Phantom Secrets MCP Server

Delegate everything to AI. Without sharing a single key.

Phantom hands every AI tool a worthless phm_ token. The local proxy injects the real key at the network layer. Full access. Zero exposure.

Quick start · Why Phantom? · MCP setup · Docs · phm.dev

▶ Watch the 45-second demo  ·  🛡 Security model  ·  📋 Threat model  ·  💬 Discussions

Why Phantom?

AI coding agents read your .env files. Once a real API key enters an LLM's context window, it leaks — via prompt injection, session logs, malicious MCP servers, or training data. GitGuardian reports AI-assisted commits leak secrets at 2× the baseline rate.

Every other secrets manager protects keys at rest and in transit. Phantom protects them in context:

• 🔒 Real keys never enter the LLM — .env contains only phm_ tokens; the proxy swaps them at the network edge.

• ⚡ 10-second setup — npx phantom-secrets init and you're protected. No accounts, no DNS, no MITM cert dance.

• 🧰 Works with every AI tool — Claude Code, Cursor, Windsurf, Codex, GitHub Copilot. Anything that reads .env.

• 🦀 Open source, local-first, MIT — your secrets live in your OS keychain. The optional cloud sync is end-to-end encrypted; the server only ever sees ciphertext.

Used by developers who don't want to choose between delegating to AI and not pasting their Stripe key into a chat window.

Related MCP server: Kova Mind MCP Server

Quick Start

$ npx phantom-secrets init
# Auto-detects .env, .env.local, or .env in subdirectories
# Stores real secrets in OS keychain, rewrites .env with phantom tokens
# Auto-configures Claude Code MCP server if detected

$ phantom agent doctor
# One human-readable readiness check for AI-agent safety

$ phantom exec -- claude
# Authenticated proxy running on 127.0.0.1:54321
# AI sees phantom tokens; proxy injects real keys

Windows

The same commands work on Windows. npx phantom-secrets init installs via npm as on macOS/Linux.

After phantom start --daemon, the CLI detects your shell and prints the matching env-var syntax. For reference:

PowerShell:

$env:OPENAI_BASE_URL = "http://127.0.0.1:PORT/openai/_phantom/TOKEN/"
$env:PHANTOM_PROXY_PORT = "PORT"
$env:PHANTOM_PROXY_TOKEN = "TOKEN"

cmd.exe:

set OPENAI_BASE_URL=http://127.0.0.1:PORT/openai/_phantom/TOKEN/
set PHANTOM_PROXY_PORT=PORT
set PHANTOM_PROXY_TOKEN=TOKEN

Git Bash / WSL: use the export X=Y syntax from the main quick-start.

Notes:

• PHANTOM_PROXY_TOKEN is the proxy session authenticator. By default, phantom exec and phantom start include it in local *_BASE_URL values as /_phantom/TOKEN/ so unmodified SDKs work. Header-aware clients can set PHANTOM_PROXY_HEADER_AUTH_ONLY=1 and send x-phantom-proxy-token: $PHANTOM_PROXY_TOKEN instead.

• If phantom.exe fails to run with "Application Control policy has blocked this file," Windows Smart App Control is honoring the downloaded file's Mark-of-the-Web tag. One-time fix from PowerShell: Get-ChildItem "$env:USERPROFILE\.phantom-secrets\bin\*.exe" | Unblock-File.

• The pre-commit hook installed by phantom init is a #!/bin/sh script. Native git from the command line invokes it via Git for Windows' bundled sh.exe, which is what the official Git for Windows installer ships. GUI clients (GitHub Desktop, some IDE integrations) may run with a stripped-down PATH that lacks sh.exe and silently skip the hook — for these, run commits from a terminal, or use phantom check --staged directly. CI is the durable safety net regardless.

• Windows-on-ARM64 not yet packaged — x64 only. Tracker: #1.

How It Works

  .env file (safe to leak)          OS Keychain / Vault
  +--------------------------+      +---------------------+
  | OPENAI_API_KEY=phm_a7f3  | ---> | sk-real-secret-key  |
  | STRIPE_KEY=phm_c9d1...   |      | sk_live_real-key... |
  +--------------------------+      +---------------------+
           |                                 |
           v                                 v
  AI Agent (Claude, Cursor)         Phantom Proxy (127.0.0.1)
  +--------------------------+      +------------------------------+
  | Reads .env               |      | Intercepts HTTP requests     |
  | Sees only phm_ tokens    | ---> | Replaces phm_ with real keys |
  | Makes API calls to proxy |      | Forwards over TLS to real API|
  +--------------------------+      +------------------------------+

1. phantom init reads .env, stores real secrets in the OS keychain, rewrites .env with phm_ tokens

2. phantom exec -- claude starts a local reverse proxy, sets SDK-compatible service base URLs such as OPENAI_BASE_URL=http://127.0.0.1:PORT/openai/_phantom/TOKEN/, exposes PHANTOM_PROXY_TOKEN to the child process, and launches the command

3. API calls hit the proxy, which authenticates the local session, removes the local auth token before forwarding, replaces phantom tokens with real secrets, and forwards over TLS

4. When the session ends, the proxy shuts down and the proxy session token is invalid. Phantom tokens remain worthless placeholders outside an authenticated proxy session.

MCP Integration (Claude Code, Cursor, Windsurf, Codex)

Phantom ships an MCP server so AI coding tools can manage secrets directly -- without ever seeing real values.

• Vault — phantom_list_secrets, phantom_status, phantom_init, phantom_add_secret_interactive, phantom_add_secret (deprecated; refuses plaintext), phantom_remove_secret, phantom_rotate, phantom_copy_secret

• Detection + diagnostics — phantom_doctor, phantom_why, phantom_check, phantom_env

• Local-to-cloud — phantom_wrap, phantom_unwrap, phantom_sync, phantom_cloud_push, phantom_cloud_pull, phantom_cloud_status

• Teams — phantom_team_list, phantom_team_create, phantom_team_members, phantom_team_invite, phantom_team_key_publish, phantom_team_vault_push, phantom_team_vault_pull

Mutating tools require an explicit confirm: true parameter so a prompt-injected agent can't silently mutate state. Real secret values are never accepted as MCP tool arguments; new secrets are entered out-of-band in a trusted terminal.

One command per AI client — Phantom writes the right config file in the right place:

phantom setup --client claude     # .claude/settings.local.json (project)
phantom setup --client cursor     # ~/.cursor/mcp.json
phantom setup --client windsurf   # ~/.codeium/windsurf/mcp_config.json
phantom setup --client codex      # ~/.codex/config.toml
phantom setup --client claude --print   # snippet to stdout for any other client

If phantom-mcp isn't on PATH, Phantom falls back to npx -y phantom-secrets-mcp so the config still works on a fresh machine. Restart the AI tool after running phantom setup so it picks up the new config.

Phantom works with any tool that supports the Model Context Protocol.

Cloud Sync + Dashboard

Sync vaults across machines with end-to-end encryption. The server never sees plaintext.

$ phantom login
# Opens GitHub OAuth (device code flow)

$ phantom cloud push
# Encrypted client-side, uploaded to phm.dev

$ phantom cloud pull   # on another machine
# Downloaded and decrypted locally

$ phantom open
# Opens https://phm.dev/dashboard — read-only view of your projects,
# vault sizes, last sync, plan tier, and team membership.

Cloud sync uses ChaCha20-Poly1305 with a client-side passphrase derived via Argon2id. The server stores only ciphertext.

Team vaults (Pro)

Multiple developers can share a single E2E-encrypted vault per project. Server only ever stores ciphertext + per-member ciphertext shares.

$ phantom team create "engineering"
# Creates a team; you become the owner.

$ phantom team invite <team_id> <github-username>
# Invites by GitHub login.

$ phantom team key-publish <team_id>
# Registers your X25519 public key on the team.
# (Run once per team; the private key stays in the OS keychain.)

$ phantom team vault-push <team_id>
# Encrypts the current project's vault with a fresh symmetric key,
# wraps that key (X25519 + ChaCha20-Poly1305) for every member that
# has a registered public key, then uploads.

$ phantom team vault-pull <team_id>   # on a teammate's machine
# Pulls, decrypts the per-member share with their private key,
# decrypts the vault, writes secrets locally.

Team memberships and member lists are visible in the read-only dashboard at phm.dev/dashboard/team.

Command Reference

Features

• Encrypted vault -- OS keychain (macOS Keychain / Secure Enclave, Linux Secret Service, Windows Credential Manager) with encrypted file fallback for CI/Docker. Argon2id hardened to OWASP balanced (m=64 MiB, t=3, p=1)

• Phantom tokens -- 256-bit CSPRNG phm_ placeholders in .env, rotatable on demand

• Authenticated proxy sessions -- each proxy run generates a fresh PHANTOM_PROXY_TOKEN; CLI-generated SDK URLs include it for compatibility, and header-aware clients can opt into x-phantom-proxy-token with PHANTOM_PROXY_HEADER_AUTH_ONLY=1

• Streaming token replacement -- For text/* and application/x-www-form-urlencoded request bodies, phantom tokens are replaced frame-by-frame without buffering the full payload; a 67-byte carry buffer handles tokens that straddle chunk boundaries. JSON bodies use a buffered path to preserve field-level F9 scoping.

• Full SSE/streaming support -- Response streaming preserved end-to-end for OpenAI, Anthropic, and other streaming APIs

• Smart detection -- Heuristic engine distinguishes secrets (*_KEY, *_TOKEN, sk-*, ghp_*) from config (NODE_ENV, PORT)

• Platform sync -- Push/pull secrets to Vercel and Railway

• Pre-commit hook -- Blocks commits containing unprotected secrets

• MCP server -- 25 tools for Claude Code, Cursor, Windsurf, and Codex to manage secrets without seeing values

• Cloud sync -- E2E encrypted zero-knowledge vault sync across machines

• Export/import -- Encrypted backup and restore (--passphrase); plaintext JSON export to stdout (--json --allow-plaintext); import from Doppler, Infisical, dotenvx, 1Password, or plain .env via --from

• Tamper-evident audit log -- PHANTOM_AUDIT=1 writes vault events as JSONL to ~/.phantom/audit.log. Each entry is chained with HMAC-SHA256; phantom audit verify detects tampering. phantom audit show/tail/path for log access.

• Response scrubbing -- Prevents secrets from leaking in API responses back to the AI

• Script wrapping -- phantom wrap patches package.json so every npm script runs through the proxy

• Watch mode -- phantom watch monitors .env files for new unprotected secrets

• Multi-project scanner -- phantom init --all <DIR> protects every git repo with a .env under <DIR> in one command (with --dry-run); --jobs N controls parallelism

• Multi-IDE setup -- phantom setup --client claude|cursor|windsurf|codex writes the right MCP config for each AI tool, or --print for a generic snippet

• Agent readiness -- phantom agent doctor and phantom agent report --json answer whether a repo is safe for Claude Code, Codex, Cursor, Windsurf, and other agents

• Enriched diagnostics -- phantom doctor reports install source, vault backend, audit-log status, Argon2 params, and MCP wiring per client

• Secret explainer -- phantom why <KEY> explains detection heuristics

• Cross-project copy -- phantom copy shares secrets between project vaults

• Team vaults -- Shared vaults with role-based access control

• Built-in service routing -- OpenAI, Anthropic, Stripe, Supabase, and custom services via .phantom.toml

• Threat model -- See THREAT_MODEL.md for assets, actors, mitigations, and known gaps

Installation

npm (recommended)

$ npm install -g phantom-secrets

Or use directly with npx:

$ npx phantom-secrets init

Claude Code MCP

$ claude mcp add phantom-secrets-mcp -- npx phantom-secrets-mcp

Cargo

$ cargo install phantom-secrets

Architecture

5-crate Rust workspace + Next.js cloud backend:

apps/web -- Next.js backend at phm.dev for cloud vault sync, GitHub OAuth, and Stripe billing.

npm packages: phantom-secrets (CLI), phantom-secrets-mcp (MCP server).

CI runs the Rust test suite and clippy across the workspace before release.

Security

• Secrets never on disk in your project directory -- real values live only in the OS keychain or encrypted vault

• ChaCha20-Poly1305 encryption for file vault and cloud sync, Argon2id key derivation

• Zero-knowledge cloud -- server stores only ciphertext; encryption key never leaves the client

• 256-bit CSPRNG tokens -- phm_ prefix ensures they never collide with real API key formats

• Proxy binds 127.0.0.1 only -- never exposed to the network

• Secrets zeroized from memory after injection via the zeroize crate

• Allowlist model -- proxy only injects secrets for explicitly configured service patterns

See SECURITY.md for the responsible disclosure policy and THREAT_MODEL.md for the full threat model (assets, actors, mitigations, known gaps, cryptography summary).

Pricing

Links

• phm.dev -- Cloud dashboard and account management

• Getting Started Guide

• Security Model

• Threat Model

• Troubleshooting

• Contributing

Contributing

We love PRs. Start with CONTRIBUTING.md, pick a good first issue, or open a discussion to talk through an idea. Be excellent to each other — see CODE_OF_CONDUCT.md.

Star history

If Phantom saves you from leaking a key — or even just from worrying about it — please star the repo ⭐. It's the single biggest signal we use to know what to build next.

License

MIT — see LICENSE.