHub.
• Apache License 2.0 (LICENSE). "Maplith" and the Maplith logo are trademarks of Maplith (TRADEMARK.md).