NullWire-MCP

⚡ NullWire-MCP

See the traffic. Never the secrets.

A zero-dependency, RAM-only network inspector that lets your AI assistant debug HTTP, HTTPS and WebSocket traffic, with every secret scrubbed before the model ever sees it.

Quick start · How it works · What gets redacted · MCP tools · Configuration · CLI reference · Security model

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🧠 Why NullWire exists

Your AI assistant is great at debugging an API call, until the request it needs to read carries an Authorization header, a session cookie, a database URL or a customer's email. Pasting raw traffic into a chat means pasting your secrets with it.

NullWire sits between your app and the network. It records what passes through, scrubs every secret out of the recorded copy, and hands that clean copy to your assistant through the Model Context Protocol. Your app keeps working exactly as before, because the live traffic is never touched.

  your app ──► NullWire (127.0.0.1) ──► the real server

│ ├─ forwards every byte, unmodified └─ keeps a scrubbed copy in RAM ──► your AI assistant (MCP)

✨ At a glance

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🚀 Quick start

1. Install it

Pick whichever fits your machine. Every method checks the download against the release's SHA256SUMS.txt and installs nothing if it doesn't match. Release binaries also carry signed GitHub build provenance, and each release includes a CycloneDX SBOM (nullwire-sbom.cdx.json).

With Node.js (no install step): npx

npx -y nullwire-mcp install --client all

Nothing to download by hand: the launcher fetches and verifies the binary on first run and keeps it in a cache folder. Your MCP clients are then set to run npx -y nullwire-mcp.

macOS, Linux and Termux: install script

curl -fsSL https://raw.githubusercontent.com/VoxNode-ux/nullwire-mcp/main/scripts/install.sh | sh -s -- --setup

Installs to ~/.local/bin (or $PREFIX/bin on Termux). --setup also registers NullWire with your MCP clients. Drop it to install only. --uninstall removes everything again.

Windows: install script

irm https://raw.githubusercontent.com/VoxNode-ux/nullwire-mcp/main/scripts/install.ps1 | iex

nullwire-mcp install --client all

Installs to `%LOCALAPPDATA%\Programs\nullwire-mcp` and adds it to your user PATH. To pass options, run it as `& ([scriptblock]::Create((irm https://raw.githubusercontent.com/VoxNode-ux/nullwire-mcp/main/scripts/install.ps1))) -Setup`.

Homebrew and Scoop

brew install VoxNode-ux/nullwire/nullwire-mcp                                   # macOS, Linux

scoop bucket add nullwire https://github.com/VoxNode-ux/scoop-nullwire # Windows scoop install nullwire-mcp

Both packages are generated from the templates in [`packaging/`](packaging/README.md).

Download a release by hand

chmod +x nullwire-linux-amd64

sha256sum -c SHA256SUMS.txt --ignore-missing # verify the download (macOS: shasum -a 256 -c) gh attestation verify nullwire-linux-amd64 --repo VoxNode-ux/nullwire-mcp # optional: verify signed build provenance

</details>

Build from source

go install github.com/VoxNode-ux/nullwire-mcp@latest

or

git clone https://github.com/VoxNode-ux/nullwire-mcp && cd nullwire-mcp CGO_ENABLED=0 go build -trimpath -ldflags="-s -w" -o nullwire-mcp .

Go 1.26 or newer. There is nothing to `go get`: the module has no dependencies.

Docker

docker run -i --rm ghcr.io/voxnode-ux/nullwire-mcp

The server speaks MCP over stdio, so run it with -i. The proxy listens on the container's own loopback by design, so a published port (-p) cannot reach it. On Linux, add --network host to use it from the host's 127.0.0.1.

2. Add it to your MCP clients

One command registers NullWire with every supported client it finds on your machine:

nullwire-mcp install --client all --dry-run   # look first: nothing is written

nullwire-mcp install --client all # then do it, and restart the client

It covers Claude Desktop, Claude Code, Cursor, Windsurf, VS Code, Cline, Roo Code, Gemini CLI and Codex CLI. See Connect your MCP clients for details, or add it by hand:

# Claude Code

claude mcp add nullwire -- /path/to/nullwire-mcp

// Claude Desktop, Cursor, Windsurf, Cline and other JSON-configured clients

{ "mcpServers": { "nullwire": { "command": "/path/to/nullwire-mcp", "args": ["-port", "8080"] } } }

The client starts NullWire, and NullWire starts the proxy in the same process. A live status bar on stderr shows what is happening:

⚡ [NullWire-MCP] Proxy 127.0.0.1:8080 | RAM Ring: 3/50 | Scrubbed: 7 Tokens, 2 Cookies, 1 IPs | Disk: 0B

3. Send some traffic through it

# Plain HTTP through the proxy

curl -x http://127.0.0.1:8080 http://httpbin.org/headers

HTTPS through the proxy (a blind tunnel, see "How it works")

curl -x http://127.0.0.1:8080 https://example.com

HTTPS with full request visibility: the reverse gateway

nullwire-mcp -target https://api.example.com curl http://127.0.0.1:8080/v1/things -H "Authorization: Bearer sk-live-..."

4. Ask your assistant

*"Use inspect_traffic to show my last 5 requests and tell me why the third one returned 401."*

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🔭 How it works

flowchart LR

A[Your app or curl] -->|HTTP_PROXY / base URL| P[NullWire proxy 127.0.0.1:8080] P -->|unmodified bytes| S[(Real server)] S -->|unmodified bytes| P P --> C[Capture copy] C --> R[Redaction layers] R --> B[(RAM ring 50 flows)] B -->|MCP over stdio| M[AI assistant]

The key idea: the model reads a scrubbed copy, your app talks to the real server. Nothing the proxy forwards is rewritten, so debugging never changes the behaviour you are debugging.

Four ways to capture traffic

Why no HTTPS interception? Reading HTTPS from a forward proxy would require a custom root certificate installed on your machine. That is key material and a trust-store change, the opposite of a zero-footprint tool. The reverse gateway gets you the same visibility with no certificate games.

Several APIs at once

Give each upstream a name. The first path segment picks the upstream and is removed before forwarding:

nullwire-mcp -target openai=https://api.openai.com,anthropic=https://api.anthropic.com

export OPENAI_BASE_URL=http://127.0.0.1:8080/openai/v1 # → https://api.openai.com/v1 export ANTHROPIC_BASE_URL=http://127.0.0.1:8080/anthropic # → https://api.anthropic.com

Names are letters, digits, ., _ and - (up to 32 characters, case-insensitive). One unnamed URL may be added as the default for paths that match no name. An X-Target-URL header overrides everything for a single request.

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🧰 MCP tools

NullWire exposes three tools over stdio. It speaks MCP protocol versions 2026-07-28, 2025-11-25 and 2024-11-05, and accepts JSON-RPC batches.

A flow looks like this (illustrative):

{

"id": 7, "timestamp": "2026-10-31T09:14:02Z", "method": "POST", "url": "https://api.example.com/v1/charge", "request_headers": { "Authorization": "[REDACTED_TOKEN#a1b2c3]", "Content-Type": "application/json" }, "request_body": "{\"card_token\":\"[REDACTED_TOKEN#9f3e21]\",\"amount\":4200}", "status_code": 401, "response_body": "{\"error\":\"invalid_api_key\"}", "latency_ms": 143, "redaction_count": 2 }

Tags are stable and correlatable. [REDACTED_TOKEN#a1b2c3] is a short salted hash, so the same secret gets the same tag everywhere in one run. Your assistant can see that two requests used the *same* token without learning it. The salt is random per run, so tags can't be compared across restarts or reversed.

Tag kinds: TOKEN, COOKIE, IP and KEY (private key