Phantom

AI uses your keys. Safely.

AI coding agents read your .env files, putting API keys into LLM context windows where they leak via prompt injection, session logs, malicious MCP servers, or training data. GitGuardian reports AI-assisted commits leak secrets at 2x the baseline rate.

Phantom replaces real secrets with inert tokens. A local proxy swaps them back at the network layer. The AI never sees a real key.

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 exec -- claude
# Proxy running on 127.0.0.1:54321 — AI sees phantom tokens, proxy injects real keys

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 OPENAI_BASE_URL=http://127.0.0.1:PORT/openai (and equivalents for other services)
3. API calls hit the proxy, which replaces phantom tokens with real secrets and forwards over TLS
4. When the session ends, the proxy shuts down. Phantom tokens are worthless outside the proxy.

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. 9 tools available: list, status, init, add, remove, rotate, cloud push, cloud pull, cloud status.

Claude Code

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

Cursor

Add to Cursor Settings > Features > MCP Servers:

• Name: phantom
• Command: npx phantom-secrets-mcp

Windsurf

Add to ~/.codeium/windsurf/mcp_config.json:

{"phantom": {"command": "npx", "args": ["phantom-secrets-mcp"]}}

Codex / Other MCP Clients

Add to your MCP configuration:

{"phantom": {"command": "npx", "args": ["phantom-secrets-mcp"]}}

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

Cloud Sync

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

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

Command Reference

Command	Description
phantom init	Import .env secrets into vault, rewrite with phantom tokens
phantom exec -- <cmd>	Start proxy and run a command with secret injection
phantom start / stop	Manage proxy lifecycle (standalone/daemon mode)
phantom list	Show secret names stored in vault (never values)
phantom add <KEY> <VAL>	Add a secret to the vault
phantom remove <KEY>	Remove a secret from the vault
phantom reveal <KEY>	Print a secret value (or --clipboard to copy)
phantom status	Show proxy state, vault info, and mapped services
phantom rotate	Regenerate all phantom tokens (old ones become invalid)
phantom doctor	Check configuration and vault health
phantom check	Scan for unprotected secrets (pre-commit hook)
phantom sync	Push secrets to Vercel / Railway
phantom pull	Pull secrets from Vercel / Railway into vault
phantom setup	Configure Claude Code MCP server + hooks
phantom env	Generate .env.example for team onboarding
phantom export	Export vault to encrypted backup file
phantom import	Import vault from encrypted backup
phantom login	Authenticate with Phantom Cloud via GitHub OAuth
phantom logout	Clear cloud credentials
phantom cloud push	Push encrypted vault to Phantom Cloud
phantom cloud pull	Pull and decrypt vault from Phantom Cloud

Features

• Encrypted vault -- OS keychain (macOS Keychain / Secure Enclave, Linux Secret Service) with encrypted file fallback for CI/Docker
• Session-scoped tokens -- 256-bit CSPRNG phantom tokens with phm_ prefix, rotatable on demand
• Streaming proxy -- Full SSE/streaming support 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 -- 9 tools for Claude Code to manage secrets without seeing values
• Cloud sync -- E2E encrypted zero-knowledge vault sync across machines
• Export/import -- Encrypted backup and restore with passphrase protection
• Built-in service routing -- OpenAI, Anthropic, Stripe, Supabase, and custom services via .phantom.toml

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

Architecture

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

Crate	Role
phantom-core	Config (.phantom.toml), .env parsing/rewriting, token generation, auth, cloud client
phantom-vault	VaultBackend trait: OS keychain + encrypted file fallback, ChaCha20-Poly1305 crypto
phantom-proxy	HTTP reverse proxy on 127.0.0.1 with SSE/streaming, token replacement, TLS forwarding
phantom-cli	clap-based CLI binary, 21 commands
phantom-mcp	MCP server binary (rmcp SDK), stdio transport, 9 tools

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).

56 tests across all crates, zero clippy warnings.

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 full threat model.

Pricing

	Free	Pro	Enterprise
Local vaults	Unlimited	Unlimited	Unlimited
Cloud vaults	1	Unlimited	Unlimited
MCP server	Yes	Yes	Yes
Cloud sync	Yes	Yes	Yes
Team features	--	--	Yes
Price	$0	$8/mo	Contact us

Links

• phm.dev -- Cloud dashboard and account management
• Getting Started Guide
• Security Model
• Troubleshooting
• Contributing

License

MIT -- see LICENSE