shinjuku-shield

Shinjuku Shield

The Shinjuku Shield wallet: a self-custody wallet that pays x402 URLs privately from a shielded USDC balance on Solana. It also pays for AI answers privately, in a terminal chat or for your agent app. Its mcp command runs a local MCP server (stdio) for your agent. Your keys never leave your machine.

This is version 0.3.131. The npm packages shinjuku-shield and shinjuku-shielded hold the same files. The command is shinjuku.

Set up

npm install -g shinjuku@0.3.131
shinjuku setup

Type the two lines as they are. npx install shinjuku does not work: npx reads install as the name of another npm package. To set up without installing, type npx shinjuku@0.3.131 setup.

Setup makes the wallet on this machine, a private passphrase file, and the checked proof tools (about 191 MB), and writes config.json. It also writes a recovery file: copy it to two offline places, then delete it from this machine. --add-to claude-code (or claude-desktop, cursor) also adds the server to that host's config.

The shinjuku command

Every wallet command works after shinjuku, for example shinjuku balance, shinjuku chat or shinjuku infer start. shinjuku help lists them.

Add it to your agent host

Claude Code:

claude mcp add --scope user shinjuku -- npx -y --no-audit --no-fund shinjuku-shield@0.3.131 mcp

Claude Desktop (claude_desktop_config.json) or Cursor (~/.cursor/mcp.json):

{ "mcpServers": { "shinjuku": { "command": "npx", "args": ["-y", "--no-audit", "--no-fund", "shinjuku-shield@0.3.131", "mcp"] } } }

On native Windows, if the host cannot find npx, use "command": "cmd" and put "/c", "npx" at the start of args. The server's name in host configs is shinjuku.

Add funds

Ask your agent "Add 0.50 USDC to my shielded balance". It calls wallet_add_funds and gives a one-time address. Send USDC on Solana to it from any wallet or exchange. Cents work (from 0.01 USDC), and you need no SOL. The USDC becomes private by itself.

Pay

Spending limits are optional and off by default: only the balance bounds a payment. To set them, give setup --max-payment, --max-session, or --max-cumulative, in USDC (0.05 = 5 cents).

x402_discover finds sellers in public x402 listings, x402_preview shows the price, and x402_pay pays.

Private AI

Each answer is paid from your shielded balance, through Tor: the AI provider sees your words, not your IP address, and the chain does not show which wallet paid. The wallet keeps no copy of a conversation.

• shinjuku chat: a chat in this terminal. Each answer has a cap (0.05 USDC by default) and each chat has a cap (1 USDC by default).
• shinjuku infer start: a local AI address for an agent app that speaks the OpenAI API. It prints the base_url (http://127.0.0.1:11402/v1) and an api key. It keeps running in the background after the terminal closes; shinjuku infer status shows it, and shinjuku infer stop stops it. Your agent can also start it with the MCP tool inference_server. It serves the OpenAI Chat Completions API (/v1/chat/completions, streaming too) and /v1/models. Apps that use the OpenAI Responses API (/v1/responses) do not work with it yet.
• inference_chat (MCP): one answer for your agent.

Needs

• Node.js 22.21 or later, or Node.js 24 or later (node --version shows yours; a --tor run needs NODE_USE_ENV_PROXY, which Node.js 23 does not have).
• Linux, or Windows with WSL. macOS is not supported: the provers are Linux programs.
• Tor, for private AI (and for --tor).

The package has no install scripts. node_modules/.bin and the global npm folder must not be writable by other users: the MCP server holds your wallet keys.

This package holds one wallet release, unchanged. The shinjukuRelease and shinjukuSha256 fields in package.json name that release. Compare the hash with the Releases table in ShinjukuStaition/shinjuku-shield. Versions are published from GitHub Actions with npm provenance.

The full guide is ShinjukuStaition/shinjuku-shield.

License

LICENSE.txt (the Shinjuku Shielded wallet license, all rights reserved) and THIRD_PARTY_NOTICES.txt (the open-source packages inside the file) ship unchanged from the release. manifest.json names the source commit and every bundled package.