@wundervault/mcp-server

A zero-knowledge secrets vault for AI agents. Every API key you paste into an agent chat or a `.env` file ends up in context windows, transcripts, and provider logs. Wundervault's answer: the agent never receives the secret at all. It asks for *work* — "run this deploy with the key injected" — and a local daemon decrypts the secret, injects it into the subprocess environment, zeroes the buffer, and scrubs the output before the agent sees any of it.

This repo is the MCP server that exposes that workflow to any Model Context Protocol client — Claude Code, Cursor, Cline, and others.

Don't trust the claim — test it: the zero-knowledge property is independently verifiable at your own network boundary in about 5 minutes (browser DevTools or a mitmproxy canary test). Guide + our own test transcript: wundervault.com/verify.

How it works

┌──────────────┐  MCP (stdio)  ┌───────────────────┐  ciphertext only  ┌───────────────────┐
│   AI agent   │──────────────▶│  wundervault-mcp  │◀─────────────────▶│  wundervault.com  │
│ (Claude, …)  │◀──────────────│  + local daemon   │                   │ stores encrypted  │
└──────────────┘ "burned" ack  │  decrypts HERE    │                   │ blobs, no keys    │
                               └─────────┬─────────┘                   └───────────────────┘
                                         │  secret → subprocess env
                                         │  (buffer zeroed after spawn)
                                         ▼
                               ┌───────────────────┐
                               │   your command    │ stdout/stderr scrubbed
                               │ (deploy, API, …)  │ before the agent sees it
                               └───────────────────┘

Secrets are encrypted client-side (AES-256-GCM via Web Crypto) before upload. The hosted service only ever stores ciphertext — it cannot derive the key, the passphrase, or the plaintext.

Install

npm install -g @wundervault/mcp-server

Quick Start

{
  "mcpServers": {
    "wundervault": {
      "command": "wundervault-mcp",
      "env": {
        "WUNDERVault_AGENT_VAULT_URL": "https://wundervault.com",
        "WUNDERVault_AGENT_VAULT_API_KEY": "wv_agent_|",
        "WUNDERVault_AGENT_KEY": ""
      }
    }
  }
}

Or using a credentials file:

wundervault-mcp --credentials ~/.wundervault/creds.json

New account? wundervault.com has a 90-second agent onboarding flow that generates this config for you.

Security Model

• Zero-knowledge: The encryption key lives only in the MCP server process. The Wundervault server never sees it.
• Burn-after-reading: Plaintext secrets are never returned to the calling agent. After decryption, the agent receives only `"Secret retrieved and burned."`.
• Exec scrubbing: Command stdout/stderr are scrubbed of the plaintext before being returned; shell-escape patterns (`$()`, backticks, `sh -c`, `eval`) and file redirects of secrets are rejected *before* decryption.
• Directive integrity: Server-side directive signatures (PBKDF2-HMAC-SHA256, 600k iterations) are verified before any secret is released.
• Timing-safe: HMAC comparison uses `crypto.timingSafeEqual`.
• Tiered access: Per-entry access tiers are enforced server-side; high-tier secrets require human approval before an agent can use them.

Honest limitations

• The platform is open-core: this MCP server and the browser crypto are AGPL-3.0 so you can audit everything that touches your secrets, but the hosted service itself is not open source.
• A local daemon must run next to the agent; fully air-gapped setups don't fit.
• By design the agent can never read a secret's value — if your workflow needs the model to *reason about* the secret itself, this is the wrong shape.

Tools

`vault_entries_list`

List all vault entries available to this agent. Returns entry IDs and secret names — no values.

Input: {}
Output: "Vault entries (N):\n  [entry_id]  secret_name  (tier: read)"

`vault_entry_get`

Retrieve and decrypt a vault secret. Optionally execute a command with it.

Input:
  entry_id: string          # from vault_entries_list
  purpose: string           # audit log reason
  exec?: string             # optional shell command

Output: "Secret retrieved and burned." (plaintext NEVER returned)

Secure exec pattern (sudo example):

sudo -S systemctl restart nginx |",
  "agent_encryption_key": ""
}

CLI Options

wundervault-mcp [options]

  --api-key      Agent API key
  --enc-key      Encryption key (base64 URL-safe)
  --url          API base URL (default: https://wundervault.com)
  --credentials    Path to credentials JSON file
  --help              Show help

Agent wallets (x402)

An x402 payment is just a signature, and a wallet key is a

vault secret like any other. Store the key at tier 2, have the agent sign the

payment payload through `vault_exec`, and the key is injected into a local signing

subprocess — it never enters the model context, and every use needs the owner's

approval first (the agent's denied call carries a request id; approval is scoped

to that agent + secret, once or for a 15/60-minute window). We ran this

end-to-end on Base Sepolia — the verified run is written up at

wundervault.com/agent-wallets.

Payment-specific policy (spend caps, payee allowlists) is not built yet:

compatible, not productized.

Sandbox / demo mode

Set `WUNDERVAULT_MOCK=1` to run the server without a `wundervault-agent`

daemon or any credentials. In this mode every tool call returns a representative

response clearly labelled `[DEMO MODE]` instead of contacting the vault — **no

real secret is ever involved**. This exists so you can poke at the tool surface

without an account, and so MCP directory scanners and CI

(e.g. Glama) can start the server, exercise each tool, and

validate the build with no live vault. It is off by default and is never

enabled in production.

"env": { "WUNDERVAULT_MOCK": "1" }   // demo/CI only — returns fake, labelled output

Building from source

git clone https://github.com/wundervault/wundervault-mcp.git
cd wundervault-mcp
npm install
npm run build   # compiles TypeScript to dist/
npm test        # run the test suite

License

Licensed under the GNU Affero General Public License v3.0 or later (`AGPL-3.0-or-later`). See LICENSE.

Wundervault is open-core: this MCP server and the client are open source; the hosted service at wundervault.com is a commercial offering. For commercial or hosting inquiries, get in touch via wundervault.com/contact.