The security layer
for AI agents.

Install and make a test file

Homebrew installs NockGuard and the Wall on macOS. The sample filesystem server needs Node.js with npx. Linux users can follow the release download and checksum steps in the README install guide ↗.

# macOS
$ brew install nocktechnologies/tap/nockguard

$ QS=$(mktemp -d)
$ cd "$QS"
$ printf 'NockGuard read succeeded\n' > hello.txt
$ pwd -P

Copy the physical folder path printed by pwd -P into <QS> below. Use fixture and executable paths without spaces for this example.

Initialize, connect, and verify

$ nockguard init
$ nockguard keygen --agent coder

The starter policy lives at ~/.nockguard/policy.yaml and allows coder to call read_file. Existing policies are preserved; check your coder rules if you already have one.

GUI clients may not inherit your shell's executable search path. Run these in the same terminal and copy their outputs into <NOCKGUARD_PATH>, <NPX_PATH>, and <SHELL_PATH> below:

$ command -v nockguard
$ command -v npx
$ printf '%s\n' "$PATH"

Point one MCP filesystem server through NockGuard, replacing all four placeholders:

{
  "mcpServers": {
    "files": {
      "command": "<NOCKGUARD_PATH>",
      "args": ["proxy", "--upstream", "<NPX_PATH> -y @modelcontextprotocol/server-filesystem <QS>", "--agent", "coder"],
      "env": {"PATH": "<SHELL_PATH>"}
    }
  }
}

Save the config and restart or reload the MCP client. Ask it to call read_file on <QS>/hello.txt; after the read succeeds, verify the signed trail and open the local Wall:

$ nockguard verify --agent coder
$ nockguard wall --agent coder

A successful routed read creates a signed trail. nockguard verify --agent coder checks its integrity and reports PROTECTED for a non-empty, fully checkpointed trail. For a blocked-write canary, the README explains the acceptance check against a local MCP stub and links its script. nockguard selftest uses synthetic probes and reports PROVEN for the firewall gate; it does not prove your client is wired through this proxy.